JP6684694B2 - Multilayer structure having fluorescent ethylene-vinyl alcohol copolymer - Google Patents

Description

  The present invention relates to a multilayer structure having a fluorescent ethylene-vinyl alcohol copolymer. More specifically, the present invention relates to a multilayer structure having a fluorescent ethylene-vinyl alcohol copolymer that can detect defects in the ethylene-vinyl alcohol copolymer-containing layer easily and at low cost and has excellent recoverability.

  Conventionally, resin compositions containing fluorescent substances have been used for various purposes. For example, there has been developed a method for detecting foreign matter and irregular shape using a container body having an excited luminescent substance that is excited by ultraviolet irradiation to emit light (Patent Document 1).

  Further, as a resin composition used for applications such as a sealing material for solar cell materials and a glass plate for construction, a resin composition containing a fluorescent substance capable of absorbing ultraviolet rays and converting into visible light has been developed (Patent Reference 2).

  Furthermore, as an ethylene-vinyl alcohol copolymer resin composition having a beautiful appearance, an ethylene-vinyl alcohol copolymer resin composition containing a fluorescent whitening agent that emits fluorescence has been developed (Patent Document 3).

JP, 2005-265812, A JP, 2005-221879, A JP, 2009-242644, A

  However, although Patent Document 1 mentions that it is possible to detect abnormalities in the container sealed portion due to fluorescence due to ultraviolet irradiation, it is possible to use an ethylene-vinyl alcohol copolymer layer effective for protecting contents such as extending the shelf life of food. No mention is made of whether the defect can be detected.

  In Patent Document 2, although the types and amounts of the fluorescent substance and the additive are mentioned, ethylene-vinyl alcohol copolymer is not exemplified as the thermoplastic resin composition containing the fluorescent substance, and No mention is made of laminates. Further, there is no mention of using it for the purpose of detecting defects. Further, there is no mention of a laminate having a fluorescent substance-containing ethylene-vinyl alcohol copolymer layer.

  Although Patent Document 3 mentions the amount of the fluorescent whitening agent added, whether or not it has sufficient fluorescence for defect detection within the range of the amount added and fatty acid salts suitable for defect detection are mentioned. Absent.

  Further, in applications such as sheet forming, unnecessary parts (hereinafter referred to as “scraps”) of the sheet after obtaining the formed product are collected and reused. However, there is a problem that the resin composition deteriorates when the scrap is reused, and a defect such as a fish eye occurs in the molded product. In all of Patent Documents 1 to 3 mentioned above, no influence is given to the recoverability (fisheye) of scraps composed of a laminate of a fluorescent substance-containing ethylene-vinyl alcohol copolymer and another resin such as polyolefin. .

  Therefore, the most important barrier layer (ethylene-vinyl alcohol copolymer layer) in the barrier packaging material can be detected, and there is no sufficient knowledge about the multilayer structure suitable for recovery.

  The present invention provides a multilayer structure having a fluorescent ethylene-vinyl alcohol copolymer, which can detect defects in the ethylene-vinyl alcohol copolymer-containing layer easily and at low cost, and has excellent recoverability. With the goal. Moreover, it aims at providing the defect detection method in the said multilayer structure.

  The present inventors have conducted extensive studies to solve the above-mentioned problems, and as a result, each of the layer (X) containing the resin composition (A) and the layer (Y) containing the thermoplastic resin (B) are respectively formed. In a multilayer structure having at least one layer, the resin composition (A) has an ethylene-vinyl alcohol copolymer (C) (hereinafter, also referred to as “EVOH (C)”), a fluorescent substance (D), and A molar amount of the fluorescent substance (D) and the fatty acid aluminum salt (E), which contains the fatty acid aluminum salt (E) and has a predetermined value with the content of the fluorescent substance (D) in the resin composition (A). By finding the ratio (E / D), it was found that the above-mentioned problems can be solved, and further research was conducted based on this finding to complete the present invention.

That is, the present invention relates to the following inventions.
[1] A multilayer structure having at least one layer (X) including the resin composition (A) and at least one layer (Y) including the thermoplastic resin (B), wherein the resin composition ( A) contains an ethylene-vinyl alcohol copolymer (C), a fluorescent substance (D), and a fatty acid aluminum salt (E), and the content of the fluorescent substance (D) in the resin composition (A). Is 1 to 20 μmol / g, and the molar ratio (E / D) of the fluorescent substance (D) to the fatty acid aluminum salt (E) is 0.025 to 0.50;
[2] The multilayer structure according to [1], wherein the fluorescent substance (D) is coumarin or a coumarin derivative;
[3] The multilayer structure of [1] or [2], wherein the fatty acid aluminum salt (E) is a higher fatty acid aluminum salt having 12 to 24 carbon atoms (E1);
[4] The multilayer structure according to any one of [1] to [3], wherein the higher fatty acid aluminum salt having 12 to 24 carbon atoms (E1) is aluminum stearate;
[5] The multilayer structure according to any one of [1] to [4], wherein the thermoplastic resin (B) is one or more selected from the group consisting of polyolefin, polyester, polyamide, and polystyrene;
[6] The multilayer structure according to any one of [1] to [5], which has a structure in which the layer (Y) is laminated on at least one surface of the layer (X) via an adhesive layer;
[7] A packaging material containing the multilayer structure according to any one of [1] to [6];
[8] A pipe including the multilayer structure according to any one of [1] to [6];
[9] A fuel tank including the multilayer structure according to any one of [1] to [6];
[10] A defect detection method for irradiating the multilayer structure according to any one of [1] to [6] with ultraviolet rays.

