Barrier films and laminates

Abstract

A barrier film comprising a base material film that contains a polyolefin, wherein when both surfaces of the barrier film are analyzed by means of an x-ray fluorescence spectrometer, the value obtained by dividing the sum of the x-ray fluorescence intensities from chlorine detected on both surfaces by the thickness of the base material film ([the sum of the x-ray fluorescence intensities from chlorine] / [the thickness of the base material film]) is 0.015 kcps / µm or lower.

Description

[Technical Field]

[0001] This disclosure relates to barrier films and laminates, and more particularly to barrier films and laminates suitable for recycling. [Background technology]

[0002] In recent years, there has been a growing global recognition that environmental problems such as marine pollution caused by plastic waste and other waste management issues are becoming increasingly serious and posing a global threat. In Japan, the Ministry of the Environment formulated the "Plastic Resource Recycling Strategy" in May 2019 to comprehensively promote the recycling of plastic resources, and it was explicitly stated that 100% of used plastics will be effectively utilized through reuse and recycling by 2035.

[0003] In response to these social circumstances, the demand for packaging materials suitable for material recycling is increasing. In recycling, the generally adopted process involves cutting the collected packaging materials, separating and washing them as needed, and then melting and mixing them using an extruder.

[0004] In material recycling, packaging materials made by laminating multiple resins such as nylon, polyethylene terephthalate, and polyolefin present a problem in that separating and recovering the resins from each layer is difficult. Therefore, the movement towards monomaterial packaging materials (using a single material) is accelerating.

[0005] On the other hand, in the field of packaging materials, gas barrier properties are often required to suppress the deterioration of the quality of the contents. In such cases, aluminum foil or transparent gas barrier film is used, but aluminum foil can be problematic from an environmental perspective and in terms of visibility of the contents, so the use of transparent gas barrier film is becoming more common. From the perspective of monomaterialization of packaging materials, there is a growing demand for barrier films using polypropylene film as the base material, and proposals to address this have been made, as shown in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2000-254994 [Patent Document 2] International Publication No. 2016 / 158794 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, there was a problem in that barrier films sometimes deteriorated and became discolored during material recycling, making them unsuitable for recycling. Resin deterioration is likely to occur during the process of melting and mixing packaging materials.

[0008] Therefore, the purpose of this disclosure is to provide a barrier film and laminate with excellent recyclability that can suppress discoloration during recycling. [Means for solving the problem]

[0009] To achieve the above objective, this disclosure provides a barrier film comprising a base film containing a polyolefin, wherein when both sides of the barrier film are analyzed with an X-ray fluorescence analyzer, the value obtained by dividing the sum of the X-ray fluorescence intensities of chlorine detected from both sides by the thickness of the base film (sum of X-ray fluorescence intensities of chlorine / thickness of base film) is 0.015 kcps / μm or less.

[0010] Olefin resins such as polypropylene and polyethylene used for the base film of barrier films are liable to be oxidized by heat, and an oxidative decomposition reaction is likely to occur when they melt at high temperatures. Along with the oxidative decomposition reaction, the mechanical and physical properties of the resin deteriorate, and if the reaction progresses further, the resin will carbonize and the appearance will change to brown or black. Resin in which such an oxidative decomposition reaction has occurred is difficult to use as a recycled product. As a result of intensive research, the inventor has found that chlorine present in the barrier film acts as a catalyst for the oxidative decomposition reaction of olefin resins and promotes the oxidative decomposition reaction, and that the amount of chlorine present required to promote the oxidative decomposition changes depending on the film thickness. And when analyzing both sides of the barrier film with a fluorescent X-ray analyzer, by making the value obtained by dividing the sum of the fluorescent X-ray intensities of chlorine detected from both sides by the thickness of the base film (sum of fluorescent X-ray intensities of chlorine / thickness of base film) 0.015 kcps / μm or less, it was found that oxidative decomposition of the polyolefin in the barrier film during recycling can be suppressed and coloring can be suppressed. Therefore, a barrier film that satisfies the above conditions can have suppressed coloring during recycling and excellent recyclability.

[0011] The above barrier film may further include a gas barrier layer formed on at least one surface of the above base film. By providing the above gas barrier layer, the gas barrier property of the barrier film is improved. Also, chlorine present in the barrier film is derived not only from the base film itself but also from the gas barrier layer. However, by making the above value (sum of fluorescent X-ray intensities of chlorine / thickness of base film) 0.015 kcps / μm or less, coloring during recycling can be suppressed even if chlorine derived from the gas barrier layer is present. Therefore, a barrier film excellent in recyclability and gas barrier property can be provided.

[0012] The gas barrier layer may include a vapor deposition layer containing an inorganic oxide. The inorganic oxide may include aluminum oxide, silicon oxide, or a mixture thereof. By providing the gas barrier layer with the vapor deposition layer, the gas barrier property of the barrier film can be further improved.

[0013] The gas barrier layer may include a gas barrier coating layer. By providing the gas barrier layer with the gas barrier coating layer, the gas barrier property of the barrier film can be further improved. Further, by forming the gas barrier coating layer on the vapor deposition layer, the vapor deposition layer can be protected.

