Recycled film and method for producing recycled film

Abstract

To provide a recycled film produced by using a regenerated raw material of a polyamide-based resin recovered from a film containing the polyamide-based resin and having sufficient strength as a product, and to provide a method for producing the recycled film.SOLUTION: The recycled film includes a layer composed of a resin raw material containing a recycled raw material of a polyamide resin recovered from a film containing a polyamide resin and a raw material of a polyamide resin. In a molecular weight distribution curve for the layer obtained through gel permeation chromatography, an area of a region having a molecular weight of 500 or less is 5.0% or less of a total peak area. The impact strength of the recycled film is 0. 5J or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a recycled film and a method for producing the recycled film. [Background technology]

[0002] JP 2018-534184 A (Patent Document 1) discloses a method for separating a composition containing polyamide and polyethylene terephthalate, in which the polyamide and polyethylene terephthalate are each separated and recovered from the composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-534184 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a recycled film manufactured using recycled raw materials of polyamide-based resin recovered from films containing polyamide-based resin, the recycled film having sufficient strength, etc. for use as a product, and a method for manufacturing the recycled film. [Means for solving the problem]

[0005] A recycled film according to one aspect of the present invention includes a layer made of a resin material containing recycled polyamide resin material recovered from a film containing polyamide resin and virgin polyamide resin material. In a molecular weight distribution curve for the layer obtained by gel permeation chromatography, the area of ​​a region where the molecular weight is 500 or less is 5.0% or less of the total peak area. The impact strength of the recycled film is 0.5 J or more.

[0006] The present inventors have found that when a recycled film is produced using a polyamide resin recovered from a film containing the polyamide resin, the strength of the recycled film tends to decrease due to a decrease in the molecular weight of the polyamide resin. As a result, the strength of the recycled film may fall below a sufficient standard for a product. In a recycled film according to one aspect of the present invention, in the molecular weight distribution curve for the layer, the area of ​​the region where the molecular weight is 500 or less is 5.0% or less of the total peak area, and the impact strength of the recycled film is 0.5 J or more. Therefore, with this recycled film, the decrease in the molecular weight of the polyamide resin is suppressed, and therefore the decrease in the strength of the recycled film can be suppressed.

[0007] In the recycled film, the area of ​​the region may be 3.0% or less of the total peak area, and the impact strength may be 0.7 J or more.

[0008] In this recycled film, the decrease in molecular weight of the polyamide-based resin is further suppressed, so that the decrease in strength of the recycled film can be further suppressed.

[0009] The recycled film may have a puncture strength of 5.0 N or more.

[0010] The recycled film may have a weight average molecular weight of 45,000 or more in the molecular weight distribution curve.

[0011] In the recycled film, the layer may be an intermediate layer, and the recycled film may further include an adjacent layer laminated to at least one of the layers.

[0012] A method for producing a recycled film according to another aspect of the present invention includes the steps of recovering recycled raw material of polyamide-based resin from a film containing polyamide-based resin, preparing virgin raw material of polyamide-based resin, and producing a recycled film using the recycled raw material and the virgin raw material. In the step of recovering the recycled raw material, the polyamide-based resin is not heated to 200°C or higher.

[0013] In this method for producing recycled films, the polyamide resin is not heated to 200°C or higher in the process of recovering recycled raw materials. Therefore, this method for producing recycled films prevents the molecular weight of the polyamide resin from decreasing in the process of recovering recycled raw materials, making it possible to produce recycled films with sufficient strength.

[0014] In the method for producing the recycled film, the step of recovering the recycled raw material may include a step of granulating the polyamide resin.

[0015] According to this method for manufacturing recycled film, the recycled raw materials are recovered as granular material after granulation, and relatively little heat is applied to the polyamide-based resin during the recycled raw material recovery process, which suppresses the decrease in molecular weight of the polyamide-based resin during the recycled raw material recovery process, making it possible to produce recycled film with sufficient strength. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a recycled film manufactured using recycled raw materials of polyamide-based resin recovered from films containing polyamide-based resin, the recycled film having sufficient strength, etc. for use as a product, and a method for manufacturing the recycled film. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram schematically illustrating an example of a cross section of a recycled film according to an embodiment. [Figure 2]1 is a flowchart showing a manufacturing procedure for a recycled film. [Figure 3] 1 is a flowchart showing a procedure for recovering recycled raw materials of polyamide resin. [Figure 4] FIG. 2 is a diagram schematically illustrating an example of a cross section of a film waste material. [Figure 5] FIG. 10 is a diagram schematically illustrating a cross section of an example in which another layer is further laminated on the recycled film according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described in detail below with reference to the drawings. Note that the same or corresponding parts in the drawings are designated by the same reference numerals, and their description will not be repeated. Furthermore, for ease of understanding, each drawing is drawn schematically with objects appropriately omitted or exaggerated.

