Method for separating and recovering plastic substrates

Abstract

To provide a method for separating and recovering a laminate suitable for plastic recycling, which has an excellent detachment property of a coating layer such as a printing layer and an adhesive layer, and further suppresses redeposition of a detached coating layer component by suppressing curling of a base material even under a condition where the amount of a laminate is large during detachment treatment.SOLUTION: There is provided a method for separating and recovering a plastic base material, comprising the steps of: detaching a coating layer by bringing the laminate having a plastic base material and at least one coating layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer into contact with a detaching liquid to detach the coating layer; and recovering the detached plastic base material, which is a method for separating and recovering a laminate in which a content of the laminate is 0.5 mass% or more based on the total mass of the detaching liquid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for separating and recovering a plastic substrate from a laminate including at least a plastic substrate layer and a coating layer.

Background Art

[0002] In recent years, packages made of plastic films, plastic bottles, and other plastic products have been discarded as garbage in the ocean, causing environmental pollution problems. These plastic products are decomposed in seawater into submicron-sized fragments (microplastics) and float in the seawater. There is concern that such microplastics are ingested by marine organisms such as fish and concentrated in the organisms, which may also affect the health of seabirds and humans that ingest such marine organisms as food.

[0003] Examples of the above plastic products include food packaging packages having a multilayer structure using plastic films. In such food packaging packages, various plastic substrates such as polyester substrates, nylon substrates (NY), polypropylene substrates (PP), and polyethylene substrates (PE) are used as film substrates. These film substrates are printed with printing ink, bonded to other film substrates or thermally melted resin substrates through an adhesive or the like, and then cut and heat-sealed to form a package. However, such food packaging packages having a multilayer structure have a problem that they cannot be recycled as they are because a plurality of incompatible different materials are mixed.

[0004] Regarding the material recycling of such packaging materials with a multi-layer structure, for example, Patent Documents 1 and 2 disclose a technique for detaching a printed layer from a laminate having a release layer containing a polyurethane resin having a predetermined acid value by treating the laminate with an aqueous alkali solution, not only from a single-sided printed structure but also from a multi-layer structure. Patent Document 3 discloses a technique for detaching an adhesive layer from a laminate having a multi-layer structure by treating the laminate with an aqueous alkali solution containing a polyester polyol-based adhesive having a predetermined acid value.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the detachment processes described in Patent Documents 1 to 3, in order to improve the processing efficiency, when the processing amount of the laminate with respect to the aqueous alkali solution is increased, the collision between the base materials increases, the base materials entangle the coating layer and curl, and it has been found that a new problem is that the detachability decreases. This was particularly remarkable in the case of a base material of an olefin resin. Further, since the coating layer components in the treatment liquid also increase, the coating layer after detachment easily reattaches to the base material. Furthermore, when the stirring speed is increased to improve the detachability, there arises a problem that the detached coating layer is finely dispersed and easily reattaches to the plastic base material. Here, "reattachment" means that a detachment layer such as a printed layer or an adhesive layer detached from the base material is finely dispersed by stirring and reattaches to the base material again, which causes coloring of the recovered base material and deterioration of the properties of the recycled material. That is, a molding material (hereinafter, also referred to as a recycled material or a recycled base material) obtained by recycling a plastic base material to which the printed layer has reattached as described above causes a decrease in appearance due to coloring and a decrease in physical properties. When the base material curls, not only does it become difficult to detach the coating layer, but it also entraps the dispersion of the detached coating layer and cannot be removed in the cleaning process, which causes deterioration of the properties of the recycled material.

[0007] Therefore, an object of the present invention is to provide a method for separating and recovering a laminate suitable for plastic recycling, which is excellent in the detachability of a coating layer such as a printed layer or an adhesive layer by suppressing curling of the base material even under conditions where the amount of the laminate during the detachment treatment is large, and further suppresses reattachment of the detached coating layer components. Furthermore, an object of the present invention is to provide a method for manufacturing a high-quality molding material obtained by thermoforming the recovered plastic base material.

Means for Solving the Problems

[0008] As a result of intensive studies, the inventors have found effective means for suppressing curling. That is, the present invention is a method for separating and recovering a plastic substrate, including a step of bringing a laminate having a plastic substrate and a coating layer into contact with a stripping liquid to strip the coating layer, and a step of recovering the stripped plastic substrate. The content of the laminate is 0.5% by mass or more based on the total mass of the stripping liquid. After the stripping step, the present invention relates to a method for separating and recovering a laminate, wherein the ratio of the plastic substrate in a state where the substrate is wound one or more times from the end of the substrate is less than 50% by mass with respect to all the plastic substrates after the stripping step.

[0009] Also, the present invention is a method for separating and recovering a plastic substrate, including a step of bringing a laminate having a plastic substrate and a coating layer into contact with a stripping liquid to strip the coating layer, and a step of recovering the stripped plastic substrate. The content of the laminate is 0.5% by mass or more based on the total mass of the stripping liquid. When measuring the volumes of 5 g of the laminate (A) before the stripping step and 5 g of the plastic substrate (B) after the stripping step using a graduated cylinder (inner diameter 5 cm) of 5.0×10 -4 m 3 the volume of (B) is more than 1 times and less than 4 times the volume of (A). The present invention relates to a separation and recovery method.

[0010] Also, the present invention is a method for separating and recovering a plastic substrate, including a step of bringing a laminate having a plastic substrate and a coating layer into contact with a stripping liquid to strip the coating layer, and a step of recovering the stripped plastic substrate. The content of the laminate is 0.5% by mass or more based on the total mass of the stripping liquid. The stripping liquid contains a compound having an HLB value greater than 0 and less than 20 and water. The present invention relates to a separation and recovery method, wherein the long side of the laminate immediately before stripping is 1 mm to 3 cm and accounts for 50% by weight or more of the entire laminate.

[0011] The present invention also relates to the separation and recovery method described above, wherein the release liquid contains a surfactant and water.

[0012] The present invention also relates to the separation and recovery method described above, wherein the coating layer includes a printing layer, and the content of the printing layer is 0.01% by mass or more based on the total mass of the release liquid.

[0013] The present invention further has a step of cutting the laminate before bringing the laminate into contact with the release liquid. The present invention relates to the separation and recovery method described above, wherein 50% by mass or more of the laminate after the cutting step has a long side of 3 cm or less.

[0014] The present invention also relates to the separation and recovery method described above, wherein at least one of the coating layers contains a compound having an acidic group.

[0015] The present invention also relates to the separation and recovery method described above, wherein the plastic substrate is an olefin substrate.

[0016] The present invention also relates to a method for producing a molding material, characterized by melt-kneading the plastic substrate recovered by the separation and recovery method described above.

[0017] The present invention also relates to a method for producing a molded article, characterized by heat-molding the molding material obtained by the production method described above.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a method for separating and recovering a plastic substrate from a laminate suitable for plastic recycling, which is excellent in the releasability of a coating layer such as a printing layer and an adhesive layer, and further suppresses reattachment of the released coating layer components, by suppressing curling of the substrate under conditions where the amount of the printing layer during the release process is large. Furthermore, it is possible to provide a method for producing a high-quality molding material obtained by heat-molding the recovered plastic substrate.

Embodiments for Carrying Out the Invention

[0019] Embodiments of the present invention will be described in detail below. However, the descriptions of the embodiments or requirements described below are merely examples of the embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist thereof.

[0020] In a method for separating and recovering a plastic substrate from a laminate having a plastic substrate and a coating layer, in order to improve the processing efficiency, when increasing the amount of the laminate with respect to the release liquid, the amount of the coating layer with respect to the release liquid also increases, so the releasability deteriorates. Furthermore, the coating layer components after desorption are likely to reattach to the substrate after desorption. Furthermore, under stirring conditions, since the collision frequency of the laminate increases, there has been a problem that the laminate and the plastic substrate after desorption tend to curl. Also, by stirring, innumerable wrinkles are formed on the substrate. Generally, the volume of the substrate after the desorption step is larger than that before the desorption step. However, due to the curling of the plastic substrate after desorption, the volume of the substrate also tends to be further increased.

[0021] The inventors have found that, under the condition that the amount of the laminate with respect to the release liquid is large, by desorbing so that the ratio of the plastic substrates that are curled after the desorption step is less than 50% by mass with respect to all the plastic substrates after the desorption step, it is possible to effectively suppress reattachment while maintaining excellent releasability of the coating layer. This is considered to be due to the appropriate control of the polarity and interfacial free energy of the substrate surface.

[0022] In order for the ratio of the plastic substrates that are curled after the desorption step to be less than 50% by mass, means such as selecting the conditions during the desorption test such as temperature, containing a surfactant in the release liquid, and reducing the size of the laminate are exemplified, but it is not limited thereto, and it is preferable to appropriately combine each means. Details of each means will be described later.

[0023] <Separation and recovery method> The method for separating and recovering the laminate of the present invention includes a step of bringing a laminate having a plastic substrate and a coating layer in contact with the plastic substrate into contact with a release liquid to release the coating layer and separating and recovering the plastic substrate, wherein the content of the laminate is 0.5% by mass or more based on the total mass of the release liquid, and the ratio of the curled plastic substrate after the release step is less than 50% by mass based on the total plastic substrate after the release step, and / or the volume ratio before and after the release step is 1 time or more and less than 4 times.

[0024] <Step of releasing the coating layer (also referred to as the release step)> The separation and recovery method of the present invention includes a step of bringing a plastic substrate and a laminate having a coating layer in contact with the plastic substrate into contact with a release liquid to release the coating layer. Hereinafter, the coating layer released from the substrate by the release liquid is also referred to as a release layer.

[0025] In the present invention, "release" means that the release layer is dissolved or swollen by the release liquid and peeled off, so that the substrate is released from the laminate, and includes both forms: (1) when the release layer is dissolved and released from the substrate; (2) when the release layer is not dissolved but peeled off by neutralization, swelling, etc. and released from the substrate.

[0026] Since the present invention aims to obtain the plastic substrate after release as a recycled substrate or a regenerated substrate, a mode in which as much as possible of the release layer and the like are removed from the plastic substrate is preferable. Specifically, it is preferable that at least 50% by mass or more of the release layer has been released out of 100% by mass of the release layer. More preferably, 60% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more of the release layer has been released. It does not necessarily mean that the coating layer is peeled off from the interface with the substrate.

[0027] <Curling of the plastic substrate> In the present invention, the state in which the end of the plastic substrate is involved and wound one or more times is hereinafter referred to as "curl". The involved part may be the whole or a part of the substrate. A state in which the substrate is bent in a U-shape or folded in a V-shape is not a state of being wound one or more times in appearance. If the laminate curls before peeling, it becomes difficult to peel the coating layer and separate the plastic substrate. Further, if the plastic substrate curls after peeling, the dispersion of the coating layer after peeling is involved inside the curl, making it difficult to remove by washing after the peeling step, leading to a deterioration in the properties of the recycled material.

[0028] In the present invention, the ratio of the plastic substrate that curls after the peeling step is preferably less than 50% by mass, more preferably less than 30% by mass, still more preferably less than 20% by mass, and particularly preferably less than 10% by mass with respect to all the plastic substrates after the peeling step. When the plastic substrate that curls is less than 50% by mass, as described above, the peelability of the coating layer is improved, and the involvement and re-adhesion of the peeled coating layer components are also suppressed, so that a high-performance recycled material can be obtained.

