Recycled-resin composition and method for producing recycled-resin composition

Abstract

Provided is a technique capable of producing a film having sufficient impact resistance and a good appearance from a recycled-resin composition including a recycled material.　The recycled-resin composition comprises a resin-including recycled material and an antioxidant and has an oxidation induction time, as determined at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018, in the range of 18 minutes to 50 minutes inclusive.

Description

Recycled resin composition, method for producing recycled resin composition

[0001] The present disclosure relates to a recycled resin composition and a method for producing the recycled resin composition.

[0002] This application claims priority based on Japanese Patent Application No. 2025-017012 filed on February 4, 2025, and Japanese Patent Application No. 2025-017018 filed on February 4, 2025, and incorporates by reference all the descriptions contained in the above Japanese applications.

[0003] Generally, plastic films are lightweight, chemically stable, easy to process, flexible and have high strength, and can be mass-produced, and are used in various applications. Examples of their uses include packaging materials for food products, pharmaceuticals, etc., drip packs, shopping bags, posters, tapes, optical films used in liquid crystal TVs, etc., protective films, window films laminated to windows, plastic greenhouses, building materials, and so on, covering a wide range. Specific materials for plastic films include, for example, thermoplastic resins such as polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polycarbonate, polyamide, polyethylene terephthalate, and polybutylene terephthalate, and thermosetting resins such as epoxy resins, polyurethanes, and polyimides.

[0004] In recent years, due to the increasing environmental awareness, the recycling of plastic products has been expected. Among them, as material recycling, post-industrial recycling (abbreviation: PIR) that recovers waste materials during manufacturing and reuses them for the same product or other products, or post-consumer recycling (abbreviation: PCR) that recovers post-consumer plastic products and reuses this plastic for the same product or other products is required. Patent Document 1 below discloses a technique related to a sealant film containing recycled polyethylene resin. Specifically, Patent Document 1 describes that as recycled polyethylene, those obtained by subjecting those recovered from used polyethylene molded articles or waste materials during their manufacturing to various treatments such as pulverization, washing filtration, and extraction can be used.

[0005] International Publication No. 2022 / 124229

[0006] Generally, resin films are manufactured by forming a film from molten resin using methods such as extrusion molding and casting. When recycling waste materials generated during the manufacture of such resin films, or recycled resin films, the recycled resin is subjected to many heat processes, leading to degradation. It is difficult to obtain resin films with excellent physical properties from degraded resin. Furthermore, resin films containing recycled materials are required to have a good appearance with a sufficiently small amount of yellowing or foreign matter.

[0007] This disclosure is made in view of the above circumstances and aims to provide a technology that enables the production of a film having sufficient impact resistance and a good appearance from a recycled resin composition containing recycled materials.

[0008] Some aspects of this disclosure provide the following [1] to

[24] .

[0009] [1] A recycled resin composition comprising a recycled material containing resin and an antioxidant, wherein the oxidation induction time, measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018, is in the range of 18 minutes to 50 minutes.

[0010] [2] The recycled resin composition according to [1] above, wherein the antioxidant comprises at least one selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants.

[0011] [3] The recycled resin composition according to [1] or [2] above, wherein the antioxidant comprises a phenolic antioxidant and a phosphorus-based antioxidant, the phenolic antioxidant comprises pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and the phosphorus-based antioxidant comprises tris(2,4-di-t-butylphenyl)phosphite.

[0012] [4] The recycled resin composition according to [1] or [2] above, wherein the antioxidant comprises a phosphoric acid-based antioxidant having a phenol skeleton.

[0013] [5] The recycled resin composition according to [4] above, wherein the phosphoric acid-based antioxidant comprises 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosfepin-6-yl)oxy]propyl]-2-methylphenol.

[0014] [6] The recycled resin composition according to any one of [1] to [5] above, wherein the total content of antioxidants in the recycled resin composition is 0.05% by mass or more and 1% by mass or less.

[0015] [7] The recycled resin composition according to any one of [1] to [6] above, wherein the recycled material contains a polyolefin resin as the main resin, and the proportion of the polyolefin resin in the recycled material is 80% by mass or more.

[0016] [8] The recycled resin composition according to any one of [1] to [7], further comprising a virgin resin of the same type as the resin contained in the recycled material.

[0017] [9] When the recycled resin composition is molded into pellets, the melt tension obtained by measuring at a temperature of 230°C and a take-up speed of 200 mm / second is in the range of 0.03 N to 0.12 N, and the maximum area of ​​domains observed in a cross-section parallel to the molding direction is 100 μm². ２ The recycled resin composition described in any of the above [1] to [8], which is as follows:

[0018]

[10] A recycled resin composition according to any one of [1] to [9] above, comprising the recycled material in a proportion of 10% by mass or more.

[0019]

[11] The recycled resin composition according to any one of [1] to

[10] above, wherein the recycled material is a post-industrial recycled material.

[0020]

[12] The recycled resin composition according to any one of [1] to

[10] above, wherein the recycled material is a post-consumer recycled material.

[0021]

[13] The recycled material is a recycled resin composition according to any one of [1] to

[12] above, wherein the oxidation induction time measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018 is 15 minutes or less.

[0022]

[14] A film formed from any of the recycled resin compositions described in [1] to

[13] above.

[0023]

[15] A laminate comprising the film described in

[14] above.

[0024]

[16] A packaging material comprising the laminate described in

[15] above.

[0025]

[17] A packaging bag made by forming a bag from the packaging material described in

[16] above.

[0026]

[18] A method for producing a film, comprising extruding a recycled resin composition according to any one of [1] to

[13] above to obtain a film.

[0027]

[19] A method for producing a recycled resin composition, comprising obtaining a recycled material containing resin, and blending the recycled material with other components including an antioxidant to obtain a recycled resin composition, wherein the recycled material and the other components are blended such that the oxidation induction time of the recycled resin composition, as measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018, is 18 minutes or more and 50 minutes or less.

[0028]

[20] A method for producing the recycled resin composition according to

[19] , comprising: preparing one or more mixtures containing the recycled material and the other components; measuring the oxidation induction time for each of the one or more mixtures; determining the proportions of the recycled material and the other components based on the measurement results; and obtaining the recycled resin composition.

[0029]

[21] A method for producing the recycled resin composition according to

[19] or

[20] , wherein the recycled material has an oxidation induction time of 15 minutes or less, as measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018.

[0030]

[22] A method for producing a recycled resin composition according to any one of

[19] to

[21] , further comprising extruding a first resin composition containing the resin and an antioxidant to obtain a film prior to obtaining the recycled material, and obtaining at least a portion of the film as the recycled material.

[0031]

[23] The recycled resin composition is melt-extruded to obtain strands, and the strands are cut to obtain pellets, wherein the obtained pellets have a melt tension obtained by measuring at a temperature of 230°C and a take-up speed of 200 mm / second in the range of 0.03 N to 0.12 N, and the maximum area of ​​domains observed in a cross-section parallel to the molding direction is 100 μm². ２ A method for producing a recycled resin composition according to any one of

[19] to

[22] above, comprising melt-extruding the recycled resin composition so that the following can be obtained.

[0032]

[24] A method for producing a film, comprising extruding the recycled resin composition produced by any of the manufacturing methods described in

[19] to

[23] above to obtain a film.

[0033] This disclosure provides a technology that enables the production of a film having sufficient impact resistance and a good appearance from a recycled resin composition containing recycled materials.

[0034] Figure 1 is a perspective view showing an example of the structure of a pellet. Figure 2 is a scanning electron microscope image of a cross-section of the pellet. Figure 3 is a cross-sectional view showing an example of the structure of a film obtained by molding a recycled resin composition. Figure 4 is a cross-sectional view showing an example of the structure of a film obtained using a recycled resin composition. Figure 5 is a cross-sectional view showing an example of the structure of a film obtained using a recycled resin composition. Figure 6 is a cross-sectional view showing an example of the structure of a laminate containing a film obtained using a recycled resin composition. Figure 7 is a cross-sectional view showing an example of the structure of a laminate containing a film obtained using a recycled resin composition. Figure 8 is a cross-sectional view showing an example of the structure of a laminate containing a film obtained using a recycled resin composition. Figure 9 is a cross-sectional view showing an example of the structure of a laminate containing a film obtained using a recycled resin composition. Figure 10 is a cross-sectional view showing an example of the structure of a laminate containing a film obtained using a recycled resin composition.

[0035] Embodiments of the present disclosure will be described below with reference to the drawings. The embodiments described below are more specific to any of the above aspects. The matters described below can be incorporated into each of the above aspects individually or in combination.

[0036] Furthermore, the embodiments described below are illustrative of configurations for embodying the technical concept of this disclosure, and the technical concept of this disclosure is not limited by the following specific examples. Various modifications can be made to the technical concept of this disclosure within the technical scope defined by the claims described herein.

[0037] <1> Recycled resin composition The recycled resin composition according to this embodiment contains a recycled material containing resin and an antioxidant, and the oxidation induction time measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018 is 18 minutes or more and 50 minutes or less.

[0038] <1.1> Recycled Material As the recycled material, for example, a post-consumer recycled (PCR) material or a post-industrial recycled (PIR) material can be used. Here, the PCR material is a recycled material made from post-consumer plastic products collected from the market. For example, it is one or more of beverage, detergent or seasoning bottles and packaging bags, food containers for bento or cup noodles, food packaging bags and garbage bags, and plastic products such as hangers, stationery, daily necessities, household appliances and toys. The PIR material is a recycled material made from waste generated during the manufacture of plastic products. For example, it is one or more of defective products that do not become products discharged from the factory, end materials generated during the process of making products, and plastic products used for transportation and packaging.

[0039] The PIR material has less dust adhesion and less variation in composition compared to the PCR material. Therefore, when the PIR material is used, the quality of the recycled material and the recycled resin composition is more stable than when the PCR material is used.

[0040] When using the PCR material, since there is a possibility that dirt adheres to the surface during use, it may be pre-washed with a surfactant, an alkaline solution, an organic solvent, etc.

[0041] In any case of using either material, from the viewpoint that the recycled material can reduce the content of the auxiliary constituent materials or additives described later and suppress the generation of foreign matters, it is preferable that the recycled material has undergone purification steps such as pulverization, washing, filtration, extraction, chemical treatment, specific gravity separation, etc.

