Gas barrier laminate and packaging bag

Abstract

To provide a gas barrier laminate that prevents water vapor barrier capability from decreasing even when bent.SOLUTION: A gas barrier laminate 10 comprises a paper substrate 1, a first resin layer 2, a vapor deposition layer 3 and a second resin layer 4 in the stated order. In the paper substrate 1, a rate of a change in CD dimensions at 40°C and 90% RH, compared with the CD dimensions at 40°C and 20% RH, is 1.0% or less. A surface of the paper substrate 1, facing the vapor deposition layer 3 with the first resin layer 2 interposed between them, has specular gloss at 85 degrees of 50 or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gas barrier laminate and a packaging bag. [Background technology]

[0002] In many fields, such as food, beverages, pharmaceuticals, and chemicals, packaging materials suitable for the contents are used to package the items as the contents. In these applications, the packaging materials are required to have gas barrier properties that prevent the transmission of oxygen, water vapor, and the like, which cause deterioration of the contents.

[0003] In recent years, the momentum to move away from plastic has been building due to growing environmental awareness sparked by the problem of marine plastic waste, etc. In the field of packaging materials, too, there is a growing demand to replace plastic packaging materials with paper-based packaging materials.

[0004] Paper has a crease retention property, also called dead-hold property. Therefore, a packaging material mainly made of paper has a feature that it can be easily processed into a package such as a packaging bag. In addition, the above-mentioned gas barrier property can be imparted to a packaging material mainly made of paper by providing a barrier layer such as a water vapor barrier layer and a gas barrier layer (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-69783 A Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors have found that when a packaging material having a barrier layer provided on a paper base material is used for packaging bags having creases, particularly packaging bags that include portions folded at acute angles such as pillow bags, three-sided sealed bags and gusset bags, cracks occur in the barrier layer at the creases, reducing the water vapor barrier properties.

[0007] Therefore, an object of the present invention is to provide a gas barrier laminate that is less likely to experience a decrease in water vapor barrier properties even when folded. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a gas barrier laminate comprising a paper base material, a first resin layer, a vapor deposition layer, and a second resin layer in this order, wherein the paper base material has a CD dimension change rate of 1.0% or less at a temperature of 40°C and a relative humidity of 90% RH compared to the CD dimension at a temperature of 40°C and a relative humidity of 20%, and the paper base material has an 85 degree specular gloss of 50 or more on a surface facing the vapor deposition layer with the first resin layer sandwiched therebetween.

[0009] According to another aspect of the present invention, there is provided the gas barrier laminate according to the above aspect, wherein the second resin layer contains a polyolefin having a polar group.

[0010] According to yet another aspect of the present invention, there is provided the gas barrier laminate according to any one of the above aspects, wherein the second resin layer has a thickness of 2 μm or more and 10 μm or less.

[0011] According to yet another aspect of the present invention, there is provided the gas barrier laminate according to any one of the above aspects, wherein the vapor deposition layer has a thickness of 30 nm or more and 100 nm or less.

[0012] According to yet another aspect of the present invention, there is provided a packaging bag including the gas barrier laminate according to any one of the above aspects. According to yet another aspect of the present invention, there is provided a packaging bag according to the above aspect having a fold. Effect of the Invention

[0013] According to the present invention, it is possible to provide a gas barrier laminate in which the water vapor barrier property is unlikely to deteriorate even when the gas barrier laminate is folded. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view of a gas barrier laminate according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view that illustrates an example of a packaging bag that can be produced from the gas barrier laminate of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are more specific embodiments of any of the above aspects. The following items can be incorporated into each of the above aspects alone or in combination.

[0016] The embodiments described below are merely examples of configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited by the materials, shapes, structures, etc. of the components described below. Various modifications can be made to the technical idea of ​​the present invention within the technical scope defined by the claims.

[0017] In addition, elements having the same or similar functions are given the same reference numerals in the drawings referred to below, and duplicated explanations are omitted. In addition, the drawings are schematic, and the relationship between dimensions in one direction and dimensions in another direction, the relationship between the dimensions of one member and the dimensions of another member, etc. may differ from the actual ones.

[0018] <1> Gas barrier laminate Fig. 1 is a cross-sectional view of a gas barrier laminate according to one embodiment of the present invention. The gas barrier laminate 10 shown in Fig. 1 includes a paper substrate 1, a first resin layer 2, a vapor deposition layer 3, and a second resin layer 4, in this order.

