Method for manufacturing plastic films

Abstract

The present invention provides a method for producing a plastic film made of a mixed resin using repellets, which can produce a plastic film of good quality. [Solution] A method for manufacturing a plastic film, comprising a repellet production step of obtaining repellet from a fluff assembly, and a film manufacturing step of manufacturing a film from raw material pellets containing the repellet, wherein the fluff assembly comprises a first fluff mainly containing a first raw material and a second fluff mainly containing a second raw material, the repellet contains the first raw material and the second raw material, and the first raw material and the second raw material are different from each other.

Description

Technical Field

[0005] , ,

[0001] The present invention relates to a method for manufacturing a plastic film.

Background Art

[0002] Plastic films are used as packaging materials for various applications such as foods, beverages, chemicals, industrial products, etc. Their roles include ingredient labeling of the contents, manufacturing date, design of the product, and advertising. In the production of plastic films, the resin used as the raw material may be pelletized and then used for film formation.

[0003] Patent Documents 1 and 2 disclose heat-shrinkable films manufactured using pellets. In the production of plastic films, depending on the desired performance, etc., films may be formed from a mixed resin containing a plurality of resins. In this case, usually, a plurality of types of pellets made from different raw materials are melt-kneaded to obtain a mixed resin, which is then pelletized once or directly used for the production of plastic films without pelletization. Pellets include virgin pellets made from unused virgin plastic as the raw material and re-pellets made from recycled plastic as the raw material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When obtaining a mixed resin by melt-kneading multiple types of pellets made from different raw materials, uniformity of the mixed resin is required. This is because the uniformity of the mixed resin affects the quality of the plastic film obtained thereafter. Multiple types of pellets have different melting points and melting timings due to their different raw materials. They also have different viscosities after melting. In order to obtain a uniform mixed resin, if the screw rotation speed is increased to apply high shear force or the melting temperature is increased during melt-kneading, the high thermal history and high shear force will cause a decrease in molecular weight, leading to a deterioration in the quality of the mixed resin. This deterioration in the quality of the mixed resin affects the quality of the plastic film obtained thereafter.

[0006] Therefore, the present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a plastic film made of a mixed resin using repellets, which can produce a plastic film of good quality. [Means for solving the problem]

[0007] The present invention relates to the following examples [1] to [5]. [1] A repellet production process to obtain repellets from fluff aggregates, The process includes a film-forming step in which a film is formed using raw material pellets containing the aforementioned repellets, The aforementioned fluff aggregate comprises a first fluff containing a first raw material as its main component and a second fluff containing a second raw material as its main component. The repellets include the first raw material and the second raw material, A method for manufacturing a plastic film, wherein the first and second raw materials are different from each other. [2] The process further comprises a preparation step of preparing the fluff assembly from a plastic label before the repellet production step, The aforementioned plastic label comprises a label substrate and a printing layer. The method for manufacturing a plastic film according to [1], wherein the preparation step includes a step of crushing the plastic label and a step of removing the printed layer. [3] The preparation steps described above are: Preparation step a for obtaining the first fluff from a first plastic label containing the first raw material, The process includes a preparation step b for obtaining the second fluff from a second plastic label containing the second raw material, The method for manufacturing a plastic film according to [2], wherein the preparation steps a and b are performed in the same step or in separate steps. [4] The first raw material and the second raw material both consist of thermoplastic resins. The method for producing a plastic film according to [1] or [2], wherein the thermoplastic resin is one or more selected from the group consisting of polyester resins, polystyrene resins, polyester-polystyrene mixed resins, polyolefin resins, and vinyl chloride resins. [5] The method for producing a plastic film according to [1] or [2], wherein the raw material pellets include virgin pellets. [Effects of the Invention]

[0008] The present invention provides a manufacturing method that allows for the production of high-quality plastic films made of mixed resins using repellets. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a flowchart showing an example of a method for manufacturing a plastic film according to the present invention. [Figure 2] Figure 2 is a schematic diagram showing an example of the relationship between the label substrate and the fluff assembly in the present invention. [Figure 3] Figure 3 is a flowchart showing another example of a method for manufacturing a plastic film according to the present invention. [Modes for carrying out the invention]

[0010] The following describes a method for manufacturing a plastic film according to this embodiment, as an example of the present invention. However, the scope of the present invention is not limited to what is described below.

