Desorption treatment liquid, as well as a method for manufacturing a recycled plastic substrate, a method for manufacturing a molding material, and a method for manufacturing a molded article.

Abstract

The present invention aims to provide a desorption treatment liquid that is excellent in desorption properties of the desorption layer and suppression of re-adhesion of components desorbed from the desorption layer, thereby obtaining a high-quality plastic substrate for recycling. [Solution] A desorption treatment liquid for removing the desorption layer by contacting a laminate having a plastic substrate and a desorption layer with the desorption treatment liquid, The aforementioned desorption treatment liquid contains a surfactant, water, and a basic compound. The surfactant comprises a cationic surfactant and a nonionic surfactant. The cationic surfactant is 60% by mass or less of the total mass of the cationic surfactant and the nonionic surfactant, A desorption treatment solution wherein the content of the cationic surfactant is 1 to 100% by mass relative to the content of the basic compound.

Description

[Technical Field]

[0001] The present invention relates to a desorption treatment liquid for separating and recovering a plastic substrate from a laminate comprising at least a desorption layer on a plastic substrate, and to a method for producing a recyclable plastic substrate. [Background technology]

[0002] Recycling of plastic products, including plastic films made from polyester, nylon (NY), polypropylene (PP), and polyethylene (PE) substrates, is being considered. Among the aforementioned plastic products, multi-layered food packaging is made by printing ink onto a film substrate and then forming a bag to create the package (packaging material). Alternatively, it is made by laminating it with other film substrates or heat-melt resin substrates via adhesives, and then forming a bag and heat-sealing it to create the package. However, because such food packaging contains coloring components and incompatible dissimilar materials, if it is reused as is, the quality of the recycled plastic will inevitably deteriorate, and the plastic will not be recycled as a material.

[0003] Regarding the material recycling of multi-layered packaging materials, for example, Patent Document 1 discloses that using a cationic surfactant with a specific structure is effective in detaching the film substrate. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2025-4545 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the conventional peeling process, the use of a cationic surfactant suppresses damage to the plastic substrate. However, the content of the cationic surfactant is high with respect to the basic compound, and depending on the structure of the laminate, there may be deterioration of reattachment and discoloration of the plastic substrate, resulting in deterioration of the quality of the recycled material.

[0006] An object of the present invention is to provide a treatment liquid for peeling that is excellent in the peeling property of the peeling layer and the suppression of reattachment of the components peeled from the peeling layer, and can obtain a high-quality plastic substrate for recycling.

Means for Solving the Problems

[0007] The treatment liquid for peeling of the present invention is a treatment liquid for peeling a plastic substrate and a laminate having a peeling layer by bringing them into contact with the treatment liquid for peeling to peel the peeling layer, where the treatment liquid for peeling contains a surfactant, water, and a basic compound, the surfactant includes a cationic surfactant and a nonionic surfactant, the cationic surfactant is 60% by mass or less based on the total mass of the cationic surfactant and the nonionic surfactant, the content of the cationic surfactant is 1 to 100% by mass with respect to the content of the basic compound.

Effects of the Invention

[0008] According to the present invention described above, it is possible to provide a treatment liquid for peeling that is excellent in the peeling property of the peeling layer and the suppression of reattachment of the components peeled from the peeling layer, suppresses discoloration of the plastic substrate, and can obtain a high-quality plastic substrate for recycling. Further, according to the present invention, it is possible to provide a method for producing a plastic substrate for recycling, a molding material, and a molded body.

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail. The description of the embodiments or requirements described below is an example of the embodiments of the present invention, and the present invention can be modified within the scope of solving the problems. In this specification, "re - adhesion" means that inclusions such as a printed layer or an adhesive layer peeled from a substrate are finely dispersed by stirring and re - adhere to the substrate, which causes coloring of the recovered plastic substrate and deterioration of the properties of the recycled material. A~B means greater than or equal to A and less than or equal to B. Each of the various components described in this specification can be used alone or in combination of two or more, unless otherwise noted. When two or more are used in combination, the content or percentage content uses the total value. Also, the numerical values specified in this specification are values obtained by the methods of the examples described later.

[0010] <Desorption treatment liquid> The desorption treatment liquid of the present invention (hereinafter also referred to as the treatment liquid) is a desorption treatment liquid for contacting a plastic substrate and a laminate having a desorption layer to desorb the desorption layer.

[0011] The desorption treatment liquid of the present invention contains a surfactant, water, and a basic compound.

[0012] The mechanism by which the desorption treatment liquid of the present invention can solve the problems is speculated as follows. The surfactant used in the desorption treatment liquid of the present invention includes a cationic surfactant and a non - ionic surfactant. It is speculated that the combined use of the cationic surfactant and the non - ionic surfactant makes it easier for the treatment liquid to penetrate into the desorption layer (for example, a primer layer, a printed layer, an adhesive layer, etc.), promoting desorbability. Also, the surfactant adsorbs on the surface of the desorbed desorption components and the substrate, preventing the re - adhesion of the finely dispersed printed layer, etc. Therefore, the recycled plastic substrate to be recovered has high quality.

[0013] The total content ratio of the surfactant is preferably 0.01~5% by mass, more preferably 0.05~2.5% by mass in 100% by mass of the treatment liquid. When the content ratio of the surfactant in the treatment liquid is 0.01% by mass or more, desorbability and re - adhesion resistance are further improved. Also, when it is 5% by mass or less, foaming can be more suppressed.

[0014] [Cationic surfactant] Cationic surfactants are compounds in which the hydrophilic group has a positive ion when dissolved in water. From the viewpoint of detachability, cationic surfactants preferably have at least one alkyl group having 8 to 24 carbon atoms, more preferably 9 to 22 carbon atoms, and even more preferably 10 to 18 carbon atoms. Furthermore, the alkyl group may be linear or branched.

[0015] Cationic surfactants are compounds that use an anion of an organic or inorganic acid as a counteranion. The counteranion is not particularly limited, but examples include organic acids such as carboxylic acids, sulfonic acids, and organophosphoric acids. Examples include hydrofluoric acid, hydrochloric acid, bromic acid, iodic acid, sulfuric acid, nitric acid, phosphoric acid, and inorganic acids such as carbonic acid.

[0016] Examples of cationic surfactants include alkylamine salts, quaternary ammonium salts, and pyridium salts. Cationic surfactants include alkylamine salts such as alkylamine acetate, N-alkyl(C14~C18) trimethylenediamine oleate, alkyl(C8~C18) trimethylenediamine adipate, octadecylamine bromide, behenamidopropyl dimethylamine, and stearylamine acetate. Halogens of quaternary ammonium compounds such as trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, trimethyloctyl ammonium chloride, dimethyl dioleyl ammonium chloride, methyl oleyl diethanol ammonium chloride, dodecyl benzyl triethyl ammonium chloride, alkyl benzyl dimethyl ammonium chloride, lignoceryl trimethyl ammonium chloride, and cetyl trimethyl ammonium chloride. Pyridinium salts such as laurylpyridinium chloride, laurylpyridinium bromide, cetylpyridinium chloride, cetylpyridinium bromide, 4-alkylmercaptopyridine, and poly(vinylpyridine)-dodecyl bromide. Examples include quaternary ammonium sulfate salts such as laurylpyridinium disulfate, octyldimethylethylammonium ethyl sulfate, lauryldimethylethylammonium ethyl sulfate, stearyldimethylhydroxyethylammonium p-toluenesulfonate, and palmityldimethylethylammonium ethyl sulfate.

[0017] The cationic surfactant is preferably an alkylamine salt or a quaternary ammonium salt, more preferably a quaternary ammonium salt, and even more preferably a sulfate salt of a quaternary ammonium. Quaternary ammonium salts have high alkali resistance, which can improve the processing efficiency of the desorption process. Furthermore, from an environmental perspective, sulfate salts of quaternary ammonium are preferred.

[0018] Cationic surfactants may be used alone or in combination of two or more types.

[0019] The content of cationic surfactant is 60% by mass or less, based on 100% by mass of the total of cationic and nonionic surfactants, preferably 1 to 60% by mass, and more preferably 5 to 50% by mass. When an appropriate amount is included, the desorption properties are improved, the ink fragments after desorption tend to aggregate easily, and discoloration of the plastic substrate is suppressed, making it easier to obtain a high-quality recyclable plastic substrate.

[0020] The content of the cationic surfactant is preferably 1 to 100 parts by mass, more preferably 1.25 to 50 parts by mass, and even more preferably 1.5 to 30 parts by mass, per 100 parts by mass of the basic compound. A content of 1 part by mass or more further improves desorption properties. Furthermore, a content of 100 parts by mass or less suppresses discoloration of the plastic substrate, making it easier to obtain a high-quality recyclable plastic substrate.

[0021] The content of the cationic surfactant is preferably 0.001 to 2.5% by mass, more preferably 0.005 to 1.25% by mass, and even more preferably 0.075 to 1% by mass, per 100% by mass of the desorption treatment solution. A cationic surfactant content of 0.001% by mass or more in the treatment solution further improves desorption performance. Furthermore, a content of 2.5% by mass or less suppresses discoloration of the substrate.

[0022] [Nonionic surfactants] Nonionic surfactants are compounds whose hydrophilic groups do not form ions when dissolved in water. Nonionic surfactants are preferably alkylene oxide adducts to which alkylene oxide (hereinafter also referred to as AO) is added, and more preferably compounds obtained by adding alkylene oxide to an alcohol having active hydrogen, compounds obtained by adding alkylene oxide to an amine, or compounds obtained by adding alkylene oxide to a fatty acid. The above addition may be random addition or block addition. Furthermore, the number of carbon atoms in the alkylene oxide is preferably 2 to 4. The nonionic surfactant is preferably an alcohol-based nonionic surfactant obtained by adding an alkylene oxide having 2 to 4 carbon atoms to an alcohol, or a fatty acid-based nonionic surfactant obtained by adding an alkylene oxide having 2 to 4 carbon atoms to a fatty acid or fatty acid ester, with the alcohol-based nonionic surfactant obtained by adding an alkylene oxide having 2 to 4 carbon atoms to an alcohol being more preferred.

[0023] [Alcohol-based nonionic surfactant] Examples of alcohol-based nonionic surfactants include alkylene oxide adducts of primary or secondary alcohols having 8 to 24 carbon atoms, or alkylene oxide adducts of alkylphenols having 8 to 12 carbon atoms. Examples of primary or secondary alcohols having 8 to 24 carbon atoms include octyl alcohol, decyl alcohol, lauryl alcohol, stearyl alcohol, oleyl alcohol, dodecyl alcohol, arachidyl alcohol, behenyl alcohol, lignoceryl alcohol, myristyl alcohol, and the like. The number of carbon atoms is preferably 8 to 24, and more preferably 10 to 22. Within this range, the elimination properties are improved. Furthermore, examples of alkylene oxides to be added to the alcohol include ethylene oxide, propylene oxide, and butylene oxide. Among these, ethylene oxide is preferred. The number of moles of alkylene oxide to be added is preferably 1 to 100 moles, and more preferably 2 to 50 moles, per mole of alcohol or alkylphenol. Within this range, the desorption properties are improved.