  According to the present invention, it is possible to detect a defect in an ethylene-vinyl alcohol copolymer-containing layer easily and at low cost, and to provide a multilayer structure having a fluorescent ethylene-vinyl alcohol copolymer having excellent recoverability. You can That is, by using the multilayer structure of the present invention, the defects of the ethylene-vinyl alcohol copolymer layer can be visually identified only by irradiating with ultraviolet rays. Further, the multilayer structure of the present invention is excellent in recoverability, and can facilitate scrap recovery of a laminate (multilayer structure) of a fluorescent substance-containing ethylene-vinyl alcohol copolymer layer and a thermoplastic resin layer.

  The multilayer structure of the present invention is a multilayer structure having at least one layer (X) composed of the resin composition (A) and at least one layer (Y) containing the thermoplastic resin (B), The resin composition (A) is an ethylene-vinyl alcohol copolymer (C) (hereinafter sometimes abbreviated as "EVOH (C)"), a fluorescent substance (D), and a fatty acid aluminum salt (E). And the content of the fluorescent substance (D) in the resin composition (A) is 1 to 20 μmol / g, and the molar ratio (E) of the fluorescent substance (D) and the fatty acid aluminum salt (E) is / D) is 0.025 to 0.50.

  In the present specification, the upper limit value and the lower limit value of the numerical range (content of each component, value calculated from each component, each physical property, etc.) can be appropriately combined. In addition, in the present specification, the term “defect” means a state in which the layer is ruptured, a state in which a layer has a hole, a state in which a cut is made, or the like.

[Layer (X)]
The layer (X) is composed of the resin composition (A). The resin composition (A) contains EVOH (C), a fluorescent substance (D), and a fatty acid aluminum salt (E). The resin composition (A) may be substantially composed only of EVOH (C), the fluorescent substance (D), and the fatty acid aluminum salt (E), and may contain other components described below. Good. In the present specification, “substantially containing only a certain component” means that the content of components other than the component is less than 10% by mass, preferably less than 5% by mass, and more preferably 1% by mass. %, And more preferably less than 0.5% by mass.

[EVOH (C)]
EVOH (C) is a copolymer having ethylene units and vinyl alcohol units. EVOH (C) is obtained, for example, by saponifying a copolymer containing ethylene and a vinyl ester using an alkali catalyst or the like. Examples of vinyl esters include vinyl acetate, but other fatty acid vinyl esters (vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, Vinyl pivalate and vinyl versatate) can also be used.

The degree of saponification of the vinyl ester component of EVOH (C) is preferably 90 mol% or more, more preferably 95 mol% or more, further preferably 96 mol% or more, and 98 mol% or more. Is particularly preferable, and most preferably 99 mol% or more. By setting the degree of saponification to the above lower limit or more, the gas barrier property of the resin composition (A) can be improved. Further, the upper limit of the saponification degree may be 99.99 mol%. The degree of saponification can be determined by a known method such as ¹ H-NMR measurement.

The ethylene unit content of EVOH (C) is preferably 15 mol% or more, more preferably 20 mol% or more, and further preferably 23 mol%. The ethylene unit content is preferably 60 mol% or less, more preferably 55 mol% or less, and further preferably 50 mol% or less. If the ethylene unit content is less than 15 mol%, the melt moldability of the resin composition (A) may be reduced. When the ethylene unit content exceeds 60 mol%, the gas barrier property of the resin composition (A) may be deteriorated. The ethylene unit content can be determined by a known method such as ¹ H-NMR measurement.

  The EVOH (C) may have a unit derived from a monomer other than ethylene and vinyl ester and its saponified product as long as the object of the present invention is not impaired. When the EVOH (C) has the other monomer unit, the content of the other monomer unit with respect to the total structural units of the EVOH (C) is preferably 30 mol% or less, and 20 mol% It is more preferably at most, more preferably at most 10 mol%, and particularly preferably at most 5 mol%. When EVOH (C) has a unit derived from the other monomer, the lower limit value may be 0.05 mol% or 0.10 mol%. Examples of the other monomer include unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, and itaconic acid, or their anhydrides, salts, or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; Amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid or salts thereof; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane, γ -Vinylsilane compounds such as methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride and the like.

  The content of EVOH (C) in the resin composition (A) is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and 95 It is particularly preferably at least mass% and most preferably at least 98 mass%. The content of EVOH (C) in the resin composition (A) is preferably 99.99 mass% or less. When the content of EVOH (C) in the resin composition (A) is within the above range, the multilayer structure of the present invention can exhibit high gas barrier properties.

  EVOH (C) may be used alone or in combination of two or more.

[Fluorescent substance (D)]
As the fluorescent substance (D), known substances can be used without particular limitation. Examples thereof include pyrazoline, stilbene, triazine, thiazole, benzoxazole, xanthone, triazole, oxazole, thiophene, coumarin and their derivatives. Among them, coumarin or a coumarin derivative is preferable from the viewpoints of excellent handleability, good compatibility with the later-described fatty acid aluminum salt (E), and further improved conversion efficiency from ultraviolet rays to visible light.

