Laminated packaging material

Abstract

To provide a packaging material that can form a packaging material composed of resin types with low environmental impact, can improve the gas barrier performance and durability required for packaging materials, and has a low amount of volatile components.SOLUTION: A laminated packaging material comprises at least one base film having a resin layer comprising a polyolefin-based resin as a main constituent component, an adhesive layer, and a heat-sealable resin layer, wherein at least one of the base films is a laminated gas barrier film having a gas barrier layer, an oxygen permeability value (A) of 30 to 1500 ml / m2 d MPa is obtained when a base film (a) having the lowest oxygen permeability among the laminated base films alone is measured under conditions of 23°C×65%RH, an oxygen permeability value (P) of 60 ml / m2 d MPa or less is obtained when a laminated packaging material (p) formed by bonding the base film to a heat-sealable resin via the adhesive layer is measured under the same conditions, and a barrier value improvement rate before and after bonding represented by the following formula (1) is 10 or more: barrier value improvement rate before and after film bonding=(A / P) Formula (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated packaging material used in the packaging fields of foods, pharmaceuticals, industrial products, etc. More specifically, it relates to an environmentally friendly laminated packaging material that is excellent in gas barrier properties, processability, and toughness, and is convenient to use. [Background technology]

[0002] In recent years, regulations aimed at reducing the use of disposable plastics have been strengthened in Europe and other countries around the world. Behind this trend is growing international awareness of resource recycling and the worsening waste problems in emerging countries. As a result, there is a demand for environmentally friendly products that comply with the 3Rs (recycle, reuse, reduce) when it comes to plastic packaging materials for food, pharmaceuticals, etc.

[0003] One possibility for making packaging materials more environmentally friendly is to make them from the same recyclable material, i.e., to make them mono-material. For example, polyester-based or polyolefin-based materials are being considered as materials for making mono-materials.

[0004] While there is a demand for packaging materials with a low environmental impact, as mentioned above, the current situation is that the properties required of packaging materials themselves are becoming increasingly multifunctional for convenience. For example, a pouch that does not use aluminum foil and can be used in a microwave oven must simultaneously have gas barrier properties, heat resistance, toughness (bag tear resistance and pinhole resistance), and high sealability. To achieve this, it is necessary to bond different materials, each with different functions, together. A typical structure is at least three layers, with a vapor-deposited polyester film on the outside, a polyamide film in the middle, and a polyolefin-based heat-sealable resin dry-laminated with an adhesive on the inside (content side). While this structure can achieve the desired performance, the bonding of different materials results in poor recyclability, making it less than the aforementioned environmentally friendly packaging material.

[0005] Taking these points into consideration, research is underway to determine whether it is possible to design an ideal packaging material that has the multifunctionality of a bag, as described above, using the same material that can be made into a monomaterial.

[0006] In the design of polyester-based monomaterial packaging materials, a polyester-based sealant with improved low adsorption and heat resistance has been disclosed as an alternative to conventional polyolefin-based sealants (see, for example, Patent Document 1). The sealant in Patent Document 1 satisfies heat sealability and heat resistance by separating the heat-sealable layer from the other layers and separately controlling the raw material composition of each layer. However, there is a problem in that the heat-sealability is inferior to the sealing strength of polyolefin-based sealants, and in terms of heat resistance, it is currently unable to withstand harsh processes such as boiling and retort processing.

[0007] On the other hand, polyolefin-based monomaterial packaging design allows for the use of polyolefin-based heat-sealing resins as sealants, offering the advantage of ensuring sufficient heat-sealing properties compared to the aforementioned polyester-based sealants. The sealant must be thick enough to provide sufficient sealing, and it accounts for a large proportion of the package. This is another major reason for the promotion of polyolefin-based monomaterial packaging design. However, polyolefin-based packaging has the problem of inferior gas barrier performance compared to conventional packaging with barrier properties. While polypropylene film has water vapor barrier properties, its performance is not sufficient compared to, for example, transparent inorganic vapor-deposited polyester film, which is generally considered to have excellent water vapor barrier properties, and its oxygen barrier properties are also very poor.

[0008] In response to this, films have been used in which polypropylene film is laminated with polymer resin compositions generally considered 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 to 4). However, gas barrier coated films made using the above-mentioned polymer resin compositions, such as polyvinyl alcohol and ethylene-vinyl alcohol copolymer, are highly humidity-dependent, resulting in a decrease in gas barrier properties under high humidity conditions. They also lack the moist heat resistance required for sterilization processes such as boiling and retorting. Furthermore, while polyvinylidene chloride resin and polyacrylonitrile have low humidity dependence, they have problems such as insufficient absolute barrier values and a high risk of generating hazardous substances during disposal or incineration. Furthermore, the polypropylene film used in these films lacks sufficient heat resistance, resulting in problems such as wrinkles on the surface and reduced performance due to expansion and contraction of the film caused by heating during printing, lamination, and sterilization.

[0009] Regarding the improvement of the gas barrier properties of polypropylene films, attempts have been made to develop stable gas barrier performance that is independent of humidity by laminating an inorganic thin film (for example, Patent Document 5). However, there were problems such as inferior absolute values of gas barrier performance (particularly oxygen barrier performance) compared to conventional polyester vapor-deposited films and vulnerability to physical damage compared to the aforementioned coated barrier films. In particular, polypropylene films have lower dimensional stability than polyester films and tend to stretch and contract, which has led to the problem of the barrier film being prone to destruction. In addition, barrier materials in which polyolefin-based sealants are vapor-deposited have also been investigated (for example, Patent Document 6), but although they exhibit water vapor barrier performance, there were problems such as insufficient oxygen barrier performance.

[0010] To address the above issues, attempts have been made to provide a protective layer with gas barrier properties on top of an inorganic thin film. For example, one method involves coating an inorganic thin film with a water-soluble polymer, an inorganic layered compound, and a metal alkoxide or its hydrolyzate, followed by the sol-gel process to form a composite of the inorganic material containing the inorganic layered compound and the water-soluble polymer on the inorganic thin film (see, for example, Patent Document 7). While this method can improve gas barrier performance and reduce physical damage to the inorganic thin film, damage to the inorganic thin film layer remains unavoidable when subjected to severe physical loads such as bending. In particular, films with excellent barrier performance tend to be prone to cracking, resulting in a greater rate of barrier deterioration when subjected to bending loads. A drawback of good barrier performance is the tendency for volatile components, such as residual solvents and foaming gases, to remain in the layer during adhesive application, leading to issues of migration into food and poor appearance. While extending the aging time after processing can reduce volatile components, this has not been possible due to concerns about delivery. Furthermore, from the perspective of environmental impact, there were concerns that the coating material used for the protective layer would need to be environmentally friendly, that the additional processing steps required to laminate the protective layer would require the use of various solvents, and of course, laminating the protective layer would also lead to increased costs. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-165059 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-52501 [Patent Document 3] Japanese Patent Application Publication No. 4-359033 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-231221 [Patent Document 5] WO2017 / 221781 [Patent Document 6] Patent No. 3318479 [Patent Document 7] International Publication No. WO2021 / 112243 Summary of the Invention [Problem to be solved by the invention]

[0012] In the above patent documents, it was difficult to achieve both the mono-materialization of packaging materials and the various performances required of packaging materials, particularly gas barrier performance and its durability, and the early reduction of residual volatile components, and therefore it was not possible to design packaging materials that were both environmentally friendly and highly convenient.

[0013] The present invention has been made in view of the above problems in the prior art. In other words, the object of the present invention is to provide a packaging material that can form a laminate structure made up of resin types that have a low environmental impact, can improve the gas barrier performance and durability required of packaging materials, and can quickly reduce the volatile components in the packaging material. [Means for solving the problem]

[0014] The present inventors have discovered that by laminating, via an adhesive, a laminate film in which a barrier layer having a predetermined range of gas barrier performance is laminated on a substrate film containing a polyolefin-based resin layer, it is possible to quickly reduce residual volatile components, to expect a significant improvement in barrier performance after lamination, and to maintain barrier performance even after physical loads such as bending. Furthermore, they have discovered that by laminating a sealant made of a polyolefin-based component, it is possible to provide an environmentally friendly and highly convenient packaging material, which has led to the completion of the present invention.

[0015] That is, the present invention comprises the following configurations. 1. A laminated packaging material having at least one substrate film having a resin layer mainly composed of a polyolefin resin, an adhesive layer, and a heat-sealable resin layer, wherein at least one of the substrate films is a laminated gas barrier film having a gas barrier layer, and the substrate film (a) having the lowest oxygen permeability among the laminated substrate films alone has an oxygen permeability value (A) of 30 to 1500 ml / m2 measured under conditions of 23°C x 65% RH. 2 ·d·MPa, and the oxygen permeability (P) of a laminated packaging material (p) made by laminating a base film with a heat-sealable resin via an adhesive layer is 60 ml / m 2 1. A laminated packaging material characterized in that the barrier value improvement rate before and after lamination, expressed by the following formula (1), is 10 or more: Barrier value improvement rate before and after film lamination = (A / P) Formula (1) 2. The laminated packaging material described in 1., characterized in that the oxygen permeability value (G) after performing a twist-bend test 25 times at 23°C using the laminated packaging material with a Gelbo Flex Tester is 65 ml / m2·d·MPa or less. 3. A laminated packaging material according to 1. or 2., characterized in that the time required for the volatile components to volatilize to zero immediately after the laminated packaging material (p) is produced by laminating a base film to a heat-sealing resin via an adhesive is within 30 hours. 4. The laminated packaging material according to any one of 1. to 3., wherein the base film comprises the base film (a) and another base film (b), the base film (b) being a laminated barrier film having a resin layer and a gas barrier layer, and the base film (a) and the resin layer constituting the base film (b) are mainly composed of the same type of polyolefin-based resin. 5. The laminated packaging material according to any one of 1. to 4., characterized in that it has two or less sheets of the base film. 6. The laminated packaging material according to any one of 1. to 5., wherein the resin layer constituting the base film and the heat-sealable resin layer are mainly composed of the same type of polyolefin resin. 7. The laminated packaging material according to any one of 1. to 6., wherein the adhesive layer is made of a polyurethane-based, polyester-based, or polyamine-based resin material. 8. A laminated packaging material according to any one of 1. to 7., wherein the gas barrier layer is an inorganic thin film layer made of any one of aluminum, aluminum oxide, silicon oxide, and a composite oxide of silicon oxide and aluminum oxide. 9. The laminated packaging material according to any one of 1. to 8., wherein the gas barrier layer is a coating layer made of any one of polyvinyl alcohol resin, polyester resin, and polyurethane resin. 10. The laminated packaging material according to any one of 1. to 9., wherein an anchor coat layer is laminated between the base film and the gas barrier layer. 11. The laminated packaging material according to any one of 1. to 10., which is used for boiling or retorting. 12. The laminated packaging material according to any one of 1. to 10., which is used for heating in a microwave oven. 13. A packaging bag made using the laminated packaging material according to any one of 1 to 12 above. 14. A package in which an item is packaged using the laminated packaging material according to any one of 1 to 12 above or the packaging bag according to claim 13. [Effects of the Invention]

[0016] By using this technology, the present inventors have been able to provide a packaging material that is environmentally friendly, has the barrier properties and durability required of packaging materials, and contains a small amount of volatile components. DETAILED DESCRIPTION OF THE INVENTION

[0017] The packaging material of the present invention is a laminated packaging material having at least one substrate film having a resin layer mainly composed of a polyolefin resin, an adhesive layer, and a heat-sealable resin layer, wherein at least one of the substrate films is a laminated gas barrier film having a gas barrier layer, and the substrate film (a) has the lowest oxygen permeability among the substrate films alone, and the oxygen permeability value (A) measured under conditions of 23°C x 65% RH is 30 to 1500 ml / m 2 The laminated packaging material is characterized in that, when the oxygen permeability value of a laminated packaging material (p) obtained by laminating a base film to a heat-sealable resin via an adhesive layer is measured under the same conditions as above and is taken as (P), the barrier value improvement rate before and after lamination is 10 or more. Note that the phrase "as the main constituent" above means that the material is contained in 50 mass% or more of the constituent components.

