Multilayer structure, packaging bag, and method for manufacturing packaging material

Abstract

Provided is a multilayer structure comprising a sealant layer (α) and a base material layer (β), wherein: the multilayer structure has the sealant layer (α) in one outermost layer and has the base material layer (β) on the other outermost layer; the oxygen permeation rate of the sealant layer (α), which is measured at 20°C and 65% RH, ks 100 mL⋅20 μm / (m2⋅day⋅atm) or less; the static friction coefficient μα of the exposed surface of the sealant layer (α) is 0.30-1.00; the static friction coefficient μβ of the exposed surface of the base material layer (β) is 0.20-0.39; and the multilayer structure is used in ultrasonic sealing. Thus, when the multilayer structure is welded through ultrasonic sealing, it is possible to manufacture a packaging bag having high sealing strength, an exceptional appearance, and exceptional gas barrier properties.

Description

Multilayer structure, packaging bag, and method for manufacturing packaging material

[0001] The present invention relates to a multilayer structure including a sealant layer and a base layer. It also relates to a packaging bag obtained by welding the sealant layers of the multilayer structure together and a method for manufacturing the same. It also relates to a vacuum insulation material including the packaging bag. It also relates to a film roll formed by winding a film made of the multilayer structure. It also relates to a method for manufacturing a packaging material including a multilayer structure including a sealant layer and a base layer.

[0002] Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") is excellent in transparency, gas barrier properties, aroma retention, solvent resistance, oil resistance, etc., and by taking advantage of these properties, it is sometimes used as a sealant layer of multilayer structures used in food packaging materials, industrial chemical packaging materials, agricultural chemical packaging materials, pharmaceutical packaging materials, vacuum insulation materials, etc.

[0003] For example, Patent Document 1 describes a heat-sealable film having a heat-sealable layer containing EVOH, and also describes a heat-sealable film consisting of a multilayer structure in which an EVOH layer and other resins are laminated. It is claimed that by placing an EVOH layer as the innermost layer in this heat-sealable film, a packaging material with excellent aroma retention can be provided. Various resins, such as polyolefin, polyamide, and polyester, are exemplified as other resins to be laminated with the EVOH layer. Specific examples of the multilayer structure include a layer having a higher melting point than EVOH, such as a polyamide layer, a polyester layer, and paper. The examples also include a multilayer structure consisting of an EVOH layer and a polyamide layer. Furthermore, while an ultrasonic sealer is mentioned among the examples of heat-sealing methods, the examples only describe the use of a hot plate heat sealer.

[0004] Furthermore, Patent Document 2 describes a vacuum insulation material in which a core material is vacuum-sealed inside an outer packaging material made of a multilayer structure having a heat-sealing layer containing EVOH. It is said that this vacuum insulation material can maintain high thermal insulation properties for a long period of time by heat-sealing the EVOH layer as the innermost layer. In the examples of Patent Document 2, a layered outer packaging material in which a high-melting-point layer such as a polyester layer, a polyamide layer, or an aluminum foil is disposed outside the EVOH heat-sealing layer is heated using a hot plate to heat-seal the heat-sealing layers together, thereby producing a vacuum insulation material.

[0005] JP 2012-41076 A, WO 2017 / 047701 B1

[0006] As described in Patent Documents 1 and 2, when EVOH layers contained in a multilayer structure are heat-sealed together, a high-melting-point resin layer is often disposed on the outside of the EVOH layer. However, melt-molding a high-melting-point resin requires high temperatures, which poses a problem of increased energy requirements during molding. Furthermore, when the multilayer structure is recovered and melt-molded again, there is a risk that the EVOH may be deteriorated by melt-kneading at high temperatures. On the other hand, when a low-melting-point resin layer is disposed on the outside of a sealant layer containing EVOH and heat-sealed by heating using a hot plate, poor appearance is likely to occur, and it is not easy to increase the seal strength.

[0007] The present invention has been made to solve these problems, and has an object to provide a multilayer structure including a sealant layer and a base layer, which can be used to produce a packaging bag that has high seal strength, excellent appearance, and excellent gas barrier properties when the multilayer structure is welded by ultrasonic sealing. Another object is to provide a packaging bag obtained by welding the sealant layers of such a multilayer structure. Another object is to provide a vacuum insulation material including the packaging bag thus obtained. Another object is to provide a method for producing a packaging bag from the multilayer structure. Another object is to provide a film roll formed by winding a film made of such a multilayer structure. A further object is to provide a method for producing a packaging material including a multilayer structure including a sealant layer and a base layer, which can produce a packaging material that has high seal strength, excellent appearance, and excellent gas barrier properties by welding the sealant layer of the multilayer structure, even if the melting point of the sealant layer is similar to or higher than the melting point of the base layer.

[0008] The above-mentioned problems are solved by the following invention: [1] A multilayer structure comprising a sealant layer (α) and a substrate layer (β), wherein the multilayer structure has the sealant layer (α) as one outermost layer and the substrate layer (β) as the other outermost layer, and wherein the oxygen transmission rate of the sealant layer (α) measured at 20°C and 65% RH in accordance with ISO14663-2 Annex C (1999) is 100 mL 20 μm / (m ２・day・atm) or less, and the coefficient of static friction μα of the surface of the sealant layer (α) measured in accordance with the tilt method of JIS P8147 (2010) is 0.30 or more and 1.00 or less, and the coefficient of static friction μβ of the surface of the base material layer (β) is 0.20 or more and 0.39 or less, and the multilayer structure is for ultrasonic sealing. [2] The multilayer structure according to [1], wherein the sealant layer (α) contains at least one selected from the group consisting of ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polyamide, cyclic polyolefin, and polyacrylonitrile as a main component. [3] The multilayer structure according to [2], wherein the sealant layer (α) contains an ethylene-vinyl alcohol copolymer as a main component, and the ethylene unit content of the ethylene-vinyl alcohol copolymer is 20 mol% or more and 50 mol% or less. [4] The multilayer structure according to any one of [1] to [3], wherein the base material layer (β) contains at least one selected from the group consisting of polypropylene and polyethylene as a main component. [5] The multilayer structure according to any one of [1] to [4], wherein the Young's modulus of the base material layer (β) measured at a temperature of 23 °C, a relative humidity of 50%, and a tensile speed of 50 mm / min in accordance with ISO 527-1:2019 is 0.05 GPa or more and 3.0 GPa or less. [6] The multilayer structure according to any one of [1] to [5], wherein the glass transition temperature Tgβ of the base material layer (β) is not higher than the glass transition temperature Tgα of the sealant layer (α). [7] The multilayer structure according to any one of [1] to [6], wherein the thickness of the sealant layer (α) is 1 μm or more and 100 μm or less. [8] The multilayer structure according to any one of [1] to [7], wherein the thickness of the base material layer (β) is 10 μm or more and 200 μm or less. [9] The multilayer structure according to any one of [1] to [8], wherein the thickness of the multilayer structure is 40 μm or more and 300 μm or less.

[10] The multilayer structure according to any one of [1] to [9], wherein the ratio (β / α) of the thickness of the base material layer (β) to the thickness of the sealant layer (α) is 1 / 10 or more and 30 / 1 or less.

[11] The multilayer structure according to any one of [1] to

[10] , wherein the sealant layer (α) is not substantially stretched.

[12] The multilayer structure according to any one of [1] to [eleven], wherein the sealant layer (α) and the base material layer (β) are laminated via an adhesive layer (γ).

[13] Water vapor permeability measured in accordance with ISO 15106-2:2003 is 15 g / m. ２

[14] The multilayer structure according to any one of [1] to

[13] , wherein the sealant layers (α) are stacked so that they are in contact with each other, and then welded together at a seal width of 3 mm, a frequency of 39 kHz, an amplitude of 19 μm, and a pressure-bonding time of 0.3 seconds, and the seal strength at a tensile speed of 300 mm / min measured in accordance with JIS Z 1707 (2019) is 10 N / 15 mm or more.

[15] A packaging bag obtained by stacking the multilayer structures according to any one of [1] to

[14] so that the sealant layers (α) are in contact with each other, and then irradiating them with ultrasonic waves to weld the sealant layers (α) together.

[16] A vacuum insulation material comprising the packaging bag according to

[15] and a core material disposed inside the packaging bag, wherein the inside of the packaging bag is decompressed.

[17] A method for producing a packaging bag, comprising a step of stacking the multilayer structures according to any one of [1] to

[14] so that the sealant layers (α) are in contact with each other, and then irradiating them with ultrasonic waves to weld the sealant layers (α) together.

[18] A multilayer structure comprising a sealant layer (α) and a base layer (β), wherein the multilayer structure has the sealant layer (α) as one outermost layer and the base layer (β) as the other outermost layer, the surface moisture content of the sealant layer (α) is 0.5% by mass or more and 7.0% by mass or less, and the oxygen transmission rate of the sealant layer (α) measured in accordance with ISO 14663-2 Annex C (1999) at 20°C and 65% RH is 100 mL 20 μm / (m ２

[19] A film roll formed by winding a film made of the multilayer structure according to

[18] .

[20] A method for producing a packaging material including a multilayer structure having a sealant layer (α) and a base layer (β), the method comprising a sealing step of welding the sealant layer (α) by applying ultrasonic waves, the method comprising the step of: ２.day.atm) or less, wherein the melting point Tmα (°C) of the sealant layer (α) and the melting point Tmβ (°C) of the base layer (β) satisfy the following formula (1), and the packaging material has the sealant layer (α) as an innermost layer and the base layer (β) as an outermost layer. Tmα - Tmβ ≧ -5 (1)

[21] The manufacturing method according to

[20] , wherein, in the sealing step, two of the multilayer structures are stacked so that the sealant layers (α) are in contact with each other, and then ultrasonic waves are applied from the base layer (β) side to weld the sealant layers (α) together.

[22] The manufacturing method according to

[20] or

[21] , wherein, in the sealing step, the frequency of the ultrasonic waves applied is 15 kHz or more and 50 kHz or less.

[23] The manufacturing method according to any one of

[20] to

[22] , wherein, in the sealing step, the amplitude of the ultrasonic waves applied is 5 μm or more and 100 μm or less.

[0009] According to the multilayer structure of the present invention, by welding the multilayer structure by ultrasonic sealing, it is possible to produce a packaging bag with high seal strength, excellent appearance, and excellent gas barrier properties. This allows for greater flexibility in the layer configuration of packaging bags that require gas barrier properties. The bag can be suitably used for various applications, such as vacuum insulation materials. Furthermore, according to the manufacturing method of the present invention, when producing a packaging material including a multilayer structure having a sealant layer and a base layer, even if the melting point of the sealant layer is equal to or higher than the melting point of the base layer, it is possible to produce a packaging material with high seal strength, excellent appearance, and excellent gas barrier properties by welding the sealant layer of the multilayer structure by ultrasonic irradiation. This also allows for greater flexibility in the layer configuration of packaging materials that require gas barrier properties.

[0010] The present invention relates to a multilayer structure comprising a sealant layer (α) and a substrate layer (β). The multilayer structure has a sealant layer (α) as one outermost layer and a substrate layer (β) as the other outermost layer, and the sealant layer (α) has an oxygen transmission rate of 100 mL 20 μm / (m) measured at 20°C and 65% RH in accordance with ISO 14663-2 Annex C (1999). ２The static friction coefficient μα of the exposed surface of the sealant layer (α) is 0.30 or more and 1.00 or less, and the static friction coefficient μβ of the exposed surface of the base layer (β) is 0.20 or more and 0.39 or less, as measured in accordance with the inclination method of JIS P8147 (2010). The multilayer structure is for ultrasonic sealing.

