Sealant film, packaging material and packaging bag

Abstract

To provide a sealant film which has sufficient reliability during heat sealing, piercing strength and film formation property, while containing a recycled material containing two or more kinds of resins, a packaging material and a packaging bag.SOLUTION: A sealant film 1a includes a recycled material-containing layer 2 containing a recycled material containing two or more kinds of resins, and a sealant layer 3 laminated on one main surface of the recycled material-containing layer, wherein the sealant film 1a is subjected to electron beam irradiation treatment, and arithmetic surface roughness of a surface S3a on a side opposite to the recycled material-containing layer 2 side of the sealant layer 3 is 0.5 μm or more and 5 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sealant film, a packaging material, and a packaging bag. [Background technology]

[0002] In general, plastic films have properties such as light weight, chemical stability, ease of processing, flexibility and strength, and the ability to be mass-produced, and are therefore used in a wide variety of applications. Their applications are diverse, including packaging materials for food products, pharmaceuticals, etc., intravenous drip packs, shopping bags, posters, tapes, optical films used in LCD televisions, etc., protective films, window films attached to windows, greenhouses, building materials, etc. Specific materials include thermoplastic resins such as polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polycarbonate, polyamide, polyethylene terephthalate, and polybutylene terephthalate, and thermosetting resins such as epoxy resin, polyurethane, and polyimide.

[0003] The appropriate plastic material is selected depending on the application, and multiple types of plastics are sometimes layered together to form a laminate. In addition, multiple plastic materials can be mixed in one layer to compensate for the shortcomings of a single material.

[0004] Recycling plastic products is expected to be a key part of addressing recent environmental issues, and various recycling methods are being considered. For example, PET bottles can be recycled by cleaning and crushing them, and then reused as raw materials, and chemical recycling technology has been established to convert them into monomers.

[0005] Furthermore, as a means of recycling polyethylene materials, the use of recycled polyethylene for applications such as films has been considered. For example, Patent Document 1 listed below proposes a sealant film containing recycled polyethylene resin. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2022 / 124229 Summary of the Invention [Problem to be solved by the invention]

[0007] Some recycled materials contain different types of resins. The present inventors have investigated the possibility of recycling such recycled materials as raw materials for sealant films, and have found that a sealant film having a layer containing recycled materials may have reduced reliability during heat sealing.

[0008] On the other hand, film products such as sealant films are required to have the property of being able to be molded without the occurrence of folds or wrinkles from the film formation to the winding up (hereinafter also referred to as "film formability"). If the film has insufficient film formability, the film after winding is likely to have poor appearance due to folds or wrinkles.

[0009] Furthermore, packaging bags such as pouches are typically produced by forming a packaging material with a sealant film. However, if pinholes form in the packaging material that constitutes the packaging bag due to friction during transportation, outside air or components of the base material layer may enter the packaging bag, potentially affecting the hygiene of the contents. Furthermore, when filling the packaging bag with contents that have sharp corners, there is a risk of pinholes forming from the inside to the outside of the packaging bag. Therefore, it is desirable that the sealant film used as the packaging material has excellent puncture strength.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a sealant film, a packaging material, and a packaging bag that contain recycled materials containing two or more types of resins, while having sufficient reliability during heat sealing, puncture strength, and film-forming properties. [Means for solving the problem]

[0011]

[0003] In order to solve the above problems, the present inventors have investigated factors that reduce reliability during heat sealing, and have found that when different types of resins are mixed in a layer containing recycled material, aggregates are formed by resin components other than the resin with the highest content ratio, and when these aggregates cause excessively large protrusions on the surface of the sealant film, air entrapment occurs during heat sealing. Based on this knowledge, the present inventors have conducted further investigations and found that a sealant film prepared so that the surface roughness of the sealant layer meets specific conditions can solve the above problems related to reliability and film formability, and further, by applying a predetermined treatment, can also have sufficient puncture strength, thereby completing the present invention.

[0012] One aspect of the present invention relates to the following [1] to [9].

[0013] [1] A sealant film comprising a recycled material-containing layer containing recycled material containing two or more types of resin, and a sealant layer laminated on one main surface of the recycled material-containing layer, wherein the sealant film has been subjected to electron beam irradiation treatment, and the arithmetic surface roughness of the surface of the sealant layer opposite to the recycled material-containing layer is 0.5 μm or more and 5 μm or less. [2] The sealant film according to [1], wherein the thickness of the sealant layer is 5 μm or more and 70 μm or less. [3] The sealant film according to [1] or [2], wherein the maximum height H of the convex portions on the surface of the sealant layer is 0.5 μm or more and 10 μm or less, and the ratio [W / H] of the width W at half the maximum height H to the maximum height H of the convex portions having the maximum height H is 20 or less. [4] A sealant film according to any one of [1] to [3], wherein the resin with the highest content ratio among the two or more resins contained in the recycled material is a polyethylene-based resin or a polypropylene-based resin. [5] The sealant film according to any one of [1] to [4], further comprising an auxiliary layer laminated on the other main surface of the recycled material-containing layer. [6] The sealant film according to [5], wherein the auxiliary layer contains the same type of virgin resin as the resin with the highest content in the recycled material-containing layer. [7] A packaging material comprising the sealant film according to any one of [1] to [6]. [8] The packaging material described in [7], wherein the content of plastic material contained in the recycled material is 10% by mass or more based on the total amount of plastic material in the packaging material. [9] A packaging bag made from the packaging material described in [7] or [8]. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a sealant film, a packaging material, and a packaging bag that contain recycled materials containing two or more types of resins and that have sufficient reliability during heat sealing, puncture strength, and film-forming properties. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view showing one embodiment of a sealant film according to the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view illustrating the shape of a convex portion in the sealant film shown in FIG. [Figure 3] FIG. 2 is a schematic cross-sectional view showing another embodiment of the sealant film according to the present invention. [Figure 4] 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention. [Figure 5] 1 is a schematic cross-sectional view showing one embodiment of a packaging material according to the present invention. [Figure 6] FIG. 2 is a schematic cross-sectional view showing another embodiment of a packaging material according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail. Note that Figures 1 to 6 are schematic diagrams, and the size and shape of each part are appropriately exaggerated for ease of understanding. Furthermore, the embodiments shown below are merely examples of configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited to the materials, shapes, structures, etc. of the components described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0017] <Sealant film> The sealant film of this embodiment comprises a recycled material-containing layer containing recycled material containing two or more types of resin, and a sealant layer laminated on one main surface of the recycled material-containing layer, and has been subjected to electron beam (EB) irradiation treatment.

[0018] Fig. 1 is a schematic cross-sectional view showing one embodiment of a sealant film. The sealant film 1a shown in Fig. 1 includes a recycled material-containing layer 2 and a sealant layer 3 laminated on one main surface of the recycled material-containing layer 2.

[0019] (Recycled material containing layer) Examples of recycled materials contained in the recycled material-containing layer include post-consumer recycled (PCR) materials such as bottles and packaging bags for beverages, detergents, and seasonings that have been collected from the market, food containers for lunch boxes and instant noodles, packaging bags for food and garbage bags, and plastic products such as hangers, stationery, daily necessities, home appliances, and toys; and post-industry recycled (PIR) materials such as defective products that do not become products discharged from factories, scraps generated during the manufacturing process, and plastic products used for transportation and packaging.

[0020] In the sealant film of this embodiment, from the viewpoint of material recycling of plastic films, a laminate (packaging material) made by bonding together multiple types of resin sheets, a packaging bag made from such a laminate, a laminate (packaging material) made by bonding together the same types of resin sheets, or a packaging bag made from such a laminate, or a mixture of these may be used. Examples of packaging bags include refill pouches for toiletries.