（式中、Ｒ¹は水素原子、Ｃ₁〜Ｃ₄アシル基、カルボキシ基、Ｃ₁〜Ｃ₂₀アルコキシカルボニル基、シアノ基、ニトロ基の各基又は、Ｎ、Ｓ、及びＯからなる群から選ばれるヘテロ原子を１つ又は２つ含む芳香族残基を表し、Ｒ²は水素原子、ヒドロキシ基、メチル基、クロロ基、ブロモ基、トリフルオロメチル基の各基を表し、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶はそれぞれ独立して、水素原子、フルオロ基、クロロ基、ブロモ基、ヒドロキシ基、ニトロ基、Ｃ₁〜Ｃ₄アルキル基、Ｃ₁〜Ｃ₄アルコキシ基、アミノ基、Ｃ₁〜Ｃ₄アルキル基で１つ又は２つ置換されていてもよい１級又は２級アミノ基、Ｃ₁〜Ｃ₄アシル基の各基を表す。）で表されるクマリン系化合物が例示される。具体的には、ヒドロキシクマリン、７−ヒドロキシ−４−メチルクマリン、７−ジエチルアミノ−４−メチルクマリン等が挙げられる。このうち、ヒドロキシクマリン（上記一般式（Ｉ）においてＲ¹、Ｒ²、Ｒ³、Ｒ⁴、Ｒ⁵、Ｒ⁶の少なくとも１つがヒドロキシ基であるクマリン系化合物）、特に４−ヒドロキシクマリンが好ましい。 As the coumarin derivative, the following general formula (I)

(In the formula, R ¹ is a hydrogen atom, a C _{1 to} C ₄ acyl group, a carboxy group, a C _{1 to} C ₂₀ alkoxycarbonyl group, a cyano group, a nitro group, or a group consisting of N, S, and O. Represents an aromatic residue containing one or two heteroatoms selected, R ² represents a hydrogen atom, a hydroxy group, a methyl group, a chloro group, a bromo group or a trifluoromethyl group, and R ³ and R ⁴ , R ⁵ and R ⁶ are each independently a hydrogen atom, a fluoro group, a chloro group, a bromo group, a hydroxy group, a nitro group, a C _{1 to} C ₄ alkyl group, a C _{1 to} C ₄ alkoxy group, an amino group, A coumarin-based compound represented by a primary or secondary amino group which may be substituted with one or two C ₁ -C ₄ alkyl groups, or a C ₁ -C ₄ acyl group). To be done. Specific examples thereof include hydroxycoumarin, 7-hydroxy-4-methylcoumarin and 7-diethylamino-4-methylcoumarin. Of these, hydroxycoumarin (a coumarin-based compound in which at least one of R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ^{6 in} the above general formula (I) is a hydroxy group), particularly 4-hydroxycoumarin is preferable. .

  The content of the fluorescent substance (D) in the resin composition (A) is 1 μmol / g or more, preferably 1.5 μmol / g or more, and more preferably 2 μmol / g or more. The content of the fluorescent substance (D) in the resin composition (A) is 20 μmol / g or less, preferably 18 μmol / g or less, more preferably 15 μmol / g or less, and 12 μmol / G or less is particularly preferable. When the content of the fluorescent substance (D) is less than 1 μmol / g, it becomes difficult to visually identify the defect in the layer (X). Further, when the content of the fluorescent substance (D) is more than 20 μmol / g, the scrap recoverability of the multilayer structure of the present invention is deteriorated.

[Fatty acid aluminum salt (E)]
The resin composition (A) contains a fatty acid aluminum salt (E). By using the fatty acid aluminum salt (E) in combination with the fluorescent substance (D), the fluorescence intensity of the fluorescent substance (D) in the layer (X) can be further increased. This allows the layer (X) defect to be visually identified. Further, by containing the fatty acid aluminum salt (E), formation of fish eyes can be suppressed in the scrap of the multilayer structure of the present invention.

  In the present invention, "fatty acid aluminum" is a concept including any of mono-fatty acid aluminum, di-fatty acid aluminum and tri-fatty acid aluminum. The “fatty acid” may be a fatty acid in which a part of the alkyl chain is substituted with a hydroxy group. The fatty acid aluminum salt (E) may be a lower / intermediate fatty acid aluminum salt such as aluminum acetate, but is preferably a higher fatty acid aluminum salt (E1) having 12 to 24 carbon atoms. The carbon number of the higher fatty acid is preferably 13 or more, more preferably 14 or more. The carbon number of the higher fatty acid is preferably 22 or less, more preferably 20 or less. By using the higher fatty acid aluminum salt (E1) having 12 or more and 24 or less carbon atoms, it is possible to further suppress the formation of fish eyes in the scrap of the multilayer structure.

  Among the higher fatty acid aluminum salts (E1), particularly preferred are aluminum stearate, aluminum palmitate or aluminum montanate, with aluminum stearate or aluminum palmitate being preferred, and aluminum stearate being more preferred. The fatty acid aluminum salt (E) may be used alone or in combination of two or more.

Aluminum stearate is a metal soap in which three organic molecules each having a side chain R of CH ₃ (CH ₂ ) _16- , an alkyl chain and a carboxy group, and one aluminum are electrically neutral. , Has various uses as a material dispersed in a resin. In addition, you may use the thing by which a part of alkyl chain was substituted by the hydroxy group. For example, aluminum 12-hydroxystearate can also be used.

  The molar ratio (E / D) of the fluorescent substance (D) and the fatty acid aluminum salt (E) is 0.025 or more, preferably 0.05 or more, and more preferably 0.08 or more. . The molar ratio (E / D) is 0.50 or less, preferably 0.45 or less, and more preferably 0.40 or less. When the molar ratio (E / D) is less than 0.025, it becomes difficult to visually identify the defects in the layer (X). Further, if the molar ratio (E / D) exceeds 0.50, the scrap recoverability of the multilayer structure of the present invention deteriorates.