[0019] [1. Composition of recycled film] FIG. 1 is a diagram schematically illustrating an example of a cross section of a recycled film 10 according to the present embodiment. Referring to FIG. 1, the recycled film 10 is a polyamide-based film. The recycled film 10 includes a first adjacent layer 11, an intermediate layer 12, and a second adjacent layer 13. The intermediate layer 12 is located between the first adjacent layer 11 and the second adjacent layer 13 in the thickness direction of the recycled film 10. The first adjacent layer 11 and the second adjacent layer 13 are each located closer to the surface of the recycled film 10 than the intermediate layer 12.

[0020] The total thickness of the recycled film 10 is, for example, 10 μm to 50 μm, preferably 10 μm to 30 μm, more preferably 10 μm to 25 μm, and even more preferably 10 μm to 20 μm. The ratio of the thickness of the intermediate layer 12 to the sum of the thicknesses of the first adjacent layer 11 and the second adjacent layer 13 is, for example, 15:85 to 85:15, preferably 30:70 to 70:30, and more preferably 40:60 to 60:40.

[0021] The first adjacent layer 11 and the second adjacent layer 13 are each made of a resin material containing virgin material. The intermediate layer 12 is made of a resin material containing recycled polyamide-based resin material recovered from a film containing polyamide-based resin and virgin polyamide-based resin material. Virgin materials also include chemically recycled resin materials and biomass-derived resin materials. The resin contained in each of the first adjacent layer 11, the intermediate layer 12, and the second adjacent layer 13 is not particularly limited, and examples include polyamide-based resin, ethylene-vinyl alcohol copolymer (EVOH), polyethylene-based resin, etc. For example, the polyamide-based resin may be any of aromatic polyamide, aliphatic polyamide, and polyamide elastomer. The first adjacent layer 11 and the second adjacent layer 13 may also be made of different resin materials.

[0022] Examples of aromatic polyamides include amorphous aromatic polyamides (amorphous nylons) obtained by polycondensation of aliphatic diamines such as hexamethylenediamine with dicarboxylic acids such as terephthalic acid and isophthalic acid or derivatives thereof. Preferred examples of aromatic polyamides include copolymers of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid.

[0023] Examples of aromatic polyamides include crystalline aromatic polyamides obtained by polycondensation of aromatic diamines such as metaxylenediamine and paraxylenediamine with dicarboxylic acids or derivatives thereof such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, and isophthalic acid. Preferred examples of aromatic polyamides include crystalline aromatic polyamides such as polymetaxylylene adipamide (MXD-nylon). Examples of polyamide elastomers include polyether ester amide elastomers.

[0024] As the aliphatic polyamide, aliphatic nylon and its copolymers can be preferably used.Specific examples of the aliphatic polyamide include polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecaneamide (nylon-11), polylauryllactam (nylon-12), polyethylenediamineadipamide (nylon-2,6), polytetramethyleneadipamide (nylon-4,6), polyhexamethyleneadipamide (nylon-6,6), polyhexamethylenesebacamide (nylon-6,10), polyhexamethylenedodecamide (nylon-6,12), polyoctamethyleneadipamide (nylon-8,6), and polydecamethyleneadipamide (nylon-10,8).

[0025] Specific examples of aliphatic polyamides that can be preferably used include caprolactam / lauryllactam copolymer (nylon-6 / 12), caprolactam / ω-aminononanoic acid copolymer (nylon-6 / 9), caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,6), lauryllactam / hexamethylenediammonium adipate copolymer (nylon-12 / 6,6), ethylenediamine adipamide / hexamethylenediammonium adipate copolymer (nylon-2,6 / 6,6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6,6 / 6,10), and ethyleneammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6 / 6,6 / 6,10). These aliphatic polyamides may be used alone or in combination of two or more.

[0026] Examples of EVOH include the following. The ethylene content of EVOH is preferably about 55 mol% or less, more preferably about 20 mol% to 50 mol%, and even more preferably about 25 mol% to 44 mol%. The degree of saponification of the vinyl acetate component of EVOH is preferably about 90 mol% or more, more preferably about 95 mol% or more. EVOH may further contain small amounts of comonomers such as α-olefins such as propylene, isobutene, α-octene, α-dodecene, and α-octadecene; unsaturated carboxylic acids or derivatives thereof (e.g., salts, partial alkyl esters, complete alkyl esters, nitriles, amides, and anhydrides); and unsaturated sulfonic acids or salts thereof.