[0024] [Fatty acid-based nonionic surfactants] Examples of fatty acid-based nonionic surfactants include alkylene oxide adducts of fatty acids having 10 to 24 carbon atoms, oils and fats consisting of esters of the aforementioned saturated or unsaturated fatty acids having 10 to 24 carbon atoms with glycerol, alkylene oxide adducts of mixtures of the oils and fats with 2 to 10 polyhydric alcohols, esters of the fatty acids having 10 to 24 carbon atoms with alcohols, and alkylene oxide adducts of the esters. The fatty acids having 10 to 24 carbon atoms include compounds containing saturated, unsaturated, or both. The above-mentioned fatty acids having 10 to 24 carbon atoms include, for example, saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid; unsaturated fatty acids such as palmitoleic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, erucic acid, and ricinoleic acid; and fatty acid mixtures such as cocoic acid and coconut acid. Examples of polyhydric alcohols with 2 to 10 valencies include ethylene glycol, propylene glycol, glycerin, polyglycerin, sorbitol, sorbitan, and sucrose. The type and number of moles of alkylene oxide added are the same as described in the section on [alcohol-based nonionic surfactants] above.

[0025] [Amine-based nonionic surfactants] Amine-based nonionic surfactants include AO adducts of saturated or unsaturated primary or secondary amines having 8 to 36 carbon atoms. Examples of amines include 2-ethylhexylamine, di-2-ethylhexylamine, laurylamine, dilaurylamine, tetradecylamine, ditetradecylamine, hexadecylamine, dihexadecylamine, stearylamine, distearylamine, oleylamine, and dioleylamine. The type of AO and the number of moles added are the same as described above.

[0026] Nonionic surfactants may be used alone or in combination of two or more types.

[0027] The content of the nonionic surfactant is preferably 0.001 to 7% by mass, and more preferably 0.005 to 5% by mass, per 100% by mass of the desorption treatment solution. A nonionic surfactant content of 0.001% by mass or more in the treatment solution further improves desorption and re-adhesion properties. Furthermore, a content of 7% by mass or less further suppresses foaming.

[0028] [Basic compounds] The basic compound is preferably sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), ammonia, barium hydroxide (Ba(OH)2), or sodium carbonate (Na2CO3), and more preferably at least one selected from the group consisting of sodium hydroxide and potassium hydroxide. The content of the basic compound is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 1.5 to 10% by mass, per 100% by mass of the treatment solution. When the content of the basic compound is within the above range, the treatment solution can maintain sufficient basicity to recover the plastic substrate by dissolving or swelling the desorption layer described later, which is preferable from the viewpoint of desorption properties.

[0029] [Antifoaming agent] The treatment solution of the present invention may further contain an antifoaming agent. By using the antifoaming agent in combination with the surfactant described above, foaming of the treatment solution can be suppressed. Antifoaming agents are generally compounds with extremely high lipophilicity and an HLB value of 1 to 3. Examples of the above-mentioned defoaming agents include silicone-based compounds and non-silicone-based compounds.

[0030] (Silicone-based compounds) Examples of silicone compounds include emulsion type, self-emulsifying type, oil type, oil compound type, and solvent type. Emulsion-type silicone defoamers are silicone-based defoamers that are formed by emulsifying a silicone oil compound with an activator to create an O / W type emulsion. Examples include "KM-89" and "KM-98" from Shin-Etsu Chemical Co., Ltd., "FC2913" and "SILFOAM SE47" from Asahi Kasei Wacker Silicone Co., Ltd., and "BYK-015" and "BYK-1640" from Big Chemie Japan Co., Ltd. Self-emulsifying silicone-based defoamers are 100% by mass active ingredients that form an emulsion when diluted and mixed with water. Examples include "KS-540" and "X-50-1176" from Shin-Etsu Chemical Co., Ltd., and "SILFOAM SD670" and "SILFOAM SD850" from Asahi Kasei Wacker Silicone Co., Ltd. Oil-type defoamers are 100% by mass silicone oil defoamers that do not contain solvents or additives. Examples include "KM-89" and "KM-98" from Shin-Etsu Chemical Co., Ltd., "AK350" and "AK12500" from Asahi Kasei Wacker Silicone Co., Ltd., and "BYK-1770" from Big Chemie Japan Co., Ltd. Oil compound type defoamers are silicone-based defoamers that combine silicone oil with silica particles. Examples include "KM-89" and "KM-98" from Shin-Etsu Chemical Co., Ltd., "SILFOAM SC370" and "PULPSIL22274VP" from Asahi Kasei Wacker Silicone, and "BYK-017" and "BYK-018" from Big Chemie Japan. Solvent-type defoamers are silicone-based defoamers in which silicone oil is dissolved in a solvent. Examples include "KM-89" and "KM-98" from Shin-Etsu Chemical Co., Ltd., and "BYK-019" and "BYK-025" from Big Chemie Japan.

[0031] (Non-silicone compounds) Examples of the above-mentioned non-silicone compounds include fatty acid ester compounds, urea resin compounds, paraffin compounds, polyoxyalkylene glycol compounds, acrylic ester copolymers, ester polymers, ether polymers, amide polymers, emulsified mineral oils, polysiloxane adducts, fluorine compounds, vinyl polymers, acetylene alcohol, acrylic polymers, special vinyl polymers, ethylene glycol, and higher alcohols (octyl alcohol, cyclohexanol, etc.).

[0032] The defoaming agent may be used alone or in combination of two or more types. The content of the defoaming agent is preferably 0.001 to 5% by mass, and more preferably 0.003 to 3% by mass, per 100% by mass of the defoaming treatment liquid. When the content of the defoaming agent is 0.001% by mass or more, foaming becomes less likely. When it is 5% by mass or less, defoaming and re-adhesion properties are improved. From the viewpoint of having good alkali resistance and not reducing desorption and re-adhesion properties when combined with a surfactant, at least one of the group consisting of emulsion-type silicone compounds, self-emulsifying silicone compounds, and non-silicone compounds is preferred as the defoaming agent.

[0033] (Other ingredients) The desorption treatment liquid of the present invention may contain other components. Examples of other components include chelating agents, antioxidants, rust inhibitors, preservatives, viscosity modifiers, and the like.

[0034] <Laminate> The processing liquid of the present invention is used to separate and recover a plastic substrate from a laminate having at least a desorption layer on the plastic substrate. The desorption layer in contact with the plastic substrate is detached from the plastic substrate by the processing liquid of the present invention, allowing the plastic substrate to be recovered and recycled.

[0035] [Plastic substrate] Examples of plastic substrates include those containing 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. Among these, from the viewpoint of reuse as a recycled substrate, substrates containing polyolefin resin (polyolefin substrates) and substrates containing polyester resin (polyester substrates) are preferred, and polyolefin substrates containing polyolefin resin are more preferred.

[0036] The thickness of the plastic substrate is not particularly limited and may be selected as appropriate depending on the application. The thickness is preferably 5 to 1000 μm, more preferably 10 to 300 μm, even more preferably 10 μm to 100 μm, and particularly preferably 12 μm to 50 μm.

[0037] Furthermore, the plastic substrate can contain aluminum foil, a metal vapor-deposited layer such as aluminum, or a metal oxide vapor-deposited layer such as silica or alumina as a gas barrier substrate. From an economic standpoint, the thickness of the aluminum foil is preferably 3 to 50 μm. The aluminum foil, aluminum vapor-deposited layer, and alumina vapor-deposited layer dissolve and desorb in an aqueous solution containing a basic compound, and therefore function as a desorption layer as referred to in this invention. As a result, they can be separated from adjacent plastic substrates by coming into contact with the processing solution of this invention.

[0038] Plastic substrates include single-resin substrates and substrates in which multiple identical or different layers are laminated directly or via an adhesive layer. Hereinafter, a plastic substrate consisting of one or more layers will also be referred to as a plastic substrate layer. Similarly, a polyolefin substrate consisting of one or more layers will also be referred to as a polyolefin substrate layer.

[0039] (Polyolefin base material) Polyolefin substrates have a low specific gravity and float to the surface of the treatment solution, making it easy for components detached from the desorption layer (especially highly lipophilic components) to reattach. However, by using the treatment solution of the present invention, it is possible to achieve both desorption properties and reattachment inhibition. Examples of polyolefin substrate layers include plastic substrates such as polyethylene (PE) and biaxially oriented polypropylene (OPP), as well as sealant substrates such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), acid-modified polyethylene, unoriented polypropylene (CPP), aluminum-deposited polypropylene (VMOPP), acid-modified polypropylene, and copolymerized polypropylene. The thickness of the polyolefin substrate layer is not particularly limited and may be appropriately selected depending on the application, but is preferably 5 to 200 μm, and more preferably 10 to 150 μm.

[0040] (Polyester base material) Examples of polyester substrates include biaxially oriented polyester (PET), aluminum-deposited polyester (VMPET), and shrinkable polyester (shrinkable PET). The thickness of the polyester substrate is not particularly limited and can be appropriately selected depending on the application, but is preferably 5 to 1000 μm, and more preferably 10 to 100 μm.

[0041] (Structure of the laminate) The laminate of the present invention may have a plastic substrate and a desorption layer, and may further have other layers.

[0042] The laminate may have the following configuration, for example. (1) A laminate comprising a plastic substrate layer and a printed layer in this order, wherein the printed layer is a desorption layer. (2) A laminate comprising a plastic layer, a primer layer, and a printed layer in this order, wherein the primer layer is a desorption layer. (3) A laminate comprising a first substrate layer, a printing layer, an adhesive layer, and a second substrate layer in this order, wherein at least one of the printing layer and the adhesive layer is a desorption layer, and the substrate in contact with the desorption layer is a plastic substrate. (4) A laminate comprising a first substrate layer, a primer layer, a printing layer, an adhesive layer, and a second substrate layer in this order, wherein at least one of the primer layer and the adhesive layer is a desorption layer, and the substrate in contact with the desorption layer is a plastic substrate. (5) A laminate comprising a first substrate layer, an adhesive layer, and a second substrate layer in this order, wherein the adhesive layer is a desorption layer, and at least one of the substrates is a plastic substrate. (6) A laminate comprising a first substrate layer, a vapor deposition layer, a printed layer, an adhesive layer, and a second substrate layer in this order, wherein at least one of the vapor deposition layer and the adhesive layer is a desorption layer, and the substrate in contact with the desorption layer is a plastic substrate.

