Sealing film and laminated film

Abstract

The present application provides a sealing film and a laminated film which contain recycled materials and are excellent in handling. More specifically, the present application relates to a sealing film (10) containing recycled materials which are used as raw materials for a laminate obtained by laminating a plurality of resin layers formed of only a polyethylene-based resin film with an adhesive layer interposed therebetween, the sealing film (10) being a multilayer structure of at least 2 layers or more, and having a virgin resin layer not containing recycled materials at an end surface (14, 15) on at least one side in the thickness direction, and a laminated film (16) obtained by laminating the sealing film (10) with a base material film (17).

Description

Technical Field

[0001] This invention relates to sealing films and laminated films. Background Technology

[0002] Patent document 1 describes the following manufacturing method: a synthetic resin containing aluminum foil is fed to an extruder, the aluminum foil is crushed and mixed, the particles are granulated, and the particles taken from cooling water are dehydrated and dried so that the moisture content is less than 0.1%.

[0003] Patent document 2 describes a laminated film formed by stacking a recycled polyethylene layer and a linear low-density polyethylene layer.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2009-073028 Patent Document 2: Japanese Patent Application Publication No. 2023-040660 Summary of the Invention Paragraph 0036 of Patent Document 1 describes the manufacture of various molded products such as blocks, bricks, piles, fences, boards, sheets, injection molded products, and multi-layer containers from recycled granules, but does not describe the use of sealing films for packaging bags, etc.

[0005] In paragraph 0044 of Patent Document 2, a linear low-density polyethylene layer that does not contain recycled polyethylene is described as the innermost layer, and in paragraph 0086, a laminated film having a recycled polyethylene layer is described as being used to manufacture synthetic resin products such as packaging bodies, but it is not described as being used for sealing films such as packaging bags.

[0006] Sealing films are laminated with substrate films, which are used as other resin films, before being used in the manufacture of packaging bags, etc. Before being laminated with other resin films, the sealing film is treated as a monomer film. Therefore, further improvements are needed to use laminated films with recycled polyethylene layers as sealing films. During horizontal recycling from packaging bag to packaging bag, it is difficult to remove impurities such as adhesives, inks, and additives; improvements are needed to ensure that even with these impurities, the film still possesses the strength required for use as a sealing film.

[0007] The present invention was made in view of the above circumstances, and its object is to provide a sealing membrane containing recycled material and having excellent operability, and a laminated membrane containing the sealing membrane.

[0008] To address the aforementioned issues, one aspect of the present invention includes the following approach.

[0009] The first method is a sealing film comprising a recycled material using a laminate as a raw material, the laminate being formed by stacking multiple resin layers consisting only of polyethylene resin films separated by adhesive layers, the sealing film being a multilayer structure with at least two layers, and having a virgin resin layer not containing the recycled material at at least one end face in the thickness direction.

[0010] The second method is the same as the first method, where the two end faces of the sealing film in the thickness direction have a virgin resin layer that does not contain the recycled material.

[0011] The third method involves, in either the first or second method, the density of the virgin resin contained in the sealing membrane being 0.910 g / cm³. 3 Above and 0.930 g / cm 3 the following.

[0012] The fourth method is that, in any of the methods 1 to 3, the content ratio of the recycled material relative to the total weight of the sealing membrane is 50% by weight or less.

[0013] The fifth method is any one of the methods 1 to 4, wherein the recycled material comprises high-density polyethylene.

[0014] The sixth method is any one of the methods 1 to 5, wherein the recycled material comprises printing ink components or polyurethane adhesives.

[0015] Method 7 is any one of methods 1 to 6, in which the total light transmittance of the sealing film is 65% to 90%.

[0016] The eighth method is a laminated film, which is formed by laminating a substrate film with a sealing film of any of the methods 1 to 7.

[0017] According to the present invention, it is possible to provide sealing films and laminated films that contain recycled materials and have excellent operability. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view showing an example of the sealing film of this embodiment.

