Printed item and method for producing recycled base material

Abstract

Provided are: a method for producing a recycled board, the method making it possible to suppress coloration of an alkali solution after a coating film is removed from a plastic base material by treatment with the alkali solution; and a printed item having a removable coating film, the printed item being suitable for use in the method for producing the recycled board.　Provided is a printed item in which there are laminated, in the stated order: a base material; a primer layer that can be removed from the base material by treatment with an alkali solution; an ink layer containing a colorant and at least one resin selected from the group consisting of acrylic resins, urethane resins, polyamide resins, rosin resins, and polyester resins; and a varnish layer.

Description

Printed matter and method for manufacturing recycled substrate

[0001] The present invention relates to a printed matter having a coating that can be detached from a substrate, and a method for producing a recycled substrate from the printed matter.

[0002] In recent years, the marine plastic problem has become apparent due to the breakdown of plastic discarded or dumped in the ocean into tiny particles (microplastics) in seawater. These microplastics enter the bodies of marine organisms, where they accumulate, raising concerns that they may impact the health of seabirds and humans through the food chain. Recycling is one way to address this issue. Improving the recycling rate of resources such as flexible packaging and plastic bottles will prevent plastic from entering the ocean. However, current recycling methods pose a challenge: the printed layer on the plastic substrate does not detach during the recycling process and becomes mixed into the plastic, causing a deterioration in color and physical properties, thereby reducing the value of the recycled plastic. Solving this issue by enabling the removal of the coating from the plastic substrate during the recycling process would increase the value of recycled plastic, leading to the entry of new recyclers and the establishment of municipal sorting and collection systems. This would improve recycling rates and potentially alleviate the marine plastic problem. Therefore, there is a need to develop a method for removing the coating from the plastic substrate during the recycling process. Furthermore, film-forming materials widely used on plastic substrates are being replaced with toluene-free and methyl ethyl ketone (MEK)-free materials in consideration of their impact on worker health and the environment. Therefore, materials that solve the above-mentioned problems must be developed taking this into consideration.

[0003] Prior art discloses a method for removing a coating printed on a heat-shrinkable PET film containing a styrene-acrylic acid resin, a phenolic resin, or a styrene-maleic acid resin as a vehicle using alkaline water (Patent Document 1). Similarly, a method for removing the coating using alkaline water has been disclosed (Patent Documents 2 and 3). However, these techniques only guarantee the properties of specific heat-shrinkable PET substrates and have limitations, such as the need to provide an additional coating layer separate from the coating layer. Therefore, they are not suitable for recycling general-purpose plastic substrates, including polyolefins. Meanwhile, organic solvent-based printing inks for alkaline water removal using a urethane resin with an acid value as a binder resin have also been disclosed (Patent Documents 4, 5, and 6). However, few of the developments for promoting the removal of printed films have considered the release of the removed coating into a cleaning solution. In particular, the colored pigments contained in the ink are released into the cleaning solution during cleaning, causing coloration, which leads to wastewater treatment problems and actually increases the environmental burden, but no effective solution has been clearly stated.

[0004] Japanese Patent No. 3822738 Japanese Patent No. 4653913 Japanese Patent No. 4451071 Japanese Patent No. 6638802 Japanese Patent No. 6631964 Japanese Patent Publication No. 2020-169280

[0005] The problem to be solved by the present invention is to provide a method for producing a recycled substrate that can suppress coloration of the alkaline solution after detachment when a coating is detached from a plastic substrate by treatment with an alkaline solution, and to provide a printed matter having a detachable coating that can be suitably used in the method for producing a recycled substrate.

[0006] As a result of extensive research to solve the above problems, the inventors discovered that the above problems can be solved by placing a removable primer layer between the substrate and the ink layer as a coating that is detached from the substrate by treatment with an alkaline solution, and then placing a varnish layer on top of the ink layer, in a printed matter having a substrate, primer layer, ink layer, and varnish layer laminated in that order, and thus completed the present invention.

[0007] That is, the present invention encompasses the following aspects. [1] A printed matter comprising a substrate, a primer layer removable from the substrate by treatment with an alkaline solution, an ink layer containing a colorant and at least one resin selected from the group consisting of acrylic resin, urethane resin, polyamide resin, rosin resin, and polyester resin, and a varnish layer, laminated in this order. [2] The printed matter described in [1], wherein the varnish layer contains a resin selected from the group consisting of urethane resin, cellulose derivative, and polyester resin. [3] The printed matter described in [1] or [2], wherein the varnish layer contains either (i) a urethane resin and a cellulose derivative, or (ii) a urethane resin, a cellulose derivative, and a polyisocyanate. [4] The printed matter described in [1] or [2], wherein the varnish layer is a crosslinked coating film. [5] The printed matter described in [1] or [2], wherein the primer layer contains a urethane resin or polyvinyl alcohol. [6] A method for producing a recycled substrate, comprising treating the printed matter according to [1] with an alkaline solution to remove the primer layer from the substrate, thereby obtaining a recycled substrate. [7] The alkaline solution has a pH of 9 or higher and contains a nonionic surfactant.

[0008] The present invention provides a method for producing a recycled substrate that can suppress coloration of the alkaline solution after detachment when a coating is detached from a plastic substrate by treatment with an alkaline solution, and a printed material having a removable coating that can be suitably used in the method for producing a recycled substrate.

[0009] The present invention will be described in detail below. Note that the following explanation of the constituent elements is an example for explaining the present invention, and the present invention is not limited to these contents.

[0010] (Printed matter) The printed matter of the present invention comprises a laminate comprising a substrate, a removable primer layer, an ink layer, and a varnish layer, laminated in this order. The primer layer is a film that can be removed from the substrate by treatment with an alkaline solution. The ink layer contains a colorant and at least one resin selected from the group consisting of acrylic resin, urethane resin, polyamide resin, rosin resin, and polyester resin. Each layer constituting the laminate will be described below.

[0011] <Substrate> The substrate is preferably a plastic substrate, and examples thereof include films and laminates made of polyamide resins such as nylon 6, nylon 66, and nylon 46; polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; biodegradable resins such as polyhydroxycarboxylic acids such as polylactic acid; aliphatic polyester resins such as poly(ethylene succinate) and poly(butylene succinate); thermoplastic resins such as polyolefin resins such as polypropylene and polyethylene, polyimide resins, polyarylate resins, and mixtures thereof. Among these, films and laminates made of polyethylene terephthalate, polyester, polyamide, polyethylene, and polypropylene are preferred, and polyethylene terephthalate, polypropylene, or polyethylene are more preferred when the releasability of the composition according to the present invention is important. These substrate films may be unstretched or stretched films, and their manufacturing method is not limited. The thickness of the substrate film is also not particularly limited, but is generally within the range of 1 to 500 μm.

[0012] The printing surface of the substrate is preferably surface-modified by corona discharge treatment or chemical treatment, and may be vapor-deposited with silica, alumina, or the like.

[0013] <Ink Layer> The ink layer is formed using a composition for forming an ink layer. The composition for forming an ink layer contains a colorant. The composition for forming an ink layer also contains at least one type of resin A selected from the group consisting of acrylic resins, urethane resins, polyamide resins, rosin resins, and polyester resins. The composition for forming an ink layer may contain other resins in addition to the above-mentioned resin A. The composition for forming an ink layer may also contain an organic solvent, and may also contain other components such as auxiliaries and acidic additives. The components of the composition for forming an ink layer are described below.

[0014] <<Colorant>> Examples of the colorant component include color dyes and / or color pigments, and among these, color pigments (hereinafter also simply referred to as pigments) are preferred.

[0015] Pigment Examples of the pigment used in the present invention include inorganic pigments and organic pigments used in general inks, paints, recording agents, etc. From the viewpoint of effectively suppressing coloration of the alkaline solution after desorption, organic pigments are preferred.

[0016] Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, anthraquinone pigments, anthanthrone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, azomethine azo pigments, flavanthrone pigments, diketopyrrolopyrrole pigments, isoindoline pigments, indanthrone pigments, and carbon black pigments. Other examples include carmine 6B, lake red C, permanent red 2B, disazo yellow, pyrazolone orange, carmine FB, cromophtal yellow, cromophtal 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. Both non-acid-treated and acid-treated pigments can be used. Specific examples of preferred organic pigments are listed below.

[0017] Examples of black pigments include C.I. Pigment Black 1, C.I. Pigment Black 6, C.I. Pigment Black 7, C.I. Pigment Black 9, and C.I. Pigment Black 20.

[0018] Examples of indigo pigments include C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:5, C.I. Pigment Blue 15:6, C.I. Pigment Blue 16, C.I. Pigment Blue 17:1, C.I. Pigment Blue 22, C.I. Pigment Blue 24:1, C.I. Pigment Blue 25, C.I. Pigment Blue 26, C.I. Pigment Blue 60, C.I. Pigment Blue 61, C.I. Pigment Blue 62, C.I. Pigment Blue 63, C.I. Examples of pigments that can be used include C.I. Pigment Blue 64, C.I. Pigment Blue 75, C.I. Pigment Blue 79, and C.I. Pigment Blue 80.

[0019] Examples of green pigments include C.I. Pigment Green 1, C.I. Pigment Green 4, C.I. Pigment Green 7, C.I. Pigment Green 8, C.I. Pigment Green 10, and C.I. Pigment Green 36.

[0020] Examples of red pigments include C.I. Pigment Red 1, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 4, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 8, C.I. Pigment Red 9, C.I. Pigment Red 10, C.I. Pigment Red 11, C.I. Pigment Red 12, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 17, C.I. Pigment Red 18, C.I. Pigment Red 19, C.I. Pigment Red 20, C.I. Pigment Red 21, C.I. C.I. Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 31, C.I. Pigment Red 32, C.I. Pigment Red 38, C.I. Pigment Red 41, C.I. Pigment Red 43, C.I. Pigment Red 46, C.I. Pigment Red 48, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, C.I. Pigment Red 48:4, C.I. Pigment Red 48:5, C.I. Pigment Red 48:6, C.I. Pigment Red 49, C.I. Pigment Red 49:1, C.I. Pigment Red 49:2, C.I. Pigment Red 49:3, C.I. Pigment Red 52, C.I. Pigment Red 52:1, C.I. Pigment Red 52:2, C.I. Pigment Red 53, C.I. Pigment Red 53:1, C.I. Pigment Red 53:2, C.I. Pigment Red 53:3, C.I. Pigment Red 54, C.I. Pigment Red 57, C.I. Pigment Red 57:1, C.I. Pigment Red 58, C.I. Pigment Red 58:1, C.I. Pigment Red 58:2, C.I. Pigment Red 58:3, C.I. Pigment Red 58:4, C.I. Pigment Red 60:1, C.I. Pigment Red 63, C.I. Pigment Red 63:1, C.I. Pigment Red 63:2, C.I. Pigment Red 63:3, C.I. Pigment Red 64:1, C.I. Pigment Red 68, C.I. Pigment Red 68, C.I. Pigment Red 81:1, C.I. Pigment Red 83,C.I. Pigment Red 88, C.I. Pigment Red 89, C.I. Pigment Red 95, C.I. Pigment Red 112, C.I. Pigment Red 114, C.I. Pigment Red 119, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 136, C.I. Pigment Red 144, C.I. Pigment Red 146, C.I. Pigment Red 147, C.I. Pigment Red 149, C.I. Pigment Red 150, C.I. Pigment Red 164, C.I. Pigment Red 166, C.I. Pigment Red 168, C.I. Pigment Red 169, C.I. Pigment Red 170, C.I. Pigment Red 171, C.I. Pigment Red 172, C.I. Pigment Red 175, C.I. Pigment Red 176, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 179, C.I. Pigment Red 180, C.I. Pigment Red 181, C.I. Pigment Red 182, C.I. Pigment Red 183, C.I. Pigment Red 184, C.I. Pigment Red 185, C.I. Pigment Red 187, C.I. Pigment Red 188, C.I. Pigment Red 190, C.I. Pigment Red 192, C.I. Pigment Red 193, C.I. Pigment Red 194, C.I. Pigment Red 200, C.I. Pigment Red 202, C.I. Pigment Red 206, C.I. Pigment Red 207, C.I. Pigment Red 208, C.I. Pigment Red 209, C.I. Pigment Red 210, C.I. Pigment Red 211, C.I. Pigment Red 213, C.I. Pigment Red 214, C.I. Pigment Red 216, C.I. Pigment Red 215, C.I. Pigment Red 216, C.I. Pigment Red 220, C.I. Pigment Red 221, C.I. Pigment Red 223, C.I. Pigment Red 224, C.I. Pigment Red 226, C.I. Pigment Red 237, C.I. Pigment Red 238, C.I. Pigment Red 239, C.I. Pigment Red 240, C.I. Pigment Red 242, C.I. Pigment Red 245,C.I. Pigment Red 247, C.I. Pigment Red 248, C.I. Pigment Red 251, C.I. Pigment Red 253, C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Red 256, C.I. Pigment Red 257, C.I. Pigment Red 258, C.I. Pigment Red 260, C.I. Pigment Red 262, C.I. Pigment Red 263, C.I. Pigment Red 264, C.I. Pigment Red 266, C.I. Pigment Red 268, C.I. Pigment Red 269, C.I. Pigment Red 270, C.I. Examples of suitable pigments include C.I. Pigment Red 271, C.I. Pigment Red 272, and C.I. Pigment Red 279.