[0011] The method for manufacturing a plastic film in this embodiment comprises a repellet production step of obtaining repellet from a fluff assembly, and a film manufacturing step of forming a film using raw material pellets containing the repellet, wherein the fluff assembly comprises a first fluff mainly containing a first raw material and a second fluff mainly containing a second raw material, and the repellet comprises the first raw material and the second raw material, the first raw material and the second raw material being different from each other.

[0012] Figure 1 is a flowchart showing an example of a method for manufacturing a plastic film according to the present invention. As shown in Figure 1, the method for manufacturing a plastic film according to this embodiment includes a repellet generation step S1 and a film manufacturing step S2, and by going through the repellet generation step S1 and the film manufacturing step S2, the final product, a plastic film, can be manufactured. The method for manufacturing a plastic film according to the present invention may include a preparation step S0 for preparing a fluff assembly before the repellet generation step S1.

[0013] In the repellet production process S1, the fluffs forming the fluff aggregate are thin and can be easily melted by heating. Therefore, even if there are differences in melting temperature and melt viscosity after melting between the first and second fluffs, the repellet production process S1 can produce repellets made of a highly uniform mixed resin from a fluff aggregate containing the first and second fluffs. In the film manufacturing process S2, a plastic film made of a mixed resin with good quality can be manufactured using raw material pellets containing such repellets.

[0014] The first fluff contained in the fluff aggregate is a crushed piece of the label base material in the first plastic label, and the second fluff is a crushed piece of the label base material in the second plastic label. Using FIG. 2, the relationship between the label base material and the fluff will be described. FIG. 2 is a schematic diagram showing an example of the relationship between the label base material and the fluff aggregate in the present invention. As shown in FIG. 2, the label base material 10 becomes fluff 21. That is, the fluff 21 is a crushed piece of the label base material 10. The label base material 10 and the fluff 21 may contain a main component and may also contain a subcomponent. Impurities 22 may adhere to the label base material 10 and the fluff 21. The fluff aggregate 20 is an aggregate of fluff containing the fluff 21 and may contain impurities 22. The impurities 22 may be attached to the fluff 21 or may not be attached. The main component contained in the label base material 10 and the fluff 21 is a thermoplastic resin. The subcomponent contained in the label base material 10 is a component used for forming a label base material other than the thermoplastic resin, and examples thereof include a colorant, a plasticizer, an anti-blocking agent, and an antistatic agent. The impurities 22 contained in the fluff aggregate 20 include, for example, components of a printing layer and components of an adhesive. Examples of the components of the printing layer and the adhesive include a vehicle, a tackifier, a colorant, a lubricant, an antistatic agent, and an organic solvent.

[0015] (First raw material, second raw material) In this embodiment, the first and second raw materials are both thermoplastic resins and are different from each other. The thermoplastic resin is one or more selected from the group consisting of, for example, polyester resins, polystyrene resins, polyester-polystyrene mixed resins, polyolefin resins, and vinyl chloride resins. Examples of polyester resins include aromatic polyester resins such as polyethylene terephthalate resins, polybutylene terephthalate resins, polyethylene naphthalate resins, and alicyclic polyester resins, and aliphatic polyester resins such as polycaprolactone resins and polylactic acid resins. Examples of polystyrene resins include general-purpose polystyrene and styrene-butadiene block copolymers. Examples of polyolefin resins include polyethylene resins, polypropylene resins, and cyclic olefin resins. Polyester-polystyrene mixed resin is a resin obtained by mixing a polyester resin and a polystyrene resin, and refers to a thermoplastic resin containing 10% to 90% by mass of polyester resin and 10% to 90% by mass of polystyrene resin in either the first or second raw material. The thermoplastic resin may have some of its constituent monomers modified. Examples of modification include urethane modification, glycol modification, phenol modification, cresol modification, acid modification, acid anhydride modification, etc., and these can be used individually or in combination.

[0016] In this embodiment, the first raw material and the second raw material are different from each other. In this specification, when determining whether the first raw material and the second raw material are different from each other, the determination is made by comparing a specific thermoplastic resin contained in the first raw material (hereinafter also referred to as the "specific thermoplastic resin of the first raw material") with a specific thermoplastic resin contained in the second raw material (hereinafter referred to as the "specific thermoplastic resin of the second raw material").