[0011] The present invention will be described in detail below. In this specification, the term "main component" refers to the component that is contained in the largest amount by mass. The term "outermost layer" is not limited to the layer present on the outermost side, distinguishing between the front and back sides. That is, a multilayer structure consisting of two or more layers has two outermost layers, one outermost layer and the other outermost layer. In addition, in the case of a structure that distinguishes between an inside and an outside, such as a bag or container, the inner outermost layer may be referred to as the "innermost layer" and the outer outermost layer as the "outermost layer." In addition, the "thickness" of a layer, film, or multilayer structure in this specification refers to the average value of thicknesses measured at any five locations.

[0012] [Sealant layer (α)] The sealant layer (α) is made of a gas barrier resin. Specifically, the sealant layer (α) has an oxygen transmission rate of 100 mL·20 μm / (m), measured at 20° C. and 65% RH in accordance with ISO 14663-2 Annex C (1999). ２ ·day·atm) or less. By making the sealant layer (α) from a gas barrier resin, gas leakage from the heat-sealed portion can be effectively suppressed. Furthermore, by making the sealant layer (α) from a gas barrier resin the innermost layer of the packaging material, it is possible to provide a packaging material that is excellent in aroma retention, solvent resistance, and oil resistance. The oxygen transmission rate per 20 μm of thickness of the resin constituting the sealant layer (α) is 100 mL·20 μm / (m ２ The oxygen transmission rate is preferably 50 mL·20 μm / (m ２ ·day·atm) or less, and more preferably 20 mL·20 μm / (m ２ ·day·atm) or less, and more preferably 10 mL·20 μm / (m ２·day·atm) or less. When particularly high gas barrier properties are required, ２ ·day·atm) or less, and 3 mL·20 μm / (m ２ It is more preferable that the temperature is 1000°C or less (day·atm).

[0013] The sealant layer (α) is not particularly limited as long as it is made of a resin having the above-mentioned oxygen transmission rate. The sealant layer (α) preferably contains at least one resin selected from the group consisting of ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PET), polyamide (PA), cyclic polyolefin, and polyacrylonitrile as a main component. It is more preferable that the sealant layer (α) contains more than 50% by mass of this resin, even more preferably 70% by mass or more, and in some cases, it is particularly preferable that the sealant layer (α) contains 80% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more. The upper limit of the content of these resins may be 100% by mass. All of these resins are thermoplastic resins with excellent gas barrier properties. Among these, EVOH has high gas barrier properties and is particularly suitable as a resin for use in the sealant layer (α) of the present invention.

[0014] The EVOH used in the sealant layer (α) is usually obtained by saponifying a copolymer of ethylene and a vinyl ester such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate. The production and saponification of the copolymer of ethylene and a vinyl ester can be carried out by known methods. The saponification degree of the vinyl ester component of the ethylene-vinyl alcohol copolymer is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 99 mol% or more. By setting the saponification degree to 90 mol% or more, the gas barrier property can be improved. The saponification degree of the ethylene-vinyl alcohol copolymer may be 100 mol% or less, or may be 99.99 mol% or less. The saponification degree of the ethylene-vinyl alcohol copolymer can be measured by nuclear magnetic resonance ( １H-NMR measurement is performed to measure the peak area of ​​the hydrogen atoms contained in the vinyl ester structure and the peak area of ​​the hydrogen atoms contained in the vinyl alcohol structure.

[0015] The ethylene unit content of the EVOH used in the sealant layer (α) is preferably 20 mol% or more and 50 mol% or less. An ethylene unit content of 20 mol% or more provides a packaging material with high seal strength and good appearance. The ethylene unit content is more preferably 25 mol% or more, even more preferably 30 mol% or more, and particularly preferably 35 mol% or more. On the other hand, an ethylene unit content of 50 mol% or less provides a packaging material with good gas barrier properties. The ethylene unit content is more preferably 48 mol% or less, even more preferably 46 mol% or less.

[0016] The EVOH used in the sealant layer (α) may contain units derived from other monomers other than ethylene, vinyl esters, and saponified vinyl esters, as long as the object of the present invention is not impaired. When the EVOH contains such other monomer units, the content of such other monomer units relative to the total monomer units of the EVOH is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. When the EVOH contains such other monomer-derived units, the lower limit may be 0.05 mol% or 0.10 mol%. Examples of the other monomers include alkenes such as propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, and 4-acyloxy-3-methyl- 1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methylenepentene unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, or the like, 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, methallylsulfonic acid, or salts thereof; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, and the like.

[0017] When the EVOH is a blend of two or more different types of EVOH, the average ethylene unit content or saponification degree of the entire EVOH is taken as the ethylene unit content or saponification degree of the EVOH.

[0018] When the sealant layer (α) is an EVOH layer, the content of EVOH among the resins contained in the EVOH layer is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 97% by mass or more and 100% by mass or less.

[0019] The sealant layer (α) may be a polyamide layer. The polyamide layer usually contains polyamide as a main component. Polyamide is a resin containing an amide bond. Polyamide can be obtained, for example, by ring-opening polymerization of a lactam having a three- or more-membered ring, polycondensation of a polymerizable ω-amino acid, or polycondensation of a dibasic acid and a diamine. Examples of polyamides include polycapramide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecaneamide (nylon 11), polylauryl lactam (nylon 12), polyethylenediamineadipamide (nylon 26), polytetramethyleneadipamide (nylon 46), polyhexamethyleneadipamide (nylon 66), polyhexamethylenesebacamide (nylon 610), polyhexamethylenedodecamide (nylon 612), polyoctamethyleneadipamide (nylon 86), polydecamethyleneadipamide (nylon 108), caprolactam / lauryl lactam copolymer (nylon 6 / 12), caprolactam / ω-aminononanoic acid copolymer (nylon 6 / 9), caprolactam / hexamethylene Examples of the polymerizable monomer include diammonium adipate copolymer (nylon 6 / 66), lauryllactam / hexamethylenediammonium adipate copolymer (nylon 12 / 66), hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon 66 / 610), ethylenediammonium adipate / hexamethylenediammonium adipate copolymer (nylon 26 / 66), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon 6 / 66 / 610), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalamide (nylon 6T), and hexamethylene isophthalamide / terephthalamide copolymer (nylon 6I / 6T).

[0020] The sealant layer (α) may be a polyester layer. The polyester contained in the polyester layer is typically a polycondensation product of an aromatic dicarboxylic acid and an aliphatic diol. Among these, polyethylene terephthalate (PET) and copolymers thereof are preferably used. PET copolymers contain, as dicarboxylic acid units, monomer units derived from terephthalic acid as the main component, with minor components including monomer units derived from isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, and the like. Furthermore, PET copolymers contain, as diol units, monomer units derived from ethylene glycol as the main component, with minor components including monomer units derived from 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like.

[0021] The sealant layer (α) may be a cyclic polyolefin. Examples of the cyclic polyolefin that can be used include a ring-opening polymer of a cyclic olefin such as norbornene.

[0022] The sealant layer (α) may be polyacrylonitrile. The polyacrylonitrile may be a homopolymer of acrylonitrile or a copolymer obtained by copolymerizing a copolymerizable monomer. Examples of the copolymerizable monomer include styrene and methyl acrylate, and typical copolymers include acrylonitrile-styrene copolymer (SAN) and acrylonitrile-styrene-methyl acrylate copolymer (ASA).

[0023] The sealant layer (α) may contain metal salts, carboxylic acid compounds, phosphate compounds, boron compounds, antioxidants, UV absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, other resins, etc. In particular, the inclusion of silica particles in the sealant layer (α) may reduce the static friction coefficient μα of the surface of the sealant layer (α). The particle size (laser method: d50) of the silica particles may be 1 μm or more and 10 μm or less. The particle size may be 2 μm or more and 8 μm or less. The content of the silica particles may be 10 ppm or more and 1500 ppm or less. The content of the silica particles may be 20 ppm or more or 30 ppm or more. Furthermore, the content of the silica particles may be 1000 ppm or less or 500 ppm or less.

[0024] The MFR (190°C, 2.16 kg load) of the sealant layer (α) is preferably 0.5 g / 10 min or more and 20 g / 10 min or less. By having an MFR within this range, good extrusion moldability and high seal strength can be obtained. The MFR is more preferably 0.8 g / 10 min or more, and even more preferably 1 g / 10 min or more. On the other hand, the MFR is more preferably 15 g / 10 min or less, and even more preferably 10 g / 10 min or less.

[0025] The glass transition point (Tgα) of the sealant layer (α) is preferably 45°C or higher and 65°C or lower. A glass transition point (Tgα) of 45°C or higher allows the formation of a sealant layer with excellent gas barrier properties. Tgα is more preferably 48°C or higher, and even more preferably 50°C or higher. On the other hand, a glass transition point (Tgα) of 65°C or lower allows the seal strength to be increased. Tgα is more preferably 62°C or lower, and even more preferably 60°C or lower.

[0026] The melting point (Tmα) of the sealant layer (α) is preferably 150°C or higher and 200°C or lower. A melting point (Tmα) of 150°C or higher allows the formation of a sealant layer with excellent gas barrier properties. Tmα is more preferably 155°C or higher, and even more preferably 160°C or higher. On the other hand, a melting point (Tmα) of 200°C or lower allows the seal strength to be increased. Tmα is more preferably 192°C or lower, and even more preferably 185°C or lower.

[0027] The sealant layer (α) may be stretched, but is preferably not substantially stretched in consideration of ease of ultrasonic welding.

[0028] The thickness of the sealant layer (α) is preferably 1 μm or more and 100 μm or less. When the thickness of the sealant layer (α) is 1 μm or more, good gas barrier properties and high seal strength can be obtained. The thickness is more preferably 2 μm or more, even more preferably 5 μm or more, and even more preferably 10 μm or more. On the other hand, if the thickness of the sealant layer (α) exceeds 100 μm, the multilayer structure becomes heavy and its flexibility decreases. The thickness is more preferably 80 μm or less, and even more preferably 60 μm or less.

[0029] [Base layer (β)] The base layer (β) is a layer made of a thermoplastic resin other than the sealant layer (α), and the type thereof is not particularly limited. Polyolefin, polyester, polyamide, etc. can be used, but a polyolefin layer is preferred.

[0030] Examples of polyolefins used in the base layer (β) include polyethylenes such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene; ethylene-vinyl acetate copolymer; ethylene-propylene copolymer; polypropylene (homo, random, block); propylene-α-olefin copolymer (α-olefin having 4 to 20 carbon atoms); polybutene; and polypentene, or other olefin homopolymers or copolymers thereof. Among these, it is preferable for the base layer (β) to contain at least one selected from the group consisting of polypropylene and polyethylene as the main component, with polypropylene being more preferred. Here, polyethylene refers to an ethylene homopolymer and a copolymer of 80 mol% or more ethylene and less than 20 mol% of a non-ethylene monomer. Representative examples of non-ethylene monomers include, but are not limited to, α-olefins such as propylene, n-butene, isobutylene, 1-hexene, and 1-octene. Furthermore, polypropylene refers to a propylene homopolymer and a copolymer of 70 mol% or more propylene and less than 30 mol% of a non-propylene monomer. Therefore, the polypropylene may be a homopolypropylene, or a random copolymer polypropylene or a block copolymer polypropylene copolymerized with preferably 10% by mass or less, more preferably 5% by mass or less, of ethylene.

[0031] The lower limit of the melt flow rate (MFR) of the polyolefin used in the base layer (β) is preferably 0.5 g / 10 min, more preferably 0.8 g / 10 min, and even more preferably 1.0 g / 10 min. The upper limit of the MFR is preferably 15 g / 10 min, and more preferably 10 g / 10 min.

