JP5804776B2 - Multilayer structure and manufacturing method thereof - Google Patents

Description

  The present invention relates to a multilayer structure having eight or more resin layers and a method for producing the same, and more particularly to a multilayer structure having excellent gas barrier properties, melt moldability and durability, and a method for producing the same.

  Nowadays, laminated films having an ethylene-vinyl alcohol copolymer layer are used for food and medical packaging materials by utilizing their high gas barrier properties, stretchability, thermoformability and the like. Recently, for the purpose of improving various performances such as gas barrier properties, various multilayer structures in which a plurality of resin layers each having a thickness of micron order or submicron order have been proposed.

  As a conventional multilayer structure in which a plurality of resin layers of ethylene-vinyl alcohol copolymer are laminated, for example, (1) a fluid barrier material such as ethylene-vinyl alcohol copolymer and an elastomer material such as thermoplastic polyurethane are used. It can be used with an elastomeric barrier film (see Japanese Patent Publication No. 2002-524317) in which ten or more microlayer polymer composites are alternately laminated, and (2) a hard polymer material such as an ethylene-vinyl alcohol copolymer. A multilayer film (see Japanese Patent Application Publication No. 2003-512201) having alternating layers with a flexible polymer material has been developed.

  The multilayer structure as described above is usually formed by a coextrusion method or the like. Here, since this multilayer structure has a small thickness for each layer and is a multilayer laminate, it is not easy to melt-mold each layer and the whole. If the melt moldability is not good, the thickness of each layer becomes non-uniform so that the durability may be lowered or sufficient gas barrier properties may not be exhibited. However, in the conventional multilayer structures (1) and (2), no special measures for improving melt formability are taken.

Special Table 2002-524317 Special table 2003-512201 gazette

  The present invention has been made in view of these disadvantages, and is excellent in melt moldability, and as a result, has high gas barrier properties and characteristics such as gas barrier properties even when used with deformation such as stretching or bending. An object is to provide a multilayer structure capable of maintaining the above. It is another object of the present invention to provide a method for manufacturing a multilayer structure having such characteristics while suppressing an increase in manufacturing cost.

The invention made to solve the above problems is
A multilayer structure comprising eight or more resin layers,
As this resin layer, it has A layer which consists of a resin composition containing gas barrier resin, and B layer which consists of a resin composition which adjoins this A layer and contains a thermoplastic resin,
Or less of the extensional viscosity eta _B of the resin composition of the extensional viscosity eta _A and B layer of the resin composition of the layer A in the measurement conditions are both 1,000 Pa · s or more, and the elongation viscosity ratio eta _A / Η _B is 0.02 or more and 50 or less.
(Measurement condition)
Temperature: a temperature that is 25 ° C. higher than the melting point of the melting point of the resin composition of the A layer and the melting point of the resin composition of the B layer (the outflow start temperature for a resin composition having no melting point) Elongation rate: 500 (1 / sec )

  Since the multilayer structure has the multilayer structure, it has excellent gas barrier properties. In addition, the multilayer structure is formed by limiting the extensional viscosity of the resin composition of the A layer and the resin composition of the B layer and the ratio of the layer structure, thereby reducing the thickness of each layer to one micron order or submicron. Even if it is an order, it is excellent in each layer and the whole melt moldability. Therefore, according to the multilayer structure, it is excellent in durability, and characteristics such as gas barrier properties can be maintained even when used after being deformed such as stretching or bending.

  The A layer and the B layer may be alternately stacked. Thus, by alternately laminating the A layer and the B layer, high adhesiveness can be expressed between the laminated layers. As a result, it is possible to further improve the interlayer adhesion of the multilayer structure, as well as gas barrier properties, durability, and the like.

  The average thickness of one layer of the A layer and / or B layer is preferably 0.01 μm or more and 10 μm or less. By setting the average thickness of the A layer and / or the B layer in the above range, the number of layers can be increased even when the entire thickness of the multilayer structure is the same. As a result, the gas barrier property of the multilayer structure can be increased. Further, durability and the like can be further improved.

The product η _A · T _A of the extension viscosity η _A of the resin composition of the layer _A and the average thickness T _{A of} this layer, and the extension viscosity η _B of the resin composition of the layer _B and the average thickness T _{B of} this layer The product η _B · T _B is preferably 500 Pa · s · μm or more and 500,000 Pa · s · µm or less. Thus, melt moldability can be further improved by making the product of the extensional viscosity of the resin composition of each layer and the average thickness of this layer into the above range.

The specific _{(η A · T A) /} (η B · T B) of the product of η _A · _{T A} and η _B · _{T B,} preferably 0.01 or more and 100 or less. Thus, by making the ratio of the above products in the A layer and the B layer within a predetermined range, for example, when forming by coextrusion, it becomes easier to control each layer to a desired thickness, and the melt moldability is further improved. Can do.

  The thickness of the multilayer structure is preferably 0.1 μm or more and 1,000 μm or less. By making the thickness of the multilayer structure in the above range, coupled with making the average thickness of the A layer and / or B layer in the above range, the gas barrier property while maintaining applicability to the food packaging material, etc. Melt moldability, durability, etc. can be further improved.

  The gas barrier resin may be an ethylene-vinyl alcohol copolymer. By using an ethylene-vinyl alcohol copolymer as the gas barrier resin, the gas barrier property of the multilayer structure can be further improved.

  The ethylene unit content of the ethylene-vinyl alcohol copolymer is preferably 3 mol% or more and 70 mol% or less. Thus, by making ethylene unit content into the said range, the gas-barrier property of the said multilayered structure can improve, and in addition, melt moldability can be improved, and durability etc. are improved by this high melt moldability. be able to.

  The saponification degree of the ethylene-vinyl alcohol copolymer is preferably 80 mol% or more. Thus, by setting the degree of saponification within the above range, the gas barrier property of the multilayer structure can be further improved, and the moisture resistance can be improved. In addition, by setting the degree of saponification within the above range, the interlaminar adhesion with the B layer, and consequently the durability, etc. can be improved.

（上記式（Ｉ）中、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ独立に、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、カルボキシル基又はハロゲン原子を有していてもよい
上記式（ＩＩ）中、Ｒ^４、Ｒ^５、Ｒ^６及びＲ^７は、それぞれ独立に、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と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、カルボキシル基又はハロゲン原子を有していてもよい。） The ethylene-vinyl alcohol copolymer has at least one selected from the group consisting of the following structural units (I) and (II),
The content of these structural units (I) or (II) with respect to all the structural units is preferably 0.5 mol% or more and 30 mol% or less.

(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, represents an aromatic hydrocarbon group or a hydroxyl group having 6 to 10 carbon atoms. ^Further, optionally pair is bound of R 1, ^{R 2} and ^{R 3 (where,} of R 1, ^{R 2} and ^{R 3} And the above-mentioned aliphatic hydrocarbon group, alicyclic hydrocarbon group having 3 to 10 carbon atoms, or aromatic hydrocarbon having 6 to 10 carbon atoms. The group may have a hydroxyl group, a carboxyl group or a halogen atom. In the above formula (II), R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom or a C 1-10 fatty acid. Group hydrocarbon group, alicyclic hydrocarbon group having 3 to 10 carbon atoms, aromatic hydrocarbon group having 6 to 10 carbon atoms, or Represents a hydroxyl group, and 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 carboxyl group, or a halogen atom. May be included.)

  As described above, the ethylene-vinyl alcohol copolymer of the A layer has the structural unit (I) or (II) in the above content range, whereby the flexibility and processing characteristics of the resin composition constituting the A layer. Therefore, interlayer adhesion, stretchability, melt moldability, and the like of the multilayer structure can be improved.

  The thermoplastic resin may be at least one resin selected from the group consisting of thermoplastic polyurethane, polyamide, a resin having a functional group capable of reacting with a group possessed by the gas barrier resin, and an elastomer. According to the multilayer structure, interlayer adhesion, durability, and the like can be further improved by using the resin as the thermoplastic resin.

  It is preferable that the thermoplastic resin includes a polyamide, and the polyamide is a polyamide-based elastomer made of a block copolymer having nylon as a hard segment. By using such a polyamide-based elastomer, melt moldability and the like can be further improved.

  The polyamide elastomer hard segment is preferably made of nylon 6. By using such a polyamide-based elastomer, melt moldability and the like can be further improved.

  The thermoplastic resin includes a resin having a functional group capable of reacting with a group of the gas barrier resin in the molecule, and the resin is present in the presence of a carboxylic acid-modified polyolefin and a metal salt thereof, a boronic acid group or water. The resin may be at least one resin selected from the group consisting of a thermoplastic resin having a boron-containing group that can be converted into a boronic acid group, and a vinyl ester copolymer. By using the resin, interlayer adhesion between the A layer and the B layer is further improved. Therefore, the multilayer structure can further improve gas barrier properties, durability, and the like.

  It is preferable that the thermoplastic resin includes an elastomer, and the elastomer is a styrene elastomer having a functional group capable of reacting with a group of the gas barrier resin in the molecule. By using such a styrene-based elastomer for the resin composition of the B layer, the durability of the multilayer structure can be further enhanced.

  In the multilayer structure, it is preferable that a binding reaction occurs at the interface between the A layer and the B layer. Thus, higher interlayer adhesiveness is demonstrated by couple | bonding by the covalent bond or the ionic bond between the molecules of the resin composition which comprises A layer and B layer. As a result, the gas barrier property, durability, etc. of the multilayer structure can be further improved.

Moreover, another invention made in order to solve the said subject is:
A method for producing the multilayer structure,
It is characterized by molding by a multilayer coextrusion method using a resin composition containing a gas barrier resin and a resin composition containing a thermoplastic resin. The manufacturing method of the multilayer structure is excellent in melt molding of each layer and the whole, and as a result, a multilayer structure having high gas barrier properties and durability is manufactured easily and reliably while suppressing an increase in manufacturing cost. be able to.

  As described above, the multilayer structure of the present invention is excellent in melt moldability, and as a result, has a high gas barrier property and has properties such as a gas barrier property even when used after being deformed such as stretching or bending. Can be maintained. Moreover, according to the method for producing a multilayer structure of the present invention, a multilayer structure having such characteristics can be produced easily and reliably while suppressing an increase in production cost.

  Hereinafter, embodiments of the present invention will be described in detail.

  The multilayer structure includes eight or more resin layers. As this resin layer, it has A layer which consists of a resin composition containing gas barrier resin, and B layer which consists of a resin composition containing a thermoplastic resin.

  Hereinafter, the layer structure of the multilayer structure, the extensional viscosity of the A layer and the B layer, the relationship between the A layer, the B layer, the A layer, and the B layer, and the manufacturing method will be described in this order.

<Layer structure of the multilayer structure>
The multilayer structure includes eight or more resin layers. As a result of being able to suppress the occurrence of defects such as pinholes and cracks by the structure in which eight or more resin layers are laminated in this way, the multilayer structure has a higher gas barrier property, durability, etc. due to the structure itself. It has the characteristics. From this viewpoint and the manufacturing viewpoint, the total number of resin layers is preferably 10 or more, more preferably 15 or more, and particularly preferably 18 or more. For the same reason, the number of layers in each of the A layer and the B layer is preferably 4 or more, more preferably 6 or more, and still more preferably 8 or more.

  As this resin layer, it has at least 2 types of A layer and B layer, and it is also possible to have other C layers. Thus, by laminating a total of 8 or more layers including two or more layers including the A layer composed of the gas barrier resin-containing resin composition and the B layer composed of the thermoplastic resin-containing resin composition, the high gas barrier property possessed by the A layer. And a multilayer structure having both the high stretchability and thermoformability of the B layer. In addition, the multilayer structure can maintain gas barrier properties even by repeatedly using deformation such as stretching and bending due to the laminated structure of the A layer and the B layer.

  The A layer may be composed of a single resin composition, or may be composed of a plurality of types of resin compositions as long as the gas barrier resin is included. Further, the B layer may be composed of a single resin composition like the A layer, or may be composed of a plurality of types of resin compositions including a thermoplastic resin.

The stacking order of the A layer and the B layer is not particularly limited as long as at least the A layer and the B layer have adjacent portions.
(1) A, B, A, B... A, B (that is, (AB) _n )
(2) A, B, A, B ... A (that is, (AB) _n A)
(3) B, A, B, A ... B (that is, (BA) _n B)
(4) A, A, B, B... B, B (that is, (AABB) _n )
A stacking order such as can be adopted. Moreover, when it has other C layers, for example,
(5) A, B, C... A, B, C (that is, (ABC) _n )
A stacking order such as can be adopted.

  In particular, as the stacking order of the A layer and the B layer, it is preferable that the A layer and the B layer are alternately stacked as in the above (1), (2), or (3). By alternately laminating in this way, the multilayer structure is excellent in gas barrier properties and flexibility. In addition, a strong adhesive force between the A layer and the B layer, which will be described later, can be applied between all the layers, and the occurrence of defects such as delamination is remarkably reduced. As a result, characteristics such as gas barrier properties of the multilayer structure and The effect of the present invention to increase the durability of the characteristics is more effectively exhibited.

  The lower limit of the thickness of the multilayer structure is preferably 0.1 μm, more preferably 1 μm, and even more preferably 5 μm. On the other hand, the upper limit of the thickness of the multilayer structure is preferably 1,000 μm, more preferably 700 μm, and even more preferably 500 μm. When the thickness of the multilayer structure is smaller than the above lower limit, the strength is insufficient and it may be difficult to use. On the other hand, when the thickness of the multilayer structure exceeds the above upper limit, flexibility, moldability and the like may be lowered, leading to an increase in manufacturing cost. Here, the thickness of the multilayer structure is obtained by measuring the thickness of the cross section at an arbitrarily selected point of the multilayer structure.

  The lower limit of the average thickness of one layer A is preferably 0.01 μm, more preferably 0.05 μm, and still more preferably 0.1 μm. On the other hand, the upper limit of the average thickness of the A layer is preferably 10 μm, more preferably 7 μm, further preferably 5 μm, and particularly preferably 2 μm. If the average thickness of one layer A is smaller than the above lower limit, it becomes difficult to mold with a uniform thickness, and the gas barrier property and durability of the multilayer structure may be lowered. On the contrary, if the average thickness of one layer A exceeds the above upper limit, if the average thickness of the entire multilayer structure is the same, it becomes difficult to increase the number of layers, and the gas barrier property improving effect by the above-mentioned multilayers is increased. There is a possibility that it cannot be expected, and the stretchability and melt moldability of the multilayer structure may be lowered. In addition, the average thickness of one layer of A layer means the value which remove | divided the sum total of the thickness of all the A layers contained in the said multilayered structure by the number of layers of A layer.

  For the same reason, the lower limit of the average thickness of the B layer is preferably 0.01 μm, more preferably 0.05 μm, and further preferably 0.1 μm. On the other hand, the upper limit of the average thickness of the B layer is preferably 10 μm, more preferably 7 μm, further preferably 5 μm, and particularly preferably 2 μm. In addition, the average thickness of one layer of B layer means the value which remove | divided the sum total of the thickness of all the B layers contained in the said multilayered structure by the number of layers of B layer.

<Extension viscosity of layer A and layer B>
The extensional viscosity eta _B of the resin composition of the extensional viscosity eta _A and B layer of the resin composition of layer A, the following measurement conditions, and that both the 1,000 Pa · s or more, more 2,000 Pa · s Preferably, 3,000 Pa · s or more is more preferable. On the other hand, the extensional viscosity η _A and η _B are both preferably 50,000 Pa · s or less, more preferably 20,000 Pa · s or less, and even more preferably 10,000 Pa · s or less. By setting the extensional viscosities η _A and η _B in the above ranges, the melt moldability of each layer and the whole is increased, and the gas barrier properties and durability of the resulting multilayer structure can be improved.

When the extensional viscosity η _A and η _B are smaller than the lower limit, 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 and uneven thickness of each layer before lamination are obtained. In addition, the reduction in width becomes large, and it becomes impossible to obtain a multilayer structure having a uniform and target size. On the other hand, if the extensional viscosity η _A and η _B exceed the above upper limit, for example, when performing melt coextrusion lamination or melt extrusion molding under high speed take-up conditions, film breakage is likely to occur, and high speed film formability is significantly impaired. In addition, die swell is likely to occur, and it may be difficult to obtain a thin multilayer structure or each layer before lamination. If the extensional viscosity η _A and η _B exceed the above upper limit, the torque applied to the extruder becomes too high, and extrusion spots and weld lines may easily occur.
(Measurement condition)
Temperature: a temperature that is 25 ° C. higher than the melting point of the melting point of the resin composition of the A layer and the melting point of the resin composition of the B layer (the outflow start temperature for a resin composition having no melting point) Elongation rate: 500 (1 / sec )
In addition, the extensional viscosity in this invention says the value measured by a capillary flow measuring method.

The extensional viscosity ratio eta _A / eta _B of the extensional viscosity eta _B of the resin composition of the extensional viscosity eta _A and B layer of the resin composition of the layer A is 0.02 or more and 50 or less, 0.2 or 5 The following is preferable, and 0.3 or more and 3 or less are more preferable. Thus, even if it is a multilayered structure which made the thickness of each layer 1 layer the micron order or the submicron order by making the extensional viscosity of both resin compositions close, it is excellent in melt moldability. Therefore, according to the multilayer structure, it is excellent in durability, and characteristics such as gas barrier properties can be maintained even when used after being deformed such as stretching or bending. When the elongational viscosity ratio η _A / η _B is out of the above range, for example, when both layers are formed by coextrusion, it becomes difficult to form both layers in a preferable state, and the appearance and durability are deteriorated. May occur.

  In addition, the elongation viscosities of the resin compositions of the A layer and the B layer at the measurement temperature and at an elongation rate of 100 (1 / sec) and 1,000 (1 / sec) satisfy the above ranges, respectively. It is preferable that the above range is satisfied at any stretching speed. Thus, the melt moldability of the multilayer structure can be further improved by using a resin composition that satisfies the same relationship of extensional viscosity even when the extension rate is 100 (1 / sec) and 1,000 (1 / sec). Can be increased.

The eta _A and A Soisso the average thickness _{T A} and the product eta _A · _{T A,} and as the product eta _B · _{T B} between the average thickness _{T B} of the extensional viscosity eta _B and B Soisso are both 500 Pa · s · μm or more and 500,000 Pa · s · μm or less is preferable, 1,000 Pa · s · μm or more and 100,000 Pa · s · μm or less is more preferable, 2,000 Pa · s · μm or more and 50,000 Pa · s.・ Μm or less is more preferable, and 3,000 Pa · s · μm or more and 30,000 Pa · s · μm or less is particularly preferable. Thus, melt moldability can be further improved by making the product of the extensional viscosity of the resin composition of each layer and the average thickness of this layer into the above range.

