Recycled film and method for producing the same

Abstract

To provide a recycled film as a form of material recycling using a waste plastic mixture recovered without a complex separation process, and a method for producing the recycled film.SOLUTION: A recycled film includes a waste plastic mixture, polyethylene, and a compatibilizer. The waste plastic mixture contains a thermoplastic resin as a main component. The compatibilizer contains at least one selected from the group consisting of an ionomer resin and a maleic anhydride-modified polyolefin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a recycled film containing a waste plastic mixture and a method for producing the same.

Background Art

[0002] Regarding absorbent articles such as used disposable diapers, it is expected that the amount of waste to be disposed of will increase with the aging of the population. Also, due to the high water content caused by the high molecular weight water-absorbing material, incineration as waste requires time and may lead to an increase in greenhouse gas emissions. Therefore, various studies have been conducted on the development of recycling technologies for the constituent materials of absorbent articles.

[0003] By the way, the constituent materials (main components) of absorbent articles are roughly classified into high molecular weight water-absorbing materials, pulp, and other plastics (hereinafter referred to as "waste plastic mixtures"). Among these, the recycling of high molecular weight water-absorbing materials and pulp has reached a certain level, and the development of recycling technologies for the remaining waste plastic mixtures is desired.

[0004] For example, Patent Document 1 proposes a method for recycling used absorbent articles containing excrement and urine, which includes a first step of separating pulp fibers from used absorbent articles containing excrement and urine to obtain recycled pulp fibers, a second step of solidifying the constituent materials of the remaining absorbent articles from which the pulp fibers have been separated to obtain solid fuel, and a third step of supplying the wastewater containing organic substances generated in the first step to a microbial fuel cell to obtain electric power and purify the wastewater.

[0005] In addition, Patent Document 2 proposes a method for manufacturing a recycled product, which includes a material separation step of separating a plurality of the used absorbent articles into at least a plurality of the films and the absorbent material, a film sorting step of sorting the separated plurality of films into a plurality of types of recycled films according to the filler content, and a pellet forming step of forming a plurality of types of recycled resin pellets according to the filler content using the sorted plurality of types of recycled films.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the recycling method described in Patent Document 1, although the treatment rate of used absorbent articles containing excrement and urine is 90% by mass or more, the remaining constituent materials of the absorbent articles from which pulp fibers have been separated (corresponding to a waste plastic mixture) are thermally recycled as solid fuel and not recycled as a material (material recycling).

[0008] In the method for manufacturing a recycled product described in Patent Document 2, although it is material recycling to form recycled resin pellets and recycled films using a plurality of films (corresponding to a waste plastic mixture) separated from the absorbent material of used absorbent articles, a complicated sorting process is required for this purpose. Further, in this method, since sorting is by specific gravity, sufficient sorting is not achieved and it is difficult to ensure the quality of the films. Also, since sorting by specific gravity usually uses water, it is necessary to dry sufficiently during recycling.

[0009] The present invention has been made in view of such a point, and an object thereof is to provide a recycled film as material recycling using a waste plastic mixture recovered without undergoing a complicated separation process, and a method for producing the same.

Means for Solving the Problems

[0010] The inventors of the present invention have found that by using a specific compatibilizer, a waste plastic mixture (and a resin mixture mixed with polyethylene) separated and recovered from pulp and a superabsorbent polymer constituting an absorbent article can be used to form a film (material recycling can be performed) without undergoing a complicated separation process (at the separation level as solid fuel).

[0011] In order to achieve the above object, the recycled film of the present invention is a recycled film containing a waste plastic mixture, polyethylene, and a compatibilizer, wherein the waste plastic mixture contains a thermoplastic resin as a main component, and the compatibilizer contains at least one selected from the group consisting of an ionomer resin and a maleic anhydride-modified polyolefin.

[0012] The article of the present invention is characterized by using the recycled film.

[0013] The method for producing a recycled film of the present invention is a method for producing a recycled film containing a waste plastic mixture, polyethylene, and a compatibilizer, and includes a compounding step of kneading the waste plastic mixture, a first polyethylene, and the compatibilizer to obtain pellets, and an inflation step of dry blending the pellets and a second polyethylene and then performing inflation molding.

[0014] Moreover, the method for manufacturing a recycled film of the present invention is a method for manufacturing a recycled film containing a waste plastic mixture, polyethylene, and a compatibilizer, comprising: a first compounding step of obtaining fluff or pre-pellets by kneading the waste plastic mixture and first polyethylene; a second compounding step of kneading the fluff or pre-pellets and second polyethylene to obtain pellets; and an inflation step of dry-blending the pellets and third polyethylene and then performing inflation molding.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a recycled film as material recycling using a waste plastic mixture recovered without undergoing a complicated separation process and a method for manufacturing the same.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be specifically described. It should be noted that the present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the gist of the present invention.

[0017] <Recycled Film> The recycled film according to this embodiment contains, as essential three components, a waste plastic mixture, polyethylene (PE), and a compatibilizer. By using a compatibilizer described later, the waste plastic mixture recovered without undergoing a complicated separation process is subjected to material recycling.