[0017] The specific thermoplastic resin of the first raw material is determined as follows. When the thermoplastic resin contained in the first raw material exceeds 90% by mass, the thermoplastic resin (hereinafter also referred to as "single substance") is used as the specific thermoplastic resin of the first raw material. When the thermoplastic resin contained in the first raw material is less than 10% by mass, the thermoplastic resin is not the specific thermoplastic resin of the first raw material. When the thermoplastic resin contained in the first raw material does not exceed 90% by mass, excluding the thermoplastic resin less than 10% contained in the first raw material, the specific thermoplastic resin of the first raw material is a single substance composed of one kind of thermoplastic resin contained in the first raw material and 10% by mass or more and 90% by mass or less, or a mixture composed of a plurality of thermoplastic resins contained in the first raw material and 10% by mass or more and 90% by mass or less. That is, the specific thermoplastic resin of the first raw material may be a single substance or a mixture. The above-mentioned polyester-polystyrene mixed resin is a mixture. In addition, the specific thermoplastic resin of the first raw material is preferably contained in the first raw material at 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The specific thermoplastic resin of the second raw material is determined in the same manner as the determination of the specific thermoplastic resin of the first raw material described above.

[0018] When the first raw material and the second raw material are "different from each other", when one is a single substance and the other is a mixture, they are regarded as "different from each other". When both the first raw material and the second raw material are single substances, when the constituent monomers of the specific thermoplastic resin of the first raw material and the specific thermoplastic resin of the second raw material exceed 50 mol% and are different, the first raw material and the second raw material are regarded as "different from each other". When both the first raw material and the second raw material are mixtures, the specific thermoplastic resin of the first raw material and the specific thermoplastic resin of the second raw material are compared with the same content as above. When both specific thermoplastic resins are not all the same, the first raw material and the second raw material are regarded as "different from each other". In this specification, the constituent monomer refers to the monomer constituting the thermoplastic resin.

[0019] Examples of the case where the first raw material and the second raw material are "different from each other" include combinations such as (specific thermoplastic resin of the first raw material: specific thermoplastic resin of the second raw material) shown below. (Polyester resin: Polystyrene resin), (Polyester resin: Polyolefin resin), (Polyester resin: Polyester / Polystyrene mixed resin), (Polyolefin resin: Polyester / Polystyrene mixed resin), (Polyester resin: Polyvinyl chloride resin), (Polyethylene terephthalate resin: Polylactic acid resin), (Polyethylene resin: Polypropylene resin)

[0020] (First flag, second flag) The first fluff contains the first raw material as its main component, and the second fluff contains the second raw material as its main component. The first fluff and the second fluff are different from each other. The difference between the first fluff and the second fluff means that the first raw material contained as its main component in the first fluff is different from the second raw material contained as its main component in the second fluff. From the viewpoint of producing a good plastic film, the first fluff preferably contains 60% or more by volume of the first raw material, more preferably 70% or more by volume, even more preferably 80% or more by volume, and even more preferably 90% or more by volume. From the viewpoint of producing a good plastic film, the second fluff preferably contains 60% or more by volume of the second raw material, more preferably 70% or more by volume, even more preferably 80% or more by volume, and even more preferably 90% or more by volume. The first fluff and the second fluff may contain auxiliary components.

[0021] (Fluff aggregate) The fluff assembly comprises a first fluff and a second fluff. In this specification, the thermoplastic resin that is the main component of the first fluff is used as the first raw material, and the thermoplastic resin that is the main component of the second fluff is used as the second raw material. From the viewpoint of producing a good plastic film, the fluff assembly preferably contains 80% by mass or more of the first fluff and the second fluff, more preferably 90% by mass or more, and even more preferably 100% by mass. The fluff assembly may further contain other fluffs different from the first fluff and the second fluff. Note that the term "fluff assembly" refers to a state in which different fluffs are mixed together. The fluff assembly may contain impurities such as components of the printing layer.

[0022] It is preferable that the fluffs contained in the fluff aggregate have a uniform shape. As mentioned above, non-uniformity in melting time is likely to occur between multiple types of pellets made from different raw materials. However, by ensuring that the fluffs contained in the fluff aggregate have a uniform shape, non-uniformity in melting time among the fluffs can be further suppressed.

[0023] The thickness of the fluffs in the fluff aggregate is preferably 5 μm to 200 μm, and more preferably 10 μm to 150 μm. The maximum length of the fluffs in the fluff aggregate is preferably 0.5 mm to 10 mm. For example, the fluffs are 0.5 mm to 10 mm in length, 0.5 mm to 10 mm in width, and 5 μm to 200 μm in thickness. Because the size of the fluffs is within the above range, fluffs of different sizes can be easily melted together.