[0021] Examples of purple pigments include C.I. Pigment Violet 1, C.I. Pigment Violet 2, C.I. Pigment Violet 3, C.I. Pigment Violet 3:1, C.I. Pigment Violet 3:3, C.I. Pigment Violet 5:1, C.I. Pigment Violet 13, C.I. Pigment Violet 19 (γ type, β type), C.I. Pigment Violet 23, C.I. Pigment Violet 25, C.I. Pigment Violet 27, C.I. Pigment Violet 29, C.I. Pigment Violet 31, C.I. Pigment Violet 32, C.I. Pigment Violet 36, C.I. Pigment Violet 37, C.I. Examples of suitable pigments include C.I. Pigment Violet 38, C.I. Pigment Violet 42, and C.I. Pigment Violet 50.

[0022] Examples of yellow pigments include C.I. Pigment Yellow 1, C.I. Pigment Yellow 3, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, Pigment Yellow 17, C.I. Pigment Yellow 24, C.I. Pigment Yellow 42, C.I. Pigment Yellow 55, C.I. Pigment Yellow 62, C.I. Pigment Yellow 65, C.I. Pigment Yellow 74, C.I. Pigment Yellow 83, C.I. Pigment Yellow 86, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 95, C.I. Pigment Yellow 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 117, C.I. Pigment Yellow 120, Pigment Yellow 125, C.I. Pigment Yellow 128, C.I. Pigment Yellow 129, C.I. Pigment Yellow 137, C.I. Pigment Yellow 138, C.I. Pigment Yellow 139, C.I. Pigment Yellow 147, C.I. Pigment Yellow 148, C.I. Pigment Yellow 150, C.I. Pigment Yellow 151, C.I. Pigment Yellow 153, C.I. Pigment Yellow 154, C.I. Pigment Yellow 155, C.I. Pigment Yellow 166, C.I. Pigment Yellow 168, C.I. Examples of pigments that can be used include C.I. Pigment Yellow 174, C.I. Pigment Yellow 180, C.I. Pigment Yellow 185, and C.I. Pigment Yellow 213.

[0023] Examples of orange pigments include C.I. Pigment Orange 5, C.I. Pigment Orange 13, C.I. Pigment Orange 16, C.I. Pigment Orange 34, C.I. Pigment Orange 36, C.I. Pigment Orange 37, C.I. Pigment Orange 38, C.I. Pigment Orange 43, C.I. Pigment Orange 51, C.I. Pigment Orange 55, C.I. Pigment Orange 59, C.I. Pigment Orange 61, C.I. Pigment Orange 64, C.I. Pigment Orange 71, and C.I. Pigment Orange 74.

[0024] Examples of brown pigments include C.I. Pigment Brown 23, C.I. Pigment Brown 25, and C.I. Pigment Brown 26. Among these, preferred pigments include C.I. Pigment Black 7 as a black pigment, C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, and C.I. Pigment Blue 15:6 as indigo pigments, C.I. Pigment Green 7 as a green pigment, and C.I. Pigment Red 57:1, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, and C.I. Pigment Red 146, C.I. Pigment Red 242, C.I. Pigment Red 185, C.I. Pigment Red 122, C.I. Pigment Red 178, C.I. Pigment Red 149, C.I. Pigment Red 144, C.I. Pigment Red 166, as purple pigments C.I. Pigment Violet 23, C.I. Pigment Violet 37, as yellow pigments C.I. Pigment Yellow 83, C.I. Pigment Yellow 14, C.I. Pigment Yellow 180, C.I. Pigment Yellow 139, as orange pigments C.I. Pigment Orange 38, C.I. Pigment Orange 13, C.I. Pigment Orange 34, C.I. Pigment Orange 64, and the like, and it is preferable to use at least one or two or more selected from this group.

[0025] Examples of inorganic pigments include carbon black, titanium oxide, red iron oxide, aluminum, mica, zinc oxide, barium sulfate, calcium carbonate, and silica. Also usable are glittering pigments (Metashine; Nippon Sheet Glass Co., Ltd.) in which a metal or metal oxide is coated on a base material of glass flakes or aggregate flakes. From the standpoints of cost and coloring power, it is preferable to use carbon black for black ink, titanium oxide for white ink, aluminum for gold and silver ink, and mica for pearl ink.

[0026] The total content of pigments is not particularly limited, but for example, in an ink layer-forming composition, from the viewpoint of ensuring the coloring power of the composition, the content of pigments is preferably 1 to 60 parts by mass, and more preferably 5 to 40 parts by mass, per 100 parts by mass of the total amount of the composition. The total content of white pigments may be 15 to 60 parts by mass, or may be 20 to 40 parts by mass, per 100 parts by mass of the total amount of the composition. The total content of colored organic pigments may be 1 to 30 parts by mass, or may be 5 to 25 parts by mass, per 100 parts by mass of the total amount of the pigment composition. Any combination of these upper and lower limits may be used.

[0027] <<Resin>> The composition for forming the ink layer contains at least one type of resin A selected from the group consisting of acrylic resins, urethane resins, polyamide resins, rosin resins, and polyester resins. The composition for forming the ink layer may contain a resin other than resin A. For example, it may contain other resins such as cellulose-based resins, ketone resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubbers, chlorinated rubbers, butyral resins, and petroleum resins. These may be used in appropriate combinations.

[0028] - Urethane Resin - The number average molecular weight of the urethane resin is preferably within the range of 15,000 to 100,000. If the number average molecular weight of the urethane resin is less than 15,000, the blocking resistance, chemical resistance, etc. of the ink layer forming composition tend to be reduced, while if it exceeds 100,000, the viscosity of the composition tends to be high, making it difficult to obtain the desired print density.

[0029] The urethane resin contained in the ink layer forming composition preferably uses polyester polyol and / or polyether polyol as its reaction raw material.

[0030] The number-average molecular weight of the polyester polyol is preferably 3,000 to 7,000. If the number-average molecular weight of the polyester polyol is less than 3,000, the urethane resin film tends to become hard, and adhesion to the polyester film is likely to decrease. If the number-average molecular weight is greater than 7,000, the urethane resin film tends to become brittle, and the blocking resistance of the film is likely to decrease. On the other hand, the amount of polyester polyol is preferably 1 to 50 parts by mass per 100 parts by mass of the urethane resin. If the amount of polyester polyol is less than 1 part by mass, the solubility of the polyurethane resin in ketone, ester, and alcohol-based solvents decreases, and adhesion, particularly to high-performance barrier films, tends to decrease. Furthermore, the resolubility of the urethane resin film in these solvents decreases, and the reproducibility of printed materials tends to decrease. Furthermore, if the amount exceeds 50 parts by mass, the urethane resin film tends to become excessively soft, and blocking resistance tends to decrease.

[0031] The number average molecular weight of the polyester polyol is a value measured by gel permeation chromatography (GPC) under the following conditions: Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation) Column: The following columns manufactured by Tosoh Corporation were used, connected in series. "TSKgel G5000" (7.8 mm I.D. x 30 cm) x 1 tube "TSKgel G4000" (7.8 mm I.D. x 30 cm) x 1 tube "TSKgel G3000" (7.8 mm I.D. x 30 cm) x 1 tube "TSKgel G2000" (7.8 mm I.D. x 30 cm) x 1 tube Detector: RI (differential refractometer) Column temperature: 40°C Eluent: tetrahydrofuran (THF) Flow rate: 1.0 mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass) Standard sample: A calibration curve was prepared using the following standard polystyrene. (Standard polystyrene) "TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation "TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

[0032] As the polyester polyol, for example, one obtained by a known esterification reaction between a compound having two or more hydroxyl groups and a polybasic acid can be used.

[0033] The compound having two or more hydroxyl groups is used as a chain extender, and examples thereof include glycols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, and neopentyl glycol. Examples of compounds that can be used include glycols having a branched structure such as 2-isopropyl-1,4-butanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-ethyl-1,6-hexanediol, 3,5-heptanediol, and 2-methyl-1,8-octanediol; aliphatic polyols such as trimethylolpropane, trimethylolethane, pentaerythritol, sucrose, methylene glycol, glycerin, and sorbitol; and aromatic polyols such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone, each of which has a number average molecular weight in the range of 50 to 400. These chain extenders may be used alone or in combination of two or more.

[0034] Examples of the polybasic acid that can be used include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, and anhydrides of these acids. These polybasic acids may be used alone or in combination of two or more.

[0035] The polyether polyol preferably has a number average molecular weight of 100 to 4000. Examples of polyether polyols include polyether polyols of polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran, and the like. Specifically, known, general-purpose polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol may be used, with polyethylene glycol being preferred. By incorporating polyester polyol and / or polyether polyol within the above range, adhesion, particularly to the substrate film, is significantly improved, resulting in excellent blocking resistance.

[0036] If the number average molecular weight of the polyether polyol is less than 100, the urethane resin film tends to be hard, and the adhesion to the polyester film is likely to be reduced. If the number average molecular weight is more than 4000, the urethane resin film tends to be brittle, and the blocking resistance of the film is likely to be reduced. The number average molecular weight of the polyether polyol can be determined by measuring it by gel permeation chromatography (GPC) under the same conditions as the polyester polyol.

[0037] Examples of diisocyanate compounds used in the urethane resin in the ink layer forming composition include various known aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, etc. that are generally used in the production of urethane resins. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dimeryl diisocyanate, isocyanate, isophorone diisocyanate (3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate; 5-isocyanato-1-(isocyanomethyl)-1,3,3-trimethylcyclohexane), dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, m-tetramethylxylylene diisocyanate, 4,4-diphenylmethane diisocyanate, tolylene diisocyanate, bis-chloromethyl-diphenylmethane-diisocyanate, 2,6-diisocyanato-benzyl chloride, and dimer diisocyanate in which the carboxyl groups of dimer acid are converted to isocyanate groups. These diisocyanate compounds can be used alone or in combination of two or more.

[0038] Examples of chain extenders used in the urethane resin in the ink layer forming composition include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, etc., 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.

[0039] Furthermore, the amine value of the urethane resin used in the ink layer-forming composition is preferably 10.0 mgKOH / g or less. If the amine value exceeds 10.0 mgKOH / g, blocking resistance tends to deteriorate, and the stability of the second-component after addition of a curing agent also deteriorates. From the viewpoint of maintaining good blocking resistance and second-component stability while maintaining plate fogging resistance, adhesion, and extrusion lamination strength, the amine value is more preferably in the range of 1.0 to 5.0 mgKOH / g, and even more preferably in the range of 1.0 to 3.5 mgKOH / g.

[0040] - Acrylic Resin - Acrylic resins can be obtained by copolymerizing various (meth)acrylate monomers and, if necessary, other polymerizable unsaturated group-containing compounds.

[0041] The monomer constituting the acrylic resin is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-pentafluoropropyl (meth)acrylate, perfluorocyclohexyl (meth)acrylate, and glycerol. (Meth)acrylic monomers such as ricidyl (meth)acrylate, allyl glycidyl ether, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, (meth)acrylamide, N-monoalkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isobutoxymethyl (meth)acrylamide, 2-aziridinylethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, acrolein, diacetone (meth)acrylamide, and acetoacetoxyethyl (meth)acrylate can be used. Note that the term "(meth)acrylate" refers to either or both of acrylate and methacrylate, and "(meth)acrylic" refers to either or both of acrylic and methacrylic.