[0018] (Waste Plastic Mixture) The waste plastic mixture is one of the resin components constituting the recycling film. The waste plastic mixture is, for example, a recovered product of absorbent articles (one of the constituent materials of absorbent articles) separated from paper pulp and superabsorbent polymers from absorbent articles. Examples of absorbent articles include disposable diapers, urine pads, sanitary napkins, bed sheets, pet sheets, etc. Absorbent articles may be used individually or in combination of two or more types. Note that the absorbent articles may be pre-use products or used (post-use) products containing excrement and urine.

[0019] The waste plastic mixture may be defective products or offcuts (pre-consumer products) generated during the production of absorbent articles, or recycled materials (post-consumer products) recovered and separated from pre-use or post-use absorbent articles. The waste plastic mixture may be in a state where separation is not sufficient, recovered without undergoing a complicated separation process (at the separation level as solid fuel).

[0020] The waste plastic mixture is a resin mixture containing various resins and contains a thermoplastic resin as a main component. In this specification, the main component refers to a component whose content exceeds 50% by mass based on the total amount of 100% by mass of the components contained in the waste plastic mixture. Examples of the thermoplastic resin contained as the main component of the waste plastic mixture include polypropylene (PP), styrene resins, polyethylene terephthalate (PET), polyethylene, polyurethane, and the like. Examples of the styrene resin include polystyrene (PS), styrene-based elastomers (synthetic resins), and the like. These thermoplastic resins may be contained alone or in combination of two or more in the waste plastic mixture. In other words, the waste plastic mixture may contain at least one thermoplastic resin such as polypropylene, styrene resin, polyethylene terephthalate, polyethylene, and polyurethane as a main component. Among them, the waste plastic mixture preferably contains at least polypropylene and styrene resin, and more preferably contains more than 50% by mass, preferably 60% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more of polypropylene and styrene resin in total.

[0021] In addition to the above main components (thermoplastic resins), the waste plastic mixture may contain, for example, components contained in absorbent articles (residual components remaining after separation treatment, hereinafter simply referred to as "residual components") within a range that does not inhibit the object of the present invention. Examples of the residual components include pulp (cotton-like pulp); superabsorbent polymers; carbonate components (such as calcium carbonate); resins other than the above main components, and the like. The residual components may be contained alone or in combination of two or more in the waste plastic mixture. The content of the residual components (the total of each content when two or more types are included) is, for example, 20% by mass or less, 10% by mass or less based on the total amount of 100% by mass of the components contained in the waste plastic mixture.

[0022] As described above, the waste plastic mixture may contain, as the thermoplastic resin constituting the main component, polypropylene, styrene resin, polyethylene terephthalate, polyethylene, and polyurethane; and at least one of paper pulp and a carbonate component as the remaining components. Thus, the waste plastic mixture may be in a state where separation is not sufficient, and may contain a small amount of paper pulp, carbonate component, superabsorbent polymer, etc. unintentionally as the remaining components.

[0023] The components and contents of the waste plastic mixture can be confirmed, for example, using infrared spectroscopy. Examples of the measurement method include a method in which a waste plastic mixture in a certain amount (e.g., 1 kg) is pulverized into fine powder, well stirred to be uniform, and then sampled and quantified. A general-purpose plastic pulverizer can be used for pulverization.

[0024] Note that the waste plastic mixture is not particularly limited to those derived from absorbent articles as long as it contains the same components as above. For example, it may be derived from a film for food packaging (such as a zip lock), or a shrink film for PET bottles. The film-derived product may be a pre-consumer product or a post-consumer product.

[0025] The content of the waste plastic mixture in the recycled film (when two or more types are included, the total of each content) is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 4.5% by mass or more, from the viewpoint of improving the tensile properties of the film, with respect to the total amount of 100% by mass of the components contained in the recycled film, and preferably 15% by mass or less, more preferably 13% by mass or less, from the viewpoint of the moldability of the film. Note that although it is possible to manufacture the recycled film even if it is less than 1% by mass, the recycling rate decreases, so the value as a recycled product becomes low.

[0026] (Polyethylene) Polyethylene is one of the resin components that make up the recycled film and is the main component of the film. Polyethylene is a component intentionally added (contained) as a raw material for the recycled film, separate from the polyethylene that may be contained in the waste plastic mixture. In the manufacturing method of the recycled film described later, polyethylene is included in the masterbatch (pellet) formed in the compounding process, raw materials such as prepellets and fluff (scaly pulverized matter) formed as needed (hereinafter also referred to as "resin composition for compounding"); and the raw material used for inflation molding in the inflation process (hereinafter also referred to as "resin composition for molding").

[0027] Examples of polyethylene include high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), etc. Polyethylene may be used alone or in combination of two or more. Among polyethylenes, linear low-density polyethylene is preferred from the viewpoint of improving the physical properties (tensile properties) of the film.

