Laminated structure

Abstract

To provide a laminated layered body which has a laminated structure composed of substantially a single resin species having a low environmental load and has necessary performance required for packaging materials, including gas barrier properties, heat-seal properties and toughness.SOLUTION: A laminated layered body according to the present invention comprises two stretched base films each containing a polypropylene-based resin as a starting material and one heat-sealable resin layer which are laminated together with an adhesive interposed therebetween. At least one of the base films is a multi-layer film that has, on one surface thereof, a coated layer or an inorganic thin-film layer each having a polyvinyl alcohol-based copolymer and an inorganic layered compound, the heat-sealable resin layer is made of olefin-based resin containing polypropylene or a polyethylene resin as a main component, and the laminated layered body satisfies the requirements (a) to (d). (a) The laminated layered body has puncture strength of 15 N or more. (b) The laminated layered body has an oxygen permeability of 20 ml / m2 d MPa or less under a 23°C×65%RH environment, and also has a water vapor permeability of 2.0 g / m2 d or less under a 40°C×90%RH environment. (c) When the seal layer for the laminated layered body and another seal layer for the laminated layered body are heat-sealed with each other at 160°C under 0.2 MPa for 2 seconds, the heat seal strength is 15 N / 15 mm or more. (d) When the laminated layered body is heat-treated at 120°C for 5 minutes, the shrinkage ratio of the laminated layered body is 1.8% or less in either of the MD direction of the base film or the TD direction of the base film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to laminates used in the packaging of food, pharmaceuticals, industrial products, and the like. More specifically, it relates to an environmentally friendly laminate that is excellent in gas barrier properties, processability, toughness, and convenience. [Background technology]

[0002] In recent years, regulations aimed at reducing the use of single-use plastics have been strengthened in Europe and around the world. This is due to a growing international awareness of resource recycling and the worsening waste problem in emerging countries. As a result, there is a demand for environmentally friendly products from the perspective of the 3Rs (recycle, reuse, reduce) for plastic packaging materials used for food, pharmaceuticals, and other products.

[0003] As one possibility for creating environmentally friendly packaging materials, as mentioned above, the idea of ​​making packaging materials from a single recyclable material, i.e., monomaterialization, is being actively explored. For example, polyester-based and olefin-based materials are being investigated for monomaterialization.

[0004] While there is a demand for packaging materials with a low environmental impact, the properties required of packaging materials themselves are becoming increasingly multifunctional for convenience. For example, a pouch that can be used in a microwave oven without using aluminum foil requires gas barrier properties, heat resistance, toughness (resistance to tearing and pinholes), and high sealing performance all in one packaging bag. To achieve this, it is necessary to laminate different materials, each with a different function, and a common configuration is at least three layers, with a vapor-deposited polyester film on the outside, a polyamide film in the middle layer, and an olefin-based heat-sealable resin on the inside (contents side) dry-laminated with an adhesive. While this configuration can achieve the desired performance, it has the problem of being poorly recyclable due to the lamination of different materials, and therefore cannot be considered an environmentally friendly packaging material.

[0005] Considering these points, research is underway to determine whether it is possible to design an ideal packaging material that possesses the multi-functional properties of a bag, as described above, even when using the same material that can be monomaterialized.

[0006] In the design of polyester monomaterial packaging, polyester sealants with improved low adsorption and heat resistance have been disclosed as an alternative to conventional olefin-based sealants (see, for example, Patent Document 1). The sealant in Patent Document 1 satisfies both heat-sealability and heat resistance by separating the heat-sealable layer from the other layers and controlling the raw material composition of each layer separately. However, it has the problem that its heat-sealability is inferior to that of olefin-based sealants in terms of seal strength, and in terms of heat resistance, it cannot withstand harsh treatments such as boiling or retort processing.

[0007] On the other hand, olefin-based monomaterial packaging designs have had the problem of inferior gas barrier performance compared to conventional packaging with barrier properties. Although polypropylene film has water vapor barrier properties, it does not have sufficient values ​​compared to, for example, transparent inorganic vapor-deposited polyester film, which is generally considered to have excellent water vapor barrier properties, and it also has the problem of having very poor oxygen barrier properties.

[0008] In response to this, films have been used in which polypropylene films are laminated with polymer resin compositions that are generally said to have relatively high oxygen barrier properties, such as polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinylidene chloride resin, and polyacrylonitrile (see, for example, Patent Documents 2-4). However, gas barrier coating films using the above-mentioned polymer resin compositions of polyvinyl alcohol and ethylene vinyl alcohol copolymer have a large humidity dependence, resulting in a decrease in gas barrier properties under high humidity. Furthermore, while polyvinylidene chloride resin and polyacrylonitrile have low humidity dependence, they have problems such as insufficient absolute barrier value and a high risk of generating harmful substances during disposal and incineration. Moreover, all of the aforementioned barrier coating layers required a film thickness of at least 0.5 μm to exhibit sufficient barrier performance. If the film thickness of the coating layer is thick, recycling may become difficult, and it is also unsuitable from the viewpoint of monomaterialization using a single material.

[0009] Regarding the improvement of the gas barrier properties of polypropylene films, attempts have been made to achieve stable gas barrier performance without humidity dependence by laminating inorganic thin films (for example, Patent Document 5). However, there were problems such as inferior absolute gas barrier performance (especially oxygen barrier performance) compared to conventional polyester vapor-deposited films, and weakness to physical damage compared to the aforementioned coated barrier films. In addition, barrier materials obtained by vapor deposition on olefin-based sealants have also been investigated (for example, Patent Document 6), but there were problems such as insufficient oxygen barrier performance despite exhibiting water vapor barrier performance. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2017-165059 [Patent Document 2] Japanese Patent Publication No. 2000-52501 [Patent Document 3] Japanese Patent Application Publication No. 4-359033

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0011] In the above-mentioned patent documents, it is difficult to achieve both the mono-materialization of the packaging material and various performances required for the packaging material, and a packaging material that is environmentally friendly and highly convenient has not been designed.

[0012] The present invention has been made against the background of such problems of the prior art. That is, the problem of the present invention is to form a laminate structure composed of substantially a single resin type with a small environmental load, and to provide a laminate laminate having necessary performances such as gas barrier properties, heat sealability, and further processing suitability required for the packaging material.

Means for Solving the Problems

[0013] The inventors of the present invention greatly improved the gas barrier performance by using a laminated film in which a predetermined coating layer adapted to the required performance is laminated on a polypropylene-based stretched base film, and further ensured toughness and heat resistance by laminating two sheets of the laminated film. Finally, by laminating a sealant composed of an olefin-based component, mono-materialization was realized while maintaining high heat sealability. From the above, the inventors have found that a laminate laminate that is environmentally friendly and highly convenient can be provided, and thus the present invention has been completed.