[0018] The present invention will be described in detail below. [Base film mainly composed of polyolefin resin] The packaging material of the present invention includes a substrate film primarily composed of a polyolefin resin. The substrate film is preferably a substrate film primarily composed of a polypropylene resin (hereinafter referred to as a polypropylene resin film), and more preferably a stretched film. The stretched polypropylene resin film used as the substrate film in the present invention is preferably a biaxially stretched film. Known biaxially stretched polypropylene resin films can be used as the biaxially stretched polypropylene resin film, and the raw materials and blending ratios thereof are not particularly limited. For example, the biaxially stretched polypropylene resin film may be a polypropylene homopolymer (propylene homopolymer), or a random copolymer or block copolymer containing 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 to modify the physical properties, such as petroleum resins and terpene resins.

[0019] In the present invention, the polypropylene-based resin constituting the base film is preferably a propylene homopolymer that contains substantially no comonomer other than propylene, and even if a comonomer is contained, the comonomer amount is preferably 0.5 mol% or less. The upper limit of the comonomer amount is more preferably 0.3 mol%, and even more preferably 0.1 mol%. Within this range, crystallinity is improved, dimensional change at high temperatures is reduced, i.e., the elongation rate when heated to a certain temperature (hereinafter referred to as thermal elongation rate) is reduced, and heat resistance is improved. Improved heat resistance stabilizes the lamination process of the barrier layer, resulting in stabilized barrier performance. A trace amount of comonomer may be contained within a range that does not significantly reduce crystallinity.

[0020] The biaxially oriented polypropylene resin film used in the present invention may be a single-layer film or a laminated film. However, in order to achieve the object of the present invention, a laminated film is preferred. The type of laminate, the number of layers, and the lamination method are not particularly limited and can be selected from known methods. However, it is preferable to improve the lamination strength and the adhesive strength of coating agents by controlling the surface roughness and flexibility of the substrate film surface.

[0021] As a means for improving the lamination strength of the base film and the interfacial adhesion strength with an inorganic thin film layer, a coating agent, etc., a mixture of two or more polypropylene-based resins with different melt flow rates (MFR) may be used as the polypropylene-based resin constituting the surface layer of the base film. It is assumed that when the difference in melt flow rate (MFR) between two or more polypropylene resins in a polypropylene resin blend is small, the crystallization rate and degree of crystallization of each polypropylene resin do not differ significantly, making it easier for minute irregularities to form on the surface. However, care must be taken because if the cooling rate of the unstretched sheet during film production is slow, the surface irregularities caused by spherulites will become large, and if the stretching temperature is too high during longitudinal or transverse stretching, the surface irregularities will easily become large. The polypropylene resins may be polypropylene homopolymers containing no copolymerization components, or polypropylene resins copolymerized with ethylene and / or an α-olefin having 4 or more carbon atoms at 5.0 mol% or less. The copolymerization components of the copolymerized polypropylene resins are preferably 4.0 mol% or less, more preferably 3.5 mol% or less. The copolymerization components of the copolymerized polypropylene resins are preferably 1.0 mol% or more, more preferably 1.5 mol% or more, even more preferably 2.0 mol% or more, and particularly preferably 2.5 mol% or more. Examples of α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. Polar copolymer components such as maleic acid may also be used.

[0022] From a practical standpoint, the lower limit of the xylene-soluble content of the polypropylene resin constituting the base film is preferably 0.1% by mass. The upper limit of the xylene-soluble content is preferably 7% by mass, more preferably 6% by mass, and even more preferably 5% by mass. Within this range, crystallinity is improved, the thermal elongation rate is smaller, and heat resistance is improved.

[0023] 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. The lower limit of the MFR is more preferably 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 the above range, the mechanical load is small, and extrusion and stretching are easy. The upper limit of the MFR is preferably 20 g / 10 min. The upper limit of the MFR is more preferably 17 g / 10 min, even more preferably 16 g / 10 min, and particularly preferably 15 g / 10 min. Within the above range, stretching is easy, thickness unevenness is reduced, and the stretching temperature and heat setting temperature can be easily increased, resulting in a smaller heat elongation and improved heat resistance.

[0024] From the viewpoint of heat resistance, the substrate film may be a uniaxially stretched film in the longitudinal direction (MD) or the transverse direction (TD), but is preferably a biaxially stretched film. In the present invention, by stretching the above-mentioned preferred raw materials at least uniaxially, a film with low thermal elongation at high temperatures and high heat resistance, which was not expected with conventional polypropylene films, can be obtained. Examples of stretching methods include simultaneous biaxial stretching and sequential biaxial stretching, but sequential biaxial stretching is preferred from the viewpoint of improving flatness, dimensional stability, thickness unevenness, etc.

[0025] In the sequential biaxial stretching method, a 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 through a T-die, and extruded onto a chill roll at a temperature of 10°C to 100°C to obtain an unstretched sheet. The sheet is then stretched in the machine direction (MD) at a ratio of 3.0 to 8.0 times at a temperature of 120°C to 165°C, and subsequently, after preheating in a tenter, stretched in the transverse direction (TD) at a ratio of 4.0 to 20.0 times at a temperature of 155°C to 175°C. After biaxial stretching, the sheet can be heat-set at a temperature of 165°C to 175°C while allowing for relaxation of 1% to 15%.

[0026] In order to set the heat elongation percentage of the substrate film of the present invention within the above-mentioned range, the film is preferably produced by the following method. First, the upper limit of the stretching temperature in the machine direction (MD) is preferably the film melting point (Tm) - 7°C, more preferably Tm - 10°C, and even more preferably Tm - 12°C. Within this range, the heat elongation rate can be easily reduced, and the film is less likely to melt onto the stretching rolls and be difficult to stretch, resulting in little deterioration in quality. Stretching in the machine direction may be performed in two or more stages using three or more pairs of stretching rolls. By dividing the stretching into multiple stages, strain during stretching can be reduced, making it easier to reduce the heat elongation rate.

[0027] The upper limit of the stretching ratio in the transverse direction (TD) is preferably 15, more preferably 12, and even more preferably 10. If the upper limit is exceeded, the heat elongation rate will be high and the film will be prone to breakage during stretching. The lower limit of the TD stretching temperature is preferably 150°C, more preferably 152°C, even more preferably 154°C, and particularly preferably 156°C. If the temperature is 150°C or higher, the film is stretched in a sufficiently softened state, making it easier to reduce the heat elongation. The upper limit of the TD stretching temperature is preferably 164°C, more preferably 162°C, and even more preferably 160°C. A higher temperature is preferred to reduce the heat elongation.

[0028] The lower limit of the heat setting temperature after transverse direction (TD) stretching is preferably 168° C., more preferably 170° C., and even more preferably 173° C. If the temperature is 168° C. or higher, the heat elongation rate is unlikely to increase, and there is no need to perform a long treatment to reduce the heat elongation rate.

[0029] It is preferable to relax the film during heat setting. The lower limit of the relaxation rate is preferably 2%, more preferably 3%. If the relaxation rate is less than this, the thermal elongation rate may become high.

[0030] Furthermore, in order to reduce the thermal shrinkage rate, the film produced by the above process may be wound into a roll and then annealed offline.

[0031] To improve handling (e.g., winding after lamination), the substrate film used in the present invention preferably contains particles to form protrusions on the film surface. Examples of particles to be contained in the film include inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, and alumina, as well as heat-resistant polymer particles such as acrylic, PMMA, nylon, polystyrene, polyester, and benzoguanamine-formaldehyde condensates. From the perspective of transparency, a low particle content in the film is preferred, for example, 1 ppm to 1000 ppm. The average particle diameter is preferably 1.0 to 3.0 μm, more preferably 1.0 to 2.7 μm. The average particle diameter is measured by taking a photograph using a scanning electron microscope, measuring the Feret's diameter in the horizontal direction using an image analyzer, and expressing it as the average value. Furthermore, from the perspective of transparency, it is preferable to select particles with a refractive index close to that of the resin used. In addition, the film may contain antioxidants, ultraviolet absorbers, antistatic agents, dyes, lubricants, nucleating agents, adhesives, antifogging agents, flame retardants, antiblocking agents, inorganic or organic fillers, etc., to impart various functions to the film as needed.

[0032] In addition to the polypropylene-based resin used in the present invention, other resins can be used to improve the mechanical properties of the base film, the adhesion to the ink layer or adhesive layer laminated on the gas barrier coating layer, reduce the environmental load, etc., within the scope of the present invention. Examples include polyethylene resins, polypropylene resins other than those mentioned above, random copolymers which are copolymers of propylene with ethylene and / or an α-olefin having 4 or more carbon atoms, and various elastomers.

[0033] The polyethylene resin that can be used for the substrate film in the present invention is a resin containing ethylene as a main component. For example, any ethylene homopolymer such as high-pressure low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, or high-density polyethylene can be used. In addition, crystalline or low-crystalline or non-crystalline random or block copolymers with monomers such as α-olefins such as propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1, vinyl acetate, (meth)acrylic acid, and (meth)acrylic acid esters, or mixtures thereof can also be used. The polyethylene resin is preferably contained in an amount of 1% by weight or more and 25% by weight or less, based on the total of 100 of the polypropylene resin and polyethylene resin constituting the substrate. When it is 1% by weight or more, the heat seal strength, blocking resistance, and anti-fogging properties are improved. It is more preferably 5% by weight or more, and even more preferably 8% by weight or more. When it is 20% by weight or less, rigidity is easily maintained. It is more preferably 18% by weight or less, and even more preferably 15% by weight or less. From the viewpoints of heat resistance, transparency, mechanical properties, and film-forming properties, the melting point of the polyethylene resin is preferably in the range of 100° C. or more and 135° C. or less, more preferably 105° C. or more and 130° C. or less. The density, measured in accordance with JIS K7112, is preferably 0.90 g / cm3 or more and 0.94 g / cm3 or less, more preferably 0.91 g / cm3 or more and 0.94 g / cm3 or less. The melt flow rate (MFR) (190°C, 2.16 kgf) of the polyethylene resin is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more, and from the viewpoint of further stabilizing moldability, it is preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, and even more preferably 10 g / 10 min or less.

[0034] From the viewpoint of low environmental impact, plant-derived polyethylene resins may be used as the polyethylene resin of the present invention. The bio-based content of the polyethylene resin measured in accordance with ISO 16620 is preferably 50% or more and 100% or less, more preferably 70% or more and 100% or less, and even more preferably 80% or more and 100% or less.

[0035] In the present invention, the thickness of the substrate film is set arbitrarily 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 150 μm or less. If the thickness is too thin, handling tends to be poor. On the other hand, if the thickness is too thick, not only is there a problem in terms of cost, but when wound into a roll and stored, poor flatness is likely to occur due to a curl.