[0024] (Plastic label) A plastic label comprises a printing layer and a label substrate whose main component is a thermoplastic resin. Preferably, the plastic label includes a first plastic label and a second plastic label. The first plastic label contains a first raw material. The second plastic label contains a second raw material. The first plastic label and the second plastic label are different from each other. The difference between the first plastic label and the second plastic label means that the first raw material contained in the first plastic label and the second raw material contained in the second plastic label are different from each other. The plastic label may further include other plastic labels different from the first plastic label and the second plastic label.

[0025] In this specification, a thermoplastic resin, which is the main component of the label substrate of the first plastic label, is referred to as the first raw material, and a thermoplastic resin, which is the main component of the label substrate of the second plastic label, is referred to as the second raw material. The label substrate of the first plastic label contains the first raw material as its main component. From the viewpoint of producing a good plastic film, the label substrate of the first plastic label preferably contains 60% by volume or more of the first raw material, more preferably 70% by volume or more, even more preferably 80% by volume or more, and even more preferably 90% by volume or more. The label substrate of the second plastic label contains the second raw material as its main component. From the viewpoint of producing a good plastic film, the label substrate of the second plastic label preferably contains 60% by volume or more of the second raw material, more preferably 70% by volume or more, even more preferably 80% by volume or more, and even more preferably 90% by volume or more. The label substrates of the first plastic label and the label substrates of the second plastic label may contain auxiliary components used in the formation of the label substrates.

[0026] The plastic label can be any known type of plastic label. Examples of known plastic labels include shrink labels, wrap labels, stretch labels, and tack labels. Shrink labels are attached to the container by heat shrinkage. Wrap labels are attached by wrapping them around the container and then bonding or fusing the label ends. Stretch labels are attached to the container by self-stretching. Tack labels are attached to the container by using an adhesive such as a pressure-sensitive adhesive. These plastic labels may be used individually or in combination of two or more types. Preferably, the plastic label is a shrink label that can be attached to the container without using an adhesive.

[0027] The form and shape of plastic labels are not particularly limited as long as they can form a fluff aggregate. Examples include film-like materials, tubular materials formed by bonding the ends of film-like materials with a solvent or heat seal, tubular materials after shrinkage attached to molded products or containers by heat shrinkage, film-like materials that have been unpacked by perforations after being attached to molded products or containers, and coarsely crushed materials thereof.

[0028] The history of a plastic label is not particularly limited. Examples of the history of a plastic label include products that have been distributed to the market, products that are not yet on the market, unused products, products that have undergone intermediate processing, leftover products, defective products, prototypes, and discarded products. The label substrate and printing layer of the plastic label may be of different types, or they may be of the same type. In addition, part or all of the printing layer of the plastic label may have detached.

[0029] The label substrate may or may not have heat shrinkability. Furthermore, the label substrate may or may not have self-shrinkability. Heat shrinkability refers to the property of shrinking at least in the main stretching direction when heated to a heat shrinkage temperature (e.g., 70°C to 100°C). Self-stretchability refers to the property of stretching when a tensile force is applied in one direction and returning to approximately the original length when the tensile force is released.

[0030] The label substrate may be transparent or opaque. A colorless, transparent label substrate does not contain, for example, air (voids, etc.), pigments, dyes, or other colorants. A colored, transparent label substrate contains known transparent colorants. An opaque label substrate may contain known opaque colorants and may contain fine air bubbles due to stretched voids and foaming.

[0031] The label substrate may be a single-layer substrate consisting of one layer, or a multilayer substrate consisting of two or more layers. The thickness of the label substrate is sufficient to obtain fluff, and may be, for example, 10 μm to 100 μm.

[0032] The printed layer of a plastic label is a layer formed by including conventionally known inks, and can provide design and aesthetic appeal to the plastic label. Examples of conventionally known inks include water-based inks, oil-based inks, and UV-curable inks. For oil-based inks, for example, a mixture of colorants such as pigments and dyes, a binder resin, and an organic solvent with additives may be used. For water-based inks, a mixture of a colorant, a water-soluble or water-dispersible binder resin, and additives may be used. For UV-curable inks, a mixture of a colorant, a UV-curable monomer, a UV-curable oligomer, a resin, a photopolymerization initiator, and other additives may be used. Examples of additives include lubricants, anti-blocking agents, and anti-settling agents. Methods for forming the printed layer include gravure printing, flexographic printing, screen printing, toner printing, and inkjet printing.

