Method for manufacturing raw materials for release film and method for manufacturing recycled release film

Abstract

To provide raw materials for release films that can be used to obtain good appearance while reusing used release films.SOLUTION: The raw material (M) for release films (y) is made from used release films (y). In the thermal mass differential thermal analysis (TG-DTA analysis) of the raw material (M) for release films, the oxidation start temperature (Ts) obtained when the temperature is increased from 25°C under air at a rate of 5°C / minute is 120°C or higher and 350°C or lower.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a raw material for a release film, a recycled release film, and a method for producing the same. [Background technology]

[0002] Release films are used when manufacturing molded products, when manufacturing laminates by bonding different materials, etc. Specific examples include release films that are used by being placed between a coverlay film and a hot plate when manufacturing a flexible printed circuit board (FPC) by bonding a coverlay film (CL film) to a flexible film with exposed circuits (circuit-exposed film) via an adhesive by hot pressing, and release films that are used by being placed between a mold and an object to be molded in the manufacturing process of a semiconductor device.

[0003] Since such release films are used and discarded in factories, it is extremely effective in terms of resource utilization to be able to collect and recycle the release films. Conventionally, release films have been recycled by various methods. For example, Patent Document 1 (JP 2023-23947 A) discloses a technology for removing a release layer from a polyester film having a readily soluble resin layer and a release layer in order on one side of the polyester film together with the readily soluble resin layer. In addition, Patent Document 2 (JP 2022-122830 A) discloses that a predetermined layer is removed from a laminated polyester film, and then a highly pure polyester film is taken out and reused. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-23947 A [Patent Document 2] JP 2022-122830 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional method for recycling release films involves separating and peeling off the release layer, the base material layer, etc., and extracting and reusing only the desired material. Therefore, only a portion of the material is reused, and there is room for improvement in terms of effective reuse of the release film. Furthermore, release films obtained using raw materials recycled from used release films contain impurities called fish eyes, and are insufficient in terms of obtaining a good appearance. [Means for solving the problem]

[0006] The present inventors conducted a study focusing on the development of a raw material for release films made by recycling used release films, and found that by controlling the thermogravimetric differential thermal analysis (TG-DTA analysis) of the raw material for release films as an index, the occurrence of fish eyes can be suppressed and a good appearance can be obtained in some cases, but not in other cases. Specifically, they found that it is effective to set the oxidation onset temperature (Ts) obtained by thermogravimetric differential thermal analysis (TG-DTA analysis) to 120°C or higher and 350°C or lower, and completed the first invention. Furthermore, the present inventors conducted further research and unexpectedly found that used release film could be crushed, heated and melted, and processed into pellets, which could then be used as a raw material for the release film and recycled release film could be produced by extrusion processing or the like, thus completing the second invention.

[0007] According to the present invention, the following techniques are provided for a raw material for a release film and a method for producing a recycled release film.

[0008] [1] A raw material for release films that uses used release films as raw materials, A raw material for release films, in which the raw material for release films has an oxidation onset temperature (Ts) of 120°C or higher and 350°C or lower when heated in air from 25°C at a rate of 5°C / min in thermogravimetric differential thermal analysis (TG-DTA analysis). [2] The raw material for a release film according to [1], A raw material for release films, comprising a substance having a melting point of 150°C or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or more. [3] The raw material for a release film according to [1] or [2], A release film, wherein T1 / T2 is 1.0 or more, where T1 (MPa) is the Young's modulus measured on the used release film, and T2 (MPa) is the Young's modulus measured on a test piece prepared using the release film raw material according to the following procedure a. Procedure a: A 100 μm thick film is produced using the T-die extrusion method, and the film is punched out to a test piece measuring 25 mm (width) x 100 mm (length) x 100 μm (thickness). [4] A raw material for a release film according to any one of [1] to [3], A release film, wherein the breaking elongation measured on the used release film is S1 (%), and the breaking elongation measured on a test piece prepared using the release film raw material according to the following procedure a is S2 (%), and the S1 / S2 is 4.5 or less. Procedure a: A 100 μm thick film is produced using the T-die extrusion method, and the film is punched out to a test piece measuring 25 mm (width) x 100 mm (length) x 100 μm (thickness). [5] A raw material for a release film according to any one of [1] to [4], A raw material for release films, comprising a first antioxidant. [6] A raw material for a release film according to any one of [1] to [5], A pellet-shaped solid material for release films. [7] A recycled release film comprising the release film raw material described in any one of [1] to [6]. [8] The recycled release film according to [7], The release film includes a release layer, an intermediate layer, and a sub-release layer, A recycled release film, wherein the intermediate layer and / or the secondary release layer comprises a raw material for a release film. [9] The recycled release film according to [7] or [8], A recycled release film comprising a second antioxidant.

[10] A method for recycling used release films, comprising the step of producing a recycled release film using the release film raw material described in any one of [1] to [6].

[11] A method for producing a raw material for a release film using a used release film, comprising: A step of crushing the used release film to obtain a crushed material; A step of heating and melting the pulverized material; A step of processing the heated and melted pulverized material into pellets; The method for producing a raw material for a release film comprising the steps of:

[12] A method for producing a raw material for a release film according to

[11] , In the step of heating and melting, The method for producing a raw material for a release film further comprises a step of subjecting the heat-melted pulverized material to an element to remove foreign matter.

[13] A method for producing a raw material for a release film according to

[12] , The method for producing a raw material for a release film, wherein the average pore size of the element is 3 μm to 100 μm.

[14] A method for producing a raw material for a release film according to

[12] or

[13] , The element is made of a porous material.

[15] A method for producing a raw material for a release film according to any one of

[12] to

[14] , The method for producing a raw material for a release film, wherein the element is made of metal.

[16] A method for producing a raw material for a release film according to any one of

[11] to

[15] , A method for producing a raw material for a release film, wherein in the step of heating and melting, a first antioxidant is added, and the pulverized material is heated and melted together with the first antioxidant.

