Coating agent and multilayer structure using same

Abstract

The present invention provides a coating agent which contains a modified ethylene-vinyl alcohol copolymer (A), wherein: the modified ethylene-vinyl alcohol copolymer (A) comprises structural units (Ia), (Ib) and (Ic) represented by the specific formulae; the respective content ratios a, b and c (% by mole) of the structural units (Ia), (Ib) and (Ic) satisfy formulae (1) to (3); and the degree of saponification (DS), as expressed by formula (4), of the modified ethylene-vinyl alcohol copolymer (A) is 90% by mole or more. A solution of this coating agent exhibits excellent storage stability; and a coating film obtained by applying this coating agent has good appearance and good gas barrier properties. (1): 21 ≤ a ≤ 55 (2): 0.1 ≤ c ≤ 10 (3): (100 - (a + c)) × 0.9 ≤ b ≤ (100 - (a + c)) (4): DS = ((total number of moles of hydrogen atoms from among X, Y and Z) / (total number of moles of X, Y and Z)) × 100

Description

Coating agent and multilayer structure using the same

[0001] The present invention relates to a coating agent containing a modified ethylene-vinyl alcohol copolymer and a multilayer structure using the same.

[0002] Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as EVOH) has excellent gas barrier properties, oil resistance, and solvent resistance, and is suitable for use in packaging materials, films, sheets, containers, and the like in various packaging fields. EVOH is often used as one layer of a multilayer structure, and in such cases, an EVOH film is formed by coating with an EVOH solution. In recent social trends aiming for a circular economy, over-packaging, which imparts more functionality than necessary to packaging materials, is avoided. From the perspective of imparting the minimum necessary functionality to packaging materials, precise thickness control technology for the EVOH layer is required. Recycling packaging materials and reusing them as packaging materials also contributes to a circular economy. For example, while EVOH does not adversely affect recyclability even when mixed in small amounts with polyolefin resins, recyclability deteriorates as the proportion of EVOH in the packaging material increases. Therefore, there is a demand for EVOH that exhibits high gas barrier properties even in small amounts.

[0003] Generally, aqueous alcohol is used as a solvent for EVOH solutions (see Patent Document 1). EVOH solutions used for coating typically require long-term storage at room temperature, but the storage temperature often changes between day and night. However, conventional EVOH solutions have poor storage stability, particularly at low temperatures, and tend to gel. Therefore, they must be stored at temperatures above 50°C or must be redissolved by heating before coating. If the EVOH in the solution whitens due to aggregation or other factors during storage, the EVOH coating obtained by coating becomes uneven in thickness. Since uneven thickness of the EVOH coating leads to a decrease in the gas barrier properties of the packaging material, it has been necessary to control the coating thickness to a greater than necessary. Furthermore, when coating an EVOH solution, depending on the drying conditions, the coating may become white or cloudy, requiring strict condition control to prevent this.

[0004] Previous studies have been conducted to solve the above problems, and it has been reported that a hydrous alcohol solution of EVOH modified with vinylpyrrolidone has excellent storage stability (Patent Document 2). It has also been reported that a hydrous alcohol solution of EVOH containing boric acid and a hydrous alcohol solution of EVOH containing an ether group also have excellent storage stability (Patent Documents 3 and 4).

[0005] Furthermore, it is important to impart gas barrier properties to paper packaging in order to prevent the oxidative deterioration of the contents. To this end, it has been proposed to laminate a gas barrier layer on paper, consisting of a first layer containing an ethylene-modified polyvinyl alcohol resin and an inorganic layered compound and a second layer made of ethylene-modified polyvinyl alcohol (Patent Document 5). Furthermore, sterilization technology is also used in combination to extend the shelf life of the contents. Retort paper cups have been proposed as a paper barrier packaging material suitable for retort sterilization technology (Patent Document 6).

[0006] Japanese Patent Publication No. 47-48489 Japanese Patent Laid-Open No. 63-139954 Japanese Patent Laid-Open No. 2-47144 Japanese Patent Laid-Open No. 2004-161854 Japanese Patent Laid-Open No. 2009-184138 Japanese Patent Laid-Open No. 2014-5031

[0007] However, although the methods described in Patent Documents 2 to 4 improve the storage stability of the solution, the effect is not necessarily sufficient. Therefore, there is a demand for an EVOH solution with even better storage stability and a coating agent containing the same. There is also a demand for achieving both such storage stability and the gas barrier properties of the EVOH coating film formed after coating.

[0008] Furthermore, it has been found that although a laminate containing an ethylene-modified polyvinyl alcohol resin as described in Patent Document 5 has excellent gas barrier properties, cracks may occur in packages having sharp bends, which may deteriorate the storage stability of the contents, and there is room for improvement.

[0009] The present invention has been made in view of the above-mentioned problems, and aims to provide a coating agent that has good solution storage stability and that provides a coating film with good appearance and gas barrier properties upon application. It also aims to provide a multilayer structure using such a coating agent. It is still another aim to provide a multilayer structure that has good gas barrier properties despite using a paper substrate and can maintain good gas barrier properties even after bending.

[0010] As a result of extensive research, the present inventors have found that the use of a coating agent containing a specific modified ethylene-vinyl alcohol copolymer can improve the storage stability of a solution, and that application of the coating agent can provide a coating film with good appearance and gas barrier properties. Based on this finding, further research has led to the present invention.

[0011] The above-mentioned problems are solved by providing a coating agent containing a modified ethylene-vinyl alcohol copolymer (A), wherein the modified ethylene-vinyl alcohol copolymer (A) contains structural units (Ia), (Ib), and (Ic) represented by the following formulas, the contents (mol %) a, b, and c of the structural units (Ia), (Ib), and (Ic) satisfy the following formulas (1) to (3), and the degree of saponification (DS) of the modified ethylene-vinyl alcohol copolymer (A), represented by the following formula (4), is 90 mol % or more. 21≦a≦55 (1) 0.1≦c≦10 (2) [100-(a+c)]×0.9≦b≦[100-(a+c)] (3) DS=[(total number of moles of hydrogen atoms among X, Y, and Z) / (total number of moles of X, Y, and Z)]×100 (4) [wherein a, b, and c are the content (mol %) of each structural unit relative to 100 mol % of the total of all structural units, and W is a methyl group or R ２ -OY, where X, Y, and Z each independently represent a hydrogen atom, a formyl group, or an alkanoyl group having 2 to 10 carbon atoms; R １ represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms. The alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. R２ represents an alkylene group having 1 to 9 carbon atoms or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. * represents a bonding site.]

[0012] In this case, in the structural unit (Ic), W is R ２ is a group represented by —OY, and R １ is a single bond, and R ２ is a methylene group, and Y and Z are hydrogen atoms. It is also preferable that the modified ethylene-vinyl alcohol copolymer (A) has a degree of saponification (DS) of 99 mol% or more. It is also preferable that the content of the modified ethylene-vinyl alcohol copolymer (A) in the coating agent is 1 to 50% by weight.

[0013] It is also preferable that the coating agent contains an ethylene-vinyl alcohol copolymer (B) other than the modified ethylene-vinyl alcohol copolymer (A), and that the ethylene content of the ethylene-vinyl alcohol copolymer (B) is 21 to 55 mol%. It is also preferable that the total content of the modified ethylene-vinyl alcohol copolymer (A) and the ethylene-vinyl alcohol copolymer (B) in the coating agent is 1 to 50 wt%. It is also preferable that the coating agent contains 10 to 10,000 ppm of inorganic fine particles having an average particle size of 0.1 to 10 μm. It is also preferable that the inorganic fine particles are amorphous silica.

[0014] It is preferable that the coating agent contains a solvent, and the solvent is a mixed solvent of alcohol and water. In this case, the light transmittance T of the coating agent at a wavelength of 800 nm and an optical path length of 1 cm after storage at 20° C. for 7 days is ７ (%) and the light transmittance T of the coating agent at a wavelength of 800 nm with an optical path length of 1 cm before storage. ０ (%) difference (T ０ -T ７ It is more preferable that the change in the solution viscosity after storage of the coating agent at 20°C for one week is within 50% of that before storage.

[0015] A preferred embodiment of the present invention is a multilayer structure obtained by applying the above coating agent onto a substrate.

[0016] A multilayer structure comprising a layer coated with the coating agent and a paper layer is also a preferred embodiment of the present invention. In this case, the basis weight of the paper layer is 15 to 800 g / m ２ It is more preferable that the modified ethylene-vinyl alcohol copolymer (A) contains alkali metal ions and that the content thereof is 2.5 to 22 μmol / g. It is also more preferable that the oxygen permeability of the multilayer structure measured in accordance with JIS-K7126-2 (2006) Part 2 (Isobaric Method) under conditions of 20°C and 65% RH is 20 cc / (m ２ It is more preferable that the heat seal strength of the multilayer structure measured in accordance with JIS Z 0238 over a width of 15 mm is 300 gf / 15 mm or more.

[0017] It is also more preferable that the multilayer structure further includes an intermediate layer and a sealant layer. It is even more preferable that the intermediate layer includes a thermosetting resin or a thermoplastic resin (f). It is even more preferable that the sealant layer includes a thermoplastic resin (g). It is particularly preferable that the thermoplastic resin (f) and the thermoplastic resin (g) include at least one selected from the group consisting of polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

[0018] It is also more preferable that the weight M1 of the paper layer and the total weight M2 of the other layers satisfy the following formula (5): 1≦M1 / M2≦300 (5)

[0019] A preferred embodiment of the multilayer structure is a package including the multilayer structure and having one or more folds. In this case, it is more preferred that the contents of the package are food, and that the water activity of the food is 0.10 to 0.94.

[0020] According to the present invention, a coating agent is provided that has excellent solution storage stability and that produces a coating film with good appearance and gas barrier properties. A multilayer structure obtained by applying such a coating agent to a substrate has good appearance and gas barrier properties. Furthermore, a multilayer structure including a layer coated with such a coating agent and a paper layer has good gas barrier properties despite using a paper substrate (paper layer), and maintains good gas barrier properties even after bending.

[0021] FIG. 1 is a diagram showing an example of a vertical form fill seal pouch including a multilayer structure of the present invention.

[0022] The following describes an example of an embodiment of the present invention (hereinafter, sometimes referred to as "this embodiment"). However, the embodiment shown below is an example for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following description. Furthermore, although preferred embodiments are shown in this specification, a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters shown as numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. In this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less."

[0023] [Modified ethylene-vinyl alcohol copolymer (A)] The modified ethylene-vinyl alcohol copolymer (A) used in the coating agent of the present invention contains structural units (Ia), (Ib), and (Ic) represented by the following formulas: Hereinafter, the modified ethylene-vinyl alcohol copolymer (A) may be abbreviated as modified EVOH (A).

[0024]

[0025] In the above formula, a, b, and c represent the content (mol %) of each monomer unit relative to the total of all monomer units (100 mol %), W represents a methyl group or R ２ X, Y, and Z each independently represent a hydrogen atom, a formyl group, or an alkanoyl group having 2 to 10 carbon atoms; R １represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms. The alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. R ２ represents an alkylene group having 1 to 9 carbon atoms or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. * represents a bonding site.

[0026] In the present invention, the modified EVOH (A) contains the structural units (Ia), (Ib), and (Ic) represented by the above formula, and the contents (mol %) a, b, and c of the structural units (Ia), (Ib), and (Ic) satisfy the following formulas (1) to (3): 21≦a≦55 (1) 0.1≦c≦10 (2) [100-(a+c)]×0.9≦b≦[100-(a+c)] (3)

[0027] In the present invention, the degree of saponification (DS) of the modified EVOH (A) is expressed by the following formula (4), and the degree of saponification (DS) is 90 mol% or more: DS = [(total number of moles of X, Y, and Z that are hydrogen atoms) / (total number of moles of X, Y, and Z)] × 100 (4).

[0028] The modified EVOH (A) used in the present invention contains, in addition to ethylene units and vinyl alcohol units, units having a quaternary carbon in the main chain. The quaternary carbon in the main chain has the effect of preventing crystallization due to steric hindrance and also functions to enhance solution stability. Furthermore, since the modified EVOH (A) contains primary hydroxyl groups, it exhibits high gas barrier properties due to strong hydrogen bonding. Therefore, by using a coating agent containing modified EVOH (A), it is possible to improve the gas barrier properties of the coating film formed after application while maintaining high solution stability.

[0029] In the structural unit (Ic), R １ represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. １is preferably a single bond. The number of carbon atoms in the alkylene group is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less. The number of carbon atoms in the alkyleneoxy group is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less.

[0030] In the structural unit (Ic), W is a methyl group or R ２ -OY, and Y and Z each independently represent a hydrogen atom, a formyl group, or an alkanoyl group having 2 to 10 carbon atoms. From the viewpoint of further improving the solution stability and gas barrier properties, W is preferably a methyl group or R ２ It is preferable that Y is a group represented by —OH (i.e., Y is a hydrogen atom), and W is R ２ It is more preferable that R is a group represented by —OH (i.e., Y is a hydrogen atom) and Z is a hydrogen atom. ２ Among the groups represented by —OH, R ２ is preferably an alkylene group, more preferably an ethylene group or a methylene group, and even more preferably a methylene group.

