Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D31/00—Bags or like containers made of paper and having structural provision for thickness of contents
  • B65D31/02—Bags or like containers made of paper and having structural provision for thickness of contents with laminated walls
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/10—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of paper or cardboard
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B29/00—Layered products comprising a layer of paper or cardboard
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D31/00—Bags or like containers made of paper and having structural provision for thickness of contents
  • B65D31/10—Bags or like containers made of paper and having structural provision for thickness of contents with gusseted sides

Definitions

• the inventors have considered various laminates including a paper base, a first resin layer, a vapor-deposited aluminum layer, and a second resin layer as laminates having good environmental compatibility. As a result, the inventors discovered that such laminates have a problem in that they have high water vapor permeability and are unstable.
• the present disclosure provides a laminate that exhibits high and stable water vapor barrier performance, and a packaging bag using the same.
• the present disclosure provides the following laminate and packaging bag.
• paper Compared to plastic films, paper exhibits greater dimensional changes due to moisture absorption and release.
• the moisture content in paper varies depending on the production lot.
• the moisture content in paper changes depending on the environmental atmosphere during the manufacturing, storage, and use of the gas barrier laminate.
• Paper produced continuously by a paper-making machine exhibits greater expansion and shrinkage in a cross direction (CD), because the fibers are oriented in a machine direction (MD) of the paper-making machine.
• CD cross direction
• MD machine direction
• the vapor-deposited layer cannot conform to the dimensional changes of the paper due to changes in its moisture content, causing defects parallel to the MD to occur, as shown in the Examples described below.
• the defects break the continuity of the vapor-deposited aluminum layer and thus increase the water vapor permeability of the laminate.
• the second resin layer is formed, for example, by wet-coating a mixture of a resin and a solvent onto the vapor-deposited aluminum layer to form a coating film, and then drying the coating film. During the drying of the coating film, the evaporation of the solvent and the formation of the second resin layer proceed.
• the solvent contained in the second resin layer may undergo bumping. Such bumping of the solvent may cause micro-sized defects in the second resin layer, as will be described in the Examples below.
• similar defects may occur in the second resin layer when the coating film for forming the second resin layer is dried. These defects in the second resin layer may reach the vapor-deposited aluminum layer, as will be described in the Examples below. Such defects in the vapor-deposited aluminum layer may make the water vapor barrier performance unstable.
• the laminate exhibits high and stable water vapor barrier performance.
• a laminate that exhibits high and stable water vapor barrier performance, and a packaging bag using the same are provided.
• a laminate according to this embodiment has a structure in which at least a paper base, a first resin layer, a vapor-deposited aluminum layer, and a second resin layer are laminated in this order.
• the thickness of the vapor-deposited aluminum layer is 60 nm or more and less than 100 nm.
• FIG. 1 is a schematic cross-sectional view showing a laminate according to one embodiment.
• a laminate 10 according to one embodiment includes a paper base 3, a first resin layer 1, a vapor-deposited aluminum layer 4, and a second resin layer 2 in this order.
• the thickness of the laminate 10 may be 20 to 100 ⁇ m, 30 to 80 ⁇ m, or 40 to 60 ⁇ m. When the thickness of the laminate 10 is within this range, the laminate 10 can obtain a higher water vapor barrier performance more stably.
• the water vapor permeability of the gas barrier laminate 10 at a temperature of 40°C and a relative humidity of 90% may be 5 g/(m 2 ⁇ day) or less, 4 g/(m 2 ⁇ day) or less, 3 g/(m 2 ⁇ day) or less, 2 g/(m 2 ⁇ day) or less, or 1 g/(m 2 ⁇ day) or less.
• Water vapor permeability as used herein refers to a value measured by the method described in relation to the Examples below.
• the paper base 3 may be paper whose main component is plant pulp. Specific examples of the paper base 3 include high-quality paper, special high-quality paper, coated paper, art paper, cast-coated paper, imitation paper, kraft paper, and glassine paper.
• the basis weight of the paper base 3 may be 20 to 500 g/m 2 , or 30 to 100 g/m 2 .
• the paper base 3 may have a coating layer provided at least on the side of the paper base 3 that contacts the first resin layer 1.
• the paper base 3 may have at least a paper layer and the coating layer.
• the coating layer may be provided on both surfaces of the paper base 3.
• the coating layer may contain, for example, any of various copolymers such as styrenebutadiene, styrene-acrylic, and ethylene-vinyl acetate copolymers, polyvinyl alcohol resins, cellulose resins, and paraffin (wax) as a binder resin, and clay, kaolin, calcium carbonate, talc, or mica as a filler.
• the coating layer may be a clay coating layer containing at least clay as a filler.
• the dimensional change rate of the paper base 3 in the cross direction (CD) from 40°C and 20% RH to 40°C and 90% RH may be 0.3% or more, 0.4% or more, or 0.6% or more, and may be 1.5% or less, 1.3% or less, or 1.0% or less.
