Laminate

Abstract

The present invention aims to provide a laminate that reduces the amount of residual solvent in the paper substrate by reducing the amount of adhesive composition, while possessing excellent oxygen barrier properties and flexibility, and maintaining excellent oxygen barrier properties even after the Gelboflex test. [Solution] A laminate comprising a paper substrate layer, an adhesive layer formed from an adhesive composition laminated on at least one surface of the paper substrate layer, and a metal vapor deposition layer laminated on the surface of the adhesive layer opposite to the surface adjacent to the paper substrate layer, wherein the surface roughness of the paper substrate layer is 2 μm or less, and the oxygen permeability of the laminate is 3 cc / m 2 A stacked material with a value of less than / day.

Description

[Technical Field]

[0001] This invention relates to laminates and laminates used in packaging applications.

[0002] In the field of packaging technology, packaging materials with excellent gas barrier properties are attracting attention as a way to suppress the deterioration of the quality of various contents such as food, industrial products, pharmaceuticals, and cosmetics. Plastics, in particular, are used as the main component of packaging materials because they have excellent functions as packaging materials, including not only gas barrier properties but also adhesion and sealability. However, in recent years, there has been growing concern about the environmental pollution caused by plastic materials, and in order to reduce the environmental burden, technologies that replace the functions conventionally performed by plastics with materials mainly composed of paper are attracting attention, and gas barrier laminates containing paper substrates are being investigated.

[0003] For example, Patent Document 1 discloses an oxygen-absorbing coated laminate comprising at least a base layer, an oxygen barrier layer, and an oxygen-absorbing coating layer, wherein the oxygen barrier layer comprises one or more selected from the group consisting of metal foil, a resin film with an inorganic vapor deposition layer, a resin coating film or resin film made of an oxygen barrier resin, and barrier paper, and the barrier paper has a layer structure comprising at least a base paper and an oxygen barrier resin layer, and the oxygen barrier resin layer is laminated so as to be located on the oxygen-absorbing coating layer side, and the oxygen-absorbing coating layer is a layer formed from a specific oxygen-absorbing coating agent composition, and a technology is disclosed that achieves excellent barrier properties against oxygen gas and water vapor, as well as various properties such as low odor and fragrance retention. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-14245 [Overview of the project] [Problems that the invention aims to solve]

[0005] Compared to plastic materials, paper substrates tend to absorb large amounts of solvents, and these solvents are more likely to remain in the paper substrate. Such residual solvents can cause changes and deterioration of the contents, and in the case of food products in particular, they can impair flavor and quality, posing a major food hygiene issue. To reduce the residual solvent in the paper substrate, one might consider reducing the amount of solvent in the composition directly applied to the paper substrate (e.g., adhesive composition). However, reducing the thickness of the composition may impair the various physical properties (e.g., tackiness, oxygen barrier properties, and flexural resistance) achieved by the application of the composition. Therefore, the present invention aims to provide a laminate that reduces the amount of residual solvent in the paper substrate by reducing the amount of adhesive composition, while possessing excellent oxygen barrier properties and flexural resistance, and maintaining excellent oxygen barrier properties even after the Gelboflex test. [Means for solving the problem]

[0006] The present inventors have found that by using a laminate comprising a paper substrate layer having a specific range of surface roughness, an adhesive layer, and a metal vapor deposition layer, and using a laminate having a specific range of oxygen permeability, the amount of residual solvent in the paper substrate can be reduced by decreasing the amount of adhesive composition, while maintaining excellent oxygen barrier properties and flexibility, and excellent oxygen barrier properties can be maintained even after the Gelboflex test, thus completing the present invention.

[0007] In other words, the present invention is A paper substrate layer, An adhesive layer formed from an adhesive composition is laminated on at least one surface of the paper substrate layer, A metal vapor deposition layer is laminated on the surface opposite to the side adjacent to the paper substrate layer, among the two surfaces of the adhesive layer, A laminate having, The surface roughness of the paper substrate layer is 2 μm or less. The oxygen permeability of the aforementioned laminate is 3 cc / m³ 2 less than or equal to / day This provides a laminate. The present invention also provides the laminate, wherein the void ratio of the paper base material layer is 30% or less. The present invention also provides the laminate, wherein the water vapor transmission rate (MVTR) is 3 g / m 2 / day or less. The present invention also provides the laminate, wherein the average thickness of the adhesive layer is 1 μm or more and 3 μm or less. The present invention also provides the laminate, wherein the adhesive composition contains an adhesive and a solvent. The present invention also provides the laminate, wherein the adhesive is an ester-based adhesive or an ether-based adhesive. The present invention also provides the laminate, wherein the solvent is ethyl acetate. Furthermore, the present invention provides the laminate, wherein the laminate is used for packaging applications. Furthermore, the present invention provides the laminate, wherein the packaging is used for food packaging.

Advantages of the Invention

[0008] According to the present invention, by laminating a paper base material layer, an adhesive layer, and a metal vapor deposition layer having a specific range of surface roughness and setting it within a specific range of oxygen permeability, it is possible to reduce the amount of residual solvent in the paper base material, and to provide a laminate having excellent oxygen barrier properties and flex resistance, and capable of maintaining excellent oxygen barrier properties even after a gel flex test. The effects of the present invention are not necessarily limited to the effects described herein, and may be any of the effects described in this specification.