[0028] Examples of linear low-density polyethylene include linear low-density polyethylene produced using a metallocene catalyst or a Ziegler catalyst. Linear low-density polyethylene preferably has a melt mass flow rate (MFR) of 0.5 g / 10 min to 2.5 g / 10 min, more preferably 1 g / 10 min to 2 g / 10 min. The MFR may be measured in accordance with the provisions of JIS K 7210-1:2014. For example, the measurement conditions for linear low-density polyethylene are a temperature of 190 °C and a load of 2.16 kg. Linear low-density polyethylene preferably has a density of 0.91 g / cm 3 or more.

[0029] The polyethylene (the first to third polyethylenes described later) contained in the above resin composition for compound and the resin composition for molding may be of the same type or different types. The polyethylene may be a commercially available product or a recycled product. Recycled products include, for example, those derived from various containers such as food storage and medicine bottles, pipes, sheets, etc. Specific examples (commercially available products) of polyethylene include, for example, those described in the examples.

[0030] The content of polyethylene in the recycled film (when two or more types are included, the total of each content) is preferably more than 50% by mass, more preferably 80% by mass or more, and still more preferably 85% by mass or more, from the viewpoint of film formability, with respect to 100% by mass of the total amount of components contained in the recycled film, and is preferably 95% by mass or less from the viewpoint of improving the tensile properties of the film. The content of polyethylene in the recycled film is the same as the total of the respective contents of the polyethylene (the first to second polyethylenes or the first to third polyethylenes) contained in the above resin composition for compound and the resin composition for molding.

[0031] (Compatibilizer) Since waste plastic mixtures (especially polypropylene, polystyrene, and styrene-based elastomers) are generally incompatible with polyethylene, the compatibilizer is a component used as a raw material for recycled films together with these resins. Also, because it is a recovered material, the components and their contents are unstable. The compatibilizer plays an important role in making a recycled film from a waste plastic mixture. Here, in the recycled film according to this embodiment, among various compatibilizers, at least one compatibilizer of an ionomer resin and a maleic anhydride-modified polyolefin (hereinafter also referred to as "specific compatibilizer") is used. The specific compatibilizer may be used alone or in combination of two or more types. In other words, the specific compatibilizer may contain only the ionomer resin, may contain only the maleic anhydride-modified polyolefin, or may contain both the ionomer resin and the maleic anhydride-modified polyolefin. Commercially available products may be used as the compatibilizer.

[0032] Ionomer resin refers to a thermoplastic resin in which polymers are aggregated using the cohesive force of metal ions (such as sodium ions and zinc ions). Examples of ionomer resins include ethylene-based ionomer resins, urethane-based ionomer resins, styrene-based ionomer resins, and ionomer resins using fluorine-based polymers. Among them, ethylene-based ionomer resins are preferred. Ethylene-based ionomer resins have an ion-crosslinked ethylene chain as a basic structure, and examples include resins obtained by crosslinking a polymer having a polyethylene unit and an acrylic acid unit with metal ions. Specific examples (commercially available products) of ionomer resins include those described in the examples.

[0033] Examples of maleic anhydride-modified polyolefins include maleic anhydride-modified polyethylene (such as LLDPE) and maleic anhydride-modified polypropylene. Specific examples (commercially available products) of maleic anhydride-modified polyolefins include those described in the examples.

[0034] The content of the compatibilizer in the recycled film (when two or more types are included, the total of each content) is preferably 0.5% by mass or more, more preferably 1% by mass or more, from the viewpoint of the moldability of the film, with respect to 100% by mass of the total amount of the components contained in the recycled film, and is preferably 3% by mass or less from the viewpoint of improving the tensile properties of the film.

[0035] The recycled film according to this embodiment may contain the following components within a range that does not inhibit the object of the present invention, in addition to the above three essential components.

[0036] (Modifier) The modifier may be included in a resin composition used as a raw material for pre-pellets formed in a compounding step, for example, in a method for manufacturing a recycled film. By using a resin composition containing a slurry obtained by mixing the modifier and water, the compounding step can be carried out in the presence of high-pressure steam described later or in the presence of subcritical water, and it is expected to act and function as moisture for realizing the subcritical state.

[0037] Examples of the modifier include cellulose-based modifiers such as sodium carboxymethyl cellulose (CMC). When a cellulose-based modifier is used, reinforcement of the recycled film by the cellulose-based fibers is expected.

[0038] The content of the modifier in the recycled film (when two or more types are included, the total of each content) is, for example, 0.05% by mass or more and 0.5% by mass or less with respect to 100% by mass of the total amount of the components contained in the recycled film.

[0039] (Additive) Examples of the additive include pigments (colorants), slip agents, fillers, stabilizers, plasticizers, and the like. The content of the additive in the recycled film (when two or more types are included, the total of each content) is, for example, 0.5% by mass or more and 3% by mass or less with respect to 100% by mass of the total amount of the components contained in the recycled film.