[0014] The gas barrier coating layer may be a layer formed using a composition for forming a gas barrier coating layer containing at least one of a silicon compound represented by the following general formula (1) and its hydrolyzate, at least one of a silicon compound represented by the following general formula (2) and its hydrolyzate, and a water-soluble polymer having a hydroxyl group. Si(OR 1 )4…(1) (R 2 Si(OR 3 )3) n …(2) [In general formulas (1) and (2), R 1 and R 3 each independently represent CH3, C2H5, or C2H4OCH3, R 2 represents an organic functional group, and n represents an integer of 1 or more.]

[0015] Further, the gas barrier coating layer may be a layer formed using a composition for forming a gas barrier coating layer containing a polyurethane resin, a water-soluble polymer having a hydroxyl group, and a curing agent. Here, the polyurethane resin may include a reaction product of an acid group-containing polyurethane resin containing an acid group and a polyamine compound having an amino group.

[0016] If the gas barrier coating layer is formed using any of the above-mentioned gas barrier coating layer forming compositions, the above value (sum of chlorine fluorescence X-ray intensities / thickness of the base film) can be reduced, thereby improving recyclability and obtaining superior gas barrier properties.

[0017] In the barrier film described above, the polyolefin may be polypropylene. In this case, the heat resistance of the barrier film can be improved.

[0018] The disclosure also provides a laminate comprising two or more resin films containing polyolefin, wherein when each resin film is peeled from the laminate and both sides of all the resin films are analyzed with an X-ray fluorescence analyzer, the value obtained by dividing the sum of the X-ray fluorescence intensities of chlorine detected from all sides of all the resin films by the thickness of the laminate (sum of X-ray fluorescence intensities of chlorine / thickness of the laminate) is 0.015 kcps / μm or less.

[0019] In a laminate comprising two or more resin films containing polyolefin, by ensuring that the sum of the chlorine fluorescence X-ray intensities detected from all surfaces of each resin film divided by the thickness of the laminate (sum of chlorine fluorescence X-ray intensities / thickness of the laminate) is 0.015 kcps / μm or less, oxidative decomposition of the polyolefin in the barrier film during recycling can be suppressed, thereby suppressing discoloration. Therefore, a laminate that satisfies the above conditions can exhibit excellent recyclability due to suppressed discoloration during recycling. [Effects of the Invention]

[0020] According to this disclosure, it is possible to provide a barrier film and laminate with excellent recyclability that can suppress discoloration during recycling. [Brief explanation of the drawing]

[0021] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the barrier film disclosed herein. [Figure 2] This is a schematic cross-sectional view showing one embodiment of the laminate of the present disclosure. [Modes for carrying out the invention]

[0022] The embodiments of this disclosure will be described in detail below.

[0023] The barrier film of this embodiment comprises a base film containing polyolefin. Furthermore, when both sides of the barrier film are analyzed with an X-ray fluorescence analyzer, the value obtained by dividing the sum of the X-ray fluorescence intensities of chlorine detected from both sides by the thickness of the base film (sum of X-ray fluorescence intensities of chlorine / thickness of base film) is 0.015 kcps / μm or less.

[0024] The laminate of this embodiment comprises two or more resin films containing polyolefin. Furthermore, when each resin film is peeled off from the laminate and both sides of all the resin films are analyzed with an X-ray fluorescence analyzer, the value obtained by dividing the sum of the X-ray fluorescence intensities of chlorine detected from all sides of all the resin films by the thickness of the laminate (sum of X-ray fluorescence intensities of chlorine / thickness of the laminate) is 0.015 kcps / μm or less.

[0025] In this specification, the above values ​​(sum of chlorine fluorescent X-ray intensities / thickness of the substrate film) and (sum of chlorine fluorescent X-ray intensities / thickness of the laminate) are referred to as "chlorine content" (unit: kcps / μm).

[0026] <Barrier film> The barrier film of this embodiment comprises at least a base film containing polyolefin, and may have other layers besides the base film. The barrier film may further comprise a gas barrier layer formed on at least one surface of the base film. This gas barrier layer may comprise one or both of an inorganic oxide-containing vapor-deposited layer and a gas barrier coating layer. Furthermore, the barrier film may comprise an anchor coat layer between the base film and the gas barrier layer.

[0027] Figure 1 is a schematic cross-sectional view showing a barrier film according to one embodiment. The barrier film 100 shown in Figure 1 comprises a base film 1, an anchor coat layer 2, and a gas barrier layer 10 in that order. The gas barrier layer 10 comprises a vapor-deposited layer 3 and a gas barrier coating layer 4. The individual layers constituting the barrier film will be described below.

[0028] [Base film 1] The base film 1 is a support layer and contains polyolefin. The base film 1 may be a polyolefin film with polyolefin as the main component. Here, "main component" refers to a component whose content in the film is 50% by mass or more. The polyolefin content in the base film 1 may be 50% by mass or more, 80% by mass or more, or 100% by mass, based on the total amount of the base film 1. The higher the polyolefin content in the base film 1, the better the recyclability.

[0029] Examples of polyolefins include polyethylene and polypropylene, but from the viewpoint of heat resistance, polypropylene is preferred. As for polypropylene, from the viewpoint of heat resistance, homopolypropylene, which is a homopolymer of propylene, is preferred. However, within limits that do not impair heat resistance, copolymers containing α-olefins or blends of homopolypropylene and other polypropylenes can also be used. Furthermore, for the purpose of improving adhesion, the above copolymers or blends may be placed on the surface layer of the polypropylene film.

[0030] The base film 1 may be stretched or unstretched. The polypropylene film used as the base film 1 may be a film obtained by forming the polypropylene resin into a sheet and stretching the sheet by conventional means to be uniaxially or biaxially oriented, or it may be an unstretched film.

