Desorption primer composition, printed material, and recycling method

Abstract

The present invention provides a desorption primer composition for forming the desorption primer layer of a printed material laminated in the order of at least a plastic substrate, a desorption primer layer, and a printed layer, wherein the desorption primer composition contains at least a (meth)acrylic resin and an aqueous solvent mainly composed of water, and the (meth)acrylic resin has an acid value of 10 to 90 mgKOH / g and a glass transition temperature of -30°C to 90°C. This solves the problem.

Description

[Technical Field]

[0001] The present invention relates to a primer composition, printed matter, and recycling method that can be detached from a plastic substrate. [Background technology]

[0002] In recent years, the problem of marine plastic pollution has become apparent, stemming from the decomposition of plastics discarded and dumped into the ocean, resulting in microplastics. These microplastics enter the bodies of marine organisms, accumulate, and are feared to affect the health of seabirds and humans through the food chain. One way to address this marine plastic problem is recycling. Improving the recycling rate of resources such as flexible packaging and plastic bottles will help prevent plastic from entering the ocean. However, current recycling practices face a challenge: the printed layer on plastic substrates does not detach during the recycling process, and its inclusion in the plastic causes deterioration of color and physical properties, reducing the value of recycled plastic. If the printed layer can be detached from the plastic substrate during the recycling process, this problem can be solved, leading to an increase in the value of recycled plastic. As a result, it is expected that new recycling companies will enter the market, municipalities will improve their separate collection systems, and this will contribute to improving the marine plastic problem. Therefore, there is a need to develop materials that can form a printed layer that can be detached from the plastic substrate during the recycling process. On the other hand, the printed layer needs not only the blocking resistance required of conventional inks, but also the ability to resist friction and scratching during normal use, as well as during tape removal. Achieving both detachability during the recycling process and resistance to these requirements has been difficult.

[0003] Furthermore, since materials used to form printing layers on plastic substrates are increasingly being replaced with toluene-free and methyl ethyl ketone (MEK)-free alternatives due to concerns about worker health and the environment, materials that address the above issues must also be developed with this in mind.

[0004] Conventional technologies disclose a method in which a coating layer containing styrene-maleic acid resin, rosin-maleic acid resin, or acrylic acid copolymer resin is placed between printed layers on a heat-shrinkable PET film, and the coating layer is removed with alkaline water (Patent Documents 1 and 2). However, these technologies are limited to solvent-based systems, and from an environmental perspective, water-based systems are needed. Examples have also been disclosed in which deinking of the topcoat ink layer is achieved by using a water-based resin as the coating layer (Patent Documents 3 and 4). However, Patent Document 3 has the problem that the ink is limited to active energy curing inks, and Patent Document 4 uses a water-based urethane resin primer, leaving the problem of low coating film durability. In addition, it is said that deinking is possible even under strong alkali and low temperatures. That is, there is a problem that the coating film will deink under normal usage conditions such as when strong alkaline substances such as detergents adhere to printed materials in daily life. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-84670 [Patent Document 2] Japanese Patent Publication No. 2004-240029 [Patent Document 3] Patent No. 7404578 [Patent Document 4] Japanese Patent Publication No. 2017-114930 [Overview of the project] [Problems that the invention aims to solve]

[0006] In view of the above, the object of the present invention is to provide a deinking primer composition that exhibits printing performance (adhesion, abrasion resistance, scratch resistance, blocking resistance, and shrinkage suitability) equivalent to conventional inks on general-purpose plastic substrates, while simultaneously possessing alkali resistance at low temperatures and achieving deinking performance at high temperatures and low alkali concentrations. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors have found that a desorption primer composition for forming the desorption primer layer in a printed material laminated in the order of at least a plastic substrate, a desorption primer layer, and a printed layer, wherein the desorption primer composition contains at least a (meth)acrylic resin and an aqueous solvent mainly composed of water, and the (meth)acrylic resin has an acid value of 10 to 90 mgKOH / g and a glass transition temperature of -30°C to 90°C can solve the above problems, and have completed the present invention.