[0027] Examples of polyethylene-based resins include branched low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer resin, and mixtures thereof. Examples also include ethylene-based copolymers containing ethylene as the main component and an α-olefin as a copolymerization component. The copolymers may be random copolymers or block copolymers. Examples of α-olefins include α-olefins having 3 to 20 carbon atoms, such as propylene, 1-butene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. The proportion of the α-olefin copolymer is preferably 1 to 25 mol %. The polyethylene-based resin may also be a mixture of different ethylene-α-olefin random copolymers. Furthermore, the polyethylene-based resin may contain an ethylene-based elastomer.

[0028] An adhesive layer may be provided to bond the first adjacent layer 11, the intermediate layer 12, and the second adjacent layer 13 to each other. Examples of resins for the adhesive layer include polyolefin resins such as polypropylene resins and polyethylene resins (LLDPE, HDPE, LDPE), modified polyolefins, modified styrene elastomers, polyester elastomers, and modified polyester elastomers, and these resins may be mixed. The resin for the adhesive layer is composed of an appropriate resin raw material depending on the resin of the adjacent layer.

[0029] Furthermore, an additional adjacent layer may be provided on at least one of the surface of the first adjacent layer 11 opposite the surface adjacent to the intermediate layer 12 and the surface of the second adjacent layer 13 opposite the surface adjacent to the intermediate layer 12. That is, the additional adjacent layer may be provided on both sides of the recycled film 10, or on one side of the recycled film 10. The resin contained in the additional adjacent layer is not particularly limited, and may be a polyamide-based resin, an ethylene-vinyl alcohol copolymer (EVOH), a polyethylene-based resin, a polyester-based resin, or the like. An adhesive layer may be provided to bond the first adjacent layer 11, the second adjacent layer 13, and the additional adjacent layer together.

[0030] These resin layers may contain other resins or additives. Examples of such resins include modified ethylene acetate, vinyl acetate copolymer, methacrylic acid copolymer ionomer, α-olefin, unsaturated carboxylic acid or its salt, partial alkyl ester, complete alkyl ester, nitrile, amide, anhydride, comonomer such as unsaturated sulfonic acid or its salt, polyester elastomer, polyamide elastomer, polyolefin elastomer, polystyrene elastomer, polyurethane elastomer, polyvinyl chloride elastomer, and ionomer polymer. Mechanically recycled resin materials are also included.

[0031] Examples of additives include modifiers, antioxidants, antiblocking agents, heat stabilizers, antifogging agents, antistatic agents, lubricants, ultraviolet protection agents, light stabilizers, flame retardants, antibacterial agents, fluorescent brighteners, flex resistance agents, colorants, and fillers.

[0032] In a molecular weight distribution curve (hereinafter simply referred to as "molecular weight distribution curve") obtained by gel permeation chromatography for the intermediate layer 12, the area of ​​the region where the molecular weight is 500 or less is 5.0% or less of the total peak area, and preferably the area of ​​the region where the molecular weight is 500 or less is 3.0% or less of the total peak area. Furthermore, in the molecular weight distribution curve, the weight average molecular weight (Mw) is 45,000 or more and 150,000 or less, preferably 45,000 or more and 120,000 or less, more preferably 45,000 or more and 100,000 or less, even more preferably 45,000 or more and 90,000 or less, even more preferably 50,000 or more and 90,000 or less, even more preferably 50,000 or more and 80,000 or less, and even more preferably 50,000 or more and 70,000 or less.

[0033] The ratio of the area of ​​the region with a molecular weight of 500 or less to the total peak area (hereinafter also referred to as the "molecular weight area ratio") and the weight average molecular weight (Mw) are each measured by gel permeation chromatography (GPC). Each value is a standard PMMA equivalent value. The molecular weight area ratio is obtained by calculating the area ratio of the region with a molecular weight of 500 or less in the molecular weight distribution curve obtained by GPC. The total peak area is the sum of the peak areas in the region from a molecular weight of 0 to the highest molecular weight at which the area becomes 0 at the base of the high molecular weight side.

[0034] The impact strength of the recycled film 10 is 0.5 J or more, and preferably 0.7 J or more. The puncture strength of the recycled film 10 is 5.0 N or more, and preferably 7.0 N or more. For example, the impact strength is measured according to JIS-P8134, and the puncture strength is measured according to JIS Z-1707.

[0035] The present inventors have found that when a recycled film is produced using polyamide resin recovered from a film containing polyamide resin, the strength of the recycled film tends to decrease due to a decrease in the molecular weight of the polyamide resin. As a result, the strength, etc. of the recycled film may fall below the standards sufficient for a product. The recycled film 10 according to this embodiment ensures sufficient strength, etc. for a product.

