Raw material for release film, recycled release film, and method for producing the same

Abstract

To provide a raw material for a mold release film capable of obtaining good appearance while reusing a used mold release film.SOLUTION: The raw material (M) for a release film of the present invention uses a used release film (y) as a raw material, and has an oxidation starting temperature (Ts) of 120 °C or higher and 350 °C or lower, which is obtained when the temperature is raised from 25 °C at a rate of 5 °C / min in air in a thermogravimetric differential thermal analysis (TG-DTA analysis) of the raw material (M) for a release film.SELECTED DRAWING: None

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

[0003] Since such release films are used and discarded within factories, being able to recover and recycle them is extremely effective in terms of resource utilization, etc. 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 that order on one side of the polyester film, together with the readily soluble resin layer. Furthermore, Patent Document 2 (JP 2022-122830 A) discloses removing a predetermined layer from a laminated polyester film, and then extracting and reusing a highly pure polyester film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-23947 [Patent Document 2] Japanese Patent Publication No. 2022-122830 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional methods for recycling release films involve 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 release films. 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 have focused on the development of a raw material for release films recycled from used release films and conducted research, and have found that by using thermogravimetric differential thermal analysis (TG-DTA analysis) of the raw material for release films as an indicator and controlling this, it is possible to suppress the occurrence of fisheyes and obtain a good appearance in some cases, but not in other cases. Specifically, they have 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 have completed the first invention. Furthermore, the inventors of the present invention 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 release film and recycled release film could be produced by extrusion processing or the like, thereby completing the second invention.

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

[0008] [1] A raw material for release films that uses used release films as raw materials, A release film raw material in which, in a thermogravimetric differential thermal analysis (TG-DTA analysis), the oxidation onset temperature (Ts) obtained when the temperature is raised from 25°C in air at a rate of 5°C / min is 120°C or higher and 350°C or lower. [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 in which 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 size of 25 mm (width) x 100 mm (length) x 100 μm (thickness) to use as a test piece. [4] A raw material for a release film according to any one of [1] to [3], A release film in which 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 ratio 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 size of 25 mm (width) x 100 mm (length) x 100 μm (thickness) to use as a test piece. [5] A raw material for a release film according to any one of [1] to [4], A raw material for a release film, 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 raw material for release films according to 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 a step of producing a recycled release film using the release film raw material according to any one of [1] to [6].

[11] A method for producing a raw material for a release film using a used release film, A step of crushing the used release film to obtain a crushed product; a step of heating and melting the pulverized material; A step of processing the heated and melted pulverized material into pellets; A 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 heated and 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 element has an average pore size of 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 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 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 method for producing a raw material for a release film, wherein 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.

[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 a recycled release film according to

[20] , 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 using any one selected from the group consisting of a coextrusion method, an extrusion lamination method, a dry lamination method, and an inflation method. [Effects 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 still providing a good appearance, and a method for effectively reusing release film in a simple manner. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a flowchart showing the procedure for producing a raw material (M) for a release film according to the present embodiment. [Figure 2] 1 is a flowchart showing the manufacturing procedure of the recycled release film (z) of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, the expression "a to b" in the description 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." Furthermore, unless otherwise specified, each component and material exemplified in this specification may be used alone or in combination of two or more types.

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

[0013] <Raw material for release film (M)> The release film raw material (M) is made from 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 release film raw material (M), and to obtain a good appearance. The details of the reason for this are not clear, but it is speculated as follows. First, it is thought that the low Ts (°C) of the release film raw material (M) is intended to cause the release film raw material (M) to contain gel components with relatively low molecular weight. These gel components then become the cause of foreign matter known as fisheyes 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 fisheyes while maintaining good thermal efficiency.

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

[0016] The oxidation onset temperature (Ts) is the temperature at which weight gain and temperature rise are first observed in the TG and DTA curves obtained by thermogravimetric differential thermal analysis (TG-DTA analysis), and is the temperature at which oxidation begins. For example, because 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 rise. In other words, the oxidation onset temperature can be identified because oxidation simultaneously causes a temperature increase and a weight increase.

[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, so substances having a melting point of 150° C. or less are oxidized and prone to gelation, but by including a substance having a melting point of 200° C. or more, oxidation is less likely to occur, and the occurrence of gelation of the release film raw material (M) as a whole can be reduced.

[0018] It is preferable that the release film raw material (M) further contains a first antioxidant, which effectively suppresses 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 physical properties equivalent to those of 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 according to 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 size of 25 mm (width) x 100 mm (length) x 100 μm (thickness) to use as a test piece.

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

[0022] (condition ii) When 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 (%), 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 size of 25 mm (width) x 100 mm (length) x 100 μm (thickness) to use as a test piece.