[Other ingredients]
As the resin composition (A), other resin other than EVOH (C) and other additives other than the fluorescent substance (D) and the fatty acid aluminum salt (E) can be used as the other components. You may contain in the range which is not inhibited.

  Examples of the other resin include polyolefin and the like. However, when the resin composition (A) contains the other resin, the content of the other resin with respect to all the resin components in the resin composition (A) is preferably 10% by mass or less, and 5% by mass or less. % Or less, more preferably 3% by mass or less. Since the resin component contained in the resin composition (A) is substantially composed of only EVOH (C), the gas barrier property and the scrap recoverability can be further improved.

  Examples of the other additives include known additives such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, antiblocking agents, and desiccants. However, the content of the additive is preferably 2 parts by mass or less, and more preferably 1 part by mass or less, with respect to 100 parts by mass of EVOH (C). By reducing the content of the additive, it becomes easier to visually confirm the defects, and the scrap recoverability can be improved.

  As the antioxidant, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4′-thiobis- (6-t-butylphenol, 2,2′- Methylene-bis (4-methyl-6-t-butylphenol, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, octadecyl-3- (3 Examples include ', 5-di-t-butyl-4'-hydroxyphenyl) propionate and 4,4'-thiobis- (6-t-butylphenol).

  As the ultraviolet absorber, ethyl-2-cyano-3,3-diphenyl acrylate, 2- (2′-hydroxy-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′) -T-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, etc. Can be mentioned.

  Examples of the plasticizer include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, and phosphoric acid ester.

  Examples of the antistatic agent include pentaerythritol monostearate, sorbitan monopalmitate, sulfated oleic acid, polyethylene oxide, carbowax and the like.

  Examples of the lubricant include ethylenebisstearylamide, butyl stearate, calcium stearate, zinc stearate and the like.

  Examples of the colorant include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, titanium oxide, red iron oxide and the like.

  Examples of the filler include glass fiber, mica, ballastonite and the like.

  In addition, the resin composition (A) may contain various acids and compounds such as fatty acid aluminum salt (E) and various metal salts from the viewpoint of thermal stability or viscosity adjustment. Examples of the various acids include carboxylic acids, phosphoric acid compounds, and boron compounds, and examples of the various metal salts include alkali metal salts and alkali metal salts. Note that these compounds may be used by mixing with EVOH (C) in advance.

(Carboxylic acid and / or carboxylate ion)
By being contained in the resin composition (A), the carboxylic acid and / or the carboxylate ion improves the coloring resistance of the resin composition during melt molding.

  Carboxylic acid is a compound having one or more carboxy groups in the molecule. The carboxylate ion is a hydrogen ion of the carboxy group of carboxylic acid desorbed. The carboxylic acid contained in the resin composition (A) may be a monocarboxylic acid, a polyvalent carboxylic acid compound having two or more carboxy groups in the molecule, or a combination thereof. The polycarboxylic acid does not include a polymer. Further, the polyvalent carboxylic acid ion is one in which at least one hydrogen ion of the carboxy group of the polyvalent carboxylic acid is eliminated. The carboxy group of the carboxylic acid may have an ester structure, and the carboxylic acid ion may form a salt with a metal.

  The monocarboxylic acid is not particularly limited, and examples thereof include formic acid, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, acrylic acid, methacrylic acid, benzoic acid and 2-naphthoic acid. These carboxylic acids may have a hydroxy group or a halogen atom. Examples of the carboxylate ion include those in which the hydrogen ion of the carboxy group of each of the above-mentioned carboxylic acids has been eliminated. The pKa of the monocarboxylic acid (including the monocarboxylic acid that gives a monocarboxylic acid ion) is preferably 3.5 or more, more preferably 4 or more, from the viewpoint of the pH adjusting ability and melt moldability of the composition. Examples of such monocarboxylic acids include formic acid (pKa = 3.68), acetic acid (pKa = 4.74), propionic acid (pKa = 4.85), butyric acid (pKa = 4.80), and the like. Acetic acid is preferable from the viewpoint of easy handling.

  The polycarboxylic acid is not particularly limited as long as it has two or more carboxy groups in the molecule, and examples thereof include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, and adipine. Acids, aliphatic dicarboxylic acids such as pimelic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid; tricarboxylic acids such as aconitic acid; 1,2,3,4-butanetetracarboxylic acid, ethylenediaminetetraacetic acid, etc. A carboxylic acid having 4 or more carboxy groups; a hydroxycarboxylic acid such as tartaric acid, citric acid, isocitric acid, malic acid, mutic acid, tartronic acid, citramalic acid; Ketocarboxylic acids such as ketoglutaric acid; amino acids such as glutamic acid, aspartic acid and 2-aminoadipic acid It is below. Incidentally, examples of the polyvalent carboxylate ion include these anions. Among these, succinic acid, malic acid, tartaric acid, and citric acid are particularly preferable because they are easily available.

  When the resin composition (A) contains a carboxylic acid and / or a carboxylate ion, the content thereof should be 0.01 μmol / g or more in terms of carboxylic acid radicals from the viewpoint of coloring resistance during melt molding. Is preferable, more preferably 0.05 μmol / g or more, still more preferably 0.5 μmol / g or more. Also, it is preferably 20 μmol / g or less, more preferably 15 μmol / g or less, and further preferably 10 μmol / g or less in terms of carboxylic acid radical.

