Laminated films and packaging materials

Abstract

The present invention addresses the problem of providing a laminated film that can form a laminated structure composed mainly of a polypropylene film and composed of almost a single resin type having a low environmental load, the laminated film having required performance such as gas barrier properties or adhesiveness required for packaging materials, as well as processing suitability. In order to solve the problem, the present invention provides a laminated film in which a coating layer having a polyvinyl alcohol-based copolymer and an inorganic layered compound is provided on at least one surface of the base film, the laminated film satisfying requirements (a) to (d) below. (a) The base film is a stretched film using a propylene-based resin. (b) The coating weight of the coating layer is 0.10 g / m2 to 0.50 g / m2. (c) In a total reflection infrared absorption spectrum of the laminated film, the ratio (P1 / P2) of a peak intensity (P1) having an absorption maximum in a region of 1040±10cm-1 to a peak intensity (P2) having an absorption maximum in a region of 3300±10cm-1 is within the range of 3.0-25.0. (d) The arithmetic mean roughness in 2 square μm of the coating layer on the laminated film is within the range of 2.0-8.0 nm.

Description

[Technical Field]

[0001] The present invention relates to a gas barrier laminate film, and more specifically to a gas barrier coated film that imposes a small environmental load during production and disposal, and that combines both excellent gas barrier performance and sufficient adhesive strength for use as a packaging material. [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] The required performance of the aforementioned environmentally friendly packaging materials is (1) that they are made from recyclable materials, (2) that they have gas barrier properties that can block various gases and extend the shelf life, and (3) that they have a laminate structure that has a low environmental impact (for example, they do not use organic solvents). The advantages of using recycled materials include the fact that the amount of materials used is small, and that recycling is possible by converting them into monomaterials.

[0004] In recent years, the use of polypropylene film has been attracting attention as a way to achieve the above-mentioned (2) and (3). Polypropylene film is widely used for a wide range of applications, including packaging for food and various other products, electrical insulation, and surface protection. Due to its molecular structure, polypropylene film is capable of exhibiting high water vapor barrier properties. Furthermore, since polypropylene- or polyethylene-based heat-seal resins are commonly used as sealants to bond the surface substrate film, using, for example, polypropylene film for the surface substrate and an unstretched polypropylene sheet for the sealant makes it possible to achieve a mono-material packaging material as a whole while still maintaining gas barrier properties, enabling the design of environmentally friendly packaging materials that are easy to recycle.

[0005] However, with regard to the gas barrier property (2) above, although polypropylene film has water vapor barrier property, the water vapor barrier property is not sufficient compared to, for example, transparent inorganic vapor-deposited polyester film, which is generally considered to have excellent water vapor barrier property, and there is a problem that the oxygen barrier property is very poor. In response to this, films have been used in which a polymer resin composition, which is generally considered to have relatively high oxygen barrier property, such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride resin, or polyacrylonitrile, is laminated onto a polypropylene film (see, for example, Patent Documents 1 to 3).

[0006] However, gas barrier coated films made from the polymer resin compositions of polyvinyl alcohol and ethylene-vinyl alcohol copolymer are highly humidity-dependent, and therefore exhibit a decrease in gas barrier properties under high humidity conditions. Polyvinylidene chloride resin and polyacrylonitrile, while less humidity-dependent, have problems with insufficient absolute barrier values ​​and the risk of generating hazardous substances during disposal or incineration.

[0007] As a method for improving the humidity dependency of vinyl alcohol-based resins, a gas barrier coated film has been proposed in which a coating layer of vinyl alcohol-based resin mixed with a silane-based crosslinking agent is laminated. In this case, since the vinyl alcohol-based resin is crosslinked by silanol groups, humidity dependency is low and good gas barrier properties are exhibited (see, for example, Patent Documents 4 and 5).

[0008] However, these gas barrier coated films require sufficient heat treatment to crosslink them, and when the substrate is a polypropylene film, they do not provide sufficient properties as packaging materials due to deterioration of mechanical properties and heat wrinkles during processing. In addition, the heat treatment during processing requires a large amount of thermal energy, which is undesirable from the perspective of environmental load. Furthermore, their water vapor barrier performance is still insufficient.