Brief Description of the Drawings

[0009] [Figure 1] It is a diagram showing an example of the structure of the laminate according to an embodiment of the present invention. [Figure 2] It is an enlarged image showing an observation image for void ratio calculation in Example 1. [Figure 3]This is an enlarged image showing the observation image used for calculating the void ratio in Comparative Example 1. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the present invention will be described in detail below. However, this technology is not limited to the embodiments described below. In this specification, "X~Y" indicating a range includes the preceding and succeeding numerical values ​​X and Y, and means "X or greater and Y or less". Furthermore, the upper limit (less than or equal to) and lower limit (greater than or equal to) of each numerical range (~) can be arbitrarily combined as desired.

[0011] 1. Laminate A laminate according to an embodiment of the present invention includes a paper substrate layer, an adhesive layer formed from an adhesive composition laminated on at least one surface of the paper substrate layer, and a metal vapor deposition layer laminated on the surface of the adhesive layer opposite to the surface adjacent to the paper substrate layer. An example of the structure of a laminate according to an embodiment of the present invention is shown in Figure 1. As shown in Figure 1, the laminate 10 of the present invention includes a paper substrate layer 11, an adhesive layer 12, and a metal vapor deposition layer 13, the surface roughness of the paper substrate layer 11 is 2 μm or less, and the oxygen permeability of the laminate 10 is 3 cc / m 2 It is less than or equal to / day.

[0012] The laminate according to the present invention, by providing a paper substrate layer having a specific range of surface roughness, an adhesive layer, and a metal vapor deposition layer, reduces the amount of residual solvent in the paper substrate while having excellent oxygen barrier properties and flexibility, and can maintain excellent oxygen barrier properties even after the Gelboflex test.

[0013] The following describes in more detail each layer of the laminate according to the embodiment of the present invention.

[0014] (1) Paper base layer The paper substrate layer in this technology is composed of a paper substrate and has a surface roughness of 2 μm or less. By including the paper substrate layer in place of at least a portion of the conventionally used plastic, the amount of plastic used is reduced while at least some of the functions of the plastic are performed. The paper used in this technology refers to paper manufactured by bonding plant fibers or other fibers. The paper used in this technology is not particularly limited, and any type of paper can be used, as long as it does not impair the function or effect of this technology. Examples of such paper include fine paper, medium-quality paper, recycled paper, kraft paper, glassine paper, semi-glassine paper, parchment paper, rayon paper, gravure paper, art paper, coated paper, and synthetic paper. These paper substrates may be single-layer paper substrates using each type individually, or, if necessary, multi-layer paper substrates formed by laminating these paper substrates. Among these, from the viewpoint of the roughness of the paper substrate layer, paper such as glassine paper, semi-glassine paper, parchment paper, rayon paper, gravure paper, art paper, and coated paper, in which at least the surface of the paper substrate layer to which the adhesive layer is applied has been processed, is preferred. By using paper with such surface treatment, even when the amount of adhesive is reduced, the paper substrate layer and the metal vapor deposition layer adhere sufficiently, reducing the amount of residual solvent in the paper substrate layer, while maintaining excellent oxygen barrier properties and flexibility, and excellent oxygen barrier properties even after the Gelboflex test. The details of why such effects are obtained by having such a paper substrate layer are not clear, but it is presumed that by using a paper substrate layer with low surface roughness and excellent smoothness, when the adhesive composition is applied to the surface, the adhesive composition is evenly applied, so that the paper substrate layer and the metal vapor deposition layer can adhere sufficiently even with a small amount of adhesive composition, and the amount of residual solvent in the paper substrate layer can be reduced. Furthermore, it is presumed that an adhesive composition applied to a paper substrate with low surface roughness forms an adhesive layer with a uniform thickness and few irregularities, thus providing stable oxygen barrier properties and flexibility of the adhesive layer.

[0015] In this technology, a lower amount of residual solvent in the paper substrate layer is preferable; for example, 30 mg / m² 2It is preferably the following, 20 mg / m 2 More preferably, it is the following, 10 mg / m 2 It is particularly preferable that the amount of residual solvent in the paper base material layer is 30 mg / m 2 By being the following, changes and deterioration of the contents due to the presence of residual solvent can be prevented. Especially in the case of food, changes in flavor and quality can be prevented, and problems in food hygiene can be solved.

[0016] The weight of the paper base material in the present technology is not particularly limited, and can be freely set as long as the functions and effects of the present technology are not impaired. From the viewpoint of realizing excellent oxygen barrier properties and bending resistance while reducing the amount of residual solvent in the laminate, the upper limit value of the weight of the paper base material is preferably a weight of 70 g / m 2 or less, more preferably a weight of 65 g / m 2 or less, and still more preferably a weight of 60 g / m 2 or less. The lower limit value of the weight of the paper base material is preferably a weight of 20 g / m 2 or more, more preferably a weight of 30 g / m 2 or more, and even more preferably a weight of 40 g / m 2 or more. If it is less than 20 g / m[[ID=2】] 2 it is not preferable because deformation of the paper base material is likely to occur when the adhesive composition is applied. On the other hand, if it exceeds 70 g / m 2 the solvent of the adhesive composition is difficult to volatilize and may remain in the paper base material, which is not preferable.