[0036] The haze of the substrate film of the present invention is preferably transparent from the viewpoint of visibility of contents, and specifically is preferably 6% or less, more preferably 5% or less, and even more preferably 4% or less. Haze tends to deteriorate, for example, when the stretching temperature or heat setting temperature is too high, when the cooling roll (CR) temperature is high and the cooling rate of the stretched raw sheet is slow, or when there is too much low molecular weight, so it can be controlled within the above range by adjusting these.

[0037] Furthermore, the base film layer in the present invention may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, surface roughening treatment, or known anchor coat treatment, printing, decoration, etc., as long as the object of the present invention is not impaired. Generally, it is preferable to use a resin with good adhesiveness, such as polyurethane or polyester, for the anchor coat, and the anchor coat layer for improving the barrier layer in the present invention will be described later.

[0038] The packaging material of the present invention requires at least one substrate film having a gas barrier layer. However, bonding two or more substrate films together is expected to improve the toughness and gas barrier performance of the packaging material, and therefore may be used appropriately depending on the application. In terms of toughness, using two biaxially oriented polypropylene films, which generally have high puncture strength, enables a packaging design that compares favorably with, for example, a configuration using two different materials, such as polyester film and polyamide film, which are widely used as packaging materials. In terms of gas barrier performance, using two substrate films makes the intermediate film less susceptible to the influences of external environments, such as temperature and humidity and external bending, thereby enabling more stable gas barrier performance. In this sense, when two substrate films are used, it is particularly preferable that the coating layer or inorganic thin film layer having gas barrier performance be laminated to the intermediate film.

[0039] [Gas barrier layer] In the present invention, at least one of the substrate films must be a laminated substrate film having a gas barrier layer. The gas barrier layer must be either a coating layer (A) mainly composed of an organic substance or an inorganic thin film layer (B) mainly composed of an inorganic substance, as described below. Furthermore, in order to enhance the barrier properties of the gas barrier layer, an anchor coat (C) described below can be laminated together with a protective layer to protect the barrier layer.

[0040] [Coating layer (A)] In the present invention, a coating layer (A) may be provided as a gas barrier layer. However, in the present invention, the provision of the coating layer (A) increases the number of steps, which increases costs, and depending on the film thickness, may make recycling difficult, which may impose a burden on the environment. This must be taken into consideration when designing the present invention.

[0041] The coating weight of the coating layer (A) is preferably 0.10 to 0.70 (g / m²). The lower limit of the coating weight of the coating layer (A) is preferably 0.15 (g / m²) or more, more preferably 0.20 (g / m²) or more, and even more preferably 0.25 (g / m²) or more, and the upper limit is preferably 0.65 (g / m²) or less, more preferably 0.60 (g / m²) or less, and even more preferably 0.55 (g / m²) or less. If the coating weight of the coating layer (A) exceeds 0.70 (g / m²), the gas barrier properties are improved, but the cohesive strength within the coating layer becomes insufficient and the uniformity of the coating layer is reduced, resulting in unevenness (increased haze, whitening) or defects in the coating appearance, or insufficient gas barrier properties and adhesiveness. Furthermore, from the perspective of processability, a thick coating thickness may cause blocking. Furthermore, there is a concern that this may have a negative impact on the recyclability of the film, and the environmental impact will be greater due to the increased consumption of raw materials, solvents, etc. On the other hand, if the thickness of the coating layer (A) is less than 0.10 (g / m2), there is a risk that sufficient gas barrier properties and interlayer adhesion may not be obtained.

[0042] The resin composition used for the coating layer (A) formed on the surface of the laminated film of the present invention is preferably a polyvinyl alcohol-based polymer. Polyvinyl alcohol-based polymers are primarily composed of vinyl alcohol units, and their high cohesion due to their hydrogen-bonded structure is expected to significantly improve barrier performance. The polymerization degree and saponification degree of the polyvinyl alcohol-based polymer are determined based on the desired gas barrier properties and the viscosity of the coating solution. The high viscosity of the aqueous solution and its tendency to gel make coating difficult, so a polymerization degree of 2600 or less is preferred from the viewpoint of coating workability. A saponification degree of less than 90% does not provide sufficient oxygen gas barrier properties under high humidity conditions, while a saponification degree of more than 99.7% makes it difficult to prepare the aqueous solution, is prone to gelation, and is not suitable for industrial production. Therefore, the saponification degree is preferably 90 to 99.7%, and more preferably 93 to 99%. In the present invention, various copolymerized or modified polyvinyl alcohol polymers, such as polyvinyl alcohol polymers copolymerized with ethylene and silanol-modified polyvinyl alcohol polymers, can also be used within the scope of not impairing processability or productivity.

[0043] The coating layer (A) of the present invention may contain an inorganic layered compound. The presence of the inorganic layered compound is expected to provide a labyrinth effect against gases, improving gas barrier properties. Furthermore, the addition of the inorganic layered compound can suppress humidity dependency of gas barrier properties. Examples of materials include clay minerals (including synthetic products thereof) such as smectite, kaolin, mica, hydrotalcite, and chlorite. Specific examples include montmorillonite, beidellite, saponite, hectorite, sauconite, stevensite, kaolinite, nacrite, dickite, halloysite, hydrated halloysite, tetrasilylic mica, sodium taeniolite, muscovite, margarite, phlogopite, talc, antigorite, chrysotile, pyrophyllite, vermiculite, xanthophyllite, and chlorite. Furthermore, scaly silica and the like can also be used as an inorganic layered compound. These may be used alone or in combination. Among these, smectite (including synthetic products thereof) is particularly preferred because it has a high effect of improving the water vapor barrier property.

[0044] Furthermore, inorganic layered compounds are preferably those containing redox-active metal ions, particularly iron ions. Among these, montmorillonite, a type of smectite, is preferred from the viewpoints of coating suitability and gas barrier properties. As montmorillonite, known compounds conventionally used in 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. HO represents interlayer water. m and ω represent positive real numbers.) Among these, those in which W in the formula is Na are preferred because they cleave in an aqueous medium.

[0045] The size and shape of the inorganic layered compound are not particularly limited, but the particle size (major axis) 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, dispersibility will be poor, which may result in deterioration of the coatability and coat appearance of the coating layer (A). On the other hand, the aspect ratio is 50 to 5000, more preferably 100 to 4000, and even more preferably 200 to 3000.

[0046] The blending ratio of the resin composition to the inorganic layered compound in the coating layer of the present invention is preferably 75 / 25 to 35 / 65 (wt%), more preferably 70 / 30 to 40 / 60 (wt%), and even more preferably 65 / 35 to 45 / 55 (wt%). If the blending ratio of the inorganic layered compound is less than 25%, the barrier performance may be insufficient. On the other hand, if it is more than 65%, the dispersibility may be poor, which may result in poor coating properties and poor adhesion.

[0047] The coating layer (A) of the present invention may contain various crosslinking agents to improve the film's cohesive strength and wet heat-resistant adhesion, as long as the crosslinking 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, as they can crosslink with hydroxyl-containing resin compositions and inorganic thin film layers. Commonly used silicon-based crosslinking agents include metal alkoxides and silane coupling agents. Metal alkoxides are compounds represented by the general formula M(OR)n (M: Si or Al, R: alkyl groups such as CH3 or C2H5). Specific examples include tetraethoxysilane [Si(OC2H5)4] and triisopropoxyaluminum Al[OCH(CH3)2]3. Examples of silane coupling agents include those having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, those having an amino group such as 3-aminopropyltrimethoxysilane, those having a mercapto group such as 3-mercaptopropyltrimethoxysilane, those having an isocyanate group such as 3-isocyanatepropyltriethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate. Other crosslinking agents that may be used in combination include oxazoline compounds, carbodiimide compounds, and epoxy compounds. However, when recyclability is important, the amount of crosslinking agent used must be considered.

[0048] When a crosslinking agent is incorporated, its amount in the coating layer is preferably 0.05 to 4.00% by mass, more preferably 0.10 to 3.50% by mass, and even more preferably 0.15 to 3.00% by mass. By adjusting the amount within the above range, the film hardens and the cohesive strength improves, resulting in a film with excellent water-resistant adhesion. If the amount exceeds 3.00% by mass, the amount of uncrosslinked portions increases, or the film hardens due to excessive hardening, which may actually result in a decrease in adhesion. On the other hand, if the amount is less than 0.05% by mass, sufficient cohesive strength may not be obtained.

[0049] In the present invention, from the viewpoint of visibility of the contents, the film haze after lamination of the coating layer (A) is preferably 20% or less, more preferably 18% or less, and even more preferably 16% or less. If the haze is greater than 20%, transparency will be significantly reduced and there is a concern that it may affect the surface irregularities, leading to poor appearance in subsequent printing processes, etc. The haze can be adjusted by the composition ratio of the coating layer (A), solvent conditions, film thickness, etc. Here, the haze was evaluated in accordance with JIS K7136 using a turbidity meter (NDH2000, manufactured by Nippon Denshoku Corporation).

[0050] The coating method for the resin composition for the coating layer is not particularly limited as long as it is a method that can coat the surface of a film to form a layer, and for example, a conventional coating method such as gravure coating, reverse roll coating, wire bar coating, or die coating can be used.

[0051] When forming the coating layer (A), it is preferable to apply the resin composition for the coating layer, pre-dry it at a relatively low temperature to evaporate the solvent, and then dry it 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 lower than 80°C, the coating layer may not be sufficiently dried. If the pre-drying temperature is higher than 110°C, the coating layer may dry before it has time to spread, resulting in poor appearance.

[0052] On the other hand, the main drying temperature is preferably 110 to 140°C, more preferably 115 to 135°C, and even more preferably 120 to 130°C. If the main drying temperature is less than 110°C, film formation of the coating layer (A) will not proceed, resulting in reduced cohesive strength and adhesiveness, which may adversely affect the barrier properties. If the temperature exceeds 140°C, the film may become too hot, making it brittle and causing significant wrinkles due to heat shrinkage.

[0053] The drying time for preliminary drying is preferably 3.0 to 10.0 seconds, more preferably 3.5 to 9.5 seconds, and even more preferably 4.0 to 9.0 seconds. The drying time for main drying is preferably 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, care must be taken as drying conditions vary depending on the type of heat transfer medium and the intake and exhaust conditions of the drying oven. Furthermore, additional heat treatment for 1 to 4 days at a temperature as low as possible, specifically 40 to 60°C, can be performed separately from drying, which is even more effective in accelerating the formation of the coating layer (A).

[0054] [Inorganic thin film layer (B)] In the present invention, the surface of the base film may have an inorganic thin film layer (B) as a gas barrier layer. The inorganic thin film layer (B) is a thin film made of a metal or an inorganic oxide. There are no particular limitations on the material forming the inorganic thin film layer as long as it can be formed into a thin film. However, from the viewpoint of gas barrier properties, inorganic oxides such as silicon oxide (silica), aluminum oxide (alumina), and mixtures of silicon oxide and aluminum oxide are preferred. In particular, complex oxides of silicon oxide and aluminum oxide are preferred from the viewpoint of achieving both flexibility and density of the thin film layer. In this complex oxide, the mixing ratio of silicon oxide to aluminum oxide is preferably in the range of 20 to 70 mass% Al in terms of the mass ratio of the metal components. If the Al concentration is less than 20 mass%, the water vapor barrier properties may be reduced. On the other hand, if the Al concentration exceeds 70 mass%, the inorganic thin film layer tends to become hard, and there is a risk that the film will be destroyed during secondary processing such as printing or lamination, resulting in a reduction in gas barrier properties. The silicon oxide referred to here is a variety of silicon oxides such as SiO and SiO2, or a mixture thereof, and the aluminum oxide is a variety of aluminum oxides such as AlO and Al2O3, or a mixture thereof.