[0009] On the other hand, as a means for further improving the barrier performance, a gas barrier coated film has been proposed in which a resin layer containing inorganic layered particles of a specific particle size and aspect ratio is laminated to a vinyl alcohol resin. In this case, the inorganic layered particles dispersed in the resin layer cause a detouring effect of gas molecules, resulting in good gas barrier properties (see, for example, Patent Documents 6 and 7).

[0010] However, in these gas barrier coated films, the inorganic layered particles are often not uniformly dispersed in the coating, which results in impaired adhesion to the substrate film and reduced laminate strength.Furthermore, fully satisfactory performance has not been achieved in terms of improving both oxygen barrier property and water vapor barrier property.

[0011] All of the aforementioned barrier coating layers needed to be at least 0.5 μm thick to achieve sufficient barrier performance. A thick coating layer could make recycling difficult and was also unsuitable from the perspective of mono-materialization. Furthermore, during processing steps such as printing, there were issues with poor printing due to unevenness and irregularities in the coating. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-52501 [Patent Document 2] Japanese Patent Application Publication No. 4-359033 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-231221 [Patent Document 4] Japanese Patent Application Publication No. 4-345841 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-95782 [Patent Document 6] Japanese Patent Application Publication No. 9-111017 [Patent Document 7] Japanese Patent Application Laid-Open No. 2005-35167 Summary of the Invention [Problem to be solved by the invention]

[0013] In the above Patent Documents 1 to 3, not only were the barrier performance insufficient, but environmentally friendly designs were not considered. Patent Documents 4 and 5 did not consider appropriate coating processing of polypropylene films, and water vapor barrier properties were not fully discussed. Patent Document 6 did not consider improvements in adhesiveness or water vapor barrier properties. Patent Document 7 did not consider oxygen barrier properties. Furthermore, none of the documents considered improving processability or environmental friendliness by reducing the thickness of the coating layer. In other words, there has not previously been a material that satisfies all three of the performance requirements for the aforementioned environmentally friendly packaging material: (1) containing recyclable materials as constituent materials, (2) having gas barrier properties that can block various gases and extend the shelf life, and (3) having a laminate structure that is easy to recycle and has a low environmental impact (mono-material).

[0014] 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 laminate film that can form a laminate structure composed of almost a single resin type, mainly consisting of polypropylene film, which has a low environmental impact, and that has the necessary performance such as gas barrier properties, adhesiveness, and processability required for packaging materials. [Means for solving the problem]

[0015] The present inventors discovered that by laminating a specific coating layer tailored to the required performance on a polypropylene film, it is possible to significantly improve gas barrier performance and provide a film that has a low environmental impact, and this discovery led to the completion of the present invention.

[0016] That is, the present invention comprises the following configurations. 1. A laminated film having a coating layer containing a polyvinyl alcohol copolymer and an inorganic layer compound on at least one surface of a base film, the laminated film comprising: (a) a base film having a thickness of 100 μm or more; d) A laminated film characterized by satisfying the requirement. (a) The base film is a stretched film using a propylene-based copolymer. (b) The coating weight of the coating layer is 0.10 g / m 2 More than 0.50g / m 2 It must be less than or equal to: (c) In the total reflection infrared absorption spectrum of the laminated film, 1040±10 cm -1 The peak intensity (P1) has an absorption maximum in the region of 3000±10cm -1 (d) The arithmetic mean roughness of the coating layer on the laminated film in a 2 μm square area is 2.0 to 8.0. A laminated film characterized by a thickness in the range of nm. 2. The oxygen permeability of the laminated film under an environment of 23°C x 65% RH is 50 ml / m 2 ·d·MPa or less and water vapor permeability of 4g / m under 40℃×90%RH environment 2 1. The laminated film according to 1., wherein the thickness is d or less. 3. The laminated film according to 1. or 2., wherein the inorganic layered compound of the coating layer contains a montmorillonite-based compound as a constituent component. 4. A packaging material comprising the laminate film according to any one of 1. to 3. above, and an olefin-based sealant layer laminated on one side of the laminate film. [Effects of the Invention]