• the dimensional change rate of the paper base 3 in the machine direction (MD) from 40°C and 20% RH to 40°C and 90% RH may be 0.05% or more and 0.20% or less.
• the thickness of the coating layer may be 1.5 ⁇ m or more and 15 ⁇ m or less.
• the thickness of the coating layer may be 1.8 ⁇ m or more, 3 ⁇ m or more, 5 ⁇ m or more, or 6 ⁇ m or more.
• the thickness of the coating layer may be 12 ⁇ m or less, or 10 ⁇ m or less. When the thickness of the coating layer is within this range, the laminate 10 can obtain a higher water vapor barrier performance more stably.
• the thickness of the paper base 3 may be 20 to 100 ⁇ m, 30 to 80 ⁇ m, or 40 to 60 ⁇ m. When the thickness of the paper base 3 is within this range, the laminate 10 can obtain a higher water vapor barrier performance more stably.
• the ratio of the thickness of the coating layer to the thickness of the entire paper base 3 may be 3 to 25%, or 5 to 20%. When this ratio is within this range, the laminate 10 can obtain a higher water vapor barrier performance more stably.
• the weight ratio of the paper to the total weight of the laminate is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.
• the weight ratio of the paper to the total weight of the laminate is 50% by mass or more, it is possible to sufficiently reduce the amount of plastic materials used. This allows the laminate as a whole to be labelled as made of paper and also improves recyclability.
• the first resin layer 1 is provided on a surface of the paper base 3 to improve adhesion between the paper base 3 and a vapor-deposited aluminum layer 4 described later, and to improve the gas barrier performance of the laminate.
• the first resin layer 1 may contain at least one selected from the group consisting of a polyolefin having an acidic group, a polyvinyl alcohol resin, and a polyurethane resin.
• the first resin layer 1 is preferably a polyolefin having an acidic group and a polyurethane resin, and more preferably a polyolefin having an acidic group.
• the first resin layer 1 contains a polyolefin having an acidic group
• the first resin layer 1 can be highly flexible, can prevent the vapor-deposited aluminum layer 4 described later from cracking after being bent (folded), and can improve the adhesion between the first resin layer 1 and the vapor-deposited aluminum layer 4.
• the first resin layer 1 contains a polyolefin having an acidic group
• a dense film that provides water vapor barrier properties is formed due to the crystallinity of the polyolefin.
• the crystallinity of the polyolefin provides water vapor barrier properties, and the presence of acidic groups provides tight adhesion to the vapor-deposited aluminum layer 4.
• the polyolefin having an acidic group may have at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and carboxylic ester.
• polyolefin having an acidic group examples include copolymers of ethylene or propylene with unsaturated carboxylic acids (unsaturated compounds having a carboxyl group, such as acrylic acid, methacrylic acid, and maleic anhydride) or unsaturated carboxylic acid esters, and salts of carboxylic acids neutralized with basic compounds. Further examples include copolymers of ethylene or propylene with vinyl acetate, epoxy compounds, chlorine compounds, urethane compounds, and polyamide compounds.
• the first resin layer 1 preferably contains an ethylene-unsaturated carboxylic acid copolymer, since this makes its water vapor barrier performance more stable.
• polystyrene resin having an acidic group examples include copolymers of acrylic acid ester and maleic anhydride, ethylene-vinyl acetate copolymers, and ethylene-glycidyl methacrylate copolymers.
• metal ions such as sodium or potassium ions
• a resin in which the acidic groups are neutralized with ammonia e.g., ZAIKTHENE AC, manufactured by Sumitomo Seika Chemicals Company, Limited
• ionomer resins in which the acidic groups are neutralized with sodium hydroxide or potassium hydroxide e.g., the CHEMIPEARL series manufactured by Mitsui Chemicals, Inc.
• the amount of remaining metal ions can be confirmed by the IR spectrum of the first resin layer.
• the ratio (A COOX /A COOH ) of the peak area associated with the salts of carboxyl groups (A COOX ) to the peak area associated with the carboxyl groups (A COOH ) to 0.1 or less, it is possible to suppress pitting corrosion of the vapor-deposited aluminum layer even if the laminate is stored for a long period of time.
• the peak associated with carboxyl groups appears near 1700 cm -1
• the peak associated with salts of carboxyl groups appears generally between 1490 and 1620 cm -1 , although this depends on the type of salt.
• the peak associated with sodium salts of carboxyl groups and potassium salts of carboxyl groups appear near 1540 cm -1 .
• the peak associated with ammonium salts of carboxyl groups appears near 1520 cm -1 .
• the first resin layer 1 contains a polyvinyl alcohol resin
• a polyvinyl alcohol resin has hydroxyl groups. This facilitates binding of the polyvinyl alcohol to a metal such as aluminum in the vapor-deposited aluminum layer 4, and in turn facilitates improving the adhesion between the vapor-deposited aluminum layer 4 and the first resin layer 1.