[0032] The glass transition point (Tgβ) of the polyolefin used in the substrate layer (β) is preferably −150° C. or higher and 40° C. or lower. A substrate layer with a high elastic modulus can be formed by having a glass transition point (Tgβ) of −150° C. or higher. Tgβ is more preferably −100° C. or higher, and even more preferably −50° C. or higher. On the other hand, a glass transition point (Tgβ) of 40° C. or lower can provide flexibility. Tgβ is more preferably 20° C. or lower, and even more preferably 0° C. or lower.

[0033] The melting point (Tmβ) of the polyolefin used in the base layer (β) is preferably 110° C. or higher and 170° C. or lower. The multilayer structure of the present invention can provide a packaging material with high seal strength and excellent appearance even if the melting point (Tmβ) of the base layer (β) is low. If Tmβ is low, heat resistance and water vapor barrier properties may be reduced, so Tmβ is more preferably 150° C. or higher.

[0034] The polyolefin content in the polyolefin layer is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 97% by mass or more and 100% by mass or less. The polyolefin layer may contain, as components other than polyolefin, antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, heat stabilizers, resins other than polyolefins, and the like.

[0035] The Young's modulus of the substrate layer (β), measured in accordance with ISO 527-1:2019 at a temperature of 23°C, a relative humidity of 50%, and a tensile speed of 50 mm / min, is preferably 0.05 GPa or more and 3.0 GPa or less. Having a Young's modulus in this range results in a good balance between rigidity and flexibility of the multilayer structure of the present invention. The Young's modulus is more preferably 0.1 GPa or more, even more preferably 0.3 GPa or more, and particularly preferably 0.8 GPa or more. On the other hand, the Young's modulus is more preferably 2.5 GPa or less, and even more preferably 2.3 GPa or less.

[0036] The base layer (β) may be a single layer containing a thermoplastic resin as a main component, or may be a multi-layer structure in which each layer contains the same or different thermoplastic resins as a main component. The base layer (β) may be formed by co-extrusion molding.

[0037] The base layer (β) may be a stretched layer or a non-stretched layer. It is preferable that the base layer (β) is stretched in at least one direction, since this increases the rigidity and strength of the multilayer structure of the present invention. Furthermore, when the base layer (β) is a polyolefin layer, the stretching provides excellent water vapor barrier properties. It is particularly preferable that the base layer (β) is a biaxially stretched polypropylene layer.

[0038] The thickness of the substrate layer (β) is preferably 10 μm or more and 200 μm or less. When the thickness of the substrate layer (β) is 10 μm or more, the multilayer structure can exhibit sufficient moisture resistance. The thickness of the substrate layer (β) is more preferably 15 μm or more, and even more preferably 20 μm or more. On the other hand, when the thickness of the substrate layer (β) is 200 μm or less, the multilayer structure can exhibit sufficient flexibility and can also be made lighter. The thickness of the substrate layer (β) is more preferably 100 μm or less, and even more preferably 50 μm or less.

[0039] [Adhesive layer (γ)] In the multilayer structure of the present invention, it is preferable that the sealant layer (α) and the base layer (β) are laminated via an adhesive layer (γ). When a multilayer structure is produced by dry laminating a preformed film constituting the sealant layer (α) and a film constituting the base layer (β), a curable adhesive is preferably used. When a multilayer structure is produced by coextrusion molding, an adhesive thermoplastic resin is preferably used.

[0040] When the multilayer structure of the present invention is produced by coextrusion molding, polyolefins having polar functional groups such as carboxyl groups, carboxylic anhydride groups, and epoxy groups are preferably used. Among these, maleic anhydride-modified polyolefins are preferred, and maleic anhydride-modified polypropylene and maleic anhydride-modified polyethylene are appropriately used. In this case, coextrusion molding is performed so that the adhesive layer (γ) is disposed between the sealant layer (α) and the substrate layer (β).

[0041] A two-component urethane adhesive is preferably used when dry laminating films together. This urethane adhesive is made by mixing a liquid containing a polyol component and a liquid containing an isocyanate component and then curing the mixture. This adhesive can strongly bond films made of different materials together via an adhesive layer.

[0042] The thickness of the adhesive layer (γ) is preferably 0.5 μm or more and 50 μm or less. When the thickness of the adhesive layer (γ) is 0.5 μm or more, good adhesive strength can be obtained. The thickness of the adhesive layer (γ) is more preferably 1 μm or more, and even more preferably 1.5 μm or more. On the other hand, when the thickness of the adhesive layer (γ) is 50 μm or less, the weight of the multilayer structure of the present invention can be reduced and cost increases can be suppressed. The thickness of the adhesive layer (γ) is more preferably 30 μm or less, and even more preferably 20 μm or less. In the case of coextrusion molding, it is not easy to reduce the thickness of the adhesive layer (γ), and the thickness is preferably 3 μm or more, and more preferably 5 μm or more. On the other hand, in the case of dry lamination, it is not easy to increase the thickness of the adhesive layer (γ), and the thickness is preferably 10 μm or less, and more preferably 5 μm or less.

[0043] [Intermediate layer (δ)] Another intermediate layer (δ) may be provided between the sealant layer (α) and the substrate layer (β). Examples of the intermediate layer (δ) include layers made of ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PET), polyamide (PA), polypropylene (PP), polyethylene (PE), etc. The intermediate layer (δ) may be a single layer or a multilayer. The intermediate layer (δ) may also have a vapor-deposited layer such as an aluminum vapor-deposited layer, an aluminum oxide vapor-deposited layer, or a silicon oxide vapor-deposited layer. The intermediate layer (δ) may be stretched.

[0044] [Relationship between the Thermal Properties of the Sealant Layer (α) and the Base Layer (β)] It is also preferable that the glass transition temperature Tgβ of the base layer (β) is equal to or lower than the glass transition temperature Tgα of the sealant layer (α). This makes it easier to mold the multilayer structure of the present invention at low temperatures, thereby reducing the environmental impact. Furthermore, even in a configuration in which a polyolefin layer with excellent water vapor barrier properties is disposed on the outer side and an EVOH layer with excellent gas barrier properties and aroma retention properties is disposed as the innermost layer, a packaging material with high seal strength, excellent appearance, and excellent gas barrier properties can be produced. The value of (Tgα - Tgβ) is more preferably 30°C or higher, and even more preferably 50°C or higher. Furthermore, the value of (Tgα - Tgβ) is usually 200°C or lower.

[0045] In the multilayer structure of the present invention, the melting point Tmα (°C) of the sealant layer (α) and the melting point Tmβ (°C) of the substrate layer (β) may satisfy the following formula (1): Satisfying formula (1) means that the melting point Tmα (°C) of the sealant layer (α) is similar to or higher than the melting point Tmβ (°C) of the substrate layer (β) (the difference in melting points is within 5°C): Tmα - Tmβ ≧ -5 (1)

[0046] Usually, when a multilayer structure having a base layer (β) and a sealant layer (α) is heat-sealed, the melting point Tmβ (°C) of the base layer (β) is set sufficiently higher than the melting point Tmα (°C) of the sealant layer (α). This allows only the low-melting-point sealant layer (α) to melt even when the outer high-melting-point base layer (β) is directly heated by a hot plate or the like, so that the sealant layer (α) can be welded while preventing the base layer (β) from melting and deteriorating its appearance. However, when the above formula (1) is satisfied, the base layer (β) also melts when the sealant layer (α) is welded, which inevitably leads to deterioration of the appearance. Ultrasonic sealing using the multilayer structure of the present invention can provide a method for producing a packaging material that has high sealing strength, excellent appearance, and excellent gas barrier properties, even in such cases. Therefore, the use of the multilayer structure of the present invention is of great significance.

[0047] Thus, by having a value of (Tmα - Tmβ) of -5°C or higher, the multilayer structure of the present invention can be molded at low temperatures, thereby reducing the environmental impact. Furthermore, even in a configuration in which a polyolefin layer with excellent water vapor barrier properties is disposed on the outer side and an EVOH layer with excellent gas barrier properties and aroma retention properties is disposed as the innermost layer, a packaging material with high seal strength, excellent appearance, and excellent gas barrier properties can be produced. The value of (Tmα - Tmβ), which is the left side of formula (1), is preferably -3°C or higher, more preferably -1°C or higher, and even more preferably 0°C or higher. Furthermore, the value of (Tmα - Tmβ) is preferably 100°C or lower, more preferably 60°C or lower, even more preferably 30°C or lower, and particularly preferably 15°C or lower.

[0048] In this specification, the melting point Tmα (°C) and the melting point Tmβ (°C) are determined in accordance with ISO 11357-1 (2016) using a differential scanning calorimeter by increasing the temperature from 30°C to 250°C at a rate of 10°C / min, followed by cooling at 50°C / min, and then measuring the peak temperature during a second heating at a rate of 10°C / min. In addition, the glass transition temperature Tgα and the glass transition temperature Tgβ are determined in accordance with ISO 11357-2 (2020) by cooling from 30°C to 0°C at a rate of 50°C / min, holding for 2 minutes, then heating from 0°C to 241°C at a rate of 20°C / min, holding for 5 minutes, then cooling from 241°C to -13°C at a rate of 50°C / min, holding for 5 minutes, and then heating from -13°C to 241°C at a rate of 20°C / min (secondary heating). The temperature is determined from the intersection of the tangent to the low-temperature baseline and the inflection point.

[0049] [Multilayer Structure] The multilayer structure of the present invention has a sealant layer (α) as one outermost layer and a substrate layer (β) as the other outermost layer. An adhesive layer (γ) may be provided between the sealant layer (α) and the substrate layer (β). Another layer may be provided between the sealant layer (α) and the substrate layer (β). The another layer may be an intermediate layer (δ) other than the sealant layer (α), the substrate layer (β), and the adhesive layer (γ), and the intermediate layer (δ) may include an aluminum vapor-deposited layer, an aluminum oxide vapor-deposited layer, or a silicon oxide vapor-deposited layer. Specific examples of the layer configuration of the multilayer structure include the following: Here, " / " means that the layers are laminated via the adhesive layer (γ) or directly, and " / / " means that the layers are laminated via the adhesive layer (γ). (1) Sealant layer (α) / / Base layer (β) (2) Sealant layer (α) / / Intermediate layer (δ) / / Base layer (β) (3) Sealant layer (α) / / Intermediate layer (δ) / / Intermediate layer (δ) / / Base layer (β)

[0050] The total thickness of the multilayer structure of the present invention is preferably 40 μm or more and 300 μm or less. If the total thickness is too thin, the rigidity decreases, making it difficult to maintain the shape during the filling operation, and filling defects are likely to occur. The total thickness is more preferably 45 μm or more, and even more preferably 50 μm or more. On the other hand, if the total thickness is too thick, the seal strength decreases and the weight increases. The total thickness is more preferably 200 μm or less, and even more preferably 100 μm or less.

[0051] The preferred thicknesses of the sealant layer (α) and the substrate layer (β) are as described above, but the ratio (β / α) of the thickness of the substrate layer (β) to the thickness of the sealant layer (α) is preferably 1 / 10 or more and 30 / 1 or less. If the thickness ratio (β / α) is less than 1 / 10, the flexibility of the multilayer structure of the present invention may be insufficient and it may be broken by impact. The ratio (β / α) is more preferably 1 / 5 or more, and even more preferably 1 / 3 or more. On the other hand, if the thickness ratio (β / α) exceeds 30 / 1, the gas barrier properties and seal strength of the multilayer structure may be insufficient. The ratio (β / α) is more preferably 10 / 1 or less, and even more preferably 5 / 1 or more.