[0019] As will be described in detail later, the rate of change in the dimension in the CD direction at a temperature of 40°C and a relative humidity of 90% RH relative to the dimension in the CD direction at a temperature of 40°C and a relative humidity of 20% (hereinafter sometimes simply referred to as "dimensional change rate") is 1.0% or less. Furthermore, the surface of the paper substrate 1 facing the deposition layer 3 with the first resin layer 2 sandwiched therebetween has an 85 degree specular gloss of 50 or more. Such a gas barrier laminate 10 not only has high water vapor barrier properties initially, but can also maintain sufficient water vapor barrier properties even after being folded.

[0020] The present inventors speculate as follows as to why the gas barrier laminate 10 exhibits the above-mentioned effects.

[0021] When the 85 degree specular gloss of the surface of the paper base material 1 is low, there are large irregularities on this surface. The first resin layer 2 formed on such a surface has a large variation in thickness. If the first resin layer 2 includes a thin portion or does not cover a part of the surface of the paper base material 1, high barrier properties cannot be achieved.

[0022] Furthermore, if the 85 degree specular gloss of the surface of the paper base material 1 is low, the smoothness of the first resin layer 2 formed thereon is likely to be low. If the first resin layer 2 is not smooth, the deposition material cannot be deposited uniformly thereon, and micro defects may occur in the deposition layer 3.

[0023] If there are large irregularities on the surface of the paper base material 1 or if there are micro-defects in the vapor-deposited layer 3, these are likely to cause cracks in the vapor-deposited layer 3 when the gas barrier laminate 10 is folded.

[0024] In addition to the above-mentioned microdefects, the deposition layer 3 is believed to have a number of cracks or defects caused by transportation scratches, scratches caused by transfer-through when wound into a roll, etc., and the second resin layer 4 is believed to have a number of cracks or defects caused by volumetric shrinkage of the resin, etc.

[0025] When the dimensional change rate is large, cracks or defects tend to become larger with changes in relative humidity. In particular, cracks or defects in the second resin layer 4 tend to become larger when the layer is bent. When the cracks or defects become larger, the water vapor barrier property decreases.

[0026] In the gas barrier laminate 10, the surface of the paper base material 1 has a high 85-degree specular gloss and is therefore excellent in smoothness. Therefore, the thickness of the first resin layer 2 does not become non-uniform due to the presence of large irregularities on the surface of the paper base material 1, and the surface does not include any part not covered by the first resin layer 2.

[0027] In addition, since the 85 degree specular gloss of the surface of the paper substrate 1 is high, the first resin layer 2 formed thereon can have excellent smoothness. Therefore, the deposition layer 3 does not frequently have micro defects.

[0028] In the gas barrier laminate 10, the dimensional change rate of the paper base material 1 is small. The dimensional change rate of the gas barrier laminate 10 is mainly affected by the dimensional change rate of the paper base material 1. Therefore, in the gas barrier laminate 10, the expansion of cracks or defects due to changes in relative humidity is unlikely to occur.

[0029] Therefore, the gas barrier laminate 10 not only has high water vapor barrier properties at an early stage, but also maintains sufficient water vapor barrier properties even after being folded.

[0030] The thickness of the gas barrier laminate 10 may be 20 μm or more and 100 μm or less, 30 μm or more and 80 μm or less, or 40 μm or more and 60 μm or less. When the thickness of the gas barrier laminate 10 is within the above range, the gas barrier laminate 10 can obtain better water vapor barrier properties not only at the initial stage but also after being folded.

[0031] <1.1>Paper base material The paper base material 1 includes a paper layer 1A and a coating layer 1B. That is, the paper base material 1 here is a coated paper.

[0032] Here, the coating layer 1B is provided on the surface of the paper layer 1A facing the first resin layer 2, but it may be provided on the reverse side, or on both sides of the paper layer 1A. The coating layer 1B may be omitted.

[0033] The paper base material 1 can be paper whose main component is plant-derived pulp. Specific examples of this paper include fine paper, special fine paper, coated paper, art paper, cast-coated paper, imitation paper, kraft paper, and glassine paper. The basis weight of the paper base material 1 is 20 to 200 g / m 2 , or 30 to 100 g / m 2 It may be.