[0029] In the present invention, when the treatment amount of the laminate with respect to the peeling liquid is increased, a tendency for the plastic substrate to curl is recognized. Since a method for preventing curl cannot be uniquely expressed, the invention was specified in terms of the curled state or the volume ratio before and after the peeling step. However, when the peeling liquid contains a compound having an HLB value greater than 0 and less than 20 and water, and the long side of the laminate immediately before peeling is 1 mm to 3 cm and accounts for 50% by weight or more of the whole laminate, there is a particular tendency not to curl.

[0030] [Long side] Note that the long side of the laminate is the long side when the rectangle circumscribing the laminate is set to have the minimum area as viewed from the surface side of the laminate. Since the long side of a normal laminate exceeds 3 cm, a step of cutting the laminate so that the long side of the laminate becomes 3 cm or less is required before the peeling step. It is preferable that the laminate with a long side of 3 cm or less after cutting accounts for 50% by weight or more of the entire laminate. Also, a laminate with a long side of 1 mm or more after cutting is preferable in terms of ease of recovering the base material.

[0031] <Volume ratio before and after the peeling step> The degree of curling of the laminate can be specified by using a graduated cylinder (inner diameter 5 cm) of 5.0×10 -4 m 3 and measuring the volume per 5 g of each sample, and calculating the volume ratio (B) / (A) before and after the peeling step. In the peeling step, since the laminate is stirred, countless wrinkles are formed in the base material. Generally, the volume of the base material after the peeling step is larger than that before the peeling step. In order to improve the processing efficiency, when the amount of the laminate with respect to the peeling liquid is increased, the collision frequency of the laminate increases, and the base material curls by involving the end portion in order to reduce the interfacial free energy and reduce the surface area with the peeling liquid. When the base material curls, the volume of the base material becomes even larger. As described above, when the base material curls, the peelability decreases and reattachment is promoted, causing deterioration of the properties of the recycled material. Therefore, the lower the volume ratio before and after the peeling step, the more preferable. The volume ratio before and after the peeling step is preferably 1 time or more and less than 4 times, more preferably 3 times or less, and even more preferably 2 times or less.

[0032] <Peeling liquid> The peeling liquid may be any liquid that can swell and dissolve the coating layer, and can be appropriately selected in consideration of the ease of peeling of the coating layer described later. Examples of such a peeling liquid include water, a basic aqueous solution, and an acidic aqueous solution. From the viewpoints of environmental aspects and maintaining the properties of the recycled material using the recovered plastic base material, an aqueous solution is preferably used. The peeling liquid preferably contains 50% by mass or more of water, more preferably 70% by mass or more, and even more preferably 80% by mass or more. These release liquids may be heated. The temperature of the release liquid when immersing the laminate is preferably in the range of 25 to 120°C, more preferably 30 to 100°C, and particularly preferably 50 to 80°C. The higher the release temperature, the more preferable it is from the viewpoint of releasability, and the lower the release temperature, the more preferable it is from the viewpoints of substrate curl suppression and re-adhesion suppression.

[0033] From the viewpoint of detaching the urethane-based adhesive layer commonly used in packaging materials, the release liquid is more preferably a basic aqueous solution containing a basic compound.

[0034] The immersion time in the release liquid is preferably in the range of 1 minute to 24 hours, more preferably 1 minute to 12 hours, still more preferably 1 minute to 6 hours, and even more preferably 1 minute to 1 hour.

[0035] In order to improve the release efficiency, it is preferable to perform stirring, vibration, circulation, etc. of the release liquid. The rotational speed of the stirring blade is preferably 80 to 5000 rpm, more preferably 80 to 4000 rpm.

[0036] [Compound with HLB value greater than 0 and less than 20] The release liquid preferably contains a compound with an HLB value greater than 0 and less than 20. In particular, when containing a surfactant described later, a substrate that does not curl tends to be obtained.

[0037] [Surfactant] The release liquid preferably contains water and a surfactant. The surfactant mainly plays a role in improving the releasability of the coating layer. This is presumably because, due to the action of the surfactant, the release liquid easily penetrates into the coating layer such as the primer layer, the printing layer, and the adhesive layer, promoting the releasability. Also, when increasing the amount of the laminate with respect to the release liquid in separation and recovery, the laminate and the separated base material tend to curl with the ink pieces peeled off and the like being involved, and even if immersed in the release liquid, it is difficult to cleanly remove the ink pieces and the like involved in the curl. However, since the release liquid contains a surfactant, the surfactant is adsorbed on the surfaces of the laminate and the separated base material, suppressing the curl. As a result, the releasability is improved and reattachment can be suppressed. Furthermore, when the release liquid contains a surfactant, it is possible to release the coating layer in contact with the plastic base material even without a release layer.

[0038] The HLB value is an index value regarding the affinity of the surfactant for water and oil, and is equally divided with the HLB value of a substance having no hydrophilic group being 0 and the HLB value of a substance having only a hydrophilic group being 20. The concept of HLB was proposed by William Griffin of Atlas Powder Company in 1949, and several methods for determining by calculation have been proposed. In the present invention, the HLB value can be obtained from the following formula by the Griffin method. Formula) HLB = 20 × [(molecular weight of the hydrophilic group contained in the surfactant) / (molecular weight of the surfactant)] Examples of the hydrophilic group contained in the surfactant include a hydroxyl group and an ethyleneoxy group.

[0039] The HLB value of the surfactant in the present invention is preferably 7 or more. By having an HLB of 7 or more, excellent releasability and reattachment prevention performance are exhibited. The HLB value of the surfactant is preferably 8 or more, more preferably 10 or more. Also, the HLB value of the surfactant is preferably 20 or less, more preferably 19 or less, still more preferably 17 or less. When the HLB value is 20 or less, it is preferable because of excellent defoaming properties.

[0040] Examples of the type of surfactant include nonionic, anionic, cationic, and amphoteric surfactants, and an appropriate type and blending amount can be selected and used according to the required characteristics. From the viewpoints of releasability and foaming property, it is preferably at least one selected from the group consisting of anionic surfactants and nonionic surfactants. In addition, it is preferable that the surfactant has a structure in which an alkylene oxide (hereinafter also referred to as AO) is added, since the releasability and the prevention of reattachment are improved.

[0041] (Nonionic surfactant) The nonionic surfactant is not particularly limited, but is preferably an alkylene oxide adduct to which an alkylene oxide is added. More preferably, it is a compound obtained by adding an alkylene oxide to alcohols having active hydrogen, a compound obtained by adding an alkylene oxide to amines, or a compound obtained by adding an alkylene oxide to fatty acids. The above addition may be either random addition or block addition. The number of carbon atoms of the alkylene oxide is preferably 2 to 4 carbon atoms. More preferably, the nonionic surfactant is an alcohol-based nonionic surfactant obtained by adding an alkylene oxide having 2 to 4 carbon atoms to alcohols.

[0042] [Alcohol-based nonionic surfactant] Examples of the alcohol-based nonionic surfactant include alkylene oxide adducts of primary or secondary alcohols having a total carbon number of 8 to 24, or alkylene oxide adducts of alkylphenols having a total carbon number of 8 to 12. The above primary or secondary alcohols having a total carbon number of 8 to 24 may be either saturated or unsaturated. Examples of the above primary or secondary alcohols having a total carbon number of 8 to 24 include lauryl alcohol, stearyl alcohol, oleyl alcohol, dodecyl alcohol, arachidyl alcohol, behenyl alcohol, lignoceryl alcohol, myristyl alcohol, and the like. In addition, examples of the alkylene oxide added to alcohols include ethylene oxide, propylene oxide, and butylene oxide, and it is preferable to use ethylene oxide as an essential component. The number of moles of the added alkylene oxide is preferably 1 to 100 moles, more preferably 2 to 50 moles, per 1 mole of the alcohols or alkylphenol. When within the above range, it is preferable because the desorbability is particularly excellent.

[0043] 〔Fatty acid-based nonionic surfactant〕 The structure of the fatty acid-based nonionic surfactant is not particularly limited. For example, it includes an alkylene oxide adduct of a higher fatty acid having 10 to 24 carbon atoms in total, an oil or fat composed of an ester of the above-described saturated or unsaturated higher fatty acid having 10 to 24 carbon atoms in total and glycerin, and further an alkylene oxide adduct of a mixture of the above-described oil or fat and a polyhydric alcohol having 2 to 10 valences. The higher fatty acid having 10 to 24 carbon atoms in total may be either saturated or unsaturated. Examples of the higher fatty acid having 10 to 24 carbon atoms in total include saturated higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid; unsaturated higher fatty acids such as palmitoleic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, erucic acid, and ricinoleic acid; Examples of the polyhydric alcohol having 2 to 10 valences include ethylene glycol, propylene glycol, glycerin, polyglycerin, sorbitol, sorbitan, and sucrose. The type and number of moles of the added alkylene oxide are the same as those described in the section of 〔Alcohol-based nonionic surfactant〕 described above.

[0044] 〔Amine-based nonionic surfactant〕 Examples of amine-based nonionic surfactants include AO adducts of saturated or unsaturated primary or secondary amines having a total carbon number of 8 to 36. Examples of amines include 2-ethylhexylamine, di-2-ethylhexylamine, laurylamine, dilaurylamine, tetradecylamine, ditetradecylamine, hexadecylamine, dihexadecylamine, stearylamine, distearylamine, oleylamine, dioleylamine, and the like. Also, the type and number of moles of AO added are the same as described above.

[0045] (Anionic surfactant) The anionic surfactant is preferably a non-soap-based surfactant, and examples thereof include sulfonic acid-based anionic surfactants, sulfate ester-based anionic surfactants, carboxylic acid-based anionic surfactants, and phosphate ester-based anionic surfactants.

[0046] [Sulfonic acid-based anionic surfactant] Examples of the sulfonic acid-based anionic surfactant include alkyl sulfonic acid, alkyl benzene sulfonic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, alkyl methyl taurine, sulfosuccinic acid diester, alkylene oxide adducts of sulfonic acid, and salts thereof. Specific examples include hexane sulfonic acid, octane sulfonic acid, decane sulfonic acid, dodecane sulfonic acid, toluene sulfonic acid, cumene sulfonic acid, octyl benzene sulfonic acid, dodecyl benzene sulfonic acid, dinitrobenzene sulfonic acid, and lauryl dodecyl phenyl ether disulfonic acid, and the like can be used.

[0047] [Sulfate ester-based anionic surfactant] Examples of the sulfate ester-based anionic surfactant include sulfate esters (alkyl ether sulfates), alkylene oxide adducts of sulfate esters, and salts thereof. Specific examples include lauryl sulfate, myristyl sulfate, and polyoxyethylene lauryl ether sulfate, and the like can be used.

[0048] [Carboxylic acid anionic surfactant] Examples of the carboxylic acid anionic surfactant include alkyl carboxylic acid, alkylbenzene carboxylic acid, alkylene oxide adducts of carboxylic acid, and salts thereof. Specific examples include lauric acid, myristic acid, palmitic acid, stearic acid, polyoxyethylene lauryl ether acetic acid, polyoxyethylene tridecyl ether acetic acid, and the like.