[0017] The thickness of the paper substrate in this technology is not particularly limited and can be freely set as long as it does not impair the function or effect of this technology. From the viewpoint of reducing the amount of residual solvent in the laminate while achieving excellent oxygen barrier properties and flexibility, the upper limit of the paper substrate thickness is preferably 70 μm or less, more preferably 65 μm or less, and even more preferably 60 μm or less. The lower limit of the paper substrate thickness is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. A thickness below 20 μm is undesirable because it makes the paper substrate more prone to deformation when the adhesive composition is applied. On the other hand, a thickness exceeding 70 μm is undesirable because the solvent tends to remain due to the thickness of the paper substrate.

[0018] (2) Adhesive layer The adhesive layer of the laminate according to this technology is formed from an adhesive composition and is laminated on at least one surface of the paper substrate layer. The adhesive layer of this technology adheres the paper substrate layer and the metal vapor deposition layer and also exhibits oxygen barrier properties. Furthermore, the adhesive layer of this technology can be formed, for example, by applying the adhesive composition to the surface of the metal vapor deposition layer and drying it.

[0019] In this technology, a lower amount of residual solvent in the adhesive layer is preferable; for example, 30 mg / m² 2 Preferably, it is 20 mg / m² 2 More preferably, the following is 10 mg / m² 2 The following is particularly preferable: The amount of residual solvent in the adhesive layer is 30 mg / m². 2 The following factors suppress the deterioration of the adhesive composition due to residual solvents, thereby preventing a decrease in oxygen barrier properties and adhesive strength.

[0020] The thickness of the adhesive layer in this technology is not particularly limited, but it is preferable to have a small thickness from the viewpoint of reducing the amount of residual solvent in the laminate. The upper limit of the adhesive layer thickness is preferably 3 μm or less, more preferably 2.5 μm or less, and even more preferably 2 μm or less. The lower limit of the adhesive layer thickness is preferably 1 μm or more. A thickness below 1 μm is undesirable because the oxygen barrier properties and adhesive properties of the adhesive layer are not fully exhibited. On the other hand, a thickness exceeding 3 μm is undesirable because solvent tends to remain in the adhesive layer.

[0021] The adhesive composition for the adhesive layer of this technology is not particularly limited, as long as it does not impair the function or effect of this technology, and any adhesive composition can be used. The adhesive composition may be a solvent type containing an adhesive and a solvent, or a solvent-free type that does not contain a solvent. From the viewpoint of maintaining sufficient adhesion between the paper substrate layer and the metal vapor deposition layer while reducing the thickness of the adhesive layer, it is preferable that the adhesive composition is a solvent type containing an adhesive and a solvent. Furthermore, the adhesive composition of this technology may be a one-component curing adhesive, or a two-component curing adhesive containing a main component and a curing agent.

[0022] <Adhesive> Examples of adhesives used in the adhesive composition of this technology include ester-based adhesives, ether-based adhesives, vinyl-based adhesives, (meth)acrylic-based adhesives, amide-based adhesives, amino resin-based adhesives, urethane-based adhesives containing polyols and isocyanates, silicone-based adhesives, vinyl-based adhesives, phenolic resin-based adhesives, olefin-based adhesives, epoxy-based adhesives, and rubber-based adhesives. One or more of these can be used as needed.

[0023] Among these, ester-based adhesives, ether-based adhesives, and urethane-based adhesives containing polyols and isocyanates are preferred from the viewpoint of improving the adhesive properties of the adhesive composition while achieving excellent oxygen barrier properties and flexibility. The polyol in the urethane-based adhesive is not particularly limited as long as it is a compound having two or more hydroxyl groups (-OH) in one molecule, but examples include polyether-based polyols, polyester-based polyols, polymer polyols, and acrylic polyols. The isocyanate in the urethane-based adhesive is not particularly limited as long as it is a compound having two or more isocyanate groups (-NCO) in one molecule, but examples include aromatic polyisocyanates such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), and isophorone diisocyanate (IPDI), aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), and aromatic aliphatic polyisocyanates such as xylylene diisocyanate (XDI), and can be used individually or in combination of two or more as needed. These adhesives are highly flexible and processable, and the resulting adhesive layer exhibits good adhesion, excellent oxygen barrier properties, and flexibility. Commercial urethane adhesives may be used; for example, a combination of "PASLIM VM001" (manufactured by DIC Corporation) and "PASLIM VM108CP" (manufactured by DIC Corporation) may be used.

[0024] <Solvent> The solvent in the adhesive composition in this technology is mainly used as a solvent for the adhesive. While not particularly limited as long as it is a solvent commonly used in adhesive compositions, it is preferable that the solvent readily dissolves the adhesive and has a low boiling point and excellent volatility to suppress the amount of residual solvent in the laminate. Examples of solvents in this technology include single organic solvents and mixed organic solvents. Examples of single organic solvents include alcohol-based solvents such as methanol, ethanol, n-propanol, isopropanol, n-butyl alcohol, isobutyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone; aromatic solvents such as toluene, xylene, ethylbenzene, and mesitylene; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; chlorine-based solvents such as chloroform, carbon tetrachloride, dichloromethane, and trichloroethylene; and dimethylformamide, dimethylacetamide, and n-methyl-2-pyrrolidone. Examples of mixed organic solvents include toluene / methanol, toluene / isopropanol, n-propanol / cyclohexane, n-propanol / methylcyclohexane, cyclohexanone / n-propanol, and cyclohexanone / methyl ethyl ketone. Among these, from the viewpoint of use in food packaging, solvents that do not impair food hygiene are preferred, for example, methyl ethyl ketone and / or ethyl acetate are more preferred, and ethyl acetate is particularly preferred.