[0023] Furthermore, S2 (%) is preferably 150 to 650%, more preferably 250 to 550%, and even more preferably 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 that constitutes the release film raw material (M) (the resin material that constitutes the release film (x)) and the manufacturing method of the release film raw material (M) described below.

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

[0026] <Manufacturing 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 release film raw material (M) is produced using a used release film (y), as explained 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 the heating and pressurizing process of the 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 the form of either a sheet or a roll. The release film (x) before use will be described in detail later.

[0031] The used release film (y) is pulverized so that it can be easily pelletized by heating and melting later and the concentration of the components becomes uniform. The pulverization method is not particularly limited, and known methods 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) made from the release film raw material (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). The used release film (y) may be pulverized after cleaning or removing foreign matter and dirt that has adhered 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 set appropriately depending on the constituent material of the used release film (y) as long as the pulverized material can be uniformly kneaded.

[0033] Furthermore, a first antioxidant may be added during heat melting, which inhibits oxidation of the pulverized material and facilitates improving the appearance of the recycled release film (z) formed using the release film raw material (M). The details of the reason for this are not clear, but it is speculated as follows. First, the resin components contained in the used release film (y) generate radicals and oxidize due to heat or the passage of time, causing some molecules to crosslink and gel. The gelled components then later become the cause of foreign matter known as fisheyes 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, thereby suppressing the occurrence of fisheyes and 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 any known antioxidant can be used, such as a hindered phenol-based antioxidant, a thioether-based antioxidant, a phosphorus-based antioxidant, a hindered amine-based antioxidant, a thiol-based antioxidant, a benzotriazole-based antioxidant, a benzophenone-based antioxidant, a hydroxylamine-based antioxidant, a salicylic acid ester-based antioxidant, or a triazine-based antioxidant, etc. One or more 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, stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)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 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-propanediyl bis[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. diphosphite compounds such as 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis(phenyl-di-alkyl(C12-C15) phosphite), and 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[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 esters include bis(1,2,2,6,6-pentamethyl-4-piperidyl) butylmalonate, 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 antioxidant 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 salicylate antioxidants include phenyl salicylate, p-octylphenyl salicylate, and p-tert-butylphenyl salicylate. Examples of triazine-based antioxidants include 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 greater than the above lower limit, it is possible to prevent the pulverized material from being oxidized to produce low-molecular-weight components, thereby preventing 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 the above upper limit or less, it is possible to suppress a decrease in the mechanical strength of the recycled release film (z) due to the presence of the first antioxidant.

[0045] For example, a known granulator may be used, the pulverized material may be fed into an 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 crosslinking some of the molecules of the resin component contained in the used release film (y) due to oxidation caused by heating and melting, an unmelted component, or a carbonized component. By applying the pulverized material in a heated and melted state to the element, the melted part passes through the element, while the unmelted part remains on the element or inside the element as a gel.

[0047] (element) The element is used to remove foreign matter, and is capable of filtering crushed material that has been heated and melted using a filter medium. Examples of filter media include flat ones with a mesh formed on the surface, ones with multiple pores that run linearly through them in a bundle, and porous bodies with multiple pores that are continuous and randomly distributed in three dimensions. Among these, from the viewpoint of improving filtration accuracy, a porous body with multiple pores randomly distributed in three dimensions and continuous is preferable. An example of a porous body is a sintered metal 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 even more preferably 30 μm to 50 μm. By setting the average pore size of the element to be equal to or greater than the above lower limit, the filtration rate can be improved and production efficiency can be increased.By setting the average pore size of the element to be equal to or less than the above upper limit, foreign matter can be more reliably removed and filtration accuracy can be increased.

[0049] The constituent material of the element may be a resin, inorganic fiber, metal, etc. Among these, a metal element is preferred in terms of obtaining high heat resistance and mechanical strength, and a sintered metal element is more preferred in terms of increasing filtration accuracy.

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

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

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

[0053] <Used release film (y)> The used release film (y) has a multilayer 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] Furthermore, the used release film (y) preferably contains a substance having a melting point of 150°C or lower as measured by differential scanning calorimetry (DSC) and a substance having a melting point of 200°C or higher. That is, in the method for producing a release film raw material (M) using the used release film (y), excessive heating is applied to the substance having a melting point of 150°C or lower. In contrast, in the method for producing a 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 fisheyes is suppressed and a recycled release film (z) having a good appearance can be obtained. Furthermore, by including 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 method for producing the release film raw material (M) using used release film (y).

[0055] Examples of the used release film (y) include 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 these, it is preferable to use one or more selected from TPX, PBT, PET, and PTT, which are substances with a melting point of 200°C or higher by DSC, and one or more selected from EMMA, EMA, EVA, and PE, which are substances with a melting point of 150°C or lower by DSC. This allows for a good balance between releasability and conformability in the release film (x) before use, and facilitates the realization of a method for producing a release film raw material (M) using the used release film (y).