[0031] In the structural unit (Ic), R ２ represents an alkylene group having 1 to 9 carbon atoms or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. ２ is preferably the alkylene group. The number of carbon atoms in the alkylene group is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less. The number of carbon atoms in the alkyleneoxy group is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less. In the structural unit (Ic), when W is R ２ is a group represented by —OY, and R １ is a single bond, and R ２ is preferably a methylene group, and Y and Z are preferably hydrogen atoms.

[0032] In the structural units (Ib) and (Ic), when X, Y, or Z is a hydrogen atom, the modified EVOH (A) has a hydroxyl group, and when X, Y, or Z is a formyl group or an alkanoyl group, the modified EVOH (A) has an ester group. The alkanoyl group is preferably an alkanoyl group having 2 to 5 carbon atoms, more preferably an acetyl group, a propanoyl group, or a butanoyl group, and even more preferably an acetyl group. It is preferable that X, Y, and Z are all hydrogen atoms or a mixture containing hydrogen atoms.

[0033] Examples of the structural unit (Ic) include structural units (IIc) and (IIIc) represented by the following formulae, with the structural unit (IIc) being preferred.

[0034]

[0035] In the structural unit (IIc), R ３ and R ４ each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and the alkyl group may contain a hydroxyl group, an alkoxy group, or a halogen atom.

[0036]

[0037] In the present invention, in order to improve the gas barrier property, R ３ and R ４ is preferably a hydrogen atom.

[0038] In modified EVOH (A), a represents the content (mol %) of (Ia) relative to all monomer units, and the content a of (Ia) is 21 to 55 mol % (Equation (1)). If the content a is less than 21 mol %, the thermal stability decreases when melt-kneaded and recycled, making gels and particles more likely to occur. The content a is preferably 26 mol % or more, and more preferably 30 mol % or more. On the other hand, if the content a exceeds 55 mol %, the gas barrier properties of modified EVOH (A) under low humidity conditions (e.g., humidity of 65%) become insufficient. The content a is preferably 52 mol % or less, and more preferably 46 mol % or less.

[0039] In modified EVOH (A), c represents the content (mol %) of (Ic) relative to all monomer units, and is 0.1 to 10 mol % (Equation (2)). If the content c is less than 0.1 mol %, the solution stability of modified EVOH (A) will be insufficient. The content c is preferably 0.3 mol % or more, more preferably 0.5 mol % or more, even more preferably 0.8 mol % or more, particularly preferably 1.0 mol % or more, and in some cases 1.2 mol % or more is preferred. On the other hand, if the content c exceeds 10 mol %, the strength of the film will decrease. The content c is preferably 9 mol % or less, more preferably 8 mol % or less, even more preferably 7 mol %, particularly preferably 5 mol % or less, and in some cases 4 mol % or less or 3 mol % or less is preferred.

[0040] In modified EVOH (A), b represents the content (mol %) of (Ib) relative to all monomer units, and b satisfies formula (3). If b does not satisfy formula (3), the gas barrier properties of the coating film obtained by coating will be insufficient. b preferably satisfies the following formula (3'), and more preferably the following formula (3"). In formula (Ib), when X is two or more functional groups selected from the group consisting of a hydrogen atom, a formyl group, and an alkanoyl group having 2 to 10 carbon atoms (i.e., when vinyl alcohol units and vinyl ester units are simultaneously contained), b is the sum of these functional groups: [100 - (a + c)] x 0.95 < b < [100 - (a + c)] (3') [100 - (a + c)] x 0.98 < b < [100 - (a + c)] (3")

[0041] In modified EVOH (A), the degree of saponification (DS) is defined by formula (4), and the degree of saponification (DS) is 90 mol% or more. Here, the "total number of moles of hydrogen atoms among X, Y, and Z" refers to the number of moles of hydroxyl groups, and the "total number of moles of X, Y, and Z" refers to the total number of moles of hydroxyl groups and ester groups. If the degree of saponification (DS) is less than 90 mol%, sufficient barrier performance cannot be obtained, and the thermal stability of modified EVOH (A) becomes insufficient, making it prone to gels and lumps when melt-kneaded and recycled. Furthermore, the reduced thermal stability tends to reduce long-run moldability during high-temperature molding. The degree of saponification (DS) is preferably 95 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more. In order to have particularly excellent barrier properties and thermal stability, the degree of saponification (DS) is preferably 99 mol% or more, more preferably 99.5 mol% or more, and even more preferably 99.8 mol% or more. The degree of saponification (DS) is usually 100 mol% or less.

[0042] The degree of saponification (DS) can be determined by nuclear magnetic resonance (NMR). The contents of the monomer units represented by a, b, and c can also be determined by NMR. The modified EVOH (A) used in the present invention is usually a random copolymer. The fact that it is a random copolymer can be confirmed by the results of NMR or melting point measurements.

[0043] The melt flow rate (MFR) (190°C, under a load of 2160 g) of the modified EVOH (A) is preferably 0.1 to 30 g / 10 min, more preferably 0.3 to 25 g / 10 min, and even more preferably 0.5 to 20 g / 10 min. However, for modified EVOHs having a melting point near or exceeding 190°C, the MFR is measured under a load of 2160 g at multiple temperatures equal to or higher than the melting point, and the MFR is plotted on a semi-logarithmic graph with the reciprocal of absolute temperature on the horizontal axis and the logarithm of the MFR on the vertical axis, and the value extrapolated to 190°C is expressed as a value. If the MFR is less than 0.1 g / 10 min, the viscosity of the solution relative to the solids concentration is too high, making it impossible to obtain a coating having the required thickness in a single application, resulting in insufficient gas barrier properties or requiring multiple applications, reducing productivity. If the MFR exceeds 30 g / 10 min, the viscosity of the solution relative to the solid content will be too low, and even a slight difference in the viscosity of the solution will result in a large change in the thickness of the coating, making it impossible to impart stable gas barrier properties to the packaging material.

[0044] [Production of Modified EVOH (A)] Next, the production of modified EVOH (A) will be described. The structural unit (Ib) containing X is usually obtained by saponifying a vinyl ester. Therefore, X is a functional group that can be saponified or a functional group generated by saponification, and specific examples of X include a mixture of a hydrogen atom, a formyl group, or an alkanoyl group having 2 to 10 carbon atoms. Considering the availability of the monomer (vinyl acetate) and production costs, it is more preferable that X be a mixture of a hydrogen atom and an acetyl group.

[0045] On the other hand, the structural unit (Ic) containing Y and Z can be produced by copolymerizing a monomer having an ester group, such as an unsaturated monomer having a 1,3-diester structure, followed by saponification, or can also be produced by directly copolymerizing a monomer having a hydroxyl group, such as an unsaturated monomer having a 1,3-diol structure. Therefore, Y and Z may each be a hydrogen atom alone, or a mixture of a hydrogen atom and a formyl group or an alkanoyl group having 2 to 10 carbon atoms, or more preferably a mixture of a hydrogen atom and an acetyl group.

[0046] The modified EVOH (A) may contain structural units derived from other ethylenically unsaturated monomers copolymerizable with the vinyl ester represented by formula (V) and the unsaturated monomer represented by formula (VI) or (VII), as described below, within the scope of not impairing the effects of the present invention. Examples of such other ethylenically unsaturated monomers include α-olefins such as propylene, n-butene, isobutylene, and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylic ester group; methacrylic acid and its salts; unsaturated monomers having a methacrylic ester group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts (e.g., quaternary salts); methyl vinyl ether; vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, and allyl chloride; unsaturated dicarboxylic acids and salts or esters thereof such as maleic acid, itaconic acid, and fumaric acid; vinylsilane compounds such as vinyltrimethoxysilane; and isopropenyl acetate.

[0047] The method for producing the modified EVOH (A) used in the present invention is not particularly limited, and examples thereof include a method in which ethylene, a vinyl ester represented by the following formula (V), and an unsaturated monomer represented by the following formula (VI) are radically polymerized to obtain a copolymer, and then the copolymer is saponified.

[0048]

[0049] In formula (V), R ５ represents a hydrogen atom or an alkyl group having 1 to 9 carbon atoms. Examples of vinyl esters represented by formula (V) include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, and vinyl caproate. From an economical viewpoint, vinyl acetate is more preferable.

[0050]

[0051] In formula (VI), R ３ and R ４ is the same as the structural unit (IIc). ６ and R ７ each independently represents a hydrogen atom or an alkyl group having 1 to 9 carbon atoms. Examples of the unsaturated monomer represented by formula (VI) include 2-methylene-1,3-propanediol diacetate, 2-methylene-1,3-propanediol dipropionate, and 2-methylene-1,3-propanediol dibutyrate. Among these, 2-methylene-1,3-propanediol diacetate is preferably used because of its ease of production. In the case of 2-methylene-1,3-propanediol diacetate, R ３ and R ４ is a hydrogen atom, and R ６ and R ７ is a methyl group.

[0052] In place of the unsaturated monomer represented by the formula (VI), an unsaturated monomer represented by the following formula (VII) may be copolymerized. In this case, the unsaturated monomer represented by the formula (VII) may be copolymerized by saponification treatment. ５ Only the vinyl ester units containing

[0053]

[0054] In formula (VII), R ３ and R ４ is the same as the structural unit (IIc). Examples of the unsaturated monomer represented by formula (VII) include 2-methylene-1,3-propanediol and 2-methylene-1,3-butanediol.

[0055] The unsaturated monomers represented by formulas (VI) and (VII) have high copolymerization reactivity with vinyl ester monomers, and therefore the copolymerization reaction proceeds easily. Therefore, it is easy to increase the degree of modification and polymerization of the resulting modified ethylene-vinyl ester copolymer. Furthermore, even if the polymerization reaction is terminated at a low polymerization rate, the amount of unreacted unsaturated monomer remaining at the end of the polymerization is small, making the process environmentally and cost-effective. In this respect, the unsaturated monomers represented by formulas (VI) and (VII) are superior to other monomers containing only one carbon atom bearing a functional group at the allylic position, such as allyl glycidyl ether and 3,4-diacetoxy-1-butene. Here, the unsaturated monomer represented by formula (VI) is more reactive than the unsaturated monomer represented by formula (V).

[0056] The polymerization method for producing a modified ethylene-vinyl ester copolymer by copolymerizing ethylene, a vinyl ester represented by the above formula (V), and an unsaturated monomer represented by the above formula (VI) or (VII) may be any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. Furthermore, known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be used as the polymerization method. Bulk polymerization or solution polymerization, in which polymerization proceeds without a solvent or in a solvent such as alcohol, is usually used. When obtaining a modified ethylene-vinyl ester copolymer with a high degree of polymerization, emulsion polymerization is one option.

[0057] The solvent used in the solution polymerization method is not particularly limited, but examples thereof include alcohols, and lower alcohols such as methanol, ethanol, propyl alcohol, etc. are more preferred. The amount of solvent used in the polymerization reaction solution may be selected taking into consideration the viscosity-average degree of polymerization of the desired modified EVOH (A) and chain transfer of the solvent. The weight ratio of the solvent to the total monomers (solvent / total monomers) contained in the reaction solution is usually in the range of 0.01 to 10, preferably in the range of 0.03 to 3, and more preferably in the range of 0.05 to 1.

[0058] The polymerization initiator used in copolymerizing ethylene, the vinyl ester represented by the formula (V) above, and the unsaturated monomer represented by the formula (VI) or (VII) above is selected from known polymerization initiators, such as azo initiators, peroxide initiators, and redox initiators, depending on the polymerization method. Examples of azo initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). Examples of peroxide initiators include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanate, α-cumyl peroxyneodecanate, and acetyl peroxide; acetylcyclohexylsulfonyl peroxide; and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate. Potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like may also be combined with the above initiators. Redox initiators are polymerization initiators that combine, for example, the above peroxide initiators with reducing agents such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, and Rongalit. The amount of polymerization initiator used is adjusted depending on the polymerization rate. The amount of polymerization initiator used is preferably 0.01 to 0.2 mol, more preferably 0.02 to 0.15 mol, per 100 mol of vinyl ester monomer. The polymerization temperature is not particularly limited, but is suitably from room temperature to about 150°C, and preferably from 40°C to 100°C.

[0059] When copolymerizing ethylene, a vinyl ester represented by the above formula (V), and an unsaturated monomer represented by the above formula (VI) or (VII), the copolymerization may be carried out in the presence of a chain transfer agent, as long as the effects of the present invention are not impaired. Examples of chain transfer agents include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; and phosphinates such as sodium phosphinate monohydrate. Among these, aldehydes and ketones are preferred. The amount of chain transfer agent added to the polymerization reaction solution is determined depending on the chain transfer coefficient of the chain transfer agent and the degree of polymerization of the desired modified ethylene-vinyl ester copolymer, but generally 0.1 to 10 parts by weight per 100 parts by weight of the vinyl ester monomer is preferred.