[0052] In the multilayer structure of the present invention, the static friction coefficient μα of the exposed surface of the sealant layer (α) is preferably 0.30 or more and 1.00 or less. A static friction coefficient μα of 0.30 or more effectively generates frictional heat, increasing the seal strength. The static friction coefficient μα is more preferably 0.35 or more, even more preferably 0.40 or more, and particularly preferably 0.45 or more. If the static friction coefficient μα is too small, slippage may occur during ultrasonic welding. On the other hand, if the static friction coefficient μα is 1.00 or less, the contacting sealant layers (α) slide smoothly against each other, making it easier to open the packaging bag when filling it with contents, and tending to reduce filling errors. The static friction coefficient μα is more preferably 0.90 or less, even more preferably 0.80 or less, and particularly preferably 0.70 or less. If the static friction coefficient μα is too large, the bag may not open smoothly when opened using an automatic filling device, etc., and slippage may occur during sealing. The static friction coefficient in the present invention is measured in accordance with the inclination method of JIS P8147 (2010).

[0053] In addition, the static friction coefficient μβ of the exposed surface of the base layer (β) is also an important value when ultrasonically sealing, and it is preferable that the static friction coefficient μβ is 0.20 or more and 0.39 or less. When the static friction coefficient μβ is 0.20 or more, frictional heat is generated effectively and the seal strength is increased. The static friction coefficient μβ is more preferably 0.22 or more, and even more preferably 0.24 or more. On the other hand, when the static friction coefficient μβ is 0.39 or less, the appearance of the sealed portion tends to be improved and the seal strength tends to be improved. The static friction coefficient μβ is more preferably 0.37 or less, even more preferably 0.35 or less, and particularly preferably 0.33 or less.

[0054] The static friction coefficient μα of the exposed surface of the sealant layer (α) is preferably larger than the static friction coefficient μβ of the exposed surface of the base layer (β). The ratio of the static friction coefficient μα to the static friction coefficient μβ (μα / μβ) is more preferably 1.2 or more, even more preferably 1.4 or more, and particularly preferably 1.6 or more. On the other hand, the ratio of the static friction coefficient μα to the static friction coefficient μβ (μα / μβ) is usually 4 or less.

[0055] The oxygen transmission rate (OTR) of the multilayer structure of the present invention is 50 mL / (m ２ It is preferable that the oxygen transmission rate is less than 10 mL / (m ２ ·day·atm), and more preferably less than 5 mL / (m ２ ·day·atm), and particularly preferably less than 2 mL / (m ２ ・day・atm).

[0056] The water vapor transmission rate (WVTR) of the multilayer structure of the present invention is 15 g / (m ２ It is preferable that the water vapor transmission rate is less than 9 g / (m ２ ·day), and more preferably less than 8 g / (m ２ ·day), and particularly preferably less than 5 g / (m ２ ・day).

[0057] The method for producing the multilayer structure of the present invention is not particularly limited. The sealant layer (α) and the base layer (β) may be formed simultaneously by coextrusion molding, or a film consisting of a pre-prepared sealant layer (α) and a pre-prepared base layer (β) may be dry-laminated. When produced by coextrusion molding, it is preferable to provide a thermoplastic adhesive resin layer as the adhesive layer (γ). When produced by dry lamination, it is preferable to provide a curable adhesive layer as the adhesive layer (γ). Suitable adhesive layers (γ) are as described above.

[0058] When producing the multilayer structure of the present invention by coextrusion, the resins used for the sealant layer (α), substrate layer (β), and adhesive layer (γ) are melted in extruders, then merged and extruded through a die to produce the multilayer structure. In this case, if the substrate layer (β) has a high melting point, the temperature near the die must be increased even if the sealant layer (α) has a low melting point. When the sealant layer (α) is an EVOH layer, molding at high temperatures can result in the accumulation of degraded materials in the die. Therefore, it is advantageous to mold the multilayer structure of the present invention in which the melting point of the substrate layer (β) is not higher than that of the sealant layer (α). The coextrusion method is not particularly limited, and the resin may be extruded into a flat shape using a T-die, or may be extruded into a circular shape and expanded by inflation molding. Alternatively, a tubular multilayer structure can be obtained by extruding into a cylindrical shape using a circular die.

[0059] When the multilayer structure of the present invention is produced by dry lamination, a film to be the sealant layer (α) and a film to be the base layer (β) are dry-laminated using an adhesive to produce the multilayer structure. In this case, a pre-stretched film can also be dry-laminated. As a preferred embodiment, a pre-stretched base layer (β) and an unstretched sealant layer (α) can also be dry-laminated. This can achieve high seal strength while improving the strength and rigidity of the base layer (β).

[0060] In the multilayer structure of the present invention, the surface moisture content of the sealant layer (α) is preferably 0.5% by mass or more and 7.0% by mass or less. That is, it is preferable to perform ultrasonic welding when the surface moisture content is within the above range. In particular, when the sealant layer (α) is made of EVOH, the surface moisture content is preferably within the above range. A surface moisture content of 0.5% by mass or more on the surface of the sealant layer (α) increases the seal strength when ultrasonically welded. The surface moisture content is more preferably 2% by mass or more, and even more preferably 4% by mass or more. On the other hand, a surface moisture content of 7% by mass or less on the surface of the sealant layer (α) can prevent the film from sticking. The surface moisture content is more preferably 6.5% by mass or less, and even more preferably 6% by mass or less. The surface moisture content is measured, for example, using an "UMAREX Moisture Finder Compact" manufactured by UMAREX GmbH & Co.

[0061] In order to ensure that the surface moisture content of the sealant layer (α) falls within the above range, it is preferable to condition the moisture content after producing the multilayer structure of the present invention. However, since films are generally stored in a rolled state, even if the moisture content is conditioned while the film is still wound, moisture only penetrates from the edge of the film, making it impossible to uniformly moisten the film surface. Therefore, it is preferable to actively supply moisture while unwinding the film from the roll to supply moisture to the sealant layer (α) in a short period of time. Although it is possible to moisten the film immediately before the sealing step, this is likely to result in unevenness. Considering productivity, it is convenient to perform the moistening operation in the factory where the multilayer structure is produced and then wind it up. That is, a film roll formed by winding up a multilayer structure having a sealant layer (α) with the above surface moisture content is a preferred embodiment.

[0062] Here, when the surface moisture regain of the sealant layer (α) is set within the above range, the seal strength at the time of ultrasonic welding may be improved even if the static friction coefficient μα and the static friction coefficient μβ are not necessarily within the above-mentioned predetermined ranges. That is, a multilayer structure comprising a sealant layer (α) and a base layer (β), the multilayer structure having the sealant layer (α) as one outermost layer and the base layer (β) as the other outermost layer, the surface moisture content of the sealant layer (α) being 0.5% by mass or more and 7.0% by mass or less, and the oxygen transmission rate of the sealant layer (α) measured at 20°C and 65% RH in accordance with ISO 14663-2 Annex C (1999) is 100 mL·20 μm / (m ２ The object of the present invention can also be achieved by providing a multilayer structure having a thermal expansion coefficient of 1000 kJ / cm2 or less (1000 kJ / cm2 / day atm) and the multilayer structure is for ultrasonic sealing. The same applies to a film roll formed by winding a film made of such a multilayer structure.

[0063] When the multilayer structure of the present invention is stacked so that the sealant layers (α) are in contact with each other and then welded at a seal width of 3 mm, a frequency of 39 kHz, an amplitude of 19 μm, and a pressure bonding time of 0.3 seconds, the seal strength at a tensile speed of 300 mm / min measured in accordance with JIS Z 1707 (2019) is preferably 10 N / 15 mm or more. In this case, the seal strength is more preferably 13 N / 15 mm or more, even more preferably 15 N / 15 mm or more, and particularly preferably 16 N / 15 mm or more.

[0064] [Sealing Process] When producing a packaging material using the multilayer structure of the present invention, it is preferable to include a sealing process in which the sealant layer (α) is welded by irradiating ultrasonic waves onto a multilayer structure comprising a sealant layer (α) and a base layer (β). Generally, when sealing a resin multilayer structure, two multilayer structures are stacked and sandwiched between hot plates under pressure to melt and bond the contacting resin layers. However, when the melting point of the sealant layer (α) is similar to or higher than that of the base layer (β), as in the multilayer structure of the present invention, applying pressure between hot plates melts the base layer (β), resulting in poor appearance of the sealed portion. In contrast, when ultrasonic waves are irradiated, frictional heat is generated on the surface of the sealant layer (α), allowing the sealant layer (α) to be welded without damaging the appearance of the base layer (β). In a preferred sealing process, two multilayer structures are stacked so that the sealant layers (α) are in contact with each other, and then ultrasonic waves are irradiated to weld the sealant layers (α) together. At this time, the frictional heat generated between the two sealant layers (α) due to the ultrasonic vibration melts the sealant layer (α), which then cools and solidifies, bonding the two together.

[0065] In the sealing step, a commercially available ultrasonic welding machine can be used. Typically, the sealant layer (α) can be welded by pressing an ultrasonic horn attached to the ultrasonic welding machine while vibrating it. The seal width is generally determined by the width of the tip of the ultrasonic horn. The seal width is usually 0.5 mm or more and 20 mm or less. The seal width may be 1 mm or more, or 2 mm or more. On the other hand, the seal width may be 15 mm or less, 10 mm or less, or 5 mm or less.

[0066] The frequency of the ultrasonic waves irradiated in the sealing step is preferably 15 kHz or more and 50 kHz or less. When the frequency is 15 kHz or more, the amount of heat generated in the sealant layer (α) is sufficient, which tends to increase the seal strength, and the time until welding is shortened, which tends to suppress misalignment between the multilayer structures. The frequency is more preferably 18 kHz or more, and even more preferably 20 kHz or more. On the other hand, when the frequency is 50 kHz or less, misalignment between the multilayer structures due to vibration tends to be suppressed, and the seal strength also tends to increase. Furthermore, when the frequency is below the above upper limit, deterioration of the horn tends to be suppressed. The frequency is more preferably 45 kHz or less, and even more preferably 40 kHz or less.

[0067] The amplitude of the ultrasonic waves irradiated in the sealing step is preferably 5 μm or more and 100 μm or less. When the amplitude is 5 μm or more, the amount of heat generated in the sealant layer (α) is sufficient, and the seal strength tends to increase. The amplitude is more preferably 10 μm or more, and even more preferably 20 μm or more. On the other hand, when the amplitude is 100 μm or less, deterioration of the horn tends to be suppressed. The amplitude is more preferably 80 μm or less, and even more preferably 60 μm or less.

[0068] The time for irradiating the multilayer structure of the present invention with ultrasonic waves is preferably 0.02 seconds or more and 5 seconds or less. When the irradiation time is 0.02 seconds or more, sufficient seal strength tends to be obtained. The irradiation time is more preferably 0.05 seconds or more, and even more preferably 0.1 seconds or more. On the other hand, when the irradiation time is 5 seconds or less, the appearance tends to be good and productivity tends to be improved. The irradiation time is more preferably 2 seconds or less, and even more preferably 1 second or less.

[0069] It is preferable that the seal strength of the sealed portion thus sealed through the sealing process is high. Specifically, the seal strength of the portion welded by ultrasonic irradiation, measured in accordance with JIS Z 1707 (2019) at a temperature of 23°C, a relative humidity of 50%, and a tensile speed of 300 mm / min, is preferably 10 N / 15 mm or more. The seal strength is more preferably 13 N / 15 mm or more, even more preferably 15 N / 15 mm or more, and particularly preferably 16 N / 15 mm or more.