[0031] The base film 1 may contain known additives, such as antioxidants, stabilizers, lubricants such as calcium stearate, fatty acid amides, and erucic acid amides, organic additives such as antistatic agents, and particulate lubricants such as silica, zeolite, thyroid, hydrotalcite, and silicon particles, depending on the purpose.

[0032] The polyolefin resin used in the base film 1, such as homopolypropylene and propylene copolymer, may be a recycled resin, or a resin obtained by polymerizing biomass-derived raw materials such as plants. When using these resins, they may be used alone or mixed with resins polymerized from conventional fossil fuels.

[0033] The thickness of the base film 1 (thickness T1 in Figure 1) is not particularly limited. Depending on the application, the thickness can be 6 to 200 μm, but from the viewpoint of obtaining excellent recyclability and excellent impact resistance, it may be 9 to 50 μm or 12 to 38 μm.

[0034] [Anchor Coat Layer 2] An anchor coat layer (undercoat layer) 2 may be provided on the surface of the base film 1 to which the vapor-deposited layer 3 is laminated. The anchor coat layer 2 can provide effects such as improving the adhesion performance between the base film 1 and the vapor-deposited layer 3, improving the smoothness of the surface of the base film 1, and suppressing the occurrence of cracks in the vapor-deposited layer 3 caused by the elongation of the base film 1. Furthermore, the improved smoothness makes it easier to deposit the vapor-deposited layer 3 uniformly without defects, and makes it easier to exhibit high barrier properties. The anchor coat layer 2 can be formed using an anchor coat layer forming composition (anchor coat agent).

[0035] Examples of resins used in anchor coating agents include acrylic resins, epoxy resins, acrylic urethane resins, polyester polyurethane resins, and polyether polyurethane resins. An anchor coating layer 2 can be formed using these resins, or an anchor coating agent containing components that react to form these resins.

[0036] The thickness of the anchor coat layer 2 is not particularly limited, but is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.03 to 3 μm, and particularly preferably in the range of 0.05 to 2 μm. When the thickness of the anchor coat layer 2 is above the lower limit, a more sufficient interlayer adhesion strength tends to be obtained, while when it is below the upper limit, the desired gas barrier properties tend to be more easily exhibited.

[0037] [Vapour-deposited layer 3] A vapor-deposited layer 3 containing an inorganic oxide can be laminated onto at least one surface of the base film 1 to provide barrier properties. The vapor-deposited layer 3 containing an inorganic oxide consists of a vapor-deposited film of an inorganic oxide such as aluminum oxide, silicon oxide, tin oxide, magnesium oxide, or a mixture thereof, and can be any layer that is transparent and has gas barrier properties such as oxygen and water vapor. Considering various antibacterial resistances, among these, the use of aluminum oxide and silicon oxide is particularly preferable. However, the material used for the vapor-deposited layer 3 in this embodiment is not limited to the inorganic oxides mentioned above, and any material that meets the above conditions can be used.

[0038] The optimal thickness of the deposited layer 3 varies depending on the type and composition of the inorganic oxide used, but generally, a range of 5 to 300 nm is desirable, and the value is selected as appropriate. The thickness of the deposited layer 3 may also be 5 to 100 nm. When the film thickness is 5 nm or more, a uniform film is easily obtained, and because the film thickness is sufficient, it tends to be able to fully function as a gas barrier layer. On the other hand, when the film thickness is 300 nm or less, it is easier to maintain flexibility in the thin film, and it tends to suppress the occurrence of cracks in the thin film due to external factors such as bending and stretching after film formation. Since these effects are more easily obtained, it is more preferable for the thickness of the deposited layer 3 to be in the range of 10 to 150 nm.

[0039] There are various methods for forming the vapor-deposited layer 3 on the substrate film 1, and it can be formed by a conventional vacuum deposition method. Other thin-film formation methods such as sputtering, ion plating, and plasma vapor deposition (CVD) can also be used. However, considering productivity, vacuum deposition is currently the most superior method. For the vacuum deposition method, it is preferable to use one of the following heating methods: electron beam heating, resistance heating, or induction heating. However, considering the wide range of selectivity for evaporation materials, electron beam heating is more preferable. Furthermore, to improve the adhesion between the vapor-deposited layer 3 and the substrate film 1, and to improve the density of the vapor-deposited layer 3, it is also possible to perform deposition using plasma-assisted or ion-beam-assisted methods. Additionally, to increase the transparency of the vapor-deposited film, reactive deposition using various gases such as oxygen during deposition is also acceptable.

[0040] To enhance the adhesion between the base film 1 and the vapor-deposited layer 3, surface treatments such as plasma treatment or corona treatment may be applied to the surface of the base film 1, or the above-mentioned anchor coat layer 2 may be provided between the base film 1 and the vapor-deposited layer 3. By applying these surface treatments or by providing the anchor coat layer 2, performance such as adhesion and barrier properties after heat sterilization is improved.