[0040] The recycled film according to this embodiment configured as described above is a film obtained by material recycling of a waste plastic mixture recovered from absorbent articles or the like without going through a complicated separation process, and is excellent in moldability and tensile properties. Specifically, the recycled film preferably has a tensile strength of 11.8 MPa or more. The recycled film preferably has a tensile elongation of 400% or more. The recycled film preferably has a tear strength of 3 N or more. Thus, the quality of the recycled film is ensured.

[0041] <Article using recycled film (uses of recycled film)> The recycled film thus obtained can be used for various purposes. For example, it can be used as a diaper collection bag or, after being formed into multiple layers, as a packaging film for absorbent articles, enabling horizontal recycling.

[0042] <Method for manufacturing recycled film> The recycled film according to this embodiment can be manufactured by the inflation method (inflation molding). In this manufacturing method, it is preferable to pre-manufacture the masterbatch to be subjected to the inflation process. Examples of the manufacturing method of the recycled film according to this embodiment include the following three methods. Specific manufacturing conditions include, for example, the conditions described in the examples.

[0043] (Manufacturing method 1 of recycled film) The manufacturing method 1 of the recycled film includes a compounding process 1 and an inflation process 1.

[0044] [Compounding process 1] The compounding process 1 is a process of forming a masterbatch to be subjected to the subsequent inflation process 1. For example, a resin mixture (resin composition for compounding) is prepared by dry-blending a waste plastic mixture, a first polyethylene, and a specific compatibilizer in a predetermined blending amount (content). The resin composition for compounding is melt-kneaded, extruded from a die, and cut into a predetermined size. Through the above processes, for example, pellet-shaped or strand-shaped masterbatch (pellets) is obtained.

[0045] [Inflation process 1] The inflation process 1 is a process of inflation molding using the masterbatch obtained in the compounding process 1. For example, a resin mixture (molding resin composition) is prepared by dry blending the masterbatch and the second polyethylene in a predetermined blending amount. The molding resin composition is melt-kneaded, extruded from a die in a tubular shape, expanded from the inside by the pressure of air, and then cooled. Through the above steps, a recycled film, which is an inflation molded product formed in a tubular shape, can be manufactured.

[0046] The inflation molding may be performed in a single layer or in multiple layers. When performing the inflation molding in multiple layers, for example, in the case of a three-layer structure, by making the intermediate layer contain a large amount of components derived from the waste plastic mixture and using polyethylene that does not contain the waste plastic mixture in the outer layer, the applications of the recycled film can be expanded.

[0047] Examples of the method of co-extrusion of molten resins for multi-layer molding include a pre-die lamination method in which the molten resins are brought into contact before the die, an in-die lamination method in which they are brought into contact inside the die, and an out-die lamination method in which they are brought into contact after being discharged from a plurality of concentric lips of the die.

[0048] (Manufacturing Method 2 of Recycled Film) The manufacturing method 2 of the recycled film includes a compounding process 2-1, a compounding process 2-2, and an inflation process 2. That is, the manufacturing method 2 is different from the above manufacturing method 1 in that it includes two compounding processes.

[0049] [Compounding Process 2-1] Compound process 2-1 is the first compound process that forms fluff to be used as a raw material in the subsequent compound process 2-2. For example, a resin mixture is prepared by dry blending a waste plastic mixture and first polyethylene in a predetermined compounding ratio. The resin mixture is melt-kneaded, extruded in a belt shape from a T-die, and pulverized. Through the above steps, for example, scaly fluff is obtained. Note that the fluff (the resin mixture used as its raw material) does not contain a specific compatibilizer.

[0050] [Compound process 2-2] Compound process 2-2 is the second compound process that forms a masterbatch to be used in the subsequent inflation process 2. For example, a resin mixture (compounding resin composition) is prepared by dry blending the fluff obtained in compound process 2-1, second polyethylene, and a specific compatibilizer in a predetermined compounding ratio. The compounding resin composition is melt-kneaded, extruded from a die, and cut into a predetermined size. Through the above steps, for example, pellet-shaped or strand-shaped masterbatch (pellets) is obtained.

[0051] [Inflation process 2] Inflation process 2 is a process of inflation molding using the masterbatch obtained in compound process 2-2. For example, a resin mixture (molding resin composition) is prepared by dry blending the masterbatch and third polyethylene in a predetermined compounding ratio. Other than the above, the same process sequence as inflation process 1 can be applied.

[0052] (Manufacturing method 3 of recycled film) The manufacturing method 3 of recycled film includes a compound process 3-1, a compound process 3-2, and an inflation process 3. That is, the manufacturing method 3 is different from the above manufacturing method 1 in that it includes two compound processes. Also, the melting and kneading conditions in the first compound process 3-1 of the manufacturing method 3 are different from the melting and kneading (normal kneading) conditions in the first compound process 2-1 of the above manufacturing method 2.

