Production method of laminate having removable coating film and recycled base material

Abstract

To provide a laminate which has a coating film removable from a base material by treatment with an alkaline solution and which can suppress coloring of the alkaline solution after removal when the coating film is removed.SOLUTION: The present invention relates to a laminate having a coating film capable of being removed from a film base material by treatment with an alkaline solution. The coating film is printed matter having a first layer containing at least a binder resin, a second layer arranged on the first layer and containing a pigment and the binder resin, and a varnish layer arranged on the second layer. The present invention also provides a production method of a recycled base material obtained by treating the printed material with an alkaline solution to remove the first layer, the second layer, and the varnish layer from the plastic film.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a laminate having a removable coating on a substrate, and a method for producing a recycled substrate having a removable coating. [Background technology]

[0002] In recent years, the marine plastic problem caused by plastics discarded or dumped in the ocean being broken down in seawater and broken down into microplastics (microplasticization) has become evident. It is feared that these microplastics will enter the bodies of marine organisms, become concentrated, and affect the health of seabirds and humans through the food chain. One way to improve this marine plastic problem is recycling. Improving the recycling rate of resources such as soft packaging materials and plastic bottles will prevent plastics from entering the ocean. However, with current recycling, there is an issue that the film printed on the plastic substrate does not come off during the recycling process and gets mixed into the plastic, causing a deterioration in color and physical properties, and reducing the value of the recycled plastic. If it is possible to remove the film from the plastic substrate during the recycling process and solve this problem, the value of the recycled plastic will increase, leading to the entry of new recyclers and the establishment of separate collection by local governments. It is believed that this will improve the recycling rate and improve the marine plastic problem. Therefore, there is a demand for the development of a composition that allows the film to be removed during the recycling process.

[0003] In addition, organic solvent-based printing inks, which are widely used as film-forming materials for plastic substrates, are being replaced by toluene-free and methyl ethyl ketone (MEK)-free materials out of consideration for their impact on worker health and the environment. Therefore, materials that solve the above issues must be developed with this in mind.

[0004] In the prior art, a method is disclosed in which a film containing a styrene-acrylic acid resin, a phenolic resin, and a styrene-maleic acid resin as a vehicle printed on a heat-shrinkable PET film is removed with alkaline water (Patent Document 1). Similarly, a method is disclosed in which a coating layer containing a styrene-maleic acid resin, a rosin-maleic acid resin, and an acrylic acid copolymer resin is placed between printed layers of a heat-shrinkable PET film, and the coating layer is removed with alkaline water (Patent Documents 2 and 3). Furthermore, organic solvent-based printing inks for alkaline water removal that use urethane resins having an acid value as a binder resin are also disclosed (Patent Documents 4, 5, and 6). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3822738 [Patent Document 2] Patent No. 4653913 [Patent Document 3] Patent No. 4451071 [Patent Document 4] Patent No. 6638802 [Patent Document 5] Patent No. 6631964 [Patent Document 6] JP 2020-169280 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the coatings described in Patent Documents 1 to 6 have the problem that the alkaline solution after the desorption treatment is colored with a color derived from the colorant contained in the printing ink. If the alkaline solution after the desorption treatment is colored, a decolorization treatment is required in addition to an alkaline neutralization treatment when discharging the water. In addition, a problem has been pointed out in which plastics that have been deinked are recolored by the colored deinking treatment solution, resulting in a decrease in recycling value.

[0007] For this reason, it is required that the alkaline treatment solution used after the desorption treatment does not cause coloration derived from the ink.

[0008] Decolorization treatments include coagulation and sedimentation treatments, biological treatments (biological treatments), and oxidation treatments using oxidizing agents such as ozone (O3). However, biological treatments are insufficient in reducing the color of colored solutions derived from colorants, while oxidation treatments increase costs in order to achieve a sufficient color reduction effect. There are also problems with the decolorization treatment itself being an environmental burden in terms of energy.

[0009] An object of the present invention is to provide a laminate having a coating that can be removed from a substrate by treatment with an alkaline solution, and that, when the coating is removed, can suppress coloration of the alkaline solution after the removal. [Means for solving the problem]

[0010] As a result of extensive research into solving the above problems, the inventors discovered that the above problems could be solved by providing a varnish layer on top of a layer containing a pigment that affects the coloring of the alkaline solution, and thus completed the present invention.

[0011] That is, the present invention is a laminate having a coating that can be detached from a film substrate by treatment with an alkaline solution, the coating being a printed matter having at least a first layer containing a binder resin, a second layer provided on the first layer and containing a pigment and a binder resin, and a varnish layer provided on the second layer.

[0012] The present invention also provides a method for producing a recycled substrate, which is a laminate having a coating that can be detached from a film substrate by treatment with an alkaline solution, the coating being for a printed matter having at least a first layer containing a binder resin, a second layer containing a pigment and a binder resin provided on the first layer, and a varnish layer provided on the second layer, and which is obtained by treating the first layer, second layer, and third layer with an alkaline solution to detach them from the plastic film. Effect of the Invention

[0013] According to the present invention, a printed matter can be obtained on which a coating that can be detached from a plastic film is formed by treatment with an alkaline solution. When the coating is detached by treatment with an alkaline solution, coloring of the alkaline solution after detachment can be suppressed, and the plastic film after the coating is detached can be reused as a high-quality recycled substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in detail below. Note that the following description of the constituent elements is merely an example for explaining the present invention, and the present invention is not limited to the contents thereof.

[0015] The printed matter of the present invention has a multi-layer structure in which a first layer is laminated on a plastic film, a second layer is provided on the first layer, and a varnish layer is provided on the second layer. The first layer is preferably a white printed layer having a white pigment or a primer layer having no pigment. The second layer is preferably a color printed layer having a pigment other than a white pigment. The third layer is a layer in direct contact with the second layer and is a varnish layer containing no pigment.

[0016] It is generally known that when a film containing a binder resin and a pigment is removed by treatment with an alkaline solution, the alkaline solution after removal is significantly colored. However, in the case of the printed matter of the present invention, the coloring of the alkaline solution after removal is significantly suppressed, and a clear alkaline solution is obtained. Although the mechanism of action by which such a significant effect of suppressing coloring of the alkaline solution after removal is obtained has not been fully elucidated, an example of a presumed mechanism of action will be described.

[0017] In general printed matter, the binder resin, which has low resistance to alkali, is decomposed to allow the printed film to be detached from the substrate, while the binder resin is decomposed by the alkaline solution, causing the pigment to diffuse into the alkaline solution, and the alkaline solution is colored with the color derived from the pigment. In contrast, in the printed matter of the present invention, the varnish layer, which is a component, is provided in close contact with the pigment-containing film, so that the pigment-containing film does not dissolve in the alkaline solution and peels off together with the varnish layer when peeled off, thereby suppressing coloration of the alkaline solution.