[0042] The recycled material may be pelletized. For example, the collected material may be finely cut, extruded by an extruder, cut by a pelletizer, and formed into pellets and used as the recycled material.

[0043] Examples of the resin contained in the recycled material include thermoplastic resins, thermosetting resins, and cured products thereof (including cross-linked bodies). The recycled material may be a single-component system containing a single resin or a multi-component system containing a plurality of resins.

[0044] Examples of the thermoplastic resin include polyolefin resins, polystyrene resins, acrylic resins, polycarbonate resins, polyester resins, polyamide resins, etc. Examples of the thermosetting resin include epoxy resins, polyurethane resins, polyimide resins, etc.

[0045] Examples of the polyolefin resin include polyethylene resins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and ethylene-α-olefin copolymers, and polypropylene resins such as homopolypropylene (PP), block polypropylene, random polypropylene, and propylene-α-olefin copolymers. Note that the recycled material may contain two or more polyolefin resins.

[0046] The recycled material may be a single material or may contain a plurality of materials. When the recycled material contains a plurality of materials, the material with the largest proportion (by mass) among the constituent materials is called the main constituent material, and the other materials are called sub-constituent materials. Examples of the main constituent material include the resins described above.

[0047] The types of resins contained in the recycled material can be confirmed by measurement using a microscopic infrared spectrophotometer or the like.

[0048] The content of the resin contained in the recycled material can be measured by using a known method such as an extraction method.

[0049] Examples of the sub-constituent materials of the recycled material containing a plurality of materials include inks, adhesives, thermoplastic resins other than the main constituent material, aluminum, alumina, silica, etc. The sub-constituent materials may contain two or more of these. Also, the sub-constituent materials may be mixed and dispersed in the main constituent material or may be contained in another layer laminated on the layer containing the main constituent material.

[0050] From the viewpoint of use in sealant layers or adhesion to other layers, the recycled material may contain polyolefin resin as the main resin. In this case, the proportion of polyolefin resin in the recycled material may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more. Also, in this case, the proportion of polyolefin resin in the recycled resin composition may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more. Furthermore, even when manufacturing a stretch film using the recycled resin composition, it is preferable that the recycled material contains polyolefin resin as the main resin.

[0051] The recycled material may contain, in addition to the polyolefin resin, other resins other than polyolefin resins. Examples of other resins include polyester resins and polyamide resins. The total proportion of resins other than polyolefin resins in the recycled material may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 1% by mass or less. Furthermore, the total proportion of resins other than polyolefin resins in the recycled resin composition may be 20% by mass or less, 10% by mass or less, 5% by mass or less, or 1% by mass or less.

[0052] Recycled materials may contain antioxidants. Resin compositions used in the manufacture of plastic products typically contain antioxidants in addition to the resin. For example, this resin composition contains at least one of a radical scavenger, such as a phenolic antioxidant, and a peroxide decomposer, such as a phosphorus-based antioxidant, as antioxidants. Radical scavengers trap alkyl radicals or peroxy radicals generated by oxidative degradation of the resin during heat treatment in the manufacture of plastic products by reacting with them, thereby suppressing chain reactions caused by radicals. Peroxide decomposers decompose peroxides that can generate the above radicals by reacting with them, thereby suppressing the generation of radicals. At least a portion of these antioxidants is oxidized during heat treatment in the manufacture of plastic products, thereby preventing oxidation of the resin. At least a portion of the antioxidants is consumed during the above heat treatment, but not all of them are consumed. Recycled materials may contain these unconsumed antioxidants.

[0053] Recycled materials may contain only one type of antioxidant, or two or more types. Examples of antioxidants that may be included in recycled materials are those similar to those mixed with recycled materials, and are described in detail below.

[0054] From the viewpoint of reducing environmental impact, the proportion of recycled material in the recycled resin composition is preferably in the range of 10% by mass or more and 100% by mass or less, and more preferably in the range of 50% by mass or more and 100% by mass or less.

[0055] <1.2> Antioxidant Recycled Resin Composition contains an antioxidant in addition to the recycled material described above. That is, the recycled resin composition is composed by mixing an antioxidant with the recycled material. The recycled resin composition may contain one type of antioxidant as the antioxidant to be mixed with the recycled material described above, or it may contain two or more types of antioxidants.

[0056] The antioxidant to be mixed with the recycled material is, for example, at least one of a radical scavenger and a peroxide decomposer. As a radical scavenger, for example, a phenolic antioxidant can be used. As a peroxide decomposer, for example, a phosphorus-based antioxidant can be used.

[0057] Examples of phenolic antioxidants include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], 3,9- Bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane), 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid), 4-[[4,6-bis(octylthio)-1,3,5-triazine-2-yl]amino]-2,6-di-tert-butylphenol, diethyl[[3,5-bis(1,1 Examples include dimethylethyl-4-hydroxyphenyl]methyl phosphate, 3,3',3'',5,5',5'', hexa-t-butyl-a,a',a'', (mesitylene-2,4,6-triyl)tri-p-cresol, hexamethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. Commercially available phenolic antioxidants include Irganox® 1010 (manufactured by BASF Japan Ltd.), Irganox® 1076 (manufactured by BASF Japan Ltd.), Irganox® 1098 (manufactured by BASF Japan Ltd.), Irganox® 565 (manufactured by BASF Japan Ltd.), Cyanox 1790 (manufactured by Solvay), and Adeka Stab® AO-80 (manufactured by ADEKA Corporation).

[0058] Phosphorus-based antioxidants include tris(2,4-di-t-butylphenyl) phosphite, and, if necessary, trisnonylphenyl phosphites such as 6,6',6"-[nitrilotris(ethyleneoxy)]tris(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepine), bis(2,4-di-t-butyl-6-methylphenyl)ethyl phosphite, tris(mono or dinonylphenyl) phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-diphosphite, bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphorous acid, tetrakis(2,4-di-t-butylphenyl)[1,1-biphenyl]-4,4'-diylbisphosphine Examples include ionite and bis(2,4-di-t-butylphenyl)pentaerythritol phosphite. Commercially available phosphorus-based antioxidants include Irgaphos® 168 (manufactured by BASF Japan Ltd.), Irgaphos® 12 (manufactured by BASF Japan Ltd.), Irgaphos® 38 (manufactured by BASF Japan Ltd.), Adekastab® 329K (manufactured by ADEKA Corporation), Adekastab® PEP36 (manufactured by ADEKA Corporation), Adekastab® 2112 (manufactured by ADEKA Corporation), Hostanox® P-EPQ (manufactured by Clariant Chemicals Co., Ltd.), and GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.), and Sumirizer® GP (manufactured by Sumitomo Chemical Co., Ltd.).

[0059] Phenolic antioxidants and phosphorus-based antioxidants may be used individually or in combination of multiple types. When the antioxidant contains both a phenolic antioxidant and a phosphorus-based antioxidant, from the viewpoint of making the polymer less susceptible to degradation due to the synergistic effect of the two, it is preferable that the amount of the phenolic antioxidant be in the range of 25% to 60% by mass and the amount of the phosphorus-based antioxidant be in the range of 40% to 75% by mass, based on the total amount of antioxidants. To make it easier to obtain a synergistic effect, it is preferable that the antioxidant contains pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (e.g., Irganox® 1010) and tris(2,4-di-t-butylphenyl) phosphite (e.g., Irgaphos® 168).

[0060] The antioxidant may be a phosphorus-based antioxidant having a phenol skeleton. An example of a phosphorus-based antioxidant having a phenol skeleton is 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosfepin-6-yl)oxy]propyl]-2-methylphenol, and a commercially available product is Sumirizer® GP (manufactured by Sumitomo Chemical Co., Ltd.). Note that phosphorus-based antioxidants having a phenol skeleton also fall under the category of phenol-based antioxidants. Phosphorus-based antioxidants having a phenol skeleton can exhibit both the effects of phenol-based antioxidants (e.g., the effect of stabilizing polymers by scavenging radicals) and phosphorus-based antioxidants (e.g., the effect of decomposing unstable peroxides into stable compounds), and may therefore be used alone.

[0061] The total antioxidant content in the recycled resin composition, that is, the ratio of the sum of the antioxidants contained in the recycled material and the antioxidants mixed with the recycled material to the recycled resin composition, may be within the range of 0.05% by mass to 1% by mass. Having the total antioxidant content in the recycled resin composition within this range allows for an appropriate oxidation induction time for the recycled resin composition. Specifically, as will be described in more detail later, the oxidation induction time of the recycled resin composition, measured at 220°C under an oxygen atmosphere in accordance with JIS K 7351:2018, can be within the range of 18 minutes to 50 minutes. Furthermore, the total antioxidant content may be within the range of 0.1% by mass to 0.95% by mass, or within the range of 0.35% by mass to 0.9% by mass. Note that "antioxidants contained in the recycled material" can also be rephrased as antioxidants derived from the recycled material.

[0062] <1.3> The virgin resin recycled resin composition may further contain virgin resin of the same type as the resin contained in the recycled material. Examples of virgin resins include those of the same type as the resins listed as contained in the recycled material. Note that polyethylene 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 can be considered as the same type of resin.

[0063] The recycled resin composition may contain multiple polyethylene-based resins with different melting points, melt flow rates (MFRs), etc. The resins contained in the recycled material and the virgin resins may be the same, the same and different, or partially the same and the remainder the same and different. The virgin resins can be used individually or in combination of two or more.

[0064] When a recycled resin composition contains virgin resin, the proportion of the resin contained in the recycled material to the total of the resin contained in the recycled material and the virgin resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. From the viewpoint of recycling, it is preferable to increase this proportion, and it is preferable that the resin in the recycled resin composition does not contain virgin resin and consists only of the resin contained in the recycled material. However, from the viewpoint of obtaining desired physical properties in a film manufactured using the recycled resin composition, it is preferable to decrease this proportion, preferably 90% by mass or less, more preferably 75% by mass or less, and even more preferably 55% by mass or less.

[0065] <1.4> Additives The recycled resin composition may optionally contain additives such as compatibilizers, nucleating agents, reinforcing fillers, heat stabilizers, weathering agents, light stabilizers, plasticizers, ultraviolet absorbers, antistatic agents, flame retardants, flame retardant enhancers, slip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, dispersants, copper damage inhibitors, neutralizing agents, anti-foaming agents, weld strength improvers, natural oils, synthetic oils, and waxes. Additives may be used individually or in combination of two or more.