[0025] The upper limit of the solvent content in the adhesive composition in this technology is not particularly limited, but from the viewpoint of reducing residual solvent content while achieving excellent oxygen barrier properties and flexibility, it is preferably 85% by mass or less, more preferably 80% by mass or less, and particularly preferably 75% by mass or less, relative to the total mass of the adhesive composition. Furthermore, the lower limit of the solvent content in the adhesive composition in this technology is preferably 20% by mass or more, more preferably 25% by mass or more, and particularly preferably 30% by mass or more, relative to the total mass of the adhesive composition.

[0026] While there are no particular limitations on the upper limit of the amount of adhesive composition to be used, from the viewpoint of achieving excellent oxygen barrier properties and flexibility while reducing the amount of residual solvent, 3 g / m² in dry state is recommended. 2 Preferably, it is 2.5 g / m 2 More preferably, the following is true: 2 g / m 2 The following is particularly preferable. Furthermore, the lower limit for the amount of adhesive layer used is 1 g / m². 2 It is preferable that the above conditions are met.

[0027] The adhesive layer in this technology may be formed by coating and drying an adhesive composition. The coating method for the adhesive composition is not particularly limited, but for example, gravure roll method, reverse roll method, offset gravure method, kiss coat method, reverse kiss coat method, wire bar coat method, spray coat method, impregnation method, etc. may be used.

[0028] The thickness of the adhesive layer in this technology is not particularly limited and can be freely set as long as it does not impair the function or effect of this technology. From the viewpoint of reducing the amount of residual solvent in the laminate while achieving excellent oxygen barrier properties and flexibility, the upper limit of the adhesive layer thickness is preferably 3 μm or less, more preferably 2.5 μm or less, and even more preferably 2 μm or less. The lower limit of the adhesive layer thickness is preferably 1 μm or more. If it is less than 1 μm, it is undesirable because the adhesive layer becomes too thin, impairing the oxygen barrier properties. On the other hand, if it exceeds 3 μm, the amount of adhesive composition used increases, making it easier for solvent to remain in the laminate, which is undesirable.

[0029] The adhesive layer in this technology may contain additives such as plasticizers, release agents, antioxidants, oxygen absorbers, UV absorbers, light stabilizers, antistatic agents, antiblocking agents, flame retardants, crosslinking agents, and colorants, as needed.

[0030] (3)Metal deposition layer The metal vapor-deposited layer of the laminate according to this technology is, for example, a layer obtained by vapor-depositing metal onto the surface of a layered substrate such as a sheet or film, and is laminated on the surface opposite to the side adjacent to the paper substrate layer of the adhesive layer. By providing a metal vapor-deposited layer in the laminate according to this technology, excellent oxygen barrier properties and flexibility resistance can be provided to maintain the quality of the contents.

[0031] Examples of substrates for the metal vapor deposition layer include resin, paper, cloth, wood, and glass. However, from the viewpoint of use in packaging applications, resin is preferred, and thermoplastic resin is particularly preferred. Examples of thermoplastic resins include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate; and vinyl resins such as polyvinyl chloride, polyvinyl acetate / polyvinyl alcohol, and ethylene-vinyl alcohol copolymer. Furthermore, the substrate may be in the form of a sheet or film, and when a thermoplastic resin film is used as the substrate, it may be either a stretched film or an unstretched film.

[0032] Examples of metals to be deposited on the substrate include metals such as aluminum, gold, silver, copper, nickel, chromium, germanium, selenium, titanium, tin, and zinc; metal oxides such as silicon oxide, aluminum oxide, and magnesium oxide; and metal nitrides such as silicon nitride. However, from the viewpoint of oxygen barrier properties, it is preferable to use metals (metal compounds) containing aluminum, such as aluminum or aluminum oxide.

[0033] The thickness of the metal (metal compound) deposited in the metal deposition layer of this technology is not particularly limited and can be freely set as long as it does not impair the function and effects of this technology. From the viewpoint of maintaining excellent oxygen barrier properties, flexibility, and light shielding properties, the upper limit of the metal film thickness is preferably 1000 Å or less, more preferably 700 Å or less, and even more preferably 500 Å or less. The lower limit of the metal film thickness is preferably 100 Å or more, more preferably 150 Å or more, and even more preferably 200 Å or more. If it is less than 100 Å, the metal film thickness becomes too thin, which is undesirable because it impairs the oxygen barrier properties, flexibility, and light shielding properties. On the other hand, if it exceeds 1000 Å, the mechanical strength of the metal deposition layer decreases and the oxygen barrier function is impaired, which is undesirable.

[0034] The method for forming the metal deposition layer in this technology is not particularly limited, but examples include vacuum deposition, ion plating (IP), sputtering, chemical vapor deposition (CVD), and atomic layer deposition (ALD). Among these, vacuum deposition is preferred from the viewpoint of productivity of the metal deposition layer.