[0043] The following are examples of laminate configurations of the present invention, but are not limited to these. In the following examples, " / " indicates the boundary between each layer. In the following configurations, the "substrate layer" does not have to be a single layer, but may be a laminate in which multiple substrates are stacked. Hereinafter, layers prefixed with "desorption" refer to the desorption layer as defined in the present invention. • Plastic substrate layer / Deleasible printing layer • Plastic substrate layer / Desorption primer layer / Printing layer • Plastic substrate layer / Deleasible printing layer / Deleasible adhesive layer / Plastic substrate layer • Plastic substrate layer / Detachable primer layer / Printing layer / Detachable adhesive layer / Plastic substrate layer • Plastic substrate layer / Printing layer / Detachable adhesive layer / Plastic substrate layer • Plastic substrate layer / Detachable adhesive layer / Plastic substrate layer • Plastic substrate layer / Detachable primer layer / Printing layer / Detachable adhesive layer / Vapor deposition layer / Plastic substrate layer

[0044] <Desorption layer> The desorption layer can be any layer that can be desorbed from the plastic substrate by the desorption treatment solution of the present invention. The desorption layer is preferably a layer containing a water-soluble resin or a compound having an acidic group that is easily compatible with basic compounds, and more preferably a layer containing a compound having an acidic group. Furthermore, the desorption layer is a layer in contact with the plastic substrate layer to be recovered, and is, for example, at least one layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer. That is, the at least one layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer is preferably a layer containing a water-soluble resin and / or a compound having an acidic group, and more preferably a layer containing a compound having an acidic group. The compound having an acidic group is a resin or a low molecular weight compound. These water-soluble resins or compounds having an acidic group may be used individually or in combination of two or more.

[0045] At least one layer selected from the group consisting of the primer layer, printing layer, and adhesive layer may contain a resin component (hereinafter also referred to as binder resin) which may include a water-soluble resin or a resin having an acidic group, and may contain both a binder resin and a low-molecular-weight compound having an acidic group. The following describes the cases where the desorption layer is a primer layer, a printing layer, or an adhesive layer.

[0046] [Primer layer] The primer layer can control the delamination properties, adhesion, and aesthetic appearance of layers other than the plastic substrate and the delamination layer when they are present. Furthermore, the method of forming the primer layer is not limited and can be done by known methods. When the desorption layer is a primer layer, the primer layer is positioned in contact with the plastic substrate. The primer layer is desorbed from the plastic substrate by dissolution, peeling, etc., by the treatment solution. The primer layer is preferably a water-soluble resin or a compound having an acidic group (except for water-soluble resins).

[0047] (Water-soluble resin) Water-soluble resins are resins that swell or dissolve in water at 25-95°C and can be detached from polyolefin substrates. Examples of water-soluble resins include water-soluble polyester resins, water-soluble polyamide resins, water-soluble polyimide resins, water-soluble acrylic resins, water-soluble polyurethane resins, water-soluble polyallylamine resins, water-soluble phenolic resins, water-soluble epoxy resins, water-soluble phenoxy resins, water-soluble urea resins, water-soluble melamine resins, and polyvinyl alcohol resins, as well as modified products of these resins. Among these, polyvinyl alcohol (PVA) resin is preferred from the viewpoint of availability and desorption properties. Water-soluble resins can be used individually or in combination of two or more types. If the water-soluble resin has film-forming properties, it may be used as the binder resin constituting the primer layer.

[0048] The water-soluble resin content in the primer layer is preferably 50% by mass or more, and more preferably 70% by mass or more. However, the content is preferably 99% by mass or less.

[0049] Polyvinyl alcohol resins include not only unmodified polyvinyl alcohol, but also modified polyvinyl alcohol obtained by copolymerizing various monomers during the production of vinyl ester resins and then saponifying the resulting product, and modified polyvinyl alcohol obtained by modifying unmodified polyvinyl alcohol and introducing various functional groups.

[0050] Polyvinyl alcohol resins include resins containing structural units having primary hydroxyl groups in their side chains, and ethylene-modified polyvinyl alcohol resins. Among these, polyvinyl alcohol resins containing structural units having primary hydroxyl groups in their side chains are preferred because they have excellent melt-molding properties and excellent water solubility. The number of primary hydroxyl groups in these structural units is usually 1 to 5, preferably 1 to 2, and more preferably 1. It is also preferable that they have secondary hydroxyl groups in addition to primary hydroxyl groups.

[0051] The degree of saponification of polyvinyl alcohol resin (measured in accordance with JIS K 6726) is typically 60 to 100 mol%. The preferred range of the degree of saponification varies depending on the modified species. For example, in the case of unmodified polyvinyl alcohol resin, the preferred range is typically 60 to 99.9 mol%, with 70 to 99.0 mol% being preferred and 75 to 98.5% being more preferred. For modified polyvinyl alcohol resin containing side-chain 1,2-diol structural units, the preferred degree of saponification is typically 60 to 99.9 mol%, with 65 to 99.8 mol% being preferred and 70 to 99.5 mol% being more preferred. The degree of saponification of ethylene-modified polyvinyl alcohol resin modified with a small amount of ethylene is usually 60 mol% or more, preferably 70 to 99.5 mol%, and more preferably 75 to 99.0 mol%. A saponification degree within the above range is preferable because it results in excellent water solubility and good desorption properties. Furthermore, it improves coating properties when forming the primer layer.

[0052] The average degree of polymerization of polyvinyl alcohol resin (measured in accordance with JIS K 6726) is typically 100 to 3000, preferably 150 to 2000, more preferably 180 to 1000, and even more preferably 200 to 800.

[0053] (Compounds containing acidic groups) Compounds containing acidic groups include resins containing acidic groups or low-molecular-weight compounds containing acidic groups. The presence of acidic groups in the primer layer promotes swelling, dissolution, and peeling in a basic aqueous solution, resulting in superior desorption properties.

[0054] The content of the compound having an acidic group in the primer layer is preferably 0.1 to 95% by mass, and more preferably 0.5 to 90% by mass.

[0055] [Low molecular weight compounds containing acidic groups] Low molecular weight compounds having an acidic group are compounds with a molecular weight of 1,000 or less, and include, for example, 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, melitic 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 oxaloacetate; carboxylic acid derivatives such as amino acids and nitrocarboxylic acids; and acid anhydrides such as trimellitic anhydride and pyromellitic anhydride. Low molecular weight compounds having acidic groups can be used in combination with resins having acidic groups or known binder resins that constitute known primer layers.

[0056] [Resin containing acidic groups] Examples of resins containing acidic groups include cellulose resins, urethane resins, polyamide resins, vinyl chloride / vinyl acetate copolymers, ketone resins, polyester resins, and (meth)acrylic resins. Examples of the acidic groups include carboxyl groups, phosphate groups, sulfo groups, sulfide groups, etc., or esters or salts thereof. Furthermore, examples of resins containing acidic groups include rosin-modified resins with acid values, such as maleated rosin and fumarated rosin. Furthermore, resins having acidic groups include polymerizable monomers having acidic groups such as carboxylate groups (e.g., itaconic acid, maleic acid, fumaric acid, cinnamic acid); polymerizable monomers that are acid anhydrides (e.g., itaconic acid, maleic anhydride); polymerizable monomers having sulfonic acid groups (e.g., sulfonated styrene); polymerizable monomers having sulfonamide groups (e.g., vinylbenzenesulfonamide); radical copolymers such as styrene-(meth)acrylic resin, styrene-(anhydride)maleic acid resin, terpene-(anhydride)maleic acid resin, and acid-modified polyolefin resins, which are copolymerized from these acidic polymerizable monomers. Resins containing acidic groups may be used alone or in combination of two or more types.

[0057] From the viewpoint of printability, the resin having acidic groups preferably includes one or more selected from the group consisting of urethane resins having acidic groups, acrylic resins having acidic groups, and rosin-modified resins.

[0058] [Urethane resin containing acidic groups] Examples of urethane resins having acidic groups include urethane resins obtained by reacting a polyol having acidic groups with a polyisocyanate, resins obtained by acid-modifying the hydroxyl groups in a urethane resin obtained by reacting a polyol with a polyisocyanate, and resins obtained by acid-modifying the amino groups 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. Furthermore, as an acidic urethane resin, a resin obtained by reacting a carboxylic acid (hydroxy acid) containing one or more hydroxyl groups with a polyisocyanate can also be mentioned. By using a hydroxy acid as the polyol, an acid value derived from the carboxyl group can be imparted to the main chain of the urethane resin, thereby improving its desorption properties. In addition, if the above-mentioned acidic urethane resin has isocyanate groups, a urea bond may be introduced by reacting a polyamine with a portion of the isocyanate groups to form a urethane urea.

[0059] Polyol Polyols are a general term for compounds having at least two hydroxyl groups in a single molecule. The number-average molecular weight of polyols is preferably 500 to 10,000, and more preferably 1,000 to 5,000. The above number-average molecular weight can be calculated from the hydroxyl value of the polyol, and the hydroxyl value refers to the measurement value according to JIS K0070. 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.

[0060] The polyol is preferably at least one polyol selected from the group consisting of polyester polyols, polyether polyols, and polycarbonate polyols. Furthermore, the polyol may also include other types such as dimer diol, hydrogenated dimer diol, and castor oil modified polyol. In other words, it is preferable that the above-mentioned urethane resin contains at least one polyol-derived structural unit selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol. Since the detachability is improved by alkaline hydrolysis of the ester bond site of the polyester polyol, a urethane resin containing a polyester polyol-derived structural unit is more preferable. The content of polyol-derived structural units is preferably 10 to 75% by mass, more preferably 15 to 70% by mass, and even more preferably 20 to 65% by mass in the urethane resin. The content of polyester polyol-derived structural units is preferably 5% by mass or more, more preferably 30% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, out of the total structural units derived from polyol.

[0061] Hydroxy acid The polyol described above may contain a hydroxyl acid. The hydroxyl acid is a compound having a hydroxyl group, which is an active hydrogen group, and an acidic functional group. Examples of the acidic functional group include a carboxyl group and a sulfonic acid group. Among these, the carboxyl group is preferred. The hydroxyl acid is preferably a dimethylolalkanoic acid such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid.

[0062] Polyisocyanates The polyisocyanate is not particularly limited and can be selected from conventionally known polyisocyanates, but it is preferable that it contains diisocyanate or triisocyanate, and is particularly preferable that it contains aromatic, aliphatic, or alicyclic diisocyanate. These may be used alone or in combination of two or more.

[0063] Polyamines Diamines are preferred as polyamines. Diamines having hydroxyl groups are even more preferred because they can introduce hydroxyl groups into the urethane resin.

[0064] The acid value of the urethane resin having an acidic group is preferably 15 mg KOH / g or higher, more preferably 15 to 70 mg KOH / g, and even more preferably 20 to 50 mg KOH / g. If the KOH concentration is 15 mg / g or higher, the desorption properties by the processing solution are further improved. If the KOH concentration is 70 mg / g or lower, the adhesion to the substrate and retort resistance are further improved. The hydroxyl value of the urethane resin is preferably 1 to 35 mg KOH / g, and more preferably 10 to 30 mg KOH / g. A value of 1 mg KOH / g or higher further improves desorption properties. A value of 35 mg KOH / g or lower further improves adhesion to the substrate.

