Method for recycling film and recycled film

Abstract

To provide a reclamation method of a film and a regenerated film.SOLUTION: A reclamation method of a film includes the steps of: measuring an amount of a foreign matter in a used film; and performing material recycling, chemical recycling, or thermal recycling.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for recycling a film and a recycled film. [Background technology]

[0002] Films are used in various industrial fields. In recent years, the evolution of IoT (Internet of Things) has led to a rapid increase in electronic devices such as CPUs installed in computers and smartphones, and the number of multilayer ceramic capacitors (MLCCs), which are important for driving electronic devices, has also increased explosively. The general manufacturing method for MLCCs is to laminate ceramic green sheets and electrodes on a release film, which has a release layer on a base film, and dry and harden the laminate, peel the laminate from the release film, stack multiple layers, and sinter. In this process, the release film is discarded as unnecessary material during the process.

[0003] In other words, the recent explosive increase in the number of MLCCs has led to an increase in the amount of release films discarded as unnecessary material, which has resulted in the burden on the environment becoming an issue. From the viewpoint of releasability, the components of the release layer contained in the release film used in the manufacturing process of MLCCs generally have a composition different from the components that make up the film. Therefore, when a method is implemented in which the release film with the release layer is reused as is, or the release film with the release layer is remelted and reused as a molded product containing a film (hereinafter sometimes referred to as material recycling), the components of the release layer are present as foreign matter, and therefore reuse may not be possible.

[0004] Furthermore, amid the social changes of the COVID-19 pandemic, the demand for tablets, notebook PCs, displays, etc. is increasing due to an increase in remote work, and the demand for polarizing films, which are components of liquid crystal monitors, is also growing. Polarizing films are generally made of laminates made of polyvinyl alcohol resin and triacetyl cellulose resin. In order to reduce damage to such laminates during the manufacturing process of liquid crystal monitors, it is common for a protective film to be attached to the laminate.

[0005] The manufacturing method of this protective film generally includes a process of using a release film for processing as a process of forming an adhesive on one side of the protective film for laminating with a polarizing film. That is, the process is such that an adhesive is applied to the release surface of the release film for processing, and then the film is laminated to one side of the protective film, and the release film for processing is peeled off to transfer the adhesive to one side of the protective film. The release film for processing used in the process of forming the adhesive is not reusable in the case where the release film with the release layer is reused as it is or material recycling is performed, because the components of the release layer are present as foreign matter, as with the release film used in the manufacturing process of MLCC.

[0006] Patent Document 1 discloses a technique in which wax is kneaded into a film and used as a release film without providing a release layer. Patent Document 2 discloses a method in which a release film having a release layer is washed with a metal brush and the film is reused after the release layer is removed. Patent Document 3 discloses a method in which a water-soluble resin layer is provided between the release layer and the polyester film, and the release layer is removed by washing with water, and then the film is reused. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2013 / 15260 [Patent Document 2] JP 2012-171276 A [Patent Document 3] Patent Publication No. 4284936 Summary of the Invention [Problem to be solved by the invention]

[0008] However, none of the documents describes a recycling method that includes a step of measuring the amount of impurities, and there is a concern that depending on the amount of impurities contained in the used film, there may be too much foreign matter to reuse the film. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following configuration. [I] A method for reusing film, comprising the steps of measuring the amount of impurities in a used film, and performing one of material recycling, chemical recycling, and thermal recycling. [II] The method for recycling a film according to [I], wherein the used film is a film that has been used as a base film for release. [III] The method for recycling a film described in [I] or [II], wherein the used film is a film in which a release layer is provided on at least one side of the film, a release layer is then provided on the release layer of the film having the release layer, the release layer is then released from the film having the release layer and the release layer, and the residue of the release layer and the release layer are then removed from the film having the release layer from which the release layer has been released. [IV] The method for recycling a film according to any one of [I] to [III], wherein the removal of the residue of the release layer and the release layer is carried out using at least one of light, water, and a solvent. [V] A method for recycling a film described in [III] or [IV], wherein the step of measuring the amount of impurities in the used film includes a step of measuring the residue of the release layer and the residue of the release layer contained in the used film. [VI] A method for recycling film described in any of claims [I] to [V], comprising, after the step of measuring the amount of impurities in the used film, a step of determining whether to perform material recycling, chemical recycling, or thermal recycling based on the amount of impurities. [VII] A method for recycling a film described in any one of [I] to [VI], wherein the amount of impurities in the used film is 0.001% by weight or more and 0.2% by weight or less, when the total weight of the used film is 100% by weight, and the method includes a step of performing material recycling. [VIII] A recycled film obtained by using raw materials recycled from used film, wherein the amount of impurities in the used film is 0.001% by weight or more and 0.2% by weight or less when the total weight of the used film is 100% by weight. [IX] A recycled film obtained from raw materials recycled from used film, in which the amount of barium titanate contained in the recycled film is 0.001% by weight or more and 0.2% by weight or less when the weight of the entire recycled film is taken as 100% by weight. [X] The recycled film according to [VIII] or [IX], wherein the used film is a film used as a base film for release. [XI] The raw material is used film for 25 seconds. -1 More than 250sec -1 The recycled film according to any one of [VIII] to [X], which is obtained by material recycling having a process of melting at the following shear rate: [XII] The recycled film according to any one of [VIII] to [XI], which is used for release purposes. Effect of the Invention