[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 on the release layer side is in contact with the object to be molded, which has 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 whether to stretch or unstretch can be determined as appropriate, it is preferable to use a stretched film when improving the rigidity of the film, and an unstretched film when improving formability.The stretching can be carried out using known methods 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] In addition to the above-mentioned thermoplastic resin, the resin composition for the release layer may contain additives such as antioxidants, slip agents, antiblocking agents, antistatic agents, colorants such as dyes and pigments, stabilizers, impact resistance 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 0.01 to 50 μm, more preferably 0.5 to 30 μm, and even more preferably 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 sub-release layer can be formed using the same resin composition as the release layer, and may be the same as or different from the resin composition of the release layer.

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

[0064] [Cushion layer] The cushion layer imparts good conformability and also provides appropriate stiffness to the entire release film (y). The cushion layer is preferably interposed between the release layer and the auxiliary release layer. In this embodiment, the layer interposed between the release layer and the auxiliary release layer is also referred to as 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, etc. 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 can be used to form the cushion layer include a mixture of ethylene and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polybutylene terephthalate (PBT), polypropylene (PP) and ethylene-methyl methacrylate copolymer (EMMA), a mixture of polypropylene (PP), ethylene-methyl acrylate copolymer (EMA) and polymethylpentene resin, and a mixture of polypropylene (PP), ethylene-methacrylic acid copolymer (EMAA) and polymethylpentene resin.

[0067] The cushion layer may further contain a rubber component, such as a styrene-based thermoplastic elastomer such as a styrene-butadiene copolymer or a styrene-isoprene copolymer, a thermoplastic elastomer material such as 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 additives such as antioxidants, slip agents, antiblocking agents, antistatic agents, colorants such as dyes and pigments, stabilizers, impact resistance agents such as fluororesins and silicone rubber, and inorganic fillers such as titanium oxide, calcium carbonate, and talc.

[0069] Examples of methods 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 using the raw material for the release film (M). This reduces the environmental load, improves recyclability, and produces a recycled release film (z) with good release film properties.

[0071] The recycled release film (z) has a multilayer structure in which at least a release layer and a cushion layer are laminated, and at least one of the layers uses the release film raw material (M). The recycled release film (z) may also be mixed with raw materials other than the release film raw material (M). Furthermore, the proportion of the release film raw material (M) 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 virgin raw materials are used. On the other hand, the proportion of the release film raw material (M) used as the raw material for the recycled release film (z) is preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on the total amount of the recycled release film (z). By setting the proportion of the release film raw material (M) used as the raw material for 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 surface 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] Furthermore, when a release film raw material (M) is used for the cushion layer and a resin raw material other than the release film raw material (M) is used for the release layer, it is preferable that the release film raw material (M) and some of the resins constituting the release layer are the same type. For example, when the release film raw material (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 of resin, the interlayer strength between the cushion layer using the release film raw material (M) and the release layer in the recycled release film (z) can be increased, making it easier to suppress interlayer delamination during use of the recycled release film (z). That is, by improving the resistance to interlayer peeling due to heat and pressure, the film is suitable for use as a release film.

[0074] The recycled release film (z) may be used for the same purpose as the release film (x), or may be used for a different purpose. For example, it is suitable for use in press laminating a reinforcing plate for improving the strength of a connector 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 a 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 to be 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.

[0077] The recycled release film (z) is preferably formed by 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 used release film (y) includes a step of producing recycled release film (z) using the above-mentioned raw material for 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 a reduction in the environmental burden, etc. The method for producing 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 particularly 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 achieving the object of the present invention are included in the present invention. [Example]

[0083] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions 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°C Polymethylpentene (TPX): Part Number RT31 (Mitsui Chemicals) 232°C

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

[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 supplied to three extruders, respectively, 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), the used release films (y) shown in Table 1 were each produced by the following procedure. First, using the prepared release film (x), a substrate (FPC) was laminated with a coverlay film having an opening on an insulating substrate with 100 / 100 μm L / S electrical wiring, and the release film (x) was then heat-pressed at 175°C, 2 MPa, vacuumed for 20 seconds, and heat-pressed for 2 minutes. After the heat-pressing, 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 by the following procedure. [Antioxidants] First antioxidant: "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 (Nippon Wire Mesh Co., Ltd., average pore size 55 μm, #300)