[0065] The mass-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 mass-average molecular weight, and Mn represents the number-average molecular weight. A molecular weight distribution of 6 or less results in excellent desorption properties, drying properties of the primer composition, and retort resistance. Furthermore, the smaller the molecular weight distribution, i.e., the sharper the molecular weight distribution, the more uniform the dissolution and peeling action by the processing solution occurs, further improving the desorption properties of the plastic substrate. The molecular weight distribution is more preferably 5 or less, and even more preferably 4 or less. In addition, a molecular weight distribution of 1.5 or more is preferred, and 1.2 or more is more preferred. In this specification, Mw, Mn, and molecular weight distribution (Mw / Mn) are polystyrene-equivalent values ​​obtained by gel permeation chromatography (GPC).

[0066] The urethane resin having acidic groups may also have amino groups. The amine value of the urethane resin is preferably 0.1 to 20 mg KOH / g, and more preferably 1 to 10 mg KOH / g. Adhesion to the substrate is further improved when the amine value is within the above range.

[0067] The number of urethane bonds in the acidic urethane resin is preferably 1 to 3 mmol / g, and more preferably 1.5 to 2 mmol / g. The number of urea bonds in the acidic urethane resin is preferably 0 to 3 mmol / g, and more preferably 0.2 to 1 mmol / g. The total number of urethane bonds and urea bonds in the acidic urethane resin is preferably 1 to 6 mmol / g, and more preferably 1.7 to 3 mmol / g. By setting the number of urethane bonds and urea bonds in the acidic urethane resin within the above range, the deleasability and adhesion to the substrate are further improved.

[0068] [Acrylic resin containing acidic groups] Acrylic resins having acidic groups include polymers obtained by polymerizing monomers containing (meth)acrylic monomers having carboxyl groups, such as (meth)acrylic acid and maleic acid, or polymers obtained by polymerizing monomers containing (meth)acrylic monomers having functional groups, such as 2-hydroxyethyl (meth)acrylate and glycidyl (meth)acrylate, and then reacting the functional groups with a compound having carboxyl groups and reacting with such functional groups (such as maleic anhydride) to introduce carboxyl groups into the acrylic resin. Examples of monomers other than (meth)acrylic monomers having carboxyl groups include (meth)acrylic monomers such as methyl (meth)acrylate and butyl (meth)acrylate; and vinyl monomers such as maleic acid, maleic anhydride, styrene, vinyl acetate, butadiene, and acrylonitrile. The acid value of the acrylic resin having an acidic group is preferably 50 mg KOH / g or higher, and more preferably 100 mg KOH / g or higher.

[0069] [Rosin-modified resin] Rosin-modified resins are resins obtained by modifying rosin. Rosin is a mixture of resin acids such as abietic acid, palastic acid, isopimal acid, and levopimal acid. Resin acids contain hydrophilic and chemically active carboxyl groups and may contain compounds with conjugated double bonds. Therefore, rosin-modified resins can be synthesized by methods such as condensation polymerization by combining rosin with polyhydric alcohols or polybasic acids, by adding resol, a phenol condensate, to the benzene ring contained in the rosin skeleton, or by Diels-Alder reaction with dienophiles such as maleic anhydride or maleic acid to add a maleic acid or maleic anhydride skeleton. Rosin-modified resins can be obtained and used as commercially available products.

[0070] Examples of rosin-modified resins include maleated rosin, fumarated rosin, rosin-modified maleic acid resin, rosin-modified fumaric acid resin, rosin-modified phenolic resin, rosin-modified alkyd resin, and rosin-modified polyester resin. Among these, resins containing a moiety in their structure derived from at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride are preferred. A resin that "contains a moiety in its structure derived from at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride" is a resin prepared using at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride as part of the raw materials. Examples include rosin-modified maleic acid resins and rosin-modified fumaric acid resins obtained by condensation polymerization of maleic acid or fumaric acid as part of a polybasic acid, maleated rosin and fumarated rosin having a structure in which maleic acid, maleic anhydride, fumaric acid, or fumaric anhydride are added as dienophiles by a Diels-Alder reaction, and resins obtained by further polymerization of other chemical species using the functional groups contained therein.

[0071] The acid value of the rosin-modified resin is preferably 10 to 400 mg KOH / g, and more preferably 100 to 300 mg KOH / g.

[0072] (Other ingredients) The primer layer may contain resins other than water-soluble resins or compounds having acidic groups. Other resins include, for example, 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 copolymer resins, 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. Other resins may be used individually or in combination of two or more types. Among these, the primer layer preferably contains at least one resin selected from the group consisting of cellulose resin, vinyl chloride resin, rosin resin, and acrylic resin, with vinyl chloride resin and acrylic resin being more preferred. The preferred mass ratio of the urethane resin having acidic groups to the other resin (urethane resin having acidic groups: other resin) is 95:5 to 50:50. Within this range, when the printed layer is peeled off together with the primer layer in a basic aqueous solution, the printed layer is more easily peeled off in a thin film state, making it easier to recover the plastic substrate.

[0073] The primer layer may contain an extender pigment. Examples of extender pigments include metal oxides such as silica, barium sulfate, kaolin, clay, calcium carbonate, magnesium carbonate, zinc oxide, and zirconium oxide. Among these, silica is preferred, and hydrophilic silica is preferred.

[0074] The average particle size of the extender pigment is preferably 0.5 to 10 μm, and more preferably 1 to 8 μm. The extender pigment content in the primer layer is preferably 0.5 to 10% by mass, and more preferably 1 to 5% by mass. When the average particle size and extender pigment content are within the above ranges, the wettability of the printed layer is improved and the image quality is enhanced.

[0075] The primer layer may be a layer obtained by crosslinking a urethane resin having the above-mentioned acidic groups with a curing agent. By introducing a crosslinked structure into the primer layer, for example, penetration and bleeding of the printed layer formed on the primer layer are suppressed, making it easier to obtain excellent image quality. Examples of curing agents include polyisocyanates. Examples of polyisocyanates include aliphatic polyisocyanates and aromatic aliphatic polyisocyanates. The curing agent may be used alone or in combination of two or more types.

[0076] The primer layer may also contain additives. Examples of additives include dispersants, wetting agents, adhesion aids, leveling agents, defoamers, antistatic agents, viscosity modifiers, metal chelates, trapping agents, antiblocking agents, wax components other than those listed above, silane coupling agents, and the like.

[0077] The thickness of the primer layer is preferably 0.5 to 3.0 μm, more preferably 0.6 to 2.0 μm, and even more preferably in the range of 0.8 to 1.5 μm.

[0078] [Print layer] A printing layer is a layer that forms any printed pattern for purposes such as decoration, adding aesthetic appeal, indicating contents, expiration date, manufacturer, or seller information, and includes solid printing layers. When the desorption layer is a printed layer, the printed layer is positioned in contact with the plastic substrate. The printed layer is desorbed from the plastic substrate by dissolution and peeling using a processing solution. The printed layer preferably contains a colorant and a water-soluble resin or a compound having an acidic group (excluding water-soluble resins). The method of forming the printed layer is not limited and can be formed using known methods. From the viewpoint of printability, the printing layer preferably contains one or more of the following: a urethane resin having an acidic group, an acrylic resin having an acidic group, and a rosin-modified resin. The embodiments of the above-mentioned water-soluble resin and compound having an acidic group, as well as the urethane resin having an acidic group, acrylic resin having an acidic group, and rosin-modified resin can be described by referring to the descriptions of (water-soluble resin), (compound having an acidic group), [urethane resin having an acidic group], [acrylic resin having an acidic group], and [rosin-modified resin] in the above-mentioned section on [primer layer].

[0079] (Coloring agent) The printed layer may be colored or colorless, and preferably contains known colorants used in printing inks and paints. Examples of colorants include inorganic pigments, organic pigments, dyes, metal powders that give metallic luster, near-infrared absorbing materials, ultraviolet absorbing materials, and the like. Examples of inorganic pigments include colored pigments such as titanium dioxide, red iron oxide, Prussian blue, ultramarine, carbon black, and graphite; and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. Furthermore, since the desorption treatment solution contains basic compounds, it is preferable to use a pigment that does not dissolve in a basic aqueous solution and has alkali resistance as the coloring agent. Preventing pigment dissolution facilitates the reuse of the basic aqueous solution. The alkali resistance of a pigment is generally estimated by its skeleton or structure. Examples of alkali-resistant pigments include inorganic pigments, phthalocyanine pigments (e.g., CI Pigment Blue 15), and insoluble azo pigments (e.g., CI Pigment Yellow 83). When the pigment is titanium dioxide, the titanium dioxide content in the printed layer is preferably 20 to 80% by mass, and more preferably 30 to 75% by mass. Furthermore, when the pigment is one or more selected from the group consisting of inorganic pigments other than titanium dioxide, extender pigments, and organic pigments, the content of each of these pigments is preferably 0.5 to 60% by mass, and more preferably 10 to 50% by mass, based on 100% by mass of the printed layer.

[0080] (Other ingredients) The printed layer may contain a pigment derivative and / or a resin-type dispersant as a dispersant for the colorant. Pigment derivatives are compounds in which acidic or basic substituents are introduced into the backbone of a pigment. The content 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, based on the mass of the colorant. When the pigment derivative content is 0.01% by mass or more, the delamination of the plastic substrate is excellent. Furthermore, when it is 10% by mass or less, re-adhesion of the printed layer can be suppressed. The resin-type dispersant works by adsorbing onto the colorant and stabilizing its dispersion in printing inks, etc., and can be appropriately selected from known resin-type dispersants. The content 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 mass of the colorant. When the content of the resin-type dispersant is 0.01% by mass or more, the delamination of the plastic substrate is excellent. Furthermore, when it is 30% by mass or less, the water resistance of the printed layer is excellent.

[0081] The printed layer may contain resins other than water-soluble resins or compounds containing acidic groups. Examples of such resins include fiber-derived resins such as nitrocellulose and cellulose acetate propionate; chlorinated polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, acrylic, urethane resin and acrylic urethane, polyamide, polybutyral, cyclocompound rubber, and chlorinated rubber resins. The resins may be used individually or in combination of two or more types.

[0082] The thickness of the printed layer is preferably 0.1 μm or more and 100 μm or less, more preferably 0.1 μm or more and 10 μm or less, and even more preferably 1 μm or more and 5 μm or less.