[0042] In addition to the (meth)acrylic monomers, the polymerizable unsaturated group-containing compound may also be vinyl monomers such as vinyl acetate, vinyl propionate, vinyl versatate, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, (meth)acrylonitrile, styrene, α-methylstyrene, divinylstyrene, isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, and N-vinylpyrrolidone. These may be used alone or in combination of two or more.

[0043] The number average molecular weight of the acrylic resin is not particularly limited, but is preferably 3,000 to 50,000, and more preferably 10,000 to 30,000.

[0044] -Polyamide Resin- Polyamide resins can be obtained by reacting a polycarboxylic acid compound with a polyamine or a polyisocyanate compound. Examples of the polycarboxylic acid compound include succinic acid, maleic acid, fumaric acid, itaconic acid, azelaic acid, mesaconic acid, citraconic acid, sebacic acid, glutaconic acid, adipic acid, malonic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, nadic acid, methylnadic acid, octyl succinic acid, and anhydrides of these acids, polymerized fatty acids such as linoleic acid dimers and trimers, dodecanedioic acid, C21 dibasic acids, and dimer acids (polymerized fatty acids obtained by polymerizing unsaturated fatty acids such as oleic acid and linoleic acid).

[0045] Furthermore, aliphatic polycarboxylic acids having 7 to 20 carbon atoms, such as 1,2,4-butanetricarboxylic acid and 1,2,5-hexanetricarboxylic acid, alicyclic polycarboxylic acids having 9 to 20 carbon atoms, such as 1,2,4-cyclohexanetricarboxylic acid, aromatic polycarboxylic acids having 9 to 20 carbon atoms, such as 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid and pyromellitic acid, as well as trivalent or higher polycarboxylic acids, such as anhydrides and lower alkyl (methyl, butyl, etc.) esters of these.

[0046] Examples of polyamines used to obtain polyamide resins include diamines such as ethylenediamine, propylenediamine, diaminobutane, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminodecane, and diaminododecane; and trivalent or higher amines such as diethylenetriamine and triethylenetetramine.

[0047] The number average molecular weight of the polyamide resin is not particularly limited, but is preferably 5,000 to 20,000, and more preferably 500 to 10,000.

[0048] - Rosin Resin - The rosin resin may contain 20% by mass or more of a rosin-derived structure, and preferably has a softening point (ring and ball method) of 30°C to 180°C, more preferably 50 to 170°C. Suitable examples of the rosin resin include polymerized rosin resin, rosin-modified maleic acid resin, and rosin-modified fumaric acid resin. The acid value of the rosin resin is preferably 50 to 350 (mgKOH / g). Suitable examples of the rosin resin include Aradigm R-95 and Marquid No. 32, both manufactured by Arakawa Chemical Industries, Ltd.

[0049] The weight-average molecular weight of the rosin-modified maleic acid resin or the rosin-modified fumaric acid resin is preferably at least 500, more preferably at least 700, and even more preferably at least 1000. By setting the weight-average molecular weight within the above range, it is possible to achieve a good balance between adhesion to the substrate and releasability in an alkaline solution.

[0050] The weight average molecular weight of the rosin-modified maleic acid resin or rosin-modified fumaric acid resin is preferably not more than 50,000, more preferably not more than 30,000, more preferably not more than 10,000, more preferably not more than 5,000, and even more preferably not more than 2,000. By setting the weight average molecular weight within the above range, the viscosity of the ink can be reduced, and a balance can be achieved between adhesion to the substrate and releasability in an alkaline solution.

[0051] The weight average molecular weight of the rosin-modified maleic acid resin or rosin-modified fumaric acid resin is preferably 500 to 50,000, more preferably 700 to 520,000, more preferably 1,000 to 10,000, and even more preferably 1,000 to 5,000. By setting it within the above range, printability can be improved.

[0052] -Polyester Resin- Various known polyester resins can be used as the polyester resin. Polyester resins can be obtained by reacting glycol with a dibasic acid or its derivative as an essential component. Of course, polyester resins can also be obtained by using an ester-forming derivative such as a dibasic acid anhydride or a dibasic acid lower alkyl ester instead of the dibasic acid, not only through a polycondensation reaction but also through an addition reaction or an ester exchange reaction. Examples of such polyester resins include aliphatic polyester polyols obtained by reacting an aliphatic glycol such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, decanediol, or cyclohexanedimethanol with an aliphatic dibasic acid such as succinic acid, adipic acid, sebacic acid, fumaric acid, suberic acid, azelaic acid, 1,10-decamethylenedicarboxylic acid, or cyclohexanedicarboxylic acid as the essential raw material components, and aromatic polyester polyols obtained by reacting an aliphatic glycol such as ethylene glycol, propylene glycol, or butanediol with an aromatic dibasic acid such as terephthalic acid, isophthalic acid, or naphthalenedicarboxylic acid as the essential raw material components. Examples of such polyester resins include the "Polylite" series manufactured by DIC Corporation and the "Kuraray Polyol" series manufactured by Kuraray Co., Ltd.

[0053] <<Resin Content in Ink Layer-Forming Composition>> The resin content in the ink layer-forming composition is not particularly limited, but is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, relative to 100 parts by mass of the total amount of the composition. The total content is preferably 60 parts by mass or less, more preferably 55 parts by mass or less. When two or more types of resins are contained in the ink layer-forming composition, the preferred range of the content is the total amount of the resins contained therein.

[0054] <<Organic Solvent>> The ink layer forming composition may contain an organic solvent. The organic solvent is not particularly limited, but examples thereof include aromatic hydrocarbon organic solvents such as toluene, xylene, Solvesso #100, and Solvesso #150, aliphatic hydrocarbon organic solvents such as hexane, methylcyclohexane, heptane, octane, and decane, and various ester organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, normal propyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate. Examples of water-miscible organic solvents include alcohols such as methanol, ethanol, propanol, butanol, isopropyl alcohol, and normal propyl 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. Among these, various ester-based organic solvents and various alcohol-based organic solvents are preferred, with isopropyl alcohol and ethyl acetate being more preferred. These can be used alone or in combination of two or more.

[0055] The content of the organic solvent is not particularly limited, but is preferably 20% by mass or more, and more preferably 30% by mass or more, relative to 100 parts by mass of the total amount of the ink layer-forming composition, and is preferably 70% by mass or less, more preferably 65% ​​by mass or less, more preferably 60% by mass or less, and more preferably 55% by mass or less.

[0056] <<Other Components>> The composition for forming the ink layer may further contain other components such as auxiliaries and acidic additives, as required.

[0057] Examples of the auxiliary that can be used appropriately include waxes such as paraffin wax, polyethylene wax, and carnauba wax for imparting friction resistance, slipperiness, etc.; fatty acid amide compounds such as oleic acid amide, stearic acid amide, and erucic acid amide; silicone and non-silicone antifoaming agents for suppressing foaming during printing; and dispersants. Nonionic dispersants are preferred as dispersants.

[0058] The acid value of the dispersant is preferably 30 mgKOH / g or less, more preferably 25 mgKOH / g or less, and even more preferably 20 mgKOH / g or less, and may be, for example, 1 mgKOH / g or more, or even 3 mgKOH / g or more.

[0059] The content of the dispersant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, more preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of the colorant (e.g., pigment), and is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, more preferably 75 parts by mass or less, more preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

[0060] The acidic additive may be, for example, an organic acid or a resin having an acidic group. The acid value of the acidic additive is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more, more preferably 40 mgKOH / g or more, and more preferably 50 mgKOH / g or more. The acid value is preferably 900 mgKOH / g or less, more preferably 850 mgKOH / g or less, more preferably 800 mgKOH / g or less, more preferably 750 mgKOH / g or less, more preferably 700 mgKOH / g or less, more preferably 650 mgKOH / g or less, more preferably 600 mgKOH / g or less, and more preferably 550 mgKOH / g or less. By setting the acid value within the above range, both alkaline solution releasability and adhesion to other layers can be achieved.

[0061] Furthermore, when emphasis is placed on releasability in an alkaline solution, the OH content is preferably 50 mgKOH / g or more, more preferably 100 mgKOH / g or more, more preferably 200 mgKOH / g or more, more preferably 300 mgKOH / g or more, more preferably 400 mgKOH / g or more, more preferably 500 mgKOH / g or more, and particularly preferably 550 mgKOH / g or more. When emphasis is placed on adhesion to other layers, the OH content is preferably 550 mgKOH / g or less, more preferably 500 mgKOH / g or less, more preferably 400 mgKOH / g or less, more preferably 300 mgKOH / g or less, and more preferably 200 mgKOH / g or less.

[0062] When importance is placed on both the alkaline solution releasability and the adhesion to other layers, the acid value is preferably in the range of 1 to 900 mgKOH / g, more preferably 3 to 850 mgKOH / g, more preferably 5 to 800 mgKOH / g, more preferably 10 to 750 mgKOH / g, more preferably 20 to 700 mgKOH / g, more preferably 30 to 650 mgKOH / g, more preferably 40 to 600 mgKOH / g, and more preferably 50 to 550 mgKOH / g.

[0063] When emphasis is placed on releasability in an alkaline solution, the OH concentration is preferably 50 to 900 mgKOH / g, more preferably 65 to 900 mgKOH / g, more preferably 80 to 900 mgKOH / g, more preferably 100 to 900 mgKOH / g, more preferably 200 to 900 mgKOH / g, more preferably 300 to 900 mgKOH / g, more preferably 400 to 900 mgKOH / g, more preferably 500 to 900 mgKOH / g, and more preferably 550 to 900 mgKOH / g. When emphasis is placed on adhesion to other layers, the OH concentration is preferably 1 to 550 mgKOH / g, more preferably 1 to 500 mgKOH / g, more preferably 1 to 400 mgKOH / g, more preferably 1 to 300 mgKOH / g, and more preferably 1 to 200 mgKOH / g.

[0064] When both alkaline solution releasability and adhesion to other layers are satisfied, the molecular weight of the acidic additive is preferably 50 or more, preferably 60 or more, preferably 80 or more, preferably 100 or more, preferably 150 or more, preferably 200 or more, preferably 250 or more, and preferably 300 or more. Also, the molecular weight is preferably 2000 or less, preferably 1800 or less, preferably 1500 or less, preferably 1200 or less, and preferably 1000 or less. The molecular weight range is preferably 50 to 2000, preferably 50 to 1800, preferably 50 to 1500, preferably 60 to 1500, preferably 80 to 1500, preferably 100 to 1500, preferably 150 to 1500, preferably 200 to 1500, preferably 250 to 1500, preferably 300 to 1500, preferably 300 to 1200, and preferably 300 to 1000.

[0065] The organic acid refers to a low molecular weight organic compound having an acidic group. Preferred examples of the low molecular weight compound having an acidic group include saturated fatty acids, unsaturated fatty acids, hydroxy acids, aromatic carboxylic acids, dicarboxylic acids, tricarboxylic acids, oxocarboxylic acids, and carboxylic acid derivatives, and these can be used singly or in combination.

[0066] Examples of saturated fatty acids include lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, decanoic acid, undecanoic acid, and dodecanoic acid. Examples of unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid. Examples of hydroxy acids include lactic acid, malic acid, and citric acid. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, mellitic acid, and ketone. Examples of the dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, dimer acid, fumaric acid, maleic acid, azelaic acid, etc.; examples of the tricarboxylic acids include aconitic acid and trimer acid, etc.; examples of the oxocarboxylic acids include pyruvic acid and oxaloacetic acid, etc.; examples of the carboxylic acid derivatives include amino acids and nitrocarboxylic acids, and these can be used singly or in combination. In addition, citric acid, butyric acid, caproic acid, enanthic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, eleostearic acid, arachidic acid, sebacic acid, etc. are compliant with the so-called Swiss Ordinance, and it is preferable to use substances that comply with various regulations.