[0060] After polymerization for a predetermined time has reached a predetermined conversion, a polymerization inhibitor is added as necessary, unreacted ethylene gas is removed by evaporation, and unreacted vinyl ester and unsaturated monomers represented by formula (VI) or (VII) are then removed. For example, a method for removing these compounds may be employed in which the polymerization solution from which ethylene has been removed is continuously fed at a constant rate from the top of a column packed with Raschig rings, vapor of an organic solvent, preferably an alcohol having a boiling point of 100°C or less, and most preferably methanol, is blown into the bottom of the column, and a mixed vapor of the organic solvent and unreacted vinyl ester, etc. is distilled from the top of the column, and the copolymer solution from which unreacted vinyl ester, etc. has been removed is taken out from the bottom of the column.

[0061] An alkali catalyst is added to the copolymer solution from which unreacted vinyl ester and the like have been removed, and the vinyl ester component in the copolymer is saponified. The saponification method can be either continuous or batchwise. Examples of alkali catalysts that can be used include sodium hydroxide, potassium hydroxide, and alkali metal alcoholates. Methanol is preferred as the solvent used for saponification. For example, the saponification conditions are as follows: (1) Concentration of ethylene-vinyl ester copolymer in the solution: 10 to 50% by weight (2) Reaction temperature: 30 to 150°C (3) Amount of catalyst used: 0.005 to 0.6 equivalents (per vinyl ester component) (4) Time (average residence time in the case of a continuous method): 10 minutes to 6 hours

[0062] Generally, when saponification is carried out in a continuous system, methyl acetate produced by saponification can be removed more efficiently, and therefore a resin with a high degree of saponification can be obtained with a smaller amount of catalyst than in a batch system. Furthermore, in the case of a continuous system, saponification must be carried out at a higher temperature to prevent the EVOH produced by saponification from precipitating. Therefore, in a continuous system, it is preferable to set the reaction temperature and catalyst amount within the following ranges: Reaction temperature: 70 to 150°C Catalyst usage amount: 0.005 to 0.1 equivalents (per vinyl ester component)

[0063] By saponifying the modified ethylene-vinyl ester copolymer in this manner, a solution or paste containing modified EVOH (A) is obtained. At this time, the vinyl ester units in the copolymer are converted to vinyl alcohol units. At the same time, the ester bonds derived from the unsaturated monomer represented by formula (VI) are also hydrolyzed and converted to a 1,3-diol structure. In this way, different types of ester groups can be simultaneously hydrolyzed by a single saponification reaction.

[0064] The modified EVOH (A) after the saponification reaction contains an alkali catalyst, by-product salts such as sodium acetate and potassium acetate, and other impurities, and these may be removed by neutralization and washing as necessary. When the modified EVOH (A) after the saponification reaction is washed with ion-exchanged water or the like containing almost no metal ions, chloride ions, etc., some catalyst residues such as sodium acetate and potassium acetate may remain in the modified EVOH (A).

[0065] The solution or paste containing the modified EVOH (A) thus obtained usually contains 50 parts by weight or more of alcohol per 100 parts by weight of EVOH, and the alcohol is preferably methanol.

[0066] The method for washing the solution or paste containing modified EVOH (A) and the method for adjusting the water content are not particularly limited, but can be carried out as follows. Water is added to the solution or paste containing modified EVOH (A) while heating and stirring, and the alcohol is distilled off to precipitate modified EVOH (A). The temperature during this process is preferably 50 to 100°C. The precipitated modified EVOH (A) is washed with water, an aqueous acetic acid solution, or the like. The temperature during this process is preferably 5 to 50°C. The washed modified EVOH is dried as necessary. For example, it is dried at 50 to 100°C for 1 to 24 hours. The water content of the modified EVOH (A) can be adjusted by the washing and drying conditions during this process.

[0067] <Other Components Contained in Modified EVOH (A)> It is preferable that the modified EVOH (A) contains alkali metal ions. By containing alkali metal ions in the modified EVOH (A), adhesion between adjacent layers can be improved when a multilayer structure is formed, and as a result, gas barrier properties can be maintained before and after bending.

[0068] The lower limit of the alkali metal ion content (content in the dry product) is preferably 2.5 μmol / g, more preferably 3.5 μmol / g, and even more preferably 4.5 μmol / g. On the other hand, the upper limit of this content is preferably 22 μmol / g, more preferably 16 μmol / g, and even more preferably 10 μmol / g. When the metal ion content is greater than the lower limit, interlayer adhesion is improved, and gas barrier properties can be maintained before and after bending. On the other hand, when the alkali metal ion content is less than the upper limit, gel generation during melt extrusion can be suppressed.

[0069] Examples of alkali metal ions include ions of lithium, sodium, potassium, rubidium, cesium, etc., but from the viewpoint of industrial availability, sodium or potassium ions are more preferred.

[0070] The alkali metal salt that provides the alkali metal ion is not particularly limited, and examples thereof include aliphatic carboxylates, aromatic carboxylates, phosphates, metal complexes, etc. of lithium, sodium, potassium, etc. Specific examples of the alkali metal salt include sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate, and the sodium salt of ethylenediaminetetraacetic acid. Among these, sodium acetate, potassium acetate, and sodium phosphate are particularly preferred because they are easily available.

[0071] It is also preferred that the modified EVOH (A) contains alkaline earth metal ions. Examples of alkaline earth metal ions include ions of beryllium, magnesium, calcium, strontium, barium, etc., but from the viewpoint of industrial availability, magnesium or calcium ions are more preferred. When the modified EVOH (A) contains alkaline earth metal ions, defects such as gels and lumps are reduced and recyclability is improved.

[0072] Furthermore, as long as the object of the present invention is not hindered, the modified EVOH (A) may be one to which a heat stabilizer, an antioxidant, and inorganic fine particles are blended.

[0073] Among inorganic fine particles, amorphous silica is preferred because it exhibits an anti-blocking effect and also functions to improve the gas barrier properties of the modified EVOH (A). The amount of inorganic fine particles added is preferably 10 to 10,000 ppm, more preferably 100 to 3,000 ppm, and most preferably 500 to 1,500 ppm.

[0074] [Coating Agent] The coating agent of the present invention contains the modified EVOH (A). The solvent used in the coating agent of the present invention is not particularly limited as long as it can dissolve the modified EVOH (A), but preferred examples include alcohols such as methanol, ethanol, propyl alcohol, and butyl alcohol; dialkyl sulfoxides such as dimethyl sulfoxide; amides such as dimethylformamide; N-methylpyrrolidone; and mixed solvents of these with water.

[0075] Among these, the use of a mixed solvent of alcohol and water is particularly preferred from the viewpoints of solubility and economy. As the alcohol to be used in this case, an aliphatic alcohol having 4 or less carbon atoms is preferred from the viewpoints of solubility, dissolution temperature, volatility (drying speed), economy, etc. Among the aliphatic alcohols having 4 or less carbon atoms, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol are particularly preferred, with n-propyl alcohol being the most suitable. In this case, two or more of these alcohols may be used simultaneously.

[0076] The blending ratio of alcohol to water in the mixed solvent is not particularly limited and is appropriately adjusted depending on the type of alcohol, the composition of the modified EVOH (A), the concentration of the modified EVOH (A), the coating conditions (temperature, etc.), the intended use, etc. Typically, the alcohol content in the mixed solvent is 1 to 99% by weight. From the viewpoints of solubility and solution storage stability, the alcohol content in the mixed solvent is preferably 40% by weight or more, and more preferably 50% by weight or more. For the same reasons, the alcohol content in the mixed solvent is preferably 90% by weight or less, and more preferably 80% by weight or less. In this case, the only component in the mixed solvent other than the alcohol is preferably water.

[0077] The content of modified EVOH (A) contained in the coating agent of the present invention is preferably 1 to 50 wt %. If it is less than 1 wt %, the amount of solvent used increases, which is economically disadvantageous, and it may be difficult to achieve a thick coating thickness. The content is more preferably 5 wt % or more, and even more preferably 10 wt % or more. Since modified EVOH (A) is resistant to crystallization even at relatively high concentrations and has good storage stability, it is preferable to use it as a highly concentrated solution. On the other hand, if the content of modified EVOH (A) exceeds 50 wt %, the solution viscosity may become too high, making coating difficult, and the solution may not have sufficient storage stability. The content is more preferably 40 wt % or less, and even more preferably 30 wt % or less.

[0078] The coating agent of the present invention may contain, together with the modified EVOH (A), an ethylene-vinyl alcohol copolymer (B) other than the modified EVOH (A). The ethylene-vinyl alcohol copolymer (B) does not contain the structural unit (Ic) but contains the structural units (1a) and (1b). The ethylene-vinyl alcohol copolymer (B) is preferably an unmodified EVOH (hereinafter, sometimes abbreviated as unmodified EVOH (B)). The unmodified EVOH (B) used here is appropriately selected depending on the composition of the modified EVOH (A) and the intended use, but the inclusion of the unmodified EVOH (B) increases the freedom in the selection and incorporation of other additives without impairing the gas barrier properties of the resulting coating.

[0079] When the coating agent of the present invention contains unmodified EVOH (B), a coating having good barrier properties and appearance can be obtained if the ethylene content of the unmodified EVOH (B) is 21 to 65 mol%. The ethylene content of the unmodified EVOH (B) is preferably 25 mol% or more, more preferably 28 mol% or more, and in some cases, 30 mol% or more, 35 mol% or more, 40 mol% or more, or 45 mol% or more is preferred. The ethylene content of the unmodified EVOH (B) is preferably 60 mol% or less, and in some cases, 58 mol% or less, or 55 mol% or less is preferred.

[0080] When the coating agent of the present invention contains unmodified EVOH (B), the total content of modified EVOH (A) and unmodified EVOH (B) is preferably 1 to 50 wt % based on the total weight of the coating agent. If the total content is less than 1 wt %, the amount of solvent used increases, which is economically disadvantageous, and it may be difficult to achieve a thick coating thickness. More preferably, it is 5 wt % or more, and even more preferably, it is 10 wt % or more. On the other hand, if the total content exceeds 50 wt %, the solution viscosity may become too high, making coating difficult, and the storage stability of the solution may become insufficient. More preferably, it is 40 wt % or less, and even more preferably, it is 30 wt % or less.

[0081] When the coating agent of the present invention contains unmodified EVOH (B), the weight ratio (A / B) of modified EVOH (A) to unmodified EVOH (B) is usually 1 / 99 to 99 / 1. The weight ratio (A / B) is preferably 90 / 10 or less, and more preferably 80 / 20 or less. The addition of modified EVOH (A) can improve the storage stability of the solution.

[0082] In the coating agent of the present invention, when the modified EVOH (A) contains a mixture of two or more different types of modified EVOH (A) or a modified EVOH (A) and an unmodified EVOH (B), the content, degree of saponification and MFR of each structural unit are used as average values ​​calculated from the blending weight ratio.

[0083] The coating agent may contain a boron compound within the scope of the present invention. Examples of boron compounds include boric acids, boric acid esters, borate salts, boron hydrides, etc. Specifically, examples of boric acids include orthoboric acid, metaboric acid, and tetraboric acid, examples of borate esters include triethyl borate and trimethyl borate, and examples of borates include alkali metal salts, alkaline earth metal salts, and borax of the above-mentioned various boric acids. Among these compounds, orthoboric acid (hereinafter sometimes simply referred to as boric acid) is preferred.

[0084] When a boron compound is used, the content of the boron compound in the coating agent is preferably 20 to 2000 ppm, more preferably 50 to 1000 ppm, in terms of elemental boron relative to the modified EVOH (A). Blending the boron compound within this range further improves the storage stability of the solution. EVOH blended with a boron compound can also be used as the modified EVOH (A). In this case, the content of the boron compound in the modified EVOH (A) is preferably 20 to 2000 ppm, more preferably 50 to 1000 ppm, in terms of elemental boron.

[0085] The coating agent may contain a phosphate compound to the extent that it does not interfere with the object of the present invention. This may stabilize the quality (coloration, etc.) of the resin. The phosphate compound used in the present invention is not particularly limited, and various acids such as phosphoric acid and phosphorous acid, and salts thereof, can be used. The phosphate may be contained in the form of any of primary phosphate, secondary phosphate, and tertiary phosphate, with primary phosphate being preferred. The cation species is also not particularly limited, but alkali metal salts are preferred. Among these, sodium dihydrogen phosphate and potassium dihydrogen phosphate are preferred. When using a modified EVOH (A) containing a phosphate compound, the content of the phosphate compound in the modified EVOH (A) is preferably 200 ppm or less, more preferably 5 to 100 ppm, and even more preferably 5 to 50 ppm, calculated as phosphate radicals.