[0055] The thickness of the inorganic thin film layer (B) is usually 1 to 100 nm, preferably 5 to 50 nm. If the thickness of the inorganic thin film layer (B) is less than 1 nm, it may be difficult to obtain satisfactory gas barrier properties, while if the thickness is excessively greater than 100 nm, the corresponding improvement in gas barrier properties cannot be obtained and is actually disadvantageous in terms of flex resistance and production costs.

[0056] The method for forming the inorganic thin film layer (B) is not particularly limited, and any known vapor deposition method may be appropriately employed, such as physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, or chemical vapor deposition (CVD). A typical method for forming the inorganic thin film layer (B) will be described below, taking silicon oxide / aluminum oxide-based thin films 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 source. These deposition sources are typically particles, and the particle size is preferably such that the pressure during deposition does not change, with a preferred particle diameter being 1 mm to 5 mm. Heating methods such as resistance heating, high-frequency induction heating, electron beam heating, and laser heating can be used. Furthermore, reactive vapor deposition using reactive gases such as oxygen, nitrogen, hydrogen, argon, carbon dioxide, and water vapor, or ozone addition or ion-assisted deposition can also be employed. Furthermore, the film formation conditions can be changed as desired by applying a bias to the deposition target (the laminated film to be deposited), heating or cooling the deposition target, etc. The deposition materials, reactive gases, bias, heating or cooling of the deposition target, etc. can be changed in the same way when using the sputtering method or the CVD method.

[0057] [Anchor coat layer (C)] In the present invention, an anchor coat layer (C) may be provided as an auxiliary layer to ensure sufficient gas barrier properties and adhesiveness when the aforementioned gas barrier layer is laminated. The presence of an anchor coat layer can suppress the exposure of oligomers and antiblocking agents from the polypropylene resin. Furthermore, when laminating other layers on the anchor coat layer (C), the adhesion between layers can be enhanced. In particular, when forming an inorganic thin film layer, not only adhesion is enhanced, but the formation of the inorganic layer can also be promoted by smoothing the surface, which is expected to improve gas barrier properties. Additionally, by using a material with a certain level of gas barrier properties (referred to as gas barrier auxiliary properties) for the anchor coat layer (C) itself, the gas barrier performance of the film can be significantly improved when the aforementioned gas barrier layer is laminated.

[0058] When only the anchor coat layer (C) is laminated, the gas barrier auxiliary property of the film is that the oxygen permeability is 10,000 ml / m under an environment of 23°C x 65% RH. 2 d MPa or less is preferable in terms of exhibiting good gas barrier properties after laminating the gas barrier layer. 2 ·d·MPa or less, more preferably 8000ml / m 2 ·d·MPa or less. Oxygen permeability is 10000ml / m 2 If the pressure exceeds 1.5 MPa, sufficient gas barrier performance cannot be obtained even after laminating the gas barrier layer, making it difficult to use in applications where high gas barrier properties are required.

[0059] In the present invention, the adhesion amount of the anchor coat layer (C) is 0.10 to 0.50 g / m 2 This allows the anchor coat layer (C) to be uniformly controlled during coating, resulting in a film with fewer coating irregularities and defects. Furthermore, the anchor coat layer (C) contributes to suppressing oligomer exposure, stabilizing the haze after wet heat treatment. The amount of anchor coat layer (C) deposited is preferably 0.15 g / m 2 More preferably, 0.20 g / m 2 More preferably, 0.35 g / m2 or more, preferably 0.50 g / m 2 or less, more preferably 0.45 g / m 2 less than 0.40 g / m 2 The adhesion amount of the anchor coat layer (C) is 0.50 g / m or less. 2 If the thickness exceeds 0.10 g / m, the gas barrier auxiliary property will improve, but the cohesive force inside the anchor coat layer will be insufficient and the uniformity of the anchor coat layer will also decrease, resulting in unevenness and defects in the coat appearance. In terms of processability, a thick film thickness may cause blocking or increase manufacturing costs. Furthermore, there is a concern that it may have a negative impact on the recyclability of the film, and the amount of raw materials, solvents, etc. used will increase, which will increase the environmental impact. On the other hand, if the thickness of the anchor coat layer (C) is 0.10 g / m, 2 If it is less than this, there is a risk that sufficient gas barrier assisting properties and interlayer adhesion may not be obtained.

[0060] The resin composition used for the anchor coat layer (C) of the present invention may be a resin such as a urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, or polybutadiene-based resin to which an epoxy-based, isocyanate-based, or melamine-based curing agent has been added. It may further contain a silicon-based crosslinking agent, an oxazoline compound, a carbodiimide compound, or an epoxy compound. In particular, the inclusion of a urethane resin is preferred because, in addition to the barrier performance due to the high cohesiveness of the urethane bond itself, the polar groups interact with the inorganic thin film layer, and the presence of amorphous portions provides flexibility, thereby reducing damage even when a bending load is applied. Polyester resins are also preferred because they are expected to have the same effect. In the present invention, it is particularly preferred to include a polyurethane containing polyester and isocyanate as constituent components, and it is even more preferred to add a silicon-based crosslinking agent from the viewpoint of improving adhesion.

[0061] In terms of gas barrier assisting properties, the urethane resin used in the anchor coat layer (C) of the present invention is preferably a urethane resin containing an aromatic or araliphatic diisocyanate component as a main constituent. Among these, it is particularly preferable to use a metaxylylene diisocyanate component. By using such a resin, the cohesive strength of the urethane bond can be further enhanced due to the stacking effect between aromatic rings, resulting in good gas barrier assisting properties.

[0062] In the present invention, the proportion of aromatic or araliphatic diisocyanate in the urethane resin used in the anchor coat layer (C) is preferably 50 mol % or more (50 to 100 mol %) in 100 mol % of the polyisocyanate component. The total proportion of aromatic or araliphatic diisocyanate is preferably 60 to 100 mol %, more preferably 70 to 100 mol %, and even more preferably 80 to 100 mol %. If the total proportion of aromatic or araliphatic diisocyanate is less than 50 mol %, good gas barrier assist properties may not be obtained.

[0063] The urethane resin used in the anchor coat layer (C) of the present invention may be blended with various crosslinking agents to improve the cohesive strength of the film and improve its wet heat resistance adhesion. Examples of crosslinking agents include silicon-based crosslinking agents, oxazoline compounds, carbodiimide compounds, and epoxy compounds. Among these, silicon-based crosslinking agents are particularly preferred because they can improve water-resistant adhesion, particularly with inorganic thin film layers. Other crosslinking agents that may be used in combination include oxazoline compounds, carbodiimide compounds, and epoxy compounds.

[0064] As the silicon-based crosslinking agent, from the viewpoint of crosslinking inorganic matter and organic matter, silane coupling agent is preferred.As the silane coupling agent, hydrolyzable alkoxysilane compound, for example, halogen-containing alkoxysilane (chloro C2-4 alkyl tri C1-4 alkoxysilane such as 2-chloroethyl trimethoxysilane, 2-chloroethyl triethoxysilane, 3-chloropropyl trimethoxysilane, 3-chloropropyl triethoxysilane, etc.), alkoxysilane having epoxy group [2-glycidyloxyethyl trimethoxysilane, 2-glycidyloxyethyl triethoxysilane, 3-glycidyloxypropyl triethoxysilane, etc.] trimethoxysilane, glycidyloxy C2-4 alkyltriC1-4 alkoxysilanes such as 3-glycidyloxypropyltriethoxysilane, glycidyloxydiC2-4 alkyldiC1-4 alkoxysilanes such as 3-glycidyloxypropylmethyldimethoxysilane and 3-glycidyloxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-(3,4-epoxycyclohexyl)propyl (epoxycycloalkyl)C2-4 alkyltriC1-4 alkoxysilanes such as 2-aminoethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc.], alkoxysilanes having an amino group [aminoC2-4 alkyltriC1-4 alkoxysilanes such as 2-aminoethyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc., aminodiC2-4 alkyldiC1-4 alkoxysilanes such as 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, etc., 2-[N-(2-aminoethyl)amino] (2-aminoC2-4 alkyl)aminoC2-4 alkyltriC1-4 alkoxysilanes such as 3-[N-(2-aminoethyl)amino]ethyltrimethoxysilane, 3-[N-(2-aminoethyl)amino]propyltrimethoxysilane, and 3-[N-(2-aminoethyl)amino]propyltriethoxysilane; (aminoC2-4 alkyl)aminodiC2-4 alkyldiC1-4 alkoxysilanes such as 3-[N-(2-aminoethyl)amino]propylmethyldimethoxysilane and 3-[N-(2-aminoethyl)amino]propylmethyldiethoxysilane;Alkoxysilanes with mercapto groups (mercapto C2-4 alkyltri C1-4 alkoxysilanes such as 2-mercaptoethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc.; mercapto di C2-4 alkyldi C1-4 alkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc.), alkoxysilanes with vinyl groups (vinyltri C1-4 alkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, etc.), ethylene Examples include alkoxysilanes having a hydrophilically unsaturated bond group [(meth)acryloxyC2-4 alkyltriC1-4 alkoxysilanes such as 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethyltriethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, and 3-(meth)acryloxypropyltriethoxysilane; and (meth)acryloxydiC2-4 alkyldiC1-4 alkoxysilanes such as 3-(meth)acryloxypropylmethyldimethoxysilane and 3-(meth)acryloxypropylmethyldiethoxysilane]. These silane coupling agents can be used alone or in combination. Of these silane coupling agents, silane coupling agents having an amino group are preferred.

[0065] The silicon-based crosslinking agent is preferably added to the coating layer in an amount of 0.05 to 4.00% by mass, more preferably 0.10 to 3.50% by mass, and even more preferably 0.15 to 3.00% by mass. The addition of a silicon-based crosslinking agent promotes film hardening and improves cohesive strength, resulting in a film with excellent water-resistant adhesion and also expected to prevent oligomer exposure. If the amount added exceeds 3.00% by mass, the film hardens and improves cohesive strength, but some unreacted portions may remain, potentially reducing interlayer adhesion. On the other hand, if the amount added is less than 0.05% by mass, sufficient cohesive strength may not be obtained.

[0066] The polyester resin used in the anchor coat layer (C) of the present invention is produced by polycondensation of a polycarboxylic acid component and a polyhydric alcohol component. The molecular weight of the polyester resin is not particularly limited as long as it can provide sufficient film toughness, coatability, and solvent solubility for use as a coating material, but the number average molecular weight is 1,000 to 50,000, more preferably 1,500 to 30,000. The functional group at the polyester end is also not particularly limited, and may be an alcohol end, a carboxylic acid end, or both. However, when an isocyanate-based curing agent is used in combination, it is necessary to use a polyester polyol that is predominantly alcohol-terminated.