[17] A method for producing a raw material for a release film according to

[16] , A method for producing a raw material for a release film, wherein the amount of the first antioxidant added is 500 to 30,000 ppm.

[18] A method for producing a raw material for a release film according to any one of

[11] to

[17] , The used release film has a multilayer structure in which at least a release layer and a cushion layer are laminated.

[19] A method for producing a raw material for a release film according to any one of

[11] to

[18] , The used release film comprises a substance having a melting point of 150°C or less as measured by differential scanning calorimetry (DSC), and a substance having a melting point of 200°C or more as measured by differential scanning calorimetry (DSC).

[20] A method for producing a recycled release film, comprising a film formation step of forming a recycled release film using a raw material for release film obtained by the method for producing a raw material for release film according to any one of

[11] to

[19] .

[21] A method for producing the recycled release film according to

[20] , The method for producing a recycled release film, wherein in the film formation step, the raw material for the release film and a second antioxidant are mixed to form the recycled release film.

[22] A method for producing a recycled release film according to

[20] or

[21] , In the film forming step, The method for producing a recycled release film includes forming the recycled release film by any one selected from a coextrusion method, an extrusion lamination method, a dry lamination method, and an inflation method. Effect of the Invention

[0009] According to the present invention, there are provided a raw material for a release film that allows reuse of used release film while providing a good appearance, and a method for effectively reusing a release film in a simple manner. [Brief description of the drawings]

[0010] [Figure 1] 1 is a flowchart showing a manufacturing procedure of the raw material for release films (M) of the present embodiment. [Diagram 2] 1 is a flowchart showing the manufacturing procedure of the recycled release film (z) of the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In this specification, the expression "a to b" in the explanation of a numerical range means a or more and b or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less." In addition, each component and material exemplified in this specification may be used alone or in combination of two or more types, unless otherwise specified.

[0012] Hereinafter, an embodiment of the present invention will be described in detail. FIG. 1 is a flow chart showing the steps of producing a raw material for a release film (M) of this embodiment, and FIG. 2 is a flow chart showing the steps of producing a recycled release film (z) of this embodiment.

[0013] <Raw material for release film (M)> The release film raw material (M) utilizes used release film (y) as a raw material, and in a thermogravimetric differential thermal analysis (TG-DTA analysis) of the release film raw material (M), the oxidation onset temperature (Ts) obtained when the temperature is increased from 25°C in air at a rate of 5°C / min is 120°C or higher and 350°C or lower.

[0014] This makes it possible to suppress the occurrence of fish eyes in the recycled release film (z) produced using the raw material for release films (M), and to obtain a good appearance. Although the details of the reason are not clear, it is speculated as follows. First, it is thought that the low Ts (°C) of the release film raw material (M) is intended to include gel components with relatively low molecular weight in the release film raw material (M). The gel components later become the cause of foreign matter called fish eyes in the recycled release film (z). Therefore, it is thought that by controlling the Ts (°C) of the release film raw material (M), it is possible to reduce the gel components and suppress the occurrence of fish eyes while maintaining good thermal efficiency.

[0015] Ts (° C.) is preferably 190° C. or higher, and from the viewpoint of further reducing fisheyes, is more preferably 200° C. or higher. On the other hand, Ts (° C.) is preferably 350° C. or lower, and from the viewpoint of improving thermal efficiency, is more preferably 300° C. or lower, and further preferably 250° C. or lower.

[0016] The oxidation onset temperature (Ts) is the temperature at which weight gain and temperature rise are first observed in the TG curve and DTA curve obtained by thermogravimetric differential thermal analysis (TG-DTA analysis), and is the temperature at which oxidation begins. For example, since temperature rise can be caused by factors other than oxidation, such as combustion and crystallization, it is necessary to identify both the weight gain and the temperature gain. In other words, the oxidation onset temperature can be identified because oxidation causes both a temperature increase and a weight increase at the same time.

[0017] The release film raw material (M) preferably contains a substance having a melting point of 150° C. or less as measured by differential scanning calorimetry (DSC), and a substance having a melting point of 200° C. or more. That is, in the production method of the release film raw material (M), excessive heating is applied, and therefore substances having a melting point of 150° C. or less are oxidized and easily gelled, but by containing a substance having a melting point of 200° C. or more, oxidation is prevented, and the occurrence of gelling of the release film raw material (M) as a whole can be reduced.

[0018] It is preferable that the raw material for the release film (M) further contains a first antioxidant, which effectively inhibits the occurrence of fisheyes and further reduces the occurrence of fisheyes. The first antioxidant will be described in detail below.

[0019] According to the release film raw material (M) of this embodiment, the recycled release film produced using the release film raw material (M) can have the same physical properties as the release film before recycling. Specifically, it is preferable that the release film raw material (M) is configured to satisfy the following conditions i and ii.

[0020] (Condition i) When the Young's modulus measured for a used release film is T1 (MPa) and the Young's modulus measured for a test piece prepared using the release film raw material in the following procedure a is T2 (MPa), T1 / T2 is preferably 1.0 or more, more preferably 1.03 or more. On the other hand, T1 / T2 is preferably 1.2 or less, more preferably 1.1 or less. Procedure a: A 100 μm thick film is produced using the T-die extrusion method, and the film is punched out to a test piece measuring 25 mm (width) x 100 mm (length) x 100 μm (thickness).

[0021] Furthermore, T2 (MPa) is preferably from 200 to 3000 MPa, more preferably from 500 to 2000 MPa, and further preferably from 700 to 1500 MPa.

[0022] (condition ii) When the breaking elongation measured for the used release film is S1 (%) and the breaking elongation measured for a test piece prepared using the release film raw material in the following procedure a is S2 (%), S1 / S2 is preferably 4.5 or less, more preferably 4.3 or less. On the other hand, S1 / S2 is preferably 2.0 or more, more preferably 2.4 or more, and even more preferably 2.7 or more. Procedure a: A 100 μm thick film is produced using the T-die extrusion method, and the film is punched out to a test piece measuring 25 mm (width) x 100 mm (length) x 100 μm (thickness).