[0049] [Phosphate ester anionic surfactant] Examples of the phosphate ester anionic surfactant include phosphate esters (alkyl ether phosphate esters), alkylene oxide adducts of phosphate esters, and salts thereof. Specific examples include octyl phosphate ester, lauryl phosphate ester, tridecyl phosphate ester, myristyl phosphate ester, cetyl phosphate ester, stearyl phosphate ester, polyoxyethylene octyl ether phosphate ester, polyoxyethylene lauryl ether phosphate ester, and the like.

[0050] The anionic surfactant preferably has an alkyl group having 2 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms, more preferably an alkyl group having 8 to 18 carbon atoms. The alkyl group or the alkenyl group may be linear or branched. When the anionic surfactant is an alkylene oxide adduct, examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and ethylene oxide is preferred. The number of moles of alkylene oxide added is preferably 1 to 12 moles, more preferably 1 to 8 moles, per mole of alcohols or alkylphenols. Being within the above range is preferred because the desorbability is particularly excellent.

[0051] Examples of the salts constituting the anionic surfactant described above include metal salts such as sodium, potassium, magnesium, and calcium. These salts may be used alone or in combination of two or more. Among them, as the anionic surfactant, from the viewpoints of desorbability and prevention of reattachment, sulfonate type and phosphate type are preferable, and more preferably, alkyl sulfonate, polyoxyalkylene alkyl ether sulfonate, polyoxyalkylene alkyl ether phosphate, etc.

[0052] (Cationic surfactant) Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts. Specifically, stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl tallow ammonium chloride, dimethyldioleyl ammonium chloride, methyloleyl diethanol chloride, tetramethyl ammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl pyridinium disulfate, cetyl pyridinium bromide, 4-alkyl mercapto pyridine, poly(vinyl pyridine)-dodecyl bromide, dodecyl benzyl triethyl ammonium chloride, etc. can be used.

[0053] (Amphoteric surfactant) Examples of the amphoteric surfactant include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctyl polyaminoethyl glycine, and imidazoline derivatives.

[0054] These surfactants may be used alone or in combination of two or more. The content of the surfactant in the release liquid is preferably in the range of 0.001 to 10% by mass, more preferably in the range of 0.005 to 7% by mass, still more preferably in the range of 0.03 to 5% by mass, and particularly preferably in the range of 0.05 to 3% by mass, based on the mass of the release liquid. When it is 0.001% by mass or more, it is preferable because it suppresses the curling of the substrate and has excellent releasability, and also suppresses the reattachment of the released coating layer components. When it is 10% by mass or less, it is preferable from the viewpoint of defoaming property.

[0055] [Defoaming agent] In the present invention, it is also preferable that the release liquid further contains a defoaming agent. By using the defoaming agent in combination with the above-mentioned surfactant, good defoaming property can be exhibited without reducing the releasability and the prevention of reattachment, and the foaming caused by the surfactant can be suppressed. Examples of the defoaming agent include silicone-based compounds and non-silicone-based compounds.

[0056] (Silicone-based compound) Examples of the silicone-based compound include emulsion type, self-emulsifying type, oil type, oil compound type, and solvent type. The emulsion type is a silicone-based defoaming agent obtained by emulsifying a silicone oil compound with an activator to form an O / W type (oil in water type) emulsion. Examples include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., "FC2913" and "SILFOAM SE47" manufactured by Asahi Kasei Wacker Silicone, and "BYK-015" and "BYK-1640" manufactured by BYK-Chemie Japan. The self-emulsifying type is a silicone-based defoaming agent with 100% active ingredient that forms an emulsion state by dilution and mixing with water. Examples include "KS-540" and "X-50-1176" manufactured by Shin-Etsu Chemical Co., Ltd., and "SILFOAM SD670" and "SILFOAM SD850" manufactured by Asahi Kasei Wacker Silicone. The oil type is an antifoaming agent of 100% silicone oil without solvents or additives. Examples include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., "AK350" and "AK12500" manufactured by Asahi Kasei Wacker Silicone, and "BYK-1770" manufactured by BYK-Chemie Japan. The oil compound type is a silicone-based antifoaming agent in which silica particles are blended with silicone oil. Examples include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., "SILFOAM SC370" and "PULPSIL22274VP" manufactured by Asahi Kasei Wacker Silicone, and "BYK-017" and "BYK-018" manufactured by BYK-Chemie Japan. The solvent type is a silicone-based antifoaming agent in which silicone oil is dissolved in a solvent. Examples include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., and "BYK-019" and "BYK-025" manufactured by BYK-Chemie Japan.

[0057] (Non-silicone-based compound) Examples of the above non-silicone-based compounds include fatty acid ester-based compounds, urea resin-based compounds, paraffin-based compounds, polyoxyalkylene glycol-based compounds, acrylic ester copolymers, ester-based polymers, ether-based polymers, amide-based polymers, emulsion types of mineral oil, polysiloxane adducts, fluorine-based compounds, vinyl-based polymers, acetylene alcohols, acrylic polymers, special vinyl-based polymers, ethylene glycol, and higher alcohols (such as octyl alcohol and cyclohexanol).

[0058] The antifoaming agent may be used alone or in combination of two or more. The content of the antifoaming agent in the release liquid is preferably in the range of 0.0001 to 5% by mass, more preferably in the range of 0.001 to 4.5% by mass, still more preferably in the range of 0.01 to 4% by mass, yet more preferably in the range of 0.02 to 3.5% by mass, and particularly preferably in the range of 0.03 to 3% by mass, based on the mass of the release liquid. When it is 0.0001% by mass or more, the antifoaming property is excellent, and when it is 5% by mass or less, the release property and the reattachment prevention property are excellent.

[0059] The above defoamer has good alkali resistance and is preferably at least one selected from the group consisting of emulsion-type silicone compounds, self-emulsifying silicone compounds, and non-silicone compounds from the viewpoint of being less likely to reduce the releasability and anti-re-adhesion property when combined with the above surfactant.

[0060] [Basic compound] As described above, from the viewpoint of peeling off the urethane-based adhesive layer commonly used in the packaging material, a basic aqueous solution containing a basic compound is preferably used as the release liquid used in the present invention. The above basic compound is not particularly limited. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH) 2 ), ammonia, barium hydroxide (Ba(OH) 2 ), sodium carbonate (Na 2 CO 3 ) is preferably used. More preferably, it is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide. The content of the basic compound in the basic aqueous solution is preferably in the range of 0.1 to 20% by mass, more preferably 0.3 to 15% by mass, and still more preferably 0.5 to 10% by mass based on the mass of the basic aqueous solution. When within the above range, the basic aqueous solution can maintain sufficient basicity to dissolve or swell the release layer described later to peel off the plastic substrate.

[0061] The release liquid penetrates from the end portion of the laminate and contacts the release layer, and by dissolving or swelling, separates the plastic substrate from the release layer. Therefore, in order to efficiently proceed with the peeling process, the laminate is preferably in a state where the release layer is exposed on the cross-section when it is cut or pulverized and immersed in the release liquid. In such a case, the substrate layer can be peeled off in a shorter time.

[0062] <Content of the laminate before peeling (also referred to as the processing amount)> When separating the laminate in the release liquid, the content of the laminate is 0.5% by mass or more, preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 8% by mass or less, still more preferably 1.5% by mass or more and 7% by mass or less, and particularly preferably 2% by mass or more and 6% by mass or less, based on the total mass of the release liquid. Being 0.1% by mass or more is preferable from the viewpoint of processing efficiency. Being 10% by mass or less is preferable from the viewpoints of releasability and prevention of reattachment.

[0063] <Step of Separating and Recovering the Plastic Substrate> After the release step, the separated plastic substrate is recovered. As the recovery method, known means can be applied by utilizing the difference in physical property values between the plastic substrate after release and the coating layer piece after release. For example, means of floating and sinking utilizing specific gravity, or means of centrifugation can be applied. Also, when the sizes of the plastic substrate after release and the coating layer after release are different, means of sorting using a net can be applied. After separation and recovery, the recovered plastic substrate can be made into a recycled substrate through steps such as washing with water and drying, for example. The recycled substrate can be made into pellets by melt-kneading processing, or can be made into a molded body by heat molding, for example.

[0064] <Laminate> The laminate used in the present invention includes a plastic substrate and a coating layer. The coating layer includes, for example, at least one coating layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer. By peeling the layer in contact with the plastic substrate with the above-described release liquid, it becomes possible to recover and recycle the plastic substrate. In the present invention, in order to improve the releasability, it is preferable to provide a primer layer having high affinity with the release liquid in contact with the plastic substrate layer.

[0065] <Printing Layer> In the present invention, the printing layer may be provided in contact with the plastic substrate, and when the laminate has a primer layer, it may be provided in contact with the primer layer. The printing layer is a layer that forms an arbitrary printing pattern for the purpose of decoration, imparting aesthetic sense, indicating contents, expiration date, manufacturer or seller, etc., and includes a solid printing layer. The printing layer may be formed of a single layer or a plurality of layers. When the printing layer contains a water-soluble resin or a compound having an acidic group described later, it also functions as a release layer. The printing ink used to form the printing layer can be produced by dissolving and / or dispersing at least a colorant, a dispersant, and a binder resin in a solvent, and may contain other components as necessary.

[0066] When separating the laminate in the release liquid, the content of the printing layer is 0.01% by mass or more, preferably 0.05% by mass or more and 1% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, based on the total mass of the release liquid. When it is 0.01% by mass or more, it is preferable from the viewpoint of processing efficiency. When it is 1% by mass or less, it is preferable from the viewpoint of preventing reattachment.

[0067] [Colorant] The printing layer may be colored or colorless, and contains a known colorant used in printing ink or paint. Such colorants are not particularly limited, and in addition to inorganic pigments, organic pigments, and dyes, metal powders that give metallic luster, near-infrared absorbing materials, and ultraviolet absorbing materials may also be used. Examples of the inorganic pigment include colored pigments such as titanium oxide, red iron oxide, ultramarine blue, cobalt blue, carbon black, and graphite; extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. As the organic pigment, soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, condensed polycyclic pigments, etc. are preferably used. In addition to these, pigments described by the generic names of the Color Index can be appropriately used. Among them, when the stripping liquid is a basic aqueous solution, pigments that do not elute into the basic aqueous solution and have alkali resistance are preferred. By preventing the elution of the pigment, the reuse of the basic aqueous solution becomes easy. The alkali resistance of the pigment is generally estimated from the skeleton or structure of the pigment. Examples of pigments with alkali resistance include inorganic pigments, C.I. Pigment Blue 15, and C.I. Pigment Yellow 83. When the pigment is titanium oxide, the content of titanium oxide is preferably 20 to 80% by mass, more preferably 30 to 75% by mass in the printing layer. When the pigment is an inorganic pigment, extender pigment, or organic pigment other than titanium oxide, the content of each of these pigments is preferably 0.5 to 60% by mass, more preferably 10 to 50% by mass in the printing layer.

[0068] [Dispersant] The printing layer contains a pigment derivative and / or a resin type dispersant as a dispersant for the colorant, thereby improving the peelability. Furthermore, the dispersion stability and stability over time of the ink are improved. These may be used alone, but it is preferable to use them in combination because the dispersion stability and stability over time are further improved.