[0008] In other words, the present invention provides a desorption primer composition for forming the desorption primer layer of a printed material laminated in the order of at least a plastic substrate, a desorption primer layer, and a printed layer, wherein the desorption primer composition contains at least a (meth)acrylic resin and an aqueous solvent mainly composed of water, and the (meth)acrylic resin has an acid value of 10 to 90 mgKOH / g and a glass transition temperature of -30°C to 90°C.

[0009] Furthermore, the present invention provides a printed material comprising at least a plastic substrate, a desorption primer layer, and a printed layer laminated in that order, wherein the desorption primer layer is formed from the above-mentioned desorption primer composition.

[0010] Furthermore, the present invention provides a recycling method for recovering a plastic substrate from which a printed layer has been removed from a printed matter laminated in the order of at least a plastic substrate, a primer layer for detachment, and a printed layer, wherein the primer layer for detachment is formed of a primer composition for detachment, and the printed matter is immersed in an alkaline aqueous solution to detach the printed layer from the plastic substrate.

Advantages of the Invention

[0011] A printed matter including a primer layer for detachment formed of the primer composition for detachment of the present invention exhibits printing performance (adhesion, abrasion resistance, scratch resistance, blocking resistance, and shrinkage suitability) equivalent to that of conventional inks even on a general-purpose plastic substrate, and at the same time has alkali resistance at low temperatures and can achieve detachment performance at high temperatures and low alkali concentrations.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the primer composition for detachment of the present invention and each part constituting a printed matter having the same will be described in detail.

[0013] In the present specification, “(meth)acryl” means acrylic and / or methacrylic, and “(meth)acrylate” means acrylate and / or methacrylate.

[0014] <Primer Composition for Detachment> The primer composition for detachment of the present invention is a composition for forming a primer layer for detachment. That is, the primer layer for detachment is a coating layer of the primer composition for detachment of the present invention. The primer layer for detachment is formed on a plastic substrate, and by laminating a printed layer on the primer layer for detachment, the printed layer can be detached from the plastic substrate. The primer composition for detachment contains at least a (meth)acrylic resin and an aqueous solvent mainly composed of water, and the (meth)acrylic resin has an acid value of 10 to 90 mgKOH / g and a glass transition temperature of -30°C to 90°C.

[0015] While a resist ink composition can also be mentioned as a composition to be removed from a substrate in a similar manner to the present invention, this resist ink composition is intended to remove the coating film from the substrate in advance, leaving a portion of it, in order to process the substrate. Therefore, it is fundamentally different in its use and purpose from the desorption primer composition of the present invention, which is intended to desorb the entire laminated printed layer and recycle the substrate, and thus does not fall under the category of well-known technologies of the present invention.

[0016] Furthermore, the delamination primer composition of the present invention has the function of adhering to the printed layer made of ink and peeling off the plastic substrate under certain conditions. Its application differs from that of an ink composition that is required not to peel off the substrate, and their purposes are contradictory.

[0017] <(meth)acrylic resin> The desorption primer composition of the present invention contains a (meth)acrylic resin. Here, (meth)acrylic resin refers to a resin having constituent units derived from (meth)acrylic acid ester monomers, and examples include acrylic resin, styrene-acrylic resin, polyester-acrylic resin, urethane-acrylic resin, vinyl chloride vinyl acetate copolymer-acrylic resin, silicone-acrylic resin, acrylamide resin, epoxy-acrylic resin, and the like. In other words, (meth)acrylic resin refers to a resin obtained by (co)polymerizing (meth)acrylic acid ester as an essential monomer, and, if necessary, with other polymerizable unsaturated group-containing compounds.

[0018] Examples of (meth)acrylic acid ester monomers 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, perfluoro Examples include cyclohexyl (meth)acrylate, glycidyl (meth)acrylate, allyl glycidyl ether, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(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, acetoacetoxyethyl (meth)acrylate, etc. The (meth)acrylic acid ester monomer may be a single type or a combination of two or more types.