[0086] The coating agent may contain inorganic fine particles as long as the object of the present invention is not hindered. The inorganic fine particles are preferably inorganic oxide particles, and more preferably silicon oxide particles or metal oxide particles. The metal constituting the metal oxide particles is preferably at least one selected from the group consisting of aluminum, magnesium, zirconium, cerium, tungsten, molybdenum, titanium, and zinc. Specific examples of inorganic oxides constituting the inorganic oxide particles include silicon oxide, aluminum oxide, zirconium oxide, magnesium oxide, cerium oxide, tungsten oxide, molybdenum oxide, titanium oxide, zinc oxide, and composites thereof, with silicon oxide being preferred. Among silicon oxides, amorphous silica is particularly preferred. As the inorganic oxide, one type of inorganic oxide may be used alone, or two or more types may be used in combination. Among inorganic fine particles, amorphous silica particles are particularly preferred because they exhibit an antiblocking effect and improve the gas barrier properties of the modified EVOH (A). The content of inorganic fine particles in the coating agent is preferably 10 to 10,000 ppm, more preferably 300 to 10,000 ppm, even more preferably 500 to 3,000 ppm, and even more preferably 700 to 1,500 ppm. The average particle size of the inorganic fine particles dispersed in the solution is 0.1 to 30 μm. If the average particle size is less than 0.1 μm, the slip properties of the coating film will be insufficient. The average particle size is preferably 1 μm or more, more preferably 2 μm or more. If the average particle size is more than 30 μm, the film will become lumpy, resulting in poor appearance. The average particle size is preferably 10 μm or less.

[0087] The coating agent of the present invention may contain various additives as needed. Examples of such additives include surfactants, antioxidants, plasticizers, heat stabilizers, UV absorbers, antistatic agents, lubricants, colorants, fillers, soluble inorganic salts, and other polymeric compounds. These may be added to the coating agent of the present invention to the extent that they do not impair the effects of the present invention.

[0088] The coating agent of the present invention can be applied to various substrates by any method, including dispensing from a casting head, roll coating, doctor knife coating, spray coating, immersion, and brush coating. After coating, the coating is dried and, if necessary, heat-treated. Drying conditions vary depending on factors such as the coating thickness, but a temperature of 50 to 130°C and a time of 10 seconds to 10 minutes are preferred. Heat-treatment conditions are preferably a temperature of 100 to 150°C and a time of 10 seconds to 10 minutes. The coating thickness (dry base) is preferably 0.5 to 20 μm, more preferably 1 to 15 μm. A thickness of 0.5 μm or less may result in insufficient gas barrier properties. On the other hand, a thickness greater than 20 μm may require additional coating operations to achieve the desired coating thickness, potentially reducing productivity.

[0089] The storage stability of the solution is confirmed by two indicators: viscosity stability and transparency stability.

[0090] If the viscosity of an EVOH solution changes during storage, this can cause variations in the thickness during coating. For example, if the viscosity of the solution decreases significantly during continuous coating for one week, the thickness of the resulting coating film decreases, and the gas barrier properties of the multilayer structure deteriorate. Therefore, an EVOH solution that exhibits little change in viscosity during solution storage is preferred. From this perspective, when the solution of the modified EVOH (A) is stored in an environment of 20°C for 7 days, the initial solution viscosity V before storage is ０ (cP) vs. solution viscosity V after 7 days of storage ７ (cP) change rate | (V ７ -V ０ ) / V ０ is preferably 50% or less, more preferably 30% or less, even more preferably 20% or less, and most preferably 10% or less.

[0091] When the transparency (light transmittance) of an EVOH solution decreases during storage, EVOH fine particles that cause light scattering are generated in the solution. The generation of such EVOH fine particles prevents a uniform coating from being obtained, and the gas barrier property and light transmittance decrease. Therefore, the light transmittance T of the solution measured at 20°C, a wavelength of 800 nm, and an optical path length of 1 cm immediately after preparation of the modified EVOH (A) solution is ０ and the light transmittance T ７ The difference between (T ０ -T ７ ) is usually 99% or less, preferably 25% or less, more preferably 20% or less, even more preferably 10% or less, particularly preferably 5% or less, and most preferably remains substantially unchanged.

[0092] The coating agent of the present invention has excellent storage stability and is unlikely to become cloudy even when stored for a long period of time between the preparation of the solution and coating. Therefore, it can be transported at room temperature, and heating immediately before coating is generally not necessary. The coating film thus obtained is excellent in transparency, gas barrier properties, and flexibility. In contrast, a solution of unmodified EVOH often becomes cloudy during storage. If the solution is applied as is, not only is the gas barrier properties significantly reduced, but the resulting coating also becomes cloudy.

[0093] [Multilayer structure obtained by applying the coating agent to a substrate] The substrate to which the coating agent of the present invention is applied is not particularly limited, and examples include resin, metal, paper, and wood. Among these, substrates made of resin, particularly thermoplastic resin, are preferred. Examples of such thermoplastic resins include polyolefin, polyamide, polyester, polystyrene, polyvinyl chloride, poly(meth)acrylic acid ester, polyvinylidene chloride, polyacetal, polycarbonate, polyvinyl acetate, polyurethane, and polyacrylonitrile. Various copolymers can also be used. By applying the coating agent of the present invention to the substrate, a multilayer structure is formed in which a layer made of modified EVOH (A) is formed on the surface. The thickness of the layer made of modified EVOH (A) (thickness of the coating film) is as described above.

[0094] When the coating agent of the present invention is coated onto the substrate, it is preferable to subject the coating surface of the substrate to a physical treatment such as corona treatment (for example, when the substrate is a film made of a polyolefin such as polyethylene, the treatment is performed to the extent that the surface tension of the substrate becomes 37 to 45 dyne / cm) or to apply a polyurethane anchor coating agent, in order to ensure more reliable adhesion between the substrate surface and the layer formed by applying the coating agent.

[0095] Multilayer structures obtained by applying the coating agent of the present invention to various substrates are preferred embodiments of the coating agent of the present invention. The resulting multilayer structures have excellent gas barrier properties, aroma retention, and oil resistance, and are widely used in various fields. They are particularly suitable for use in packaging materials (films, sheets, containers, etc.) for foods, beverages, medicines, pharmaceuticals, etc. Furthermore, the coating film obtained by coating and the multilayer structure containing the same have excellent flexibility and flex resistance, making multilayer structures obtained by applying the coating agent of the present invention to flexible substrates such as films and sheets particularly useful, and suitable for use as, for example, flexible pouches. Furthermore, the coating film obtained by coating also has excellent stretchability, making it suitable to apply a stretching operation after coating the coating agent on the substrate. The multilayer structures thus obtained are suitable for use as, for example, stretched films and thermoformed containers. The coating agent of the present invention is also useful as a surface coating material for wallpaper, card cases, desk mats, and other products made from flexible polyvinyl chloride resins containing a plasticizer. Such coating materials prevent bleeding of the plasticizer from the flexible polyvinyl chloride resin and further prevent surface contamination.

[0096] [Multilayer structure comprising a paper layer and a layer comprising modified EVOH (A)] A multilayer structure comprising a paper layer and a layer comprising the modified EVOH (A) (hereinafter sometimes abbreviated as "modified EVOH (A) layer") is suitably used as a packaging material, etc., as described below. Such a multilayer structure can also be produced using the coating agent of the present invention described above. The modified EVOH (A) layer can be formed by applying the coating agent to a paper substrate that forms the paper layer.

[0097] The multilayer structure may be composed of only a paper layer and a modified EVOH (A) layer, or may have other layers in addition to the paper layer and the modified EVOH (A) layer, as described below. From the viewpoint of not impairing the recyclability of the paper, it is preferable that the modified EVOH (A) layer and other layers are disposed on only one side of the paper layer. On the other hand, in order to impart good gas barrier properties, the modified EVOH (A) layer and other layers may be disposed on both sides of the paper layer. The gas barrier properties of the multilayer structure can be evaluated based on the measured oxygen permeability, specifically by the method described in the Examples.

[0098] <Gas barrier property> Gas barrier property is a function of preventing gas permeation, and is, for example, the oxygen transmission rate (OTR) measured in accordance with JIS-K7126-2 (2006) Part 2 (constant pressure method) under conditions of 20°C and 65% RH. ２ The oxygen permeability of "20 cc / m² / day atm" means that the amount of oxygen permeated per unit area of ​​the multilayer structure per day is 20 cc at 1 atmosphere. ２ ·day·atm or less, and 10cc / m ２ ·day·atm or less is more preferable, 5 cc / m ２ ·day·atm or less is more preferable, and 1 cc / m ２ If the oxygen transmission rate is equal to or less than the upper limit, when the multilayer structure is used as a package, oxidation deterioration of the contents is suppressed, and the storage stability is further improved.

[0099] <Gas barrier properties before and after folding> When a multilayer structure is processed to produce a package, the multilayer structure may be folded. In the case of a multilayer structure including a paper layer, excessive stress is applied to the folded portion, which may cause cracks to form in the other layers. If such cracks occur in the package when contents are placed in the package and stored, the gas barrier properties will be reduced, and the contents will deteriorate. Therefore, in a package including a 360-degree folded portion produced using the multilayer structure including a paper layer and a layer made of modified EVOH (A), the ratio (OTR2 / OTR1) of the oxygen transmission rate (OTR2) of a portion cut out so as to be centered on the folded portion to the oxygen transmission rate (OTR1) of a portion cut out so as not to include the folded portion is preferably less than 10, more preferably less than 5, and even more preferably less than 3.

[0100] <Heat Seal Strength> If the heat seal strength of the package is good, the sealability is improved, the contents are protected from oxidation by oxygen and deterioration due to moisture, and the shelf life can be extended. For example, the heat seal strength of the multilayer structure having a width of 15 mm is measured in accordance with JIS Z 0238. The heat seal strength of the multilayer structure is preferably 300 gf / 15 mm or more, more preferably 500 gf / 15 mm or more, even more preferably 800 gf / 15 mm or more, and particularly preferably 1500 gf / 15 mm or more. When the multilayer structure has such a heat seal strength, the sealability of the contents is improved, damage to the package during distribution, etc. can be reduced, and the shelf life can be extended.

[0101] <Paper Layer> Examples of paper substrates used in the paper layer include films or sheets containing pulp, fillers, chemicals, and pigments. Examples of pulp include chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), and sulfite pulp; mechanical pulps such as stone-ground pulp and thermomechanical pulp; wood fibers such as deinked pulp and recycled paper pulp; and non-wood fibers obtained from kenaf, bamboo, hemp, etc. These pulps can be used alone or in combination. Among these, chemical pulp, mechanical pulp, and wood fiber are preferred, and chemical pulp is more preferred, from the viewpoints of easily suppressing the incorporation of foreign matter into the base paper and the occurrence of discoloration over time when used paper containers are recycled, and of easily achieving a good surface texture when printed.

[0102] Fillers used in paper substrates include known fillers such as white carbon, talc, kaolin, clay, heavy calcium carbonate, light calcium carbonate, titanium oxide, zeolite, and synthetic resin fillers. Fillers can be used alone or in combination. Chemicals include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents (e.g., neutral sizing agents), water-resistant agents, water retention agents, thickeners, lubricants, retention aids, drainage aids, and paper strength agents, and these may be used alone or in combination. Retention aids include aluminum sulfate and various anionic, cationic, nonionic, and amphoteric agents. Dry strength agents include polyacrylamide and cationized starch, and wet strength agents include polyamidoamine epichlorohydrin. These agents are added to a level that does not affect formation or runnability. Examples of neutral sizing agents include alkyl ketene dimers, alkenyl succinic anhydrides, and neutral rosin sizing agents. Examples of pigments include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as solid, hollow, and core-shell pigments. These can be used alone or in combination. Furthermore, dyes, fluorescent whitening agents, pH adjusters, antifoaming agents, pitch control agents, slime control agents, and the like can also be added as needed. The surface of the paper substrate may also be treated with various chemicals or pigments.

[0103] The method for producing the paper base material (papermaking) is not particularly limited, and the paper base material can be produced by acidic papermaking, neutral papermaking, or alkaline papermaking using a known Fourdrinier former, on-top hybrid former, gap former machine, or the like.

[0104] The method for treating the surface of the paper substrate is not particularly limited, but known coating devices such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, and a curtain coater can be used.

[0105] Examples of the paper substrate (base paper) obtained in this manner include various known types such as fine paper, medium-quality paper, coated paper, one-side glossy paper, kraft paper, one-side glossy kraft paper, bleached kraft paper, unbleached kraft paper, rayon paper, tissue paper, glassine paper, paperboard, white paperboard, cellophane, and liner.

[0106] The paper substrate may have a transparent coating layer on one or both sides of the base paper as part of the paper substrate. Forming a transparent coating layer on the base paper improves the surface strength and smoothness of the base paper. It also improves the coatability when coating a pigment. The transparent coating layer may contain a starch-derived polymer compound as a binder. The amount of coating liquid to be applied when forming the transparent coating layer is 0.1 to 4.0 g / m2 in terms of solid content per side. ２ is preferred, and 0.5 to 2.5 g / m ２ is more preferable. For example, a coating liquid containing as a main component starch, various starches such as oxidized starch, polyacrylamide, polyvinyl alcohol, or other water-soluble polymers may be applied to the base paper using a coater (coating machine) such as a size press, gate roll coater, premetering size press, curtain coater, or spray coater. In order to ensure a uniform coating layer after coating, it is preferable to pre-calender the base paper before coating using an online soft calender, online chilled calender, or the like to smooth the base paper in advance.