[0069] (Pigment Derivative) A pigment derivative is a compound in which a substituent is introduced into the skeleton of the pigment. In the printing ink, the skeleton of the pigment of the pigment derivative adsorbs on the surface of the pigment in the printing ink, and the substituent portion of the pigment derivative is oriented in the solvent in the printing ink, thereby having an action of dispersing the pigment in the printing ink. As the pigment derivative, for example, those obtained by adding functional groups such as carboxyl group, sulfonic acid group, carbonyl group, and sulfonyl group to the skeletons of pigments such as phthalocyanine-based, azo-based, anthraquinone-based, and quinacridone-based pigments, and salts thereof can be preferably used. These can be used alone or in combination.

[0070] As commercially available pigment derivatives, Solsperse 5000, Solsperse 12000 (manufactured by Lubrizol Japan), BYK-SYNERGIST 2100, BYK-SYNERGIST 2105 (manufactured by BYK-Chemie Japan), Efka 6745, Efka 6750 (manufactured by BASF), etc. can be preferably used. These can be used alone or in combination.

[0071] The pigment derivative preferably exhibits the same or a similar color as the pigment in the ink. For example, when adding to black ink or cyan ink, a phthalocyanine pigment derivative can be preferably used as the pigment derivative.

[0072] The total amount of the pigment derivative is preferably 0.01 to 10% by mass, more preferably 0.05 to 6% by mass, and even more preferably 0.1 to 4% by mass with respect to the whole colorant. When it is 0.01% by mass or more, the dispersion stability of the printing ink becomes good and the releasability is also improved. Also, being 0.01 to 10% by mass contributes to the improvement of the releasability and the suppression of reattachment, and it can be recycled into a high-quality recycled molding material.

[0073] (Resin type dispersant) The resin-type dispersant has an affinity site for the pigment composition that has the property of adsorbing to the pigment composition and a site compatible with the pigment composition carrier, and functions to adsorb to the pigment composition and stabilize the dispersion in the pigment composition carrier. Specific examples of the resin-type dispersant include polycarboxylic acid esters such as polyurethane and polyacrylate, unsaturated polyamides, polycarboxylic acids, polycarboxylic acid (partial) amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid alkylamine salts, polysiloxanes, long-chain polyamino amidine salts, hydroxyl group-containing polycarboxylic acid esters, and modified products thereof, oil-based dispersants such as amides and salts thereof formed by the reaction of poly(lower alkyleneimine) and a polyester having a free carboxyl group, (meth)acrylic acid-styrene copolymers, (meth)acrylic acid-(meth)acrylate copolymers, styrene-maleic acid copolymers, polyvinyl alcohol, polyvinyl pyrrolidone and other water-soluble resins and water-soluble polymer compounds, polyester-based, modified polyacrylate-based, ethylene oxide / propylene oxide adduct compounds, phosphate ester-based, etc. These can be used alone or in combination of two or more, but are not necessarily limited thereto.

[0074] The total amount of the resin-type dispersant is preferably 0.01 to 30% by mass, more preferably 0.05 to 20% by mass, and even more preferably 0.1 to 10% by mass based on the total amount of the colorant. When it is 0.01% by mass or more, the dispersion stability of the printing ink is good and the desorbability is also improved. Also, when it is 30% by mass or less, the water resistance of the printing layer is good.

[0075] [Binder resin] As the binder resin for the printing layer, for example, nitrocellulose-based, fiber materials such as cellulose acetate propionate, chlorinated polypropylene-based, vinyl chloride-vinyl acetate copolymer-based, polyester-based, acrylic-based, urethane resin-based and acrylic urethane-based, polyamide-based, polybutyral-based, cyclized rubber-based, chlorinated rubber-based binders, or binders using a combination thereof as appropriate can be used. When a water-soluble resin or a compound having an acidic group described later is included, the printing layer also functions as a release layer. These resins may be used alone or in combination of two or more.

[0076] [Primer layer] The laminate used in the present invention may have a primer layer. When the laminate has a primer layer, the primer layer is preferably arranged in contact with the plastic substrate and formed from a primer composition having a water-soluble resin or a compound having an acidic group, and plays a role of detaching the plastic substrate by dissolution or peeling with a release liquid.

[0077] (Water-soluble resin) The water-soluble resin may be any resin that swells or dissolves in water and can be detached from the plastic substrate. The water may be heated to about 25 to 100 °C. Thereby, the primer layer can be detached with water (including warm water). Such resins can be selected from known resins as long as the water solubility is not impaired. For example, water-soluble polyester resin, water-soluble polyamide resin, water-soluble polyimide resin, water-soluble acrylic resin, water-soluble polyurethane resin, water-soluble polyallylamine resin, water-soluble phenol resin, water-soluble epoxy resin, water-soluble phenoxy resin, water-soluble urea resin, water-soluble melamine resin, polyvinyl alcohol resin, and modified products of these resins can be mentioned. These can be used alone or in combination of two or more. Among them, polyvinyl alcohol (PVA) resin is preferably used from the viewpoints of easy availability and detachability. When the water-soluble resin has film-forming properties, the water-soluble resin may be used as the binder resin constituting the primer layer.

[0078] As the polyvinyl alcohol resin, in addition to unmodified polyvinyl alcohol, various monomers may be copolymerized during the production of vinyl ester resins, and modified polyvinyl alcohol obtained by saponifying this, or various post-modified polyvinyl alcohols in which various functional groups are introduced into unmodified polyvinyl alcohol by post-modification may be used. Further, those obtained by further post-modifying the modified polyvinyl alcohol may also be used. These modifications can be carried out within a range that does not impair the water solubility of the polyvinyl alcohol resin. These resins may be used alone or in combination of two or more.

[0079] Preferred examples of the polyvinyl alcohol resin include resins containing a structural unit having a primary hydroxyl group in the side chain and ethylene-modified polyvinyl alcohol resins. Among them, a polyvinyl alcohol resin containing a structural unit having a primary hydroxyl group in the side chain is preferred in terms of excellent melt moldability and further excellent water solubility. The number of primary hydroxyl groups in these structural units is usually 1 to 5, preferably 1 to 2, more preferably 1. Further, it is preferable to have a secondary hydroxyl group in addition to the primary hydroxyl group.

[0080] The saponification degree (measured in accordance with JIS K 6726) of the polyvinyl alcohol resin used in the present invention is usually 60 to 100 mol%. Further, the preferable range of the saponification degree varies depending on the modification type. For example, in the case of an unmodified polyvinyl alcohol resin, it is usually 60 to 99.9 mol%, preferably 70 to 99.0 mol%, more preferably 75 to 98.5%. The saponification degree of the modified polyvinyl alcohol resin containing a side chain 1,2-diol structural unit is usually 60 to 99.9 mol%, preferably 65 to 99.8 mol%, more preferably 70 to 99.5%. If such a saponification degree is too low, the water solubility tends to decrease. The saponification degree of the ethylene-modified polyvinyl alcohol resin modified with a small amount of ethylene is usually 60 mol% or more, preferably 70 to 99.5 mol%, particularly preferably 75 to 99.0 mol%. When the saponification degree is within the above range, it is preferable because it has excellent water solubility and good releasability. Also, it is preferable because it also has excellent coatability when forming the primer layer.

[0081] The average degree of polymerization of the polyvinyl alcohol resin (measured in accordance with JIS K 6726) is usually 100 to 3000, preferably 150 to 2000, more preferably 180 to 1000, and particularly preferably 200 to 800.

[0082] (Compound having an acidic group) As the compound having an acidic group, a resin having an acidic group or a low molecular compound having an acidic group may be used. Thereby, the primer layer can be removed with the basic aqueous solution described above.

[0083] Examples of the resin in the resin having an acidic group include cellulose-based resins, urethane resins, polyamide resins, vinyl chloride / vinyl acetate copolymers, ketone resins, polyester resins, and (meth)acrylic resins. Examples of the above acidic group include a carboxy group, a phosphoric acid group, a sulfo group, a sulfino group, etc. or their esters or salts. Further, as the resin having an acidic group, a rosin-modified resin having an acid value such as maleated rosin or fumarated rosin can be used. Further, as the resin having an acidic group, polymerizable monomers having a carboxy group such as itaconic acid, maleic acid, fumaric acid, cinnamic acid; polymerizable monomers which are acid anhydrides such as itaconic anhydride, maleic anhydride; polymerizable monomers having a sulfonic acid group such as sulfonated styrene; polymerizable monomers having a sulfonamide group such as vinylbenzenesulfonamide; radical copolymers such as styrene-(meth)acrylic resin, styrene-(anhydrous)maleic acid resin, terpene-(anhydrous)maleic acid resin copolymerized with polymerizable monomers having an acidic group, and acid-modified polyolefin resins can be used. These may be used alone or in combination of two or more.

[0084] The low-molecular-weight compound having an acidic group refers to a compound having no molecular weight distribution and having a molecular weight of 1,000 or less. Examples of such compounds include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid; unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid; hydroxy acids such as lactic acid, malic acid, and citric acid; aromatic carboxylic acids such as benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, and cinnamic acid; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid; tricarboxylic acids such as aconitic acid; oxocarboxylic acids such as pyruvic acid and oxaloacetic acid; carboxylic acid derivatives such as amino acids and nitrocarboxylic acids; and acid anhydrides such as trimellitic anhydride and pyromellitic anhydride. The low-molecular-weight compound having an acidic group can be used in combination with the resin having the acidic group described above or a known binder resin constituting a known primer layer to form a primer layer.

[0085] From the viewpoint of recoatability, the primer layer preferably contains a compound having an acidic group. Further, from the viewpoint of printability, it preferably contains a urethane resin having an acidic group, an acrylic resin having an acidic group, or a rosin-modified resin. The primer layer may contain these resins alone or in combination of two or more.

[0086] [Urethane Resin Having an Acidic Group] The urethane resin having an acidic group is not particularly limited. Examples thereof include a urethane resin obtained by reacting a polyol having an acidic group with a polyisocyanate, a resin obtained by acid-modifying a hydroxyl group in a urethane resin obtained by reacting a polyol with a polyisocyanate, and a resin obtained by acid-modifying an amino group in a urethane-urea resin obtained by reacting a polyamine with an isocyanate group in a urethane resin obtained by reacting a polyol with a polyisocyanate. Further, as the urethane resin having an acidic group, a resin obtained by reacting a polyol containing a hydroxy acid and a polyisocyanate may be used. By using a hydroxy acid as the polyol, an acid value derived from a carboxy group can be imparted to the urethane resin, and the releasability can be improved. Further, when the urethane resin having the acidic group has an isocyanate group, a polyamine may be reacted with a part of the isocyanate group to introduce a urea bond, and it may be a urethane urea.

[0087] 《Polyol》 A polyol is a general term for compounds having at least two hydroxyl groups in one molecule. The number average molecular weight of the polyol is preferably 500 to 10,000, more preferably 1,000 to 5,000. The above number average molecular weight is calculated from the hydroxyl value of the polyol, and the hydroxyl value refers to the measured value according to JIS K 0070. When the number average molecular weight of the polyol is 500 or more, the flexibility of the primer layer is excellent and the adhesion to the plastic substrate is improved. When the number average molecular weight is 10,000 or less, the blocking resistance to the plastic substrate is excellent.