[0014] That is, the present invention has the following configuration. (1) A laminated laminate comprising two stretched base films made from polypropylene resin and one heat-sealable resin layer laminated together via an adhesive, wherein at least one of the base films is a laminated film having a coating layer or an inorganic thin film layer having a polyvinyl alcohol copolymer and an inorganic layered compound on one side, and the heat-sealable resin layer is made of an olefin resin mainly composed of polypropylene or polyethylene resin, and the laminated laminate satisfies the following requirements (a) to (d). (a) The puncture strength of the laminate is 15N or more. (b) The oxygen permeability of the laminated structure at 23°C × 65%RH is 20 ml / m². 2 • Water vapor transmission rate of 2.0 g / m³ under conditions of d·MPa or less and 40°C × 90%RH. 2 • Must be less than or equal to d. (c) The seal strength when the seal layers of the laminated structure are heat-sealed at 160°C, 0.2 MPa, and 2 seconds is 15 N / 15 mm or more. (d) The shrinkage rate of the laminated structure when heated at 120°C for 5 minutes is 1.8% or less in both the MD direction and the TD direction of the base film. (2) The laminate according to (1), characterized in that the inorganic layered compound of the coating layer contains a montmorillonite-based compound as a constituent component. (3) The amount of the coating layer is 0.10 g / m 2 More than 0.50g / m 2 The laminate according to (1) or (2), characterized in that it is as follows: (4) The laminate according to (1) to (3), characterized in that the inorganic thin film layer is a layer made of aluminum oxide, silicon oxide, or a composite oxide of silicon oxide and aluminum oxide. (5) The laminate according to any one of (1) to (4), characterized in that at least one of the base films is a base film whose heat shrinkage rate at 150°C for 5 minutes is 10% or less in both the MD direction and the TD direction. [Effects of the Invention]

[0015] Through this technology, the inventors have made it possible to provide laminated materials that possess the necessary properties such as barrier properties, heat sealability, and toughness required for packaging materials, while also being environmentally conscious. [Modes for carrying out the invention]

[0016] The laminated structure of the present invention is a laminated structure comprising two stretched base films made from a polypropylene resin and one heat-sealable resin layer laminated together via an adhesive, wherein at least one of the base films is a laminated film having a coating layer or an inorganic thin film layer having a polyvinyl alcohol copolymer and an inorganic layered compound on one side, and the heat-sealable resin layer is made of an olefin resin mainly composed of polypropylene or polyethylene resin, and the laminated structure is characterized in that it satisfies the following requirements (a) to (d). (a) The puncture strength of the laminate is 15N or more. (b) The oxygen permeability of the laminated structure at 23°C × 65%RH is 20 ml / m². 2 • Water vapor transmission rate of 2 g / m³ at d·MPa or less and under 40°C × 90%RH conditions. 2 • Must be less than or equal to d. (c) The seal strength when the seal layers of the laminated structure are heat-sealed at 160°C, 0.2 MPa, and 2 seconds is 15 N / 15 mm or more. (d) The shrinkage rate of the laminated structure when heated at 120°C for 5 minutes is 1.8% or less in both the MD direction and the TD direction of the base film.

[0017] The present invention will be described in detail below. [Base film layer] In the present invention, the propylene-based resin stretched film used as the base film is preferably a biaxially oriented film. The biaxially oriented polypropylene resin film can be any known biaxially oriented polypropylene resin film, and its raw materials and mixing ratios are not particularly limited. For example, it may be a polypropylene homopolymer (propylene homopolymer), a random copolymer or block copolymer with propylene as the main component and one or more α-olefins selected from ethylene, butene, pentene, hexene, etc., or a mixture of two or more of these polymers. Furthermore, known additives such as antioxidants, antistatic agents, and plasticizers may be added for the purpose of modifying physical properties, and for example, petroleum resins or terpene resins may be added.

[0018] Furthermore, the biaxially oriented polypropylene resin film used in the present invention may be a single-layer film, or a laminated film in which multiple resin films including the biaxially oriented polypropylene resin film are laminated together. In the case of a laminated film, the type of laminate, the number of layers, the lamination method, etc., are not particularly limited and can be arbitrarily selected from known methods depending on the purpose.

[0019] In the present invention, the polypropylene resin constituting the base film is preferably a propylene homopolymer that is substantially free of comonomers, and even if it contains comonomers, the amount of comonomers is preferably 0.5 mol% or less. The upper limit of the amount of comonomers is more preferably 0.3 mol%, and even more preferably 0.1 mol%. Within this range, crystallinity is improved, dimensional changes at high temperatures are reduced, that is, the elongation rate when heated to a certain temperature (hereinafter referred to as the heating elongation rate) is reduced, and heat resistance is improved. In addition, a small amount of comonomers may be included as long as it does not significantly reduce crystallinity.

[0020] The polypropylene resin constituting the base film preferably contains a propylene homopolymer obtained solely from propylene monomers, and most preferably, even if it is a propylene homopolymer, it does not contain heterogeneous bonds such as head-to-head bonds.

[0021] From a practical standpoint, the lower limit of xylene-soluble content in the polypropylene resin constituting the base film is preferably 0.1% by mass. The upper limit of xylene-soluble content is preferably 7% by mass, more preferably 6% by mass, and even more preferably 5% by mass. Within these ranges, crystallinity is improved, the thermal elongation is reduced, and the heat resistance is improved.

[0022] In the present invention, the lower limit of the melt flow rate (MFR) (230°C, 2.16 kgf) of the polypropylene resin is preferably 0.5 g / 10 min. More preferably, the lower limit of the MFR is 1.0 g / 10 min, even more preferably 2.0 g / 10 min, particularly preferably 4.0 g / 10 min, and most preferably 6.0 g / 10 min. Within this range, the mechanical load is small, and extrusion and stretching are easy. The upper limit of the MFR is preferably 20 g / 10 min. More preferably, the upper limit of the MFR is 17 g / 10 min, even more preferably 16 g / 10 min, and particularly preferably 15 g / 10 min. Within this range, stretching is easy, thickness variations are reduced, the stretching temperature and heat setting temperature can be increased, the heat elongation is smaller, and the heat resistance is improved.

[0023] The aforementioned base film may be a uniaxially oriented film in the longitudinal direction (MD direction) or transverse direction (TD direction) from the viewpoint of heat resistance, but a biaxially oriented film is preferred. In the present invention, by stretching at least uniaxially, a film with high heat resistance can be obtained, which has a low thermal shrinkage rate at high temperatures that could not be expected with conventional polypropylene films. Examples of stretching methods include simultaneous biaxial stretching and sequential biaxial stretching, but sequential biaxial stretching is preferred from the viewpoint of providing good flatness, dimensional stability, and thickness uniformity.

[0024] In the sequential biaxial stretching method, polypropylene resin is heated and melted in a single-screw or twin-screw extruder to a resin temperature of 200°C to 280°C, formed into a sheet using a T-die, and extruded onto a chill roll at a temperature of 10°C to 100°C to obtain an unstretched sheet. Next, it is roll-stretched in the longitudinal direction (MD direction) at 120°C to 165°C to 3.0 to 8.0 times its original size. Subsequently, after preheating in a tenter, it can be stretched in the transverse direction (TD direction) at a temperature of 155°C to 175°C to 4.0 to 20.0 times its original size. Furthermore, after biaxial stretching, a heat-setting treatment can be performed at a temperature of 165°C to 175°C while allowing for a relaxation of 1% to 15%.

[0025] In this invention, it is preferable that the heat shrinkage rate of the base film at 150°C for 5 minutes is 10% or less in both the MD direction and the TD direction. This stabilizes the dimensional change of the base material and further improves the quality during printing and lamination. Furthermore, it improves the appearance of the sealed portion when sealing the laminated structure. The heat shrinkage rate at 150°C for 5 minutes is preferably 8% or less, more preferably 7% or less, with a lower limit of 0%. If the heat shrinkage rate at 150°C for 5 minutes exceeds 10%, heat wrinkles and sagging are more likely to occur during processing, which may reduce the quality of the printed surface, laminated surface, and sealed surface. Furthermore, the heat shrinkage rate at 120°C for 5 minutes is preferably 0.8% or less, more preferably 0.7% or less, with a lower limit of -0.8%. If the heat shrinkage rate at 120°C for 5 minutes exceeds 1%, heat wrinkles and sagging are more likely to occur during processing, which may reduce the quality of the printed surface, laminated surface, and sealed surface.