[0017] This technology has made it possible for the present inventors to provide a laminated film that is environmentally friendly and has the necessary properties required for packaging materials, such as barrier properties, adhesive properties, and processability. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below. [Base film layer] The propylene-based resin stretched film used as the base film in the present invention is preferably a biaxially stretched film. Known biaxially stretched polypropylene-based resin films can be used as the biaxially stretched polypropylene-based resin film, and the raw materials, blending ratios, etc. are not particularly limited. For example, in addition to polypropylene homopolymers (propylene homopolymers), random copolymers or block copolymers containing propylene as the main component with one or more α-olefins selected from ethylene, butene, pentene, hexene, etc., or mixtures of two or more of these polymers may also be used. 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] The biaxially oriented polypropylene resin film used in the present invention may be a single-layer film or a laminated film in which a plurality of resin films including the biaxially oriented polypropylene resin film are laminated. 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.

[0020] In the present invention, the polypropylene resin constituting the base film is preferably a propylene homopolymer that is substantially free of comonomer, and even if it contains comonomer, 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, the heat shrinkage rate at high temperatures is reduced, and heat resistance is improved. Note that a trace amount of comonomer may be contained within a range that does not significantly reduce crystallinity.

[0021] The polypropylene resin constituting the base film preferably contains a propylene homopolymer obtained only from propylene monomers, and even if it is a propylene homopolymer, it is most preferable that it does not contain heterogeneous bonds such as head-to-head bonds.

[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 shrinkage at high temperatures is reduced, 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, the stretching temperature and heat setting temperature can be easily increased, the heat shrinkage rate is smaller, and heat resistance is improved.

[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 at least uniaxially, a film with low heat shrinkage 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, 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 temperature of 120°C to 165°C to a ratio of 3.0 to 8.0. Subsequently, after preheating in a tenter, the sheet can be stretched in the transverse direction (TD) at a temperature of 155°C to 175°C to a ratio of 4.0 to 20.0. 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] The substrate film used in the present invention preferably contains particles to form protrusions on the film surface to improve handling (e.g., winding properties after lamination). Examples of particles to be contained in the film include inorganic particles such as silica, kaolinite, talc, calcium carbonate, zeolite, and alumina, and heat-resistant polymer particles such as acrylic, PMMA, nylon, polystyrene, polyester, and benzoguanamine-formalin condensate. From the viewpoint of transparency, the particle content in the film is preferably low, for example, 1 ppm to 1000 ppm. Furthermore, from the viewpoint of transparency, it is preferable to select particles with a refractive index close to that of the resin used. Furthermore, the film may contain antioxidants, UV absorbers, antistatic agents, dyes, lubricants, nucleating agents, adhesives, antifogging agents, flame retardants, antiblocking agents, inorganic or organic fillers, and the like to impart various functions as needed.

[0027] Other than the polypropylene resin used in the present invention, the film may contain a resin to the extent that the object of the present invention is not impaired in order to improve the mechanical properties of the base film and the adhesion to the ink layer or adhesive layer laminated on the gas barrier coating layer, etc. Examples of such a resin include 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.

[0028] 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 100 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.

[0029] The haze of the polypropylene film used as the substrate of the present invention is preferably transparent from the viewpoint of visibility of the contents, specifically, preferably 6% or less, more preferably 5% or less, and even more preferably 4% or less. 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. Here, haze was evaluated in accordance with JIS K7136 using a turbidity meter (Nippon Denshoku, NDH2000).

[0030] Furthermore, the base film layer in the present invention may be subjected to corona discharge treatment, glow discharge treatment, flame treatment, surface roughening treatment, or known anchor coating treatment, printing, decoration, etc., as long as the treatment does not impair the object of the present invention. However, since a resin other than polyolefin, such as polyurethane or polyester, is generally used for the anchor coating, it is preferable not to perform anchor coating treatment from the viewpoint of monomaterials.

[0031] [Coating layer] In the present invention, the substrate film has a coating layer for the purpose of improving the gas barrier performance and adhesiveness of the substrate film, but in the present invention, it is necessary to design the substrate film while taking into consideration the environmental impact of providing the coating layer, such as increased costs due to the additional steps and difficulty in recycling depending on the coating layer thickness.