• such a first resin layer 1 is highly flexible and can suppress cracking of the vapor-deposited aluminum layer 4 after being bent (folded).
• the oxygen barrier performance of the laminate can be improved.
• the polyvinyl alcohol resin is a resin containing vinyl alcohol as a constituent unit, and examples of the polyvinyl alcohol resin include fully saponified polyvinyl alcohol resin, partially saponified polyvinyl alcohol resin, modified polyvinyl alcohol resin, and ethylene-vinyl alcohol copolymer resin.
• the polyurethane resin is obtained by bonding the acid groups of an acid group-containing polyurethane with the amino groups of a polyamine as a crosslinking agent.
• the polyurethane resin is a reaction product of an acid group-containing polyurethane and a polyamine, or is formed by crosslinking an acid group-containing polyurethane with a polyamine.
• the bond between the acid groups of the acid group-containing polyurethane and the amino groups of the polyamine may be an ionic bond (e.g., an ionic bond between a carboxyl group and a tertiary amino group), or may be a covalent bond (e.g., an amide bond).
• the acid group-containing polyurethane forming a part of the polyurethane resin is anionic and self-emulsifying since it has an acid group, and thus it is also called an anionic self-emulsifying polyurethane.
• the acid groups of the acid group-containing polyurethane can bond with the amino groups (for example, primary amino groups, secondary amino groups, or tertiary amino groups) of the polyamine forming a part of the polyurethane resin.
• the acid group may be a carboxyl group, sulfonic acid group, or the like.
• the acid group can be usually neutralized with a neutralizer (base) and may form a salt and a base.
• the acid group may be located at the terminal or side chain of acid group-containing polyurethane, and is preferably located at the side chain.
• the acid value of the acid group-containing polyurethane can be selected within a range allowing the acid group-containing polyurethane to be water-dispersible, and can be 5 to 100 mgKOH/g, 10 to 70 mgKOH/g, or 15 to 60 mgKOH/g.
• the acid value of the acid group-containing polyurethane is greater than or equal to the lower limit of this range, it is easy to make the acid group-containing polyurethane dispersible in water, and this facilitates ensuring uniform dispersion of the polyurethane resin and other materials, and dispersion stability of the coating agent.
• the acid value of the acid group-containing polyurethane is measured by a method according to JIS K 0070.
• the sum of the urethane group concentration and the urea group concentration of the acid group-containing polyurethane may be 15% by mass or more, and may be in a range of 20 to 60% by mass from the viewpoint of gas barrier performance.
• the sum of the urethane group concentration and the urea group concentration is greater than or equal to the above lower limit, the first resin layer 1 is likely to exhibit a good gas barrier performance.
• the sum of the urethane group concentration and the urea group concentration is smaller than or equal to the upper limit of the above range, it facilitates preventing the first resin layer 1 from becoming rigid and brittle.
• the urethane group concentration refers to a ratio of the molecular weight of the urethane group (59 g/equivalent) to the molecular weight of the constituent unit of the polyurethane resin.
• the urea group concentration refers to a ratio of the molecular weight of the urea group (primary amino group (amino group): 58 g/equivalent, secondary amino group (imino group): 57 g/equivalent) to the molecular weight of the constituent unit of the polyurethane resin.
• the urethane group concentration and the urea group concentration can be calculated based on the feed ratios of the reactants, that is, based on the proportion of each component used.
• the acid group-containing polyurethane resin can at least have rigid units (units including a hydrocarbon ring) and short-chain units (e.g., units including a hydrocarbon chain).
• the constituent units of the acid group-containing polyurethane resin may have a hydrocarbon ring (at least one of aromatic and non-aromatic hydrocarbon rings) derived from a polyisocyanate component, a polyhydroxy acid component, a polyol component, or an elongated chain component (especially, at least a polyisocyanate component).
• the polyurethane resin may have an aromatic ring, and therefore the constituent units of the acid group-containing polyurethane may have an aromatic hydrocarbon ring as the hydrocarbon ring.
• the weight proportion of a unit having a hydrocarbon ring in the total weight of all constituent units of the acid group-containing polyurethane can be 10 to 70% by mass, 15 to 65% by mass, or 20 to 60% by mass.
• the proportion of the unit having a hydrocarbon ring is greater than or equal to the lower limit of the above range, the first resin layer 1 is likely to exhibit a good gas barrier performance.
• the proportion of the unit having a hydrocarbon ring is smaller than or equal to the upper limit, it facilitates preventing the first resin layer 1 from becoming rigid and brittle.
• the number average molecular weight of the acid group-containing polyurethane can be appropriately selected, and it may be 800 to 1,000,000, 800 to 200,000, or 800 to 100,000. When the number average molecular weight of the acid group-containing polyurethane is smaller than or equal to the upper limit of the above range, a coating agent with an appropriate viscosity is likely to be obtained. When the number average molecular weight of the acid group-containing polyurethane is greater than or equal to the lower limit of the above range, the first resin layer 1 is likely to exhibit good gas barrier performance.