[0019] Examples of polymerizable unsaturated group-containing compounds include 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. The polymerizable unsaturated group-containing compound may be a single compound or a combination of two or more compounds.

[0020] Furthermore, the (meth)acrylic resin may be a product of reaction with a self-crosslinking component. In other words, the (meth)acrylic resin may be of the self-crosslinking type. Examples of self-crosslinking components include isocyanate compounds, epoxy compounds, amine compounds, melamine compounds, hydrazine compounds, aldehyde compounds, oxazoline compounds, and aziridine compounds. The content of the self-crosslinking component is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 6 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the solid content of the (meth)acrylic resin. Having the content of the self-crosslinking component within the above range may result in good storage stability of the desorption primer composition.

[0021] (Meth)acrylic resins can be produced, for example, by polymerizing various monomers in the presence of a polymerization initiator at a temperature range of 50°C to 180°C, more preferably 80°C to 150°C. Examples of polymerization methods include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Furthermore, when (meth)acrylic resins are copolymers, they may be random copolymers, block copolymers, graft copolymers, etc., from the viewpoint of their polymerization mode.

[0022] The weight-average molecular weight of the (meth)acrylic resin is preferably between 2,000 and 1,500,000, from the viewpoint of achieving both desorption properties and adhesion to plastic substrates. The weight-average molecular weight of (meth)acrylic resin can be determined by gel permeation chromatography (GPC).

[0023] (Meth)acrylic resin may be used as an aqueous resin after undergoing a neutralization reaction. The aqueous resin may be in emulsion form or dissolved form. The (meth)acrylic resin of the present invention is preferably a (meth)acrylic resin emulsion having a core-shell structure. This core-shell emulsion refers to a state in which a first polymer is dispersed in an aqueous medium by a second polymer, and usually the second polymer is located on the outermost surface of the resin particles to form the shell portion, and part or all of the first polymer often forms the core portion.

[0024] The (meth)acrylic resin content in the desorption primer composition of the present invention is preferably in the range of 5% to 70% by mass, and more preferably in the range of 10% to 50% by mass, relative to the total amount of the desorption primer composition.

[0025] The content of (meth)acrylic resin in the desorption primer composition of the present invention is preferably 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, based on the total solid content of the desorption primer composition. Within the above range, the decolorizing primer composition of the present invention provides excellent adhesion to the plastic substrate when forming the printed layer and an appropriate viscosity as a decolorizing primer composition, resulting in good work efficiency during manufacturing and printing layer formation, and enabling uniform decolorization of the printed layer during the deinking process. Furthermore, inks generally contain pigments and many additives from the viewpoint of image formation and coating film properties, so their delamination properties vary greatly depending on various factors such as the type and concentration of pigments and the printing thickness. By applying ink as a topcoat on the delamination primer composition, the printed layer can be suitably delaminated regardless of the delamination properties of the ink itself. In particular, if 50% by mass or more of the solid content of the primer composition is (meth)acrylic resin components, the topcoat ink layer can be uniformly delaminated during alkali treatment, regardless of the type and concentration of the pigments in the topcoat ink, the printing thickness, etc., and the topcoat ink layer can be efficiently delaminated.

[0026] <Glass transition temperature of (meth)acrylic resin> The (meth)acrylic resin of the present invention is a (meth)acrylic resin having a glass transition temperature (Tg) of -30°C or higher and 90°C or lower. If the glass transition temperature is below -30°C, the abrasion resistance, scratch resistance, and blocking resistance may deteriorate. If the glass transition temperature is above 90°C, the adhesion, detachability, and shrinkage suitability may deteriorate. From the viewpoint of more effectively improving adhesion, abrasion resistance, scratch resistance, blocking resistance, detachability, and shrinkage suitability, the glass transition temperature (Tg) of the (meth)acrylic resin is more preferably -30°C or higher and 50°C or lower, even more preferably -30°C or higher and 20°C or lower, and even more preferably -30°C or higher and 0°C or lower.