[0041] [Gas barrier coating layer 4] A gas barrier coating layer 4 can also be provided on the vapor deposition layer 3 for the purpose of protecting the vapor deposition layer 3 and complementing the barrier property. The gas barrier coating layer 4 is not particularly limited as long as it can achieve the above object and has recyclability. Examples of the composition for forming the gas barrier coating layer 4 include a solution obtained by mixing one or more silicon compounds or their hydrolyzates with a water-soluble polymer, a solution obtained by mixing one or more silicon compounds or their hydrolyzates with a water-soluble polymer, an inorganic layered compound, and a silane coupling agent, or a solution obtained by mixing an aqueous polyurethane resin with a water-soluble polymer. After coating these compositions for forming the gas barrier coating layer on the vapor deposition layer 3 and then heating and drying, the gas barrier coating layer 4 can be formed. In the composition for forming the gas barrier coating layer, known additives such as isocyanate compounds, silane coupling agents, dispersants, stabilizers, viscosity modifiers, and colorants can be added as necessary within a range that does not impair the gas barrier property.

[0042] Examples of the composition for forming the gas barrier coating layer include a composition containing at least one of the silicon compounds represented by the following general formula (1) and their hydrolyzates, at least one of the silicon compounds represented by the following general formula (2) and their hydrolyzates, and a water-soluble polymer having a hydroxyl group. By using the above composition for forming the gas barrier coating layer, the barrier film and the laminate can reduce their chlorine content, enhance recyclability, and have excellent gas barrier properties. Si(OR 1 )4…(1) (R 2 Si(OR 3 )3) n …(2) [In general formulas (1) and (2), R 1 and R 3 each independently represent CH3, C2H5, or C2H4OCH3, R 2 represents an organic functional group, and n represents an integer of 1 or more.]

[0043] The compound represented by the above general formula (1) is R 1 Any compound represented by CH3, C2H5, or C2H4OCH3 can be used, but tetraethoxysilane is preferred.

[0044] Examples of water-soluble polymers containing hydroxyl groups include polyvinyl alcohol and its modified forms, polyacrylic acid, starch, and cellulose. Among these, polyvinyl alcohol and its modified forms are preferred from the viewpoint of obtaining superior gas barrier properties. By using water-soluble polymers, flexibility can be imparted to the gas barrier coating layer, and the occurrence of cracks can be suppressed.

[0045] The water resistance of the gas barrier coating layer can be improved by including the compound represented by the above general formula (2) or its hydrolysate in the gas barrier coating layer composition. In the compound represented by the above general formula (2), R 2 The organic functional group represented by preferably includes hydrophobic functional groups such as vinyl groups, epoxy groups, methacryloxy groups, ureido groups, and isocyanate groups. 2 The inclusion of hydrophobic functional groups further enhances the water resistance of the gas barrier coating layer. Furthermore, n in general formula (2) may be an integer of 1 or greater.

[0046] When the compound represented by general formula (2) is a polymer, a trimer is preferred, and from the viewpoint of further improving water resistance, the general formula (NCO-R 4 Si(OR3)3)3 (wherein, R 4 (CH2) m A more preferred option is 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate, represented as (where m is an integer greater than or equal to 1). This is a condensate of 3-isocyanate alkylalkoxysilane.

[0047] In a gas barrier coating layer forming composition, the amounts of each of the above components are not particularly limited, but Si(OR 1 )4 to SiO2, R 2 Si(OR3)3 is R 2When converted to Si(OH)3, the solid content ratio is SiO2 / (R 2 The Si(OH)3 / water-soluble polymer) ratio may be within the range of 100 / 100 to 100 / 30.

[0048] Another example of a gas barrier coating layer forming composition is a composition containing a polyurethane resin, a water-soluble polymer having hydroxyl groups, and a curing agent, wherein the polyurethane resin includes a reaction product of an acid-group-containing polyurethane resin containing acid groups and a polyamine compound having amino groups. By using the above gas barrier coating layer forming composition, the chlorine content of barrier films and laminates can be reduced, improving their recyclability and providing excellent gas barrier properties.

[0049] The above-mentioned acid group-containing polyurethane resin can be any resin capable of bonding with the amino group of the polyamine compound constituting the polyurethane resin, and examples of acid groups include carboxyl groups and sulfonic acid groups. For example, an acid group-containing polyurethane resin having constituent units containing cyclic hydrocarbons and constituent units containing chain hydrocarbons can be used. Specific examples of acid group-containing polyurethane resins include carboxylic acid-modified polyurethane resins and sulfonic acid-modified polyurethane resins. These can be used individually or in combination of two or more.

[0050] The amino group in the above polyamine compound may be a primary, secondary, or tertiary amino group. Specific examples of polyamine compounds include alkylenediamines and polyalkylene polyamines. These can be used individually or in combination of two or more.

[0051] Examples of water-soluble polymers containing hydroxyl groups include polyvinyl alcohol and its modified forms, polyacrylic acid, starch, and cellulose. Among these, polyvinyl alcohol and its modified forms are preferred from the viewpoint of obtaining superior gas barrier properties.

[0052] The curing agent is not limited to any curing agent capable of curing the gas barrier coating layer formation composition. The curing agent may also be a silane coupling agent.

[0053] Examples of silane coupling agents include compounds represented by the following general formula (3). Si(OR 11 ) p (R 12 ) 3-p R 13 …(3) In the above general formula (3), R 11 R represents an alkyl group such as a methyl group or an ethyl group. 12 R represents a monovalent organic group such as an alkyl group, aralkyl group, aryl group, alkenyl group, acryloxy group, or alkyl group substituted with a methacryloxy group. 13 indicates a monovalent organic functional group, and p is an integer from 1 to 3. Note that R 11 or R 12 If there are multiple instances, R 11 Mutual or R 12 They may be the same or different. 13 Examples of monovalent organic functional groups include vinyl groups, epoxy groups, mercapto groups, amino groups, or isocyanate groups. Among these, monovalent organic functional groups containing epoxy groups are preferred. In this case, the composition can have better hot water resistance upon curing.