When the thickness of each layer becomes too thin, melt molding becomes difficult. To compensate for this, the resin composition preferably has a certain degree of extensional viscosity. Therefore, the product (η _A · T _A and η _B · T _B) is, in the case of less than the above lower limit, there are cases where the melt moldability decreases, specifically, such as melt co-extrusion lamination or melt extrusion Neck-in and film swaying become significant during extrusion film formation, and the resulting multilayer structure and the thickness variation and width reduction of each layer before lamination become large, so that a multilayer structure having a uniform and target dimension can be obtained. There is a risk of disappearing. On the other hand, when this product exceeds the above upper limit, the thermoformability may be deteriorated, for example, the surface of each layer is likely to be rough, the film is cut, the die swell, the extrusion spots, and the weld line are easily generated.

The specific _{(η A · T A) /} (η B · T B) of the product of η _A · _{T A} and η _B · _{T B,} preferably 0.01 or more and 100 or less, is 0.1 to 10 More preferably, it is 0.2 or more and 5 or less. Thus, by making the ratio of the above products in the A layer and the B layer within a predetermined range, for example, when forming by coextrusion, it becomes easier to control each layer to a desired thickness, and the melt moldability is further improved. Can do. When the ratio of the product is out of the above range, the moldability of both layers can be maintained satisfactorily, such as surface roughness of one layer, film breakage, thickness unevenness, width reduction, and adhesive deterioration. There are cases where it is not possible.

<A layer>
The A layer is a layer made of a resin composition containing a gas barrier resin. When the resin composition constituting the A layer contains a gas barrier resin, a multilayer structure having excellent gas barrier properties can be obtained.

The gas barrier resin is a resin having a function of preventing the permeation of gas, and specifically, oxygen measured according to the method described in JIS-K7126 (isobaric method) under the condition of 20 ° C.-65% RH. It refers to a resin having a permeation rate of 100 mL · 20 μm / (m ² · day · atm) or less. The oxygen permeation rate of the gas barrier resin used in the present invention is preferably 50 mL · 20 μm / (m ² · day · atm) or less, more preferably 10 mL · 20 μm / (m ² · day · atm) or less.

  Examples of such a gas barrier resin include ethylene-vinyl alcohol copolymer (hereinafter also referred to as “EVOH”), polyamide, polyester, polyvinylidene chloride, acrylonitrile copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, A polyvinyl alcohol etc. can be mentioned.

  Among these gas barrier resins, polyamide, polyester resin, and EVOH are preferable from the viewpoint of gas barrier properties, and EVOH is particularly preferable from the viewpoint of melt moldability, adhesion to the B layer, etc. in addition to gas barrier properties.

<polyamide>
The polyamide is a polymer having an amide bond and can be obtained by ring-opening polymerization of lactam, polycondensation of aminocarboxylic acid or diamine and dicarboxylic acid, and the like.

  Examples of the lactam include ε-caprolactam and ω-laurolactam.

  Examples of the aminocarboxylic acid include 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and paraaminomethylbenzoic acid.

  Examples of the diamine include tetramethylene diamine, hexamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4-trimethylhexamethylene diamine, 2,4,4-trimethylhexamethylene diamine, and 5-methylnonamethylene. Diamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane Bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminopropyl) piperazine, aminoethylpiperazine, etc. It can be.

  Examples of the dicarboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecane dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, norbornane dicarboxylic acid, tricyclodecane dicarboxylic acid, penta Cyclododecane dicarboxylic acid, isophorone dicarboxylic acid, 3,9-bis (2-carboxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, trimellitic acid, trimesic acid, pyromellitic acid, Examples include tricarballylic acid, terephthalic acid, isophthalic acid, phthalic acid, 2-methylterephthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and tetralindicarboxylic acid.

  Examples of the polycondensation method for synthesizing the polyamide include a method of polycondensation in a molten state, and a method of once heat-treating in a solid phase after polycondensation in a molten state to obtain a low-viscosity polyamide. Solid phase polymerization). As a polycondensation method in a molten state, for example, an aqueous solution of a nylon salt of a diamine and a dicarboxylic acid is heated under pressure and polycondensed in a molten state while removing water and condensed water, and the diamine is converted into a dicarboxylic acid in a molten state. In addition to the direct addition, there can be mentioned a method of polycondensation under normal pressure.

  Specific polyamides that are polycondensates of the above compounds include, for example, polycaprolactam (nylon 6), polylaurolactam (nylon 12), polyhexamethylenediadipamide (nylon 66), polyhexamethylene azelamide ( Nylon 69), polyhexamethylene sebacamide (nylon 610), nylon 46, nylon 6/66, nylon 6/12, 11-aminoundecanoic acid condensation product (nylon 11) Examples include aromatic polyamides such as hexamethylene isophthalamide (nylon 6IP), metaxylenediamine / adipic acid copolymer (nylon MXD6), and metaxylenediamine / adipic acid / isophthalic acid copolymer. These can be used alone or in combination of two or more.

  Among these polyamides, nylon MXD6 having excellent gas barrier properties is preferable. As the diamine component of this nylon MXD6, metaxylylenediamine is preferably contained in an amount of 70 mol% or more, and as the dicarboxylic acid component, adipic acid is preferably contained in an amount of 70 mol% or more. By obtaining nylon MXD6 from a monomer having the above blending range, more excellent gas barrier properties and mechanical performance can be exhibited.

<polyester>
The polyester is a polymer having an ester bond and can be obtained by polycondensation of a polyvalent carboxylic acid and a polyol. Examples of the polyester used as the gas barrier resin of the multilayer structure include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyglycolic acid (PGA), aromatic liquid crystal polyester, and the like. These may be used alone or in combination of two or more. Among these polyesters, PGA and wholly aromatic liquid crystal polyesters are preferable from the viewpoint of high gas barrier properties.

<PGA>
PGA is a homopolymer or copolymer having a structural unit (GA) represented by —O—CH ₂ —CO—. 60 mass% or more is preferable, as for the content rate of the said structural unit (GA) in PGA, 70 mass% or more is more preferable, and 80 mass% or more is further more preferable. Moreover, as this upper limit, 100 mass% is preferable. If the content ratio of the structural unit (GA) is smaller than the lower limit, the gas barrier property may not be sufficiently exhibited.

  Production methods of PGA include (1) a method of synthesizing by dehydrating polycondensation of glycolic acid, (2) a method of synthesizing by dealcoholating polycondensation of glycolic acid alkyl ester, and (3) glycolide (1,4-dioxane-2). , 5-dione) and the like.

As a method for synthesizing PGA as a copolymer, in each of the above synthesis methods, as a comonomer, for example,
Ethylene oxalate (1,4-dioxane-2,3-dione), lactide, lactones (for example, β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ -Valerolactone, ε-caprolactone, etc.), cyclic monomers such as trimethylene carbonate, 1,3-dioxane;
Hydroxycarboxylic acids such as lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 6-hydroxycaproic acid or alkyl esters thereof;
A substantially equimolar mixture of an aliphatic diol such as ethylene glycol or 1,4-butanediol and an aliphatic dicarboxylic acid such as succinic acid or adipic acid or an alkyl ester thereof;
And the like may be copolymerized by appropriately combining with glycolide, glycolic acid or glycolic acid alkyl ester.

  As a specific method of the ring-opening polymerization of the above (3), glycolide is used in the presence of a small amount of a catalyst (for example, a cationic catalyst such as tin organic carboxylate, tin halide, antimony halide, etc.). A method of heating to a temperature of ° C. can be mentioned. This ring-opening polymerization is preferably performed by a bulk polymerization method or a solution polymerization method.

  In the ring-opening polymerization, glycolide used as a monomer can be obtained by a sublimation depolymerization method or a solution phase depolymerization method of a glycolic acid oligomer.

  As the solution phase depolymerization method, for example, (1) a mixture containing a glycolic acid oligomer and at least one high-boiling polar organic solvent having a boiling point in the range of 230 to 450 ° C. is used under normal pressure or reduced pressure. This oligomer is heated to a temperature at which depolymerization of the oligomer occurs, and (2) the oligomer is dissolved in a solvent until the residual ratio (volume ratio) of the melt phase of the oligomer is 0.5 or less. The oligomer is further depolymerized by further heating at a temperature, (4) the dimer cyclic ester (glycolide) formed is distilled together with a high-boiling polar organic solvent, and (5) glycolide is recovered from the distillate. A method can be mentioned.

  Examples of the high boiling polar organic solvent include bis (alkoxyalkyl esters) phthalates such as di (2-methoxyethyl) phthalate, alkylene glycol dibenzoates such as diethylene glycol dibenzoate, and aromatic carboxyls such as benzylbutyl phthalate and dibutyl phthalate. Examples thereof include aromatic phosphates such as acid esters and tricresyl phosphate. In addition to the high-boiling polar organic solvent, polypropylene glycol, polyethylene glycol, tetraethylene glycol, or the like can be used in combination as an oligomer solubilizer as necessary.

<Fully aromatic liquid crystalline polyester>
The wholly aromatic liquid crystal polyester is a liquid crystalline polyester in which both a polyvalent carboxylic acid as a monomer and a polyol are aromatic compounds. This wholly aromatic liquid crystalline polyester can be obtained by polymerizing by a known method in the same manner as ordinary polyester.

  Examples of aromatic polycarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, 3,3′-biphenyldicarboxylic acid, 4,4′-methylenedibenzoic acid, diphenic acid and the like can be mentioned. These can be used alone or in combination of two or more.

  Examples of aromatic polyols include hydroquinone, methylhydroquinone, 4,4'-dihydroxydiphenyl, resorcinol, phenylhydroquinone, 3,4'-bisphenol A, and the like. These can be used alone or in combination of two or more.

  Further, the wholly aromatic liquid crystalline polyester is obtained by polymerizing an aromatic compound having a hydroxy group and a carboxyl group such as hydroxybenzoic acid and hydroxynaphthoic acid, or the above aromatic polyvalent carboxylic acid and aromatic group. It can also be obtained by copolymerizing the polyol.

<EVOH>
Hereinafter, EVOH suitably used as the gas barrier resin of the multilayer structure of the present invention will be described in detail.

  EVOH contained in the resin composition of the A layer has an ethylene unit and a vinyl alcohol unit as main structural units. The EVOH may contain one or more other structural units in addition to the ethylene unit and the vinyl alcohol unit.

  This EVOH is usually obtained by polymerizing ethylene and a vinyl ester and saponifying the resulting ethylene-vinyl ester copolymer.

  The lower limit of the ethylene unit content of EVOH (that is, the ratio of the number of ethylene units to the total number of monomer units in EVOH) is preferably 3 mol%, more preferably 10 mol%, still more preferably 20 mol%. 25 mol% is particularly preferable. On the other hand, the upper limit of the ethylene unit content of EVOH is preferably 70 mol%, more preferably 60 mol%, still more preferably 55 mol%, and particularly preferably 50 mol%. If the ethylene unit content of EVOH is smaller than the above lower limit, the water resistance, hot water resistance and gas barrier property under high humidity of the multilayer structure may be lowered, or the melt moldability of the multilayer structure may be deteriorated. . On the contrary, when the ethylene unit content of EVOH exceeds the upper limit, the gas barrier property of the multilayer structure may be deteriorated.

  The lower limit of the saponification degree of EVOH (that is, the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH) is preferably 80 mol%, more preferably 95 mol%, 99 mol% Is particularly preferred. On the other hand, the upper limit of the saponification degree of EVOH is preferably 99.99 mol%. If the saponification degree of EVOH is smaller than the above lower limit, the melt moldability may be lowered, and in addition, the gas barrier property of the multilayer structure may be lowered, and the coloring resistance and moisture resistance may be unsatisfactory. There is. Conversely, if the saponification degree of EVOH exceeds the above upper limit, an increase in gas barrier properties and the like with respect to an increase in the production cost of EVOH cannot be expected so much. Such EVOH can be used alone, but an embodiment in which EVOH is blended with EVOH having a saponification degree exceeding 99 mol% is also suitable.

The EVOH 1,2-glycol bond structural unit content G (mol%) satisfies the following formula (2), and the intrinsic viscosity is preferably 0.05 L / g or more and 0.2 L / g or less. In the following formula (2), E is the ethylene unit content (mol%) in EVOH (provided that E ≦ 64 (mol%)).
G ≦ 1.58−0.0244 × E (2)

  The characteristic that the humidity dependency of the gas barrier property of the obtained multilayer structure is reduced by including EVOH having such a content G of 1,2-glycol bond structural unit and intrinsic viscosity as the resin composition of the A layer Is exhibited, and it has good transparency and gloss, and can be easily laminated with other thermoplastic resins. Therefore, the suitability of the multilayer structure as a material for food packaging or the like can be improved. The content G of the 1,2-glycol bond structural unit is S.I. According to the method described in Aniya et al. (Analytical Science Vol. 1, 91 (1985)), an EVOH sample can be made into a dimethyl sulfoxide solution and measured by a nuclear magnetic resonance method at a temperature of 90 ° C.

  EVOH preferably has at least one selected from the group consisting of the structural units (I) and (II). As a minimum of content with respect to all the structural units of the said structural unit (I) or (II), 0.5 mol% is preferable, 1 mol% is more preferable, 1.5 mol% is further more preferable. On the other hand, the upper limit of the content of the structural unit (I) or (II) is preferably 30 mol%, more preferably 15 mol%, and even more preferably 10 mol%. As a result of the resin composition of the A layer having the structural units shown in (I) or (II) in the above range, the flexibility and processing characteristics of the resin composition constituting the A layer are improved. The stretchability and melt moldability of the 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 A cycloalkyl 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. Among these, More preferably, they are each independently a hydrogen atom, a methyl group, a hydroxyl group or a hydroxymethyl group. By being such R ¹ , R ² and R ³ , the stretchability and melt moldability of the multilayer structure can be further improved.

  The method of incorporating the structural unit (I) in EVOH is not particularly limited. For example, in the polymerization of ethylene and vinyl ester, a method of copolymerizing a monomer derived from the structural unit (I) and the like. Can be mentioned. Monomers derived from this 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, 4 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 can be mentioned. Among them, 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, 3 1,4-diacetoxy-1-butene is preferred. Specifically, among them, propylene, 3-acetoxy-1-propene, 3-acetoxy-1-butene, 4-acetoxy-1-butene, and 3,4-diacetoxy-1-butene are preferable. 1,4-diacetoxy-1-butene is particularly preferred. In the case of an alkene having an ester, it is derived into the structural unit (I) during the 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 is preferably an alkyl group or an alkenyl group. From the viewpoint of placing particular emphasis on the gas barrier properties of the multilayer structure, it is particularly preferable that one of R ⁶ and R ⁷ is a methyl group or an ethyl group, and the other is a hydrogen atom. It is also particularly preferred 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.

  The method for containing the structural unit (II) in EVOH is not particularly limited, and a method for containing EVOH obtained by a saponification reaction by reacting it with a monovalent epoxy compound is used. As the monovalent epoxy compound, compounds represented by the following formulas (III) to (IX) are preferably used.

In the above formulas (III) to (IX), R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms (an alkyl group or an alkenyl group). Group), an alicyclic hydrocarbon group having 3 to 10 carbon atoms (such as a cycloalkyl group or a cycloalkenyl group), or an aliphatic hydrocarbon group having 6 to 10 carbon atoms (such as a phenyl group). 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-epoxy. Butane, 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- Epoxy hexane, 5-methyl-1,2-epoxy hexane, 3-ethyl-1,2-epoxy hexane, 3-propyl-1,2-epoxy Sun, 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-epoxyheptane, 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, 5-ethyl-1,2-epoxyheptane, 4-methyl-2,3-epoxyheptane, 4 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-epoxy Heptane, 1,2-epoxyoctane, 2,3-epoxyoctane, 3,4-epoxyoctane, 4,5-epoxyoctane, 1,2-epoxynonane, 2,3-epoxynonane, 3,4-epoxynonane 4,5-epoxynonane, 1,2-epoxydecane, 2,3-epoxydecane, 3,4-epoxydecane, 4,5-epoxydecane, 5,6-d Poxydecane, 1,2-epoxyundecane, 2,3-epoxyundecane, 3,4-epoxyundecane, 4,5-epoxyundecane, 5,6-epoxyundecane, 1,2-epoxydodecane, 2,3-epoxydodecane 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- Pokishihekisan, 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, 1, 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-epoxy Ci-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, 4,5 Epoxy-1-pentanol, 5,6-epoxy-1-hexanol, 6,7-epoxy-1-heptanol, 7,8-epoxy-1-octanol, 8,9-epoxy-1-nonanol, 9,10 -Epoxy-1-decanol, 10,11-epoxy-1-undecanol, etc. are mentioned.

  Examples of the monovalent epoxy compound represented by the formula (V) include ethylene glycol monoglycidyl ether, propanediol monoglycidyl ether, butanediol monoglycidyl ether, pentanediol monoglycidyl ether, hexanediol monoglycidyl ether, heptanediol mono Examples thereof include glycidyl 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, and 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 above 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-pen Tanol, 2,3-epoxy-1-hexanol, 3,4-epoxy-2-hexanol, 4,5-epoxy-3-hexanol, 1,2-epoxy-3-hexanol, 2,3-epoxy-4- Methyl-1-hexanol, 2,3-epoxy-4-ethyl-1-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-4-nonanol, 1,2-epoxy-3-nonanol, 2,3-epoxy-1- Decanol, 3,4-epoxy-2-decanol, 4,5-epoxy-3-decanol, 5,6-epoxy-4-decanol, 6,7-epoxy-5-decanol, 3,4-epoxy-5 Examples include 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, 1, Examples include 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 can be mentioned.

  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 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 above formulas. Specifically, from the viewpoint of reactivity with EVOH and gas barrier properties of the resulting multilayer structure, 1,2-epoxybutane, 2,3-epoxybutane, epoxypropane, epoxyethane, and glycidol are preferred. Epoxypropane and glycidol are particularly preferred. In applications requiring sanitary properties such as food packaging applications, beverage packaging applications, and pharmaceutical packaging applications, 1,2-epoxybutane, 2,3-epoxybutane, epoxypropane, or epoxyethane should be used as the epoxy compound. It is particularly preferable to use epoxypropane.

  Next, a method for producing EVOH will be specifically described. The copolymerization method of ethylene and vinyl ester 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.

  As vinyl ester used for polymerization, fatty acid vinyl such as vinyl acetate, vinyl propionate and vinyl pivalate can be used.

  In the above polymerization, a monomer that can be copolymerized in addition to the above components, for example, alkenes other than those described above; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, or anhydrides thereof Products, salts, mono- or dialkyl esters, etc .; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid; Vinyl ethers, vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride and the like can be copolymerized in a small amount. Moreover, a vinyl silane compound can be contained as 0.0002 mol% or more and 0.2 mol% or less as a copolymerization component. Here, examples of the vinylsilane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane, and γ-methacryloyloxypropylmethoxysilane. Of these, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used.

  The solvent 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. As such a solvent, for example, alcohols such as methanol, ethanol, propanol, n-butanol and tert-butanol; dimethyl sulfoxide and the like can be used. Among them, methanol is particularly preferable in that removal and separation after the reaction is easy.