[0067] The acid value of the organic acid is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more, more preferably 40 mgKOH / g or more, more preferably 50 mgKOH / g or more, more preferably 60 mgKOH / g or more, more preferably 70 mgKOH / g or more, more preferably 80 mgKOH / g or more, more preferably 90 mgKOH / g or more, and particularly preferably 100 mgKOH / g or more. The acid value is preferably 900 mgKOH / g or less, more preferably 850 mgKOH / g or less, more preferably 800 mgKOH / g or less, more preferably 750 mgKOH / g or less, more preferably 700 mgKOH / g or less, more preferably 650 mgKOH / g or less, more preferably 600 mgKOH / g or less, and more preferably 550 mgKOH / g or less. By setting the acid value within the above range, it is possible to achieve both alkaline solution releasability and adhesion to other layers.

[0068] Furthermore, when emphasis is placed on releasability in an alkaline solution, the OH content is preferably 100 mgKOH / g or more, more preferably 150 mgKOH / g or more, more preferably 200 mgKOH / g or more, more preferably 250 mgKOH / g or more, more preferably 300 mgKOH / g or more, more preferably 350 mgKOH / g or more, more preferably 400 mgKOH / g or more, more preferably 450 mgKOH / g or more, more preferably 500 mgKOH / g or more, and more preferably 550 mgKOH / g or more. When emphasis is placed on adhesion to other layers, the OH content is preferably 550 mgKOH / g or less, more preferably 500 mgKOH / g or less, more preferably 400 mgKOH / g or less, more preferably 300 mgKOH / g or less, and more preferably 200 mgKOH / g or less.

[0069] When importance is placed on both the alkaline solution releasability and the adhesion to other layers, the acid value is preferably in the range of 1 to 900 mgKOH / g, more preferably 3 to 850 mgKOH / g, more preferably 10 to 800 mgKOH / g, more preferably 20 to 750 mgKOH / g, more preferably 30 to 700 mgKOH / g, more preferably 50 to 650 mgKOH / g, more preferably 80 to 600 mgKOH / g, and more preferably 100 to 550 mgKOH / g. Furthermore, when emphasis is placed on releasability in an alkaline solution, the viscosity is preferably 100 to 900 mgKOH / g, more preferably 150 to 900 mgKOH / g, more preferably 200 to 900 mgKOH / g, more preferably 250 to 900 mgKOH / g, more preferably 300 to 900 mgKOH / g, more preferably 350 to 900 mgKOH / g, more preferably 400 to 900 mgKOH / g, more preferably 450 to 900 mgKOH / g, more preferably 500 to 900 mgKOH / g, and more preferably 550 to 900 mgKOH / g. Furthermore, when emphasis is placed on adhesion to other layers, the viscosity is preferably 1 to 550 mgKOH / g, more preferably 1 to 500 mgKOH / g, more preferably 1 to 400 mgKOH / g, more preferably 1 to 300 mgKOH / g, and more preferably 1 to 200 mgKOH / g.

[0070] The organic acid preferably has 3 or more carbon atoms, preferably 4 or more, preferably 5 or more, preferably 6 or more, preferably 7 or more, and preferably 8 or more. By setting the number of carbon atoms of the organic acid within the above range, adhesion to other layers can be improved. Furthermore, the number of carbon atoms of the organic acid is preferably 20 or less, preferably 18 or less, and preferably 16 or less. By setting the number of carbon atoms of the organic acid within the above range, dispersibility in an aqueous medium can be improved. The range of the number of carbon atoms of the organic acid is preferably 3 to 20, preferably 3 to 18, preferably 4 to 18, preferably 5 to 18, preferably 6 to 18, preferably 6 to 16, preferably 7 to 16, and preferably 8 to 16.

[0071] When emphasis is placed on releasability from other layers and water resistance of the coating, the solubility of the organic acid in 100 g of water at 25°C is preferably less than 2 g, more preferably less than 1.8 g, even more preferably less than 1.5 g, and particularly preferably less than 1.2 g.

[0072] Examples of the resin having an acid group include resins having an acid value such as cellulose-based resins, ketone resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubbers, chlorinated rubbers, butyral resins, and petroleum resins; radical copolymers such as styrene-(meth)acrylic resins, styrene-maleic anhydride resins, and terpene-maleic anhydride resins, which are copolymerized with polymerizable monomers having an acid group, such as polymerizable monomers having a carboxyl group (e.g., itaconic acid, maleic acid, fumaric acid, cinnamic acid, or anhydrides thereof), polymerizable monomers having a sulfonic acid group (e.g., sulfonated styrene), and polymerizable monomers having a sulfonamide group (e.g., vinylbenzenesulfonamide); and acid-modified polyolefin resins (excluding the above-mentioned resins). These resins can be used singly or in combination. As the resin having an acid group, styrene-maleic anhydride resins are more preferred.

[0073] The acid value of the resin having an acidic group is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more, more preferably 40 mgKOH / g or more, and particularly preferably 50 mgKOH / g or more. The acid value is preferably 300 mgKOH / g or less, more preferably 280 mgKOH / g or less, more preferably 260 mgKOH / g or less, more preferably 240 mgKOH / g or less, more preferably 220 mgKOH / g or less, and particularly preferably 200 mgKOH / g or less. By adjusting the acid value within the above range, alkaline solution releasability and adhesion to other layers can be achieved at the same time.

[0074] Furthermore, when emphasis is placed on releasability in an alkaline solution, the OH content is preferably 50 mgKOH / g or more, more preferably 60 mgKOH / g or more, more preferably 70 mgKOH / g or more, more preferably 80 mgKOH / g or more, more preferably 90 mgKOH / g or more, and particularly preferably 100 mgKOH / g or more. When emphasis is placed on adhesion to other layers, the OH content is preferably 200 mgKOH / g or less, more preferably 180 mgKOH / g or less, more preferably 160 mgKOH / g or less, more preferably 140 mgKOH / g or less, more preferably 120 mgKOH / g or less, and particularly preferably 100 mgKOH / g or less. When importance is placed on both the alkaline solution releasability and the adhesion to other layers, the acid value is preferably in the range of 1 to 300 mgKOH / g, preferably 3 to 300 mgKOH / g, preferably 5 to 280 mgKOH / g, more preferably 10 to 260 mgKOH / g, more preferably 20 to 240 mgKOH / g, more preferably 30 to 220 mgKOH / g, more preferably 40 to 200 mgKOH / g, and more preferably 50 to 200 mgKOH / g.

[0075] Furthermore, when emphasis is placed on releasability in an alkaline solution, the viscosity is preferably 50 to 300 mgKOH / g, more preferably 60 to 300 mgKOH / g, more preferably 70 to 300 mgKOH / g, more preferably 80 to 300 mgKOH / g, more preferably 90 to 300 mgKOH / g, and more preferably 100 to 300 mgKOH / g. When emphasis is placed on adhesion to other layers, the viscosity is preferably 1 to 200 mgKOH / g, more preferably 1 to 180 mgKOH / g, more preferably 1 to 160 mgKOH / g, more preferably 1 to 140 mgKOH / g, more preferably 1 to 120 mgKOH / g, and more preferably 1 to 100 mgKOH / g.

[0076] When the resin having an acidic group is a styrene-maleic anhydride resin, the weight average molecular weight of the resin having an acidic group is preferably at least 500, more preferably at least 700, and even more preferably at least 1000. By setting the weight average molecular weight of the resin having an acidic group within the above range, it is possible to achieve a good balance between adhesion to other layers and releasability in an alkaline solution.

[0077] Furthermore, when the resin having an acidic group is a styrene-maleic (anhydride) resin, the weight average molecular weight of the resin having an acidic group is preferably not more than 100,000, more preferably not more than 70,000, more preferably not more than 50,000, and even more preferably not more than 30,000. By setting the weight average molecular weight of the resin having an acidic group within the above range, the viscosity of the ink layer-forming composition can be reduced, and further, a balance can be achieved between adhesion to other layers and releasability in an alkaline solution.

[0078] When the resin having an acidic group is a styrene-maleic (anhydride) resin, the weight-average molecular weight range of the resin having an acidic group is preferably 500 to 100,000, more preferably 700 to 30,000, more preferably 1,000 to 50,000, and even more preferably 1,000 to 30,000. By setting the weight-average molecular weight of the resin having an acidic group within the above range, printability can be improved.

[0079] From the viewpoints of resolubility of the ink layer-forming composition, suppression of blocking in the printed matter, improvement of print density, and adhesion to other layers, the content of the acidic additive as solids is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more, preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and more preferably 50 parts by mass or less, relative to 100 parts by mass of the total amount of the ink layer-forming composition. The content of the acidic additive as solids is preferably in the range of 0.1 to 60 parts by mass, more preferably 0.5 to 55 parts by mass, more preferably 1 to 50 parts by mass, more preferably 1.5 to 45 parts by mass, and more preferably 2 to 40 parts by mass.

[0080] When the acidic additive is an organic acid, the content of the organic acid as solids, relative to 100 parts by mass of the total amount of the ink layer-forming composition, is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more, preferably 20 parts by mass or less, more preferably 18 parts by mass or less, more preferably 16 parts by mass or less, more preferably 14 parts by mass or less, more preferably 12 parts by mass or less, and more preferably 10 parts by mass or less. The content of the organic acid as solids is preferably in the range of 0.1 to 20 parts by mass, more preferably 0.2 to 18 parts by mass, more preferably 0.3 to 16 parts by mass, more preferably 0.5 to 14 parts by mass, more preferably 1 to 12 parts by mass, more preferably 1.5 to 10 parts by mass, and more preferably 2 to 10 parts by mass.

[0081] When the acidic additive is a resin having an acidic group, the content of the resin having an acidic group as solid content, relative to 100 parts by mass of the total amount of the ink layer forming composition, is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more, and preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and more preferably 50 parts by mass or less. The content of the acidic additive as solid content is preferably in the range of 0.1 to 60 parts by mass, more preferably 0.5 to 55 parts by mass, more preferably 1 to 50 parts by mass, more preferably 1.5 to 45 parts by mass, and more preferably 2 to 40 parts by mass.

[0082] In addition to the above, water, wetting agents, adhesion aids, leveling agents, antistatic agents, viscosity modifiers, metal chelates, trapping agents, antiblocking agents, isocyanate-based curing agents, and silane coupling agents may also be used as needed.

[0083] The viscosity of the ink layer-forming composition, as measured at 25°C using a Zahn Cup #4 manufactured by Rigo Co., Ltd., is preferably 6 seconds or more, more preferably 10 seconds or more, and even more preferably 13 seconds or more, and is preferably 25 seconds or less, more preferably 20 seconds or less, and even more preferably 18 seconds or less.

[0084] The surface tension of the ink layer-forming composition is preferably 25 mN / m or more, more preferably 33 mN / m or more. Also, it is preferably 50 mN / m or less, more preferably 43 mN / m or less. By appropriately increasing the surface tension of the ink layer-forming composition, it is possible to suppress dot bridging (staining on the printed surface caused by adjacent dots in a halftone dot area joining together) while maintaining the wettability of the ink layer-forming composition to other layers. By appropriately decreasing the surface tension of the ink layer-forming composition, it is possible to increase the wettability of the ink layer-forming composition to other layers and suppress repelling.

[0085] <Primer Layer> The primer layer is a coating that can be detached from the substrate by treatment with an alkaline solution. The primer layer can be any known layer that can be detached from the substrate by treatment with an alkaline solution, and can be, for example, one that dissolves or swells in the alkaline solution by hydrolysis or the like, thereby being detached from the substrate. As long as a coating that can be detached from the substrate by treatment with an alkaline solution can be formed, the type of primer layer-forming composition that forms the primer layer is not particularly limited. For example, a composition containing a urethane resin or polyvinyl alcohol is preferred, or a composition containing a resin having an acidic group is also preferred. Examples of resins having an acidic group include polyurethane resins having an acid value, resins having an acid value such as rosin-modified maleic acid resins and rosin-modified fumaric acid resins; radical copolymer resins such as (meth)acrylic resins, styrene-(meth)acrylic resins, styrene-maleic acid (anhydride) resins, and terpene-maleic acid (anhydride) resins, which are copolymerized with polymerizable monomers having an acidic group, such as polymerizable monomers having a carboxyl group (e.g., acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, or anhydrides thereof), polymerizable monomers having a sulfonic acid group (e.g., sulfonated styrene), and polymerizable monomers having a sulfonamide group (e.g., vinylbenzenesulfonamide); and acid-modified polyolefin resins, which can be used singly or in combination. Among these, compositions containing urethane resins or polyvinyl alcohol are more preferred in the present invention, and compositions containing urethane resins or polyvinyl alcohols having an acid value of 8 to 45 mgKOH / g are more preferred.