[0067] The Tg of the polyester resin used in the anchor coat layer (C) of the present invention is preferably 10°C or higher. If the temperature is lower than this, the resin will become tacky after the coating operation, making it more susceptible to blocking and making the winding operation after coating difficult. If the Tg is 10°C or lower, it will be difficult to prevent blocking even under conditions where the pressure near the winding core is high, even with the addition of an anti-blocking agent. The Tg temperature is more preferably 15°C or higher, and even more preferably 20°C or higher.

[0068] The polyester resin used in the anchor coat layer (C) of the present invention is prepared by polycondensation of a polycarboxylic acid component and a polyhydric alcohol component. The polycarboxylic acid component of the polyester resin used in the present invention is characterized by containing at least one ortho-oriented aromatic dicarboxylic acid or its anhydride. Ortho-orientation improves solubility in solvents, enabling uniform coating on the substrate. A uniformly coated film reduces variation in barrier performance, thereby contributing to the suppression of oligomer whitening. Furthermore, ortho-orientation results in a film with excellent flexibility and improved interfacial adhesion, which reduces damage to the substrate due to wet heat treatment and leads to the suppression of oligomers. Examples of aromatic polycarboxylic acids or anhydrides thereof in which a carboxylic acid is substituted at the ortho-position include orthophthalic acid or anhydride, naphthalene 2,3-dicarboxylic acid or anhydride, naphthalene 1,2-dicarboxylic acid or anhydride, anthraquinone 2,3-dicarboxylic acid or anhydride, and 2,3-anthracene carboxylic acid or anhydride. These compounds may have a substituent at any carbon atom of the aromatic ring. Examples of the substituent include a chloro group, a bromo group, a methyl group, an ethyl group, an i-propyl group, a hydroxyl group, a methoxy group, an ethoxy group, a phenoxy group, a methylthio group, a phenylthio group, a cyano group, a nitro group, an amino group, a phthalimide group, a carboxyl group, a carbamoyl group, an N-ethylcarbamoyl group, a phenyl group, and a naphthyl group. Furthermore, polyester polyols containing these compounds in an amount of 70 to 100 mol% relative to 100 mol% of the total polycarboxylic acid components are particularly preferred because they not only effectively improve barrier properties but also have excellent solvent solubility, which is essential for coating materials.

[0069] In the present invention, other polycarboxylic acid components may be copolymerized within the range that does not impair the effects of the invention. Specifically, examples of aliphatic polycarboxylic acids that can be used include succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid; examples of unsaturated bond-containing polycarboxylic acids include maleic anhydride, maleic acid, and fumaric acid; examples of alicyclic polycarboxylic acids include 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; and examples of aromatic polycarboxylic acids include terephthalic acid, isophthalic acid, pyromellitic acid, trimellitic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, diphenic acid and its anhydride, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid, and anhydrides or ester-forming derivatives of these dicarboxylic acids; and examples of polybasic acids that can be used alone or in mixtures of two or more thereof include p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and ester-forming derivatives of these dihydroxycarboxylic acids. Among these, succinic acid, 1,3-cyclopentanedicarboxylic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalic acid, and diphenic acid are preferred from the viewpoint of organic solvent solubility and gas barrier properties.

[0070] The polyhydric alcohol component of the polyester used in the anchor coat layer (C) of the present invention is not particularly limited as long as it can synthesize a polyester that exhibits gas barrier reinforcing properties, but it is preferable for it to contain a polyhydric alcohol component containing at least one selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, cyclohexanedimethanol, and 1,3-bishydroxyethylbenzene. Among these, it is most preferable to use ethylene glycol as the main component, because it is presumed that the fewer the number of carbon atoms between oxygen atoms, the less flexible the molecular chain becomes and the more difficult oxygen permeates.

[0071] In the present invention, it is preferable to use the polyhydric alcohol component described above, but other polyhydric alcohol components may also be copolymerized as long as the effects of the present invention are not impaired. Specific examples of diols include 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Examples of trihydric or higher alcohols include glycerol, trimethylolpropane, trimethylolethane, tris(2-hydroxyethyl)isocyanurate, 1,2,4-butanetriol, pentaerythritol, and dipentaerythritol. Polyesters containing glycerol and tris(2-hydroxyethyl)isocyanurate in combination are particularly preferred, as they have a moderately high crosslinking density due to their branched structure, resulting in good solubility in organic solvents and excellent barrier properties.

[0072] Examples of catalysts that can be used in the reaction to obtain the polyester of the present invention include tin-based catalysts such as monobutyltin oxide and dibutyltin oxide, titanium-based catalysts such as tetraisopropyltitanate and tetrabutyltitanate, and acid catalysts such as zirconia-based catalysts such as tetrabutylzirconate. It is preferable to use a combination of the above-mentioned titanium-based catalysts, such as tetraisopropyltitanate and tetrabutyltitanate, which have high activity in esterification reactions, with the above-mentioned zirconia catalyst. The amount of the catalyst used is 1 to 1,000 ppm, more preferably 10 to 100 ppm, based on the total mass of the reaction raw materials used. If the amount is less than 1 ppm, it is difficult to obtain the catalytic effect, while if it exceeds 1,000 ppm, problems such as inhibition of the urethanization reaction may occur when an isocyanate curing agent is used.

[0073] In the present invention, when a polyester resin is used as the main component of the coating agent constituting the anchor coat layer (C), it is particularly preferable to use an isocyanate-based curing agent to form a urethane resin. In this case, the coating layer becomes crosslinked, which has the advantage of improving heat resistance, abrasion resistance, and rigidity. Therefore, it is easy to use in boiling and retort packaging. On the other hand, there are problems with the liquid not being reusable after mixing with the curing agent, and a curing (aging) process is required after coating. Examples of advantages include the fact that, as a simple overcoat varnish, there is no risk of thickening of the coating liquid, coating production is easy to manage, the coating liquid can be diluted and reused, and a curing process (so-called aging process) is not required. In this case, the polyester used can be terminated with a polyol, a polycarboxylic acid, or a mixture of these without any problems. On the other hand, the resin of the coating layer is linear, which may result in insufficient heat resistance or abrasion resistance, or problems with use in boiling and retort packaging.

[0074] When a curing agent is used in the coating layer, an isocyanate curing system is preferred from the standpoint of heat resistance of the film, since it is a coating on a film. In this case, the resin component of the coating material must be polyester polyol. On the other hand, when an epoxy compound is used as the curing agent, polyester polycarboxylic acid is required. In these cases, the coating layer becomes crosslinked, which has the advantage of improving heat resistance, abrasion resistance, and rigidity. Therefore, it is easy to use in boiled and retort packaging. However, there are problems with this, such as the liquid not being reusable after mixing with the curing agent, and the need for a curing (aging) process after application.

[0075] When the polyester has hydroxyl groups, the polyisocyanate compound used in the present invention reacts at least partially to form a urethane structure, thereby making the resin component highly polar and causing aggregation between polymer chains, thereby further enhancing the gas barrier function. Furthermore, when the resin of the coating material is a linear resin, crosslinking with a trivalent or higher polyisocyanate can impart heat resistance and abrasion resistance. The polyisocyanate compound used in the present invention may be a diisocyanate, a trivalent or higher polyisocyanate, a low-molecular-weight compound, or a high-molecular-weight compound, but it is preferable to contain an aromatic ring or an aliphatic ring as part of the skeleton from the viewpoint of improving the gas barrier function. Examples of isocyanates having an aromatic ring include toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and naphthalene diisocyanate; examples of isocyanates having an aliphatic ring include hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, and norbornane diisocyanate, as well as trimers of these isocyanate compounds, and compounds containing terminal isocyanate groups obtained by reacting an excess amount of these isocyanate compounds with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine, or high-molecular-weight active hydrogen compounds such as various polyester polyols, polyether polyols, and polyamides.

[0076] The method for forming the anchor coat layer (C) is not particularly limited, and conventionally known methods such as coating methods can be used. Among coating methods, offline coating and in-line coating methods are preferred. For example, in the case of in-line coating, which is performed in the process of producing a base film layer, the conditions for drying and heat treatment during coating depend on the coating thickness and the conditions of the equipment, but it is preferable to send the film to a stretching process in the perpendicular direction immediately after coating and dry it in the preheating zone or stretching zone of the stretching process. In such cases, it is usually preferable to use a temperature of about 50 to 250°C.

[0077] The method for applying the resin composition for the anchor coat layer (C) is not particularly limited as long as it is a method that can apply the resin composition to the film surface to form a layer, and for example, conventional coating methods such as gravure coating, reverse roll coating, wire bar coating, and die coating can be used.

[0078] When forming the anchor coat layer (C), it is preferable to apply the resin composition for the anchor coat layer and then heat-dry it. The drying temperature is preferably 100 to 145°C, more preferably 110 to 140°C, and even more preferably 110 to 130°C. If the drying temperature is below 100°C, the anchor coat layer may not be sufficiently dried. On the other hand, if the drying temperature exceeds 145°C, the film may be overheated, causing it to become brittle or shrink, resulting in poor processability. In particular, it is particularly preferable to first volatilize the solvent at a relatively low temperature of 80 to 110°C immediately after application, and then dry it at 120°C or higher, as this will result in a uniform film. In addition to drying, additional heat treatment at as low a temperature as possible is also more effective in promoting the formation of the anchor coat layer.

[0079] [Protective layer on an inorganic thin film] In the present invention, a protective layer may be provided on the inorganic thin film layer, which is a gas barrier layer. The provision of the protective layer allows processing such as printing to be performed directly on the barrier layer side. However, in the present invention, it is necessary to design the protective layer with due consideration given to the environmental impact, such as increased costs due to the additional steps, environmental pollution caused by the solvent used, and difficulty in recycling depending on the film thickness.

[0080] In the present invention, the amount of the protective layer is set to 0.10 to 0.40 (g / m 2) is preferable. This allows the protective layer to be uniformly controlled during coating, resulting in a film with fewer coating irregularities and defects. In addition, the cohesive force of the protective layer (D) itself is improved, and the adhesion between the inorganic thin film layer and the protective layer is also strengthened. The coating weight of the protective layer is preferably 0.13 (g / m 2 ) or more, more preferably 0.16 (g / m 2 ) or more, more preferably 0.19 (g / m 2 ) or more, and preferably 0.37 (g / m 2 ) or less, more preferably 0.34 (g / m 2 ) or less, more preferably 0.31 (g / m 2 ) or less. The amount of adhesion of the protective layer (D) is 0.40 (g / m 2 ), the cohesive force inside the protective layer becomes insufficient and the uniformity of the protective layer also decreases, which can result in unevenness or defects in the coat appearance and insufficient gas barrier and adhesive properties. On the other hand, if the protective layer thickness is more than 0.10 (g / m 2 If the thickness is less than 1 / 2 mm, sufficient gas barrier properties and interlayer adhesion may not be obtained.

[0081] The resin composition used for the protective layer formed on the surface of the inorganic thin film layer of the present invention may be a polyvinyl alcohol-based, urethane-based, polyester-based, acrylic-based, titanium-based, isocyanate-based, imine-based, polybutadiene-based resin, or the like, and may further contain an epoxy-based, isocyanate-based, melamine-based, silanol-based, or other curing agent.

[0082] The method for applying the resin composition for the protective layer is not particularly limited as long as it is a method that can apply the resin composition for the protective layer to the surface of a film to form a layer. For example, a conventional coating method such as gravure coating, reverse roll coating, wire bar coating, or die coating can be used.