[0034] The coat layer 1B prevents the raw material of the first resin layer 2 from seeping into the paper layer when the first resin layer 2 is formed. The coat layer 1B can also play a role of filling the unevenness of the paper layer. This allows the first resin layer 2 to be formed uniformly without defects. For example, various copolymers such as styrene-butadiene, styrene-acrylic, and ethylene-vinyl acetate, polyvinyl alcohol resin, cellulose resin, paraffin (WAX), etc. can be used as the binder resin in the coat layer 1B. The coat layer 1B may contain clay, kaolin, calcium carbonate, talc, mica, etc. as a filler. The coat layer 1B may be a clay coat layer containing at least clay as a filler.

[0035] When the paper substrate 1 has a coating layer 1B, the thickness of the coating layer 1B may be 1.5 μm or more and 15 μm or less. The thickness of the coating layer 1B may be 1.8 μm or more, 3 μm or more, 5 μm or more, or 6 μm or more. The thickness of the coating layer 1B may be 12 μm or less, or 10 μm or less. When the thickness of the coating layer 1B is within the above range, the gas barrier laminate 10 can obtain better water vapor barrier properties not only at the initial stage but also after being folded.

[0036] The thickness of the paper substrate 1 may be 20 to 100 μm, 30 to 80 μm, or 40 to 60 μm. When the thickness of the paper substrate 1 is within the above range, the gas barrier laminate 10 can have better water vapor barrier properties not only initially but also after being folded.

[0037] The ratio of the thickness of the coating layer 1B to the thickness of the paper base material 1 may be 3 to 25%, or 5 to 20%. When this ratio is within the above range, the gas barrier laminate 10 can obtain better water vapor barrier properties not only initially but also after being folded.

[0038] The surface of the paper base material 1 facing the vapor deposition layer 3 with the first resin layer 2 sandwiched therebetween has an 85 degree specular gloss of 50 or more. This 85 degree specular gloss may be 55 or more, or may be 60 or more. Moreover, this 85 degree specular gloss is, for example, 90 or less.

[0039] Here, the 85-degree specular gloss is a value measured in accordance with JIS Z8741:1997. The 85-degree specular gloss is the arithmetic average of values ​​obtained by measuring at any five points such that a plane including the illumination direction and the light receiving direction is perpendicular to the surface of the paper base material 1 and parallel to the MD direction of the paper base material 1. Note that the value of the 85-degree specular gloss is sometimes indicated with the mark "%", but the mark "%" is omitted here.

[0040] The dimensional change rate of the paper base material 1 is 1.0% or less. The dimensional change rate of the paper base material 1 may be 0.8% or less, 0.7% or less, or 0.6% or less. The dimensional change rate of the paper base material 1 may be 0% or more, or 0.1% or more. The dimensional change rate of the paper base material 1 may be affected by the thickness of the coating layer 1B, the content of the filler in the coating layer 1B, the basis weight of the paper, and the like.

[0041] The dimensional change rate of the gas barrier laminate 10 is significantly affected by the dimensional change rate of the paper base material 1. Therefore, by reducing the dimensional change rate of the paper base material 1, the dimensional change rate of the gas barrier laminate 10 can be reduced.

[0042] The dimensional change rate is a value measured by the following method. First, the paper base material 1 is cut to a predetermined size to obtain a sample for measurement. This sample is left in a thermohygrostat chamber at a temperature of 40° C. and a relative humidity of 20% for three days. After that, the length L of the sample in the CD direction is measured in the thermohygrostat chamber. 20% Next, the sample is left in a thermohygrostat with a temperature of 40°C and a relative humidity of 90% for three days. After that, the length L of the sample in the CD direction is measured in the thermohygrostat. 90% Then, measure the length L 20% and L 90% The following formula (1): Dimensional change rate (%) = (L 90% -L 20% ) / L 20% ×100 …(1) Substitute this into the right side of the equation to calculate the dimensional change rate (%).

[0043] The proportion of the paper base material 1 in the gas barrier laminate 10 is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. From the viewpoint of reducing the amount of plastic used, it is preferable that this proportion is large. Furthermore, if this proportion is 50% by mass or more, in Japan, the gas barrier laminate 10 can be treated as paper under the Container and Packaging Recycling Law. The proportion of the paper base material 1 in the gas barrier laminate 10 may be 90% by mass or less, or may be 80% by mass or less.