[0083] [Adhesive layer] When the desorption layer is an adhesive layer, the adhesive layer is positioned in contact with the plastic substrate. The adhesive layer is detached from the plastic substrate by dissolution and peeling using a desorption treatment solution. To impart desorption ability, the adhesive layer is preferably based on an adhesive typically used for laminates having a plastic substrate, and contains, for example, a compound having an acidic group (excluding water-soluble resins). Alternatively, it is preferable that at least a portion of the resin constituting the adhesive is a resin having an acidic group. When the adhesive layer contains a resin having an acidic group or a low-molecular-weight compound having an acidic group, swelling, dissolution, and peeling of the adhesive layer are promoted in a basic aqueous solution, resulting in superior desorption properties. The embodiments of the above-mentioned compounds having acidic groups, resins having acidic groups, and low-molecular-weight compounds having acidic groups can be described by referring to the description of (compounds having acidic groups) in the [primer layer] section above. Furthermore, the method for forming the adhesive layer is not limited and can be formed using known methods.

[0084] The adhesive layer may be a cured product of an adhesive containing a polyester polyol having acidic groups and at least one polyisocyanate selected from the group consisting of aliphatic polyisocyanates and aromatic aliphatic polyisocyanates, from the viewpoint of deleasability. The above cured product corresponds to a resin having acidic groups. Furthermore, the adhesive layer may be a cured product of an adhesive comprising a polyester polyol, at least one polyisocyanate selected from the group consisting of aliphatic polyisocyanates and aromatic aliphatic polyisocyanates, and a low molecular weight compound having an acidic group.

[0085] (Polyester polyol) Polyester polyols can contain polyester polyols having acidic groups. The inclusion of such polyester polyols is preferable because, when a basic aqueous solution is used as the treatment solution, the ester bonds have a high affinity for basic compounds, improving the desorption properties. Polyester polyols may be used alone or in combination of two or more types.

[0086] Polyester polyols are not particularly limited, but examples include polyester polyols obtained by reacting a carboxyl group component with a hydroxyl group component; and polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, and poly(β-methyl-γ-valerolactone). Examples of the carboxyl group component include 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, and other dibasic acids or their dialkyl esters or mixtures thereof. Examples of the hydroxyl group components mentioned above 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 above-mentioned carboxyl group components and hydroxyl group components may be used in combination.

[0087] The polyester polyol may also be a polyester urethane polyol obtained by reacting the hydroxyl groups in the polyol with polyisocyanate. The presence of urethane bonds in the polyester polyol provides excellent heat resistance and adhesive properties. Examples of the above polyisocyanates 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.

[0088] Furthermore, 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 for the introduction of acidic carboxyl groups into the polyester polyol. Examples of acid anhydrides include pyromellitic anhydride, mellitic anhydride, trimellitic anhydride, and trimellitic anhydride esters. Examples of trimellitic anhydrides include ethylene glycol bisanhydrotrimellitate and propylene glycol bisanhydrotrimellitate.

[0089] The acid value of the polyester polyol is preferably 5.0 mg KOH / g or higher, and more preferably 10.0 mg KOH / g or higher. Furthermore, the acid value of the polyester polyol is preferably 100 mg KOH / g or lower, and more preferably 80 mg KOH / g or lower. When the acid value of the polyester polyol is within the above range, when it comes into contact with a basic aqueous solution, the basic aqueous solution penetrates and decomposes the polyester polyol, further improving its desorption properties. When an adhesive contains multiple polyester polyols, the total acid value of the polyester polyols can be determined from the acid value of each individual polyester polyol and its mass ratio.

[0090] 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 even more preferably 7,000 to 15,000. When the number-average molecular weight of the polyester polyol is 3,000 or more, it exhibits not only good coating properties but also sufficient retort suitability, and when it is 20,000 or less, it improves not only coating properties but also delamination properties.

[0091] The polyester polyol component may be composed of multiple polyester polyol components in combination to satisfy the various physical properties required for packaging materials. For example, it may contain polyester polyols with a number average molecular weight of 5,000 to 20,000, and further, to improve adhesion to the substrate, it may also contain polyester polyols with a number average molecular weight of less than 3,000. The content of polyester polyols with a number average molecular weight of less than 3,000 is preferably 0 to 30% by mass, and more preferably 0 to 20% by mass, based on the total mass of polyester polyols. A content of 30% by mass or less improves retort resistance.

[0092] (Other polyols) The adhesive constituting the adhesive layer may contain polyols other than polyester polyols. The polyols that may be contained other than polyester polyols are not particularly limited and include, for example, polycarbonate polyols, polycaprolactone polyols, polyether polyols, polyolefin polyols, acrylic polyols, silicone polyols, castor oil-based polyols, and fluorine-based polyols.

[0093] (Polyisocyanate) To form the adhesive layer, the polyisocyanate to be combined with the polyester polyol described above is preferably at least one selected from the group consisting of known aliphatic polyisocyanates and aromatic aliphatic polyisocyanates.

[0094] Aliphatic polyisocyanates include, for example, 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); and polyisocyanates such as allophanate-type, nurate-type, biuret-type, and adduct-type derivatives or complexes thereof derived from the above diisocyanates. The aforementioned derivatives are preferably of the nurate type or adduct type, and more preferably of the adduct type obtained by reaction with a polyol. Furthermore, polyisocyanates derived from hexamethylene diisocyanate (hereinafter also referred to as HDI), which allows for a good balance between leaving properties and laminate properties, are preferred.

[0095] Aromatic aliphatic polyisocyanates include, for example, aromatic aliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω′-diisocyanate-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanate-1-methylethyl)benzene or mixtures thereof; and polyisocyanates such as allophanate-type, nurate-type, biuret-type, adduct-type derivatives or complexes thereof derived from the above aromatic aliphatic diisocyanates.

[0096] (Other polyisocyanates) The adhesive may contain polyisocyanates other than aliphatic polyisocyanates and aromatic aliphatic polyisocyanates, to the extent that it does not impair the effects of the present invention. Examples of such polyisocyanates include aromatic diisocyanates such as toluene diisocyanate and diphenylmethane diisocyanate; and polyisocyanates such as derivatives or complexes thereof of the above diisocyanates.

[0097] The mixing ratio of the polyol and polyisocyanate may be such that the molar ratio (NCO / OH) of isocyanate groups in the polyisocyanate to hydroxyl groups in the polyol is 0.3 to 10.0. The molar ratio (NCO / OH) is preferably 0.3 to 7.0, and more preferably 0.5 to 5.0.

[0098] (Other ingredients) The adhesive layer may contain silane coupling agents, phosphorus oxygen acids or their derivatives, leveling agents, defoaming agents, reaction accelerators, as well as inorganic fillers (e.g., silica, alumina, mica, talc, aluminum flakes, glass flakes), layered inorganic compounds, stabilizers (e.g., antioxidants, heat stabilizers, UV absorbers, hydrolysis inhibitors), rust inhibitors, thickeners, plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, fillers, nucleating agents, catalysts for adjusting the curing reaction, etc.

[0099] [Method for manufacturing recycled plastic substrates] A recyclable plastic substrate can be manufactured using the recovery method described later. The recyclable plastic substrate may be a substrate that has been fragmented by crushing, cutting, pulverizing, etc. The method for manufacturing a recyclable plastic substrate of the present invention includes, for example, a desorption step of contacting at least a plastic substrate layer and a desorption layer in contact with the plastic substrate layer with a desorption treatment liquid to desorb the desorption layer, and a recovery step of recovering the plastic substrate after the desorption step to obtain a recyclable plastic substrate.

[0100] [Recyclable plastic substrates] After the desorption layer is detached from the laminate and the plastic substrate is recovered, the obtained plastic substrate is washed with water and dried to obtain a high-quality recyclable plastic substrate. The removal rate of the desorption layer on the surface of the substrate is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the area of ​​the desorption layer before detachment. The resulting recycled plastic substrate can be processed into pellets using an extruder or the like, and reused as recycled resin.

[0101] [Desorption process] In the present invention, the desorption step of the plastic substrate includes a step of bringing the plastic substrate, a desorption layer in contact with the plastic substrate, and a desorption treatment liquid into contact with the desorption layer to desorb it.

[0102] In the desorption process for the plastic substrate of the present invention, since the recovered plastic substrate can be used as a molding material, it is preferable that a certain amount of the desorption layer is desorbed from the plastic having at least a desorption layer. Specifically, at the end of the process, it is preferable that 50% or more by mass of the 100% by mass of the desorption layer is desorbed in terms of area or film thickness, more preferably 60% or more by mass, even more preferably 80% or more by mass, and particularly preferably 90% or more by mass.

[0103] The desorption treatment liquid penetrates from the edges of the laminate and comes into contact with the desorption layer, dissolving or swelling the desorption layer and separating it from the plastic substrate. Therefore, in order to efficiently proceed with desorption, it is preferable that the laminate is cut or crushed so that the desorption layer is exposed at the cross-section when immersed in the treatment liquid. In such a case, the substrate layer can be desorbed in a shorter time.

[0104] The temperature of the treatment solution when immersing the plastic substrate is preferably 25 to 120°C, more preferably 30 to 120°C, and even more preferably 30 to 80°C. The immersion time in the treatment solution for the plastic substrate is preferably 1 minute to 24 hours, more preferably 1 minute to 12 hours, and even more preferably 1 minute to 6 hours. The amount of desorption treatment solution used is preferably 50,000 to 100,000 times the mass of the plastic substrate, more preferably 100,000 to 10,000 times, and it is preferable to stir or circulate the treatment solution to improve the desorption efficiency. The rotation speed is preferably 80 to 5,000 rpm, and more preferably 80 to 4,000 rpm.

[0105] [Recovery Process] In the present invention, the plastic substrate recovery step includes a step of recovering the plastic substrate obtained by the desorption step. It is preferable to obtain a recyclable plastic substrate by following the steps of detaching the desorption layer from the plastic substrate, recovering the plastic substrate, and then washing and drying the obtained plastic substrate.

[0106] In the method for producing a recyclable plastic substrate of the present invention, the median diameter of the impurity component derived from the desorption layer is preferably 1 μm or larger. Having a median diameter of 1 μm or larger for the impurity component derived from the desorption layer suppresses the re-adhesion of the impurity component to the substrate, making it easier to obtain a higher-performance recycled material. The median diameter of the impurities originating from the desorption layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and particularly preferably 20 μm or more. Furthermore, the median diameter of the impurities originating from the desorption layer is 1000 μm or less, or 800 μm or less. A median diameter of 1000 μm or less facilitates the separation of the substrate after desorption from the impurities originating from the desorption layer.

[0107] In this invention, the median diameter (D50) and span value A of the impurity components originating from the desorption layer are measured by a laser diffraction particle size distribution analyzer. The span value A is expressed by the following formula. A = (D90 - D10) / D50 D10: Volume-based particle size distribution obtained by laser diffraction particle size distribution measurement of detached printing layer components. Cumulative 10% diameter of the distribution D90: Volume-based particle size distribution obtained by laser diffraction particle size distribution measurement of detached printed layer components. Cumulative 90% diameter of the distribution

[0108] The span value A represents the particle size distribution width of impurities originating from the desorption layer. A larger value indicates a wider particle size distribution and a tendency to include fine printing layer components that are more likely to re-adhere to the substrate. The span value A is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less. A span value of 10 or less is preferable because it suppresses the reattachment of impurities originating from the desorption layer.