[0021] The recycled material contained in the recycled material-containing layer includes two or more resins. Examples of the two or more resins include thermoplastic resins, thermosetting resins, and cured products thereof (including crosslinked products). The two or more resins also include, for example, resin components (such as thermosetting resins) that constitute adhesives and their cured products.

[0022] Examples of thermoplastic resins include polyolefin resins, acrylic resins, polycarbonate resins, polyester resins, polyamide resins, etc. Examples of thermosetting resins include epoxy resins, polyurethane resins, polyimide resins, etc.

[0023] Examples of polyolefin resins include polyethylene-based resins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and ethylene-α-olefin copolymers, as well as polypropylene-based resins such as homopolypropylene (PP), block polypropylene, random polypropylene, and propylene-α-olefin copolymers.

[0024] Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polylactic acid.

[0025] An example of the polyamide resin is nylon 6.

[0026] The two or more resins may include a first resin that is contained in the recycled material at the highest ratio and a second resin that is incompatible with the first resin or that may form aggregates in the first resin. The type of resin contained in the recycled material-containing layer can be confirmed using a microscopic infrared spectrophotometer or the like.

[0027] The first resin and the second resin may be the following combinations: (a) Thermoplastic resins, thermosetting resins and their hardened products (b) Hydrocarbon-based resins and heteroatom-containing resins (c) A resin that dissolves in a predetermined solvent and a resin that does not dissolve in the predetermined solvent

[0028] Examples of the hydrocarbon resin in (b) include polyolefin resins and polystyrene resins, and examples of the heteroatom-containing resin include acrylic resins, polyester resins, and polyamide resins.

[0029] Examples of the predetermined solvent in (c) include aromatic hydrocarbons, chlorinated hydrocarbons, etc. Examples of resins that dissolve in the predetermined solvent include uncrosslinked resins, etc. Examples of resins that do not dissolve in the predetermined solvent include crosslinked resins, cured thermosetting resins, etc.

[0030] The first resin having the highest content in the recycled material may be a polyethylene resin or a polypropylene resin from the viewpoint of recycling packaging bags for pouch products, etc. In this case, the second resin may be, for example, at least one of polyester resin, polyamide resin, and a resin component constituting an adhesive and its cured product.

[0031] The content of the first resin in the recycled material-containing layer may be 75 to 98 mass %, 75 to 95 mass %, or 80 to 90 mass % based on the total mass of the recycled material-containing layer.

[0032] The content of the second resin in the recycled material-containing layer may be 2 to 33 parts by mass, 5 to 33 parts by mass, or 11 to 25 parts by mass relative to 100 parts by mass of the first resin.

[0033] The content of recycled material in the recycled material-containing layer may be 13 mass% or more, 33 mass% or more, 50 mass% or more, or 100 mass% based on the total mass of the recycled material-containing layer.

[0034] The resin having the highest content in the recycled material-containing layer may be the same as the resin having the highest content in the recycled material, for example, at least one polyethylene resin selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0035] The recycled material-containing layer may contain virgin material such as virgin resin. The virgin material may be blended so that the resin with the highest content in the recycled material is the same as the resin with the highest content in the recycled material-containing layer. The virgin material may be, for example, the same as the polyolefin resin described above, and may be at least one polyethylene resin selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0036] The recycled material-containing layer may contain aggregates derived from the second resin, for example, and from the viewpoint of ensuring reliability during heat sealing, the aggregates may have a maximum diameter of 20 μm or less. If the maximum diameter of the aggregates is 20 μm or less, it becomes easier to prevent the formation of convex portions having a height of more than 10 μm or convex portions having a height of 0.5 μm to 10 μm and a width-to-height ratio at half the height of more than 20 on the surface of the sealant layer.

[0037] The recycled material-containing layer may contain aggregates with a maximum diameter of 40 μm to 100 μm, 50 μm to 90 μm, or 60 μm to 80 μm.

[0038] The agglomerates and their maximum diameters can be confirmed by the following method. The aggregates contained in the recycled material-containing layer can be confirmed as domains (hereinafter also referred to as "low transmission brightness regions") whose transmission brightness is lower than that of the surrounding area when the sealant film is observed through transmission from a direction in which the sealant film is viewed in plan view, and the maximum diameter of the low transmission brightness region can be obtained by the following procedure. (i) Using a stereomicroscope system SZX16 (product name, manufactured by Olympus Corporation), observation images (image size: 243 μm × 851 μm) of the sealant film in the planar direction are obtained at 10 random locations. (ii) The 10 images obtained are analyzed using WinROOF2021 (product name, manufactured by Mitani Corporation). In the image analysis, the low-transmittance brightness region and the surrounding high-transmittance brightness region are binarized to calculate the maximum diameter in each low-transmittance brightness region. Note that, during binarization, the visual shape of the low-transmittance brightness region can be matched with the colored range by appropriately combining the following operations. (a) Adjusting brightness and contrast to emphasize low-transparency areas (b) Adjust the threshold to match the visible low-transmittance brightness area with the colored range. (c) If there are areas where adjacent low-transmittance brightness areas are recognized as one area, or areas where perforated low-transmittance brightness areas are recognized as multiple areas, perform division or integration processing as necessary.

[0039] In order to reduce the maximum diameter of the aggregates in the recycled material-containing layer, for example, the following adjustment means can be mentioned. (a) Reducing the proportion of recycled material in the recycled material-containing layer (b) Increasing the content of the first resin in the recycled material. (c) When extruding a recycled material-containing layer, increase the screw rotation speed. (d) When extruding the recycled material-containing layer, the narrowing of the flow path is avoided as much as possible, and a mechanism is created in which elongation stress is not easily applied. (e) Recycled materials are used by pelletizing them using a twin-screw extruder or by mixing them with virgin resin to form a masterbatch.

[0040] The recycled material-containing layer may have a thickness of 20 to 100 μm.

[0041] (sealant layer) The sealant layer has an uneven surface on the side opposite to the recycled material-containing layer, and the surface (for example, S shown in FIG. 1) 3a The arithmetic surface roughness Ra of the film, as specified in JIS B 0601:2001, is 0.5 μm or more and 5 μm or less. If Ra is 5 μm or less, it is possible to prevent a decrease in reliability (for example, a decrease in low-temperature heat sealability) due to air entrapment when overlapping sealant films and heat sealing them. In addition, it is less likely that problems such as a decrease in impact resistance or puncture resistance due to a localized thinning of the thickness of the recessed portions will occur. On the other hand, if Ra is 0.5 μm or more, the coefficient of friction will not be too high, allowing for appropriate slip properties and making it less likely that wrinkles will occur during film formation.

[0042] From the above viewpoint, the Ra may be 0.5 μm or more and 4 μm or less, 0.5 μm or more and 3 μm or less, 0.5 μm or more and 2 μm or less, 0.5 μm or more and 1.5 μm or less, 1.0 μm or more and 4 μm or less, 1.0 μm or more and 3 μm or less, or 1.0 μm or more and 2 μm or less.

[0043] Methods for adjusting the Ra include, in addition to the method of adjusting the maximum diameter of the aggregates described above, changing the thickness of the sealant layer, incorporating an antiblocking agent into the sealant layer, and forming predetermined irregularities on the surface of the sealant layer (for example, pressing a nip roll against the molten resin when cooling and solidifying it during film formation).