  Examples of the catalyst used for polymerization include 2,2-azobisisobutyronitrile, 2,2-azobis- (2,4-dimethylvaleronitrile), 2,2-azobis- (4-methoxy-2,4). -Dimethylvaleronitrile), 2,2-azobis- (2-cyclopropylpropionitrile) and other azonitrile initiators; isobutyryl peroxide, cumylperoxyneodecanoate, diisopropylperoxycarbonate, di-n- Organic peroxide initiators such as propyl peroxydicarbonate, t-butyl peroxyneodecanoate, lauroyl peroxide, benzoyl peroxide, t-butyl hydroperoxide, and the like can be used.

  As superposition | polymerization temperature, it is 20-90 degreeC, Preferably it is 40-70 degreeC. The polymerization time is 2 to 15 hours, preferably 3 to 11 hours. The polymerization rate is 10 to 90%, preferably 30 to 80%, relative to the charged vinyl ester. The resin content in the solution after polymerization is 5 to 85%, preferably 20 to 70%.

  After polymerization for a predetermined time or after reaching a predetermined polymerization rate, a polymerization inhibitor is added as necessary, and after removing unreacted ethylene gas, unreacted vinyl ester is removed. As a method for removing the unreacted vinyl ester, for example, the above 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 may be employed in which a mixed vapor of an organic solvent such as methanol and unreacted vinyl ester is distilled from the top, and a copolymer solution from which unreacted vinyl ester has been removed is removed from the bottom of the column.

  Next, an alkali catalyst is added to the copolymer solution to saponify the copolymer. The saponification method can be either a continuous type or a batch type. As this alkali catalyst, for example, sodium hydroxide, potassium hydroxide, alkali metal alcoholate and the like are used.

  As the conditions for saponification, for example, in the case of a batch system, the copolymer solution concentration is 10 to 50%, the reaction temperature is 30 to 65 ° C., and the amount of catalyst used is 0.02 to 1.0 per mole of vinyl ester structural unit. Mole, saponification time is 1-6 hours.

  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 EVOH after the saponification reaction is washed with water containing almost no metal ions such as ion-exchanged water, chloride ions, or the like, a part of sodium acetate, potassium acetate or the like may remain.

  The resin composition constituting the A layer may contain one or more compounds selected from a phosphoric acid compound, a carboxylic acid, and a boron compound depending on the embodiment. By including such a phosphoric acid compound, carboxylic acid or boron compound in the resin composition of the A layer, various performances of the multilayer structure can be improved.

  Specifically, the thermal stability during melt molding of the multilayer structure can be improved by including a phosphoric acid compound in the resin composition of the A layer containing EVOH or the like. 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 is not particularly limited as a counter cation species, but an alkali metal ion Or 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 compound conversion content of a phosphoric acid compound in a dry resin composition of A layer), 1 ppm is preferred, 10 ppm is more preferred, and 30 ppm is still more preferred. On the other hand, the upper limit of the content of the phosphoric acid compound is preferably 10,000 ppm, more preferably 1,000 ppm, and even more preferably 300 ppm. If the content of the phosphoric acid compound is less than the above lower limit, coloring during melt molding may become intense. In particular, since the tendency is remarkable when the heat history is accumulated, a molded product obtained by molding the resin composition pellet may be poor in recoverability. On the other hand, if the content of the phosphoric acid compound exceeds the above upper limit, there is a risk that gels and blisters of the molded product are likely to occur.

  Moreover, by containing carboxylic acid in the resin composition of A layer containing EVOH etc., there exists an effect which controls the pH of a resin composition, prevents gelatinization, and improves thermal stability. As the carboxylic acid, acetic acid or lactic acid is preferable from the viewpoint of cost and the like.

  The lower limit of the carboxylic acid content (the carboxylic acid content in the dry resin composition of the A layer) is preferably 1 ppm, more preferably 10 ppm, and even more preferably 50 ppm. On the other hand, the upper limit of the carboxylic acid content is preferably 10,000 ppm, more preferably 1,000 ppm, and even more preferably 500 ppm. If the carboxylic acid content is less than the lower limit, coloring may occur during melt molding. Conversely, if the content of carboxylic acid exceeds the above upper limit, the interlayer adhesion may be insufficient.

Furthermore, the inclusion of a boron compound in the resin composition of the A layer containing EVOH or the like has an effect of improving thermal stability. Specifically, when a boron compound is added to a resin composition composed of EVOH, it is considered that a chelate compound is formed between EVOH and the boron compound. By using such EVOH, the heat stability is higher than that of normal EVOH. It is possible to improve and improve mechanical properties. The boron compound is not particularly limited, and examples thereof include boric acids, boric acid esters, borates, and borohydrides. Specifically, examples of boric acids include orthoboric acid (H ₃ BO ₃ ), metaboric acid, and tetraboric acid, and examples of boric acid esters include triethyl borate and trimethyl borate. 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.

  As a minimum of content of a boron compound (boron conversion content of a boron compound in a dry resin composition of A layer), 1 ppm is preferred, 10 ppm is more preferred, and 50 ppm is still more preferred. On the other hand, the upper limit of the boron compound content is preferably 2,000 ppm, more preferably 1,000 ppm, and even more preferably 500 ppm. If the boron compound content is less than the above lower limit, the effect of improving the thermal stability by adding the boron compound may not be obtained. On the contrary, when the content of the boron compound exceeds the above upper limit, 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 containing EVOH is not particularly limited. For example, when preparing pellets of the resin composition containing EVOH or the like, the resin composition contains A method of adding and kneading 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 is illustrated. From the viewpoint of homogeneous dispersion in these, 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, safety of work environment, and the like. During these additions, a metal salt described later, a resin other than EVOH, other additives, and the like can be added simultaneously.

  In addition, as a method of containing a phosphoric acid compound, a carboxylic acid, and a boron compound, a method in which pellets or strands obtained by an extruder or the like after the saponification are immersed in a solution in which those substances are dissolved is homogeneously dispersed. It is preferable at the point which can be made. Also in this method, water is preferably used as the solvent for the same reason as described above. 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 of the A layer preferably contains 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 of the A layer is improved, so that a multilayer structure having a good appearance can be obtained. Examples of such a compound include a conjugated diene compound having a structure in which at least two carbon-carbon double bonds and one carbon-carbon single bond are alternately connected, and three carbon-carbon double bonds. A triene compound having a structure in which two carbon-carbon single bonds are alternately connected; a conjugated polyene compound having a structure in which a larger number of carbon-carbon double bonds and carbon-carbon single bonds are alternately connected; Examples thereof include conjugated triene compounds such as 2,4,6-octatriene. 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. It is.

  Examples of the compound having a conjugated double bond include a carboxyl 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. It may have other various functional groups such as a group, sulfide group, thiol group, sulfonic acid group and salt thereof, phosphoric acid group and salt thereof, phenyl group, halogen atom, double bond and triple bond. 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. The multiple bond in the functional group may be in a position capable of conjugating with the conjugated double bond. For example, 1-phenylbutadiene having a phenyl group and sorbic acid having a carboxyl group also have the conjugated double bond referred to here. Included in compounds. Specific examples of this compound include, for example, 2,4-diphenyl-4-methyl-1-pentene, 1,3-diphenyl-1-butene, 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 more excellent appearance, a compound containing a conjugated double bond between aliphatic groups is preferred, and a conjugated double bond having a polar group such as a carboxyl group and a salt thereof, or a hydroxyl group is preferred. Also preferred are compounds comprising. 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 is preferably 0.1 ppm, more preferably 1 ppm, further preferably 3 ppm, and more preferably 5 ppm or more from the viewpoint of the effect exerted. Particularly preferred. On the other hand, the upper limit of the content of this compound is preferably 3,000 ppm, more preferably 2,000 ppm, still more preferably 1,500 ppm, and particularly preferably 1,000 ppm from the viewpoint of the effect exerted.
As a method for adding the compound having a conjugated double bond, for example, in the case of EVOH, adding after polymerization as described above and before the saponification improves surface smoothness and extrusion stability. This is preferable. Although the reason for this is not necessarily clear, it is considered that the compound having a conjugated double bond has an effect of preventing alteration such as EVOH before saponification and / or during the saponification reaction.

  The resin composition of layer A is a resin other than the gas barrier resin, or a heat stabilizer, an ultraviolet absorber, an antioxidant, a colorant, and a filler, in addition to the above additives, within a range not impairing the object of the present invention. Various additives may be included. When the resin composition of layer A contains additives other than the above additives, the amount is preferably 50% by mass or less, more preferably 30% by mass or less, based on the total amount of the resin composition. In particular, it is particularly preferably 10% by mass or less.

<B layer>
B layer is a layer which consists of a resin composition containing a thermoplastic resin. The multilayer structure can improve stretchability and thermoformability by laminating a B layer made of a resin composition containing a thermoplastic resin. Moreover, since the multilayer structure can strengthen the interlayer adhesion between the B layer and the A layer, it has high durability and can maintain gas barrier properties and stretchability even when deformed.

  The thermoplastic resin is not particularly limited as long as it is a resin that is softened by being heated to a glass transition temperature or a melting point, and exhibits plasticity. However, thermoplastic polyurethane (hereinafter also referred to as “TPU”), polyamide, and the gas barrier described above. The resin may be at least one resin selected from the group consisting of a resin having a functional group capable of reacting with a group of the functional resin (hereinafter also simply referred to as “functional group-containing resin”) and an elastomer. According to the multilayer structure, thermoformability, interlayer adhesion, and the like can be further enhanced by using the above resin as the thermoplastic resin.

<TPU>
TPU is composed of polymer polyol, organic polyisocyanate, chain extender and the like. This polymer polyol is a substance having a plurality of hydroxyl groups, and can be 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). These polymer polyols may be used alone or in combination of two or more. Among these, a polyester polyol or a polycarbonate polyol is preferable because it has a carbonyl group that reacts with a hydroxyl group or the like of the gas barrier resin in the layer A, and the interlayer adhesion of the resulting multilayer structure is high. Particularly preferred.

  For example, the polyester polyol can be obtained by condensing an ester-forming derivative such as dicarboxylic acid, its ester or its anhydride and a low molecular weight polyol by direct esterification or transesterification, or by opening a lactone according to a conventional method. It can be produced by polymerization.

  It does not specifically limit as dicarboxylic acid which comprises polyester polyol, What is generally used in manufacture of polyester can be used. 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- Aliphatic dicarboxylic acids having 4 to 12 carbon atoms such as methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; terephthalic acid, isophthalate Examples thereof include aromatic dicarboxylic acids such as acids, orthophthalic acid, and naphthalenedicarboxylic acid. These dicarboxylic acids may be used alone or in combination of two or more. Among these, an aliphatic dicarboxylic acid having 6 to 12 carbon atoms in that it has a carbonyl group that is more easily reacted with a hydroxyl group or the like of the gas barrier resin in the A layer, and the interlayer adhesion of the multilayer structure becomes higher. Are preferred, with adipic acid, azelaic acid or sebacic acid being particularly preferred.

  It does not specifically limit as a low molecular polyol which comprises a polyester polyol, The thing generally used in manufacture of polyester can be used. 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, B hexane dimethanol, cyclooctane dimethanol, an alicyclic diol such as dimethyl cyclooctane dimethanol; and 1,4-bis (beta-hydroxyethoxy) aromatic dihydric alcohol and benzene. These low molecular polyols may be used alone or in 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-dimethyl The aliphatic diol having 5 to 12 carbon atoms having a methyl group in the side chain such as -1,9-nonanediol easily reacts with the ester group in the polyester polyol and the hydroxyl group of the gas barrier resin in the A layer. It is preferable in that the interlayer adhesion of the obtained multilayer structure is further increased. Moreover, when mixing and using 2 or more types as a low molecular polyol, the C5-C12 aliphatic diol which has a methyl group in this side chain is a ratio of 50 mol% or more with respect to the whole quantity of a low molecular polyol. More preferably, it is used. Furthermore, a small amount of a trifunctional or higher functional low molecular polyol can be used in combination with the low molecular polyol. Examples of the trifunctional or higher functional low molecular polyol include trimethylolpropane, trimethylolethane, glycerin, 1,2,6-hexanetriol, and the like.

  Examples of the lactone 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 alone or in combination of two or more. Among these, polytetramethylene glycol is preferable.

  Examples of the polycarbonate polyol include aliphatic groups having 2 to 12 carbon atoms such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol. A diol or a mixture thereof obtained by subjecting diphenyl carbonate or phosgene or the like to condensation polymerization is preferably used.

  As a minimum of the number average molecular weight of the above-mentioned polymer polyol, 500 is preferred, 600 is more preferred, and 700 is still more preferred. 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 good, and the elasticity of the obtained TPU becomes poor. Therefore, 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, resulting in the formation of a lump of gel-like material, etc. As a result, a stable TPU may not 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.

  The organic polyisocyanate is not particularly limited, and a known organic diisocyanate generally used for production of TPU is 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 thereof include aromatic diisocyanates such as diisocyanate; 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 in that the strength and bending resistance of the resulting multilayer structure can be improved. These organic diisocyanates may be used alone or in combination of two or more.

  As the chain extender, a chain extender generally used in the production of TPU is used, and a low molecular weight compound having a molecular weight of 300 or less having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule is preferably used. 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, bis (β -Hydroxyethyl) terephthalate, diols such as xylylene glycol and the like. Among these, an aliphatic diol having 2 to 10 carbon atoms is preferable, and 1,4-butanediol is particularly preferable in that the stretchability and thermoformability of the obtained multilayer structure are further improved. These chain extenders may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  As a method for producing TPU, the above-mentioned polymer polyol, organic polyisocyanate and chain extender are used and produced using a known urethanization reaction technique, and any of the prepolymer method and the one-shot method is used. can do. Among these, it is preferable to perform melt polymerization in the substantial absence of a solvent, and it is particularly preferable to perform continuous melt polymerization using a multi-screw extruder.

  In 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 nitrogen content of TPU is determined by appropriately selecting the use ratio of the polymer polyol and the organic diisocyanate, but practically it is preferably in the range of 1 to 7%. Moreover, the resin composition of B layer may use the suitable catalyst which accelerates | stimulates reaction of organic polyisocyanate and high molecular polyol as needed.

  The hardness of TPU is preferably from 50 to 95 as Shore A hardness, more preferably from 55 to 90, and even more preferably from 60 to 85. Use of a material having a hardness in the above range is preferable because a laminated structure having excellent mechanical strength and durability and excellent flexibility can be obtained.

<polyamide>
Polyamide is a polymer having an amide group in the main chain, and is obtained by polycondensation of a lactam having three or more members, a polymerizable ω-amino acid, or a dibasic acid and a diamine. Specific examples of polyamides include polycapramide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecanamide (nylon 11), polylauryl lactam (nylon 12). ), Polyethylenediamine adipamide (nylon 26), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebamide (nylon 610), polyhexamethylene dodecamide (Nylon 612), polyoctamethylene adipamide (nylon 86), polydecamethylene adipamide (nylon 108), or caprolactam / lauryl lactam copolymer (nylon 6/12), caprolactam / ω-aminononanoic acid copolymer Combined (Nylon 6 9), caprolactam / hexamethylene diammonium adipate copolymer (nylon 6/66), lauryl lactam / hexamytylene diammonium adipate copolymer (nylon 12/66), hexamethylene diammonium adipate / hexamethylene diammonium sebacate Copolymer (nylon 66/610), ethylene diammonium adipate / hexamethylene diammonium adipate copolymer (nylon 26/66), caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon 6) / 66/610), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalamide (nylon 6T), hexamethylene isophthalamide / te Phthalamide copolymer (nylon 6I / 6T) and the like.

  In these polyamides, as diamines, aliphatic diamines introduced with substituents such as 2,2,4- or 2,4,4-trimethylhexamethylenediamine, aromatics such as methylenedibenzylamine and metaxylylenediamine are used. Group diamines may be used, and they may be used to modify polyamides. Further, as the dicarboxylic acid, an aliphatic dicarboxylic acid introduced with a substituent such as 2,2,4- or 2,4,4-trimethyladipic acid, an alicyclic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid, Aromatic dicarboxylic acids such as phthalic acid, xylylene dicarboxylic acid, alkyl-substituted terephthalic acid, isophthalic acid, or naphthalene dicarboxylic acid may be used, and they may be used to modify the polyamide.

  One or more kinds of these polyamides can be used. Among these polyamides, the amide group in the polyamide is more likely to react with the hydroxyl group of the gas barrier resin in the A layer, so that the interlayer adhesion of the multilayer structure becomes higher. Or a hexamethylene isophthalamide / terephthalamide copolymer (nylon 6I / 6T) is preferable. In the hexamethylene isophthalamide / terephthalamide copolymer, the molar ratio (I / T) of isophthalic acid (I) units / terephthalic acid (T) units is in the range of 60/40 to 100/0 (molar ratio). It is preferable that it is in the range of 65/35 to 90/10 (molar ratio). The polyamide is also preferably a caprolactam / lauryl lactam copolymer, that is, a nylon 6/12 main component. The ratio of 6 components (caprolactam component) and 12 components (lauryl lactam component) contained in the polyamide is not particularly limited, but the ratio of 12 components to the total mass of the polyamide is preferably 5 to 60% by mass, More preferably, it is 50 mass%. Moreover, the relative viscosity of these polyamides is not particularly limited, but is preferably 1.0 to 4.0 from the viewpoint of further enhancing the adhesive force between the A layer and the B layer in the obtained multilayer structure. .

  Among these polyamides, aliphatic polyamides are preferable from the viewpoint of flexibility.

  Moreover, it is preferable from a viewpoint of a softness | flexibility that it is a polyamide-type elastomer which consists of a block copolymer which has nylon (polyamide part) in a hard segment as polyamide. A typical polyamide-based elastomer is shown in the following formula. This elastomer is preferably one obtained by condensing a polyamide part and a polyether part. The polyamide part becomes a hard segment, and the polyether part becomes a soft segment.

  In the above formula, p is 5 or 11. l, m, and n are arbitrary natural numbers.

  The polyamide part used in the polyamide elastomer is nylon 6, nylon 10, nylon 6-6, nylon 11, nylon 12, nylon 6-12, nylon 6-10, nylon 6 / 6-6 copolymer, nylon 6 -6 / 6-10 copolymer, nylon 6-11, nylon 6-6 / 6-10 / 6 copolymer and the like. Among these, an elastomer using nylon 6 is preferable from the viewpoint of flexibility and adhesion to the A layer.

  Examples of the polyether portion used in the polyamide elastomer include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol.

  The mass ratio of the polyamide part / polyether part in the polyamide-based elastomer is not particularly limited, but can be arbitrarily selected within the range of, for example, 80/20 to 20/80.