[0070] One method for adjusting the static friction coefficient μα of the surface of the sealant layer (α) is to adjust the arithmetic mean roughness (Ra) of the cast roll surface, which the surface of the sealant layer (α) first contacts when melt-molding a film. As the arithmetic mean roughness (Ra) of the cast roll surface increases, the surface irregularities of the surface of the sealant layer (α) to which it is transferred increase, resulting in a smaller static friction coefficient μα of that surface. Therefore, using a matte roll may result in an excessively small static friction coefficient μα, and it may be preferable to use a mirror-finished roll to increase the static friction coefficient μα. Furthermore, when melt-molding a film, the static friction coefficient μα can also be increased by simultaneously extruding the molten resin onto the cast roll and blowing air through an air slit to press the molten resin onto the cast roll. These methods can be appropriately employed to obtain the desired static friction coefficient μα. These techniques can also be employed to adjust the static friction coefficient μβ of the surface of the substrate layer (β).

[0071] Also, a method for producing a packaging material including a multilayer structure having a sealant layer (α) and a base layer (β) includes a sealing step of welding the sealant layer (α) by applying ultrasonic waves, and the oxygen transmission rate of the sealant layer (α) measured at 20°C and 65% RH in accordance with ISO14663-2 Annex C (1999) is 100 mL 20 μm / (m ２The object of the present invention can also be achieved by the packaging material having the sealant layer (α) as the innermost layer and the substrate layer (β) as the outermost layer, wherein the melting point Tmα (°C) of the sealant layer (α) and the melting point Tmβ (°C) of the substrate layer (β) satisfy the following formula (1): Tmα - Tmβ≧-5 (1) In this case, the details of each constituent element are as described above.

[0072] [Packaging Material] The packaging material produced using the multilayer structure of the present invention includes a multilayer structure having a sealant layer (α) and a base layer (β), with the sealant layer (α) as the innermost layer and the base layer (β) as the outermost layer, and the sealant layer (α) is sealed by the sealing step described above. Typically, a packaging bag can be produced by welding the sealant layers (α) of the multilayer structure of the present invention to each other. A packaging material can also be produced by welding the sealant layer (α) of the multilayer structure of the present invention to a multilayer structure of a different configuration. Even in this case, it is preferable to fuse the sealant layer (α) to a layer made of the same resin as the sealant layer (α) from the viewpoints of seal strength, gas barrier properties, aroma retention, etc. That is, if the sealant layer (α) is an EVOH layer, it is preferable to fuse it to the EVOH layer.

[0073] The form of the packaging material produced using the multilayer structure of the present invention is not particularly limited, but a packaging bag is one suitable embodiment. When producing a packaging bag, it is preferable to overlap and seal the multilayer structures so that the sealant layers (α) of the multilayer structures are in contact with each other. For example, a three-sided bag can be produced by sealing three sides using two multilayer structures. Alternatively, a bag can be produced by sealing two opposing sides of a single multilayer structure folded with the sealant layer (α) on the inside. Furthermore, sealing can be achieved by gluing the sealant layers (α) at ​​both ends of a rolled-up single multilayer structure together. Alternatively, the packaging material of the present invention may be a container sealed with a lid made of a multilayer structure or a tube container made of a multilayer structure. In either form, it is preferable that all parts that come into contact with the contents are made of the sealant layer (α) or an equivalent barrier material from the viewpoints of aroma retention, chemical resistance, and gas barrier properties.

[0074] The packaging material produced in this way has excellent gas barrier properties, chemical resistance, and aroma retention, and can be used for a variety of purposes. It is suitable as a packaging material for storing foods that are prone to oxidative deterioration, such as tuna and mayonnaise, lipophilic organic chemicals such as pesticides, pharmaceuticals, and sunscreen, and foods that require flavor retention, such as juice and coffee.

[0075] Furthermore, it is also suitable that the packaging material produced using the multilayer structure of the present invention is a vacuum packaging bag. Vacuum packaging bags sealed by the method of the present invention have reduced gas permeation at the sealed portion, so that oxygen penetration into the packaging bag through the sealed portion can be reduced after vacuum packaging. Such vacuum packaging bags are suitable for packaging contents that are desired to be packaged in a vacuum state, such as foods and other items that are prone to oxidative deterioration, and core materials for vacuum insulation materials.

[0076] A particularly useful application of the vacuum packaging bag is as a vacuum insulation material. A vacuum insulation material is a vacuum packaging bag in which a core material is placed and the inside is reduced in pressure. Examples of the core material used here include glass fiber and polyurethane foam. In this case, the vacuum packaging bag containing the core material is also called an outer packaging material. When a core material is placed inside the packaging bag and the bag is sealed while maintaining a vacuum state inside, the sealant layer has gas barrier properties, so this vacuum insulation material can effectively prevent air from entering the packaging bag and can maintain its insulation properties for a long period of time.

[0077] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0078] [Materials used] EVOH-1: EVOH, ethylene unit content 32 mol%, saponification degree 99.9 mol%, MFR (190°C, 2.16 kg load) 1.6 g / 10 min, melting point 183°C, OTR 0.4 mL 20 μm / (m ２ · day · atm) · EVOH-2: EVOH, ethylene unit content 44 mol%, saponification degree 99.9 mol%, MFR (190 ° C, 2.16 kg load) 5.7 g / 10 min, melting point 165 ° C, OTR 1.5 mL · 20 μm / (m ２· day · atm) · EVOH-3: EVOH, ethylene unit content 48 mol%, saponification degree 99.9 mol%, MFR (190 ° C, 2.16 kg load) 6.4 g / 10 min, melting point 160 ° C, OTR 3.2 mL · 20 μm / (m ２ · day · atm) · PET: "MA2101M" (manufactured by Unitika Ltd., polyethylene terephthalate, melting point 255°C), OTR 51mL · 20μm / (m ２ · day · atm) · PA: Nylon 6, "Unitika Nylon 6A1030BRF" (manufactured by Unitika Ltd., melting point 220°C), OTR 32mL · 20µm / (m ２· day · atm) · OPET-1: "MA2101M" (PET, melting point 255°C, manufactured by Unitika Ltd.) was dried at 70°C for 4 hours, then dried at 130°C for 8 hours, and then melted at 270°C in a single-screw extruder equipped with a hopper dryer. The molten resin was extruded from the die onto a take-up roll (arithmetic mean roughness Ra: 0.2 μm) at 30°C. At the same time, air controlled at an air pressure of 0.2 MPa was blown through an air slit at a wind speed of 30 m / s to obtain an unstretched film having a thickness of 270 μm. The obtained unstretched film having a thickness of 270 μm was stretched 3.0 times in the longitudinal direction and 3.0 times in the transverse direction in a 110°C atmosphere using a tenter-type simultaneous biaxial stretching machine, and further heat-treated for 5 seconds in a tenter set at 110°C. The film edges were cut to obtain a biaxially stretched film having a thickness of 30 μm, OPET-1. OPA-1: "Unitika Nylon 6 A1030BRF" (manufactured by Unitika Ltd., nylon 6, melting point 220 ° C.) was melted at 250 ° C. in a single-screw extruder, and the molten resin was extruded from the die onto a take-up roll (mirror surface: arithmetic mean roughness Ra: 0.2 μm) at 30 ° C. Simultaneously, air controlled at an air pressure of 0.2 MPa was blown through the air slit at a wind speed of 30 m / sec to obtain an unstretched film with a thickness of 270 μm. The obtained unstretched film with a thickness of 270 μm was then contacted with hot water at 85 ° C. for 30 seconds, and then stretched 3.0 times in the longitudinal direction and 3.0 times in the transverse direction using a tenter-type simultaneous biaxial stretching machine in an atmosphere of 190 ° C., and further heat-treated for 5 seconds in a tenter set at 190 ° C. The film edges were cut to obtain a biaxially stretched OPA-1 with a thickness of 30 μm.OPP-1: "Sun Tox OP PA30" (manufactured by Sun Tox Co., Ltd., biaxially oriented polypropylene film, thickness 30 μm, static friction coefficient on the outer surface of the film roll of 0.26) OPP-2: "Sun Tox OP HL82" (manufactured by Sun Tox Co., Ltd., biaxially oriented polypropylene film, thickness 30 μm, static friction coefficient on the outer surface of the film roll of 0.36) OPP-3: "Sun Tox OP PM30" (manufactured by Sun Tox Co., Ltd., biaxially oriented polypropylene film, thickness 20 μm, static friction coefficient on the inner surface of the film roll of 0.21) OPP-4: "Lamytack SSO double-sided treatment" (manufactured by J Film Co., Ltd., biaxially oriented polypropylene film, thickness 30 μm, static friction coefficient on the outer surface of the film roll of 0.15) OPP-5: "Lamytack SSO one-sided treatment" (manufactured by J Film Co., Ltd., biaxially oriented polypropylene film, thickness 30 μm, static friction coefficient on the outer surface of the film roll of 0.40) OPP-6: "Sun Tox-OP PA30" (manufactured by Sun Tox Co., Ltd., biaxially oriented polypropylene film, thickness 20 μm, static friction coefficient on the outer surface of the film roll of 0.25) (20 μm) outer surface of the roll OPP-7: "Sun Tox-OP PA30" (manufactured by Sun Tox Co., Ltd., biaxially oriented polypropylene film, thickness 60 μm, static friction coefficient on the outer surface of the film roll of 0.33) OPP-8: "Pylen (registered trademark) P2161" (manufactured by Toyobo Co., Ltd., biaxially oriented polypropylene film, thickness 30 μm, melting point 165°C), OTR 1400 mL / (m. ２day·atm) OPP-9: "Novatec (registered trademark) FL203D" (Japan Polypropylene Corporation, polypropylene, melting point 160°C) CPP-1: "Pylen (registered trademark) Film-CT P1011" (Toyobo Co., Ltd., unstretched polypropylene film, thickness 30 μm, static friction coefficient on the inner surface of the film roll of 0.30) LLDPE: "Rix (registered trademark) L4102" (Toyobo Co., Ltd., unstretched linear low-density polyethylene, thickness 30 μm, melting point 120°C, static friction coefficient on the inner surface of the film roll of 0.30) PP-1: "F-704NP" (Prime Polymer Co., Ltd., polypropylene) PP-2: "Novatec (registered trademark) FL203D" (Japan Polypropylene Corporation, polypropylene, melting point 160°C) Ad-1: Two-component urethane adhesive ("Takelac (registered trademark) A-520" and "Takenate (registered trademark) A-50" manufactured by Mitsui Chemicals, Inc.) Ad-2: "Admer (registered trademark) QF500" (maleic anhydride-modified polypropylene manufactured by Mitsui Chemicals, Inc.) Si-1: "SYLYSIA (registered trademark) 320" (synthetic silica particles manufactured by Fuji Silysia Chemical Ltd.)

[0079] The melting points of the above materials were determined in accordance with ISO 11357-1 (2016) using a differential scanning calorimeter "Q2000" manufactured by TA Instruments, by heating from 30°C to 250°C at a rate of 10°C / min, followed by cooling at 50°C / min, and then measuring the peak temperature during a second heating at a rate of 10°C / min. When measuring PET, the maximum temperature was 270°C. The oxygen transmission rate (OTR) was measured at 20°C and 65% RH in accordance with ISO 14663-2 Annex C (1999).

[0080] [Evaluation Method] Evaluations (1) and (2) performed in all Examples, Comparative Examples, and Reference Examples were carried out as follows.

[0081] (1) Arithmetic mean roughness (Ra) of cast roll surface The surface roughness (arithmetic mean roughness (Ra)) of the cast roll used in forming the monolayer film of the sealant layer (α) in the examples and comparative examples was measured using a small surface roughness measuring instrument Surftest "SJ-400" (contact type) manufactured by Mitutoyo Corporation, in accordance with JIS B 0601 (1994) with a cutoff value (λc) of 2.5 mm and an evaluation length (l) of 7.5 mm.