[0032] The coating layer adhesion weight is 0.10 to 0.50 (g / m 2 ) is preferable. When a coating layer using a polyvinyl alcohol copolymer and an inorganic layered compound, which will be described later, is used on the above-mentioned polypropylene resin substrate, the present inventors have found that by setting the coating amount within the above-mentioned specific range, it is possible to achieve a balance between gas barrier properties, coat appearance, adhesion, and recyclability. This makes it possible to uniformly control the coating layer during coating, resulting in a film with fewer coating irregularities and defects. In addition, since the coating layer is thin, it can contribute to reducing foreign matter during recycling. The lower limit of the coating layer coating amount is preferably 0.15 (g / m 2 ) or more, more preferably 0.20 (g / m 2 ) or more, more preferably 0.25 (g / m 2 ) or more, and the upper limit is preferably 0.45 (g / m 2 ) or less, more preferably 0.40 (g / m 2 ) or less, more preferably 0.35 (g / m 2 ) or less. The coating layer adhesion weight is 0.50 (g / m 2 ), the gas barrier properties improve, but the cohesive force inside the coating layer becomes insufficient and the uniformity of the coating layer also decreases, which can result in unevenness (increased haze, whitening) or defects in the coat appearance, or in insufficient gas barrier properties and adhesiveness. In terms of processability, a thick film thickness can also cause blocking. Furthermore, there is a concern that it may have a negative effect on the recyclability of the film. On the other hand, if the coating layer thickness is 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.

[0033] A polyvinyl alcohol polymer is desirable as the resin composition used for the coating layer formed on the surface of the laminated film of the present invention. Polyvinyl alcohol 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 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.

[0034] The coating layer of the present invention contains an inorganic layered compound. The presence of the inorganic layered compound is expected to provide a labyrinth effect against gases, improving 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 the inorganic layered compound. These compounds may be used alone or in combination of two or more. Among these, smectite (including synthetic products thereof) is particularly preferred due to its high water vapor barrier property improvement effect.

[0035] 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.

[0036] 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. On the other hand, the aspect ratio is 50 to 5000, more preferably 100 to 4000, and even more preferably 200 to 3000.

[0037] The compounding ratio of the polyvinyl alcohol copolymer and the inorganic layer 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%). %, more preferably 65 / 35 to 45 / 55 (wt%). If the blending ratio is less than 25%, the barrier performance may be insufficient, whereas if it is more than 65%, the dispersibility may be poor, which may result in poor coating properties and poor adhesion.

[0038] In the present invention, the ratio (P1 / P2) of the peak intensity (P1) having an absorption maximum in the 1040±10 cm-1 region to the peak intensity (P2) having an absorption maximum in the 3300±10 cm-1 region in the total reflection infrared absorption spectrum of the coating layer must be within the range of 3.0 to 25.0. It is preferably within the range of 4.0 to 24.0, and more preferably within the range of 5.0 to 23.0. The peak at 1040±10 cm-1 is a peak derived from the silica molecular structure and serves as an indicator of the amount of silica bonded to the inorganic layered compound in the coating layer. The peak at 3300±10 cm-1 is a peak derived from hydroxyl groups and serves as an indicator of the amount of hydroxyl groups in the coating layer. (P1 / P2) represents the ratio of silica bond to hydroxyl groups. Having this ratio within the above range allows silica particles to be arranged in the film without inhibiting hydrogen bonding of hydroxyl groups, resulting in maximum gas barrier performance. Adhesion is also achieved. If the (P1 / P2) ratio is less than 3.0, the amount of silica bonded in the coating layer is low, resulting in a lack of a labyrinth effect, making it difficult to achieve satisfactory gas barrier properties. Furthermore, in terms of processability, the coating layer may be prone to blocking. On the other hand, if the (P1 / P2) ratio exceeds 25.0, the gas barrier properties are improved, but the film becomes brittle, which is unfavorable in terms of adhesion when formed into a laminate. Furthermore, the dispersibility of the coating liquid may be impaired, leading to concerns about poor appearance (increased haze, whitening) during coating. To achieve a (P1 / P2) value for the coating layer within the specified numerical range, it is necessary to use the aforementioned materials in the specified coating amounts, furthermore, to set the compounding ratio of the materials within the aforementioned appropriate range, and combine it with the drying and heat treatment conditions described below.