[0053] [Compound Process 3-1] Compound Process 3-1 is the first compound process that forms prepellets to be used as raw materials in the subsequent Compound Process 3-2. For example, water (slurry) containing a predetermined amount of a modifier (cellulose-based modifier) is prepared. The mixing ratio (mass ratio) of water to the cellulose-based modifier is not particularly limited, and for example, it is about water:cellulose-based modifier = 95:5 to 99.5:0.5. A resin mixture is prepared by blending this slurry with a waste plastic mixture and first polyethylene in a predetermined blending amount. The resin mixture is melt-kneaded in the presence of "high-pressure steam", in the presence of "subcritical water", or under conditions of a combination thereof, extruded from a die, and pelletized. Through the above steps, for example, pellet-shaped or strand-shaped prepellets are obtained. Note that the prepellets (the resin mixture used as their raw material) do not contain a specific compatibilizer.

[0054] In this specification, "high-pressure steam" refers to water (gas) whose temperature is equal to or higher than the boiling point (100°C) of water at atmospheric pressure and equal to or lower than the critical point of water (374°C, 22.1 MPa), and whose saturated steam pressure is equal to or lower than that in the temperature range.

[0055] In this specification, "subcritical water" refers to water (subcritical water, liquid) in a high-temperature and high-pressure state near the critical point but not reaching the critical point. More specifically, "subcritical water" refers to water (liquid) whose temperature is equal to or higher than the boiling point of water at atmospheric pressure and equal to or lower than the critical point of water, and whose pressure is at least near the saturated steam pressure.

[0056] In [Compound Process 3-1], in order to realize kneading in the presence of "high-pressure steam" or "subcritical water", for example, a co-rotating twin-screw extruder equipped with a pressure regulating valve (pressure control valve) in the middle part of the cylinder and a vent (dehydration (degassing) hole) in the terminal (rear end) part is used. The kneading conditions using the twin-screw extruder may be adjusted as appropriate. For example, the pressure and temperature in the middle part of the cylinder may be set to the maximum pressure (e.g., 0.3 to 10 MPa) and the maximum temperature (e.g., 180 to 240 °C). In this case, the pressure and temperature may be gradually increased from the tip of the cylinder to the middle part so as to reach the maximum pressure and the maximum temperature, while the pressure and temperature may be gradually decreased from the maximum pressure and the maximum temperature from the middle part to the terminal part of the cylinder.

[0057] By performing the kneading of the resin mixture in Compound Process 3-1 in the presence of "high-pressure steam", in the presence of "subcritical water", or in the presence of "high-pressure steam" and "subcritical water", an improvement in the tensile properties of the recycled film is expected. Further, since the presence of water is a prerequisite for kneading in the above presence, it is not necessary to sufficiently dry the waste plastic mixture (material cycle) used in Compound Process 3-1.

[0058] [Compound Process 3-2] Compound Process 3-2 is a second compound process for forming a masterbatch to be used in the subsequent inflation process 3. For example, a resin mixture (compound resin composition) obtained by dry-blending the prepellets obtained in Compound Process 3-1, a second polyethylene, and a specific compatibilizer in a predetermined compounding amount is prepared. The compound resin composition is melt-kneaded, extruded from a die, and cut into a predetermined size. Through the above steps, for example, pellet-shaped or strand-shaped masterbatch (pellets) can be obtained.

[0059] [Inflation Process 3] The inflation step 3 is a step of performing inflation molding using the masterbatch obtained in the compounding step 3-2. For example, a resin mixture (molding resin composition) in which the masterbatch and the third polyethylene are dry-blended in a predetermined blending amount is prepared. Other than the above, the same process sequence as in the inflation step 1 can be applied.

[0060] The extruder is not particularly limited, but it is preferable to use a twin-screw extruder in each compounding step and a single-screw extruder in each inflation step.

[0061] In each compounding step, if necessary, the resin mixture may be kneaded in the presence of "high-pressure steam", in the presence of "subcritical water", or in the presence of "high-pressure steam" and "subcritical water". In each compounding step, if necessary, the waste plastic mixture or resin mixture (to be subjected to kneading) may be pulverized by a known method before kneading.

[0062] In each inflation step, after cooling the inflation molded product (recycled film), for example, treatments such as gravure printing and gusset processing may be performed. The recycled film may be wound, for example, by a winder.

[0063] In the method for manufacturing a recycled film according to this embodiment configured as described above, a recycled film containing a waste plastic mixture as a raw material can be manufactured without going through a complicated separation step. The recycled film obtained by this manufacturing method has, for example, a width (width when the inflation molded product is folded) of about 100 mm to 500 mm (circumference of about 300 mm to 1000 mm) and a thickness of about 30 μm to 100 μm.