[0109] [Method for manufacturing molding materials] In the present invention, the molding material is a raw material used when molding a molded product, and may consist only of a recycled plastic base material, or it may also contain plastics other than recycled plastics, colorants, additives, etc. The present invention's method for producing a molding material preferably includes the step of melting and kneading the obtained recycled plastic substrate at 140 to 290°C before producing the molding material. The manufacturing of the molding material preferably involves, for example, melting and kneading the recycled plastic substrate in an extruder equipped with a screw, and then cooling it to 40°C or below. More specifically, the process preferably includes the steps of supplying the recycled plastic substrate from a supply port, melting and kneading the recycled plastic substrate supplied from the supply port in a melting and kneading section, and then discharging the molding material melted and kneaded in the melting and kneading section from a discharge section and cooling it to obtain the molding material. The shape of the molding material is not particularly limited and can be rod-shaped, granular, cubic, rectangular, irregular, etc. Among these, it is preferable to cut the molding material molded into a rod shape into pellets.

[0110] From the viewpoint of obtaining a uniform molding material, the temperature during melt mixing is preferably 140 to 290°C, more preferably 145 to 280°C, and even more preferably 150 to 270°C. It is also preferable to add a compatibilizer during melt mixing.

[0111] [Method for manufacturing molded products] A molded body can be produced by heat-molding the molding material obtained by the above manufacturing method. The heat-molding method is not particularly limited and examples include injection molding, extrusion molding, blow molding, and compression molding. Molded articles produced using recycled plastic substrates obtained by the method for producing recycled plastic substrates of the present invention are of high quality because the functional layer and other components are separated by the desorption layer, and can be used in a variety of fields, such as home appliances, stationery, automobile parts, toys, sporting goods, medical equipment, and building or construction materials.

[0112] [Masterbatch] The method for manufacturing a molded article of the present invention may involve mixing the above-mentioned molding material with a masterbatch. The masterbatch is not particularly limited as long as it is compatible with recycled plastics, and generally, a mixture of a thermoplastic resin such as polyethylene resin or polypropylene resin and a colorant can be used. The thermoplastic resin included in the masterbatch may be used alone or in combination of two or more types. The masterbatch may contain alkali metal, alkaline earth metal, or zinc metal soaps, hydrotalcite, nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants, antistatic agents, flame retardants such as halogenated, phosphorus-based, or metal oxides, lubricants such as ethylenebisalkylamide, antioxidants, ultraviolet absorbers, and fillers, to the extent that they do not impair the effects of the present invention.

[0113] <Example of an embodiment> Examples of embodiments of this disclosure are given below. This disclosure is not limited to the following.

[0114] <1> The desorption treatment liquid of this disclosure is a desorption treatment liquid for removing the desorption layer by bringing a laminate having a plastic substrate and a desorption layer into contact with the desorption treatment liquid, The aforementioned desorption treatment liquid contains a surfactant, water, and a basic compound. The surfactant comprises a cationic surfactant and a nonionic surfactant. The cationic surfactant is 60% by mass or less of the total mass of the cationic surfactant and the nonionic surfactant, The content of the cationic surfactant is 1 to 100% by mass relative to the content of the basic compound. <2> The amount of cationic surfactant is 50% by mass or less of the total mass of cationic surfactants and nonionic surfactants. <1> Desorption treatment solution. <3> The total mass of cationic surfactants and nonionic surfactants relative to the entire desorption treatment solution is 0.01 to 5% by mass. <1> or <2> Desorption treatment solution. <4> Furthermore, it contains an antifoaming agent, <1> ~ <3> Any of the desorption treatment solutions. <5> A desorption step involves bringing a plastic substrate and a laminate having a desorption layer adjacent to the plastic substrate into contact with a desorption treatment liquid to desorb the desorption layer, A method for producing a recyclable plastic substrate, comprising a recovery step of recovering the plastic substrate after the detachment step to obtain a recyclable plastic substrate, The aforementioned desorption treatment liquid contains a surfactant, water, and a basic compound. The surfactant comprises a cationic surfactant and a nonionic surfactant, wherein the cationic surfactant is 60% by mass or less of the total mass of the cationic surfactant and the nonionic surfactant. A method for producing a recyclable plastic substrate, wherein the content of the cationic surfactant is 1 to 100% by mass relative to the content of the basic compound. <6> <5> A method for producing a molding material, comprising the step of melting and kneading a recycled plastic substrate obtained by the manufacturing method at 140 to 290°C, and then producing a molding material. <7> <6> A method for manufacturing a molded article, comprising the step of heat-molding a molding material obtained by the manufacturing method. [Examples]

[0115] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples. Note that "parts" refers to "parts by mass" and "%" refers to "percentage by mass".

[0116] <Molecular weight and molecular weight distribution> The mass-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 converted molecular weights using polystyrene as a standard substance. The measurement conditions are shown below. GPC device: Showa Denko Shodex GPC-104 Columns: The following columns were used, connected in series. Two Shodex LF-404 tubes manufactured by Showa Denko. Showa Denko Shodex LF-G Detector: RI (Differential Refractometer) Measurement conditions: Column temperature 40°C Eluent: Tetrahydrofuran Flow rate: 0.3mL / min

[0117] <Acid value, hydroxyl value> The acid value and hydroxyl value were measured according to the method described in JIS K 0070 (1992).

[0118] <Manufacturing of primer compositions and resins for printing inks> [Synthesis Example 1-1] (Polyurethane resin P1) In a reactor equipped with a reflux condenser, dropping funnel, gas inlet tube, stirrer, and thermometer, 152.2 parts of PPA (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 (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 (n-propyl acetate) were charged while introducing nitrogen gas. The mixture was reacted at 90°C for 5 hours to obtain a urethane prepolymer solution having isocyanate groups at the ends. Next, a mixture of 19.2 parts AEA (2-(2-aminoethylamino)ethanol) and 350 parts IPA (isopropyl alcohol) was added dropwise to the obtained urethane prepolymer solution 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 non-volatile content, resulting in a polyurethane resin P1 solution with a non-volatile content concentration of 30%, a mass-average molecular weight of 27,000, Mw / Mn = 3.1, and a hydroxyl value of 34.2 mgKOH / g.

[0119] [Synthesis Example 1-2] (Polyurethane resin P2) In a reactor equipped with a reflux condenser, dropping funnel, gas inlet tube, stirrer, and thermometer, 135.7 parts of PPA (polyester polyol with a number average molecular weight of 2,000, consisting of a polycondensate of propylene glycol and adipic acid), 13.6 parts of PPG (polyether polyol with a number average molecular weight of 2,000, consisting of polypropylene glycol), 28.3 parts of DMPA (2,2-dimethylolpropanoic acid), 105.7 parts of IPDI (isophorone diisocyanate), and 200 parts of NPAC (n-propyl acetate) were charged while introducing nitrogen gas. The mixture was reacted at 90°C for 5 hours to obtain a urethane prepolymer solution having isocyanate groups at the ends. Next, a mixture of 16.7 parts AEA (2-(2-aminoethylamino)ethanol) and 350 parts IPA (isopropyl alcohol) was added dropwise to the obtained urethane prepolymer solution 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 non-volatile content, resulting in a polyurethane resin P2 solution with a non-volatile content concentration of 30%, a mass-average molecular weight of 30,000, Mw / Mn = 3.0, an acid value of 39.3 mg KOH / g, and a hydroxyl value of 30.5 mg KOH / g.

[0120] [Synthesis Example 1-3] (Polyurethane resin P3) In a reactor equipped with a reflux condenser, dropping funnel, gas inlet tube, stirrer, and thermometer, 108.6 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), 40.7 parts of PEG (a polyether polyol with a number average molecular weight of 2,000, consisting of polyethylene glycol), 28.3 parts of DMPA (2,2-dimethylolpropanoic acid), 105.7 parts of IPDI, and 200 parts of NPAC were charged while introducing nitrogen gas. The mixture was reacted at 90°C for 5 hours to obtain a prepolymer solution having isocyanate groups at the ends. Next, a mixture of 16.7 parts AEA and 150 parts IPA was added dropwise to the resulting urethane prepolymer solution at room temperature over 60 minutes. Then, 10.0 parts of 28% aqueous ammonia and 690 parts of deionized water were gradually added to neutralize the carboxyl groups in the resin, thereby making it water-soluble. Next, NPAC and IPA were removed by vacuum distillation to obtain an aqueous solution of polyurethane resin P3 with a non-volatile content of 30%, a mass-average molecular weight of 32,000, Mw / Mn = 3.3, an acid value of 39.3 mgKOH / g, and a hydroxyl value of 30.5 mgKOH / g. However, the acid value of P3 is the value before neutralization.

[0121] [Synthesis Example 1-4] (Acrylic Resin P4) In a reactor equipped with a reflux condenser, dropping funnel, gas inlet tube, stirrer, and thermometer, 70 parts styrene, 23 parts acrylic acid, 7 parts 2-hydroxyethyl methacrylate, 40 parts EA (ethyl acetate), and 40 parts IPA were charged while introducing nitrogen gas. The mixture was heated to 90°C, and 1 part AIBN (azobisisobutyronitrile) and 15 parts EA were added, and the polymerization reaction was carried out for 4 hours. Then, 0.1 parts AIBN and 3 parts EA were added and reacted for 2 hours to obtain an acrylic resin solution. The obtained acrylic resin solution was adjusted for non-volatile content by adding EA to obtain acrylic resin P4 with a non-volatile content concentration of 30.0%, a mass-average molecular weight of 27,000, an acid value of 179.1 mgKOH / g, and a hydroxyl value of 30.2 mgKOH / g.

[0122] <Composition for forming primer layer> [Manufacturing Example 1-1] (Primer Composition A1) Primer composition A1 was obtained by stirring and mixing 87 parts of polyurethane resin P2 solution, 5 parts of EA, 5 parts of IPA, and 3 parts of silica particles (P-73, manufactured by Mizusawa Chemical Co., Ltd.: hydrophilic silica particles with an average particle size of 3.8 μm) in a disperser.

[0123] [Manufacturing Examples 1-2 to 1-4] (Primer Compositions A2 to A4) Primer compositions A2 to A4 were obtained using the same method as in Production Example 1-1, except that the raw materials and mixing ratios shown in Table 1 were changed.

[0124] <Manufacturing of printing inks> [Manufacturing Example 2-1] (Printing Ink R1) Ten parts of blue pigment PB15 (CIPigment Blue 15), 25 parts of polyurethane resin P1 solution (5 / 9 of the total amount), 5 parts of PVC (vinyl chloride-vinyl acetate copolymer resin (Solvine TAO, manufactured by Nisshin Chemical, 30% non-volatile content, EA solution)), 10 parts of EA (1 / 2 of the total amount), and 10 parts of IPA (1 / 2 of the total amount) were mixed and stirred, and dispersed for 20 minutes using a sand mill as a bead mill. Then, 20 parts of polyurethane resin P1 solution (4 / 9 of the total amount), 10 parts of EA (1 / 2 of the total amount), and 10 parts of IPA (1 / 2 of the total amount) were mixed and stirred to obtain printing ink R1. Note that the total amount refers to, for example, "10 parts of EA (1 / 2 of the total amount)," meaning that 10 parts are used when a total of 20 parts of EA are used.