[0019] Figure 2 This is a cross-sectional view showing an example of a laminate of raw materials that become recycled materials.

[0020] Figure 3 This is a cross-sectional view showing an example of a laminated film including the sealing film of this embodiment. Detailed Implementation

[0021] The present invention will now be described based on preferred embodiments.

[0022] like Figure 1 As shown, the sealing film 10 of this embodiment has a multilayer structure with at least two layers. Examples of methods for manufacturing multilayer structures include multilayer blow molding, multilayer T-die molding, dry lamination, and extrusion lamination.

[0023] The multilayer structure illustrated in the figure includes two end layers 11 and 13 facing the thickness direction, and an intermediate layer 12 stacked between the end layers 11 and 13. A multilayer structure with at least two layers can be a two-layer multilayer structure formed by the end layers 11 and 13, or a multilayer structure with three or more layers including one or two or more intermediate layers 12.

[0024] In addition to including end layers 11, 13 on at least one side, the sealing membrane 10 also includes a recycled material made from polyethylene resin film.

[0025] Recyclable materials, such as Figure 2 The laminate 20 is manufactured using the laminate as a raw material, as shown. The laminate 20 is formed by stacking multiple resin layers 21, 22, 23, which are formed solely of polyethylene resin film, with adhesive layers 24, 25 in between. The number of resin layers 21, 22, 23 is not particularly limited and is not limited to the 3 layers shown in the example. It can also be 2 or 4 or more layers.

[0026] At least one end layer 11, 13 is a virgin resin layer that does not contain the recycled material. Therefore, at least one end surface 14, 15 is formed of a virgin resin layer, thus facilitating hygiene management of the surface in contact with the contents and enabling good sealing when the sealing films 10 are heat-fused together. Preferably, both end layers 11, 13 are virgin resin layers, and both end surfaces 14, 15 do not contain recycled material.

[0027] Examples of polyethylene-based resins include linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). Polyethylene-based resins can be homopolymers of ethylene or copolymers with ethylene as the main component.

[0028] Examples of monomers (comonomers) other than ethylene include one or more of the following: α-olefins such as 1-butene, 1-hexene, and 1-octene; cyclic olefins such as norbornene; vinyl acetate; vinyl chloride; and acrylic acid. When monomers containing ester groups, such as vinyl acetate, are copolymerized, polyethylene resins can be copolymers in which a portion of the ester groups is saponified to include vinyl alcohol.

[0029] The proportion of ethylene in the structural monomers of polyethylene-based resins is preferably 50% by weight or more, for example, it can be 80% to 100% by weight. The ethylene or comonomer can be a compound derived from fossil resources such as petroleum, a compound derived from biomass such as plants, or a compound obtained through chemical recycling. Chemical recycling refers to a process of generating monomers and other compounds through the chemical treatment of raw materials from recycled materials.

[0030] The resin contained in the polyethylene resin layer may be only polyethylene resin, or it may contain other resins. Preferably, the polyethylene resin layer is formed of 80% or more, 90% or more, or 95% or more of polyethylene resin. Each polyethylene resin layer may be composed of one type of polyethylene resin, or it may be composed of two or more types of polyethylene resin.

[0031] Polyethylene-based resins may contain additives other than the resin itself. The types of additives are not particularly limited; examples include antioxidants, lubricants, anti-blocking agents, flame retardants, UV absorbers, light stabilizers, antistatic agents, colorants, and crosslinking agents. Additives can be components compatible with the resin or components incompatible with the resin.

[0032] The virgin resin layer is a layer of polyethylene resin formed from virgin polyethylene resin. Virgin polyethylene resin refers to the resin first used in an article after being manufactured by industrial polymerization of monomers; in the following description, it is sometimes simply referred to as "virgin resin". Virgin resin may contain monomers obtained through the aforementioned chemical recycling.