[0023] Moreover, S2 (%) is preferably from 150 to 650%, more preferably from 250 to 550%, and further preferably from 300 to 500%.

[0024] The release film raw material (M) that satisfies the above Ts (°C) and conditions i and ii can be prepared by devising the resin material constituting the release film raw material (M) (the resin material constituting the release film (x)) and the manufacturing method of the release film raw material (M) described later.

[0025] The raw material for the release film (M) is a pellet-shaped solid, which improves the ease of handling and increases the reusability of the used release film (y).

[0026] <Production method of raw material for release film (M)> The method for producing the raw material for the release film (M) will be described below.

[0027] The raw material for the release film (M) is produced using a used release film (y) as described in the production method below, which allows the used release film (y) to be reused simply and effectively.

[0028] The method for producing the release film raw material (M) of this embodiment is a method for producing the release film raw material (M) using a used release film (y), and includes the following steps in order (see FIG. 1). [Step 1] A step of crushing used release film (y) to obtain crushed material. [Step 2] Heating and melting the pulverized material [Step 3] A step of processing the heated and melted pulverized material into pellets. This allows the used release film (y) to be effectively reused in a simple manner. That is, the process of peeling or separating each layer from the used release film (y) can be omitted, and the used release film (y) can be reused in its entirety.

[0029] Each step will be described in detail below.

[0030] [Process 1] First, a used release film (y) is prepared. The used release film is a release film that has been used during heating and pressurization in the manufacturing process of a molded product, and is deformed to fit the outer shape of the molded product, or is partially expanded or contracted. The used release film (y) may be in either a sheet or roll form. The release film (x) before use will be described in detail later.

[0031] The used release film (y) is pulverized so as to facilitate subsequent heating and melting for pelletization and to ensure a uniform concentration of the components. The pulverization method is not particularly limited, and a known method can be used. For example, a known pulverizer can be used to cut and pulverize the film into lengths of 1 to 50 mm. In order to improve the appearance of the recycled release film (z) using the raw material for release films (M), it is preferable that excessive frictional heat is not generated during pulverization. The pulverized material is a collection of fragments of the pulverized used release film (y). In addition, the used release film (y) may be pulverized after cleaning or removing foreign matter and dirt adhering thereto during use by a known method.

[0032] [Process 2] Next, the obtained pulverized material is heated and melted, whereby the materials contained in the used release film (y) can be melted and uniformly mixed. The heating method is not particularly limited, and any known method can be used. The heating temperature and heating time may be appropriately set depending on the constituent material of the used release film (y) as long as the pulverized material can be uniformly kneaded.

[0033] In addition, a first antioxidant may be added during the heat melting process, which suppresses oxidation of the pulverized material and facilitates improving the appearance of the recycled release film (z) formed using the release film raw material (M). Although the details of the reason are not clear, it is speculated as follows. First, the resin components contained in the used release film (y) generate radicals due to heat or the passage of time, and are oxidized, causing some of the molecules to crosslink with each other and gelling. The gelled components then later become the cause of foreign matter called fish eyes in the recycled release film (z). Therefore, by adding a first antioxidant during the heat melting process, when oxidation is likely to occur, oxidation can be effectively suppressed, and it is believed that the generation of fish eyes can be suppressed, making it possible to obtain a recycled release film (z) with a good appearance.

[0034] (First Antioxidant) The first antioxidant is not particularly limited, and a known antioxidant can be used, for example, hindered phenol-based antioxidants, thioether-based antioxidants, phosphorus-based antioxidants, hindered amine-based antioxidants, thiol-based antioxidants, benzotriazole-based antioxidants, benzophenone-based antioxidants, hydroxylamine-based antioxidants, salicylic acid ester-based antioxidants, triazine-based antioxidants, etc. One or more types selected from these can be used.

[0035] Specific examples of the hindered phenol antioxidant include 4-[[4,6-bis(octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene.

[0036] Specific examples of thioether-based antioxidants include 4,4'-thiobis[2-t-butyl-5-methylphenol]bis[3-(dodecylthio)propionate], thiobis[2-(1,1-dimethylethyl)-5-methyl-4,1-phenylene]bis[3-(tetradecylthio)propionate], pentaerythritol tetrakis(3-n-dodecylthiopropionate), bis(tridecyl)thiodipropionate, and 2,2-bis({[3-(dodecylthio)propionyl]oxy}methyl)-1,3-propanediylbis[3-(dodecylthio)propionate].

[0037] Specific examples of phosphorus-based antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, tris(dinonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, and 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Nonophosphite compounds: 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis(phenyl-di-alkyl (C12-C15) phosphite), 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and other diphosphite compounds.

[0038] Specific examples of the hindered amine antioxidant include bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n- Examples of such butylmalonate include bis(1,2,2,6,6-pentamethyl-4-piperidyl), dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate, N,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate, and bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate.

[0039] Specific examples of thiol-based antioxidants include pentaerythritol tetrakis(3-mercaptobutyrate) and 1,3,5-tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0040] Specific examples of the benzotriazole-based antioxidant include 1,2,3-benzotriazole (1H-benzotriazole), 1H-benzotriazole sodium salt, 4-methyl-1H-benzotriazole, 5-methyl-1H-benzotriazole, 4-methyl-1H-benzotriazole potassium salt, 5-methyl-1H-benzotriazole potassium salt, 4-methyl-1H-benzotriazole amine salt, 5-methyl-1H-benzotriazole amine salt, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, and 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole.

[0041] Specific examples of the benzophenone-based antioxidants include 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, 2,2'dihydroxy-4-methoxybenzophenone, 2,2'dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, and 2-hydroxy-4-methoxy-2'-carboxybenzophenone.