[0054] Examples of silane coupling agents include vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylethyldiethoxysilane; mercapto group-containing silane coupling agents such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropylmethyldimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatetopropyltriethoxysilane. These silane coupling agents may be used individually or in combination of two or more types.

[0055] In the gas barrier coating layer forming composition, the amounts of each component are not particularly limited, but it is preferable that, based on the total solid content of the gas barrier coating layer forming composition, the polyurethane resin content is 45% to 75% by mass, the water-soluble polymer content is 20% to 35% by mass, and the curing agent content is 5% to 20% by mass. By satisfying these content ratios, the resulting gas barrier coating layer can have excellent resistance to abuse and excellent resistance to hot water.

[0056] The above gas barrier coating layer forming composition may or may not contain an inorganic layered mineral as an inorganic layered compound. An inorganic layered mineral refers to an inorganic compound in which unit crystal layers are stacked to form a single layered particle.

[0057] Examples of inorganic layered minerals include hydrated silicates such as phyllosilicate minerals. Specifically, hydrated silicates include kaolinite clay minerals such as halloysite, kaolinite, and endelite; antigorite clay minerals such as antigorite and chrysotile; smectite clay minerals such as montmorillonite and beidelite; vermiculite clay minerals such as vermiculite; and micas such as synthetic mica, muscovite, and phlogopite. These can be used individually or in combination of two or more.

[0058] It is preferable that the content of inorganic layered minerals in the gas barrier coating layer-forming composition is less than 2% by mass, based on the total solid content. In this case, the laminate strength of the resulting gas barrier coating layer can be improved compared to when the inorganic layered mineral content is 2% by mass or more. The inorganic layered mineral content may be 0% by mass.

[0059] The thickness of the gas barrier coating layer 4 is preferably 0.05 to 2 μm, more preferably 0.1 to 1 μm, and even more preferably 0.3 to 0.5 μm. When the thickness of the gas barrier coating layer 4 is 2 μm or less, it is easier to reduce the amount of chlorine in the barrier film and laminate, and it is easier to suppress discoloration when the barrier film and laminate are recycled. When the thickness of the gas barrier coating layer 4 is 0.05 μm or more, the gas barrier properties of the barrier film and laminate can be improved.

[0060] <Laminate> The laminate of this embodiment comprises two or more resin films containing polyolefin, and may have other layers besides the resin films. The laminate may further comprise a gas barrier layer formed on at least one surface of one of the resin films. This gas barrier layer may comprise one or both of an inorganic oxide-containing vapor-deposited layer and a gas barrier coating layer. Furthermore, the laminate may comprise an anchor coat layer between the resin film and the gas barrier layer. The laminate may be formed by further laminating a resin film on one surface of the barrier film of this embodiment described above. In this case, the base film included in the barrier film is the first resin film, and the resin film further laminated on the barrier film is the second resin film. The second resin film may be laminated on the barrier film via an adhesive layer. The second resin film may be a sealant layer.

[0061] Figure 2 is a schematic cross-sectional view showing a laminate according to one embodiment. The laminate 200 shown in Figure 2 has a structure in which a sealant layer 6 as a resin film is laminated on the gas barrier coating layer 4 side of the barrier film 100 via an adhesive layer 5. The laminate 200 comprises two layers, a base film 1 and a sealant layer 6, as a resin film containing polyolefin.

[0062] [Adhesive layer 5] For example, the adhesive layer 5 can be made from a polyester-isocyanate resin, a urethane resin, or a polyether resin. From the viewpoint of improving hot water resistance, a two-component curing type urethane adhesive can be preferably used.

[0063] [Sealant layer 6] The sealant layer 6 is a layer that provides heat-sealing properties to the laminate 200 and contains polyolefin. The sealant layer 6 may be a polyolefin film with polyolefin as the main component. Here, "main component" refers to a component whose content in the film is 50% by mass or more. The polyolefin content in the sealant layer 6 may be 50% by mass or more, 80% by mass or more, or 100% by mass, based on the total amount of the sealant layer 6. The higher the polyolefin content in the sealant layer 6, the better the recyclability.

[0064] Examples of polyolefins include polyethylene and polypropylene, but from the viewpoint of heat resistance, polypropylene is preferred. For polypropylene, from the viewpoint of heat sealability, it is preferable to use a copolymer or blend of propylene and α-olefin. Among these, it is preferable to use a propylene-ethylene random copolymer or a propylene-ethylene block copolymer. Furthermore, it is preferable to use the same type of polyolefin for the sealant layer 6 and the base film 1. For example, if homopolypropylene is used for the base film 1, it is preferable to use homopolypropylene for the sealant layer 6 as well.

[0065] The polyolefin film used in the sealant layer 6 may be stretched or unstretched, but from the viewpoint of lowering the heat fusion temperature compared to the base film 1 and improving heat sealability, it is preferable that it be an unstretched film. In this case, it is preferable that the base film 1 is a stretched film.

[0066] The sealant layer 6 may contain known additives, such as antioxidants, stabilizers, lubricants like calcium stearate, fatty acid amides, and erucic acid amides, organic additives like antistatic agents, and particulate lubricants like silica, zeolite, thyroid, hydrotalcite, and silicon particles, depending on the purpose.