[0082] (2) Static Friction Coefficient The static friction coefficient of the exposed surface of the multilayer structure obtained in the Examples and Comparative Examples was calculated by calculating the tangent (tan θ) of the angle at which slipping began using a slip angle measuring device manufactured by Toyo Seiki Seisaku-sho, Ltd., in accordance with the tilt method of JIS P8147 (2010).

[0083] The evaluations (3) to (9) performed in Examples 1-1 to 1-23, Comparative Examples 1-1 to 1-6, and Reference Examples 1-1 to 1-3 were carried out as follows.

[0084] (3) Glass transition temperature (Tg) For the monolayer film of the sealant layer (α) and the monolayer film of the base layer (β) prepared in the examples and comparative examples, the respective glass transition temperatures (Tg(α) and Tg(β)) were measured in accordance with ISO11357-2:2020 using a differential scanning calorimeter "Q2000" manufactured by TA Instruments. The temperature conditions were: cooling from 30 ° C. to 0 ° C. at a rate of 50 ° C. / min, holding for 2 minutes, and then heating from 0 ° C. to 241 ° C. at a rate of 20 ° C. / min (first heating), holding for 5 minutes, then cooling from 241 ° C. to -13 ° C. at a rate of 50 ° C. / min, and then holding for 5 minutes, then heating from -13 ° C. to 241 ° C. at a rate of 20 ° C. / min (second heating). The glass transition temperature was determined from the intersection of the tangent to the original baseline and the inflection point measured in the second heating. The maximum temperature during the measurement of PET was 270°C.

[0085] (4) Young's modulus The monolayer film of the sealant layer (α) and the monolayer film of the base layer (β) obtained in the examples and comparative examples were cut into strips 100 mm long and 15 mm wide so that the machine direction (MD direction) during film production was the longitudinal direction to obtain test pieces. The obtained test pieces were subjected to a tensile test at a temperature of 23°C, a relative humidity of 50%, and a tensile speed of 50 mm / min using an autograph AGS-H model manufactured by Shimadzu Corporation in accordance with ISO 527-1:2019, to measure the Young's modulus in the machine direction (MD direction).

[0086] (5) Appearance of Film Roll In the examples and comparative examples, when the sealant layer (α) was formed, the width of the overlap of the single-layer film was measured with a stainless steel ruler at the end of the film roll on which the sealant layer (α) was wound, when 100 m was wound onto the winding roll, and the result was evaluated according to the following criteria: A: End misalignment less than 1.0 mm B: End misalignment 1.0 mm or more and less than 2.0 mm C: End misalignment 2.0 mm or more and less than 3.0 mm D: End misalignment 3.0 mm or more and less than 5.0 mm E: End misalignment 5.0 mm or more

[0087] (6) Seal strength after ultrasonic sealing The sealant layers (α) of the multilayer structures obtained in the examples and comparative examples were overlapped with each other and pressed together using an ultrasonic welding machine "SONOPET JII400 series oscillator unit press model" manufactured by Seidensha Electronics Co., Ltd., with a seal width of 3 mm, a frequency of 39 kHz, an amplitude of 19 μm, and a pressing time of 0.3 seconds. The obtained multilayer structure after ultrasonic sealing was measured for seal strength (N / 15 mm) using a tensile tester at a temperature of 23 ° C, a relative humidity of 50%, and a tensile speed of 300 mm / min in accordance with the method described in JIS Z 1707 (2019), and evaluated according to the following criteria. A: 13.0 N / 15 mm or more B: 10.0 N / 15 mm or more and less than 13.0 N / 15 mm C: 7.0 N / 15 mm or more and less than 10.0 N / 15 mm D: Less than 7.0 N / 15 mm

[0088] (7) Appearance of seal after ultrasonic sealing The end face of the sealed portion of the multilayer structure ultrasonically sealed by the method described in the evaluation method (6) above was checked, and the degree of misalignment was measured using a stereomicroscope and evaluated according to the following criteria: A: Less than 0.1 mm B: 0.1 mm or more and less than 0.5 mm C: 0.5 mm or more and less than 1.0 mm D: 1.0 mm or more and less than 1.5 mm E: The substrate layer (β) melted and whitened during the welding operation.

[0089] (8) Water Vapor Transmission Rate (WVTR) of Multilayer Structure The multilayer structures obtained in the Examples and Comparative Examples were attached to a water vapor transmission rate measuring device with the substrate layer (β) facing the carrier gas side, and the water vapor transmission rate was measured under the following conditions in accordance with ISO15106-2:2003 (isobaric method). The obtained water vapor transmission rates were evaluated according to the following criteria. (Conditions) Device: MOCON PERMATRAN W3 / 33 manufactured by MOCON Corporation Temperature: 40°C Humidity on water vapor supply side: 90% RH Humidity on carrier gas side: 0% RH Carrier gas flow rate: 50 mL / min (Evaluation) A: 5.0 g / (m ２ ・day) or less B: 5.0 g / (m ２ ・day) or more 8.0g / (m ２ ・day) or less C: 8.0 g / (m ２ ・day) or more 9.0g / (m ２ ・day) or less D: 9.0 g / (m ２ ・day) or more 15.0g / (m ２ ・day) less than E: 15.0 g / (m ２ ・day) or more and less than 30.0g / (m2・day) F: 30.0g / (m2・day) or more

[0090] (9) Oxygen Transmission Rate (OTR) of Sealant Layer (α) From the single-layer film of the sealant layer (α) obtained in the Examples and Comparative Examples, a circular sample having a diameter of 90 mm was cut out from the center in the width direction. The sample was conditioned under conditions of 20°C and 65% RH, and then measured using an oxygen transmission rate measuring device (Modern Control's "OX-Tran 2 / 20" (detection limit 0.01 mL / (m ２ The oxygen transmission rate was measured at 20°C and 65% RH in accordance with ISO 14663-2 annex C using a 1000 kJ / day atm (1000 kJ / day·atm) test tube.

[0091] The evaluations (10) to (13) performed in Examples 2-1 to 2-20 and Comparative Examples 2-1 to 2-4 were carried out as follows.

[0092] (10) Appearance after welding The appearance of the welded multilayer structures obtained in Examples and Comparative Examples after welding was visually evaluated according to the following criteria: A: No displacement of the welded part B: Displacement of 1 mm or less was observed in the welded part C: Displacement of more than 1 mm to less than 5 mm was observed in the welded part D: The substrate layer (β) melted and whitened during the welding operation

[0093] (11) Seal Strength The seal strength (N / 15 mm) of the welded multilayer structures obtained in the examples and comparative examples was measured using a tensile tester in accordance with the method described in JIS Z 1707 (2019) under conditions of a temperature of 23°C, a relative humidity of 50%, and a tensile speed of 300 mm / min, and evaluated according to the following criteria: A: 16.0 N / 15 mm or more B: 15.0 N / 15 mm or more and less than 16.0 N / 15 mm C: 13.0 N / 15 mm or more and less than 15.0 N / 15 mm D: 10.0 N / 15 mm or more and less than 13.0 N / 15 mm E: Less than 10.0 N / 15 mm

[0094] (12) Defective Rate During Filling The multilayer structures obtained in Examples 2-1 to 2-20 and Comparative Example 2-4 were cut into two pieces of A4 size (210 mm × 297 mm), and then the sealant layers (α) were overlapped on each other. Three sides were ultrasonically welded using an ultrasonic sealing machine “SONOPET JII970” manufactured by Seidensha Electronics Co., Ltd. under the conditions of a seal width of 3 mm, a frequency of 28.5 kHz, an amplitude of 40 μm, a pressure of 0.1 MPa, and a pressure bonding time of 0.3 seconds, to produce a three-sided bag of 20 cm in length × 15 cm in width. Furthermore, two sheets of the multilayer structures obtained in Comparative Examples 2-1 to 2-3 were cut into A4 size (210 mm x 297 mm), and the sealant layers (α) were then overlapped. The sealant layers (α) were then heat-sealed at three edges using a hot plate heat sealer (HBS-280 bag, manufactured by Hirai Shoji Co., Ltd.) at a temperature of 190°C and a pressure of 0.1 MPa for 1 second to produce three-sided bags measuring 20 cm long x 15 cm wide. The resulting three-sided bags were filled with 300 g of dried bonito flakes (1 g each) using a rotary automatic filling machine, then sealed and packaged. The product defect rate per 300 bags was determined. When ultrasonic welding was performed, misalignment of the seal occurred in some cases, and when heat sealing was performed using a hot plate, the seal melted excessively and whitened in some cases. Packaging bags with a seal misalignment of 5 mm or more or bags with whitening were deemed defective. A: 99.0% or more B: 98.0% or more C: 97.0% or more D: 95.0% or more E: Less than 95.0%

[0095] (13) Oxygen Transmission Rate (OTR) A portion was cut out from the multilayer structure obtained in the examples and comparative examples, and the OTR was measured using an oxygen transmission rate measuring device, OX-TRAN2 / 21 model (detection limit: 0.01 mL / (m ２ The OTR was measured using a 2.0 mL / (m 2 ) / day / atm (2.0 mL / (m 2 )) under conditions of 20°C and 65% RH in accordance with the method described in ISO 14663-2 Annex C (1999), and was evaluated according to the following criteria: A: 2.0 mL / (m 2 ) / day / atm ( ... ２ · day · atm) or less B: 2.0 mL / (m ２ ・day・atm) or more 5.0mL / (m ２ · day · atm) or less C: 5.0 mL / (m ２ ・day・atm) or more 10.0mL / (m ２· day · atm) or less D: 10.0 mL / (m ２ ・day・atm) or more 50.0mL / (m ２ ・day・atm) or less E: 50.0 mL / (m ２ ・day・atm) or more

[0096] [Example 1-1] (Preparation of a monolayer film of sealant layer (α)) 60 ppm of Si-1 (inorganic silica particles) was added to EVOH-1, and the mixture was dry-blended by stirring in a 100 L blender for 10 minutes. A monolayer film having a thickness of 30 μm was then prepared under the following conditions. (Film-forming conditions) Extruder: 40 mmφ single-screw extruder (manufactured by Plastics Technology Research Institute Co., Ltd.) L / D: 26 Screw: Full-flight Screw rotation speed: 30 rpm Screen mesh: 50 mesh / 100 mesh / 50 mesh Die shape: T-type, lip width 550 mm, lip spacing 0.7 mm Extruder set temperature: C1 / C2 / C3 / D = 170°C / 230°C / 230°C / 230°C Cast roll surface arithmetic mean roughness Ra: 0.2 μm Air slit: None Take-up roll temperature: 80°C Thickness: 30 μm Film winding length: 50 m The obtained monolayer film and film roll of sealant layer (α) were evaluated for Tg, Young's modulus, OTR, and roll appearance according to the evaluation methods described above. The results are shown in Table 1. OPP-1 was used as the monolayer film of the substrate layer (β). The Tg and Young's modulus of the substrate layer (β) were evaluated according to the above-mentioned evaluation methods. The results are shown in Table 1.