[0010] According to the present invention, the environmental load can be reduced by reusing used films. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below with reference to specific examples.

[0012] The present invention is a method for recycling film, which includes a step of measuring the amount of impurities in a used film, and a step of performing any one of material recycling, chemical recycling, and thermal recycling.

[0013] The film in the present invention is preferably a polyester film from the viewpoint of the diversity of uses and depolymerization properties. The polyester is composed of a dicarboxylic acid component and a diol component. In this specification, the component refers to the smallest unit that can be obtained by hydrolysis of the polyester. Examples of the dicarboxylic acid component constituting such a polyester include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, or ester derivatives thereof.

[0014] Examples of diol components constituting such polyesters include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol, alicyclic diols such as cyclohexanedimethanol and spiroglycol, and diols in which multiple units of the above-mentioned diols are linked together. Among these, from the viewpoints of mechanical properties and transparency, polyesters in which polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and PET dicarboxylic acid components are copolymerized with isophthalic acid or naphthalenedicarboxylic acid, and PET diol components are copolymerized with cyclohexanedimethanol, spiroglycol, or diethylene glycol are copolymerized with a portion of the PET diol components are preferably used.

[0015] In the present invention, the used film refers to a film that has been used as a product for a specific purpose. By reusing a film that has been used as a product for a specific purpose and lost its performance, which would otherwise be discarded, it is possible to reduce the environmental load. Examples of used films include substrate films for release, and examples of substrate films for release include substrates of used adhesive tapes, release papers of adhesive tapes, and films for product manufacturing processes. Among these, films for product manufacturing processes, particularly release films for MLCC manufacturing processes and polarizing film manufacturing processes, have been used in increasing amounts in recent years, and therefore recycling them is preferable because it reduces the amount of waste and leads to a reduction in the environmental load. When recycling a release film for an MLCC manufacturing process, it is preferable to recycle the substrate film, which is the largest amount among the components that make up the release film, because this can greatly contribute to reducing the environmental load.

[0016] In general, recycling of used films includes the above-mentioned material recycling (a method of reusing used films as they are, or a method of reusing used films as molded bodies after remelting), as well as a method of burning used films to use them as thermal energy (hereinafter, sometimes referred to as thermal recycling), and a method of purifying polymer constituent units by depolymerizing used films and repolymerizing them to reuse them as polymers (hereinafter, sometimes referred to as chemical recycling). Examples of chemical recycling methods include the method described in JP 2009-167266 A. In the recycling method of the present invention, either method may be used for recycling, but in thermal recycling, there is a concern that carbon dioxide is generated by combustion, which may have an environmental impact, and in chemical recycling, there is a concern that the number of steps before recycling is increased, which may reduce the recycling rate. From the viewpoint of reducing environmental load, it is preferable to material recycle used films, but on the other hand, material recycling of used films containing a large amount of impurities may cause problems such as the generation of foreign matter. Compared to material recycling, chemical recycling can be used even when the used film contains a large amount of impurities, and thermal recycling can be used even when the used film contains even more impurities. When recycling used film, the amount of impurities that may have a negative effect is measured, and which type of recycling to use is selected based on the amount of impurities. For used film with an impurity content that is suitable for material recycling, material recycling can be used, which can greatly reduce the environmental burden.

[0017] The film recycling method of the present invention needs to include a step of measuring the amount of impurities in the used film. By measuring the amount of impurities in the used film, it becomes possible to select an appropriate recycling method depending on the amount of impurities, for example, and to recycle the film with high recycling efficiency. This step may be performed immediately after obtaining the used film, or immediately before a step of material recycling, chemical recycling, or thermal recycling, or both.

