Method for producing treated waste water and method for treating waste liquid

Abstract

To provide a method for producing treated waste water and a method for treating waste liquid, which are excellent in coagulation of detached layer pieces in waste liquid obtained when a detachment layer is detached from a laminate using a detachment liquid and have high transparency, and to provide a method for producing treated waste water and a method for treating waste liquid capable of exhibiting excellent detachment properties and reattachment suppression properties even when the recovered treated waste water is reused as the detachment liquid.SOLUTION: A method for producing treated waste water includes: a flocculation step in which detached layer pieces in a waste liquid are flocculated to obtain an aggregate; and a separation step of separating the aggregate. The waste liquid is obtained when a laminate having at least a plastic substrate layer and a release layer in contact with the plastic substrate layer is immersed in a release liquid to release the release layer and form the detached layer piece. The waste liquid contains the detached layer pieces and a chelating agent and / or a chelating compound.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing treated wastewater and a method for treating waste liquid.

Background Art

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

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

[0004] Regarding the material recycling of such packaging materials with a multilayer structure, for example, Patent Document 1 discloses a technique for detaching a printing layer from a laminate having a single-sided printing structure or a multilayer structure by treating the laminate provided with a release layer containing a polyurethane resin having a predetermined acid value with an aqueous alkali solution. Patent Document 2 discloses a technique for detaching an adhesive layer from a laminate having a multilayer structure by treating the laminate provided with a polyester polyol-based adhesive having a predetermined acid value with an aqueous alkali solution. Patent Document 3 discloses a waste liquid treatment method for recovering a water-soluble resin from waste liquid generated when removing a display coating having a printing substrate and a display coating containing a water-soluble resin from the printed matter.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the waste liquid obtained in the detachment step described in Patent Documents 1 and 2, detachment layer pieces such as a printed layer and an adhesive layer detached from the substrate are floating in a state of being finely dispersed by stirring. When this waste liquid is discarded, since it is a suspension containing a large amount of floating substances derived from the detachment layer, it is difficult to perform wastewater treatment. Also, even if the waste liquid is recovered and reused in the detachment step, since the detachment layer pieces are dispersed, the detachability decreases, and furthermore, there is a problem that the detachment layer pieces reattach to the plastic substrate. "Reattachment" means that a detachment layer such as a printed layer or an adhesive layer detached from the substrate is finely dispersed by stirring and reattaches to the substrate. A molding material obtained by recycling such a substrate causes a deterioration in appearance due to coloring and a deterioration in physical properties.

[0007] In Patent Document 3, a metal salt is added to the waste liquid after detachment and heat-treated to salting out and recover the water-soluble resin, but there are problems with the aggregability and the transparency of the wastewater after treatment, and the wastewater after treatment was not suitable for reuse.

[0008] Accordingly, an object of the present invention is to provide a method for producing treated wastewater and a method for treating wastewater, which are excellent in the aggregability of the release layer pieces in the wastewater obtained when the release layer is released from the laminate with the release liquid and further have high transparency. Another object of the present invention is to provide a method for producing treated wastewater and a method for treating wastewater, which can exhibit excellent releasability and reattachment suppression ability even when the recovered treated wastewater is reused as the release liquid.

Means for Solving the Problems

[0009] As a result of intensive studies by the present inventors, it has been found that the above problems can be solved by the method for producing treated wastewater and the method for treating wastewater shown below. That is, the present invention relates to the following [1] to

[16] .

[0010] [1] A method for producing treated wastewater, comprising an aggregation step of aggregating the release layer pieces in the wastewater to obtain aggregates, and a separation step of separating the aggregates, wherein the wastewater is obtained when a laminate comprising at least a plastic base material layer and a release layer in contact with the plastic base material layer is immersed in a release liquid to release the release layer to form the release layer pieces, and the wastewater contains the release layer pieces and a chelating agent and / or a chelating compound. The wastewater is obtained when a laminate comprising at least a plastic base material layer and a release layer in contact with the plastic base material layer is immersed in a release liquid to release the release layer to form the release layer pieces. The wastewater contains the release layer pieces and a chelating agent and / or a chelating compound.

[0011] [2] The method for producing treated wastewater according to [1], wherein the total content of the chelating agent and the chelating compound is 0.001 to 10% by mass based on 100% by mass of the total amount of the liquid component and the release layer pieces in the wastewater.

[0012] [3] The method for producing treated wastewater according to [1] or [2], wherein the total content of the chelating agent and the chelating compound is 0.001 to 45% by mass based on 100% by mass of the resin component in the wastewater.

[0013] [4] The method for producing treated wastewater according to any one of [1] to [3], wherein the wastewater contains a chelating agent.

[0014] [5] The method for producing treated wastewater according to [4], wherein the chelating agent contains at least one selected from the group consisting of aminocarboxylic acid-based chelating agents, hydroxycarboxylic acid-based chelating agents, and phosphoric acid-based chelating agents.

[0015] [6] The method for producing treated wastewater according to any one of [1] to [3], wherein the waste liquid contains a chelate compound.

[0016] [7] The method for producing treated wastewater according to [6], wherein the chelate compound contains a titanium chelate and / or a zirconium chelate.

[0017] [8] The method for producing treated wastewater according to any one of [1] to [7], wherein the waste liquid is basic.

[0018] [9] The method for producing treated wastewater according to any one of [1] to [8], wherein the waste liquid contains a surfactant.

[0019]

[10] The method for producing treated wastewater according to any one of [1] to [9], wherein the release layer is at least one layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer.

[0020]

[11] The method for producing treated wastewater according to any one of [1] to

[10] , wherein the release layer contains a chelating agent and / or a chelate compound.

[0021]

[12] The method for producing treated wastewater according to any one of [1] to

[11] , wherein the release liquid contains a chelating agent and / or a chelate compound.

[0022]

[13] The method for producing treated wastewater according to any one of [1] to

[12] , wherein the release layer contains an oil-soluble resin.

[0023]

[14] The method for producing treated wastewater according to any one of [1] to

[13] , wherein the release layer contains a compound having an acidic group.

[0024]

[15] The method for producing treated wastewater according to any one of [1] to

[14] , which is used for immersing a laminate including at least a plastic base material layer and a release layer in contact with the plastic base material layer in a release liquid containing the treated wastewater to release the release layer.

[0025]

[16] A waste liquid treatment method including a coagulation step of coagulating release layer pieces in waste liquid to obtain aggregates, and a separation step of separating the aggregates, wherein the waste liquid is obtained when a laminate including at least a plastic base material layer and a release layer in contact with the plastic base material layer is immersed in a release liquid to release the release layer to form the release layer pieces, the waste liquid treatment method, wherein the waste liquid contains the release layer pieces and a chelating agent and / or a chelate compound. [Effect of the Invention]

[0026] According to the present invention, it is possible to provide a method for producing treated wastewater and a method for treating waste liquid, which are excellent in the aggregability of release layer pieces in the waste liquid obtained when the release layer is released from the laminate with a release liquid and have high transparency. Further, according to the present invention, it is possible to provide a method for producing treated wastewater and a method for treating waste liquid, which can exhibit excellent releasability and anti-redeposition ability even when the recovered treated wastewater is reused as a release liquid. [Embodiments for Carrying Out the Invention]

[0027] Hereinafter, embodiments of the present invention will be described in detail. However, the description of the following embodiments or requirements is an example of the embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist thereof.

[0028] The method for producing treated wastewater according to an embodiment of the present invention includes a coagulation step of coagulating exfoliated layer pieces in the waste liquid to obtain aggregates, and a separation step of separating the aggregates from the treated wastewater. The waste liquid is obtained by immersing a laminate including at least a plastic base material layer and an exfoliating layer in contact with the plastic base material layer in an exfoliating liquid to exfoliate the exfoliating layer to obtain the exfoliated layer pieces, and the waste liquid contains a chelating agent and / or a chelate compound.

[0029] Since the waste liquid contains a chelating agent and / or a chelate compound, in the coagulation step, the finely dispersed exfoliated layer pieces can be coagulated with high efficiency. Then, in the separation step, by separating the obtained aggregates by filtration or the like, highly transparent treated wastewater can be obtained. Further, the treated wastewater can be reused as an exfoliating liquid for exfoliating the exfoliating layer from a laminate including a plastic base material and an exfoliating layer. Since the treated wastewater contains a chelating agent and / or a chelate compound, it is excellent in the exfoliating property of the exfoliating layer and the ability to suppress reattachment of the exfoliated layer pieces to the plastic base material.

[0030] <Method for producing treated wastewater> The method for producing treated wastewater according to an embodiment of the present invention includes a coagulation step of coagulating exfoliated layer pieces in the waste liquid to obtain aggregates, and a separation step of separating the aggregates. The waste liquid is obtained by immersing a laminate including at least a plastic base material layer and an exfoliating layer in contact with the plastic base material layer in an exfoliating liquid to exfoliate the exfoliating layer to obtain the exfoliated layer pieces, and the waste liquid contains a chelating agent and / or a chelate compound.

[0031] <Waste liquid treatment method> The waste liquid treatment method according to an embodiment of the present invention includes a coagulation step of coagulating exfoliated layer pieces in the waste liquid to obtain aggregates, and a separation step of separating the aggregates. The waste liquid is obtained when a laminate including at least a plastic base material layer and an exfoliating layer in contact with the plastic base material layer is immersed in an exfoliating liquid to exfoliate the exfoliating layer to obtain the exfoliated layer pieces, and the waste liquid contains a chelating agent and / or a chelate compound.

[0032] <Coagulation step> The method for producing treated drainage and the waste liquid treatment method according to an embodiment of the present invention include a coagulation step of coagulating exfoliated layer pieces in the waste liquid to obtain aggregates. The coagulation step can be performed, for example, by heat-treating the waste liquid containing exfoliated layer pieces and a chelate and / or a chelate compound at a temperature of a certain level or higher. The method of heat treatment is not particularly limited and can be performed by known means. When adding a chelate and / or a chelate compound to the waste liquid before the coagulation step, it is preferable to perform a stirring treatment.

[0033] From the viewpoint of aggregability, the temperature of the heat treatment in the coagulation step is preferably 20 to 80°C, more preferably 25 to 90°C or higher, and still more preferably 40 to 100°C or higher.

[0034] From the viewpoint of aggregability, the time of the heat treatment in the coagulation step is preferably 1 minute or longer, more preferably 5 minutes or longer, and still more preferably 10 minutes or longer. Also, from the viewpoint of working efficiency, the time of the heat treatment in the coagulation step is preferably 120 minutes or shorter, more preferably 90 minutes or shorter, and still more preferably 60 minutes or shorter.

[0035] <Separation step> The method for producing treated wastewater and the method for treating waste liquid according to embodiments of the present invention include a separation step of separating the above-mentioned aggregates. The separation step is preferably carried out after the above-mentioned aggregation step, and more preferably carried out after the above-mentioned aggregation step. The separation method is not particularly limited, and examples include centrifugation, filter filtration, decantation, rotary drum screen, automatic scraping bar screen, inclined wire screen, etc., but filtration is preferred.

[0036] <Waste liquid> In an embodiment of the present invention, the waste liquid is obtained when a laminate including at least a plastic base material layer and a release layer in contact with the plastic base material layer is immersed in a release liquid to release the release layer to form the release layer pieces. At this time, although the plastic base material remains in the waste liquid, the plastic base material may be recovered and removed, or may be subjected to the embodiments of the present invention without being recovered and removed. Further, in the waste liquid, the released release layer components such as the printed layer and the adhesive layer are finely dispersed by stirring and exist as release layer pieces.