[0066] 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).

[0067] Examples of heat stabilizers include hindered amine compounds.

[0068] Examples of ultraviolet absorbers include benzophenone compounds, benzotriazole compounds, and benzoate compounds.

[0069] Examples of antistatic agents include nonionic compounds, cationic compounds, and anionic compounds.

[0070] Examples of flame retardants include halogen compounds, phosphorus compounds, nitrogen compounds, inorganic compounds, boron compounds, silicone compounds, sulfur compounds, and red phosphorus compounds.

[0071] Examples of flame retardant additives include antimony compounds, zinc compounds, bismuth compounds, magnesium hydroxide, and clayey silicates.

[0072] Examples of antiblocking agents include acrylic particles, styrene particles, styrene-acrylic particles and their crosslinked products, polyurethane particles, polyester particles, silicone particles, fluorine particles, copolymers thereof, clay compound particles such as zeolite, pyrophyllite, talc, smectite, vermiculite, mica, chlorite, kaolin minerals and sepiolite, oxide particles such as silica, titanium oxide, alumina, silica-alumina, zirconia, zinc oxide and strontium oxide, hydroxide particles such as aluminum hydroxide and strontium hydroxide, carbonate particles such as strontium carbonate, chloride particles such as strontium chloride, sulfate particles such as strontium sulfate, nitrate particles such as strontium nitrate, and glass particles.

[0073] <1.5> Oxidation Induction Time The recycled resin composition of this embodiment has an oxidation induction time measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018, which is in the range of 18 minutes to 50 minutes. The recycled resin composition may also have an oxidation induction time in the range of 20 minutes to 40 minutes.

[0074] The oxidation induction time mentioned above represents the antioxidant capacity of the antioxidant contained in the recycled resin composition. The antioxidant capacity of the antioxidant also depends on the amount of antioxidant contained in the composition. As mentioned above, the amount of antioxidant contained in the recycled resin composition is the total amount of antioxidant contained in the composition, that is, the proportion of the total amount of antioxidant contained in the recycled material and the amount of antioxidant mixed with the recycled material in the composition. If the oxidation induction time is too short, the deterioration of the resin cannot be sufficiently suppressed during the heat treatment performed when manufacturing a film from the recycled resin composition, making it difficult to obtain a film with excellent physical properties such as impact resistance. In the recycled resin composition of this embodiment, by having the above oxidation induction time in the range of 18 minutes to 50 minutes, a film with excellent physical properties such as impact resistance can be obtained.

[0075] Furthermore, it is desirable that films obtained from recycled resin compositions have a sufficiently low number of yellowings or foreign matter particles and possess a good appearance. The yellowing or foreign matter particles that occur in the film are thought to be caused by charring of the resin or resin gel resulting from thermal degradation due to insufficient antioxidants in the recycled resin composition. Conversely, it is also thought that decomposition products produced when there are too many antioxidants in the recycled resin composition, causing the residual antioxidants themselves to degrade due to thermal degradation, may also be a cause.

[0076] The oxidation induction time of recycled resin compositions also depends on the antioxidant content in the composition. Specifically, if the antioxidant content is low, the oxidation induction time tends to be short, resulting in accelerated thermal degradation and the formation of resin charring or resin gel-like foreign matter. Conversely, if the antioxidant content is high, the oxidation induction time becomes too long, resulting in yellowing due to thermal degradation of the residual antioxidant, or the formation of decomposition products as foreign matter. Such yellowing or foreign matter impairs the appearance of the film.

[0077] Therefore, from the viewpoint of obtaining a film with a good appearance and a sufficiently small amount of yellowing or foreign matter, it is preferable to ensure that the oxidation induction time of the recycled resin composition is within an appropriate range. In the recycled resin composition of this embodiment, by having the above-mentioned oxidation induction time in the range of 18 minutes to 50 minutes, the occurrence of yellowing or foreign matter is effectively suppressed, and a film with a good appearance can be obtained.

[0078] Furthermore, the oxidation induction time of the recycled resin composition can be controlled to an appropriate range by adjusting the type of antioxidant in the composition or the amount of that antioxidant present.

[0079] Furthermore, in the recycled resin composition of this embodiment, the oxidation induction time of the recycled material contained in the composition may be 15 minutes or less. The oxidation induction time of the recycled material is measured at 220°C under an oxygen atmosphere in accordance with JIS K 7351:2018, similar to the oxidation induction time of the recycled resin composition described above. If the oxidation induction time of the recycled material is 15 minutes or less, for example, if the recycled resin composition contains a large amount of antioxidant, discoloration or the generation of foreign matter caused by the antioxidant can be suppressed more effectively, making it easier to obtain a film with a good appearance.

[0080] The oxidation induction time described above can be measured, for example, using a chemiluminescence analyzer (Tohoku Electronics Industry Co., Ltd.: Model No.: CLA-FS54) in accordance with the following procedure compliant with JIS K 7351:2018. First, a pelletized recycled resin composition is prepared as the measurement sample. Next, a certain amount of the measurement sample is weighed into an aluminum sample container with an inner diameter between 20 mm and 30 mm, and the oxidation induction time is measured by observing the change in emission intensity using a chemiluminescence analyzer. The measurement conditions are as follows: the mass of the measurement sample is 0.2 g, the temperature is kept constant at 220°C, the atmosphere is an oxygen atmosphere, the oxygen flow rate is 50 mL / min, the exposure time is 1 second, and the measurement time is 7 hours.

[0081] A chemiluminescence analyzer is a measuring device that detects the amount of chemiluminescence in a sample, and the oxidation induction time is the time until the amount of chemiluminescence increases significantly when measured under an oxygen atmosphere. For example, in the case of a resin composition containing a polyolefin resin and an antioxidant, the oxidation induction time is the time from the start of heating until the effect of the antioxidant, etc., on suppressing chemiluminescence wears off, and the longer this time, the less easily the polyolefin resin tends to oxidize.

[0082] <2> Method for Manufacturing Recycled Resin Composition The above recycled resin composition can be manufactured, for example, by the following method. That is, the method for manufacturing the recycled resin composition includes obtaining a recycled material containing resin, and blending the recycled material with other components including an antioxidant to obtain a recycled resin composition, wherein the recycled material and other components are blended so that the oxidation induction time, measured at 220°C under an oxygen atmosphere in accordance with JIS K 7351:2018 for recycled resin compositions, is 18 minutes or more and 50 minutes or less. Each step will be described in detail below.

[0083] First, recycled material containing resin is obtained. For example, prior to obtaining the recycled material, a first resin composition containing resin and an antioxidant is extruded to obtain a film. Then, at least a portion of this film is obtained as recycled material.

[0084] Furthermore, for example, when collecting plastic waste materials to obtain recycled materials, the collected waste materials are washed and crushed. Subsequently, if necessary, the crushed material may be subjected to chemical separation treatment to separate it by resin type, or to stripping and deinking treatment to remove the printed layer, or both of these treatments may be performed.

[0085] Next, the recycled material is blended with other components, including an antioxidant, to obtain a recycled resin composition containing the recycled material and the antioxidant. At this time, the recycled resin composition obtained is prepared so that the oxidation induction time, measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018, falls within the above range. Here, "other components" means components other than the recycled material and include at least an antioxidant. Furthermore, the other components may further include, in addition to the antioxidant, at least one of the virgin resin and additives mentioned above.

[0086] Specifically, this is done by considering the type and content of resins and antioxidants contained in the recycled material, and the type and amount of antioxidants added in other components that are mixed with the recycled material, and adjusting the mixing amount and mixing ratio of the recycled material and other components that contain antioxidants. In this case, if necessary, the other components mixed with the recycled material may contain virgin resin of the same type as the resin contained in the recycled material, and the content thereof (the amount of virgin resin added to be mixed with the recycled material) may be adjusted.

[0087] Prior to preparing the recycled resin composition so that the oxidation induction time is within the above range, it is preferable to prepare one or more mixtures containing recycled material and other components including antioxidants, measure the oxidation induction time for each of the one or more mixtures, and determine the blending of recycled material and other components in the recycled resin composition based on these measurement results. "Determining the blending" means determining the types of recycled material and other components including antioxidants, their respective amounts, blending ratios, etc.

[0088] For example, the oxidation induction time for the above mixture is measured under the same conditions as the oxidation induction time for the recycled resin composition. In this case, if the oxidation induction time obtained for a certain mixture falls within the range described above for the recycled resin composition, the blend of recycled material and other components in that mixture, or a similar blend, can be determined as the blend for the recycled resin composition. Furthermore, if the oxidation induction time is measured for two or more mixtures that differ only in the amount of antioxidant added (the amount of antioxidant mixed with the recycled material), the amount of antioxidant added to achieve the target oxidation induction time can be interpolated or extrapolated from the relationship between the amount of antioxidant added and the oxidation induction time.

[0089] The measurement of oxidation induction time for a mixture may be performed under different conditions than those used for the measurement of oxidation induction time for the recycled resin composition. In this case, the relationship between the oxidation induction time obtained for the recycled resin composition under the above-described measurement conditions and the oxidation induction time obtained under other measurement conditions should be obtained in advance.

[0090] The recycled material used in the preparation of the above mixture is, for example, obtained from recycled material used in the manufacture of recycled resin compositions.

[0091] The recycled material used to prepare the above mixture is, in other examples, the same type of recycled material used to manufacture the recycled resin composition. For example, if the recycled material is PIR material, the variation in the composition of the PIR material supplied from the factory is small. Therefore, even if the recycled material used to prepare the above mixture is different from the recycled material used to manufacture the recycled resin composition, as long as those recycled materials are, for example, PIR material supplied from the same factory, the difference in their compositions will be small. Thus, the formulation in the recycled resin composition can be determined by measuring the oxidation induction time of the mixture. Furthermore, even if the recycled material is PCR material, if it is known that the recycled material used to manufacture the recycled resin composition has approximately the same composition as the recycled material used to prepare the above mixture, the formulation in the recycled resin composition can be determined by measuring the oxidation induction time of the mixture.