[0018] The coating provided on the printed matter of the present invention exhibits a remarkable effect of inhibiting discoloration of the alkaline solution after detachment when the coating is detached from the substrate by treatment with an alkaline solution. This makes it possible to prevent water pollution and environmental load caused by colored wastewater. In addition, since raw materials and manufacturing equipment for decolorization of colored wastewater are not required, it is possible to reduce manufacturing costs when recycling substrates. Furthermore, since no step for decolorization is required, the recycling efficiency of the substrate is excellent, and the alkaline solution can be reused, it is very useful industrially.

[0019] <First liquid ink composition forming the first layer> First, the first liquid ink composition forming the first layer will be described. The first liquid ink composition contains a binder resin, an organic solvent, and water and various additives as necessary. The first liquid ink composition also preferably contains a pigment, particularly a white pigment.

[0020] <<Binder resin>> The binder resin used in the present invention is not particularly limited as long as it is a general-purpose binder resin in gravure ink or flexo ink, and examples thereof include cellulose-based resins such as cellulose acetate propionate (CAP), cellulose acetate butyronate (CAB), cellulose nitrate, and other cellulose-based resins, urethane-based resins, rosin-based resins, chlorinated polyolefin resins, polyamide-based resins, acrylic resins, polyvinyl-based resins such as vinyl chloride-vinyl acetate copolymer resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, and polyvinyl chloride resins, polyester resins, alkyd resins, ketone resins, cyclized rubber, chlorinated rubber, butyral, and petroleum resins.

[0021] Among these, from the viewpoint of contributing to the promotion of detachment of the coating by treatment with an alkaline solution, resins having acidic groups, such as cellulose-based resins, ketone resins, polyester resins, rosin-modified maleic acid resins, rosin-modified fumaric acid resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubber, chlorinated rubber, butyral resins, and petroleum resins, are preferred.

[0022] In order to achieve both adhesion to the film substrate and promotion of detachment in the detachment treatment, it is preferable to use a cellulose-based resin in combination with a polyurethane resin, or a cellulose-based resin in combination with an acrylic resin, and it is also preferable to further add a rosin-based resin such as a rosin-modified maleic acid resin or a rosin-modified fumaric acid resin to these combined resins. Among these, a combination selected from soluble cellulose / urethane resin, soluble cellulose / acrylic resin, or soluble cellulose / rosin resin is preferable.

[0023] In the binder resin of the first layer, the total amount of the urethane-based resin, nitrocellulose, acrylic-based resin, and rosin-based resin is preferably 15 mass% or more, preferably 30 mass% or more, preferably 40 mass% or more, and preferably 50 mass% or more, relative to the total amount of the binder resin of the first layer.

[0024] (Cellulose-based resin) Examples of cellulose resins include cellulose acetate propionate, cellulose acetate butyrate and other cellulose ester resins, nitrocellulose (also called soluble cellulose), hydroxyalkyl cellulose, and carboxyalkyl cellulose. The cellulose ester resin preferably has an alkyl group, and examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, and a hexyl group, and the alkyl group may further have a substituent.

[0025] (nitrocellulose) Of the above, cellulose-based resins are preferably nitrocellulose. The molecular weight is preferably 5,000 to 200,000 in weight average molecular weight, more preferably 10,000 to 50,000. The glass transition temperature is preferably 120°C to 180°C. In particular, when used in combination with polyurethane resin, it is expected that blocking resistance and other physical properties of the ink film will be improved.

[0026] Nitrocellulose is preferably obtained by reacting natural cellulose with nitric acid to replace three hydroxyl groups in the six-membered ring of the anhydrous glucopyranose group in the natural cellulose with nitric acid to produce a nitric acid ester.

[0027] The use of nitrocellulose is suitable because it can provide high dispersibility in white pigments and therefore can improve the strength of the printing ink coating. The nitrocellulose preferably has a nitrogen content of 10 to 13% by mass and an average degree of polymerization of 30 to 500, and more preferably has a nitrogen content of 10 to 13% by mass and an average degree of polymerization of 45 to 290.

[0028] The amount of soluble nitrocellulose added is preferably 1 to 20% by mass, and more preferably 5 to 10% by mass, based on the total amount of ink solids, from the viewpoint of contributing to the promotion of film detachment.

[0029] (Polyurethane resin) The polyurethane resin is not particularly limited as long as it is a polyurethane resin obtained by reacting a polyol with a polyisocyanate. For example, various known polyols generally used in the production of polyurethane resins can be used as the polyol, and one or more of them may be used in combination. For example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5 pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropionate, etc. Saturated or unsaturated low molecular weight polyols (1), such as ethylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, and pentaerythritol; these low molecular weight polyols (1) and sebacic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, and trimellitic acid. polyester polyols (2) obtained by dehydration condensation or polymerization of polyvalent carboxylic acids such as pyromellitic acid or their anhydrides; polyester polyols (3) obtained by ring-opening polymerization of cyclic ester compounds, such as lactones such as polycaprolactone, polyvalerolactone, and poly(β-methyl-γ-valerolactone); polycarbonate polyols (4) obtained by reacting the low molecular weight polyols (1) or the like with, for example, dimethyl carbonate, diphenyl carbonate, ethylene carbonate, phosgene, or the like; polybutadiene glycols (5); glycols (6) obtained by adding ethylene oxide or propylene oxide to bisphenol A; and acrylic polyols (7) obtained by copolymerizing one or more hydroxyethyl groups, hydroxypropyl acrylate, hydroxybutyl acrylate, or the like, or the corresponding methacrylic acid derivatives, in one molecule, with, for example, acrylic acid, methacrylic acid, or an ester thereof.

[0030] Examples of the polyisocyanate include various known aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates that are generally used in the production of polyurethane resins. For example, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1-methyl-2,4-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-2,5-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-3,5-phenylene diisocyanate, 1-ethyl-2,4-phenylene diisocyanate, 1-isopropyl-2,4-phenylene diisocyanate, 1,3-dimethyl-2,4-phenylene diisocyanate, 1,3-dimethyl-4,6-phenylene diisocyanate, 1,4-dimethyl-2,5-phenylene diisocyanate, diethylbenzene diisocyanate, diisopropylbenzene diisocyanate, 1-methyl-3,5-diethylbenzene diisocyanate, Aromatic polyisocyanates such as zene diisocyanate, 3-methyl-1,5-diethylbenzene-2,4-diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 1-methyl-naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 1,1-dinaphthyl-2,2'-diisocyanate, biphenyl-2,4'-diisocyanate, biphenyl-4,4'-diisocyanate, 3-3'-dimethylbiphenyl-4,4'-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, and diphenylmethane-2,4-diisocyanate;Aliphatic or alicyclic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclopentylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-di(isocyanatemethyl)cyclohexane, 1,4-di(isocyanatemethyl)cyclohexane, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate, and 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, these diisocyanate compounds can be used alone or in combination of two or more kinds.

[0031] A chain extender can also be used. Examples of the chain extender include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and the like, as well as amines having a hydroxyl group in the molecule, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. These chain extenders can be used alone or in combination of two or more.