[0037] The waste liquid contains a chelating agent and / or a chelate compound. By containing a chelating agent and / or a chelate compound in the waste liquid, the above-mentioned release layer pieces can be aggregated with high efficiency. The chelating agent and / or the chelate compound only need to be contained in the waste liquid in the aggregation step. That is, the chelating agent and / or the chelate compound may be added to the waste liquid before the aggregation step, may be contained in the above-mentioned release liquid in advance, or may be dissolved in the release liquid or the waste liquid from the above-mentioned release layer, but it is preferable to perform the above-mentioned addition before the aggregation step, more preferably contained in the above-mentioned release liquid in advance and perform the above-mentioned addition before the aggregation step, and still more preferably contained in the release liquid and the release layer in advance and perform the above-mentioned addition before the aggregation step.

[0038] The treated wastewater is not only easier to dispose of compared to the waste liquid, but as described above, it can also be reused as the release liquid. By containing a chelating agent and / or a chelate compound in the treated wastewater, it also contributes to improving the releasability and suppressing the reattachment during reuse.

[0039] [Chelating agent] The chelating agent is considered to have an effect of aggregating the desorbed layer pieces based on electrical interaction. Examples of the chelating agent include aminocarboxylic acid-based, hydroxycarboxylic acid-based, phosphoric acid-based, polyacrylic acid, acrylic acid-maleic acid copolymer, other compounds having two or more nitrogen atoms with coordination ability, and other compounds having two or more oxygen atoms with coordination ability.

[0040] From the viewpoint of aggregability, one or more selected from the group consisting of aminocarboxylic acid-based, hydroxycarboxylic acid-based, phosphoric acid-based, polyacrylic acid, and acrylic acid-maleic acid copolymer are preferable as the chelating agent, and one or more selected from the group consisting of aminocarboxylic acid-based, hydroxycarboxylic acid-based, and phosphoric acid-based are more preferable.

[0041] Examples of aminocarboxylic acid chelating agents include diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraminehexaacetic acid (TTHA), dicarboxymethylglutamic acid (GLDA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), 1,3-propanediaminetetraacetic acid (PDTA), 1,3-diamino-2-hydroxypropanetetraacetic acid (DPTA-OH), etc. Examples of hydroxycarboxylic acid chelating agents include gluconic acid, malic acid, succinic acid, citric acid, lactic acid, tartaric acid, etc. Examples of phosphoric acid chelating agents include hydroxyethylidenediphosphonic acid (HEDP), nitrilotris(methylenephosphonic acid) (NTMP), phosphonobutanetricarboxylic acid (PBTC), hexametaphosphate, etc. Examples of compounds having a coordination ability with two or more nitrogen atoms other than those mentioned above include ethylenediamine, bipyridine, phenanthroline, porphyrin, etc. Examples of compounds having a coordination ability with two or more oxygen atoms other than those mentioned above include crown ether, etc. However, this does not include the case where the chelating agent is a surfactant having a hydrophilic part and a lipophilic part.

[0042] [Chelate compound] The chelate compound is a compound formed by the chelating agent forming a complex with a metal ion. Examples of the metal ion include magnesium (II), calcium (II), strontium (II), manganese (II), nickel (II), barium (II), aluminum (III), gold (III), cerium (III, IV), cobalt (II, III), chromium (III), copper (II), europium (III), iron (II, III), gallium (III), germanium (IV), indium (III), lanthanum (III), palladium (II), platinum (II, IV), rhodium (II, III), ruthenium (II, III, IV), scandium (III), silicon (IV), samarium (III), titanium (IV), uranium (IV), zinc (II), zirconium (IV).

[0043] As the chelate compound used in the waste liquid of the present invention, from the viewpoint of aggregability, one or more selected from the group consisting of titanium chelate, zirconium chelate, and aluminum chelate are preferable, and among them, titanium chelate and / or zirconium chelate are preferable.

[0044] Examples of the titanium chelate include titanium alkoxides such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, tetramethyl titanate, tetra stearyl titanate, triethanolamine titanate, titanium acetylacetonate, titanium ethyl acetoacetate, titanium lactate, octylene glycol titanate, titanium tetraacetylacetonate, etc.

[0045] Examples of the zirconium chelate include zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxyacetylacetonate bis(ethyl acetoacetate), zirconium dibutoxy bis(ethyl acetoacetate), zirconium tetraacetylacetonate, etc.

[0046] Examples of aluminum chelates include aluminum diisopropionate ethylacetoacetate, aluminum tris(ethylacetoacetate), aluminum diisopropylate alkylacetoacetate, aluminum tris(acetylacetate), aluminum monoacetylacetate bis(ethylacetoacetate), aluminum dimethoxide monomethylacetoacetate, aluminum diisobutoxide monomethylacetoacetate, aluminum disec-butoxide monomethylacetoacetate, and the like.

[0047] These chelating agents and / or chelate compounds may be used alone or in combination of two or more. The total content ratio of the chelating agent and the chelate compound in the waste liquid (one may be 0) is preferably in the range of 0.001 to 10% by mass, more preferably in the range of 0.005 to 7% by mass, still more preferably in the range of 0.03 to 5% by mass, and particularly preferably in the range of 0.05 to 3% by mass, based on 100% by mass of the total amount of the liquid component and the exfoliated layer pieces in the waste liquid. Here, in the present invention, the liquid component in the waste liquid includes components that are completely dissolved in the liquid. When the above content ratio is 0.001% by mass or more, it is preferable because of excellent desorbability during reuse and aggregability of the exfoliated layer pieces during waste liquid treatment, and when it is 10% by mass or less, it is preferable from the viewpoint of the stability of the treated waste water.

[0048] From the viewpoint of improving desorbability during reuse of the treated waste water, the waste liquid is preferably basic. That is, the pH of the waste liquid is preferably greater than 7, more preferably greater than 7 and 14 or less, still more preferably in the range of 10 to 14, and particularly preferably in the range of 12 to 14. The basic compound for making the waste liquid basic is not particularly limited. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH) 2 ), ammonia, barium hydroxide (Ba(OH) 2 ), sodium carbonate (Na 2 CO 3) is preferably used. More preferably, it is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide.

[0049] [Surfactant] From the viewpoint of improving the releasability during the reuse of the treated wastewater, it is preferable that the waste liquid contains a surfactant. The surfactant may be added to the waste liquid before the coagulation step, may be contained in the release liquid in advance, or may be dissolved in the release liquid or the waste liquid from the above release layer, but it is preferably contained in the release liquid in advance. The surfactant mainly plays a role in improving the releasability of the release layer. This is presumably because the action of the surfactant makes it easier for the release liquid to penetrate into the release layer such as the primer layer, the printing layer, and the adhesive layer, and the releasability is promoted. Also, it is considered that the surfactant adsorbs on the surface of the released release layer pieces and the base material, preventing the reattachment of the finely dispersed release layer pieces. In addition, when increasing the amount of the laminate with respect to the release liquid in the separation and recovery, the laminate and the separated base material tend to curl with the ink pieces peeled off being caught, and even if immersed in the release liquid, it is difficult to cleanly remove the ink pieces and the like caught in the curl. However, since the release liquid contains a surfactant, the surfactant adsorbs on the surface of the laminate and the separated base material, suppressing the curling. As a result, the releasability can be improved and reattachment can be suppressed.

[0050] The HLB value of the surfactant in the embodiment of the present invention is preferably 7 or more. By having an HLB of 7 or more, excellent releasability and reattachment prevention as described above are exhibited. The HLB value of the surfactant is preferably 8 or more, more preferably 10 or more. Also, the HLB value of the surfactant is preferably 20 or less, more preferably 19 or less, still more preferably 17 or less. When the HLB value is 20 or less, it is preferable because it has excellent defoaming properties.

[0051] The HLB value is an index value regarding the affinity of a surfactant for water and oil, and is obtained by equally dividing the HLB value of a substance having no hydrophilic group as 0 and that of a substance having only a hydrophilic group as 20. The concept of HLB was proposed by William Griffin of Atlas Powder Company in 1949, and several methods for determining it by calculation have been proposed. In the embodiments of the present invention, the HLB value can be obtained from the following formula by the Griffin method. Formula) HLB = 20 × [(Molecular weight of hydrophilic group contained in surfactant) / (Molecular weight of surfactant)] Examples of the hydrophilic group contained in the surfactant include a hydroxyl group and an ethyleneoxy group.

[0052] Examples of the types of surfactants include nonionic, anionic, cationic, and amphoteric, and appropriate types and blending amounts can be selected and used according to the required characteristics. From the viewpoints of releasability and foaming property, preferably, it is at least one selected from the group consisting of an anionic surfactant and a nonionic surfactant. In addition, the surfactant preferably has a structure in which an alkylene oxide (hereinafter also referred to as AO) is added, because the releasability and the prevention of reattachment are improved.

[0053] (Nonionic surfactant) The nonionic surfactant is not particularly limited, but preferably, it is an alkylene oxide adduct to which an alkylene oxide is added. More preferably, it is a compound obtained by adding an alkylene oxide to alcohols having active hydrogen, a compound obtained by adding an alkylene oxide to amines, or a compound obtained by adding an alkylene oxide to fatty acids. The above addition may be either random addition or block addition. In addition, the number of carbon atoms of the alkylene oxide is preferably 2 to 4 carbon atoms. More preferably as the nonionic surfactant, it is an alcohol-based nonionic surfactant obtained by adding an alkylene oxide having 2 to 4 carbon atoms to alcohols.

[0054] [Alcohol-based nonionic surfactant] Examples of the alcohol-based nonionic surfactant include alkylene oxide adducts of primary or secondary alcohols having 8 to 24 carbon atoms in total, or alkylene oxide adducts of alkylphenols having 8 to 12 carbon atoms in total. The primary or secondary alcohol having 8 to 24 carbon atoms in total may be either saturated or unsaturated. Examples of the primary or secondary alcohol having 8 to 24 carbon atoms in total include lauryl alcohol, stearyl alcohol, oleyl alcohol, dodecyl alcohol, arachidyl alcohol, behenyl alcohol, lignoceryl alcohol, myristyl alcohol, and the like. Examples of the alkylene oxide added to the alcohols include ethylene oxide, propylene oxide, and butylene oxide, and it is preferable to contain ethylene oxide as an essential component. The number of moles of the alkylene oxide added is preferably 1 to 100 moles, more preferably 2 to 50 moles, per 1 mole of the alcohol or alkylphenol. This range is preferable because the desorbability is particularly excellent.

[0055] [Fatty acid-based nonionic surfactant] The structure of the fatty acid-based nonionic surfactant is not particularly limited. Examples thereof include alkylene oxide adducts of higher fatty acids having 10 to 24 carbon atoms in total, fats and oils composed of esters of the above-described saturated or unsaturated higher fatty acids having 10 to 24 carbon atoms and glycerin, and further alkylene oxide adducts of mixtures of the above-described fats and oils and polyhydric alcohols having 2 to 10 carbon atoms. The higher fatty acid having 10 to 24 carbon atoms in total may be either saturated or unsaturated. Examples of the higher fatty acids having 10 to 24 carbon atoms in total include saturated higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid; unsaturated higher fatty acids such as palmitoleic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, erucic acid, and ricinoleic acid. Examples of the polyhydric alcohols having 2 to 10 valences include ethylene glycol, propylene glycol, glycerin, polyglycerin, sorbitol, sorbitan, and sucrose. The type and the number of moles added of the alkylene oxide are the same as those described in the section of [Alcohol-based nonionic surfactant] mentioned above.