  The lower limit of the amount of terminal carboxyl groups of the polyamide is preferably 1 μeq (equivalent) / g, more preferably 3 μeq / g, and even more preferably 5 μeq / g. On the other hand, the upper limit of the amount of the terminal carboxyl group is preferably 1000 μeq / g, more preferably 800 μeq / g, and still more preferably 600 μeq / g. By setting the amount of the terminal carboxyl group within this range, the hydroxyl group of the gas barrier resin in the A layer reacts with not only the amide group of the polyamide in the B layer but also the terminal carboxyl group, whereby the A layer and the B layer Can be bonded more firmly, and the interlayer adhesion of the multilayer structure can be further improved. When the amount of terminal carboxyl groups is smaller than the above lower limit, the interlayer adhesion of the multilayer structure may be lowered. On the contrary, when the amount of terminal carboxyl groups exceeds the above upper limit, the weather resistance of the multilayer structure may be deteriorated. The amount of terminal carboxyl groups of polyamide can be quantified by dissolving a polyamide sample in benzyl alcohol, using phenolphthalein as an indicator, and titrating with a sodium hydroxide solution.

<Functional group-containing resin>
The functional group-containing resin has a functional group in the molecule that can react with the group of the gas barrier resin. Examples of groups possessed by the gas barrier resin include hydroxyl groups possessed by EVOH, amide groups possessed by polyamide resins, ester groups possessed by polyester resins, and the like. The multilayer structure can improve stretchability and thermoformability by laminating a B layer made of a resin composition containing such a functional group-containing resin. Further, in the multilayer structure, a bonding reaction occurs at the interface between the B layer and the A layer, and the interlayer adhesion can be strengthened. And stretchability can be maintained.

  The functional group capable of reacting with the group possessed by the gas barrier resin contained in the layer A is not particularly limited as long as it is a functional group capable of reacting with the group possessed by the gas barrier resin. For example, a carboxyl group or an anhydride thereof Groups, metal carboxylate groups, boronic acid groups, boron-containing groups that can be converted to boronic acid groups in the presence of water, ester groups, urea groups, carbonate groups, ether groups, imino groups, acetal groups, epoxy groups, isocyanate groups Etc. are exemplified. Among these, in the presence of carboxyl group, metal carboxylate group, boronic acid group, and water, the interlaminar adhesion between A layer and B layer is very high, and the durability of the resulting multilayer structure is particularly excellent. Boron-containing groups and ester groups that can be converted to boronic acid groups are preferred.

  Examples of the functional group-containing resin include a carboxylic acid-modified polyolefin or a metal salt thereof, a boronic acid group or a thermoplastic resin having a boron-containing group that can be converted into a boronic acid group in the presence of water, a vinyl ester copolymer, Polyester resin, acrylic resin, butyral resin, alkyd resin, polyethylene oxide resin, cellulose resin, melamine resin, styrene-acrylic acid copolymer, phenol resin, urea resin, melamine alkyd resin, epoxy resin, Examples include polyisocyanate resins. Also, copolymers or modified products of these resins can be used. Among them, the interlaminar adhesion becomes very high, the durability of the resulting multilayer structure is particularly excellent, and the stretchability and melt moldability are also improved, so that the carboxylic acid-modified polyolefin or its metal salt, boronic acid group Alternatively, a thermoplastic resin having a boron-containing group that can be converted to a boronic acid group in the presence of water, or a vinyl ester copolymer is preferable, and a carboxylic acid-modified polyolefin is particularly preferable. As the functional group-containing resin, one type or a plurality of types can be used.

  The carboxylic acid-modified polyolefin is a polyolefin having a carboxyl group or an anhydride group thereof in the molecule. The carboxylic acid-modified styrene elastomer described later is also included in the carboxylic acid-modified polyolefin. In addition, the metal salt of a carboxylic acid-modified polyolefin is a polyolefin having a carboxyl group or its anhydride group in the molecule, or all or part of the carboxyl group or anhydride group contained in the polyolefin is a metal carboxylate group. It exists in a form. One or more kinds of such carboxylic acid-modified polyolefins or metal salts thereof can be used.

  The carboxylic acid-modified polyolefin is obtained by, for example, chemically bonding an ethylenically unsaturated carboxylic acid or an anhydride thereof to an olefin polymer (for example, by an addition reaction or a graft reaction), or an olefin and an unsaturated carboxylic acid or It can be obtained by copolymerizing the anhydride or the like. The metal salt of the carboxylic acid-modified polyolefin can be obtained, for example, by substituting all or part of the hydrogen ions of the carboxyl group contained in the carboxylic acid-modified polyolefin with metal ions.

  When the carboxylic acid-modified polyolefin is obtained by chemically bonding an ethylenically unsaturated carboxylic acid or its anhydride to an olefin polymer, the olefin polymer may be polyethylene (low pressure, medium pressure, high pressure), Polyolefins such as linear low density polyethylene, polypropylene, bolibene, polystyrene; copolymers of olefins and comonomers (such as vinyl acetate, unsaturated carboxylic acid esters, conjugated diene compounds) that can be copolymerized with the olefins, such as ethylene- Examples thereof include a vinyl acetate copolymer, an ethylene-acrylic acid ethyl ester copolymer, and a copolymer of styrene and a conjugated diene compound. Among these, in the obtained multilayer structure, interlaminar adhesion, stretchability and thermoformability are particularly improved, so that a linear low density polyethylene, an ethylene-vinyl acetate copolymer (vinyl acetate content 5 to 5). 55 mass%) or ethylene-acrylic acid ethyl ester copolymer (content of acrylic acid ethyl ester 8 to 35 mass%) is preferred, linear low density polyethylene or ethylene-vinyl acetate copolymer (vinyl acetate A content of 5 to 55% by weight is particularly preferred.

  Examples of the ethylenically unsaturated carboxylic acid or anhydride thereof chemically bonded to the olefin polymer include ethylenically unsaturated monocarboxylic acid, ethylenically unsaturated dicarboxylic acid or anhydride thereof. In addition, a compound in which all or a part of the carboxyl groups of the carboxylic acid are esterified can be used, and the carboxylic acid-modified polyolefin can be obtained by hydrolyzing the ester group after the polymerization. it can. Specific examples of these compounds include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, and fumaric acid monomethyl ester. . Among them, an ethylenically unsaturated dicarboxylic acid anhydride is particularly preferable in that it has an acid anhydride group that easily reacts with a hydroxyl group such as EVOH constituting the A layer, and the resulting multilayer structure is excellent in interlayer adhesion. As a specific compound, maleic anhydride is particularly preferable.

  The lower limit of the amount of addition or grafting (modification degree) of such an ethylenically unsaturated carboxylic acid or anhydride to the olefin polymer is preferably 0.01% by mass with respect to the olefin polymer. 0.02% by mass is more preferable. On the other hand, the upper limit of the addition amount or graft amount (modification degree) is preferably 15% by mass, and more preferably 10% by mass. When the addition amount or the graft amount is less than the lower limit, the interlayer adhesion is lowered, and the durability of the multilayer structure may be lowered. On the contrary, when the addition amount or the graft amount exceeds the above upper limit, the resin composition is highly colored, and the appearance of the multilayer structure may be deteriorated.

  As a method for chemically bonding an ethylenically unsaturated carboxylic acid or an anhydride thereof to an olefin polymer by an addition reaction or a graft reaction, for example, in the presence of a solvent (such as xylene) or a catalyst (such as a peroxide). And performing a radical reaction.

  Further, when the carboxylic acid-modified polyolefin is obtained by copolymerization of an olefin and an unsaturated carboxylic acid, that is, when the carboxylic acid-modified polyolefin is an olefin-unsaturated carboxylic acid copolymer, the olefin to be used is From the viewpoint of improving the stretchability and melt moldability of the resulting multilayer structure, α-olefins such as ethylene, propylene, and 1-butene are preferable, and ethylene is particularly preferable. On the other hand, examples of the unsaturated carboxylic acid used include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, monomethyl maleate, monoethyl maleate, and maleic anhydride. Among them, acrylic acid or methacrylic acid is particularly preferable because it is easily available. Moreover, the said olefin-unsaturated carboxylic acid copolymer may contain other monomers other than an olefin and unsaturated carboxylic acid as a copolymerization component. Examples of such other monomers include vinyl esters such as vinyl acetate and vinyl propionate; methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, Examples thereof include unsaturated carboxylic acid esters such as methyl methacrylate, isobutyl methacrylate and diethyl maleate; carbon monoxide.

  The lower limit of the content of unsaturated carboxylic acid units in this olefin-unsaturated carboxylic acid copolymer is preferably 2 mol% as the content of unsaturated carboxylic acid units relative to all structural units in the copolymer. More preferred is mol%. On the other hand, the upper limit of the content of the unsaturated carboxylic acid unit is preferably 15 mol%, more preferably 12 mol%. When the content of the unsaturated carboxylic acid unit is smaller than the above lower limit, the interlaminar adhesion is lowered, and the durability of the multilayer structure may be lowered. On the other hand, when the content of the unsaturated carboxylic acid unit exceeds the above upper limit, the resin composition becomes highly colored and the appearance of the multilayer structure may be deteriorated.

  As the olefin-unsaturated carboxylic acid copolymer, a polymer obtained by random copolymerization of an olefin and an unsaturated carboxylic acid or an anhydride thereof is preferable. Among them, ethylene and an unsaturated carboxylic acid or an anhydride thereof are preferably used. More preferred is a polymer obtained by random copolymerization.

  Examples of the metal ions constituting the metal salt of the carboxylic acid-modified polyolefin include alkali metal ions such as lithium, sodium and potassium; alkaline earth metal ions such as magnesium and calcium; d-block metal ions such as zinc. The neutralization degree in the metal salt of the carboxylic acid-modified polyolefin, that is, the ratio of the metal carboxylate group to the total number of carboxyl groups and metal carboxylate groups in the metal salt of the carboxylic acid-modified polyolefin is not particularly limited, but the lower limit of the neutralization degree Is preferably 5 mol%, more preferably 10 mol%, and even more preferably 30 mol%. On the other hand, the upper limit of the degree of neutralization is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. When the degree of neutralization is less than the above lower limit, the interlayer adhesion is lowered, and the durability of the multilayer structure may be lowered. On the other hand, when the degree of neutralization exceeds the above upper limit, the resin composition is intensely colored, and the appearance of the multilayer structure may be deteriorated.

  The lower limit of the melt flow rate (MFR) (under 190 ° C. and 2160 g load) of the carboxylic acid-modified polyolefin or its metal salt is preferably 0.05 g / 10 min, more preferably 0.2 g / 10 min, 5 g / 10 min is more preferable. On the other hand, the upper limit of the melt flow rate is preferably 50 g / 10 minutes, more preferably 40 g / 10 minutes, and even more preferably 30 g / 10 minutes.

  A thermoplastic resin having a boron-containing group (hereinafter also referred to as “boronic acid-derived group”) that can be converted to a boronic acid group in the presence of a boronic acid group or water is a boronic acid represented by the following formula (X) It is a thermoplastic resin having a boron-containing group in the molecule that has a group in the molecule or can be converted into a boronic acid group.

  The boron-containing group that can be converted to a boronic acid group in the presence of water is not particularly limited as long as it is a boron-containing group that can be converted to a boronic acid group by hydrolysis in the presence of water. A boronic acid ester group represented by the following formula (XII), a boronic acid base represented by the following formula (XIII), and the like. Here, the boron-containing group that can be converted to a boronic acid group in the presence of water is water, a mixed liquid of water and an organic solvent (toluene, xylene, acetone, etc.), or a 5% boric acid aqueous solution and the above organic solvent. Means a group that can be converted to a boronic acid group when hydrolysis is carried out under conditions of a reaction time of 10 minutes to 2 hours and a reaction temperature of room temperature to 150 ° C.

  In the above formula (XI), X and Y are a hydrogen atom, an aliphatic hydrocarbon group (such as a linear or branched alkyl group or alkenyl group having 1 to 20 carbon atoms), an alicyclic hydrocarbon group (cycloalkyl). Group or a cycloalkenyl group) and an aromatic hydrocarbon group (such as a phenyl group or a biphenyl group). X and Y may be the same group or different groups. X and Y may be bonded (except when at least one of X and Y is a hydrogen atom). The aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group may have other groups such as a hydroxyl group, a carboxyl group, and a halogen atom.

In the above formula (XIII), R ¹³ , R ¹⁴ and R ¹⁵ are each independently 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 (such as a cycloalkyl group or a cycloalkenyl group), and an aromatic hydrocarbon group (such as a phenyl group or a biphenyl group). R ¹³ , R ¹⁴ and R ¹⁵ may be the same group or different groups. M represents an alkali metal or an alkaline earth metal. The aliphatic hydrocarbon group, alicyclic hydrocarbon group or aromatic hydrocarbon group may have other groups such as a hydroxyl group, a carboxyl group, a halogen atom and the like.

  Specific examples of the boronic acid ester group represented by the formula (XI) include boronic acid dimethyl ester group, boronic acid diethyl ester group, boronic acid dibutyl ester group, boronic acid dicyclohexyl group, boronic acid ethylene glycol ester group, boronic acid Propylene glycol ester group (boronic acid 1,2-propanediol ester group, boronic acid 1,3-propanediol ester group), boronic acid neopentyl ester group, boronic acid catechol ester group, boronic acid glycerin ester group, boronic acid triester Examples include a methylolethane ester group and a boronic acid diethanolamine ester group. Specific examples of the boronic acid base represented by the formula (XIII) include sodium boronate base, potassium boronate base, calcium boronate base and the like.

  The content of the boronic acid-derived group in the thermoplastic resin is not particularly limited, but from the viewpoint of increasing the interlayer adhesion in the multilayer structure, the boronic acid-derived group of all the structural units of the polymer constituting the thermoplastic resin. The lower limit of the content is preferably 0.0001 meq (equivalent) / g, more preferably 0.001 meq / g. On the other hand, the upper limit of the content of the boronic acid derivative group is preferably 1 meq / g, more preferably 0.1 meq / g. When the content of the boronic acid-derived group is smaller than the above lower limit, the interlayer adhesiveness is lowered, and the durability of the multilayer structure may be lowered. On the other hand, when the content of the boronic acid-derived group exceeds the above upper limit, the resin composition is highly colored, and the appearance of the multilayer structure may be deteriorated.

  Examples of suitable base polymers of the thermoplastic resin having a boronic acid-derived group include polyethylene (ultra-low density, low density, medium density, high density), ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate. Olefin polymers such as copolymer, ethylene-vinyl acetate copolymer, polypropylene, ethylene-propylene copolymer; polystyrene, styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadiene copolymer, styrene-diene block Styrenic polymers such as hydrogenated copolymers (hydrogenated products such as styrene-isoprene-block copolymer, styrene-butadiene copolymer, styrene-isoprene-styrene block copolymer); polymethyl acrylate, Such as polyethyl acrylate and polymethyl methacrylate ) Acrylic acid ester polymers; vinyl halide polymers such as polyvinyl chloride and polyvinylidene fluoride; semi-aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyvalerolactone, polycaprolactone, polyethylene succinate, polybutylene Examples thereof include aliphatic polyesters such as succinate.

  The melt flow rate (MFR) (value measured at 230 ° C. under a load of 2160 g) of the thermoplastic resin having a boronic acid-derived group is preferably 0.01 to 500 g / 10 minutes, and preferably 0.1 to 50 g / 10. Minutes are more preferred. As a thermoplastic resin having such a boronic acid derivative group, one type or a plurality of types can be used.

  Next, a representative method for producing a thermoplastic resin having the boronic acid derivative group will be described. First production method: An olefin polymer having a boronic acid-derived group is obtained by reacting a borane complex and a boric acid trialkyl ester with an olefin polymer having a carbon-carbon double bond in a nitrogen atmosphere. After obtaining an olefin polymer having a dialkyl ester group, it is obtained by reacting water or alcohols. If an olefin polymer having a double bond at the terminal is used as a raw material in this production method, an olefin polymer having a boronic acid derivative group at the terminal can be obtained. If an olefin polymer having a double bond in the side chain and main chain is used as a raw material, an olefin polymer having a boronic acid derivative group mainly in the side chain can be obtained.

  Typical production examples of the olefin polymer having a double bond as a raw material are as follows: 1) A method using a normal olefin polymer and utilizing a double bond existing in a trace amount at the terminal; 2) A normal olefin polymer A method of thermally decomposing a polymer under oxygen-free conditions to obtain an olefin polymer having a double bond at the end; 3) having a double bond by copolymerization of an olefin monomer and a diene monomer The manufacturing method which obtains an olefin type polymer is mentioned. For 1), a known olefin polymer production method can be used, but a production method using a Philips method or a method using a metallocene polymerization catalyst as a polymerization catalyst without using hydrogen as a chain transfer agent (for example, DE4030399) is available. preferable. 2) can be obtained by thermally decomposing an olefin polymer at a temperature of 300 to 500 ° C. in an oxygen-free condition such as a nitrogen atmosphere or a vacuum condition by a known method (for example, US2835659, 3087922). . With respect to 3), a method for producing an olefin-diene copolymer using a known Ziegler catalyst (for example, JP-A-50-44281, DE3021273) can be used.

  As the borane complex used above, borane-tetrahydrofuran complex, borane-dimethyl sulfide complex, borane-pyridine complex, borane-trimethylamine complex, borane-triethylamine complex and the like are preferable. Of these, borane-dimethylsulfide complex, borane-trimethylamine complex and borane-triethylamine complex are more preferred. The reaction charge of the borane complex is preferably in the range of 1/3 equivalent to 10 equivalents with respect to the total number of double bonds of the olefin polymer. Further, as the boric acid trialkyl ester, boric acid lower alkyl esters such as trimethyl borate, triethyl borate, tripropyl borate, tributyl borate and the like are preferable. The reaction charge amount of the boric acid trialkyl ester is preferably in the range of 1 to 100 equivalents with respect to the total number of double bonds of the olefin polymer. Although it is not necessary to use a solvent in particular, saturated hydrocarbon solvents such as hexane, heptane, octane, decane, dodecane, cyclohexane, ethylcyclohexane and decalin are preferred.

  The reaction temperature when the borane complex or boric acid trialkyl ester is reacted with the olefin polymer is usually room temperature to 300 ° C, preferably 100 to 250 ° C. The reaction time is usually 1 minute to 10 hours, preferably 5 minutes to 5 hours.

  As conditions for reacting the olefin polymer having a boronic acid dialkyl ester group obtained above with water or alcohols, an organic solvent such as toluene, xylene, acetone, ethyl acetate or the like is usually used as a reaction solvent, water; Monohydric alcohols such as methanol, ethanol, butanol; ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, neopentyl glycol, glycerin, trimethylolmethane, pentaerythritol, di It can be obtained by reacting a polyhydric alcohol such as pentaerythritol with a large excess of 1 to 100 equivalents or more with respect to the boronic acid dialkyl ester group.

  Second process for producing a thermoplastic resin having a boronic acid-derived group: an olefin polymer having a boronic acid-derived group at the terminal is an olefin monomer or vinyl monomer in the presence of a thiol having a boronic acid-derived group Alternatively, it can be obtained by radical polymerization of at least one selected from diene monomers.