[0044] <1.2>First resin layer The first resin layer 2 is provided on the surface of the paper base material 1 to improve adhesion between the paper base material 1 and a deposition layer 3 described below and to improve the gas barrier properties of the gas barrier laminate. The first resin layer 2 is also called an anchor coat layer.

[0045] The first resin layer 2 may contain a polyolefin having a polar group. By containing a polyolefin having a polar group, the first resin layer 2 has excellent flexibility, and cracking of the deposition layer described below after bending (folding) can be suppressed, and the adhesion between the first resin layer 2 and the deposition layer 3 can be improved. Furthermore, by containing a polyolefin having a polar group, a dense film can be formed due to the crystallinity of the polyolefin, and water vapor barrier properties are expressed. The water vapor barrier properties are expressed due to the crystallinity of the polyolefin, and the presence of a polar group results in adhesion with the deposition layer 3.

[0046] The polyolefin having a polar group may have at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic ester.

[0047] As the polyolefin having a polar group, a copolymer of ethylene or propylene with an unsaturated carboxylic acid (an unsaturated compound having a carboxyl group, such as acrylic acid, methacrylic acid, or maleic anhydride), an unsaturated carboxylic acid ester, or a salt obtained by neutralizing a carboxylic acid with a basic compound may be used. In addition, a copolymer of vinyl acetate, an epoxy compound, a chlorine compound, a urethane compound, a polyamide compound, or the like may also be used.

[0048] Specific examples of polyolefins having a polar group include copolymers of acrylic acid ester and maleic anhydride, ethylene-vinyl acetate copolymers, and ethylene-glycidyl methacrylate copolymers.

[0049] The first resin layer 2 may contain other components in addition to the polyolefin having a polar group, such as polyolefins other than the polyolefin having a polar group, silane coupling agents, organic titanates, polyacrylics, polyesters, polyurethanes, polycarbonates, polyureas, polyamides, polyimides, melamines, and phenols.

[0050] The content of the polyolefin having a polar group in the first 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.

[0051] The thickness of the first resin layer 2 may be, for example, 0.5 μm or more, 1 μm or more, 2 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the first resin layer 2 is 0.5 μm or more, the unevenness of the paper base material 1 described above can be efficiently filled, and the deposition layer 3 described below can be laminated uniformly. Also, if the thickness of the first resin layer 2 is 20 μm or less, the deposition layer 3 can be laminated uniformly while suppressing costs.

[0052] Examples of the solvent contained in the coating liquid for forming the first resin layer 2 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of characteristics, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

[0053] The first resin layer 2 can be provided by applying a coating liquid containing the above-mentioned polyolefin having a polar group and a solvent, etc., onto the paper substrate 1, and drying the coating film. The particle size of the polyolefin emulsion having a polar group in the coating liquid is not particularly limited, but may specifically be 1 nm or more, 0.1 μm or more, 1 μm or less, 0.7 μm or less, or 0.5 μm or less.

[0054] <1.3> Vapor deposited layer The vapor-deposited layer 3 is a layer formed by vapor-depositing a metal or an inorganic compound. The vapor-deposited layer 3 may be a layer obtained by vapor-depositing aluminum, or may be a layer obtained by vapor-depositing aluminum oxide (AlO x ), silicon oxide (SiO x ) etc.

[0055] The thickness of the deposition layer 3 may be appropriately set depending on the application of the gas barrier laminate 10, but is preferably 10 to 300 nm, and more preferably 30 to 100 nm. By setting the thickness of the deposition layer 3 to 10 nm or more, it is easy to ensure sufficient continuity of the deposition layer 3, and by setting the thickness to 300 nm or less, it is possible to sufficiently suppress the occurrence of curling and cracking, and it is easy to achieve sufficient gas barrier performance and flexibility. Furthermore, by setting the thickness of the deposition layer 3 to 30 nm or more and 100 nm or less, the deposition layer 3 becomes less likely to crack, and sufficient water vapor barrier properties can be obtained even after bending.

