Recycle film, multilayer film, and packaging material

Abstract

A recycle film 1 is a film formed from a resin composition including a recycle material, wherein the resin composition includes resin components which are either resins included in the recycle material only or a combination of the resins included in the recycle material and a virgin material incorporated in an amount of 100 parts by mass or less per 100 parts by mass of the recycle material, and the recycle material comprises a polyethylene-based resin and a resin that is not a polyethylene-based resin. When examined through transmission from a plan-view direction, the recycle film contains domains having lower transparency lightness than the surroundings. The domains have a maximum area of 1,000 μm2 or less and a maximum aspect ratio of 10 or less. The recycle film has an elongation at rupture of 400% or higher.

Description

Recycled films, laminated films, and packaging materials

[0001] This invention relates to recycled film, laminated film, and packaging material.

[0002] Generally, plastic films are lightweight, chemically stable, easy to process, flexible, strong, and can be mass-produced, making them suitable for a wide range of applications. Their uses include packaging materials for food and pharmaceuticals, intravenous drip bags, shopping bags, posters, tapes, optical films used in LCD televisions, protective films, window films, greenhouses, building materials, and much more. Materials used for plastic films include thermoplastic resins such as polyethylene, polypropylene, polystyrene, acrylic polymethyl methacrylate, polycarbonate, polyamide, polyethylene terephthalate, and polybutylene terephthalate, as well as thermosetting resins such as epoxy resins, polyurethane, and polyimide.

[0003] Plastic films are made by selecting appropriate plastic materials according to their intended use, and sometimes multiple layers are stacked to form laminated films. Furthermore, in plastic films, the shortcomings of single materials are compensated for by mixing multiple plastic materials into a single layer. In addition, plastic films may contain aluminum to provide light-blocking properties, printing inks to enhance the product's design, and adhesives to bond incompatible plastic materials.

[0004] In response to recent environmental issues, the recycling of plastic products is expected to play a significant role, and various recycling methods are being considered. For example, in the field of PET bottles, material recycling, which involves washing and crushing collected products for reuse as raw materials, and chemical recycling, which involves monomerization, have been established technologies.

[0005] Globally, there is a growing trend towards policies that prohibit the use of resin products made solely from petroleum-derived resins, making the use of recycled materials essential. The use of recycled materials is also being considered in the field of film products such as packaging materials. For example, Patent Document 1 below proposes a sealant film in which an intermediate layer containing recycled polyethylene is placed between two virgin polyethylene layers made using virgin material that has never been processed.

[0006] International Publication No. 2022 / 124229

[0007] Material recycled materials from packaging often contain different types of resins. Patent Document 1 mentioned above does not provide a specific evaluation of the intermediate layer formed from material recycled materials from packaging. Therefore, when the present inventors investigated using material recycled materials from packaging as a raw material for plastic film, they found that the mechanical strength of the resulting plastic film may decrease.

[0008] This invention has been made in view of the above circumstances, and aims to provide a recycled film and a laminated film having sufficient mechanical strength, while being mainly composed of recycled material containing two or more types of resin.

[0009] The inventors investigated the factors that reduce the mechanical strength of recycled film and found that when different types of resins are mixed in recycled film, aggregates are formed by resin components other than the resin with the highest content ratio. These aggregates become the starting point for fracture in the recycled film, reducing its mechanical strength. The inventors then conducted further investigations and found that a recycled film in which the size and shape of the aggregates are within a predetermined range, and which also has a predetermined elongation at break, possesses sufficient mechanical strength (particularly impact resistance) even though the recycled material mainly consists of two or more types of resins. This led to the completion of the present invention.

[0010] The present invention relates to the following [1] to

[12] .

[0011] [1] A recycled film made by forming a film of a resin composition containing recycled material, wherein the resin component contained in the resin composition is only the resin contained in the recycled material, or the resin contained in the recycled material and a virgin material blended in an amount of 100 parts by mass or less per 100 parts by mass of the recycled material, wherein the recycled material includes a polyethylene resin and a resin other than a polyethylene resin, and includes a domain whose transmitted brightness is smaller than the surrounding area when the recycled film is observed from a direction of plan view, and the domain has a maximum area of ​​1000 μm ２A recycled film that is as follows, and has a maximum aspect ratio of 10 or less, and the elongation at break of the recycled film is 400% or more. [2] The recycled film according to [1], having a thickness of 20 μm or more and 200 μm or less. [3] The recycled film according to [1] or [2], having a breaking energy of 10 J / mm or more. [4] The recycled film according to any one of [1] to [3], wherein the recycled material is derived from post-consumer recycling or post-industry recycling. [5] The recycled film according to any one of [1] to [4], wherein the recycled material has been treated with an alkaline solution. [6] The recycled film according to any one of [1] to [5], wherein the polyethylene resin content in the recycled material is 80% by mass or more based on the total amount of the recycled material. [7] A laminated film comprising the recycled film according to any one of [1] to [6] and a functional layer provided on at least one main surface of the recycled film. [8] The laminated film according to [7], wherein the functional layer is a substrate laminated on one main surface of the recycled film via an adhesive layer, and the recycled film is a sealant layer. [9] The laminated film according to [7] or [8], wherein the content of plastic material contained in the recycled film is 10% by mass or more, based on the total amount of plastic material in the laminated film.

[10] A packaging material comprising the recycled film according to any one of [1] to [6].

[11] The packaging material according to

[10] , further comprising a substrate laminated on the recycled film via an adhesive layer, wherein the recycled film is a sealant layer.

[12] The packaging material according to

[10] or

[11] , wherein the content of plastic material contained in the recycled film is 10% by mass or more, based on the total amount of plastic material in the packaging material.

[0012] According to the present invention, it is possible to provide a recycled film that has sufficient mechanical strength while being mainly composed of recycled material containing two or more types of resins, and a laminated film equipped therewith.