[0042] Specific examples of the hydroxylamine-based antioxidant include hydroxylamine, hydroxylamine nitrate, hydroxylamine sulfate, hydroxylamine phosphate, hydroxylamine hydrochloride, hydroxylamine citrate, and hydroxylamine oxalate.

[0043] Specific examples of the salicylic acid ester antioxidant include phenyl salicylate, p-octylphenyl salicylate, and p-tert-butylphenyl salicylate. An example of the triazine-based antioxidant is 2,4-bis(allyl)-6-(2-hydroxyphenyl)-1,3,5-triazine.

[0044] The amount of the first antioxidant added is preferably 500 to 30,000 ppm, more preferably 1,000 to 10,000 ppm, and even more preferably 1,500 to 5,000 ppm. By setting the amount of the first antioxidant to be equal to or more than the lower limit, it is possible to prevent the pulverized material from being oxidized to produce low molecular weight components, and as a result, it is possible to prevent the appearance of the recycled release film (z) from being deteriorated by the low molecular weight components. On the other hand, by setting the amount of the first antioxidant to be equal to or less than the above upper limit, it is possible to suppress a decrease in the mechanical strength of the recycled release film (z) caused by the presence of the first antioxidant.

[0045] For example, a known granulator may be used, the pulverized material may be fed into the extruder with a feeder, and the antioxidant may be fed from a side hopper with another feeder.

[0046] Next, the heated and melted pulverized material is passed through an element to remove foreign matter. The foreign matter is a gel-like component formed by the resin component contained in the used release film (y) being oxidized by heating and melting, and some of the molecules being crosslinked, an unmelted component, or a carbonized component. By applying the pulverized material in a heated and melted state to the element, the molten part passes through the element, while the unmelted part solidifies into a gel-like substance and remains on or inside the element.

[0047] (element) The element is used to remove foreign matter. The element can filter the pulverized material in a heated and molten state using a filter medium. Examples of filter media include flat filter media with a mesh pattern formed on the surface, filter media with multiple pores running linearly through them in bundles, and porous media with multiple pores randomly distributed in three dimensions and continuous. Among them, from the viewpoint of increasing the filtering accuracy, it is preferable to use a porous body in which a plurality of pores are randomly distributed in three dimensions and are continuous. An example of the porous body is a metal sintered element. This makes it easier to entangle the gel and remove foreign matter.

[0048] The average pore size of the element is preferably 3 μm to 100 μm, more preferably 10 μm to 60 μm, and further preferably 30 μm to 50 μm. By setting the average pore size of the element to be equal to or larger than the lower limit, the filtration speed can be improved and production efficiency can be increased. By setting the average pore size of the element to be equal to or smaller than the upper limit, foreign matter can be more reliably removed and filtration accuracy can be increased.

[0049] Examples of the constituent material of the element include elements made of resin, inorganic fiber, metal, etc. Among them, elements made of metal are preferable from the viewpoint of obtaining high heat resistance and mechanical strength, and sintered metal elements are more preferable from the viewpoint of improving filtration accuracy.

[0050] [Process 3] Next, the heat-melted pulverized material is processed into pellets. By processing into pellets, the entire pulverized material can be used as a raw material for the recycled release film (z) and the handling properties can be improved.

[0051] The pellets are processed by a known method using a known granulator or the like.

[0052] The raw material for the release film (M) can be obtained by the above-mentioned steps. In addition, in the method for producing the raw material for the release film (M) of this embodiment, additives may be further used according to the purpose.

[0053] <Used release film (y)> The used release film (y) has a multi-layer structure in which at least a release layer and a cushion layer are laminated. The used release film (y) may further have a sub-release layer on the surface opposite to the release layer.

[0054] In addition, the used release film (y) preferably contains a substance having a melting point of 150° C. or less as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200° C. or more. That is, in the method for producing the release film raw material (M) using the used release film (y), the substance having a melting point of 150° C. or less is subjected to excessive heating. In contrast, in the method for producing the release film raw material (M) of the present embodiment, the first antioxidant is used and foreign matter is removed by an element, so that the occurrence of fish eyes is suppressed and a recycled release film (z) having a good appearance can be obtained. Furthermore, by containing a substance having a melting point of 200° C. or higher, oxidation of the release film raw material (M) due to heating can be reduced in the production method of the release film raw material (M) using the used release film (y).

[0055] In addition, the used release film (y) may be, for example, one or more selected from polymethylpentene (TPX), ethylene-methyl methacrylate copolymer (EMMA), polyethylene terephthalate resin (PET), polyethylene terephthalate glycol resin (PETG), polybutylene terephthalate resin (PBT), polytrimethylene terephthalate resin (PTT), ethylene-methyl acrylate copolymer resin (EMA), ethylene-vinyl acetate resin (EVA), and polyethylene resin (PE). Among them, it is preferable to include one or more selected from TPX, PBT, PET, and PTT, which are substances having a melting point of 200°C or more by DSC, and one or more selected from EMMA, EMA, EVA, and PE, which are substances having a melting point of 150°C or less by DSC. This makes it easier to realize a manufacturing method of a release film raw material (M) using the used release film (y) while maintaining a good balance between releasability and tracking ability in the release film (x) before use.

[0056] An example of the used release film (y) will be described below. In this embodiment, the release film (y) may have a laminated structure in which a release layer, a cushion layer, and a sub-release layer are laminated in this order. The release film (y) is placed so that the surface of the release layer is in contact with the molding object having a circuit or the like.

[0057] [Release layer] The release layer is formed using a resin composition for a release layer. The release layer may be a stretched or unstretched film made of a resin composition for a release layer.While it can be appropriately determined whether to stretch or unstretch, it is preferable to use a stretched film when improving the rigidity of the film, and an unstretched film when improving the formability.The stretching can be carried out by using a known method such as sequential biaxial stretching, simultaneous biaxial stretching, and tubular stretching.