[0027] Note that the glass transition temperature (Tg) refers to the so-called calculated glass transition temperature, which is the value calculated using the method described below. (Formula 1) 1 / Tg(K)=(W1 / T1)+(W2 / T2)+...(Wn / Tn) (Equation 2) Tg(°C) = Tg(K) - 273 In Equation 1, W1, W2, ...Wn represent the mass percentage of each monomer relative to the total mass of monomers used in the production of the polymer, and T1, T2, ...Tn represent the glass transition temperature (K) of the homopolymer of each monomer. The values ​​of T1, T2, ...Tn are those listed in PolymerHandbook (Fourth Edition, edited by J. Brandrup, E. Himmmergut, and E. A. Grulke). For monomers whose homopolymer glass transition temperature is not listed in PolymerHandbook, the glass transition temperature was measured using a differential scanning calorimeter "DSCQ-100" (manufactured by TA Instruments) in accordance with JIS K7121. Specifically, the polymer, from which the solvent had been completely removed by vacuum suction, was subjected to a heating rate of 20°C / min, and the change in heat quantity was measured in the range of -100°C to +200°C. The point where a line equidistant in the vertical direction from the extended line of each baseline intersected the curve of the stepwise transition portion of the glass transition was defined as the glass transition temperature.

[0028] <(meth)acrylic resin acid value> The (meth)acrylic resin of the present invention is a (meth)acrylic resin with an acid value of 10 to 90 mg / KOH. If the acid value (also referred to as "AV") of the above (meth)acrylic resin is 10 mg KOH / g or higher, the desorption properties can be improved more effectively, and if it is 90 mg KOH / g or lower, the alkali resistance, adhesion, and shrinkage suitability at low temperatures can be improved more effectively. From a similar viewpoint, the acid value of the above (meth)acrylic resin is preferably 85 mg KOH / g or lower, more preferably 65 mg KOH / g or lower, and even more preferably 50 mg KOH / g or lower. The acid value refers to the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 gram of resin.

[0029] In this embodiment, the (meth)acrylic resin is preferably an acrylic resin (i.e., a resin obtained by polymerizing substantially only (meth)acrylic acid ester monomers) or a styrene-acrylic resin (i.e., a resin obtained by copolymerizing styrene monomer and (meth)acrylic acid ester monomer), and more preferably an acrylic resin. That is, the (meth)acrylic resin of the present invention is preferably a homopolymer or copolymer of (meth)acrylate or a copolymer obtained by copolymerizing styrene monomer and (meth)acrylic acid ester monomer, and more preferably a homopolymer or copolymer of (meth)acrylate. In this case, adhesion, blocking resistance, heat resistance, water friction resistance, and alcohol resistance can be more effectively improved.

[0030] The (meth)acrylic resin of the present invention can be made aqueous by introducing a carboxyl group into the molecule and neutralizing it with a basic compound, or by forming a protective colloid with a known emulsifier or polymer. As the basic compound, an amine compound is preferred, and the use of ammonia is preferred.

[0031] The (meth)acrylic resin of the present invention is preferably alkali-insoluble from the viewpoint of alkali resistance at room temperature. Here, alkali-insolubleness is determined based on the following method. To 100g of a 2% by mass sodium hydroxide aqueous solution heated to 70°C, 3g of resin component as solid content was added and stirred for 5 minutes. The solution was then left standing for 1 day while maintaining its temperature at 70°C. After 1 day, the solution was allowed to cool to room temperature (25°C), and the NTU (Nephelometric Turbidity Unit) was measured using a Lovibond TB 300 IR turbidimeter (Tintmaker). The solution was also filtered using Whatman FILTER PAPER No. 1 (cytiva), and any undissolved resin component and precipitates due to the room temperature adjustment were visually inspected. If the turbidity is 50 NTU or higher, or if there are undissolved particles, the resin component is judged to be alkali-insoluble. If the turbidity is less than 50 NTU, and there are no undissolved resin components or precipitates due to exposure to room temperature, the resin component is judged to be alkali-soluble.