• the number average molecular weight of the acid group-containing polyurethane is a value measured by gel permeation chromatography (GPC) relative to a polystyrene standard.
• the acid group-containing polyurethane may be crystalline for the purpose of improving the gas barrier performance.
• the glass transition temperature of the acid group-containing polyurethane may be 100°C or higher, 110°C or higher, or 120°C or higher. When the glass transition temperature of the acid group-containing polyurethane is 100°C or higher, the first resin layer 1 is likely to exhibit a good gas barrier performance.
• the glass transition temperature of the acid group-containing polyurethane may be 200°C or lower, 180°C or lower, or 150°C or lower. Therefore, the glass transition temperature of the acid group-containing polyurethane may be 100 to 200°C, 110 to 180°C, or 120 to 150°C.
• the glass transition temperature of the acid group-containing polyurethane is measured by differential scanning calorimetry (DSC).
• the polyamine forming a part of the polyurethane resin is a compound having two or more basic nitrogen atoms.
• the basic nitrogen atoms are nitrogen atoms capable of bonding to the acid groups of the acid group-containing polyurethane, and for example, each of them may be a nitrogen atom in an amino group such as a primary amino group, a secondary amino group, or a tertiary amino group.
• the polyamine is not particularly limited as long as it can bond to the acid groups of the acid group-containing polyurethane and improve the gas barrier performance, and it may be any of various compounds having two or more basic nitrogen atoms.
• the polyamine may be a polyamine having two or more amino groups of at least one type selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group.
• Examples of the polyamine include alkylene diamines, polyalkylene polyamines, and silicon compounds having a plurality of basic nitrogen atoms.
• Examples of the alkylene diamines include alkylene diamines having a carbon number of 2 to 10, such as ethylene diamine, 1,2-propylene diamine, 1,3-propylene diamine, 1,4-butane diamine, and 1,6-hexamethylene diamine.
• Examples of the polyalkylene polyamines include tetraalkylene polyamines.
• Examples of the silicon compounds having a plurality of basic nitrogen atoms include silane coupling agents having a plurality of basic nitrogen atoms, such as 2-[N-(2-aminoethyl)amino]ethyl trimethoxysilane, and 3-[N-(2-aminoethyl)amino]propyl triethoxysilane.
• the amine value of the polyamine may be 100 to 1900 mgKOH/g, 150 to 1900 mgKOH/g, 200 to 1900 mgKOH/g, 200 to 1700 mgKOH/g, or 300 to 1500 mgKOH/g.
• the amine value of the polyamine is greater than or equal to the lower limit of this range, the first resin layer 1 is likely to exhibit good gas barrier performance.
• the amine value of the polyamine is smaller than or equal to the upper limit of this range, the polyurethane resin tends to be dispersed in water stably.
• the amine value of the polyamine is measured by the following method.
• sample amount S g A precise weighing is performed for 0.5 to 2 g of a sample (sample amount S g).
• the precisely weighed sample is mixed with 30 g of ethanol, and dissolved therein.
• Bromophenol blue was added as an indicator to the solution obtained above to perform titration with 0.2 mol/L of ethanol-hydrochloric acid solution (titer f).
• titer f a point where the color of solution changes to a color between green and yellow is set as an end point, and a titer amount (AmL) at this point is used to calculate an amine value using the following calculation formula 1.
• AmL titer amount
• the molar ratio of the acid groups of the acid group-containing polyurethane to the basic nitrogen atoms of the polyamine may be 10/1 to 0.1/1, or 5/1 to 0.2/1.
• the first resin layer 1 is likely to develop a good oxygen barrier performance when the ratio of acid groups to basic nitrogen atoms is within this range.
• the polyurethane resin may be a polyurethane resin that is commercially available, or may be a polyurethane resin manufactured by a known manufacturing method.
• the method of manufacturing the polyurethane resin is not particularly limited, and may be an ordinary technique for making polyurethane resin water-based, such as an acetone method or a prepolymer method.
• urethanization catalysts such as amine-based catalysts, tin-based catalysts, and lead-based catalysts may be used as appropriate.
• the acid group-containing polyurethane resin can be prepared by reacting a polyisocyanate compound, a polyhydroxy acid, and, if necessary, at least one of a polyol component and a chain extender component in an inert organic solvent such as ketones such as acetone, ethers such as tetrahydrofuran, or nitriles such as acetonitrile.
• an inert organic solvent such as ketones such as acetone, ethers such as tetrahydrofuran, or nitriles such as acetonitrile.