[0033] The printed layer may be a single layer or a multi-layer layer. The thickness of the printed layer can be appropriately selected depending on the application, for example, it can be approximately 0.1 μm to 10 μm. Depending on its function, the printed layer may be a design printed layer, a base printed layer, a surface coating layer, etc., and these may be provided as a single layer or in appropriate combinations, and the area in which each layer is provided may also be appropriately selected. Depending on the purpose, the area in which the printed layer is formed may also be appropriately selected.

[0034] (Repellet) Repellets can be obtained from a fluff assembly containing a first fluff and a second fluff. That is, a repellet contains a first fluff mainly composed of the first raw material and a second fluff mainly composed of the second raw material. From the viewpoint of uniform mixing, it is preferable that the repellet contains 90% by volume or more of thermoplastic resin, more preferably 95% by volume or more, and even more preferably 100% by volume. Repellets may contain components other than thermoplastic resin. Repellets do not contain virgin pellets, which will be described later.

[0035] The shape and size of the repellets are not particularly limited. Examples of repellet shapes include prismatic, cylindrical, and granular shapes, with cylindrical shapes being preferred from the viewpoint of ease of handling. The size of the repellets may be a diameter of 0.5 mm or more and 5 mm or less, and a maximum length of 0.5 mm or more and 5 mm or less.

[0036] (Raw material pellets) The raw material pellets include refelliced ​​pellets and can be used in the production of plastic films. In other words, the raw material pellets include a first raw material and a second raw material. The raw material pellets may also include virgin pellets, and it is preferable that they include virgin pellets.

[0037] The raw material pellets may contain other thermoplastic resins different from the first and second raw materials. The raw material pellets may consist only of the first and second raw materials.

[0038] The shape and size of the raw material pellets are not particularly limited. Examples of raw material pellet shapes include prismatic, cylindrical, and granular shapes, and cylindrical shapes are preferred from the viewpoint of ease of handling. The size of the raw material pellets may be a diameter of 0.5 mm or more and 5 mm or less, and a maximum length of 0.5 mm or more and 5 mm or less.

[0039] The virgin pellets described above are included in the raw material pellets in a mixed state with repellets and are used in the film manufacturing process. The virgin pellets contain one type of thermoplastic resin as their main component. The thermoplastic resin included as the main component of the virgin pellets is the same type of thermoplastic resin as described above. The virgin pellets may contain one type of virgin pellet, or two or more types of virgin pellets may be combined and included. From the viewpoint of facilitating mixing with repellets, it is preferable that the virgin pellets contain one of the thermoplastic resins included as a main component in at least one of the first and second raw materials.

[0040] <Method for manufacturing plastic film> As shown in Figure 1, the method for manufacturing a plastic film according to the present invention comprises a repellet generation step S1 and a film manufacturing step S2, and by going through the repellet generation step S1 and the film manufacturing step S2, the final product, a plastic film, can be manufactured. The method for manufacturing a plastic film according to the present invention may include a preparation step S0 for preparing a fluff assembly before the repellet generation step S1.

[0041] (Preparation process S0) Preparation step S0 is performed before the repellet production step S1 and is a step of preparing a fluff assembly from plastic labels. As shown in Figure 1, preparation step S0 includes a crushing step S01 and a removal step S02. The crushing step S01 and the removal step S02 may be performed in either order. Preparation step S0 may, for example, have the removal step S02 performed after the crushing step S01, or the crushing step S01 performed after the removal step S02. In preparation step S0, after the crushing step S01 and the removal step S02, the fluff can be mixed to prepare a fluff assembly. The prepared fluff assembly may contain components of the printed layer removed in the removal step S02. Preparation step S0 may have a known drying step to remove moisture adhering to the prepared fluff assembly.

[0042] In the crushing process S01, the plastic label is crushed into label fragments. Here, label fragments refer to the plastic label that has been crushed in the crushing process S01, regardless of the order of the processes. Therefore, label fragments may be crushed plastic labels, or crushed plastic labels from which the printing layer has been removed in the removal process S02. The crushed plastic labels from which the printing layer has been removed in the removal process S02 are called fluffs, and a mixture of multiple fluffs is called a fluff aggregate.

[0043] The crushing step S01 may be able to crush the plastic label by methods such as cutting using a slitter, shredder, or guillotine blade, or crushing using a crusher or grinder, and may be able to crush the plastic label uniformly, or may be able to crush the plastic label at 20 mm intervals.

[0044] The temperature in the crushing process S01 may be below the temperature at which the plastic label melts, and may be 50°C or less.