[0018] Furthermore, the method for recycling a film of the present invention must include a step of performing any one of material recycling, chemical recycling, and thermal recycling. By performing any one of these recycling methods, it is possible to reuse used film that would otherwise be discarded, thereby reducing the environmental load.

[0019] In the present invention, the used film is not particularly limited in terms of how it has been used, but if it is a film used as a base film for release, it is preferable because it leads to a reduction in environmental load since it is a film that would otherwise be discarded. The base film for release is used by providing a release layer on at least one side of the base film, then providing a release layer on the release layer of the film having the release layer, and then releasing the release layer from the film having the release layer and the release layer, and the base film provided with the release layer after the process of releasing the release layer is often discarded.

[0020] When the used film is a release film for use in the MLCC manufacturing process or polarizing film manufacturing process, the release layer generally uses an alkyd resin-based release agent, a polyolefin-based release agent, a long-chain alkyl group-containing resin-based release agent, a fluorine-based release agent, a silicone-based release agent, or a mixed or copolymer resin-based release agent of an organic system and a silicone system. In this case, when the base film is mainly composed of polyester, the release agent components all have molecular structures significantly different from those of polyester, so that when a base film with a certain amount or more of the release agent component remaining is material-recycled, it becomes a foreign matter and adversely affects the properties of the recycled film. In addition, when the used film is a release film for the MLCC manufacturing process, the object to be released is generally a metal such as barium titanate, which is the main component of the green sheet, or titanium, silver, platinum, or copper, which is the main component of the electrode. However, when the base film is mainly composed of polyester, the release agent components all have molecular structures significantly different from polyester, so that when the base film with a certain amount or more of the release agent components remaining is material-recycled, the release agent components become foreign matter and adversely affect the properties of the recycled film. On the other hand, as will be described later in detail, when a recycled film recycled from a used film as a raw material is used for release purposes, the effect of improving the release property can be obtained by including a certain amount of such release agent components or release object components in the recycled film. Therefore, when recycling a used film as a raw material, it is a preferable embodiment to include the release agent components to an extent that does not form foreign matter in the recycled film.

[0021] When the used film of the present invention is a base film for release, as described above, the residue of the release layer and the release layer become impurities in the base film, so it is preferable that the used film is a film from which the residue of the release layer and the release layer have been removed.

[0022] The method for removing the residue of the release layer and the release layer is not particularly limited. For example, a method of removing using one or more of light, water or an aqueous solution, and a solvent, and a method of scraping off using physical force can be mentioned. As described in JP 2001-310970 A, a method of cutting a film having heterogeneous layers laminated thereon and washing it in an alkaline solution generates an alkaline solution as waste liquid. Therefore, from the viewpoint of reducing the environmental load, it is preferable to remove the residue of the release layer and the release layer using light or water.

[0023] When removing the release layer and the release layer by light irradiation, it is preferable to provide a layer (absorption layer) between the base film and the release layer in advance, which absorbs the energy of the irradiated light and disappears by sublimation or evaporation. As the absorption layer, a combination of a sublimable dye such as phthalocyanine vanadium, a material having a property of absorbing light such as aluminum or carbon black, and a material having a self-decomposition property such as nitrocellulose can be used. As the light to be irradiated, a laser light having an oscillation peak at a specific wavelength is preferably used from the viewpoint of high energy impartation. It is also a preferred embodiment to select an oscillation peak according to the absorption layer.

[0024] When the release layer and the release layer are removed by washing with water, a method is preferably used in which a layer containing a water-soluble component is provided in advance between the base film and the release layer, or a method in which a water-soluble component is included in the release layer. Examples of the water-soluble component include starch and polyvinyl alcohol. Since the used film of the present invention is used as a film for processing, polyvinyl alcohol having heat resistance and solvent resistance is preferably used as the water-soluble component. When polyvinyl alcohol is used as the water-soluble component, it is also effective to use polyvinyl alcohol with low crystallinity in order to improve the solubility in water. Examples of polyvinyl alcohol with low crystallinity include those with a saponification degree of 50 to 80, those with a polymerization degree of 500 or less, those with a bulky side chain group such as an ethanediol group, and combinations thereof.