[0013] This is a cross-sectional shape showing an example of a recycled film. This is a schematic diagram illustrating the aspect ratio of domains formed inside the recycled film. This is a cross-sectional shape showing an example of a laminated film. This is a cross-sectional shape showing another example of a laminated film. This is a cross-sectional shape showing yet another example of a laminated film. This is a planar observation image of the recycled film of Example 1.

[0014] The embodiments of the present invention will be described in detail below. Figures 1 to 5 are schematic diagrams, and the size and shape of each part have been exaggerated as appropriate to facilitate understanding. Furthermore, the embodiments described below illustrate configurations for realizing 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 described in the patent claims.

[0015] <Recycled Film> The recycled film of this embodiment is a recycled film made by forming a film of a resin composition containing recycled material, wherein the resin component contained in the resin composition is only the resin contained in the recycled material, or the resin contained in the recycled material and virgin material blended in an amount of 100 parts by mass or less per 100 parts by mass of the recycled material, and the recycled material includes polyethylene resin and resin other than polyethylene resin.

[0016] Figure 1 is a schematic cross-sectional view showing an example of a recycled film according to this embodiment. The recycled film 1 is formed by creating a film from a resin composition containing recycled material.

[0017] The recycled film of this embodiment includes a domain (hereinafter also referred to as the "low transmittance region") in which the transmittance brightness is lower than the surrounding area when the recycled film is observed from a planar view, and the domain has a maximum area of ​​1000 μm². ２The following conditions are met: the maximum aspect ratio is 10 or less, and the elongation at break is 400% or more. By satisfying the above conditions, the recycled film of this embodiment can have sufficient mechanical strength even though it is mainly composed of recycled material containing polyethylene resin and resins other than polyethylene resin.

[0018] The maximum area and maximum aspect ratio of the low-transmittance brightness region are calculated using the following procedure: (i) Using the SZX16 stereomicroscope system (manufactured by Olympus Corporation, product name), 10 random observation images (image size: 243 μm × 851 μm) of the recycled film in the planar direction are acquired. (ii) The 10 acquired images are analyzed using WinROOF2021 (manufactured by Mitani Corporation, product name). In the image analysis, the area, minimum diameter, and maximum diameter of each low-transmittance brightness region are calculated by binarizing the low-transmittance brightness region and the surrounding high-transmittance brightness region. When binarizing, the visual shape of the low-transmittance brightness region and the colored range can be matched by appropriately combining the following operations. (a) Brightness and contrast adjustments are used to emphasize low-transparency areas. (b) The threshold is adjusted to match the visible low-transparency areas with the colored areas. (c) If adjacent low-transparency areas are recognized as a single area, or if perforated low-transparency areas are recognized as multiple areas, splitting or merging processes are performed as needed.

[0019] Figure 2 is a schematic diagram illustrating the aspect ratio of domains formed in recycled film. Domain 4 is shown in Figure 2. The aspect ratio of domain 4 is the maximum diameter (long axis) D Ｌ and minimum diameter (short axis) D Ｓ Ratio D Ｌ / D Ｓ This means that the minimum aspect ratio is 1, and the shape of the low-transmittance brightness region is not limited to the elliptical shape shown in Figure 2.

[0020] In order to reduce the maximum area and the maximum aspect ratio of the low transmittance brightness region in the recycled film, for example, the following adjustment means can be mentioned. (a) Increase the content ratio of the first resin in the recycled material. (b) When extrusion molding the recycled film, increase the screw rotation speed. (c) When extrusion molding the recycled film, avoid narrowing the flow path as much as possible and adopt a mechanism in which elongation stress is not easily applied. (d) Use the recycled material by repelletizing or mixing it with virgin resin using a twin-screw extruder to make a masterbatch.

[0021] In order to increase the average value of the brightness in the recycled film, for example, methods such as reducing the maximum area of the low transmittance brightness region by the above-described adjustment means can be mentioned. Further, in order to reduce the standard deviation of the brightness in the recycled film, for example, methods such as selecting a resin to be mixed with the recycled material to increase the fluidity so that the domains forming the low transmittance brightness region are not localized can be mentioned.

[0022] From the viewpoint of mechanical strength, the maximum area of the domain may be 500 μm ２ or less, and may be 100 μm ２ or less.

[0023] From the viewpoint of compatibility with general production equipment and increasing the content ratio of the recycled material in the recycled film, the maximum area of the domain may be 50 μm ２ or more, and may be 400 μm ２ or more.

[0024] From the viewpoint of mechanical strength, the aspect ratio of the domain may be 6 or less, and may be 3 or less.

[0025] From the viewpoint of compatibility with general production equipment and increasing the content ratio of the recycled material in the recycled film, the aspect ratio of the domain may be 3 or more, and may be 6 or more.

[0026] The elongation at break of the recycled film can be calculated, for example, by a tensile test in accordance with JIS Z 1710 using a tensile tester (manufactured by Shimadzu Corporation, product name "AGS-X").

[0027] From the viewpoint of having sufficient mechanical strength, the recycled film of this embodiment may have a break elongation of 400% or more, or 500% or more.

[0028] The elongation at break of recycled film can be adjusted, for example, by the proportion of polyethylene resin in the recycled material.

[0029] From the viewpoint of mechanical strength and handling, the thickness of the recycled film may be 20 μm or more, 40 μm or more, or 50 μm or more.

[0030] From a handling standpoint, the thickness of the recycled film may be 200 μm or less, or 180 μm or less.

[0031] From the viewpoint of ensuring that the recycled film has sufficient mechanical strength, the breaking energy of the recycled film may be 10 J / mm or more, and may be 12 J / mm or more.

[0032] The breaking energy of recycled film can be calculated, for example, by using a film impact tester and conducting an impact resistance test in accordance with ASTM-D3420.

[0033] The polyethylene resin content in recycled film may be 50% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, based on the total amount of recycled film. From the viewpoint of making it easier to reduce the domain size, the polyethylene resin content in recycled film is preferably 80% by mass or more, and more preferably 90% by mass or more, based on the total amount of recycled film.