[0032] In addition, a monovalent active hydrogen compound can be used as a terminal blocking agent for the purpose of stopping the reaction. Examples of such compounds include dialkylamines such as di-n-butylamine, and alcohols such as ethanol and isopropyl alcohol. Furthermore, when it is particularly desired to introduce a carboxyl group into the polyurethane resin, amino acids such as glycine and L-alanine can be used as a reaction stopping agent. These terminal blocking agents can be used alone or in combination of two or more.

[0033] The urethane resin used in the first liquid ink composition may be a urethane resin having an acidic group in order to promote the peelability of the film.

[0034] The weight average molecular weight of the polyurethane resin is preferably in the range of 10,000 to 100,000, and more preferably 15,000 to 80,000.

[0035] The amount of polyurethane resin added is preferably 1 to 30% by mass, and more preferably 5 to 25% by mass, based on the total amount of ink solids.

[0036] (Acrylic resin) The acrylic resin is not particularly limited as long as it is a copolymer of a polymerizable monomer mainly composed of (meth)acrylic acid ester. Examples of the polymerizable monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, iso-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and phenoxyethyl (meth)acrylate. The polymerization method is not particularly limited, and those obtained by known bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. can be used.

[0037] The acrylic resin used in the first liquid ink composition may be an acrylic resin having an acidic group from the viewpoint of promoting the peelability of the film. Examples of acrylic resins having an acidic group include polymers obtained by polymerizing monomers containing (meth)acrylic monomers having an acidic group such as (meth)acrylic acid or maleic acid, and 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 carboxyl group. The above-mentioned "(meth)acrylate" refers to either or both of acrylate and methacrylate, and "(meth)acrylic" refers to either or both of acrylic and methacrylic.

[0038] The weight average molecular weight of the acrylic resin is preferably in the range of 5,000 to 200,000, and more preferably in the range of 10,000 to 100,000.

[0039] The amount of the acrylic resin added is 0.1 to 5.0% by mass, preferably 0.5 to 2.0% by mass, based on the ink solid content.

[0040] (rosin resin) The rosin-based resin used in the present invention can be any rosin or rosin derivative that is widely used for printing inks, without any particular limitation. Specifically, the rosin or rosin derivative is rosins or carboxyl group-containing derivatives thereof. Rosins include gum rosin, wood rosin, tall oil rosin, disproportionated rosin, hydrogenated rosin, and polymers thereof. Rosin derivatives include carboxyl group-containing derivatives such as rosin derivatives to which unsaturated carboxylic acids such as maleic acid, fumaric acid, itaconic acid, and crotonic acid have been added.

[0041] The amount of the rosin resin added is preferably 1 to 20% by mass, and more preferably 2 to 10% by mass, based on the total amount of ink solids.

[0042] In the present invention, it is preferable to use a rosin-modified maleic acid resin, which is a maleic acid derivative of rosin, or a rosin-modified fumaric acid resin, which is a fumaric acid derivative of rosin, in order to promote the stability over time of the liquid printing ink and the releasability of the film. The rosin-modified maleic acid resin or rosin-modified fumaric acid resin used in the present invention is not particularly limited, and any known rosin-modified maleic acid resin or rosin-modified fumaric acid resin can be used. The rosin-modified maleic acid resin or rosin-modified fumaric acid resin preferably has an acid value of 25 mgKOH / g or more and 320 mgKOH / g or less, and particularly preferably has an acid value of 100 mgKOH / g or more and 320 mgKOH / g or less.

[0043] Examples of commercially available rosin-based resins include Marquid No. 1, 2, 5, 6, 8, 31, 32, 33, 34, and 3002 manufactured by Arakawa Chemical Industries, Ltd., and Harimamac R-80, T-80, R-100, M-453, M-130A, 135GN, 145P, R-120AH, Haritac 4851, 4821, 4740, and 28JA manufactured by Harima Chemical Industries, Ltd.

[0044] (polyester resin) Furthermore, the first liquid ink composition may use a polyester resin as the binder resin.

[0045] The polyester resin is not particularly limited as long as it is a polyester resin obtained by reacting an alcohol with a carboxylic acid using a known esterification polymerization reaction.

[0046] Examples of alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaerythritol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, and isosorbide. These may be used alone or in combination of two or more. Among these, polyfunctional alcohols are preferred.

[0047] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, linoleic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, and 1,4-cyclohexanedicarboxylic acid. These may be used alone or in combination of two or more. Among these, polyfunctional carboxylic acids are preferred.

[0048] The weight average molecular weight of the polyester resin is preferably 500 to 6000, and more preferably 1400 to 5500. The amount of polyester resin added is 0.1 to 5.0% by mass, preferably 0.5 to 2.0% by mass, based on the ink solid content.

[0049] In the first liquid ink composition, the binder resin is preferably used in the range of 0.15 to 50% by mass, and most preferably in the range of 1 to 40% by mass, based on the first liquid ink composition.

[0050] (Organic solvent) The organic solvent used in the first liquid ink composition is not particularly limited, and examples thereof include aromatic hydrocarbon organic solvents such as toluene, xylene, Solvesso #100, Solvesso #150, etc.; aliphatic hydrocarbon organic solvents such as hexane, methylcyclohexane, heptane, octane, decane, etc.; and various ester-based organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, normal propyl acetate, butyl acetate, amyl acetate, ethyl formate, butyl propionate, etc. Examples of water-miscible organic solvents include various organic solvents such as alcohols such as methanol, ethanol, propanol, butanol, and isopropyl alcohol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, and glycol ethers such as ethylene glycol (mono, di) methyl ether, ethylene glycol (mono, di) ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di) methyl ether, diethylene glycol (mono, di) ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, di) methyl ether, propylene glycol (mono, di) methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol (mono, di) methyl ether. These can be used alone or in combination of two or more. In addition, from the perspective of both work hygiene during printing and the harmfulness of packaging materials, ethyl acetate, propyl acetate, Isopropanol, normal propanol, etc. are used, and aromatic solvents such as toluene and methyl It is more preferable not to use a ketone solvent such as diethyl ketone.

[0051] (White pigment) The first liquid ink composition may be provided as a primer layer for facilitating removal of the coating from the plastic film without containing a pigment, but it is preferable to contain a white pigment and use the first liquid ink composition as a white ink layer. By containing a white pigment in the first printed layer to form a white printed layer, the laminate in which the printed layer containing the white pigment as the background and the printed layer with the colored pigment forming the pattern are laminated can be easily peeled off by an alkaline treatment liquid and coloring of the alkaline treatment liquid can be suppressed.