[0033] Virgin resins can be easily controlled in terms of composition, degree of polymerization, density, melting point, etc., to achieve the desired physical properties. Therefore, virgin resins can be used stably. However, compared with recycled materials, they have a greater environmental impact during the manufacturing and polymerization processes of monomers.

[0034] In the raw materials of the recycled material, resin layers 21, 22, and 23 are polyethylene resin layers formed from polyethylene resin. The polyethylene resin in the recycled material refers to resin that is manufactured by industrial polymerization of monomers, used in products, and then recycled, or recycled when not used in products, and reused through processes such as crushing and dissolving without reverting to monomers. In the following description, it is sometimes simply referred to as "recycled material".

[0035] Products using polyethylene resins include films, sheets, bags, and molded products. Scrap materials from films and sheets, as well as discarded packaging films and bags, can be used as raw materials for recycling. As raw materials for recycling, they can be laminates consisting solely of multiple resin layers formed from polyethylene resin films separated by adhesive layers, or they can partially utilize other raw materials. Examples of other raw materials include, for instance, 20% by weight or less, and 10% by weight or less.

[0036] Recycled materials undergo thermal processes during the pre-recycling manufacturing process and are subjected to further thermal processes during recycling, crushing and dissolving, and post-recycling manufacturing. Furthermore, they are subjected to mechanical, optical, and chemical stresses both before and after recycling. Therefore, even when processed from raw materials with similar properties, such as scraps and unused waste, recycled materials can sometimes perform worse than virgin resins.

[0037] Furthermore, recycled materials are sometimes processed in a state mixed with various raw materials during recycling. For example, sometimes they are processed without adequately distinguishing between polyethylene resins with different compositions, degrees of polymerization, densities, melting points, etc., and / or without adequately removing additives, impurities, and other foreign matter. Therefore, it is sometimes difficult to obtain stable properties, or foreign matter may affect the properties of the resin.

[0038] While raw materials can be selected based on their intended use, it can be difficult to select and differentiate them when the raw materials are composite materials. For example, polyethylene resin films sometimes contain laminates of resins with lower density, such as LDPE and LLDPE, and higher density, such as HDPE and MDPE.

[0039] As described above, when using a laminate 20, which is formed by stacking multiple resin layers 21, 22, 23 made solely of polyethylene resin film with adhesive layers 24, 25 in between, as the raw material, it is difficult to peel off the adhesive layers 24, 25 and separate the resin layers 21, 22, 23, even if the resin layers 21, 22, 23 are of different types of polyethylene resin. Therefore, it is not easy to adjust the quality of the recycled material.

[0040] The density of the virgin resin contained in the sealing membrane 10 is preferably 0.910 g / cm³. 3 Above and 0.930 g / cm 3 The following applies. This improves the processing adaptability of recycled materials. If the density of the virgin resin is too low, there is a risk of easy blocking. As the virgin resin used for the sealing film 10, resins with lower density, such as LDPE and LLDPE, are preferred.

[0041] The content of recycled material relative to the total weight of the sealing film 10 is preferably 50% by weight or less. By mixing virgin resin with properties suitable for sealants with recycled material whose quality is difficult to adjust, it is possible to balance environmental impact reduction and quality assurance. The content of recycled material can be selected from at least one of 50% by weight, 40% by weight, 30% by weight, 20% by weight, 10% by weight, and 5% by weight as the upper or lower limit.

[0042] From the viewpoint of improving the quality of the sealing membrane 10, it is preferable to use recycled materials such as LDPE and LLDPE, which have properties suitable for sealants. However, the quantity of raw materials for recycled materials is sometimes difficult to ensure due to limitations such as scraps from sealant materials. Therefore, it is preferable that the recycled material includes HDPE.

[0043] HDPE is suitable as a substrate film for polyethylene resin films, therefore, as a raw material, laminate 20 can be used to make a composite film that includes a substrate film and a sealing film.

