Sealant film, packaging material and packaging bag

Abstract

To provide a sealant film, a packaging material and a packaging bag which have sufficient reliability and film production property during heat sealing, while containing a recycled material containing two or more kinds of resins.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 arithmetic surface roughness of a surface S3a on a side opposite to the side of the recycled material-containing layer 2 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 Art

[0002] Generally, plastic films have properties such as being lightweight, chemically stable, easy to process, flexible and strong, and capable of mass production, and are used in various applications. Examples of its uses include packaging materials for packaging food products, pharmaceuticals, etc., drip packs, shopping bags, posters, tapes, optical films used in liquid crystal televisions, etc., protective films, window films adhered to windows, greenhouses, building materials, and so on. Specific materials include, for example, thermoplastic resins such as polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, and thermosetting resins such as epoxy resins, polyurethanes, and polyimides.

[0003] An appropriate plastic material is selected according to the application, and furthermore, a plurality of them are stacked to form a laminate. There is also a way of using by mixing a plurality of plastic materials in one layer to compensate for the disadvantages of a single material.

[0004] In recent efforts regarding environmental problems, the recycling of plastic products is expected, and various recycling methods are being studied. For example, for PET bottles, material recycling in which the collected products are washed and pulverized and reused as raw materials, and chemical recycling in which they are monomerized, have been established.

[0005] Also, as material recycling of polyethylene, using recycled polyethylene for applications such as films has been studied. For example, Patent Document 1 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] [Problems to be Solved by the Invention]

[0007] Some recycled materials contain resins of different types. Therefore, when the inventors studied recycling such recycled materials as raw materials for sealant films, it became clear that in a sealant film provided with a layer containing a recycled material, the reliability during heat sealing may decrease.

[0008] On the other hand, film products such as sealant films are required to have the property (hereinafter also referred to as "film formability") that they can be formed without breakage or wrinkle generation from film formation to winding. If the film formability of the film is insufficient, appearance defects due to breakage or wrinkles are likely to occur in the wound film.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a sealant film, a packaging material, and a packaging bag that contain a recycled material containing two or more types of resins and have sufficient reliability during heat sealing and film formability. [Means for Solving the Problems]

[0010] In order to solve the above problems, the inventors of the present invention studied the factors that reduce the reliability during heat sealing. As a result, when different types of resins are mixed in the layer containing recycled materials, aggregates are formed by resin components other than the resin with the largest content ratio, and when excessive protrusions are generated on the surface of the sealant film due to these aggregates, it was found that air biting occurs during heat sealing. Then, based on such findings, the inventors of the present invention further studied and found that a sealant film prepared such that the surface roughness of the sealant layer satisfies specific conditions can solve the above problems, and thus the present invention was completed.

[0011] One aspect of the present invention relates to the following [1] to [9].

[0012] [1] A sealant film comprising a recycled material-containing layer containing a recycled material containing two or more resins, and a sealant layer laminated on one main surface of the recycled material-containing layer, wherein the arithmetic surface roughness of the surface of the sealant layer on the side 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 protrusions on the surface of the sealant layer is 0.5 μm or more and 10 μm or less, and for the protrusions having the maximum height H, the ratio [W / H] of the width W at half of the maximum height H to the maximum height H is 20 or less. [4] The sealant film according to any one of [1] to [3], wherein the resin having the largest 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 a virgin resin of the same type as the resin having the largest content ratio 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 according to [7], wherein the content of the plastic material contained in the recycled material is 10% by mass or more based on the total amount of the plastic material in the packaging material. [9] A packaging bag formed from the packaging material according to [7] or [8]. [Advantages of the Invention]

[0013] According to the present invention, it is possible to provide a sealant film, a packaging material, and a packaging bag that contain a recycled material containing two or more resins and have sufficient reliability during heat sealing and film-forming properties. [Brief Description of the Drawings]

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0015] Hereinafter, embodiments of the present invention will be described in detail. Note that FIGS. 1 to 6 are schematic diagrams, and the sizes, shapes, etc. of each part are exaggerated as appropriate for easy understanding. Further, the embodiments shown below illustrate the configurations for embodying the technical idea of the present invention, and the technical idea of the present invention is not limited to the following in terms of the material, shape, structure, etc. of the constituent parts. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0016] <Sealing film> The sealing film of this embodiment includes a recycled material-containing layer containing a recycled material containing two or more kinds of resins, and a sealing layer laminated on one main surface of the recycled material-containing layer.

[0017] FIG. 1 is a schematic cross-sectional view showing an embodiment of the sealing film. The sealing film 1a shown in FIG. 1 includes a recycled material-containing layer 2 and a sealing layer 3 laminated on one main surface of the recycled material-containing layer 2.

[0018] (Recycled material-containing layer) Examples of the recycled material contained in the recycled material-containing layer include those called post-consumer recycle (PCR), such as market-recovered bottles and packaging bags for beverages, detergents, and seasonings, food containers for bento and cup noodles, packaging bags for food and garbage bags, plastic finished products such as hangers, stationery, daily necessities, household appliances, and toys, and those called post-industrial recycle (PIR), such as defective products that do not become products discharged from factories, end materials generated during the process of making products, and plastic products used for transportation and packaging.

[0019] When the recycled material is a material recycled material, the material recycled material may be washed and pulverized as necessary. The material recycled material has the advantage of requiring less energy during recycling compared to a resin obtained by chemical recycling such as pyrolysis. Therefore, the greater the proportion of the material recycled material in the recycled material-containing layer, the smaller the environmental load can be.