[0036] As described above, in the molecular weight distribution curve obtained by gel permeation chromatography for the intermediate layer 12, the area of ​​the region where the molecular weight is 500 or less is 5.0% or less of the total peak area. In addition, the impact strength of the recycled film 10 is 0.5 J or more. Therefore, with the recycled film 10, the decrease in the molecular weight of the polyamide-based resin is suppressed, and therefore the decrease in the strength of the recycled film can be suppressed.

[0037] [2. Manufacturing method of recycled film] 2 is a flowchart showing the manufacturing procedure of the recycled film 10 according to this embodiment. Each step shown in this flowchart is performed by various devices or workers.

[0038] 2, first, recycled raw materials of polyamide-based resin are recovered from waste film materials containing polyamide-based resin (step S100). For example, the recycled raw materials of polyamide-based resin are recovered by separating the polyamide-based resin from the waste film materials. Specific recovery procedures for recycled raw materials are described below.

[0039] 3 is a flowchart showing the procedure for recovering recycled raw materials for polyamide resin. Each step shown in this flowchart is performed by various devices or workers.

[0040] 3, first, the waste film 20 to be recycled is crushed (step S200). The waste film 20 is crushed, for example, by a dry crusher having a punching mesh with a mesh size of 10 mm. As a result, the waste film 20 is broken into a large number of film pieces.

[0041] FIG. 4 is a schematic diagram illustrating an example of a cross section of a waste film 20. As shown in FIG. 4, the waste film 20 includes, for example, a polyamide-based resin layer 21, a printed layer 22, and a polyester-based resin layer 23. The printed layer 22 is formed between the polyamide-based resin layer 21 and the polyester-based resin layer 23. The printed layer 22 is composed of, for example, a coloring component (colorant) such as ink that forms a pattern. The polyester-based resin layer 23 is composed of, for example, polyethylene terephthalate (PET), polyethylene terephthalate / isophthalate, polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), or polybutylene naphthalate (PBN). These may be used alone or in combination. If necessary, the waste film 20 may contain other resins compatible with the polyester-based resin. The polyamide-based resin layer 21, the printed layer 22, and the polyester-based resin layer 23 do not have to be laminated in the configuration shown in FIG. 4. In addition to these layers, a polyethylene resin layer or an aluminum layer may be laminated. The layer configuration varies depending on the intended use.

[0042] The waste film 20 may be collected from the city or from a factory or the like. That is, the waste film 20 may be PIR (Post Industrial Recycle) material or PCR (Post Consumer Recycle) material. The waste film 20 may include various types of film with various types of printing. Furthermore, the waste film 20 does not necessarily have to include various types of film with various types of printing, and may include, for example, only one type of film. For example, only one specific type of film may be recycled as waste film from waste materials collected from a factory or the like.

[0043] Referring again to FIG. 3, once the waste film 20 is pulverized into numerous film fragments, the numerous film fragments are dissolved (step S210). This dissolution is performed, for example, using a dissolution tank. A metal basket is provided inside the dissolution tank. For example, numerous film fragments are placed in the basket, and the dissolution tank is heated to 170 to 190°C, and a preheated dissolving liquid (e.g., propylene glycol) is then poured into the dissolution tank. In this state, the solution is dissolved by stirring for, for example, 10 to 120 minutes. Note that during the dissolution process, the system may be under air or a nitrogen atmosphere.

[0044] After the numerous film pieces have been dissolved, filtration and recovery of the insoluble resin components (polyester-based resin components) are performed (step S220). For example, the solution in the dissolution tank is transported to a cooling tank while being maintained at 170 to 190°C. At this time, the insoluble resin components are recovered.

[0045] After filtration and recovery of the insoluble resin component, a step for precipitating the polyamide-based resin component is performed (step S230). For example, the solution in the dissolution tank is transferred to a cooling tank, and then the solution in the cooling tank is cooled to 40°C or less. This causes the polyamide-based resin component to precipitate. In this step, the system may be under air or a nitrogen atmosphere.

[0046] When the polyamide-based resin component precipitates, the precipitate is separated by filtration (step S240). For example, the slurry liquid containing the polyamide-based resin precipitated in the cooling tank is transported to a centrifuge, and the liquid and the precipitate are separated by filtration by operating the centrifuge. As a result, a cake of the polyamide-based resin component remains in the centrifuge as a filtered residue.