[0056] The deposition layer 3 is preferably formed by a vacuum deposition means from the viewpoint of water vapor and oxygen gas barrier performance and film uniformity. There are known deposition means such as vacuum deposition, sputtering, and chemical vapor deposition (CVD), but vacuum deposition is preferred because of its high deposition rate and high productivity. Among the vacuum deposition methods, deposition means using electron beam heating is particularly effective because the deposition rate can be easily controlled by the irradiation area and electron beam current, and the temperature of the deposition material can be raised and lowered in a short time.

[0057] <1.4>Second resin layer The second resin layer 4 is provided on the surface of the vapor-deposited layer 3 so as to be in contact with the vapor-deposited layer 3. The second resin layer 4 is also called an overcoat layer. The second resin layer 4 may contain a polyolefin having a polar group.

[0058] The polyolefin having a polar group may have at least one selected from a carboxyl group, a salt of a carboxyl group, a carboxylic anhydride group, and a carboxylic ester.

[0059] As polyolefins having polar groups, those obtained by copolymerizing ethylene or propylene with unsaturated carboxylic acids (unsaturated compounds having carboxyl groups such as acrylic acid and methacrylic acid) or unsaturated carboxylic acid esters, or salts obtained by neutralizing carboxylic acids with basic compounds, etc. Alternatively, copolymers with vinyl acetate, epoxy compounds, chlorine compounds, urethane compounds, polyamide compounds, etc. may be used.

[0060] Specific examples of polyolefins having a polar group include copolymers of acrylic acid ester and maleic anhydride, ethylene-vinyl acetate copolymers, and ethylene-glycidyl methacrylate copolymers.

[0061] By including a polyolefin having a polar group, the second resin layer 4 has excellent flexibility, can suppress cracking of the deposition layer after bending (folding), and has excellent adhesion to the deposition layer 3. Furthermore, by including the polyolefin having the above-mentioned polar group, a dense film can be formed due to the crystallinity of the polyolefin, and water vapor barrier properties are exhibited. Furthermore, by including the polar group, the second resin layer 4 can also function as a heat seal layer, so there is no need to provide a separate heat seal layer.

[0062] The second resin layer 4 may contain other components in addition to the polyolefin having a polar group, such as a silane coupling agent, an organic titanate, polyacrylic, polyester, polyurethane, polycarbonate, polyurea, polyamide, a polyolefin emulsion, polyimide, melamine, and phenol.

[0063] The content of the polyolefin having a polar group in the second resin layer 4 may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0064] The thickness of the second resin layer 4 may be, for example, 0.05 μm or more, 0.5 μm or more, 1 μm or more, 2 μm or more, 20 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the second resin layer 4 is 0.05 μm or more, the layer can fully fulfill the role of the heat seal layer described above. If the thickness of the second resin layer 4 is 20 μm or less, the layer can fully exert adhesion and barrier properties with the deposition layer while suppressing costs. If the thickness of the second resin layer 4 is 2 μm or more and 10 μm or less, the deposition layer is less likely to crack, and sufficient water vapor barrier properties can be obtained even after bending.

[0065] In the gas barrier laminate 10, when the second resin layer 4 contains a polyolefin having a polar group, the thickness of the second resin layer 4 is 2 μm or more and 10 μm or less, and the thickness of the vapor deposition layer 3 is 30 nm or more and 100 nm or less, the vapor deposition layer 3 is less likely to crack, and the effect of obtaining sufficient water vapor barrier properties even after bending is particularly remarkable.

[0066] Examples of the solvent contained in the coating liquid for forming the second resin layer 4 include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. Among these, from the viewpoint of characteristics, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene, ethyl acetate, methyl ethyl ketone, and water are preferred. Furthermore, from the viewpoint of the environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, and water are preferred.

[0067] The second resin layer 4 can be provided by applying a coating liquid containing the above-mentioned polyolefin having a polar group and a solvent on the deposition layer 3 and drying the coating. The melting point of the polyolefin having a polar group in the coating liquid is preferably 70 to 160°C, more preferably 80 to 120°C. If the melting point of the polyolefin having a polar group is low, there is an advantage that the start-up temperature during heat sealing can be lowered. If the melting point of the polyolefin having a polar group is high, there is an increased risk of blocking in a high-temperature environment, so an anti-blocking agent may be added. The particle size of the polyolefin emulsion is not particularly limited, but the particle size may be specifically 1 nm or more, 0.1 μm or more, 1 μm or less, 0.7 μm or less, or 0.5 μm or less.