[0088] The polyol is not particularly limited, and more preferably, at least one polyol selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol is used. Further, the polyol may contain other dimer diols, hydrogenated dimer diols, castor oil-modified polyols, etc. That is, the urethane resin preferably contains a structural unit derived from at least one polyol selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol. Since the releasability is improved by the alkaline hydrolysis of the ester bond site of the polyester polyol, it more preferably contains a structural unit derived from the polyester polyol. The content of the structural unit derived from the polyol is preferably 10 to 75% by mass, more preferably 15 to 70% by mass, and still more preferably 20 to 65% by mass based on the total amount of the urethane resin. The content of the structural unit derived from the polyester polyol is preferably 5% by mass or more, more preferably 30% by mass or more, still more preferably 60% by mass or more, and particularly preferably 80% by mass or more based on the total amount of the structural units derived from the polyol.

[0089] 《Hydroxy Acid》 The above polyol may contain a hydroxy acid. The above hydroxy acid refers to a compound having both a hydroxyl group which is an active hydrogen group and an acidic functional group in one molecule. The acidic functional group indicates a functional group that can be neutralized with potassium hydroxide when measuring the acid value, and specifically includes a carboxy group, a sulfonic acid group, etc., and preferably a carboxy group. As such a hydroxy acid, for example, dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid are preferably used.

[0090] 《Polyisocyanate》 The above polyisocyanate is not particularly limited and can be selected from conventionally known polyisocyanates. Preferably, it contains a diisocyanate or a triisocyanate, and more preferably contains an aromatic, aliphatic or alicyclic diisocyanate. These may be used alone or in combination of two or more.

[0091] 《Polyamine》 The polyamine for forming the urethane urea is not particularly limited and is preferably a diamine compound. Also, a diamine having a hydroxyl group may be used in terms of being able to introduce a hydroxyl group into the urethane resin.

[0092] The acid value of the urethane resin having an acidic group is preferably 15 mgKOH / g or more, more preferably 15 to 70 mgKOH / g, and even more preferably 20 to 50 mgKOH / g. When it is 15 mgKOH / g or more, the desorbability by the desorbing liquid is good, so it is preferable. When it is 70 mgKOH / g or less, the substrate adhesion and retort resistance are good, so it is preferable. The hydroxyl value of the urethane resin is preferably 1 to 35 mgKOH / g, more preferably 10 to 30 mgKOH / g. When it is 1 mgKOH / g or more, the desorbability by the desorbing liquid is good, so it is preferable. When it is 35 mgKOH / g or less, the substrate adhesion is good, so it is preferable.

[0093] The weight average molecular weight of the urethane resin having an acidic group is preferably 10,000 to 100,000, more preferably 15,000 to 70,000, and even more preferably 15,000 to 50,000. The molecular weight distribution (Mw / Mn) of the urethane resin is preferably 6 or less. Mw represents the weight average molecular weight, and Mn represents the number average molecular weight. When the molecular weight distribution is 6 or less, it is excellent in desorbability, drying property of the primer composition, and retort resistance. Further, the smaller the molecular weight distribution, that is, the sharper the molecular weight distribution, the more uniform the dissolution and peeling action by the desorbing liquid occurs, and the desorbability of the plastic substrate is improved. The molecular weight distribution is more preferably 5 or less, and even more preferably 4 or less. Also, the molecular weight distribution is preferably 1.5 or more, more preferably 1.2 or more. In the present invention, Mw, Mn, and the molecular weight distribution (Mw / Mn) are polystyrene conversion values determined by gel permeation chromatography (GPC).

[0094] The urethane resin having an acidic group may have an amine value. When the urethane resin has an amine value, the amine value is preferably 0.1 to 20 mgKOH / g, more preferably 1 to 10 mgKOH / g. When it is within the above range, the substrate adhesion is excellent.

[0095] The urethane bond number of the polyurethane resin having an acidic group is preferably 1 to 3 mmol / g, more preferably 1.5 to 2 mmol / g. Also, the urea bond number is preferably 0 to 3 mmol / g, more preferably 0.2 to 1 mmol / g. Further, the total of the urethane bond number and the urea bond number is preferably 1 to 6 mmol / g, more preferably 1.7 to 3 mmol / g. By setting the urethane bond number and the urea bond number within the corresponding ranges, the releasability and the substrate adhesion are improved.

[0096] [Acrylic resin having an acidic group] Examples of the acrylic resin having an acidic group include polymers obtained by polymerizing monomers containing (meth)acrylic monomers having acidic groups such as (meth)acrylic acid and maleic acid; resins obtained by polymerizing monomers containing (meth)acrylic monomers having hydroxyl groups or glycidyl groups and then modifying the functional groups to introduce carboxyl groups (for example, maleic anhydride-modified resins). The acid value of the acrylic resin having an acidic group is preferably 50 mgKOH / g or more, more preferably 100 mgKOH / g or more.

[0097] [Rosin-modified resin] The rosin-modified resin is a resin prepared using rosin as one of the raw materials. Rosin contains resin acids such as abietic acid, palustric acid, isopimaric acid, and levopimaric acid as a mixture. These resin acids contain hydrophilic and chemically active carboxyl groups, and some of them have conjugated double bonds. Therefore, various rosin-modified resins are prepared by, for example, condensation polymerization by combining polyhydric alcohols and polybasic acids, adding resole, which is a condensate of phenol, to the benzene ring contained in the rosin skeleton, or causing a Diels-Alder reaction with dienophiles such as maleic anhydride or maleic acid to add a maleic acid or maleic anhydride skeleton. Such rosin-modified resins are commercially available in various types, and it is also possible to obtain and use them.

[0098] Examples of the rosin-modified resin include maleated rosin, fumarated rosin, rosin-modified maleic acid resin, rosin-modified fumaric acid resin, rosin-modified phenol resin, rosin-modified alkyd resin, and rosin-modified polyester resin. In the present invention, any rosin-modified resin may be used, but among them, those containing a site derived from at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride in their structure are preferably used. The "resin containing a site derived from at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride in its structure" means a resin prepared using at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride as a part of the raw materials. For example, a rosin-modified maleic acid resin and a rosin-modified fumaric acid resin obtained by polycondensing maleic acid or fumaric acid as a part of polybasic acids, maleated rosin and fumarated rosin having a structure in which maleic acid, maleic anhydride, fumaric acid, or fumaric anhydride is added by a Diels-Alder reaction as a dienophile, and resins obtained by polymerizing other chemical species using the functional groups contained therein, etc.

[0099] The acid value of the rosin-modified resin is preferably 10 to 400 mgKOH / g, more preferably 100 to 300 mgKOH / g.

[0100] (Other components) The primer layer may contain a water-soluble resin or a resin other than a compound having an acidic group. Examples of such resins include cellulose resins, polyamide resins, vinyl chloride resins such as vinyl chloride-vinyl acetate copolymer resins or vinyl chloride-acrylic copolymer resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, acrylic resins, styrene resins, dammar resins, styrene-acrylic copolymers, polyester resins, alkyd resins, terpene resins, phenol-modified terpene resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyral, polyacetal resins, petroleum resins, and modified resins thereof. These resins may be used alone or in combination of two or more. Among them, the primer layer preferably contains at least one resin selected from the group consisting of cellulose resins, vinyl chloride resins, rosin resins, and acrylic resins. More preferably, it contains a vinyl chloride resin or an acrylic resin. The mass ratio of the urethane resin having an acidic group to the other resin (urethane resin having an acidic group: other resin) is preferably 95:5 to 50:50. When it is within the above range, when the printing layer peels off together with the primer layer in a basic aqueous solution, the printing layer peels off in a thin film state, which is preferable because it is easy to recover.

[0101] The primer layer may contain an extender pigment. Examples of the extender pigment include metal oxides such as silica, barium sulfate, kaolin, clay, calcium carbonate, magnesium carbonate, zinc oxide, and zirconium oxide. Among them, silica is preferably used, and more preferably hydrophilic silica. The average particle diameter of the extender pigment is preferably 0.5 to 10 μm, and more preferably 1 to 8 μm. The content of the extender pigment is preferably 0.5 to 10% by mass in the primer layer, and more preferably 1 to 5% by mass. When the average particle diameter and the content of the extender pigment are within the above ranges, the wettability of the printing layer is improved and the image quality is improved.

[0102] The primer layer may be a layer in which a urethane resin having the acidic group described above is crosslinked with a curing agent. By introducing a crosslinked structure into the primer layer, penetration and bleeding of the printing layer formed on the primer layer can be suppressed, and excellent image quality can be exhibited. Examples of the curing agent include polyisocyanates. The polyisocyanate is not particularly limited and can be selected from conventionally known polyisocyanates. Examples thereof include aliphatic polyisocyanates and araliphatic polyisocyanates. These may be used alone or in combination of two or more.

[0103] The primer layer may further contain known additives. Examples of the known additives include dispersants, wetting agents, adhesion aids, leveling agents, defoaming agents, antistatic agents, viscosity modifiers, metal chelates, trapping agents, antiblocking agents, wax components other than the above, and silane coupling agents.

[0104] The thickness of the primer layer is preferably in the range of 0.5 to 3.0 μm, more preferably 0.6 to 2.0 μm, and still more preferably 0.8 to 1.5 μm, and can be formed by using a known method.

[0105] [Adhesive layer] The laminate of the present invention may have an adhesive layer. When the laminate has an adhesive layer, the adhesive layer is preferably disposed in contact with the plastic substrate, contains a compound having an acidic group, and plays a role of detaching the plastic substrate by dissolution and peeling with a detachment liquid. By the adhesive layer containing a resin having an acidic group or a low molecular compound having an acidic group, the adhesive layer can be detached using the basic aqueous solution described above. For the compound having an acidic group, the resin having an acidic group, and the low molecular compound having an acidic group, the description of (the compound having an acidic group) in the section of [primer layer] described above can be cited. The method for forming the adhesive layer is not limited and can be formed by using a known method.

[0106] From the perspective of releasability, the adhesive layer may be a cured product of an adhesive containing a polyester polyol having an acidic group and at least one polyisocyanate selected from the group consisting of aliphatic polyisocyanates and araliphatic polyisocyanates. The above cured product corresponds to a resin having an acidic group. Also, the adhesive layer may be a cured product of an adhesive containing a polyester polyol, at least one polyisocyanate selected from the group consisting of aliphatic polyisocyanates and araliphatic polyisocyanates, and a low molecular compound having an acidic group.

[0107] (Polyester polyol) The polyester polyol only needs to have an acidic group and can be appropriately selected from known polyester polyols. By containing such a polyester polyol, when an aqueous basic solution is used as the release liquid, it has an ester bond with high affinity for basic compounds, which is preferable because the releasability is improved. The polyester polyol may be used alone or in combination of two or more.

[0108] The polyester polyol is not particularly limited, but a polyester polyol obtained by reacting a carboxy group component and a hydroxyl group component; a polyester polyol obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, poly(β-methyl-γ-valerolactone), etc. are preferably used. Examples of the above carboxy group component include dibasic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, phthalic anhydride, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, itaconic anhydride, etc., or their dialkyl esters or mixtures thereof. Examples of the hydroxyl group component include diols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, butylene glycol, neopentyl glycol, trimethylolpropane, glycerin, 1,6 - hexanediol, 1,4 - butanediol, 1,4 - cyclohexanedimethanol, 3 - methyl - 1,5 - pentanediol, 3,3′ - dimethylolheptane, 1,9 - nonanediol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol, polyether polyol, polycarbonate polyol, polyolefin polyol, acrylic polyol, polyurethane polyol, or mixtures thereof. Two or more of the carboxy group component and the hydroxyl group component may be used in combination.