[0052] The white pigment used in the present invention may be any white pigment that is commonly used in liquid printing inks, such as titanium oxide, barium sulfate, calcium carbonate, silica, zinc oxide, zinc sulfide, mica, talc, pearl, etc. Among these, titanium oxide is preferred, and it is preferable that the titanium oxide content be 80% by mass or more based on the total white pigment. (Titanium dioxide) The titanium oxide used in the present invention is not particularly limited in its manufacturing method, shape, crystal form and particle size, and any known titanium oxide can be used. For example, the titanium oxide particles may be manufactured by the chlorine method or the sulfuric acid method. Those manufactured by the sulfuric acid method are preferred in terms of suppressing the wear of the doctor blade. The crystal form of the titanium oxide particles may be rutile, anatase, or brookite. The rutile type is preferred in that a higher hiding power can be obtained. The average particle diameter of the titanium oxide particles is preferably 0.1 to 1.0 μm, more preferably 0.1 to 0.5 μm, and even more preferably 0.2 to 0.3 μm, in order to achieve high gloss and hiding power. If the average particle diameter of the titanium oxide particles is less than 0.1 μm, the hiding power decreases, and the doctor blade is likely to leave unscraped areas, which may cause plate fogging. If the average particle diameter of the titanium oxide particles exceeds 1.0 μm, the hiding power and gloss may decrease.

[0053] The titanium oxide preferably has a treatment layer made of at least alumina and / or silica on its surface.

[0054] In titanium dioxide that has been surface-treated with alumina and / or silica, silica is generally used to adjust the acid-base state of the titanium dioxide surface and to impart durability to the resulting ink or paint film, while alumina is used to improve the wetting of titanium dioxide during dispersion. Surface treatment methods for titanium dioxide include aqueous treatment and gas phase treatment. From the viewpoint of dispersion stability, the ratio of the amount of treated silica to the amount of treated alumina is preferably 35% by mass or more and 80% by mass or less. The amount of the inorganic substance relative to the titanium oxide is not necessarily limited, but is generally 30 parts or less relative to 100 parts of the titanium oxide. Titanium oxide surface-treated with silica and alumina may be a commercially available product, and is commercially available from titanium oxide manufacturers such as Ishihara Sangyo Kaisha, Ltd. and Teika Co., Ltd. For example, there are commercially available varieties in which the amount of silica treated is greater than the amount of alumina treated, and varieties in which the amount of alumina treated is greater than the amount of silica treated, and titanium oxide in which the amount of alumina treated falls within the above-mentioned ratio range can also be obtained.

[0055] The mass ratio of alumina and silica can be estimated from the amount of alumina and silica present together with titanium oxide on the surface of titanium oxide. The amount ratio of alumina and silica present can be confirmed by analyzing and comparing the amount of alumina or silica adsorbed on the surface of titanium oxide using fluorescent X-rays, ESCA, etc. In particular, measurement using fluorescent X-rays is simple and highly accurate. Silica and alumina are present on the surface of titanium oxide, and some of them may exist as free particles, and the total amount can be measured by measuring using fluorescent X-rays. For quantitative analysis using fluorescent X-rays, an analytical method using a calibration curve using standard materials has been established. Therefore, the mass ratio of alumina and silica present on the surface of commercially available titanium oxide can be confirmed by measuring using fluorescent X-rays, and titanium oxides with various mass ratios can be used.

[0056] The content of the white pigment depends on the desired ink performance, but for a white ink that requires standard hiding power and high plate fogging, it is usually preferable to design the content to be about 10 to 50% by mass relative to the total mass of the ink. Also, it is preferable that the white pigment is contained in a ratio of 30 to 90% by weight in terms of the solid content weight ratio in the ink composition.

[0057] The first liquid ink composition may further contain, as necessary, an extender pigment, a wax, a leveling agent, an antifoaming agent, a plasticizer, an infrared absorbing agent, an ultraviolet absorbing agent, a fragrance, a flame retardant, and the like. In addition, the first liquid ink composition may contain components such as an acidic additive for promoting peeling of the coating. Examples of the acidic additive include low molecular weight organic compounds having an acidic group, such as saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, and carboxylic acid derivatives.

[0058] The first liquid ink composition can be produced by dissolving and / or dispersing a binder resin and, if necessary, a white pigment, etc., in an organic solvent. Specifically, a white pigment dispersion is produced by dispersing a white pigment in an organic solvent with a binder resin, and other compounds, etc., are added to the obtained pigment dispersion, if necessary, to produce an ink.

[0059] The particle size distribution of the pigment in the pigment dispersion can be adjusted by appropriately adjusting the size of the grinding media of the dispersing machine, the packing rate of the grinding media, the dispersion treatment time, the discharge speed of the pigment dispersion, the viscosity of the pigment dispersion, etc. As the dispersing machine, for example, a commonly used roller mill, ball mill, pebble mill, attritor, sand mill, etc. can be used.

[0060] When air bubbles or unexpectedly large particles are contained in the ink, they degrade the quality of the printed matter, so it is preferable to remove them by filtration, etc. As the filter, a conventionally known filter can be used.

[0061] The viscosity of the ink produced by the above method is preferably in the range of 10 mPa s or more from the viewpoint of preventing sedimentation of the pigment and adequately dispersing it, and 1000 mPa s or less from the viewpoint of workability during ink production and printing. The above viscosity is measured at 25°C using a Tokimec B-type viscometer.

[0062] The viscosity of the ink can be adjusted by appropriately selecting the types and amounts of raw materials used, the binder resin, the white pigment, the organic solvent, etc. The viscosity of the ink can also be adjusted by adjusting the particle size and particle size distribution of the pigment in the ink.

[0063] <Second liquid ink composition for forming second layer> Next, the second liquid ink composition for forming the second layer will be described. The second liquid ink composition contains a binder resin, a pigment, an organic solvent, and, if necessary, water and various additives.

[0064] <<Binder resin>> The binder resin used in the second liquid ink composition is not particularly limited as long as it is a general-purpose binder resin in gravure ink or flexographic ink, and the same as that in the first liquid ink composition described above can be used. The binder resin used in the second liquid ink composition is preferably excellent in adhesion to the first layer and in blocking prevention, and preferably contains at least a resin selected from a cellulose resin, a polyamide resin, a urethane resin, an acrylic resin, or a vinyl chloride resin, and is preferably any combination selected from a urethane resin / vinyl chloride resin, a urethane resin / cellulose resin, a polyamide resin / cellulose resin, an acrylic resin / cellulose resin, or a vinyl chloride resin / cellulose resin.

[0065] From the viewpoint of further improving the adhesion between the first layer and the second layer, the binder resin contained in the second layer preferably contains at least one resin selected from the binder resins contained in the first layer, and may be composed only of a resin selected from the binder resins contained in the first layer.

[0066] The urethane resin, cellulose resin, and acrylic resin may be the same as those used in the first liquid ink composition described above.

[0067] (Vinyl chloride resin) As the vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin is preferred because it is versatile. As the vinyl chloride-vinyl acetate copolymer resin, there is no particular limitation as long as it is a copolymer of vinyl chloride and vinyl acetate. The molecular weight is preferably 5,000 to 100,000 in weight average molecular weight, more preferably 10,000 to 70,000. In 100% by mass of the solid content of the vinyl chloride-vinyl acetate copolymer resin, the structure derived from vinyl acetate monomer is preferably 1 to 30% by mass, and the structure derived from vinyl chloride monomer is preferably 70 to 95% by mass. In this case, the solubility in organic solvents is improved, and further, the adhesion to the substrate, the coating properties, the scratch resistance, etc. are improved. From the viewpoint of solubility in organic solvents, it is also preferable that the polyvinyl alcohol contains a hydroxyl group derived from a vinyl alcohol structure. The hydroxyl value is preferably 20 to 200 mgKOH / g. The glass transition temperature is preferably 50°C to 90°C. The amount of vinyl chloride-vinyl acetate copolymer resin added is preferably 0.15 to 40% by mass, and more preferably 1.0 to 35% by mass, based on the total amount of the coating agent.