[0045] In removal step S02, the printing layer of the plastic label is removed, and the label substrate or label piece is removed from the plastic label. Removal step S02 is, for example, a step of bringing the plastic label into contact with a processing solution. The processing solution is selected to dissolve or swell at least the printing layer of the plastic label. In removal step S02, the printing layer on the plastic label may be partially removed or completely removed, and it is preferable that the printing layer is completely removed.

[0046] An example of removal step S02 is described below. In removal step S02, the plastic label is brought into contact with the treatment solution and the plastic label is gently immersed for about 10 minutes, or the plastic label is stirred while immersed. The temperature of the treatment solution at this time can be room temperature (approximately 15°C to 25°C) or ambient temperature (approximately 1°C to 30°C). Note that the temperature of the treatment solution refers to the surface temperature of the plastic label at the time of removal step S02. Note that the temperature of the treatment solution may be room temperature, but from the viewpoint of efficiently removing the printing layer from the plastic label, the temperature of the treatment solution may be higher than room temperature. The treatment solution is preferably alkaline with a pH of approximately 11 to 14 and contains components that dissolve or swell the water-based ink and oil-based ink contained in the printing layer at room temperature. In other words, it is preferable that the treatment solution contains both components that dissolve or swell water-based ink and components that dissolve or swell oil-based ink. By using such a treatment solution, both water-based and oil-based inks can be removed. Furthermore, all water-based and oil-based inks contained in the plastic label can be simultaneously dissolved or swollen, allowing the printed layer to be detached and removed from the plastic label. In addition, if the printed layer includes an ultraviolet-curable ink layer, it is preferable that the treatment solution further contains a component that dissolves or swells the ultraviolet-curable ink.

[0047] The treatment solution may include, for example, a solution containing at least one component selected from the group consisting of an alkaline component, a surfactant, a glycol-based solvent (e.g., glycol ether), and a high-boiling point solvent (e.g., a polymer alcohol). A solution containing an alkaline component and a surfactant is preferred. The treatment solution may also contain components other than those mentioned above. The surfactant may be an ionic surfactant (anionic surfactant, cationic surfactant, amphoteric surfactant) or a nonionic surfactant, and multiple components from these may be used in combination. As the alkaline component, alkali metal hydroxides such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), alkali metal carbonates such as sodium carbonate (Na2CO3), alkali metal bicarbonates such as sodium bicarbonate (NaHCO3), or aqueous ammonia can be used. The concentration of the alkaline component in the treatment solution can be appropriately selected within a range that does not impair the delamination ability, operability, or workability of the printed layer, for example, 0.1 to 10% by mass, preferably 0.5 to 5% by mass, and more preferably 1 to 3% by mass. By bringing the processing solution into contact with the printed layer or plastic label, water-based inks and / or oil-based inks can be dissolved or swollen at room temperature.

[0048] Furthermore, the treatment solution may be a mixture of an aqueous ink remover containing a component that dissolves or swells aqueous ink and an oil-based ink remover containing a component that dissolves or swells oil-based ink. This makes it possible to easily produce a treatment solution containing both a component that dissolves or swells aqueous ink and a component that dissolves or swells oil-based ink.

[0049] The water-based ink remover is not particularly limited as long as it dissolves or swells water-based ink at room temperature. The water-based ink remover may be, for example, a water-based ink remover commercially available for the purpose of removing water-based ink, or it may be a commercially available agent (remover, cleaning agent, etc.) for purposes other than the removal of water-based ink.

[0050] The oil-based ink remover is not particularly limited as long as it dissolves or swells the oil-based ink layer at room temperature. The oil-based ink remover may be, for example, an oil-based ink remover commercially available for the purpose of removing oil-based ink, or it may be a commercially available agent (remover, cleaning agent, etc.) for purposes other than oil-based ink removal.

[0051] Figure 3 is a flowchart illustrating another example of a method for manufacturing a plastic film according to the present invention. As shown in Figure 3, preparation step S0 may include preparation step a and preparation step b. In preparation step a, a first fluff can be obtained from a first plastic label containing a first raw material as the main component. In preparation step b, a second fluff can be obtained from a second plastic label containing a second raw material as the main component. When preparation step S0 includes preparation step a and preparation step b, it is sufficient that a fluff assembly in which the first fluff and the second fluff are mixed is prepared. Preparation steps a and b may be, for example, performed in the same step in a first embodiment, or they may be performed in separate steps in a second embodiment. In the second embodiment, it is preferable to have a step of mixing the first fluff obtained in preparation step a and the second fluff obtained in preparation step b, and this mixing step yields a fluff assembly in which the first fluff and the second fluff are mixed.