[0086] In addition to the resins described above, the primer layer-forming composition may contain solvents such as organic solvents and aqueous solvents, additives, and the like. Examples of additives include the same auxiliaries and acidic additives that can be added to the ink layer-forming composition described above. Preferred embodiments of the primer layer-forming composition include a first embodiment of the primer layer-forming composition, which is an aqueous urethane resin composition, and a second embodiment of the primer layer-forming composition, which contains polyvinyl alcohol. These embodiments of the primer layer-forming composition are described below.

[0087] <<First Aspect of Primer Layer-Forming Composition>> A first aspect of the primer layer-forming composition is a primer layer-forming composition comprising an aqueous urethane resin composition. The aqueous urethane resin composition according to the present invention contains a urethane resin (A) and an aqueous medium (B). The aqueous urethane resin composition according to the present invention is a urethane resin (A) obtained by reacting an aromatic polyester polyol (a1) containing an aromatic dicarboxylic acid (a1-1) as a raw material monomer with a polyisocyanate (a2), and optionally a chain extender, etc., dispersed in an aqueous medium (B). The concentration of aromatic rings derived from the raw material monomer of the aromatic dicarboxylic acid (a1-1) in the urethane resin (A) is, for example, 1 mmol / g or more. The concentration of ester bond groups in the urethane resin (A) is, for example, 1 mmol / g or more. The acid value of the urethane resin (A) is, for example, 8 to 45 mgKOH / g.

[0088] <<<Urethane Resin (A)>>> The urethane resin (A) is a general term for polymeric compounds having a urethane bond (—NHCOO—), and in the present invention, comprises a reaction product obtained by reacting (crosslinking / curing reaction) an aromatic polyester polyol (a1) with a polyisocyanate (a2). The urethane resin (A) may further contain another polyol (a3) ​​in addition to the aromatic polyester polyol (a1) and the polyisocyanate (a2), or may be a reaction product of the aromatic polyester polyol (a1), the polyisocyanate (a2), and the other polyol (a3).

[0089] - Aromatic Polyester Polyol (a1) - The aromatic polyester polyol (a1) can be produced, for example, by subjecting an aromatic dicarboxylic acid (a1-1) and a polyol (a1-2) to an esterification reaction.

[0090] Examples of the aromatic dicarboxylic acid (a1-1) that can be used when producing the aromatic polyester polyol (a1) include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, and 1,2-bis(phenoxy)ethane-P,P'-dicarboxylic acid, as well as their acid anhydrides or ester-forming derivatives; aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid and their ester-forming derivatives; and sulfonic acid group-containing aromatic dicarboxylic acids such as 5-sulfoisophthalic acid and their ester-forming derivatives.

[0091] In addition to the aromatic dicarboxylic acid (a1-1), an aliphatic carboxylic acid or an alicyclic carboxylic acid can be used in combination. Examples include aliphatic dicarboxylic acids such as succinic acid, succinic anhydride, adipic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, maleic anhydride, and fumaric acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and anhydrides or ester-forming derivatives thereof. These may be used alone or in combination of two or more.

[0092] Examples of the polyol (a1-2) that can be used include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 2,5-hexanediol, 1,6-hexanediol, 1,7-heptanediol, and neopentyl glycol.

[0093] Specifically, the aromatic dicarboxylic acid (a1-1) and the polyol (a1-2) can be reacted, if necessary, in the presence of a catalyst in a reaction vessel purged with an inert gas such as nitrogen, under atmospheric pressure or reduced pressure. The reaction is preferably carried out at a temperature in the range of 100°C to 300°C.

[0094] Examples of catalysts that can be used include acetates of alkali metals or alkaline earth metals, and compounds containing zinc, manganese, cobalt, antimony, germanium, titanium, tin, zirconium, etc. Among these, it is preferable to use tetraalkyl titanates and tin oxalate, which are effective in transesterification reactions and polycondensation reactions.

[0095] When producing the urethane resin (A), other polyols (a3) ​​and the like can also be used in combination with the aromatic polyester polyol (a1) and the polyisocyanate (a2).

[0096] As the other polyol (a3), polyols similar to the above polyol (a1-2) can be used, and for example, relatively low molecular weight polyols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 2,5-hexanediol, 1,6-hexanediol, 1,7-heptanediol, and neopentyl glycol can be used.

[0097] -Polyisocyanate (a2)- Examples of the polyisocyanate (a2) that reacts with the polyol (a1) to form the urethane resin (A) include aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate, and aliphatic or alicyclic structure-containing diisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. These may be used alone or in combination of two or more. Among these, the use of one or more selected from the group consisting of isophorone diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate is more preferred from the viewpoint of improving the substrate adhesion and deinking ability of the resulting primer layer.

[0098] The urethane resin (A) can be produced, for example, by reacting the aromatic polyester polyol (a1), the polyisocyanate (a2), and optionally the polyol (a3), and optionally a chain extender, in the absence of a solvent or in the presence of an organic solvent. When the organic solvent is used, it is preferable to remove the organic solvent by a method such as distillation when dispersing the urethane resin (A) in the aqueous medium (B).

[0099] Examples of organic solvents that can be used when producing the urethane resin (A) include ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; acetates such as ethyl acetate and butyl acetate; nitriles such as acetonitrile; dimethylformamide and N-methylpyrrolidone, which can be used alone or in combination of two or more.

[0100] The chain extender that can be used when producing the urethane resin (A) can be used for the purpose of increasing the molecular weight of the urethane resin (A) and improving the durability of the resulting film, etc. Examples of the chain extender that can be used when producing the urethane resin (A) include polyamines and other active hydrogen atom-containing compounds.

[0101] Examples of polyamines include diamines such as ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, and 1,4-cyclohexanediamine; N-hydroxymethylaminoethylamine, N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine, N-ethylaminoethylamine, and N-methylaminopropylamine; Examples of suitable hydrazines include ethylenetriamine, dipropylenetriamine, and triethylenetetramine; hydrazine, N,N'-dimethylhydrazine, and 1,6-hexamethylenebishydrazine; succinic dihydrazide, adipic dihydrazide, glutaric dihydrazide, sebacic dihydrazide, and isophthalic dihydrazide; β-semicarbazidopropionic hydrazide, 3-semicarbazidopropylcarbazate, and semicarbazido-3-semicarbazidomethyl-3,5,5-trimethylcyclohexane, and it is preferable to use ethylenediamine.

[0102] Other active hydrogen-containing compounds that can be used include, for example, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, neopentyl glycol, sucrose, methylene glycol, glycerin, and sorbitol; phenols such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone; and water.

[0103] The chain extender can be used during or after the reaction of the aromatic polyester polyol (a1) with the polyisocyanate (a2). The chain extender can also be used when dispersing the urethane resin (A) in the aqueous medium (B) to make it aqueous.

[0104] - Characteristics of Urethane Resin (A) - The aromatic ring concentration derived from the raw material monomer of aromatic dicarboxylic acid (a1-1) in the urethane resin (A) is preferably 1 mmol / g or more. The aromatic ring concentration is determined by calculating the number of moles of aromatic rings contained in 1 g of the urethane resin (A). A specific calculation method will be described later. From the viewpoint of improving the substrate adhesion and deinking ability of the resulting primer layer, the aromatic ring concentration is preferably 1.5 mmol / g or more, and more preferably 2 mmol / g or more. From the viewpoint of good film-forming properties of the primer layer, the aromatic ring concentration is preferably 6 mmol / g or less, and more preferably 5 mmol / g or less.

[0105] The ester bond group concentration in the urethane resin (A) is preferably 1 mmol / g or more. The ester bond group concentration is determined by calculating the number of moles of ester bond groups contained in 1 g of the urethane resin (A). A specific calculation method will be described later. From the viewpoint of improving the substrate adhesion and deinking ability of the resulting primer layer, the ester bond group concentration is preferably 2 mmol / g or more, more preferably 4 mmol / g or more, and from the viewpoint of good blocking resistance of the primer layer, the ester bond group concentration is preferably 9 mmol / g or less, more preferably 7 mmol / g or less.

[0106] The acid value of the urethane resin (A) is preferably 8 to 45 mgKOH / g. The acid value is the amount of acid per 1 g of resin calculated by titrating the acid with an alkali, converted into mg of potassium hydroxide, according to JIS K0070. An acid value of 8 mgKOH / g or more can improve aqueous dispersion stability, and is preferably 15 mgKOH / g or more, and more preferably 20 mgKOH / g or more. An acid value of 45 mgKOH / g or less can ensure good adhesion to polyester substrates, and is preferably 40 mgKOH / g or less, and more preferably 30 mgKOH / g or less.

[0107] The value obtained by dividing the mass of the raw material monomer of polyisocyanate (a2) contained in 1 g of urethane resin (A) by the NCO equivalent weight of the raw material monomer of polyisocyanate (a2) is preferably 1.0 to 6.0 mmol / g. If this value is 1.0 mmol / g or more, the substrate adhesion and deinking ability of the resulting primer layer can be improved, and it is more preferably 1.5 mmol / g or more, and even more preferably 1.8 mmol / g or more. If it is 6.0 mmol / g or less, the film-forming properties of the primer layer can be ensured, and it is more preferably 5.0 mmol / g or less, and even more preferably 4.0 mmol / g or less.

[0108] The weight-average molecular weight of the urethane resin (A) is preferably 10,000 to 100,000. From the viewpoints of blocking resistance to the substrate and hydrolysis stability of the resin, the weight-average molecular weight of the urethane resin (A) is preferably 20,000 or more, more preferably 30,000 or more. Furthermore, from the viewpoints of low viscosity during aqueous dispersion, productivity, etc., the weight-average molecular weight is preferably 80,000 or less, more preferably 60,000 or less.

[0109] In the present invention, the weight average molecular weight was measured by gel permeation chromatography (GPC) under the above-mentioned conditions.

[0110] The glass transition temperature of the urethane resin (A) is preferably 0 to 110°C.

[0111] <<<Aqueous Medium (B)>>> Examples of the aqueous medium (B) that serves as a solvent for the urethane resin (A) include water, water-miscible organic solvents, and mixtures thereof. Examples of water-miscible organic solvents include alcohols such as methanol, ethanol, n- and isopropanol; ketones such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol, and propylene glycol; alkyl ethers of polyalkylene glycol; and N-methyl-2-pyrrolidone. In the present invention, water alone may be used, or a mixture of water and a water-miscible organic solvent may be used, or a water-miscible organic solvent alone may be used. From the standpoints of safety and environmental impact, water alone or a mixture of water and a water-miscible organic solvent is preferred, with water alone being particularly preferred.

[0112] When dispersing the urethane resin (A) in the aqueous medium (B), a machine such as a homogenizer can be used as needed.

[0113] The aqueous urethane resin composition of the present invention preferably contains 5 to 50% by mass, and more preferably 10 to 25% by mass, of the urethane resin (A) relative to the total amount of the aqueous urethane resin composition, and preferably contains 50 to 95% by mass, and more preferably 75 to 90% by mass of the aqueous medium (B) relative to the total amount of the urethane resin composition.

[0114] <<<Other Additives>>> In the aqueous urethane resin composition according to the present invention, various additives may be used as needed, such as a film-forming aid, a crosslinking agent, a curing accelerator, a plasticizer, an antistatic agent, a wax, a light stabilizer, a flow modifier, a dye, a leveling agent, a rheology control agent, an ultraviolet absorber, an antioxidant, a photocatalytic compound, an inorganic pigment, an organic pigment, and an extender pigment.

[0115] Among the additives, the emulsifier and leveling agent may cause a decrease in the durability of the resulting film, etc., and therefore, when high durability is required for the film, etc., they are preferably used in an amount of 5 mass % or less, based on the total amount of the aqueous urethane resin composition.