[0026] In the present invention, it is preferable to incorporate particles into the base film to form protrusions on the film surface in order to impart handling properties (e.g., windability after lamination). Examples of particles to be incorporated into the film include inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, and alumina, and heat-resistant polymer particles such as acrylic, PMMA, nylon, polystyrene, polyester, and benzoguanamine-formaldehyde condensate. From the viewpoint of transparency, it is preferable that the particle content in the film be low, for example, 1 ppm to 1000 ppm. Furthermore, the preferred average particle diameter is 1.0 to 3.0 μm, and more preferably 1.0 to 2.7 μm. The method for measuring the average particle size here is to take a photograph with a scanning electron microscope, measure the horizontal Ferret diameter using an image analyzer, and display the average value. Furthermore, from the viewpoint of transparency, it is preferable to select particles with a refractive index close to that of the resin used. Furthermore, the film may contain antioxidants, ultraviolet absorbers, antistatic agents, dyes, lubricants, nucleating agents, adhesives, anti-fogging agents, flame retardants, anti-blocking agents, inorganic or organic fillers, etc., in order to impart various functions as needed.

[0027] Other materials besides the polypropylene resin used in this invention may be incorporated into the film, to the extent that they do not impair the objectives of this invention, for purposes such as improving the mechanical properties of the base film and the adhesion to the ink layer and adhesive layer laminated on the gas barrier coating layer. Examples include polypropylene resins other than those mentioned above, random copolymers which are copolymers of propylene and ethylene and / or α-olefins having 4 or more carbon atoms, and various elastomers.

[0028] In the present invention, the thickness of the base film can be arbitrarily set according to each application, but the lower limit is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 4 μm or more. On the other hand, the upper limit of the thickness is preferably 300 μm or less, more preferably 250 μm or less, even more preferably 200 μm or less, and particularly preferably 100 μm or less. If the thickness is too thin, handling is likely to be poor. On the other hand, if the thickness is too thick, not only are there cost issues, but when stored wound in a roll, poor flatness due to curling is likely to occur.

[0029] The haze of the polypropylene film used as the base material of the present invention is preferably transparent from the viewpoint of visibility of the contents, specifically preferably 6% or less, more preferably 5% or less, and even more preferably 4% or less. The haze tends to worsen when, for example, the stretching temperature or heat setting temperature is too high, the cooling roll (CR) temperature is high and the cooling rate of the stretched raw material sheet is slow, or there is too much low molecular weight, so it can be controlled within the above range by adjusting these factors.

[0030] Furthermore, the base film layer in the present invention may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, surface roughening treatment, etc., as long as the objective of the present invention is not impaired, and may also be subjected to known anchor coating treatments, printing, decoration, etc. Generally, it is preferable to use a resin with good adhesion, such as polyurethane or polyester, for the anchor coating.

[0031] [Coating layer] In the present invention, it is preferable to have a coating layer for the purpose of improving the gas barrier performance and adhesion of the base film. However, in the present invention, it is necessary to design with consideration to the fact that providing a coating layer increases costs due to the increased number of processes and imposes environmental burdens, such as difficulty in recycling depending on the film thickness.

[0032] The amount of coating layer attached is 0.10 to 0.50 (g / m²). 2) is preferable. When a coating layer using a polyvinyl alcohol - based copolymer and an inorganic layered compound described later is used for the above - mentioned polypropylene - based resin substrate, the inventors have found that by setting it within the range of the specific adhesion amount, all of gas barrier properties, coat appearance, adhesiveness, and recyclability can be achieved simultaneously. As a result, the coating layer can be uniformly controlled during coating, and as a result, a film with less coating unevenness and defects is obtained. Also, since the coating layer is thin, it can contribute to reducing foreign substances during recycling. The adhesion amount of the coating layer preferably has a lower limit of 0.15 (g / m 2 ) or more, more preferably 0.20 (g / m 2 ) or more, still more preferably 0.25 (g / m 2 ) or more, and an upper limit preferably of 0.45 (g / m 2 ) or less, more preferably 0.40 (g / m 2 ) or less, still more preferably 0.35 (g / m 2 ) or less. When the adhesion amount of the coating layer exceeds 0.50 (g / m 2 ), the gas barrier properties are improved, but the cohesive force inside the coating layer becomes insufficient, and the uniformity of the coating layer also decreases. As a result, unevenness (increase in haze, whitening) and defects may occur in the coat appearance, and the gas barrier properties and adhesiveness may not be fully exhibited. Also, in terms of processability, there is a risk of blocking due to the thick film thickness. Furthermore, there is a concern that it may have an adverse effect on the recyclability of the film. On the other hand, when the film thickness of the coating layer is less than 0.10 (g / m 2 ), there is a possibility that sufficient gas barrier properties and interlayer adhesion cannot be obtained.

[0033] A polyvinyl alcohol polymer is preferred as the resin composition used for the coating layer formed on the surface of the laminated film of the present invention. Polyvinyl alcohol polymers mainly consist of vinyl alcohol units, and a significant improvement in barrier performance can be expected due to their high cohesiveness based on hydrogen bonding structures. The degree of polymerization and degree of saponification of the polyvinyl alcohol polymer are determined based on the desired gas barrier properties and the viscosity of the coating aqueous solution. Regarding the degree of polymerization, a value of 2600 or less is preferred for ease of coating, as high aqueous solution viscosity and a tendency to gel make coating difficult. Regarding the degree of saponification, if it is less than 90%, sufficient oxygen gas barrier properties cannot be obtained under high humidity, and if it exceeds 99.7%, it is difficult to prepare the aqueous solution, and it is prone to gelation, making it unsuitable for industrial production. Therefore, a degree of saponification of 90 to 99.7% is preferred, and more preferably 93 to 99%. Furthermore, in the present invention, various copolymerized or modified polyvinyl alcohol polymers, such as polyvinyl alcohol polymers copolymerized with ethylene and polyvinyl alcohol polymers modified with silanol, can also be used, as long as they do not impair processability or productivity.

[0034] The coating layer of the present invention contains an inorganic layered compound. The presence of the inorganic layered compound is expected to create a labyrinthine effect on gases, thereby improving gas barrier properties. Furthermore, the addition of the inorganic layered compound can suppress the humidity dependence of the gas barrier properties. Examples of materials include clay minerals (including their synthetic products) such as smectite, kaolin, mica, hydrotalcite, and chlorite. Specifically, examples include montmorillonite, beiderite, saponite, hectorite, souconite, stevensite, kaolinite, nacrite, dickite, halloysite, hydrated halloysite, tetrasilicic mica, sodium teniolite, muscovite, margalite, phlogopite, talc, antigolite, chrysotile, pyrophyllite, vermiculite, xanthophyllite, and chlorite. In addition, flaky silica and the like can also be used as inorganic layered compounds. These may be used individually or in combination of two or more. Among these, smectite (including its synthetic products) is particularly preferred because of its high effectiveness in improving water vapor barrier properties.

[0035] Furthermore, as the inorganic layered compound, it is preferable that it contains redox metal ions, particularly iron ions. Among such compounds, montmorillonite, a type of smectite, is preferred in terms of coating suitability and gas barrier properties. As the montmorillonite, known types that have been conventionally used as gas barrier agents can be used. For example, the following general formula: (X,Y)2~3Z4O10(OH)2·mH2O·(Wω) (In the formula, X represents Al, Fe(III), or Cr(III). Y represents Mg, Fe(II), Mn(II), Ni, Zn, or Li. Z represents Si or Al. W represents K, Na, or Ca. H2O represents intercalated water. m and ω represent positive real numbers.) Among these, the one in which W in the formula is Na is preferred because it cleaves in an aqueous medium.

[0036] The size and shape of the inorganic layered compound are not particularly limited, but the particle size (longest diameter) is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less. If the particle size is larger than 5 μm, the dispersibility will be poor, which may result in deterioration of the coating properties and appearance of the coating layer. On the other hand, the aspect ratio is 50 to 5000, more preferably 100 to 4000, and even more preferably 200 to 3000.