[0092] When recycled resin compositions are used in film molding, handling is improved if the recycled resin composition is in pellet form. Therefore, it is preferable to process the recycled resin composition into pellet form. Possible manufacturing methods include, for example, dry blending in a blender and then pressing to form pellets, or extrusion melt molding using a single-screw or twin-screw extruder to form a string and then cutting it into pellets. Furthermore, from the viewpoint of dispersibility of antioxidants, virgin resins, etc., it is preferable to manufacture the recycled resin composition by extrusion molding, which can be expected to provide high dispersibility, and manufacturing using a twin-screw extruder is even more preferable.

[0093] <3> Recycled resin composition pellets As described above, when a recycled resin composition is used in the manufacture of a film, the recycled resin composition may be molded into pellets from the viewpoint of ease of handling.

[0094] In recycled resin compositions, recycled materials often contain a mixture of various resins, making it difficult to achieve uniform melt properties (fluidity). Therefore, even if a film is formed using a recycled resin composition containing recycled materials, the mechanical strength of the film may not be sufficient. For example, stretch film, which is wrapped around materials for fixing or protection during transportation, has a small thickness, so if the uniformity of the melt properties during film formation is low, it is prone to breakage or punctures during use. For this reason, it is currently difficult to use recycled resin in the manufacture of stretch film. For this reason, it is desirable to be able to manufacture films using pelletized recycled resin compositions with excellent mass productivity, even when the film thickness is reduced.

[0095] Therefore, when the recycled resin composition of this embodiment is molded into pellets, the melt tension obtained by measuring at a temperature of 230°C and a take-up speed of 200 mm / second is in the range of 0.03 N to 0.12 N, and the maximum area of ​​domains observed in a cross-section parallel to the molding direction is 100 μm². ２ The following is preferable:

[0096] With pellets of such recycled resin composition, it is possible to manufacture films with sufficient impact resistance and a good appearance using these pellets, and even when the thickness of the film is reduced, it is possible to manufacture it with excellent mass productivity.

[0097] Figure 1 is a perspective view showing an example of a pellet, and also a diagram showing the molding direction. The pellet 100 is made by molding a recycled resin composition into pellets, and contains recycled resin. The melt tension of the pellet 100, obtained by measuring at a temperature of 230°C and a take-up speed of 200 mm / second, is in the range of 0.03 N to 0.12 N.

[0098] The melt tension is a value obtained by measurement using an apparatus comprising, for example, a heated cylinder equipped with a capillary die, a take-up roller that takes up the strand discharged from the cylinder via the capillary die, a fixed pulley between the capillary die and the take-up roller on which the strand is stretched to a wheel, a movable pulley between the capillary die and the fixed pulley on which the wheel is suspended from the strand, and a tension measuring cell connected to the shaft of the movable pulley. The heated cylinder equipped with the capillary die is one described in JIS K7199:1999. An example of this apparatus is the Rheograph 20 capillary rheometer manufactured by GOTTFERT.

[0099] In this melt tension measurement, pellets are introduced into a cylinder, the temperature is set to 230°C, and the molten resin is extruded from a capillary die. The capillary die used has an inner diameter of 2 mm and a length of 20 mm. The extrusion speed is set to 0.436 mm / second. The strand obtained from this extrusion is then taken up at a take-up speed of 200 mm / second, and the tension is measured over several seconds. The average tension during this period is then calculated. This average tension is then obtained as the melt tension.

[0100] If the melt tension is too low, the molten resin is difficult to stretch during the formation of the film or the recycled resin-containing layer that makes up the film, making it difficult to obtain a layer of uniform thickness. Conversely, if the melt tension is too high, the resin film or the recycled resin-containing layer that makes up the film is prone to breakage, making continuous film formation difficult. On the other hand, when the melt tension is of an appropriate size, that is, when the melt tension of the pellet 100 is in the range of 0.03 N to 0.12 N, the molten resin can be sufficiently stretched without breakage, even if the thickness of the resin film or the recycled resin-containing layer that makes up the film is reduced.

[0101] Figure 2 is a scanning electron microscope image showing a cross-section of the pellet. In the pellet 100, the maximum size of the domain 102 observed in a cross-section parallel to the molding direction D is 100 μm.２ The following applies: Pellet 100 can be obtained by cutting the strand. Therefore, pellet 100 has a roughly columnar shape, for example, a roughly cylindrical shape or a roughly elliptical shape. Accordingly, the forming direction D of pellet 100 (the length direction of the strand) is the height direction of the columnar body such as the cylindrical body and the elliptical body, i.e., the direction indicated by the arrow. Note that this forming direction D is the left-right direction in Figure 2.

[0102] When a cross-section of the pellet 100 parallel to the molding direction D is observed with a scanning electron microscope, an image can be obtained showing that domains 102 are scattered within the main resin 101, as shown in Figure 2. Here, the "main resin" is the resin that has the highest content in the pellet 100 and forms the continuous phase. The "domains" are made of resins different from the main resin (not limited to thermoplastic resins, but also including thermosetting resins such as adhesives) and are dispersed lumps within the continuous phase.

[0103] Domain 102 is made of a different material from the main resin 101. Therefore, the main resin 101 and domain 102 have different melt viscosities. If the maximum area of ​​domain 102 is too large, the flow of the molten resin is inhibited, which can easily result in film formation defects such as uneven thickness or the formation of pores. On the other hand, if the maximum area of ​​domain 102 is small, i.e., the maximum of domain 102 is 100 μm. ２ In the following cases, the flow of the molten resin is not inhibited, and therefore, a layer with a uniform thickness and no pores can be obtained.

[0104] Thus, by using the pellets 100 having the above characteristics, it becomes possible to manufacture films using pellets containing recycled resin with excellent mass productivity, even when the thickness of the film is reduced.

[0105] <4> Method for manufacturing pellets Pellets of the recycled resin composition described above (for example, the pellets shown in Figures 1 and 2) can be manufactured by melting the obtained recycled resin composition and molding it into pellets. That is, the method for manufacturing pellets includes obtaining a recycled material containing resin, blending the recycled material with other components including an antioxidant to obtain a recycled resin composition, and further including melt-extruding the recycled resin composition to obtain strands, and cutting the strands to obtain pellets.

[0106] In this manufacturing method, when selecting the recycled resin composition and performing melt extrusion, the resulting pellets 100 are obtained in such a way that they satisfy the above-mentioned requirements regarding melt tension and maximum domain area. Specifically, the resulting pellets 100 have a melt tension measured at a temperature of 230°C and a take-up speed of 200 mm / second that is in the range of 0.03 N to 0.12 N, and the maximum area of ​​the domains 102 observed in a cross-section parallel to the molding direction is 100 μm². ２ Perform the following steps to obtain the following:

[0107] The melt tension can be kept within the above range by adjusting the composition of the recycled resin composition. Furthermore, the following means can be used to reduce the maximum area of ​​domain 102. Preferably, a combination of the following means is used. Note that the following means are merely examples, and measures that lead to a reduction in the size and aspect ratio of domain 102 are not limited to those below. (1) Reduce the proportion of recycled resin in the pellet 100. (2) Increase the proportion of the resin with the largest content in the pellet 100. (3) Increase the screw rotation speed of the extruder. (4) Use an extruder die in which the diameter decreases gradually from the inlet to the outlet of the molten resin, thereby creating a configuration that makes it difficult for tensile stress to be applied to the molten resin or strand. (5) Manufacture pellets 100 from molten resin produced by melting and kneading pellets produced without using virgin resin again using a twin-screw extruder. (6) A pellet manufactured without using virgin resin is used as a masterbatch and melt-mixed with virgin resin in a twin-screw extruder to produce pellets 100 from this molten resin. (7) A screen with a small opening diameter is installed inside the extruder, immediately before the die. (8) A compatibilizer is added to improve the affinity between the main resin 101 contained in the recycled resin and the other components contained in the pellets 100.

[0108] <5> Film The film of this embodiment is molded from the recycled resin composition described above, or from pellets of the recycled resin composition. Despite being manufactured from recycled resin, this film has excellent physical properties such as sufficient impact resistance and a good appearance. Furthermore, this film can be recycled and used in the manufacture of recycled resin compositions or films, in which case a film with excellent physical properties such as sufficient impact resistance and a good appearance can be obtained.

[0109] Figure 3 is a cross-sectional view showing an example of the structure of a film (resin film) obtained by molding a recycled resin composition. As shown in Figure 3, the film 1 consists of a recycled resin-containing layer 1a. As described above, the recycled resin-containing layer 1a is formed by molding a recycled resin composition, or pellets of the recycled resin composition, into a film.

[0110] The recycled resin-containing layer 1a constituting the film 1 may consist solely of recycled resin, or it may consist of recycled resin and one or more other components. The one or more other components may be, for example, virgin resin and one or more additives.

[0111] The thickness of film 1 may be 20 μm or more, 50 μm or more, or 100 μm or more. Furthermore, the thickness of film 1 may be 200 μm or less, 150 μm or less, or 120 μm or less. Therefore, the thickness of film 1 may be within the range of 20 μm to 200 μm, within the range of 50 μm to 150 μm, or within the range of 100 μm to 120 μm.

[0112] This film 1 can be used, for example, as a sealant film for packaging materials, a part of a sealant film for packaging materials, a base film for packaging materials, or a label base. Furthermore, film 1 can be used on its own. For example, film 1 itself can be used as a packaging material such as a stretch film.

[0113] <6> Method for Manufacturing Film This film 1 can be manufactured, for example, by extruding a recycled resin composition. For example, the recycled resin composition is melted using an injection molding machine or an extrusion molding machine (e.g., a single-screw extruder) and a film is formed via a feed block or a multi-manifold and a T-die. Alternatively, the recycled resin composition is made into a film by the inflation method. The temperature conditions for film formation or filmmaking may be appropriately changed depending on the type of resin used. For example, the temperature conditions for film formation using an injection molding machine or an extrusion molding machine should be in the range of 170°C to 280°C. For example, the temperature conditions for filmmaking by the inflation method should be in the range of 120°C to 230°C. As mentioned above, pellets of the recycled resin composition may also be used.

[0114] A method for manufacturing a film according to another embodiment includes a first step of obtaining a first film by extruding a first resin composition containing a resin and an antioxidant, and a second step of obtaining a second film by extruding a second resin composition containing at least a portion of the first film as recycled material and further containing an antioxidant. In this method, the first and second resin compositions are prepared such that the oxidation induction time, measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018, is in the range of 18 minutes to 50 minutes.