[0025] The used film from which the release layer and the release layer have been removed by the above-mentioned method (hereinafter, sometimes referred to as the used film after cleaning) is preferably subjected to a step of measuring the amount of impurities contained in the film. When the used film is a process release film, the residue of the release material and the release layer are measured as impurities. Furthermore, from the characteristics of the above-mentioned recycling method, it is preferable to include a step of determining whether to perform material recycling, chemical recycling, or thermal recycling depending on the amount of impurities contained in the used film. By including this step, it is preferable to efficiently reduce environmental load and recycle. In particular, when the amount of impurities in the used film is 0.001% by weight or more and 0.2% by weight or less when the weight of the entire used film is 100% by weight, it is preferable to reuse the used film by a recycling method including a step of performing material recycling from the viewpoint of recycling efficiency and load reduction.

[0026] When the amount of impurities exceeds 0.2% by weight when the weight of the entire used film is taken as 100% by weight, the recycled film obtained by material recycling contains a lot of foreign matter, and it may be difficult to obtain the desired properties. When material recycling is a method in which used film is used as a recycled film as it is, a lot of foreign matter is also generated on the film surface, so that when used as a base material for a release film, for example, the release properties may not be sufficient. In addition, when material recycling is a method in which used film is melted again and used as a raw material, the raw material may deteriorate, or other raw materials mixed with the raw material may also deteriorate, and it may not be possible to form it into a film.

[0027] On the other hand, if an attempt is made to reduce the amount of impurities to less than 0.001% by weight when the total weight of the used film is taken as 100% by weight, the damage to the base film during the impurity removal process will be so great that the mechanical strength of the recycled film may decrease or it may not be able to withstand re-melting.

[0028] In addition, when the used film is a release film used in the manufacturing process of MLCC, the impurities contained in the film include barium titanate, which is a component of the object to be released, and silicone, which is a component of the release agent. If a recycled film is obtained by material recycling using a used film containing a large amount of such release agent components or object to be released components as a raw material, a problem occurs in that a large amount of foreign matter is generated. However, if a used film containing a very small amount of release agent components or object to be released components is used as a raw material for material recycling, the releasability of the obtained recycled film is improved. Therefore, it is preferable that the amount of barium titanate contained in the used film is 0.001% by weight or more and 0.2% by weight or less.

[0029] A preferred embodiment of the present invention is a recycled film that is material-recycled from used film, and has an impurity content of 0.001% by weight or more and 0.2% by weight or less when the weight of the entire used film is taken as 100% by weight. In particular, when the recycled film is material-recycled from used film that was used as a base film for release, it is preferable to use the recycled film for release purposes (for example, as a base film for release) because it can provide good releasability while maintaining mechanical properties.

[0030] In particular, when a used film used as a release substrate film in the manufacturing process of MLCC is used as the raw material for the recycled film, the composition contained as impurities includes barium titanate, which is the component to be released, and silicone, which is the release component. Since barium titanate is an inorganic substance, when it is present in a small amount in the film, it disperses in the film and can play the role of a lubricant. In addition, since silicone is present in the form of a film as a release layer, when it is present in a small amount in the film, the silicone present on the film surface becomes the starting point of surface unevenness, improving the releasability. In particular, a used film used as a release substrate film as the raw material for the recycled film is immersed in a 25-second vacuum chamber. -1 More than 250sec -1The material recycling process, which involves a melting step at a shear rate below 40 sec, is preferable in terms of improving the release properties of the recycled film, since barium titanate and silicone are dispersed uniformly and in fine shapes. A more preferable shear rate is 40 sec -1 Over 180sec -1 The following is the result.

[0031] The impurities contained in the recycled film are preferably barium titanate and silicone, but it may contain both or only one of them.

[0032] In particular, barium titanate is preferably contained since it is an inorganic substance and therefore easily disperses in the film and plays a role as a lubricant, and its content is preferably 0.001% by weight or more and 0.2% by weight or less.

[0033] [Characteristics evaluation method] A. Amount of impurities in the film (wt%) The film is cut into pieces of 1 cm square or less, fed into an extruder with vent holes, melted and extruded at 290°C under reduced pressure of 200 torr or less, and molded into chips. A predetermined amount A (g) of the chips is weighed out, melted again at 290°C, and then filtered through a 400 mesh filter. After the predetermined amount has been poured, the filter is washed with OCP (orthochlorophenol) to dissolve the polymer, and only the components insoluble in OCP are taken out and dried at 100°C for 1 hour, after which the weight B (g) is weighed out, and B is divided by A to obtain a percentage to determine the amount of impurities in the film.