[0034] The polyethylene resin content in recycled film may be 99.9% by mass or less, or 99% by mass or less, based on the total amount of recycled film.

[0035] (Resin composition containing recycled materials) As raw materials for recycled materials, for example, post-consumer recyclables (PCR) such as market-recovered beverage, detergent, and seasoning bottles and packaging bags, food containers for bento boxes and cup noodles, packaging bags for food and garbage bags, plastic finished products such as hangers, stationery, daily necessities, household appliances, and toys, and post-industrial recyclables (PIR) such as defective products that do not become products discharged from factories, end materials generated during the process of making products, and plastic waste used for transportation and packaging can be used. Compared with PCR, PIR has less dirt adhesion, and the plastic materials are also uniform for collecting specific plastic products, so the quality of recycled materials is also stable. In addition, plastic waste used as raw materials for recycled materials is preferable from the aspect of stabilizing the quality of recycled materials and the formed recycled film with polyethylene as a sealant layer.

[0036] The recycled material may be mainly composed of a polyethylene-based resin. "Mainly composed of a polyethylene-based resin" means that the content of the polyethylene-based resin in the recycled material is 50% by mass or more based on the total amount of the recycled material. The content of the polyethylene-based resin in the recycled material may be 70% by mass or more, 80% by mass or more, or 90% by mass or more based on the total amount of the recycled material. From the viewpoint that the domain size is likely to become small, the content of the polyethylene-based resin in the recycled material is preferably 80% by mass or more, and more preferably 90% by mass or more based on the total amount of the recycled material.

[0037] Examples of the polyethylene-based 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.

[0038] Examples of resins other than polyethylene resins include thermoplastic resins other than polyethylene resins and their cured products, thermosetting resins and their cured products (including crosslinked products). Resins other than polyethylene resins also include, for example, resin components constituting adhesives (such as thermosetting resins) and their cured products.

[0039] Examples of thermoplastic resins other than polyethylene resins include polyolefin resins other than polyethylene resins, acrylic resins, polycarbonate resins, polyester resins, polyamide resins, etc. Examples of thermosetting resins include epoxy resins, polyurethane resins, polyimide resins, etc.

[0040] Examples of polyolefin resins other than polyethylene resins include polypropylene resins such as homopolypropylene (PP), block polypropylene, random polypropylene, and propylene-α olefin copolymers.

[0041] Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polylactic acid, etc.

[0042] Examples of polyamide resins include nylon 6, etc.

[0043] Resins other than polyethylene resins may be one of the resins other than polyethylene resins described above, or may be a mixture containing two or more resins.

[0044] The types of resins contained in recycled materials can be confirmed by differential scanning calorimetry (DSC), microscopic infrared spectrophotometer, etc.

[0045] When the resin component contained in the resin composition is a virgin material blended at 100 parts by mass or less with respect to 100 parts by mass of the resin contained in the recycled material, from the viewpoint of recyclability, the content of the virgin material in the resin component may be 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less with respect to 100 parts by mass of the recycled material.

[0046] Furthermore, the proportion of the resin contained in the recycled material within the resin components of the resin composition may be 48% by mass or more, based on the total amount of resin components, and may be 90% by mass or more, 95% by mass or more, or 99% by mass or more from the viewpoint of recyclability.

[0047] Resin compositions containing recycled materials may contain various additives as needed. Examples of additives include compatibilizers, nucleating agents, reinforcing fillers, antioxidants, heat stabilizers, weathering agents, light stabilizers, plasticizers, UV absorbers, antistatic agents, flame retardants, flame retardant enhancers, slip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, dispersants, copper damage inhibitors, neutralizing agents, anti-bubble agents, weld strength improvers, natural oils, synthetic oils, waxes, etc. These may be used individually or in combination of two or more.

[0048] The compatibilizer may be a reactive or non-reactive compatibilizer. Examples of compatibilizers include acid-modified polyolefin resins, ethylene-vinyl acetate copolymers, ethylene-methyl methacrylate copolymers, and ethylene-vinyl alcohol copolymers.

[0049] Examples of nucleating agents and reinforcing fillers include metals such as talc, silica, clay, montmorillonite, calcium carbonate, lithium alumina carbonate, titanium dioxide, 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).

[0050] Examples of antioxidants include phenolic compounds, organophosphite compounds, and thioether compounds.

[0051] Examples of heat stabilizers include hindered amine compounds.

[0052] Examples of UV absorbers include benzophenone compounds, benzotriazole compounds, and benzoate compounds.

[0053] Examples of antistatic agents include nonionic compounds, cationic compounds, and anionic compounds.

[0054] Examples of flame retardants include halogen compounds, phosphorus compounds, nitrogen compounds, inorganic compounds, boron compounds, silicone compounds, sulfur compounds, and red phosphorus compounds.

[0055] Examples of flame retardant additives include antimony compounds, zinc compounds, bismuth compounds, magnesium hydroxide, and clayey silicates.

[0056] Examples of antiblocking agents include acrylic particles, styrene particles, styrene-acrylic particles and their crosslinked products, polyurethane particles, polyester particles, silicon particles, fluorine particles, copolymers thereof, zeolites, pyrophyllites, talc, smectite, vermiculite, mica, chlorite, kaolin minerals, clay compound particles such as sepiolite, silica, titanium dioxide, alumina, silica-alumina, zirconia, zinc oxide, strontium oxide, aluminum hydroxide, strontium carbonate, strontium chloride, strontium sulfate, strontium nitrate, strontium hydroxide, and glass particles.

[0057] In recycled films formed from resin compositions containing recycled materials that include polyethylene-based resins and resins other than polyethylene-based resins, the resins other than polyethylene-based resins may form aggregates and create the domains described above. In this case, examples of materials constituting the aggregates include thermoplastic resins other than polyethylene-based resins and their cured products, and thermosetting resins and their cured products (including crosslinked products). Of these, thermosetting resins and their cured products do not melt with polyethylene-based resins and therefore tend to form aggregates.

[0058] The recycled film of this embodiment can be used as a base film or a sealant film. When the recycled film of this embodiment is used as a base film, it may be a base film for pouches.