[0037] The blending ratio of the polyvinyl alcohol copolymer to the inorganic layered compound in the coating layer of the present invention is preferably 75 / 25~35 / 65 (wt%), more preferably 70 / 30~40 / 60 (wt%), and even more preferably 65 / 35~45 / 55 (wt%). If the blending ratio of the inorganic layered compound is less than 25 wt%, the barrier performance may be insufficient. On the other hand, if it is more than 65 wt%, dispersibility will be poor, which may lead to deterioration of coating properties and adhesion.

[0038] In this invention, the total reflection infrared absorption spectrum of the coating layer is 1040±10 cm⁻¹. -1The peak intensity (P1) has an absorption maximum in the region and is 3300±10cm. -1 The ratio (P1 / P2) of peak intensities (P2) with absorption maxima in the region must be within the range of 3.0 to 25.0. Preferably, it is in the range of 4.0 to 24.0, and more preferably, in the range of 5.0 to 23.0. 1040±10cm -1 The peak is derived from the silica molecular structure and serves as an indicator of the amount of silica bonding originating from inorganic layered compounds in the coating layer. Also, 3300±10cm -1 The peak is derived from hydroxyl groups and serves as an indicator of the amount of hydroxyl groups in the coating layer. (P1 / P2) represents the ratio of silica bonds to hydroxyl groups. When this ratio is within the above range, silica particles are arranged in the film without inhibiting the hydrogen bonding of hydroxyl groups, resulting in maximum gas barrier performance. Adhesion can also be achieved simultaneously. If (P1 / P2) is less than 3.0, the amount of silica bonds in the coating layer is small, and the labyrinth effect cannot be obtained, making it difficult to obtain satisfactory gas barrier performance. In addition, the coating layer may become more prone to blocking in terms of processability. On the other hand, if (P1 / P2) exceeds 25.0, gas barrier performance improves, but the film becomes brittle, which is disadvantageous in terms of adhesion when used as a laminate. Furthermore, the dispersibility of the coating liquid deteriorates, raising concerns about poor appearance during coating (haze increase, whitening). In order to set the (P1 / P2) value of the coating layer within the predetermined numerical range, it is necessary to use the aforementioned materials to achieve the predetermined adhesion amount, furthermore, to set the material mixing ratio within the aforementioned appropriate range, and to combine this with the drying and heat treatment conditions described later.

[0039] The coating layer of the present invention may contain various crosslinking agents to improve the cohesive strength of the film and its resistance to moisture and heat adhesion, provided that such agents do not impair gas barrier properties or productivity. Examples of crosslinking agents include silicon-based crosslinking agents, oxazoline compounds, carbodiimide compounds, epoxy compounds, and isocyanate compounds. Among these, silicon-based crosslinking agents are particularly preferred from the viewpoint of improving water-resistant adhesion with the inorganic layer. Other crosslinking agents such as oxazoline compounds, carbodiimide compounds, and epoxy compounds may also be used in combination. However, if recyclability is a priority, it is preferable to add or omit as little crosslinking agent as possible.

[0040] In this invention, the film haze after lamination of the coating layer is preferably 20% or less, more preferably 18% or less, and even more preferably 16% or less, from the viewpoint of the visibility of the contents. If the haze is greater than 20%, in addition to a significant deterioration in transparency, there is a concern that it will also affect the surface irregularities, which may lead to poor appearance in subsequent printing processes, etc. The haze can be adjusted by the composition ratio of the coating layer, solvent conditions, film thickness, etc. Here, the haze was evaluated in accordance with JIS K7136, using a turbidimeter (NDH2000, manufactured by Nippon Denshoku).

[0041] The coating method for the resin composition for the coating layer is not particularly limited as long as it is a method of coating the film surface to form a layer. For example, conventional coating methods such as gravure coating, reverse roll coating, wire bar coating, and die coating can be used.

[0042] When forming the coating layer, it is preferable to apply the resin composition for the coating layer, pre-dry it at a relatively low temperature to first evaporate the solvent, and then perform the main drying at a high temperature, as this will result in a uniform film. The pre-drying temperature is preferably 80 to 110°C, more preferably 85 to 105°C, and even more preferably 90 to 100°C. If the pre-drying temperature is below 80°C, the coating layer may not dry completely. If the pre-drying temperature is above 110°C, drying may proceed before the coating layer has a chance to spread evenly, potentially resulting in a poor appearance.

[0043] On the other hand, the drying temperature is preferably 110 to 140°C, more preferably 115 to 135°C, and even more preferably 120 to 130°C. If the drying temperature is below 110°C, the formation of the coating layer will not proceed, reducing cohesiveness and adhesion, which may negatively affect the barrier properties. If the temperature exceeds 140°C, the film may be subjected to too much heat, making it brittle or causing large wrinkles due to thermal shrinkage.

[0044] The preferred drying time for pre-drying is 3.0 to 10.0 seconds, more preferably 3.5 to 9.5 seconds, and even more preferably 4.0 to 9.0 seconds. Similarly, the preferred drying time for the main drying is 3.0 to 10.0 seconds, more preferably 3.5 to 9.5 seconds, and even more preferably 4.0 to 9.0 seconds. However, it is important to note that the drying conditions may vary depending on the type of heat transfer medium and the intake and exhaust conditions of the drying oven. In addition to drying, applying an additional heat treatment for 1 to 4 days at the lowest possible temperature range, specifically 40 to 60°C, is also more effective in promoting the formation of the coating layer.

[0045] [Inorganic thin film layer] In the present invention, an inorganic thin film layer (A) may be provided on the surface of the substrate film for the purpose of improving gas barrier performance. The inorganic thin film layer (A) is a thin film made of a metal or an inorganic oxide. The material used to form the inorganic thin film layer is not particularly limited as long as it can be made into a thin film, but from the viewpoint of gas barrier properties, inorganic oxides such as silicon dioxide (silica), aluminum oxide (alumina), and mixtures of silicon dioxide and aluminum oxide are preferred. In particular, a composite oxide of silicon dioxide and aluminum oxide is preferred because it can achieve both flexibility and density in the thin film layer. In this composite oxide, the mixing ratio of silicon dioxide and aluminum oxide is preferably in the range of 20 to 70% by mass of Al in terms of the mass ratio of the metal content. If the Al concentration is less than 20% by mass, the water vapor barrier properties may be low. On the other hand, if it exceeds 70% by mass, the inorganic thin film layer tends to harden, and there is a risk that the film will be destroyed during secondary processing such as printing or lamination, reducing the gas barrier properties. In this context, silicon oxide refers to various silicon oxides such as SiO and SiO2, or mixtures thereof, while aluminum oxide refers to various aluminum oxides such as AlO and Al2O3, or mixtures thereof.

[0046] The thickness of the inorganic thin film layer (A) is typically 1 to 100 nm, preferably 5 to 50 nm. If the thickness of the inorganic thin film layer (A) is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties. On the other hand, if it is made excessively thick beyond 100 nm, the corresponding improvement in gas barrier properties cannot be obtained, and it may even be disadvantageous in terms of flexibility and manufacturing costs.

[0047] There are no particular restrictions on the method for forming the inorganic thin film layer (A). For example, any known deposition method such as vacuum deposition, sputtering, ion plating, or other physical deposition methods (PVD), or chemical deposition (CVD), can be used as appropriate. Below, a typical method for forming the inorganic thin film layer (A) will be described using a silicon oxide / aluminum oxide thin film as an example. For example, when using vacuum deposition, a mixture of SiO2 and Al2O3, or a mixture of SiO2 and Al, is preferably used as the deposition raw material. These deposition raw materials are usually particles, and it is desirable that the size of each particle is such that the pressure during deposition does not change, with a preferred particle size of 1 mm to 5 mm. For heating, methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be used. It is also possible to use reactive deposition by introducing oxygen, nitrogen, hydrogen, argon, carbon dioxide, water vapor, etc. as a reaction gas, or by using means such as ozone addition or ion assistance. Furthermore, the film deposition conditions can be arbitrarily changed, such as by applying a bias to the substrate (the laminated film used for deposition) or by heating or cooling the substrate. These deposition materials, reaction gases, bias, heating / cooling of the substrate can also be similarly modified when using sputtering or CVD methods.