[0068] The polyolefins having a polar group contained in the first resin layer 2 and the second resin layer 4 may be the same or different.

[0069] <2> packaging bag FIG. 2 is a perspective view that illustrates an example of a packaging bag that can be produced from the gas barrier laminate of FIG.

[0070] The packaging bag 20 shown in Fig. 2 is a gusset bag. The packaging bag 20 includes the gas barrier laminate 10 described with reference to Fig. 1. The gas barrier laminate 10 is made into the packaging bag 20 so that the second resin layer 4 faces inward and the paper base material 1 faces outward. The packaging bag 20 can be made into a packaged article by putting contents therein and optionally sealing the opening at the top.

[0071] The packaging bag 20 has creases. That is, the packaging bag 20 has places where the gas barrier laminate 10 is folded, here, folding parts B1 and B2. The folding part B1 is a place where the gas barrier laminate 10 is folded in a valley direction when viewed from the inside of the packaging bag 20. On the other hand, the folding part B2 is a place where the gas barrier laminate 10 is folded in a mountain direction when viewed from the inside of the packaging bag 20.

[0072] The packaging bag 20 may be formed by folding one gas barrier laminate 10 in half so that the second resin layers 4 face each other, then appropriately folding the gas barrier laminate into a desired shape, and then heat sealing the gas barrier laminate into a bag shape. Alternatively, the packaging bag 20 may be formed by stacking two gas barrier laminates so that the second resin layers 4 face each other, and then heat sealing the gas barrier laminate into a bag shape.

[0073] The heat seal strength of the packaging bag 20 may be 2 N or more, or may be 4 N or more. The upper limit of the heat seal strength is not particularly limited, but may be, for example, 10 N or less.

[0074] The packaging bag 20 can contain contents such as food, medicine, etc. It is particularly suitable for containing food such as sweets.

[0075] The packaging bag 20 can maintain high water vapor barrier properties even though it has the folded parts B1 and B2.

[0076] In this embodiment, a gusset bag is given as an example of a packaging bag, but the gas barrier laminate according to this embodiment may be used to produce, for example, a pillow bag, a three-side sealed bag, or a standing pouch.

[0077] The gas barrier laminate according to the present embodiment may be used to manufacture a packaging bag without creases, such as a four-sided sealed bag. Even in such a packaging bag, creases may occur, for example, during transportation of a packaged article containing contents therein. Even in such a case, the gas barrier laminate can maintain high water vapor barrier properties. EXAMPLES

[0078] Tests carried out in relation to the present invention are described below.

[0079] <Preparation of gas barrier laminate> (Example 1) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 A water dispersion of polyolefin containing a salt of a carboxyl group (solid content concentration: 20% by mass) was applied to one side of the paper substrate using a bar coater at a wet coating amount of 15 g / m 2 This was then dried in an oven to form a first resin layer.

[0080] Next, a vapor-deposited layer made of aluminum was formed on the first resin layer by vacuum deposition. The vapor-deposited layer had a thickness of 50 nm. Thereafter, an aqueous dispersion of polyolefin containing a salt of a carboxyl group was applied onto the deposition layer using a bar coater, and the applied dispersion was dried in an oven to form a second resin layer. The thickness of the second resin layer was 3 μm. In this manner, a gas barrier laminate was obtained.

[0081] (Example 2) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Ryuo Coat (55g / m2) manufactured by Daio Paper Corporation, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0082] (Example 3) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of this, we used coated wrapping paper (grammage 50g / m2) manufactured by Xianhe Co., Ltd. 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0083] (Example 4) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of this, we used coated wrapping paper (60g / m2) manufactured by Xianhe Co., Ltd. 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0084] (Example 5) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Algro Vitess (60g / m2) manufactured by Sappi, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0085] (Example 6) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of this, we used coated wrapping paper (60g / m2) manufactured by Xianhe Co., Ltd. 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that a vapor-deposited layer of silica was formed instead of the vapor-deposited layer of aluminum.

[0086] (Example 7) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of this, we used coated wrapping paper (60g / m2) manufactured by Xianhe Co., Ltd. 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that a vapor-deposited layer of alumina was formed instead of a vapor-deposited layer of aluminum.