[0020] In the sealant film of the present embodiment, from the viewpoint of material recycling of the plastic film, a laminate (packaging material) obtained by laminating a plurality of types of resin sheets, a packaging bag formed by bag-making the laminate, a laminate (packaging material) obtained by laminating resin sheets of the same type, or a packaging bag formed by bag-making the laminate, and the like may be used, and those obtained by mixing these may also be used. Examples of the packaging bag include a refill pouch for toiletries.

[0021] The recycled material contained in the recycled material-containing layer contains two or more types of resins. Examples of the two or more types of resins include thermoplastic resins, thermosetting resins, and cured products (including crosslinked products) thereof. Note that the two or more types of resins also include, for example, resin components constituting an adhesive (such as a thermosetting resin) and cured products thereof.

[0022] Examples of the thermoplastic resin include polyolefin resins, acrylic resins, polycarbonate resins, polyester resins, polyamide resins, and the like. Examples of the thermosetting resin include epoxy resins, polyurethane resins, polyimide resins, and the like.

[0023] Examples of the polyolefin resin 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, and polypropylene-based resins such as homopolypropylene (PP), block polypropylene, random polypropylene, and propylene-α-olefin copolymers.

[0024] Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polylactic acid, and the like.

[0025] Examples of the polyamide resin include nylon 6 and the like.

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

[0027] The first resin and the second resin may be the following combinations. (a) A thermoplastic resin and a thermosetting resin and its cured product (b) A hydrocarbon-based resin and a heteroatom-containing resin (c) A resin soluble in a predetermined solvent and a resin insoluble in the predetermined solvent

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

[0029] Examples of the predetermined solvent in (c) include aromatic hydrocarbons, chlorinated hydrocarbons, and the like. Examples of the resin soluble in the predetermined solvent include uncrosslinked resins and the like. Examples of the resin insoluble in the predetermined solvent include crosslinked resins, cured thermosetting resins, and the like.

[0030] As the first resin having the largest content ratio in the recycled material, it may be a polyethylene-based resin or a polypropylene-based resin from the viewpoint of recycling packaging bags such as pouch products. In this case, the second resin may be, for example, at least one of a polyester resin, a polyamide resin, and a resin component constituting an adhesive and a cured product thereof.

[0031] The content of the first resin in the recycled material-containing layer may be 75 to 98% by mass, 75 to 95% by mass, or 80 to 90% by 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 with respect to 100 parts by mass of the first resin.

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

[0034] The resin having the largest content ratio in the recycled material-containing layer and the resin having the largest content ratio in the recycled material may be the same. Such a resin may be, for example, at least one polyethylene-based 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 materials such as virgin resin. The virgin materials may be blended so that the resin having the largest content ratio in the recycled material is the same as the resin having the largest content ratio in the recycled material-containing layer. As the virgin material, for example, the same materials as the above-described polyolefin resin can be used, and at least one polyethylene-based 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) may be used.

[0036] The recycled material-containing layer may contain aggregates derived from, for example, the above-described second resin. From the viewpoint of ensuring reliability during heat sealing, the maximum diameter of the aggregates may be 20 μm or less. When the maximum diameter of the aggregates is 20 μm or less, it becomes easier to suppress the generation of protrusions with a height exceeding 10 μm or protrusions with a height of 0.5 μm to 10 μm and a ratio of width to height at half of the height exceeding 20 on the surface of the sealant layer.

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

[0038] The aggregates and their maximum diameter can be confirmed by the following method. The aggregates contained in the recycled material-containing layer can be confirmed as domains having a lower transmission brightness than the surroundings (hereinafter, also referred to as "low transmission brightness regions") when observed through transmission in the direction of plan view of the sealant film, and the maximum diameter of the low transmission brightness regions can be obtained by the following procedure. (i) Using a stereomicroscope system SZX16 (manufactured by Olympus Corporation, product name), randomly obtain 10 observation images (image size: 243 μm × 851 μm) in the plane direction of the sealant film. (ii) Analyze the obtained 10 images using WinROOF2021 (manufactured by Mitani Shoko Co., Ltd., product name). In the image analysis, the maximum diameter in each low light transmittance region is calculated by binarizing the low light transmittance region and the high light transmittance region around it. When binarizing, the visual shape and coloring range of the low light transmittance region can be matched by appropriately combining the following operations. (a) Emphasize the low light transmittance region by adjusting brightness and contrast (b) Adjust the threshold value to match the visible low light transmittance region and the coloring range (c) When there are places where adjacent low light transmittance regions are recognized as one region or where perforated low light transmittance regions are recognized as multiple regions, perform splitting or merging processing as necessary.

[0039] To reduce the maximum diameter of the aggregates in the recycled material-containing layer, for example, the following adjustment means can be mentioned. (i) Reduce the content ratio of the recycled material in the recycled material-containing layer (ii) Increase the content ratio of the first resin in the recycled material (iii) When extruding the recycled material-containing layer, increase the screw rotation speed (iv) When extruding the recycled material-containing layer, avoid narrowing the flow path as much as possible and use a mechanism where elongation stress is less likely to be applied. (v) Use the recycled material by repelletizing or mixing it with virgin resin using a twin-screw extruder to make a masterbatch.

[0040] The thickness of the recycled material-containing layer may be 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 defined in JIS B 0601:2001 is 0.5 μm or more and 5 μm or less. When Ra is 5 μm or less, when heat-sealing with the sealant film overlapped, it is possible to suppress a decrease in reliability due to air entrapment (for example, a decrease in low-temperature heat-sealing property). Also, defects such as the thickness of the concave portion becoming locally thin and the impact resistance and puncture resistance decreasing are less likely to occur. On the other hand, when Ra is 0.5 μm or more, the coefficient of friction does not become too large, and it is possible to have appropriate slipperiness, and wrinkles are less likely to occur during film formation of the film.