[0068] (Polyamide resin) The polyamide resin is, for example, a thermoplastic polyamide soluble in an organic solvent that can be obtained by polycondensation of a polybasic acid and a polyamine. In particular, a polyamide resin containing a reaction product of an acid component containing a polymerized fatty acid and / or a dimer acid with an aliphatic and / or aromatic polyamine is preferable, and further, a polyamide resin containing a portion of a primary and secondary monoamine is preferable.

[0069] Examples of polybasic acids used as raw materials for polyamide resins include, but are not limited to, adipic acid, sebacic acid, azelaic acid, phthalic anhydride, isophthalic acid, suberic acid, glutaric acid, fumaric acid, pimelic acid, oxalic acid, malonic acid, succinic acid, maleic acid, terephthalic acid, 1,4-cyclohexyldicarboxylic acid, trimellitic acid, dimer acid, hydrogenated dimer acid, and polymerized fatty acid. Among these, polyamide resins containing a structure derived from dimer acid or polymerized fatty acid as the main component (50% by mass or more in the polyamide resin) are preferred. Here, polymerized fatty acid is obtained by cyclization reaction of unsaturated fatty acid, and includes monobasic fatty acid, dimerized polymerized fatty acid (dimer acid), trimerized polymerized fatty acid, and the like. Fatty acids constituting dimer acid or polymerized fatty acid include those derived from natural oils such as soybean oil, palm oil, and rice bran oil, and those obtained from oleic acid and linoleic acid are preferred. The polybasic acid may be used in combination with a monocarboxylic acid, such as acetic acid, propionic acid, lauric acid, palmitic acid, benzoic acid, or cyclohexane carboxylic acid.

[0070] Examples of the polyamine include polyamines, primary or secondary monoamines, etc. Examples of the polyamines used in the polyamide resin include aliphatic diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, and methylaminopropylamine, and aliphatic polyamines such as diethylenetriamine and triethylenetetramine, and examples of the alicyclic polyamines include cyclohexylenediamine and isophoronediamine. Examples of the aromatic aliphatic polyamines include xylylenediamine, and examples of the aromatic polyamines include phenylenediamine and diaminodiphenylmethane. Examples of the primary and secondary monoamines include n-butylamine, octylamine, diethylamine, monoethanolamine, monopropanolamine, diethanolamine, and dipropanolamine.

[0071] The amount of the polyamide resin added is preferably 0.15 to 40% by mass, and more preferably 1.0 to 35% by mass, based on the total amount of the coating agent.

[0072] (Pigments) The second liquid ink composition contains a pigment. Examples of the pigment used in the second liquid ink composition include inorganic pigments and organic pigments used in general inks, paints, recording materials, etc. From the viewpoint of effectively exerting the effect of suppressing coloring of the alkaline solution after desorption, the pigment used in the pigment composition of the present invention is preferably an organic pigment.

[0073] Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, kaolin clay, talc, mica, etc. Also usable is a glittering pigment (Metashine: Nippon Sheet Glass Co., Ltd.) made of glass flakes or aggregate flakes as a base material and coated with a metal or metal oxide.

[0074] When the first liquid ink composition contains a white pigment, the second liquid ink composition preferably contains a pigment other than the white pigment, and preferably contains an organic pigment. The organic pigment (A) is not limited to the following examples, but may be a soluble azo, an insoluble azo, an azo, a phthalocyanine, a halogenated phthalocyanine, anthraquinone, anthanthrone, dianthraquinonyl, anthrapyrimidine, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, flavanthrone, diketopyrrolopyrrole, isoindoline, indanthrone, or carbon black pigment. Further examples include carmine 6B, lake red C, permanent red 2B, disazo yellow, pyrazolone orange, carmine FB, chromophthalic yellow, chromophthalic red, phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone magenta, quinacridone red, indanthrone blue, pyrimidine yellow, thioindigo bordeaux, thioindigo magenta, perylene red, perinone orange, isoindolinone yellow, aniline black, diketopyrrolopyrrole red, and daylight fluorescent pigments.

[0075] The pigment is preferably contained in an amount sufficient to ensure the concentration and coloring power of the ink composition for lamination, i.e., 1 to 50% by weight based on the total weight of the ink composition, and 10 to 90% by weight in terms of the solid content ratio in the ink composition. These pigments can be used alone or in combination of two or more kinds.

[0076] (Organic solvent) The organic solvent used in the second liquid ink composition is not particularly limited, and the same organic solvent as that used in the first liquid ink composition can be used.

[0077] The second liquid ink composition may further contain, as required, an extender pigment, a wax, a leveling agent, a defoaming agent, a plasticizer, an infrared absorbing agent, an ultraviolet absorbing agent, an aromatic agent, a flame retardant, and the like.

[0078] The second liquid ink composition can be produced by dissolving and / or dispersing a binder resin, a pigment, and optionally a white pigment, in an organic solvent. Specifically, a pigment dispersion is produced by dispersing a pigment in an organic solvent with a binder resin, and other compounds, etc., are added to the resulting pigment dispersion as required to produce an ink.

[0079] <Varnish composition for forming varnish layer> Next, the varnish composition that forms the varnish layer will be described. The varnish composition of the present invention forms a layer that is provided directly on the second layer, and contains at least a binder resin and an organic solvent.

[0080] The binder resin used in the varnish composition is not particularly limited as long as it is a general-purpose binder resin in gravure ink or flexographic ink, and the same resins as those listed in the first liquid ink composition and the second liquid ink composition can be used. Among them, it is preferable to use a resin selected from cellulose-based resins such as cellulose acetate propionate resin and cellulose acetate butyrate resin, acrylic resins, vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, etc. By containing these resins, it is possible to achieve excellent adhesion to the second layer and maintain the strength of the third layer. Therefore, it is possible for the first layer, the second layer, and the varnish layer to peel off as an integrated film, and coloring of the alkaline solution can be suppressed. Among them, it is preferable to use any combination selected from vinyl chloride resin / cellulose resin, or acrylic resin / cellulose resin.

[0081] In order to further improve the adhesion between the second layer and the varnish layer, it is preferable that the binder resin contained in the varnish layer contains at least one resin selected from the binder resins contained in the second layer, and it may be composed only of a resin selected from the binder resins contained in the second layer.

[0082] The varnish composition according to the present invention preferably contains a curing agent. That is, the varnish layer is preferably a crosslinked coating film formed by the varnish composition containing a curing agent. When the varnish layer is a crosslinked coating film, coloring of the alkaline solution when the first layer and the second layer are detached from the substrate can be more preferably suppressed.