[0034] B. Recycling rate (%) The used film is stored for one week in a warehouse with humidity controlled at 50°C and 30% RH, and then its weight is measured and designated as W1. When the used film is subjected to a process for removing the release object and the release layer, the film after the process (the used film after cleaning) is designated as W1. Then, the weight of the composition obtained by recycling is measured using the used film. In the case of material recycling in which the used film or the used film after washing is reused as it is, the weight of the film is measured after storing it for one week in a warehouse with humidity controlled at 50°C and 30% RH, and this weight is designated as W2. In the case of material recycling in which the used film or the used film after washing is melted again and molded into a film, the weight of the molded film is measured after storing it for one week in a warehouse with humidity controlled at 50°C and 30% RH, and this weight is designated as W3. The obtained W2 or W3 is divided by W1 to obtain a percentage, which is the recycling yield. In the case of chemical recycling, the weight of the constituent components (monomer composition) of the obtained polyester is measured, and the weight of the polyester converted from this weight is calculated and designated as W4. W4 is then divided by W1 to obtain a percentage, which is the recycling yield. In the case of thermal recycling, since no usable composition is obtained after recycling, the recycling yield is set to 0%.

[0035] C. Release film peeling force (N / m) A polyester adhesive tape (No. 31B, width 19 mm, manufactured by Nitto Denko Corporation) is attached to the release layer side of the release film, and the 180° peel strength is measured using VPA-H200 manufactured by Kyowa Interface Science Co., Ltd. The obtained value is converted to N / m and evaluated as follows.

[0036] A: Peel strength is 0.55mN / m or less B: Peel force is greater than 0.55 mN / m and less than 0.70 mN C: Peel strength exceeds 0.70mN / m D. Barium titanate content A sample is weighed out, decomposed under pressure with nitric acid, hydrofluoric acid, and perchloric acid, then heated and concentrated, and dissolved in dilute nitric acid to a constant volume. The amount of barium and titanium elements in this solution is measured using an ICP emission spectrometer (Hitachi High-Tech Science PS3520VDDII), and the content in the sample is calculated and converted into the amount of barium titanate.

[0037] When the sample is in the form of a film roll, the sample is cut into a rectangle whose long side is the entire length in the width direction of the film. EXAMPLES

[0038] The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these. Hereinafter, Examples 1 to 6 and 8 to 10 will be read as Reference Examples 1 to 6 and 8 to 10.

[0039] [Production of Coating A] 100 parts by weight of an addition reaction type silicone resin release agent (manufactured by Dow Corning Toray Silicones Co., Ltd., product name LTC750A) and 2 parts by weight of a platinum catalyst (manufactured by Dow Corning Toray Silicones Co., Ltd., product name SRX212) were mixed in toluene as a solvent to give a solids content of 5% by weight, to obtain Coating A.

[0040] [Preparation of Coating Agent B] Polyvinyl alcohol "Kuraray Poval (registered trademark)" 5-74 (saponification degree 74, polymerization degree 500) manufactured by Kuraray Co., Ltd. was dissolved in water to a concentration of 2% by weight, to obtain Coating Agent B.

[0041] [Production of Coating Agent C] Coating Agent C was obtained by mixing 55 parts by weight of "Clear Lacquer (registered trademark)" manufactured by Washin Paint Co., Ltd. as a coating agent containing nitrocellulose, 5 parts by weight of FDN-010 (phthalocyanine vanadium, sublimation temperature 340°C) manufactured by Yamada Chemical Co., Ltd. as a light absorbing material, 20 parts by weight of Epicoat 828 manufactured by Mitsubishi Chemical Corporation as an epoxy resin, 19 parts by weight of melamine resin ("U-Ban (registered trademark)" 2061 manufactured by Mitsui Chemicals, Inc.) as a hardener, and 1 part by weight of catalyst (Light Ester PM manufactured by Kyoei Chemical Co., Ltd.).

[0042] [Production of dielectric paste A] 100 parts by weight of barium titanate (manufactured by Fuji Titanium Kogyo Co., Ltd., product name HPBT-1), 10 parts by weight of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., product name BL-1), 5 parts by weight of dibutyl phthalate, and 60 parts by weight of toluene-ethanol (weight ratio 30:30) were added to glass beads with a number average particle size of 2 mm, mixed and dispersed in a jet mill for 20 hours, and then filtered to produce a paste-like dielectric paste.

[0043] [Production of Coating Agent D] Polyvinyl alcohol "GOHSENOL (registered trademark)" OKS8089 (degree of saponification 88, degree of polymerization 500, ethanediol groups introduced into the side chain groups) manufactured by Mitsubishi Chemical Corporation was dissolved in water to make a concentration of 2% by weight, to obtain Coating Agent D.