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

[0043] As a method for adjusting the Ra, in addition to the method of adjusting the maximum diameter of the aggregates described above, changing the thickness of the sealant layer, adding an antiblocking agent to the sealant layer, and imparting predetermined unevenness to the surface of the sealant layer (for example, pressing a nip roll when cooling and solidifying the molten resin during film formation) and the like can be mentioned.

[0044] From the viewpoint of ensuring reliability during heat-sealing, the convex portion (P shown in FIG. 2) on the above surface (S shown in FIG. 2) of the sealant layer 3a ) may have a height (H shown in FIG. 2) of 10 μm or less, may be 0.5 to 9 μm, or may be 0.5 to 8 μm. Also, from the same viewpoint, the width (W shown in FIG. 2) at half of the height of the convex portion may be 200 μm or less, may be 1 to 150 μm, or may be 1 to 100 μm. Note that FIG. 2 is a schematic cross-sectional view for explaining the shape of the convex portion in the sealant film shown in FIG. 1. As shown in FIG. 2, the convex portion P 3a ) 3a 3a ) 3amay also occur when the surface S of the sealant layer 3 is raised by the aggregate 50 generated in the recycled material-containing layer. 3a This may be caused by the raising of the surface S of the sealant layer 3 by the aggregate 50 generated in the recycled material-containing layer.

[0045] The convex portion on the surface of the sealant layer has 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 of the maximum height H to the maximum height H of the convex portion having the maximum height H may be 20 or less, the H may be 0.5 to 9 μm, and the ratio [W / H] may be 1 to 18. In this case, it is advantageous in terms of (i) improving the content rate of the recycled material in the recycled material-containing layer, (ii) improving the content rate of the recycled material in the sealant film by thinning the sealant layer, (iii) improving productivity by reducing the pressure applied during cooling or hot pressing during film formation, etc.

[0046] As the material for forming the sealant layer, a material having appropriate flexibility such as a thermoplastic resin and having good processability such as processability by an extruder can be used. Examples of such materials include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and polypropylene having a homopolymer, random copolymer, or block copolymer, ethylene-vinyl acetate copolymer obtained by copolymerizing an olefin such as low-density polyethylene (LDPE) and vinyl acetate, ethylene-methyl acrylate copolymer (EMA) obtained by modifying the side chain of an olefin, ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), and ethylene-methacrylic acid copolymer (EMAA). These may be used alone or in combination of two or more.

[0047] From the viewpoint of heat sealability, the sealant layer can contain the same resin as the resin having the largest content ratio in the recycled material-containing layer. For example, when the resin having the largest content ratio in the recycled material-containing layer is a polyethylene-based resin, the sealant layer may contain a polyethylene-based resin, and the polyethylene-based resin may be the main component (for example, the content ratio in the sealant layer is 95% by mass or more). Further, when the resin having the largest content ratio in the recycled material-containing layer is a polypropylene-based resin, the sealant layer may contain a polypropylene-based resin, and the polypropylene-based resin may be the main component (for example, the content ratio in the sealant layer is 95% by mass or more).

[0048] From the viewpoint of reducing the maximum height H and the ratio [W / H] described above, the sealant layer may contain a polypropylene-based resin.

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

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

[0051] From the viewpoints of heat sealability and rigidity, the crystallinity based on the heat of fusion using a differential scanning calorimeter (DSC) of the polypropylene-based resin may be 25% or more and 60% or less, or may be 30% or more and 55% or less.

[0052] In this specification, the crystallinity of the polypropylene-based resin is determined 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 perfect crystal with a crystallinity of 100% obtained from theoretical calculations, and the crystallinity of the sample is determined as follows in the following formula. Crystallinity [%] = (ΔHm / ΔH100) × 100 Note that as the heat of fusion ΔH100 of the perfect crystal, the value described in the following reference can be adopted. For example, the ΔH100 of polypropylene can be 207 J / g.) Reference: The Japan Society of Plastic and Rubber Processing: Plastic Materials in Forming Processing, 335 (2011), Morikita Publishing Co., Ltd.

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

[0054] The thickness of the sealant layer may be 5 μm or more and 70 μm or less. In this case, it becomes easy to prevent the aggregates contained in the recycled material-containing layer from being exposed from the sealant layer, and it also becomes easy to ensure the rigidity of the entire sealant film and increase the content ratio of the recycled material in the sealant film. As a result, in the sealant film, material recycling of the recycled material containing two or more kinds of resins can be realized more effectively. 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, 20 μm or more and 60 μm or less.

[0055] In the recycled material-containing layer and the sealant layer, compatibilizers, nucleating agents, reinforcing fillers, antioxidants, heat stabilizers, weathering agents, light stabilizers, plasticizers, ultraviolet absorbers, antistatic agents, flame retardants, flame retardant aids, slip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, dispersants, copper corrosion inhibitors, neutralizing agents, anti-foaming agents, weld strength improvers, natural oils, synthetic oils, waxes and other additives may be blended as necessary. The additives may be used singly or in combination of two or more.

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

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

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

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

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

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

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

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

[0064] In the sealant film of this 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 to 16, may be 0.5 to 14, or may be 0.7 to 12.