  The thiol having a boronic acid derivative group as a raw material is obtained by adding alcohols or water after reacting diborane or a borane complex with a thiol having a double bond in a nitrogen atmosphere. Here, examples of the thiol having a double bond include 2-propene-1-thiol, 2-methyl-2-propene-1-thiol, 3-butene-1-thiol, and 4-pentene-1-thiol. . Among these, 2-propene-1-thiol or 2-methyl-2-propene-1-thiol is preferable. As the borane complex used here, those similar to the above are used, and among them, a borane-tetrahydrofuran complex or a borane-dimethylsulfide complex is particularly preferably used. The amount of diborane or borane complex added is preferably about 1 equivalent with respect to the thiol having a double bond. The reaction conditions are preferably from room temperature to 200 ° C. Examples of the solvent include ether solvents such as tetrahydrofuran (THF) and diglyme; saturated hydrocarbon solvents such as hexane, heptane, ethylcyclohexane and decalin, among which tetrahydrofuran is preferable. As alcohols added after the reaction, lower alcohols having 1 to 6 carbon atoms such as methanol and ethanol are preferable, and methanol is particularly preferable.

  In the presence of the thiol having a boronic acid derivative group thus obtained, at least one selected from olefinic monomers, vinylic monomers, and diene monomers is subjected to radical polymerization so as to be terminated. A polymer having a boronic acid derivative group is obtained. An azo or peroxide initiator is usually used for the polymerization. The polymerization temperature is preferably in the temperature range from room temperature to 150 ° C. The addition amount of thiol having a boronic acid derivative group is preferably about 0.001 to 1 mmol per gram of monomer, and the addition method of thiol is not particularly limited, but monomers such as vinyl acetate, styrene, etc. It is preferable to feed the thiol into the polymerization system during polymerization, and when using something that is difficult to chain transfer such as methyl methacrylate, the thiol is first charged into the polymerization system. It is preferable to keep it.

  Third production method of a thermoplastic resin having a boronic acid derivative group: The thermoplastic resin having a boronic acid derivative group in the side chain is composed of a monomer having a boronic acid derivative group, the olefin monomer, and a vinyl monomer. And at least one monomer selected from diene monomers. Examples of the monomer having a boronic acid derivative group include 3-acryloylaminobenzeneboronic acid, 3-acryloylaminobenzeneboronic acid ethylene glycol ester, 3-methacryloylaminobenzeneboronic acid, and 3-methacryloylaminobenzeneboronic acid. Examples include ethylene glycol ester, 4-vinylphenylboronic acid, 4-vinylphenylboronic acid ethylene glycol ester, and the like.

  The thermoplastic resin having a boronic acid derivative group in the side chain includes, for example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, citraconic acid, fumaric acid, and maleic anhydride, and the above olefinic monomers. , Producing a random copolymer or graft copolymer with at least one monomer selected from vinyl monomers and diene monomers, and condensing carboxyl groups contained in the polymer with carbodiimide or the like It is obtained by an amidation reaction with an amino group-containing boronic acid such as m-aminophenylbenzeneboronic acid or m-aminophenylboronic acid ethylene glycol ester, or with or without an agent.

  In the vinyl ester copolymer, it is preferable that at least 30 mol% or more of vinyl ester units are based on all structural units constituting the copolymer. When the ratio of the vinyl ester unit in the copolymer is less than 30 mol%, the interlayer adhesion of the multilayer structure may be lowered. Examples of the vinyl esters include fatty acid vinyls such as vinyl acetate, vinyl formate, vinyl propionate, and vinyl pivalate. Among these, vinyl acetate is particularly preferable because it is easily available. In the vinyl ester copolymer, copolymerizable components that can be copolymerized with vinyl ester include olefins such as ethylene and propylene; styrenes such as styrene and p-methylstyrene; halogens such as vinyl chloride. Examples include olefins; (meth) acrylic esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate; dienes such as butadiene and isoprene; unsaturated nitriles such as acrylonitrile. These copolymer components can be used alone or in combination. The glass transition point (Tg) of the vinyl ester copolymer can be adjusted by changing the type and amount of the copolymer component. Specific examples of the vinyl ester copolymer include ethylene-vinyl acetate copolymer, propylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, methyl acrylate-vinyl acetate copolymer, acrylonitrile-acetic acid. A vinyl copolymer etc. are illustrated. Among these, an ethylene-vinyl acetate copolymer is particularly preferable because the interlayer adhesion, stretchability and melt moldability of the resulting multilayer structure are particularly improved.

  What blended the said functional group containing resin with other resin can also be used as a resin composition of B layer. By blending with other resins, the functional group concentration contained in the resin composition of the B layer can be controlled, and physical properties such as thermal stability, melt viscosity, and adhesion to the A layer can be controlled.

  Such other resins are required to have properties capable of forming a laminate, and polyolefins are mentioned as preferred resins. In particular, when the functional group-containing resin is a resin obtained by modification, the other resin preferably has the same monomer unit as that of the resin before modification. That is, for example, when the above-mentioned carboxylic acid-modified polyolefin is used as the functional group-containing resin, the unmodified polyolefin is used as another resin (for example, maleic anhydride-modified linear low-density polyethylene and unmodified linear low-density Preferred is a blend with polyethylene). When a carboxylic acid-modified styrene elastomer is used, it is preferable to use the unmodified styrene elastomer as another resin. The ratio of the functional group-containing resin to the other resin is appropriately selected depending on the required performance, but the mass ratio of the functional group-containing resin / the other resin is preferably 2/98 to 40/60.

  Moreover, in order to improve the moisture resistance of the said multilayer structure as another resin, it is also preferable to contain an alicyclic olefin polymer in the resin composition of B layer. When the alicyclic olefin polymer is contained in the resin composition of the B layer, the mass ratio of the functional group-containing resin / alicyclic olefin polymer is preferably 2/98 to 40/60, and 5/95 to 30/70 is more preferable.

  An alicyclic olefin polymer is a polymer having a repeating unit containing an alicyclic structure. Examples of the alicyclic structure include a saturated cyclic hydrocarbon (cycloalkane) structure and an unsaturated cyclic hydrocarbon (cycloalkene) structure. From the viewpoint of mechanical strength and heat resistance, a cycloalkane structure and a cycloalkene structure are exemplified. A structure is preferable, and a cycloalkane structure is most preferable among them. The alicyclic structure may be in the main chain or in the side chain, but those containing an alicyclic structure in the main chain are preferred from the viewpoint of mechanical strength, heat resistance and the like. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, more preferably 5 to 15 in the range of mechanical strength, heat resistance, In addition, properties such as moldability of the resin layer are highly balanced.

  The alicyclic olefin polymer includes homopolymers and copolymers of alicyclic olefins and derivatives thereof (hydrogenated products and the like). The polymerization method may be addition polymerization or ring-opening polymerization.

  Examples of the alicyclic olefin polymer include a ring-opening polymer of a monomer having a norbornene ring (hereinafter referred to as a norbornene monomer) and a hydrogenated product thereof, an addition polymer of a norbornene monomer, and a norbornene monomer. An addition copolymer of a polymer and a vinyl compound, a monocyclic cycloalkene addition polymer, an alicyclic conjugated diene polymer, a vinyl alicyclic hydrocarbon polymer, and a hydrogenated product thereof. Furthermore, the polymer in which an alicyclic structure is formed by hydrogenation after polymerization, such as an aromatic olefin hydrogenated product of an aromatic olefin polymer, has reached a structure equivalent to the alicyclic olefin polymer. . The polymerization method of the alicyclic olefin and the method of hydrogenation performed as necessary are not particularly limited and can be performed according to a known method.

  Moreover, what has a polar group is also contained in an alicyclic olefin polymer. Examples of the polar group include a hydroxyl group, a carboxyl group, an alkoxyl group, an epoxy group, a glycidyl group, an oxycarbonyl group, a carbonyl group, an amino group, an ester group, and a carboxylic acid anhydride group. Acid anhydride groups are preferred. The method for obtaining the alicyclic olefin polymer having a polar group is not particularly limited. For example, (i) an alicyclic olefin monomer containing a polar group is homopolymerized, or with other monomers. A method of copolymerizing; (ii) a carbon-carbon unsaturated bond-containing compound having a polar group is grafted to an alicyclic olefin polymer not containing a polar group, for example, in the presence of a radical initiator, A method of introducing a group; and the like.

As the alicyclic olefin monomer containing a polar group used in the method (i), 8-hydroxycarbonyltetracyclo [4.4.0.1 ^2,5 . ^{17, 10} ] dodec-3-ene, 5-hydroxycarbonylbicyclo [2.2.1] hept-2-ene, 5-methyl-5-hydroxycarbonylbicyclo [2.2.1] hept-2-ene , 5-carboxymethyl-5-hydroxycarbonylbicyclo [2.2.1] hept-2-ene, 8-methyl-8-hydroxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-carboxymethyl-8-hydroxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 5-exo-6-endo-dihydroxycarbonylbicyclo [2.2.1] hept-2-ene, 8-exo-9-endo-dihydroxycarbonyltetracyclo [4. 4.0.1 ^2,5 . Carboxyl group-containing alicyclic olefin monomers such as ^{17, 10} ] dodec-3-ene; bicyclo [2.2.1] hept-2-ene-5,6-dicarboxylic anhydride, tetracyclo [4. 4.0.1 ^2,5 . 1 ^7,10 ] dodec- ³ -ene-8,9-dicarboxylic anhydride, hexacyclo [6.6.1.1 ^3,6 . 1 ^10,13 . 0 ^2,7 . 0 ^9,14] heptadec-4-ene-11,12-acid anhydride such as a dicarboxylic acid anhydride group-containing alicyclic olefin monomer; and the like.

Specific examples of the monomer for obtaining an alicyclic olefin polymer containing no polar group used in the method (ii) include bicyclo [2.2.1] hept-2-ene (common name: norbornene). ), 5-ethyl-bicyclo [2.2.1] hept-2-ene, 5-butyl-bicyclo [2.2.1] hept-2-ene, 5-ethylidene-bicyclo [2.2.1]. Hept-2-ene, 5-methylidene-bicyclo [2.2.1] hept-2-ene, 5-vinyl-bicyclo [2.2.1] hept-2-ene, tricyclo [4.3.0. 1 ^2,5] deca-3,7-diene (trivial name: dicyclopentadiene), tetracyclo ^{[8.4.0.1 11,14.} 0 ^2,8 ] tetradeca-3,5,7,12,11-tetraene, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dec-3-ene (common name: tetracyclododecene), 8-methyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-ethyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-methylidene-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-ethylidene-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-vinyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-propenyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13] pentadeca-3,10-diene, pentacyclo [7.4.0.1 ^3,6. 1 ^10,13 . 0 ^2,7 ] pentadeca-4,11-diene, cyclopentene, cyclopentadiene, 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene, 8-phenyl-tetracyclo [4.4. 0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene and the like.

  Examples of the carbon-carbon unsaturated bond-containing compound having a polar group used in the method (ii) include acrylic acid, methacrylic acid, α-ethylacrylic acid, 2-hydroxyethyl (meth) acrylic acid, maleic acid, Fumaric acid, itaconic acid, endocis-bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid, methyl-endocis-bicyclo [2.2.1] hept-5-ene-2,3 -Unsaturated carboxylic acid compounds such as dicarboxylic acid; unsaturated carboxylic acid anhydrides such as maleic anhydride, chloromaleic anhydride, butenyl succinic anhydride, tetrahydrophthalic anhydride, citraconic anhydride; and the like.

  The method of blending the above functional group-containing resin with another resin is not particularly limited as long as it is uniformly blended, and may be a dry blend that is blended in a solid state or pelletized with a melt extruder. It may be a melt blend. Examples of the melt blending method include a method using a ribbon blender, a mixer kneader, a pelletizer, a mixing roll, an extruder, and an intensive mixer. Among these, it is preferable to use a single-screw or twin-screw extruder from the viewpoint of process simplicity and cost. The blending temperature is appropriately selected depending on the properties of the equipment, the type of resin, the blending ratio, etc., but in many cases it is in the range of 150 to 300 ° C. Moreover, when forming a multilayer structure, it can also melt-knead using the extruder attached to the molding machine.

<Elastomer>
By using an elastomer as the thermoplastic resin, the stretchability and thermoformability of the multilayer structure can be improved.

  Elastomer refers to a resin that has elasticity near room temperature. Specifically, the resin is stretched twice under room temperature (20 ° C.), held in that state for 1 minute, and the original length within 1 minute. A resin having the property of shrinking to less than 1.5 times the thickness. The elastomer is structurally a polymer having a hard segment and a soft segment in the polymer chain.

  Examples of such elastomers include styrene elastomers, olefin elastomers, polydiene elastomers, polyvinyl chloride elastomers, chlorinated polyethylene elastomers, polyurethane elastomers, polyester elastomers, polyamide elastomers, and fluororesin elastomers. At least one selected from the group consisting of: Among these, from the viewpoint of ease of molding, at least one selected from the group consisting of styrene elastomers, olefin elastomers, polydiene elastomers, polyurethane elastomers, polyester elastomers and polyamide elastomers is preferably used. An elastomer is more preferably used.

  Moreover, as such an elastomer, it can select suitably from well-known thermoplastic elastomers and non-thermoplastic elastomers, but it is preferable to use a thermoplastic elastomer for melt molding.

  Examples of the thermoplastic elastomer include styrene thermoplastic elastomer, olefin thermoplastic elastomer, polydiene thermoplastic elastomer, polyvinyl chloride thermoplastic elastomer, chlorinated polyethylene thermoplastic elastomer, polyurethane thermoplastic elastomer, and polyester. And at least one selected from the group consisting of thermoplastic thermoplastic elastomers, polyamide thermoplastic elastomers, and fluororesin thermoplastic elastomers. Among these, from the viewpoint of ease of molding, from the group consisting of a styrene thermoplastic elastomer, an olefin thermoplastic elastomer, a polydiene thermoplastic elastomer, a polyurethane thermoplastic elastomer, a polyester thermoplastic elastomer, and a polyamide thermoplastic elastomer. At least one selected from the above is preferably used, and a styrenic thermoplastic elastomer is more preferably used.

<Styrenic thermoplastic elastomer>
Although it does not specifically limit as said styrene-type elastomer, The copolymer which consists of a vinyl aromatic compound and a conjugated diene compound / or its hydrogenated substance can be mentioned.

  Although it does not specifically limit as said vinyl aromatic, For example, styrene, (alpha) -methyl styrene, 2-methyl styrene, 4-methyl styrene, 4-propyl styrene, 4-t- butyl styrene, 4-cyclohexyl styrene, 4- Such as dodecylstyrene, 2-ethyl-4-benzylstyrene, 4- (phenylbutyl) styrene, 2,4,6-trimethylstyrene, monofluorostyrene, difluorostyrene, monochlorostyrene, dichlorostyrene, methoxystyrene, t-butoxystyrene, etc. Examples thereof include styrenes; vinyl group-containing aromatic compounds such as vinylnaphthalenes such as 1-vinylnaphthalene and 2-vinylnaphthalene; vinylene group-containing aromatic compounds such as indene and acenaphthylene. Only one type of vinyl aromatic monomer unit may be used, or two or more types may be used. However, a unit derived from styrene is preferable.

  The conjugated diene compound is not particularly limited, and examples thereof include butadiene, isoprene, 3,4-polymerized isoprene, 2,3-dimethylbutadiene, pentadiene, and hexadiene. These diene compounds may be hydrogenated polymer blocks made of the conjugated diene compound.

  The styrenic elastomer preferably has a functional group capable of reacting with a group possessed by the gas barrier resin contained in the layer A (note that a styrenic elastomer having such a functional group is also included in the functional group-containing resin. ) Examples of the functional group include the above-described carboxyl group, metal carboxylate group, boronic acid group, and boron-containing group that can be converted to a boronic acid group in the presence of water, an ester group, etc. It is done.

  As an example of the above-mentioned styrenic elastomer having a functional group, a styrenic elastomer having a carboxyl group (carboxylic acid-modified styrenic elastomer) is, for example, (1) chemically treating an ethylenically unsaturated carboxylic acid or its anhydride with a styrenic elastomer. Or (2) copolymerizing a vinyl aromatic compound, a conjugated diene compound / or a hydrogenated product thereof, an unsaturated carboxylic acid or an anhydride thereof, etc. Can be obtained. Moreover, the styrene-type elastomer which has a metal carboxylate group can be obtained by substituting all or one part of the hydrogen ion of the carboxyl group contained in the said styrene-type elastomer with a metal ion, for example.

  What blended the styrene-type elastomer which has the said functional group with other resin can also be used as a resin composition of B layer. By blending with another resin, the functional group concentration and the like contained in the resin composition of the B layer can be controlled, and physical properties such as thermal stability, melt viscosity, and adhesion to the A layer can be controlled.

  Such other resin is required to have a property capable of forming a laminate, and an unmodified styrene-based elastomer is mentioned as a preferred resin. That is, when a carboxylic acid-modified styrene elastomer is used, it is preferable to use the unmodified styrene elastomer as another resin. The ratio of the functional group-containing resin to the other resin is appropriately selected depending on the required performance, but the mass ratio of the functional group-containing styrene elastomer / other resin (unmodified styrene elastomer, etc.) is 2/98 to It is preferable that it is 40/60.

<Olefin-based thermoplastic elastomer>
Examples of the olefin-based thermoplastic elastomer include thermoplastic elastomers using a polyolefin such as polypropylene and polyethylene as a hard segment and ethylene-propylene-diene copolymer rubber as a soft segment. There are blended and implantable types. Mention may also be made of maleic anhydride-modified ethylene-butene-1 copolymer, maleic anhydride-modified ethylene-propylene copolymer, halogenated butyl rubber, modified polypropylene, modified polyethylene and the like.

<Polydiene thermoplastic elastomer>
Examples of the polydiene-based thermoplastic elastomer include 1,2-polybutadiene-based TPE and trans 1,4-polyisoprene-based TPE, hydrogenated conjugated diene-based TPE, epoxidized natural rubber, and maleic anhydride-modified products thereof. it can.

  1,2-polybutadiene-based TPE is a polybutadiene containing 90% or more of 1,2-bonds in the molecule, and includes crystalline syndiotactic 1,2-polybutadiene as a hard segment and amorphous 1 as a soft segment. , 2-Polybutadiene.

  On the other hand, trans 1,4-polyisoprene-based TPE has a trans 1,4-structure of 98% or more, and includes crystalline trans 1,4-segment as a hard segment and amorphous trans 1 as a soft segment. , 4-segment.

<Polyvinyl chloride (PVC) thermoplastic elastomer>
Generally, the following three types of polyvinyl chloride-based thermoplastic elastomers (TPVC) are listed. Note that this TPVC may also be a modified product such as maleic anhydride-modified PVC.

(1) High molecular weight PVC / plasticized PVC blend type TPVC
This type of TPVC uses PVC having a high molecular weight as a hard segment and having a function of a crosslinking point at a microcrystalline portion, and PVC softened with a plasticizer as a soft segment.