[0035] The metal deposition to obtain the metal deposition layer may be performed directly on the substrate, or the substrate surface may be pre-treated. Examples of surface treatments before metal deposition include corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, oxidation treatment using chemicals, and surface treatment by applying primer coats, undercoats, anchor coats, adhesives, or deposition anchor coats.

[0036] For the metal vapor deposition layer in this technology, commercially available products may be used, such as "VMCPP 2703" (manufactured by Toray Film Processing Co., Ltd.).

[0037] 2. Physical properties (1) Oxygen barrier properties The laminate according to this technology achieves excellent oxygen barrier properties even when the amount of adhesive is reduced, by using a laminate having a paper substrate layer with low surface roughness, an adhesive layer, and a metal vapor deposition layer. The oxygen barrier properties of the laminate according to this technology can be evaluated by the oxygen permeability. The laminate according to this technology has an oxygen permeability of 3 cc / m³. 2 It exhibits excellent oxygen barrier properties when the value is less than / day.

[0038] <Oxygen permeability of laminated material> The oxygen permeability of the laminate relating to this technology may be, for example, a measurement result obtained by measuring using an oxygen permeability measuring device (Mocon, OX-TRAN 2 / 21) in accordance with JIS K 7126, under conditions of a temperature of 23±2°C and a humidity of 0%RH.

[0039] While there is no particular upper limit to the oxygen permeability of the laminate relating to this technology, from the viewpoint of maintaining excellent oxygen barrier properties, 3 cc / m² is recommended. 2 Preferably less than / day, 2cc / m 2 It is more preferable that it be less than or equal to / day, and 1 cc / m 2It is particularly preferable that the oxygen permeability is less than or equal to / day. The lower limit of the oxygen permeability of the laminate relating to this technology is not particularly limited, as a lower oxygen permeability allows for the maintenance of superior barrier properties, but for example, 0 cc / m 2 The oxygen permeability of the laminate related to this technology may be 3 cc / m³ or more. 2 A value of less than / day is preferable from the viewpoint of maintaining excellent barrier properties, as the laminate has excellent oxygen impermeability.

[0040] <Oxygen permeability of laminate after Gelboflex test> While there are no particular limitations on the upper limit of oxygen permeability of the laminate after the Gelboflex test related to this technology, from the viewpoint of the laminate having excellent flexibility and maintaining excellent oxygen barrier properties even after the Gelboflex test, 100 cc / m² is set. 2 It is preferable that it be less than or equal to / day, and 80cc / m 2 It is more preferable that it be less than or equal to / day, and 50cc / m 2 It is particularly preferable that the oxygen permeability is less than or equal to / day. The lower limit of the oxygen permeability after the Gelboflex test of the laminate relating to this technology is not particularly limited, as a lower oxygen permeability allows for the maintenance of superior barrier properties, but for example, 0 cc / m 2 It could be more than / day.

[0041] In this technology, the oxygen permeability after the Gelboflex test may be, for example, the measurement result obtained by performing a Gelboflex test on the laminate relating to this technology under the following conditions and measuring the oxygen permeability after the test using the method described above. <Gelboflex Test Conditions> A Gelvo Flex Test was conducted using a Gelvo Flex Tester (BE1005, manufactured by Tester Sangyo Co., Ltd.) in accordance with ASTM F392. Specifically, the bending action involved twisting the material 440° while pushing it in 90 mm, followed by moving it straight forward 65 mm, and this process was repeated five times.

[0042] (2) Water vapor barrier properties The water vapor barrier properties of the laminate according to this technology can be evaluated by its water vapor transmission rate (MVTR). The laminate according to this technology has a water vapor transmission rate (MVTR) of 3 g / m³. 2 By being below / day, it exhibits not only excellent oxygen barrier properties but also superior water vapor barrier properties.

[0043] While there is no particular upper limit to the water vapor transmission rate (MVTR) of the laminate relating to this technology, from the viewpoint of having excellent water vapor barrier properties, 3 g / m 2 It is preferable that the amount be less than or equal to / day, which is 2 g / m². 2 It is more preferable that it be less than or equal to / day, or 1 g / m² 2 It is particularly preferable that the water vapor permeability is less than or equal to / day. The lower limit of the water vapor permeability of the laminate relating to this technology is not particularly limited, as a lower water vapor permeability allows for the maintenance of superior water vapor barrier properties, but for example, 0 g / m 2 It could be more than / day.

[0044] (3)Surface roughness In this technology, the surface roughness of the paper substrate refers to the arithmetic mean roughness (Sa) measured on the surface of the paper substrate layer to which the adhesive layer is applied. The upper limit of the surface roughness of the paper substrate in this technology is preferably 2 μm or less, more preferably 1.5 μm or less, and particularly preferably 1 μm or less, from the viewpoint of achieving excellent oxygen barrier properties and flexibility while reducing the amount of residual solvent. The lower limit of the surface roughness of the paper substrate in this technology is not particularly limited, but is preferably 0.1 μm or more. The numerical range of the average roughness of the paper substrate in this technology may be specified by combining either of these upper and lower limits, and the average roughness may be, for example, 0.1 μm to 2 μm, preferably 0.1 μm to 1.5 μm, and more preferably 0.1 μm to 1 μm. When the surface roughness of the paper substrate in this technology is 2 μm or less, the smoothness of the paper substrate is improved, and the adhesion of the adhesive layer is improved. It is also preferable because the void ratio, which indicates the porosity of the adhesive on the surface of the paper substrate layer, can be kept low. This makes it possible to sufficiently bond the metal vapor-deposited layer to the adhesive layer even when the amount of adhesive composition is reduced, thereby achieving excellent oxygen barrier properties and flexibility while reducing the amount of residual solvent. On the other hand, if the surface roughness exceeds 2 μm, the void ratio increases due to the surface roughness, requiring a large amount of adhesive composition to sufficiently bond the paper substrate layer and the metal vapor-deposited layer, and residual solvent from the adhesive composition may remain, which is undesirable. The arithmetic mean roughness Sa may be measured, for example, according to JIS B0681.