[0058] The resin composition for the release layer contains a thermoplastic resin. Examples of the thermoplastic resin include polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polytrimethylene terephthalate resin (PTT), poly 4-methyl 1-pentene resin (TPX (registered trademark): hereinafter also referred to as polymethylpentene resin), syndiotactic polystyrene resin (SPS), polypropylene resin (PP), and copolymer resins copolymerized with other components. These may be used alone or in combination of two or more.

[0059] The resin composition for the release layer may contain, in addition to the above-mentioned thermoplastic resin, additives such as antioxidants, slip agents, antiblocking agents, antistatic agents, colorants such as dyes and pigments, stabilizers, and the like, impact resistance imparting agents such as fluororesins and silicone rubber, and inorganic particles such as titanium oxide, calcium carbonate, talc, and silica.

[0060] The thickness of the release layer is preferably from 0.01 to 50 μm, more preferably from 0.5 to 30 μm, and further preferably from 1.0 to 25 μm.

[0061] [Sub-release layer] The sub-release layer is a layer that forms the surface that comes into contact with the press hot plate when hot pressing is performed using the release film (y).

[0062] The auxiliary release layer can be formed using the same resin composition as the release layer, and may be the same resin composition as the release layer or may be different.

[0063] The thickness of the sub-release layer is preferably from 0.01 to 50 μm, more preferably from 0.5 to 40 μm, and further preferably from 1.0 to 35 μm.

[0064] [Cushion layer] The cushion layer imparts good conformability and appropriate stiffness to the entire release film (y). The cushion layer is preferably interposed between the release layer and the sub-release layer. In this embodiment, the layer interposed between the release layer and the sub-release layer is also called an intermediate layer, and the cushion layer may be an intermediate layer.

[0065] The cushion layer is formed using a resin composition for the cushion layer. The resin composition for the cushion layer contains a thermoplastic resin. Examples of the thermoplastic resin include ethylene copolymers; α-olefin polymers such as polyethylene and polypropylene; α-olefin copolymers having propylene, butene, pentene, hexene, methylpentene, and the like as polymer components; engineering plastic resins such as polyethersulfone (PES) and polyphenylene sulfide (PPS); and polymethylpentene resins. These may be used alone or in combination of two or more.

[0066] Examples of mixtures that may form the cushion layer include mixtures of ethylene and ethylene-methyl methacrylate copolymer (EMMA), mixtures of polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), mixtures of polybutylene terephthalate (PBT), polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), mixtures of polypropylene (PP), ethylene-methyl acrylate copolymer (EMA) and polymethylpentene resin, and mixtures of polypropylene (PP), ethylene-methacrylic acid copolymer (EMAA) and polymethylpentene resin.

[0067] The cushion layer may further include a rubber component, such as a styrene-based thermoplastic elastomer, such as a styrene-butadiene copolymer or a styrene-isoprene copolymer, an olefin-based thermoplastic elastomer, an amide-based elastomer, or a polyester-based elastomer, or a rubber material, such as natural rubber, isoprene rubber, chloroprene rubber, or silicone rubber.

[0068] The cushion layer may contain antioxidants, slip agents, antiblocking agents, antistatic agents, colorants such as dyes and pigments, additives such as stabilizers, impact resistance imparting agents such as fluororesins and silicone rubber, and inorganic fillers such as titanium oxide, calcium carbonate, and talc.

[0069] Examples of the method for forming the cushion layer include known methods such as air-cooled or water-cooled inflation extrusion and T-die extrusion.

[0070] <Recycled release film (z)> The recycled release film (z) is a film formed by using the raw material for the release film (M). This results in a recycled release film (z) with good release film properties that reduces the environmental load and improves recyclability.

[0071] The recycled release film (z) has a multi-layer structure in which at least a release layer and a cushion layer are laminated, and at least one of the layers is made of the release film raw material (M). The recycled release film (z) may be mixed with raw materials other than the release film raw material (M). The proportion of the raw material (M) for the release film used as the raw material for the recycled release film (z) is preferably 95% by mass or less, more preferably 93% by mass or less, and even more preferably 90% by mass or less, based on the total amount of the recycled release film (z). By being in this range, it is possible to maintain the same performance as when using an unused raw material. On the other hand, the proportion of the release film raw material (M) used as the raw material of the recycled release film (z) is preferably 2 mass% or more, more preferably 5 mass% or more, even more preferably 10 mass% or more, and even more preferably 20 mass% or more, based on the total amount of the recycled release film (z). By setting the ratio of the release film raw material (M) used as the raw material of the recycled release film (z) within the above range, it is possible to effectively utilize resources while maintaining good performance as a release film.

[0072] The recycled release film (z) may further have a sub-release layer on the side opposite to the release layer. In this case, it is preferable to use the release film raw material (M) for at least one of the cushion layer and the sub-release layer, and it is more preferable to use the release film raw material (M) for the cushion layer.

[0073] In addition, when the cushion layer uses the raw material for the release film (M) and the release layer uses a resin raw material other than the raw material for the release film (M), it is preferable that the raw material for the release film (M) and a part of the resin constituting the release layer are the same type. For example, when the raw material for the release film (M) contains one or more resins selected from polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polytrimethylene terephthalate resin (PTT), poly 4-methyl 1-pentene resin (TPX (registered trademark): hereinafter also referred to as polymethylpentene resin), syndiotactic polystyrene resin (SPS), polypropylene resin (PP) and copolymer resins copolymerized with other components, it is preferable that the release layer also contains the same type of resin. By containing the same type, the interlayer strength between the cushion layer using the raw material for the release film (M) and the release layer in the recycled release film (z) can be increased, and it is easy to suppress the occurrence of interlayer delamination when the recycled release film (z) is used. That is, by improving resistance to interlayer peeling due to heating and pressure, the film is suitable for use as a release film.