[0125] [Manufacturing Examples 2-2 to 2-3] (Printing Inks R2 to R3) Printing inks R2 to R3 were obtained using the same method as in ink manufacturing example 2-1, except that the raw materials and mixing ratios shown in Table 1 were used. The mixing amounts in Table 1 are the sum of the mixing during dispersion and the mixing afterward.

[0126] [Table 1]

[0127] The abbreviations used in Table 1 are shown below. Maleinized rosin resin: A solution prepared by diluting Marquid No. 32 (acid value 130 mg KOH / g, non-volatile content 100%) manufactured by Arakawa Chemical Industries, Ltd., with ethyl acetate to a non-volatile content of 30%. PVA resin: Kuraray Co., Ltd. Kuraray Poval 5-88 (saponification degree 86.5-89.0%) non-volatile content aqueous solution, 15% aqueous solution. PB15: CIPigment Blue 15 PVC resin: Vinyl chloride-vinyl acetate copolymer resin (Solvine TAO, manufactured by Nisshin Chemical, 30% non-volatile content, EA solution) EA: Ethyl acetate IPA: Isopropyl alcohol

[0128] <Manufacturing of polyols used in adhesives> [Synthesis Example 2-1] (Polyester Polyol B1) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet, 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. The mixture was heated to 250°C while stirring under a nitrogen stream, and the esterification reaction was carried out. After the predetermined amount of water was distilled off and the acid value was reduced to 5 mg KOH / g or less, the reaction was continued, and the pressure was gradually reduced to 1 mmHg or less for 5 hours to perform a deglycolization reaction to obtain a polyester polyol. Subsequently, 35 parts of isophorone diisocyanate were gradually added, and the reaction was carried out at 150°C for approximately 2 hours to obtain a polyester polyurethane polyol. 12.0 parts of ethylene glycol bisanhydrotrimellitate were added to 100 parts of this polyester polyurethane polyol, and the mixture was reacted at 180°C for approximately 2 hours. Subsequently, the mixture was diluted with ethyl acetate until the non-volatile content reached 50%, thereby obtaining a solution of partially acid-modified polyester polyol B1 with a number average molecular weight of 9,000 and an acid value of 30.3 mg KOH / g.

[0129] [Synthesis Example 2-2] (Polyester Polyol B2) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet, 58 parts ethylene glycol, 412 parts diethylene glycol, 343 parts neopentyl glycol, 517 parts isophthalic acid, and 393 parts adipic acid were charged. The mixture was heated to 250°C while stirring under a nitrogen atmosphere to carry out the esterification reaction. After a predetermined amount of water was distilled off and the reaction continued until the acid value was 5 mg KOH / g or less, 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. 4.0 parts trimellitic anhydride was added to 100 parts of this polyester polyol and reacted at 180°C for approximately 2 hours. Subsequently, the mixture was diluted with ethyl acetate until the non-volatile content concentration reached 50%, yielding a solution of partially acid-modified polyester polyol B2 with a number-average molecular weight of 2,000 and an acid value of 23.5 mg KOH / g.

[0130] <Preparation of polyisocyanates> [Preparation Example 1] (Polyisocyanate C1) Coronate 2785 (a biuret-type polyisocyanate derived from hexamethylene diisocyanate, manufactured by Tosoh Corporation) was diluted with ethyl acetate to adjust the non-volatile content to 50% and NCO% to 9.6% to obtain a solution of polyisocyanate C1.

[0131] <Adhesive manufacturing> [Manufacturing Example 3-1] (Adhesive D1) 90 parts of polyester polyol B1 solution, 10 parts of polyester polyol B2 solution, and 8 parts of polyisocyanate C1 solution were mixed, and EA was added to prepare an adhesive solution with a non-volatile content of 30%.

[0132] [Manufacturing Example 3-2] (Adhesive D2) A 5% non-volatile adhesive solution was prepared by mixing 90 parts of polyester polyol B1 solution, 10 parts of polyester polyol B2 solution, and 8 parts of polyisocyanate C1 solution, and then adding EA.

[0133] <Manufacturing of laminates> The manufacturing method for the laminate is described below. The primer composition and 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 Rigosha)) before use. The thickness of the primer layer and the printing layer were each prepared to be approximately 1.5 μm.

[0134] [Manufacturing Example 4-1] (Laminate S1) Diluted printing ink R2 was printed onto the corona-treated surface of OPP (one-sided corona-treated biaxially oriented polypropylene film, 30 μm thick) using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate S1 consisting of a desorbed printing layer (R2) and a polyolefin substrate layer (OPP).

[0135] [Manufacturing example 4-2] (laminate S2) Laminate S2 was obtained using the same method as in Manufacturing Example 4-1, except that the printing ink was changed to the one described in Table 2.

[0136] [Manufacturing Example 4-3] (Laminate S3) Diluted primer composition A1 and printing ink R1 were printed in this order onto the corona-treated surface of OPP (one-sided corona-treated biaxially oriented polypropylene film, 30 μm thick) using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm. The printed material was then dried at 50°C to obtain a laminate S3 consisting of a printed layer (R1), a desorbed primer layer (A1), and a polyolefin substrate layer (OPP).

[0137] [Manufacturing examples 4-4 to 4-6] (laminate S4 to 6) Laminates S4-6 were obtained using the same method as in Production Example 4-3, except that the primer composition was changed to the one shown in Table 2.

[0138] [Manufacturing Examples 4-7 to 4-15] (Laminated bodies S7 to 15) Laminates S7-15 were obtained using the same method as in Manufacturing Example 4-1, except that the base material was changed to the one described in Table 2.

[0139] [Manufacturing Example 4-16] (Laminate S16) Adhesive D2 was applied to a double-sided treated OPP (double-sided corona-treated stretched polypropylene film, 30 μm thick) using a gravure coater equipped with a gravure plate with a plate depth of 15 μm, and dried at 80°C to form an adhesive layer. On the adhesive layer, LDPE (pelletized low-density polyethylene, pellets) was extruded and laminated at a melting temperature of 310°C to create a laminate with the vapor-deposited surface of VMOPP (aluminum-deposited polyolefin film, 20 μm thick). Next, adhesive D2 was applied to the OPP side (non-deposited side) of VMOPP using a gravure coater equipped with a gravure plate with a plate depth of 15 μm, and an adhesive layer was formed by drying at 80°C. LDPE was then extruded and laminated onto the adhesive layer at 310°C to bond it to CPP (unoriented polypropylene film, 40 μm thick) and create a laminate. Next, diluted printing ink R2 was applied to the side of the OPP that was not coated with D2, using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm. The material was then dried at 50°C to obtain a laminate S16 consisting of a delamination printing layer (R2) / polyolefin substrate layer (double-sided treated OPP) / adhesive layer (D2) / resin layer (LDPE) / vapor-deposited olefin substrate layer (VMOPP) / adhesive layer (D2) / resin layer (LDPE) / polyolefin substrate layer (CPP).

[0140] [Manufacturing Example 4-17] (Laminate L1) Diluted primer composition A1 and printing ink R1 were printed in this order onto the corona-treated surface of OPP (single-sided corona-treated stretched polypropylene film, 30 μm thick) using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm. The printed material was then dried at 50°C to obtain a laminate with the composition OPP / A1 / R1. Next, adhesive D1 is applied to the printed layer of the resulting laminate using a dry laminating machine, with a drying rate of 2 g / m². 2 After coating and drying to achieve the desired result, the material was laminated with CPP (unoriented polypropylene film, 40 μm thick) to obtain a laminate L1 consisting of a polyolefin substrate layer (OPP), a desorption primer layer (A1), a printed layer (R1), an adhesive layer (D1), and a polyolefin substrate layer (CPP).

[0141] [Manufacturing Examples 4-18~4-25, 4-32] (Laminates L2~9, 16) Laminates L2-9 and L16 were obtained using the same method as in Manufacturing Example 4-17, except that the substrate, primer composition, printing ink, and adhesive were changed to those listed in Table 2. Note that for L16, the printing ink was printed directly onto the substrate without using a primer composition.

[0142] [Manufacturing Example 4-26] (Laminate L10) Diluted primer composition A1 and printing ink R1 were printed in this order onto NY (nylon film, 15 μm thick) using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate with the structure NY / A1 / R1. Next, adhesive D1 is applied to the printed layer of the resulting laminate using a dry laminating machine, with a drying rate of 2 g / m². 2 After coating and drying to achieve the desired result, the material was bonded to the vapor-deposited surface of VMPET (aluminum vapor-deposited polyester film, 15 μm thick) to obtain a laminate consisting of a polyamide substrate layer (NY) / desorption primer layer (A1) / printing layer (R1) / adhesive layer (D1) / vapor-deposited polyester substrate layer (VMPET). Next, adhesive D1 is applied to the PET surface (non-deposited surface) of the resulting VMPET laminate using a dry laminating machine, with a drying rate of 2 g / m². 2 After coating and drying to achieve the desired result, the material was laminated with LLDPE (one-sided corona-treated low-density polyethylene film, 40 μm thick) to obtain a laminate L10 consisting of a polyamide substrate layer (NY) / primer layer (A1) / printed layer (R1) / adhesive layer (D1) / deposited polyester substrate layer (VMPET) / adhesive layer (D1) / polyolefin substrate layer (LLDPE).

[0143] [Manufacturing Examples 4-27~4-29] (Laminate L11~13) Laminates L11-13 were obtained using the same method as in Manufacturing Example 4-26, except that the substrate, primer composition, printing ink, and adhesive were changed to those listed in Table 2.

[0144] [Manufacturing Example 4-30] (Laminate L14) Diluted primer composition A1 and printing ink R1 were printed in this order onto OPP (one-sided corona-treated stretched polypropylene film, 30 μm thick) using a gravure printing press equipped with a gravure plate with a plate depth of 30 μm. The printed material was then dried at 50°C to obtain a laminate consisting of an olefin substrate layer (OPP), a primer layer (A1), and a printed layer (R1). Next, adhesive D2 was applied onto the printed layer of the resulting laminate using a gravure coater equipped with a gravure plate with a plate depth of 15 μm, and dried at 80°C to form an adhesive layer. LDPE (low-density polyethylene pellets) was then extruded and laminated onto the adhesive layer at a melting temperature of 310°C, bonding it to the vapor-deposited surface of VMPET (aluminum-deposited polyester film, 15 μm thick), thereby obtaining a laminate. Next, adhesive D2 was applied to the PET surface of VMPET using a gravure coater equipped with a gravure plate with a plate depth of 15 μm, and an adhesive layer was formed by drying at 80°C. LDPE was extruded and laminated onto the adhesive layer at 310°C to bond it with CPP (unoriented polypropylene film, 40 μm thick), resulting in a laminate L14 consisting of a polyolefin substrate layer (OPP) / primer layer (A1) / printing layer (R1) / adhesive layer (D2) / resin layer (LDPE) / deposited polyester substrate layer (VMPET) / adhesive layer (D2) / resin layer (LDPE) / polyolefin substrate layer (CPP).