[0045] The surface roughness (arithmetic mean roughness Sa) of the paper substrate layer related to this technology can be measured, for example, using a laser microscope (Olympus OLS500 3D measuring laser microscope, objective lens: MPLAPOM20xLEXT). Specifically, in accordance with JIS B0681, an image for analysis of the paper substrate layer is obtained under the following image observation conditions. The obtained image for analysis is subjected to correction processing for tilt removal, noise removal, and shape removal (4D curved surface), and the surface roughness of the paper substrate layer of each laminate is measured. The average value of the surface roughness measured four times under these conditions is calculated as the arithmetic mean roughness Sa of the paper substrate layer. <Image observation conditions> Scanning mode: 3D accuracy priority + color Monitor magnification: 23.6x Measurement area: 645.579μm×647.009μm

[0046] (4) Void fraction In this technology, the void ratio of the paper substrate represents the void ratio of the adhesive on the surface of the paper substrate layer to which the adhesive is applied. The void ratio of the paper substrate in this technology can be measured, for example, by creating a laminated sample for void ratio measurement and using a laser microscope (Olympus OLS500 3D measuring laser microscope, objective lens: MPLAPOM20xLEXT). The specific measurement method is described below.

[0047] First, a laminated sample is created using a transparent film instead of a metal vapor-deposited layer. Specifically, an adhesive was applied to an unoriented polypropylene film (CPP#30, Pyrene®, manufactured by Toyobo Co., Ltd.). The adhesive and application conditions were the same as in the examples described below. The film coated with the adhesive was dried in a drying oven at 50°C for 10 seconds, laminated with a paper substrate at 0.5 MPa using a laminator, and left to stand for 40 hours under conditions of 23°C and 50% RH to obtain a laminated sample.

[0048] Next, the void ratio is measured by observing the laminated sample perpendicular to the laminate from the unstretched polypropylene film side using a laser microscope (Olympus 3D measuring laser microscope, OLYMPUS OLS500, objective lens: MPLAPOM20xLEXT). Specifically, first, an observation image is obtained under the following image observation conditions. Using an analysis application, the areas bonded by adhesive and the areas without adhesive (void areas) are detected from the obtained analysis image. The void area is calculated from the measured area representing the total area of ​​the analysis image and the area of ​​the bonded areas using the following formula (1), and the void ratio is calculated using the following formula (2). <Image observation conditions> Magnification: 20x the objective lens Monitor magnification: 23.6x

[0049]

number

[0050]

number

[0051] The upper limit of the void ratio of the paper substrate in this technology is not particularly limited, but from the viewpoint of reducing the amount of residual solvent while maintaining excellent barrier properties, it is preferably 30% or less, more preferably 20% or less, and particularly preferably 10% or less. The lower limit of the void ratio of the paper substrate in this technology is not particularly limited, but the lower the better, but for example, it is 0% or more. The numerical range of the void ratio of the paper substrate in this technology may be specified by combining either of these upper and lower limits, and the void ratio may be, for example, 0% to 30%, preferably 0% to 20%, and more preferably 0% to 10%. When the void ratio of the paper substrate in this technology is 30% or less, even if the amount of adhesive is reduced, it becomes possible to sufficiently adhere to the metal vapor deposition layer via the adhesive layer, and excellent oxygen barrier properties and flexibility can be achieved while reducing the amount of residual solvent. On the other hand, if the void ratio exceeds 30%, the void ratio of the adhesive on the surface of the paper substrate layer increases, requiring a large amount of adhesive composition to adequately bond the paper substrate layer and the metal vapor deposition layer, and solvent residue from the adhesive composition may remain, which is undesirable.

[0052] 3. Method for manufacturing the laminate One embodiment of the manufacturing method for a laminate according to this technology includes a coating step of applying the adhesive composition to the metal vapor-deposited layer, a first drying step of drying the metal vapor-deposited layer coated with the adhesive composition to form an adhesive layer, a lamination step of bonding a paper substrate layer to the surface of the adhesive layer of the laminate formed by laminating the metal vapor-deposited layer and the adhesive layer, and a second drying step of drying the obtained laminate. Each step will be described below.

[0053] <Coating Process> In the coating process, the adhesive composition is applied to the metal vapor-deposited layer. This coating process is carried out, for example, using a wire bar, and the dry film thickness of the adhesive layer is 2 g / m². 2 It could be coated in such a way.

[0054] <1st drying process> In the first drying step, the metal vapor-deposited layer coated with the adhesive composition is dried. Drying can be performed using a drying oven. The drying temperature is, for example, 30°C to 80°C, preferably 40°C to 70°C, and more preferably 50°C to 60°C. The drying time is, for example, 2 seconds to 30 seconds, preferably 3 seconds to 20 seconds, and more preferably 5 seconds to 10 seconds.