[0067] The polyolefin resin used in the sealant layer 6, such as homopolypropylene and propylene copolymer, may be a recycled resin, or a resin obtained by polymerizing biomass-derived raw materials such as plants. When using these resins, they may be used alone or mixed with resins polymerized from conventional fossil fuels.

[0068] The thickness of the sealant layer 6 is not particularly limited. Depending on the application, the thickness can be 6 to 200 μm, but from the viewpoint of obtaining excellent recyclability and excellent impact resistance, it may be 10 to 150 μm or 20 to 100 μm.

[0069] The overall thickness of the laminate 200 (thickness T2 in Figure 2) is not particularly limited. Depending on the application, the thickness can be 10 to 400 μm, but may be 20 to 200 μm or 50 to 150 μm.

[0070] When material recycling barrier film 100 or laminate 200, one method involves crushing the recovered barrier film 100 or laminate 200, feeding the crushed material into an extruder and melting it at a temperature above its melting point, then pelletizing the molten material for reuse. Alternatively, the molten material can be molded as is and used for other purposes.

[0071] Olefin resins such as polypropylene and polyethylene are easily oxidized by heat, and oxidative decomposition reactions readily occur when they melt at high temperatures. As a result of oxidative decomposition, the mechanical and physical properties of the resin deteriorate, and if the reaction progresses further, the resin carbonizes, resulting in a discoloration of brown or black. Resins that have undergone such oxidative decomposition cannot be used as recycled products.

[0072] In this embodiment, the recyclable barrier film 100 must have a value (sum of chlorine X-ray fluorescence intensities / thickness of base film 1) of 0.015 kcps / μm or less when the sum of the X-ray fluorescence intensities of chlorine (Cl) detected on both sides of the barrier film 100 (F11 and F12 in Figure 1) is divided by the thickness of the base film 1 (T1 in Figure 1).

[0073] Furthermore, in this embodiment, the recyclable laminate 200 requires that when the base film 1 and sealant layer 6 are peeled off from the laminate 200 as individual resin films, and both sides of the base film 1 and sealant layer 6 (F21 and F22, and F23 and F24 in Figure 2) are analyzed using an X-ray fluorescence analyzer, the sum of the X-ray fluorescence intensities of chlorine detected from all surfaces of the base film 1 and sealant layer 6 divided by the thickness of the laminate 200 (T2 in Figure 2) (sum of X-ray fluorescence intensities of chlorine / thickness of the laminate 200) must be 0.015 kcps / μm or less.

[0074] In the barrier film 100 and laminate 200, if the amount of chlorine determined by the above method is 0.015 kcps / μm or less, the discoloration during recycling (melting) described above can be suppressed, and the barrier film 100 will have excellent recyclability. Furthermore, if the amount of chlorine is 0.015 kcps / μm or less, the deterioration of the mechanical and physical properties of the resin during recycling (melting) can also be suppressed.

[0075] For X-ray fluorescence analysis, for example, a Rigaku Supermini wavelength-dispersive X-ray fluorescence analyzer can be used. Before measurement, a PHA-prepared sample (manufactured by Rigaku) ​​is used to confirm that the resolution of the PC detector is 45% or less. The measurement is performed under the conditions shown below. Detection spectrum: Cl-KA X-ray inter-excitation conditions: Target Pb, tube voltage 50kV, tube current 4.00mA Spectroscopic crystal: PET Detector: PC (Proportional Counter) Scan conditions: Start angle 62.0deg, end angle 69.0deg, step 0.05deg, time 0.2sec, speed 15deg / min., peak angle 65.44deg Measurements were performed under the above conditions, and the resulting net intensity (kcps) of chlorine atoms (Cl) was defined as the X-ray intensity of the film surface.

[0076] Chlorine acts as a catalyst for the oxidative decomposition reaction of resins as described above, promoting the reaction. The amount of chlorine required for the oxidative decomposition to be promoted varies depending on the thickness of the film, so it is necessary to divide the sum of chlorine atoms (Cl) detected by X-ray fluorescence analysis by the thickness of the film. If this value (chlorine amount = sum of X-ray fluorescence intensities of chlorine / thickness of the base film or laminate) is higher than 0.015 kcps / μm, the amount of chlorine in the barrier film or laminate is too high, leading to oxidative decomposition, discoloration, and difficulty in recycling. From the viewpoint of further improving recyclability, it is more preferable that the above chlorine amount is 0.012 kcps / μm or less. The above chlorine amount can be adjusted, for example, by the thickness, composition, and manufacturing method of the base film 1, sealant layer 6, and gas barrier coating layer 4.

[0077] The barrier film and laminate of this embodiment can be suitably used in a variety of applications, such as packaging products like containers and bags, sheet molded products like decorative sheets and trays, optical films, resin plates, various label materials, lid materials, and laminate tubes, and is particularly suitable for use in packaging products. Examples of packaging products include pillow bags, standing pouches, three-sided sealed bags, and four-sided sealed bags. Furthermore, the barrier film and laminate of this embodiment can also be used in packaging products that undergo boiling or retorting processes. [Examples]

[0078] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0079] <Preparation of coating solution> The following coating solutions A to D were prepared as gas barrier coating layer forming compositions to be used in the examples and comparative examples.