[0032] <Aqueous solvents> The desorption primer composition of the present invention contains an aqueous solvent mainly composed of water. Here, "mainly composed of water" means that 50% by mass or more of the total amount of medium in the desorption primer is water. This medium also includes water and solvents contained in the (meth)acrylic resin and other components. Examples of aqueous solvents used in this embodiment include water alone or organic solvents miscible with water. Examples of the above organic solvents include alcohol-based solvents such as methanol, ethanol, propanol, butanol, and isopropyl alcohol; ketone-based solvents such as acetone, methyl ethyl ketone, and cycloxanone; and glycol ether-based organic solvents 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. The aqueous solvent may be used alone or in combination of two or more types.

[0033] The above-mentioned aqueous solvent is preferably contained in an amount of 50% to 95% by mass, and more preferably in an amount of 65% to 90% by mass, relative to the total amount of the desorption primer composition.

[0034] <Other ingredients> The desorption primer composition of the present invention may contain other components. These other components include other resins; various additives such as film-forming aids, crosslinking agents, curing accelerators, plasticizers, antistatic agents, waxes, light stabilizers, flow regulators, leveling agents, rheology control agents, defoaming agents, antiblocking agents, infrared absorbers, ultraviolet absorbers, antioxidants, extender pigments, fragrances, flame retardants, and photocatalytic compounds; and colorants such as dyes, inorganic pigments, and organic pigments. The desorption primer composition of the present invention preferably contains 5% to 70% by mass of (meth)acrylic resin and 50% to 95% by mass of an aqueous medium, based on the total amount of the desorption primer composition. Therefore, from the viewpoint of ensuring a sufficient content of (meth)acrylic resin, the desorption primer composition of the present invention preferably does not contain a colorant.

[0035] Other resins mentioned above include, for example, cellulose resins, urethane resins, polyamide resins, vinyl chloride-vinyl acetate copolymer resins, ketone resins, polyester resins, rosin-modified maleic acid resins and rosin-modified fumaric acid resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, cyclized rubber, chlorinated rubber, butyral resins, petroleum resins, and other resins, as well as radical copolymers such as styrene-(anhydride) maleic acid resins and terpene-(anhydride) maleic acid resins, which are copolymers of polymerizable monomers such as itaconic acid, maleic acid, fumaric acid, cinnamic acid or their acid anhydrides, polymerizable monomers having sulfonic acid groups such as sulfonated styrene, and polymerizable monomers having sulfonamide groups such as vinylbenzenesulfonamide, and acid-modified polyolefin resins, which can be used individually or in combination.

[0036] (Manufacturing of desorption primer composition) The method for producing the desorption primer composition of this embodiment is not particularly limited, but for example, a desorption primer composition can be obtained by dispersing a mixture of the above-mentioned aqueous solvent with additives as needed, then adding (meth)acrylic resin, aqueous solvent, and additives such as surfactants as needed, and stirring and mixing. For the above dispersion and stirring and mixing, dispersers such as bead mills, Eiger mills, sand mills, gamma mills, and attritors, which are commonly used in the production of inks for flexographic printing or gravure printing, can be used.

[0037] When the desorption primer composition of the present invention is applied by flexographic printing or gravure printing, its viscosity should be 7 to 50 seconds, more preferably 12 to 40 seconds, using a Zaan Cup #3 manufactured by Rigosha at 25°C. Furthermore, the surface tension of the desorption primer composition at 25°C is preferably 25 to 50 mN / m. The lower the surface tension of the desorption primer composition, the better the wettability of the desorption primer composition to plastic substrates such as films. On the other hand, if the surface tension exceeds 50 mN / m, the wettability of the desorption primer composition to plastic substrates such as films decreases, which is likely to cause repulsion. From a similar viewpoint, the surface tension of the desorption primer composition at 25°C is more preferably 33 mN / m or higher, and more preferably 43 mN / m or lower.