[0039] In the present invention, the arithmetic mean roughness of the coating layer measured under an atomic force microscope (AFM) of 2 μm square is preferably 2.0 to 8.0 nm. This allows the coating layer to maintain uniformity and exhibit stable barrier performance, while the formation of surface irregularities primarily resulting from the coordination of the inorganic layered particles enhances adhesion and blocking resistance. The arithmetic mean roughness is preferably 2.5 nm or more, more preferably 3.0 nm or more, and even more preferably 3.5 nm or more, and is preferably 7.5 nm or less, more preferably 7.0 nm or less, and even more preferably 6.5 nm or less. If the arithmetic mean roughness exceeds 8.0 nm, the surface becomes too rough and the uniformity of the coating layer decreases, resulting in unevenness and defects in the coating appearance, which may reduce printability, adhesion, and barrier properties. On the other hand, if the arithmetic mean roughness is less than 2.0 nm, the surface may be too flat, potentially reducing adhesion and ink transfer during printing. Furthermore, the blocking resistance described below may also deteriorate, potentially resulting in blocking when the film is wound into a roll. To achieve an arithmetic mean roughness value within the specified numerical range, it is necessary to use the materials described above to achieve the specified deposition amount, and further to set the compounding ratio of the materials within the appropriate range described above, in combination with the dilution conditions of the coating liquid and the drying and heat treatment conditions described below.

[0040] The coating layer of the present invention may contain various crosslinking agents to improve the cohesive strength and moist heat-resistant adhesion of the film, 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, isocyanate compounds, and the like. Among these, silicon-based crosslinking agents are particularly preferred from the viewpoint of improving water-resistant adhesion, particularly with the inorganic thin film layer, by incorporating a silicon-based crosslinking agent. Other crosslinking agents that may be used in combination include oxazoline compounds, carbodiimide compounds, epoxy compounds, and the like. However, when emphasis is placed on recyclability, it is preferable not to incorporate a crosslinking agent.

[0041] In the present invention, from the viewpoint of visibility of the contents, the film haze after lamination of the coating layer is preferably 20% or less, more preferably 18% or less, and even more preferably 16% or less. 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, solvent conditions, film thickness, etc. Here, the haze was evaluated in accordance with JIS K7136 using a turbidity meter (NDH2000, manufactured by Nippon Denshoku).

[0042] 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.

[0043] When forming a coating layer, it is preferable to apply a 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.

[0044] 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 below 110°C, film formation of the coating layer may 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 large wrinkles due to heat shrinkage.

[0045] 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 furnace. Furthermore, additional heat treatment for 1 to 4 days at a temperature as low as possible, specifically 40 to 60°C, can be even more effective in accelerating the formation of the coating layer.

[0046] [Packaging materials] When the laminated film of the present invention is used as a packaging material, it is preferable to form a laminate having a heat-sealable resin layer called a sealant. The heat-sealable resin layer is usually formed on the coating layer, but may also be formed on the outer side of the base film layer (the surface opposite to the surface on which the coating layer is formed). The heat-sealable resin layer is usually formed by extrusion lamination or dry lamination. The thermoplastic polymer forming the heat-sealable resin layer may be any polymer that can sufficiently exhibit sealant adhesion, and examples thereof include olefin-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 high versatility in terms of durability, seal strength, cost, and mono-materialization. The thickness of the sealant layer is 20 to 100 mm. The thickness is preferably 100 μm, more preferably 30 to 90 μm, and even more preferably 40 to 80 μm. If the thickness is less than 20 μm, sufficient seal strength may not be obtained, and the bag may be difficult to handle due to its lack of stiffness. On the other hand, if the thickness exceeds 100 μm, the bag may be difficult to handle due to its strong stiffness, and the price may be high.