[0107] The paper substrate may be subjected to a smoothing treatment as required. For the smoothing treatment, a smoothing treatment device such as a normal super calender, gloss calender, soft calender, heat calender, or shoe calender can be used. The smoothing treatment device is used on-machine or off-machine as appropriate, and the shape of the pressure device, the number of pressure nips, heating, etc. are also adjusted as appropriate.

[0108] The basis weight of the paper substrate can be selected appropriately depending on the desired qualities and handling properties of the packaging, but is usually 15 to 800 g / m２ In the case of packaging materials used for food packaging, bags, paper containers, cardboard boxes, cups, etc., the basis weight of the paper substrate is 25 to 600 g / m ２ Furthermore, for bags or soft packaging materials described later, the density is more preferably 30 to 150 g / m ２ , 170 to 600 g / m for paper containers ２ , 150 to 300 g / m for cardboard liners ２ , 120 to 200 g / m for the core ２ When the basis weight of the paper substrate is equal to or less than the upper limit, the heat seal strength is improved, and when it is equal to or more than the lower limit, the mechanical strength is improved and problems during the production of the package are reduced.

[0109] <Other Layers> The multilayer structure comprising a paper layer and a layer made of modified EVOH (A) preferably further comprises an intermediate layer or a sealant layer as other layers. When an intermediate layer is provided, it is preferably laminated directly onto the paper layer in order to suppress a decrease in gas barrier property after bending, and the modified EVOH (A) layer is preferably laminated directly onto the intermediate layer. When a sealant layer is provided, it is preferably disposed on the outermost layer side in order to improve the heat seal strength of the multilayer structure. Specific examples of the layer configuration of the multilayer structure are shown below. Here, " / " means that the layer is directly laminated, and " / / " means that the layer is laminated via an adhesive layer. Paper layer / modified EVOH (A) layer, Modified EVOH (A) layer / paper layer / modified EVOH (A) layer, Modified EVOH (A) layer / paper layer / modified EVOH (A) layer / paper layer / modified EVOH (A) layer, Paper layer / intermediate layer / modified EVOH (A) layer, Paper layer / intermediate layer / modified EVOH (A) layer / sealant layer, Paper layer / intermediate layer / modified EVOH (A) layer / sealant layer, Modified EVOH (A) layer / intermediate layer / paper layer / modified EVOH (A) layer / paper layer / modified EVOH (A) layer, Modified EVOH (A) layer / intermediate layer / paper layer / modified EVOH (A) layer / paper layer / modified EVOH (A) layer / sealant layer, Modified EVOH (A) layer / intermediate layer / paper layer / modified EVOH (A) layer / paper layer / modified EVOH (A) layer / sealant layer, Modified EVOH (A) layer / intermediate layer / paper layer / intermediate layer / modified EVOH (A) layer / paper layer / modified EVOH (A) layer, Modified EVOH (A) layer / intermediate layer / paper layer / intermediate layer / modified EVOH (A) layer / paper layer / modified EVOH (A) layer / sealant layer, Modified EVOH (A) layer / intermediate layer / paper layer / intermediate layer / modified EVOH (A) layer / paper layer / modified EVOH (A) layer / sealant layer Modified EVOH (A) layer / intermediate layer / paper layer / intermediate layer / modified EVOH (A) layer / paper layer / intermediate layer / modified EVOH (A) layer, Modified EVOH (A) layer / intermediate layer / paper layer / intermediate layer / modified EVOH (A) layer / sealant layer, Modified EVOH (A) layer / intermediate layer / paper layer / intermediate layer / modified EVOH (A) layer / paper layer / intermediate layer / modified EVOH (A) layer / / sealant layer.

[0110] <Intermediate Layer> The intermediate layer may be an anchor coat layer formed by applying an anchor coat agent and drying it, or may be a thermoplastic resin layer formed by melt extrusion.

[0111] The anchor coating agent used to form the intermediate layer may be any resin with a heat resistance temperature of 135°C or higher, such as a vinyl-modified resin, an epoxy resin, a urethane resin, or a polyester resin. An anchor coating agent consisting of an acrylic or methacrylic resin having two or more hydroxyl groups in its structure and an isocyanate compound as a curing agent is particularly preferred. A silane coupling agent may be used in combination with this as an additive, and soluble nitrocellulose may also be used in combination to enhance heat resistance.

[0112] The thermoplastic resin intermediate layer preferably uses an adhesive resin containing a carboxylic acid-modified polyolefin that is adhesive to the modified EVOH (A). The carboxylic acid-modified polyolefin may be a modified olefin polymer containing a carboxyl group obtained by chemically bonding (e.g., addition reaction, graft reaction, etc.) an ethylenically unsaturated carboxylic acid, its ester, or its anhydride to an olefin polymer. Examples of the olefin polymer include polyolefins such as polyethylene (e.g., low-density polyethylene, medium-density polyethylene, high-density polyethylene), linear low-density polyethylene, polypropylene, and polybutene, as well as copolymers of olefins with other monomers (e.g., vinyl esters, unsaturated carboxylic acid esters, etc.) (e.g., ethylene-vinyl acetate copolymer, ethylene-acrylic acid ethyl ester copolymer, etc.). Linear low-density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content: 5 to 55% by mass), and ethylene-acrylic acid ethyl ester copolymer (acrylic acid ethyl ester content: 8 to 35% by mass) are preferred, with linear low-density polyethylene and ethylene-vinyl acetate copolymer being particularly preferred. Examples of the ethylenically unsaturated carboxylic acid, its ester, or its anhydride include ethylenically unsaturated monocarboxylic acid, its ester, ethylenically unsaturated dicarboxylic acid, its mono- or diester, or its anhydride, among which ethylenically unsaturated dicarboxylic acid anhydride is preferred.Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, etc., and maleic anhydride is particularly preferred.

[0113] The amount of ethylenically unsaturated carboxylic acid or its anhydride added or grafted to the olefin polymer (modification degree) is, for example, preferably 0.0001% to 15% by mass, more preferably 0.001% to 10% by mass, based on the olefin polymer. The addition reaction or graft reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be carried out, for example, by radical polymerization in the presence of a solvent (e.g., xylene) and a catalyst (e.g., peroxide). The melt flow rate (MFR, under a load of 2,160 g) of the carboxylic acid-modified polyolefin thus obtained, measured at 210°C, is preferably 0.2 g / 10 min to 30 g / 10 min, more preferably 0.5 g / 10 min to 10 g / 10 min. These adhesive resins may be used alone or in combination of two or more.

[0114] In the present invention, the lower limit of the average thickness of the intermediate layer is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. If the thickness is above the lower limit, the deterioration of gas barrier properties after bending is further suppressed. Furthermore, the upper limit of the average thickness is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less. If the thickness is below the upper limit, the recyclability of the paper is improved.

[0115] <Sealant Layer> The sealant layer may be a resin layer formed by applying a coating agent and drying it, or may be a thermoplastic resin layer formed by melt extrusion.

[0116] Coating agents used to form the sealant layer include any resin with a heat resistance temperature of 135°C or higher, such as vinyl-modified resin, epoxy resin, urethane resin, or polyester resin, as well as polylactic acid (PLA) resin, styrene-acrylic acid ester copolymer, polyolefin copolymer, and ethylene-methacrylic acid copolymer. Among these, anchor coating agents consisting of an acrylic or methacrylic resin having two or more hydroxyl groups in its structure and an isocyanate compound as a curing agent are particularly preferred. A silane coupling agent may also be used as an additive, and soluble nitrocellulose may also be used to enhance heat resistance.

[0117] The thermoplastic resin constituting the sealant layer is not particularly limited as long as it is a resin that softens and exhibits plasticity when heated to its glass transition temperature or melting point, and examples thereof include polyolefin resins (polyethylene resins, polypropylene resins, etc.), grafted polyolefin resins graft-modified with unsaturated carboxylic acids or their esters, halogenated polyolefin resins, ethylene-vinyl acetate copolymer resins, ethylene-acrylic acid copolymer resins, ethylene-acrylic acid ester copolymer resins, polyester resins, polyamide resins, polyvinyl chloride resins, polyvinylidene chloride resins, acrylic resins, polystyrene resins, vinyl ester resins, ionomers, polyester elastomers, polyurethane elastomers, aromatic or aliphatic polyketones, etc. Polyolefin resins are particularly preferred because of their good mechanical strength and moldability, and polyethylene resins and polypropylene resins are more preferred.

[0118] The thermoplastic resin layer may contain additives as long as the object of the present invention is not impaired. Examples of additives include resins other than the thermoplastic resins, heat stabilizers, UV absorbers, antioxidants, colorants, fillers, etc. When the thermoplastic resin layer contains additives other than the thermoplastic resins, the content of the additives is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total amount of the thermoplastic resin layer.

[0119] The thermoplastic resin layer contains a thermoplastic resin as a main component, and may contain either a single thermoplastic resin or a mixture of multiple thermoplastic resins as a main component.

[0120] The lower limit of the average thickness of the sealant layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. A thickness equal to or greater than the lower limit provides good heat seal strength. The upper limit of the average thickness is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, and particularly preferably 30 μm or less. A thickness equal to or less than the upper limit improves paper recyclability.

[0121] The lower limit of the ratio (M1 / M2) of the weight M1 of the paper layer to the total weight M2 of the other layers is preferably 1.00 or more, more preferably 1.25 or more, even more preferably 2.33 or more, and particularly preferably 4.00 or more. A ratio above the lower limit improves the recyclability of the paper. An example of a method for calculating M2 is to add up the weight of each layer calculated from the thickness of each layer obtained by measuring the cross section of the obtained multilayer structure and the specific gravity of each layer. The upper limit of the ratio (M1 / M2) is preferably 300 or less, more preferably 100 or less, and even more preferably 50 or less. A ratio below the upper limit reduces stress at the folded portion when the product is made into a package, and suppresses deterioration of gas barrier properties.

[0122] <Method for producing a multilayer structure comprising a paper layer and a layer made of modified EVOH (A)> Examples of the layering method used to produce the multilayer structure include solution coating methods (direct gravure roll coating, gravure roll coating, kiss coating, reverse roll coating, Fontaine coating, and transfer roll coating) and extrusion coating, and a combination of these methods can be used. The modified EVOH (A) layer may be formed by directly applying the coating agent to the paper substrate that will form the paper layer, or by forming other layers, such as the intermediate layer described above, on the paper substrate and then applying the coating agent to the other layers. The thickness of the modified EVOH (A) layer (thickness of the coating film) is as described above.

[0123] <Uses of Multilayer Structure Comprising a Paper Layer and a Layer of Modified EVOH (A)> One preferred use of the multilayer structure is a package. This package may be composed solely of the multilayer structure, or may be composed of the multilayer structure and other components. The package can be produced by various methods. For example, a container (package) may be produced by joining a sheet-like multilayer structure or a film material (hereinafter simply referred to as "film material") containing the multilayer structure and molding it into a predetermined container shape. The package containing the multilayer structure can be applied to various uses by taking advantage of its excellent gas barrier properties. This package is preferably used in uses requiring gas barrier properties against oxygen or uses in which the interior of the package is replaced with various functional gases. For example, the package is preferably used as a food package. In addition to food packages, the package is also preferably used as a package for packaging chemicals such as pesticides and medicines; medical equipment; industrial materials such as machine parts and precision materials; clothing, etc.

[0124] The multilayer structure may be fabricated into various packages, such as vertical form-fill-seal bags, pouches, vacuum packages, cup-shaped containers, bags, container lids, or in-mold labels.

[0125] <Vertical form, fill, and seal bag> The package including the multilayer structure may be a vertical form, fill, and seal bag. An example is shown in FIG. 1. The vertical form, fill, and seal bag 10 shown in FIG. 1 is formed by sealing a multilayer structure 11 on three sides: two end portions 11a and a body portion 11b. The vertical form, fill, and seal bag 10 can be manufactured using a vertical form, fill, and seal machine. Various methods are used to manufacture bags using a vertical form, fill, and seal machine. In any method, the contents are supplied into the bag through an opening at the top, and the opening is then sealed to produce a vertical form, fill, and seal bag. The vertical form, fill, and seal bag is made, for example, of a single film material heat-sealed on three sides: the top end, the bottom end, and the sides. The vertical form, fill, and seal bag obtained using the multilayer structure maintains excellent gas barrier performance even after manufacturing, thereby preventing quality deterioration of the contents over a long period of time.

[0126] <Uses of the Package> The package including the multilayer structure has excellent gas barrier properties, and when the contents of the package are food, the effect of preserving the quality of the contents can be further enhanced. In order to inhibit the growth of microorganisms in the food and further improve the shelf life of the food, the water activity of the food in the package is preferably 0.94 or less, more preferably 0.80 or less, and even more preferably 0.60 or less. On the other hand, since an excessively low water activity can deteriorate the taste and texture of the food, the water activity of the food is preferably 0.10 or more.

[0127] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The evaluation methods used in the following synthesis examples, examples, and comparative examples are shown below.