[0087] (Example 8) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of this, we used coated wrapping paper (60g / m2) manufactured by Xianhe Co., Ltd. 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that a first resin layer was formed by the following method. That is, in this example, a water solution of a polyvinyl alcohol resin having a polymerization degree of 500 (solid content concentration: 10% by mass) was applied to one surface of the paper substrate using a bar coater in a wet coating amount of 30 g / m2. 2 This was then dried in an oven to form a first resin layer.

[0088] (Example 9) The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Ryuo Coat (55g / m2) manufactured by Daio Paper Corporation, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that a first resin layer was formed by the following method. That is, in this example, a water solution of a polyvinyl alcohol resin having a polymerization degree of 500 (solid content concentration: 10% by mass) was applied to one surface of the paper substrate using a bar coater in a wet coating amount of 30 g / m2. 2 This was then dried in an oven to form a first resin layer.

[0089] Comparative Example 1 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Glassine N (basis weight 30.5 g / m) manufactured by Nippon Paper Industries Co., Ltd. 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0090] Comparative Example 2 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Enza HS Rapping Paper (60g / m2) manufactured by APP, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0091] Comparative Example 3 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Solide Lucent (40g / m2) manufactured by UPM, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0092] Comparative Example 4 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Solid Strong (60g / m2) manufactured by UPM, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0093] Comparative Example 5 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Brilliant Express (40g / m2) manufactured by UPM, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0094] Comparative Example 6 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Brilliant Duo (62g / m2) manufactured by UPM, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that 2-methyl-2-propanediol was used.

[0095] Comparative Example 7 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Solide Lucent (40g / m2) manufactured by UPM, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that a first resin layer was formed by the following method. That is, in this example, a water solution of a polyvinyl alcohol resin having a polymerization degree of 500 (solid content concentration: 10% by mass) was applied to one surface of the paper substrate using a bar coater in a wet coating amount of 30 g / m2. 2 This was then dried in an oven to form a first resin layer.

[0096] Comparative Example 8 The paper base material was Fuji Kako Co., Ltd.'s Tokukomo S (grammage 52.3 g / m 2 Instead of Flex Pack (60g / m2) manufactured by UPM, 2 A gas barrier laminate was obtained in the same manner as in Example 1, except that a first resin layer was formed by the following method. That is, in this example, a water solution of a polyvinyl alcohol resin having a polymerization degree of 500 (solid content concentration: 10% by mass) was applied to one surface of the paper substrate using a bar coater in a wet coating amount of 30 g / m2. 2This was then dried in an oven to form a first resin layer.

[0097] <Evaluation> (Measurement of dimensional change rate) From each of the paper substrates used in the production of the gas barrier laminates according to Examples 1 to 9 and Comparative Examples 1 to 8, a measurement sample in the form of a strip having a length of 150 mm in the CD direction and a width of 20 mm was cut out.

[0098] Each sample was left in a thermohygrostat set at a temperature of 40° C. and a relative humidity of 20% for 3 days. After that, the length L of the sample in the CD direction was measured using a glass scale in the thermohygrostat. 20% was measured.

[0099] Next, the sample was left in a thermohygrostat set at a temperature of 40° C. and a relative humidity of 90% for 3 days. After that, the length L of the sample in the CD direction was measured using a glass scale in the thermohygrostat. 90% was measured.

[0100] And the length L 20% and L 90% to the following formula (1): Dimensional change rate (%) = (L 90% -L 20% ) / L 20% ×100 …(1) The dimensional change rate (%) was calculated by substituting the right side of the formula: The results are shown in Tables 1 to 3.

[0101] (Measurement of 85 degree specular gloss) For each of the paper substrates used in the manufacture of the gas barrier laminates according to Examples 1 to 9 and Comparative Examples 1 to 8, the 85-degree specular gloss of the surface on which the first resin layer was to be formed was measured. For this measurement, a RHOPOINT IQ appearance measuring device manufactured by Rhopoint was used. For each paper substrate, the measurement using the appearance measuring device was performed at any five points such that a plane including the illumination direction and the light receiving direction was perpendicular to the surface of the paper substrate and parallel to the MD direction of the paper substrate 1, and the arithmetic average of the values ​​thus obtained was taken as the 85-degree specular gloss.