[0044] From the viewpoint of ensuring reliability during heat sealing, the surface of the sealant layer (S shown in Figure 2) 3a ) in the convex part (P shown in Figure 2 3a ) is the height (H shown in Figure 2 3a From the same viewpoint, the width at half the height of the convex portion (W shown in FIG. 2) may be 10 μm or less, 0.5 to 9 μm, or 0.5 to 8 μm. 3a ) may be 200 μm or less, may be 1 to 150 μm, or may be 1 to 100 μm. FIG. 2 is a schematic cross-sectional view for explaining the shape of the protrusions in the sealant film shown in FIG. 1. As shown in FIG. 2, the protrusions P 3a The surface S of the sealant layer 3 is formed by the aggregates 50 generated in the recycled material-containing layer. 3a It may also be caused by the uplift of

[0045] The convex portions on the surface of the sealant layer may have a maximum height H of 0.5 μm or more and 10 μm or less, and the ratio [W / H] of the width W at half the maximum height H to the maximum height H of the convex portions having the maximum height H may be 20 or less, or the above H may be 0.5 to 9 μm and the ratio [W / H] may be 1 to 18. This is advantageous in terms of (a) improving the recycled material content in the recycled material-containing layer, (b) improving the recycled material content in the sealant film by reducing the thickness of the sealant layer, and (c) improving productivity by being able to reduce the pressure applied during cooling or hot pressing during film formation.

[0046] The material for forming the sealant layer may be a thermoplastic resin or other material that has adequate flexibility and good processability, for example, suitability for processing using an extruder. Examples of such materials include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and polypropylenes having homopolymers, random copolymers, and block copolymers; ethylene-vinyl acetate copolymers obtained by copolymerizing olefins such as low-density polyethylene (LDPE) with vinyl acetate; and ethylene-methyl acrylate copolymers (EMA), ethylene-ethyl acrylate copolymers (EEA), ethylene-butyl acrylate copolymers (EBA), and ethylene-methacrylic acid copolymers (EMAA) obtained by modifying the side chains of olefins. These materials may be used alone or in combination.

[0047] From the viewpoint of heat sealing property, the sealant layer may contain the same type of resin as the resin with the highest content in the recycled material-containing layer, and virgin resin may be blended to achieve this. For example, if the resin with the highest content in the recycled material-containing layer is a polyethylene-based resin, the sealant layer may contain a polyethylene-based resin, or the polyethylene-based resin may be the main component (e.g., the content in the sealant layer is 95% by mass or more). Also, if the resin with the highest content in the recycled material-containing layer is a polypropylene-based resin, the sealant layer may contain a polypropylene-based resin, or the polypropylene-based resin may be the main component (e.g., the content in the sealant layer is 95% by mass or more).

[0048] The sealant layer may contain a polypropylene resin from the viewpoint of reducing the above-mentioned Ra, maximum height H, and ratio [W / H].

[0049] From the viewpoint of film processability, the MFR of the polyethylene resin may be 0.05 to 15 g / 10 min, or 0.1 to 8 g / 10 min. The MFR here refers to a value measured in accordance with JIS K7210 (190°C, load 2.16 kg).

[0050] From the viewpoint of film processability, the MFR of the polypropylene resin may be 0.05 to 20 g / 10 min, or 0.1 to 10 g / 10 min. The MFR here refers to a value measured in accordance with JIS K7210 (230°C, load 2.16 kg).

[0051] From the viewpoint of heat sealing property and rigidity, the crystallinity of the polypropylene resin as measured by the heat of fusion using a differential scanning calorimeter (DSC) may be 25% or more and 60% or less, or 30% or more and 55% or less.

[0052] In this specification, the crystallinity of a polypropylene-based resin is calculated from the ratio of the heat of fusion ΔHm obtained by integrating the endothermic peak during melting of the sample to the heat of fusion ΔH100 of a completely crystalline body having a crystallinity of 100% obtained by theoretical calculation, according to the following formula: Crystallinity [%]=(ΔHm / ΔH100)×100 The heat of fusion ΔH100 of a completely crystalline substance can be the value described in the following document. For example, the ΔH100 of polypropylene can be 207 J / g. Reference: Japan Society of Plastics Processing: Plastic Materials in Molding Processing, 335 (2011), Morikita Publishing Co., Ltd.

[0053] The sealant layer may contain the above resin as a virgin material. Alternatively, from the viewpoint of the stability of heat sealing performance, the sealant layer may not contain recycled material.

[0054] The thickness of the sealant layer may be 5 μm or more and 70 μm or less. In this case, it is easy to prevent the aggregates contained in the recycled material-containing layer from being exposed from the sealant layer, and it is easy to ensure the rigidity of the entire sealant film and to increase the content of recycled material in the sealant film. This makes it possible to more effectively realize material recycling of recycled materials containing two or more resins in the sealant film. The thickness of the sealant layer may be 5 μm or more and 60 μm or less, 5 μm or more and 55 μm or less, 5 μm or more and 50 μm or less, 5 μm or more and 40 μm or less, 5 μm or more and 30 μm or less, 5 μm or more and 20 μm or less, 10 μm or more and 65 μm or less, 10 μm or more and 60 μm or less, 10 μm or more and 55 μm or less, 10 μm or more and 50 μm or less, 10 μm or more and 40 μm or less, 10 μm or more and 30 μm or less, 15 μm or more and 60 μm or less, or 20 μm or more and 60 μm or less.

[0055] The recycled material-containing layer and the sealant layer may contain additives such as compatibilizers, nucleating agents, reinforcing fillers, antioxidants, heat stabilizers, weathering agents, light stabilizers, plasticizers, UV absorbers, antistatic agents, flame retardants, flame retardant aids, slip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, dispersants, copper inhibitors, neutralizing agents, bubble inhibitors, weld strength improvers, natural oils, synthetic oils, waxes, etc. The additives may be used alone or in combination of two or more.

[0056] Examples of nucleating agents and reinforcing fillers include talc, silica, clay, montmorillonite, calcium carbonate, lithium alumina carbonate, titanium oxide, metals such as aluminum, iron, silver, and copper, hydroxides such as aluminum hydroxide and magnesium hydroxide, celluloses such as cellulose microfibrils and cellulose acetate, fibrous fillers such as glass fibers, polyethylene terephthalate fibers, nylon fibers, polyethylene naphthalate fibers, aramid fibers, vinylon fibers, and polyacrylate fibers, carbons such as carbon nanotubes, and elastomers such as ethylene propylene rubber (EPR).

[0057] Examples of the antioxidant include phenolic compounds, organic phosphite compounds, and thioether compounds.

[0058] Examples of the heat stabilizer and light stabilizer include hindered amine compounds.

[0059] Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, and benzoate compounds.

[0060] Examples of the antistatic agent include nonionic compounds, cationic compounds, and anionic compounds.

[0061] Examples of the flame retardant include halogen-based compounds, phosphorus-based compounds, nitrogen-based compounds, inorganic compounds, boron-based compounds, silicone-based compounds, sulfur-based compounds, and red phosphorus-based compounds.

[0062] Examples of the flame retardant aid include antimony compounds, zinc compounds, bismuth compounds, magnesium hydroxide, and clay silicates.

[0063] Examples of the anti-blocking agent include acrylic particles, styrene particles, styrene-acrylic particles and crosslinked products thereof, polyurethane particles, polyester particles, silicon particles, fluorine particles, copolymers thereof, zeolite, pyrophyllite, talc, smectite, vermiculite, mica, chlorite, kaolin minerals, clay compound particles such as sepiolite, silica, titanium oxide, alumina, silica alumina, zirconia, zinc oxide, strontium oxide, aluminum hydroxide, strontium carbonate, strontium chloride, strontium sulfate, strontium nitrate, strontium hydroxide, and glass particles.