[0083] Any known hardener can be used for the varnish composition, but it is preferable to use a polyisocyanate-based hardener (crosslinking agent) that uses an aromatic isocyanate such as diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, or naphthalene diisocyanate, or an alicyclic isocyanate such as isophorone diisocyanate or norbornene diisocyanate.

[0084] In order to improve the adhesion between the second layer and the varnish layer, the resin component formed by the above-mentioned binder resin and curing agent preferably accounts for 70 mass% or more of the total solid content in the varnish composition, preferably 90 mass% or more, and more preferably 95 mass% or more.

[0085] The organic solvent may be the same as that used in the first liquid ink composition and the second liquid ink composition. The varnish composition may also contain wax, a chelating crosslinking agent, an extender pigment, a leveling agent, a defoaming agent, a plasticizer, an infrared absorbing agent, an ultraviolet absorbing agent, a fragrance, a flame retardant, and the like, for the purpose of imparting the basic physical properties desired to the coating composition.

[0086] The varnish composition can be produced by dissolving and / or dispersing the binder resin and, if necessary, various additives in an organic solvent.

[0087] <Printed material> The printed matter of the present invention is a multi-layer printed matter in which a plastic substrate / a first layer / a second layer / a varnish layer are laminated. The first layer, the second layer, and the varnish layer can be formed by printing on various film substrates using the above-mentioned compositions, respectively. For example, when the first layer is a white printed layer and the second printed layer is a color printed layer, and the film substrate / a white printed layer / a color printed layer / a varnish layer are laminated in this order, the white printed layer is used as the background of the pattern, and the color printed layer) can form a pattern using a colorant.

[0088] By having a varnish layer, the printed matter of the present invention can prevent the first layer and the second layer from dissolving in the alkaline solution and becoming colored in the detachment process of the first layer and the second layer, and can peel off as a flaky film together with the varnish layer. The size of the peeled off film is preferably larger from the viewpoint of preventing re-adhesion to the plastic substrate and removing the peeled film to reuse the alkaline solution. Specifically, it is preferable that the average of the longest part is, for example, 0.01 mm or more, 0.1 mm or more, or even 1 mm or more. When the film using the printed matter of the present invention is detached, it can be confirmed that the alkaline solution after detachment does not exhibit a color derived from the pigment, and the flaky film is precipitated or floating. Therefore, it is possible to prevent the film after peeling from re-adhering to the film substrate, and the precipitate can be easily collected using a filter or the like.

[0089] Examples of the film substrate include films and laminates made of thermoplastic resins such as polyethylene terephthalate (hereinafter sometimes referred to as PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate, polyamides such as nylon 6, nylon 66, and nylon 46, polyhydroxycarboxylic acids such as polylactic acid, aliphatic polyester resins such as poly(ethylene succinate) and poly(butylene succinate), polyolefins such as polypropylene (CPP: non-oriented polypropylene film, OPP: biaxially oriented polypropylene film), polyethylene (LLDPE: low density polyethylene film, HDPE: high density polyethylene film), polyimide, polyarylate, polystyrene, polyacrylonitrile, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and mixtures thereof. Among them, films made of polyester, polyamide, polyethylene, and polypropylene can be preferably used. In terms of the releasability of the pigment composition of the present invention, polyethylene terephthalate, polypropylene, or polyethylene is more preferable. These substrate films may be unstretched or stretched films, and the manufacturing method is not limited. The thickness of the substrate film is not particularly limited, but is usually in the range of 1 to 500 μm.

[0090] The printing surface of the substrate is preferably subjected to surface modification by corona discharge treatment or chemical treatment, and silica, alumina, etc. may be vapor-deposited.

[0091] (Laminate other layers) The printed matter of the present invention may be used alone or may further include other films or substrates. As the other substrates, in addition to the above-mentioned stretched film, unstretched film, and transparent vapor deposition film, porous substrates such as paper, wood, and leather can also be used. The adhesive used when attaching the other substrates may or may not be a gas barrier adhesive as described above.

[0092] <Packaging material> The printed matter and laminate of the present invention can be used as packaging materials for protecting foods, daily necessities, etc. When used as a packaging material, the layer structure can be changed depending on the contents, the environment of use, and the form of use.

[0093] The packaging material of the present invention can be obtained, for example, by using a laminate having a sealant film, overlapping the faces of the sealant film so that they face each other, and then heat-sealing the peripheral edge. Examples of the bag-making method include folding or overlapping the laminate of the present invention so that the faces of the inner layers (the faces of the sealant film) face each other, and heat-sealing the peripheral edge, for example, by a side seal type, a two-sided seal type, a three-sided seal type, a four-sided seal type, an envelope seal type, a grooving seal type, a pleated seal type, a flat bottom seal type, a square bottom seal type, a gusset type, or other heat seal type. The packaging material of the present invention can take various forms depending on the contents, the environment of use, and the form of use. Self-supporting packaging materials (standing pouches) are also possible. Heat sealing can be performed by known methods such as bar seal, rotary roll seal, belt seal, impulse seal, high frequency seal, and ultrasonic seal.

[0094] (Method of removing coating from substrate) According to the present invention, a recycled substrate can be produced by removing the coating from the substrate by treating the printed matter with an alkaline solution.

[0095] The detachment step includes a step of immersing the printed matter in an alkaline solution while heating and stirring at 20 to 90° C. or ultrasonically vibrating the printed matter. Heating and stirring and ultrasonic vibration may be performed simultaneously. The heating temperature is preferably 30° C. or higher, more preferably 40° C. or higher, more preferably 50° C. or higher, and more preferably 60° C. or higher, and it is more preferable to perform heating and stirring and ultrasonic vibration simultaneously.

[0096] The alkaline solution used in the desorption step is not limited, but preferably has a pH of 9 or higher, and is preferably an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, an aqueous solution of sodium hydrogen carbonate, an aqueous solution of potassium hydrogen carbonate, an aqueous solution of sodium dihydrogen carbonate, an aqueous solution of potassium dihydrogen carbonate, etc. The aqueous solutions of sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium dihydrogen carbonate, potassium dihydrogen carbonate, etc. are preferably aqueous solutions with a concentration of 0.5% by mass to 10% by mass, and more preferably aqueous solutions with a concentration of 1% by mass to 5% by mass.

[0097] The alkaline solution may contain a water-soluble organic solvent, such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol dibutyl ether, diethylene glycol monomethyl ether (methyl carbitol), diethylene glycol dimethyl ether, diethylene glycol monoethyl ether (carbitol), diethylene glycol diethyl ether (diethyl carbitol), diethylene glycol monobutyl ether (butyl carbitol), diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, diethylene glycol monoethyl ether (carbitol), diethylene glycol diethyl ether (diethyl carbitol), diethylene glycol monobutyl ether (butyl carbitol), diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, diethylene glycol monoethyl ether (carbitol), diethylene glycol diethyl ether (diethyl carbitol), diethylene glycol monobutyl ether (butyl carbitol), diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, diethylene glycol monoethyl ether (carbitol), diethylene glycol diethyl ether (diethyl carbitol), diethylene glycol monoethyl ether (butyl carbitol), diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, diethylene glycol monoethyl ether (methyl carbitol), ... Examples of such an alkyl ether include glycol monomethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methylene dimethyl ether (methylal), propylene glycol monobutyl ether, tetrahydrofuran, acetone, diacetone alcohol, acetonylacetone, acetylacetone, ethylene glycol monomethyl ether acetate (methyl cellosolve acetate), diethylene glycol monomethyl ether acetate (methyl carbitol acetate), diethylene glycol monoethyl ether acetate (carbitol acetate), ethyl hydroxyisobutyrate, and ethyl lactate. These may be used alone or in combination of two or more.