• the acid group-containing polyurethane resin can be prepared by reacting a polyisocyanate compound, a polyhydroxy acid, and a polyol component in an inert organic solvent (in particular, hydrophilic or water-soluble organic solvent) to generate a prepolymer having an isocyanate group at the terminal, followed by neutralization by using a neutralizer for dissolution or dispersion into an aqueous medium, reaction with a chain extender component added thereto, and removal of the organic solvent.
• Polyamine is added to the aqueous dispersion of the acid group-containing polyurethane thus obtained, and the mixture is heated as necessary to prepare a polyurethane resin in the form of an aqueous dispersion.
• the heating temperature can be 30 to 60°C.
• the first resin layer 1 may contain one or more other components in addition to a polyolefin having an acidic group, a polyvinyl alcohol resin, and a polyurethane resin.
• the other components include polyolefins other than the polyolefin having the acidic group, a silane coupling agent, organic titanate, a polyacrylic material, polyester, polyurethane, polycarbonate, polyurea, polyamide, polyimide, melamine, and phenol.
• the content of at least one selected from the group consisting of a polyolefin having an acidic group, a polyvinyl alcohol resin, and a polyurethane resin in the first resin layer 1 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.
• the thickness of the first resin layer 1 may be, for example, 0.5 ⁇ m or more, 1 ⁇ m or more, 2 ⁇ m or more, and 20 ⁇ m or less, 10 ⁇ m or less, or 5 ⁇ m or less.
• the thickness of the first resin layer 1 is 0.5 ⁇ m or more, the unevenness of the paper base described above can be efficiently leveled, and the vapor-deposited aluminum layer described below can be laminated uniformly.
• the thickness of the first resin layer 1 is 20 ⁇ m or less, the vapor-deposited aluminum layer can be laminated uniformly while keeping the cost down.
• Examples of the solvent contained in a coating solution of the first resin layer 1 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used singly or in combination of two or more.
• the solvent is preferably methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, or water. From an environmental viewpoint, the solvent is preferably methyl alcohol, ethyl alcohol, isopropyl alcohol, or water.
• the first resin layer 1 can be provided by applying a coating solution containing the above-described polyolefin having an acidic group, polyvinyl alcohol resin, or polyurethane resin, the solvent, and the like onto the paper base 3 to form a coating film, and then drying the coating film.
• the vapor-deposited aluminum layer 4 is a layer formed by vapor deposition of aluminum or an aluminum compound.
• the vapor-deposited aluminum layer may be obtained by vapor deposition of aluminum, or may contain aluminum oxide (AlO x ), silicon oxide (SiO x ), or the like.
• the thickness of the vapor-deposited aluminum layer 4 is 60 nm or more, and may be more than 60 nm, 65 nm or more, 67 nm or more, 70 nm or more, more than 70 nm, 75 nm or more, 80 nm or more, 85 nm or more, or 90 nm or more.
• the thickness of the vapor-deposited aluminum layer 4 is less than 100 nm, and may be 95 nm or less, 90 nm or less, or 85 nm or less.
• the thickness of the vapor-deposited aluminum layer 4 may be 60 nm or more and less than 100 nm, 60 nm or more and less than 95 nm or less, 65 nm or more and less than 90 nm or less, 67 nm or more and less than 85 nm or less, 65 nm or more and less than 95 nm or less, 70 nm or more and less than 95 nm or less, 75 nm or more and less than 95 nm or less, 80 nm or more and less than 95 nm or less, or 85 nm or more and less than 95 nm or less.
• the thickness of the vapor-deposited layer 4 is measured by the method described in relation to the Examples below.
• the second resin layer 2 is provided on the surface of the vapor-deposited aluminum layer 4 so as to be in contact with the vapor-deposited aluminum layer 4.
• the second resin layer 2 may contain a polyolefin having an acidic group.
• the polyolefin having an acidic group may have at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and carboxylic ester.
• polyolefin having an acidic group examples include copolymers of ethylene or propylene with unsaturated carboxylic acids (unsaturated compounds having a carboxyl group, such as acrylic acid and methacrylic acid) or unsaturated carboxylic acid esters, and salts of carboxylic acids neutralized with basic compounds. Further examples include copolymers of ethylene or propylene with vinyl acetate, epoxy compounds, chlorine compounds, urethane compounds, and polyamide compounds.
• polystyrene resin having an acidic group examples include copolymers of acrylic acid ester and maleic anhydride, ethylene-unsaturated carboxylic acid copolymers, ethylene-vinyl acetate copolymers, and ethylene-glycidyl methacrylate copolymers.
• the second resin layer 2 contains a polyolefin having an acidic group
• the second resin layer 2 can be highly flexible, can prevent the vapor-deposited aluminum layer from cracking after being bent (folded), and can improve its adhesion with the vapor-deposited aluminum layer.
• the second resin layer 2 contains the above-described polyolefin having an acidic group, a dense film that provides water vapor barrier properties is formed due to the crystallinity of the polyolefin.