[0059] <Method for manufacturing recycled film> The recycled film of this embodiment can be manufactured by a method comprising, for example, step A of preparing a resin composition containing recycled material, and step B of forming a film from the resin composition containing recycled material to obtain a recycled film.

[0060] (Process A) In Process A, a resin composition containing recycled material is prepared.

[0061] Recycled material can be obtained from the raw materials of the various recycled materials described above. It can be obtained by recovering, washing, and crushing the raw materials of the recycled material, or by melt-molding a mixture with other components in an extruder and forming it into pellets. In step A, a mixture obtained by mixing recycled material and virgin material may also be melt-molded into pellets in an extruder.

[0062] Recycled materials may be subjected to separation treatments to remove components other than polyethylene resin or to isolate polyethylene resin in order to increase the content of polyethylene resin, and may be subjected to at least one of the following treatments. Recycled materials subjected to these separation treatments may be highly transparent. (a) Chemical treatment (b) Filter treatment

[0063] In chemical treatment, the raw materials of the recycled material after washing (e.g., pulverized material) can be treated with chemicals to remove resins other than polyethylene resins, as well as adhesives and ink components. This reduces the amount of dispersion of components other than polyethylene resins that cause domains in the recycled film.

[0064] In chemical treatment, for example, the printed layer can be removed by treatment with an alkaline solution containing a surfactant, as described later. This reduces the amount of foreign matter that causes domains in the recycled film produced from the recycled material raw materials.

[0065] One example of chemical treatment is alkaline solution treatment, which involves impregnating the raw materials of recycled materials with an alkaline solution.

[0066] Basic compounds found in alkaline solutions include, for example, sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium hydroxide (Ca(OH)). ２ ), barium hydroxide (Ba(OH) ２ ), sodium carbonate (Na ２ CO ３ Examples include tetramethylammonium hydroxide, etc. The content of basic compounds in the alkaline solution may be 0.5% by mass or more, 1% by mass or more, or 2% by mass or more, and may be 20% by mass or less, 15% by mass or less, or 10% by mass or less, based on the total amount of the alkaline solution.

[0067] The alkaline solution may contain a surfactant. The surfactant primarily plays a role in improving the desorption properties of the printing layer and adhesive. This is because the surfactant makes it easier for the alkaline solution to penetrate the printing layer and adhesive, thereby promoting their desorption. In addition, the surfactant adsorbs onto the surface of the desorbed components (various desorbed layers) and the deinking substrate, which can suppress the re-adhesion of the desorbed components to the deinking substrate.

[0068] The temperature of the alkaline solution may be 30°C or higher, 40°C or higher, or 50°C or higher, and may be 100°C or lower, 90°C or lower, or 80°C or lower.

[0069] The raw materials for the recycled material may be 2% by mass or more, 3% by mass or more, or 5% by mass or more, and may be 50% by mass or less, 40% by mass or less, or 30% by mass or less, relative to the total amount of the alkaline solution.

[0070] The contact time (immersion time or stirring time) between the recycled material raw material and the alkaline aqueous solution may be 3 minutes or more, 10 minutes or more, or 15 minutes or more, and may be 5 hours or less, 4 hours or less, or 3 hours or less.

[0071] When stirring an alkaline solution, the stirring speed may be 20 rpm or more, 50 rpm or more, or 100 rpm or more, and may be 5000 rpm or less, 4000 rpm or less, or 3000 rpm or less.

[0072] In the filtering process, the fluid obtained by molten recycled material raw materials can be filtered using a predetermined filter. This reduces the amount of foreign matter that causes domains in the recycled film produced from the recycled material raw materials, and suppresses the generation of large domains.

[0073] The pore size of the filter used in the filtering process may be 4 μm or larger, 20 μm or larger, or 80 μm or larger, and may be 450 μm or smaller, 260 μm or smaller, or 180 μm or smaller.

[0074] In the filtering process, the filtration rate of the fluid containing the molten raw materials of the recycled material may be 180 mL / min or more, 360 mL / min or more, 540 mL / min or more, or 900 mL / min or more, and may be 3600 mL / min or less, 2700 mL / min or less, 1800 mL / min or less, or 1400 mL / min or less.

[0075] In the filtering process, the melting temperature of the recycled material may be 170°C or higher, 200°C or higher, or 230°C or higher, and may be 300°C or lower, 280°C or lower, or 250°C or lower.

[0076] Furthermore, when using a resin composition containing recycled material that has undergone the separation process described above, the recycled material that has not been pelletized (for example, crushed waste material) may be directly fed into the film-forming machine. By omitting the step of pelletizing the recycled material containing polyethylene resin, or a mixture of recycled material containing polyethylene resin and other components, thermal degradation of the material can be suppressed.

[0077] (Step B) In Step B, a conventionally known film-forming method can be employed. For example, a resin component containing recycled material can be melted in an injection molding machine or an extrusion molding machine (e.g., a twin-screw extruder), and then a film can be formed using a T-die via a feed block or multi-manifold, or by an inflation method.

[0078] A resin composition containing recycled material may contain only recycled material, or it may further contain virgin material or the aforementioned additives to impart various desired properties such as viscosity adjustment and mechanical property enhancement. Furthermore, when mixing recycled material and virgin material, it may be a dry blend in which the virgin material and recycled material are simultaneously put into a hopper and melt-kneaded to form a film, or it may be a melt blend in which the virgin material and recycled material are melt-kneaded separately in a twin-screw extruder to form a masterbatch.

[0079] From the viewpoint of reducing aggregates in recycled film, methods such as repelletizing using a twin-screw extruder, molding under high shear conditions, or incorporating acid-modified polyethylene resin as a compatibilizer may be used.