[0064] In the sealant film of the present embodiment, the ratio Tr / Ts of the thickness Tr of the recycled material-containing layer to the thickness Ts of the sealant layer may be 0.3-16, 0.5-14, or 0.7-12.

[0065] The sealant film of the present embodiment is subjected to electron beam irradiation treatment, which increases the crosslink density of the resin contained in the sealant film by electron beam irradiation, thereby further improving the mechanical strength of the sealant film.

[0066] The electron beam irradiation treatment may be carried out from the side opposite to the side of the sealant film where the sealant layer is provided (in the case of a packaging material provided with a sealant film, the side opposite to the surface that comes into contact with the contents or filled material).

[0067] The sealant film of this embodiment may be subjected to electron beam irradiation treatment during or after the formation of the laminate or packaging material described below. For example, an ink layer or an overcoat layer that is cured by electron beam irradiation may be provided on the sealant film, and the electron beam irradiation conditions may be set so that the sealant film is irradiated with a predetermined dose of electron beams when these layers are cured. In particular, in the case of multi-color printing, further strength improvement can be expected by accumulating the EB irradiation of each color. Furthermore, in the case of a packaging material in which a sealant film is laminated with a gas barrier layer, a base film, or the like, the electron beam irradiation conditions may be set so that the sealant film is irradiated with a predetermined dose of electron beams during EB sterilization performed after pouching or filling with contents. From the viewpoint of improving puncture strength, etc., the acceleration voltage and irradiation energy of the electron beam may be adjusted so that the electron beam dose on the sealant film is preferably 10 KGy or more and 2000 KGy or less, or 20 KGy or more and 500 KGy or less. From the same viewpoint, the dose of the electron beam, the acceleration voltage of the electron beam, and the irradiation energy may be adjusted so that the gel fraction of the sealant film falls within the range described below.

[0068] The sealant film of this embodiment may have a gel fraction of 0.5% or more and 85% or less, or 20% or more and 80% or less, as calculated by the following method. The gel fraction can be used as an indicator of crosslink density, and when the gel fraction is in the above range, it is easy to achieve both an improvement in the mechanical strength of the sealant film by increasing the crosslink density of the recycled material-containing layer and ensuring heat sealability by preventing excessive crosslinking of the sealant layer. (Calculation method of gel fraction) The gel fraction is calculated by utilizing the insolubility of the crosslinked portion in a solvent, and can be calculated by immersing the sealant film in an organic solvent such as xylene, drying the remaining insoluble film, measuring its mass, and then calculating the gel fraction from the mass of the sealant film before dissolution and the mass of the insoluble film after drying. Specifically, the gel fraction can be calculated by the following procedure. (i) First, Xg of sealant film was wrapped in Yg of stainless steel mesh and heated and immersed in a solvent. The heating temperature and immersion time were 120°C and 8 hours, respectively. (ii) Next, the sealant film wrapped in the stainless steel mesh is removed from the solvent and vacuum dried at 60°C for 3 hours. (iii) The mass (Zg) of the sealant film wrapped in the stainless steel mesh after drying is measured, and the gel fraction is calculated using the following formula (1). Gel fraction (mass%) = [(ZY) / X] × 100 ... (1)

[0069] Even with a low EB irradiation dose, physical strength may be improved by EB irradiation, and even a slight increase in gel fraction is considered to be crosslinking. In such cases, a shift in melting peak intensity to lower temperatures and a decrease in melting enthalpy are observed in DSC (differential scanning calorimetry) analysis.

[0070] The sealant film of this embodiment may have a multilayer structure in which desired physical properties are complemented by laminating another layer. Fig. 3 is a schematic cross-sectional view showing another embodiment of the sealant film. The sealant film 1b shown in Fig. 3 comprises a recycled material-containing layer 2, a sealant layer 3 laminated on one main surface of the recycled material-containing layer 2, and an auxiliary layer 4 laminated on the other main surface of the recycled material-containing layer 2. In this case, too, the surface S of the sealant layer 3 opposite to the recycled material-containing layer 2 side is 3b The arithmetic surface roughness Ra specified in JIS B 0601:2001 can satisfy the above-mentioned conditions.

[0071] The auxiliary layer 4 may be configured to contain a high-density resin in order to further increase the rigidity of the sealant film 1b, and may be configured to contain a resin having a density similar to that of the resin constituting the sealant layer 3 (for example, a density difference of 0.1 kg / m 2) in order to suppress curling due to thermal shrinkage of the sealant film 1b. 3 The resin may contain a compound selected from the group consisting of hydroxybenzoates, ...

[0072] Furthermore, when auxiliary layer 4 is intended to function as a laminating layer, it may have the same configuration as the above-described sealant layer 3. Furthermore, auxiliary layer 4 may contain the same type of resin as the resin with the highest content in recycled material-containing layer 2. In this case, higher laminating strength makes it easier to improve adhesion with other layers.

[0073] The auxiliary layer 4 may contain one or more of the above-mentioned additives, if necessary.

[0074] Furthermore, when auxiliary layer 4 is made to function as a laminate layer, the arithmetic surface roughness Ra, as defined in JIS B 0601:2001, of the surface of auxiliary layer 4 opposite to recycled material-containing layer 2 may be 0.03 μm or more and 5 μm or less, 0.04 μm or more and 3 μm or less, or 0.05 μm or more and 2 μm or less. In this case, when another layer is laminated on the laminate layer via an adhesive, it becomes easy to prevent lamination defects caused by the occurrence of defective areas where the adhesive does not adhere.

[0075] The Ra of the auxiliary layer 4 can be adjusted by changing the thickness of the auxiliary layer 4. In this case, the thickness of the auxiliary layer may be 5 μm or more and 100 μm or less, 10 μm or more and 90 μm or less, or 20 μm or more and 80 μm or less, from the viewpoints of suppressing lamination defects and reducing costs.

[0076] The electron beam irradiation treatment may be performed on the sealant film 1b from the side opposite to the side where the sealant layer is provided (the auxiliary layer side) (in a packaging material including a sealant film, the side opposite to the surface that comes into contact with the contents or filled material). The sealant film 1b may have the above-mentioned gel fraction.

[0077] <Method of manufacturing sealant film> The sealant film of the present embodiment can be produced by a conventionally known method, for example, a method of extrusion laminating a recycled material-containing film formed from a resin composition constituting the recycled material-containing layer with a resin composition constituting the sealant layer, or a method of forming the recycled material-containing layer and the sealant layer by coextrusion molding can be used.

[0078] In the former method, the recycled material-containing film can be produced by melting the resin composition constituting the recycled material-containing layer in an injection molding machine or extrusion molding machine (e.g., a twin-screw extruder) and then forming the film in a T-die through a feed block or multi-manifold, or by an inflation method. The recycled material can be produced by collecting, cleaning, and pulverizing various types of plastic waste, melt-molding them in an extruder, and pelletizing them. For extrusion lamination, an extrusion laminating machine or the like can be used.

[0079] In the latter method, for example, a sealant film can be produced by melt-kneading and co-extruding the resin composition constituting the recycled material-containing layer and the resin composition constituting the sealant layer using a multi-layer extrusion molding machine.

[0080] The resin composition constituting the recycled material-containing layer may contain only recycled material, or may further contain virgin resin or additives to impart various desired properties such as viscosity adjustment, mechanical property reinforcement, etc. Furthermore, when the recycled material and virgin resin are mixed, they may be dry-blended in which the virgin resin and the recycled material are simultaneously charged into a hopper and melt-kneaded to form a film, or they may be melt-blended in which the virgin resin and the recycled material are separately melt-kneaded in a twin-screw extruder to form a masterbatch.