[0044] From the perspective of improving the quality of the sealing film 10, it is preferable to thoroughly remove various materials such as printing ink components and polyurethane adhesives. However, there is a risk that the processing of recycled materials becomes more complex and the price increases. Therefore, the recycled material preferably contains printing ink components or polyurethane adhesives. The recycled material containing printing ink components can be a material with a lower total light transmittance than the virgin resin. For example, the total light transmittance of the sealing film 10 can be 90% or less. However, compared with a sealing film formed solely from recycled material, it has a virgin resin layer that does not contain recycled material, thus enabling a higher total light transmittance. For example, the total light transmittance of the sealing film 10 can be 65% or more. In addition, the sealing film containing recycled material has a lower total light transmittance than a sealing film made solely from virgin resin, thus providing excellent light-blocking and concealment properties.

[0045] The printing ink component is useful for ensuring the display surface and improving design during the production of polyethylene resin films, while the polyurethane adhesive is useful for bonding between resin layers 21, 22, and 23. Therefore, the laminate 20, as a raw material, can be a composite film comprising a printing layer (not shown) and adhesive layers 24 and 25.

[0046] The sealing film 10 can be used to laminate with the substrate film 17 to manufacture a laminated film 16. The sealing film 10 accounts for a large proportion of the laminated film 16, so increasing the recycling rate of the sealing film 10 is beneficial to increasing the recycling rate of the laminated film 16.

[0047] The substrate film 17 is not particularly limited and can include polyolefin resins such as polyethylene (PE) and polypropylene (PP), polyester resins such as polyethylene terephthalate (PET), and polyamide resins such as nylon (Ny). The substrate film 17 can be a single layer or two or more layers. Furthermore, considering subsequent recycling, the substrate film 17 is preferably a PE-based resin.

[0048] Although not specifically illustrated, the laminated film 16 may have at least one selected from a printed layer, an adhesive layer, a barrier resin layer such as ethylene-vinyl alcohol copolymer (EVOH), a metal vapor-deposited layer such as aluminum, a metal foil such as aluminum foil, an inorganic vapor-deposited layer such as silica or alumina, or an extruded resin layer such as PE. The sealing film 10 and the substrate film 17 may be bonded together using a polyurethane-based adhesive.

[0049] The laminated film 16 can be used to manufacture packaging containers such as packaging bags. Specific examples of packaging bags include three-side seal bags, four-side seal bags, pillow bags, gusseted bags, and stand-up pouches.

[0050] The size of the packaging bag is not particularly limited. For example, when it is used as a replacement container, the height in the vertical direction is about 100-500mm, and the width in the horizontal direction is about 70-300mm. As for the filling volume, 100cm is preferred. 3 ~5000cm 3 about.

[0051] A packaging bag is a packaged product (a bag containing contents) obtained by sealing it while it is filled with specified contents. The state of the contents is not particularly limited and can include fluids such as liquids, powders, and granules, or solids such as articles. The type of contents is not particularly limited and can include detergents, pharmaceuticals, cosmetics, medicines, beverages, seasonings, inks, paints, fuels, etc.

[0052] The present invention has been described above based on preferred embodiments; however, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention. Examples of changes include the addition, substitution, omission, and other modifications of constituent elements.

[0053] Example The present invention will now be described in detail based on embodiments.

[0054] Based on the layer composition and layer ratio shown in Table 1, a sealing film 10 with three layers—outer (end layer 13), middle (intermediate layer 12), and inner (end layer 11)—was manufactured by multi-layer blow molding. The layer ratio is the relative weight ratio obtained by product of the thickness and density of each layer. The recycling rate is the weight ratio (wt%) of recycled material used in each layer. In the layer composition, "R" indicates a layer with a recycling rate greater than 0 wt%, and "V" indicates a virgin resin layer with a recycling rate of 0 wt%.

[0055] As a recyclable material, polyethylene resin is obtained by laminating an HDPE layer and an LLDPE layer together using a laminate with a printing ink layer and a polyurethane adhesive layer as raw material and then re-granulating it.