[0056] [Amine-based nonionic surfactant] Examples of the amine-based nonionic surfactant include AO adducts of saturated or unsaturated primary or secondary amines having 8 to 36 carbon atoms in total. Examples of the amines include 2-ethylhexylamine, di-2-ethylhexylamine, laurylamine, dilaurylamine, tetradecylamine, ditetradecylamine, hexadecylamine, dihexadecylamine, stearylamine, distearylamine, oleylamine, dioleylamine, and the like. Also, the type and the number of moles added of AO are the same as those described above.

[0057] (Anionic surfactant) The anionic surfactant is preferably a non-soap-based surfactant, and examples thereof include sulfonic acid-based anionic surfactants, sulfuric acid ester-based anionic surfactants, carboxylic acid-based anionic surfactants, and phosphoric acid ester-based anionic surfactants.

[0058] [Sulfonic acid-based anionic surfactant] Examples of the sulfonic acid-based anionic surfactant include alkyl sulfonic acid, alkyl benzene sulfonic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, alkyl methyl taurine, sulfosuccinic acid diester, alkylene oxide adducts of sulfonic acid, and salts thereof. Specific examples include hexane sulfonic acid, octane sulfonic acid, decane sulfonic acid, dodecane sulfonic acid, toluene sulfonic acid, cumene sulfonic acid, octyl benzene sulfonic acid, dodecyl benzene sulfonic acid, dinitrobenzene sulfonic acid, and lauryl dodecyl phenyl ether disulfonic acid, etc.

[0059] Sulfate-based anionic surfactant Examples of the sulfate-based anionic surfactant include sulfate esters (alkyl ether sulfates), alkylene oxide adducts of sulfate esters, and salts thereof. Specific examples include lauryl sulfate, myristyl sulfate, and polyoxyethylene lauryl ether sulfate, etc.

[0060] Carboxylic acid-based anionic surfactant Examples of the carboxylic acid-based anionic surfactant include alkyl carboxylic acid, alkyl benzene carboxylic acid, alkylene oxide adducts of carboxylic acid, and salts thereof. Specific examples include lauric acid, myristic acid, palmitic acid, stearic acid, polyoxyethylene lauryl ether acetic acid, and polyoxyethylene tridecyl ether acetic acid, etc.

[0061] Phosphate ester-based anionic surfactant Examples of the above-mentioned phosphate ester anionic surfactant include phosphate esters (alkyl ether phosphate esters), alkylene oxide adducts of phosphate esters, and salts thereof. Specific examples include octyl phosphate ester, lauryl phosphate ester, tridecyl phosphate ester, myristyl phosphate ester, cetyl phosphate ester, stearyl phosphate ester, polyoxyethylene octyl ether phosphate ester, polyoxyethylene lauryl ether phosphate ester, etc., which can be used.

[0062] The anionic surfactant preferably has an alkyl group having 2 to 24 carbon atoms or an alkenyl group having 2 to 24 carbon atoms, and more preferably has an alkyl group having 8 to 18 carbon atoms. The alkyl group or the alkenyl group may be linear or branched. When the anionic surfactant is an alkylene oxide adduct, examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and ethylene oxide is preferred. The number of moles of the added alkylene oxide is preferably 1 to 12 moles, more preferably 1 to 8 moles, per mole of alcohols or alkylphenols. Being within the above range is preferable because the desorbability is particularly excellent.

[0063] Examples of the salts constituting the above-mentioned anionic surfactant include metal salts such as sodium, potassium, magnesium, and calcium. These salts may be used alone or in combination of two or more. Among them, as the anionic surfactant, from the viewpoints of desorbability and prevention of reattachment, sulfonate type and phosphate type are preferred, and more preferably alkyl sulfonate, polyoxyalkylene alkyl ether sulfonate, polyoxyalkylene alkyl ether phosphate, etc.

[0064] (Cationic surfactant) Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Specifically, stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl tallow ammonium chloride, dimethyldioleylammonium chloride, methyl oleyl diethanol chloride, tetramethylammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide, dodecylbenzyltriethylammonium chloride, etc. can be used.

[0065] (Amphoteric surfactant) Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethyl glycine, and imidazoline derivatives.

[0066] These surfactants may be used alone or in combination of two or more. The content of the surfactant in the release liquid is preferably in the range of 0.001 to 7% by mass, more preferably in the range of 0.005 to 5% by mass, and still more preferably 0.03 to 3% by mass, based on the mass of the release liquid. It is preferable that the content is 0.001% by mass or more because it is excellent in releasability and reattachment prevention property, and it is preferable that the content is 7% by mass or less from the viewpoints of defoaming property and ink aggregability.

[0067] [Defoaming agent] From the viewpoint of improving the releasability during the reuse of the treated wastewater, it is preferable that the waste liquid contains a defoaming agent. The defoaming agent may be added to the waste liquid before the aggregation step, may be contained in the release liquid in advance, or may be dissolved in the release liquid or the waste liquid from the above release layer, but it is preferably contained in the release liquid in advance. In the embodiments of the present invention, by using an antifoaming agent in combination with the above-described surfactant, good antifoaming properties can be exhibited without reducing the releasability and the prevention of reattachment, and the foaming caused by the surfactant can be suppressed. Examples of the antifoaming agent include silicone-based compounds and non-silicone-based compounds.

[0068] (Silicone-based compound) Examples of the silicone-based compound include emulsion type, self-emulsifying type, oil type, oil compound type, and solvent type. The emulsion type is a silicone-based antifoaming agent obtained by emulsifying a silicone oil compound with an activator into an O / W type (oil in water type) emulsion. Examples include "KM-89" and "KM-98" manufactured by Shin-Etsu Chemical Co., Ltd., "FC2913" and "SILFOAM SE47" manufactured by Asahi Kasei Wacker Silicone Co., Ltd., and "BYK-015" and "BYK-1640" manufactured by BYK-Chemie Japan Co., Ltd. The self-emulsifying type is a silicone-based antifoaming agent with 100% active ingredient that becomes an emulsion state by dilution and mixing with water. Examples include "KS-540" and "X-50-1176" manufactured by Shin-Etsu Chemical Co., Ltd., "SILFOAM SD670" and "SILFOAM SD850" manufactured by Asahi Kasei Wacker Silicone Co., Ltd. The oil type is a 100% silicone oil antifoaming agent that does not contain solvents or additives. Examples include "KF-96" and "KF-6701" manufactured by Shin-Etsu Chemical Co., Ltd., "AK350" and "AK12500" manufactured by Asahi Kasei Wacker Silicone Co., Ltd., and "BYK-1770" manufactured by BYK-Chemie Japan Co., Ltd. The oil compound type is a silicone-based antifoaming agent in which silica particles are blended in silicone oil. Examples include "KS-66" and "KS-69" manufactured by Shin-Etsu Chemical Co., Ltd., "SILFOAM SC370" and "PULPSIL 22274VP" manufactured by Asahi Kasei Wacker Silicone Co., Ltd., and "BYK-017" and "BYK-018" manufactured by BYK-Chemie Japan Co., Ltd. The solvent type is a silicone-based defoamer in which silicone oil is dissolved in a solvent. Examples include "KS-602A" and "FA-600" manufactured by Shin-Etsu Chemical Co., Ltd., and "BYK-019" and "BYK-025" manufactured by BYK-Chemie Japan.

[0069] (Non-silicone-based compound) Examples of the non-silicone-based compound include fatty acid ester-based compounds, urea resin-based compounds, paraffin-based compounds, polyoxyalkylene glycol-based compounds, acrylic ester copolymers, ester-based polymers, ether-based polymers, amide-based polymers, emulsion types of mineral oil, polysiloxane adducts, fluorine-based compounds, vinyl-based polymers, acetylene alcohols, acrylic polymers, special vinyl-based polymers, ethylene glycol, and higher alcohols (such as octyl alcohol and cyclohexanol).

[0070] The defoamer may be used alone or in combination of two or more. The content of the defoamer in the release liquid is preferably in the range of 0.0001 to 5% by mass, more preferably in the range of 0.001 to 4.5% by mass, still more preferably in the range of 0.01 to 4% by mass, yet more preferably in the range of 0.02 to 3.5% by mass, and particularly preferably in the range of 0.03 to 3% by mass, based on the mass of the release liquid. When it is 0.0001% by mass or more, the defoaming property is excellent, and when it is 5% by mass or less, the releasability and the prevention of reattachment are excellent.

[0071] From the viewpoint that the defoamer has good alkali resistance and is less likely to reduce the releasability and the prevention of reattachment when combined with the surfactant, it is preferably at least one selected from the group consisting of emulsion-type silicone-based compounds, self-emulsifying silicone-based compounds, and non-silicone-based compounds.

[0072] <Release liquid> The release liquid preferably uses water and / or an organic solvent as a medium. If necessary, further, basic compounds, acidic compounds, fluorine-based compounds, surfactants, defoamers, etc. may be appropriately contained in consideration of the ease of detachment of the release layer described later. Examples of such a release liquid include a neutral aqueous solution, a basic aqueous solution, an acidic aqueous solution, and a fluorine-based solution. From the viewpoints of the environment and maintaining the properties of the recycled material using the recovered plastic substrate, an aqueous solution is preferred, and a basic aqueous solution is more preferred. These release liquids may be used after heating. The release liquid preferably contains 50% by mass or more of water, more preferably 70% by mass or more, and still more preferably 80% by mass or more.

[0073] The release liquid preferably contains a chelating agent and / or a chelate compound. When the release liquid contains a chelating agent and / or a chelate compound, the aggregability of the released layer pieces is further improved in the aggregation step described later, which also contributes to improving the releasability of the released layer when the treated wastewater is reused. The preferred forms of the chelating agent and the chelate compound contained in the release liquid can refer to the description in the above item of <waste liquid>. The content (including the case where one is 0) of the chelating agent and the chelate compound in the release liquid is preferably in the range of 0.001 to 10% by mass, more preferably in the range of 0.005 to 7% by mass, still more preferably in the range of 0.03 to 5% by mass, and particularly preferably in the range of 0.05 to 3% by mass, based on the mass of the release liquid. It is preferably 0.001% by mass or more because it is excellent in releasability during reuse and aggregability of the released layer pieces in the aggregation step, and preferably 10% by mass or less from the viewpoint of the stability of the release liquid.

[0074] [Basic compound] As described above, as the release liquid, a basic aqueous solution containing a basic compound is preferably used. The basic compound is not particularly limited. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH) 2 ), ammonia, barium hydroxide (Ba(OH) 2 ), sodium carbonate (Na 2 CO 3 ) are preferably used. More preferably, it is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide. The content of the basic compound in the basic aqueous solution is preferably in the range of 0.5 to 20% by mass, more preferably 1 to 15% by mass, and still more preferably 3 to 15% by mass, based on the mass of the basic aqueous solution.

[0075] [Acidic compound] When the release liquid is an acidic aqueous solution, it contains an acidic compound. Examples of the acidic compound include hydrogen chloride, sulfuric acid, nitric acid, citric acid, and oxalic acid.

[0076] [Fluorine-based compound] When the release liquid is a fluorine-based solution, it contains a fluorine-based compound. Examples of the fluorine-based compound include hydrogen fluoride, sodium fluoride, and ammonium fluoride.

[0077] Furthermore, the release liquid preferably contains a surfactant, and more preferably contains a surfactant and an antifoaming agent. Preferred forms of the surfactant and the antifoaming agent contained in the release liquid can be referred to the description in the section of <Waste liquid> above.

[0078] <Release> In the embodiments of the present invention, "release" means, for example, that the substrate is detached from the laminate by the release layer being dissolved or swollen and peeled off by the release liquid, and includes both forms: (1) the case where the release layer is dissolved and the substrate is detached, and (2) the case where the release layer is not dissolved but peeled off by neutralization or swelling, etc., and the substrate is detached.