[0080] (Coating solution A) A solution prepared by mixing (a), (b), and (c) shown below, such that (a) / (b) / (c) = 70 / 20 / 10 (solid content by mass ratio). (a) Solution: Hydrolyzed by adding 72.1 g of 0.1 N hydrochloric acid to 17.9 g of tetraethoxysilane and 10 g of methanol and stirring for 30 minutes, resulting in a hydrolysis solution with a solid content of 5% by mass (on an SiO2 basis). (b) Solution: A water / methanol solution containing 5% by mass of polyvinyl alcohol (water:methanol mass ratio is 95:5). (c) Solution: A hydrolysis solution of 1,3,5-tris(3-trialkoxysilylpropyl) isocyanurate diluted to a solid content of 5% by mass with a mixture of water and isopropyl alcohol (water:isopropyl alcohol mass ratio is 1:1).

[0081] (Coating liquid B) A solution prepared by mixing an aqueous dispersion of polyurethane resin (aqueous polyurethane dispersion, trade name "Takelac® WPB-341", manufactured by Mitsui Chemicals, Inc., solid content concentration: 30% by mass), a 5% by mass aqueous solution of polyvinyl alcohol, and 3-glycidoxypropyltrimethoxysilane in a solid content ratio of 75:20:5.

[0082] (Coating liquid C) A solution prepared by mixing liquids (d) and (e) shown below, such that liquid (d) / liquid (e) = 45 / 55 (solid content by mass ratio). (d) Solution: A solution prepared by mixing polyvinyl alcohol and montmorillonite in a mass ratio of 15 / 1, and diluting it with a mixture of water / isopropyl alcohol = 95 / 5 (mass ratio) to a solid content of 6.5% by mass. (e) Solution: A hydrolyzed solution prepared by combining tetraethoxysilane and 3-glycidoxypropyltrimethoxysilane in a mass ratio of 10 (SiO2 equivalent) / 1, hydrolyzing with 0.3N hydrochloric acid, and diluting with a water / methanol mixture of 1 / 1 (mass ratio) to a solid content of 11% by mass.

[0083] (Coating liquid D) A polyvinylidene chloride resin solution (solid content 5% by mass) is prepared by dissolving a polyvinylidene chloride resin (manufactured by Asahi Kasei Corporation, trade name "Saran Resin F216") in a mixed organic solvent of toluene and methyl ethyl ketone (mass ratio: toluene / methyl ethyl ketone = 1 / 2).

[0084] [Examples 1, 2 and Comparative Examples 1-4] <Fabrication of barrier film> A stretched polypropylene film with a thickness of 20 μm was prepared as the base film. On one side of the base film, an acrylic polyol was mixed with tolylene diisocyanate in an equal amount to the OH groups of the acrylic polyol, diluted with ethyl acetate to a total solid content of 5% by mass, and β-(3,4-epoxycyclohexyl)trimethoxysilane was added at 5% by mass relative to the total solid content. This solution was then coated and dried by gravure coating to form an anchor coat layer with a thickness of 0.1 μm. Next, a thin film of silicon dioxide with a thickness of 30 nm was deposited on the anchor coat layer by reactive vapor deposition using high-frequency excited ion plating in an oxygen atmosphere under reduced pressure to form a vapor-deposited layer. Furthermore, a gas barrier coating layer was formed on the vapor-deposited layer. The gas barrier coating layer was formed by applying one of the coating solutions A to D by the gravure coating method and then drying it under conditions of 80°C for 20 seconds. The types of coating solutions and the thickness of the gas barrier coating layer are shown in Table 1.

[0085] [Example 3] <Fabrication of laminates> A laminate was prepared by dry lamination using a two-component curing urethane adhesive to bond a 60 μm thick unstretched polypropylene film, which serves as a sealant layer, to the gas barrier coating layer side of the barrier film prepared in Example 1.

[0086] [Example 4] <Fabrication of laminates> A laminate was prepared in the same manner as in Example 3, except that the barrier film prepared in Comparative Example 1 was used.

[0087] [Comparative Example 5] <Fabrication of laminates> A laminate was prepared in the same manner as in Example 3, except that the barrier film prepared in Comparative Example 4 was used.

[0088] (Measurement of chlorine content) The chlorine content of the barrier films and laminates obtained in the examples and comparative examples was measured using an X-ray fluorescence analyzer (Rigaku Corporation, Supermini wavelength-dispersive X-ray fluorescence analyzer). Before measurement, a PHA-prepared sample (Rigaku Corporation) was used to confirm that the resolution of the PC detector was 45% or less. The measurements were performed under the following conditions. The net intensity (kcps) of chlorine atoms (Cl) obtained from the measurements under the following conditions was used as the X-ray intensity of the film surface. Detection spectrum: Cl-KA X-ray inter-excitation conditions: Target Pb, tube voltage 50kV, tube current 4.00mA Spectroscopic crystal: PET Detector: PC (Proportional Counter) Scan conditions: Start angle 62.0deg, end angle 69.0deg, step 0.05deg, time 0.2sec, speed 15deg / min., peak angle 65.44deg

[0089] For barrier films, the X-ray fluorescence intensity (kcps) of chlorine atoms detected from both sides was measured, and the sum of the X-ray fluorescence intensities of chlorine atoms from both sides was calculated. The sum of the calculated X-ray fluorescence intensities of chlorine atoms divided by the thickness of the barrier film was defined as the chlorine content (kcps / μm). For laminates, the base film and sealant layer were peeled from the laminate, and the X-ray fluorescence intensity (kcps) of chlorine atoms detected from both sides of each resin film was measured, and the sum of the X-ray fluorescence intensities of chlorine atoms from all sides was calculated. The sum of the calculated X-ray fluorescence intensities of chlorine atoms divided by the thickness of the laminate was defined as the chlorine content (kcps / μm). The results are shown in Tables 1 and 2.