[0044] [Production of Coating Agent E] After adding 97 parts of butyl acrylate, 3 parts of acrylic acid, 0.2 parts of azobisisobutyronitrile as a polymerization initiator, and 233 parts of ethyl acetate, nitrogen gas was introduced and the mixture was substituted with nitrogen for about 1 hour while stirring. The flask was then heated to 60°C and reacted for 7 hours to obtain an acrylic polymer with a weight average molecular weight (Mw) of 1.1 million. To this acrylic polymer solution (solid content of 100 parts by weight), 0.8 parts by weight of trimethylolpropane tolylene diisocyanate (trade name "Coronate L", manufactured by Nippon Polyurethane Industry Co., Ltd.) as an isocyanate crosslinking agent and 0.1 parts of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added to prepare a pressure-sensitive adhesive composition (Coating Agent E).

[0045] [Production of PET-A] Terephthalic acid and ethylene glycol were polymerized in the usual manner using antimony trioxide as a catalyst to obtain melt-polymerized PET. The resulting melt-polymerized PET had a glass transition temperature of 81°C, a melting point of 255°C, an intrinsic viscosity of 0.62, and a terminal carboxyl group content of 20 eq. / t.

[0046] [Production of PET-1] PET-A was vacuum dried at 160°C for 2 hours, then put into an extruder, melted at 280°C, and extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a heated roll group, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a roll group at a temperature of 25°C to obtain a uniaxially stretched film. While holding both ends of the obtained uniaxially stretched film with clips, it was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter. Further, it was heat-set for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, it was uniformly cooled slowly in a cooling zone, and then wound up to obtain a film (PET-1) with a thickness of 30 μm.

[0047] [Production of PET-2] PET-A was vacuum dried at 160°C for 2 hours, then put into an extruder, melted at 280°C, and extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a heated roll group, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a roll group at a temperature of 25°C to obtain a uniaxially stretched film. The obtained uniaxially stretched film was coated with coating agent B using a Mayer bar so that the thickness after stretching and drying was 0.1 μm, and then stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter while holding both ends of the film with clips. Further, the film was heat-set for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, the film was uniformly cooled slowly in a cooling zone, and then wound up to obtain a film (PET-2) with a thickness of 30 μm.

[0048] [Production of PET-3] Coating agent C was applied to one side of PET-1 using a gravure coater so that the coating thickness after drying would be 0.1 μm, and the film was dried and cured at 100° C. for 20 seconds to obtain a film.

[0049] [Production of PET-4] PET-A was vacuum dried at 160°C for 2 hours, then put into an extruder, melted at 280°C, and extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a heated roll group, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a roll group at a temperature of 25°C to obtain a uniaxially stretched film. The obtained uniaxially stretched film was coated with coating agent D using a Mayer bar so that the thickness after stretching and drying was 0.1 μm, and then stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter while holding both ends of the film with clips. Further, the film was heat-set for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, the film was uniformly cooled slowly in a cooling zone, and then wound up to obtain a film (PET-2) with a thickness of 30 μm.

[0050] Example 1 PET-1 was used as the base film, and one side of the PET-1 was coated with coating agent A by gravure coating so that the coating thickness after drying would be 0.1 μm, to obtain a release film roll. Dielectric paste A was applied to the obtained release film as the release object by die coating so that the thickness after drying would be 1.0 μm. Thereafter, the dielectric was released from the obtained laminate, and the release object was peeled off to obtain a used film roll.

[0051] The resulting used roll was cut and weighed to measure the amount of impurities. Since the amount of impurities was 0.3% by weight, thermal recycling was selected as the recycling method and recycling was performed. The recycling yield was 0%.

[0052] Example 2 Chemical recycling was selected as a recycling method for the used film obtained in the same manner as in Example 1, and chemical recycling was performed by the method described in JP 2009-167266 A to obtain terephthalic acid. The yield of the obtained terephthalic acid was 62% based on the amount converted to PET.

[0053] Example 3 Material recycling was selected as the recycling method for the used film obtained in the same manner as in Example 1, and the used film was cut and washed with an aqueous sodium hydroxide solution according to the method described in JP-A-2001-310970. The amount of impurities in the washed used film was then measured. The washed used film was then dried at 160°C for 2 hours under reduced pressure of 200 torr or less, and then placed in a melt extruder and melt extruded at 280°C. The shear rate during extrusion was 45 sec -1 It was.