[0047] The resulting cake is granulated by mechanical processing such as a compression granulator or tableting (step S250). This results in a granular recycled raw material. In compression granulation, the cake is compressed and molded into granules. For example, the resulting granules are dried in a fluidized bed dryer to obtain a granular dried recycled raw material of the polyamide resin component. In step S250, additives (e.g., heat stabilizers, antioxidants, UV absorbers, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, fluorescent brighteners, virgin raw materials, antiblocking agents) may be added to the cake. Granulation in step S250 increases the bulk density of the recycled raw material, thereby reducing the space required for storing the recycled raw material.

[0048] The following examples of the granulation method using the obtained cake include: (1) An extrusion granulation method in which a binder and other ingredients are added to a cake, kneaded, and then pressure is applied to extrude the kneaded cake through a screen with many holes to form granules. (2) Agitation granulation method in which a solution of a binder or the like is dropped onto the cake while stirring it, causing the cake to aggregate into spherical or elliptical particles and granulate. (3) A fluidized bed granulation method in which hot air is blown in from below and a solution of a binder or the like is sprayed onto the fluidized cake to aggregate or coat the cake and grow it into granules. (4) A rolling granulation method in which cake is placed in a granulation container such as a rotating pan or drum, and a solution of a binder or the like is sprayed onto the cake, causing the particles to collide and bond with each other, growing the cake into granules. (5) A compression granulation method in which a cake is compressed and molded using a mold roll or the like having cavities of the required shape and size, and then crushed as necessary to obtain granules.

[0049] Referring again to FIG. 2, once recycled raw materials of polyamide-based resin are collected, virgin raw materials of polyamide-based resin are prepared (step S110). The order of steps S100 and S110 is not limited to this. Step S110 may be performed before step S100. Thereafter, recycled film 10 is produced by using the recycled raw materials collected in step S100 and the virgin raw materials prepared in step S110 (step S120). For example, recycled film 10 is produced by extrusion molding in which a layer made of resin raw materials including virgin raw materials, a layer made of resin raw materials in which recycled raw materials and virgin raw materials are mixed, and a layer made of resin raw materials including virgin raw materials are laminated in this order.

[0050] [3. Features] As described above, in the recycled film 10 according to the present embodiment, the area of ​​the region where the molecular weight is 500 or less in the molecular weight distribution curve obtained by gel permeation chromatography for the intermediate layer 12 is 5.0% or less of the total peak area. In addition, the impact strength of the recycled film 10 is 0.5 J or more. Therefore, with the recycled film 10, the decrease in the molecular weight of the polyamide-based resin is suppressed, and therefore the decrease in the strength of the recycled film can be suppressed.

[0051] Furthermore, in the method for producing recycled film 10 according to the present embodiment, the polyamide resin is not heated to 200°C or higher in the process of recovering the recycled raw material of the polyamide resin. Therefore, the method for producing recycled film 10 prevents the molecular weight of the polyamide resin from decreasing in the process of recovering the recycled raw material, making it possible to produce a recycled film with sufficient strength.

[0052] 4. Other Embodiments The concept of the above embodiment is not limited to the embodiment described above. Hereinafter, examples of other embodiments to which the concept of the above embodiment can be applied will be described.

[0053] The layer structure of the recycled film 10 according to the above embodiment is not limited to the above structure. For example, the recycled film 10 according to the above embodiment may further include other layers. For example, a surface layer may be laminated on one or both surfaces of the recycled film 10 via an adhesive layer.

[0054] Fig. 5 is a schematic cross-sectional view of an example in which another layer is further laminated on the recycled film 10 according to the embodiment. As shown in Fig. 5, in the recycled film 10A, a surface layer 14 is laminated on a second adjacent layer 13 via an adhesive layer 15. The adhesive layer 15 is made of a resin material containing, for example, a polyester-based elastomer, and the surface layer 14 is made of a resin material containing, for example, a polyester-based resin.

[0055] The structure of the waste film 20 is not limited to that described in the above embodiment. The layer structure of the waste film 20 may be, for example, as follows: In the waste film 20, a polyethylene (PE) layer / polyamide layer / PE layer may be laminated in this order. In this case, for example, an aromatic solvent, a cyclic terpene solvent, a cyclic ether solvent, or a cyclic aliphatic solvent may be used as the solvent. The PE layer may then be dissolved in a heated solvent, and the insoluble polyamide layer may be recovered and dried. Furthermore, the resulting PE solution may be cooled to precipitate PE, and the precipitate may be filtered out to recover and reuse PE.