[0079] <Laminate> In the embodiments of the present invention, the laminate includes at least a plastic substrate layer and a release layer in contact with the plastic substrate layer. The release layer in contact with the plastic substrate becomes a release piece by being detached by the release liquid described below, and the plastic substrate can be recovered and recycled. The laminate is preferably used as a packaging material. Here, the packaging material refers to any type such as a tray, film, pouch, box, etc., as long as it can protect the contents, but is more preferably a flexible packaging material.

[0080] <Configuration of laminate> The following is an example of the laminate structure in the embodiments of the present invention, but it is not limited thereto. In the following configurations, the "plastic substrate layer" does not necessarily have to be a single layer, and a plurality of substrates may be laminated. · Plastic substrate layer / Printing layer · Plastic substrate layer / Primer layer / Printing layer · Plastic substrate layer / Printing layer / Adhesive layer / Plastic substrate layer · Plastic substrate layer / Primer layer / Printing layer / Adhesive layer / Plastic substrate layer · Plastic substrate layer / Printing layer / Adhesive layer / Plastic substrate layer · Plastic substrate layer / Primer layer / Printing layer / Adhesive layer / Vapor deposition layer / Plastic substrate layer

[0081] In the laminate, the layer in contact with the plastic substrate layer is a release layer, and as described later, the release layer preferably contains a chelate compound and / or a chelating agent. However, not only the release layer, but also a layer that does not directly contact the plastic substrate, for example, the printing layer in contact with the primer layer, preferably contains a chelate compound and / or a chelating agent, which contributes to the improvement of the releasability during reuse and the cohesiveness during the aggregation process.

[0082] <Plastic substrate layer> The plastic substrate layer is composed of a single or a plurality of plastic substrates. When there are a plurality of plastic substrates, they may be the same or different. Further, when there are a plurality of plastic substrates, they may be adhered to each other via an adhesive layer. Further, when there are a plurality of plastic substrates, when the release layer detaches from the plastic substrate layer, they may separate into individual plastic substrates or remain integrated. Examples of the plastic substrate include polyolefin resin, polyester resin, polyamide resin, polystyrene resin, vinyl chloride resin, vinyl acetate resin, ABS resin, acrylic resin, acetal resin, polycarbonate resin, polyvinyl alcohol resin, and cellulose-based plastics.

[0083] From the perspective of reusing as a recycled substrate, the plastic substrate is preferably a polyolefin substrate containing a polyolefin resin. Examples of such substrates containing a polyolefin resin 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), acid-modified polypropylene, and copolymerized polypropylene.

[0084] The thickness of the plastic substrate layer is not particularly limited and may be appropriately selected according to the application. The thickness is preferably 5 to 1000 μm, more preferably 10 to 300 μm, still more preferably 10 μm to 100 μm, and particularly preferably 12 μm to 50 μm. Examples of the gas barrier substrate include aluminum foil, a metal vapor deposition layer such as aluminum, and a metal oxide vapor deposition layer such as silica or alumina. The thickness of the aluminum foil is preferably in the range of 3 to 50 μm from an economic perspective. Also, the aluminum foil, aluminum vapor deposition layer, and alumina vapor deposition layer dissolve in a basic aqueous solution and desorb, so they function as a desorption layer described later and can separate the adjacent polyolefin resin.

[0085] <Desorption layer> The desorption layer in the embodiment of the present invention is a layer that can be desorbed from the plastic substrate by a known desorbing liquid and preferably contains a chelating agent and / or a chelate compound. By including a chelating agent and / or a chelate compound in the desorption layer, the aggregability of the desorption layer pieces is further improved in the aggregation step described later, which also contributes to the improvement of the desorbability of the desorption layer during reuse. Preferred embodiments of the chelating agent and chelate compound contained in the desorption layer can refer to the descriptions of [Chelating agent] and [Chelate compound] in the section of <Waste liquid> above. The total content ratio (including the case where one is 0) of the chelating agent and chelate compound contained in the desorption layer is preferably 0.1 to 5% by mass, more preferably 0.5 to 4% by mass, based on the entire layer.

[0086] In one embodiment, the release layer is preferably a layer containing an oil-soluble resin. In the present invention, the oil-soluble resin refers to a resin that dissolves in a solvent satisfying at least one of the following (1) and (2). (1) The polar parameter δp of the Hansen solubility parameter (HSP) satisfies 0 ≦ δp ≦ 13.0 (2) The hydrogen bond parameter δh of the Hansen solubility parameter (HSP) satisfies 1.0 ≦ δh ≦ 23.0 The oil-soluble resin may itself be a compound having an acidic group described later, or may be used in combination with a compound having the acidic group.

[0087] Further, the release layer is preferably a layer containing a water-soluble resin or a layer containing a compound having an acidic group. By having a release layer containing a water-soluble resin or a compound having an acidic group in the laminate, the release liquid penetrates more into the release layer, the release layer is likely to swell, and the peeling of the base material is promoted. As a result, it is presumed that the releasability of the release layer is significantly increased. The release layer is preferably a layer containing a cured product of a water-soluble resin or a compound having an acidic group if it is water-soluble after curing or has unreacted acidic groups.

[0088] Further, since the release layer is a layer in contact with the plastic base material layer, it is preferably at least one layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer. That is, it is preferable that at least one layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer is a layer containing a water-soluble resin or a compound having an acidic group. The compound having an acidic group may be a resin or a low-molecular compound. These water-soluble resins or compounds having an acidic group may be used alone or in combination of two or more.

[0089] At least one layer selected from the group consisting of the above primer layer, printing layer, and adhesive layer may contain a binder resin component (hereinafter also referred to as a binder resin) that constitutes these layers, and the binder resin may contain a water-soluble resin or a resin having an acidic group, or may contain a binder resin and a low molecular compound having an acidic group. Hereinafter, the cases where the release layer is a primer layer, a printing layer, or an adhesive layer will be described respectively.

[0090] [Primer layer] When the release layer is a primer layer, the primer layer is disposed in contact with the plastic substrate, preferably contains a chelating agent and / or a chelate compound. Also preferably, it has a water-soluble resin or a compound having an acidic group, and plays a role of detaching the plastic substrate by dissolution or peeling with a release liquid.

[0091] (Water-soluble resin) The water-soluble resin may be any resin that can swell or dissolve in water and can be detached from the plastic substrate. The water may be heated to about 25 to 100 °C. Thereby, the primer layer can be detached with water (including warm water). Such resins can be selected from known resins as long as their water solubility is not impaired. For example, 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 phenol resins, water-soluble epoxy resins, water-soluble phenoxy resins, water-soluble urea resins, water-soluble melamine resins, polyvinyl alcohol resins, and modified products of these resins can be mentioned. These can be used alone or in combination of two or more. Among them, from the viewpoints of availability and detachability, polyvinyl alcohol (PVA) resin is preferably used. When the water-soluble resin has film-forming properties, a water-soluble resin may be used as the binder resin constituting the primer layer. Examples of the water-soluble resin include a resin that is water-soluble and has an acidic group, and a resin that is water-soluble and does not have an acidic group. The water-soluble resin may be, for example, a resin that is water-soluble and does not have an acidic group.

[0092] As the polyvinyl alcohol resin, in addition to unmodified polyvinyl alcohol, modified polyvinyl alcohol obtained by copolymerizing various monomers during the production of vinyl ester resins and saponifying them, or various post-modified polyvinyl alcohols in which various functional groups are introduced into unmodified polyvinyl alcohol by post-modification may be used. Further, those obtained by further post-modifying the modified polyvinyl alcohol may also be used. These modifications can be carried out within a range that does not impair the water solubility of the polyvinyl alcohol resin. These resins may be used alone or in combination of two or more.

[0093] Preferred examples of the polyvinyl alcohol resin include resins containing structural units having primary hydroxyl groups in the side chain and ethylene-modified polyvinyl alcohol resins. Among them, a polyvinyl alcohol resin containing structural units having primary hydroxyl groups in the side chain is preferred in terms of excellent melt moldability and further excellent water solubility. The number of primary hydroxyl groups in these structural units is usually 1 to 5, preferably 1 to 2, and more preferably 1. In addition to the primary hydroxyl groups, it is preferable to have secondary hydroxyl groups. Examples of the polyvinyl alcohol resin containing structural units having primary hydroxyl groups in the side chain include, for example, a modified polyvinyl alcohol resin containing side chain 1,2-diol structural units.

[0094] In an embodiment of the present invention, the saponification degree of the polyvinyl alcohol resin (measured in accordance with JIS K 6726) is usually 60 to 100 mol%. Further, the preferable range of the saponification degree varies depending on the modified type. For example, in the case of an unmodified polyvinyl alcohol resin, it is usually 60 to 99.9 mol%, preferably 70 to 99.0 mol%, more preferably 75 to 98.5%. The saponification degree of the modified polyvinyl alcohol resin containing a side chain 1,2-diol structural unit is usually 60 to 99.9 mol%, preferably 65 to 99.8 mol%, more preferably 70 to 99.5 mol%. If the saponification degree is too low, the water solubility tends to decrease. The saponification degree of the ethylene-modified polyvinyl alcohol resin modified with a small amount of ethylene is usually 60 mol% or more, preferably 70 to 99.5 mol%, particularly preferably 75 to 99.0 mol%. When the saponification degree is within the above range, it is preferable because the water solubility is excellent and the desorbability is good. Further, it is preferable because the coatability is also excellent when forming the primer layer.

[0095] The average degree of polymerization of the polyvinyl alcohol resin (measured in accordance with JIS K 6726) is usually 100 to 3000, preferably 150 to 2000, more preferably 180 to 1000, particularly preferably 200 to 800.

[0096] (Compound having an acidic group) As the compound having an acidic group, a resin having an acidic group or a low molecular compound having an acidic group may be used. Thereby, the primer layer can be desorbed with the basic aqueous solution described above. The resin having an acidic group may be, for example, a water-soluble resin or an oil-soluble resin as long as it has an acidic group.

[0097] Examples of the resin in the resin having an acidic group include cellulose-based resins, urethane resins, polyamide resins, vinyl chloride / vinyl acetate copolymers, ketone resins, polyester resins, and (meth)acrylic resins. Examples of the above acidic group include carboxy group, phosphoric acid group, sulfo group, sulfino group, etc. or their esters or salts. In addition, as the resin having an acidic group, a rosin-modified resin having an acid value such as maleated rosin or fumarated rosin can be used. In addition, as the resin having an acidic group, a polymerizable monomer having a carboxy group such as itaconic acid, maleic acid, fumaric acid, cinnamic acid; a polymerizable monomer that is an acid anhydride such as itaconic anhydride, maleic anhydride; a polymerizable monomer having a sulfonic acid group such as sulfonated styrene; a polymerizable monomer having a sulfonamide group such as vinylbenzenesulfonamide; A radical copolymer such as a styrene-(meth)acrylic resin, a styrene-(anhydrous)maleic acid resin, or a terpene-(anhydrous)maleic acid resin copolymerized with a polymerizable monomer having an acidic group, or an acid-modified polyolefin resin can be used. These may be used alone or in combination of two or more.

[0098] The low molecular weight compound having an acidic group refers to a compound having no molecular weight distribution and having a molecular weight of 1,000 or less. Examples of such compounds include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid; unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, sorbic acid; hydroxy acids such as lactic acid, malic acid, citric acid; aromatic carboxylic acids such as benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, cinnamic acid; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid; tricarboxylic acids such as aconitic acid; oxocarboxylic acids such as pyruvic acid, oxaloacetic acid; carboxylic acid derivatives such as amino acids, nitrocarboxylic acids; and acid anhydrides such as trimellitic anhydride, pyromellitic anhydride. The low molecular weight compound having an acidic group can form a primer layer by being used in combination with the resin having an acidic group described above or a known binder resin constituting a known primer layer.