[0054] The obtained molten material was extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a group of heated rolls, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a group of rolls at a temperature of 25°C to obtain a uniaxially stretched film. The obtained uniaxially stretched film was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter while holding both ends with clips. Further, heat fixing was performed for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, after uniformly cooling in a cooling zone, the film was wound up to obtain a film roll with a thickness of 30 μm. The recycling rate was evaluated from the weight of the obtained film roll. Furthermore, the obtained film roll was coated with coating agent A by a gravure coating method so that the coating thickness after drying was 0.1 μm, and a release film roll was obtained. The physical properties of the obtained release film are shown in Table. The film had slightly poor releasability.

[0055] Example 4 The used film roll obtained in the same manner as in Example 1 was introduced into a water washing device equipped with a drying furnace having an unwinding and winding device, and washed while immersed in 100°C water for 2 minutes under a tension of 30 N / m, and then dried at 120°C for 2 minutes to obtain a washed used film roll. The amount of impurities in this washed used film roll was measured, and since the amount of impurities was 0.3% by weight, thermal recycling was selected as the recycling method, and recycling was performed. The recycling yield was 0%.

[0056] Example 5 Except for using PET-2 as the base film, the same procedure as in Example 1 was followed to obtain a used film roll, and the amount of impurities was measured. Since the amount of impurities was 0.3% by weight, thermal recycling was selected as the recycling method, and recycling was performed. The recycling yield was 0%.

[0057] Example 6 A used film roll after washing was obtained in the same manner as in Example 4, except that PET-2 was used as the base film. 1.0 kg of this used film roll after washing was weighed and cut to measure the amount of impurities. The amount of impurities was 0.01% by weight. The recycling rate was calculated from the weight of the film roll after washing, and the film was used as a base material and coated by gravure coating so that the coating thickness after drying was 0.1 μm, to obtain a release film roll. The physical properties of the obtained release film are shown in Table. The film had excellent release properties.

[0058] Example 7 From the used film roll after washing obtained in the same manner as in Example 6, 1.0 kg was weighed and cut, and the amount of impurities was measured. Since the amount of impurities was 0.01% by weight, the used film roll after washing was all cut and dried at 160°C for 2 hours under a reduced pressure of 200 torr or less, and then placed in a melt extruder and melt extruded at 280°C. The shear rate during extrusion was 45 sec -1 It was.

[0059] The obtained molten material was extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a group of heated rolls, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a group of rolls at a temperature of 25°C to obtain a uniaxially stretched film. The obtained uniaxially stretched film was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter while holding both ends with clips. Further, heat fixing was performed for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, after uniformly cooling in a cooling zone, the film was wound up to obtain a film roll with a thickness of 30 μm. The recycling rate was evaluated from the weight of the obtained film roll. Furthermore, the obtained film roll was coated with coating agent A by a gravure coating method so that the coating thickness after drying was 0.1 μm, and a release film roll was obtained. The physical properties of the obtained release film are shown in Table. The film had excellent releasability.

[0060] Example 8 A used film roll was obtained in the same manner as in Example 1, except that PET-3 was used as the substrate. The film roll was irradiated with a continuous wave laser beam having a wavelength of 1064 nm and an intensity of 20 W over the entire width of the film from the side having the release layer and the residue of the released material between the unwinding and winding devices, using a laser marker MDX1500 manufactured by Keyence Corporation. The used film roll irradiated with this light was introduced into a water washing device equipped with a drying furnace having an unwinding and winding device, and washed while immersed in water at 100°C for 2 minutes under a tension of 30 N / m, and then dried at 120°C for 2 minutes to obtain a used film roll after washing. The amount of impurities in the used film after washing was measured, and since the amount of impurities was 0.08% by weight, the used film roll after washing was all cut, dried at 160°C for 2 hours under a reduced pressure of 200 torr or less, and then put into a melt extruder and melt extruded at 280°C. The shear rate during extrusion was 45 sec -1 It was.

[0061] The obtained molten material was extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a group of heated rolls, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a group of rolls at a temperature of 25°C to obtain a uniaxially stretched film. The obtained uniaxially stretched film was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter while holding both ends with clips. Further, heat fixing was performed for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, after uniformly cooling in a cooling zone, the film was wound up to obtain a film roll with a thickness of 30 μm. The recycling rate was evaluated from the weight of the obtained film roll. Furthermore, the obtained film roll was coated with coating agent A by a gravure coating method so that the coating thickness after drying was 0.1 μm, and a release film roll was obtained. The physical properties of the obtained release film are shown in Table. The film had excellent releasability.