[0109] The polyester polyol may be a polyester urethane polyol obtained by reacting a polyisocyanate with the hydroxyl groups in the polyol. The presence of urethane bonds in the polyester polyol exhibits excellent heat resistance and adhesiveness. Examples of the polyisocyanate include 2,4 - tolylene diisocyanate, 2,6 - tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5 - naphthalene diisocyanate, hexamethylene diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0110] Alternatively, the polyester polyol may be an acid anhydride - modified product obtained by reacting an acid anhydride with the hydroxyl groups in the polyol. This allows the introduction of carboxy groups, which are acidic groups, into the polyester polyol. Examples of the acid anhydride include pyromellitic anhydride, mellitic anhydride, trimellitic anhydride, and trimellitic acid ester anhydride. Examples of the trimellitic acid ester anhydride include ethylene glycol bisanhydrotrimellitate and propylene glycol bisanhydrotrimellitate.

[0111] The acid value of the polyester polyol is preferably 5.0 mgKOH / g or more, more preferably 10.0 mgKOH / g or more. Also, the acid value of the polyester polyol is preferably 100 mgKOH / g or less, more preferably 80 mgKOH / g or less. When the acid value of the polyester polyol is within the above range, when it is brought into contact with the release liquid which is a basic aqueous solution, the basic aqueous solution penetrates and decomposes, and more excellent releasability is exhibited. When the adhesive contains a plurality of polyester polyols, the acid value of the entire polyester polyol can be obtained from the acid value of each polyester polyol component and its mass ratio.

[0112] The number average molecular weight (Mn) of the polyester polyol is preferably 3,000 to 25,000, more preferably 5,000 to 20,000, and particularly preferably 7,000 to 15,000. When the number average molecular weight of the polyester polyol is 3,000 or more, not only the coatability but also sufficient retort resistance can be exhibited, and when it is 20,000 or less, not only the coatability but also the releasability is improved, which is preferable.

[0113] In order to satisfy various physical properties required for the packaging material, a plurality of polyester polyol components may be used in combination for the polyester polyol content. For example, it may contain a polyester polyol having a number average molecular weight of 5,000 to 20,000. Further, in order to improve the substrate adhesion, it may contain a polyester polyol having a number average molecular weight of less than 3,000. The content of the polyester polyol having a number average molecular weight of less than 3,000 is preferably 0 to 30% by mass, more preferably 0 to 20% by mass based on the total mass of the polyester polyol. When it is 30% by mass or less, the retort resistance can be maintained.

[0114] (Other polyols) The adhesive that constitutes the adhesive layer may contain other polyols other than polyester polyol. The polyols that may be contained in addition to the polyester polyol are not particularly limited, and examples thereof include polycarbonate polyol, polycaprolactone polyol, polyether polyol, polyolefin polyol, acrylic polyol, silicone polyol, castor oil-based polyol, and fluorine-based polyol.

[0115] (Polyisocyanate) In order to constitute the adhesive layer, the polyisocyanate combined with the above-mentioned polyester polyol is preferably at least one selected from the group consisting of known aliphatic polyisocyanates and araliphatic polyisocyanates.

[0116] Examples of the aliphatic polyisocyanate include acyclic aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, and 1,2-butylene diisocyanate; alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (hereinafter referred to as isophorone diisocyanate); polyisocyanates such as allophanate type, nurate type, biuret type, and adduct type derivatives derived from the above diisocyanates, or complexes thereof. Preferably, the derivatives are of the nurate type or the adduct type, and more preferably the adduct type. As the aliphatic polyisocyanate, a polyisocyanate derived from hexamethylene diisocyanate (hereinafter also referred to as HDI), which easily ensures the balance between desorbability and laminate physical properties, is preferred.

[0117] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene or a mixture thereof; polyisocyanates such as allophanate type, nurate type, biuret type, adduct type derivatives derived from the above aromatic aliphatic diisocyanates, or a complex thereof.

[0118] (Other polyisocyanates) The adhesive may contain other polyisocyanates other than aliphatic polyisocyanates and aromatic aliphatic polyisocyanates as long as the effects of the present invention are not impaired. Examples of such polyisocyanates include aromatic diisocyanates such as toluene diisocyanate and diphenylmethane diisocyanate; polyisocyanates such as derivatives of the above diisocyanates or a complex thereof.

[0119] The mixing ratio of the above polyol and polyisocyanate may be adjusted so that the molar ratio (NCO / OH) of the isocyanate group of the polyisocyanate to the hydroxyl group in the polyol is 0.3 to 10.0. Preferably, it is 0.3 to 7.0, and more preferably 0.5 to 5.0.

[0120] (Other components) In addition to the silane coupling agent, phosphoric acid or its derivative, leveling agent, defoaming agent, and reaction accelerator, the adhesive layer may contain an inorganic filler (e.g., silica, alumina, mica, talc, aluminum flake, glass flake), a layered inorganic compound, a stabilizer (e.g., antioxidant, heat stabilizer, ultraviolet absorber, hydrolysis inhibitor), rust inhibitor, thickener, plasticizer, antistatic agent, lubricant, antiblocking agent, colorant, filler, crystal nucleating agent, catalyst for adjusting the curing reaction, etc.

[0121] <Plastic substrate layer> Examples of the plastic base material include polyolefin resin, polyester resin, polyamide resin, polystyrene resin, vinyl chloride resin, vinyl acetate resin, ABS resin, acrylic resin, acetal resin, polycarbonate resin, polyvinyl alcohol resin, and cellulose-based plastics.

[0122] From the perspective of reuse as a recycled base material, the plastic base material is preferably a polyolefin base material containing a polyolefin resin. Examples of such a base material containing a polyolefin resin include plastic base materials such as polyethylene (PE) and biaxially oriented polypropylene (OPP), and sealant base materials such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), acid-modified polyethylene, unoriented polypropylene (CPP), acid-modified polypropylene, and copolymerized polypropylene. The plastic base material may be gas barrier-treated to form a gas barrier base material.

[0123] The thickness of the plastic base material layer is not particularly limited and may be appropriately selected according to the application. Preferably it is 5 to 200 μm, more preferably 10 to 150 μm. The thinner the thickness, the easier the base material is to curl, and the higher the degree of difficulty of peelability. Examples of the gas barrier base material include a plastic base material having a metal vapor deposition layer such as aluminum foil or aluminum, or a metal oxide vapor deposition layer such as silica or alumina. The thickness of the aluminum foil is often used in the range of 3 to 50 μm from an economic perspective. Also, the aluminum foil, aluminum vapor deposition layer, and alumina vapor deposition layer dissolve and peel off in a basic aqueous solution, so they function as a release layer and can separate the adjacent polyolefin resin.

[0124] An example of the laminate structure of the present invention is given below, but it is not limited thereto. Also, in the following configuration, the "base material layer" does not necessarily have to be a single layer, and it may be a laminate in which a plurality of base materials are laminated. · Plastic base material layer / Printing layer · Plastic base material layer / Primer layer / Printing layer · Plastic substrate layer / Printing layer / Adhesive layer / Plastic substrate layer · Plastic substrate layer / Primer layer / Printing layer / Adhesive layer / Plastic substrate layer · Substrate layer / Printing layer / Adhesive layer / Plastic substrate layer · Plastic substrate layer / Primer layer / Printing layer / Adhesive layer / Vapor deposition layer / Plastic substrate layer

[0125] <Method for manufacturing plastic substrate> Using the separation and recovery method described above, a plastic substrate can be manufactured. The plastic substrate may be a substrate fragmented by crushing, cutting, pulverizing, etc. The method for manufacturing a plastic substrate includes, for example, preparing a laminate including at least a plastic substrate layer and a coating layer, and recovering the plastic substrate by the above separation and recovery method.

[0126] <Method for manufacturing molding material> By melt-kneading the plastic substrate recovered by the separation and recovery method described above, a molding material can be manufactured. The method for manufacturing the molding material of the present invention preferably includes the following steps 1 to 3. Alternatively, the above separation and recovery method of the laminate or the method for manufacturing the plastic substrate may include at least the following step 1, and the method for manufacturing the molding material may include at least the following step 3. When the molding material contains a masterbatch, the following step 4 may further be included. (Step 1) A step of crushing the laminate, immersing it in a release liquid, and releasing the plastic substrate from the laminate, or a step of crushing the laminate, immersing it in a release liquid, and releasing the coating layer from the laminate (Step 2) A step of recovering the plastic substrate obtained in Step 1 and washing it with water (Step 3) A step of melt-kneading the plastic substrate obtained in Step 2 to obtain a recycled resin (Step 4) A step of mixing a masterbatch with the recycled resin obtained in Step 3 to obtain a molding material

[0127] The method for crushing the laminate in Step 1 is not particularly limited. For example, methods using a jaw crusher, impact crusher, cutter mill, stamp mill, ring mill, roller mill, jet mill, or hammer mill can be mentioned. Step 2 may further include a drying step if necessary. By Step 2, a recovered plastic substrate (also referred to as a substrate after recycling or a recycled plastic substrate) can be obtained.

[0128] In the melt-kneading method in Step 3, various additives such as antioxidants can be added as needed, mixed with a Henschel mixer, tumbler, disperser, etc., and then kneaded using a batch kneader such as a kneader, roll mill, super mixer, Henschel mixer, sugar mixer, vertical granulator, high-speed mixer, farmatrix, ball mill, steel mill, sand mill, vibration mill, attritor, Banbury mixer, a twin-screw extruder, single-screw extruder, rotor-type twin-screw kneader, etc., to mix and disperse. Thereby, a recycled resin which is a resin composition is obtained. The shape of the recycled resin is not particularly limited and may be pellet form, powder form, granular form, or bead form. It is preferable to use a twin-screw extruder for the melt-kneading step.

[0129] [Masterbatch] The molding material of the present invention can further contain a masterbatch. The masterbatch is not particularly limited as long as it has compatibility with the recycled resin. Generally, a material obtained by kneading a thermoplastic resin such as a polyethylene resin or polypropylene resin and a colorant can be used. The thermoplastic resin contained in the masterbatch may be used alone or in combination of two or more. The masterbatch in the present invention may contain, within a range that does not inhibit the effects of the present invention, metal soaps of alkali metals, alkaline earth metals, or zinc, hydrotalcite, nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants, antistatic agents, flame retardants such as halogen-based, phosphorus-based, or metal oxides, lubricants such as ethylene bisalkylamide, antioxidants, ultraviolet absorbers, and fillers.

[0130] <Formed body> A formed body can be obtained by thermoforming a molding material obtained by the above-described manufacturing method. The thermoforming method is not particularly limited, and examples thereof include injection molding, extrusion molding, blow molding, and compression molding. The molding material produced using the plastic substrate recovered by the separation and recovery method of the present invention has a high quality because the printing layer is detached and reattachment of the detached components is suppressed, and it can be used in various fields such as home appliances, stationery, automotive parts, toys and sports goods, materials for medical and construction materials.