[0099] From the perspective of recoating suitability, the primer layer preferably contains a compound having an acidic group. Further, from the perspective of printability, it preferably contains a urethane resin having an acidic group, an acrylic resin having an acidic group, or a rosin-modified resin. The primer layer may contain these resins alone or in combination of two or more.

[0100] [Urethane resin having an acidic group] The urethane resin having an acidic group is not particularly limited. For example, a urethane resin obtained by reacting a polyol having an acidic group with a polyisocyanate, a resin obtained by acid-modifying a hydroxyl group in a urethane resin obtained by reacting a polyol with a polyisocyanate, and a resin obtained by acid-modifying an amino group in a urethane-urea resin obtained by reacting a polyamine with an isocyanate group in a urethane resin obtained by reacting a polyol with a polyisocyanate can be mentioned. Further, as the urethane resin having an acidic group, a resin obtained by reacting a polyol containing a hydroxy acid and a polyisocyanate may be used. By using a hydroxy acid as the polyol, an acid value derived from a carboxy group can be imparted to the urethane resin, and the releasability can be improved. Further, when the urethane resin having an acidic group has an isocyanate group, a polyamine may be reacted with a part of the isocyanate group to introduce a urea bond to form a urethane-urea.

[0101] 《Polyol》 Polyol is a general term for compounds having at least two hydroxyl groups in one molecule. The number average molecular weight of the polyol is preferably 500 to 10,000, more preferably 1,000 to 5,000. The above number average molecular weight is calculated from the hydroxyl value of the polyol, and the hydroxyl value refers to the measured value according to JIS K 0070. When the number average molecular weight of the polyol is 500 or more, the flexibility of the primer layer is excellent and the adhesion to the plastic substrate is improved. When the number average molecular weight is 10,000 or less, the blocking resistance to the plastic substrate is excellent.

[0102] The polyol is not particularly limited, and more preferably, at least one polyol selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol is used. Further, the polyol may include other dimer diols, hydrogenated dimer diols, castor oil-modified polyols, and the like. That is, it is preferable that the urethane resin contains a structural unit derived from at least one polyol selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol. Since the ester bond site of the polyester polyol is hydrolyzed by alkali to improve the releasability, it is more preferably one containing a structural unit derived from polyester polyol. The content of the structural unit derived from polyol is preferably 10 to 75% by mass, more preferably 15 to 70% by mass, and still more preferably 20 to 65% by mass based on the total amount of the urethane resin. The content of the structural unit derived from polyester polyol is preferably 5% by mass or more, more preferably 30% by mass or more, still more preferably 60% by mass or more, and particularly preferably 80% by mass or more based on the total amount of the structural units derived from polyol.

[0103] 《Hydroxy Acid》 The above polyol may contain a hydroxy acid. The above hydroxy acid refers to a compound having both a hydroxyl group, which is an active hydrogen group, and an acidic functional group in one molecule. The acidic functional group refers to a functional group that can be neutralized with potassium hydroxide when measuring the acid value, and specifically includes a carboxy group, a sulfonic acid group, etc., and preferably a carboxy group. As such a hydroxy acid, for example, dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid are preferably used.

[0104] 《Polyisocyanate》 The above polyisocyanate is not particularly limited and can be selected from conventionally known polyisocyanates. Preferably, it contains a diisocyanate or a triisocyanate, and more preferably, it contains an aromatic, aliphatic or alicyclic diisocyanate. These may be used alone or in combination of two or more.

[0105] 《Polyamine》 The polyamine for forming the urethane urea is not particularly limited and is preferably a diamine compound. Also, a diamine having a hydroxyl group may be used in view of the ability to introduce a hydroxyl group into the urethane resin.

[0106] The acid value of the urethane resin having an acidic group is preferably 15 mgKOH / g or more, more preferably 15 to 70 mgKOH / g, and still more preferably 20 to 50 mgKOH / g. When it is 15 mgKOH / g or more, the desorbability with the desorbing liquid is good, so it is preferable. When it is 70 mgKOH / g or less, the substrate adhesion and retort resistance are good, so it is preferable. The hydroxyl value of the urethane resin is preferably 1 to 35 mgKOH / g, more preferably 10 to 30 mgKOH / g. When it is 1 mgKOH / g or more, the desorbability with the desorbing liquid is good, so it is preferable. When it is 35 mgKOH / g or less, the substrate adhesion is good, so it is preferable.

[0107] The weight average molecular weight of the urethane resin having an acidic group is preferably 10,000 to 100,000, more preferably 15,000 to 70,000, and still more preferably 15,000 to 50,000. The molecular weight distribution (Mw / Mn) of the urethane resin is preferably 6 or less. Mw represents the weight average molecular weight, and Mn represents the number average molecular weight. When the molecular weight distribution is 6 or less, it is excellent in desorbability, drying property of the primer composition, and retort resistance. Also, the smaller the molecular weight distribution, that is, the sharper the molecular weight distribution, the more uniformly the dissolution or peeling action by the desorbing liquid occurs, and the desorbability of the plastic substrate is improved. The molecular weight distribution is more preferably 5 or less, and still more preferably 4 or less. Also, the molecular weight distribution is preferably 1.5 or more, and more preferably 1.2 or more. In this specification, Mw, Mn, and molecular weight distribution (Mw / Mn) are polystyrene-equivalent values determined by gel permeation chromatography (GPC).

[0108] The urethane resin having an acidic group may have an amine value. When the urethane resin has an amine value, the amine value is preferably 0.1 to 20 mgKOH / g, more preferably 1 to 10 mgKOH / g. When within the above range, the adhesion to the substrate is excellent.

[0109] The urethane bond number of the polyurethane resin having an acidic group is preferably 1 to 3 mmol / g, more preferably 1.5 to 2 mmol / g. Also, the urea bond number is preferably 0 to 3 mmol / g, more preferably 0.2 to 1 mmol / g. Further, the total of the urethane bond number and the urea bond number is preferably 1 to 6 mmol / g, more preferably 1.7 to 3 mmol / g. By setting the urethane bond number and the urea bond number within the corresponding range, the releasability and the prevention of reattachment are improved.

[0110] 〔Acrylic resin having an acidic group〕 Examples of the acrylic resin having an acidic group include polymers obtained by polymerizing monomers containing (meth)acrylic monomers having acidic groups such as (meth)acrylic acid and maleic acid; resins obtained by polymerizing monomers containing (meth)acrylic monomers having a hydroxyl group or a glycidyl group and then modifying the functional group to introduce a carboxy group (for example, maleic anhydride-modified resins). The acid value of the acrylic resin having an acidic group is preferably 50 mgKOH / g or more, more preferably 100 mgKOH / g or more.

[0111] 〔Rosin-modified resin〕 The rosin-modified resin is a resin prepared using rosin as one of the raw materials. Rosin contains resin acids such as abietic acid, palustric acid, isopimaric acid, and levopimaric acid as a mixture. These resin acids contain hydrophilic and chemically active carboxyl groups, and some of them have conjugated double bonds. Therefore, various rosin-modified resins are prepared by, for example, condensation polymerization by combining polyhydric alcohols and polybasic acids, adding resole, which is a condensate of phenol, to the benzene ring contained in the rosin skeleton, or causing a Diels-Alder reaction with maleic anhydride or maleic acid, which is a dienophile, to add a maleic acid or maleic anhydride skeleton. Such rosin-modified resins are commercially available in various types, and it is also possible to obtain and use them.

[0112] Examples of rosin-modified resins include maleated rosin, fumarated rosin, rosin-modified maleic acid resin, rosin-modified fumaric acid resin, rosin-modified phenol resin, rosin-modified alkyd resin, and rosin-modified polyester resin. In the embodiments of the present invention, any rosin-modified resin may be used. Among these, those containing a site derived from at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride in their structure are preferably used. The "resin containing a site derived from at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride in its structure" means a resin prepared using at least one selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride as part of the raw materials. For example, rosin-modified maleic acid resin and rosin-modified fumaric acid resin obtained by condensation polymerization of maleic acid or fumaric acid as part of polybasic acids, maleated rosin and fumarated rosin having a structure in which maleic acid, maleic anhydride, fumaric acid, or fumaric anhydride is added by a Diels-Alder reaction as a dienophile, and resins obtained by polymerizing other chemical species using the functional groups contained therein, etc.

[0113] The acid value of the rosin-modified resin is preferably 10 to 400 mgKOH / g, more preferably 100 to 300 mgKOH / g.

[0114] (Other components) The primer layer may contain a water-soluble resin or a resin other than a compound having an acidic group. Examples of such resins include cellulose resins, polyamide resins, vinyl chloride resins such as vinyl chloride-vinyl acetate copolymer resins or vinyl chloride-acrylic copolymer resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, acrylic resins, styrene resins, dammar resins, styrene-acrylic copolymer resins, polyester resins, alkyd resins, terpene resins, phenol-modified terpene resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyrals, polyacetal resins, petroleum resins, and modified resins thereof. These resins may be used alone or in combination of two or more. Among them, the primer layer preferably contains at least one resin selected from the group consisting of cellulose resins, vinyl chloride resins, rosin resins, and acrylic resins. More preferably, it contains a vinyl chloride resin or an acrylic resin. The mass ratio of the urethane resin having an acidic group to the other resin (urethane resin having an acidic group: other resin) is preferably 95:5 to 50:50. When within the above range, when the printing layer peels off together with the primer layer in a basic aqueous solution, the printing layer peels off in a thin film state, which is preferable because it is easy to recover.

[0115] The primer layer may contain an extender pigment. Examples of the extender pigment include metal oxides such as silica, barium sulfate, kaolin, clay, calcium carbonate, magnesium carbonate, zinc oxide, and zirconium oxide. Among them, silica is preferably used, and hydrophilic silica is more preferably used. The average particle diameter of the extender pigment is preferably 0.5 to 10 μm, more preferably 1 to 8 μm. The content of the extender pigment is preferably 0.5 to 10% by mass in the primer layer, more preferably 1 to 5% by mass. When the average particle diameter and the content of the extender pigment are within the above ranges, the wettability of the printing layer is improved and the image quality is improved.

[0116] The primer layer may be a layer in which the urethane resin having the acidic group described above is crosslinked with a curing agent. By introducing a crosslinked structure into the primer layer, penetration and bleeding of the printing layer formed on the primer layer are suppressed, and excellent image quality can be exhibited. Examples of the curing agent include polyisocyanates. The polyisocyanate is not particularly limited and can be selected from conventionally known polyisocyanates. Examples thereof include aliphatic polyisocyanates and araliphatic polyisocyanates. These may be used alone or in combination of two or more.

[0117] The primer layer may further contain known additives. Examples of the known additives include dispersants, wetting agents, adhesion aids, leveling agents, defoaming agents, antistatic agents, viscosity modifiers, metal chelates, trapping agents, antiblocking agents, wax components other than the above, and silane coupling agents.

[0118] The thickness of the primer layer is preferably in the range of 0.3 to 10 μm, more preferably 0.6 to 5 μm, still more preferably 0.8 to 3 μm, and can be formed using a known method.