[0081] To reduce the size of aggregates in the recycled material-containing layer, the layer may be repelletized using a twin-screw extruder, molded under high shear conditions, or may contain an acid-modified polyolefin resin or the like as a compatibilizer.

[0082] The film can be cooled using a cooling method that is compatible with the molding machine. For example, in the T-die method, air cooling methods such as an air chamber, vacuum chamber, or air knife, or water cooling methods such as dipping a cooling roll in a cold water pan can be used.

[0083] Furthermore, for example, in the case of the T-die method, in order to adjust the Ra of the sealant layer, a predetermined surface shape can be imparted to the sealant layer by pressing the molten resin with a nip roll when cooling and solidifying it using a chill roll with a predetermined surface shape. A method for imparting a surface shape by shaping may be a method in which a nip roll made of silicone rubber, NBR rubber, fluororesin, or the like is contacted with a chill roll and a pressure of 0.1 MPa or more is applied, and the molten resin is then poured into the contact area and cooled. The chill roll may be one that has been machined from metal or shaped by blasting. The surface shape of the chill roll may be a randomly uneven shape, and the surface roughness can be adjusted by changing the particle size and treatment time (amount) during blasting. The Ra of the auxiliary layer can also be adjusted in the same manner as above.

[0084] The sealant film of this embodiment can also be produced by a heat press method. In the heat press method, a flat film can be molded by compressing it between heated rolls or a heated plate. The thickness of the molded product can be controlled by adjusting the compression pressure. Single-layer films produced by heat press may be stacked and then heat pressed again to form a laminate, or a pre-laminated flat film may be prepared and the film thickness adjusted by heat press. Furthermore, to adjust the surface roughness, when a predetermined surface shape is to be formed on the film, the predetermined surface shape may be formed on the surface of a roll or a flat plate and then transferred. The surface shape may be a random uneven shape, and the surface roughness can be adjusted by changing the particle size and treatment time (amount) during blast treatment.

[0085] In this embodiment, the sealant film produced as described above can be subjected to electron beam irradiation treatment. Electron beam irradiation improves the crosslink density of the resin contained in the sealant film, thereby improving the mechanical strength (particularly, puncture strength) of the sealant film. The electron beam irradiation treatment is preferably performed from the side opposite to the side on which the sealant layer of the sealant film is provided (in the case of a packaging material provided with a sealant film, the side opposite to the surface that comes into contact with the contents or filled material).

[0086] In addition, the sealant film produced as described above has an arithmetic surface roughness on the surface of the sealant layer opposite to the recycled material-containing layer that satisfies the above-mentioned conditions, so that the mechanical strength (particularly, puncture strength) can be easily improved by electron beam irradiation. Furthermore, the maximum height H and ratio [W / H] of the convex portions on the surface of the sealant layer specified by the above-mentioned method satisfy the above-mentioned conditions, so that the mechanical strength (particularly, puncture strength) can be easily improved by electron beam irradiation.

[0087] As an apparatus that can be used to irradiate a sealant film with an electron beam, a conventionally known low-energy type is preferably used, such as a curtain-type electron beam irradiation apparatus (LB1023, manufactured by i-Electron Beam Inc.), a line-type low-energy electron beam irradiation apparatus (EB-ENGINE, manufactured by Hamamatsu Photonics K.K.), and a drum-roll type electron beam irradiation apparatus (EZ-CURE, manufactured by i-Electron Beam Inc.).

[0088] The dose of the electron beam irradiated to the sealant film and the acceleration voltage of the electron beam can be set as appropriate, and may be adjusted as appropriate within a range in which the electron beam does not reach the sealant layer when irradiated to the main surface of the sealant film opposite the sealant layer side. In this case, the crosslink density of the sealant layer is improved by the electron beam, and a decrease in the heat sealability of the sealant layer can be suppressed. In addition, the dose of the electron beam, the acceleration voltage of the electron beam, and the irradiation energy may be adjusted so that the gel fraction of the sealant film falls within the above-mentioned range.

[0089] The dose of the electron beam may be 10 kGy or more and 2000 kGy or less, or 20 kGy or more and 500 kGy or less.

[0090] The acceleration voltage of the electron beam may be 30 kV or more and 300 kV or less, 50 kV or more and 300 kV or less, or 50 kV or more and 250 kV or less.

[0091] The irradiation energy of the electron beam may be 20 keV or more and 750 keV or less, 25 keV or more and 500 keV or less, 30 keV or more and 400 keV or less, or 20 keV or more and 200 keV or less.

[0092] The oxygen concentration in the electron beam irradiation apparatus may be 500 ppm or less, or may be 100 ppm or less. By performing electron beam irradiation under such conditions, it is possible to suppress the generation of ozone and also to prevent the radicals generated by electron beam irradiation from being deactivated by oxygen in the atmosphere. Such conditions can be achieved, for example, by creating an inert gas (nitrogen, argon, etc.) atmosphere inside the apparatus.

[0093] The sealant film may be subjected to a surface modification treatment to improve suitability for subsequent processes. For example, the surface to be laminated may be subjected to a surface modification treatment to improve printability and lamination suitability when laminating with other layers or substrate films. Examples of surface modification treatments include methods for oxidizing the film surface to express functional groups, such as corona discharge treatment, plasma treatment, and flame treatment, and wet process modifications such as coating with an easy-adhesion layer.

[0094] The method for producing the sealant film is not limited to the above-mentioned method, and the sealant film produced by the molding machine may be subjected to in-line or off-line stretching treatment. There are no limitations on the addition of other necessary steps or additives as appropriate.

[0095] <Laminate> The laminate of this embodiment includes the sealant film of this embodiment described above. FIG. 4 is a schematic cross-sectional view showing one embodiment of the laminate of this embodiment. The laminate 10a shown in FIG. 4 further includes a gas barrier layer 12 on the side of the auxiliary layer 4 opposite to the recycled material-containing layer 2 side in the sealant film 1b shown in FIG. 3. The laminate 10a can have improved gas barrier properties (for example, oxygen barrier properties and water vapor barrier properties). The gas barrier layer may have a single-layer structure or a multilayer structure.

[0096] Examples of the gas barrier layer 12 include a vapor-deposited layer (vapor-deposited film) made of a metal or inorganic oxide, a metal foil such as aluminum foil, and a film of an ethylene-vinyl alcohol copolymer, a polyamide resin, a polyvinylidene chloride resin, a polyacrylonitrile resin, or the like.

[0097] The vapor-deposited layer may have a single layer structure or a multilayer structure. Examples of the vapor-deposited layer include a vapor-deposited layer composed of a metal such as aluminum, and an inorganic oxide such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide.

[0098] The deposition layer can be formed by a conventionally known method, for example, physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition, and can be appropriately selected depending on the deposition material, etc.

[0099] When the vapor-deposited layer is an aluminum vapor-deposited film, the OD value thereof may be from 2 to 3.5 in terms of productivity, oxygen barrier property, and water vapor barrier property of the laminate. Note that, in this specification, the OD value refers to the value measured in accordance with JIS-K-7361.

[0100] When the vapor-deposited layer is an inorganic oxide layer using silicon oxide, the O / Si ratio of the inorganic oxide layer may be 1.5 or more from the viewpoint of transparency. Furthermore, the O / Si ratio may be 2.0 or less from the viewpoint of barrier properties. To obtain the above-mentioned effects more fully, the O / Si ratio of the inorganic oxide layer may be 1.5 or more and 2.0 or less, or 1.6 or more and 1.8 or less.