[0047] [Adhesive layer] The adhesive layer used in the present invention can be a general-purpose laminating adhesive. For example, solvent-free, aqueous, or hot-melt adhesives based on poly(ester)urethane, polyester, polyamide, epoxy, poly(meth)acrylic, polyethyleneimine, ethylene-(meth)acrylic acid, polyvinyl acetate, (modified) polyolefin, polybutadiene, wax, or casein can be used. Among these, urethane or polyester adhesives are preferred in terms of heat resistance and flexibility to accommodate dimensional changes in each substrate. 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. To achieve sufficient adhesion, the coating weight after drying is preferably 1 to 8 g / m². More preferably, it is 2 to 7 g / m². 2 , and more preferably 3 to 6 g / m 2 The coating amount is 1g / m 2 If it is less than 8 g / m, it will be difficult to bond the entire surface, and the adhesive strength will decrease. 2 If the amount exceeds this, it takes a long time for the film to completely cure, unreacted material is likely to remain, and adhesive strength decreases.

[0048] Furthermore, the laminate film of the present invention may have at least one or more printed layers or other plastic substrates and / or paper substrates laminated between the substrate film layer and the heat-sealable resin layer or on the outer side thereof.

[0049] 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.

[0050] The laminate of the present invention has an oxygen permeability of 50 ml / m under conditions of 23°C x 65% RH. 2 In order to achieve good gas barrier properties, it is preferable that the gas barrier strength is 40 ml / m or less. 2 ·d·MPa or less, preferably 30ml / m 2 ·d·MPa or less. Oxygen permeability is 50ml / m 2 If the gas barrier strength exceeds 1.5 MPa, it becomes difficult to meet the requirements for high gas barrier properties. 2 If the oxygen permeability is less than 1 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.

[0051] The laminate of the present invention has a water vapor permeability of 4.0 g / m under the conditions of 40°C x 90% RH. 2 d or less is preferable in terms of exhibiting good gas barrier properties. Furthermore, by controlling the coating amount of the coating layer components described above, it is possible to obtain a coating amount of preferably 3.5 g / m 2 ·d or less, preferably 3.0 g / m 2d or less. The water vapor permeability is 4.0 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.

[0052] The laminate of the present invention preferably has a laminate strength of 1.0 N / 15 mm or more under conditions of 23°C x 65% RH, more preferably 1.5 N / 15 mm or more, and even more preferably 2.0 N / 15 mm or more. If the laminate strength is less than 1.0 N / 15 mm, peeling may occur due to bending load or heat during sealing, resulting in a deterioration in barrier properties or leakage of contents. Furthermore, hand tearability may also be impaired. [Example]

[0053] 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. The films were evaluated by the following measurement methods.

[0054] (1) Thickness of laminated film Measurement was carried out using a dial gauge in accordance with JIS K7130-1999 Method A.

[0055] (2) Haze of laminated film Measured using a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136. (3) Coating Weight In each example and comparative example, each laminated film obtained at the stage of laminating a coating layer on a base film was used as a sample, and a 100 mm × 100 mm test piece was cut out from this sample, and the coating layer was wiped off with ethanol. The amount of adhesion was calculated from the change in mass of the film before and after wiping. (4) Measurement method for total reflection infrared absorption spectrum of laminated film In each example and comparative example, the total reflection infrared absorption spectrum of the coating layer surface of each laminate film obtained at the stage of laminating the coating layer on the substrate film was measured by total reflection infrared spectroscopy, and the peak intensity (P1) having an absorption maximum in the region of 1040±10 cm-1 and the peak intensity (P2) having an absorption maximum in the region of 3000±10 cm-1 were determined, and the intensity ratio (P1 / P2) was calculated. Each peak intensity was calculated from the peak height obtained by vertically connecting the baseline of zero absorbance and each peak top.

[0056] (5) Measurement method for arithmetic mean roughness of coating layer The surface roughness of the laminated film was measured using a scanning probe microscope (SPM) (Shimadzu Corporation, SPM9700) (cantilever: OMCL-AC200TS provided by Olympus, observation mode: phase mode). Specifically, SPM images were taken of the film surface over a 2 μm square field of view. The resulting images were corrected for tilt in the X, Y, and Z directions using the tilt correction function of the SPM's software, and the arithmetic mean roughness was calculated. The arithmetic mean roughness was calculated by extracting a reference length from the roughness curve, which was obtained by removing surface waviness components longer than a specified wavelength from the cross-sectional curve using a high-pass filter, along the mean line of the extracted section. The X axis of the extracted section was aligned with the mean line, and the Y axis was aligned with the vertical magnification. The roughness curve was then expressed as y = f(X), and the value calculated using the following equation was expanded two-dimensionally: Ra=1 / L∫L0 |f(x)|dx L: Reference length