[0097] (Preparation of Multilayer Structure) A two-component urethane adhesive Ad-1 (Takelac (registered trademark) A-520 and Takenate (registered trademark) A-50 manufactured by Mitsui Chemicals, Inc.) was applied to one side of the monolayer film of the base layer (β) to a dry thickness of 2 μm and dried to form an adhesive layer (γ). The sealant layer (α) obtained above was then laminated and dry laminated to prepare a multilayer structure (sealant layer (α) / adhesive layer (γ) / base layer (β)). The sealant layer (α) was laminated so that the surface that came into contact with the cast roll during film formation was the exposed surface of the multilayer structure. The base layer (β) was laminated so that the surface with a static friction coefficient of 0.26 was the exposed surface. The obtained multilayer structure was stored at 23°C and 50% RH for 1 day, and then the static friction coefficient, seal strength, seal appearance, and WVTR of each exposed surface were evaluated according to the evaluation methods described above. The results are shown in Table 1.

[0098] [Examples 1-2, 1-3, 1-11 to 1-14, 1-17, 1-18, Comparative Examples 1-3 and 1-4] A sealant layer (α) and a multilayer structure were prepared and evaluated in the same manner as in Example 1-1, except that the base layer (β) shown in Table 1 was used instead of OPP-1. The results are shown in Table 1.

[0099] [Examples 1-4 and 1-7] A sealant layer (α) and a multilayer structure were prepared and evaluated in the same manner as in Example 1-1, except that the amount of silica particles Si-1 added to the sealant layer (α) was changed as shown in Table 1. The results are shown in Table 1.

[0100] [Example 1-5] A sealant layer (α), a base layer (β), and a multilayer structure were produced and evaluated in the same manner as in Example 1-1, except that, when producing a monolayer film of the sealant layer (α), an air slit with an air outlet gap of 0.3 mm was provided at a position 3 cm above the take-up roll, and air controlled to a pressure of 0.2 MPa was blown through the air slit at a wind speed of 30 m / s. The results are shown in Table 1.

[0101] [Example 1-6] The conditions for producing a monolayer film were adjusted, and the resulting monolayer film having a thickness of 270 μm was brought into contact with hot water at 85°C for 30 seconds, and then stretched to 3.0 times in the longitudinal direction and 3.0 times in the transverse direction using a tenter-type simultaneous biaxial stretching machine in an atmosphere of 90°C, and further heat-treated for 5 seconds in the tenter set at 170°C to produce a biaxially stretched EVOH film having a thickness of 30 μm. A sealant layer (α), a base layer (β), and a multilayer structure were produced and evaluated in the same manner as in Example 1-1, except that the conditions for producing the monolayer film were adjusted, and the resulting monolayer film having a thickness of 270 μm was brought into contact with hot water at 85°C for 30 seconds, and then stretched to 3.0 times in the longitudinal direction and 3.0 times in the transverse direction using a tenter-type simultaneous biaxial stretching machine in an atmosphere of 90°C, and further heat-treated for 5 seconds in the tenter set at 170°C. The sealant layer (α), a base layer (β), and a multilayer structure were produced and evaluated in the same manner as in Example 1-1. The results are shown in Table 1.

[0102] [Example 1-8] A sealant layer (α), a base layer (β), and a multilayer structure were produced and evaluated in the same manner as in Example 1-6, except that the amount of silica particles Si-1 was changed to 300 ppm, and when forming a monolayer film of the sealant layer (α), an air slit with an air outlet gap of 0.3 mm was provided at a position 3 cm above the take-up roll, and air controlled to a pressure of 0.2 MPa was blown through the air slit at a wind speed of 30 m / s. The results are shown in Table 1.

[0103] [Example 1-9] A sealant layer (α) and a multilayer structure were prepared and evaluated in the same manner as in Example 1-1, except that silica particles Si-1 were not added to the sealant layer (α). The results are shown in Table 1.

[0104] [Example 1-10] A sealant layer (α) and a multilayer structure were prepared and evaluated in the same manner as in Example 1-1, except that EVOH-2 was used instead of EVOH-1 in the sealant layer (α) and silica particles Si-1 were not added. The results are shown in Table 1.

[0105] Examples 1-15 and 1-16 A sealant layer (α) and a multilayer structure were prepared and evaluated in the same manner as in Example 1-1, except that the thickness of the sealant layer (α) was changed as shown in Table 1. The results are shown in Table 1.

[0106] [Examples 1-19 and 1-20] A sealant layer (α) and a multilayer structure were prepared and evaluated in the same manner as in Example 1-1, except that the biaxially stretched film shown in Table 1 was used as the sealant layer (α). The results are shown in Table 1.

[0107] Example 1-21 EVOH-1 was dry-blended with 300 ppm Si-1 (inorganic particles) in a 100 L blender by stirring for 10 minutes to obtain a dry blend for the sealant layer (α). Using PP-1 as the material for the base layer (β) and Ad-2 as the material for the adhesive layer (γ), a cylindrical multilayer structure was produced using an inflation extrusion molding machine under the following conditions. The base layer (β) was a laminate of three layers with a thickness of 10 μm, resulting in a base layer (β) with a thickness of 30 μm. (Conditions for producing multilayer structure) Layer configuration of multilayer structure: [Outer surface side] Base layer (β) / Adhesive layer (γ) / Sealant layer (α) [Inner surface side] = 30 μm / 3 μm / 30 μm (total thickness 60 μm) Apparatus: 5-type 5-layer inflation extrusion molding machine (manufactured by Dr Collin) Die temperature: 210° C. Blow-up ratio: 2.7 Take-up speed: 4 m / min Film folded diameter width: 25 cm (Conditions for base layer (β) extruder) Extruder: 30φ single-screw extruder (manufactured by Dr Collin) Rotation speed: 20 rpm Extrusion temperature: Feed section / Compression section / Metering section = 170° C. / 190° C. / 210° C. (Conditions for adhesive layer (γ) extruder) Extruder: 20φ single-screw extruder (manufactured by Dr Collin) Rotation speed: 20 rpm Extrusion temperature: feeding section / compression section / metering section=170°C / 190°C / 210°C (Conditions of sealant layer (α) extruder) Extruder: 30φ single-screw extruder (manufactured by Dr Collin) Rotation speed: 24 rpm Extrusion temperature: feeding section / compression section / metering section=190°C / 210°C / 210°C The obtained cylindrical multilayer structure was cut into a flat shape and used instead of the multilayer structure of Example 1-1, except that the multilayer structure was evaluated in the same manner as in Example 1-1. In addition, a monolayer film of the sealant layer (α) having a thickness of 30 μm was formed without extruding any layers other than the sealant layer (α), and a monolayer film of the base layer (β) having a thickness of 30 μm was formed without extruding any layers other than the base layer (β), and the Tg, Young's modulus, OTR, and roll appearance of each monolayer film were evaluated according to the above-mentioned evaluation methods.

[0108] [Comparative Example 1-1] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 1-1, except that the amount of silica particles Si-1 was changed to 1200 ppm and a cast roll with a matte surface and an arithmetic mean roughness Ra of 5 μm was used. The results are shown in Table 1.

[0109] [Comparative Example 1-2] A sealant layer (α) and a multilayer structure were prepared and evaluated in the same manner as in Example 1-6, except that the silica particles Si-1 were not added to the sealant layer (α). The results are shown in Table 1.

[0110] [Comparative Example 1-5] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 1-1, except that OPP-1 was used as the sealant layer (α) and LLDPE was used as the base layer (β). The results are shown in Table 1.

[0111] [Comparative Example 1-6] A sealant layer (α) and a multilayer structure were produced and evaluated in the same manner as in Example 1-5, except that, when producing a monolayer film of the sealant layer (α), the screw rotation speed of the extruder was changed to 10 rpm, air controlled to a pressure of 0.4 MPa was blown through the air slit at a speed of 60 m / sec, and silica particles Si-1 were not added. The results are shown in Table 1.

[0112] [Reference Examples 1-1 to 1-3] Using the multilayer structures obtained in Examples 1-1, 1-12, and 1-14, sealant layers (α), base layers (β), and multilayer structures were prepared and evaluated in the same manner as in Example 1-1, except that hot plate sealing (heat sealing) was performed under the following conditions instead of ultrasonic sealing. The results are shown in Table 1. (Hot Plate Sealing Method) The sealant layers (α) of the multilayer structures were overlapped with each other and pressure-bonded for 1 second using a hot plate heat sealer (Bag Sealer HBS-280, manufactured by Hirai Shoji Co., Ltd.) at a temperature of 200°C and a pressure of 0.1 MPa.

[0113]

[0114] [Example 1-22] The multilayer structure obtained in Example 1-1 was evaluated in the same manner as in Example 1-1, except that it was stored for one day in an environment of 40°C and 90% RH. The surface moisture content of the sealant layer (α) of Example 1-1, measured by the method described below, was 3.0% by mass, and the surface moisture content of the sealant layer (α) of the multilayer structure after storage under the above conditions was 5.9% by mass. (Surface moisture content of sealant layer (α)) The surface moisture content of the exposed surface of the sealant layer (α) of the multilayer structures produced in Examples 1-1 and 1-22 was measured using a Laserliner (registered trademark) Moisture Finder DX manufactured by UMAREX GmbH & Co. KG.

[0115] [Example 1-23] A multilayer structure was produced and evaluated in the same manner as in Example 1-1, except that the multilayer structure was not stored at 23°C and 50% RH for 1 day. The surface moisture content of the resulting multilayer structure was measured by the method described in Example 1-22, and was found to be 1.0 mass%.

[0116] The multilayer structure of Example 1-22, in which the surface moisture content of the sealant layer (α) was higher than that of Example 1-1, had a better seal strength after ultrasonic sealing as measured by the method described in the above evaluation method (6) than the multilayer structure of Example 1-1. Also, the multilayer structure of Example 1-1, in which the surface moisture content of the sealant layer (α) was higher than that of Example 1-23, had a better seal strength after ultrasonic sealing as measured by the method described in the above evaluation method (6) than the multilayer structure of Example 1-23.

[0117] Example 2-1 EVOH-2 was melted at 220°C using a single-screw extruder, and the molten resin was extruded from a die with a lip opening of 0.7 mm onto a cast roll (mirror surface: arithmetic mean roughness Ra 0.2 μm) at 80°C to obtain a monolayer film (sealant layer (α)) with a thickness of 30 μm. The obtained monolayer film was laminated with OPP-8, which is the substrate layer (β), using an adhesive to produce a multilayer structure of sealant layer (α) / adhesive layer (γ) / substrate layer (β). When laminating the substrate layer (β), a two-component urethane adhesive Ad-1 ("Takelac A-520" and "Takenate A-50" manufactured by Mitsui Chemicals, Inc.) was applied to the substrate layer (β) so that the thickness after drying was 2 μm, and then dried to provide an adhesive layer (γ), which was then laminated by a dry lamination method. The sealant layer (α) was laminated so that the surface that came into contact with the casting roll during film formation was the exposed surface of the multilayer structure. The static friction coefficient and OTR of the resulting multilayer structure were measured according to the above-mentioned evaluation methods. The results are shown in Table 2.

[0118] The resulting multilayer structure was laminated with the sealant layers (α) on top of each other and ultrasonically sealed using a Seidensha Electronics Co., Ltd. ultrasonic sealing machine "SONOPET JII970" at a seal width of 3 mm, a frequency of 28.5 kHz, an amplitude of 40 μm, a pressure of 0.1 MPa, and a sealing time of 0.3 seconds to obtain a multilayer structure after ultrasonic welding. The appearance and seal strength of the resulting multilayer structure after ultrasonic welding were measured based on the evaluation methods described above. The results are shown in Table 2.

[0119] [Examples 2-2 to 2-7] Multilayer structures and multilayer structures after ultrasonic welding were produced and evaluated in the same manner as in Example 2-1, except that the ultrasonic welding conditions were changed as shown in Table 2. The results are shown in Table 2.

[0120] [Example 2-8] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-1, except that a cast roll with a matte surface and an arithmetic mean roughness Ra of 2.3 μm was used. The results are shown in Table 2.