• the acidic group provides tight adhesion to the vapor-deposited aluminum layer. Since the second resin layer 2 contains the polyolefin having an acidic group, it can also function as a heat seal layer, which eliminates the need to provide a separate heat seal layer.
• the second resin layer 2 preferably contains an ethylene-unsaturated carboxylic acid copolymer, since this makes its water vapor barrier performance more stable.
• the second resin layer 2 may contain one or more other components in addition to the polyolefin having an acidic group.
• the other components include a silane coupling agent, organic titanate, a polyacrylic material, polyester, polyurethane, polycarbonate, polyurea, polyamide, polyolefin emulsions, polyimide, melamine, and phenol.
• the content of the polyolefin having an acidic group in the second resin layer 2 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.
• the inventors found that, when the second resin layer adjacent to the vapor-deposited aluminum layer contains metal ions such as sodium or potassium ions, when the laminate is stored for a long period of time, the metal ions may corrode the aluminum, causing pinhole defects in the vapor-deposited aluminum layer, as with the first resin layer.
• a resin in which the acidic groups are neutralized with ammonia e.g., ZAIKTHENE AC, manufactured by Sumitomo Seika Chemicals Company, Limited
• the amount of remaining metal ions can be confirmed by the IR spectrum of the second resin layer, as with the first resin layer.
• the ratio (A COOX /A COOH ) of the peak area associated with the salts of carboxyl groups (A COOX ) to the peak area associated with the carboxyl groups (A COOH ) to 0.1 or less, it is possible to suppress pitting corrosion of the vapor-deposited aluminum layer even if the laminate is stored for a long period of time.
• the thickness of the second resin layer 2 may be, for example, 0.05 ⁇ m or more, 0.5 ⁇ m or more, 1 ⁇ m or more, 2 ⁇ m or more, and 20 ⁇ m or less, 10 ⁇ m or less, or 5 ⁇ m or less.
• the thickness of the second resin layer 2 is 0.05 ⁇ m or more, it can sufficiently fulfill the role of the heat seal layer described above.
• the thickness of the second resin layer 2 is 20 ⁇ m or less, it can exhibit sufficient adhesion to the vapor-deposited aluminum layer and sufficient barrier performance while keeping the cost down. Further, when the thickness of the second resin layer 2 is 2 ⁇ m or more and 10 ⁇ m or less, the vapor-deposited aluminum layer is less likely to crack, and sufficient water vapor barrier performance and oil resistance can be exerted even after the laminate is folded.
• Examples of the solvent contained in a coating solution of the second resin layer 2 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used singly or in combination of two or more.
• the solvent is preferably methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, or water. From an environmental viewpoint, the solvent is preferably methyl alcohol, ethyl alcohol, isopropyl alcohol, or water.
• the second resin layer 2 can be provided by applying a coating solution containing the above-described polyolefin having an acidic group, the solvent, and the like onto the vapor-deposited aluminum layer to form a coating film, and then drying the coating film.
• the melting point of the polyolefin having an acidic group in the coating solution is preferably 70 to 160°C, more preferably 80 to 120°C.
• the melting point of the polyolefin having an acidic group is 160°C or lower, it tends to be possible to reduce the onset temperature during heat sealing.
• the melting point of the polyolefin having an acidic group is 70°C or higher, blocking is less likely to occur in a high-temperature environment.
• the particle size is large in order to reduce the contact area.
• the particle size may specifically be 1 nm or more, 0.1 ⁇ m or more, and may be 1 ⁇ m or less, 0.7 ⁇ m or less, or 0.5 ⁇ m or less.
• Fig. 2 is a perspective view illustrating a gusset bag 20 made of the laminate 10.
• the upper opening of the gusset bag 20 is sealed to produce a packaging bag.
• the gusset bag 20 has portions where the laminate 10 is folded (folded portions B1 and B2).
• the folded portion B1 is a portion where the laminate 10 is valley-folded as viewed from the innermost layer side
• the folded portion B2 is a portion where the laminate 10 is mountain-folded as viewed from the innermost layer side.
• the packaging bag may be produced by folding a sheet of the laminate in two such that portions of the second resin layer 2 face each other, further folding the laminate as appropriate so as to obtain a desired shape, and then performing heat sealing such that a bag is formed. It is also possible to stack two sheets of the laminate so that their second resin layers 2 face each other, and then performing heat sealing such that the sheets form a bag.
• the heat seal strength may be 2N or more, or 4N or more.
• the upper limit of the heat seal strength is not particularly limited, but may be, for example, 10 N or less.
• the packaging bag may contain food, pharmaceuticals, or the like. In particular, among foods, it is suitable for containing sweets and the like.
• the packaging bag according to this embodiment exhibits high and stable water vapor barrier performance even though it uses a paper base.
• a gusset bag is given as an example of a packaging bag; however, the laminate according to this embodiment may be used to produce, for example, a pillow bag, a three-side-sealed bag, or a standing pouch.
• the following clay-coated papers 1 to 3 were prepared as paper bases.