[0057] (6) Evaluation method for oxygen permeability In each example and comparative example, the laminated film obtained at the stage of laminating the coating layer on the substrate film was used as a sample, and the oxygen permeability was measured in an atmosphere of 23°C and 65%RH using an oxygen permeability measuring device (OX-TRAN (registered trademark) 1 / 50 manufactured by MOCON) in accordance with JIS-K7126 Method B. The oxygen permeability was measured in the direction in which oxygen permeates from the substrate film side to the coating layer side.

[0058] (7) Evaluation method for water vapor permeability In each example and comparative example, each laminate film obtained at the stage of laminating the coating layer on the substrate film was used as a sample, and the water vapor permeability was measured in an atmosphere of a temperature of 40°C and a humidity of 90% RH using a water vapor permeability measuring device ("PERMATRAN-W 3 / 33MG" manufactured by MOCON) in accordance with JIS-K7129 Method B. The water vapor permeability was measured in the direction in which water vapor permeated from the substrate film side to the coating layer side.

[0059] (8) Evaluation of blocking resistance of laminated film In each example and comparative example, each laminated film obtained at the stage of laminating the coating layer on the substrate film was used as a sample, and the sample was cut into a strip of 15 mm width and 200 mm length and prepared into two sets. After preparation, one drop of water (approximately 0.02 g) was dropped onto the coating surface of one of the samples, then the coating surface of the other sample was placed on top of it, sandwiched between glass plates, and dried at 40°C for 24 hours to evaporate the water.The two strips were then peeled off and the adhesion state of the film was confirmed.If the film was so adhered that it was torn when peeled off, it was rated as x, and if the film could be peeled off smoothly without being torn, it was rated as o.

[0060] (9) Evaluation of solvent volatility of coating layer In each example and comparative example, each laminated film obtained at the stage of laminating a coating layer onto a base film was used as a sample, and when the coating layer was lightly pressed with a paper towel, if the coating layer adhered to the paper towel, it was judged as ×, indicating insufficient solvent evaporation, and if the coating layer did not adhere to the paper towel, it was judged as ◯, indicating sufficient solvent evaporation.

[0061] (10) Appearance evaluation of the coating layer In each example and comparative example, each laminated film obtained at the stage of laminating the coating layer on the base film was used as a sample, and films that were visually inspected for defects such as missing parts, streaks, or unevenness in the coating layer were judged to have a poor appearance and were rated as x, while films that did not have the above defects were judged to have a good appearance and were rated as o.

[0062] [Preparation of laminated body] A polyurethane adhesive (Takelac A525S / Takenate A50 manufactured by Mitsui Chemicals, Inc.) was applied to the laminates obtained in the Examples and Comparative Examples so that the thickness after drying at 80°C would be 3 μm. An unstretched polypropylene film (P1128 manufactured by Toyobo Co., Ltd.; thickness 30 μm; referred to as CPP) was then dry-laminated on a metal roll heated to 60°C, and the laminate was aged at 40°C for 4 days to obtain a laminate gas barrier laminate for evaluation (hereinafter sometimes referred to as "laminate a").

[0063] (11) Evaluation method for laminate strength The laminated body prepared above was cut into a width of 15 mm and a length of 200 mm to prepare a test piece, and the laminate strength (normal state) was measured using a Tensilon universal material testing machine (Tensilon UMT-II-500 model, manufactured by Toyo Baldwin Co., Ltd.) under conditions of a temperature of 23°C and a relative humidity of 65%. The laminate strength was measured at a tensile speed of 200 mm / min when the laminated film layer and the heat-sealable resin layer of each laminated film obtained in the examples and comparative examples were peeled at a peel angle of 90 degrees.

[0064] The coating liquids used in the present examples and comparative examples are described in detail below. The coating liquids used in Examples 1 to 6 and Comparative Examples 1 to 10 and shown in Table 1

[0065] [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.