[0121] Example 2-9 A multilayer structure and a multilayer structure after ultrasonic welding were prepared and evaluated in the same manner as in Example 2-1, except that, when preparing the sealant layer (α), air was blown through an air slit to press the molten resin onto the casting roll at the same time as extruding the molten resin onto the casting roll. The results are shown in Table 2. The air slit was located 3 cm above the casting roll, and the gap between the air outlets was 0.3 mm. The air pressure was controlled to 0.2 MPa, and the air was blown at a speed of 30 m / s.

[0122] [Examples 2-10 and 2-11] Multilayer structures and multilayer structures after ultrasonic welding were produced and evaluated in the same manner as in Example 2-1, except that the type of base layer (β) was changed as shown in Table 2. The results are shown in Table 2.

[0123] Example 2-12 A three-type, three-layer multilayer structure was produced using coextrusion equipment under the following conditions: EVOH-2 as the sealant layer (α), PP-2 as the base layer (β), and Ad-2 as the adhesive layer (γ). Specifically, the molten resin was extruded onto a cast roll at 80°C (arithmetic mean roughness Ra: 0.2 μm) so that the sealant layer (α) side was in contact with the cast roll, producing a multilayer structure with a sealant layer (α) / adhesive layer (γ) / base layer (β) ratio of 30 μm / 10 μm / 30 μm. The resulting multilayer structure was evaluated in the same manner as in Example 2-1. Furthermore, a multilayer structure after ultrasonic welding was produced and evaluated in the same manner as in Example 2-1. The results are shown in Table 2. (Extruder) Sealant layer (α): 20 mm φ extruder laboratory machine ME type CO-EXT (manufactured by Toyo Seiki Co., Ltd.) Adhesive layer (γ): 20 mm φ extruder SZW20GT-20MG-STD (manufactured by Technovel Co., Ltd.) Base material layer (β): 32 mm φ extruder GT-32-A (manufactured by Plastics Technology Research Institute) (Extrusion temperature) Sealant layer (α): Feeding section / compression section / metering section / die = 175 / 220 / 220 / 220 ° C. Adhesive layer (γ): Feeding section / compression section / metering section / die = 100 / 160 / 220 / 220 ° C. Base material layer (β): Feeding section / compression section / metering section / die = 150 / 200 / 220 / 220 ° C. (Die) 300 mm wide coat hanger die (manufactured by Plastics Technology Research Institute)

[0124] [Example 2-13] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-12, except that the thickness of the sealant layer (α) was changed as shown in Table 2. The results are shown in Table 2.

[0125] Example 2-14 A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-12, except that the thicknesses of the sealant layer (α) and the substrate layer (β) were changed as shown in Table 2, and air was blown through the air slit to press the molten resin onto the casting roll simultaneously with extrusion. The results are shown in Table 2. The air slit was located 3 cm above the casting roll, and the air outlet had a gap of 0.3 mm. The air pressure was controlled to 0.2 MPa, and the air was blown at a speed of 30 m / s.

[0126] Example 2-15 PP was melted at 220°C using a single-screw extruder, and the molten resin was extruded through a die with a lip opening of 0.7 mm onto a cast roll (arithmetic mean roughness Ra 0.2 μm) at 80°C with a surface roughness of Ra 0.2 μm. At the same time, air was blown through an air slit to press the molten resin onto the cast roll, producing a 100 μm-thick monolayer film of PP-2 (substrate layer (β)). A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-1, except that the resulting PP monolayer film was used instead of OPP-8. The results are shown in Table 2. The air slit was located 3 cm above the cast roll, and the gap between the air outlets was 0.3 mm. The air pressure was controlled to 0.2 MPa, and the air was blown at a wind speed of 30 m / s.

[0127] [Example 2-16] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-15, except that the thickness of the base layer (β) was changed as shown in Table 2. The results are shown in Table 2.

[0128] [Example 2-17] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-1, except that the thickness of the sealant layer (α) was changed to 100 μm. The results are shown in Table 2.

[0129] [Example 2-18] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-1, except that EVOH-1 was used instead of EVOH-2. The results are shown in Table 2.

[0130] [Example 2-19] A multilayer structure and a multilayer structure after ultrasonic welding were produced and evaluated in the same manner as in Example 2-1, except that the type of sealant layer (α) was changed to PET and the temperature of the single-screw extruder during production of the sealant layer (α) was changed to 280° C. The results are shown in Table 2.

[0131] [Example 2-20] A multilayer structure was produced and evaluated in the same manner as in Example 2-1, except that the type of sealant layer (α) was changed to PA and the temperature of the single-screw extruder during production of the sealant layer (α) was changed to 250° C. The results are shown in Table 2.

[0132] Comparative Example 2-1 A sealant layer (α), a multilayer structure, and a welded multilayer structure were prepared and evaluated in the same manner as in Example 2-1, except that the multilayer structure obtained in Example 2-1 was heat-sealed under the following conditions instead of ultrasonic welding. The results are shown in Table 2. (Heat-sealing conditions) The sealant layer (α) was superimposed on the multilayer structure obtained in Comparative Example 2-1, and pressure-sealed for 1 second using a hot plate heat sealer (Bag Sealer HBS-280, manufactured by Hirai Shoji Co., Ltd.) at a temperature of 190°C and a pressure of 0.1 MPa.

[0133] Comparative Example 2-2 A multilayer structure was produced and evaluated in the same manner as in Comparative Example 2-1, except that EVOH-3 was used instead of EVOH-2 and the temperature of the hot plate heat sealer was set to 170° C. The results are shown in Table 2.

[0134] Comparative Example 2-3 A multilayer structure was produced and evaluated in the same manner as in Comparative Example 2-1, except that OPP-8 was used instead of the single layer film of EVOH-2. The results are shown in Table 2.

[0135] [Comparative Example 2-4] A multilayer structure and a welded multilayer structure were produced and evaluated in the same manner as in Comparative Example 2-3, except that the multilayer structure obtained in Comparative Example 2-3 was ultrasonically welded in the same manner as in Example 2-1 instead of heat sealing. The results are shown in Table 2.

[0136]

Claims

1. A multilayer structure comprising a sealant layer (α) and a substrate layer (β), wherein the multilayer structure has the sealant layer (α) as one outermost layer and the substrate layer (β) as the other outermost layer, and the oxygen transmission rate of the sealant layer (α) measured at 20°C and 65% RH in accordance with ISO14663-2 Annex C (1999) is 100 mL 20 μm / (m ２ a static friction coefficient μα of an exposed surface of the sealant layer (α) is 0.30 or more and 1.00 or less, and a static friction coefficient μβ of an exposed surface of the base layer (β) is 0.20 or more and 0.39 or less, as measured in accordance with the inclination method of JIS P8147 (2010), and the multilayer structure is for ultrasonic sealing.

2. The multilayer structure according to claim 1, wherein the sealant layer (α) contains, as a main component, at least one selected from the group consisting of ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polyamide, cyclic polyolefin, and polyacrylonitrile.

3. The multilayer structure according to claim 2, wherein the sealant layer (α) contains an ethylene-vinyl alcohol copolymer as a main component, and the ethylene unit content of the ethylene-vinyl alcohol copolymer is 20 mol % or more and 50 mol % or less.

4. The multilayer structure according to claim 1, wherein the substrate layer (β) contains, as a main component, at least one selected from the group consisting of polypropylene and polyethylene.

5. The multilayer structure according to claim 1, wherein the Young's modulus of the substrate layer (β) is 0.05 GPa or more and 3.0 GPa or less, as measured in accordance with ISO 527-1:2019 at a temperature of 23°C, a relative humidity of 50%, and a tensile speed of 50 mm / min.

6. The multilayer structure according to claim 1, wherein the glass transition temperature Tgβ of the substrate layer (β) is equal to or lower than the glass transition temperature Tgα of the sealant layer (α).

7. The multilayer structure according to claim 1, wherein the thickness of the sealant layer (α) is 1 μm or more and 100 μm or less.

8. The multilayer structure according to claim 1, wherein the thickness of the substrate layer (β) is 10 μm or more and 200 μm or less.

9. The multilayer structure according to claim 1, wherein the thickness of the multilayer structure is 40 μm or more and 300 μm or less.

10. The multilayer structure according to claim 1, wherein the ratio (β / α) of the thickness of the substrate layer (β) to the thickness of the sealant layer (α) is 1 / 10 or more and 30 / 1 or less.

11. The multilayer structure of claim 1, wherein the sealant layer (α) is substantially unstretched.

12. The multilayer structure according to claim 1, wherein the sealant layer (α) and the substrate layer (β) are laminated via an adhesive layer (γ).

13. Water vapor permeability measured in accordance with ISO15106-2:2003 is 15g / m ２ 10. The multilayer structure of claim 1, wherein the average particle size is less than 100 μm.

14. The multilayer structure according to claim 1, wherein the sealant layers (α) are stacked so that they are in contact with each other and then welded together at a seal width of 3 mm, a frequency of 39 kHz, an amplitude of 19 μm, and a compression time of 0.3 seconds, and the seal strength at a tensile speed of 300 mm / min is 10 N / 15 mm or more as measured in accordance with JIS Z 1707 (2019).

15. A packaging bag obtained by stacking the multilayer structure according to any one of claims 1 to 14 so that the sealant layers (α) are in contact with each other, and then irradiating them with ultrasonic waves to weld the sealant layers (α) together.

16. A vacuum insulation material comprising the packaging bag according to claim 15 and a core material disposed inside the packaging bag, the interior of the packaging bag being reduced in pressure.

17. A method for producing a packaging bag, comprising the steps of stacking the multilayer structure according to any one of claims 1 to 14 so that the sealant layers (α) are in contact with each other, and then irradiating the stack with ultrasonic waves to weld the sealant layers (α) together.

18. A multilayer structure comprising a sealant layer (α) and a substrate layer (β), wherein the multilayer structure has the sealant layer (α) as one outermost layer and the substrate layer (β) as the other outermost layer, wherein the surface moisture content of the sealant layer (α) is 0.5% by mass or more and 7.0% by mass or less, and wherein the oxygen transmission rate of the sealant layer (α) measured at 20°C and 65% RH in accordance with ISO14663-2 Annex C (1999) is 100 mL 20 μm / (m ２ .times.day.atm) or less, and the multilayer structure is for ultrasonic sealing.

19. A film roll comprising a film made of the multilayer structure according to claim 18 wound thereon.

20. A method for producing a packaging material including a multilayer structure having a sealant layer (α) and a base layer (β), comprising a sealing step of welding the sealant layer (α) by irradiating it with ultrasound, wherein the oxygen transmission rate of the sealant layer (α) is 100 mL 20 μm / (m) as measured at 20°C and 65% RH in accordance with ISO14663-2 Annex C (1999). ２ a melting point Tmα (°C) of the sealant layer (α) and a melting point Tmβ (°C) of the base material layer (β) satisfy the following formula (1), and the packaging material has the sealant layer (α) as an innermost layer and the base material layer (β) as an outermost layer. Tmα - Tmβ ≧ -5 (1) 21. The manufacturing method according to claim 20, wherein in the sealing step, two of the multilayer structures are stacked so that the sealant layers (α) are in contact with each other, and then ultrasonic waves are applied from the substrate layer (β) side to weld the sealant layers (α) together.

22. The manufacturing method according to claim 20 or 21, wherein the frequency of the ultrasonic waves irradiated in the sealing step is 15 kHz or more and 50 kHz or less.

23. The manufacturing method according to claim 20 or 21, wherein the amplitude of the ultrasonic waves irradiated in the sealing step is 5 μm or more and 100 μm or less.

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