[0115] The resin contained in the first resin composition may be the virgin resin described above, or it may be a resin derived from recycled material containing resin. From the viewpoint of reducing the amount of foreign matter contamination, the resin contained in the first resin composition may be a virgin polyolefin resin. Furthermore, the antioxidant contained in the first resin composition may be at least one selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants.

[0116] The second resin composition used in the second step may have the same composition as the recycled resin composition described above.

[0117] The second film obtained in the second step, despite being manufactured from recycled resin, possesses excellent physical properties such as sufficient impact resistance and a good appearance. Furthermore, the second film can be recycled and used in the manufacture of recycled resin compositions or films, in which case a film with excellent physical properties such as sufficient impact resistance and a good appearance can be obtained. This method is particularly suitable for post-industrial recycling.

[0118] <7> Laminate The laminate of this embodiment comprises the film described above. This laminate may have a structure in which one or more other layers are laminated on the film described above. For example, as shown in Figure 4, a laminate 2A may be constructed by laminating a film 1 (see Figure 3) made of a recycled resin-containing layer 1a and a recycled resin-free layer 2. Alternatively, as shown in Figure 5, a laminate 2B may be constructed with a film 1 made of a recycled resin-containing layer 1a, and a recycled resin-free layer 2 and a recycled resin-free layer 3 sandwiching it. The recycled resin-containing layer 1a included in laminates 2A and 2B may, for example, serve as a base film or a sealant film or as a part thereof.

[0119] The resins constituting the recycled resin-free layers 2 and 3 may be the same type of resin or different types of resins. For example, these resins can be selected from polyethylene, polypropylene, polystyrene, polymethyl methacrylate, ethylene vinyl acetate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyacrylonitrile, polylactic acid, cyclic polyolefin, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, and derivatives thereof. If the same type of resin as the resin with the highest content among the recycled resins constituting the recycled resin-containing layer 1a is used as the resins constituting the recycled resin-free layers 2 and 3, higher adhesion can be achieved between the recycled resin-containing layer 1a and the recycled resin-free layer 2, and between the recycled resin-containing layer 1a and the recycled resin-free layer 3.

[0120] The laminate may further include other layers. For example, as shown in the laminate 2C in Figure 6, the laminate 2B and the intermediate film 5 may be bonded together via an adhesive layer 4a, and the intermediate film 5 and the surface film 7 on which the printed layer 6 is formed may be bonded together via an adhesive layer 4b. The intermediate film 5 is, for example, a nylon film. The surface film 7 is, for example, a polyethylene terephthalate film. The laminate may further include a metal layer such as an aluminum layer.

[0121] The laminate may contain two or more recycled resin-containing layers. Such a laminate may not contain a recycled resin-free layer, or it may further contain one or more recycled resin-free layers. Furthermore, the two or more recycled resin-containing layers contained in the laminate may have the same composition or different compositions.

[0122] As described above, the laminate may include layers other than the recycled resin-containing layer (i.e., layers that do not contain recycled resin). However, if the proportion of layers other than the recycled resin-containing layer in the laminate becomes large, the significance of using recycled resin diminishes. Therefore, in the laminate or the packaging material described later, the proportion of recycled resin in the total mass excluding adhesive, printing ink, and metal foil is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more.

[0123] The thickness of the laminate is preferably in the range of 20 μm to 200 μm, more preferably in the range of 50 μm to 180 μm, and even more preferably in the range of 100 μm to 150 μm. If the thickness of the laminate is too small, it is difficult to obtain the strength required for packaging materials, for example. If the thickness of the laminate is too large, the strength becomes over-specified, resulting in a waste of resin. Also, if the thickness of the laminate is too large, it becomes rough to the touch and difficult to handle. A laminate with an appropriate thickness is advantageous in that it has sufficient strength for a wide range of packaging applications and a good firmness for use.

[0124] The following describes each layer of a laminate constructed using the aforementioned film, with specific examples. As mentioned above, for example, a laminate has a structure in which one or more other layers are laminated onto a film (film 1 shown in Figure 3). The one or more other layers in the laminate are, for example, one or more base layer, intermediate layer, heat seal layer (sealant layer), and gas barrier layer. If the laminate includes a heat seal layer, the laminate can be used as a packaging material.

[0125] Figures 7 to 10 are cross-sectional views showing an example of the configuration of a laminate according to one embodiment of the present disclosure. The laminate 10A shown in Figure 7 comprises a film 1 formed from the recycled resin composition described above and a base layer 11. The laminate 10B shown in Figure 8 has a structure in which the base layer 11, the film 1, and the heat seal layer 12 are laminated in this order. The laminate 10C shown in Figure 9 has a structure in which the base layer 11, the intermediate layer 13, the film 1, and the heat seal layer 12 are laminated in this order. The laminate 10D shown in Figure 10 has a structure in which the base layer 11, the gas barrier layer 14, the film 1, and the heat seal layer 12 are laminated in this order.

[0126] <7.1> Substrate Layer The substrate layer 11 is a layer composed of a substrate film that is laminated with the film 1 in the laminates 10A to 10D. From the viewpoint of providing shielding properties, stiffness, and printability, the substrate layer 11 may be formed from polyolefin resins such as polypropylene and polyethylene, or from polyester resin or polyamide resin. Furthermore, the substrate layer 11 may be double-sided art paper, single-sided art paper, double-sided coated paper, or single-sided coated paper with a printed undercoat layer laminated on top.

[0127] The thickness of the base layer 11 is, for example, within the range of 5 μm to 30 μm, or within the range of 30 μm to 100 μm.

[0128] <7.2> Heat seal layer The material of the heat seal layer (sealant layer) 12 can be, for example, polyolefin resins such as polyethylene and polypropylene, and polyester resins (for example, polyester resins with a melting point of 240°C or less). The heat seal layer 12 provides heat sealability to the laminates 10B to 10D.

[0129] The thickness of the heat seal layer 12 is, for example, within the range of 50 μm to 200 μm, or within the range of 80 μm to 150 μm.

[0130] <7.3> Intermediate layer The materials for the intermediate layer 13 include polyolefin resins, polyethylene-vinyl acetate copolymer resins, and styrene copolymer resins. The intermediate layer 13 enhances the adhesion between the base layer 11 and the film 1, for example.

[0131] The thickness of the intermediate layer 13 is, for example, within the range of 3 μm to 100 μm, or within the range of 5 μm to 30 μm.

[0132] <7.4> Gas Barrier Layer The gas barrier layer 14 is, for example, a vapor-deposited film, or a layer composed of a film made of a polymer having gas barrier properties such as a polyamide resin or an ethylene-vinyl acetate copolymer saponified product. The gas barrier layer 14 provides gas barrier properties to the laminate 10D.

[0133] The thickness of the gas barrier layer 14 is, for example, within the range of 2 μm to 30 μm, or within the range of 10 μm to 20 μm.

[0134] <7.5> Method for Manufacturing Laminates A laminate containing a film (film having a recycled resin-containing layer 1a) 1 formed from the recycled resin composition described above can also be manufactured, for example, by molding one or more other layers simultaneously with molding the recycled resin-containing layer 1a. Alternatively, a laminate containing the recycled resin-containing layer 1a can be manufactured, for example, by using a multilayer extrusion molding machine equipped with a feed block in front of the T-die, or a multilayer extrusion molding machine equipped with a multi-manifold die.

[0135] In a method for manufacturing a laminate using a multilayer extrusion molding machine, a recycled resin composition containing recycled material is used as the raw material for the recycled resin-containing layer 1a, and a thermoplastic resin with a different composition is used as the raw material for the other layers. These raw material resins are then melt-kneaded and co-extruded to obtain the laminate.

[0136] In forming the recycled resin-containing layer 1a in the laminate, a raw material consisting solely of a recycled resin composition may be used, or a raw material mixed with virgin resin may be used to impart properties such as viscosity adjustment and mechanical property reinforcement. Specifically, the recycled resin-containing layer 1a, which contains both a recycled resin composition and virgin resin, can be formed by a dry blending method. That is, for example, pellets made of a recycled resin composition and pellets made of virgin resin can be simultaneously fed into a hopper and melt-kneaded, and the recycled resin-containing layer 1a can be directly formed from this molten resin. Alternatively, the recycled resin-containing layer 1a, which contains both recycled resin and virgin resin, can also be formed by a melt-blending method. That is, a masterbatch can be produced by melt-kneading a recycled resin composition and virgin resin in a twin-screw extruder, and pellets as this masterbatch can be fed into a hopper together with, if necessary, pellets made of virgin resin and melt-kneaded, and the recycled resin-containing layer 1a can be formed from this molten resin.

[0137] Furthermore, the laminate can also be manufactured by extrusion lamination. For example, a recycled resin-containing layer 1a can be formed using a twin-screw extruder, and then one or more recycled resin-free layers can be formed by extrusion lamination to obtain the laminate. In addition, the laminate can also be manufactured by co-extrusion molding using the inflation method.

[0138] The cooling method for the laminate is appropriately selected according to the molding machine used for its manufacture. The film 1 having the recycled resin-containing layer 1a that constitutes the laminate can be cooled in the same manner. For example, in the T-die method, air cooling methods such as air chambers, vacuum chambers, and air knives, and water cooling methods such as dipping a cooling roll into a chilled water pan can be used. Furthermore, when obtaining a film having an uneven surface structure, a method is particularly preferred in which a nip roll having a surface made of silicone rubber, NBR rubber, or fluororesin is brought into contact with a metal cooling roll having an uneven surface structure provided on its surface by cutting, and a pressure of 0.1 MPa or more is applied to the contact area, allowing molten resin to flow into the contact area for molding and cooling.

[0139] The laminate can also be manufactured by bonding film 1 and one or more other layers via an adhesive. The laminate can also be manufactured by bonding a laminate containing recycled resin layer 1a and one or more other layers via an adhesive.

[0140] The laminate can be subjected to surface modification treatment to improve its suitability for subsequent processes. For example, surface modification treatment may be performed to improve printability or lamination suitability. Suitable surface modification treatments include methods that oxidize the film surface to express functional groups, such as corona discharge treatment, plasma treatment, and flame treatment, as well as wet process modifications such as coating with an easy-adhesion layer. The same surface modification treatment can be performed not only on the laminate but also on the film 1 having the recycled resin-containing layer 1a that constitutes the laminate.