[0048] [Anchor coating layer for permanent thin films] The laminate of the present invention may have an anchor coat layer between the base film layer and the inorganic thin film layer (A) for the purpose of ensuring stable gas barrier properties and laminate strength. Examples of resin compositions used for the anchor coat layer between the base film layer and the inorganic thin film layer include resins such as urethane, polyester, acrylic, titanium, isocyanate, imine, and polybutadiene, to which curing agents such as epoxy, isocyanate, melamine, oxazoline, and carbodiimide are added. Furthermore, it is preferable to include a silane coupling agent having at least one type of organic functional group for the purpose of improving adhesion with the inorganic layer.

[0049] The method for forming the anchor coat layer is not particularly limited, and conventionally known methods such as coating methods can be employed. Among coating methods, preferred methods include the offline coating method and the in-line coating method. For example, in the case of the in-line coating method performed in the process of manufacturing the base film layer, the drying and heat treatment conditions during coating depend on the coating thickness and the conditions of the equipment, but it is preferable to immediately send the material to the stretching process in a perpendicular direction after coating and dry it in the preheating zone or stretching zone of the stretching process, and in such cases it is usually preferable to set the temperature to about 50 to 250°C.

[0050] [Protective layer on an infinitely thin film] In the present invention, a protective layer may be provided on the inorganic thin film layer. The inorganic thin film layer, which consists of a metal oxide layer, is not a completely dense film, but has minute defects scattered throughout. By coating the metal oxide layer with a specific protective resin composition described later to form a protective layer, the resin in the protective resin composition penetrates into the defects in the metal oxide layer, resulting in the effect of stabilizing the gas barrier properties. In addition, by using a material that also has gas barrier properties for the protective layer itself, the gas barrier performance of the laminated film is also improved.

[0051] In this invention, the amount of protective layer to adhere is 0.10 to 0.40 (g / m²). 2 It is preferable to have a protective layer of 0.13 g / m². This allows for uniform control of the protective layer during coating, resulting in a film with fewer coating inconsistencies and defects. Furthermore, the cohesive force of the protective layer itself is improved, and the adhesion between the inorganic thin film layer and the protective layer becomes stronger. The amount of protective layer attached is preferably 0.13 g / m². 2 ) or more, more preferably 0.16 (g / m³) 2 ) or more, more preferably 0.19 (g / m³) 2 ) or more, preferably 0.37 (g / m³) 2 ) or less, more preferably 0.34 (g / m³) 2 ) or less, more preferably 0.31 (g / m³) 2 ) or less. The amount of protective layer adhered is 0.400 (g / m²). 2When the thickness exceeds 0.10 (g / m²), the gas barrier properties improve, but the cohesive force within the protective layer becomes insufficient, and the uniformity of the protective layer also decreases, which may result in unevenness or defects in the appearance of the coating, or insufficient gas barrier properties and adhesion. On the other hand, when the thickness of the protective layer exceeds 0.10 (g / m²), the gas barrier properties improve, but the cohesive force within the protective layer becomes insufficient, and the uniformity of the protective layer also decreases, which may result in unevenness or defects in the appearance of the coating, or insufficient gas barrier properties and adhesion. 2 If the value is less than ), sufficient gas barrier properties and interlayer adhesion may not be obtained.

[0052] As the resin composition used for the protective layer formed on the surface of the inorganic thin film layer of the laminate of the present invention, resins such as urethane, polyester, acrylic, titanium, isocyanate, imine, and polybutadiene can be used, and further curing agents such as epoxy, isocyanate, and melamine may be added.

[0053] The coating method for the protective layer resin composition is not particularly limited as long as it is a method of coating the film surface to form a layer. For example, conventional coating methods such as gravure coating, reverse roll coating, wire bar coating, and die coating can be used.

[0054] When forming a protective layer, it is preferable to apply the protective layer resin composition and then heat-dry it, with a preferred drying temperature of 100 to 160°C, more preferably 110 to 150°C, and even more preferably 120 to 140°C. If the drying temperature is below 100°C, the protective layer may not dry sufficiently, or the film formation of the protective layer may not proceed, reducing cohesive strength and water-resistant adhesion, which may result in reduced barrier properties and tear resistance. On the other hand, if the drying temperature exceeds 160°C, the film may be overheated, making it brittle, reducing puncture strength, or shrinking, resulting in poor processability. It is particularly preferable to first evaporate the solvent at a relatively low temperature of 90°C to 110°C immediately after application, and then dry the protective film at 130°C or higher, as this yields a uniform and transparent film. In addition to drying, applying an additional heat treatment in the lowest possible temperature range is also more effective in promoting the formation of the protective layer.

[0055] [Heat-sealable resin layer] When the laminated film of the present invention is used as a packaging material, it is necessary to form a laminate with a heat-sealable resin layer called a sealant. The heat-sealable resin layer is usually formed by extrusion lamination or dry lamination. The thermoplastic polymer used to form the heat-sealable resin layer can be any polymer that exhibits sufficient sealant adhesion, but polyethylene resins such as olefin-based HDPE, LDPE, and LLDPE, polypropylene resin, ethylene-vinyl acetate copolymer, ethylene-α-olefin random copolymer, ionomer resin, etc., can be used. Among these, LLDPE or polypropylene resin is particularly preferred because of its high versatility from the viewpoint of durability, seal strength, cost, and monomaterialization. The thickness of the sealant layer is preferably 20 to 80 μm, more preferably 25 to 75 μm, and more preferably 30 to 70 μm. If the thickness is thinner than 20 μm, sufficient seal strength may not be obtained, and it may be difficult to handle due to a lack of stiffness. On the other hand, if the thickness exceeds 80 μm, the material becomes too stiff, reducing its handling properties as a bag, and requiring higher temperatures for sealing, which may cause heat wrinkles in the outer base film. Furthermore, the price may also increase.

[0056] [Adhesive layer] The adhesive layer used in this invention can be any general-purpose laminating adhesive. For example, solvent-free, water-based, or heat-melt adhesives mainly composed of poly(ester)urethane, polyester, polyamide, epoxy, poly(meth)acrylic, polyethyleneimine, ethylene-(meth)acrylic acid, polyvinyl acetate, (modified) polyolefin, polybutadiene, wax, or casein can be used. Among these, urethane or polyester adhesives are preferred considering heat resistance and flexibility to follow dimensional changes of each substrate. The adhesive layer can be applied by methods such as direct gravure coating, reverse gravure coating, kiss coating, die coating, roll coating, dip coating, knife coating, spray coating, fontein coating, or other methods, and the coating amount after drying is 1 to 8 g / m² to achieve sufficient adhesion.2 Preferred. More preferably 2-7 g / m 2 More preferably 3-6 g / m 2 The coating amount is 1 g / m². 2 If the amount is less than 8 g / m², it becomes difficult to bond the entire surface, and the adhesive strength decreases. 2 Beyond this point, complete curing of the film takes longer, unreacted material is more likely to remain, and the adhesive strength decreases.

[0057] Furthermore, the laminated film of the present invention may have at least one printed layer laminated between or outside the base film layer and the heat-sealable resin layer.

[0058] Water-based and solvent-based resin-containing printing inks are preferably used as the printing ink for forming the printed layer. Examples of resins used in the printing ink include acrylic resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate copolymer resins, and mixtures thereof. The printing ink may contain known additives such as antistatic agents, light-blocking agents, ultraviolet absorbers, plasticizers, lubricants, fillers, colorants, stabilizers, lubricants, defoaming agents, crosslinking agents, anti-blocking agents, and antioxidants. The printing method for forming the printed layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. For drying the solvent after printing, known drying methods such as hot air drying, hot roll drying, and infrared drying can be used.