[0080] Regarding the cooling method for the film, it is possible to use methods similar to those used for the molding machine described above. For example, in the T-die method, air cooling methods such as air chambers, vacuum chambers, and air knives, or water cooling methods such as dipping the cooling roll into a chilled water pan can be used. Furthermore, when imparting surface irregularities through shaping, a method may be used in which molten resin is introduced into a contact area between a nip roll made of silicone rubber, NBR rubber, or fluororesin and a cooling roll made of machined metal, under a pressure of 0.1 MPa or higher, and then cooled.

[0081] In the manufacturing method of this embodiment, the recycled film may be subjected to surface modification treatment for the purpose of improving post-process suitability such as printability and lamination suitability. As surface modification treatments, methods that cause functional groups to appear by oxidizing the film surface, such as corona discharge treatment, plasma treatment, and flame treatment, or wet process modification treatments such as coating of an easy-adhesion layer can be used.

[0082] Furthermore, in the manufacturing method of this embodiment, the recycled film formed by the molding machine can be subjected to in-line or off-line stretching, and other necessary processes can be performed as appropriate.

[0083] <Laminated Film> The laminated film of this embodiment comprises the recycled film of this embodiment. In the laminated film of this embodiment, a functional layer may be provided on one side of the recycled film.

[0084] For example, when a laminated film is used as a food packaging material, a film with gas barrier properties is required, so the functional layer may be a gas barrier layer with gas barrier properties.

[0085] Examples of gas barrier layers include vapor-deposited layers (vapor-deposited films) made of metal or inorganic oxides, metal foils such as aluminum foil, and films made of ethylene-vinyl alcohol copolymer, polyamide resin, polyvinylidene chloride resin, polyacrylonitrile resin, etc.

[0086] The vapor-deposited layer may be a single-layer structure or a multi-layer structure. Examples of vapor-deposited layers include those composed of metals such as aluminum, as well as inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide.

[0087] The vapor-deposited layer can be formed using conventionally known methods. The formation method can be appropriately selected according to the vapor deposition material, for example, from physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition.

[0088] When the vapor-deposited layer is an aluminum vapor-deposited film, its OD value may be between 2 and 3.5 from the viewpoint of the productivity of the laminate, oxygen barrier properties, and water vapor barrier properties. In this specification, the OD value refers to the value measured in accordance with JIS-K-7361.

[0089] When the vapor-deposited layer is an inorganic oxide layer using silicon dioxide, the O / Si ratio of the inorganic oxide layer may be 1.5 or higher from the viewpoint of transparency. Also, the O / Si ratio may be 2.0 or lower from the viewpoint of barrier properties. From the viewpoint of obtaining the above effects more fully, the O / Si ratio of the inorganic oxide layer may be 1.5 or more and 2.0 or lower, or 1.6 or more and 1.8 or lower.

[0090] The O / Si ratio of the inorganic oxide layer described above can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measurement can be performed using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., product name: JPS-90MXV), with a non-monochromatic MgKα (1253.6 eV) X-ray source and 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.

[0091] The thickness of the vapor-deposited layer may be 1 nm to 150 nm, 5 nm to 60 nm, or 5 nm to 40 nm. A vapor-deposited layer thickness of 1 nm or more makes it easier to obtain oxygen barrier properties and water vapor barrier properties. A vapor-deposited layer thickness of 150 nm or less makes it easier to prevent crack formation in the vapor-deposited layer and to maintain the recyclability of the recycled film.

[0092] Furthermore, the functional layer may also be the base material. The base material is not particularly limited as long as it has mechanical strength and dimensional stability, but examples include plastic films, paper, and nonwoven fabrics. Examples of constituent materials for plastic films include polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, polystyrene, polyamides such as 6-nylon, polycarbonate, polyacrylonitrile, and polyimide. From the viewpoint of easy recycling, polyolefins such as polyethylene and polypropylene are preferred.

[0093] Figure 3 is a schematic cross-sectional view showing an example of a laminated film according to this embodiment. The laminated film 10a shown in Figure 3 comprises a recycled film 1 and a functional layer 2a laminated on one main surface of the recycled film 1.

[0094] Figure 4 is a schematic cross-sectional view showing another example of the laminated film of this embodiment. The laminated film 10b shown in Figure 4 comprises a recycled film 1 and a functional layer 2b laminated on one main surface of the recycled film 1 via an adhesive layer 3a.

[0095] Figure 5 is a schematic cross-sectional view showing yet another example of the laminated film of this embodiment. The laminated film 10c shown in Figure 5 comprises a recycled film 1, a functional layer 2b laminated on one main surface of the recycled film 1 via an adhesive layer 3a, and a functional layer 2c laminated on the main surface of the functional layer 2b opposite to the adhesive layer 3a via an adhesive layer 3b.

[0096] The adhesives constituting the adhesive layers 3a and 3b are not particularly limited, but dry laminating adhesives can be used. Examples of dry laminating adhesives include two-component curing urethane adhesives, polyester urethane adhesives, polyether urethane adhesives, acrylic adhesives, polyester adhesives, polyamide adhesives, epoxy adhesives, and the like.

[0097] The laminated film of this embodiment may have one of the following laminated structures: (1) Substrate / adhesive layer / sealant layer (2) Substrate / adhesive layer / barrier layer (e.g., gas barrier layer) / barrier substrate / adhesive layer / sealant layer (3) Substrate / adhesive layer / barrier substrate / barrier layer (e.g., gas barrier layer) / adhesive layer / sealant layer In each of the above laminated structures, at least one of the substrate, barrier substrate, and sealant layer may be the recycled film of this embodiment.

[0098] For example, the laminated film of this embodiment comprises the recycled film of this embodiment and a substrate laminated on one main surface of the recycled film via an adhesive layer, wherein the recycled film may be a sealant layer.

[0099] The laminated films shown in Figures 3 to 5, and laminated films having the above structure, can be used as packaging materials.