[0101] The O / Si ratio of the inorganic oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., trade name: JPS-90MXV) is used as the measurement device, and measurements can be performed using a non-monochromated MgKα (1253.6 eV) X-ray source at an X-ray output of 100 W (10 kV-10 mA). For quantitative analysis to determine the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used.

[0102] The thickness of the vapor-deposited layer may be 1 nm or more and 150 nm or less, 5 nm or more and 60 nm or less, or 5 nm or more and 40 nm or less. When the thickness of the vapor-deposited layer is 1 nm or more, oxygen barrier property and water vapor barrier property are easily obtained. When the thickness of the vapor-deposited layer is 150 nm or less, cracks in the vapor-deposited layer are easily prevented, and the recyclability of the sealant film is easily maintained.

[0103] The auxiliary layer 4 provided with the gas barrier layer may have the same structure as the above-described sealant layer 3. When the auxiliary layer 4 contains a polyolefin resin, the polyolefin resin preferably has high crystallinity from the viewpoints of printability, vapor deposition suitability, strength, and heat resistance. The polyolefin resin may be a virgin resin and / or a chemically recycled resin.

[0104] When the polyolefin resin is polyethylene, high-density polyethylene (HDPE) and medium-density polyethylene (MDPE) are preferred from the viewpoints of printability, strength, and heat resistance, and medium-density polyethylene is more preferred from the viewpoint of suitability for stretching. When the polyolefin resin is polypropylene, the crystallinity determined by the heat of fusion using a differential scanning calorimeter (DSC) may be 40% or more or 45% or more from the viewpoints of printability, strength, and heat resistance, and may be 60% or less or 55% or less from the viewpoint of impact resistance.

[0105] The content of non-material recycled resin (virgin resin, chemical recycled resin) in auxiliary layer 4 on which the gas barrier layer is provided can be made higher than the content of non-material recycled resin in the recycled-material-containing layer. In this case, it is possible to smooth out partial swelling caused by aggregates on the surface of the recycled-material-containing layer and improve the mechanical properties and gas barrier properties of the laminate.

[0106] The thickness of the auxiliary layer 4 on which the gas barrier layer is provided may be 20 μm or more, 40 μm or more, or 80 μm or more from the viewpoint of gas barrier properties and adhesion, and may be 150 μm or less, 120 μm or less, or 100 μm or less from the viewpoint of reducing the total thickness when used as a packaging material.

[0107] <Packaging material> The packaging material of this embodiment includes the sealant film of this embodiment described above. Fig. 5 is a schematic cross-sectional view showing one embodiment of the packaging material. The packaging material 100 shown in Fig. 5 includes a sealant film 1b including an auxiliary layer 4, and a base film 6 laminated onto the auxiliary layer 4 via an adhesive layer 5.

[0108] The base film 6 is not particularly limited as long as it has mechanical strength and dimensional stability, and examples of the base film 6 that can be used include plastic film, paper, nonwoven fabric, etc. Examples of materials that can be used for the plastic film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, polystyrene, polyamides such as 6-nylon, polycarbonate, polyacrylonitrile, and polyimide.

[0109] The base film 6 is preferably a stretched film from the viewpoint of mechanical strength and dimensional stability.

[0110] By containing the same type of resin (also referred to as "the same resin") as the resin with the highest content in the sealant film, the entire packaging material can be made into a mono-material, improving the recyclability of the packaging material. In this case, all layers constituting the sealant film (for example, the sealant layer, or the sealant layer and auxiliary layer) may contain the same type of resin as the resin with the highest content in the recycled material-containing layer.

[0111] The content of the same resin in the packaging material may be 90% by mass or more, based on the total amount of the packaging material. In this case, the packaging material can be said to be a monomaterial packaging material made of a single material. From the perspective of further improving recyclability, the content of the same resin in the packaging material may be 92.5% by mass or more, or 95% by mass or more, based on the total amount of the packaging material.

[0112] From the viewpoint of transparency, the haze value of the base film 6 may be 30% or less, or may be 20% or less. In this specification, the haze value of the film refers to the value measured in accordance with JIS K 7105.

[0113] The substrate film 6 may be subjected to a surface treatment, which can improve adhesion to adjacent layers. The method of surface treatment is not particularly limited, and examples include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and / or nitrogen gas, and glow discharge treatment, as well as chemical treatments such as oxidation treatment using chemicals.

[0114] An anchor coating layer may be provided on the surface of the base film 6 using a conventionally known anchor coating agent.

[0115] The thickness of the base film 6 may be 10 μm or more and 50 μm or less, or 12 μm or more and 30 μm or less. When the thickness of the base film is 10 μm or more, it is easy to improve the strength of the laminate. Furthermore, when the thickness of the base film is 50 μm or less, it is easy to maintain the processability of the laminate.

[0116] The adhesive layer 5 is a layer that bonds the base film 6 and the sealant film. In the packaging material 10, the auxiliary layer 4 of the sealant film and the base film 6 are bonded via the adhesive layer 5.

[0117] The adhesive constituting the adhesive layer is not particularly limited, but may be a dry laminating adhesive, such as a two-component curing urethane adhesive, a polyester urethane adhesive, a polyether urethane adhesive, an acrylic adhesive, a polyester adhesive, a polyamide adhesive, or an epoxy adhesive.

[0118] When the packaging material is used for a packaging bag for retort use, a two-component curing urethane adhesive that is retort resistant can be used.

[0119] From the viewpoint of hygiene, the adhesive layer 5 may not contain 3-glycidyloxypropyltrimethoxysilane (GPTMS).

[0120] From the viewpoint of environmental consideration, the adhesive layer 5 may contain a biomass material.

[0121] The adhesive layer 5 may not contain a solvent from the viewpoint of environmental consideration.

[0122] The adhesive layer 5 may be chlorine-free from the viewpoint of suppressing discoloration of recycled resins and the like after recycling and the generation of odors due to heat treatment.

[0123] The thickness of the adhesive layer may be 0.3 μm or more and 5.0 μm or less. From the viewpoint of adhesive strength, the thickness of the adhesive layer may be 0.3 μm or more, 0.5 μm or more, or 1 μm or more, and from the viewpoint of recyclability, the thickness may be 5.0 μm or less, 3.5 μm or less, or 2.5 μm or less. When the thickness of the adhesive layer is equal to or less than the above upper limit, the proportion of monomaterials in the packaging material can be increased.

[0124] The packaging material of the present embodiment may further include a functional layer such as a print layer and a gas barrier layer. These functional layers may be provided on the above-mentioned base film.

[0125] The printed layer may be formed on the surface of the base film on which the sealant film is provided, in which case the printed layer can be prevented from coming into contact with the outside air and from deteriorating over time.

[0126] The print layer may represent letters, patterns, symbols, or a combination thereof.

[0127] From the viewpoint of producing a packaging material with less environmental impact, the printed layer may be formed using ink derived from biomass.

[0128] The method for forming the printed layer is not particularly limited, and any conventionally known printing method such as gravure printing, offset printing, flexographic printing, etc. Among these, flexographic printing may be used from the viewpoint of environmental load.

[0129] The gas barrier layer can be provided on the substrate film and may have the same structure as the gas barrier layer 12 described above.

[0130] The gas barrier layer may also be formed by laminating a laminate film of a metal foil and a plastic film, or a plastic film with a vapor-deposited layer (vapor-deposited film) made of the above-mentioned metal or inorganic oxide, etc. Examples of plastic films include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, polystyrene, polyamides such as 6-nylon, polycarbonate, polyacrylonitrile, and polyimide.