[0119] [Printing layer] The printing layer is a layer for forming an arbitrary printing pattern for the purpose of decoration, imparting aesthetic sense, indicating contents, expiration date, manufacturer or seller, etc., and includes a solid printing layer. When the release layer is a printing layer, the printing layer is disposed in contact with the plastic substrate and preferably contains a chelating agent and / or a chelate compound. Also preferably, it contains a water-soluble resin or a compound having an acidic group and plays a role of detaching the plastic substrate by dissolution or peeling with a release liquid. The printing layer preferably contains a compound having a water-soluble resin or an acidic group (excluding the water-soluble resin) and a colorant. Also, the method for forming the printing layer is not limited and can be formed using a known method. From the viewpoint of recoatability, the printing layer preferably contains a compound containing an acidic group. Also, from the viewpoint of printability, it preferably contains a urethane resin having an acidic group, an acrylic resin having an acidic group, or a rosin-modified resin. The printing layer may contain these resins alone or in combination of two or more. The above-mentioned water-soluble resin, compound having an acidic group, urethane resin having an acidic group, acrylic resin having an acidic group, and rosin-modified resin can incorporate 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 section of [primer layer] described above.

[0120] (Colorant) The printing layer may be colored or colorless and contains known colorants used in printing inks and paints. Such colorants are not particularly limited, and in addition to inorganic pigments, organic pigments, and dyes, metal powders that give metallic luster, near-infrared absorbing materials, and ultraviolet absorbing materials may also be used. Examples of inorganic pigments include colored pigments such as titanium oxide, red iron oxide, ultramarine blue, cobalt blue, carbon black, and graphite; extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. As organic pigments, soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, condensed polycyclic pigments, etc. are preferably used. In addition to these, pigments described by the generic names of Color Index can be appropriately used. Among them, when the stripping liquid is a basic aqueous solution, pigments that do not elute into the basic aqueous solution and have alkali resistance are preferred. By preventing the elution of the pigment, the reuse of the basic aqueous solution becomes easy. The alkali resistance of the pigment is generally estimated from the skeleton or structure of the pigment. Examples of pigments with alkali resistance include inorganic pigments, C.I. Pigment Blue 15, and C.I. Pigment Yellow 83. When the pigment is titanium oxide, the content of titanium oxide is preferably 20 to 80% by mass, more preferably 30 to 75% by mass in the printing layer. When the pigment is an inorganic pigment, extender pigment, or organic pigment other than titanium oxide, the content of each of these pigments is preferably 0.5 to 60% by mass, more preferably 10 to 50% by mass in the printing layer.

[0121] (Other components) The printing layer may contain a pigment derivative or a resin-type dispersant as a dispersant for the colorant. The pigment derivative is a compound in which a substituent is introduced into the skeleton of the pigment. The content of the pigment derivative is preferably 0.01 to 10% by mass, more preferably 0.05 to 6% by mass, and still more preferably 0.1 to 4% by mass based on the mass of the colorant. When it is 0.01% by mass or more, the peelability of the plastic substrate is excellent, and when it is 10% by mass or less, reattachment of the printing layer can be suppressed. The resin-type dispersant functions to adsorb to the colorant and stabilize the dispersion in printing ink or the like, 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 still more preferably 0.1 to 10% by mass based on the mass of the colorant. When it is 0.01% by mass or more, the peelability of the plastic substrate is excellent, and when it is 30% by mass or less, the water resistance of the printing layer is excellent.

[0122] The printing layer may contain a water-soluble resin or a resin other than a compound containing an acidic group. Examples of such resins include nitrocellulose-based, fiber materials such as cellulose acetate propionate, chlorinated polypropylene-based, vinyl chloride-vinyl acetate copolymer-based, polyester-based, acrylic-based, urethane resin-based and acrylic urethane-based, polyamide-based, polybutyral-based, cyclized rubber-based, and chlorinated rubber-based resins. These resins may be used alone or in combination of two or more.

[0123] The thickness of the printing 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.

[0124] [Adhesive layer] When the release layer is an adhesive layer, the adhesive layer is disposed in contact with the plastic substrate and preferably contains a chelating agent and / or a chelating compound. Also preferably, it contains a compound having an acidic group and plays a role of detaching the plastic substrate by dissolution or peeling with a release liquid. By further containing a resin having an acidic group or a low molecular compound having an acidic group in the adhesive layer, the adhesive layer can be detached using the basic aqueous solution described above. Preferred embodiments of the compound having an acidic group, the resin having an acidic group, and the low molecular compound having an acidic group can refer to the description of (compound having an acidic group) in the section of [Primer layer] described above. Also, the method for forming the adhesive layer is not limited and can be formed using a known method.

[0125] From the viewpoint of releasability, the adhesive layer may be a cured product of an adhesive containing a polyester polyol having an acidic group and at least one polyisocyanate selected from the group consisting of aliphatic polyisocyanates and araliphatic polyisocyanates. The above cured product corresponds to a resin having an acidic group. Also, the adhesive layer may be a cured product of an adhesive containing a polyester polyol, at least one polyisocyanate selected from the group consisting of aliphatic polyisocyanates and araliphatic polyisocyanates, and a low molecular compound having an acidic group.

[0126] (Polyester polyol) The polyester polyol only needs to have an acidic group and can be appropriately selected from known polyester polyols. By including such a polyester polyol, when an aqueous basic solution is used as the release liquid, having an ester bond with high affinity for the basic compound improves the releasability, which is preferable. The polyester polyol may be used alone or in combination of two or more.

[0127] The polyester polyol is not particularly limited, but a polyester polyol obtained by reacting a carboxy group component and a hydroxyl group component; a polyester polyol obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, poly(β-methyl-γ-valerolactone), etc. are preferably used. Examples of the above carboxy group component include dibasic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, phthalic anhydride, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, itaconic anhydride, etc., or their dialkyl esters or mixtures thereof. Examples of the above hydroxyl group component include diols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, butylene glycol, neopentyl glycol, trimethylolpropane, glycerin, 1,6-hexanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, 3,3′-dimethylolheptane, 1,9-nonanediol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol, polyether polyol, polycarbonate polyol, polyolefin polyol, acrylic polyol, polyurethane polyol, etc., or mixtures thereof. Two or more of the above carboxy group component and hydroxyl group component may be used in combination.

[0128] The polyester polyol may be a polyester urethane polyol obtained by reacting a polyisocyanate with a hydroxyl group in the polyol. Since the polyester polyol has a urethane bond, it exhibits excellent heat resistance and adhesiveness. Examples of the polyisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0129] Alternatively, the polyester polyol may be an acid anhydride-modified product obtained by reacting an acid anhydride with a hydroxyl group in the polyol. Thereby, a carboxy group which is an acidic group can be introduced into the polyester polyol. Examples of the acid anhydride include pyromellitic anhydride, mellitic anhydride, trimellitic anhydride, and trimellitic acid ester anhydride. Examples of the trimellitic acid ester anhydride include ethylene glycol bisanhydrotrimellitate and propylene glycol bisanhydrotrimellitate.

[0130] The acid value of the polyester polyol is preferably 5.0 mgKOH / g or more, more preferably 10.0 mgKOH / g or more. Also, the acid value of the polyester polyol is preferably 100 mgKOH / g or less, more preferably 80 mgKOH / g or less. When the acid value of the polyester polyol is within the above range, when it is brought into contact with the release liquid which is a basic aqueous solution, the basic aqueous solution penetrates and decomposes, and more excellent releasability is exhibited. When the adhesive contains a plurality of polyester polyols, the acid value of the entire polyester polyol can be determined from the acid value of each polyester polyol component and its mass ratio.

[0131] The number average molecular weight (Mn) of the polyester polyol is preferably from 3,000 to 25,000, more preferably from 5,000 to 20,000, and particularly preferably from 7,000 to 15,000. When the number average molecular weight of the polyester polyol is 3,000 or more, the coating property is improved, and when it is 20,000 or less, not only the coating property but also the releasability is improved, which is preferable.

[0132] A plurality of polyester polyols may be used in combination. For example, it may contain a polyester polyol having a number average molecular weight of 5,000 to 20,000. Further, in order to improve the adhesion to the substrate, it may contain a polyester polyol having a number average molecular weight of less than 3,000. The content of the polyester polyol having a number average molecular weight of less than 3,000 is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, based on the total mass of the polyester polyol. When it is 30% by mass or less, the retort resistance can be maintained when the laminate is used as a packaging material.

[0133] (Other polyols) The adhesive constituting the adhesive layer may contain other polyols other than the polyester polyol. The polyols that may be contained in addition to the polyester polyol are not particularly limited, and examples thereof include polycarbonate polyol, polycaprolactone polyol, polyether polyol, polyolefin polyol, acrylic polyol, silicone polyol, castor oil-based polyol, and fluorine-based polyol.

[0134] (Polyisocyanate) In order to constitute the adhesive layer, the polyisocyanate combined with the above-mentioned polyester polyol is preferably at least one selected from the group consisting of known aliphatic polyisocyanates and araliphatic polyisocyanates.

[0135] Examples of the aliphatic polyisocyanate include acyclic aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate; alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (hereinafter referred to as isophorone diisocyanate); polyisocyanates such as allophanate type, nurate type, biuret type, adduct type derivatives derived from the above diisocyanates, or their composites; and the like. As the derivative, the nurate type and the adduct type are preferred, and the adduct type is more preferred. As the aliphatic polyisocyanate, a polyisocyanate derived from hexamethylene diisocyanate (hereinafter also referred to as HDI), which easily ensures the balance between desorbability and laminate physical properties, is preferred.

[0136] Examples of the aromatic aliphatic polyisocyanate include aromatic aliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω′-diisocyanate-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene or a mixture thereof; polyisocyanates such as allophanate type, nurate type, biuret type, adduct type derivatives derived from the above aromatic aliphatic diisocyanates, or their composites; and the like.

[0137] (Other polyisocyanates) The adhesive may contain other polyisocyanates other than aliphatic polyisocyanates and aromatic aliphatic polyisocyanates as long as the effects of the present invention are not impaired. Examples of such polyisocyanates include aromatic diisocyanates such as toluene diisocyanate and diphenylmethane diisocyanate; polyisocyanates such as derivatives of the above diisocyanates, or their composites; and the like.

[0138] The blending ratio of the above polyol and polyisocyanate may be adjusted so that the molar ratio (NCO / OH) of the isocyanate groups of the polyisocyanate to the hydroxyl groups in the polyol is 0.3 to 10.0. Preferably, it is 0.3 to 7.0, and more preferably 0.5 to 5.0.

[0139] (Other components) In addition to the silane coupling agent, phosphoric acid or its derivative, leveling agent, defoaming agent, and reaction accelerator, the adhesive layer may contain an inorganic filler (for example, silica, alumina, mica, talc, aluminum flake, glass flake), a layered inorganic compound, a stabilizer (for example, antioxidant, heat stabilizer, ultraviolet absorber, hydrolysis inhibitor), rust preventive, thickener, plasticizer, antistatic agent, lubricant, anti-blocking agent, colorant, filler, crystal nucleating agent, catalyst for adjusting the curing reaction, etc.

[0140] [Release layer piece] The release layer piece is derived from the above release layer, and is obtained by immersing at least a plastic base material layer and a laminate provided with a release layer in contact with the plastic base material layer in a release liquid to release the release layer, and is a component derived from a printing layer, an adhesive layer, a primer layer, etc. The median diameter (D50) of the release layer piece in terms of volume basis is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1.0 μm or more, and particularly preferably 2.0 μm or more. When the particle size of the release layer piece is within the above range, the cohesiveness is improved, and further, it is effective in suppressing reattachment during reuse. The median diameter is measured by a laser diffraction particle size distribution measuring device.