[0065] The sealant film of this embodiment may have a multilayer structure in which another layer is laminated to complement desired physical properties. FIG. 3 is a schematic cross-sectional view showing another embodiment of the sealant film. The sealant film 1b shown in FIG. 3 includes 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. Also in this case, the surface S on the side opposite to the recycled material-containing layer 2 side of the sealant layer 3 3b can satisfy the above-described conditions for the arithmetic surface roughness Ra defined in JIS B 0601:2001.

[0066] 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 has a density similar to that of the resin constituting the sealant layer 3 (for example, the density difference is 0.1 kg / m 3It may be configured to include a resin having the following).

[0067] Further, when the auxiliary layer 4 is given the function of a laminate layer, it may have the same configuration as the above-described sealant layer 3. Further, the auxiliary layer 4 can contain a resin of the same type as the resin having the largest content ratio in the recycled material-containing layer 2. In this case, it becomes easy to improve the adhesion to another layer by higher laminate strength.

[0068] One or more of the above-described additives may be blended into the auxiliary layer 4 as needed.

[0069] Furthermore, when the auxiliary layer 4 is given the function of a laminate layer, the arithmetic surface roughness Ra defined in JIS B 0601:2001 of the surface on the side opposite to the recycled material-containing layer 2 side of the auxiliary layer 4 may be 0.03 μm or more and 5 μm or less, may be 0.04 μm or more and 3 μm or less, or may be 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 suppress laminate defects due to the occurrence of defective portions where the adhesive does not adhere.

[0070] The Ra in the auxiliary layer 4 can be adjusted by changing the thickness of the auxiliary layer. In this case, the thickness of the auxiliary layer may be 5 μm or more and 100 μm or less, may be 10 μm or more and 90 μm or less, or may be 20 μm or more and 80 μm or less from the viewpoints of suppressing laminate defects and suppressing costs.

[0071] <Method for manufacturing a sealant film> The sealant film of the present embodiment can be manufactured by a conventionally known method. For example, a method of extrusion laminating a recycled material-containing film formed by forming 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.

[0072] In the former method, after melting the resin composition constituting the recycled material-containing layer with an injection molding machine or an extrusion molding machine (e.g., a twin-screw extruder), the film can be formed with a T-die through a feed block or a multi-manifold, or can be formed by an inflation method. As the recycled material, those obtained by collecting, washing, pulverizing various plastic waste materials, and then melt-molding them with an extruder and pelletizing them can be used. For extrusion lamination, an extrusion laminator or the like can be used.

[0073] In the latter method, for example, by using a multi-layer extrusion molding machine, the resin composition constituting the recycled material-containing layer and the resin composition constituting the sealant layer are each melt-kneaded and co-extruded to produce a sealant film.

[0074] The resin composition constituting the recycled material-containing layer may contain only the recycled material, or virgin resin and additives may be further blended to impart various desired performances such as viscosity adjustment and mechanical property reinforcement. Also, when mixing the recycled material and the virgin resin, it may be a dry blend in which the virgin resin and the recycled material are simultaneously charged into a hopper and melt-kneaded while forming a film, or it may be a melt blend in which the virgin material and the recycled material are separately melt-kneaded with a twin-screw extruder and made into a masterbatch.

[0075] From the viewpoint of reducing the aggregates in the recycled material-containing layer, repelletizing using a twin-screw extruder, molding under high shear conditions, or blending an acid-modified polyolefin resin or the like as a compatibilizer may be used.

[0076] Regarding the film cooling method, it can be used according to the molding machine. For example, in the T-die method, an air-cooling method such as an air chamber, a vacuum chamber, or an air knife, or a water-cooling method such as dipping a cooling roll into a cold water pan can be used.

[0077] Also, for example, in the case of the T-die method, in order to adjust the above Ra in the sealant layer, when cooling and solidifying the molten resin using a cooling roll having a predetermined surface shape, a predetermined surface shape can be imparted to the sealant layer by pressing with a nip roll. As a means for imparting a surface shape by shaping, a method may be adopted in which a nip roll processed from silicone rubber, NBR rubber, fluororesin, etc. and a cooling roll are brought into contact with each other under a pressure of 0.1 MPa or more, and the molten resin flows into the contact portion and is cooled. As the cooling roll, one obtained by cutting a metal or one having a shape imparted by a blasting treatment can be used. The surface shape of the cooling roll may be a random uneven shape, and the surface roughness can be adjusted by changing the particle size and treatment time (amount) during the blasting treatment. Incidentally, the above Ra in the auxiliary layer can also be adjusted in the same manner as described above.

[0078] In addition, the sealant film of this embodiment can also be produced by a method using hot pressing. In the method using hot pressing, a flat film can be formed by compressing it between heating rolls or with a heated flat plate. The thickness of the molded product can be controlled by adjusting the compression pressure at this time. A single-layer film produced by hot pressing may be stacked and hot pressed again for lamination, or a pre-laminated flat film may be prepared and the film thickness may be adjusted by hot pressing. Also, as an adjustment of the surface roughness, when imparting a predetermined surface shape to the film, a predetermined surface shape may be provided on the surface of the roll or flat plate for transfer. 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 the blasting treatment.

[0079] The sealant film may be subjected to a surface modification treatment to improve its suitability for subsequent processes. For example, a surface modification treatment can be performed on the surface to be laminated to improve printability and lamination suitability when laminating with other layers or a base film. Examples of the surface modification treatment include methods that generate functional groups by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, and modification by wet processes such as coating with an easy-adhesion layer.