[0141] <8> The laminate containing the packaging film 1 can be used as a packaging material. The laminate may have a heat-seal layer 12 as illustrated above. The packaging material of this embodiment may consist only of the laminate described above, or it may be a processed laminate. The film 1 itself can also be used as a packaging material such as a stretch film.

[0142] <9> Packaging Bag The packaging bag of this embodiment is made by forming a bag from the packaging material described above. The packaging bag can be manufactured, for example, by bonding the heat-seal layers of a pair of packaging materials together, or by folding a single piece of packaging material so that the heat-seal layers face each other and then forming a bag.

[0143] Packaging bags include, for example, standing pouches, three-side sealed pouches, gusseted pouches, spouted pouches, or beaked pouches. The manufacturing method of the packaging bags is not particularly limited.

[0144] <10> Effects As described above, resin compositions used in the manufacture of plastic products usually contain antioxidants in addition to the resin. During heat treatment performed in the manufacture of plastic products, at least some of the antioxidants are consumed, but not all of them are consumed. Recycled materials may contain these unused antioxidants.

[0145] The amount of antioxidants contained in recycled materials varies depending on the amount of antioxidants added during the manufacturing of plastic products and the thermal history. Therefore, until now, it has been difficult to determine how much antioxidant should be added to recycled materials when manufacturing recycled resin compositions from them.

[0146] In the technology described above, the recycled resin composition is manufactured so that the oxidation induction time, measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018, falls within the above range. This oxidation induction time is a parameter related to the sum of the amount of antioxidant contained in the recycled material and the amount of antioxidant mixed with the recycled material. In other words, this oxidation induction time represents the antioxidant capacity of the antioxidant contained in the recycled resin composition. The recycled resin composition manufactured so that the oxidation induction time falls within the above numerical range makes it possible to manufacture a film with sufficient impact resistance and a good appearance.

[0147] In other words, according to the technology described above, it is possible to manufacture a film with sufficient impact resistance and a good appearance from a recycled resin composition containing recycled materials.

[0148] This disclosure will be further illustrated by the following specific examples, but will not be limited to these examples.

[0149] ≪1. Manufacturing of Recycled Resin Compositions, and Manufacturing and Evaluation of Films≫ <1.1 Manufacturing of Recycled Resin Compositions> (Example 1) LLDPE resin RS1 (manufactured by Prime Polymer Co., Ltd., product name: Evolu® SP2020) was extruded into a string shape at 180°C using a twin-screw extruder, and these were cut with a pelletizer to obtain pellets. Using these pellets as raw material, a resin film with a thickness of 150 μm was manufactured using a single-screw extruder set to a temperature of 230°C. This resin film was used as the recycled material.

[0150] The oxidation induction time of this recycled material was measured in accordance with JIS K 7351:2018 using a chemiluminescence analyzer (Tohoku Electronics Industry Co., Ltd.: Model No.: CLA-FS54) under an oxygen atmosphere and the following conditions.

[0151] [Measurement conditions] Temperature: constant at 220°C Oxygen flow rate: 50 mL / min Exposure time: 1 second Measurement time: 7 hours Sample size: 1 cm square, 150 μm The result showed that the oxidation induction time for the recycled material was 0 minutes.

[0152] Next, antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material using a feeder. This mixture was extruded into a string shape at 230°C using a twin-screw extruder, and then cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) in the total of the recycled material and antioxidant was set to 1000 ppm. The oxidation induction time of this recycled resin composition was measured in accordance with JIS K 7351:2018 using a chemiluminescence analyzer (manufactured by Tohoku Electronics Industry Co., Ltd., model number: CLA-FS54) under an oxygen atmosphere and the following conditions.

[0153] [Measurement conditions] Temperature: constant at 220°C Oxygen flow rate: 50 mL / min Exposure time: 1 second Measurement time: 7 hours Mass of measurement sample: 0.2 g As a result, the oxidation induction time of the recycled resin composition was 20 minutes.

[0154] (Example 2) Antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material from Example 1 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) to the total of the recycled material and antioxidant was set to 2000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 38 minutes.

[0155] (Example 3) Antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material from Example 1 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) to the total of the recycled material and antioxidant was set to 3000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 50 minutes.

[0156] (Example 4) Antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to LLDPE resin RS1 (manufactured by Prime Polymer Co., Ltd., product name: Evolu® SP2020) via a feeder. This mixture was extruded into a string shape at 180°C using a twin-screw extruder, and then cut with a pelletizer to obtain pellets. Here, the proportion of antioxidant to the total of resin and antioxidant (by mass) was set to 1000 ppm. Using these pellets as raw material, a resin film with a thickness of 150 μm was manufactured using a single-screw extruder set to a temperature of 230°C. This resin film was used as recycled material.

[0157] The oxidation induction time of this recycled material was measured under the same conditions as the recycled material in Example 1. As a result, the oxidation induction time was 10 minutes.

[0158] Next, antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material using a feeder. This mixture was then extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) to the total of the recycled material and antioxidant was set to 1000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 34 minutes.

[0159] (Example 5) LLDPE resin RS1 (manufactured by Prime Polymer Co., Ltd., product name: Evolu® SP2020) was mixed with antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) via a feeder. The mixture was extruded into a string shape at 180°C using a twin-screw extruder, and then cut into pellets using a pelletizer. Here, the proportion of antioxidant to the total of resin and antioxidant (by mass) was set to 2000 ppm. Using these pellets as raw material, a resin film with a thickness of 150 μm was manufactured using a single-screw extruder set to a temperature of 230°C. This resin film was used as recycled material.

[0160] The oxidation induction time of this recycled material was measured under the same conditions as the recycled material in Example 1. As a result, the oxidation induction time was 23 minutes.

[0161] Next, antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material using a feeder. This mixture was then extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) in the total of the recycled material and antioxidant was set to 2000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 45 minutes.

[0162] (Example 6) Antioxidant AO2 (BASF, product name: Irganox® 1010) and antioxidant AO3 (BASF, product name: Irgafos 168) were added to the recycled material from Example 1 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant AO2 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was set to 1000 ppm. Similarly, the proportion of antioxidant AO3 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was also set to 1000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 26 minutes.

[0163] (Example 7) Antioxidant AO2 (manufactured by BASF, product name: Irganox® 1010) and antioxidant AO3 (manufactured by BASF, product name: Irgafos 168) were added to LLDPE resin RS1 (manufactured by Prime Polymer Co., Ltd., product name: Evolu® SP2020) using a feeder. These mixtures were extruded into a string shape at 180°C using a twin-screw extruder, and then cut into pellets using a pelletizer. Here, the proportion of antioxidant AO2 in the total of the resin, antioxidant AO2, and antioxidant AO3 (by mass) was set to 1000 ppm. Also, here, the proportion of antioxidant AO3 in the total of the resin, antioxidant AO2, and antioxidant AO3 (by mass) was also set to 1000 ppm. Using these pellets as raw material, a resin film with a thickness of 150 μm was manufactured using a single-screw extruder set to a temperature of 230°C. This resin film was then used as recycled material.

[0164] The oxidation induction time of this recycled material was measured under the same conditions as the recycled material in Example 1. As a result, the oxidation induction time was 20 minutes.

[0165] Next, antioxidant AO2 (BASF, product name: Irganox® 1010) and antioxidant AO3 (BASF, product name: Irgafos 168) were added to the recycled material using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant AO2 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was set to 1000 ppm. Similarly, the proportion of antioxidant AO3 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was also set to 1000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 28 minutes.

[0166] (Example 8) LLDPE resin RS2 (manufactured by Nippon Polyethylene Co., Ltd., product name: Harmolex® NH745N) was extruded into a string shape at 180°C using a twin-screw extruder, and then cut into pellets using a pelletizer. Using these pellets as raw material, a resin film with a thickness of 150 μm was manufactured using a single-screw extruder set to a temperature of 230°C. This resin film was used as recycled material.

[0167] The oxidation induction time of this recycled material was measured under the same conditions as the recycled material in Example 1. As a result, the oxidation induction time was 0 minutes.

[0168] Next, antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material using a feeder. This mixture was then extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) in the total of the recycled material and antioxidant was set to 1000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 18 minutes.

[0169] (Example 9) Antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material of Example 8 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) in the total of the recycled material and antioxidant was set to 2000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition of Example 1. As a result, the oxidation induction time was 47 minutes.

[0170] (Example 10) Antioxidant AO2 (BASF, product name: Irganox® 1010) and antioxidant AO3 (BASF, product name: Irgafos 168) were added to the recycled material from Example 8 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant AO2 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was set to 1000 ppm. Similarly, the proportion of antioxidant AO3 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was also set to 1000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition in Example 1. As a result, the oxidation induction time was 22 minutes.

[0171] (Example 11) Antioxidant AO2 (BASF, product name: Irganox® 1010) and antioxidant AO3 (BASF, product name: Irgafos 168) were added to the recycled material of Example 8 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant AO2 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was set to 2000 ppm. Similarly, the proportion of antioxidant AO3 in the total of the recycled material, antioxidant AO2, and antioxidant AO3 (by mass) was also set to 2000 ppm. The oxidation induction time of this recycled resin composition was measured under the same conditions as the recycled resin composition of Example 1. As a result, the oxidation induction time was 48 minutes.

[0172] (Comparative Example 1) Antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material of Example 1 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant (by mass) in the total of the recycled material and antioxidant was set to 500 ppm. The oxidation induction time was measured under the same conditions as the recycled resin composition of Example 1. As a result, the oxidation induction time was 12 minutes.

[0173] (Comparative Example 2) Antioxidant AO1 (manufactured by Sumitomo Chemical Co., Ltd., product name: SumiLizer® GP) was added to the recycled material of Example 1 using a feeder. The mixture was extruded into a string shape at 230°C using a twin-screw extruder, and this was cut with a pelletizer to obtain a pelletized recycled resin composition. Here, the proportion of antioxidant to the total of the recycled material and antioxidant (by mass) was set to 3500 ppm. The oxidation induction time was measured under the same conditions as the recycled resin composition of Example 1. As a result, the oxidation induction time was 60 minutes.