[0141] From the viewpoint of cohesiveness, the content of the release layer piece is preferably 0.05 to 5.0% by mass, more preferably 0.1 to 2.5% by mass, and still more preferably 0.1 to 1.0% by mass in the total amount of 100% by mass of the liquid component and the release layer piece in the waste liquid.

[0142] <Substrate recovery> In the method for producing treated wastewater and the method for treating waste liquid according to an embodiment of the present invention, in order to recycle the detached plastic substrate, it is preferable that the plastic substrate in the waste liquid has been recovered in advance. However, the waste liquid may contain a plastic substrate, and for example, the substrate may be recovered after the aggregation step.

[0143] <Recycled substrate> After the above substrate recovery, for example, by washing and drying the obtained plastic substrate, a recycled substrate can be obtained. The removal rate of the release layer on the surface of the plastic substrate is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more with respect to the area of the release layer before detachment. In addition, the obtained recycled substrate can be processed into pellets by an extruder or the like and reused as a recycled resin.

[0144] <Reuse as the release liquid of the treated wastewater> The treated wastewater obtained by the production method of the present invention can be reused as a release liquid. That is, the treated wastewater can be used to immerse a laminate including at least a plastic substrate layer and a release layer in contact with the plastic substrate layer in a release liquid containing the treated wastewater of the wastewater treatment, and detach the release layer. Since the treated wastewater has little remaining release layer pieces, high transparency, and contains a chelating agent and / or a chelating compound, it can exhibit excellent releasability and reattachment suppression ability.

Examples

[0145] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the examples, parts and % represent parts by mass and mass % unless otherwise noted.

[0146] <Molecular weight and molecular weight distribution> The weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) were measured by GPC (gel permeation chromatography) and determined as the converted molecular weight using polystyrene as a standard substance. The measurement conditions are shown below. GPC apparatus: Shodex GPC-104 manufactured by Showa Denko K.K. Columns: The following columns were connected in series and used. Two Shodex LF-404 manufactured by Showa Denko K.K. Shodex LF-G manufactured by Showa Denko K.K. Detector: RI (differential refractometer) Measurement conditions: Column temperature 40 °C Eluent: Tetrahydrofuran Flow rate: 0.3 mL / min

[0147] <Acid value, hydroxyl value> The acid value and hydroxyl value were measured according to the method described in JIS K 0070 (1992).

[0148] <Production of primer composition and resin for printing ink> [Synthesis Example 1-1] (Polyurethane resin P1) While introducing nitrogen gas into a reactor equipped with a reflux condenser, dropping funnel, gas introduction tube, stirrer, and thermometer, 152.2 parts of PPA (a polyester polyol having a number-average molecular weight of 2,000 and consisting of a polycondensate of propylene glycol and adipic acid), 15.2 parts of PPG (a polyether polyol having a number-average molecular weight of 2,000 and consisting of polypropylene glycol), 13.6 parts of BD (1,4-butanediol), 99.8 parts of IPDI (isophorone diisocyanate), and 200 parts of NPAC (normal propyl acetate) were charged and reacted at 90 °C for 5 hours to obtain a urethane prepolymer solution having an isocyanate group at the terminal. Next, a mixture of 19.2 parts of AEA (2-(2-aminoethylamino)ethanol) and 350 parts of IPA (isopropyl alcohol) was added dropwise at room temperature over 60 minutes and then reacted at 70 °C for 3 hours to obtain a polyurethane resin solution. NPAC was added to the obtained polyurethane resin solution to adjust the solid content, and a solution of polyurethane resin P1 with a solid content concentration of 30%, a weight average molecular weight of 27,000, Mw / Mn = 3.1, an acid value of 0 mg KOH / g, and a hydroxyl value of 34.2 mg KOH / g was obtained.

[0149] [Synthesis Example 1-2] (Polyurethane Resin P2) While introducing nitrogen gas into a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet tube, a stirring device, and a thermometer, 135.7 parts of PPA, 13.6 parts of PPG, 28.3 parts of DMPA (2,2-dimethylolpropanoic acid), 105.7 parts of IPDI, and 200 parts of NPAC were charged and reacted at 90 °C for 5 hours to obtain a urethane prepolymer solution having isocyanate groups at the terminals. Next, a mixture of 16.7 parts of AEA and 350 parts of IPA was added dropwise at room temperature over 60 minutes, and then reacted at 70 °C for 3 hours to obtain a polyurethane resin solution. 150 parts of NPAC was added to the obtained polyurethane resin solution to adjust the solid content, and a solution of polyurethane resin P2 with a solid content concentration of 30%, a weight average molecular weight of 30,000, Mw / Mn = 3.0, an acid value of 39.3 mg KOH / g, and a hydroxyl value of 30.5 mg KOH / g was obtained.

[0150] [Synthesis Example 1-3] (Polyurethane Resin P3) While introducing nitrogen gas into a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet tube, a stirring device, and a thermometer, 108.6 parts of PPA, 40.7 parts of PEG (a polyether polyol having a number average molecular weight of 2,000 and consisting of polyethylene glycol), 28.3 parts of DMPA, 105.7 parts of IPDI, and 200 parts of NPAC were charged and reacted at 90 °C for 5 hours to obtain a prepolymer solution having isocyanate groups at the terminals. Next, a mixture of 16.7 parts of AEA and 150 parts of IPA was added dropwise at room temperature over 60 minutes, and then 10.0 parts of 28% aqueous ammonia and 690 parts of ion-exchanged water were gradually added to neutralize the carboxyl groups in the resin to make it water-soluble. Next, NPAC and IPA were distilled off under reduced pressure to obtain an aqueous solution of polyurethane resin P3 having a solid content concentration of 30%, a weight 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 in P3 is the value before neutralization.

[0151] <Primer layer-forming composition (primer composition)> [Production Example 1-1] (Primer composition S1) 87 parts of a polyurethane resin P2 solution, 5 parts of EA (ethyl acetate), 5 parts of IPA (isopropyl alcohol), and 3 parts of silica particles (P-73 manufactured by Mizusawa Chemical Co., Ltd.: hydrophilic silica particles with an average particle diameter of 3.8 μm) were stirred and mixed using a disper to obtain primer composition S1.

[0152] [Production Examples 1-2 to 4] (Primer compositions S2 to S4) Primer compositions S2 to S4 were obtained in the same manner as in Production Example 1-1, except that the raw materials and compounding ratios shown in Table 1 were changed.

[0153]

Table 1

[0154] The abbreviations in Table 1 are shown below. Z1: Ethylenediaminetetraacetic acid (EDTA) Y1: Tetraisopropyl titanate EA: Ethyl acetate IPA: Isopropyl alcohol

[0155] <Production of printing ink> [Production Example 2-1] (Printing ink R1) 10 parts of blue pigment P.B.15 (C.I.Pigment Blue 15), 25 parts of polyurethane resin P1 solution, 5 parts of PVC (vinyl chloride - vinyl acetate copolymer resin (Solvain TAO, manufactured by Nisshin Chemical, solid content 30%, EA solution)), 10 parts of EA, and 10 parts of IPA were mixed and stirred, and dispersion treatment was carried out for 20 minutes using a sand mill as a bead mill. Thereafter, 20 parts of polyurethane resin P1 solution, 10 parts of EA, and 10 parts of IPA were mixed and stirred to obtain printing ink R1. Table 2 shows the total compounding amounts during dispersion and post - compounding.

[0156] [Production Examples 2 - 2 to 4] (Printing Inks R2 to R4) Printing inks R2 to R4 were obtained by the same method as in Ink Production Example 2 - 1, except that the raw materials and compounding ratios shown in Table 2 were used. In Production Examples 2 - 3 and 2 - 4, a chelate was mixed together with the polyurethane resin.

[0157]

Table 2

[0158] The abbreviations in Table 2 are shown below. P.B.15: C.I.Pigment Blue 15 Z1: Ethylenediaminetetraacetic acid (EDTA) Y1: Tetraisopropyl titanate PVC: Vinyl chloride - vinyl acetate copolymer resin (Solvain TAO, manufactured by Nisshin Chemical, solid content 30%, EA solution) EA: Ethyl acetate IPA: Isopropyl alcohol

[0159] <Production of Polyol Used in Adhesive> [Synthesis Example 2 - 1] (Polyester Polyol B1) Into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen gas inlet tube, 124 parts of ethylene glycol, 212 parts of neopentyl glycol, 368 parts of 1,6 - hexanediol, 645 parts of isophthalic acid, 36 parts of adipic acid, and 265 parts of sebacic acid were charged. While stirring under a nitrogen stream, the temperature was raised to 250 °C, and an esterification reaction was carried out. A predetermined amount of water was distilled off, and the reaction was continued until the acid value reached 5 or less. Then, the pressure was gradually reduced, and a deglycolization reaction was carried out at 1 mmHg or less for 5 hours to obtain a polyester polyol. Thereafter, 35 parts of isophorone diisocyanate was gradually added, and the reaction was carried out at 150 °C for about 2 hours to obtain a polyester polyurethane polyol. To 100 parts of this polyester polyurethane polyol, 12.0 parts of ethylene glycol bisanhydrotrimellitate was added, and the reaction was carried out at 180 °C for about 2 hours. Then, it was diluted with ethyl acetate until the solid content concentration reached 50% to obtain a solution of a partially acid - modified polyester polyol B1 having a number - average molecular weight of 9,000 and an acid value of 30.3 mgKOH / g.

[0160] [Synthesis Example 2 - 2] (Polyester Polyol B2) Into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen gas inlet tube, 58 parts of ethylene glycol, 412 parts of diethylene glycol, 343 parts of neopentyl glycol, 517 parts of isophthalic acid, and 393 parts of adipic acid were charged. While stirring under a nitrogen stream, the temperature was raised to 250 °C, and an esterification reaction was carried out. A predetermined amount of water was distilled off, and the reaction was continued until the acid value reached 5 or less. Then, the pressure was gradually reduced, and a deglycolization reaction was carried out at 1 mmHg or less for 5 hours to obtain a polyester polyol. To 100 parts of this polyester polyol, 4.0 parts of trimellitic anhydride was added, and the reaction was carried out at 180 °C for about 2 hours. Then, it was diluted with ethyl acetate until the solid content concentration reached 50% to obtain a solution of a partially acid - modified polyester polyol B2 having a number - average molecular weight of 2,000 and an acid value of 23.5 mgKOH / g.

[0161] <Preparation of Polyisocyanate Solution> [Preparation Example 1] (Polyisocyanate C1) Coronate 2785 (a biuret-type polyisocyanate derived from hexamethylene diisocyanate, manufactured by Tosoh Corporation) was diluted with ethyl acetate and adjusted to a solid content concentration of 50% and NCO% = 9.6% to obtain a solution of polyisocyanate C1.

[0162] <Manufacture of Adhesive> [Production Example 3-1] (Adhesive D1) 90 parts of a polyester polyol B1 solution, 10 parts of a polyester polyol B2 solution, and 8 parts of a polyisocyanate C1 solution were blended, and ethyl acetate was added to prepare an adhesive solution with a solid content concentration of 30%.

[0163] [Production Examples 3-2 to 3] (Adhesives D2 to D3) Solutions of adhesives D2 to D3 were obtained by the same method as in Production Example 3-1, except that the raw materials and blending compositions shown in Table 3 were changed.

[0164]

Table 3

[0165] <Manufacture of Laminate> Hereinafter, the method for manufacturing a laminate will be described. The primer composition and the printing ink were each diluted with a mixed solvent of EA / IPA (mass ratio 70 / 30) to a viscosity of 15 seconds (25 °C, Zahn cup #3 (manufactured by Separation Co., Ltd.)) before use. Also, the coating amounts of the primer layer and the printing layer were adjusted to about 1.0 g / m 2 , 1.5 g / m 2 and printed.