[0059] [Characteristics of laminated materials]

[0060] The laminated material of the present invention has an oxygen permeability of 20 ml / m² under conditions of 23°C × 65%RH. 2 A gas barrier pressure of d·MPa or less is preferable for exhibiting good gas barrier properties. Furthermore, by providing a barrier layer on each film, a pressure of 18 ml / m² is preferable. 2 • d·MPa or less, more 16 ml / m³ 2 It can be set to d·MPa or less. Oxygen permeability of 20 ml / m³ 2Above d·MPa, it becomes difficult to meet the requirements for applications demanding high gas barrier properties. On the other hand, if the oxygen permeability is 0.5 ml / m³ in all cases... 2 If the oxygen permeability is less than d·MPa, although the barrier performance is excellent, residual solvent will not easily permeate to the outside of the bag, and the amount transferred to the contents may increase relatively, which is undesirable. The preferred lower limit for oxygen permeability is 0.5 ml / m³. 2 It is d·MPa or higher.

[0061] The laminates of the present invention all exhibit a water vapor transmission rate of 2.0 g / m² under 40°C × 90% RH conditions. 2 A value of d or less is preferable in terms of exhibiting good gas barrier properties. Furthermore, by providing a barrier layer on each film, a value of 1.8 g / m² is preferred. 2 • d or less, more preferably 1.6 g / m 2 It can be less than or equal to d. Water vapor transmission rate of 2.0 g / m³ 2 If the value exceeds d, it becomes difficult to meet the requirements for applications that demand high gas barrier properties. On the other hand, if the water vapor transmission rate is 0.1 g / m³ 2 If the value is less than 0.1 g / m³, while the barrier performance is excellent, residual solvent will not easily permeate to the outside of the bag, which may relatively increase the amount transferred to the contents, so this is undesirable. The preferred lower limit for water vapor permeability is 0.1 g / m³. 2 It is d or higher.

[0062] The laminated material of the present invention preferably has a puncture strength of 15N or higher, more preferably 16N or higher, and even more preferably 17N or higher, as measured in accordance with JIS Z1707. If the puncture strength is less than 15N, when used as a bag, if an external load is applied while a heavy object is placed inside, a hole may form and the contents may leak out.

[0063] It is preferable that the heat seal strength of the laminated structure of the present invention, when heat-sealed at a temperature of 160°C, a seal bar pressure of 0.2 MPa, and a sealing time of 2 seconds, is 15 N / 15 mm or more. If the heat seal strength is less than 15 N / 15 mm, the sealed portion will easily peel off, limiting its use as a packaging bag, such as making it unsuitable for applications with large contents. A heat seal strength of 16 N / 15 mm or more is preferable, and 17 N / 15 mm or more is more preferable.

[0064] The laminate of the present invention preferably has a shrinkage rate of 1.8% or less when heat-treated at 120°C for 5 minutes, in both the MD direction and the TD direction of the base film. By keeping the shrinkage rate within this range, the appearance of the sealed portion when the laminate is sealed is improved. The heat shrinkage rate at 120°C for 5 minutes is preferably 1.7% or less, more preferably 1.6% or less, and even more preferably 1.5% or less. If the shrinkage rate exceeds 1.8%, heat-induced wrinkles are more likely to occur during sealing, which may reduce the quality of the sealed surface.

[0065] The laminated structure of the present invention is expected to have improved toughness and gas barrier performance as a laminated structure by laminating two stretched base films made from polypropylene resin. In terms of toughness, by using two polypropylene stretched films, which generally have high puncture strength, it is possible to design packaging materials that are comparable to, for example, two different material configurations using PET and nylon films, which are widely used as packaging materials. Furthermore, in terms of gas barrier performance, by using two base films, the intermediate film becomes less susceptible to the influence of the external environment, such as temperature, humidity, and external bending, and can exhibit more stable gas barrier performance. In this sense, it is particularly preferable that the coating layer or indestructible thin film layer having gas barrier properties is laminated on the intermediate film.

[0066] The laminated material of the present invention preferably has a puncture strength of 15N or higher. By setting the puncture strength within this range, toughness equivalent to that of commonly used laminated materials composed of PET and nylon film can be obtained. The puncture strength is preferably 16N or higher, more preferably 17N or higher, and even more preferably 18N or higher. If the puncture strength is less than 15N, the strength when made into a bag will be insufficient, which may cause pinholes or the like to occur in protruding or bent portions.

[0067] As an evaluation criterion for monomaterialization in the laminated material of the present invention, when the ratio of the thickness of the olefin-based material to the total thickness of each film and adhesive is calculated as the monomaterial (monomate) ratio, it is preferable that the monomate ratio is 85% or higher. More preferably, it is 87.5%, and even more preferably, 90%. By setting the monomate ratio within this range, a packaging material structure that is easy to recycle can be made. If the monomate ratio is less than 85%, recycling may become difficult due to foreign matter from other materials.

[0068] In the laminated structure of the present invention, the total thickness of each film and adhesive is preferably 50 to 140 μm. More preferably 55 to 135 μm, and even more preferably 60 to 130 μm. By setting the total thickness of the laminated structure within this range, a packaging structure that exhibits necessary physical properties such as puncture strength and barrier performance can be created. If the total thickness is less than 50 μm, the bag will not have sufficient toughness, and there is a risk that the bag will tear or get punctured. On the other hand, if the total thickness exceeds 140 μm, it will become stiff and difficult to handle, and it will also lead to an increase in the cost of the packaging structure, which is not economically desirable. [Examples]

[0069] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. Various evaluations were performed using the following measurement methods.

[0070] (1) Thickness of various films Measurements were taken using a dial gauge in accordance with JIS K7130-1999 Method A.

[0071] (2) Composition and film thickness of the inorganic thin film layer The film thickness composition of the laminated films (after thin film lamination) obtained in the examples and comparative examples was measured using a fluorescent X-ray analyzer (Rigaku Corporation's "ZSX100e") according to a pre-prepared calibration curve. The excitation X-ray tube conditions were set to 50kV and 70mA.

[0072] (3) Amount of coating layer In each example and comparative example, the laminated film obtained at the stage of laminating an indeterminate thin film layer or coating layer onto a base film was used as a sample. A 100 mm × 100 mm test piece was cut from this sample, the coating layer was wiped off with ethanol, and the amount of adhesion was calculated from the change in mass of the film before and after wiping.

[0073] (4) Evaluation of the shrinkage rate of the base film by heating at 150°C for 5 minutes. In each example and comparative example, a test specimen with a width of 20 mm and a length of 300 mm is prepared so that the measurement direction (MD or TD) of the prepared base film is the longer side, and a gauge mark is made at a distance of 200 mm from the center of the test specimen. Then, the distance between the gauge marks is read to one decimal place using a metal ruler to determine the gauge mark distance A before heating. Next, the end of this test specimen is clipped and suspended from a metal bar, and placed in a heating oven heated to 150°C ± 1°C for 5 minutes. After heating, the gauge mark distance of the removed test specimen is read using a metal ruler in the same way as before heating to determine the gauge mark distance B after heating. Based on the obtained values, the heat shrinkage rate is calculated using the following formula. Heat shrinkage rate (%) = (AB) / A × 100

[0074] [Fabrication of laminated structures] (6) Preparation of laminated samples for evaluation When using a single base film, a polyurethane adhesive (TM569 / cat10L manufactured by Toyo Morton Co., Ltd.) was applied to the base film described in the Examples and Comparative Examples to a thickness of 3 μm after drying at 80°C. Then, an unstretched polypropylene film (P1128 manufactured by Toyobo; thickness 30 μm; referred to as CPP) was dry-laminated as a heat-sealable resin on a metal roll heated to 60°C, and aged at 40°C for 4 days to obtain a laminated structure for evaluation. On the other hand, when two base films were used, a polyurethane adhesive (TM569 / cat10L manufactured by Toyo Morton Co., Ltd.) was applied to the base film described in the Examples and Comparative Examples so that the thickness after drying at 80°C was 3 μm. Then, the other base film was dry-laminated on a metal roll heated to 60°C to form a winding roll. The same adhesive was applied to this roll so that the thickness after drying at 80°C was 3 μm. Then, an unstretched polypropylene film (P1128 manufactured by Toyobo; thickness 30 μm; referred to as CPP) was dry-laminated on a metal roll heated to 60°C as a heat-sealable resin, and aged at 40°C for 4 days to obtain a laminated structure for evaluation.