[0083] When forming a protective layer, it is preferable to apply the protective layer resin composition and then heat-dry it. The drying temperature is preferably 100 to 160°C, more preferably 110 to 150°C, and even more preferably 120 to 140°C. Drying temperatures below 100°C can result in insufficient drying of the protective layer, or the formation of the protective layer can be hindered, resulting in reduced cohesive strength and water-resistant adhesion, resulting in reduced barrier properties and hand-tearability. On the other hand, drying temperatures above 160°C can result in excessive heat being applied to the film, making it brittle and reducing puncture strength, or shrinking and reducing processability. It is particularly preferable to first evaporate the solvent immediately after application at a relatively low temperature of 90 to 110°C, followed by drying at 130°C or higher, as this results in a uniform and transparent film. In addition to drying, additional heat treatment at as low a temperature as possible can be even more effective in promoting the formation of the protective layer.

[0084] [Other films] In the present invention, the packaging material may contain other films in addition to the base film primarily composed of a polyolefin resin, as long as the monomaterial ratio described below is satisfied. The other films used in the present invention are, for example, films obtained by melt-extruding plastics and, as necessary, stretching them in the longitudinal and / or transverse directions, cooling, and heat setting. Examples of plastics include polyamides such as nylon 4-6, nylon 6, nylon 6-6, and nylon 12, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, as well as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene vinyl alcohol, wholly aromatic polyamides, polyamideimides, polyimides, polyetherimides, polysulfones, polystyrenes, and polylactic acids.

[0085] The other films in the present invention can have any thickness depending on the desired purpose, such as mechanical strength and transparency. Although not particularly limited, a thickness of 5 to 250 μm is usually recommended, and when used as a packaging material, a thickness of 10 to 60 μm is desirable. However, it is necessary to consider the mono-material ratio of the packaging material, which will be described later.

[0086] The other film in the present invention may be a laminated film of one or more types of plastic films. When a laminated film is used, 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.

[0087] [Heat-sealable resin layer] The packaging material of the present invention must be a laminate having a heat-sealable resin layer. The heat-sealable resin layer is typically formed by laminating the thermoplastic polymer forming the heat-sealable resin layer using extrusion lamination or dry lamination, but a film can also be prepared by co-extrusion or coating the heat-sealable resin layer. The thermoplastic polymer forming the heat-sealable resin layer may be any polymer capable of exhibiting sufficient adhesive properties, including polyolefin-based polyethylene resins such as HDPE, LDPE, and LLDPE, polypropylene resins, ethylene-vinyl acetate copolymers, ethylene-α-olefin random copolymers, and ionomer resins. Among these, LLDPE or polypropylene resins are particularly preferred due to their versatility in terms of durability, seal strength, cost, and mono-materialization. The thickness of the heat-sealable resin layer is preferably 5 to 100 μm, more preferably 10 to 95 μm, and even more preferably 15 to 90 μm. A thickness less than 5 μm may result in insufficient seal strength or may be difficult to handle due to a lack of stiffness. On the other hand, if the thickness exceeds 100 μm, the bag will be stiff and difficult to handle, and it will need to be sealed at a higher temperature, which may cause heat wrinkles on the outer base film. There is also the risk of the price becoming higher.

[0088] [Adhesive layer] The adhesive layer used in the present invention can be a general-purpose laminating adhesive. Examples include solvent-free, water-based, and hot-melt adhesives based on poly(ester)urethane, polyester, polyamide, polyamine, epoxy, poly(meth)acrylic, polyethyleneimine, ethylene-(meth)acrylic acid, polyvinyl acetate, (modified) polyolefin, polybutadiene, wax, and casein. Among these, adhesives obtained by crosslinking polyurethane, polyester, and polyamine resins are preferred from the viewpoints of heat resistance, flexibility to accommodate dimensional changes in each substrate, and improved gas barrier properties of the adhesive itself. However, caution is required because if the film becomes too hard due to crosslinking, there is a risk of reduced barrier performance after bending. It is also effective to add inorganic substances such as particles to improve barrier performance. The adhesive layer can be applied by, for example, direct gravure coating, reverse gravure coating, kiss coating, die coating, roll coating, dip coating, knife coating, spray coating, fountain coating, or other methods, and the thickness after drying is preferably 1 to 8 μm to achieve sufficient adhesiveness. It is more preferably 2 to 7 μm, and even more preferably 3 to 6 μm. If the coating thickness is less than 1 μm, it becomes difficult to bond the entire surface, and adhesive strength decreases. On the other hand, if it exceeds 8 μm, it takes a long time for the film to completely cure, unreacted material is likely to remain, and adhesive strength decreases.

[0089] [Print layer] Furthermore, the packaging material of the present invention may have at least one printed layer laminated between the base film layer and the heat-sealable resin layer or on the outside thereof. However, when printing directly on the inorganic thin film layer, it is preferable to provide a protective layer because there is a concern that the inorganic thin film layer may be scraped off by the pigment in the ink, thereby deteriorating the barrier properties. When a printed layer is provided on the barrier layer, there is a concern that the penetration effect of the adhesive layer described below into the barrier layer may be reduced. Therefore, when barrier performance is important, it is preferable to provide the printed layer on a different surface from the barrier layer so that it does not come into direct contact with the barrier layer.

[0090] As the printing ink for forming the printing layer, aqueous and solvent-based resin-containing printing inks are preferably used. Examples of resins used in printing inks 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, defoamers, crosslinking agents, anti-blocking agents, and antioxidants. The printing method for forming the printing layer is not particularly limited, and known printing methods such as offset printing, gravure printing, and screen printing can be used. To dry the solvent after printing, known drying methods such as hot air drying, heat roll drying, and infrared drying can be used.

[0091] [Characteristics of packaging materials] The packaging material of the present invention can have any conceivable laminate structure, but as mentioned above, from the viewpoint of improving toughness and gas barrier performance, one preferred structure is a laminate in which a film laminated with a gas barrier layer is sandwiched between a base film not having a gas barrier layer and a thermoplastic copolymer having a heat-sealable resin layer. In this case, by laminating a printing layer on the front side of the base film, there is also the advantage that it is not necessary to print on the film having a gas barrier layer. Other suitable structures include laminating the film with a white base film or a heat-sealable resin layer to improve hiding power, or laminating it with an ultraviolet-blocking film to provide light-blocking properties.

[0092] The packaging material of the present invention is a laminated packaging material having at least one substrate film having a resin layer mainly composed of a polyolefin resin, an adhesive layer, and a heat-sealable resin layer. Furthermore, at least one of the substrate films is a laminated gas barrier film having a gas barrier layer. The substrate film (a) having the lowest oxygen permeability among the substrate films alone has an oxygen permeability value (A) of 30 to 1500 ml / m2 measured under conditions of 23°C and 65% RH. 2The barrier value must be 1 / 2 d MPa, and when the oxygen permeability of a laminated packaging material (p) obtained by laminating a base film to a heat-sealable resin via an adhesive layer is measured under the same conditions, and this is taken as (P), the barrier value improvement rate before and after lamination, expressed by the following formula (1), is 10 or more. Barrier value improvement rate before and after film lamination = (A / P) Formula (1) In the present invention, we have found that barrier performance is significantly improved when the oxygen barrier performance of the film used is within the above range and the film is bonded to another film via an adhesive. Because the oxygen barrier performance of a polypropylene film itself is very poor, even minor defects in the barrier layer result in poorer oxygen permeability than when a polyester film is used as the substrate. While filling these defects with an adhesive can compensate for the barrier performance, we have found that the barrier repair effect is greatest in areas where there are some defects in the barrier layer (i.e., where the oxygen permeability (A) of the substrate film (a) is within the above range). While the reason for this is unclear, we believe that the presence of some defects allows the adhesive to uniformly penetrate through the barrier layer to the substrate interface (areas where the barrier film is sparse), thereby improving the barrier performance of the entire film. We believe that this allows the same level of barrier performance as that achieved by laminating multiple barrier layers in a single film to be achieved with fewer barrier layers.

[0093] The advantage of a barrier film having some defects in the barrier layer is that it has flexibility due to the low density of the film, and has high resistance to stress loads such as bending. In the present invention, the oxygen permeability value (G) of the laminated packaging material is 70 ml / m or less after performing a twist-bend test 50 times at a temperature of 23°C using a Gelbo flex tester. 2 By setting the oxygen permeability G within the above range, it is possible to obtain a packaging material with excellent bending resistance.

[0094] Furthermore, by setting the oxygen permeability (A) of the base film (a) within the above range, residual solvents and reaction gases generated from the adhesive can be quickly diffused (escaped from the film). This is expected to accelerate the curing reaction of the adhesive and shorten the aging time during lamination. Furthermore, a packaging material with excellent appearance can be obtained without the generation of bubbles in the laminate. In particular, when an adhesive with a significant barrier improvement effect is used, the volatile components have more time to diffuse, thereby further enhancing the effects of the present invention. The time required for the volatile components to completely volatilize can be measured by tracking the change in weight of the volatile components immediately after producing a laminated packaging material (p) in which the base film is bonded to the heat seal resin via the adhesive. In the present invention, the time required for the volatile components to disappear is preferably within 30 hours, more preferably within 25 hours, and even more preferably within 20 hours.

[0095] The oxygen permeability (A) of the base film (a) is 33 to 1350 ml / m 2 d MPa is preferred, and 36 to 1200 ml / m 2 ·d·MPa, more preferably 39 to 1050 ml / m 2 ·d·MPa. Oxygen permeability (A) is 30 ml / m 2 If the pressure is less than d MPa, the barrier performance of the material itself will improve due to fewer defects in the barrier layer, but the improvement in barrier performance when used as a packaging material may be small, and there is also a concern that the barrier resistance to bending may deteriorate. Furthermore, it will take a longer time for the volatile components of the adhesive to escape. On the other hand, if the oxygen permeability (A) is 1500 ml / m 2 If it is greater than d MPa, there may be too many defects, and the film may not be able to function as a barrier film even after being laminated to form a packaging material.

[0096] The barrier value improvement ratio (A / P) before and after film lamination is preferably at least 25, more preferably at least 50, and even more preferably at least 75. If (A / P) is less than 10, the effect of improving the barrier performance when used as a packaging material will be small, and there is a concern that the flex-resistant barrier property will deteriorate and the amount of residual volatile components will increase.

[0097] The packaging material of the present invention has an oxygen permeability of 60 ml / m under conditions of 23°C x 65% RH. 2 In order to achieve good gas barrier properties, it is necessary that the viscosity is 50 ml / m or less. 2 ·d·MPa or less, more preferably 40 ml / m 2 ·d·MPa or less. Oxygen permeability is 60ml / m 2 If the gas barrier strength exceeds 0.5 ml / m, it will be difficult to meet the requirements for high gas barrier properties. 2 If the oxygen permeability is less than 0.5 ml / m, the barrier performance will be excellent, but the residual solvent will be less likely to permeate to the outside of the bag, which is undesirable as it may result in a relatively increased amount of migration to the contents. 2 ·d·MPa or more.

[0098] The packaging material of the present invention has a water vapor permeability of 5.0 g / m under conditions of 40°C x 90% RH. 2 d or less is preferable in terms of exhibiting good gas barrier properties. 2 ·d or less, more preferably 3.0 g / m 2 d or less. The water vapor permeability is 5.0 g / m 2 If the water vapor permeability exceeds 0.1 g / m, it becomes difficult to use the film in applications that require high gas barrier properties. 2 If the water vapor permeability is less than 0.1 g / m, the barrier performance will be excellent, but the residual solvent will be less likely to permeate to the outside of the bag, which is undesirable because there is a risk that the amount of water vapor that migrates to the contents will increase relatively. 2 ·d or more.