[0116] Furthermore, various crosslinking agents can be used in combination with the aqueous urethane resin composition of the present invention to form films or the like with excellent durability. Examples of crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amino-based crosslinking agents, aziridine-based crosslinking agents, silane coupling agent-based crosslinking agents, carbodiimide-based crosslinking agents, and oxazolidine-based crosslinking agents. From the viewpoints of improving adhesion to substrates and improving deinking properties, the crosslinking agent is preferably used in an amount of 30% by mass or less, and more preferably 20% by mass or less, relative to the total amount of urethane resin (A). Furthermore, the crosslinking agent is preferably mixed and used immediately before coating or the like with the aqueous urethane resin composition of the present invention.

[0117] <<Primer layer-forming composition of second embodiment>> A second embodiment of the primer layer-forming composition is a primer layer-forming composition containing polyvinyl alcohol. The polyvinyl alcohol-containing primer layer is preferably a resin layer containing at least 25 mass% of polyvinyl alcohol. Hereinafter, the resin layer containing polyvinyl alcohol may be referred to as a PVA resin layer.

[0118] Polyvinyl alcohol is a colorless powder obtained by saponifying polyvinyl acetate. It is a water-soluble thermoplastic resin and is the raw material for the synthetic fiber vinylon. It is commonly abbreviated as poval or PVA. Commercially available products include Poval, Elvanol, and Exeval manufactured by Kuraray Co., Ltd., Gohsenol manufactured by Mitsubishi Chemical Corporation, and Nippon Vinyl Acetate & Poval Co., Ltd.

[0119] The degree of saponification of polyvinyl alcohol is determined by the ratio of vinyl groups in polyvinyl acetate substituted with hydroxyl groups, and a degree of saponification of 90% or more is preferred. Examples of polyvinyl alcohols with a degree of saponification of 90% or more include, but are not limited to, the following commercially available products: Kuraray Co., Ltd.'s Poval "3-98, 5-98, 28-98, 60-98, 27-96," Kuraray Co., Ltd.'s Elvanol "71-30, 90-50, T-25, T-66," Kuraray Co., Ltd.'s Exeval "AQ-4104, HR-3010, RS-2117, RS-1717," Mitsubishi Chemical Co., Ltd.'s Gohsenol "N-300, NL-0" 5, A-300, AL-06R", and Japan Vinyl Acetate & Poval Co., Ltd.'s "JC-25, JC-33, JC-40, JF-02, JF-03, JF-04, JF-05, JF-10, JF-17, JF-17L, JF-22, JM-17, JM-17L, JM-23, JM-26, JM-33, JT-05, JT-13Y", etc.

[0120] The primer layer-forming composition containing polyvinyl alcohol can be obtained by mixing the polyvinyl alcohol (C) with the aqueous medium (B). Furthermore, the resin composition containing polyvinyl alcohol according to the present invention can contain various additives as needed. Examples of additives include those listed in the "Other Additives" section above.

[0121] A primer layer can be formed by applying the primer layer-forming composition of the present invention to a substrate. As described below, an ink layer made of an ink layer-forming composition can be formed on the primer layer. The primer layer can be easily removed by treatment with an alkaline solution. Since the primer layer can be easily peeled from the substrate, the ink layer formed on the primer layer can also be easily removed from the substrate. A detailed description of the method for removing the primer layer will be provided below.

[0122] <Varnish Layer> The varnish layer is formed using a composition for forming a varnish layer. Typical components of the composition for forming a varnish layer include a binder resin, a solvent such as an organic solvent or an aqueous solvent, and additives.

[0123] The varnish layer according to the present invention has the function of suppressing discoloration of the ink layer in an alkaline solution. As long as the discoloration caused by dissolving the ink layer in an alkaline solution can be suppressed, the type of varnish layer-forming composition that forms the varnish layer is not particularly limited. However, it is preferable that the varnish layer-forming composition contains at least one resin (hereinafter also referred to as resin (B)) selected from the group consisting of urethane resins, cellulose derivatives, and polyester resins. Examples of cellulose derivatives include cellulose acetate propionate resin, cellulose acetate butyrate resin, and nitrocellulose resin.

[0124] <<Cellulose Acetate Propionate Resin>> Cellulose acetate propionate resin (hereinafter sometimes referred to as CAP) is a resin obtained by triesterifying cellulose with acetic acid and propionic acid, followed by hydrolysis. Because a composition with excellent coloration suppression effect tends to be obtained, a resin containing 0.3 to 2.5 parts by mass of acetyl groups, 42 to 46 parts by mass of propionyl groups, and 1.8 to 5 parts by mass of hydroxyl groups per 100 parts by mass of the total amount of CAP is preferably used.

[0125] <<Cellulose acetate butyrate resin>> Cellulose acetate butyrate resin (hereinafter sometimes referred to as CAB) is a resin obtained by triesterifying cellulose with acetic acid and butyric acid, followed by hydrolysis. Because a composition with excellent coloration suppression effect tends to be obtained, a resin containing 2 to 30 parts by mass of acetyl groups, 17 to 53 parts by mass of butyryl groups, and 1 to 5 parts by mass of hydroxyl groups per 100 parts by mass of total CAB can be suitably used.

[0126] <<Nitrocellulose Resin>> As the nitrocellulose resin, a typical cellulose nitrate ester obtained by treating cellulose with a mixed acid of nitric acid and sulfuric acid can be used. In addition, in order to adjust the viscosity of the composition, two or more types of nitrocellulose resins having different viscosity standards according to JIS K-6703 (industrial nitrocellulose) (e.g., H20 equivalent and L1 / 4 equivalent) may be mixed and used.

[0127] The varnish layer-forming composition may contain other resins in addition to the at least one resin (B) selected from the group consisting of the urethane resin, cellulose derivative, and polyester resin described above.

[0128] Furthermore, the varnish layer-forming composition according to the present invention is preferably a composition capable of forming a varnish layer having a heat-resistant coating function, which can effectively suppress coloration of the alkaline solution when the ink layer detaches from the substrate.

[0129] As a varnish-forming composition that forms a varnish layer with heat-resistant coating function, it is preferable to contain, for example, a compound having a cellulose skeleton, a benzene ring skeleton, an isocyanuric ring skeleton, or an alicyclic skeleton, whose homopolymer glass transition temperature (hereinafter sometimes referred to as Tg) is 100°C or higher. Specific examples of resins that can be contained in varnish-forming compositions include cellulose derivatives such as nitrocellulose (nitrocellulose), cellulose acetate, cellulose propionate, and cellulose butyrate; polyester resins with a benzene ring, such as phthalic acid, naphthalenedicarboxylic acid, and ethylene oxide (EO) adducts of bisphenol A, and / or alicyclic skeletons, such as cyclopentanediol and dimethyloltricyclodecane; aromatic isocyanates such as diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, and naphthalene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate and norbornene diisocyanate; and / or urethane resins formed by combining isocyanuric triisocyanate with a polyol and / or tris(2-hydroxyethyl)isocyanurate. The varnish-forming composition may also contain a polyisocyanate containing the above-mentioned isocyanates as a curing agent (crosslinking agent). The varnish-forming composition may also preferably contain compounds having a benzene ring and an unsaturated double bond, such as styrene or phenoxydiethylene glycol acrylate, and / or compounds having an alicyclic structure and an unsaturated double bond, such as isobornyl acrylate or dicyclopentanyl acrylate, and radical copolymers such as (meth)acrylates. Furthermore, in consideration of adhesion to olefin films, a resin with a low Tg may be mixed in. The total amount of the cellulose skeleton, benzene ring skeleton, isocyanuric ring skeleton, and alicyclic skeleton of the above-mentioned compounds is preferably 20 to 90% by weight, preferably 30 to 80% by weight, of the solid content of the varnish-forming composition.

[0130] Preferred embodiments of the varnish layer forming composition according to the present invention include (i) a varnish layer forming composition containing at least a urethane resin and a cellulose derivative, or (ii) a varnish layer forming composition containing at least a urethane resin, a cellulose derivative, and a polyisocyanate.

[0131] Furthermore, as described above, the varnish layer-forming composition according to the present invention preferably contains a polyisocyanate curing agent (crosslinking agent), and the varnish layer according to the present invention is preferably a crosslinked coating film formed from the varnish layer-forming composition. By forming the varnish layer as a crosslinked coating film, coloration of the alkaline solution when the ink layer detaches from the substrate can be more effectively suppressed.

[0132] The solvent contained in the composition for forming the varnish layer may be an organic solvent or water, and for example, the same organic solvents and aqueous media as those described in the above section <<Organic Solvent>> or those described in the section <<<Aqueous Medium (B)>>>> in <<Primer Layer>> can be used.

[0133] There are no particular restrictions on the additives that can be contained in the composition for forming the varnish layer, and for example, extender pigments, pigment dispersants, leveling agents, antifoaming agents, waxes, plasticizers, antiblocking agents, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, etc. can be contained, and the various additives described in the <<<Other Additives>>>> section in the above <<Primer Layer>> can also be contained.

[0134] <<Content of resin B in composition for forming varnish layer>>> The content of resin B is, for example, 2 parts by mass or more, more preferably 4 parts by mass or more, relative to 100 parts by mass of the total amount of the composition for forming a varnish layer. Furthermore, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less. If the content of resin B is above the above lower limit, a composition with excellent coloration suppression effect tends to be obtained. Furthermore, if the content of resin B is below the above upper limit, a composition with excellent stability tends to be obtained. Note that when two or more types of resin B are contained, the preferred range of the content is the total amount of the resins contained.

[0135] <Method of manufacturing the composition> The method of manufacturing the various compositions according to the present invention (the ink layer-forming composition, primer layer-forming composition, and varnish layer-forming composition are collectively referred to as the composition) is not particularly limited, and a conventionally known method can be used. The components of the composition may all be blended together, or they may be blended separately, such as by blending some of them first to form a premix and then blending it with the other components. The mixing method is not particularly limited, and examples include a method of stirring and mixing using a mixer or the like, a method using a three-roll mill, and a method using a disperser such as a bead mill.

[0136] The composition according to the present invention can be used in any of the known and commonly used applications, such as printing ink, paint, water-based ink for inkjet recording, etc. When used in printing ink, etc., an ink layer-forming composition is necessarily used to form an ink layer, but in the present invention, both the primer layer formed from the primer layer-forming composition and the varnish layer formed from the varnish layer-forming composition are used in printing ink, etc. together with the ink layer, so in the present invention, the meaning of the "composition" used in printing ink, etc. includes not only the ink layer-forming composition, but also the primer layer-forming composition and the varnish layer-forming composition.

[0137] <Printing Ink> The composition according to the present invention can be used as a printing ink. The printing ink is not particularly limited as long as it contains the composition according to the present invention, and can be obtained with a known composition.

[0138] The printing ink may contain, as necessary, various additives that are contained in ordinary printing inks, such as organic or inorganic fillers, antistatic agents, antifoaming agents, viscosity modifiers, polymerization inhibitors, light resistance stabilizers, weather resistance stabilizers, heat resistance stabilizers, ultraviolet absorbers, antioxidants, leveling agents, pigment dispersants, and waxes.

[0139] <Printing on Substrates> The printing ink using the composition according to the present invention has excellent adhesion to substrates and can be used for printing on paper, synthetic paper, cloth, thermoplastic resin films, plastic products, steel plates, etc., and is useful as an ink for gravure printing using a gravure printing plate made by electronic engraving or the like, or for flexographic printing using a flexographic printing plate made by a resin plate or the like.

[0140] The thickness of the printing ink formed by gravure printing or flexographic printing is preferably, for example, 10 μm or less, and more preferably 5 μm or less.

[0141] <Laminate> By printing the composition according to the present invention or a printing ink using the composition directly or via another layer on the surface of a substrate, a primer layer, an ink layer, and a varnish layer are laminated on the substrate in this order, and a printed matter consisting of a laminate of the substrate and these layers can be obtained. Here, the other layer is not particularly limited and may be a single layer or multiple layers. For example, the primer layer, the ink layer, and the varnish layer may each be composed of two or more layers.