[0131] Fig. 6 is a schematic cross-sectional view showing another embodiment of a packaging material. The packaging material 102 shown in Fig. 6 includes a laminate 10a in which a sealant film 1b having a laminated structure of a sealant layer 3, a recycled material-containing layer 2, and an auxiliary layer 4, and a gas barrier layer 12 are laminated in this order, and a base film 6 having a printed layer 7 bonded to the gas barrier layer 12 side of the laminate via an adhesive layer 5. In the packaging material 102, as described above, the printed layer 7 is formed on the surface of the base film 6 on the side where the sealant film is provided.

[0132] Each layer in the packaging material of this embodiment may contain the additives described above.

[0133] The packaging material of this embodiment can be modified in various ways in addition to the configuration described above, and may have the following configuration. (a) Sealant film of this embodiment / adhesive layer / gas barrier film / adhesive layer / substrate film (b) Sealant film / adhesive layer / gas barrier film of this embodiment (c) Sealant film of this embodiment / gas barrier layer (e.g., vapor deposition layer) / adhesive layer / substrate film The gas barrier film may be a substrate film provided with a gas barrier layer, a laminated film of a metal foil and a plastic film, or a vapor-deposited film, as described above, or may be a metal foil such as aluminum foil, or a film such as an ethylene-vinyl alcohol copolymer, a polyamide resin, a polyvinylidene chloride resin, or a polyacrylonitrile resin.

[0134] From the viewpoint of material recycling, the content of plastic material contained in the packaging material of this embodiment may be 10% by mass or more, or 25% by mass or more, based on the total amount of plastic material in the packaging material. When the packaging material of this embodiment is a laminate packaging material, materials other than plastic (for example, adhesives, printing inks, aluminum foil, etc.) may be excluded from the weight calculation.

[0135] Examples of plastic materials contained in recycled materials (so-called recycled plastics) include resins contained in the recycled materials contained in the recycled material-containing layer according to the present embodiment. Pre-consumer materials among recycled plastics may be calculated by multiplying the weight by 1 / 2.

[0136] The packaging material of this embodiment can be used for stand-up pouches, three-sided bags, two-sided bags, gusseted bags, pouches with spouts, pouches with beaks, and the like.

[0137] <Packaging bag> The packaging bag of this embodiment is made from the packaging material of this embodiment described above. The manufacturing style of the packaging bag is not particularly limited, but the packaging bag may be a stand-up pouch, a three-sided bag, a two-sided bag, a gusset bag, a pouch with a spout, a pouch with a beak, or the like. [Example]

[0138] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0139] <Preparing recycled materials> (Recycled material 1) The recycled material 1 was obtained by compressing, cutting, and granulating a film consisting of an LLDPE film (Mitsui Chemicals Tocello, product name "TUX FC-S," 100 μm thick), an adhesive layer, a PET film (Toray Advanced Film, product name "VM-PET 1310," 12 μm thick, aluminum vapor deposition), an adhesive layer, and an Ny film (Toyobo, product name "Harden Film N1100," 15 μm thick). The adhesive layer was formed by dry lamination using an adhesive mixture of DiC Dry LX-500 (DIC Graphics, product name) as the base agent, KW75 (DIC Graphics, product name) as the curing agent, and NC401 (Toyo Ink, product name) as the solvent.

[0140] (Recycled material 2) Recycled material 2 was obtained by compressing, cutting, and shaping into granules a film consisting of an LLDPE film (manufactured by Mitsui Chemicals Tohcello, product name "TUX FC-S," film thickness 100 μm), an adhesive layer, an HDPE film (manufactured by Tamapoly, product name "HF31," film thickness 35 μm), an adhesive layer, and an HDPE film (manufactured by Tamapoly, product name "HF31," film thickness 35 μm) laminated in that order. The adhesive layer was formed in the same manner as for recycled material 1.

[0141] <Preparation of sealant film> Example 1 The recycled material 1 was placed in the hopper extruding the recycled material-containing layer, and LLDPE (Prime Polymer, product name "Evolue SP1540") with 6000 ppm of antiblocking agent (Prime Polymer, product name "EAZ-20") added by dry blending was placed in the hopper extruding the sealant layer. A 30 μm-thick recycled material-containing layer and a 70 μm-thick sealant layer were coextruded using a single-screw multi-layer extruder to produce a sealant film. The screw rotation speed during extrusion of the recycled material-containing layer was 16 rpm, and narrowing of the flow path before the T-die was minimized to minimize elongational stress. The molten resin was cooled using an air knife and a cooling roll with a matte, uneven surface (surface roughness Rz: 6 μm) sandblasted.

[0142] The surface of the sealant film obtained above opposite to the sealant layer side was irradiated with electron beams under the following conditions using an electron beam irradiation device (line irradiation type low energy electron beam irradiation device EES-L-DP01, manufactured by Hamamatsu Photonics K.K.). (Irradiation conditions) Voltage: 120kV Irradiation dose: 100kGy Oxygen concentration inside the device: 100 ppm or less Line speed: 25m / min

[0143] Example 2 A sealant film was produced in the same manner as in Example 1, except that the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 43 rpm) to form a recycled material-containing layer with a thickness of 80 μm and a sealant layer with a thickness of 20 μm, and the sealant film was irradiated with electron beams.

[0144] Example 3 A sealant film was produced in the same manner as in Example 1, except that the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 48 rpm) to form a recycled material-containing layer having a thickness of 90 μm and a sealant layer having a thickness of 10 μm, and the sealant film was irradiated with electron beams.

[0145] Example 4 A sealant film was produced in the same manner as in Example 1, except that the molten resin was cooled under a pressure of 1.4 MPa using a nip roll (material: fluororesin) and a cooling roll with a matte texture (surface roughness Rz: 6 μm) created by sandblasting, and the extrusion amount of each layer was adjusted to form a recycled material-containing layer with a thickness of 90 μm and a sealant layer with a thickness of 10 μm, and the sealant film was irradiated with electron beams.

[0146] Example 5 A sealant film was produced in the same manner as in Example 1, except that recycled material 2 was placed in a hopper for extruding the recycled material-containing layer, and the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 43 rpm) to form a recycled material-containing layer with a thickness of 80 μm and a sealant layer with a thickness of 20 μm, and then irradiated with electron beams.

[0147] Example 6 A sealant film was produced in the same manner as in Example 5, except that the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 48 rpm) to form a recycled material-containing layer having a thickness of 90 μm and a sealant layer having a thickness of 10 μm, and the film was irradiated with electron beams under the same conditions as in Example 1.

[0148] Example 7 A sealant film was produced in the same manner as in Example 5, except that the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 51 rpm) to form a recycled material-containing layer with a thickness of 95 μm and a sealant layer with a thickness of 5 μm, and the sealant film was irradiated with electron beams under the same conditions as in Example 1.

[0149] Example 8 A sealant film was produced in the same manner as in Example 5, except that the molten resin was cooled under a pressure of 1.4 MPa using a nip roll (material: fluororesin) and a cooling roll with a matte texture (surface roughness Rz: 6 μm) created by sandblasting, and the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 48 rpm) to produce a recycled material-containing layer with a thickness of 90 μm and a sealant layer with a thickness of 10 μm.The sealant film was then irradiated with electron beams under the same conditions as in Example 1.

[0150] Example 9 A sealant film was produced in the same manner as in Example 2, except that recycled material 1 and LLDPE (manufactured by Prime Polymer Co., Ltd., product name "Evolue SP2040") were added to the hopper that extrudes the recycled material-containing layer in a weight ratio of 1:1, and the sealant film was irradiated with electron beams under the same conditions as in Example 1.