[0099] As an evaluation standard for the mono-material nature of the packaging material of the present invention, when the ratio of the thickness of the polyolefin-based material to the total thickness of each film and adhesive is calculated as the mono-material (mono-mate) ratio, the mono-material ratio is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. By keeping the mono-material ratio within this range, a packaging material configuration that is easy to recycle can be achieved. If the mono-material ratio is less than 70%, recycling may be difficult due to foreign matter from other materials. As described above, it is preferable to use a polypropylene resin as the polyolefin resin constituting the base film, but if a polypropylene resin is also used in the heat-sealable resin layer, the structure can be made easier to recycle. If all the polyolefin materials used are polypropylene resins, the structure can be made even easier to recycle.

[0100] In the packaging material of the present invention, the total thickness of each film and adhesive is preferably 20 to 140 μm, more preferably 25 to 135 μm, and even more preferably 30 to 130 μm. By keeping the total thickness of the packaging material within this range, a package can be obtained that exhibits necessary physical properties such as toughness and barrier performance. If the total thickness is less than 20 μm, the toughness as a bag will be insufficient, and the bag may be torn or punctured. On the other hand, if the total thickness exceeds 140 μm, the bag will become stiff and difficult to handle, and this will increase the cost of the package, which is economically undesirable.

[0101] As described above, the packaging material of the present invention has excellent barrier properties, visibility, and bending resistance, and therefore can be used as various types of packaging, such as for boiling or retort sterilization, frozen food, vacuum packaging, and microwave heating.

[0102] The form of the package using the packaging material of the present invention is not particularly limited and can take various forms, such as a three-sided or four-sided pouch, a standing pouch, a spout pouch, etc.

[0103] The contents to be filled in the packaging bag using the packaging material of the present invention are not particularly limited, and may be liquid, powder, or gel. The contents may also be food or non-food. [Example]

[0104] 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 carried out by the following measurement methods.

[0105] (1) Thickness of various films Measurement was carried out using a dial gauge in accordance with JIS K7130-1999 Method A.

[0106] (2) Composition and thickness of inorganic thin film layer (B) 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, "supermini200") based on a previously prepared calibration curve. The excitation X-ray tube conditions were 50 kV and 4.0 mA.

[0107] (3) Adhesion amount of coating layer (A) and anchor coat layer (C) In each example and comparative example, the laminated film obtained at the stage where the specified coating layer (A) and anchor coating layer (C) were laminated on the base film was used as a sample, and a 100 mm x 100 mm test piece was cut out from this sample, and the coating layer was wiped off with either water, ethanol, or acetone, and the amount of adhesion was calculated from the change in mass of the film before and after wiping.

[0108] (4) Evaluation method for oxygen permeability (A) of base film (a) The oxygen permeability of the substrate film (a) used in each example and comparative example, which had the lowest oxygen permeability among the substrate films alone, was measured in accordance with JIS-K7126 Method B using an oxygen permeability measuring device ("OX-TRAN (registered trademark) 2 / 22" manufactured by MOCON) under an atmosphere of temperature 23°C and humidity 65% RH. The oxygen permeability measurement was carried out in the direction in which oxygen permeates from the side without the coating layer to the coating layer side.

[0109] [Production of packaging materials] (5) Preparation of packaging materials for evaluation When there was only one base film, various adhesives were applied to the base film described in the Examples and Comparative Examples so that the thickness would be 3 μm after drying at 80°C, and then an unstretched polypropylene film or a linear low-density polyethylene film described below was dry-laminated as a heat-sealable resin on a metal roll heated to 60°C, and the resulting laminate was then aged at 40°C for 96 hours or more to obtain a laminate for evaluation. On the other hand, when there were two substrate films, various adhesives were applied to the substrate films described in the Examples and Comparative Examples so that the thickness after drying treatment at 80°C would be 3 μm, and then another substrate film was dry-laminated on a metal roll heated to 60°C to form a take-up roll. The same adhesive was applied to this roll so that the thickness after drying treatment at 80°C would be 3 μm, and then an unstretched polypropylene film (CPP1) or a linear low-density polyethylene film described below was dry-laminated on the metal roll heated to 60°C as a heat-sealable resin, and the resultant was aged at 40°C for 96 hours or more to obtain a packaging material for evaluation. The adhesive used was one of the following three types. The mixing ratio of each material is shown in Table 1. Adhesive 1: Base A: Polyamine / Curing agent A: Epoxy curing adhesive (Mitsubishi Gas Chemical Company, Inc. C93 / M100) Adhesive 2: Base B: Polyester / Curing agent B: Isocyanate curing adhesive (DIC VM001 / VM108CP) Adhesive 3: Base C: Polyester / Curing agent C: Isocyanate curing adhesive (TM569 / cat10L manufactured by Toyo Morton Co., Ltd.)

[0110] (6) Evaluation method for oxygen permeability of packaging materials The oxygen permeability of the packaging material prepared in (5) above was measured in accordance with JIS-K7126 Method B using an oxygen permeability measuring device (OX-TRAN (registered trademark) 2 / 22 manufactured by MOCON) under an atmosphere of 23°C and 65% RH. The oxygen permeability measurement was carried out in the direction in which oxygen permeates from the base film side of the packaging material to the heat-sealable resin layer side.

[0111] (7) Evaluation method for oxygen permeability of packaging materials after bending test The packaging material prepared in (5) above was cut into a 112 inch x 8 inch sample piece, which was mounted in a Gelbo Flex Tester (MIL-B131H, manufactured by Rigaku Kogyo Co., Ltd.) in the shape of a cylinder with a diameter of 3 (1 / 2) inches, and held at both ends with an initial gripping distance of 7 inches, a stroke of 3 (1 / 2) inches, and a twist of 400 degrees. This operation was repeated 25 times at a speed of 50 times / min under conditions of 23°C and a relative humidity of 65%. The oxygen permeability (after bending treatment) of the resulting packaging material after the bending test was measured in the same manner as above.

[0112] (8) Evaluation method for water vapor permeability of packaging materials The water vapor permeability of the packaging material prepared in (5) above was measured in accordance with JIS-K7129 Method B using a water vapor permeability measuring device ("PERMATRAN-W 3 / 33MG" manufactured by MOCON) under an atmosphere of 40°C temperature and 90% RH. The water vapor permeability was measured in the direction in which water vapor permeated from the base film side of the packaging material to the heat-sealable resin side.

[0113] (9) Evaluation method for the time required for volatile components of packaging materials to disappear The packaging material prepared in (5) above was cut into a 10 cm square sample, and the weight of the sample was measured immediately after dry lamination. The sample was stored in an environment of 40°C, and the weight was measured every 5 hours to confirm any changes. The time from immediately after dry lamination until there was no change in weight was defined as the time required for the volatile components to disappear.

[0114] (10) Evaluation criteria for mono-materialization: mono-material ratio For the packaging materials prepared in (5) 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 (monomate) ratio as an evaluation criterion for monomaterialization.

[0115] (11) Evaluation criteria for visibility and range suitability Regarding the packaging materials prepared in (5) above, as the evaluation criteria for visibility and microwave suitability, those that were transparent and did not use aluminum foil or aluminum vapor deposition in the barrier layer were rated as 'Good'.

[0116] The substrate films used in Examples 1 to 12 and Comparative Examples 1 to 4 are listed in Table 6 below. [Preparation of base film] Tables 1 to 4 show the details of the polypropylene resin raw materials used in the production of the polyolefin substrate films OPP-1 to 4, the film forming conditions, and the raw material blending ratios.

[0117] [Table 1]

[0118] [Table 2]

[0119] [Table 3]

[0120] [Table 4]

[0121] (OPP-1) The base layer (A) was made by blending 30% by weight of a propylene homopolymer (Sumitomo Chemical Co., Ltd., PP "FS2012"; copolymerization monomer amount: 0 mol%; hereinafter abbreviated as "PP-2") having Mn=81,000, Mw=320,000, MFR=2.2 g / 10 min, and mesopentad fraction [mmmm]=99.2% (Table 1) with 70% by weight of a propylene homopolymer (Sumitomo Chemical Co., Ltd., PP "FLX80E4"; copolymerization monomer amount: 0 mol%; hereinafter abbreviated as "PP-3") having Mn=65,000, Mw=240,000, MFR=7.5 g / 10 min, and mesopentad fraction [mmmm]=98.9% (Sumitomo Chemical Co., Ltd., PP "FLX80E4"; copolymerization monomer amount: 0 mol%; hereinafter abbreviated as "PP-3"). The surface layer (B) was made of a blend of 24.8 wt % of a propylene polymer (Novatec (registered trademark) PP "FL4" manufactured by Japan Polypropylene Corporation, abbreviated as "PP-5") with Mn=55,000, Mw=300,000, and MFR=5.6 g / 10 min, 72.2 wt % of a propylene polymer (Prime Polypropylene "F-300SP" manufactured by Prime Polymer Corporation, abbreviated as "PP-6") with Mn=59,000, Mw=310,000, and MFR=5.3 g / 10 min, and 3.0 wt % of the masterbatch A shown in Table 2. The base layer (A) was extruded using a 45 mm extruder, the surface layer (B) using a 25 mm extruder, and the second surface layer (B) using a 20 mm extruder. The raw resins were melted at 250 ° C and co-extruded into a sheet from a T-die. The surface layer (B) was cooled and solidified so that it came into contact with a 40 ° C cooling roll, and then stretched 4.5 times in the machine direction (MD) at 125 ° C. Then, in a tenter, both ends of the film in the transverse direction (TD) were clamped with clips, preheated at 174 ° C., stretched 8.2 times in the transverse direction (TD) at 158 ° C., and heat-set at 175 ° C. while relaxing 6.7% in the transverse direction (TD). The film-forming conditions at this time were film-forming conditions a. In this way, a biaxially oriented polypropylene film having a structure of surface layer (B) / base layer (A) / second surface layer (B) was obtained. The surface of the surface layer (B) of the biaxially oriented polypropylene film was corona treated using a corona treater manufactured by Softal Corona & Plasma GmbH at an applied current of 0.75 A, and then wound up on a winder. The thickness of the resulting film was 20 μm (thicknesses of surface layer (B) / base layer (A) / second surface layer (B) were 1.0 μm / 18.0 μm / 1.0 μm). Details of this configuration are shown in Table 4.

[0122] (OPP-2) The base layer (A) was made of 100% by weight of propylene homopolymer (PP "FL203D" manufactured by Japan Polypropylene Corporation; copolymerization monomer amount was 0 mol%; hereafter abbreviated as "PP-1") with Mn = 56,000, Mw = 310,000, MFR = 2.5 g / 10 min, and mesopentad fraction [mmmm] = 94.8% as shown in Table 1. The surface layer (B) was made of 95.2% by weight of PP-1 and 4.8% by weight of masterbatch B. The film was formed under the conditions of b in Table 3. The same conditions were used as for OPP1, but a 20 μm biaxially oriented polypropylene film was obtained. The details of this configuration are shown in Table 4.