(2) Partially cross-linked PVC / plasticized PVC blend type TPVC
This type of TPVC uses 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.

(3) PVC / elastomer alloy type TPVC
This type of TPVC uses PVC for the hard segment, rubber such as partially crosslinked NBR, polyurethane TPE, polyester TPE, and TPE for the soft segment.

<Chlorinated polyethylene (CPE) thermoplastic elastomer>
The chlorinated polyethylene thermoplastic elastomer is a soft resin obtained by reacting polyethylene with an aqueous suspension or chlorine gas in a solvent such as carbon tetrachloride. CPE uses a crystalline polyethylene part for the hard segment and a chlorinated polyethylene part for the soft segment. In CPE, both parts are mixed as a multi-block or random structure.

  CPE has different molecular properties such as chlorine content, blockiness, and residual crystallinity depending on the type of raw polyethylene, chlorination degree, and production conditions. As a result, CPE has a wide range of hardness from resin to rubber. A wide range of properties has been obtained. CPE can also have the same properties as vulcanized rubber by crosslinking, and can also be modified by modification with maleic anhydride.

<Polyester thermoplastic elastomer>
The polyester-based thermoplastic elastomer (TPEE) is a multi-block copolymer using a polyester as a hard segment in a molecule and a polyether or polyester having a low glass transition temperature (Tg) as a soft segment. TPEE has the following types depending on the molecular structure. Among them, (1) polyester / polyether type and (2) polyester / polyester type are common.

(1) Polyester / polyether type TPEE
In general, this type of TPEE uses an aromatic crystalline polyester as a hard segment and a polyether as a soft segment.

(2) Polyester / Polyester type TPEE
This type of TPEE uses an aromatic crystalline polyester as a hard segment and an aliphatic polyester as a soft segment.

(3) Liquid crystalline TPEE
This type of TPEE uses, as a special one, a rigid liquid crystal molecule as a hard segment and an aliphatic polyester as a soft segment.

<Polyamide thermoplastic elastomer>
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. Details of the polyamide-based elastomer are as described above as preferred examples of the polyamide.

<Fluoroplastic thermoplastic elastomer>
The fluororesin-based thermoplastic elastomer is an ABA block copolymer composed of a fluororesin as a hard segment and a fluororubber as a soft segment. Tetrafluoroethylene-ethylene copolymer or polyvinylidene fluoride (PVDF) is used for the hard segment fluororesin, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer for the soft segment fluororubber. Etc. are used. More specifically, it includes vinylidene fluoride rubber, tetrafluoroethylene-propylene rubber, tetrafluoroethylene-perfluoromethyl vinyl ether rubber, phosphazene fluororubber, fluoropolyether, fluoronitroso rubber, perfluorotriazine. Things.

  As with other TPEs, fluororesin-based TPE is microphase-separated and hard segments form cross-linking points.

<Polyurethane thermoplastic elastomer>
Polyurethane thermoplastic elastomers are (1) polyurethane obtained by the reaction of short chain glycol (low molecular polyol) and isocyanate as a hard segment, and (2) the reaction of long chain glycol (high molecular polyol) and isocyanate as a soft segment. A linear multi-block copolymer with the obtained polyurethane. Here, polyurethane is a general term for compounds having a urethane bond (—NHCOO—) obtained by a polyaddition reaction (urethanization reaction) of isocyanate (—NCO) and alcohol (—OH). The low molecular polyol, high molecular polyol, isocyanate (such as organic polyisocyanate) and the like constituting each segment are as described above for the description of polyurethane.

  The resin composition of the B layer contains various additives such as a resin other than a thermoplastic resin, or a heat stabilizer, an ultraviolet absorber, an antioxidant, a colorant, and a filler as long as the object of the present invention is not impaired. May be. When the resin composition of the B layer contains an additive, the amount is preferably 50% by mass or less, more preferably 30% by mass or less, more preferably 10% by mass with respect to the total amount of the resin composition. It is particularly preferred that

<Metal salt>
The multilayer structure preferably includes a metal salt in at least one resin composition of the adjacent A layer and B layer. Thus, by including a metal salt in at least one of the adjacent A layer and B layer, very excellent interlayer adhesion between the A layer and the B layer is exhibited. Due to such very excellent interlayer adhesion, the multilayer structure has high durability. The reason why such a metal salt improves the interlayer adhesion is not necessarily clear, but a bond formation reaction that occurs between the gas barrier resin in the resin composition of the A layer and the thermoplastic resin in the resin composition of the B layer. However, it can be accelerated by the presence of a metal salt. Examples of such bond formation reactions include a hydroxyl group exchange reaction that occurs between a carbamate group of TPU, an amino group of polyamide, and the like, and a hydroxyl group of a gas barrier resin, a hydroxyl group of a gas barrier resin to a residual isocyanate group in TPU, and the like. The addition reaction of polyamide, the amide formation reaction between the terminal carboxyl group of polyamide and the hydroxyl group of EVOH, and the binding reaction that occurs between the gas barrier resin and the functional group-containing resin can be considered. The metal salt may be contained in both the A-layer resin composition and the B-layer resin composition, and is contained in either the A-layer resin composition or the B-layer resin composition. Also good.

  Although it does not specifically limit as a metal salt, Alkali metal salt, alkaline-earth metal salt, or d block metal salt described in the 4th period of a periodic table is preferable at the point which raises interlayer adhesiveness more. Among these, alkali metal salts or alkaline earth metal salts are more preferable, and alkali metal salts are particularly preferable.

  The alkali metal salt is not particularly limited, and examples thereof include aliphatic carboxylates such as lithium, sodium, and potassium, aromatic carboxylates, phosphates, and metal complexes. 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.

  The alkaline earth metal salt is not particularly limited, and examples thereof include acetates or phosphates such as magnesium, calcium, barium, and beryllium. 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 also an advantage that the die adhesion amount of the molding machine of the resin that has deteriorated at the time of melt molding can be reduced.

  Although it does not specifically limit as a metal salt of d block metal described in the 4th period of a periodic table, For example, carboxylate, phosphorus, such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc And acid salts and acetylacetonate salts.

  The lower limit of the content of metal salt (content in terms of metal element based on the entire multilayer structure) is preferably 1 ppm, more preferably 5 ppm, still more preferably 10 ppm, and particularly preferably 20 ppm. On the other hand, the upper limit of the content of the metal salt is preferably 10,000 ppm, more preferably 5,000 ppm, further preferably 1,000 ppm, and particularly preferably 500 ppm. When the content of the metal salt is smaller than the above lower limit, the interlaminar adhesion is lowered, and the durability of the multilayer structure may be lowered. On the other hand, when the content of the metal salt exceeds the above upper limit, the resin composition is highly colored, and the appearance of the multilayer structure may be deteriorated.

  As a minimum of content of metal salt to each resin composition containing metal salt, 5 ppm is preferred, 10 ppm is more preferred, 20 ppm is still more preferred, and 50 ppm is especially preferred. On the other hand, the upper limit of the content of the metal salt is preferably 5,000 ppm, more preferably 1,000 ppm, still more preferably 500 ppm, and particularly preferably 300 ppm. When the content of the metal salt is smaller than the lower limit, the adhesion to the adjacent other layer is lowered, and the durability of the multilayer structure may be lowered. On the other hand, when the content of the metal salt exceeds the above upper limit, the resin composition is highly colored, and the appearance of the multilayer structure may be deteriorated.

  The method of containing this metal salt in the resin composition of the A layer or the B layer is not particularly limited, and is the same as the method of containing a phosphate compound or the like in the resin composition of the A layer as described above. The method is adopted.

<Oxygen scavenger>
The resin composition constituting the A layer and the B layer can contain various components in addition to the above metal salt and the like. Examples of such components include oxygen scavengers. This oxygen scavenger can be particularly suitably used when the resin composition constituting the B layer contains a functional group-containing resin. The oxygen scavenger can be contained in any of the resin compositions constituting the A layer and the B layer, but is preferably contained in the resin composition of the A layer.

  The oxygen scavenger is a substance having oxygen scavenging ability (oxygen absorption function). The oxygen scavenging ability refers to a function of absorbing and consuming oxygen from a given environment or reducing the amount thereof. The oxygen scavenger that can be contained in the resin composition is not particularly limited as long as it has such properties. When the resin composition contains an oxygen scavenger, oxygen scavenging ability is added, and as a result, the gas barrier property of the multilayer structure can be further improved. Various oxygen scavengers can be used, such as thermoplastic resins having oxygen scavenging ability, organic oxygen scavengers such as ascorbic acid; inorganic oxygen scavengers such as iron and sulfite Is mentioned. Of these, a thermoplastic resin having an oxygen scavenging ability is preferable from the viewpoint of high oxygen scavenging ability and easy inclusion in the resin composition of the multilayer structure.

<Thermoplastic resin with oxygen scavenging ability>
The thermoplastic resin having oxygen scavenging ability is not particularly limited as long as it is a thermoplastic resin capable of scavenging oxygen, for example, an ethylenically unsaturated hydrocarbon polymer having a carbon-carbon double bond or Examples thereof include polymer blends (excluding those having a molecular weight of 1,000 or less and having a conjugated double bond) (hereinafter, also simply referred to as “unsaturated hydrocarbon polymer”).

<Unsaturated hydrocarbon polymer>
The unsaturated hydrocarbon polymer may have a substituent or may be unsubstituted. An unsubstituted unsaturated hydrocarbon polymer is defined as any compound having at least one aliphatic carbon-carbon double bond and consisting of 100% by weight carbon and hydrogen. Substituted unsaturated hydrocarbon polymers are also defined as ethylenically unsaturated hydrocarbons having at least one aliphatic carbon-carbon double bond and consisting of about 50-99% by weight carbon and hydrogen. Preferred unsubstituted or substituted unsaturated hydrocarbon polymers are those having two or more ethylenically unsaturated groups per molecule. More preferably, it is a polymeric compound having two or more ethylenically unsaturated groups and having a weight average molecular weight equal to or greater than 1,000. The blend of ethylenically unsaturated hydrocarbon polymers can consist of a mixture of two or more substituted or unsubstituted ethylenically unsaturated hydrocarbons.

  Preferred examples of unsubstituted unsaturated hydrocarbon polymers include, but are not limited to: diene polymers such as polyisoprene, (eg trans-polyisoprene), polybutadiene (particularly 1,2- Polybutadienes, which are defined as polybutadienes having 1,2 microstructures that are 50% larger or equal), and copolymers thereof, such as styrene-butadiene. Such hydrocarbons also include: polymer compounds, such as polypentenamers, polyoctenamers, and other polymers produced by metathesis of olefins; diene oligomers such as squalene; and dicyclopentadiene, norbornadiene. , 5-ethylidene-2-norbornene, or polymers or copolymers derived from other monomers containing two or more carbon-carbon double bonds (conjugated or non-conjugated). These hydrocarbons further include carotenoids such as β-carotene.

  Preferred substituted unsaturated hydrocarbon polymers include, but are not limited to, those having an oxygen-containing moiety, such as esters, carboxylic acids, aldehydes, ethers, ketones, alcohols, peroxides, and / or hydroperoxides. . Particular examples of such hydrocarbons are condensation polymers such as polyesters derived from monomers containing carbon-carbon double bonds; unsaturated fatty acids such as oleic acid, ricinoleic acid, dehydrated ricinoleic acid, and linole Acids and their derivatives, including but not limited to esters. Such hydrocarbons include (meth) allyl (meth) acrylate.

  In the unsaturated hydrocarbon polymer, the content of carbon-carbon double bonds is preferably 0.01 to 1.0 equivalent per 100 g of polymer. By limiting the content of the double bond in the polymer to such a range, both the oxygen scavenging property and physical properties of the multilayer structure can be kept high.

  Such a polymer with reduced double bonds can be a homopolymer, a copolymer, and / or a blend of polymers. A blend of polymers is particularly desirable. Because the change in physical properties in the discontinuous phase has a relatively small impact on the overall physical properties of the blend that the continuous phase will dominate, so there is a large amount of double bonds present in the discontinuous phase. This is because it may be desirable to have a portion.

Suitable examples of homopolymers are poly (octenamer) having 0.91 equivalent double bonds per 100 g and poly (4-vinylcyclohexene) having 0.93 equivalent double bonds per 100 g. Suitable examples of copolymers _include C 1 -C ₄ alkyl acrylates and methacrylates. Other examples include 1,3-butadiene, isoprene, 5-ethylidene-2-norbornene, 4-vinylcyclohexene, 1,4-hexadiene, 1,6-octadiene and the like, and one or more vinyl monomers, For example, copolymers derived from ethylene, propylene, styrene, vinyl acetate, and / or α-olefins. Particular examples are terpolymers of ethylene, propylene and 5-ethylidene-2-norbornene. Such EPDM elastomers typically contain 3-14% by weight of 5-ethylidene-2-norbornene. Such polymers are within the requirement of 0.01 to 1.0 equivalent double bonds per 100 grams of polymer. Also suitable are partially hydrogenated ethylenically unsaturated polymers (eg, polybutadiene) having at least about 50% of the hydrogenated double bonds. There are numerous examples of blends of polymers. Particularly preferred is a blend of EPDM and 20-40% polybutadiene, EPDM and 20-40% poly (octenamer), and a 50/50 blend of polybutadiene and saturated polyolefin.

<Thermoplastic resin having a carbon-carbon double bond substantially only in the main chain>
Among such unsaturated hydrocarbon polymers, the oxygen scavenging property is very high, and from the viewpoint that it can be very easily contained in the resin composition of the multilayer structure, substantially only in the main chain. A thermoplastic resin having a carbon-carbon double bond (hereinafter also simply referred to as a “double bond-containing thermoplastic resin”) (excluding those having a molecular weight of 1,000 or less and having a conjugated double bond) is particularly preferred. Here, the thermoplastic resin “substantially having a carbon-carbon double bond only in the main chain” means that the carbon-carbon double bond present in the main chain of the thermoplastic resin is the main chain or side in the molecule. It means 90% or more of the total carbon-carbon double bonds contained in the chain. The carbon-carbon double bond present in the main chain is preferably 93% or more, more preferably 95% or more.

  Since the above double bond-containing thermoplastic resin has a carbon-carbon double bond in its molecule, it can react with oxygen efficiently, and high oxygen scavenging ability can be obtained. By including such a thermoplastic resin in the resin composition, the gas barrier property of the multilayer structure can be remarkably improved. The carbon-carbon double bond includes a conjugated double bond but does not include a multiple bond contained in an aromatic ring.

  As a minimum of content of the carbon-carbon double bond contained in the above-mentioned double bond content thermoplastic resin, 0.001 equivalent / g is preferred, 0.005 equivalent / g is more preferred, 0.01 equivalent / g Is more preferable. On the other hand, the upper limit of the carbon-carbon double bond content is preferably 0.04 equivalent / g, more preferably 0.03 equivalent / g, and still more preferably 0.02 equivalent / g. If the content of the carbon-carbon double bond is smaller than the lower limit, the resulting multilayer structure may have an insufficient oxygen scavenging function. On the other hand, when the content of the carbon-carbon double bond exceeds the above upper limit, the resin composition is highly colored, and the appearance of the resulting multilayer structure may be deteriorated.

  As described above, since the double bond-containing thermoplastic resin has a carbon-carbon double bond substantially only in the main chain, the low molecular weight decomposition accompanying the cleavage of the double bond in the side chain is caused by the reaction with oxygen. Very little generation of material. Some of the low molecular weight decomposition products are unpleasant odor substances. However, since such decomposition products are not easily generated, unpleasant odors are rarely generated. Therefore, by including such a thermoplastic resin in the resin composition, it is possible to obtain a multilayer structure having high gas barrier properties and durability, and which does not generate unpleasant odor due to oxygen scavenging. On the other hand, when a thermoplastic resin having many carbon-carbon double bonds in the side chain is used, there is no problem in terms of oxygen scavenging, but as described above, it is decomposed by cleavage of the side chain double bond. Things are generated. Therefore, an unpleasant odor is generated and the surrounding environment may be significantly impaired.

  In the above double bond-containing thermoplastic resin, when the carbon-carbon double bond in the main chain reacts with oxygen, it undergoes oxidation at the site of allyl carbon (carbon adjacent to the double bond). Is preferably not a quaternary carbon. Furthermore, since it is impossible to deny the possibility that a low molecular weight decomposition product is generated by cleavage of the main chain, the allyl carbon may be an unsubstituted carbon, that is, a methylene carbon in order to suppress this. preferable. From the above points, the double bond-containing thermoplastic resin preferably has at least one of the units represented by the following formulas (XIV) and (XV).

In the above formulas (XIV) and (XV), R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ may each independently have a hydrogen atom, an alkyl group which may have a substituent, or a substituent. It represents a good aryl group, an alkylaryl group which may have a substituent, -COOR ²⁰ , -OCOR ²¹ , a cyano group or a halogen atom. R ¹⁸ and R ¹⁹ may form a ring with a methylene group or an oxymethylene group (provided that R ¹⁸ and R ¹⁹ are both hydrogen atoms). R ²⁰ and R ²¹ represent an alkyl group which may have a substituent, an aryl group which may have a substituent, or an alkylaryl group which may have a substituent.

When R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ are alkyl groups, the number of carbon atoms is preferably 1 to 5, and when it is an aryl group, the number of carbon atoms is preferably 6 to 10; The number of carbon atoms in the case of an alkylaryl group is preferably 7-11. Specific examples of such an alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, examples of an aryl group include a phenyl group, examples of an alkylaryl group include a tolyl group, and examples of a halogen atom. Are each a chlorine atom.

  Moreover, various hydrophilic groups are mentioned as a substituent which may be contained in the double bond containing thermoplastic resin. As the hydrophilic group here, a hydroxyl group, an alkoxy group having 1 to 10 carbon atoms, an amino group, an aldehyde group, a carboxyl group, a metal carboxylate group, an epoxy group, an ester group, a carboxylic acid anhydride group, a boronic acid group, water And boron-containing groups (for example, boronic acid ester groups, boronic acid anhydride groups, boronic acid groups, etc.) that can be converted to boronic acid groups in the presence of. Among these hydrophilic groups, aldehyde group, carboxyl group, metal carboxylate group, epoxy group, ester group, carboxylic acid anhydride group, boronic acid group, containing boron that can be converted to boronic acid group in the presence of water The group is preferable in that it can react with the hydroxyl group of EVOH and the like. When the double bond-containing thermoplastic resin contains these hydrophilic groups, the thermoplastic resin becomes highly dispersible in the resin composition, and the oxygen scavenging function of the resulting multilayer structure is improved. . At the same time, this hydrophilic group reacts with a hydroxyl group or a functional group of EVOH in an adjacent layer to form a chemical bond, thereby improving interlayer adhesion and gas barrier properties of the resulting multilayer structure. Such properties and durability are further improved.

Further, among the double bond-containing thermoplastic resins, compounds in which R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ are all hydrogen atoms in the units of the above formulas (XIV) and (XV) are odorous. It is particularly preferable from the viewpoint of preventing the above. Although the reason for this is not necessarily clear, when R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ are other than hydrogen atoms, these groups are oxidized and cleaved when the thermoplastic resin reacts with oxygen. It is estimated that the odorous substance may change.