[0128] Ethylene content and degree of saponification of modified EVOH (A) and EVOH (B) Deuterated dimethyl sulfoxide was used as a solvent. １ The values ​​were calculated from the spectrum obtained by H-NMR (nuclear magnetic resonance) measurement (using a JNM-GX-500 model manufactured by JEOL Ltd.).

[0129] Melting points of modified EVOH (A) and EVOH (B) The melting points of modified EVOH (A) and EVOH (B) were measured in accordance with JIS K 7121 by increasing the temperature from 30°C to 200°C at a rate of 10°C / min, then rapidly cooling to 0°C at 50°C / min, and again increasing the temperature from 0°C to 200°C at a rate of 10°C / min (TA Instruments differential scanning calorimeter (DSC) "Q2000"). Indium was used for temperature calibration. The melting peak temperature (T ｍ ) was determined and used as the melting points of the modified EVOH (A) and EVOH (B).

[0130] Melt flow rate (MFR) of modified EVOH (A) and EVOH (B) was measured using a Melt Indexer L244 (manufactured by Takara Kogyo Co., Ltd.). Specifically, powder, chips, or pellets of the resin to be measured (modified EVOH (A) and EVOH (B), or a resin composition) were filled into a cylinder with an inner diameter of 9.55 mm and a length of 162 mm, and melted at 190°C. A load was uniformly applied to the molten resin using a plunger weighing 2160 g and having a diameter of 9.48 mm. The flow rate (g / 10 min) of the resin extruded through an orifice with a diameter of 2.1 mm located in the center of the cylinder was measured, and this was taken as the melt flow rate (MFR). For samples with melting points of 190°C or higher, measurements were taken at two conditions: 210°C and 230°C. The reciprocal of absolute temperature was plotted on a semi-logarithmic graph on the horizontal axis and the logarithm of MFR on the vertical axis, and the value extrapolated to 190°C was determined.

[0131] Quantification of Alkali Metal Ions, Metal Salts, Phosphate Compounds, and Boron Compounds 0.5 g of the resulting modified EVOH pellets was placed in a Teflon (registered trademark) pressure vessel, and 5 mL of concentrated nitric acid was added thereto and decomposed at room temperature for 30 minutes. After decomposition, the pressure vessel was capped and further decomposed by heating at 150°C for 10 minutes and then at 180°C for 5 minutes in a wet decomposition apparatus (Actac's "MWS-2"), followed by cooling to room temperature. This treated solution was transferred to a 50 mL measuring flask and made up to the desired volume with ion-exchanged water to prepare a sample solution for measurement. The contents of metal elements, phosphorus, and boron in the sample solution were measured using an ICP optical emission spectrometer (PerkinElmer's "OPTIMA 4300DV"). Quantitative analysis of these elements was performed at the following observation wavelengths. From the obtained values ​​and a calibration curve prepared using the standard solution, the contents of alkali metal ions, metal salts calculated as metal elements, phosphate compounds calculated as phosphate radicals, and boron compounds calculated as boron elements in the modified EVOH pellets were determined. Na: 589.592 nm K: 766.490 nm Mg: 285.213 nm Ca: 317.933 nm P: 214.914 nm B: 249.667 nm

[0132] - Quantification of Carboxylate Ions Dried modified EVOH (A) pellets were pulverized by freeze-pulverization. The resulting pulverized modified EVOH (A) was sieved using a 1 mm nominal sieve (compliant with JIS-Z8801 standard sieve standard). 10 g of the modified EVOH (A) powder that passed through the sieve and 50 mL of ion-exchanged water were placed in a 100 mL Erlenmeyer flask with a stopper, attached a cooling condenser, and stirred at 95°C for 10 hours for extraction. 2 mL of the resulting extract was diluted with 8 mL of ion-exchanged water. The diluted extract was quantitatively analyzed using an ion chromatograph "IC7000" manufactured by Yokogawa Electric Corporation, and the amount of carboxylate ions was quantified to calculate the amount of carboxylic acid and carboxylate ions. A calibration curve prepared using an aqueous acetic acid solution was used for quantification. Ion chromatography measurement conditions: Column: "ICE-AS-1" manufactured by Dionex IonPac Corporation Eluent: 1.0 mmol / L octanesulfonic acid solution Measurement temperature: 35°C Eluent flow rate: 1 mL / min. Sample injection volume: 50 μL

[0133] Synthesis Example 1 (1) Synthesis of Modified EVAc A 250 L pressure reactor equipped with a jacket, a stirrer, a nitrogen inlet, an ethylene inlet, and an initiator addition port was charged with vinyl acetate (in formula (V), R ５ is a methyl group; hereinafter referred to as VAc), 10 kg of methanol (hereinafter referred to as MeOH), 2-methylene-1,3-propanediol diacetate (wherein R ３ and R ４ is a hydrogen atom, and R ６ and R ７2.9 kg of MPDAc (wherein MPDAc is a methyl group) was charged and heated to 60°C, after which nitrogen bubbling was performed for 30 minutes to replace the atmosphere inside the reactor with nitrogen. Ethylene was then introduced so that the reactor pressure (ethylene pressure) became 4.9 MPa. After adjusting the temperature inside the reactor to 60°C, 60 g of 2,2'-azobis(2,4-dimethylvaleronitrile) ("V-65" manufactured by Wako Pure Chemical Industries, Ltd.) was added as a methanol solution as an initiator to start polymerization. During polymerization, the ethylene pressure was maintained at 4.9 MPa and the polymerization temperature at 60°C. After 6 hours, when the conversion of VAc reached 45%, the polymerization was terminated by cooling. The reactor was opened to remove ethylene, and then nitrogen gas was bubbled through to completely remove ethylene. Next, unreacted VAc was removed under reduced pressure, and then MeOH was added to a modified ethylene-vinyl acetate copolymer (hereinafter, sometimes referred to as modified EVAc, formula (VIII)) into which structural units derived from MPDAc had been introduced by copolymerization to prepare a 20 wt % MeOH solution.

[0134]

[0135] (2) Saponification of Modified EVAc A 20 wt % MeOH solution of the modified EVAc obtained in (1) was charged into a 500 L reaction vessel equipped with a jacket, a stirrer, a nitrogen inlet, a reflux condenser, and a solution addition port. The temperature of this solution was raised to 60°C while nitrogen was blown into it, and 0.5 equivalents of sodium hydroxide relative to the vinyl acetate units in the modified EVAc were added as a 2N MeOH solution. After the addition of the sodium hydroxide MeOH solution was completed, the temperature in the system was maintained at 60°C, and the saponification reaction was allowed to proceed for 2 hours while stirring and distilling off methyl acetate and MeOH. The saponification reaction was then stopped by adding acetic acid. Subsequently, ion-exchanged water was added while heating and stirring at 60-80°C, and MeOH was distilled out of the reaction vessel, resulting in the precipitation of modified EVOH. The precipitated modified EVOH was collected and pulverized in a mixer. The obtained modified EVOH powder was poured into a 1 g / L aqueous acetic acid solution (bath ratio 20: 20 L of aqueous solution per 1 kg of powder) and washed with stirring for 2 hours. The powder was drained, and then poured into a 1 g / L aqueous acetic acid solution (bath ratio 20) and washed with stirring for 2 hours. The drained powder was poured into ion-exchanged water (bath ratio 20), washed with stirring for 2 hours, and then drained. This procedure was repeated three times for purification. The powder was then immersed in 10 L of an aqueous solution containing 0.5 g / L of acetic acid and 0.1 g / L of sodium acetate with stirring for 4 hours, drained, and dried at 60°C for 16 hours to obtain a crude dried modified EVOH product.

[0136] (3) Content of each structural unit in modified EVAc The content of ethylene units (a mol % in formula (VIII)), the content of vinyl acetate units (b mol % in formula (VIII)) and the content of structural units derived from MPDAc (c mol % in formula (VIII)) in modified EVAc were determined by comparing the content of modified EVAc before saponification with that of vinyl acetate units (b mol % in formula (VIII)). １ Calculation was performed by H-NMR measurement.

[0137] First, a small amount of the MeOH solution of modified EVAc obtained in (1) was sampled, and the modified EVAc was precipitated in ion-exchanged water. The precipitate was collected and dried at 60°C under vacuum to obtain a dried product of modified EVAc. Next, the dried product of modified EVAc was analyzed by dimethyl sulfoxide (DMSO)-d containing tetramethylsilane as an internal standard. ６ Dissolved in 500MHz １Measurement was performed at 80°C using a H-NMR (manufactured by JEOL Ltd.: "GX-500").

[0138] Modified EVAc １ The peaks in the H-NMR spectrum are assigned as follows: 0.6 to 1.0 ppm: methylene protons (4H) of terminal ethylene units; 1.0 to 1.85 ppm: methylene protons (4H) of intermediate ethylene units, methylene protons (2H) of the main chain of structural units derived from MPDAc, and methylene protons (2H) of vinyl acetate units; 1.85 to 2.1 ppm: methyl protons (6H) of structural units derived from MPDAc and methyl protons (3H) of vinyl acetate units; 3.7 to 4.1 ppm: methylene protons (4H) of the side chain of structural units derived from MPDAc; 4.4 to 5.3 ppm: methine protons (1H) of vinyl acetate units.

[0139] According to the above attributions, when the integral value from 0.6 to 1.0 ppm is defined as x, the integral value from 1.0 to 1.85 ppm as y, the integral value from 3.7 to 4.1 ppm as z, and the integral value from 4.4 to 5.3 ppm as w, the content a (mol %) of ethylene units, the content b (mol %) of vinyl acetate units, and the content c (mol %) of structural units derived from MPDAc are calculated according to the following formulas: a = (2x + 2y - z - 4w) / (2x + 2y + z + 4w) × 100, b = 8w / (2x + 2y + z + 4w) × 100, and c = 2z / (2x + 2y + z + 4w) × 100.

[0140] As a result of calculation using the above method, the content a of ethylene units in the modified EVAc in Synthesis Example 1 was 38.0 mol%, the content b of vinyl acetate units was 60.5 mol%, and the content c of structural units derived from MPDAc was 1.5 mol%. The values ​​of a, b, and c in the modified EVAc are the same as the values ​​of a, b, and c in the modified EVOH (A) after saponification treatment.

[0141] (4) Degree of saponification of modified EVOH (A) The same applies to the modified EVOH after saponification. １ The crude dried modified EVOH obtained in (2) above was subjected to H-NMR measurement.６ Dissolved in 500MHz １ Measurement was performed at 80°C using a H-NMR (manufactured by JEOL Ltd.: "GX-500"). １ The H-NMR measurement results showed a significant decrease in peak intensity between 1.85 and 2.1 ppm, which clearly indicates that in addition to the ester groups derived from vinyl acetate in the modified EVOH, the ester groups contained in the structural units derived from MPDAc were also saponified to hydroxyl groups. The degree of saponification was calculated from the peak intensity ratio of the methyl protons of the vinyl acetate units (1.85 to 2.1 ppm) to the methine protons of the vinyl alcohol units (3.15 to 4.15 ppm). The degree of saponification of the modified EVOH (A1) of Synthesis Example 1 was 99.9 mol% or higher. The analytical results of the modified EVOH (A1) are shown in Table 1.

[0142] [Synthesis Example 2] Modified EVOH (A2) was synthesized and analyzed in the same manner as in Synthesis Example 1, except that in the step of saponifying the modified EVAc obtained in Synthesis Example 1 and then immersing the resultant in 10 L of an aqueous solution containing 0.5 g / L of acetic acid and 0.1 g / L of sodium acetate for 4 hours with stirring, an aqueous solution containing 0.02 g / L of boric acid was used in addition to acetic acid and sodium acetate. The results are shown in Table 1.

[0143] Synthesis Examples 3 to 8 Modified EVOHs (A3 to A7) and unmodified EVOH (B4) were synthesized and analyzed in the same manner as in Synthesis Example 1, except that the polymerization conditions were changed as shown in Table 1. The results are shown in Table 1.

[0144] Synthesis Example 9 EVOH (B1) (ethylene content 38 mol%, EVAL H171B, manufactured by Kuraray Co., Ltd.) was freeze-pulverized to a diameter of 0.5 mm, then placed in a 1 g / L aqueous acetic acid solution (bath ratio 20: 20 L of aqueous solution per 1 kg of powder) and washed with stirring for 2 hours. The powder was dewatered and then placed in a 1 g / L aqueous acetic acid solution (bath ratio 20) and washed with stirring for 2 hours. The dewatered powder was then placed in ion-exchanged water (bath ratio 20), washed with stirring for 2 hours, and then dewatered. This procedure was repeated three times for purification. The powder was then immersed in 10 L of an aqueous solution containing 0.5 g / L acetic acid and 0.1 g / L sodium acetate with stirring for 4 hours, then dewatered. The powder was dried at 60°C for 16 hours and then at 110°C for 6 hours to obtain a dried EVOH product.

[0145] 28 parts by weight of zinc acetylacetonate monohydrate was mixed with 957 parts by weight of 1,2-dimethoxyethane to obtain a mixed solution. 15 parts by weight of trifluoromethanesulfonic acid was added to the obtained mixed solution with stirring to obtain a solution containing a catalyst. That is, a catalyst solution was prepared by mixing 1 mole of zinc acetylacetonate monohydrate with 1 mole of trifluoromethanesulfonic acid.