Examples

[0064] Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples, and these examples can be modified and changed based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0065] <Manufacture of Recycled Film> (Examples 1 to 5, Comparative Example 1, Comparative Example 2) [Compound Process 1] The waste plastic mixture, polyethylene (first polyethylene), and compatibilizer shown in Table 1 (in the compound process column) were dry-blended in the blending amounts shown in Table 1 to obtain a mixture (resin composition for compounding). The waste plastic mixture used was the one pulverized by a plastic pulverizer (JC-5D type manufactured by Morita Seiki Kogyo Co., Ltd.). This mixture was melt-kneaded using a co-rotating twin-screw extruder under the conditions of a molding temperature of 150°C to 260°C and a screw rotation speed of 350 rpm, extruded into strands with a diameter of 2 mm to 4 mm, and the extruded kneaded product was cut to obtain a masterbatch (pellets) of the resin composition. By providing a melting zone at 260°C in the middle of the molding temperature, the above mixture was completely melted once and then kneaded. The die holder was set at 180°C. [Inflation Process 1] The masterbatch obtained in Compound Process 1 and the polyethylene (second polyethylene) shown in Table 1 (in the inflation process column) were dry-blended in the blending amounts shown in Table 1 to obtain a mixture (resin composition for molding). This mixture was melt-kneaded using a single-screw extruder under the conditions of a molding temperature of 190°C to 200°C and a screw rotation speed of 70 rpm, guided to a circular die for inflation molding, cooled and solidified by air cooling, and wound by a winder to obtain a recycled film which is an inflation molded product. The finished width of the film (width when the inflation molded product is folded) was 150 mm (circumference of the molded product: 300 mm), and the thickness was 70 μm. The specifications of the screw were full flight, L / D: 25, C / R: 3.08.

[0066] (Examples 6, 7) [Compound Process 2-1 (First Compound Process)] The waste plastic mixture and polyethylene (the first polyethylene, the polyethylene described in the upper row of the column) shown in Table 1 (Compound Process Column) were dry blended in the blending amounts shown in Table 1 to obtain a mixture. The waste plastic mixture used was the one pulverized by a plastic pulverizer (JC-5D type manufactured by Morita Seiki Kogyo Co., Ltd.). This mixture was melt-kneaded with a co-rotating twin-screw extruder under the conditions of a molding temperature of 170°C to 210°C and a screw rotation speed of 1050 rpm, and the kneaded product extruded through a T-die with a width of 350 mm and a lip opening of 5 mm was pulverized to obtain fluff of the resin composition. The specification of the screw was L / D: 28. [Compound Process 2-2 (the second compound process)] The fluff obtained in Compound Process 2-1, the polyethylene (the second polyethylene, the polyethylene described in the lower row of the column) shown in Table 1 (Compound Process Column), and a compatibilizer were dry blended in the blending amounts shown in Table 1 to obtain a mixture (resin composition for compounding). Except for using this mixture, a masterbatch (pellet) of the resin composition was obtained in the same manner as in Compound Process 1. [Inflation Process 2] The masterbatch obtained in Compound Process 2-2 and the polyethylene (the third polyethylene) shown in Table 1 (Inflation Process Column) were dry blended in the blending amounts shown in Table 1 to obtain a mixture (resin composition for molding). Except for using this mixture, a recycled film which is an inflation molded product was obtained in the same manner as in Inflation Process 1.

[0067] (Example 8, Example 12) [Compound Process 3-1 (the first compound process)] Water and sodium carboxymethyl cellulose (CMC) were put into a circular container (capacity: 20 L) at a mass ratio of water:CMC = 98.5:1.5 and mixed with a propeller-type stirrer to obtain water containing 1.5% by mass of CMC (CMC slurry). Next, the waste plastic mixture, polyethylene (the first polyethylene, the polyethylene described in the upper row of the column), and CMC slurry shown in Table 1 (in the compounding process column) were blended in the blending amounts shown in Table 1 to obtain a mixture. The waste plastic mixture used was the one pulverized by a plastic pulverizer. This mixture was melt-kneaded at a maximum set temperature of 230°C and a screw rotation speed of 60 rpm using a co-rotating twin-screw extruder equipped with a pressure regulating valve in the middle part of the cylinder and a vent at the end part, extruded into strands, and pelletized to obtain pre-pellets. The maximum pressure in the middle part was 0.5 MPa and the set temperature was 230°C. [Compounding Process 3-2 (Second Compounding Process)] The pre-pellets obtained in Compounding Process 3-1, polyethylene (the second polyethylene, the polyethylene described in the lower row of the column) shown in Table 1 (in the compounding process column), and a compatibilizer were dry-blended in the blending amounts shown in Table 1 to obtain a mixture (resin composition for compounding). A masterbatch (pellets) of the resin composition was obtained in the same manner as in Compounding Process 1 except that this mixture was used. [Inflation Process 3] The masterbatch obtained in Compounding Process 3-2 and polyethylene (the third polyethylene) shown in Table 1 (in the inflation process column) were dry-blended in the blending amounts shown in Table 1 to obtain a mixture (resin composition for molding). This mixture was melt-kneaded using a single-screw extruder at a molding temperature of 205°C and a screw rotation speed of 45 rpm, led to a circular die for inflation molding, and after inflation molding, cooled and solidified by air cooling. After gravure printing and gusset processing, it was wound up by a winder to obtain a recycled film which is an inflation molded product. The finished width of the film was 280 mm, the pitch was 60 mm (the maximum width of the film was 400 mm. The circumference of the molded product was 800 mm), and the thickness was 50 μm. The specification of the screw was L / D: 30.