• the clay-coated paper 1 was used as the paper base.
• ZAIKTHENE AC an aqueous dispersion of an ammonium salt of an ethylene-acrylic acid copolymer, manufactured by Sumitomo Seika Chemicals Company, Limited
• ZAIKTHENE AC an aqueous dispersion of an ammonium salt of an ethylene-acrylic acid copolymer, manufactured by Sumitomo Seika Chemicals Company, Limited
• the coating film was dried to obtain a first laminate in which a first resin layer (thickness: 3 ⁇ m, A COOX /A COOH : 0.03) was formed on the clay coating layer.
• CHEMIPEARL S100 an aqueous dispersion of a metal salt of an ethylene-unsaturated carboxylic acid copolymer, manufactured by Mitsui Chemicals, Inc.
• the coating film was dried to form a second resin layer (thickness: 3 ⁇ m, A COOX /A COOH : 1.25), thereby obtaining a gas barrier laminate.
• a COOX /A COOH was calculated from the following measurement method.
• the IR spectra of the first and second resin layers of the obtained gas barrier laminate were measured using a Fourier transform infrared spectrophotometer (manufactured by Perkin Elmer, product name: Frontier).
• the peak area between 1620 and 1770 cm -1 was calculated as the area of the peak associated with the carboxyl group (A COOH ).
• the peak area between 1490 and 1620 cm -1 was calculated as the area of the peak associated with the carboxyl group salt (A COOX ).
• the ratio (A COOX /A COOH ) of the area of the peak associated with the salt of the carboxyl group (A COOX ) to the area of the peak associated with the carboxyl group (A COOH ) was calculated from these results.
• a gas barrier laminate was obtained in the same manner as in Example 1, except that a vapor-deposited aluminum layer having the thickness shown in Table 1 or 2 was formed by reducing the transport speed of the first laminate during the vapor deposition of aluminum.
• a gas barrier laminate was obtained in the same manner as in Example 1, except that a vapor-deposited aluminum layer having the thickness shown in Table 2 was formed by increasing the transport speed of the first laminate during the vapor deposition of aluminum.
• the clay-coated paper 2 was used as the paper base.
• An aqueous solution of Poval 5-98 (a fully saponified PVA manufactured by Kuraray Co., Ltd.) was applied onto the surface of the paper base (onto the clay coating layer) with a gravure coater to form a coating film.
• the coating was dried to obtain a first laminate in which a first resin layer (thickness: 4 ⁇ m) was formed on the clay coating layer.
• a roll-to-roll vacuum deposition device aluminum was vapor-deposited onto the surface of the first resin layer while the first laminate was being transported, thereby forming a vapor-deposited aluminum layer (thickness: 61 nm).
• CHEMIPEARL S500 an emulsion of an acid-modified polyolefin, manufactured by Mitsui Chemicals, Inc.
• the coating film was dried to form a second resin layer (thickness: 3 ⁇ m, A COOX /A COOH : 1.25), thereby obtaining a gas barrier laminate.
• a gas barrier laminate was obtained in the same manner as in Example 3, except that a vapor-deposited aluminum layer having the thickness shown in Table 1 was formed by reducing the transport speed of the first laminate during the vapor deposition of aluminum.
• a gas barrier laminate was obtained in the same manner as in Example 3, except that a vapor-deposited aluminum layer having the thickness shown in Table 2 was formed by increasing the transport speed of the first laminate during the vapor deposition of aluminum.
• the clay-coated paper 2 was used as the paper base.
• TAKELAC WPB-341 (a polyurethane resin emulsion manufactured by Mitsui Chemicals, Inc.) was applied onto the surface of the paper base (onto the clay coating layer) with a gravure coater to form a coating film.
• the coating film was dried to obtain a first laminate in which a first resin layer (thickness: 1 ⁇ m) was formed on the clay coating layer.
• Using a roll-to-roll vacuum deposition device aluminum was vapor-deposited onto the surface of the first resin layer while the first laminate was being transported, thereby forming a vapor-deposited aluminum layer (thickness: 68 nm).
• ZAIKTHENE AC an aqueous dispersion of an ammonium salt of an ethylene-acrylic acid copolymer, manufactured by Sumitomo Seika Chemicals Company, Limited
• ZAIKTHENE AC an aqueous dispersion of an ammonium salt of an ethylene-acrylic acid copolymer, manufactured by Sumitomo Seika Chemicals Company, Limited
• the coating film was dried to form a second resin layer (thickness: 4 ⁇ m, A COOX /A COOH : 0.03), thereby obtaining a gas barrier laminate.
• a gas barrier laminate was obtained in the same manner as in Example 6, except that a vapor-deposited aluminum layer having the thickness shown in Table 1 was formed by reducing the transport speed of the first laminate during the vapor deposition of aluminum.