[0166] [Production Example 4-1] (Laminate L1) For OPP (corona-treated stretched polypropylene film, thickness 20 μm), the diluted primer composition S1 and printing ink R1 were printed in this order using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate L1 having a structure of plastic substrate layer (OPP) / primer layer (S1) / printing layer (R1).

[0167] [Production Example 4-2, 5 to 8, 11] (Laminates L2, 5 to 8, 11) Laminates L2, 5 to 8, 11 were obtained in the same manner as in Production Example 4-1, except that the substrate, primer composition, and printing ink were changed to the contents described in Table 4.

[0168] [Production Example 4-3] (Laminate L3) For OPP, the diluted printing ink R2 was printed using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate L3 having a structure of plastic substrate layer (OPP) / printing layer (R2).

[0169] [Production Example 4-4] (Laminate L4) For OPP, the diluted primer composition S1 and printing ink R1 were printed in this order using a gravure printing machine equipped with a gravure plate with a plate depth of 30 μm, and dried at 50°C to obtain a laminate having a structure of OPP / S1 / R1. Next, on the printing layer of the obtained laminate, adhesive D1 was applied and dried using a dry laminator so that the dry coating amount was 2 g / m 2 After that, it was laminated with CPP (unstretched polypropylene film, thickness 50 μm) to obtain a laminate L4 having a structure of plastic substrate layer (OPP) / primer layer (S1) / printing layer (R1) / adhesive layer (D1) / plastic substrate layer (CPP).

[0170] [Production Example 4-9, 10] (Laminates L9, 10) Laminates L9, 10 were obtained in the same manner as in Production Example 4-4, except that the adhesive was changed to the contents described in Table 4.

[0171]

Table 4

[0172] The abbreviations in Table 4 are shown below. OPP: Corona-treated stretched polypropylene film, thickness 20 μm PET: Polyethylene terephthalate film, thickness 12 μm CPP: Unstretched polypropylene film, thickness 50 μm

[0173] <Manufacture of the release treatment liquid (release liquid)> [Production Example 5-1] (Release liquid A1) 2 parts of sodium hydroxide and 98 parts of water were blended and stirred with a disper to obtain release liquid A1.

[0174] [Production Examples 5-2 to 7] (Release liquids A5-2 to 7) Release liquids A5-2 to 7 were obtained in the same manner as in Production Example 5-1 except that the blending composition described in Table 5 was changed. In addition, polyoxyethylene lauryl ether (number of POE additions; 4, HLB; 9.7) was used as the surfactant, and BYK-1650 (manufactured by BYK Chemie Japan, silicone-based emulsion type antifoaming agent, solid content concentration 27.5%) was used as the antifoaming agent.

[0175]

Table 5

[0176] The abbreviations in Table 5 are shown below. Surfactant: Polyoxyethylene lauryl ether (number of POE additions; 4, HLB; 9.7) Antifoaming agent: BYK-1650 (manufactured by BYK Chemie Japan, silicone-based emulsion type antifoaming agent, solid content concentration 27.5%) Z1: Ethylenediaminetetraacetic acid (EDTA) Z3: 1-Hydroxyethane-1,1-diphosphonic acid (HEDP) Y1: Tetraisopropyl titanate

[0177] <Separation and recovery of laminate, waste liquid treatment, and reuse of treated drainage> [Example 1] In a 2000 mL stainless steel beaker, 1000 g of release liquid A1 and 20 g of a sample obtained by cutting laminate L1 into pieces of 1 cm × 1 cm were placed, and the mixture was stirred at 70 °C and 2000 rpm for 1 hour. Then, the plastic substrate after release was removed using a 20-mesh sieve, and the waste liquid containing the release layer pieces was recovered. To 693 g of the waste liquid recovered above, 7 g of ethylenediaminetetraacetic acid (Z1) was added and stirred, and then the mixture was allowed to stand at 70 °C (coagulation step), and the coagulability was evaluated. Thereafter, the aggregates were removed using a 300-mesh filter cloth (separation step), the treated drainage was recovered, and the transparency was evaluated. Next, in a 2000 mL stainless steel beaker, 500 g of the treated drainage recovered above and 10 g of a sample obtained by cutting laminate L1 into pieces of 1 cm × 1 cm were placed, and the mixture was stirred at 70 °C and 2000 rpm, and the releasability and re-adhesion properties during the reuse of the treated drainage were evaluated.

[0178] [Examples 2 to 36, Comparative Examples 1 to 2] Except for changing the laminate, release liquid, and wastewater treatment method described in Table 6, the coagulability, transparency of the treated drainage, and releasability and re-adhesion properties during the reuse of the treated drainage were evaluated by the same method as in Example 1. In the table, "waste liquid standard" indicates that the total amount of the liquid component and the release layer pieces in the waste liquid is the standard.

[0179] <Evaluation> The evaluation methods for the coagulability, transparency of the treated drainage, and releasability and re-adhesion properties during the reuse of the treated drainage are shown below. The evaluation results are shown in Table 6.

[0180] (Coagulability of release layer) After adding a chelate to the waste liquid and stirring, the mixture was allowed to stand at 70 °C, and the aggregation of the release layer pieces dispersed in the waste liquid was visually confirmed. The time taken for the aggregates to completely settle from the start of standing was evaluated according to the following criteria. A (excellent): less than 30 minutes from the start of standing to sedimentation B (Good): From the start of static settling to sedimentation, it takes more than 30 minutes and less than 1 hour. C (Fair): From the start of static settling to sedimentation, it takes 1 hour or more and less than 2 hours. D (Poor): Even after 2 hours from the start of static settling, it has not completely sedimented.

[0181] (Transparency of Treated Wastewater) Regarding the transparency of the treated wastewater, the total light transmittance was measured using a haze meter (manufactured by JEOL Ltd., SH7000) and evaluated according to the following criteria. A (Excellent): The total light transmittance is 90% or more. B (Good): The total light transmittance is 75% or more and less than 90%. C (Fair): The total light transmittance is 60% or more and less than 75%. D (Poor): The total light transmittance is less than 60%.

[0182] (Detachability during Wastewater Reuse) 30 minutes after the start of stirring, the substrate was sampled, washed with water, and dried. The removal rate of the printed layer on the obtained substrate was visually confirmed and evaluated according to the following criteria. A (Excellent): 100% of the printed layer peels off. B (Good): More than 90% and less than 100% of the printed layer peels off. C (Fair): 80% or more and less than 90% of the printed layer peels off. D (Poor): The printed layer does not peel off. Or less than 80% of the printed layer peels off.

[0183] (Redeposition during Wastewater Reuse) 1 hour after the start of stirring, the substrate was collected with a sieve having a mesh size of 1 mm, washed with water, and dried. 15 pieces of the obtained substrate were sampled, and the 15 substrates were stacked and the color values L * x , a * x , b * x were measured using a spectrophotometer (manufactured by X-rite, X-rite eXact). Similarly, for the substrate before printing, a substrate (10 g) cut into a size of 1 cm × 1 cm was immersed in the release liquid A1 (500 g), stirred at 70°C and 2000 rpm for 1 hour, washed with water and dried, and then 15 samples were taken. The 15 substrates were stacked and the color values L * y , a * y , b * y were measured. The color difference ΔE was calculated according to the following formula, and the re-adhesion property was evaluated according to the following criteria. (Formula) ΔE = ((L * x - L * y ) 2 + (a * x - a * y ) 2 + (b * x ― b * y ) 2 ) 1 / 2 A (excellent): ΔE is less than 3 B (good): ΔE is 3 or more and less than 10 C (acceptable): ΔE is 10 or more and less than 20 D (unacceptable): Other than A to C

[0184]

Table 6

[0185] The abbreviations in Table 6 are shown below. Z1: Ethylenediaminetetraacetic acid (EDTA) Z2: Nitrilotriacetic acid (NTA) Z3: 1-Hydroxyethane-1,1-diphosphonic acid (HEDP) Z4: Citric acid Y1: Tetraisopropyl titanate Y2: Zirconia ZC-750 Y3: Fe-EDTA Y4: Zn-EDTA

[0186] From the above evaluation results, it was shown that the method of the present invention can provide a method for producing treated wastewater with excellent aggregability of the release layer pieces in the wastewater obtained when the release layer is detached from the laminate with a release liquid and with high transparency, and a method for treating the wastewater. Furthermore, it was shown that even when the treated wastewater is reused, the plastic substrate can be easily detached from the laminate, and a high-quality recycled substrate with little reattachment of the release layer can be obtained.

Claims

1. A method for producing treated wastewater, comprising a coagulation step of coagulating exfoliated layer pieces in wastewater to obtain coagulated matter, and a separation step of separating the coagulated matter, wherein the wastewater is obtained when a laminate including at least a plastic base material layer and an exfoliating layer in contact with the plastic base material layer is immersed in an exfoliating liquid to exfoliate the exfoliating layer to obtain the exfoliated layer pieces, the wastewater contains the exfoliated layer pieces and a chelating agent and / or a chelate compound.

2. The method for producing treated wastewater according to claim 1, wherein the total content of the chelating agent and the chelate compound is 0.001 to 10% by mass based on 100% by mass of the total amount of the liquid component and the exfoliated layer pieces in the wastewater.

3. The method for producing treated wastewater according to claim 1 or 2, wherein the total content of the chelating agent and the chelate compound is 0.001 to 45% by mass based on 100% by mass of the resin component in the wastewater.

4. The method for producing treated wastewater according to claim 1 or 2, wherein the wastewater contains a chelating agent.

5. The method for producing treated wastewater according to claim 4, wherein the chelating agent contains at least one selected from the group consisting of aminocarboxylic acid-based chelating agents, hydroxycarboxylic acid-based chelating agents, and phosphoric acid-based chelating agents.

6. The method for producing treated wastewater according to claim 1 or 2, wherein the wastewater contains a chelate compound.

7. The method for producing treated wastewater according to claim 6, wherein the chelate compound contains a titanium chelate and / or a zirconium chelate.

8. The method for producing treated wastewater according to claim 1 or 2, wherein the wastewater is basic.

9. The method for producing treated wastewater according to claim 1 or 2, wherein the wastewater contains a surfactant.

10. The method for producing treated wastewater according to claim 1 or 2, wherein the exfoliating layer is at least one layer selected from the group consisting of a primer layer, a printing layer, and an adhesive layer.

11. The method for producing treated wastewater according to claim 1 or 2, wherein the exfoliating layer contains a chelating agent and / or a chelate compound.

12. The method for producing treated wastewater according to claim 1 or 2, wherein the exfoliating liquid contains a chelating agent and / or a chelate compound.

13. The method for producing treated wastewater according to claim 1 or 2, wherein the exfoliating layer contains an oil-soluble resin.

14. The method for producing treated wastewater according to claim 1 or 2, wherein the exfoliating layer contains a compound having an acidic group.

15. The method for producing treated wastewater according to claim 1 or 2, which is used by immersing a laminate comprising at least a plastic base material layer and a release layer in contact with the plastic base material layer in a release liquid containing the treated wastewater to release the release layer.

16. A waste liquid treatment method including a coagulation step of coagulating the release layer pieces in the waste liquid to obtain an aggregate, and a separation step of separating the aggregate, wherein the waste liquid is obtained when a laminate comprising at least a plastic base material layer and a release layer in contact with the plastic base material layer is immersed in a release liquid to release the release layer to obtain the release layer pieces, and the waste liquid contains the release layer pieces and a chelating agent and / or a chelate compound.

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