[0068] (Examples 9 to 11, Comparative Example 3) A recycled film as an inflation molded article was obtained in the same manner as in Example 8, except that Inflation Step 1 was carried out instead of Inflation Step 3.

[0069] <Evaluation of Recycled Film> For each example and comparative example, the following items were evaluated. The results are shown in Table 1.

[0070] ≪Moldability of Film≫ In Inflation Steps 1 to 3, those that could be formed into a film were marked as "○", and those that could not be formed into a film were marked as "×".

[0071] ≪Tensile Properties of Film≫ In accordance with JIS K 7127:1999, the tensile properties of the film were measured. Specifically, a test film of test piece type 3 dumbbell was prepared, and a tensile test was carried out using a tensile testing machine (manufactured by Shimadzu Corporation, product name: Autograph AG-5000A) under the conditions of a temperature of 25°C and a tensile speed of 100 mm / min. As the tensile properties of the film, the tensile strength [MPa], tensile elongation [%], and tear strength [N] in the MD and TD were measured. Among MD and TD, the lower numerical value was taken as the measured value.

[0072]

Table 1

[0073] The various materials shown in Table 1 used for the production of the recycled film are shown below. (Waste plastic mixture) · "Waste plastic mixture derived from disposable paper diapers (before use)": A waste plastic mixture obtained by removing pulp and superabsorbent polymer from disposable paper diapers before use and separating and recovering them. The components contained in the waste plastic mixture of "disposable paper diapers (before use)" used in the examples were determined by taking a partial sample after pulverizing the mixture with a plastic pulverizer (JC-5D type manufactured by Morita Seiki Kogyo Co., Ltd.) and thoroughly stirring, and measuring the IR spectrum. When the total amount of components contained in the mixture was set to 100% by mass, it contained 65-75% by mass of polypropylene, 10-20% by mass of styrene-based elastomer, 5-10% by mass of polyethylene, 3-8% by mass of calcium carbonate, and 2-5% by mass of polyurethane. In addition, it was confirmed to contain polyethylene terephthalate and pulp as trace components. In other words, the mixture contains at least one thermoplastic resin such as polypropylene (PP), styrene-based resin, various polyethylenes, polyethylene terephthalate (PET), and polyurethane as the main component (containing at least polypropylene (PP) and styrene-based resin (exceeding 50% by mass in total)). Also, the mixture is a recovered product recovered without going through a complex separation process (at the separation level as solid fuel), and due to the insufficient separation, it contains a small amount of components such as pulp and carbonate components such as calcium carbonate in addition to the above. · "Waste plastic mixture derived from disposable paper diapers (after use)": A waste plastic mixture obtained by removing pulp and superabsorbent polymer from used disposable paper diapers containing excrement and urine and separating and recovering them. The composition (components contained) of the mixture is the same as that of "disposable paper diapers (before use)".

[0074] (Polyethylene) · "End material of infusion bag (LDPE)": An end material (pre-consumer product) produced when manufacturing an infusion bag (container for intravenous drip drugs, etc.), polyethylene containing LDPE as the main component (not containing polypropylene and styrene-based resin), MFR: 1.5-2 g / 10 min [Measurement conditions for MFR: temperature 190 °C, load 2.16 kg (hereinafter, the same applies unless otherwise specified)]. · TITANLENE (registered trademark) LDF200YZ: LDPE manufactured by Lotte Chemical Corporation, MFR: 2 g / 10 min, density: 0.922 g / cm 3 。 · High-Zex (registered trademark) 3600F: HDPE manufactured by Prime Polymer Co., Ltd., MFR: 0.98 g / 10 min, density: 0.958 g / cm 3 。 · Evolue (registered trademark) SP1520: LLDPE manufactured by Prime Polymer Co., Ltd., MFR: 2 g / 10 min, density: 0.913 g / cm 3 。 · Lotrene (registered trademark) FD0274: LDPE manufactured by QAPCO, MFR: 2.4 g / 10 min, density: 0.923 g / cm 3 。

[0075] (Modifier) · SUNROSE (registered trademark) SLD-F1: Sodium carboxymethyl cellulose (CMC) manufactured by Nippon Paper Industries Co., Ltd.