• a gas barrier laminate was obtained in the same manner as in Example 6, except that a vapor-deposited aluminum layer having the thickness shown in Table 2 was formed by increasing the transport speed of the first laminate during the vapor deposition of aluminum.
• Each measurement sample was embedded in UV-curable resin.
• the measurement sample was cut using a cryomicrotome to expose its cross section, thereby obtaining a specimen for cross-sectional observation.
• the obtained specimen was observed under a scanning electron microscope (magnification: 50,000 times), and an image of the cross section was captured.
• the thickness of the vapor-deposited aluminum layer was measured from the obtained image.
• the mean thickness of the vapor-deposited layers of the nine samples was taken as the thickness of the vapor-deposited aluminum layer. The results are shown in Tables 1 and 2.
• the water vapor permeability was measured using the MOCON method according to JIS K 7129-2, at a temperature of 40°C and a relative humidity of 90% RH. The measurement was performed twice for each of the nine measurement samples, yielding a total of 18 pieces of measurement data. The mean value of the 18 pieces of data was used as the water vapor permeability. The standard deviation of the 18 pieces of data was also calculated. The results (unit of water vapor permeability: g/(m 2 ⁇ day)) are shown in Tables 1 and 2.
• Fig. 3(a) shows a graph showing the distribution of water vapor permeability data for the gas barrier laminates of Examples 1 and 2 and Comparative Examples 1, 2 and 7, where the horizontal axis represents the film thickness of the vapor-deposited aluminum layer and vertical axis represents the water vapor permeability (unit: g/(m 2 ⁇ day)).
• Figs. 3(b) and 3(c) show graphs showing the distribution of water vapor permeability data for the gas barrier laminates of Examples 3 to 5 and Comparative Examples 3 and 4, and Examples 6 to 8 and Comparative Examples 5 and 6, respectively.
• the gas barrier laminates of Comparative Examples 1, 2 and 7 and Examples 1 and 2 were observed for defects. Specifically, an image (observation magnification: 5 ⁇ objective lens) of each laminate was captured from the lamination direction using a transmitted-light source of an optical microscope.
• Fig. 4(a) is an observed image of the gas barrier laminate of Comparative Example 2.
• Fig. 4(b) is an observed image of the gas barrier laminate of Comparative Example 1.
• Fig. 4(c) is an observed image of the gas barrier laminate of Example 1.
• Fig. 4(d) is an observed image of the gas barrier laminate of Example 2.
• Fig. 4(e) is an observed image of the gas barrier laminate of Comparative Example 7.
• a gas barrier laminate A was obtained in the same manner as in Example 3, except that the clay-coated paper 3 was used as the paper base and the thickness of the vapor-deposited aluminum layer was 36 nm.
• a gas barrier laminate B was obtained in the same manner as in Example 3, except that the clay-coated paper 3 was used as the paper base and the thickness of the vapor-deposited aluminum layer was 52 nm.
• a gas barrier laminate C was obtained in the same manner as in Example 3, except that the clay-coated paper 3 was used as the paper base and the thickness of the vapor-deposited aluminum layer was 62 nm. The gas barrier laminates A to C were observed for defects.
• Fig. 5(a) is an observed image of the gas barrier laminate A.
• Fig. 5(b) is an observed image of the gas barrier laminate B.
• Fig. 5(c) is an observed image of the gas barrier laminate C. It can be seen that, compared to the gas barrier laminates A and B, in which the thickness of the vapor-deposited aluminum layer is less than 60 nm, the gas barrier laminate C, in which the thickness of the vapor-deposited aluminum layer is 60 nm or more, had fewer light-transmitting defects, suggesting that significantly fewer defects reached the vapor-deposited aluminum layer.
• three-sided pouches (height: 10 cm, width: 7.7 cm) were produced using a bag manufacturing machine manufactured by Taisei Lamick.
• the suitability for bag manufacturing was evaluated at bag manufacturing rates of 40 to 100 bags/min, and the maximum bag manufacturing rate at which breakage of the laminate or problems in transporting did not occur was measured. The maximum value was evaluated according to the following criteria. The results are shown in Tables 1 and 2.
• Comparative Examples 1 to 6 in which the thickness of the vapor-deposited aluminum layer was less than 60 nm, had a large average water vapor permeability and a large standard deviation, indicating that their water vapor barrier performance was unstable.
• Comparative Examples 7 and 8 in which the thickness of the vapor-deposited aluminum layer is 100 nm or more, vertical wrinkles occurred in the folded portions, and sealing and cutting defects also occurred, resulting in a lower upper limit of the bag manufacturing rate. Therefore, Comparative Examples 7 and 8 are undesirable in terms of productivity. On the other hand, in Examples 1 to 8, in which the thickness of the vapor-deposited aluminum layer was less than 100 nm, the occurrence of vertical wrinkles and defective sealing and cutting was suppressed, and the upper limit of the bag manufacturing rate increased. Therefore, Examples 1 to 8 provide good productivity.

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