(Phosphate compound)
The resin composition (A) may further contain a phosphoric acid compound. By containing the phosphoric acid compound in the resin composition (A), the long-run property at the time of melt molding of the resin composition (A) can be improved.

  The phosphoric acid compound is not particularly limited, and examples thereof include various phosphorus oxygen acids such as phosphoric acid and phosphorous acid, and salts thereof. The phosphate may be contained in any form of, for example, a first phosphate, a second phosphate, and a third phosphate, and its counter cation species is not particularly limited, but it may be an alkali metal salt. Alternatively, an alkaline earth metal salt is preferable, and an alkali metal salt is more preferable. Specifically, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate is preferable from the viewpoint of improving long-run property during melt molding.

  When the resin composition (A) contains a phosphoric acid compound, its content is preferably 1 ppm or more, more preferably 5 ppm or more, and more preferably 8 ppm or more in terms of phosphate radicals in the dry resin composition. It is more preferable that there is. Further, it is preferably 500 ppm or less, more preferably 200 ppm or less, and further preferably 50 ppm or less in terms of phosphate radical conversion. When the content of the phosphoric acid compound is within the above range, the long-run property during melt molding can be further improved.

(Boron compound)
When the boron compound is contained in the resin composition (A), the long-run property at the time of melt molding of the resin composition (A) can be improved, and as a result, a gel or lump (through melt extrusion or the like is used). The appearance characteristics can be improved by suppressing the occurrence of defects, etc. occurring in the appearance of the obtained molded product. Specifically, when a boron compound is added to the resin composition, it is considered that a borate ester is formed between EVOH (C) and the boron compound, and by using such a resin composition, the boron compound is contained. It is possible to improve the long-run property as compared with the resin composition which does not.

The boron compound is not particularly limited, and examples thereof include boric acids, boric acid esters, borate salts, and borohydrides. Specifically, examples of boric acids include orthoboric acid (H ₃ BO ₃ ), metaboric acid, tetraboric acid, and the like. Examples of the borate ester include triethyl borate and trimethyl borate. Examples of the borate include alkali metal salts, alkaline earth metal salts, and borax of the various boric acids. Of these, orthoboric acid is preferable.

  When the resin composition (A) contains a boron compound, the content thereof is preferably 5 ppm or more, more preferably 10 ppm or more, and more preferably 50 ppm in terms of the boron element of the boron compound in the dry resin composition. It is more preferable that the above is satisfied. Further, it is preferably 2000 ppm or less, more preferably 1000 ppm or less, further preferably 500 ppm or less, and particularly preferably 300 ppm or less in terms of boron element. When the content of the boron compound is within the above range, the long-run property during melt molding can be further improved.

(Alkali metal salt)
Examples of the alkali metal constituting the alkali metal salt include lithium, sodium, potassium, rubidium, and cesium, but sodium or potassium is more preferable from the viewpoint of industrial availability. When the resin composition (A) contains an alkali metal, the long-run property and the interlayer adhesive force when forming a multilayer structure are improved.

  The alkali metal salt is not particularly limited, and examples thereof include aliphatic carboxylic acid salts of lithium, sodium, potassium and the like, aromatic carboxylic acid salts, phosphates, metal complexes and the like. Specific examples of the alkali metal salt include sodium acetate, potassium acetate, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and tribasic phosphate. Examples thereof include potassium, lithium dihydrogen phosphate, trilithium phosphate, sodium stearate, potassium stearate, and a sodium salt of ethylenediaminetetraacetic acid. Among these, sodium acetate, potassium acetate, and sodium dihydrogen phosphate are particularly preferable because they are easily available.

  When the resin composition (A) contains an alkali metal salt, the content of the alkali metal salt in the resin composition (A) is preferably 2.5 μmol / g or more in the dry resin composition. It is more preferably at least 0.5 μmol / g, further preferably at least 4.5 μmol / g. Further, the content of the alkali metal salt is preferably 22 μmol / g or less, more preferably 16 μmol / g or less, and further preferably 10 μmol / g or less. When the content of the alkali metal salt is 2.5 μmol / g or more, the interlayer adhesion of the multilayer structure of the present invention is more excellent, which is preferable. Further, when the content of the alkali metal salt is 22 μmol / g or less, the appearance of the layer (X) becomes better, which is preferable.

(Alkaline earth metal salt)
Examples of the alkaline earth metal include beryllium, magnesium, calcium, strontium, barium and the like, but magnesium or calcium is more preferable from the viewpoint of industrial availability. When the resin composition (A) contains an alkaline earth metal, the scrap recoverability of the multilayer structure of the present invention is improved.

  The resin composition (A) may be produced by dry blending EVOH (C), a fluorescent substance (D), and a fatty acid aluminum salt (E) when molding the multilayer structure of the present invention, The EVOH (C), the fluorescent substance (D), and the fatty acid aluminum salt (E) may be dry blended in advance, melt-kneaded, and pelletized.

[Layer (Y)]
The layer (Y) contains a thermoplastic resin (B). The layer (Y) may be substantially composed of only the thermoplastic resin (B).