[0055] <Lamination process> In the lamination process, a paper substrate layer is bonded to the surface of the adhesive layer of the laminate formed by laminating the metal vapor deposition layer and the adhesive layer. For example, a laminator can be used for bonding. The pressure during bonding is, for example, 0.1 MPa to 1 MPa, preferably 0.2 MPa to 0.8 MPa, and more preferably 0.3 MPa to 0.6 MPa.

[0056] <Second drying process> In the second drying step, the laminate is sandwiched between glass plates and dried. A drying oven may be used for drying. The drying temperature is, for example, 20°C to 70°C, preferably 30°C to 60°C, and more preferably 40°C to 50°C. The drying time is, for example, 0 hours to 168 hours, preferably 24 hours to 120 hours, and more preferably 48 hours to 96 hours. The drying humidity is, for example, 20%RH to 80%RH, preferably 30%RH to 60%RH, and more preferably 40%RH to 50%RH.

[0057] The laminate according to this technology exhibits excellent oxygen barrier properties and can therefore be suitably used in packaging containers such as pouch-type containers and tube-type containers; and in bag-shaped packaging materials such as wrapping paper and packaging bags. Furthermore, since the amount of residual solvent can be reduced by reducing the thickness of the coating adhesive, the laminate according to this technology can be suitably used in containers and packaging materials related to food in particular.

[0058] This technology can also employ the following configuration: [1] A paper substrate layer, An adhesive layer formed from an adhesive composition is laminated on at least one surface of the paper substrate layer, A metal vapor deposition layer is laminated on the surface opposite to the side adjacent to the paper substrate layer, among the two surfaces of the adhesive layer, A laminate having, The surface roughness of the paper substrate layer is 2 μm or less. The oxygen permeability of the aforementioned laminate is 3 cc / m³ 2 less than or equal to / day Laminated structure. [2] The laminate according to [1], wherein the void ratio of the paper substrate layer is 30% or less. [3] A laminate made of [1] or [2], having a water vapor transmission rate (MVTR) of 3 g / m2 / day or less. [4] The laminate according to any one of [1] to [3], wherein the average thickness of the adhesive layer is 1 μm or more and 3 μm or less. [5] The laminate according to any one of [1] to [4], wherein the adhesive composition comprises an adhesive and a solvent. [6] The laminate according to [5], wherein the adhesive is an ester-based adhesive or an ether-based adhesive. [7] The laminate according to any one of [5] to [6], wherein the solvent is ethyl acetate. [8] The laminate according to any one of [1] to [7], wherein the laminate is used for packaging purposes. [9] The laminate according to any one of [1] to [8], wherein the aforementioned packaging is used for food packaging.

[0059] 4. Examples Next, the present invention will be specifically described with reference to examples. Note that the examples described below are representative examples of the present invention, and the scope of the present invention is not limited to these examples.

[0060] (Example 1) As the metal vapor deposition layer, we prepared an aluminum vapor-deposited film (product name: VM-CPP 2703, manufactured by Toray Film Processing Co., Ltd.). Next, an adhesive composition for application to the metal vapor-deposited layer was prepared. The adhesive composition was a two-component curing type adhesive containing a main component and a curing agent. A special polyester polyol (product name: PASLIM VM001, manufactured by DIC Corporation) was used as the main component, and an aromatic-aliphatic mixed polyisocyanate (product name: PASLIM VM108CP, manufactured by DIC Corporation) was used as the curing agent. 100 parts by mass of the main component, 25 parts by mass of the curing agent, and 55 parts by mass of ethyl acetate were mixed and stirred immediately before use to obtain the adhesive composition.

[0061] The adhesive composition was applied to one surface of the aluminum vapor-deposited film. The amount of adhesive composition applied was 2 g / m². 2 The coating was performed using a wire bar. After coating the adhesive composition, the adhesive composition was dried in a drying oven at a temperature of 50°C for a drying time of 10 seconds. The adhesive composition hardened upon heating, yielding an aluminum vapor-deposited film with a laminated adhesive layer.

[0062] A glossy surface of paper (product name: Ryuoh, manufactured by Daio Paper Corporation, glossy surface roughness: 0.40 μm) was laminated to the surface of the adhesive layer of the aluminum vapor-deposited film on which the adhesive layer was laminated. This lamination was performed using a laminator (product name: Camellia 1600CL, manufactured by Lamy Corporation, 0.5 MPa). After that, the laminate was sandwiched between glass plates and left to stand for 20 hours under conditions of 23°C and 50% RH. This obtained a laminate according to Example 1 of the present invention (hereinafter referred to as "laminated body 1"). The thickness of laminate 1 was 92 ± 9 μm.