[0080] Note that the manufacturing method of the sealant film is not limited to the method described above, and an in-line or off-line stretching treatment may be performed on the sealant film formed by a film-forming machine. In addition, adding necessary processes and additives as appropriate is not restricted.

[0081] <Laminate> The laminate of the present embodiment includes the sealant film of the present embodiment described above. FIG. 4 is a schematic cross-sectional view showing one embodiment of the laminate of the present embodiment. In the laminate 10a shown in FIG. 4, a gas barrier layer 12 is further provided on the side opposite to the recycle material-containing layer 2 of the auxiliary layer 4 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, etc.). The gas barrier layer may have a single-layer structure or a laminated structure.

[0082] Examples of the gas barrier layer 12 include a vapor deposition layer (vapor deposition film) made of a metal or an inorganic oxide, a metal foil such as aluminum foil, and films such as ethylene-vinyl alcohol copolymer, polyamide-based resin, polyvinylidene chloride-based resin, and polyacrylonitrile-based resin.

[0083] The vapor deposition layer may have a single-layer structure or a laminated structure. Examples of the vapor deposition layer include vapor deposition layers composed of metals such as aluminum and inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide.

[0084] The vapor deposition layer can be formed using a conventionally known method. The forming method can be appropriately selected according to the vapor deposition material and the like, such as physical vapor deposition methods (Physical Vapor Deposition method, PVD method) such as vacuum vapor deposition method, sputtering method, and ion plating method, and chemical vapor deposition methods (Chemical Vapor Deposition method, CVD method) such as plasma chemical vapor deposition method, thermal chemical vapor deposition method, and photo chemical vapor deposition method.

[0085] When the vapor deposition layer is an aluminum vapor deposition film, its OD value may be 2 or more and 3.5 or less from the viewpoints of productivity, oxygen barrier property, and water vapor barrier property of the laminate. In this specification, the OD value means a value measured in accordance with JIS-K-7361.

[0086] When the vapor deposition 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. Also, the O / Si ratio may be 2.0 or less from the viewpoint of barrier property. From the viewpoint of obtaining the above effects more sufficiently, the O / Si ratio of the inorganic oxide layer may be 1.5 or more and 2.0 or less, or may be 1.6 or more and 1.8 or less.

[0087] The O / Si ratio of the above inorganic oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measuring device is an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., trade name: JPS-90MXV), the X-ray source uses non-monochromatized MgKα (1253.6 eV), and it can be measured with an X-ray output of 100 W (10 kV - 10 mA). For quantitative analysis to obtain the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used.

[0088] The thickness of the vapor deposition 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 deposition layer is 1 nm or more, oxygen barrier properties and water vapor barrier properties are likely to be obtained. When the thickness of the vapor deposition layer is 150 nm or less, it is easy to prevent cracks from occurring in the vapor deposition layer and easy to maintain the recyclability of the sealant film.

[0089] The auxiliary layer 4 provided with the gas barrier layer may have the same configuration as the above-described sealant layer 3. When the auxiliary layer 4 contains a polyolefin resin, the polyolefin resin preferably has higher crystallinity from the viewpoints of printability, vapor deposition suitability, strength, and heat resistance. The polyolefin resin may be a virgin resin.

[0090] When the above polyolefin resin is polyethylene, high-density polyethylene (HDPE) and medium-density polyethylene (MDPE) are preferable from the viewpoints of printability, strength, and heat resistance, and medium-density polyethylene is more preferable from the viewpoint of stretching suitability. When the above polyolefin resin is polypropylene, the crystallinity based on the heat of fusion using a differential scanning calorimeter (DSC) may be 40% or more, may be 45% or more from the viewpoints of printability, strength, and heat resistance, and may be 60% or less, may be 55% or less from the viewpoint of impact resistance.

[0091] The content ratio of the non-material recyclable resin (such as virgin resin) in the auxiliary layer 4 provided with the gas barrier layer can be made higher than the content ratio of the non-material recyclable resin in the recyclable material-containing layer. In this case, it is possible to smooth the partial swelling derived from aggregates on the surface of the recyclable material-containing layer and improve the mechanical properties and gas barrier properties of the laminate.

[0092] From the viewpoints of gas barrier properties and adhesion, the thickness of the auxiliary layer 4 provided with the gas barrier layer may be 20 μm or more, may be 40 μm or more, may be 80 μm or more, and from the viewpoint of suppressing the total thickness when used as a packaging material, it may be 150 μm or less, may be 120 μm or less, or may be 100 μm or less.

[0093] <Packaging material> The packaging material of the present embodiment includes the sealant film of the present embodiment described above. FIG. 5 is a schematic cross-sectional view showing an embodiment of the packaging material. The packaging material 100 shown in FIG. 5 includes a sealant film 1b provided with an auxiliary layer 4 and a base material film 6 laminated on the auxiliary layer 4 via an adhesive layer 5.

[0094] The base material film 6 is not particularly limited as long as it has mechanical strength and dimensional stability, and a plastic film, paper, non-woven fabric, etc. can be used. Examples of the constituent material of the plastic film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, polyamides such as polystyrene and 6-nylon, polycarbonate, polyacrylonitrile, polyimide, and the like.

[0095] From the viewpoints of mechanical strength and dimensional stability, the base material film 6 is preferably a stretched film.

[0096] The base material film 6 can be made into a single material as a whole packaging material by containing the same type of resin (also referred to as "the same resin") as the resin having the largest content ratio in the sealant film, and the recyclability of the packaging material is improved. In this case, all layers constituting the sealant film (for example, the sealant layer, or the sealant layer and the auxiliary layer) may contain the same type of resin as the resin having the largest content ratio in the recycle material-containing layer.