[0052] First embodiment: A fluff assembly A is prepared from a label assembly containing a first plastic label and a second plastic label.

[0053] Second aspect: A fluff assembly B is prepared by mixing an assembly b1 consisting of first fluffs obtained from a first plastic label and an assembly b2 consisting of second fluffs obtained from a second plastic label.

[0054] The fluff assembly prepared by preparation step S0 may be fluff assembly A, fluff assembly B, fluff assembly C which is a mixture of fluff assembly A and fluff assembly B, or fluff assembly D which is a mixture of at least one of fluff assembly A and fluff assembly B and at least one of fluff assembly b1 and fluff assembly b2. The fluff assembly prepared by preparation step S0 may have its mixing ratio of these fluff assemblies adjusted as appropriate, for example, it may be fluff assembly B' which has a different mixing ratio of fluff assembly b1 and fluff assembly b2 than fluff assembly B. The fluff assembly prepared by preparation step S0 may be a combination of two or more types selected from, for example, fluff assemblies A, B, B', C, D, etc.

[0055] (Repellet production process S1) In the repellet production step S1, repellets are produced from the fluff assemblies. The fluff assemblies, which are the starting material, may include the fluff assemblies prepared in the preparation step S0, or they may include fluff assemblies other than those prepared in the preparation step S0. Examples of fluff assemblies prepared in the preparation step S0 include fluff assemblies A, B, B', C, D, etc. In the present invention, it is preferable that the above fluff assemblies include the fluff assemblies prepared in the preparation step S0.

[0056] The fluff assembly in the repellet production step S1 includes a first fluff and a second fluff. The method for obtaining the first fluff from the first plastic label and the method for obtaining the second fluff from the second plastic label preferably involves a crushing step S01 and a removal step S02. The crushing step S01 and the removal step S02 may be performed in any order.

[0057] In the repelletization process S1, a preferred method for repelletizing from the fluff assembly is to feed the fluff assembly into an extruder, melt and knead it, and then cut the extruded molten resin into pellets. The fluff assembly is fed into the extruder in a state in which the first fluff and the second fluff are mixed. If the fluff assembly contains other fluffs different from the first and second fluffs, the first fluff, the second fluff, and the other fluffs are fed into the extruder in a state in which they are mixed. The type of extruder is not particularly limited in this invention. For example, a single-screw extruder, a twin-screw extruder, etc., can be used. In order to further mix each fluff, a known dry mixing process may be performed before feeding the fluffs into the extruder.

[0058] The temperature at which the fluff aggregate is melted and kneaded varies depending on the type of thermoplastic resin contained in the fluff aggregate, but may be, for example, 150°C to 250°C. For example, if the fluff aggregate contains a polystyrene-based resin, the temperature may be 150°C to 200°C, and if the fluff aggregate contains a polyester-based resin, the temperature may be 200°C to 250°C. By setting the melting and kneading conditions of the fluff aggregate within the above range, the resulting repellets can be made into uniformly mixed pellets.

[0059] (Film forming process S2) In the film-forming process S2, a film is formed using raw material pellets. The raw material pellets include repelletides produced in the repellet production process S1. The shape of the film may be planar, tubular, unstretched, or stretched. The film formed in the film-forming process S2 is preferably a stretched film that has been stretched at least three times in one direction from an unstretched film, and more preferably a heat-shrinkable stretched film (shrink film) that has been stretched at least three times in one direction from an unstretched film.

[0060] In the film-forming process S2, known methods can be used to form a film using raw material pellets. A planar unstretched film can be obtained, for example, by feeding raw material pellets into an extruder, extruding the melted or melt-kneaded raw material pellets in a planar shape, and cooling and solidifying them with a cooling roll. A planar stretched film can be obtained by stretching the obtained planar unstretched film in at least one direction, either the longitudinal direction (MD direction) or the transverse direction (TD direction). The obtained film may be subjected to annealing, cooling, antistatic treatment, corona discharge treatment, etc., as needed. If the raw material pellets include pellets other than repelletized pellets, each pellet may be fed into the extruder all at once, or the raw material pellets may be mixed dry before melting or melt-kneading.