[0056] The waste film 20 may also be laminated in this order: polyamide layer / EVOH / polyamide layer / PE layer. In this case, the solvent for dissolving PE may be an aromatic solvent, a cyclic terpene solvent, a cyclic ether solvent, or a cyclic aliphatic solvent. The solvent for dissolving EVOH may also be a mixed solvent of an alcohol solvent and water (the mixing ratio of the alcohol solvent to the water in the mixed solvent is, for example, greater than 0.25 and less than 6.00). The mixing ratio is (weight of water) / (weight of alcohol solvent). Then, the PE may be dissolved and removed, the EVOH may be dissolved and removed, and the insoluble polyamide layer may be collected and dried.

[0057] In the above embodiment, an adhesive layer may be provided between the layers to bond the layers together. In this case, the adhesive layer can be separated by selecting a solvent depending on the resin component that constitutes the adhesive layer.

[0058] The above describes exemplary embodiments of the present invention. That is, the detailed description and the accompanying drawings are disclosed for the purpose of illustrative explanation. Therefore, some of the components described in the detailed description and the accompanying drawings may be non-essential components for solving the problems. Therefore, just because these non-essential components are described in the detailed description and the accompanying drawings, it should not be immediately recognized that these non-essential components are essential.

[0059] Furthermore, the above-described embodiments are merely illustrative of the present invention in all respects. Various improvements and modifications to the above-described embodiments are possible within the scope of the present invention. For example, at least a portion of the configuration of any of the embodiments may be combined with at least a portion of the configuration of any of the other embodiments. In other words, when implementing the present invention, specific configurations can be appropriately adopted depending on the embodiment. [Example]

[0060] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0061] [1. Examples, Comparative Examples, and Reference Examples] Films were produced in Examples 1 to 6, Comparative Examples 1 to 4, and Reference Examples 1 to 2. The films in Examples 1 to 3 and Comparative Examples 1 and 2 had the structure shown in Fig. 1, and the films in Examples 4 to 6 and Comparative Examples 3 and 4 had the structure shown in Fig. 5. The film in Reference Example 1 had the structure shown in Fig. 1, except that the intermediate layer was replaced with only virgin polyamide resin material, and the film in Reference Example 2 had the structure shown in Fig. 5, except that the intermediate layer was replaced with only virgin polyamide resin material.

[0062] The recycled raw material contained in the intermediate layer of the films of Examples 1 and 4 was designated as recycled raw material 1, the recycled raw material contained in the intermediate layer of the films of Examples 2 and 5 was designated as recycled raw material 2, and the recycled raw material contained in the intermediate layer of the films of Examples 3 and 6 was designated as recycled raw material 3. The recycled raw material contained in the intermediate layer of the films of Comparative Examples 1 and 3 was designated as recycled raw material 4, and the recycled raw material contained in the intermediate layer of the films of Comparative Examples 2 and 4 was designated as recycled raw material 5. Each recycled raw material was obtained from the waste film shown in Figure 4. That is, each recycled raw material was obtained from the waste film in which a polyamide resin layer / printed layer / polyester resin layer were laminated in this order. Recycled raw materials 1 to 5 will be explained next.

[0063] Each of the recycled materials 1 to 3 was obtained through the steps shown in the flowchart in Figure 3. In the process of obtaining recycled materials 1 to 3, the conditions in some steps were different from each other. First, with reference to Figure 3, the conditions common to recycled materials 1 to 3 will be described. In step S200, the opening of the punching mesh of the dry grinder was 10 mm. In step S210, the temperature of the dissolution tank was 170°C. Propylene glycol was used as the dissolving liquid. In step S220, the solution in the dissolution tank was transported to a cooling tank while maintained at 170°C. In step S230, after the solution in the dissolution tank was transported to the cooling tank, the solution in the cooling tank was cooled to 40°C or below. In step S250, the temperature of the hot air blown onto the granules by the fluidized bed dryer was 110°C, and the drying time using the fluidized bed dryer was 60 minutes.

[0064] Next, the conditions for recycled raw materials 1 to 3, which differ from one another, will be explained. In the process for obtaining recycled raw material 1, in step S210, the system was placed under a nitrogen atmosphere and the stirring time was 10 minutes. In the process for obtaining recycled raw material 2, in step S210, the system was placed under air and the stirring time was 10 minutes. In the process for obtaining recycled raw material 3, in step S210, the system was placed under a nitrogen atmosphere and the stirring time was 120 minutes.

[0065] Next, the process for obtaining the recycled raw material 4 will be described. First, fluff was obtained by pulverizing a single-layer film (the film of Reference Example 1) composed only of virgin raw material of polyamide resin. The fluff was then fed into an extruder set at a maximum temperature of 280°C, and melt-kneaded to form strands. The strands were then water-cooled and cut with a cutter to obtain granules. This granule was used as the recycled raw material 4.