[0123] (OPP-3) A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as OPP1, except that the base layer (A) contained 27.0 wt% of the polypropylene homopolymer PP-2 shown in Table 1, 70.0 wt% of the polypropylene homopolymer PP-3 shown in Table 1, and 3 wt% of [PE-1: ethylene homopolymer "SLH218" manufactured by Braskem, MFR: 2.3 g / 10 min, melting point: 126°C, bio-based content: 84%, density: 0.916 g / cm3]. Details of this composition are shown in Table 4. (OPP-4) A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as OPP1, except that the surface layer (C) was made using a blend of 52.0 wt% of a propylene-ethylene copolymer (Wintech (registered trademark) PP "WFX4M" manufactured by Japan Polypropylene Corporation: abbreviated as "PP-4") with Mn=80,000, Mw=220,000, and MFR=7.0 g / 10 min shown in Table 1, 45.0% of PP-1, and 3.0% by weight of Masterbatch A shown in Table 2. The details of this composition are shown in Table 4. (OPP-5) A 20 μm biaxially oriented polypropylene film was obtained under the same conditions as OPP-2, except that the base layer (A) was made of 99.0 wt% PP-1 and 1.0 wt% stearyl diethanolamine stearate (KYM-4K, Matsumoto Oil & Fat Co., Ltd.) as an antistatic agent. The details of this composition are shown in Table 4.

[0124] (Other base films) (Vapor-deposited PET) 12 μm thick transparent vapor-deposited polyester film (Toyobo "VE100-12 μm")

[0125] (Coating layer (A)) The coating liquids used in Examples 1 to 12 and Comparative Examples 1 to 4 for forming the coating layer (A) are shown in Table 6 below.

[0126] [Polyvinyl alcohol resin (a)] To 90 parts by mass of purified water, 10 parts by mass of fully saponified polyvinyl alcohol resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: G Polymer OKS8049Q (saponification degree 99.0% or more, average polymerization degree 450)) was added, and the mixture was heated to 80°C with stirring, and then stirred for about 1 hour.The mixture was then cooled to room temperature, and a nearly transparent polyvinyl alcohol solution (PVA solution) with a solids content of 10% was obtained.

[0127] [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, was added to 95 parts by mass of purified water while stirring, and the mixture was thoroughly dispersed using a homogenizer set at 1500 rpm. The mixture was then kept at 23°C for one day to obtain an inorganic layered compound dispersion with a solid content of 5%.

[0128] [Coating liquid 1 used for coating layer 1] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for 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

[0129] (Coating of coating fluid onto film (lamination of coating layer)) The coating solution prepared above was applied to the corona-treated surface of the substrate film using a gravure roll coating method, pre-dried at 90°C for 4 seconds, and then fully dried at 120°C for 4 seconds to obtain a coating layer. The coating layer had a deposition weight of 0.30 g / m2. This was followed by a post-heat treatment at 40°C for 2 days (48 hours). In this manner, a laminated film with a coating layer was produced.

[0130] (Inorganic thin film layer (B)) The method for producing the inorganic thin film layer (A) used in each of the Examples and Comparative Examples will be described below. The inorganic thin film layer (A) used in Examples 1 to 12 and Comparative Examples 1 to 7 is shown in Table 5. (Formation of inorganic thin film layer 1) As the inorganic thin film layer 1, a composite oxide layer of silicon dioxide and aluminum oxide was formed on the substrate film or anchor coat layer by electron beam evaporation. The evaporation sources used were 3-5 mm particulate SiO2 (purity 99.9%) and Al2O3 (purity 99.9%). The thickness of the inorganic thin film layer (SiO2 / Al2O3 composite oxide layer) in the film thus obtained (film containing an inorganic thin film layer / coating layer) was 13 nm. The composition of this composite oxide layer was SiO2 / Al2O3 (mass ratio) = 70 / 30.

[0131] (Formation of inorganic thin film layer 2) Silicon oxide was vapor-deposited onto the base film or anchor coat layer to form the inorganic thin film layer 2. Using a small vacuum deposition device (ULVAC KIKO Co., Ltd., VWR-400 / ERH), the pressure was reduced to 10 Pa or less, and silicon oxide was then placed in a Nilaco vapor deposition source B-110 below the substrate and heated to evaporate, forming a silicon oxide film 30 nm thick on the film. (Formation of inorganic thin film layer 3) Metallic aluminum was vapor-deposited onto the base film or anchor coat layer to form the inorganic thin film layer 3. Using a small vacuum deposition apparatus (ULVAC KIKO Co., Ltd., VWR-400 / ERH), the pressure was reduced to 10 Pa or less, and then aluminum foil with a purity of 99.9% was placed in a Nilaco evaporation source CF-305W from below the substrate, and metallic aluminum was heated and evaporated to form a metallic aluminum film with a thickness of 30 nm on the film. (Formation of inorganic thin film layer 4) Aluminum oxide was vapor-deposited onto the base film or anchor coat layer to form the inorganic thin film layer 4. To vapor-deposit aluminum oxide onto the base film layer, the film was placed on the unwinding side of a continuous vacuum deposition machine and wound up while being run over a cooled metal drum. The continuous vacuum deposition machine was then depressurized to 10-4 Torr or less, and 99.99% pure aluminum metal was loaded into an alumina crucible below the cooling drum. The aluminum metal was then heated and evaporated, and oxygen was supplied to the vapor to cause an oxidation reaction, depositing it on the film and forming a 10 nm thick aluminum oxide film.

[0132] (Anchor coat layer (C)) The method for producing the anchor coat layer (C) used in each of the examples and comparative examples will be described below. [Polyester resin (a)] As the polyester component, polyester polyol (DIC Corporation's "DF-COAT GEC-004C": solid content 30%) was used.

[0133] [Polyisocyanate crosslinking agent (b)] As the polyisocyanate component, a trimethylolpropane adduct of metaxylylene diisocyanate ("Takenate D-110N" manufactured by Mitsui Chemicals, Inc.: solid content 75%) was used.

[0134] [Silane coupling agent (c)] As the silane coupling agent, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane ("KBM-603" manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

[0135] [Coating solution 1 for anchor coat layer 1] A solution (15% by mass) of silane coupling agent (c) dissolved in acetone and isocyanate (b) were mixed in the ratio shown below and stirred for 10 minutes using a magnetic stirrer. The resulting mixture was diluted with methyl ethyl ketone and 1-methoxy-2-propanol (hereinafter referred to as PGM), and polyester resin (a) was added to obtain the target coating solution 1. The mixing ratio is shown below. Polyester resin (a) 10.62% by mass Isocyanate (b) 4.07% by mass Silane coupling agent (c) * Acetone diluted solution 1.73 mass% Methyl ethyl ketone 69.55% by mass PGM 14.03% by mass

[0136] (Coating of coating fluid onto film (lamination of anchor coat layer)) Coating Solution 1 was applied to the corona-treated surface of the substrate film by gravure roll coating, pre-dried at 95°C for 4 seconds, and then dried at 115°C for 4 seconds to obtain an anchor coat layer. The adhesion weight of the anchor coat layer at this time was 0.40 g / m2. This was followed by a post-heat treatment at 40°C for 4 days (96 hours) to obtain the desired laminate film.

[0137] In this way, packaging materials were prepared that had a coating layer, anchor coat layer, inorganic thin film layer, or protective layer on each film, and further had a heat-sealable resin. The adhesives used are shown in Table 5.

[0138] [Table 5]

[0139] In each example and comparative example, each package was used and bonded by dry lamination using the adhesive described above to obtain a packaging material having the configuration shown in Table 6. The heat-sealable resin layer used was one of the following: (Heat sealable resin) (CPP1) 30 μm thick unstretched polypropylene film (Toyobo Co., Ltd. "P1128") The configuration of the produced packaging body is shown in Table 6. Various evaluations were also carried out on the obtained packaging body. The results are shown in Table 6.

[0140] [Table 6A]

[0141] [Table 6B] [Industrial Applicability]

[0142] According to the present invention, by forming a packaging material in which a predetermined barrier layer tailored to the required performance is laminated on a polyolefin-based base film, it is possible to significantly improve gas barrier performance and further ensure durability capable of withstanding stress loads during processing. Finally, by laminating a sealant made of an olefin-based component, it has been discovered that this contributes to the creation of a mono-material while maintaining high sealing properties. Furthermore, the packaging material of the present invention can be produced as a package with low volatile components, resulting in less food migration and fewer appearance defects. Furthermore, since the packaging material requires few processing steps and can be easily produced, and the volatile components are quickly removed, it is excellent in both economy and production stability, and can provide a gas barrier package with uniform properties.

Claims

1. A laminated packaging material comprising at least one substrate film having a resin layer mainly composed of a polyolefin resin, an adhesive layer, and a heat-sealable resin layer, wherein at least one of the substrate films is a laminated gas barrier film having a gas barrier layer, and wherein the substrate film (a) having the lowest oxygen permeability among the laminated substrate films alone has an oxygen permeability value (A) of 30 to 1500 ml / m2 measured under conditions of 23°C x 65% RH. ２ d MPa, and the oxygen permeability value (P) of a laminated packaging material (p) obtained by laminating a base film with a heat-sealable resin via an adhesive layer is 60 ml / m or more, as measured under the same conditions. ２ .d.MPa or less, and the barrier value improvement rate before and after lamination, represented by the following formula (1), is 10 or more. Barrier value improvement rate before and after film lamination = (A / P) Formula (1)

2. The laminated packaging material according to claim 1, characterized in that the oxygen permeability value (G) after performing a twist-bend test 25 times at a temperature of 23°C using the laminated packaging material with a Gelbo flex tester is 65 ml / m2·d·MPa or less.

3. 3. The laminated packaging material according to claim 1 or 2, characterized in that the time required for the volatilization of the volatile components to cease immediately after the laminated packaging material (p) is produced by laminating the base film and the heat seal resin via the adhesive is within 30 hours.

4. The laminated packaging material according to any one of claims 1 to 3, wherein the base film comprises the base film (a) and another base film (b), the base film (b) is a laminated barrier film having a resin layer and a gas barrier layer, and the base film (a) and the resin layer constituting the base film (b) contain the same type of polyolefin-based resin as a main component.

5. 5. The laminated packaging material according to claim 1, comprising two or less base films.

6. 6. The laminated packaging material according to claim 1, wherein the resin layer constituting the base film and the heat-sealable resin layer are mainly composed of the same type of polyolefin resin.

7. 7. The laminated packaging material according to claim 1, wherein the adhesive layer is made of a material selected from the group consisting of polyurethane, polyester, and polyamine resins.

8. 8. The laminated packaging material according to any one of claims 1 to 7, wherein the gas barrier layer is an inorganic thin film layer made of any one of aluminum, aluminum oxide, silicon oxide, and a composite oxide of silicon oxide and aluminum oxide.

9. 9. The laminated packaging material according to claim 1, wherein the gas barrier layer is a coating layer made of any one of polyvinyl alcohol resin, polyester resin, and polyurethane resin.

10. 10. The laminated packaging material according to claim 1, wherein an anchor coat layer is laminated between the base film and the gas barrier layer.

11. The laminated packaging material according to any one of claims 1 to 10, which is used for boiling or retorting.

12. The packaging material according to any one of claims 1 to 10, which is used for heating in a microwave oven.

13. A packaging bag constructed using the laminated packaging material according to any one of claims 1 to 12.

14. A package in which an item to be packaged is packaged using the laminated packaging material according to any one of claims 1 to 12 or the packaging bag according to claim 13.

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