[0066] [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%.

[0067] [Coating liquid 1 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Ion-exchanged water 20.00% by mass Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 35.00% by mass Inorganic layered compound separation liquid (B) 30.00% by mass

[0068] [Coating liquid 2 used for coating layer] 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 separation liquid (B) 40.00% by mass

[0069] [Coating liquid 3 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Ion-exchanged water 10.00% by mass Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 25.00% by mass Inorganic layered compound separation liquid (B) 50.00% by mass

[0070] [Coating liquid 4 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Ion-exchanged water 5.00% by mass Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 20.00% by mass Inorganic layered compound separation liquid (B) 60.00% by mass

[0071] [Coating liquid 5 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Ion-exchanged water 35.00% by mass Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 50.00% by mass

[0072] [Coating liquid 6 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Ion-exchanged water 30.00% by mass Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 45.00% by mass Inorganic layered compound separation liquid (B) 10.00% by mass

[0073] [Coating liquid 7 used for coating layer] The materials were mixed in the following proportions to prepare a coating liquid (resin composition for coating layer). Isopropyl alcohol 15.00% by mass Polyvinyl alcohol resin (A) 15.00% by mass Inorganic layered compound separation liquid (B) 70.00% by mass

[0074] [Coating liquid 8 used for coating layer] The following materials were mixed in the mass ratio shown below and dissolved by stirring for 30 minutes or more. Next, undissolved materials were removed using a filter with a nominal filtration accuracy of 50 μm to prepare a coating liquid (resin composition for coating layer). Ion-exchanged water 37.50% by mass Polyvinylidene chloride resin (C) 62.50% by mass (Saran Latex L557 manufactured by Asahi Kasei Chemicals, solid content 48%)

[0075] (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 by gravure roll coating, pre-dried at 90°C for 4 seconds, and then dried at 130°C for 4 seconds to obtain a coating layer. The coating amount after drying was 0.25 g / m 2 The coating solution constituting the coating layer, the temperature of the main drying, and the conditions of the post-heating treatment were changed as shown in Table 1 for each example and comparative example.

[0076] In this way, a laminate film having a coating layer / inorganic thin film layer on a substrate film was produced. The obtained laminate film was evaluated. The results are shown in Table 2.

[0077] [Table 1]

[0078] [Table 2] [Industrial Applicability]

[0079] According to the present invention, it is possible to provide a laminate film that can form a laminate structure composed of almost a single resin type, mainly polypropylene film, which has a low environmental impact, and that has the gas barrier properties and adhesive properties required for packaging materials. Moreover, the laminate film of the present invention has few processing steps and is easy to produce, so it is excellent in both economy and production stability, and can provide a gas barrier film with uniform properties.

Claims

1. A laminated body obtained by laminating an olefin-based sealant layer on one side of the coating layer of a laminated film, which is a laminated film having a coating layer containing a polyvinyl alcohol-based copolymer and an inorganic layered compound on at least one side of a base film, and which is characterized in that the laminated film satisfies the following requirements (a) to (e): (a) The base film is a stretched film made of a propylene-based resin. (b) The coating weight of the coating layer is 0.10 g / m ２ 0.50g / m or more ２ It must be less than or equal to: (c) In the total reflection infrared absorption spectrum of the laminated film, －１ The peak intensity (P1) has an absorption maximum in the region of 3300 ± 10 cm －１ (d) The arithmetic mean roughness of the coating layer on the laminated film in a 2 μm square area is in the range of 2.0 to 8.0 nm. (e) The laminate strength of the olefin sealant layer and the coating layer of the laminate under conditions of 23°C x 65% RH is 1.0 N / 15 mm or more.

2. The oxygen permeability of the laminated film under an environment of 23°C x 65% RH is 50 ml / m ２ ・Water vapor permeability of 4g / m under d MPa or less and 40°C x 90% RH environment ２ 2. The laminate according to claim 1, wherein the thickness is d or less.

3. 3. The laminate according to claim 1, wherein the inorganic layered compound of the coating layer contains a montmorillonite-based compound as a constituent component.

4. The laminate according to any one of claims 1 to 3, which is used as a packaging material.

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