[0066] Next, the process for obtaining the recycled raw material 5 will be described. First, fluff was obtained by pulverizing a laminated film (the film of Reference Example 2) in which PET was laminated to a layer composed only of virgin raw material polyamide resin. The fluff was then fed into an extruder set at a maximum temperature of 280°C, and melt-kneaded to form strands. The strands were then water-cooled and cut with a cutter to obtain granules. This granule was used as the recycled raw material 5.

[0067] Table 1 below shows information about the films of Examples 1 to 6, and Table 2 below shows information about the films of Comparative Examples 1 to 4 and Reference Examples 1 to 2. The films of Examples 1 to 6, Comparative Examples 1 to 4, and Reference Examples 1 to 2 were produced by extrusion molding so as to achieve the layer structure of each film. The raw material compositions constituting each layer were fed into an extruder with a barrel temperature of 160 to 260°C, extruded from a multilayer die at 200 to 260°C into sheets with a three-layer or five-layer structure, and cooled and solidified on a take-up roll at 25 to 50°C. Next, the film was longitudinally stretched 1.0 to 3.0 times using a roll stretching machine at 50 to 90°C, and then stretched at a stretch ratio of 3.5 times or more in a tenter transverse stretching machine with a preheating zone of 80 to 100°C, a stretching zone of 80 to 130°C, and a heat setting zone of 150 to 230°C, and then taken up on a winder to produce a polyamide-based multilayer film in which the take-up direction is MD (Machine Direction) and the direction perpendicular to the take-up direction is TD (Transverse Direction).

[0068] [Table 1] [Table 2]

[0069] In each of the films of Examples 1 to 6 and Comparative Examples 1 to 4, when the resin raw material contained in the intermediate layer was taken as 100 parts, the content of recycled polyamide resin raw material was 10 parts, and the content of virgin polyamide resin raw material was 90 parts.

[0070] [2. Various evaluations] The films of Examples 1 to 6, Comparative Examples 1 to 4, and Reference Examples 1 and 2 were evaluated as follows.

[0071] <2-1. Molecular weight area ratio and weight average molecular weight (Mw)> The molecular weight area ratio and weight average molecular weight (Mw) were measured by gel permeation chromatography (GPC). Each value was converted to a standard PMMA value. The molecular weight distribution was calculated as Mw / Mn from the number average molecular weight (Mn) and the weight average molecular weight (Mw). The molecular weight area ratio was obtained by calculating the area ratio of the region with a molecular weight of 500 or less in the molecular weight distribution curve obtained by GPC. The total peak area was the sum of the peak areas in the region from a molecular weight of 0 to the highest molecular weight at which the area becomes 0 at the base of the high molecular weight side.

[0072] <2-2. Impact strength> Impact strength was measured in accordance with JIS-P8134. It was measured using an impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a small ball (1 / 2 inch diameter). The sample size was 100 mm x 100 mm, and for the films of Examples 4 to 6, Comparative Examples 3 and 4, and Reference Example 2, the polyester resin layer surface was set on the side where the small balls were punched. The vibration direction of the arm was aligned with the MD direction of the sample. Measurements were performed with n=5. The temperature and humidity of the device were 10 to 40°C and 35 to 85% RH (but no condensation). The measurement results were evaluated according to the following criteria. A: 0.7J or more B: 0.5J or more, less than 0.7J C: Less than 0.5J

[0073] <2-3. Penetration strength> The puncture strength was measured in accordance with JIS Z-1707. A Strograph (manufactured by Toyo Seiki Seisakusho, Ltd.) was used as the measuring device. For the films of Examples 4 to 6, Comparative Examples 3 and 4, and Reference Example 2, the polyester resin layer surface was set on the side that would be pierced by the needle. Measurements were carried out with n=4. The measurement results were evaluated according to the following criteria. A: 7N or more B: 5N or more, less than 7N C: Less than 5N

[0074] <2-4. Tensile elongation> The film was cut into a strip measuring 10 mm wide x 100 mm long (the lengthwise direction was the same as the measurement direction of the film), and a line was drawn near the center of the lengthwise direction so that the distance between the gauge lines was 40 mm to prepare a measurement sample. The tensile elongation at break of this measurement sample was measured using a tensile tester (Strograph VE1D, manufactured by Toyo Seiki Seisaku-sho, Ltd.) according to a method conforming to JIS-K7127. The measurement ambient temperature was 23°C, the distance between the chucks was 40 mm, the same as the gauge line, and the sample was clamped at the gauge line and pulled at a speed of 200 mm / min until it broke. The tensile elongation at break was calculated from the distance between the chucks before the test and the distance between the chucks at the time of break. The test was performed four times, and the average value was calculated.