[0074] The use of the recycled release film (z) may be the same as or different from that of the release film (x). For example, it is suitable for use in press laminating a reinforcing plate for improving the strength of a connector portion or the like in the FPC manufacturing process.

[0075] <Manufacturing method of recycled release film (z)> The method for producing the recycled release film (z) is not particularly limited and any known method can be used, but it is preferable to mix the above-mentioned raw material for the release film (M) with the second antioxidant to form the recycled release film (z). This can improve the appearance and mechanical properties of the recycled release film (z).

[0076] The second antioxidant may be the same as the first antioxidant described above. The second antioxidant may be the same as the first antioxidant or may be different from the first antioxidant. The amount of the second antioxidant added is not particularly limited, but is preferably 500 to 30,000 ppm, more preferably 1,000 to 10,000 ppm, and even more preferably 1,500 to 5,000 ppm, for example.

[0077] The recycled release film (z) is preferably formed by using any method selected from the group consisting of coextrusion, extrusion lamination, dry lamination, and inflation.

[0078] <How to reuse used release film (y)> The method for recycling a used release film (y) includes a step of producing a recycled release film (z) using the above-mentioned raw material for the release film (M). This allows the raw materials contained in the used release film (y) to be reused, leading to effective use of resources and reduction of environmental burden, etc. The manufacturing method of the recycled release film (z) is as described above.

[0079] <Release film (x)> The release film (x) is a film before use, and may be in the form of a roll or a sheet.

[0080] The thickness of the release film (x) is preferably 5 μm or more and 150 μm or less, more preferably 10 μm or more and 100 μm or less, even more preferably 15 μm or more and 80 μm or less, and even more preferably 20 μm or more and 75 μm or less.

[0081] The other configurations are the same as those described for the used release film (y).

[0082] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention. EXAMPLES

[0083] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the description of these examples.

[0084] [Experiment A] (1) Preparation of release film (x) Using the following raw materials, the release films (x) shown in Table 1 were each produced according to the following procedure.

[0085] [Release layer] and [Sub-release layer] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) 225℃ Polymethylpentene (TPX): Part number RT31 (Mitsui Chemicals) 232℃

[0086] [Cushion layer (middle layer)] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) Melting point 225℃ Low-density polyethylene (LDPE): Part number R500 (manufactured by Ube Maruzen Polyethylene Co., Ltd.) Melting point 110°C Polyethylene terephthalate glycol (PETG): Part number S2008 (SK chemicals) (No melting point as it is amorphous) Polymethylpentene (TPX): Part number RT31 (Mitsui Chemicals) Melting point 232°C Polypropylene (PP): Part number E111G (Prime Polymer) Melting point 160℃

[0087] [Melt point measurement] The melting point of each raw material was measured using differential scanning calorimetry (DSC; differential scanning calorimeter, SII DSC6220).

[0088] Next, the prepared raw materials were respectively supplied to three extruders and co-extruded from a multi-manifold die to produce release films (x) each having a release layer, a cushion layer and a sub-release layer laminated in this order.

[0089] (2) Preparation of release film (y) Using the prepared release film (x), each of the used release films (y) shown in Table 1 was produced by the following procedure. First, the prepared release film (x) was used to stack the release film (x) and a substrate (FPC) in which a coverlay film with an opening was attached to an insulating substrate on which electrical wiring with an L / S of 100 / 100 μm was formed, and heat press treatment was performed at 175°C, 2 MPa, vacuum for 20 seconds, and 2 minutes. After the heat press treatment, the film was peeled off from the FPC to obtain the used release film (y).

[0090] (3) Preparation of raw material for release film (M) <Examples 1A to 6A, Comparative Examples 1A to 2A> Using the used release film (y) and the following materials and tools, the release film raw materials (M) shown in Table 1 were each produced in the following procedure. [Antioxidants] First antioxidant: Substance name "Irgacycle PS 031G" manufactured by BASF [element] Element 1: Metal fiber ("Naslon (registered trademark) NF-12N" stainless steel, manufactured by Nippon Seisen Co., Ltd., average pore size 40 μm) Element 2: Wire mesh (manufactured by Nippon Kanaami Shoko, average pore size 55 μm, #300)

[0091] The used release film (y) was pulverized under the following conditions to obtain a pulverized material. The pulverized material was then fed from a feeder into an extruder together with the amount of the first antioxidant (wt%) shown in Table 1, heated and melted under the following conditions, treated using each element shown in Table 1, extruded into a strand shape using a strand die, solidified by water cooling, and processed into pellets using a pelletizer to produce a raw material for release films (M). The temperature of the extruder was set at 240°C, and melt kneading, element treatment (removal of foreign matter), and pelletization were carried out in a single sequence. (Crushing conditions) Crusher "BO-210" manufactured by Horai ·Average particle size 5mm (Heat melting conditions) - Device "PCM-46" manufactured by Ikegai ·Temperature 240℃

[0092] (4) Measurement and evaluation [Temperature (Ts)] Using the following equipment, the oxidation onset temperature (Ts) of each release film raw material (M) was measured in a thermogravimetric differential thermal analysis (TG-DTA analysis) when the temperature was raised from 25°C in air at a rate of 5°C / min. - Device name: "STA200" manufactured by Hitachi High-Tech Corporation Conditions: 10 mg of each release film raw material was placed in an aluminum pan and heated from 25°C to 300°C at 5°C / min while flowing air at a flow rate of 200 ml / min.