[0142] <<Specific Layer Structure of Laminate>> Examples of the printed matter and laminate of the present invention include the following structures: substrate / primer layer / ink layer / varnish layer

[0143] <<Production of Laminate>> The laminate according to the present invention can be produced, for example, by the following method. A primer layer-forming composition is printed onto a plastic substrate by a printing method such as gravure printing or flexographic printing. Next, an ink layer, which is a printed layer, is formed by printing an ink layer-forming composition onto the primer layer by a printing method such as gravure printing or flexographic printing. Next, a varnish layer-forming composition is printed onto the ink layer by a printing method such as gravure printing or flexographic printing to form a varnish layer. This allows a laminate (substrate / primer layer / ink layer / varnish layer) to be obtained.

[0144] The various compositions according to the present invention can be applied to a substrate using known printing methods such as gravure printing and flexographic printing. In addition to the gravure printing and flexographic printing described above, known printing methods include, for example, a T-die coater, a lip coater, a knife coater, a curtain coater, an inkjet printer, a bar coater, a roll coater, a spray coater, a comma coater, a reverse roll coater, a direct gravure coater, a reverse gravure coater, an offset gravure coater, a roll kiss coater, a reverse kiss coater, a kiss gravure coater, a reverse kiss gravure coater, an air doctor coater, a wire bar coater, a dip coater, a blade coater, a brush coater, a die slot coater, an offset printing machine, a screen printing machine, and the like, or a combination of two or more coating methods can be used. When printing, the composition is diluted with a diluent obtained by mixing an aqueous solution, for example, an alcoholic organic solvent such as ethyl alcohol, isopropyl alcohol, or normal propyl alcohol with water, to a viscosity and concentration suitable for various printing methods such as gravure printing and flexographic printing, and is supplied to each printing unit either alone or in a mixture.

[0145] Furthermore, the method for applying the primer layer-forming composition onto the substrate can be an inline coating method in which the primer layer-forming composition is applied during a substrate stretching process (e.g., a biaxial stretching process) and then a further stretching process is performed, or an offline coating method in which the primer layer-forming composition is applied and dried after the substrate stretching process (e.g., a biaxial stretching process) to form a primer layer.

[0146] The primer layer formed using the primer layer-forming composition of the present invention has good adhesion to the substrate, and the laminate of the present invention has excellent adhesion between the substrate and the printed layer. Furthermore, the primer layer of the laminate of the present invention can be removed in a simple manner by using an alkaline solution, and the substrate and the printed layer (ink layer) can be easily peeled off. However, under temperature conditions normally used, the primer layer of the laminate of the present invention will not peel off even if an alkaline solution is applied. Therefore, under temperature conditions normally used, even if an alkaline solution happens to adhere to the laminate, it can be used safely without worrying about peeling.

[0147] (Method for manufacturing recycled substrates) The present invention can produce recycled substrates by removing the primer layer from the substrate using an alkaline solution treatment on the printed matter of the present invention described above, thereby removing the ink layer and varnish layer as well. "Removal" refers to the coating being peeled off by swelling, dissolution, erosion, etc., due to the alkaline solution treatment. In the present invention, the primer layer can be peeled off by swelling, dissolution, erosion, etc., due to the alkaline solution treatment. In one embodiment of the present invention, the primer layer provided on the substrate is removed by the alkaline solution treatment. Then, due to the removal of the primer layer, the ink layer and varnish layer are also removed from the substrate together with the primer layer. When the ink layer dissolves in the alkaline solution, the alkaline solution is colored, but the varnish layer that is removed together with the ink layer can contribute to suppressing coloration of the alkaline solution.

[0148] <Method for removing a coating from a substrate> The removal step involves immersing the printed material in an alkaline solution while heating and stirring at 20 to 90°C or while ultrasonically vibrating. Heating and stirring and ultrasonic vibration may be performed simultaneously. The heating temperature is preferably 30°C or higher, preferably 40°C or higher, preferably 50°C or higher, or preferably 60°C or higher, and it is more preferable to perform heating and stirring and ultrasonic vibration simultaneously.

[0149] 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 sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium hydrogen carbonate solution, an aqueous potassium hydrogen carbonate solution, an aqueous sodium dihydrogen carbonate solution, an aqueous potassium dihydrogen carbonate solution, etc. The aqueous sodium hydroxide solution, the aqueous potassium hydroxide solution, the aqueous sodium hydrogen carbonate solution, the aqueous potassium hydrogen carbonate solution, the aqueous sodium dihydrogen carbonate solution, the aqueous potassium dihydrogen carbonate solution, etc. are preferably aqueous solutions having a concentration of 0.5% by mass to 10% by mass, and more preferably an aqueous solution having a concentration of 1% by mass to 5% by mass.

[0150] The alkaline solution may also 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, and triethylene glycol monomethyl ether (methyl carbitol). Examples 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, and these can be used alone or in combination of two or more.

[0151] 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 may be used alone or in combination of two or more.

[0152] The alkaline solution may also contain a surfactant. Examples of the surfactant include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, anionic surfactants, nonionic surfactants, and amphoteric surfactants are preferred, and nonionic surfactants are more preferred.

[0153] Examples of anionic surfactants 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, polyoxyethylene alkyl ether phosphates, and the like. Specific examples of these include dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, and dibutylphenylphenol disulfonate.

[0154] 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 alkylolamides, alkylalkanolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers. Of 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 alkylolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers are preferred.

[0155] 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, rhamnolipid, and lysolecithin.

[0156] These surfactants can be used alone or in combination of two or more. When a surfactant is added, the amount added is preferably in the range of 0.001 to 2% by mass, more preferably 0.001 to 1.5% by mass, and even more preferably 0.01 to 1% by mass, based on the total amount of the alkaline solution.

[0157] When these surfactants are used, the alkaline solution tends to become more discolored after detachment than when the alkaline solution is used alone; however, when the primer layer detaches from the substrate, the varnish layer that is detached together with the ink layer effectively suppresses discoloration of the treatment solution.

[0158] The target printed matter or laminate is immersed in, for example, a treatment tank in an alkaline solution heated to 20 to 90° C. or ultrasonically vibrated. The heating method is not particularly limited, and known heating methods using heat rays, infrared rays, microwaves, etc. can be used. Ultrasonic vibration can be achieved, for example, by attaching an ultrasonic vibrator to the treatment tank and applying ultrasonic vibration to the warm water or alkaline solution.

[0159] It is also preferable that the alkaline solution is stirred during immersion. Examples of stirring methods include mechanically stirring the dispersion of the printed matter or laminate contained in the treatment tank with a stirring blade, water jet stirring with a water jet pump, and bubbling with an inert gas such as nitrogen gas, and these may be used in combination to achieve efficient peeling.

[0160] 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. Note that in the present invention, it is not necessary for 100% of the coating on the printed matter to be completely detached from the substrate, but it is preferable that 60% by mass or more of the 100% by mass of the coating be detached, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0161] In the desorption step, the film may be immersed in the alkaline solution once or several times. That is, the film may be immersed once and then the separated film substrate may be recovered, or the film may be immersed several times and then the film substrate may be recovered. When the film is immersed multiple times in the desorption step, the concentration of the alkaline solution may be changed. During the desorption step, known steps such as washing with water and drying may be added as appropriate.

[0162] The printed matter of the present invention has a coating formed on a substrate, which is composed of a removable primer layer, an ink layer containing a colorant, and a varnish layer laminated together. Therefore, the presence of the varnish layer can effectively suppress discoloration of the alkaline treatment solution when the coating is removed in the removal process.

[0163] The contents and effects of the present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these. Note that "parts" and "%" shown below are all based on mass.

[0164] <Concentration (mmol / g) of aromatic rings derived from raw material monomers of aromatic dicarboxylic acid (a1-1)> The number of moles of aromatic rings contained in 1 g of urethane resin is calculated. This can be calculated based on the raw materials used in the synthesis of the aromatic polyester polyol and their blending amounts. It is determined by dividing the mass of the raw material monomers of aromatic dicarboxylic acid (a1-1) contained in 1 g of urethane resin by the molecular weight of the raw material monomers of aromatic dicarboxylic acid (a1-1).

[0165] <Ester bond group concentration (mmol / g)> The number of moles of ester bond groups contained in 1 g of urethane resin is calculated. This can be calculated based on the raw materials used in the synthesis of the aromatic polyester polyol and their blend amounts. First, the ester bond group concentration in 1 g of aromatic polyester polyol (a1) is calculated using the following formula (I). Formula (I) takes into account dehydration due to ester formation.

[0166] (In formula (I), a represents the number of moles of carboxylic acid in 1 g of aromatic polyester polyol (a1).) After determining the ester bond group concentration in 1 g of aromatic polyester polyol (a1), the product of the ester bond group concentration in 1 g of aromatic polyester polyol (a1) and the proportion of aromatic polyester polyol (a1) in 1 g of urethane resin is then determined, thereby calculating the ester bond group concentration in 1 g of urethane resin.

[0167] <Acid value (mg KOH / g)> The acid value is determined as the number of mg of KOH required when the COOH groups contained in 1 g of urethane resin are titrated by the potassium hydroxide method.

[0168] <Urethane+Urea Functional Group Concentration (mmol / g)> The concentration is determined by dividing the mass of the raw material monomer of polyisocyanate (a2) contained in 1 g of urethane resin by the NCO equivalent weight of the raw material monomer of polyisocyanate (a2).

[0169] <Weight Average Molecular Weight> The weight average molecular weight is measured by gel permeation chromatography (GPC).

[0170] <Glass Transition Temperature (° C.)> The glass transition temperature is measured using a differential scanning calorimeter.

[0171] <Polyol Hydroxyl Value> Measured in accordance with the method described in JIS K1557-1.

[0172] (Layer-forming composition) The layer-forming compositions used in the examples and comparative examples are as follows. [Ink composition] [[Ink A]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> Nitrocellulose resin 30% solution Nitrocellulose DLX5-8 manufactured by Nobel, non-volatile content 30%, ethyl acetate:IPA solution Urethane resin 30% solution Urea urethane resin manufactured by DIC Corporation, number average molecular weight 14,000, non-volatile content 30%, ethyl acetate:IPA solution <Organic solvents> Isopropyl alcohol Normal propyl alcohol Ethyl acetate Normal propyl acetate Methylcyclohexane The blending ratios of the above raw materials are as shown in Table 1-1 below.

[0173] [[Ink B]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> 50% acrylic resin solution ACRYDIC WCL-1419 manufactured by DIC Corporation, number average molecular weight 16,000, non-volatile content 50%, dissolved in ethyl acetate:IPA 25% vinyl chloride-vinyl acetate copolymer resin solution Solvine A manufactured by Nissin Chemical Industry Co., Ltd., non-volatile content 25%, dissolved in methyl ethyl ketone 20% cellulose acetate butyrate solution Cellulose acetate butyrate resin (CAB-381-0.1 manufactured by Eastman Chemical Co.), non-volatile content 20%, dissolved in ethyl acetate <Organic solvents> Isopropyl alcohol Methyl ethyl ketone Ethyl acetate Toluene Normal propyl acetate The blending ratios of the above raw materials are as shown in Table 1-2 below.

[0174] [[Ink C]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> Nitrocellulose resin 40% solution Nitrocellulose DLX5-8 manufactured by Nobel Corporation, non-volatile content 40%, ethyl acetate: IPA solution Acrylic resin 50% solution Acrydic WCL-1419 manufactured by DIC Corporation, number average molecular weight 16,000, non-volatile content 50%, ethyl acetate: IPA solution <Organic solvent> Isopropyl alcohol Normal propyl acetate Propylene glycol monomethyl ether The blending ratios of the above raw materials are as shown in Table 1-3 below.

[0175] [[Ink D]] <Pigment> Pigment: phthalocyanine blue pigment (FASTOGEN BLUE FA5380 manufactured by DIC Corporation) <Resin> Nitrocellulose resin 30% solution Nitrocellulose DLX5-8 manufactured by Nobel, 30% non-volatile content, ethyl acetate:IPA solution Polyamide resin 40% solution 100 parts of dimer acid (Haridimer 270S; manufactured by Harima Chemicals Co., Ltd.), 1 part of tall oil fatty acid (Harthall FA-1; manufactured by Harima Chemicals Co., Ltd.), 5 parts of sebacic acid, 10 parts of ethylenediamine, 5 parts of hexamethylenediamine, and 0.24 parts of triphenylphosphine were placed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the system was emptied into a nitrogen atmosphere. The temperature was then slowly raised to 200°C under uniform stirring under a nitrogen stream. Subsequently, dehydration condensation was carried out at 200°C for 5 hours while stirring, and isopropyl alcohol / industrial ethanol / methylcyclohexane (mass ratio of 20 / 20 / 60) was added to obtain a tall fatty acid-derived dimer acid-modified polyamide resin solution with a solids content of 40%, a softening point of 123°C, an amine value of 2, an acid value of 8, and a number average molecular weight of 10,000. <Organic solvents> - Isopropyl alcohol - Normal propyl alcohol - Methylcyclohexane - Ethylene glycol monopropyl ether The blending ratios of the above raw materials are as shown in Table 1-4 below.