[0038] <Detachable primer layer> The detachable primer composition of the present invention forms a detachable primer layer when coated onto a plastic substrate and then dried. In other words, the detachable primer layer is formed by the detachable primer composition of the present invention. To put it another way, the detachable primer layer is a coated layer of the detachable primer composition of the present invention. As will be described later, a printed layer made of printing ink can be formed on the detachable primer layer. The detachable primer layer can be easily detached by treatment with an alkaline aqueous solution whose liquid temperature is adjusted to above a certain temperature. Since the detachable primer layer can be easily detached from the plastic substrate, the printed layer formed on top of the detachable primer layer can also be easily removed from the plastic substrate. A detailed explanation of the method for detaching the detachable primer layer will be given later.

[0039] The desorption primer composition of the present invention can be applied or coated onto a plastic substrate using known printing methods such as gravure printing and flexographic printing. Known printing methods include, in addition to gravure printing and flexographic printing, any or a combination of two or more coating methods such as T-die coater, lip coater, knife coater, curtain, inkjet, bar coater, roll coater, spray coater, comma coater, reverse roll coater, direct gravure coater, reverse gravure coater, offset gravure coater, roll kiss coater, reverse kiss coater, kiss gravure coater, reverse kiss gravure coater, air doctor coater, wire bar coater, dip coater, blade coater, brush coater, die slot coater, offset printing machine, screen printing machine, etc. When applying the coating, the material is diluted with a water-based solvent, such as an alcohol-based organic solvent like ethyl alcohol, isopropyl alcohol, or n-propyl alcohol, mixed with water, to a viscosity and concentration suitable for various printing methods such as gravure printing and flexographic printing. This diluted solvent is then supplied to each printing unit either alone or in a mixture.

[0040] Furthermore, the method for applying the desorption primer composition to the plastic substrate can be either an in-line coating method in which the desorption primer composition is applied during the stretching process of the plastic substrate (e.g., biaxial stretching) and then the stretching process is carried out further, or an offline coating method in which the desorption primer composition is applied after the stretching process of the plastic substrate (e.g., biaxial stretching) and dried to form a primer layer.

[0041] The thickness of the desorption primer layer formed using the desorption primer composition of the present invention by gravure printing, flexographic printing, or the like is preferably 10 μm or less, and more preferably 5 μm or less.

[0042] <Printed material> In this invention, the printed material refers to a laminate in which a plastic substrate, a desorption primer layer, and a printed layer are laminated in that order. The printed material consisting of the laminate may include other layers or may include multiple printed layers. The desorption primer layer may be simply referred to as the "primer layer."

[0043] When manufacturing printed materials consisting of the above laminate, if a primer layer is formed on a plastic substrate, as explained in the section above (Detachable Primer Layer), the primer layer may be formed by an in-line coating method in which the detachable primer composition of the present invention is applied during the stretching process of the plastic substrate film, and then the stretching process is carried out further. Alternatively, the primer layer may be formed by an offline coating method in which the detachable primer composition of the present invention is applied after the stretching process of the plastic substrate film, and then dried to form the primer layer.

[0044] The printed materials of the present invention can be used as packaging materials. Examples of packaging materials include packaging bags, shrink labels, and various shrink labels such as printed materials for wrap films. When used in packaging bags, the printed material of the present invention is filled with contents through its opening, and then the opening is heat-sealed to produce a product using the packaging material. The contents to be filled are not particularly limited and include confectionery, staples, processed agricultural products, processed livestock products, processed marine products, fruits, vegetables, cooked foods, dairy products and other foods; pharmaceuticals; cosmetics; detergents; vacuum insulation materials; batteries, etc. When used for shrink labels, the printed material is tubed by means of heat sealing or other methods, attached to a PET container or glass container, and then heated to a predetermined shrinkage temperature to shrink it and make it adhere tightly to the container. When used in plastic wrap films, printed materials are used for packaging irregularly shaped objects, bundling products, and providing guarantee packaging.