[0093] [Young's modulus (MPa), elongation (%)] (Preparation of test specimens) A used release film was punched out to a size of 25 mm (width) × 100 mm (length) × 100 μm (thickness) to obtain a test piece 1. The length direction of the test piece 1 was the MD direction of the used release film. A film having a thickness of 100 μm was produced by a T-die extrusion method using the raw material for release film (M). The produced film was punched out to a size of 25 mm (width) × 100 mm (length) × 100 μm (thickness) to obtain a test piece 2. The length direction of the test piece 2 was the MD direction of the film. (Young's modulus measurement) For each of test pieces 1 and 2, Young's modulus (MPa) was measured when the test pieces were stretched in the MD direction at a temperature of 23° C. and at a stretching rate of 2 mm / min in accordance with JIS K 7161 using a tensile tester. The Young's modulus (MPa) measured for test piece 1 was designated as T1, and the Young's modulus (MPa) measured for test piece 2 was designated as T2. (Measurement of elongation) For each of the test pieces 1 and 2, the breaking elongation (%) was measured when the test piece was stretched in the MD direction at a temperature of 23° C. and at a stretching rate of 200 mm / min in accordance with JIS K 7161 using a tensile tester. The breaking elongation (%) measured for the test piece 1 was designated S1, and the breaking elongation (%) measured for the test piece 2 was designated S2.

[0094] (5) Preparation and evaluation of recycled release film (z) <Examples 1A to 6A, Comparative Examples 1A to 2A> The obtained raw material for release film (M) was used as an intermediate layer, and the following raw materials were used to produce the recycled release films (z) shown in Table 1.

[0095] [Release layer] and [Sub-release layer] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) 225℃ Polymethylpentene (TPX): Part number RT31 (Mitsui Chemicals) 232℃ [Cushion layer (middle layer)] Release film raw material (M) [Antioxidants] Second antioxidant: Substance name "Irgacycle PS 031G" manufactured by BASF

[0096] The raw materials were fed into the hopper of the extruder, heated and melted in the extruder, and co-extruded from a multi-manifold die to produce a recycled release film (z) having a release layer, an intermediate layer, and a sub-release layer laminated in that order. However, in Example 3 and Comparative Example 2, the second antioxidant was mixed in advance with the raw material for the release film (M) and then charged into the hopper of the extruder.

[0097] The obtained recycled release film (z) was evaluated. [exterior] A specialist technician visually observed an arbitrary area (0.5 m square) of the recycled release film (z) and counted the number of fish eyes. The results are shown in Table 1.

[0098] [Table 1]

[0099] [Experiment B] (1) Preparation of release film (x) Using the following raw materials, the release films (x) shown in Tables 2 and 3 were each produced according to the following procedure.

[0100] [Release layer] and [Sub-release layer] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) 225℃ Polymethylpentene (TPX): Part number RT31 (Mitsui Chemicals) 232℃

[0101] [Cushion layer (middle layer)] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) Melting point 225℃ Low-density polyethylene (LDPE): Part number R500 (manufactured by Ube Maruzen Polyethylene Co., Ltd.) Melting point 110°C Polyethylene terephthalate glycol (PETG): Part number S2008 (SK chemicals) (No melting point as it is amorphous) Polymethylpentene (TPX): Part number RT31 (Mitsui Chemicals) Melting point 232°C Polypropylene (PP): Part number E111G (Prime Polymer) Melting point 160℃

[0102] [Melt point measurement] The melting point of each raw material was measured using differential scanning calorimetry (DSC; differential scanning calorimeter, SII DSC6220).

[0103] Next, the prepared raw materials were respectively supplied to three extruders and co-extruded from a multi-manifold die to produce release films (x) each having a release layer, a cushion layer and a sub-release layer laminated in this order.

[0104] (2) Preparation of release film (y) Using the prepared release film (x), the used release films (y) shown in Tables 2 and 3 were each produced by the following procedure. First, the prepared release film (x) was used to stack the release film (x) and a substrate (FPC) in which a coverlay film with an opening was attached to an insulating substrate on which electrical wiring with an L / S of 100 / 100 μm was formed, and heat press treatment was performed at 175°C, 2 MPa, vacuum for 20 seconds, and 2 minutes. After the heat press treatment, the film was peeled off from the FPC to obtain the used release film (y).

[0105] (3) Preparation of raw material for release film (M) <Examples 1B to 8B> Using the used release film (y) and the following materials and tools, the release film raw materials (M) shown in Table 2 were each produced according to the following procedure. [Antioxidants] First antioxidant: Substance name "Irgacycle PS 031G" manufactured by BASF [element] Element 1: Metal fiber ("Naslon (registered trademark) NF-12N" stainless steel, manufactured by Nippon Seisen Co., Ltd., average pore size 40 μm) Element 2: Wire mesh (Nihon Kanaami Shoko Co., Ltd., average pore size 55 μm, #300)

[0106] The used release film (y) was pulverized under the following conditions to obtain a pulverized material. The pulverized material was then fed from a feeder into an extruder together with the amount of the first antioxidant (wt%) shown in Table 2, heated and melted under the following conditions, treated using each element shown in Table 2, extruded into a strand shape through a strand die, solidified by water cooling, and processed into pellets using a pelletizer to produce a raw material for the release film (M). The temperature of the extruder was set at 240° C., and melt kneading, element treatment (removal of foreign matter), and pelletization were carried out in a single sequence. (Crushing conditions) Crusher "BO-210" manufactured by Horai ·Average particle size 5mm (Heat melting conditions) - Device "PCM-46" manufactured by Ikegai ·Temperature 240℃

[0107] <Comparative examples 1B~2B> The used release film (y) was pulverized under the same conditions as in the examples to obtain a pulverized material, which was used as a raw material for the recycled release film described below.

[0108] (4) Preparation of recycled release film (z) <Examples 1B to 8B> The obtained raw material for release film (M) was used as an intermediate layer, and the following raw materials were used to produce the recycled release film (z) shown in Table 2.