[0100] From the viewpoint of material recycling, the packaging material (or laminated film) of this embodiment may contain 10% by mass or more, 13% by mass or more, or 25% by mass or more of the total mass of plastic material in the packaging material (or laminated film) of this embodiment. Furthermore, the packaging material (or laminated film) of this embodiment may contain 10% by mass or more, 13% by mass or more, or 25% by mass or more of recycled film in terms of the mass of plastic material, based on the total amount of plastic material in the packaging material (or laminated film) of this embodiment. If the packaging material of this embodiment is a laminated packaging material, materials other than plastic (for example, adhesives, printing inks, aluminum foil, etc.) may be excluded from the mass calculation.

[0101] From the viewpoint of material recycling, the packaging material (or laminated film) of this embodiment may contain recycled material in an amount of 10% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 50% by mass or more, or 80% by mass or more, based on the total mass of the packaging material (or laminated film of this embodiment).

[0102] The packaging material of this embodiment can be used for standing pouches, three-sided pouches, gusseted pouches, spout pouches, resealable pouches, ribbed pouches, pillow packaging, and the like.

[0103] For example, the packaging material of this embodiment further comprises a substrate laminated to the recycled film of this embodiment via an adhesive layer, and the recycled film may be a sealant layer.

[0104] <Packaging Bags> The packaging bags of this embodiment are made from the packaging materials of this embodiment described above. The method of making the packaging bags is not particularly limited, but the packaging bags may be standing pouches, three-sided pouches, gusseted pouches, spout pouches, zipper pouches, peak pouches, pillow packaging, etc.

[0105] Although embodiments of the present invention have been illustrated above, it goes without saying that the present invention is not limited to the above embodiments. Furthermore, it is optional to use a combination of the above embodiments.

[0106] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0107] <Preparation of raw material film> (Raw material film 1) Raw material 1 was a multilayer film in which the following were laminated in this order: LLDPE film (manufactured by Sumika Sekisui Film Co., Ltd., product name "CLS-62C", thickness 150 μm), adhesive layer (thickness 2 μm), PET film (manufactured by Toray Film Processing Co., Ltd., product name "VM-PET 1310", thickness 12 μm, aluminum vapor deposition), adhesive layer (thickness 2 μm), and Ny film (manufactured by Toyobo, product name "Harden Film N1100", thickness 15 μm). The above adhesive layer was formed by dry lamination using an adhesive with DIC Dry LX-500 (manufactured by DIC Graphics, product name) as the main agent, KW75 (manufactured by DIC Graphics, product name) as the hardener, and NC401 (manufactured by Toyo Ink, product name) as the solvent.

[0108] (Raw material film 2) Raw material 2 was a film in which the following layers were laminated in this order: LLDPE film (manufactured by Sumika Sekisui Film Co., Ltd., product name "CLS-62C", thickness 100 μm), adhesive layer (thickness 2 μm), PET film (manufactured by Toray Film Processing Co., Ltd., product name "VM-PET 1310", thickness 12 μm, aluminum vapor deposition), adhesive layer (thickness 2 μm), and Ny film (manufactured by Toyobo, product name "Harden Film N1100", thickness 15 μm). The adhesive layer was formed in the same manner as raw material 1.

[0109] (Raw material film 3) Raw material 3 was a film in which LLDPE film (manufactured by Mitsui Chemicals Tohcello Co., Ltd., product name "TUX FC-S", thickness 100 μm), adhesive layer (thickness 2 μm), HDPE film (manufactured by Tamapoly Co., Ltd., product name "HF31", thickness 35 μm), adhesive layer (thickness 2 μm), and HDPE film (manufactured by Tamapoly Co., Ltd., product name "HF31", thickness 35 μm) were laminated in this order. The adhesive layer was formed in the same manner as raw material 1.

[0110] <Preparation of Recycled Material> (Recycled Material 1) Raw material film 1 was crushed and processed into 5 mm square film pieces. An alkaline solution was used to melt the adhesive layer and PET film from raw material 1, and LLDPE film and Ny film were extracted. The LLDPE film was then separated by specific gravity, and molded using a twin-screw extruder to produce recycled material 1.

[0111] (Recycled material 2) Recycled material 2 was produced in the same manner as recycled material 1, except that a single-screw extruder was used.

[0112] (Recycled material 3) Raw material film 1 was crushed and processed into 5 mm square films, which were then molded using a twin-screw extruder to produce recycled material 3.

[0113] (Recycled material 4) Recycled material 4 was produced in the same manner as recycled material 3, except that a single-screw extruder was used.

[0114] (Recycled material 5) Recycled material 5 was prepared in the same manner as recycled material 3, except that raw material film 2 was used.

[0115] (Recycled material 6) The raw material film 3 was crushed and processed into 5 mm square film pieces. The film pieces were fed into a single-screw extruder and melted and mixed at 170°C to obtain recycled material 6.

[0116] (Mixed material A) Raw material film 1 was crushed and processed into 5 mm square film pieces. An alkaline solution was used to melt the adhesive layer and PET film from raw material 1, and after extracting LLDPE film and Ny film, the LLDPE film was separated by specific gravity. The extracted LLDPE film and virgin material 1 (manufactured by Prime Polymer Co., Ltd., product name "Evolu SP2020") were put into a hopper in a weight ratio of 1:1, and mixed material A was produced by molding using a twin-screw extruder.

[0117] (Mixed material B) Mixed material B, which includes recycled material, was prepared in the same manner as mixed material A, except that a single-screw extruder was used.

[0118] (Calculation of the content ratio of polyethylene resin (PE resin) by DSC measurement) Using a differential scanning calorimetry system, the heat of fusion of PE resin and other thermoplastic resins, which are raw materials constituting the recycled materials, was measured individually, as well as the heat of fusion of PE resin and other thermoplastic resins in recycled materials 1 to 6 and mixed materials A and B. From these values, the content ratio of PE resin was calculated.

[0119] DSC measurements were performed under the following conditions: temperature range: 0°C to 300°C, heating rate: 10°C / min. The heat of fusion between 50°C and 140°C was defined as the heat of fusion for PE resin, between 200°C and 230°C as the heat of fusion for nylon (Ny) resin, and between 230°C and 280°C as the heat of fusion for polyethylene terephthalate (PET) resin.