[0097] 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 referred to as 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, and may be 95% by mass or more based on the total amount of the packaging material.

[0098] From the perspective of transparency, the haze value of the base film 6 may be 30% or less, and may be 20% or less. In this specification, the haze value of the film means a value measured in accordance with JIS K 7105.

[0099] The base film 6 may be surface-treated. In this case, the adhesion to an adjacent layer can be improved. 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, glow discharge treatment, and chemical treatments such as oxidation treatment using chemical agents.

[0100] An anchor coat layer may be provided on the surface of the base film 6 using a conventionally known anchor coat agent.

[0101] The thickness of the base film 6 may be 10 μm or more and 50 μm or less, and may be 12 μm or more and 30 μm or less. When the thickness of the base film is 10 μm or more, it becomes easy to improve the strength of the laminate. Also, when the thickness of the base material is 50 μm or less, it becomes easy to maintain the processability of the laminate.

[0102] The adhesive layer 5 is a layer that adheres 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 adhered via the adhesive layer 5.

[0103] The adhesive constituting the adhesive layer is not particularly limited, but an adhesive for dry lamination can be used. Examples of the adhesive for dry lamination include two-component curable urethane adhesives, polyester urethane adhesives, polyether urethane adhesives, acrylic adhesives, polyester adhesives, polyamide adhesives, epoxy adhesives, and the like.

[0104] When the packaging material is used for a retort pouch, a two-component curable urethane adhesive with retort resistance can be used.

[0105] From the perspective of environmental consideration, the adhesive layer 5 may satisfy at least one of the following conditions. (1) It does not contain 3-glycidyloxypropyltrimethoxysilane (GPTMS). (2) It contains biomass materials. (3) It does not contain solvents.

[0106] From the perspective of suppressing coloring of recycled resin and the generation of odor due to heat treatment after recycling, the adhesive layer 5 may not contain chlorine.

[0107] The thickness of the adhesive layer may be 0.3 μm or more and 5.0 μm or less. From the perspective of adhesive force manifestation, 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 perspective of recyclability, it 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 below the above upper limit value, the ratio of the single material in the packaging material can be increased.

[0108] The packaging material of the present embodiment may further include functional layers such as a printing layer and a gas barrier layer. These functional layers may be provided on the above-mentioned base film.

[0109] The printing layer may be formed on the surface of the base film on the side where the sealant film is provided. In this case, it is possible to prevent the printing layer from coming into contact with the outside air and prevent deterioration over time.

[0110] The printing layer may represent characters, patterns, symbols, combinations thereof, and the like.

[0111] From the viewpoint of producing a packaging material with less environmental impact, the printing layer may be formed using biomass-derived ink.

[0112] The method for forming the printing layer is not particularly limited, and conventionally known printing methods such as the gravure printing method, the offset printing method, and the flexographic printing method can be used. Among these, from the viewpoint of environmental impact, the flexographic printing method may be used.

[0113] The gas barrier layer can be provided on the base film and may have the same configuration as the above-described gas barrier layer 12.

[0114] Alternatively, a gas barrier layer may be provided by laminating a laminated film of a metal foil and a plastic film, or a vapor deposition film provided with a vapor deposition layer (vapor deposition film) made of the above-described metal or inorganic oxide on a plastic film. Examples of the plastic film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, polyamides such as polystyrene and 6-nylon, polycarbonate, polyacrylonitrile, and polyimide.

[0115] FIG. 6 is a schematic cross-sectional view showing another embodiment of the 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 recycle 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 printing layer 7 adhered via an adhesive layer 5 on the gas barrier layer 12 side of the laminate. In the packaging material 102, as described above, the printing layer 7 is formed on the surface of the base film 6 on the side where the sealant film is provided.

[0116] Each layer of the packaging material of this embodiment may contain the above-described additives.

[0117] In addition to the above-described configuration, the packaging material of this embodiment can be variously modified and may have the following configurations. (a) Sealant film / adhesive layer / gas barrier film / adhesive layer / substrate film of this embodiment (b) Sealant film / adhesive layer / gas barrier film of this embodiment (c) Sealant film / gas barrier layer (e.g., vapor deposition layer) / adhesive layer / substrate film of this embodiment As the above gas barrier film, the above-described substrate film provided with a gas barrier layer, a laminated film of a metal foil and a plastic film, and a vapor deposition film may be used, and a metal foil such as an aluminum foil, and a film such as an ethylene-vinyl alcohol copolymer, a polyamide-based resin, a polyvinylidene chloride-based resin, or a polyacrylonitrile-based resin may also be used.

[0118] The packaging material may include a sealant film having an auxiliary layer, a first substrate film laminated on the auxiliary layer via an adhesive layer, and a second substrate film having a printing layer laminated on the first substrate film via an adhesive layer. Further, the packaging material may include a sealant film having an auxiliary layer and a first substrate film laminated on the auxiliary layer via an adhesive layer, or may include a sealant film having an auxiliary layer, a first substrate film laminated on the auxiliary layer via an adhesive layer, and a gas barrier layer provided on the first substrate film, or may include a sealant film having an auxiliary layer, a first substrate film laminated on the auxiliary layer via an adhesive layer, and two or more functional layers such as a gas barrier layer and a printing layer provided on the first substrate film.

[0119] From the perspective of material recycling, the content of the plastic material contained in the recycled material may be 10% by mass or more, or 25% by mass or more, based on the total amount of the plastic material in the packaging material. When the packaging material of this embodiment is a laminated packaging material, materials other than plastic (for example, adhesives, printing inks, aluminum foils, etc.) may be excluded from the weight calculation.