[0090] (Evaluation of molten material coloration and meltmass flow rate) The barrier films and laminates obtained in the examples and comparative examples were cut to appropriate sizes, and melt extrusion was performed using a melt viscosity measuring device (Toyo Seiki Seisakusho Co., Ltd., product name "Melt Indexer F-F01") in accordance with the method shown in JIS K7210, under conditions of a temperature of 230°C and 2.16 kgf. The appearance of the extruded molten resin was visually observed, and the presence or absence of coloration and recyclability were evaluated as follows. A: No discoloration was observed, and it has excellent recyclability. B: Discoloration was observed, resulting in poor recyclability. C: Severely discolored, not recyclable.

[0091] Furthermore, the melt mass flow rate (MFR, unit: g / 10 min.) of the molten resin was measured when melt extrusion was performed under the above conditions. The MFR was measured five times, and the average value was used. If the MFR value is 6.0 g / min. or higher, oxidative decomposition of polypropylene has begun, and the recyclability is poor. The evaluation results for the presence or absence of coloring and the MFR are shown in Tables 1 and 2.

[0092] (Measurement of oxygen permeability) The oxygen permeability of barrier films and laminates was measured. Measurements were taken using an oxygen permeability analyzer (Modern Control, product name "OXTRAN 2 / 20") at a temperature of 30°C and a relative humidity of 70%. The measurement method conformed to JIS K7126-2 (isobaric method) and ASTM D3985-81, and the measured values ​​were expressed in units of [cm²]. 3 (STP) / m 2 The results were expressed in terms of [day·MPa]. The results are shown in Tables 1 and 2.

[0093] [Table 1]

[0094] [Table 2] [Industrial applicability]

[0095] By using the barrier film or laminate of this disclosure, recyclability is improved, and it becomes possible to produce monomaterial packaging suitable for material recycling, which is expected to contribute to solving environmental and waste problems. [Explanation of Symbols]

[0096] 1...Base film, 2...Anchor coat layer, 3...Vaporized layer, 4...Gas barrier coating layer, 5...Adhesive layer, 6...Sealant layer, 10...Gas barrier layer, 100...Barrier film, 200...Laminate.

Claims

1. A barrier film comprising a base film containing polyolefin, The substrate film further comprises a gas barrier layer formed on at least one surface of the substrate film, The gas barrier layer includes a gas barrier coating layer, The aforementioned gas barrier coating layer is a layer formed using a gas barrier coating layer forming composition containing at least one silicon compound represented by the following general formula (1) and its hydrolysate, at least one silicon compound represented by the following general formula (2) and its hydrolysate, and a water-soluble polymer having a hydroxyl group. The content of inorganic layered minerals in the gas barrier coating layer forming composition is 0% by mass based on the total amount of solids in the gas barrier coating layer forming composition. The barrier film has only one base film layer. A barrier film in which, when both sides of the barrier film are analyzed with an X-ray fluorescence analyzer, the value obtained by dividing the sum of the X-ray fluorescence intensities of chlorine detected from both sides by the thickness of the base film (sum of X-ray fluorescence intensities of chlorine / thickness of base film) is 0.015 kcps / μm or less. Si(OR 1) 4...(1) (R2Si(OR3)3)n...(2) [In general formulas (1) and (2), R1 and R3 each independently represent CH3, C2H5, or C2H4OCH3, R2 represents an organic functional group, and n represents an integer of 1 or more.]

2. The barrier film according to claim 1, wherein the gas barrier layer includes a vapor-deposited layer containing an inorganic oxide.

3. The barrier film according to claim 2, wherein the inorganic oxide comprises aluminum oxide, silicon oxide, or a mixture thereof.

4. The barrier film according to any one of claims 1 to 3, wherein the polyolefin is polypropylene.

5. A laminate comprising two resin films containing polyolefin, The laminate is formed by further laminating a sealant layer, which is the resin film, on one surface of the barrier film. The barrier film comprises a base film as the resin film and a gas barrier layer formed on at least one surface of the base film. The gas barrier layer includes a gas barrier coating layer, The aforementioned gas barrier coating layer is a layer formed using a gas barrier coating layer forming composition containing at least one silicon compound represented by the following general formula (1) and its hydrolysate, at least one silicon compound represented by the following general formula (2) and its hydrolysate, and a water-soluble polymer having a hydroxyl group. The content of inorganic layered minerals in the gas barrier coating layer forming composition is 0% by mass based on the total amount of solids in the gas barrier coating layer forming composition. The barrier film has only one base film layer. A laminate in which, when each resin film is peeled off from the laminate and both sides of all the resin films are analyzed with an X-ray fluorescence analyzer, the value obtained by dividing the sum of the X-ray fluorescence intensities of chlorine detected from all sides of all the resin films by the thickness of the laminate (sum of X-ray fluorescence intensities of chlorine / thickness of the laminate) is 0.015 kcps / μm or less. Si(OR 1) 4...(1) (R2Si(OR3)3)n...(2) [In general formulas (1) and (2), R1 and R3 each independently represent CH3, C2H5, or C2H4OCH3, R2 represents an organic functional group, and n represents an integer of 1 or more.]

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