[0061] Methods for stretching an unstretched film include, for example, roll stretching, tenter stretching, tubular stretching, and ultra-spacing stretching. These methods may be used individually or in combination of two or more. Furthermore, stretching may be performed only in the longitudinal direction (MD direction), only in the transverse direction (TD direction), or after stretching in the transverse direction, or after stretching in the longitudinal direction, or simultaneously in the longitudinal and transverse directions. Stretching may also be performed twice in the same direction. When manufacturing shrink film, which is a heat-shrinkable stretched film, for example, it may be stretched 3 to 7 times in either the longitudinal or transverse direction, and not stretched in the other direction, or stretched more than 1 time but less than or equal to 2 times.

[0062] The temperature at which the unstretched film is stretched may be, for example, 80°C to 130°C, or 85°C to 120°C.

[0063] If the raw material pellets consist solely of refelliced ​​pellets, a film can be formed by feeding the refelliced ​​pellets into an extruder and extruding the molten and kneaded refelliced ​​pellets. If the raw material pellets containing refelliced ​​pellets also contain pellets other than refelliced ​​pellets, such as virgin pellets, a film can be formed by simultaneously feeding the raw material pellets containing refelliced ​​pellets and the pellets other than refelliced ​​pellets into the extruder. To further mix the raw material pellets, a known dry mixing process may be performed before feeding the pellets into the extruder.

[0064] In the present invention, if a film made from raw material pellets has been produced, a laminated film can be manufactured by laminating a film made from other raw material pellets onto the film made from raw material pellets. Examples of other raw material pellets include raw material pellets made solely from virgin pellets. A method for manufacturing the laminated film may be, for example, a method of co-extrusion using multiple extruders.

[0065] (Layer structure of the film) The plastic film in this invention only needs to have at least one layer of plastic film made using raw material pellets containing repellets, starting from a fluff aggregate as the raw material. Therefore, the plastic film in this invention may be a single-layer film or a laminated film.

[0066] If the plastic film to be manufactured is a single-layer film, it may be, for example, film A made from raw material pellets consisting of repellets, or film B made from raw material pellets containing repellets and virgin pellets.

[0067] When the manufactured plastic film is a laminated film, it may be a two-layer film made by combining two types of films such as film A, film B, film B' which has a different mixing ratio of pellets contained in film B, and film C which is made from raw material pellets consisting of virgin pellets, or it may be a three-layer film or a multilayer film made by combining three or more types. As a preferred multilayer film, an example is a configuration in which film C or film B' is laminated on both sides of film A or film B so as to be the outermost surface of the multilayer film.

[0068] The thickness of the plastic film in this invention may be 10 μm or more and 100 μm or less, or 11 μm or more and 80 μm or less, depending on the ease of use as a film.

[0069] Furthermore, the plastic film in this invention may be subjected to surface treatments and processing such as slitting, corona treatment, printing, adhesive application, coating, and vapor deposition as needed, and can be processed with various solvents or heat sealing. The plastic film of this invention can be printed on and used as a plastic label. [Explanation of Symbols]

[0070] S0 Preparation process, S01 Crushing process, S02 Removal process, S0A Preparation process a, S0B Preparation process b, S1 Repellet production process, S2 Film formation process, 10 Label substrate, 20 Fluff assembly, 21 Fluff, 22 Impurities

Claims

1. A repellet production process to obtain repellets from fluff aggregates, The process includes a film-forming step in which a film is formed using raw material pellets containing the aforementioned repellets, The aforementioned fluff aggregate comprises a first fluff mainly containing the first raw material and a second fluff mainly containing the second raw material. The repellets include the first raw material and the second raw material, A method for manufacturing a plastic film, wherein the first and second raw materials are different from each other.

2. The process further includes a preparation step of preparing the fluff assembly from a plastic label before the repellet generation step, The aforementioned plastic label comprises a label substrate and a printing layer. The method for manufacturing a plastic film according to claim 1, wherein the preparation step includes the step of crushing the plastic label and the step of removing the printed layer.

3. The aforementioned preparation step is, Preparation step a for obtaining the first fluff from the first plastic label containing the first raw material, The process includes a preparation step b for obtaining the second fluff from a second plastic label containing the second raw material, The method for manufacturing a plastic film according to claim 2, wherein the preparation steps a and b are performed in the same step or in separate steps.

4. The first and second raw materials are both made of thermoplastic resin. The method for producing a plastic film according to claim 1 or 2, wherein the thermoplastic resin is one or more selected from the group consisting of polyester resins, polystyrene resins, polyester / polystyrene mixed resins, polyolefin resins, and vinyl chloride resins.

5. The method for producing a plastic film according to claim 1 or 2, wherein the raw material pellets include virgin pellets.

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