[0120] Examples of the plastic material (so-called recycled plastic) contained in the recycled material include the resin contained in the recycled material layer according to the above-described embodiment of the present invention. Among the recycled plastics, the pre-consumer material may be calculated by multiplying the weight by 1 / 2.

[0121] The packaging material of this embodiment can be used for standing pouches, three-side bags, gusseted bags, spouted pouches, pouches with beaks, etc.

[0122] <Packaging bag> The packaging bag of this embodiment is formed from the packaging material of the above-described embodiment. The bag-making style of the packaging bag is not particularly limited, and the packaging bag may be a standing pouch, a three-side bag, a gusseted bag, a spouted pouch, a pouch with a beak, or the like.

Examples

[0123] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

[0124] <Preparation of recycled material> (Recycled material 1) An LLDPE film (manufactured by Mitsui Chemicals Toagosei Co., Ltd., product name "TUX FC-S", film thickness 100 μm), an adhesive layer, a PET film (manufactured by Toray Film Processing Co., Ltd., product name "VM-PET 1310", film thickness 12 μm, aluminum vapor deposition), an adhesive layer, and a Ny film (manufactured by Toyobo Co., Ltd., product name "Harden Film N1100", film thickness 15 μm) are laminated in this order, and the film is compressed, cut, and molded into granules to obtain the recycled material 1. The adhesive layer is formed by dry lamination using an adhesive obtained by mixing Dick Dry LX-500 (product name, manufactured by DIC Graphics) as the main agent, KW75 (product name, manufactured by DIC Graphics) as the curing agent, and NC401 (product name, manufactured by Toyo Ink) as the solvent.

[0125] (Recycled material 2) An LLDPE film (manufactured by Mitsui Chemicals Toagosei Co., Ltd., product name "TUX FC-S", film thickness 100 μm), an adhesive layer, an HDPE film (manufactured by Tamapoli Co., Ltd., product name "HF31", film thickness 35 μm), an adhesive layer, and an HDPE film (manufactured by Tamapoli Co., Ltd., product name "HF31", film thickness 35 μm) are laminated in this order, and the film is compressed, cut, and molded into granules to obtain the recycled material 2. The adhesive layer is formed in the same manner as the recycled material 1.

[0126] <Production of the sealant film> (Example 1) Recycled material 1 was fed into the hopper for extruding the recycled material-containing layer, and LLDPE (manufactured by Prime Polymer Co., Ltd., product name "Evolue SP1540") with 6000 ppm of an antiblocking agent (manufactured by Prime Polymer Co., Ltd., product name "EAZ-20") added by dry blending was fed into the hopper for extruding the sealant layer. Using a single-screw multi-layer extruder, a recycled material-containing layer with a thickness of 30 μm and a sealant layer with a thickness of 70 μm were formed into a film by co-extrusion molding to produce a sealant film. When extruding the recycled material-containing layer, the screw rotation speed was set to 16 rpm, and narrowing of the flow path in front of the T-die was avoided as much as possible to form a mechanism where elongation stress is less likely to be applied. The molten resin was cooled by an air knife and a cooling roll provided with a matte uneven shape (surface roughness Rz: 6 μm) by sandblasting.

[0127] (Example 2) A sealant film was produced in the same manner as in Example 1, except that the extrusion amount 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.

[0128] (Example 3) A sealant film was produced in the same manner as in Example 1, except that the extrusion amount 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 with a thickness of 90 μm and a sealant layer with a thickness of 10 μm.

[0129] (Example 4) The molten resin was cooled under the condition of a pressure of 1.4 MPa using a nip roll (material: fluororesin) and a cooling roll provided with a matte uneven shape (surface roughness Rz: 6 μm) by sandblasting. A sealant film was produced in the same manner as in Example 1, except that 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.

[0130] (Example 5) Recycled material 2 was put into the hopper for extruding the recycled material-containing layer, and the extrusion amount of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 43 rpm). A sealant film was produced in the same manner as in Example 1 except that a recycled material-containing layer with a thickness of 80 μm and a sealant layer with a thickness of 20 μm were formed by film formation.

[0131] (Example 6) The extrusion amount of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 48 rpm). A sealant film was produced in the same manner as in Example 5 except that a recycled material-containing layer with a thickness of 90 μm and a sealant layer with a thickness of 10 μm were formed by film formation.

[0132] (Example 7) The extrusion amount of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 51 rpm). A sealant film was produced in the same manner as in Example 5 except that a recycled material-containing layer with a thickness of 95 μm and a sealant layer with a thickness of 5 μm were formed by film formation.

[0133] (Example 8) The molten resin was cooled under the condition of a pressure of 1.4 MPa using a nip roll (material: fluororesin) and a cooling roll provided with a matte uneven shape (surface roughness Rz: 6 μm) by sandblasting. The extrusion amount of each layer was adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 48 rpm). A sealant film was produced in the same manner as in Example 5 except that a recycled material-containing layer with a thickness of 90 μm and a sealant layer with a thickness of 10 μm were formed by film formation.

[0134] (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 put into the hopper for extruding the recycled material-containing layer so that the weight ratio was 1:1.

[0135] (Example 10) A sealant film was produced in the same manner as in Example 2, except that a block polypropylene resin (bPP) (manufactured by Nippon Polypropylene Co., Ltd., product name "Novatec PP BC6DRF") with 6,000 ppm of an anti-blocking agent (manufactured by Prime Polymer Co., Ltd., product name "EAZ-20") added by dry blending was charged into the hopper for extruding the sealant layer.