[0056] The virgin resin used is C6LLDPE, obtained by copolymerizing a comonomer with 6 carbon atoms. The density of the virgin resin is shown in Table 1.

[0057] [Table 1]

[0058] The evaluation results of the sealing membrane are shown in Table 2. The evaluation method is as follows.

[0059] (Recycling rate) The overall recyclability of the sealing membrane is calculated using the layer ratio (A) of each layer of the sealing membrane. 外 A 中 A 内 ) and recycling rate (B 外 B 中 B 内 ) Calculate according to the following formula.

[0060] "Overall recycling rate" = (A 外 B 外 +A 中 B 中 +A 内 B 内 ) / (A 外 +A 中 +A 内 ) (Process adaptability) Regarding processing adaptability, film-forming properties and adhesion were evaluated according to the following criteria.

[0061] Regarding film-forming properties, a stable bubble condition is marked as "○", a disordered but stable condition with some bubbles is marked as "△", and an unstable bubble condition is marked as "×".

[0062] Regarding adhesion, the case where there is no adhesion on the inner surface of the tube is marked as "○", the case where there is some adhesion on the inner surface of the tube but it is easy to peel off is marked as "△", and the case where there is adhesion on the inner surface of the tube and it is not easy to peel off is marked as "×".

[0063] (Dart impact test) The dart impact test was conducted according to JIS K7124-1 A method (step method). For the sealed membrane, the dart was dropped from a specified height of 0.66 m, and the impact failure mass (g) was measured. When the impact failure mass was 1200 g or more, it was recorded as 1200 g or more.

[0064] (Galbert Franks Experiment) Regarding the Gelbo-Franks test, the number of pinholes produced after bending the sealing film 500 or 1000 times was measured and evaluated using a TESTER Sangyo Co., Ltd. "-" in Table 2 indicates that the test was not conducted.

[0065] (Total light transmittance) Total light transmittance was measured according to JIS K7361. The measurement was performed using an NDH4000 illuminator manufactured by Nippon Denshoku Kogyo Co., Ltd.

[0066] [Table 2]

[0067] As shown in Table 2, at least good results were obtained in the sealing films of Examples 1-8. Furthermore, excellent results were obtained in the sealing films of Examples 4-8. Therefore, it can be seen that, according to the present invention, film-forming properties and bending resistance can be improved.

[0068] Explanation of reference numerals in the attached figures 10…Sealing film, 11, 13…End layer, 12…Intermediate layer, 14, 15…End face, 16…Laminated film, 17…Substrate film, 20…Laminate body, 21, 22, 23…Resin layer, 24, 25…Adhesive layer

Claims

1. A sealing film comprising a recycled material using a laminate as a raw material, said laminate being formed by stacking multiple resin layers consisting solely of polyethylene-based resin films separated by adhesive layers, characterized in that, The sealing film is a multilayer structure with at least two layers, and has a virgin resin layer that does not contain the recycled material on at least one end face in the thickness direction.

2. The sealing film according to claim 1, characterized in that, The two end faces of the sealing film in the thickness direction have a virgin resin layer that does not contain the recycled material.

3. The sealing film according to claim 1 or 2, characterized in that, The density of the virgin resin contained in the sealing membrane is 0.910 g / cm³. 3 Above and 0.930 g / cm 3 the following.

4. The sealing film according to any one of claims 1 to 3, characterized in that, The content of the recycled material relative to the total weight of the sealing membrane is less than 50% by weight.

5. The sealing film according to any one of claims 1 to 4, characterized in that, The recycled material comprises high-density polyethylene.

6. The sealing film according to any one of claims 1 to 5, characterized in that, The recycled material contains printing ink components or polyurethane-based adhesives.

7. The sealing film according to any one of claims 1 to 6, characterized in that, The total light transmittance of the sealing film is 65%~90%.

8. A laminated film, comprising a sealing film laminated with a substrate film according to any one of claims 1 to 7.

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