[0091] Used release film (y) was pulverized under the following conditions to obtain a pulverized product. The pulverized product was then fed from a feeder into an extruder together with the amount of first antioxidant (wt%) shown in Table 1, heated and melted under the following conditions, treated using each element shown in Table 1, extruded into strands through a strand die, solidified by water cooling, and processed into pellets using a pelletizer to produce a raw material for release film (M). The extruder temperature 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 thermogravimetric differential thermal analysis (TG-DTA analysis) when the temperature was increased from 25°C at a rate of 5°C / min in air. 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 a rate of 5°C / min while air was flowing at a 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 prepare 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 dimensions of 25 mm (width) × 100 mm (length) × 100 μm (thickness) to obtain test piece 2. The length direction of 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 using a tensile tester when they were stretched in the MD direction at a temperature of 23°C at a stretching rate of 2 mm / min in accordance with JIS K 7161. The Young's modulus (MPa) measured for test piece 1 was designated T1, and the Young's modulus (MPa) measured for test piece 2 was designated T2. (Measurement of elongation) For each of test pieces 1 and 2, the breaking elongation (%) was measured using a tensile tester when the pieces were stretched in the MD direction at a temperature of 23°C at a stretching rate of 200 mm / min in accordance with JIS K 7161. The breaking elongation (%) measured for test piece 1 was designated S1, and the breaking elongation (%) measured for 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> Using the obtained release film raw material (M) as an intermediate layer, the recycled release films (z) shown in Table 1 were each produced using the following raw materials.

[0095] [Release layer] and [Sub-release layer] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) 225°C Polymethylpentene (TPX): Part Number RT31 (Mitsui Chemicals) 232°C [Cushion layer (middle layer)] ·Raw material for release film (M) [Antioxidants] Secondary antioxidant: "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) in which a release layer, an intermediate layer, and a sub-release layer were 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 resulting recycled release film (z) was evaluated. [exterior] A specialist technician visually inspected an arbitrary area (0.5 m square) of the recycled release film (z) and counted the number of fisheyes. 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°C Polymethylpentene (TPX): Part Number RT31 (Mitsui Chemicals) 232°C

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

[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 supplied to three extruders, respectively, 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, using the prepared release film (x), a substrate (FPC) was laminated with a coverlay film having an opening on an insulating substrate with 100 / 100 μm L / S electrical wiring, and the release film (x) was then heat-pressed at 175°C, 2 MPa, vacuumed for 20 seconds, and heat-pressed for 2 minutes. After the heat-pressing, 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 by the following procedure. [Antioxidants] First antioxidant: "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] Used release film (y) was pulverized under the following conditions to obtain a pulverized product. The pulverized product was then fed from a feeder into an extruder together with the amount of 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 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℃

[0107] <Comparative examples 1B~2B> The used release film (y) was pulverized under the same conditions as in the examples to obtain a pulverized product, 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 release film raw material (M) was used as an intermediate layer, and the recycled release film (z) shown in Table 2 was produced using the following raw materials.

[0109] [Release layer] and [Sub-release layer] Polybutylene terephthalate (PBT): Part number 1100-211S (manufactured by CHANG CHUN PLASTICS) 225°C Polymethylpentene (TPX): Part Number RT31 (Mitsui Chemicals) 232°C [Cushion layer (middle layer)] ·Raw material for release film (M) [Antioxidants] Secondary antioxidant: "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) in which a release layer, an intermediate layer, and a sub-release layer were 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 (pulverized 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 that could be used to form a recycled release film (z) were marked with ◯, and those that could not be used to form a recycled release film (z) were marked with × to evaluate reusability. Furthermore, the raw materials (pulverized materials) of Comparative Examples 1B to 2B were marked as x because they bridged in the hopper of the extruder and could not be made into a film. The results are shown in Tables 2 and 3.

[0113] [exterior] A randomly selected area (0.5 m square) of the recycled release film (z) was visually observed by a specialist technician and evaluated according to the following criteria. The results are shown in Tables 2 and 3. ◎: 9 or fewer 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 Nos. 2023-145003 and 2023-145010, filed on September 7, 2023, the disclosures of which are incorporated herein in their entireties.

Claims

1. A release film raw material that uses used release films as raw materials, In a thermogravimetric differential thermal analysis (TG-DTA) of the raw material for release films, 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.

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 raw material for a release film, 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 raw material for a release film according to 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 S1 / S2 is 4.5 or less, where S1 (%) is the breaking elongation measured on the used release film, and S2 (%) is the breaking elongation measured on a test piece prepared using the raw material for a release film according to 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.

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

12. The 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 heated and melted pulverized material to an element to remove foreign matter.

13. A method for producing a raw material for a release film according to claim 12, The method for producing a raw material for a release film, wherein the element has an average pore size of 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, 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 claim 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 claim 11 or 12, The method for producing a raw material for a release film, wherein 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 forming 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. The method for producing the recycled release film according to claim 20, In the film forming step, the raw material for the release film and a second antioxidant are mixed to form the recycled release film.

22. The 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 using any one selected from the group consisting of a coextrusion method, an extrusion lamination method, a dry lamination method, and an inflation method.

Images