[0174] <1.2 Film Manufacturing> Using each of the recycled resin compositions obtained in the above examples and comparative examples as raw materials, a resin film with a thickness of 150 μm was manufactured using a single-screw extruder set to a temperature of 230°C.

[0175] <1.3 Evaluation of Film> [Evaluation of Film Impact Resistance] For the above resin film (hereinafter also referred to as recycled film), the impact strength (J), which is the force required when a projectile penetrates a 150 μm thick film, was measured using a film impact tester with a constant temperature chamber (manufactured by Toyo Seiki Seisakusho Co., Ltd., model: R) under the conditions of a 1 / 2 inch projectile size, no weight, and a temperature of 23°C. Then, using this impact strength, the impact resistance (J / mm), which is the strength per unit thickness, was calculated.

[0176] When the impact resistance of recycled film is 9 J / mm or higher, packaging bags manufactured using recycled film as a sealant film are less likely to tear when dropped. Therefore, those with an impact resistance of 9 J / mm or higher were rated "A," and those with an impact resistance of less than 9 J / mm were rated "B." The results are shown in Tables 1 to 3.

[0177] [Evaluation of YI of Film] The YI value of recycled film was measured in accordance with JIS K7373:2006 using a COH7700 spectrophotometer manufactured by Nippon Denshoku Industries Ltd., under the conditions of a D65 light source and a 2° field of view. The measured YI value was divided by the film thickness (mm) at the measurement point to obtain the YI value per unit film thickness (mm-1).

[0178] When the YI value per unit thickness of recycled film is 9 mm⁻¹ or less, it has little yellowing and a sufficiently good appearance. Therefore, films with a YI value per unit thickness of 9 mm⁻¹ or less were evaluated as "A", and films with a YI value greater than 9 mm⁻¹ were evaluated as "B". The results are shown in Tables 1 to 3.

[0179] [Evaluation of the number of foreign objects in the film] A 10 cm square sample was cut from each recycled film, and the number of foreign objects in this sample was measured using a tabletop inspection device manufactured by Futec Co., Ltd. Here, the number of foreign objects with a diameter greater than 500 μm was measured.

[0180] The number of foreign objects in a 10 cm square sample affects its appearance. Preferably, the number of foreign objects is 20 or less, more preferably 10 or less, and even more preferably 5 or less. Therefore, samples with 10 or fewer foreign objects were rated "AA," samples with more than 10 but 20 or less were rated "A," and samples with more than 20 foreign objects were rated "B." The results are shown in Tables 1 to 3.

[0181]

[0182]

[0183]

[0184] As shown in Tables 1 to 3, the resin films (recycled films) produced from the recycled resin compositions of Examples 1 to 11 had sufficient impact resistance and a good appearance despite being made from recycled resin. In contrast, the resin film produced from the recycled resin composition of Comparative Example 1 had low impact resistance and suffered from appearance defects due to foreign matter. Furthermore, the resin film produced from the recycled resin composition of Comparative Example 2 suffered from appearance defects due to yellowing.

[0185] ≪2. Pellet Production and Film Production≫ <2.1 Pellet Production> (Production of Pellet P1) A multilayer film was produced in which linear low-density polyethylene (LLDPE) film (manufactured by Mitsui Chemicals Tohcello Co., Ltd., product name: TUX FC-S, film thickness 100 μm), adhesive layer (layer thickness 3 μm), polyethylene terephthalate (PET) film (manufactured by Toray Film Processing Co., Ltd., product name: VM-PET 1310, film thickness 12 μm), adhesive layer (layer thickness 3 μm), printed layer, and nylon (Ny) film (manufactured by Toyobo Co., Ltd., product name: Harden® Film N1100, film thickness 15 μm) were laminated in this order. The adjacent films, separated by an adhesive layer, were bonded together by dry lamination using an adhesive mixture consisting of LX-500 (main component) manufactured by DIC Graphics Co., Ltd., KW75 (hardener) manufactured by DIC Graphics Co., Ltd., and NC401 (solvent) manufactured by Toyo Ink Co., Ltd.

[0186] After cutting the multilayer film, it was melted and mixed in a twin-screw extruder, and the molten resin was extruded in strand form. The twin-screw extruder die had a diameter of 4 mm at the molten resin inlet, a diameter of 4 mm at the molten resin outlet, and a distance of 140 mm from inlet to outlet. Three metal meshes (screens) arranged in the order of #40 / #80 / #40 were placed inside the twin-screw extruder directly in front of the die. The molten resin was extruded at a temperature of 230°C so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain pellets P1.

[0187] (Manufacturing of Pellet P2) The multilayer film used in the manufacturing of Pellet P1 was prepared. After cutting this multilayer film, the cut multilayer film and virgin LLDPE resin (manufactured by Prime Polymer Co., Ltd., product name: Evolu® SP3530) were melt-mixed in a twin-screw extruder so that their mass ratio was 1:1, and the molten resin was extruded in strand form. The die used for the twin-screw extruder had a molten resin inlet diameter of 4 mm, a molten resin outlet diameter of 4 mm, and a distance of 140 mm from inlet to outlet. Three metal meshes (screens) arranged in the order of #40 / #80 / #40 were placed inside the twin-screw extruder directly in front of the die. The molten resin was extruded at a temperature of 230°C so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain Pellet P2.

[0188] (Manufacturing of Pellet P3) A multilayer film was manufactured by laminating LLDPE film (manufactured by Mitsui Chemicals Tohcello Co., Ltd., product name: TUX FC-S, film thickness 95 μm), adhesive layer (layer thickness 3 μm), high-density polyethylene (HDPE) film (manufactured by Tamapoly Co., Ltd., product name: HF31, film thickness 35 μm), adhesive layer (layer thickness 3 μm), printed layer, and high-density polyethylene (HDPE) film (manufactured by Tamapoly Co., Ltd., product name: HF31, film thickness 35 μm) in this order. Adjacent films with an adhesive layer in between were bonded together by dry lamination using the same adhesive as used in the manufacturing of Pellet P1.

[0189] After cutting the multilayer film, it was melted and mixed in a twin-screw extruder, and the molten resin was extruded in strand form. The twin-screw extruder used had a molten resin inlet diameter of 4 mm, a molten resin outlet diameter of 4 mm, and a distance of 140 mm from inlet to outlet. No metal mesh (screen) was installed inside the twin-screw extruder. The molten resin was extruded at a temperature of 230°C, so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain pellets P3.

[0190] (Manufacturing of Pellet P4) A multilayer film used in the manufacturing of Pellet P1 was prepared. After cutting this multilayer film, a deinking and stripping treatment using an alkaline solution was performed for 3 hours, and then LLDPE was separated from the other resins by utilizing the difference in specific gravity. Next, this LLDPE was melted and mixed in a twin-screw extruder, and the molten resin was extruded in strand form. The die used for the twin-screw extruder had a molten resin inlet diameter of 4 mm, a molten resin outlet diameter of 4 mm, and a distance of 140 mm from inlet to outlet. No metal mesh (screen) was installed inside the twin-screw extruder. The molten resin was extruded at a temperature of 230°C so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain Pellet P4.

[0191] (Manufacturing of Pellet P5) A multilayer film used in the manufacturing of Pellet P1 was prepared. After cutting this multilayer film, a deinking and stripping treatment using an alkaline solution was performed for 1 hour, and then LLDPE was separated from the other resins by utilizing the difference in specific gravity. Next, this LLDPE was melted and mixed in a twin-screw extruder, and the molten resin was extruded in strand form. The twin-screw extruder used had a molten resin inlet diameter of 4 mm, a molten resin outlet diameter of 4 mm, and a distance of 140 mm from inlet to outlet. No metal mesh (screen) was installed inside the twin-screw extruder. The molten resin was extruded at a temperature of 230°C so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain Pellet P5.

[0192] (Manufacturing of Pellet P6) A multilayer film was manufactured by laminating LLDPE film (manufactured by Mitsui Chemicals Tohcello Co., Ltd., product name: TUX FC-S, film thickness 100 μm), adhesive layer (layer thickness 3 μm), vacuum metallized biaxially oriented polypropylene (VM-OPP) film (manufactured by RM Tohcello Co., Ltd., product name: ML OP102, film thickness 25 μm), adhesive layer (layer thickness 3 μm), printed layer, and biaxially oriented polypropylene (OPP) film (manufactured by Toyobo Co., Ltd., product name: Pyrene® Film-OT P2102, film thickness 20 μm) in this order. Adjacent films with an adhesive layer in between were bonded together by dry lamination using the same adhesive as used in the manufacturing of Pellet P1.

[0193] After cutting the multilayer film, it was melted and mixed in a twin-screw extruder, and the molten resin was extruded in strand form. The twin-screw extruder used had a molten resin inlet diameter of 4 mm, a molten resin outlet diameter of 4 mm, and a distance of 140 mm from inlet to outlet. No metal mesh (screen) was installed inside the twin-screw extruder. The molten resin was extruded at a temperature of 230°C, so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain pellet P6.

[0194] (Manufacturing of Pellet P7) A multilayer film was manufactured by laminating LLDPE film (manufactured by Mitsui Chemicals Tohcello Co., Ltd., product name: TUX FC-S, film thickness 100 μm), adhesive layer (layer thickness 3 μm), vacuum metallized PET (VM-PET) film (manufactured by Toray Film Processing Co., Ltd., product name: VM-PET 1310, film thickness 12 μm), adhesive layer (layer thickness 3 μm), printed layer, and Ny film (manufactured by Toyobo Co., Ltd., product name: Harden® Film N1100, film thickness 15 μm) in this order. Adjacent films with an adhesive layer in between were bonded together by dry lamination using the same adhesive as used in the manufacturing of Pellet P1.

[0195] After cutting the multilayer film, the cut film and virgin LLDPE resin (manufactured by Prime Polymer Co., Ltd., product name: Evolu® SP3530) were melt-mixed in a single-screw extruder so that their mass ratio was 1:1, and the molten resin was extruded in strand form. The die used for the single-screw extruder had a molten resin inlet diameter of 4 mm, a molten resin outlet diameter of 4 mm, and a distance of 140 mm from inlet to outlet. Three metal meshes (screens) arranged in the order of #40 / #80 / #40 were placed directly in front of the die inside the single-screw extruder. The molten resin was extruded at a temperature of 230°C so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain pellets P7.