Examples

[0131] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the present invention, "parts" and "%" represent parts by mass and mass%, respectively, unless otherwise noted. In addition, Example 13 is a reference example.

[0132] <Molecular weight and molecular weight distribution> The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were measured by GPC (gel permeation chromatography) and determined as the converted molecular weight using polystyrene as a standard substance. The measurement conditions are shown below. GPC apparatus: Shodex GPC-104 manufactured by Showa Denko KK Columns: The following columns were connected in series and used. Two Shodex LF-404 manufactured by Showa Denko KK Shodex LF-G manufactured by Showa Denko KK Detector: RI (differential refractometer) Measurement conditions: Column temperature 40 °C Eluent: Tetrahydrofuran Flow rate: 0.3 mL / min

[0133] <Acid value> The acid value was measured according to the method described in JIS K 0070 (1992).

[0134] <Production of Primer Composition and Resin for Printing Ink> [Synthesis Example 1-1] (Polyurethane Resin P1) While introducing nitrogen gas into a reactor equipped with a reflux condenser, dropping funnel, gas inlet tube, stirring device, and thermometer, 152.2 parts of PPA (a polyester polyol with a number average molecular weight of 2,000 consisting of a polycondensate of propylene glycol and adipic acid), 15.2 parts of PPG (a polyether polyol with a number average molecular weight of 2,000 consisting of polypropylene glycol), 13.6 parts of BD (1,4-butanediol), 99.8 parts of IPDI (isophorone diisocyanate), and 200 parts of NPAC (normal propyl acetate) were charged and reacted at 90 °C for 5 hours to obtain a urethane prepolymer solution having isocyanate groups at the terminals. Next, a mixture of 19.2 parts of AEA (2-(2-aminoethylamino)ethanol) and 350 parts of IPA (isopropyl alcohol) was added dropwise at room temperature over 60 minutes and then reacted at 70 °C for 3 hours to obtain a polyurethane resin solution. NPAC was added to the obtained polyurethane resin solution to adjust the solid content, and a solution of polyurethane resin P1 with a solid content concentration of 30%, a weight average molecular weight of 27,000, Mw / Mn = 3.1, and an acid value of 0.0 mgKOH / g was obtained.

[0135] [Synthesis Example 1-2] (Polyurethane Resin P2) While introducing nitrogen gas into a reactor equipped with a reflux condenser, dropping funnel, gas inlet tube, stirring device, and thermometer, 135.7 parts of PPA, 13.6 parts of PPG, 28.3 parts of DMPA (2,2-dimethylolpropanoic acid), 105.7 parts of IPDI, and 200 parts of NPAC were charged and reacted at 90 °C for 5 hours to obtain a urethane prepolymer solution having isocyanate groups at the terminals. Next, a mixture of 16.7 parts of AEA and 350 parts of IPA was added dropwise at room temperature over 60 minutes and then reacted at 70 °C for 3 hours to obtain a polyurethane resin solution. NPAC was added to the obtained polyurethane resin solution to adjust the solid content, and a solution of polyurethane resin P2 with a solid content concentration of 30%, a weight average molecular weight of 30,000, Mw / Mn = 3.0, and an acid value of 39.3 mgKOH / g was obtained.

[0136] <Production of Composition for Forming Primer Layer> [Production Example 1-1] (Primer Composition S1) 87 parts of the polyurethane resin P2 solution, 5 parts of EA, 5 parts of IPA, and 3 parts of silica particles (Hydrophilic silica particles P-73 manufactured by Mizusawa Chemical Co., Ltd.: average particle diameter 3.8 μm) were stirred and mixed using a disper to obtain primer composition S1.

[0137] <Production of Printing Ink> [Production Example 2-1] (Printing Ink R1) 10 parts of blue pigment P.B.15 (C.I.Pigment Blue 15), 0.2 part of BYK-SYNERGIST2100 (manufactured by BYK-Chemie Japan), 0.5 part of DISPER BYK-142 (manufactured by BYK-Chemie Japan), 24.3 parts of the polyurethane resin P1 solution, 5 parts of the PVC solution (vinyl chloride-vinyl acetate copolymer resin solution (Solvain TAO manufactured by Nisshin Chemical Co., Ltd., solid content 30%, EA solution)), 10 parts of EA, and 10 parts of IPA were mixed and stirred, and dispersion treatment was performed for 20 minutes using a sand mill as a bead mill. Then, 20 parts of the polyurethane resin P1 solution, 10 parts of EA, and 10 parts of IPA were mixed and stirred to obtain printing ink R1.

[0138] [Production Example 2-2] (Printing Ink R2) 10 parts of blue pigment P.B.15, 0.2 part of BYK-SYNERGIST2100, 0.5 part of DISPER BYK-142, 24.3 parts of the polyurethane resin P2 solution, 5 parts of the PVC solution, 10 parts of EA, and 10 parts of IPA were mixed and stirred, and dispersion treatment was performed for 20 minutes using a sand mill as a bead mill. Then, 20 parts of the polyurethane resin P2 solution, 10 parts of EA, and 10 parts of IPA were mixed and stirred to obtain printing ink R2.

[0139] <Production of Polyol Used for Adhesive> [Synthesis Example 2-1] (Polyester Polyol B1) Into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen gas inlet tube, 124 parts of ethylene glycol, 212 parts of neopentyl glycol, 368 parts of 1,6-hexanediol, 645 parts of isophthalic acid, 36 parts of adipic acid, and 265 parts of sebacic acid were charged. While stirring under a nitrogen stream, the temperature was raised to 250 °C, and an esterification reaction was carried out. A predetermined amount of water was distilled off, and the reaction was continued until the acid value reached 5 or less. Then, the pressure was gradually reduced, and a deglycolization reaction was carried out at 1 mmHg or less for 5 hours to obtain a polyester polyol. Thereafter, 35 parts of isophorone diisocyanate were gradually added, and the reaction was carried out at 150 °C for about 2 hours to obtain a polyester polyurethane polyol. To 100 parts of this polyester polyurethane polyol, 12.0 parts of ethylene glycol bisanhydrotrimellitate were added, and the reaction was carried out at 180 °C for about 2 hours. Then, it was diluted with ethyl acetate until the solid content concentration reached 50% to obtain a solution of a partially acid-modified polyester polyol B1 having a number average molecular weight of 9,000 and an acid value of 30.3 mgKOH / g.

[0140] [Synthesis Example 2-2] (Polyester Polyol B2) Into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen gas inlet tube, 58 parts of ethylene glycol, 412 parts of diethylene glycol, 343 parts of neopentyl glycol, 517 parts of isophthalic acid, and 393 parts of adipic acid were charged. While stirring under a nitrogen stream, the temperature was raised to 250 °C, and an esterification reaction was carried out. A predetermined amount of water was distilled off, and the reaction was continued until the acid value reached 5 or less. Then, the pressure was gradually reduced, and a deglycolization reaction was carried out at 1 mmHg or less for 5 hours to obtain a polyester polyol. To 100 parts of this polyester polyol, 4.0 parts of trimellitic anhydride were added, and the reaction was carried out at 180 °C for about 2 hours. Then, it was diluted with ethyl acetate until the solid content concentration reached 50% to obtain a solution of a partially acid-modified polyester polyol B2 having a number average molecular weight of 2,000 and an acid value of 23.5 mgKOH / g.

[0141] <Adjustment of Polyisocyanate> [Preparation Example 1] (Polyisocyanate C1) Coronate 2785 (a biuret-type polyisocyanate derived from hexamethylene diisocyanate, manufactured by Tosoh Corporation) was diluted with ethyl acetate and adjusted to a solid content concentration of 50% and NCO% = 9.6% to obtain a solution of polyisocyanate C1.

[0142] <Manufacture of Adhesive> [Production Example 3-1] (Adhesive D1) 90 parts of a polyester polyol B1 solution, 10 parts of a polyester polyol B2 solution, and 8 parts of a polyisocyanate C1 solution were blended, and EA was added to adjust an adhesive solution with a solid content concentration of 30%.

[0143] <Manufacture of Laminate> The method for manufacturing a laminate will be described below. The primer composition and the printing ink were each diluted with a mixed solvent of EA / IPA (mass ratio 70 / 30) to a viscosity of 15 seconds (25 °C, Zahn cup #3 (manufactured by Separation Co., Ltd.)) before use. Also, the thicknesses of the primer layer and the printing layer were each adjusted to be approximately 1.5 μm.

[0144] [Production Example 4-1] (Laminate L1) For OPP (corona-treated stretched polypropylene film, thickness 20 μm), the diluted primer composition S1 and the printing ink R1 were printed in this order using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50 °C to obtain a laminate having a structure of OPP / S1 / R1. Next, on the printing layer of the obtained laminate, adhesive D1 was applied and dried using a dry laminator so that the film thickness after drying was approximately 3 μm, and then laminated with CPP (unstretched polypropylene film, thickness 30 μm) to obtain a laminate L1 having a structure of base material layer (OPP) / primer layer (S1) / printing layer (R1) / adhesive layer (D1) / base material layer (CPP).

[0145] [Production Example 4-2] (Laminate L2) With respect to OPP, after applying and drying the adhesive D1 using a dry laminator so that the dry film thickness becomes about 3 μm, it was laminated with CPP to obtain a laminate L2 having a structure of base material layer (OPP) / adhesive layer (D1) / base material layer (CPP).

[0146] [Production Example 4-3] (Laminate L3) With respect to OPP, the diluted primer composition S1 and the printing ink R1 were printed in this order using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate L3 having a structure of base material layer (OPP) / primer layer (S1) / printing layer (R1).

[0147] [Production Example 4-4] (Laminate L4) With respect to OPP, the diluted printing ink R1 was printed using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate L4 having a structure of base material layer (OPP) / printing layer (R1).

[0148] [Production Example 4-5] (Laminate L5) With respect to OPP, the diluted printing ink R2 was printed using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate L5 having a structure of base material layer (OPP) / printing layer (R2).

[0149] [Production Example 4-6] (Laminate L6) With respect to PET (polyethylene terephthalate film, thickness 12 μm), the diluted printing ink R1 was printed using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate L6 having a structure of base material layer (PET) / printing layer (R1).

[0150]

Table 1

[0151] The abbreviations in Table 1 are shown below. OPP: Corona-treated stretched polypropylene film, thickness 20 μm CPP: Non-stretched polypropylene film, thickness 30 μm PET: Polyethylene terephthalate film, thickness 12 μm

[0152] <Manufacture of release liquid> [Production Example 5-1] (Release Liquid A1) 2 parts of sodium hydroxide and 98 parts of water were blended and stirred with a disper to obtain Release Liquid A1.

[0153] [Production Examples 5-2 to 5] (Release Liquids A2 to 5) In addition to sodium hydroxide and water, polyoxyethylene lauryl ether (HLB; 13.6) as a nonionic surfactant, polyoxyethylene alkyl ether phosphate (HLB; 12) as an anionic surfactant, and BYK-1650 (manufactured by BYK-Chemie Japan, silicone-based emulsion type antifoaming agent, solid content concentration 27.5%) as an antifoaming agent were blended according to the composition shown in Table 2. Release Liquids A2 to 5 were obtained in the same manner as in Production Example 5-1.