[0145] [Manufacturing Example 4-31] (Laminate L15) Laminate L15 was obtained using the same method as in Manufacturing Example 4-30, except that the base material and adhesive were changed to those described in Table 2.

[0146] [Table 2]

[0147] The abbreviations used in Table 2 are shown below. HSOPP: Single-sided heat-sealable polyolefin film, 30 μm thick. Anti-fog OPP: Double-sided anti-fog polyolefin film, 30 μm thick PET: Biaxially oriented polyester film, 12 μm thick WLLDPE: Milky white polyethylene film, 60 μm thick Shrink OPP: Stretched polypropylene shrink film, 20 μm thick Shrink PET: Stretched polyester shrink film, 20 μm thick Barrier PET: Transparent vapor-deposited polyester film, 12 μm

[0148] <Manufacturing of desorption treatment solution> [Manufacturing Example 5-1] (Processing Solution T1) 0.005 parts of A (lauryldimethylethylammonium ethyl sulfate) as a cationic surfactant, 0.005 parts of F (polyoxyethylene stearyl ether, POE addition number: 12, HLB: 13.9) as a nonionic surfactant, 0.001 parts of BYK-1650 (manufactured by Bic Chemie Japan, silicone emulsion type defoamer, non-volatile content concentration 27.5%) as an antifoaming agent, 0.500 parts of sodium hydroxide, and 99.489 parts of water were mixed and stirred with a disperser to obtain treatment solution T1.

[0149] Except for the raw materials and mixing ratios shown in Tables 3-1 and 3-2, treatment solutions T2 to T33 were obtained using the same method as in Production Example 5-1.

[0150] [Table 3-1]

[0151] [Table 3-2]

[0152] The symbols and terms used in Tables 3-1 and 3-2 are as follows: • Amount of surfactant A: Amount of cationic surfactant relative to the total amount of surfactants (%) • Amount of surfactant B: Amount of cationic surfactant relative to the content of basic compounds (%) A: Lauryldimethylethylammonium sulfate B: Stearyldimethylhydroxyethylammonium p-toluenesulfonate C: Cetyltrimethylammonium chloride D: Cetylpyridinium chloride E: Alkyl (C8-C18) trimethylenediamine adipic acid F: Polyoxyethylene stearyl ether, POE addition number: 12, HLB: 13.9 G: Polyoxyethylene lauryl ether, POE addition count: 4, HLB: 9.7 H: Polyoxyethylene acetylenediol, POE addition number 30, HLB: 17 I: Polyoxyethylene sorbitan monococoate, HLB: 16.7

[0153] <Collection of plastic substrates for recycling> [Example 1] 200 parts of treatment solution T1 and 8 parts of laminate S1 cut into 1cm x 1cm pieces were placed in a 1000mL stainless steel beaker and stirred at 70°C and 1500rpm. The separation and recovery status of the laminate was evaluated as follows.

[0154] [Examples 2-116, Comparative Examples 1-10] The separation and recovery state of the laminate was evaluated using the same method as in Example 1, except that the materials listed in Tables 4 and 5 were used. The results are shown in Tables 4 and 5.

[0155] <Evaluation of laminates> (Desorbency of the desorbed layer) For laminates with a desorption layer on a plastic substrate, samples were taken of the substrate 5, 10, and 30 minutes after the start of stirring, and then washed and dried. Ten samples of the obtained substrate were taken, and the removal rate (area) of the printed layer was visually confirmed and evaluated according to the following criteria for each stirring start time. A (Excellent): 100% of the printed layer peels off. B (Good): 80% to less than 100% of the printed layer peels off. C(Pass): More than 60% and less than 80% of the printing layer peels off. D(Fail): Less than 60% of the printing layer peels off.

[0156] (Re - adhesion property of contaminants derived from the release layer) In the evaluation of the release property of the release layer, after stirring for 1 hour under the above - mentioned stirring conditions, the released substrates were respectively collected, washed with water, and dried. Ten substrates obtained were sampled, and the ten substrates obtained were stacked, and the color values L * x , a * x , b * x were measured with a spectrophotometer (X - rite, X - rite eXact). For the plastic substrate itself, which is the printed substrate, ten substrates were stacked and the color values L * y , a * y , b * y were measured. The color difference ΔE before and after stirring for 1 hour was obtained by the following formula, and the re - adhesion property was evaluated according to the following criteria. (Formula) ΔE = ((L * x - L * y ) 2 +(a * x ​​​​​​​​​​​​​​​​​​​​​​​​​​​​Ten minutes after stirring began, stirring was temporarily stopped, and the height of the liquid level (above the bubbles) was visually observed and evaluated according to the following criteria. The height of 450 mL refers to the volume markings on the beaker, and a higher number indicates a higher liquid level, i.e., more bubbles are being generated. A (Excellent): The height of the liquid level (above the bubbles) during stirring is less than 450 mL. B (Good): The liquid level (above the bubbles) during stirring is 450 mL or more and less than 600 mL. C (Acceptable): The liquid level (above the bubbles) during stirring is 600 mL or more and less than 900 mL. D (Not allowed): The liquid level (above the bubbles) during stirring is 900 mL or higher.

[0158] [Table 4] [Table 5]

[0159] <Recycling of plastic substrates for recycling> [Example 117] 200 parts of treatment solution T1 and 8 parts of laminate S1 cut to a size of 1 cm x 1 cm were placed in a 1000 mL stainless steel beaker and stirred for 2 hours at 70°C and 1500 rpm. The condition of the recycled plastic substrate was evaluated as follows.

[0160] [Examples 118-135, Comparative Examples 11-13] The condition of the recycled plastic substrate was evaluated using the same method as in Example 117, except that the treatment solution was changed to the contents listed in Table 6. The results are shown in Table 6.

[0161] (Coloring of recycled plastics) The detached OPP substrate was collected, washed with water, and dried. Ten samples of the obtained substrate were taken, and the ten substrates were stacked and measured for color value b using a spectrophotometer (X-rite eXact, manufactured by X-rite). * x We measured it. Similarly, with respect to the plastic substrate itself, which is the substrate to be printed on, 10 sheets of substrate are stacked to obtain a color value b. * y We measured it. The Δb before and after 2 hours of stirring was calculated using the following formula, and the coloration was evaluated according to the following criteria. (Formula)Δb=b * x ―b * y A (Excellent): Δb is less than 5 B (Good): Δb is 5 or greater, and less than 10. C (acceptable): Δb is 10 or greater, but less than 15. D (Not acceptable): Δb is 15 or greater

[0162] (Transmittance of recycled film) The detached OPP substrate was recovered, washed with water, and dried. The OPP substrate was then extruded at 200°C using a short-axis extruder and subjected to a pelletizing process to obtain recycled resin pellets. The recycled resin was extruded at 200°C using a T-die film molding machine to produce a recycled film with a thickness of 40 μm. The coloration of the recycled film was measured using a haze meter (SH7000, manufactured by JEOL Ltd.) and evaluated according to the following criteria. A (Excellent): Total light transmittance is 70% or higher. B (Good): Total light transmittance is 50% or more but less than 70% C (acceptable): Total light transmittance is 30% or more but less than 50% D (Not acceptable): Total light transmittance is less than 30%

[0163] [Table 6]

[0164] The evaluation results above show that using the decolorization treatment liquid of the present invention allows for the quick and easy decolorization of the printed layer and adhesive layer from the packaging material without discoloring the substrate. Furthermore, even in a continuous deinking process, the re-adhesion of the remaining plastic substrate can be suppressed, resulting in a high-quality recycled substrate with minimal re-adhesion of the printed and adhesive layers. Additionally, the decolorization treatment liquid suppresses air bubbles during the process, improving decolorization performance and further inhibiting re-adhesion. Moreover, it has been shown that a high-quality molding material with minimal discoloration can be obtained.

Claims

1. A desorption treatment liquid for removing the desorption layer of a laminate having a plastic substrate and at least one layer selected from the group consisting of a primer layer, a printing layer, an adhesive layer, and a vapor deposition layer, by contacting the laminate with the desorption treatment liquid, The aforementioned desorption treatment liquid contains a surfactant, water, and a basic compound. The surfactant comprises a cationic surfactant and a nonionic surfactant. The cationic surfactant has at least one alkyl group having 8 to 24 carbon atoms, The nonionic surfactant is an alkylene oxide adduct, The basic compound is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, barium hydroxide, and sodium carbonate. The cationic surfactant is 60% by mass or less of the total mass of the cationic surfactant and the nonionic surfactant. A desorption treatment solution wherein the content of the cationic surfactant is 1 to 100% by mass relative to the content of the basic compound.

2. The desorption treatment liquid according to claim 1, wherein the cationic surfactant is 50% by mass or less of the total mass of the cationic surfactant and the nonionic surfactant.

3. The desorption treatment liquid according to claim 1 or 2, wherein the total mass of the cationic surfactant and the nonionic surfactant relative to the entire desorption treatment liquid is 0.01 to 5% by mass.

4. Furthermore, the defoaming treatment liquid according to claim 1 or 2, further comprising an antifoaming agent.

5. A desorption step involves bringing a plastic substrate and a laminate having a desorption layer adjacent to the plastic substrate into contact with a desorption treatment liquid to desorb the desorption layer, A method for producing a recyclable plastic substrate, comprising a recovery step of recovering the plastic substrate after the detachment step to obtain a recyclable plastic substrate, The desorption layer is at least one layer selected from the group consisting of a primer layer, a printing layer, an adhesive layer, and a vapor deposition layer. The aforementioned desorption treatment liquid contains a surfactant, water, and a basic compound. The surfactant comprises a cationic surfactant and a nonionic surfactant, wherein the cationic surfactant is 60% by mass or less of the total mass of the cationic surfactant and the nonionic surfactant. The cationic surfactant has at least one alkyl group having 8 to 24 carbon atoms, The nonionic surfactant is an alkylene oxide adduct, The basic compound is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, barium hydroxide, and sodium carbonate. A method for producing a recyclable plastic substrate, wherein the content of the cationic surfactant is 1 to 100% by mass relative to the content of the basic compound.

6. A method for producing a molding material, comprising the step of melting and kneading a recycled plastic substrate obtained by the manufacturing method described in claim 5 at 140 to 290°C, and then producing a molding material.

7. A method for manufacturing a molded article, comprising the step of heat-molding a molding material obtained by the manufacturing method described in claim 6.

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