[0098] The content of the water-soluble organic solvent in the alkaline solution is preferably 0.1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass. The alkaline solution may also contain a water-insoluble organic solvent. Specific examples of the water-insoluble organic solvent include alcohol-based solvents such as n-butanol, 2-butanol, isobutanol, and octanol; aliphatic hydrocarbon-based solvents such as hexane, heptane, and normal paraffin; aromatic hydrocarbon-based solvents such as benzene, toluene, xylene, and alkylbenzene; halogenated hydrocarbon-based solvents such as methylene chloride, 1-chlorobutane, 2-chlorobutane, 3-chlorobutane, and carbon tetrachloride; ester-based solvents such as methyl acetate, ethyl acetate, and butyl acetate; ketone-based solvents such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; and ether-based solvents such as ethyl ether and butyl ether. These can be used alone or in combination of two or more.

[0099] The alkaline solution may contain a surfactant, such as various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, and among these, anionic surfactants, nonionic surfactants, and amphoteric surfactants are preferred.

[0100] Examples of the anionic surfactant include alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfate ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate ester salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, and polyoxyethylene alkyl ether phosphates. Specific examples of these include dodecylbenzenesulfonates, isopropylnaphthalenesulfonates, monobutylphenylphenol monosulfonates, monobutylbiphenylsulfonates, and dibutylphenylphenol disulfonates.

[0101] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylol amides, alkyl alkanol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, polyethylene glycol polypropylene glycol block copolymers, and the like. Among these, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers are preferred.

[0102] Other surfactants that can be used include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; and biosurfactants such as spiculisporic acid, rhamnolipids, and lysolecithin.

[0103] These surfactants can be used alone or in combination of two or more. When a surfactant is added, the amount of the surfactant added is preferably in the range of 0.001 to 2 mass %, more preferably 0.001 to 1.5 mass %, and even more preferably 0.01 to 1 mass %, based on the total amount of the alkaline solution.

[0104] As a result of intensive research by the inventors, it was found that when these surfactants are used, the alkaline solution after desorption tends to be more easily colored than when the alkaline solution is used alone. On the other hand, it has been confirmed that the printed matter of the present invention can exhibit a high coloration suppression effect not only in the case of a treatment solution that does not contain a surfactant, but also in the case of a treatment solution that contains a surfactant.

[0105] The target printed matter or laminate is immersed in, for example, a treatment tank in an alkaline solution heated or ultrasonically vibrated at 20 to 90° C. The heating method is not particularly limited, and known heating methods using heat rays, infrared rays, microwaves, etc. can be used. In addition, ultrasonic vibration can be, for example, a method in which an ultrasonic vibrator is attached to the treatment tank and ultrasonic vibration is applied to the warm water or alkaline solution.

[0106] In addition, the alkaline solution is preferably stirred during immersion. Examples of the stirring method include a method of mechanically stirring the dispersion of the printed matter or laminate contained in the treatment tank with a stirring blade, a method of water flow stirring with a water flow pump, a bubbling method with an inert gas such as nitrogen gas, etc., and these methods may be used in combination to efficiently peel the printed matter or laminate.

[0107] The time for immersing the printed matter or laminate in the alkaline solution varies depending on the composition of the printed matter, but is generally in the range of 2 minutes to 48 hours. In the present invention, it is not necessary for 100% of the coating in the printed matter to be completely detached from the substrate, but it is preferable that 60% or more of the coating detaches from 100% by mass of the coating, more preferably 70% or more by mass, even more preferably 80% or more by mass, and particularly preferably 90% or more by mass.

[0108] In the desorption step, the number of times of immersion in the alkaline solution may be one or several times. That is, the immersion may be performed once, and then the process of recovering the separated film substrate may be performed, or the immersion may be performed several times, and then the process of recovering the film substrate may be performed. When the immersion is performed several times in the desorption step, the concentration of the alkaline solution may be changed. In addition, during the desorption step, known processes such as washing with water and drying may be appropriately added.

[0109] The printed matter of the present invention has a varnish layer, and the first and second layers can be peeled off as thin flaky films together with the varnish layer. Therefore, the plastic after the deinking process is not recolored by the colored deinking solution, and can be recovered as a film substrate with high recycling value. EXAMPLES

[0110] The present invention will be described more specifically with reference to examples. In the following, all "parts" and "%" are based on mass.

[0111] (Preparation of polyurethane resin solution) A 1-liter four-neck flask equipped with a stirrer, a thermometer, a Dimroth-type reflux condenser, and a nitrogen gas inlet tube was charged with 264.20 parts of polyester polyol having a number average molecular weight of 5100 obtained from adipic acid and 3-methyl-1,5-pentanediol, and heated to 50°C while stirring with nitrogen gas flowing. Then, 28.01 parts of isophorone diisocyanate was added, and the reaction was carried out at 90°C until the NCO%, which is the residual rate of isocyanate groups, reached 1.99%. After cooling, 157.34 parts of n-propyl acetate was added to obtain a urethane prepolymer solution having an isocyanate group at the end.

[0112] Next, 10.96 parts of 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 1.37 parts of monoethanolamine, 411.00 parts of n-propyl acetate, 142.00 parts of n-propyl alcohol, and 449.55 parts of the urethane prepolymer solution were added to a 1-liter four-neck flask equipped with a stirrer, a thermometer, a Dimroth-type reflux condenser, and a nitrogen gas inlet tube, and the mixture was allowed to react at 45°C for 4 hours to obtain a polyurethane resin solution 1 with a solid content of 30% and a weight average molecular weight of 48,000.

[0113] Moreover, polyurethane resin solution 2 was prepared by increasing the solid content of polyurethane resin solution 1 to 40%.

[0114] (Preparation of nitrocellulose resin solution) 71.4 parts of a mixture of isopropyl alcohol / ethyl acetate / normal propyl acetate / methylcyclohexane (mass ratio of 25 / 25 / 13 / 10) was added to 28.6 parts of industrial nitrocellulose L1 / 8 (nitrocellulose, solids content 70%, viscosity at 25.0% solution concentration 1.6-2.9% according to JIS K-6703, manufactured by Nobel) and mixed thoroughly to prepare nitrocellulose resin solution 1 with a solids content of 20%.

[0115] Nitrocellulose resin solution 2 was prepared by increasing the solid content of nitrocellulose resin solution 1 to 30%.