  Examples of the thermoplastic resin (B) include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene-α-olefin. Polyolefins which are homopolymers or copolymers of olefins such as copolymers (α-olefins having 4 to 20 carbon atoms), polybutene, polypentene; polyesters such as polyethylene terephthalate; polyester elastomers; nylon-6, nylon-6,6. And the like; polystyrene; polyvinyl chloride; polyvinylidene chloride; acrylic resin; vinyl ester resin; polyurethane elastomer; polycarbonate; chlorinated polyethylene; chlorinated polypropylene and the like. Among the above, at least one selected from the group consisting of polyolefin, polyester, polyamide, and polystyrene is preferable, and polyolefin is more preferable. These may be used alone or in combination of two or more.

[Structure of multilayer structure]
Specific examples of the structure of the multilayer structure of the present invention are shown below. Further, the following specific examples may be laminated or combined in plural layers. In addition, the layer (X) and the layer (Y) may be continuously laminated in plural layers.
2 layers: layer (Y) / layer (X),
3 layers: layer (Y) / layer (X) / layer (Y), layer (Y) / adhesive layer / layer (X),
4 layers: layer (Y) / adhesive layer / layer (X) / adhesive layer, adhesive layer / layer (Y) / adhesive layer / layer (X),
5 layers: layer (Y) / adhesive layer / layer (X) / adhesive layer / layer (Y), layer (X) / adhesive layer / layer (Y) / adhesive layer / layer (X), layer (Y) / Adhesive layer / layer (X) / adhesive layer / layer (X), adhesive layer / layer (Y) / adhesive layer / layer (X) / adhesive layer 6 layers: layer (Y) / adhesive layer / layer (X) / Adhesive layer / Layer (Y) / Adhesive layer 7 layers: Layer (Y) / Adhesive layer / Layer (X) / Adhesive layer / Layer (X) / Adhesive layer / Layer (Y)

  The multilayer structure of the present invention preferably has a structure in which the layer (Y) is laminated on at least one surface of the layer (X) via an adhesive layer, and the layer (Y) is formed on both surfaces of the layer (X). It is more preferable to have a structure in which the adhesive layers are laminated. Since the multilayer structure of the present invention has such a structure, the flex resistance of the multilayer structure can be improved.

  The adhesive resin used in the adhesive layer is preferably an adhesive resin made of a carboxylic acid-modified olefin polymer. The carboxylic acid-modified olefin-based polymer is a modified product containing a carboxy group obtained by chemically bonding an ethylenically unsaturated carboxylic acid or an anhydride thereof to the olefin-based polymer (for example, by an addition reaction or a graft reaction). It means an olefin polymer. In addition, the olefin-based polymer means a polyolefin such as polyethylene (low pressure, medium pressure, high pressure), linear low-density polyethylene, polypropylene, and boribten; a comonomer (vinyl ester, a vinyl ester, a copolymer which can copolymerize the olefin with the olefin). And a saturated carboxylic acid ester, etc.) (for example, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ethyl ester copolymer, etc.). Among them, linear low-density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content 5 to 55% by mass), ethylene-acrylic acid ethyl ester copolymer (acrylic acid ethyl ester content 8 to 35% by mass) %) Is preferred and linear low density polyethylene and ethylene-vinyl acetate copolymers are particularly preferred. Examples of the ethylenically unsaturated carboxylic acid or its anhydride include ethylenically unsaturated monocarboxylic acid or its ester, ethylenically unsaturated dicarboxylic acid, its mono- or diester, and its anhydride, and ethylenically unsaturated dicarboxylic acid anhydride. The thing is suitable. 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, and the like. It is suitable.

  The addition amount or grafting amount (modification degree) of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer is 0.01 to 15% by mass, preferably 0.02 to 10% by mass based on the olefin polymer. Is. The addition reaction and grafting reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be obtained by, for example, a radical polymerization method in the presence of a solvent (such as xylene) and a catalyst (such as peroxide). The carboxylic acid-modified polyolefin thus obtained has a melt flow rate (MFR) measured at 190 ° C. under a load of 2160 g of preferably 0.2 to 30 g / 10 minutes, more preferably 0.5 to 10 g. / 10 minutes. These adhesive resins may be used alone or in combination of two or more.

  The method for molding the multilayer structure of the present invention is not particularly limited, and examples thereof include extrusion laminating method, dry laminating method, extrusion blow molding method, coextrusion laminating method, coextrusion sheet molding method, coextrusion pipe molding method, coextrusion blow molding method. Method, co-injection molding method, solution coating method and the like. The melting temperature varies depending on the melting point of the copolymer and the like, but is preferably about 190 ° C to 270 ° C. The multilayer structure obtained by such a method is reheated to a temperature below the melting point of EVOH (C) by a method such as vacuum pressure deep drawing and blow molding, and then subjected to secondary processing. May be given.

  The multilayer structure of the present invention is formed into various molded products such as packaging materials (for example, food and drink, cosmetics, pharmaceuticals), pipes, fuel tanks, tire tube materials and the like. The shape of the multilayer structure of the present invention is not particularly limited, and may be a film, a sheet, or a container.

  When the multilayer structure of the present invention is used as a pipe, it may be used as a pipe material for transporting an organic liquid, a hot water pipe material for heating (a hot water pipe material for floor heating, etc.) and the like.

  When the multilayer structure of the present invention is used in a fuel tank, for example, a filter, a fuel gauge, a baffle plate, etc. are provided as necessary. Since the fuel tank is excellent in appearance, gas barrier property, oil resistance, scrap recoverability, etc. by including the multilayer structure of the present invention, it is preferably used as a fuel tank. Here, the fuel tank is a fuel tank mounted on an automobile, a motorcycle, a ship, an aircraft, a generator, an industrial or agricultural device, or the like, or a portable fuel tank for refueling these fuel tanks, Means a tank for supplementing fuel. Typical examples of the fuel include gasoline, particularly oxygen-containing gasoline blended with methanol, ethanol, MTBE and the like, but also include heavy oil, light oil, kerosene and the like. Among these, the fuel tank is particularly preferably used as a fuel tank for oxygen-containing gasoline.