[0196] (Manufacturing of Pellet P8) A multilayer film used in the manufacturing of Pellet P7 was prepared. After cutting this multilayer film, it was subjected to deinking and desaturation treatment using an alkaline solution, and then LLDPE was separated from the other resins by utilizing the difference in specific gravity. Next, this LLDPE was melted and mixed in a single-screw extruder, and the molten resin was extruded in strand form. The die used for the single-screw extruder had a molten resin inlet diameter of 4 mm, a molten resin outlet diameter of 4 mm, and a distance of 140 mm from inlet to outlet. No metal mesh (screen) was installed inside the single-screw extruder. The molten resin was extruded at a temperature of 230°C so that the linear velocity of the strand was 12.5 m / min. The strand was cut into granules to obtain Pellet P8.

[0197] <2.2 Film Manufacturing> (Manufacturing of Resin Films F1A to F1C) Resin films F1A to F1C were manufactured using a single-screw multi-layer extruder. Here, the temperature was set to 230°C and the take-up speed to 10 m / min. In addition, by feeding pellet P1 only into the hopper that extrudes the central layer and changing the rotation speed, resin film F1A with a thickness of 5 μm, resin film F1B with a thickness of 100 μm, and resin film F1C with a thickness of 200 μm were manufactured.

[0198] (Manufacturing of resin films F2A to F2C) Except for using pellet P2 instead of pellet P1, resin films F1A to F1C were manufactured using the same method as described above, with resin film F2A having a thickness of 5 μm, resin film F2B having a thickness of 100 μm, and resin film F2C having a thickness of 200 μm.

[0199] (Manufacturing of resin films F3A to F3C) Except for using pellet P3 instead of pellet P1, resin films F1A to F1C were manufactured using the same method as described above, with resin film F3A having a thickness of 5 μm, resin film F3B having a thickness of 100 μm, and resin film F3C having a thickness of 200 μm.

[0200] (Manufacturing of resin films F4A to F4C) Except for using pellet P4 instead of pellet P1, resin films F1A to F1C were manufactured using the same method as described above, producing resin film F4A with a thickness of 5 μm, resin film F4B with a thickness of 100 μm, and resin film F4C with a thickness of 200 μm.

[0201] (Manufacturing of resin films F5A to F5C) Except for using pellet P5 instead of pellet P1, resin films F1A to F1C were manufactured in the same manner as described above, with resin film F5A having a thickness of 5 μm, resin film F5B having a thickness of 100 μm, and resin film F5C having a thickness of 200 μm.

[0202] (Manufacturing of resin films F6A to F6C) Except for using pellet P6 instead of pellet P1, resin films F1A to F1C were manufactured using the same method as described above, producing resin film F6A with a thickness of 5 μm, resin film F6B with a thickness of 100 μm, and resin film F6C with a thickness of 200 μm.

[0203] (Manufacturing of resin films F7A to F7C) Except for using pellet P7 instead of pellet P1, resin films F1A to F1C were manufactured using the same method as described above, with resin film F7A having a thickness of 5 μm, resin film F7B having a thickness of 100 μm, and resin film F7C having a thickness of 200 μm.

[0204] (Manufacturing of resin films F8A to F8C) Except for using pellet P8 instead of pellet P1, resin films F1A to F1C were manufactured using the same method as described above, with resin film F8A having a thickness of 5 μm, resin film F8B having a thickness of 100 μm, and resin film F8C having a thickness of 200 μm.

[0205] <2.3 Evaluation> [Evaluation of Melt Viscosity of Pellet] For each of the above pellets, the melt viscosity was measured using a capillary rheometer (GOTTFERT, model Rheograph). The temperature was set to 230°C and the take-up speed was set to 200 mm / second.

[0206] [Evaluation of film-forming properties] For each of the above resin films, the thickness was measured at multiple points in the middle section (length 2 m) in the flow direction. A continuous thickness measuring machine (Fujiwork Corporation, model FT-A200R) was used to measure the thickness.

[0207] For each of the above resin films, we checked for the presence or absence of holes. Films where the difference between the measured thickness and the target thickness was within ±10% of the target thickness at all measurement locations, and no holes were observed, were given an evaluation of "A". Films where the difference between the measured thickness and the target thickness was outside the ±10% range at one or more measurement locations, or where holes were observed, were given an evaluation of "B".

[0208] [Evaluation of Mass Producibility] In the manufacturing of the above resin film, a roll sample of 50m in length was obtained without breakage, and this was given an evaluation of "A". In addition, in the manufacturing of the above resin film, a roll sample of 50m in length could not be obtained as a result of breakage, and this was given an evaluation of "B".

[0209] The evaluation results are shown in Tables 4 and 5 below.

[0210]

[0211]

[0212] As shown in Table 4, when pellets P1 to P5 were used, excellent film-forming properties and mass productivity were achieved. Although not shown in the table, similar results were obtained when a three-layer co-extruded film with a layer thickness ratio of 1:1:1 was formed by extruding non-recycled resin from two surface layer extruders and recycled material-containing resin from the middle layer extruder of a multilayer extruder.

[0213] On the other hand, as shown in Table 5, when pellet P6 was used, the melt tension was too low, resulting in an unstable molten resin film compared to when pellets P1 to P5 were used. Furthermore, it could not withstand the take-up speed of 10 m / min and broke off midway. As a result, film-forming ability and mass productivity were poor.

[0214] Furthermore, when pellet P7 was used, the domains inside the pellet were too large, resulting in perforation. When pellet P7 was used and the thickness was 100 μm or more, it was possible to manufacture a 50 m long rolled sample, but it did not have adequate strength. And when pellet P7 was used and the thickness was 5 μm, it was not even possible to manufacture a 50 m long rolled sample.

[0215] Furthermore, when using pellet P8, the melt tension was too high, making it difficult to stretch the molten resin film, resulting in unstable thickness. Although it was possible to produce a 50m rolled sample using pellet P8, variations in thickness occurred regardless of the target thickness, and the deviation from the target thickness was particularly pronounced when the thickness was set to 5μm.

[0216] 1... Resin film, 2A, 2B, 2C... Laminate, 1a... Recycled resin-containing layer, 2, 3... Recycled resin-free layer, 4a, 4b... Adhesive layer, 5... Intermediate film, 6... Printing layer, 7... Surface film, 10A, 10B, 10C, 10D... Laminate, 11... Base layer, 12... Heat seal layer, 13... Intermediate layer, 14... Gas barrier layer, 100... Pellet, 101... Main resin, 102... Domain

Claims

1. A recycled resin composition comprising a resin-containing recycled material and an antioxidant, wherein the oxidation induction time, measured at 220°C under an oxygen atmosphere in accordance with JIS K 7351:2018, is in the range of 18 minutes to 50 minutes.

2. The recycled resin composition according to claim 1, wherein the antioxidant comprises at least one selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants.

3. The recycled resin composition according to claim 1, wherein the antioxidant comprises a phenolic antioxidant and a phosphorus-based antioxidant, the phenolic antioxidant comprises pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and the phosphorus-based antioxidant comprises tris(2,4-di-t-butylphenyl)phosphite.

4. The recycled resin composition according to claim 1, wherein the antioxidant comprises a phosphoric acid-based antioxidant having a phenol skeleton.

5. The recycled resin composition according to claim 4, wherein the phosphate-based antioxidant comprises 6-tert-butyl-4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosfepin-6-yl)oxy]propyl]-2-methylphenol.

6. The recycled resin composition according to claim 1, wherein the total content of antioxidants in the recycled resin composition is 0.05% by mass or more and 1% by mass or less.

7. The recycled resin composition according to claim 1, wherein the recycled material contains a polyolefin resin as the main resin, and the proportion of the polyolefin resin in the recycled material is 80% by mass or more.

8. The recycled resin composition according to claim 1, further comprising a virgin resin of the same type as the resin contained in the recycled material.

9. When the recycled resin composition is molded into pellets, the melt tension obtained by measuring at a temperature of 230°C and a take-up speed of 200 mm / second is in the range of 0.03 N to 0.12 N, and the maximum area of ​​the domains observed in a cross-section parallel to the molding direction is 100 μm². ２ The recycled resin composition according to claim 1, which is as follows:

10. The recycled resin composition according to claim 1, comprising the recycled material in a proportion of 10% by mass or more.

11. The recycled resin composition according to claim 1, wherein the recycled material has an oxidation induction time of 15 minutes or less, as measured at 220°C in an oxygen atmosphere in accordance with JIS K 7351:2018.

12. A film formed from the recycled resin composition according to any one of claims 1 to 11.

13. A method for producing a recycled resin composition, comprising: obtaining a recycled material containing resin; and blending the recycled material with other components including an antioxidant to obtain a recycled resin composition, wherein the recycled material and the other components are blended such that the oxidation induction time of the recycled resin composition, as measured at 220°C under an oxygen atmosphere in accordance with JIS K 7351:2018, is 18 minutes or more and 50 minutes or less.

14. A method for producing a recycled resin composition according to claim 13, comprising: preparing one or more mixtures containing the recycled material and the other components; measuring the oxidation induction time for each of the one or more mixtures; and determining the proportions of the recycled material and the other components based on the measurement results to obtain the recycled resin composition.

15. The method for producing a recycled resin composition according to claim 13, wherein the recycled material has an oxidation induction time of 15 minutes or less, as measured at 220°C under an oxygen atmosphere in accordance with JIS K 7351:2018.

16. The method for producing a recycled resin composition according to claim 13, further comprising, prior to obtaining the recycled material, extruding a first resin composition containing the resin and an antioxidant to obtain a film, and obtaining at least a portion of the film as the recycled material.

17. The method further comprises: melt-extruding the recycled resin composition to obtain strands; and cutting the strands to obtain pellets, wherein the obtained pellets have a melt tension measured at a temperature of 230°C and a take-up speed of 200 mm / second, ranging from 0.03 N to 0.12 N, and the maximum domain area observed in a cross-section parallel to the molding direction is 100 μm². ２ A method for producing a recycled resin composition according to claim 13, comprising melt-extruding the recycled resin composition so as to obtain the following:

18. A method for producing a film, comprising extruding the recycled resin composition produced by the manufacturing method described in any one of claims 13 to 17 to obtain a film.

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