[0063] The oxygen permeability of the obtained laminate 1 before and after the Gelboflex test was measured according to the method described in 2.(1) above. In addition, for Example 1, a sample for calculating the void ratio was prepared using an unoriented polypropylene film instead of the aluminum vapor-deposited film, according to the method described in 2.(4), and the void ratio was calculated. The results are shown in Table 1 and Figure 2 below. As shown in Table 1, the oxygen permeability of the laminate 1 was 0.56 cc / m 2 The oxygen permeability was 36.96 cc / m³ / day, demonstrating excellent oxygen barrier properties. Furthermore, the oxygen permeability after the Gelboflex test was 36.96 cc / m³. 2 The void ratio was 5.4%, indicating excellent flexibility and maintaining good oxygen barrier properties even after the Gelboflex test. Figure 2 is a magnified image showing the observation image used for calculating the void ratio in Example 1. As shown in Figure 2, the surface of the paper substrate layer including the adhesive layer had few adhesive voids and a low void ratio of 5.4%.

[0064] [Table 1]

[0065] (Example 2) A laminate (hereinafter referred to as "laminated body 2") was obtained in the same manner as in Example 1, except that a highly smooth paper (product name: Ryuoh, manufactured by Daio Paper Corporation, surface roughness: 1.82 μm) was used as the paper substrate layer, and the rough surface of the said highly smooth paper was used as the surface layer. The thickness of laminate 2 was 92 ± 9 μm.

[0066] Various physical properties were measured for the obtained laminate 2 in the same manner as in Experimental Example 1. The results are shown in Table 1. As shown in Table 1, the oxygen permeability of the laminate 2 is 1.03 cc / m³. 2 The oxygen permeability was 85.32 cc / m³ / day, demonstrating excellent oxygen barrier properties. Furthermore, the oxygen permeability after the Gelboflex test was 85.32 cc / m³. 2 The gel exhibited excellent flexibility and maintained superior oxygen barrier properties even after the Gelboflex test. Furthermore, the surface of the paper substrate layer, including the adhesive layer, had few adhesive voids and a low void ratio of 20.0%.

[0067] (Comparative Example 1) As the paper substrate layer, ordinary paper (product name: Kinshachi, manufactured by Daio Paper Corporation, surface roughness: 2.68 μm) was used, and a laminate (hereinafter referred to as "laminated body 3") was obtained in the same manner as in Example 1, except that the rough surface of the paper substrate was bonded when forming the paper substrate layer on the surface of the adhesive layer of the aluminum vapor-deposited film. The thickness of laminate 3 was 92 ± 9 μm.

[0068] Various physical properties were measured for the obtained laminate 3 in the same manner as in Experimental Example 1. The results are shown in Table 1. As shown in Table 1, the oxygen permeability of the laminate 3 is 5.39 cc / m³. 2 The oxygen barrier performance was low, with a value of 193.96 cc / m³ / day. Furthermore, the oxygen permeability after the Gelboflex test was 193.96 cc / m³. 2 The value was / day, indicating low oxygen barrier properties. Figure 3 is a magnified image showing the observation image used for calculating the void ratio in Comparative Example 1. As shown in Figure 3, the surface of the paper substrate layer including the adhesive layer showed widespread adhesive voids, and the void ratio was 85.5%.

[0069] As shown in Table 1, regardless of the type of paper substrate or whether the surface of the paper substrate layer is processed or not, the smaller the surface roughness of the paper substrate laminated to the adhesive layer, the lower the oxygen permeability and the better the oxygen barrier properties. Furthermore, from the results of Examples 1 and 2 and Comparative Example 1, it can be seen that the upper limit of the surface roughness of a paper substrate that exhibits good oxygen barrier properties is about 2 μm. Thus, the examples demonstrate that in the present invention, by laminating a paper substrate with a surface roughness of 2 μm or less with an oxygen barrier adhesive and an aluminum vapor-deposited plastic, it is possible to reduce the thickness of the coating adhesive and decrease the amount of residual solvent while maintaining excellent oxygen barrier properties.

[0070] Furthermore, as shown in Table 1, it was found that the smaller the surface roughness of the paper substrate surface, the smaller the void ratio, indicating that the void ratio contributes to achieving excellent oxygen barrier properties. From this, the examples demonstrate that in the present invention, by having a void ratio of 30% or less, it is possible to reduce the thickness of the coating adhesive and decrease the amount of residual solvent while maintaining excellent oxygen barrier properties. [Explanation of Symbols]

[0071] 10 Laminate 11 Paper base layer 12 Adhesive layer 13 Metal deposited layer

Claims

1. A paper substrate layer, An adhesive layer formed from an adhesive composition is laminated on at least one surface of the paper substrate layer, A metal vapor deposition layer is laminated on the surface opposite to the side adjacent to the paper substrate layer, among the two surfaces of the adhesive layer, A laminate having, The surface roughness of the paper substrate layer is 2 μm or less. The oxygen permeability of the laminate is 3 cc / m³ ２ / day or less, Laminated structure.

2. The laminate according to claim 1, wherein the void ratio of the paper substrate layer is 30% or less.

3. Water vapor transmission rate (MVTR) is 3 g / m ２ The laminate according to claim 1, wherein the number of days is less than or equal to / day.

4. The laminate according to claim 1, wherein the average thickness of the adhesive layer is 1 μm or more and 3 μm or less.

5. The laminate according to claim 1, wherein the adhesive composition comprises an adhesive and a solvent.

6. The laminate according to claim 5, wherein the adhesive is an ester-based adhesive or an ether-based adhesive.

7. The laminate according to claim 5, wherein the solvent is ethyl acetate.

8. The laminate is used for packaging purposes, as described in claim 1.

9. The laminate according to claim 8, wherein the packaging is used for food packaging.

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