  Further, the fuel tank may have an antistatic coating. The antistatic coating can be performed using a conductive filler, a conductive fiber or a conductive resin. Examples of the conductive filler include metal powder such as copper and nickel. Examples of the conductive fibers include metal fibers such as iron and stainless steel; carbon black, carbon fibers, carbon fibrils described in JP-A-3-174018 and the like.

  The present invention includes various combinations of the above configurations within the technical scope of the present invention as long as the effects of the present invention are exhibited.

(Defect detection method)
The defect detection of the present invention can be carried out by irradiating the multilayer structure of the present invention with ultraviolet rays and visually confirming it. When the multi-layer structure of the present invention having a defect in the layer (X) is irradiated with ultraviolet rays, the defect site looks whiter than the surroundings and can be easily detected. It is expected that this is because the light around the defect is scattered. With such characteristics, even when the layer (X) has a structure sandwiched between the layers (Y), the defect in the layer (X) can be detected with good sensitivity. Irradiation of ultraviolet rays is not particularly limited, and a known ultraviolet irradiation device can be used.

  Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples, and many modifications can be made in the art within the technical idea of the present invention. This can be done by a person with ordinary knowledge.

[Ethylene Unit Content and Saponification Degree of EVOH (C)]
It was determined by ¹ H-NMR measurement using “JNM-GX-500 type” manufactured by JEOL Ltd. and DMSO-d ₆ as a solvent.

[Defect detection test]
(1) Test method Using the EVOH pellets obtained in Examples and Comparative Examples, a 20 mm extruder D2020 (manufactured by Toyo Seiki Seisakusho, D (mm) = 20, L / D = 20, compression ratio = 2.0, screw) : Full flight), an EVOH single layer film was produced under the following conditions.
<EVOH single layer film forming conditions>
Extrusion temperature: C1 / C2 / C3 / Die = 175 ° C./220° C./220° C./220° C.
Screw rotation speed: 40 rpm
Discharge rate: 1.2kg / hr
Take-up roll temperature: 80 ° C
Take-up roll speed: 2.0 m / min.
Film thickness: 100 μm
In addition, 20 mm extruder D2020 (manufactured by Toyo Seiki Seisakusho, D (mm) = 20, L / D = 20, compression ratio = 2.0, screw: full flight, using Umerit 1520F (manufactured by Ube Industries, Ltd., polyethylene) In (), a polyethylene single layer film was obtained under the following conditions.
<Polyethylene single layer film forming conditions>
Extrusion temperature: C1 / C2 / C3 / Die = 160 ° C / 200 ° C / 200 ° C / 200 ° C
Screw rotation speed: 40 rpm
Discharge rate: 1.2kg / hr
Take-up roll temperature: 40 ° C
Take-up roll speed: 0.4 m / min.
Film thickness: 500 μm
The obtained EVOH single-layer film and polyethylene single-layer film were each cut into A4 size, and a hole having a diameter of 5 mm was opened in the center of the EVOH single-layer film. An adhesive for dry lamination is applied to both sides of this perforated EVOH single layer film, and dry laminated with a constitution of polyethylene single layer film (500 μm) / perforated EVOH single layer film (100 μm) / polyethylene single layer film (500 μm). After drying at 80 ° C. for 3 minutes, curing was performed at 40 ° C. for 3 days to obtain a laminated film. As an adhesive for dry lamination, Takelac A-385 (manufactured by Takeda Pharmaceutical Co., Ltd.) was used as a main agent, Takenate A-50 (manufactured by Takeda Pharmaceutical Co., Ltd.) was used as a curing agent, and ethyl acetate was used as a diluting liquid. The coating amount was 4.0 g / m ² .

(2) Analytical method The resulting laminated film was irradiated with ultraviolet light having a wavelength of 365 nm using Blacklight EN-280L (manufactured by Spectronics), and the sharpness of the holes in the EVOH layer was confirmed. Defect detection was evaluated.
<Evaluation criteria>
A: The outline of the hole is clearly visible B: The hole is slightly visible C: The hole is not visible