[0075] <2-5. Gelboflex Test> Measurements were made using a Gelbo Flex Tester manufactured by Rikagaku Kogyo Co., Ltd. A film bag made into a cylindrical shape with a folded diameter of 150 mm and a length of 300 mm was attached to the Gelbo Flex Tester, and a 440° twist was applied for the first 88.9 cm, followed by a linear horizontal movement for the next 63.5 cm. This was repeated 1000 times at a test speed of 40 times / min under conditions of 25°C and 5°C, and the number of pinholes was then counted using a penetrant solution. The number of pinholes was measured at 300 cm in the center of the sample. 2 The number of pinholes was measured for the three samples, and the average value of the number of pinholes was used as the measurement result.

[0076] <2-6.Young's Modulus> A sample measuring 250 mm (MD) x 5 mm (TD) was cut out from the obtained film. Young's modulus was measured at 23°C using a Strograph VE-1D manufactured by Toyo Seiki Seisaku-sho, Ltd., in accordance with ASTM D882. Young's modulus was measured using four samples, and the average value was calculated.

[0077] <2-7. Haze> The haze value was measured using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.) at a temperature of 23°C according to a method in accordance with JIS Z7136. The haze value was measured using four samples and the average value was calculated. The measurement results were evaluated according to the following criteria. OK: Less than 10.5% NG judgment: 10.5% or more

[0078] <2-8. Glossiness> The obtained film was cut into a sample measuring 100 mm MD x 100 mm TD, and the gloss of the sample was measured at an incident angle of 45° using a VG-2000 model manufactured by Nippon Denshoku Industries Co., Ltd. according to a method in accordance with JIS Z8741.

[0079] <2-9. Color difference> The obtained film was cut into samples measuring MD 100 mm x TD 100 mm, and the L*, a*, and b* values ​​expressed in the L*a*b* color system were measured (N=10) using a color difference meter (Spectrophotometer CM-600d manufactured by Konica Minolta Japan Inc.) and the average value was calculated. From the average L*, a*, and b* values, the color difference (ΔE*ab) was calculated using the following CIE1976 L*a*b* color difference formula. ΔE*ab=[(ΔL*) 2 +(Δa*) 2 +(Δb*) 2 ] 1 / 2

[0080] [3. Evaluation Results] The evaluation results for each of the films of Examples 1 to 6 are shown in Table 3, and the evaluation results for each of the films of Comparative Examples 1 to 4 and Reference Examples 1 and 2 are shown in Table 4.

[0081] [Table 3] [Table 4]

[0082] As shown in Tables 3 and 4, the films of Examples 1 to 6 met the standards sufficient for products in terms of impact strength, puncture strength, and haze. On the other hand, the films of Comparative Examples 1 to 4 did not meet the standards sufficient for products in terms of at least one of impact strength, puncture strength, and haze. [Explanation of symbols]

[0083] 10, 10A recycled film, 11 first adjacent layer, 12 intermediate layer, 13 second adjacent layer, 14 surface layer, 15 adhesive layer, 20 film waste material, 21 polyamide resin layer, 22 printing layer, 23 polyester resin layer.

Claims

1. A recycled film, The present invention has a layer made of a resin raw material including a recycled raw material of polyamide-based resin recovered from a film containing polyamide-based resin and a virgin raw material of polyamide-based resin, In a molecular weight distribution curve for the layer obtained by gel permeation chromatography, the area of ​​a region having a molecular weight of 500 or less is 5.0% or less of the total peak area; The recycled film has an impact strength of 0.5 J or more.

2. the area of ​​the region is 3.0% or less of the total peak area, 2. The recycled film according to claim 1, wherein the impact strength is 0.7 J or more.

3. The recycled film according to claim 1 or 2, wherein the recycled film has a puncture strength of 5.0 N or more.

4. 3. The recycled film according to claim 1, wherein the weight average molecular weight in the molecular weight distribution curve is 45,000 or more.

5. the layer is an intermediate layer, 3. The recycled film of claim 1 or claim 2, further comprising an adjacent layer laminated to at least one of the layers.

6. A step of recovering recycled raw materials of polyamide-based resin from a film containing polyamide-based resin; preparing a virgin raw material of a polyamide-based resin; The method includes a step of producing a recycled film using the recycled raw material and the virgin raw material, A method for producing a recycled film, wherein the polyamide resin is not heated to 200°C or higher in the step of recovering the recycled raw material.

7. The method for producing a recycled film according to claim 6 , wherein the step of recovering the recycled raw material includes a step of granulating a polyamide-based resin.

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