  In the double bond-containing thermoplastic resin, a unit derived from a diene compound is preferable among the units of the above formulas (XIV) and (XV). By being a unit derived from a diene compound, a thermoplastic resin having such a structural unit can be easily produced. Examples of such a diene compound include isoprene, butadiene, 2-ethylbutadiene, 2-butylbutadiene, chloroprene and the like. Only 1 type of these may be used and multiple types may be used together. Examples of the double bond-containing thermoplastic resin containing units derived from these diene compounds include polybutadiene, polyisoprene, polychloroprene, and polyoctenylene. Among these, polybutadiene and polyoctenylene are particularly preferable in that the oxygen scavenging function is particularly high. Moreover, the copolymer which contains structural units other than the said structural unit as a copolymerization component as a double bond containing thermoplastic resin can also be used. Examples of such copolymer components include styrene, acrylonitrile, and propylene. When the double bond-containing thermoplastic resin is such a copolymer, the content of the units represented by the above formulas (X) and (XI) is such that the total number of units relative to all structural units of the thermoplastic resin is 50 mol% or more is preferable and 70 mol% or more is more preferable.

  The lower limit of the number average molecular weight of the double bond-containing thermoplastic resin is preferably 1,000, more preferably 5,000, still more preferably 10,000, and particularly preferably 40,000. On the other hand, the upper limit of the number average molecular weight is preferably 500,000, more preferably 300,000, still more preferably 250,000, and particularly preferably 200,000. When the molecular weight of the double bond-containing thermoplastic resin is less than 1,000 or exceeds 500,000, the resulting multilayer structure is inferior in moldability and handling properties, and the strength and elongation of the multilayer structure are poor. The mechanical properties such as the degree may decrease. Moreover, the dispersibility in a resin composition falls, As a result, there exists a possibility that the gas barrier property and oxygen scavenging performance of a multilayered structure may fall. One type or a plurality of types of the double bond-containing thermoplastic resin can be used.

The method for producing a thermoplastic resin having a carbon-carbon double bond substantially only in the main chain as described above varies depending on the type of the thermoplastic resin. For example, polybutadiene (cis-1,4-polybutadiene) ), It can be synthesized by using a cobalt-based or nickel-based catalyst as a catalyst. Specific examples of the catalyst include, for example, a combination of CoCl ₂ .2C ₅ H ₅ N complex and diethylaluminum chloride. Usable solvents include inert organic solvents, among which hydrocarbons having 6 to 12 carbon atoms, such as alicyclic hydrocarbons such as hexane, heptane, octane, decane, or toluene, benzene Aromatic hydrocarbons such as xylene are preferred. The polymerization is usually carried out in the temperature range of -78 ° C to 70 ° C for a time range of 1 to 50 hours.

  The carbon-carbon double bonds present after the polymerization may be partially reduced by hydrogen as long as the effects of the mechanical properties, gas barrier properties, oxygen scavenging performance, etc. of the multilayer structure are not impaired. Absent. At this time, it is particularly preferable to selectively reduce the carbon-carbon double bond remaining in the side chain with hydrogen.

<Transition metal salt>
The resin composition preferably further contains a transition metal salt (excluding the metal salt) together with the unsaturated hydrocarbon polymer (including a double bond-containing thermoplastic resin). By containing such a transition metal salt together with the unsaturated hydrocarbon polymer, the oxygen scavenging function of the resulting multilayer structure is further improved, and as a result, the gas barrier property is further enhanced. This is because the transition metal salt promotes the reaction between the unsaturated hydrocarbon polymer and oxygen present in the multilayer structure or oxygen that permeates through the multilayer structure. Conceivable.

  Examples of transition metal ions constituting the transition metal salt include, but are not limited to, ions such as iron, nickel, copper, manganese, cobalt, rhodium, titanium, chromium, vanadium, and ruthenium. Among these, iron, nickel, copper, manganese or cobalt ions are preferable, manganese or cobalt ions are more preferable, and cobalt ions are particularly preferable.

  Examples of the counter anion of the transition metal ion constituting the transition metal salt include a carboxylate ion and a halogen anion. Specific examples of the counter anion include, for example, acetic acid, stearic acid, acetylacetone, dimethyldithiocarbamic acid, palmitic acid, 2-ethylhexanoic acid, neodecanoic acid, linoleic acid, toluic acid, oleic acid, resin acid, capric acid, naphthene. Examples include, but are not limited to, anions, chloride ions, and acetylacetonate ions generated by ionization of hydrogen ions from acids and the like. Specific examples of particularly preferable transition metal salts include cobalt 2-ethylhexanoate, cobalt neodecanoate, and cobalt stearate. The transition metal salt may be a so-called ionomer having a polymeric counter anion.

  As a lower limit of content of the said transition metal salt, 1 ppm is preferable with respect to a resin composition in conversion of a metal element, 5 ppm is more preferable, 10 ppm is further more preferable. On the other hand, the upper limit of the content of the transition metal salt is preferably 50,000 ppm, more preferably 10,000 ppm, and further preferably 5,000 ppm. If the content of the transition metal salt is smaller than the above lower limit, the oxygen scavenging effect of the resulting multilayer structure may be insufficient. On the other hand, when the content of the transition metal salt exceeds the above upper limit, the thermal stability of the resin composition is lowered, and there is a possibility that generation of decomposition gas and generation of gels and blisters become remarkable.

<desiccant>
A desiccant is mentioned as another component of the resin composition which comprises A layer and B layer. This desiccant can also be particularly suitably used when the resin composition constituting the B layer contains a functional group-containing resin. The desiccant can be contained in any of the resin compositions constituting the A layer and the B layer, but is preferably contained in the resin composition of the A layer.

  The desiccant is a substance that absorbs moisture and can be removed from a given environment. The desiccant that can be contained in the resin composition of the multilayer structure is not particularly limited as long as it has such properties. Since the resin composition of the resin layer is kept in a dry state by containing such a desiccant, the gas barrier property of the resin layer containing the gas barrier resin can be kept high.

  As such a desiccant, for example, hydrate-forming salts, that is, salts that absorb water as crystal water, especially phosphates, particularly anhydrides thereof are most suitable in terms of their effects, but other waters Also suitable are hydrate-forming salts such as sodium borate, sodium sulfate, etc., especially its anhydrides, and other hygroscopic compounds such as sodium chloride, sodium nitrate, sugar, silica gel, bentonite, molecular sieves, A high-grade aqueous resin or the like can also be used. These can be used alone or in combination.

  The desiccant is preferably dispersed as fine particles in a matrix of a resin layer containing a gas barrier resin. In particular, the body area average diameter of particles having a major axis of 10 μm or more is 30 μm or less, preferably 25 μm. Optimally, it is effective when the thickness is 20 μm or less, and when such a finely dispersed state is formed, a highly gas barrier multi-layer structure that has never been achieved can be obtained. A composition having such a finely dispersed state can be achieved only by carefully combining special processing methods suitable for the purpose.

  The ratio of the gas barrier resin constituting the resin layer to the desiccant is not particularly limited, but a mass ratio of 97: 3 to 50:50, particularly 95: 5 to 70:30 is preferable.

  Of the desiccant particles in the resin composition constituting the resin layer, the body area average diameter of the particles having a major axis of 10 μm or more has a great influence on the gas barrier properties of the multilayer structure including the resin composition as a layer. The reason for this is not necessarily clear, but it is presumed that particles having a large particle size have a particularly inconvenient effect on the hygroscopic effect or the gas barrier property of the gas barrier resin.

  Among the above desiccants, a phosphate capable of forming a hydrate is particularly preferable. Many phosphates form a hydrate containing a plurality of water molecules as crystal water, so that the mass of water absorbed per unit mass is large, and the contribution to the improvement of gas barrier properties of the multilayer structure is great. In addition, since the number of molecules of crystal water that can contain phosphate often increases stepwise as the humidity increases, moisture can be gradually absorbed as the humidity environment changes.

Examples of such phosphates include sodium phosphate (Na ₃ PO ₄ ), trilithium phosphate (Li ₃ PO ₄ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and sodium dihydrogen phosphate (NaH ₂ PO). ₄ ), sodium polyphosphate, lithium phosphate, dilithium hydrogen phosphate, lithium dihydrogen phosphate, lithium polyphosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium monohydrogen phosphate, polyphosphorus Potassium phosphate, calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), calcium hydrogen phosphate (CaHPO ₄ ), calcium dihydrogen phosphate (Ca (H ₂ PO ₄ ) ₂ ), calcium polyphosphate, ammonium phosphate, dihydrogen phosphate Examples include ammonium, ammonium dihydrogen phosphate, and ammonium polyphosphate. Here, the polyphosphate includes diphosphate (pyrophosphate), triphosphate (tripolyphosphate), and the like. Of these phosphates, anhydrides containing no crystallization water are preferred. Further, sodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate are preferable.

  The phosphate is usually a powder. Phosphate powders that are usually available on the market have an average particle size of 15 to 25 μm and a maximum particle size of 40 to 100 μm. If a powder containing such large particles is used, the gas barrier property of the resin layer of the multilayer structure may be insufficient. When particles larger than the thickness of the resin layer of the multilayer structure are contained, the gas barrier property may be greatly lowered. Therefore, it is preferable that the particle diameter of the phosphate powder is not more than the thickness of the resin layer of the multilayer structure.

  In other words, the phosphate powder preferably has an average particle size of 10 μm or less. The average particle size is more preferably 1 μm or less. Such an average particle diameter can be measured using a particle size analyzer by, for example, a light scattering method.

  When using a phosphate as a desiccant, it is preferable to mix | blend with a dispersing agent. By blending such a dispersant, the phosphate as a desiccant can be favorably dispersed in the resin composition containing the gas barrier resin. Examples of such a dispersant include fatty acid salts, glycerin fatty acid esters, and fatty acid amides. In addition, the glycerol ester of aromatic carboxylic acid is generally liquid at room temperature, and is not suitable for dry blending with phosphate.

  Examples of the fatty acid salt include calcium stearate, zinc stearate, magnesium stearate and the like. Examples of the glycerin fatty acid ester include glycerin monostearic acid ester and monodecanoyl octanoyl glyceride. Examples of the fatty acid amide include ethylene bis stearic acid amide.

  Among these dispersants, fatty acid salts are preferably used from the viewpoint of improving the slipperiness of the phosphate powder and preventing screen clogging of the extruder during melt kneading. Of these, calcium salts, zinc salts and the like are preferable. Further, glycerin fatty acid esters are preferably used from the viewpoint of obtaining particularly good dispersibility. Among these, glycerol mono- or di-fatty acid esters are preferable, glycerol mono-fatty acid esters are more preferable, and glycerol monostearic acid esters are particularly preferable.

  Moreover, it is preferable that these dispersing agents consist of a C8-C40 compound. By having the number of carbons in such a range, good dispersibility can be obtained. A more preferable lower limit value of the carbon number is 12, and a more preferable upper limit value of the carbon number is 30.

  The compounding quantity of a dispersing agent is 1-20 mass parts with respect to 100 mass parts of phosphates. When the content of the dispersant is less than 1 part by mass with respect to 100 parts by mass of the phosphate, the generation of phosphate aggregates cannot be suppressed. The content of the dispersant is preferably 2 parts by mass or more, and more preferably 3 parts by mass or more. On the other hand, when the content of the dispersant exceeds 20 parts by weight with respect to 100 parts by weight of the phosphate, the resin composition pellets become too slippery to feed into the extruder, and the multilayer structure. The interlaminar adhesion force during the production is reduced. The content of the dispersant is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less.

<Relationship between layer A and layer B>
In the multilayer structure, the interlayer adhesion between the adjacent A layer and B layer is preferably 450 g / 15 mm or more, more preferably 500 g / 15 mm or more, further preferably 600 g / 15 mm or more, and further preferably 700 g / 15 mm or more. 800 g / 15 mm or more is particularly preferable. Thus, by setting the interlayer adhesive force between the A layer and the B layer within the above range, the interlayer adhesive property is extremely excellent, and the characteristics such as high gas barrier properties of the multilayer structure are deformed such as stretching and bending. And has very high durability. Here, the interlayer adhesive strength between the A layer and the B layer was measured using a measurement sample having a width of 15 mm under an atmosphere of 23 ° C. and 50% RH using an autograph under a tensile speed of 250 mm / min. The value of T-type peel strength between the A layer and the B layer (unit: g / 15 mm).

  Regarding the interlayer relationship of the multilayer structure, it is preferable to positively cause a binding reaction at the interface between the A layer and the B layer. As described above, a bond formation reaction between the gas barrier resin in the resin composition of the A layer and the thermoplastic resin in the resin composition of the B layer due to the inclusion of the metal salt, such as a carbamate group of TPU or an amino group of polyamide A hydroxyl group exchange reaction that occurs between the hydroxyl group of the gas barrier resin, etc., an addition reaction of the hydroxyl group of the gas barrier resin to the residual isocyanate group in TPU, an amide formation reaction between the terminal carboxyl group of polyamide and the hydroxyl group of EVOH, In addition, higher interlayer adhesion is exhibited by causing a binding reaction or the like that occurs between the gas barrier resin and the functional group-containing resin. As a result, the gas barrier property, durability, etc. of the multilayer structure can be further improved.

<Manufacturing method of the multilayer structure>
The method for producing the multilayer structure is not particularly limited as long as the A layer and the B layer are laminated and bonded satisfactorily. For example, known methods such as co-extrusion, bonding, coating, bonding, and adhesion are known. This method can be adopted. Specifically, the method for producing the multilayer structure is as follows: (1) A layer A resin composition containing a gas barrier resin such as EVOH and a B layer resin composition containing a thermoplastic resin are used. A method for producing a multilayer structure having an A layer and a B layer by an extrusion method, and (2) a resin composition for an A layer containing a gas barrier resin such as EVOH and a resin composition for a B layer containing a thermoplastic resin. First, a laminate having a layer to be an A layer and a layer to be a B layer is manufactured by a coextrusion method, and a plurality of laminates are overlapped and stretched through an adhesive to have an A layer and a B layer. Examples thereof include a method for producing a multilayer structure. Among these, from the viewpoint of high productivity and excellent interlayer adhesion, molding is performed by a multilayer coextrusion method using a resin composition containing a gas barrier resin such as EVOH (1) and a resin composition containing a thermoplastic resin. Is preferred.

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

<Application>
As described above, the multilayer structure is excellent in melt moldability and has high gas barrier properties and durability. Therefore, the multilayer structure includes food packaging materials, medical container packaging materials, other container packaging materials, industrial sheet materials, building material sheet materials, agricultural sheet materials, other sheet materials, and other various pipes. Etc. can be used.

  Examples of food packaging materials that are used for food packaging include food and confectionery packaging bags (flexible packages), food wrap films, skin pack films, stretch films, shrink films, retort containers, and the like. Since the food packaging material provided with the multilayer structure has high gas barrier properties, stretchability, thermoformability and durability, it can improve long-term storage stability and retort resistance. It can also be used as an alternative to metal cans.

  Examples of other container packaging materials include various types of container packaging materials such as cosmetics, industrial chemicals, agricultural chemicals, fertilizers, and detergents, shopping bags, garbage bags, compost bags, bag-in-boxes, and flexible tanks.

  The bag-in-box is a container in which a foldable thin inner container is combined with an outer box such as a cardboard box having stackability, portability, inner container protection, printability and the like. The base material of the outer box may be plastic or metal in addition to corrugated paper, and the shape may be a cylindrical shape in addition to the box shape. The multilayer structure of the present invention can be suitably used for the inner container of this bag-in-box. This bag-in-box includes wine, juice, mirin, soy sauce, sauce, noodle soup, milk, mineral water, sake, shochu, coffee, tea, various cooking oils, liquid fertilizer, developer, battery fluid, etc. It can be used for transportation, storage, display, etc. of non-food such as industrial chemicals.

  A flexible tank is a container formed of a flexible base material, and has a frame that supports the container, or does not have a frame, and maintains its shape by the pressure of gas, liquid, etc. stored in the container. There is something. This flexible tank can be folded and stored compactly when not in use, and can be assembled or expanded to be used as a tank when in use. By using the multilayer structure of the present invention for the base material of this flexible tank, the durability and gas barrier properties of the flexible tank can be enhanced.

  As an industrial sheet material etc., the film for device sealing materials, a gas collection film, a bioreactor etc. can be mentioned, for example.

  As a film for device sealing materials, it is used suitably for each use as which the outstanding adhesiveness, gas barrier property, durability, etc. are requested | required, such as a back sheet for solar cells, for example.

  Examples of the gas collection film include a collection bag for exhaust gas analysis, a hydrogen collection bag in a hydrogen station of a fuel cell vehicle, a hydrogen barrier film laminated on the inner surface of a high-pressure hydrogen container of a fuel cell vehicle, and the like. .

  A bioreactor refers to an apparatus that performs a biochemical reaction using a biocatalyst. The multilayer structure of the present invention can be suitably used for a reaction tank or pipe of this bioreactor. By using the multilayer structure for a bioreactor, the gas barrier property and durability of the bioreactor are improved, and the thermoformability is also excellent.

  Examples of the building material sheet material include a vacuum heat insulating plate and wallpaper. A vacuum heat insulating plate provided with the multilayer structure of the present invention has high gas barrier properties and can exhibit excellent vacuum holding ability. In addition, the wallpaper provided with the multilayer structure of the present invention is excellent in stretchability and thermoformability, so that productivity and workability are improved, and since it is excellent in durability, it can be used for a long time. .

  As an agricultural sheet material, the film for agricultural fumigation, the film for greenhouses, etc. can be mentioned, for example. When the multilayer structure of the present invention is used as, for example, a multi-film for agricultural fumigation, the gas barrier property is high, so that fumigation can be performed efficiently, and because it is excellent in durability, it is difficult to break and workability is improved. improves.

  Other sheet materials can be used as, for example, geomembranes, radon barrier films, and the like. A geomembrane is a sheet used as a water-impervious work in a waste disposal site or the like. The radon barrier film is a film for preventing diffusion of gaseous radon generated by uranium collapse in a uranium waste treatment plant. Since the multilayer structure of the present invention is excellent in gas barrier properties and durability as described above, it can be suitably used for these applications.

  Note that the classification of each application described above is based on general use, and each product is not limited to the application in the field. For example, the vacuum heat insulating plate can be used for industrial sheet materials as well as for building material sheet materials.

  The multilayer structure of the present invention is not limited to the above embodiment. For example, other layers may be included in addition to the A layer and the B layer. Although the kind of resin composition which comprises this other layer is not specifically limited, A thing with high adhesiveness between A layer and / or B layer is preferable. Other layers include functional groups that react with hydroxyl groups of the gas barrier resin in layer A and functional groups in layer B (for example, carbamate groups or isocyanate groups in the molecular chain of TPU) to form bonds. Those having a molecular chain having the formula are particularly preferred.