[0176] [Primer Composition] Primer Composition 1 (also referred to as Primer 1) to Primer Composition 2 (also referred to as Primer 2) are as follows. [[Primer 1]] 100 parts of urethane resin 1 were mixed with 9 parts of "Carbodilite SV-02" manufactured by Nisshinbo Chemical Inc., and then diluted with isopropyl alcohol (IPA) to a solids content of 10% to obtain a primer-forming composition consisting of an aqueous urethane resin composition containing a crosslinker. <Urethane Resin 1> Urethane Resin 1 was synthesized as follows. 0.74 g of polyol a, 0.20 g of isophorone diisocyanate, and 0.06 g of 2,2'-dimethylolpropionic acid were charged into a four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, and the mixture was allowed to react at 75°C for 8 hours under a nitrogen stream to obtain Urethane Resin 1. Polyol a was prepared by mixing and reacting 0.32 g of terephthalic acid (TPA), 0.32 g of isophthalic acid (IPA), 0.13 g of ethylene glycol (EG), and 0.23 g of diethylene glycol (DEG) in proportions to produce an aromatic polyester polyol. The composition and physical properties of polyol a are shown in Table 2-1 below. The composition and physical properties of urethane resin 1 are shown in Table 2-2 below. Hereinafter, Table 2-1 and Table 2-2 will be collectively referred to as Table 2.

[0177] The aromatic ring concentrations shown in Table 2 were determined as follows. Urethane resin 1 will be used as an example. First, the aromatic ring concentration in 1 g of polyol a is calculated. The mass ratio of the raw material monomer for aromatic dicarboxylic acid (a1-1) containing an aromatic ring / the molecular weight of that monomer is calculated (if there are multiple raw material monomers for aromatic dicarboxylic acid (a1-1), the sum is calculated). {0.32 (terephthalic acid content in polyol a) / 166 (molecular weight of terephthalic acid)+0.32 (isophthalic acid content in polyol a) / 166 (molecular weight of isophthalic acid)}×1000=3.8 mmol / g. Next, the product of the aromatic ring concentration in 1 g of aromatic polyester polyol (a1) and the proportion of aromatic polyester polyol (a1) in 1 g of urethane resin is calculated, to calculate the aromatic ring concentration in 1 g of urethane resin. 3.84 (aromatic ring concentration of polyol a) × 0.74 (content of polyol a in urethane resin 1) = 2.8 mmol / g

[0178] The ester bond group concentrations shown in Table 2 were determined as follows. An example will be described using urethane resin 1. First, the ester bond group concentration per gram of polyol a is calculated. If the number of moles of carboxylic acid per gram of aromatic polyester polyol (a1) is designated as a, a can be determined as follows: a = {0.32 (terephthalic acid content in polyol a) / 166 (molecular weight of terephthalic acid) + 0.32 (isophthalic acid content in polyol a) / 166 (molecular weight of isophthalic acid)} × 2 (the raw material monomer for aromatic dicarboxylic acid (a1-1) contains two carboxylic acids) = 0.00771. Next, the determined a is substituted into the above formula (I). {a / (1-a×18 (amount of water to be removed))}×1000=8.9 mmol / g Next, the product of the ester bond group concentration in 1 g of aromatic polyester polyol (a1) and the proportion of aromatic polyester polyol (a1) in 1 g of urethane resin is calculated to calculate the ester bond group concentration in 1 g of urethane resin: 8.9 (ester bond group concentration of polyol a)×0.74 (content of polyol a in urethane resin 1)=6.6 mmol / g

[0179] The urethane + urea functional group concentrations shown in Table 2 were determined as follows. An explanation will be given using Urethane Resin 1 as an example: 0.2 (content of isophorone diisocyanate in Urethane Resin 1) ÷ 111.15 (NCO equivalent weight of isophorone diisocyanate) = 1.8 mmol / g Here, the NCO equivalent weight of isophorone diisocyanate is determined by dividing the molecular weight of isophorone diisocyanate by 2, or 222.3 ÷ 2 = 111.15.

[0180] [Primer 2] Poval 28-98 (polyvinyl alcohol having a saponification degree of 90% or more) manufactured by Kuraray Co., Ltd. was diluted with water to 10% by mass to obtain a primer-forming composition containing PVA (polyvinyl alcohol).

[0181] [Varnish Compositions] Varnish composition 1 (also referred to as Varnish 1) to varnish composition 3 (also referred to as Varnish 3) were prepared as shown in Table 3 below. In Table 3 below, the abbreviations are as follows: CAP-504-0.2: Cellulose acetate propionate manufactured by Eastman Chemical Company CAB-1000: Cellulose acetate butyrate manufactured by Eastman Chemical Company NITROCELLULOSE DLX5-8: Nitrocellulose manufactured by Nobel NC LX-470EL: Polyurethane polyol manufactured by DIC Corporation KW-75: Aromatic polyisocyanate manufactured by DIC Corporation

[0182] Example 1 Production of Printed Material The prepared primer composition was printed onto a substrate (PE film) using bar coater #4 to form a solid layer measuring 240 mm long x 80 mm wide, then dried with a dryer, and then left at room temperature for at least one day to form a primer layer. Subsequently, the prepared ink composition was printed onto the dried primer layer using bar coater #4, and after printing, it was dried with a dryer to form an ink layer. Subsequently, the prepared varnish composition was printed onto the ink layer using bar coater #4, and after printing, it was dried with a dryer to form an OP varnish layer, which was then aged at 40°C for 3 days. As a result, a printed material consisting of a laminate in which a primer layer, an ink layer, and an OP varnish layer were laminated on a substrate was obtained.

[0183] <Evaluation Item 1: Ink Stripping Test> [Alkaline Solution] A stripping test was conducted under the following conditions, and the ease of stripping under each condition was compared: 0.5% by mass of sodium hydroxide, 0.3% by mass of surfactant, 70°C. Here, the surfactant used was a nonionic surfactant (Triton X-100).

[0184] [Peel test conditions] The peel test was performed under each condition with a treatment time of 10 minutes. Peeling within 5 minutes of treatment indicates fairly high performance. Test pieces of printed matter cut to a size of 20 mm x 20 mm were immersed in the solution and stirred with a stirrer. After stirring, the state of peeling was confirmed, and then the printed matter was rubbed with a finger to check whether rubbing would cause the coating film to peel. The peelability of the ink coating film under the above conditions was evaluated according to the following evaluation criteria.

[0185] [Evaluation criteria] 5: Ink film detachment confirmed within 5 minutes of stirring. Complete detachment when rubbed 4: Ink film detachment confirmed within 10 minutes of stirring. Complete detachment when rubbed 3: No ink film detachment confirmed within 10 minutes of stirring. Complete detachment when rubbed 2: No ink film detachment confirmed within 10 minutes of stirring. Partial detachment when rubbed 1: No ink film detachment confirmed within 10 minutes of stirring. No detachment confirmed even when rubbed

[0186] The results of the peelability test are shown in Table 4-1 below. From the viewpoint of practical application, a rating of 3 or higher is required.

[0187] <Evaluation Item 2: Coloring Inhibition Test> A coloring inhibition test was carried out using the produced printed matter under the following conditions.

[0188] <<Alkaline Solution>> 1 mass % sodium hydroxide, 0.3% surfactant, 70° C. Here, the surfactant used was a nonionic surfactant (Triton X-100).

[0189] <<Coloration Inhibition Test Conditions>> The coloration inhibition test was performed by treating the printed matter with the alkaline solution for 10 minutes. 50 test pieces were cut into 20 mm x 20 mm pieces, and the pieces were immersed in 500 mL of alkaline solution and stirred with a stirrer. The transparency of the alkaline solution after stirring was measured using a transparency meter according to the method of JIS (Japanese Industrial Standards) K0102.

[0190] Specifically, a transparency meter was filled with an alkaline solution in a glass cylinder with a bottom opening and graduated every 10 mm, equipped with a double cross marking on the bottom. The bottom was viewed from above, and the sample was rapidly poured out of the bottom opening until the double cross marking on the bottom was clearly visible. The water level was read at that point. This process was repeated twice, and the average value was calculated and expressed as transparency in degrees (10 mm = 1 degree). Evaluation was based on the following criteria:

[0191] The blank samples used in Examples 1 to 3 were 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 1, immersed in 500 mL of alkaline solution, and stirred with a stirrer.The blank samples used in Examples 4 to 6 were 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 4, immersed in 500 mL of alkaline solution, and stirred with a stirrer.The blank samples used in Examples 7 to 9 were 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 7, immersed in 500 mL of alkaline solution, and stirred with a stirrer.The blank samples used in Examples 10 to 12 were 50 test pieces cut to a size of 20 mm x 20 mm from the printed material obtained using the ink composition of Comparative Example 10, immersed in 500 mL of alkaline solution, and stirred with a stirrer. As blank samples for Examples 13 to 15, 50 test pieces of 20 mm x 20 mm size cut from the printed matter obtained using the ink composition of Comparative Example 13 were used, which were immersed in 500 mL of alkaline solution and stirred with a stirrer.

[0192] [Evaluation criteria] 5: Transparency 10 times or more that of the blank sample. 4: Transparency 5 times or more that of the blank sample. 3: Transparency 3 times or more that of the blank sample. 2: Transparency 1.5 times or more that of the blank sample. 1: Transparency equivalent to that of the blank sample.

[0193] The results of the coloring inhibition test are shown in Table 4-1 below. From the viewpoint of practical application, a rating of 3 or higher is required.

[0194] (Examples 2 to 15, Comparative Examples 1 to 15) Printed matter was obtained in the same manner as in Example 1, except that the layer structure in Example 1 was changed as shown in Tables 4-1 to 4-5 below. The obtained printed matter was evaluated in the same manner as in Example 1. The results are shown in Tables 4-1 to 4-5.

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201]

[0202]

[0203]

[0204]

[0205]

[0206]

[0207] From the above examples, it was found that the printed matter according to the present invention can easily remove the ink layer from the substrate by treatment with an alkaline solution, and can effectively suppress discoloration of the alkaline solution when the ink layer is removed. Since the printed matter according to the present invention has the effect of suppressing discoloration of the alkaline treatment solution, it can prevent water pollution and environmental load caused by colored wastewater. Furthermore, since raw materials and manufacturing equipment for decolorizing colored wastewater are not required, it is possible to reduce manufacturing costs when recycling substrates. Furthermore, since a decolorizing process is not required and the recycling efficiency of substrates is excellent, it is extremely useful industrially.

Claims

1. A printed matter comprising: a substrate; a primer layer that can be removed from the substrate by treatment with an alkaline solution; an ink layer that contains a colorant and at least one resin selected from the group consisting of acrylic resin, urethane resin, polyamide resin, rosin resin, and polyester resin; and a varnish layer, laminated in this order.

2. The printed matter according to claim 1, wherein the varnish layer contains a resin selected from the group consisting of urethane resins, cellulose derivatives, and polyester resins.

3. A printed matter as described in claim 1 or 2, wherein the varnish layer is either (i) a urethane resin and a cellulose derivative, or (ii) a urethane resin, a cellulose derivative, and a polyisocyanate.

4. The printed matter according to claim 1 or 2, wherein the varnish layer is a crosslinked coating film.

5. The printed matter according to claim 1 or 2, wherein the primer layer contains a urethane resin or polyvinyl alcohol.

6. A method for producing a recycled substrate, comprising treating the printed matter according to claim 1 with an alkaline solution to remove the primer layer from the substrate, thereby obtaining a recycled substrate.

7. The method for producing recycled substrates described in claim 6, wherein the alkaline solution has a pH of 9 or higher and contains a nonionic surfactant.

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