[0151] Example 10 A sealant film was produced in the same manner as in Example 2, except that block PP (manufactured by Japan Polypropylene Corporation, product name "Novatec PP BC6DRF") to which 6000 ppm of antiblocking agent (manufactured by Prime Polymer, product name "EAZ-20") was added by dry blending was placed into the hopper for extruding the sealant layer, and the sealant film was irradiated with electron beams under the same conditions as in Example 1.

[0152] Example 11 Only recycled material 1 was placed into the hopper extruding the recycled material-containing layer, LLDPE (Prime Polymer, product name "Evolue SP1540") to which 6000 ppm of antiblocking agent (Prime Polymer, product name "EAZ-20") had been added by dry blending was placed into the hopper extruding the sealant layer, and LLDPE (Prime Polymer, product name "Evolue SP1540") was placed into the hopper extruding the auxiliary layer. A 20 μm thick auxiliary layer, an 80 μm thick recycled material-containing layer, and a 20 μm thick sealant layer were formed in that order by co-extrusion molding using a single-screw multi-layer extruder to produce a sealant film. The screw rotation speed when extruding the recycled material-containing layer was 43 rpm, and the narrowing of the flow path before the T-die was avoided as much as possible, creating a mechanism that was less susceptible to elongational stress.The molten resin was cooled using an air knife and a cooling roll with a matte, uneven surface (surface roughness Rz: 6 μm) created by sandblasting to produce a sealant film.

[0153] The sealant film obtained above was irradiated with electron beams in the same manner as in Example 1.

[0154] (Reference example 1) A commercially available PE sealant film (manufactured by Tamapoly Co., Ltd., product name "MZ434") was prepared.

[0155] (Comparative Example 1) A sealant film was prepared in the same manner as in Example 1, except that no antiblocking agent was added to the sealant layer, and then irradiated with electron beams.

[0156] (Comparative Example 2) A sealant film was produced in the same manner as in Example 1, except that the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 51 rpm) to form a recycled material-containing layer having a thickness of 95 μm and a sealant layer having a thickness of 5 μm, and the sealant film was irradiated with electron beams.

[0157] (Comparative Example 3) A sealant film was produced in the same manner as in Example 1, except that recycled material 2 was placed in a hopper for extruding the recycled material-containing layer, no antiblocking agent was added to the sealant layer, and the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 43 rpm) to form a recycled material-containing layer with a thickness of 80 μm and a sealant layer with a thickness of 20 μm, and then the sealant film was irradiated with electron beams.

[0158] Comparative Example 4 A sealant film was produced in the same manner as in Example 1, except that recycled material 2 was placed in a hopper for extruding the recycled material-containing layer, and the extrusion rate of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 52 rpm) to form a recycled material-containing layer having a thickness of 98 μm and a sealant layer having a thickness of 2 μm, and then the sealant film was irradiated with electron beams.

[0159] (Comparative Example 5) A sealant film was prepared in the same manner as in Example 1, except that the amount of antiblocking agent added was changed to 600 ppm, and then irradiated with electron beams.

[0160] <Surface roughness of sealant layer> The arithmetic surface roughness Ra of the surface of the sealant layer opposite to the recycled material-containing layer side was measured in accordance with JIS B 0601:2001 standard.

[0161] <Reliability evaluation of sealant> Using a Tester Sangyo heat sealer (model TP-701-B), the sealant film heat seal layers were overlapped and sealed with a sealing pressure of 0.2 MPa, a sealing time of 1 second, and a sealing width of 10 mm. The heat sealing temperature was set to a temperature approximately 20°C above the melting point of the heat seal layer material (130°C for LLDPE, 180°C for PP). The heat seal area was then observed under a microscope and the seal was measured at 1 mm. 2 The area percentage of bubbles present in the observation area was calculated. When the area percentage of bubbles was between 0% and less than 5%, it was marked "◎", when it was between 5% and less than 10%, it was marked "〇", when it was between 10% and less than 20%, it was marked "△", and when it was 20% or more, it was marked "×".

[0162] <Convex part of laminate layer> Using a Keyence laser microscope (VK-X200 / VK-X210), the maximum height H of the convex portion on the surface of the laminate layer opposite the recycled material-containing layer (the difference in height between the highest peak and the deepest valley in a given section) and the width W at half the maximum height H of the convex portion were measured, and the ratio [W / H] to the maximum height H was calculated.

[0163] <Film-forming property evaluation> The appearance of the film was visually observed from film formation to winding, and the film formability was evaluated according to the following criteria. "Good": No folds or wrinkles were observed in the film from the film formation to the winding, and no defects in appearance due to folds or wrinkles were observed in the film after winding. "X": Folds and wrinkles occur during the process from film formation to winding, and poor appearance due to the folds and wrinkles is observed in the film after winding.

[0164] (Puncture strength) A test piece measuring 50 mm x 50 mm was cut from the sealant film. Using a Tenshiro AD-7703 (product name, manufactured by A&D Co., Ltd.) and a dedicated semicircular needle with a diameter of 1.0 mm and a tip radius of 0.5 mm, the maximum force (N) until the needle penetrated was measured under the conditions of a test speed of 50 mm / min, a load cell of 100 N, and a load range of 10 N (10%), and this was evaluated as the puncture strength. A test piece that showed a strength 1 to 1.5 times that of a commercially available sealant film (Reference Example 1) was evaluated as "Good," and a test piece that was inferior to the commercially available sealant film was evaluated as "Poor."

[0165] [Table 1]

[0166] [Table 2]

[0167] As shown in Tables 1 and 2, it was confirmed that the sealant films of Examples 1 to 11 contained recycled materials and yet had sufficient reliability during heat sealing, puncture strength, and film-forming properties. Therefore, according to the present invention, material recycling of recycled materials containing two or more resins can be realized in sealant films and packaging materials. [Explanation of symbols]

[0168] 1a, 1b... sealant film, 2... recycled material-containing layer, 3... sealant layer, 4... auxiliary layer, 5... adhesive layer, 6... base film, 7... printed layer, 10a... laminate, 12... gas barrier layer, 50... aggregate, 100, 102... packaging material.

Claims

1. A sealant film comprising: a recycled material-containing layer containing a recycled material containing two or more types of resin; and a sealant layer laminated on one main surface of the recycled material-containing layer, The sealant film is subjected to electron beam irradiation treatment, A sealant film, wherein the arithmetic surface roughness of the surface of the sealant layer opposite to the recycled material-containing layer side is 0.5 μm or more and 5 μm or less.

2. The sealant film according to claim 1, wherein the thickness of the sealant layer is 5 μm or more and 70 μm or less.

3. 2. The sealant film according to claim 1, wherein the maximum height H of the convex portions on the surface of the sealant layer is 0.5 μm or more and 10 μm or less, and the ratio [W / H] of the width W at half the maximum height H to the maximum height H of the convex portions having the maximum height H is 20 or less.

4. The sealant film according to claim 1, wherein the resin having the largest content ratio among the two or more types of resin contained in the recycled material is a polyethylene-based resin or a polypropylene-based resin.

5. The sealant film according to claim 1 , further comprising an auxiliary layer laminated on the other main surface of the recycled material-containing layer.

6. The sealant film according to claim 5 , wherein the auxiliary layer contains the same type of virgin resin as the resin having the highest content in the recycled material-containing layer.

7. A packaging material comprising the sealant film according to any one of claims 1 to 6.

8. 8. The packaging material according to claim 7, wherein the content of plastic material contained in the recycled material is 10% by mass or more based on the total amount of plastic material in the packaging material.

9. A packaging bag made from the packaging material according to claim 7.

10. A packaging bag made from the packaging material according to claim 8.

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