  In the multilayer structure of the present invention, support layers may be laminated on both sides or one side of the laminate of the above-described eight or more resin layers. The support layer is not particularly limited and may not be a resin layer. For example, a general synthetic resin layer, a synthetic resin film, or the like is also used. The means for laminating the support layer is not particularly limited, and adhesion with an adhesive, extrusion lamination, or the like is employed.

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

(Production Example 1 [Production of EVOH1])
In a polymerization tank having a cooling device and a stirrer, 20,000 parts by weight of vinyl acetate, 1020 parts by weight of methanol, and 3.5 parts of 2,2′-azobis- (4-methoxy-2,4-dimethylvaleronitrile) as a polymerization initiator. The mixture was charged with nitrogen and stirred, and then ethylene was introduced, the internal temperature was adjusted to 60 ° C., the ethylene pressure was adjusted to 59 kg / cm ² , and the temperature and pressure were maintained and stirred for 4 hours for polymerization. Next, 10 parts by mass of sorbic acid (SA) (0.05% by mass with respect to the charged vinyl acetate) was dissolved in methanol and added as a 1.5% by mass solution. The polymerization rate was 30% based on the charged vinyl acetate. This copolymerization reaction liquid was supplied to the purge and unreacted vinyl acetate was removed from the top of the tower by introducing methanol vapor from the bottom of the tower, and a 40 mass% methanol solution of this copolymer was obtained. This copolymer had an ethylene unit content of 44.5 mol% and a vinyl acetate unit content of 55.5 mol%.

This methanol solution of the copolymer was introduced into a saponification reactor, and then a sodium hydroxide / methanol solution (85 g / L) was added so as to be 0.5 equivalent to the vinyl acetate component in the copolymer. Further, methanol was added to adjust the copolymer concentration 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 was stopped by neutralization with acetic acid, and the contents were taken out from the reactor and left at room temperature to precipitate in the form of particles. EVOH1 (density: 1.19 g / cm ³ ) having a saponification degree of 99.5% was obtained by repeating the operation of draining the precipitated particles with a centrifuge and further adding a large amount of water to remove the liquid. The melting point of EVOH1 was 165 ° C.

(Production Example 2 [Production of EVOH2])
In a polymerization tank having a cooling device and a stirrer, 20,000 parts by weight of vinyl acetate, 1020 parts by weight of methanol, and 3.5 parts of 2,2′-azobis- (4-methoxy-2,4-dimethylvaleronitrile) as a polymerization initiator. The mixture was charged with nitrogen and stirred, and then ethylene was introduced, the internal temperature was adjusted to 60 ° C., the ethylene pressure was adjusted to 59 kg / cm ² , and the temperature and pressure were maintained and stirred for 4 hours for polymerization. Next, 10 parts by mass of sorbic acid (SA) (0.05% by mass with respect to the charged vinyl acetate) was dissolved in methanol and added as a 1.5% by mass solution. The polymerization rate was 30% based on the charged vinyl acetate. This copolymerization reaction liquid was supplied to the purge and unreacted vinyl acetate was removed from the top of the tower by introducing methanol vapor from the bottom of the tower, and a 40 mass% methanol solution of this copolymer was obtained. This copolymer had an ethylene unit content of 44.5 mol% and a vinyl acetate unit content of 55.5 mol%.

  This methanol solution of the copolymer was introduced into a saponification reactor, and then a sodium hydroxide / methanol solution (85 g / L) was added so as to be 0.5 equivalent to the vinyl acetate component in the copolymer. Further, methanol was added to adjust the copolymer concentration 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 was stopped by neutralization with acetic acid, and the contents were taken out from the reactor and left at room temperature to precipitate in the form of particles. The precipitated particles were removed by a centrifuge, and a large amount of water was further added to remove the solution, thereby obtaining EVOH having a saponification degree of 99.5%.

Using EVOH obtained as described above, using a twin screw extruder “TEM-35BS” (37 mmφ, L / D = 52.5) manufactured by Toshiba Machine Co. Then, unreacted epoxypropane is removed from the vent, and then a 8.2% by mass ethylenediaminetetraacetic acid trisodium hydrate aqueous solution is added as a catalyst deactivator, pelletized, and then dried. As a structural unit (II) other than the ethylene unit and the vinyl alcohol unit, an epoxypropane-modified ethylene-vinyl alcohol copolymer EVOH2 (density: 1.13 g / cm ³ ) having the following structure was obtained.

Cylinder and die temperature settings:
Resin feed port / cylinder unit inlet / adapter / die = 160/200/240/240 (° C.)
Screw rotation speed: 400rpm
Ethylene-vinyl alcohol copolymer feed amount: 16 kg / hr
Epoxypropane feed rate: 2.4 kg / hr (feed pressure 6 MPa)
Catalyst solution feed rate: 0.32 kg / hr
Catalyst adjustment: 28 parts by mass of zinc acetylacetonate monohydrate was mixed with 957 parts by mass of 1,2-dimethoxyethane to obtain a mixed solution. To the obtained mixed solution, 15 parts by mass of trifluoromethanesulfonic acid was added with stirring to obtain a catalyst solution. That is, a solution in which 1 mol of trifluoromethanesulfonic acid was mixed with 1 mol of zinc acetylacetonate monohydrate was prepared.
Catalyst deactivator aqueous solution feed rate: 0.16 kg / hr

The introduction amount (epoxybutane modification amount) of the structural unit (II) other than the ethylene unit and vinyl alcohol unit of the obtained EVOH2 is from the measurement of ¹ H-NMR (internal standard substance: tetramethylsilane, solvent: d6-DMSO). It was 5.8 mol%. The EVOH2 had a melting point of 106 ° C.

In the following Production Examples 3 to 6, the outflow start temperature and melt viscosity of the obtained TPU were measured according to the method described below.
(Outflow start temperature)
The polymer outflow rate was measured at 3 ° C. intervals by a temperature rising method using a Koka flow tester (nozzle: hole diameter 1 mm, hole length 10 mm; load: 100 kgf; temperature rising rate: 5 ° C./min). Plotting was performed with respect to the temperature in the range of 1 × 10 ^{−3 to} 5 × 10 ⁻³ ml / sec, and the temperature at which the outflow rate was 0 ml / sec was obtained by extrapolation, which was used as the outflow start temperature.

(Melt viscosity)
Using a Koka type flow tester (manufactured by Shimadzu Corporation), the melt viscosity of TPU that was dried under reduced pressure at 80 ° C. for 2 hours (1.3 × 10 ³ Pa [10 Torr] or less) with a load of 490.3 N (50 kgf) ), Nozzle dimensions = diameter 1 mm × length 10 mm, measured at a temperature of 200 ° C.

(Production Example 3 TPU1)
Polytetramethylene ether glycol (PTMEG), 1,4-butanediol (1,4-BD) and 4,4′-diphenylmethane diisocyanate (MDI) having a number average molecular weight of 1000 are converted to PTMEG: 1,4-BD: A twin screw extruder (30 mmφ, L / D) rotating in the same direction with a molar ratio of MDI = 1.0: 1.2: 2.2 and a total feed rate of 200 g / min. = 36; The heating zone was continuously fed to the front part of the heating zone (divided into three zones, the front part, the central part and the rear part), and continuous melt polymerization was carried out at 260 ° C. The obtained melt was continuously extruded into water in a strand form, then cut with a pelletizer, and the obtained pellets were dehumidified and dried at 60 ° C. for 12 hours to produce TPU1. The obtained TPU1 had a melt viscosity of 1080 Pa · s and an outflow start temperature of 171 ° C.

(Production Example 4 TPU2)
TPU2 was produced in the same manner as in Production Example 3 except that the thermoplastic polyurethane composition of Production Example 3 was changed to PTMEG: 1,4-BD: MDI = 1.0: 1.4: 2.4. . The obtained TPU2 had a melt viscosity of 3210 Pa · s and an outflow start temperature of 185 ° C.

(Production Example 5 TPU3)
TPU3 was produced in the same manner as in Production Example 3 except that the thermoplastic polyurethane composition of Production Example 3 was changed to PTMEG: 1,4-BD: MDI = 1.0: 0.6: 1.6. . The obtained TPU3 had a melt viscosity of 1115 Pa · s and an outflow start temperature of 145 ° C.

(Production Example 6 TPU4)
TPU4 was produced in the same manner as in Production Example 3 except that the thermoplastic polyurethane composition of Production Example 3 was changed to PTMEG: 1,4-BD: MDI = 1.0: 0.4: 1.4. . The obtained TPU4 had a melt viscosity of 1043 Pa · s and an outflow start temperature of 123 ° C.

(Production Example 7 [Production of PA6])
A 30 L pressure-resistant reactor was charged with ε-caprolactam (10 kg) as a polyamide monomer, 1,6-hexanediamine (82 g) and water (1.0 kg) as a molecular weight regulator, and heated to 260 ° C. with stirring to 0.5 MPa. The pressure was increased to Thereafter, the pressure was released to normal pressure, and polymerization was carried out at 260 ° C. for 3 hours. When the polymerization was completed, the reaction product was discharged in a strand form, cooled, solidified, and then cut into nylon 6 resin pellets. The obtained pellets were treated with hot water at 95 ° C. and dried to obtain nylon 6 (PA6) as polyamide. The melting point of PA6 obtained was 225 ° C.

(Production Example 8 [Production of MAh-PE])
MFR is 2.4 g / 10 min (190 ° C., under 2,160 g load), 100 parts by mass of low density polyethylene having a density of 0.92 g / cm ³ , 12 parts by mass of maleic anhydride, and 330 parts by mass of t-butylbenzene are mixed. Then, after making the nitrogen atmosphere, low density polyethylene was dissolved at 160 ° C. After dissolution, a mixture of 1.7 parts by mass of di-t-butyl peroxide and 17 parts by mass of t-butylbenzene was added with stirring and reacted for 2 hours. Next, the reaction solution was taken out and stirred at room temperature to precipitate the resin as a powder. The obtained powder was washed with acetone and then vacuum-dried to obtain white powder of maleic anhydride-modified low density polyethylene MAh-PE. The melting point of the obtained MAh-PE was 105 ° C.

[Example 1]
A multilayer structure of multilayer structure / TPU (inner layer) in which TPU1 (outer layer) / 9 layers of EVOH1 (A layer) and 8 layers of TPU1 (B layer) are alternately laminated was manufactured by the following method. In a 19-layer feed block, each resin was supplied to a co-extruder in a molten state at 190 ° C., and co-extrusion was performed to join the multilayer structure. The melt of EVOH1 and TPU1 to be merged has a uniform thickness of each layer of the extruded multilayer structure by changing each layer flow path so that it gradually increases from the surface side to the center side in the feed block. Extruded to become. In addition, the slit shape was designed so that the layer thicknesses of the adjacent A layer and B layer were substantially the same. The thus obtained laminate consisting of a total of 19 layers was rapidly cooled and solidified on a casting drum which was kept at a surface temperature of 25 ° C. and electrostatically applied. The cast film obtained by rapid cooling and solidification was pressure-bonded onto a release paper and wound up. The flow path shape and the total discharge amount were set so that the time from when the melt of EVOH1 and TPU1 merged to when rapidly solidified on the casting drum was about 4 minutes.

  The cast film obtained as described above was subjected to cross-sectional observation with DIGITAL MICROSCOPE VHX-900 (manufactured by KEYENCE). As a result, the average thickness of each of the A layer and the B layer was 1 μm, and the average thickness of the outer layer and the inner layer was 26 μm. It was a multilayer structure. In addition, each thickness was made into the average value of the measured value in 9 points | pieces selected at random.

[Examples 2 to 14, Comparative Example 1]
Example 1 except that the resins listed in Table 1 were employed, the thicknesses of the A layer and B layer listed in Table 1 were obtained, and the coextrusion was performed at the melting temperature listed in Table 1. In the same manner as described above, multilayer structures according to these examples and comparative examples were produced. In Examples 11 and 12, PEBAX MP1878 (melting point: 195 ° C.) manufactured by Arkema was used as the polyamide-based elastomer (PA Elas). In Examples 13 and 14, 20% by mass of Asahi Kasei's Tuftec M1911 (maleic anhydride-modified product) mixed with Asahi Kasei's Tuftec H1041X (unmodified product) as a styrene-based elastomer (St Elas) (outflow start temperature) : 180 ° C.).

  In Table 1, the extensional viscosity at an extension rate of 500 (1 / sec) of each resin (resin composition) forming the A layer and the B layer is shown together with the measurement temperature (melting temperature at the time of coextrusion). The extensional viscosity was measured using a Capillograph 1D type manufactured by Toyo Seiki Co., Ltd.

(Evaluation method of multilayer structure)
Each characteristic of the multilayer structure obtained in Examples 1 to 14 and Comparative Example 1 was evaluated according to the method described below. The evaluation results of these characteristics are shown in Table 1.

(1) Appearance of multilayer structure (evaluation of melt moldability)
The presence or absence of flow spots, streaks, and fish eyes in the obtained multilayer structure was visually confirmed. The appearance of the multilayer structure was judged according to the following criteria.
A: No spots, streaks or fish eyes were found.
○: Flow spots, streaks, and fish eyes were present but were few.
Δ: Flow spots, streaks, and fish eyes were conspicuous.
X: Flow spots and streaks were remarkable, and many fish eyes were present.

(2) Oxygen permeation rate of multilayer structure (evaluation of gas barrier properties)
The obtained multilayer structure was conditioned at 20 ° C.-65% RH for 5 days, and two samples of the multilayer structure having been conditioned were used to make MOCON OX-TRAN 2/20 type manufactured by Modern Control. The oxygen permeation rate was measured according to the method described in JIS-K7126 (isobaric method) under 20 ° C.-65% RH condition, and the average value was determined (unit: mL · 20 μm / m ² · day.atm).

(3) Oxygen permeation rate after bending of multilayer structure (evaluation of gas barrier property after bending)
In accordance with ASTM-F392-74, a “Gelbo Flex Tester” manufactured by Rigaku Corporation was used, and bending was repeated 5,000 times. Then, the oxygen transmission rate of the multilayer structure was measured in the same manner as described above.

  From the results shown in Table 1, each multilayer structure of the examples is excellent in appearance (melt moldability) because a resin composition having an appropriate extensional viscosity and its ratio is used for the A layer and the B layer. It can be seen that the gas barrier property and the gas barrier property after bending are excellent.

As described above, the multilayer structure of the present invention can be suitably used for food packaging materials, various containers, and the like because properties such as high gas barrier properties are maintained even against deformation such as stretching and bending.

Claims (16)

A multilayer structure comprising eight or more resin layers,
As this resin layer, it has A layer which consists of a resin composition containing gas barrier resin, and B layer which consists of a resin composition which contains this thermoplastic resin different from the above-mentioned gas barrier resin adjacent to this A layer,
The average thickness of one layer of the A layer and the B layer is 0.01 μm or more and 10 μm or less,
Or less of the extensional viscosity eta _B of the resin composition of the extensional viscosity eta _A and B layer of the resin composition of the layer A in the measurement conditions are both 1,000 Pa · s or more, and the elongation viscosity ratio eta _A / Η _B is 0.02 or more and 50 or less.
(Measurement condition)
Temperature: a temperature that is 25 ° C. higher than the melting point of the melting point of the resin composition of the A layer and the melting point of the resin composition of the B layer (the outflow start temperature for a resin composition having no melting point) Elongation rate: 500 (1 / sec )   The multilayer structure according to claim 1, wherein the A layer and the B layer are alternately laminated. The product η _A · T _A of the extension viscosity η _A of the resin composition of the layer _A and the average thickness T _{A of} this layer, and the extension viscosity η _B of the resin composition of the layer _B and the average thickness T _{B of} this layer The multilayer structure according to claim 1, wherein the product η _B · T _B is 500 Pa · s · μm or more and 500,000 Pa · s · µm or less. 4. The multilayer structure according to claim 3, wherein a ratio (η _A · T _A ) / (η _B · T _B ) of the product η _A · T _A and η _B · T _B is 0.01 or more and 100 or less.   The multilayer structure according to any one of claims 1 to 4, wherein the thickness is 0.1 µm or more and 1,000 µm or less.   The multilayer structure according to any one of claims 1 to 5, wherein the gas barrier resin is an ethylene-vinyl alcohol copolymer.   The multilayer structure according to claim 6, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer is 3 mol% or more and 70 mol% or less.   The multilayer structure according to claim 6 or 7, wherein the saponification degree of the ethylene-vinyl alcohol copolymer is 80 mol% or more. The ethylene-vinyl alcohol copolymer has at least one selected from the group consisting of the following structural units (I) and (II),
The multilayer structure according to claim 6, 7 or 8, wherein the content of these structural units (I) or (II) is from 0.5 mol% to 30 mol% with respect to all structural units.

(In 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, or carbon. the number represents the 6-10 aromatic hydrocarbon group or a hydroxyl group. ^Further, R 1, which may be a pair is bound of ^{R 2} and ^{R 3 (where,} of R 1, ^{R 2} and ^{R 3} Except when the pair is a hydrogen atom.) 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. May have a hydroxyl group, a carboxyl group or a halogen atom.
In formula (II), R ⁴ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 10 carbon atoms. Represents an aromatic hydrocarbon group or a hydroxyl group having 6 to 10 carbon atoms. R ⁴ and R ⁵ or R ⁶ and R ⁷ may be bonded (except when R ⁴ and R ⁵ or R ⁶ and R ⁷ 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 is a hydroxyl group, an alkoxy group, a carboxyl group, or a halogen atom. You may have an atom. )   2. The thermoplastic resin is at least one resin selected from the group consisting of thermoplastic polyurethane, polyamide, a resin having a functional group capable of reacting with a group of the gas barrier resin, and an elastomer. The multilayer structure according to claim 9.   The multilayer structure according to claim 10, wherein the thermoplastic resin includes a polyamide, and the polyamide is a polyamide-based elastomer made of a block copolymer having nylon as a hard segment.   The multilayer structure according to claim 11, wherein the hard segment of the polyamide-based elastomer is made of nylon 6. The thermoplastic resin includes a resin having a functional group in the molecule that can react with a group of the gas barrier resin,
This resin is selected from the group consisting of carboxylic acid-modified polyolefins and metal salts thereof, thermoplastic resins having boron-containing groups that can be converted to boronic acid groups in the presence of boronic acid groups or water, and vinyl ester copolymers. The multilayer structure according to claim 10, which is at least one kind of resin. The thermoplastic resin includes an elastomer,
The multilayer structure according to claim 10, wherein the elastomer is a styrene-based elastomer having a functional group capable of reacting with a group of the gas barrier resin in a molecule.   The multilayer structure according to any one of claims 1 to 14, wherein a binding reaction occurs at an interface between the A layer and the B layer. A method for producing a multilayer structure according to any one of claims 1 to 15,
A method for producing a multilayer structure comprising molding by a multilayer coextrusion method using a resin composition containing a gas barrier resin and a resin composition containing a thermoplastic resin.