[0102] (Measurement of water vapor permeability) The initial water vapor permeability was measured by the MOCON method for each of the gas barrier laminates according to Examples 1 to 9 and Comparative Examples 1 to 8. The measurements were carried out under conditions of a temperature of 40° C. and a relative humidity of 90%.

[0103] Next, each gas barrier laminate was folded in half, and a 1500g roller was rolled on it at a speed of 300mm / min to form creases parallel to the MD direction. The water vapor permeability of the gas barrier laminate after opening was also measured in the same manner as above. The results are shown in Tables 1 to 3.

[0104] In Tables 1 to 3, "inner fold" refers to the gas barrier laminate after it has been folded in a mountain direction when viewed from the paper substrate side, and "outer fold" refers to the gas barrier laminate after it has been folded in a valley direction when viewed from the paper substrate side.

[0105] [Table 1]

[0106] [Table 2]

[0107] [Table 3]

[0108] As shown in Tables 1 to 3, the gas barrier laminates according to Examples 1 to 9 had a water vapor permeability of 10 g / m2 or more not only in the initial state but also after bending. 2 · The condition was good for the following days.

[0109] As is apparent from these results, the gas barrier laminate of the present invention can suppress deterioration of the contents for a long period of time, even when a packaging bag having a shape with folded portions is formed. [Explanation of symbols]

[0110] Reference Signs List 1: paper base material, 1A: paper layer, 1B: coating layer, 2: first resin layer, 3: vapor deposition layer, 4: second resin layer, 10: gas barrier laminate, 20: packaging bag, B1: folded portion, B2: folded portion.

Claims

1. A gas barrier laminate comprising a paper substrate, a first resin layer, a vapor deposition layer, and a second resin layer in this order, The paper substrate has a CD dimension change rate of 1.0% or less at a temperature of 40°C and a relative humidity of 90% RH compared to a CD dimension at a temperature of 40°C and a relative humidity of 20%; The gas barrier laminate has a surface of the paper substrate facing the vapor deposition layer with the first resin layer sandwiched therebetween that has an 85° specular gloss of 50 or more.

2. The gas barrier laminate according to claim 1 , wherein the second resin layer contains a polyolefin having a polar group.

3. The gas barrier laminate according to claim 1 , wherein the second resin layer has a thickness of 2 μm or more and 10 μm or less.

4. The gas barrier laminate according to claim 1, wherein the thickness of the vapor-deposited layer is 30 nm or more and 100 nm or less.

5. A packaging bag comprising the gas barrier laminate according to any one of claims 1 to 4.

6. A process for preparing a paper substrate having a surface with an 85-degree specular gloss of 50 or more; a step of applying a first coating liquid containing a polyolefin having a polar group and a solvent onto the surface of the paper substrate and drying the formed coating film to form a first resin layer; a step of depositing a metal or an inorganic compound on the first resin layer by vacuum deposition means to form a deposition layer; a step of applying a second coating liquid containing a polyolefin having a polar group and a solvent onto the vapor-deposited layer and drying the formed coating film to form a second resin layer; A method for producing a gas barrier laminate comprising the steps of:

7. A method for manufacturing a gas barrier laminate as described in Claim 6, wherein the first resin layer is formed to have a thickness of 0.5 μm or more and 5 μm or less.

8. A method for manufacturing a gas barrier laminate as described in claim 6, wherein the second resin layer is formed to have a thickness of 2 μm or more and 10 μm or less.

9. A method for manufacturing a gas barrier laminate as described in Claim 6, wherein the second coating liquid contains the polyolefin as an emulsion, and the particle size of the emulsion is 0.1 μm or more and 1 μm or less.

10. A method for manufacturing a gas barrier laminate as described in Claim 6, wherein the process of preparing the paper substrate includes obtaining the 85-degree specular gloss by taking the arithmetic average of values ​​obtained by measuring at any five locations in accordance with JIS Z8741:1997, so that a plane containing the illumination direction and the light-receiving direction is perpendicular to the surface of the paper substrate and parallel to the MD direction of the paper substrate.

11. A method for manufacturing a gas barrier laminate as described in Claim 6, wherein the process of preparing the paper substrate includes selecting, from the paper substrates that have obtained the 85-degree specular gloss, one that has an 85-degree specular gloss of 50 or more.

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