[0146] The dried EVOH was fed at a rate of 11 kg / hr to a TEM-35BS extruder (37 mmφ, L / D=52.5, extruder set temperature 200°C, screw rotation speed 250 rpm) manufactured by Toshiba Machine Co., Ltd. The internal pressure was reduced to 60 mmHg through a vent on the inlet side of the extruder, and epoxypropane and the catalyst solution were mixed and fed at a rate of 0.4 kg / hr and 0.20 kg / hr, respectively, and then fed from the center of the extruder. Next, unreacted epoxypropane was removed at normal pressure through a vent on the outlet side of the extruder, and an 8.2 wt % aqueous solution of trisodium ethylenediaminetetraacetate trihydrate was added as a catalyst deactivator at a rate of 0.11 kg / hr from a position immediately before the extruder outlet. The resin emerging from the extruder outlet was continuously cut to obtain modified EVOH (A8). The resulting modified EVOH (A8) had an MFR of 1 g / 10 min (190°C, under a load of 2160 g) and a melting point of 161°C.

[0147] The chemical structure of the modified EVOH (A8) thus obtained, which had been modified with epoxypropane, was determined by trifluoroacetylating the modified EVOH (A8) according to the following procedure and then carrying out NMR measurement.

[0148] The modified EVOH (A8) prepared above was crushed to a particle size of 0.2 mm or less, and 1 g of this powder was placed in a 100 ml recovery flask. 20 g of methylene chloride and 10 g of trifluoroacetic anhydride were added and stirred at room temperature. One hour after the start of stirring, the modified EVOH was completely dissolved. After the modified EVOH was completely dissolved, the mixture was stirred for another hour, and then the solvent was removed using a rotary evaporator. The resulting trifluoroacetylated modified EVOH was dissolved in a mixed solvent of deuterated chloroform and trifluoroacetic anhydride (deuterated chloroform / trifluoroacetic anhydride = 2 / 1 (weight ratio)) at a concentration of 2 g / L, and subjected to 500 MHz spectroscopy using tetramethylsilane as an internal standard. １ H-NMR was measured.

[0149] Regarding the chemical structure of modified EVOH (A8) modified with epoxypropane, the contents of each structural unit were determined according to the method described in Patent Document 4. The ethylene content was 38 mol % and the epoxypropane content was 1.5 mol %. The analysis results of the obtained resin are shown in Table 1.

[0150]

[0151] [Example 1] Modified EVOH (A) Solution The modified EVOH (A1) obtained in Synthesis Example 1 was completely dissolved in a mixed solvent of n-propyl alcohol / water (weight ratio 70 / 30) to prepare a solution containing 15 wt % of modified EVOH (A1). For the coating test (production and evaluation of coated films) described below, the solution was stored for 1 day in an environment of 20°C and 65% RH after preparation and used.

[0152] Solution viscosity The solution viscosity of the prepared solution was measured at 23°C using an analog viscometer LVT (manufactured by Brookfield). The viscosity immediately after the solution preparation was measured as V ０ The viscosity of the solution after storing it in an environment of 20°C for 7 days (1 week) is V ７ Before each measurement, the solution was stirred to make it uniform, and then the viscosity was measured at 23°C for 30 minutes after the temperature had stabilized. The viscosity stability of the solution was calculated by the viscosity change during storage of the solution |(V - V) / V ０ The smaller the |, the higher the viscosity stability of the solution.

[0153] Measurement of transmittance of solution The light transmittance of the prepared solution at a wavelength of 800 nm was measured using an ultraviolet-visible spectrophotometer (UV-2450 manufactured by Shimadzu Corporation). In the measurement, the solution was stirred, left to stand, and degassed in advance, and then added to a quartz cell with an optical path length of 1 cm. The state in which only the solvent was added to the quartz cell was taken as 100% transmittance. In order to evaluate the storage stability of the solution, the solution was measured immediately after preparation (T ０ ), stored at 15°C for 1 day, and then stored at 20°C for 7 days (1 week) (T ７ ), and the light transmittance of each solution was measured at 20° C. The solution was judged to have higher stability if it could maintain a high light transmittance even after storage for a long period of time or at a low temperature.

[0154] Preparation of coated film (multilayer structure) A polyester anchor coating agent (Toyo-Morton Co., Ltd., brand AD-335A) was applied to a polyethylene terephthalate film having a thickness of 25 μm using a bar coater at a solid content of 1 g / m ２ The modified EVOH solution was then applied using a bar coater and dried for 3 minutes in a hot air dryer at 60°C. The thickness of the modified EVOH (A) layer was measured by cutting the cross section of the resulting multilayer structure with a microtome and observing it with an optical microscope, and was found to be an average thickness of 5 µm. The resulting coated film was free from whitening or cloudiness and was very transparent and beautiful.

[0155] Measurement of haze of coated film The coated film was conditioned for 5 days in an environment of 20°C and 65% RH. The haze of the coated film after conditioned humidity was measured using a haze / transmittance / reflectance meter (HR-100, manufactured by Murakami Color Research Laboratory Co., Ltd.).

[0156] Oxygen transmission rate (OTR) of coated film The coated film was conditioned for 5 days in an environment of 20°C and 65% RH. The oxygen transmission rate of the coated film after the humidity conditioning was measured using a MOCON OX-TRAN2 / 21 model manufactured by Modern Controls under conditions of 20°C and 65% RH in accordance with the method described in JIS K7126 (constant pressure method). In the measurement, two samples were measured, and the average value was calculated as the value (cc·20μm / m) converted into a value for a coating layer thickness of 20μm. ２The oxygen permeability of the polyethylene terephthalate film substrate is much higher than that of the layer formed by applying modified EVOH (A) or EVOH (B), so the influence of the substrate on the oxygen permeability of the coated film can be ignored.

[0157] The modified EVOH (A) solution did not show any decrease in permeability even after storage for 7 days. In addition, the oxygen permeability of the coated film prepared from the modified EVOH (A) solution after storage for 1 day in an environment of 20°C and 65% RH was 0.75 cc 20 μm / m ２ The coating film made from the solution after storing it at 20°C for 7 days also had a viscosity of 0.75cc 20µm / m ２ The evaluation results are shown in Tables 2 and 3.

[0158] [Example 2] Amorphous silica (brand: Sylysia 350, manufactured by Fuji Silysia Chemical Ltd., average particle size 3.9 μm) was added to a solution containing 15 wt% of the modified EVOH (A1) obtained in Example 1 so that the content relative to the modified EVOH (A1) was 1000 ppm, and the mixture was then stirred and mixed to prepare a solution. Except for using this solution, a coated film was produced, evaluated, and analyzed in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0159] [Examples 3 to 9] Modified EVOH solutions were prepared, coated films were produced, and the evaluation and analysis thereof were carried out in the same manner as in Example 1, except that the modified EVOH and solvents shown in Table 2 were used in the preparation of the modified EVOH solutions. The results are shown in Tables 2 and 3.

[0160] [Example 10] The modified EVOH solution was prepared, a coated film was produced, and the evaluation and analysis thereof were carried out in the same manner as in Example 1, except that the modified EVOH (A7) obtained in Synthesis Example 7 was used as the modified EVOH used in preparing the modified EVOH solution, N-methylpyrrolidone was used as the solvent, and the drying temperature after applying the modified EVOH solution was changed to 140°C. The results are shown in Tables 2 and 3.

[0161] Example 11 Unmodified EVOH (B4) obtained in Synthesis Example 8, having an ethylene content of 55 mol% and a degree of saponification of 99.9 mol% or more, was dissolved in n-propyl alcohol / water (mixing weight ratio 80 / 20) to prepare a solution containing 15 wt% of EVOH-B4. This solution was mixed and stirred with the solution of modified EVOH-A1 obtained in Example 1 in a weight ratio of 1:2 to prepare a coating solution. The weight ratio of modified EVOH (A) to unmodified EVOH (B) in this solution was modified EVOH (A):unmodified EVOH (B) = 2:1. Except for using this solution, a coated film was prepared, evaluated, and analyzed in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0162] Comparative Examples 1 to 5 EVOH solutions were prepared and coated films were produced in the same manner as in Example 1, except that EVOH (B1) (Comparative Example 1, ethylene content 38 mol%, EVAL H171B, manufactured by Kuraray Co., Ltd.), EVOH (B2) (Comparative Example 2, ethylene content 27 mol%, EVAL L171B, manufactured by Kuraray Co., Ltd.), EVOH (B3) (Comparative Example 3, ethylene content 24 mol%, EVAL M100B, manufactured by Kuraray Co., Ltd.), unmodified EVOH (B4) obtained in Synthesis Example 8 (Comparative Example 4), or modified EVOH (A8) modified with epoxypropane obtained in Synthesis Example 9 (Comparative Example 5) was used instead of modified EVOH (A), and the solvents shown in Table 2 were used. The storage stability of the EVOH solutions obtained in Comparative Examples 1 to 5 and the haze and oxygen permeability of the coated films were evaluated in the same manner as in Example 1. The coated films obtained in Comparative Examples 1 to 3 were hazy and had poor appearance. The evaluation results are shown in Tables 2 and 3.

[0163] Comparative Example 6 The preparation of an EVOH solution, the production of a coated film, and the evaluation and analysis thereof were carried out in the same manner as in Example 1, except that the unmodified EVOH (B4) obtained in Synthesis Example 8 was used as the EVOH used in the preparation of the EVOH solution, N-methylpyrrolidone was used as the solvent, and the drying temperature after applying the EVOH solution was changed to 140° C. The results are shown in Tables 2 and 3.

[0164]

[0165]

[0166] As shown in Tables 2 and 3, the solution of Example 1 containing modified EVOH (A) was excellent in storage stability at room temperature and low temperature, was able to form a coating film with low haze and good appearance, and also had good gas barrier properties. In contrast, the solution of Comparative Example 1 containing only unmodified EVOH (B) was inferior in storage stability, the appearance of the coating film formed, and the gas barrier properties.

[0167] Synthesis Example 10 The same procedures as in Synthesis Example 1 were repeated up to the purification of the modified EVOH powder obtained by pulverization, except that in the saponification step of the modified EVAc, the modified EVOH was placed in ion-exchanged water (bath ratio 20), stirred and washed for 2 hours, and then drained. This procedure was repeated six times. The conductivity of the washing solution after the sixth washing was measured using a CM-30ET manufactured by Toa Denpa Kogyo Co., Ltd., and found to be 3 μS / cm. The water content of the obtained hydrous modified EVOH pellets was 110% by mass. (The water content of the hydrous EVOH is expressed as the mass % based on the dried EVOH. When the mass of the hydrous pellets is Mw and the mass of the EVOH after drying is Ms, it is calculated by (Mw-Ms) / Ms×100.)

[0168] 10.5 kg of the hydrous EVOH pellets obtained above were placed in 94.5 L of an aqueous solution prepared by dissolving acetic acid (0.8 g / L), sodium acetate (0.64 g / L), and phosphoric acid (0.016 g / L) in water to obtain concentrations of 0.8 g / L, 0.64 g / L, and 0.016 g / L, respectively. The pellets were immersed at 25°C for 6 hours with occasional stirring. The hydrous EVOH pellets after immersion were dehydrated by centrifugal dehydration and then dried in a hot air dryer at 80°C for 3 hours and then at 120°C for 24 hours to obtain pellet-modified EVOH (A9) as a dried EVOH resin composition. The sodium content as an alkali metal in the modified EVOH (A9) was 200 ppm (8.7 μmol / g). The analytical results of the modified EVOH (A9) are shown in Table 5.

[0169] [Synthesis Examples 11 to 19] Pellets of modified EVAc and dry EVOH resin compositions were prepared and analyzed in the same manner as in Synthesis Example 10, except that the polymerization conditions for modified EVOH and the composition of the solution in which the hydrous modified EVOH pellets were immersed were changed as shown in Table 4. The results are shown in Table 4.

[0170]

[0171] The dried EVOH resin composition pellets thus obtained and the following materials were used to produce a multilayer structure including a paper layer and a modified EVOH (A) layer: <Paper layer> Bleached kraft paper: Snow Queen G40, basis weight 50 g / m ２ , manufactured by Daio Paper Corporation Glassine paper: thick glassine, basis weight 31 g / m ２ , manufactured by Nippon Paper Industries Co., Ltd. Bleached kraft paper: basis weight 140 g / m ２ , manufactured by Nippon Paper Industries Co., Ltd. Kraft ball: S Kraft ball, basis weight 290 g / m ２ , manufactured by Nippon Paper Industries Co., Ltd. Kraft ball: S Kraft ball, basis weight 450 g / m ２ , manufactured by Nippon Paper Industries Co., Ltd. <Intermediate layer> Anchor coating agent: "Zaixen AC" (manufactured by Sumitomo Seika Chemicals Co., Ltd., polyolefin copolymer) Adhesive resin: "Bondine TX8030" (manufactured by Arkema) <Sealant layer>: "Zaixen AC" (manufactured by Sumitomo Seika Chemicals Co., Ltd., polyolefin copolymer) Non-oriented polypropylene film (CPP, thickness 30 μm) "Torayfan RNO 3951" (manufactured by Toray Advanced Film Co., Ltd.)