[0075] (7) Method for evaluating the oxygen permeability of laminated structures For the laminated structures prepared in (6) above, the oxygen permeability was measured in accordance with JIS-K7126 Method B using an oxygen permeability measuring device (MOCON Corporation's "OX-TRAN(registered trademark) 2 / 22") under an atmosphere of 23°C and 65% RH. The oxygen permeability was measured in the direction in which oxygen permeates from the base film side to the heat-sealable resin layer side of the laminated structure.

[0076] (8) Method for evaluating the water vapor transmission rate of laminated structures For the laminated structures prepared in (6) above, the water vapor transmission rate was measured in accordance with JIS-K7129 Method B using a water vapor transmission rate measuring device (MOCON "PERMATRAN-W 3 / 33MG") under an atmosphere of 40°C and 90% RH. The water vapor transmission rate was measured in the direction in which water vapor permeated from the heat-sealable resin layer side of the laminated structure toward the base film side.

[0077] (9) Method for evaluating the heat seal strength of laminated structures The laminated material prepared in (6) above was subjected to heat seal strength measurement in accordance with JIS Z1707. The specific procedure is as follows: The heat seal surfaces of the samples were bonded together using a heat sealer. The heat sealing conditions were: upper bar temperature 160°C, lower bar temperature 30°C, pressure 0.2 MPa, and time 2 seconds. The bonded samples were cut to a seal width of 15 mm. The peel strength was measured using a universal tensile testing machine "DSS-100" (manufactured by Shimadzu Corporation) at a tensile speed of 200 mm / min. The peel strength is expressed as strength per 15 mm (N / 15 mm). For the evaluation of the seal appearance, a relative evaluation was performed, with ○ indicating a wrinkle-free seal, △ indicating partial wrinkles, and × indicating wrinkles throughout the entire surface.

[0078] (10) Method for evaluating the puncture strength of laminated structures The laminated material prepared in (6) above was sampled in 5cm squares, and the puncture strength of the film was measured in accordance with JIS Z1707 using an IMADA Corporation digital force gauge "ZTS-500N", an electric measuring stand "MX2-500N", and a puncture jig "TKS-250N". (11) Method for evaluating the heat shrinkage rate of laminated materials at 120°C for 5 minutes Prepare a test specimen with a width of 20 mm and a length of 300 mm, such that the measurement direction of the laminated material prepared in (6) above (MD or TD direction of the bonded base film) is the longer side, and mark a gauge point at a distance of 200 mm from the center of the test specimen. Then, read the distance between the gauge points to one decimal place using a metal ruler to determine the gauge point distance A before heating. Next, clip the ends of this test specimen and suspend it from a metal bar, then place it in a heating oven heated to 120°C ± 1°C for 5 minutes. After heating, read the gauge point distance of the removed test specimen using a metal ruler in the same way as before heating to determine the gauge point distance B after heating. Based on the obtained values, calculate the heat shrinkage rate using the following formula. Heat shrinkage rate (%) = (AB) / A × 100

[0079] (12) Evaluation criteria for monomaterialization: monomaterial ratio For the laminated structures prepared in (6) above, the ratio of the thickness of the olefin-based material to the total thickness of each film and adhesive was calculated as the monomaterial ratio. (13) Criteria for evaluating visibility and range suitability For the laminated structures prepared in (6) above, a transparent laminated structure was marked with a circle (○) as an evaluation criterion for visibility and range suitability.

[0080] The stretched substrate films used in this example and comparative example are listed below. These were used in Examples 1-6 and Comparative Examples 1-7, and are shown in Table 1. [Preparation of base film] Tables 1-4 show the details of the polypropylene resin raw materials used in the production of the polyolefin-based films described below, as well as the film manufacturing conditions and raw material mixing ratios.

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3]

[0084] [Table 4]

[0085] (OPP-1) For the base layer (A), the polypropylene homopolymer PP-1 shown in Table 1 was used. Furthermore, the surface layer (B) used a mixture of PP-1, a polypropylene homopolymer shown in Table 1, at a ratio of 96.4% by weight, and masterbatch A, shown in Table 2, at a ratio of 3.6% by weight. For the surface layer (C), a mixture of PP-1, a polypropylene homopolymer shown in Table 1, and masterbatch A, shown in Table 2, was used in a ratio of 94.0% by weight and 6.0% by weight. The base layer (A) was produced using a 45 mm extruder, the surface layer (B) using a 25 mm extruder, and the surface layer (C) using a 20 mm extruder. In each case, the raw resin was melted at 250°C and co-extruded into a sheet from a T-die. After cooling and solidifying so that the surface layer (B) was in contact with a cooling roll at 30°C, the film was stretched 4.5 times in the longitudinal direction (MD) at 135°C. Next, in a tenter, both ends in the width direction (TD) of the film were clamped with clips, preheated to 173°C, stretched 8.2 times in the width direction (TD) at 164°C, and then heat-set at 171°C while relaxing by 6.7% in the width direction (TD). The film-forming conditions at this time are referred to as film-forming condition a. Details of these film-forming conditions are shown in Table 3. Thus, a biaxially oriented polypropylene film with a surface layer (B) / substrate layer (A) / surface layer (C) configuration was obtained. The surface of the biaxially oriented polypropylene film surface layer (B) was corona treated using a corona treatment machine manufactured by Softal Corona & Plasma GmbH at an applied current of 0.75 A, and then wound up with a winder. The thickness of the resulting film was 20 μm (the thickness of the surface layer (B) / substrate layer (A) / surface layer (C) was 1.0 μm / 18.0 μm / 1.0 μm). The details of this configuration are shown in Table 4.

[0086] (OPP-2) The base layer (A) consisted of 40.0% by weight of polypropylene homopolymer PP-2 shown in Table 1 and 60.0% by weight of polypropylene homopolymer PP-3 shown in Table 1. Furthermore, the surface layer (B) used a mixture of PP-3, a polypropylene homopolymer shown in Table 1, at a ratio of 96.4% by weight, and masterbatch A, shown in Table 2, at a ratio of 3.6% by weight. For the surface layer (C), a mixture of PP-3, a polypropylene homopolymer shown in Table 1, and masterbatch A, shown in Table 2, was used in a ratio of 94.0% by weight and 6.0% by weight. The base layer (A) was produced using a 45 mm extruder, the surface layer (B) using a 25 mm extruder, and the surface layer (C) using a 20 mm extruder. The raw resin was melted at 250°C in each case, and co-extruded into a sheet from a T-die. After cooling and solidifying so that the surface layer (B) was in contact with a cooling roll at 30°C, the film was stretched 4.5 times in the longitudinal direction (MD) at 125°C. Next, in a tenter, both ends in the width direction (TD) of the film were clamped with clips, preheated to 168°C, stretched 8.2 times in the width direction (TD) at 155°C, and then heat-set at 165°C while relaxing by 6.7% in the width direction (TD). The film-forming conditions at this time were designated as film-forming condition b. Details of these film-forming conditions are shown in Table 3. Thus, a biaxially oriented polypropylene film with a surface layer (B) / substrate layer (A) / surface layer (C) configuration was obtained. The surface of the biaxially oriented polypropylene film surface layer (B) was corona treated using a corona treatment machine manufactured by Softal Corona & Plasma GmbH at an applied current of 0.75 A, and then wound up with a winder. The thickness of the resulting film was 20 μm (the thickness of the surface layer (B) / substrate layer (A) / surface layer (C) was 1.0 μm / 18.0 μm / 1.0 μm). The details of this configuration are shown in Table 4.