[Recovery evaluation of multilayer structure]
(1) Test method EVOH pellets obtained in Examples and Comparative Examples as EVOH layers, Yumerit 1520F (Ube Industries, polyethylene) as thermoplastic resin layers, and Admer NF587 (Mitsui Chemicals, modified polyolefin) as adhesive layers. 3) and 5 layers of thermoplastic resin layer / adhesive layer / EVOH layer / adhesive layer / thermoplastic resin layer were co-extruded to prepare a multilayer structure. The extruder used and the conditions are shown below.
Extruder 1 [EVOH layer]:
Equipment: Single-screw extruder "Lab ME CO-NXT" (manufactured by Toyo Seiki Seisakusho)
Screw diameter: 20mmφ
Screw rotation speed: 40 rpm
Cylinder set temperature: 220 ℃
Die width: 300mm
Sheet take-up speed: 1 m / min Cooling roll temperature: 60 ° C
Extruder 2 [thermoplastic resin layer]:
Equipment: Single-screw extruder "GT-32-A type" (made by Institute of Plastics Engineering)
Screw diameter: 32mmφ
Screw rotation speed: 70 rpm
Cylinder set temperature: 220 ℃
Extruder 3 [adhesive resin layer]:
Equipment: Single-screw extruder "Lab ME CO-NXT" (manufactured by Toyo Seiki Seisakusho)
Screw diameter: 20mmφ
Screw rotation speed: 40 rpm
Cylinder set temperature: 220 ℃
Film composition:
Polyethylene layer / adhesive layer / EVOH / adhesive layer / polyethylene = 200 μm / 25 μm / 50 μm / 25 μm / 200 μm (total thickness 500 μm)
The obtained multilayer structure was pulverized with a pulverizer having a diameter of 8 mmφ mesh, and the pulverized product was used to prepare a 20 mm extruder D2020 (manufactured by Toyo Seiki Seisakusho, D (mm) = 20, L / D = 20, compression ratio = 2. 0.0, screw: full flight) to obtain a recovered monolayer film under the following conditions.
Extrusion temperature: C1 / C2 / C3 / Die = 175 ° C./220° C./220° C./220° C.
Screw rotation speed: 40 rpm
Discharge rate: 1.2kg / hr
Take-up roll temperature: 80 ° C
Take-up roll speed: 2.0 m / min.
Film thickness: 100 μm

(2) Analytical method The appearance of the recovered single-layer film was visually confirmed, and defects (fish eyes) and defects (holes) were evaluated as follows.
<Evaluation criteria>
A: The appearance is beautiful and there are few defects. B: There is no problem in the appearance, but the defects are slightly noticeable. C: There are many defects. D: There are many defects, and holes are observed in the film.

[Example 1]
As EVOH (C), 2000 g of Eval F101 (manufactured by Kuraray Co., Ltd., EVOH, ethylene unit content 32 mol%, saponification degree 99.6%, MFR 1.6 g / 10 min (190 ° C., 2160 g)), fluorescent substance ( 4-hydroxycoumarin is added as D) in an amount of 0.97 g (6000 μmol) and fatty acid aluminum salt (E) is added in an amount of 0.015 g (554 μmol) in terms of aluminum, and dry-blended, and then melt-kneaded with a twin-screw extruder. Then, EVOH pellets having a diameter of about 3 mm and a length of about 3 mm were produced. Table 1 shows the amount of the substance containing the fluorescent substance (D) in the EVOH pellets and the molar ratio of the fatty acid aluminum salt (E) to the fluorescent substance (D).

  Using the EVOH pellets thus obtained, the above-described defect detection test and recovery evaluation of the multilayer structure were performed. The results are shown in Table 1.

[Examples 2 to 6 and Comparative Examples 1 to 5]
EVOH pellets were prepared in the same manner as in Example 1 except that the amounts and types shown in Table 1 below were used for EVOH (C), fluorescent substance (D), and fatty acid aluminum salt (E). The defect detection test and the recovery of the multilayer structure were evaluated. The results are shown in Table 1.

  From the above results, the multilayer structure of the present invention can detect defects in the EVOH-containing layer easily and at low cost, and can suppress the generation of fish eyes. Therefore, the fluorescent substance-containing EVOH layer and the thermoplastic resin layer It was confirmed that scrap collection of the laminated body (multilayer structure) can be facilitated.

  In Comparative Example 1 containing no fatty acid aluminum salt (E), it was not easy to detect a defect, and many defects were observed. In Comparative Example 2 in which the amount of the fatty acid aluminum salt (E) was too large, many defects were observed. In Comparative Example 3 in which the blending amount of the fluorescent substance (D) was too small, it was not easy to detect the defect. In Comparative Example 4 in which the amount of the fluorescent substance (D) was too large, many defects were observed. In Comparative Example 5 in which the fatty acid calcium salt was used instead of the fatty acid aluminum salt (E), it was not easy to detect the defect.

  The multilayer structure of the present invention is useful for manufacturing packaging materials, pipes, and fuel tanks.

Claims (10)

A multi-layer structure having at least one layer (X) comprising a resin composition (A) and at least one layer (Y) containing a thermoplastic resin (B),
The resin composition (A) contains an ethylene-vinyl alcohol copolymer (C), a fluorescent substance (D), and a fatty acid aluminum salt (E),
The content of the fluorescent substance (D) in the resin composition (A) is 1 to 20 μmol / g,
A multilayer structure having a molar ratio (E / D) of the fluorescent substance (D) to the fatty acid aluminum salt (E) of 0.025 to 0.50.   The multilayer structure according to claim 1, wherein the fluorescent substance (D) is coumarin or a coumarin derivative.   The multilayer structure according to claim 1 or 2, wherein the fatty acid aluminum salt (E) is a higher fatty acid aluminum salt having 12 to 24 carbon atoms (E1).   The multilayer structure according to claim 1, wherein the higher fatty acid aluminum salt having 12 to 24 carbon atoms (E1) is aluminum stearate.   The multilayer structure according to any one of claims 1 to 4, wherein the thermoplastic resin (B) is one or more selected from the group consisting of polyolefin, polyester, polyamide, and polystyrene.   The multilayer structure according to claim 1, having a structure in which the layer (Y) is laminated on at least one surface of the layer (X) via an adhesive layer.   A packaging material comprising the multilayer structure according to any one of claims 1 to 6.   A pipe comprising the multilayer structure according to any one of claims 1 to 6.   A fuel tank comprising the multilayer structure according to claim 1.   A defect detection method comprising irradiating the multilayer structure according to any one of claims 1 to 6 with ultraviolet rays.