[0076] (Compatibilizer) · Maricon (registered trademark) J1000MB: A product obtained by melt-kneading 10% by mass of a polyethylene-based (reactive system) ionomer composed of zinc (Zn) ions and 90% by mass of LLDPE, manufactured by Osaka Gas Chemical Co., Ltd. · Modic (registered trademark) M114: Maleic anhydride-modified (reactive system, acid anhydride graft) LLDPE manufactured by Mitsubishi Chemical Corporation, MFR: 3 g / 10 min, density: 0.92 g / cm 3 。 · Himilan (registered trademark) 1705: An ionomer formed from an ethylene-methacrylic acid copolymer and zinc ions, manufactured by Mitsui Dow Polychemicals Co., Ltd. · Taftec (registered trademark) M1911: Maleic anhydride-modified hydrogenated styrene-based thermoplastic elastomer (SEBS) manufactured by Asahi Kasei Corporation, MFR: 4.5 g / 10 min [Measurement conditions for MFR: temperature 230 °C, load 2.16 kg], density: 0.91 g / cm 3 , acid value: 2. · Taftec (registered trademark) M1913: Maleic anhydride-modified hydrogenated styrene-based thermoplastic elastomer (SEBS) manufactured by Asahi Kasei Corporation, MFR: 5 g / 10 min [Measurement conditions for MFR: temperature 230 °C, load 2.16 kg], density: 0.92 g / cm 3 , acid value: 10.

[0077] (Pigment) ·PO-CI0101 C White: A white pigment (TiO2 80% / PE 20%) manufactured by Nihon Hiromitsu Bics Co., Ltd. ·CR-60: A white pigment (TiO2 95% / PE 5%) manufactured by Ishihara Sangyo Co., Ltd.

[0078] (Slip Agent) ·TMB114: A masterbatch manufactured by Toho Co., Ltd., http: / / toho-corp.net / merchandise_0103slip.html.

[0079] <Consideration of Examples> ·In each example, although a waste plastic mixture, which is a mixture of insufficiently separated thermoplastic resins separated and recovered from absorbent articles into paper pulp and a superabsorbent polymer without undergoing a complex separation process (at the separation level as a solid fuel), is used, it has been found that a recyclable film can be formed by combining polyethylene with specific compatibilizers (ionomer resin, maleic anhydride-modified polyolefin). It has been confirmed that the waste plastic mixture can be used as a filler for the film without further separation, that is, material recycling is possible. ·On the other hand, in Comparative Examples 1 and 2 that do not contain a specific compatibilizer, films could not be formed. ·From these results, it is considered that in a recyclable film (film forming) containing a waste plastic mixture, polyethylene, and a compatibilizer, the affinity between the thermoplastic resins constituting the waste plastic mixture and polyethylene and the base resin of the compatibilizer is influential. ·From the comparison between Example 1 and 5, or the comparison between Example 6 and 7, it is considered that the composition (constituents) of the waste plastic mixture contributes more significantly to the tensile properties of the film than the elements before and after the use of the waste plastic mixture. ·From the comparison between Example 1 and 4, it is considered that LLDPE is more preferable than LDPE for improving the tensile properties of the film in terms of polyethylene. · From the comparison between Example 5 and Example 7, it is considered that the more compounding steps (kneading steps) there are, the more it contributes to the improvement of the tensile properties of the film. · From the comparison between Examples 8, 9, 10, 11 and Comparative Example 3, it was found that as the content of polyethylene (especially LLDPE) in the film decreased, the tensile properties of the film gradually decreased and finally it became impossible to form.

Industrial Applicability

[0080] As described above, the present invention is suitable for material recycling (recycled film) of waste plastic mixtures.

Claims

1. A recycled film comprising a waste plastic mixture, polyethylene, and a compatibilizer, wherein the waste plastic mixture contains a thermoplastic resin as a main component, and the compatibilizer contains at least one selected from the group consisting of an ionomer resin and a maleic anhydride-modified polyolefin. The recycled film is characterized by this.

2. The recycled film according to claim 1, wherein the waste plastic mixture contains at least one selected from the group consisting of polypropylene, styrene-based resin, polyethylene terephthalate, polyethylene, polyurethane, paper pulp, and a carbonate component.

3. The recycled film according to claim 1, wherein the waste plastic mixture contains at least polypropylene and a styrene-based resin as the thermoplastic resin.

4. The recycled film according to claim 1, wherein the waste plastic mixture is a recovered material from absorbent articles.

5. The recycled film according to claim 4, wherein the absorbent article is a used article.

6. The recycled film according to claim 1, characterized in that the tensile strength is 11.8 MPa or more.

7. An article characterized by using the recycled film according to any one of claims 1 to 6.

8. A method for producing a recycled film comprising a waste plastic mixture, polyethylene, and a compatibilizer, a compounding step of kneading the waste plastic mixture, a first polyethylene, and the compatibilizer to obtain pellets, A method for manufacturing a recycled film, comprising an inflation step of dry-blending the pellet and a second polyethylene and then performing inflation molding.

9. A method for manufacturing a recycled film, comprising a waste plastic mixture, polyethylene, and a compatibilizer, a first compounding step of obtaining fluff or pre-pellets by kneading the waste plastic mixture and a first polyethylene, a second compounding step of kneading the fluff or pre-pellets and a second polyethylene to obtain pellets, and an inflation step of dry-blending the pellets and a third polyethylene and then performing inflation molding.

10. The method for manufacturing a recycled film according to claim 8 or 9, wherein the compounding step is performed in the presence of high-pressure steam and / or in the presence of subcritical water.

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