[0120] The percentage of PE resin in recycled or virgin film was calculated using the following formula 1: Percentage of PE resin in recycled or virgin film (%) = (x / X) × 100 / [(x / X) + (y / Y) + (z / Z)] ... (Formula 1) [In Formula 1, x, y, and z represent the heat of fusion [mJ / mg] of PE resin, Ny resin, and PET resin obtained by DSC measurement of recycled or virgin film, respectively, and X, Y, and Z represent the heat of fusion [mJ / mg] of virgin PE resin, virgin Ny resin, and virgin PET resin constituting the recycled or mixed material, respectively.]

[0121] Tables 1 and 2 show the percentage of PE resin content in each recycled material and mixed materials A and B.

[0122]

[0123]

[0124] <Preparation of Recycled Film> (Example 1) Recycled material 1 was fed into a hopper for extruding recycled film, and a recycled film with a thickness of 200 μm was produced using a single-screw extruder. The mechanism was designed to avoid narrowing of the flow path in front of the T-die as much as possible.

[0125] (Example 2) A recycled film was prepared in the same manner as in Example 1, except that the thickness of the recycled film was adjusted to 50 μm.

[0126] (Example 3) A recycled film was prepared in the same manner as in Example 1, except that the thickness of the recycled film was adjusted to 20 μm.

[0127] (Example 4) Recycled material 3 was fed into a hopper for extruding recycled film, and a recycled film with a thickness of 200 μm was produced using a single-screw extruder. The mechanism was designed to minimize narrowing of the flow path before the T-die.

[0128] (Example 5) A recycled film was prepared in the same manner as in Example 4, except that the thickness of the recycled film was adjusted to 50 μm.

[0129] (Example 6) Recycled material 6 was fed into a hopper for extruding recycled film, and a recycled film with a thickness of 200 μm was produced using a single-screw extruder. The mechanism was designed to avoid narrowing of the flow path in front of the T-die as much as possible.

[0130] (Example 7) A recycled film was prepared in the same manner as in Example 6, except that the thickness of the recycled film was adjusted to 50 μm.

[0131] (Example 8) A recycled film was prepared in the same manner as in Example 1, except that mixed material A was used.

[0132] (Example 9) A recycled film was prepared in the same manner as in Example 8, except that the thickness of the recycled film was adjusted to 50 μm.

[0133] (Example 10) A recycled film was prepared in the same manner as in Example 8, except that the thickness of the recycled film was adjusted to 20 μm.

[0134] (Comparative Example 1) Recycled material 2 was fed into a hopper for extruding recycled film, and a recycled film with a thickness of 200 μm was produced using a single-screw extruder. No adjustments were made to avoid minimizing the flow path before the T-die when extruding the recycled film.

[0135] (Comparative Example 2) A recycled film was prepared in the same manner as in Comparative Example 1, except that the thickness of the recycled film was adjusted to 50 μm.

[0136] (Comparative Example 3) A recycled film was prepared in the same manner as in Comparative Example 1, except that the thickness of the recycled film was adjusted to 20 μm.

[0137] (Comparative Example 4) A recycled film was prepared in the same manner as in Example 4, except that the thickness of the recycled film was adjusted to 20 μm.

[0138] (Comparative Example 5) Recycled material 4 was fed into a hopper for extruding recycled film, and a recycled film with a thickness of 200 μm was produced using a single-screw extruder. No adjustments were made to avoid minimizing the flow path before the T-die when extruding the recycled film.

[0139] (Comparative Example 6) A recycled film was prepared in the same manner as in Comparative Example 5, except that the thickness of the recycled film was adjusted to 50 μm.

[0140] (Comparative Example 7) A recycled film was prepared in the same manner as in Comparative Example 5, except that the thickness of the recycled film was adjusted to 20 μm.

[0141] (Comparative Example 8) Recycled material 5 was fed into a hopper for extruding recycled film, and a recycled film with a thickness of 200 μm was produced using a single-screw extruder. No adjustments were made to avoid minimizing the flow path before the T-die when extruding the recycled film.

[0142] (Comparative Example 9) A recycled film was prepared in the same manner as in Comparative Example 8, except that the thickness of the recycled film was adjusted to 50 μm.

[0143] (Comparative Example 10) A recycled film was prepared in the same manner as in Comparative Example 8, except that the thickness of the recycled film was adjusted to 20 μm.

[0144] (Comparative Example 11) A recycled film was prepared in the same manner as in Example 6, except that the thickness of the recycled film was adjusted to 20 μm.

[0145] (Comparative Example 12) A recycled film was prepared in the same manner as in Example 1, except that mixed material B was used.

[0146] (Comparative Example 13) A recycled film was prepared in the same manner as in Comparative Example 12, except that the thickness of the recycled film was adjusted to 50 μm.

[0147] (Comparative Example 14) A recycled film was prepared in the same manner as in Comparative Example 12, except that the thickness of the recycled film was adjusted to 20 μm.

[0148] (Reference Example 1) Virgin material 1 (manufactured by Prime Polymer Co., Ltd., product name "Evolu SP2020") was fed into a hopper for extruding recycled film, and a virgin film with a thickness of 200 μm was produced using a single-screw extruder. No adjustments were made to avoid minimizing the flow path before the T-die when extruding the virgin film.

[0149] (Reference Example 2) A virgin film was prepared in the same manner as in Reference Example 1, except that the thickness of the virgin film was adjusted to 50 μm.

[0150] (Reference Example 3) A virgin film was prepared in the same manner as in Reference Example 1, except that the thickness of the virgin film was adjusted to 20 μm.

[0151] <Evaluation of recycled and virgin films> The polyethylene resin content, maximum domain area and maximum aspect ratio, elongation at break, and breaking strength of recycled and virgin films were evaluated using the methods described below.

[0152] (Calculation of the polyethylene resin (PE resin) content in recycled film) Based on the polyethylene resin content in recycled material and the raw materials constituting the recycled film, the PE resin content in the recycled films of Examples 1 to 10 and Comparative Examples 1 to 14, as well as the virgin films of Reference Examples 1 to 3, was calculated.