[0109] [Release layer] and [Sub-release layer] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) 225℃ Polymethylpentene (TPX): Part number RT31 (Mitsui Chemicals) 232℃ [Cushion layer (middle layer)] Release film raw material (M) [Antioxidants] Second antioxidant: Substance name "Irgacycle PS 031G" manufactured by BASF

[0110] The raw materials were fed into the hopper of the extruder, heated and melted in the extruder, and co-extruded from a multi-manifold die to produce a recycled release film (z) having a release layer, an intermediate layer, and a sub-release layer laminated in that order. However, in Examples 3 and 8, the second antioxidant was mixed in advance with the raw material for the release film (M) and then charged into the hopper of the extruder.

[0111] <Comparative examples 1B~2B> However, the raw materials (ground materials) of Comparative Examples 1B to 2B bridged in the hopper of the extruder and could not be formed into a film.

[0112] (5) Measurement and evaluation [Reusability] Using each of the release film raw materials (M) of Examples 1B to 8B, those in which the recycled release film (z) could be formed were marked with an ◯, and those in which the recycled release film (z) could not be formed were marked with an × to evaluate reusability. Moreover, the raw materials (pulverized materials) of Comparative Examples 1B to 2B were marked as x because they could not be formed into a film due to bridging in the hopper of the extruder. The results are shown in Tables 2 and 3.

[0113] [exterior] An expert technician visually observed an arbitrary area (0.5 m square) of the recycled release film (z) and evaluated it according to the following criteria. The results are shown in Tables 2 and 3. ◎: 9 or less fish eyes 〇: 10 to 29 fish eyes ×: 30 or more fish eyes

[0114] [Table 2]

[0115] [Table 3]

[0116] This application claims priority based on Japanese Patent Application No. 2023-145003 and Japanese Patent Application No. 2023-145010, filed on September 7, 2023, the disclosures of which are incorporated herein in their entirety.

Claims

1. A release film raw material using used release film as a raw material, The raw material for release films has an oxidation onset temperature (Ts) of 120°C or higher and 350°C or lower when heated in air from 25°C at a rate of 5°C / min in a thermogravimetric differential thermal analysis (TG-DTA analysis).

2. The release film raw material according to claim 1, A raw material for a release film, comprising a substance having a melting point of 150° C. or less as measured by differential scanning calorimetry (DSC), and a substance having a melting point of 200° C. or more.

3. The raw material for a release film according to claim 1 or 2, A release film raw material, wherein T1 / T2 is 1.0 or more, where T1 (MPa) is the Young's modulus measured for the used release film, and T2 (MPa) is the Young's modulus measured for a test piece prepared using the release film raw material in the following procedure a. Procedure a: A film having a thickness of 100 μm is produced by a T-die extrusion method, and the film is punched out to a size of 25 mm (width) × 100 mm (length) × 100 μm (thickness) to prepare a test piece.

4. The raw material for a release film according to claim 1 or 2, A raw material for a release film, wherein the breaking elongation measured on the used release film is S1 (%), and the breaking elongation measured on a test piece prepared using the raw material for a release film in the following procedure a is S2 (%), and S1 / S2 is 4.5 or less. Procedure a: A film having a thickness of 100 μm is produced by a T-die extrusion method, and the film is punched out to a size of 25 mm (width) × 100 mm (length) × 100 μm (thickness) to prepare a test piece.

5. The raw material for a release film according to claim 1 or 2, A raw material for a release film, comprising a first antioxidant.

6. The raw material for a release film according to claim 1 or 2, A pellet-shaped solid material for release films.

7. A recycled release film comprising the raw material for release films according to claim 1 or 2.

8. The recycled release film according to claim 7, The release film includes a release layer, an intermediate layer, and a sub-release layer, A recycled release film, wherein the intermediate layer and / or the secondary release layer comprises the raw material for the release film.

9. The recycled release film according to claim 7, A recycled release film comprising a second antioxidant.

10. A method for recycling a used release film, comprising a step of producing a recycled release film using the release film raw material according to claim 1 or 2.

11. A method for producing a raw material for a release film using a used release film, comprising the steps of: A step of crushing the used release film to obtain a crushed material; A step of heating and melting the pulverized material; A step of processing the heated and melted pulverized material into pellets; The method for producing a raw material for a release film comprising the steps of:

12. A method for producing the raw material for a release film according to claim 11, In the step of heating and melting, The method for producing a raw material for a release film further comprises a step of subjecting the heat-melted pulverized material to an element to remove foreign matter.

13. A method for producing the raw material for a release film according to claim 12, The average pore size of the element is 3 μm to 100 μm.

14. A method for producing a raw material for a release film according to claim 12 or 13, The element is made of a porous material.

15. A method for producing a raw material for a release film according to claim 12 or 13, The method for producing a raw material for a release film, wherein the element is made of metal.

16. A method for producing a raw material for a release film according to claim 11 or 12, A method for producing a raw material for a release film, wherein in the heat-melting step, a first antioxidant is added, and the pulverized material is heat-melted together with the first antioxidant.

17. A method for producing the raw material for release film according to claim 16, The method for producing a raw material for a release film, wherein the amount of the first antioxidant added is 500 to 30,000 ppm.

18. A method for producing a raw material for a release film according to claim 11 or 12, The used release film has a multilayer structure in which at least a release layer and a cushion layer are laminated.

19. A method for producing a raw material for a release film according to claim 11 or 12, The used release film comprises a substance having a melting point of 150° C. or less as measured by differential scanning calorimetry (DSC), and a substance having a melting point of 200° C. or more as measured by differential scanning calorimetry (DSC).

20. A method for producing a recycled release film, comprising a film formation step of forming a recycled release film using a raw material for a release film obtained by the method for producing a raw material for a release film according to claim 11 or 12.

21. A method for producing the recycled release film according to claim 20, The method for producing a recycled release film, wherein in the film formation step, the raw material for the release film and a second antioxidant are mixed to form the recycled release film.

22. A method for producing the recycled release film according to claim 20, In the film forming step, The method for producing a recycled release film includes forming the recycled release film by any one selected from a coextrusion method, an extrusion lamination method, a dry lamination method, and an inflation method.

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