[0172] [Example 12] Bleached kraft paper (basis weight 50 g / m ２ ) was cut to A4 size, and one side was coated with ZAIKUSEN AC using a bar coater No. 12 manufactured by Daiichi Rikagaku Co., Ltd., and dried in a dryer at 120°C for 5 minutes (paper layer / intermediate layer). Next, EVOH (A14) was added to a mixed solvent of n-propyl alcohol and water (65 wt% n-propyl alcohol, 35 wt% water) so that the solids concentration was 15 wt%, and the mixture was stirred at 80°C for 3 hours, and it was confirmed that the EVOH (A14) was completely dissolved. The resulting solution was applied to the ZAIKUSEN AC-coated side of the bleached kraft paper using a bar coater No. 10 manufactured by Daiichi Rikagaku Co., Ltd., and then dried in a dryer at 120°C for 5 minutes (paper layer / intermediate layer / modified EVOH (A) layer). A two-component adhesive (Takelac (trademark) A-385 / Takenate A-10) was applied to a non-oriented polypropylene film (CPP, 30 μm thick) at a solids content of 2.5 g / m ２After coating at a basis weight of 100g, the coating was laminated by dry lamination on the modified EVOH (A) layer side of the bleached kraft paper (paper layer / intermediate layer / modified EVOH layer) to obtain a multilayer structure consisting of paper layer / intermediate layer / modified EVOH layer / / sealant layer. A cross section was prepared using a microtome, and the thickness of each layer was measured at five points under a microscope, and the average of the measurements was taken as the thickness of each layer.

[0173] Gas Barrier Property: The oxygen permeability was evaluated as the gas barrier property. A portion was cut out from the obtained multilayer structure, and measured using an oxygen permeability measuring device, OX-TRAN2 / 20 model (detection limit: 0.01 cc / m) manufactured by MOCON INC. ２ The oxygen transmission rate was measured in accordance with the method described in JIS K7126 (constant pressure method) using a pressure of 1.0 cc / m² (day atm) under conditions of 20°C and 65% RH. The obtained value was designated OTR1 and evaluated according to the following criteria. A package including a folded portion folded 360 degrees was produced using the multilayer structure, and a portion was cut out so that the folded portion was at the center, and the oxygen transmission rate was measured. The obtained value was designated OTR2. OTR2 was also evaluated according to the following criteria. <Evaluation Criteria> A: 1.0 cc / m² ２ ・day・atm or less B: 1.0cc / m ２ ・Day・atm and greater than 5.0cc / m ２ ・day・atm or less C: 5.0cc / m ２ ・day・atm and greater than 10.0cc / m ２ ・day・atm or less D: 10.0cc / m ２ ・Day・atm and larger than 20cc / m ２ ・day・atm or less E: 20cc / m ２ ・Day・Larger than ATM

[0174] Gas barrier properties OTR2 / OTR1 before and after the folded portion The ratio (OTR2 / OTR1) of the oxygen permeability OTR1 of the portion excluding the folded portion to the oxygen permeability OTR2 of the portion including the folded portion was evaluated according to the following criteria: A: OTR2 / OTR1 is 1.0 or more and less than 1.5 B: OTR2 / OTR1 is 1.5 or more and less than 3.0 C: OTR2 / OTR1 is 3.0 or more and less than 5.0 D: OTR2 / OTR1 is 5.0 or more and less than 10.0 E: OTR2 / OTR1 is 10.0 or more

[0175] Heat Seal Strength The heat seal strength of the multilayer structure was measured in accordance with JIS Z 0238. Using the multilayer structure, strips of 15 mm in width were prepared, and the strips were stacked so that the same layers (sealant layers or modified EVOH (A) layers) were in contact with each other. The overlapping portions of 100 mm in length were heated at 160°C or 180°C under a pressure of 2.0 kgf / cm using a thermal gradient tester manufactured by Toyo Seiki Seisaku-sho, Ltd. ２ The sample was heat-sealed for 1 second at 1500 gf / 15 mm. Using this sample, the T-peel strength (unit: gf / 15 mm) was measured at a pulling rate of 300 mm / min using an autograph "AGS-H" manufactured by Shimadzu Corporation under an atmosphere of 23°C and 50% RH. Ten measurements were performed, and the average value was calculated. The higher of the values ​​obtained by heat-sealing at 160°C and 180°C was taken as the heat-seal strength and evaluated based on the following criteria: A: 1500 gf / 15 mm or more B: 800 gf / 15 mm or more but less than 1500 gf / 15 mm C: 500 gf / 15 mm or more but less than 800 gf / 15 mm D: 300 gf / 15 mm or more but less than 500 gf / 15 mm E: Less than 300 gf / 15 mm

[0176] Appearance and Taste of Packages in Cashew Nut Storage Tests The multilayer structure was cut into a rectangle measuring 17 cm in length and 32 cm in width, folded 8.5 cm from both horizontal ends, and overlapped so that the same layers at both ends met over a 1 cm width. This overlapping portion (body portion 11b in Figure 1 ) and one vertical end (end portion 11a in Figure 1 ) were heat-sealed over a 1 cm width to produce a package. 50 g of cashew nuts (water activity 0.33) were placed inside, and the other vertical end (end portion 11a in Figure 1 ) was heat-sealed to form a tight seal. This package was stored for 100 days under conditions of 23°C and 50% RH, and the appearance of the package was observed with the naked eye and rated as follows. The appearance characteristics were rated according to the following criteria: A, B, C, D, and E, in order of increasing severity of oil stains. The cashew nuts were also tasted by a panel of five people, who consensus-judged them according to the following criteria. The standard for judging taste is that the change in taste increases in the order of A, B, C, D, and E.

[0177] Appearance characteristics evaluation criteria A: No change B: Slight oil stains were observed C: Some oil stains were observed D: Slight oil stains were observed E: Oil stains were clearly observed

[0178] - Taste judgment criteria A: Almost the same as before storage B: The taste has changed slightly compared to before storage C: The taste has changed a little compared to before storage D: The taste has changed a little compared to before storage E: The taste has changed compared to before storage

[0179] The OTR1 of the multilayer structure (the portion excluding the folded portion) before being processed into a package was 0.32 cc / m ２ The OTR after bending was measured and found to be 0.35 cc / m ２ The OTR2 / OTR1 ratio was 1.1, resulting in an A rating. The heat seal strength was 2800 gf / 15 mm, resulting in an A rating. After the cashew nut storage test, the appearance of the package was evaluated and found to be unchanged, resulting in an A rating. A taste test of the cashew nuts after storage showed almost no change from before storage, resulting in an A rating.

[0180] [Examples 13 to 28, Comparative Example 7] Multilayer structures were obtained in the same manner as in Example 12, except that the type and thickness of the paper layer, the modified EVOH (A), the intermediate layer, and the heat seal layer were changed as shown in Table 5. The thickness of the modified EVOH (A) layer and the thickness of the intermediate layer were adjusted by changing the depth (count) of the bar coater. The obtained multilayer structures were evaluated in the same manner as in Example 12. The evaluation results are shown in Table 5.

[0181]

[0182] As shown in the above examples, the coating agent of the present invention has good storage stability, and the resulting coating has good gas barrier properties and appearance. Multilayer structures formed by applying the coating agent to a substrate can be suitably used for various packaging materials. Furthermore, multilayer structures comprising a layer formed by applying the coating agent and a paper layer have good gas barrier properties despite using a paper substrate (paper layer), and maintain good gas barrier properties even after bending. Furthermore, the multilayer structures have sufficient heat seal strength for use as packaging.

[0183] 10 Vertical form-fill-seal bag 11 Multilayer structure 11a End portion 11b Body portion

Claims

1. A coating agent containing a modified ethylene-vinyl alcohol copolymer (A), wherein the modified ethylene-vinyl alcohol copolymer (A) contains structural units (Ia), (Ib) and (Ic) represented by the following formulas, the contents (mol %) a, b and c of the structural units (Ia), (Ib) and (Ic) satisfy the following formulas (1) to (3), and the degree of saponification (DS) of the modified ethylene-vinyl alcohol copolymer (A) represented by the following formula (4) is 90 mol % or more. 【Chemistry 1】 21≦a≦55 (1) 0.1≦c≦10 (2) [100-(a+c)]×0.9≦b≦[100-(a+c)] (3) DS = [(total number of moles of X, Y, and Z that are hydrogen atoms) / (total number of moles of X, Y, and Z)] × 100 (4) [In the formula, a, b, and c represent the content (mol %) of each structural unit relative to 100 mol % of the total of all structural units, and W represents a methyl group or R ２ X, Y and Z each independently represent a hydrogen atom, a formyl group or an alkanoyl group having 2 to 10 carbon atoms; R １ represents a single bond, an alkylene group having 1 to 9 carbon atoms, or an alkyleneoxy group having 1 to 9 carbon atoms. The alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. R ２ represents an alkylene group having 1 to 9 carbon atoms or an alkyleneoxy group having 1 to 9 carbon atoms, and the alkylene group and the alkyleneoxy group may contain a hydroxyl group, an alkoxy group, or a halogen atom. * represents a bonding site.]

2. In the structural unit (Ic), W is R ２ is a group represented by —OY, １ is a single bond, R ２ 2. The coating agent according to claim 1, wherein is a methylene group, and Y and Z are hydrogen atoms.

3. 2. The coating agent according to claim 1, wherein the modified ethylene-vinyl alcohol copolymer (A) has a degree of saponification (DS) of 99 mol % or more.

4. 2. The coating agent according to claim 1, wherein the content of the modified ethylene-vinyl alcohol copolymer (A) is 1 to 50% by weight.

5. 2. The coating agent according to claim 1, further comprising an ethylene-vinyl alcohol copolymer (B) other than the modified ethylene-vinyl alcohol copolymer (A), the ethylene content of the ethylene-vinyl alcohol copolymer (B) being 21 to 55 mol %.

6. 6. The coating agent according to claim 5, wherein the total content of the modified ethylene-vinyl alcohol copolymer (A) and the ethylene-vinyl alcohol copolymer (B) is 1 to 50% by weight.

7. 2. The coating agent according to claim 1, comprising 10 to 10,000 ppm of inorganic fine particles having an average particle size of 0.1 to 10 μm.

8. 8. The coating agent according to claim 7, wherein the inorganic fine particles are amorphous silica.

9. 2. The coating agent according to claim 1, wherein the coating agent is a solution of the modified ethylene-vinyl alcohol copolymer (A) containing a solvent, and the solvent is a mixed solvent of alcohol and water.

10. The light transmittance T of the coating agent at a wavelength of 800 nm with an optical path length of 1 cm after storage at 20° C. for 7 days ７ (%) and the light transmittance T of the coating agent at a wavelength of 800 nm with an optical path length of 1 cm before storage ０ (%) difference (T ０ -T ７ 10. The coating agent according to claim 9, wherein the ratio of the surface area to the surface area is within 20%.

11. 10. The coating agent according to claim 9, wherein a change in solution viscosity after storage at 20°C for one week is within 50% of that before storage.

12. A multilayer structure obtained by applying the coating agent according to any one of claims 1 to 11 onto a substrate.

13. A multilayer structure comprising a layer coated with the coating agent according to any one of claims 1 to 11 and a paper layer.

14. The paper layer has a basis weight of 15 to 800 g / m ２ 14. The multilayer structure of claim 13, wherein:

15. The multilayer structure according to claim 13, wherein the modified ethylene-vinyl alcohol copolymer (A) contains alkali metal ions in an amount of 2.5 to 22 μmol / g.

16. The oxygen permeability measured in accordance with JIS-K7126-2 (2006) Part 2 (constant pressure method) under conditions of 20°C and 65% RH is 20 cc / (m ２ 14. The multilayer structure according to claim 13, wherein the viscosity is equal to or less than 1.5 MPa (day atm).

17. 14. The multilayer structure according to claim 13, which has a heat seal strength of 300 gf / 15 mm or more as measured at a width of 15 mm in accordance with JIS Z 0238.

18. 14. The multi-layer structure of claim 13, further comprising an intermediate layer and a sealant layer.

19. 20. The multi-layer structure of claim 18, wherein the intermediate layer comprises a thermosetting or thermoplastic resin (f).

20. 20. The multi-layer structure of claim 18, wherein the sealant layer comprises a thermoplastic resin (g).

21. 20. The multilayer structure according to claim 19, wherein the thermoplastic resin (f) comprises at least one selected from the group consisting of polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

22. The multilayer structure of claim 20, wherein the thermoplastic resin (g) comprises at least one selected from the group consisting of polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

23. The multilayer structure according to claim 13 , wherein a weight M1 of the paper layer and a total weight M2 of the other layers satisfy the following formula (5): 1≦M1 / M2≦300 (5)

24. A package comprising the multi-layer structure of claim 13 and having one or more folds.

25. 25. The package of claim 24, wherein the contents of the package are food products, the water activity of the food products being between 0.10 and 0.94.

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