[0136] (Example 11) Only the recycled material 1 was charged into the hopper for extruding the recycled material-containing layer, an LLDPE (manufactured by Prime Polymer Co., Ltd., product name "Evalue SP1540") with 6,000 ppm of an anti-blocking agent (manufactured by Prime Polymer Co., Ltd., product name "EAZ-20") added by dry blending was charged into the hopper for extruding the sealant layer, and an LLDPE (manufactured by Prime Polymer Co., Ltd., product name "Evalue SP1540") was charged into the hopper for extruding the auxiliary layer. Using a single-screw multi-layer extruder, a co-extrusion molding was performed to form a 20-μm-thick auxiliary layer, an 80-μm-thick recycled material-containing layer, and a 20-μm-thick sealant layer in this order to produce a sealant film. When extruding the recycled material-containing layer, the screw rotation speed was set to 43 rpm, and the narrowing of the flow path before the T-die was avoided as much as possible to form a mechanism where elongation stress is less likely to be applied. The molten resin was cooled with an air knife and a cooling roll provided with a matte uneven shape (surface roughness Rz: 6 μm) by sandblasting to produce a sealant film.

[0137] (Comparative Example 1) A sealant film was produced in the same manner as in Example 1, except that an anti-blocking agent was not added to the sealant layer.

[0138] (Comparative Example 2) A sealant film was produced in the same manner as in Example 1, except that the extrusion amounts of each layer were adjusted (the screw rotation speed when extruding the recycled material-containing layer was changed to 51 rpm) to form a 95-μm-thick recycled material-containing layer and a 5-μm-thick sealant layer.

[0139] (Comparative Example 3) Recycling material 2 was put into the hopper for extruding the recycling material-containing layer, and an anti-blocking agent was not added to the sealant layer. The extrusion amount of each layer was adjusted (the screw rotation speed when extruding the recycling material-containing layer was changed to 43 rpm), and a recycling material-containing layer with a thickness of 80 μm and a sealant layer with a thickness of 20 μm were formed into a film. A sealant film was produced in the same manner as in Example 1 except for the above.

[0140] (Comparative Example 4) Recycling material 2 was put into the hopper for extruding the recycling material-containing layer, and the extrusion amount of each layer was adjusted (the screw rotation speed when extruding the recycling material-containing layer was changed to 52 rpm), and a recycling material-containing layer with a thickness of 98 μm and a sealant layer with a thickness of 2 μm were formed into a film. A sealant film was produced in the same manner as in Example 1 except for the above.

[0141] (Comparative Example 5) A sealant film was produced in the same manner as in Example 1 except that the addition amount of the anti-blocking agent was changed to 600 ppm.

[0142] <Surface roughness of the sealant layer> In accordance with JIS B 0601:2001 standard, the arithmetic surface roughness Ra of the surface of the sealant layer on the side opposite to the recycling material-containing layer side was measured.

[0143] <Reliability evaluation during sealing> Using a heat sealer (model number TP-701-B) manufactured by Tester Industry, the seal pressure was 0.2 MPa, the seal time was 1 second, the seal width was 10 mm, and the heat seal layers of the sealant film were overlapped and sealed. The heat seal temperature was set to a temperature exceeding the melting point of the material of the heat seal layer by about 20 °C (130 °C for LLDPE and 180 °C for PP). Then, the heat seal part was observed with a microscope, and 2 the area ratio of the bubbles present in the observation area of 1 mm was determined. When the area ratio of the bubbles was 0% or more and less than 5%, it was designated as "◎"; when it was 5% or more and less than 10%, it was designated as "〇"; when it was 10% or more and less than 20%, it was designated as "△"; and when it was 20% or more, it was designated as "×".

[0144] <Convex portion of the laminate layer> Using a laser microscope (VK-X200 / VK-X210) manufactured by Keyence Corporation, the maximum height H of the convex portion (the difference in height between the highest peak and the deepest valley in a predetermined section) on the surface of the laminate layer opposite to the surface containing the recycled material layer, and the width W at half of the maximum height H of the convex portion were measured, and the ratio [W / H] to the maximum height H was calculated.

[0145] <Film-forming property evaluation> From the film formation of the film to the winding, the appearance was visually observed, and the film-forming property was evaluated according to the following criteria. "〇": No folding or wrinkling was observed during the process from film formation to winding, and no appearance defects associated with folding or wrinkling were seen in the film after winding. "×": Folding or wrinkling occurred during the process from film formation to winding, and appearance defects associated with folding or wrinkling were seen in the film after winding.

[0146]

Table 1

[0147]

Table 2

[0148] As shown in Table 1 and Table 2, it was confirmed that the sealant films of Examples 1 to 11 sufficiently had the reliability during heat sealing and the film-forming property while containing the recycled material. Therefore, according to the present invention, it is possible to realize material recycling of a recycled material containing two or more kinds of resins in a sealant film or a packaging material.

Explanation of reference numerals

[0149] 1a, 1b... Sealant film, 2... Recycled material-containing layer, 3... Sealant layer, 4... Auxiliary layer, 5... Adhesive layer, 6... Base film, 7... Printing 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 resins, and a sealant layer laminated on one main surface of the recycled material-containing layer, A sealant film, wherein 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 claim 1 , wherein the sealant layer has a thickness of 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 sealant layer contains a resin of the same type as the resin having the highest content in the recycled material-containing layer.

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 a virgin resin of the same type 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 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.

Images