[0116] (Preparation of acrylic resin solution) A solid acrylic resin (Dianal BR-90 manufactured by Mitsubishi Chemical Corporation) was dissolved in isopropyl alcohol / ethyl acetate (mass ratio of 30 / 25 / 45) with stirring to prepare a 30% solution, which was designated as an acrylic resin solution Ac.

[0117] (Preparation of rosin resin solution) 50 parts of a rosin-modified maleic acid resin (Marquid No. 0.32 (manufactured by Arakawa Chemical Industries, Ltd.)) was dissolved in 50 parts of isopropyl alcohol to obtain a rosin resin solution with a solid content of 50%.

[0118] (Preparation of Cellulose Ester Resin Solution) 80 parts of a mixture of isopropyl alcohol / normal propyl acetate (50 / 50 mass / mass ratio) was added to 20 parts of cellulose acetate butyrate CAB-381-01 (manufactured by Eastman Chemical Co.) and thoroughly mixed to prepare a cellulose ester resin solution with a solid content of 20%.

[0119] (Preparation of vinyl chloride / vinyl acetate copolymer resin solution) A vinyl chloride / vinyl acetate copolymer resin having hydroxyl groups (resin monomer composition by mass: vinyl chloride / vinyl acetate / vinyl alcohol = 92 / 3 / 5, hydroxyl value (mgKOH) = 64) was made into a 20% solids solution with ethyl acetate and propyl acetate (mass ratio 50 / 50), and this was used as a vinyl chloride / vinyl acetate copolymer resin solution.

[0120] Example 1 <Preparation of First Liquid Ink Composition> A white liquid printing ink (1-1) was prepared by kneading a total of 100 parts of 20 parts of polyurethane resin solution 2, 15 parts of nitrocellulose solution 2, 5 parts of rosin resin solution, 25 parts of titanium oxide as a white pigment, and 35 parts of a mixed solvent in which ethyl acetate / isopropyl alcohol was mixed in a 1:1 mass ratio as an organic solvent.

[0121] <Preparation of second liquid ink composition> A red liquid printing ink (2-1) was prepared by kneading a total of 100 parts of the following: 30 parts of polyurethane resin solution 1, 20 parts of nitrocellulose solution 1, 10 parts of red pigment CI Pigment Red 146, and 40 parts of a mixed solvent of ethyl acetate / isopropyl alcohol in a 1:1 mass ratio as an organic solvent.

[0122] <Adjustment of Varnish Composition> A varnish composition was prepared by mixing and stirring 40 parts of vinyl chloride-vinyl acetate copolymer resin, 20 parts of cellulose ester resin solution, 40 parts of a mixed solvent prepared by mixing ethyl acetate / methyl ethyl ketone in a 1:1 mass ratio as an organic solvent, and a total of 100 parts of aromatic polyisocyanate (DIC Dry KW75 manufactured by DIC Corporation).

[0123] <Creating printed matter> The viscosity of the white liquid printing ink (1-1) was measured in seconds at 25°C using a Zahn cup #4 (Rigo Co., Ltd.), and then adjusted to 15 seconds (25°C) using a dilution solvent of methyl ethyl ketone / ethyl acetate / isopropyl alcohol = 2 / 2 / 1 using a Zahn cup #3 (Rigo Co., Ltd.). The adjusted ink was coated on the treated surface of a biaxially oriented polypropylene film (Futamura Chemical Co., Ltd., FOR, thickness 20 μm) that had been corona discharge-treated on one side using an autoproofer (plate: Helio 175L, all solid) made by Tester Sangyo Co., Ltd. to form a first layer.

[0124] Similarly, the red liquid printing ink (2-1) was adjusted with a dilution solvent so that its viscosity became 16 seconds (25°C, Zahn cup No. 3). The adjusted ink was coated on the first layer to form a second layer, and the layers were overprinted in the order of white / red.

[0125] Next, the prepared varnish composition was coated on the second layer, and then dried with a dryer to form a varnish layer, which was then aged at 40° C. for 3 days.

[0126] As a result of the above, a printed matter of Example 1 was produced in which the first layer, the second layer, and the varnish layer were laminated on the substrate.

[0127] (Example 2, Comparative Examples 1 and 2) Printed matter was produced in the same manner as in Example 1 using each composition shown in Table 1.

[0128] <Evaluation item 1: Ink peelability> As the alkaline solution, a 1.5% sodium hydroxide solution (85° C.) was used.

[0129] Each of the printed materials was cut into test pieces measuring 20 mm x 20 mm, which were then immersed in 500 mL of an alkaline solution and stirred with a stirrer for 10 minutes.

[0130] After stirring, the test piece was washed and dried, and the ink releasability of the printed portion was evaluated by visual inspection for releasability of the printed layer.

[0131] (Evaluation Criteria) ○: 100% of the printed area peeled off. △: 50% to less than 75% of the printed area peeled off. ×: 0% to less than 50% of the printed area peeled off.

[0132] <Evaluation item 2: Coloring in alkaline solution> The coloring property of each printed matter in the alkaline solution after the peeling treatment was evaluated visually according to the following criteria.

[0133] (Evaluation Criteria) ◎: No coloring, and fragments of the printed layer of 1 mm or more were confirmed ○: No coloring, and fragments of the printed layer less than 1 mm in size were confirmed △: Lightly colored (high transparency) ×: Darkly colored (low transparency)

[0134] [Table 1]

Claims

1. A laminate having a coating that can be removed from a film substrate by treatment with an alkaline solution, The coating includes a first layer containing at least a binder resin; a second layer provided on the first layer and containing a pigment and a binder resin; A layer of varnish applied on the second layer A printed matter having the above.

2. The first layer contains at least one binder resin selected from the group consisting of urethane resin, nitrocellulose, acrylic resin, and rosin resin. The printed matter according to claim 1.

3. In the binder resin of the first layer, the total amount of the urethane resin, the soluble nitrocellulose, the acrylic resin, and the rosin resin is 15 mass% or more based on the total amount of the binder resin of the first layer. The printed matter according to claim 2.

4. The binder resin of the first layer is a combination selected from the group consisting of soluble nitrocellulose / urethane resin, soluble nitrocellulose / acrylic resin, and soluble nitrocellulose / rosin resin. The printed matter according to claim 1 or 2.

5. The varnish layer contains at least one binder resin selected from the group consisting of cellulose resin, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, and polyvinyl butyral resin. The printed matter according to claim 1 or 2.

6. The binder resin of the second layer contains at least one selected from a cellulose-based resin, a polyamide-based resin, a urethane-based resin, an acrylic-based resin, and a vinyl chloride-based resin. The printed matter according to claim 1 or 2.

7. A method for producing a recycled substrate, comprising treating the printed matter according to claim 1 or 2 with an alkaline solution to remove the first layer, the second layer and the varnish layer from the plastic film.

8. When the first layer, the second layer, and the third layer are detached from the plastic film by treatment with an alkaline solution, coloration of the alkaline solution after detachment is suppressed. A method for producing the recycled substrate according to claim 7.

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