[0087] The details of the coating liquid used for forming the coating layer in this example and comparative example are described below. These were used in Examples 1-6 and Comparative Examples 1-7, and are shown in Table 5.

[0088] [Polyvinyl alcohol resin (A)] 90 parts by mass of purified water were mixed with 10 parts by mass of fully saponified polyvinyl alcohol resin (manufactured by Nippon Synthetic Chemical Co., Ltd., trade name: G Polymer OKS8049Q, (saponification degree 99.0% or higher, average degree of polymerization 450)). The mixture was heated to 80°C while stirring, and then stirred for approximately 1 hour. After that, it was cooled to room temperature to obtain a nearly transparent polyvinyl alcohol solution (PVA solution) with a solid content of 10%.

[0089] [Inorganic layered compound dispersion (B)] Five parts by mass of montmorillonite (trade name: Kunipia F, manufactured by Kunimine Industries Co., Ltd.), an inorganic layered compound, were added to 95 parts by mass of purified water while stirring, and thoroughly dispersed using a homogenizer at a setting of 1500 rpm. The mixture was then incubated at 23°C for one day to obtain a dispersion of the inorganic layered compound with a solid content of 5%.

[0090] [Coating liquid 1 for use in the coating layer] The following materials were mixed in the specified proportions to create a coating solution (resin composition for the coating layer). Ion-exchanged water 15.00% by mass Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 30.00% by mass Inorganic layered compound dispersion (B) 40.00% by mass

[0091] [Coating liquid used for the coating layer 2] The following materials were mixed in the specified proportions to create a coating solution (resin composition for the coating layer). Ion-exchanged water 15.00% by mass Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 70.00% by mass

[0092] [Coating liquid 3 for use in the coating layer] The following materials were mixed in the mass ratio shown below and stirred for at least 30 minutes to dissolve. Then, undissolved material was removed using a filter with a nominal filtration accuracy of 50 μm to prepare a coating solution (resin composition for the coating layer). Ion-exchanged water 37.50% by mass Polyvinylidene chloride resin (C) 62.50% by mass (Saran latex L557 manufactured by Asahi Kasei Chemicals, solids content ratio 48%)

[0093] (Coating the film with a coating solution (lamination of coating layers)) The coating solution prepared above was applied by gravure roll coating to the corona-treated surface of the substrate film or to the inorganic thin film layer of the inorganic thin film described later. After pre-drying at 90°C for 4 seconds, it was fully dried at 120°C for 4 seconds to obtain a coating layer. Subsequently, a post-heat treatment was performed at 40°C for 2 days. In this manner, a laminated film with a coating layer was fabricated.

[0094] The following describes the method for preparing the inorganic thin film layer (A) used in each example and comparative example. The layers used in Examples 1-6 and Comparative Examples 1-7 are shown in Table 5.

[0095] (Formation of inorganic thin film layer A-1) As the inorganic thin film layer A-1, aluminum oxide was deposited onto the substrate film layer. The method for depositing aluminum oxide onto the substrate film layer involved setting the film on the unwinding side of a continuous vacuum deposition machine and winding the film through a cooling metal drum. At this time, the pressure of the continuous vacuum deposition machine was reduced to 10⁻⁴ Torr or less, and 99.99% pure metallic aluminum was loaded into an alumina crucible from the bottom of the cooling drum. The metallic aluminum was heated and evaporated, and oxygen was supplied into the vapor to cause an oxidation reaction, causing it to adhere and deposit onto the film, forming an aluminum oxide film with a thickness of 10 nm.

[0096] (Formation of inorganic thin film layer A-2) As inorganic thin film layer A-2, a composite oxide layer of silicon dioxide and aluminum oxide was formed on the substrate film layer by electron beam deposition. Particulate SiO2 (99.9% purity) and A12O3 (99.9% purity) of approximately 3mm to 5mm in size were used as deposition sources. The thickness of the inorganic thin film layer (SiO2 / A12O3 composite oxide layer) in the resulting film (inorganic thin film layer / coating layer-containing film) was 13nm. The composition of this composite oxide layer was SiO2 / A12O3 (mass ratio) = 60 / 40.

[0097] As described above, a film laminate was fabricated with a coating layer or an inorganic thin film layer on each film.

[0098] In each example and comparative example, the respective film laminates were bonded together using the dry lamination method with the aforementioned adhesive to produce laminated laminates with the configurations shown in Table 5. For the comparative example, a transparent vapor-deposited polyester film (Toyobo VE100-12μm; vapor-deposited PET) and a biaxially oriented polyamide film (Toyobo N1100-15μm; NY) were used as the base film. An aluminum vapor-deposited unoriented polypropylene film (Toray Processing 2703-25μm; VM-CPP) was used as the heat-sealable resin layer. The configurations of the fabricated laminated laminates are shown in Table 5. Various evaluations were also performed on the obtained laminated laminates. The results are shown in Table 5.

[0099] [Table 5A]

[0100] [Table 5B] [Industrial applicability]

[0101] The present invention significantly improves gas barrier performance by creating a laminated film in which a predetermined coating layer tailored to the required performance is laminated onto a polypropylene-based stretched substrate film. Furthermore, by laminating two of these laminated films together, toughness and heat resistance can be ensured, and finally, by laminating with a sealant made of olefin components, monomaterialization is achieved while maintaining high sealing performance. Moreover, since the laminated film of the present invention can be manufactured easily with few processing steps, it is excellent in both economic efficiency and production stability, and can provide a gas barrier laminate with homogeneous properties.

Claims

1. A laminated laminate comprising two stretched base films made from polypropylene resin and one heat-sealable unstretched resin layer laminated via an adhesive, wherein at least one of the base films is a laminated film having a coating layer or inorganic thin film layer having a polyvinyl alcohol copolymer and an inorganic layered compound on one side, and the heat-sealable resin layer is made of an olefin resin mainly composed of polypropylene or polyethylene resin, and the laminated laminate satisfies the following requirements (a) to (d). (a) The puncture strength of the laminate is 15 N or more. (b) The oxygen permeability of the laminated structure at 23°C × 65% RH is 20 ml / m². ２ - Water vapor transmission rate of 2.0 g / m³ under conditions of d MPa or less and 40°C × 90% RH. ２ - It must be less than or equal to d. (c) The seal strength when the heat-seal layers of the laminate are heat-sealed together at 160°C, 0.2 MPa, and for 2 seconds is 15 N / 15 mm or more. (d) The shrinkage rate of the laminated structure when heated at 120°C for 5 minutes is 1.8% or less in both the MD direction and the TD direction of the base film.

2. The laminate according to claim 1, characterized in that the inorganic layered compound of the coating layer contains a montmorillonite-based compound as a constituent component.

3. The amount of the coating layer is 0.10 g / m². ２ 0.50g / m or more ２ The laminate according to claim 1 or 2, characterized in that it is as follows.

4. The laminate according to any one of claims 1 to 3, characterized in that the inorganic thin film layer is a layer made of aluminum oxide, silicon oxide, or a composite oxide of silicon oxide and aluminum oxide.

5. The laminate according to any one of claims 1 to 4, characterized in that at least one of the base films is a base film having a heat shrinkage rate of 10% or less in both the MD direction and the TD direction when heated at 150°C for 5 minutes.

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