[0154]

Table 2

[0155] <Separation and recovery of laminate> [Example 1] Into a 1000 mL stainless steel beaker, 500 g of Release Liquid A3 and 25 g of a sample obtained by cutting out the laminate L1 into a size of 1.5 cm × 0.5 cm were placed, and stirred at 60 °C and 2000 rpm. The separation and recovery state of the laminate was evaluated as follows.

[0156] [Examples 2 to 16, Comparative Examples 1 to 5] Also, except that the materials, crushing size, amounts of the laminate and the printing layer with respect to the release liquid, and the temperature were changed to the contents shown in Table 3, the separation and recovery state of the laminate was evaluated in the same manner as in Example 1. Note that 0.2 g of the laminate in Comparative Example 1 corresponds to 100 samples obtained by cutting out the laminate L1 into a size of 1 cm × 1 cm. The results are shown in Table 3. Regarding the amounts of the laminate, the printing layer, and the film with respect to the stripping liquid, the densities of the primer layer, the printing layer, and the adhesive layer were calculated assuming 1 g / cm 3 , the densities of the OPP base material and the CPP base material were calculated assuming 0.91 g / cm 3 , and the density of the PET base material was calculated assuming 1.38 g / cm 3 .

[0157] <Evaluation of the laminate> (Base material separability) Regarding the laminate provided with the adhesive layer, at 20 minutes, 40 minutes, and 1 hour after the start of stirring, the base materials were sampled, washed with water, and dried respectively. Thirty sheets were randomly selected from the obtained base materials, and the thickness of the base materials was measured. From the thickness of the base materials, it was determined whether the laminate was separated between the adhesive layers and evaluated according to the following criteria. A (excellent): All 30 sheets were separated 20 minutes after the start of stirring. B (good): All 30 sheets were separated 40 minutes after the start of stirring. C (acceptable): All 30 sheets were separated 1 hour after the start of stirring. D (unacceptable): There were base materials that were not separated 1 hour after the start of stirring.

[0158] (Peelability of the printing layer) Regarding the laminate provided with the primer layer and / or the printing layer on the plastic base material, at 20 minutes, 40 minutes, and 1 hour after the start of stirring, the base materials were sampled, washed with water, and dried respectively. Ten sheets of the base material 1 after separation were sampled from the obtained base materials, and the removal area ratio of the printing layer was visually confirmed and evaluated according to the following criteria. This evaluation was carried out for those rated A to C in terms of base material separability. A (excellent): In the base material 20 minutes after the start of stirring, 90% or more of the printing layer peeled off. B (good): In the base material 40 minutes after the start of stirring, 90% or more of the printing layer peeled off. C (acceptable): In the base material 1 hour after the start of stirring, 90% or more of the printing layer peeled off. D (unacceptable): In the base material 1 hour after the start of stirring, the peeling of the printing layer was less than 90%.

[0159] (Peelability of the adhesive) Regarding the laminate provided with the adhesive layer, the base materials were sampled, washed with water, and dried at 20 minutes, 40 minutes, and 1 hour after the start of stirring, respectively. From the obtained base materials, 10 pieces of the separated base material 2 were sampled, and the presence or absence of the absorption peak of the adhesive was confirmed at 20 locations in total, 2 locations on the front and back of each base material 2, using FT-IR, and evaluated according to the following criteria. This evaluation was carried out for those with A to C evaluations in terms of base material separability. A (excellent): In the base material 20 minutes after the start of stirring, the absorption peak of the adhesive is not confirmed at 18 or more out of 20 locations. B (good): In the base material 40 minutes after the start of stirring, the absorption peak of the adhesive is not confirmed at 18 or more out of 20 locations. C (acceptable): In the base material 1 hour after the start of stirring, the absorption peak of the adhesive is not confirmed at 18 or more out of 20 locations. D (unacceptable): In the base material 1 hour after the start of stirring, the absorption peak of the adhesive is confirmed at 3 or more out of 20 locations.

[0160] (Redeposition property of the printing layer) Two hours after the start of stirring, the base materials were recovered, washed with water, and dried. From the obtained base materials, 10 pieces of the base material 1 were sampled, the obtained 10 pieces of the base materials were spread out and overlapped, and the color values L * x , a * x , b * x were measured. On the other hand, even when it was confirmed that 90% or more of the printing layer had peeled off from the base material, in the same manner, the peeled-off base materials were recovered, the 10 pieces of the base materials were spread out and overlapped, and the color values L * y , a * y , b * y were measured. The color difference ΔE between immediately after peeling and after the test end was obtained by the following formula, and the redeposition property was evaluated according to the following criteria. This evaluation was carried out for those with A to C evaluations in terms of base material separability. (Formula) ΔE = ((L *x -L * y ) 2 +(a * x -a * y ) 2 +(b * x ―b * y ) 2 ) 1 / 2 A (Excellent): ΔE is less than 3 B (Good): ΔE is 3 or more and less than 10 C (Fair): ΔE is 10 or more and less than 20 D (Poor): Other than A to C

[0161] (Re - adhesion property of the adhesive layer) Two hours after the start of stirring, the detached substrate was collected, washed with water, and dried. From the obtained substrate, 10 substrates 2 after separation were sampled, and for a total of 20 locations (2 locations on the front and back of each substrate), the presence or absence of the absorption peak of the adhesive was confirmed using FT - IR. This evaluation was carried out for those with A to C evaluations in terms of substrate separability. A (Excellent): The number of locations where the absorption peak of the adhesive was confirmed is less than 3 B (Good): The number of locations where the absorption peak of the adhesive was confirmed is 3 or more and less than 5 C (Fair): The number of locations where the absorption peak of the adhesive was confirmed is 5 or more and less than 7 D (Poor): The number of locations where the absorption peak of the adhesive was confirmed is 7 or more

[0162] (Processing efficiency) Two hours after the start of stirring, the substrate was collected, washed with water, and dried. Then, the weight of the recovered substrate was measured, and the amount relative to the charged detachment liquid was determined and evaluated according to the following criteria. A (Excellent): The amount of the recovered substrate relative to the charged detachment liquid is 3 mass% or more B (Good): The amount of the recovered substrate relative to the charged detachment liquid is 1 mass% or more and less than 3 mass% C (Fair): The amount of the recovered substrate relative to the charged detachment liquid is 0.4 mass% or more and less than 1 mass% D (Poor): The amount of the recovered substrate relative to the charged detachment liquid is less than 0.4 mass%

[0163] (Curl of the recovered substrate) Two hours after the start of stirring, the substrate was recovered, washed with water, and dried. A 1 g sample was taken from the obtained substrate, and the substrate in a state where the substrate was wound more than once from the end of the substrate (hereinafter also referred to as "curl") was separated and weighed. The ratio of the curled substrate to the total plastic substrate after detachment was determined and evaluated according to the following criteria. In Comparative Example 1, a 0.1 g sample was taken and evaluated in the same manner. A (excellent): Less than 10% by mass of the curled substrate B (good): 10% by mass or more and less than 30% by mass of the curled substrate C (fair): 30% by mass or more and less than 50% by mass of the curled substrate D (poor): 50% by mass or more of the curled substrate

[0164] (Volume ratio of fluff before and after detachment) Two hours after the start of stirring, the substrate was recovered, washed with water, and dried. A 5 g sample was taken from the obtained substrate, and the volume (A) was measured using a graduated cylinder (inner diameter 5 cm) of 5.0×10 -4 m 3 . Before the detachment test, a 5 g sample of the crushed sample of the laminate was also taken, and the volume (B) was measured in the same manner. The volume ratio of volume (B) to volume (A) was determined and evaluated according to the following criteria. In Examples 3, 15, and 16, 2 g, and in Comparative Example 1, 0.1 g was sampled and evaluated in the same manner. A (excellent): Volume (B) is less than twice volume (A) B (good): Volume (B) is 2 times or more and less than 3 times volume (A) C (fair): Volume (B) is 3 times or more and less than 4 times volume (A) D (poor): Volume (B) is 4 times or more volume (A)

[0165] (Manufacture of recycled film and evaluation of recycled material haze) Two hours after the start of stirring, the plastic substrate was recovered, washed with water and dried. Then, the recovered substrate was extruded at 200 °C using a single-screw extruder, and through a pelletizing process, pellets of recycled resin were obtained. The recycled resin was extruded at 200 °C using a T-die film forming machine to produce a recycled film with a thickness of 50 μm. The haze of the recycled film was measured using a haze meter (manufactured by JEOL Ltd., SH7000) and evaluated according to the following criteria. A (excellent): haze is 20% or less B (good): haze is more than 20% and less than 40% C (fair): haze is more than 40% and less than 60% D (poor): haze is 60% or more

[0166]

Table 3

[0167] In the current Comparative Example 1, since the throughput is small, the processing efficiency is extremely low. In Example 12 and Comparative Example 2, when no surfactant is included, the degree of curling is suppressed when the throughput is about 10 times that of the current one, but when it exceeds 100 times that of the current one, significant curling is observed. In Examples 14 and 15 and Comparative Examples 3 and 4, when the long side of the crushing size is 3 cm or more, the degree of curling is suppressed when the throughput is about 10 times that of the current one, but when it exceeds 50 times that of the current one, significant curling is observed. In Example 16 and Comparative Example 5, when the processing temperature is high, the degree of curling is suppressed when the throughput is about 10 times that of the current one, but when it exceeds 100 times that of the current one, significant curling is observed. From the above evaluation results, it was shown that with the separation and recovery method of the present invention, even when the throughput of the laminate is large, the coating layer can be easily detached from the laminate, a high-quality plastic substrate with less reattachment of the coating layer can be obtained, and furthermore, a high-grade molding material with less coloring can be obtained.

Claims

1. A method for separating and recovering a plastic film substrate, comprising the steps of: contacting a plastic film substrate and a laminate having a coating layer (except for a preheated shrink label piece) with a releasing liquid to remove the coating layer; and recovering the released plastic film substrate, The desorption liquid contains a surfactant and water, The plastic film substrate is an olefin substrate, The content of the laminate is 0.5% by mass or more based on the total mass of the desorption liquid, A method for separating and recovering a laminate, in which after the detachment step, the proportion of plastic film substrates in a state in which the substrate is wrapped around the end of the substrate one or more times is less than 50 mass% of the total plastic film substrates after the detachment step.

2. 5 g of the laminate (A) before the detachment step and 5 g of the plastic film substrate (B) after the detachment step are mixed together in a 5.0 × 10 －４ m ３ 2. The method for separating and recovering according to claim 1, wherein, when the volumes of (B) and (A) are measured using a measuring cylinder (inner diameter: 5 cm), the volume of (B) is 1 to 4 times the volume of (A).

3. A separation and recovery method as described in claim 1, wherein the long sides of the laminate immediately before detachment are 1 mm to 3 cm and account for 50% or more by weight of the entire laminate.

4. The separation and recovery method according to any one of claims 1 to 3, wherein the coating layer includes a printed layer, and the content of the printed layer is 0.01 mass% or more with respect to the total mass of the elution liquid.

5. The method further includes a step of cutting the laminate before contacting the laminate with the release liquid, The separation and recovery method according to claim 1 or 2, wherein 50 mass % or more of the laminate after the cutting step has a long side of 3 cm or less.

6. The method for separating and recovering a laminate according to any one of claims 1 to 3, wherein at least one of the coating layers contains a compound having an acidic group.

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