[0153] (Maximum Domain Area and Maximum Aspect Ratio) The maximum area and maximum aspect ratio of domains (hereinafter also referred to as "low transmittance areas") in recycled or virgin film were calculated using the following procedure: (i) Ten random observation images (image size: 243 μm × 851 μm) of the recycled film in the planar direction were acquired using the SZX16 stereomicroscope system (manufactured by Olympus Corporation). (ii) The ten obtained images were analyzed using WinROOF2021 (manufactured by Mitani Corporation). In the image analysis, the low transmittance areas and the surrounding high transmittance areas were binarized, and the following operations were appropriately performed during binarization to match the visual shape and colored range of the low transmittance areas. (a) Brightness and contrast adjustments are used to emphasize low-transparency areas. (b) The threshold is adjusted to match the visible low-transparency areas with the colored areas. (c) If adjacent low-transparency areas are recognized as a single area, or if perforated low-transparency areas are recognized as multiple areas, splitting or merging processes are performed as needed.

[0154] Figure 6 shows a planar observation image of the recycled film of Example 1, acquired using the stereomicroscope system SZX16. As shown in Figure 6, the recycled film has low transmittance brightness regions 6 and high transmittance brightness regions 7, and the maximum area and maximum aspect ratio of the domains are calculated by the image analysis described above.

[0155] (Elongation at Breaking) Recycled films from Examples 1-10 and Comparative Examples 1-14, as well as virgin films from Reference Examples 1-3, were cut into 12 mm x 100 mm specimens with the film formation direction as the longer side. These specimens were subjected to tensile testing using a tensile testing machine (Shimadzu Corporation, product name "AGS-X") with an initial chuck distance of 50 mm and a tensile speed of 300 mm / min. The chuck distance at the moment the specimen broke was measured, and the elongation at breaking was calculated using the following formula 2. The measurement conditions conformed to JIS Z 1710. Elongation at Breaking (%) = (Chuck distance at the moment the specimen broke (mm) / Initial chuck distance (mm)) × 100 … (Formula 2)

[0156] (Breaking Energy) The breaking energy was calculated by impact resistance testing. Recycled films from Examples 1 to 10 and Comparative Examples 1 to 14, as well as virgin films from Reference Examples 1 to 3, were cut into 100 mm squares to serve as test specimens. A film impact tester (manufactured by Toyo Seiki, product name "Film Impact Tester") was used to measure the breaking energy of the test specimens with a bullet size of 1 / 2 and a weighing capacity of 3.0 J. The measurement conditions followed the method compliant with ASTM-D3420.

[0157] <Overall Evaluation> For the recycled films of Examples 1 to 10 and Comparative Examples 1 to 14, and the virgin films of Reference Examples 1 to 3, a "◎" rating was given if the elongation at break was 400% or more and the breaking energy was 10 J / mm or more, a "〇" rating was given if the elongation at break was 400% or more and the breaking energy was less than 10 J / mm, and a "×" rating was given if the elongation at break was less than 400%.

[0158] The evaluation results for the recycled films of Examples 1 to 10 and Comparative Examples 1 to 14, as well as the virgin films of Reference Examples 1 to 3, are shown in Tables 3 to 7. In Tables 3 to 7, "Percentage of polyethylene resin" refers to the percentage of PE resin contained in the recycled films of Examples 1 to 10 and Comparative Examples 1 to 14, as well as the virgin films of Reference Examples 1 to 3.

[0159]

[0160]

[0161]

[0162]

[0163]

[0164] As shown in Tables 3-4, the recycled films of Examples 1-10, which satisfy the specified domain size conditions and have a breaking elongation of 400%, were confirmed to have sufficient breaking energy despite being mainly composed of recycled materials containing two or more types of resin. Such recycled films can be used to obtain sufficient mechanical strength when made into laminated films or packaging bags.

[0165] According to the present invention, it is possible to provide a recycled film that has sufficient mechanical strength while being mainly composed of recycled material containing two or more types of resins, and a laminated film equipped therewith.

[0166] 1...Recycled film, 2a, 2b, 2c...Functional layer, 3a, 3b...Adhesive layer, 4...Domain, 6...Low transmittance brightness region, 7...High transmittance brightness region, 10a, 10b, 10c...Laminated film.

Claims

1. A recycled film obtained by forming a film from a resin composition containing recycled material, wherein the resin component contained in the resin composition is only the resin contained in the recycled material, or the resin contained in the recycled material and virgin material blended in an amount of 100 parts by mass or less per 100 parts by mass of the recycled material, wherein the recycled material includes a polyethylene resin and a resin other than a polyethylene resin, and includes a domain whose transmitted brightness is smaller than the surrounding area when the recycled film is observed from a planar view, and the domain has a maximum area of ​​1000 μm². ２ A recycled film that is as follows, has a maximum aspect ratio of 10 or less, and has a break elongation of 400% or more.

2. The recycled film according to claim 1, wherein the thickness is 20 μm or more and 200 μm or less.

3. The recycled film according to claim 1, wherein the breaking energy is 10 J / mm or more.

4. The recycled film according to claim 1, wherein the recycled material is derived from post-consumer recycling or post-industry recycling.

5. The recycled film according to claim 1, wherein the recycled material has been treated with an alkaline solution.

6. The recycled film according to claim 1, wherein the polyethylene resin content in the recycled material is 80% by mass or more based on the total amount of the recycled material.

7. A laminated film comprising a recycled film according to any one of claims 1 to 6, and a functional layer provided on at least one main surface of the recycled film.

8. The laminated film according to claim 7, wherein the functional layer is a substrate laminated on one main surface of the recycled film via an adhesive layer, and the recycled film is a sealant layer.

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

10. Packaging material comprising the recycled film described in any one of claims 1 to 6.

11. The packaging material according to claim 10, further comprising a substrate laminated on the recycled film via an adhesive layer, wherein the recycled film is a sealant layer.

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

Images