[0062] Example 9 PET-4 was used as the base film, and coating agent A was applied to one side of the PET-4 by gravure coating so that the coating thickness after drying would be 0.1 μm, to obtain a release film roll. Coating agent E was applied to the obtained release film by die coating so that the thickness after drying would be 20 μm. The obtained laminate was then attached to the protective PET film of the polarizing film, and only the release film was peeled off so that coating agent E was transferred to one side of the protective PET film, to obtain a used film roll.

[0063] The obtained used film roll was introduced into a water washing device equipped with a drying furnace having an unwinding and winding device, washed while immersed in 100°C water for 2 minutes under a tension of 30 N / m, and then dried at 120°C for 2 minutes to obtain a washed used film roll. 1.0 kg of this washed used film roll was weighed and cut to measure the amount of impurities. Since the amount of impurities was 0.02% by weight, the entire washed used film roll was cut, dried at 160°C for 2 hours under a reduced pressure of 200 torr or less, and then placed in a melt extruder and melt extruded at 280°C. The shear rate during extrusion was 45 sec -1 It was.

[0064] The obtained molten material was extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a group of heated rolls, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a group of rolls at a temperature of 25°C to obtain a uniaxially stretched film. The obtained uniaxially stretched film was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter while holding both ends with clips. Further, heat fixing was performed for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, after uniformly cooling in a cooling zone, the film was wound up to obtain a film roll with a thickness of 30 μm. The recycling rate was evaluated from the weight of the obtained film roll. Furthermore, the obtained film roll was coated with coating agent A by a gravure coating method so that the coating thickness after drying was 0.1 μm, and a release film roll was obtained. The physical properties of the obtained release film are shown in Table. The film had excellent releasability.

[0065] Example 10 The washed used film roll (impurity content 0.08% by weight) obtained in the same manner as in Example 8 was cut, dried at 160°C for 2 hours under a reduced pressure of 200 torr or less, and then placed in a melt extruder and melt extruded at 280°C. The shear rate during extrusion was 10 sec -1 It was.

[0066] The obtained molten material was extruded through a die onto a casting drum with a surface temperature of 25°C to produce an unstretched sheet. The sheet was then preheated with a group of heated rolls, stretched 3.8 times in the longitudinal direction (MD direction) at a temperature of 90°C, and then cooled with a group of rolls at a temperature of 25°C to obtain a uniaxially stretched film. The obtained uniaxially stretched film was stretched 4.0 times in the width direction (TD direction) perpendicular to the longitudinal direction in a heating zone at a temperature of 110°C in a tenter while holding both ends with clips. Further, heat fixing was performed for 10 seconds at a temperature of 230°C in a heat treatment zone in the tenter. Next, after uniformly cooling in a cooling zone, the film was wound up to obtain a film roll with a thickness of 30 μm. The recycling rate was evaluated from the weight of the obtained film roll. Furthermore, the obtained film roll was coated with coating agent A by a gravure coating method so that the coating thickness after drying was 0.1 μm, and a release film roll was obtained. The physical properties of the obtained release film are shown in Table. The shear rate during melt extrusion was small, and the film had slightly poor releasability.

[0067] Comparative Example 1 The amount of impurities in the used film roll obtained in the same manner as in Example 1 was not measured, and material recycling was selected as the recycling method, and the used film roll was cut into pieces, dried at 160°C for 2 hours under a reduced pressure of 200 torr or less, and then fed into a melt extruder and melt extruded at 280°C. However, the polymer clogged the piping during extrusion, and could not be extruded. Since the amount of impurities was not measured, an appropriate recycling method could not be selected, and recycling was not possible.

[0068] [Table 1]

Claims

【Request 1】 A method for producing a recycled film for use in mold release applications, the recycled film being obtained by using a raw material obtained by material recycling of used films, the used film being used as a base film for a mold release object containing barium titanate as a component, the used film being a film having a component soluble in water, the base film of the used film being a polyester film, the amount of impurities after washing the used film being 0.001% by weight or more and 0.2% by weight or less when the weight of the entire used film is taken as 100% by weight, the raw material being a film having a shear rate of 25 sec during extrusion in a melt extruder, －１ 250 seconds or more －１ A method for producing recycled film obtained by material recycling, comprising a process of melting the film at the following shear rate:

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