[0045] <Plastic substrate> Examples of the above-mentioned plastic substrates include base film, sealant film, unstretched metal-deposited film, stretched metal-deposited film, and transparent stretched metal-deposited film.

[0046] Examples of the above-mentioned base films include polyethylene terephthalate (PET) film (OPET: biaxially oriented polyethylene terephthalate film, etc.), polybutylene terephthalate (PBT) film, polystyrene film, polyamide film, nylon film, polyacrylonitrile film, polyolefin films such as polyethylene film (OPE: biaxially oriented polyethylene film, LLDPE: low-density polyethylene film, HDPE: high-density polyethylene film) and polypropylene film (CPP: unoriented polypropylene film, OPP: biaxially oriented polypropylene film), polyvinyl alcohol film, ethylene-vinyl alcohol copolymer film, cellophane, and the like. A base film coated for purposes such as gas barrier properties may be used. Examples of commercially available coated base films include K-OPP film and K-PET film.

[0047] A shrinkable film may be used as the base film. Examples of such shrinkable films include shrinkable polypropylene, shrinkable polyvinyl chloride, shrinkable polystyrene, shrinkable polyethylene terephthalate, and hybrid polystyrene (a hybrid film of polystyrene and polyethylene terephthalate, etc.). The (meth)acrylic resin of the present invention exhibits good conformability to shrinkable films, making it easier to achieve the effects of the present invention. Furthermore, the desorption primer composition of the present invention is less prone to clouding and exhibits good shrinkage suitability when shrinking with hot water, steam, or hot air. From these viewpoints, the plastic base material of the present invention is preferably a shrinkable film. Furthermore, polystyrene is easily dissolved on the surface by the solvent in the ink, and the ink and shrinkable film adhere firmly, making detachment difficult. On the other hand, when a detachment primer layer formed by the detachment primer composition of the present invention is laminated between the printing layer and the shrinkable film, direct contact between the shrinkable film and the printing layer can be reduced, thereby reducing the influence of the ink solvent. As a result, even if the plastic substrate is a shrinkable film with poor detachability, good detachment performance can be achieved. Therefore, the plastic substrate of the present invention is more preferably a shrinkable film containing polystyrene, and more specifically, it is more preferably shrinkable polystyrene or hybrid polystyrene.

[0048] Examples of the sealant films mentioned above include CPP film (unoriented polypropylene film) and LLDPE film (linear low-density polyethylene resin film). As the above-mentioned unstretched metal-deposited film, a VM-CPP film can be used, which is obtained by depositing a metal such as aluminum onto a CPP film. As the metal-deposited stretched film mentioned above, a VM-OPP film can be used, which is an OPP film to which a metal such as aluminum has been deposited. Examples of the transparent vapor-deposited stretched films mentioned above include films obtained by vapor-depositing silica or alumina onto OPP film, PET film, nylon film, etc. Films with a coating applied to the vapor-deposited layer may also be used for purposes such as protecting the inorganic vapor-deposited layer of silica or alumina. Furthermore, metal-deposited films such as unstretched metal-deposited films, stretched metal-deposited films, and transparent stretched metal-deposited films can be described as substrate films having a vapor-deposited layer.

[0049] Furthermore, films made from materials containing biomass-derived components can also be used as plastic substrates. Biomass films are sold by various companies, and films and sheets listed in the biomass-certified product list provided by the Japan Organic Resources Association can also be used. A well-known example of a film made from biomass-derived ethylene glycol is derived from ethanol produced from biomass (biomass ethanol). For example, biomass-derived ethylene glycol can be obtained by conventionally known methods, such as a method that produces ethylene glycol via ethylene oxide from biomass ethanol. Alternatively, commercially available biomass ethylene glycol may be used; for example, the biomass ethylene glycol commercially available from India Glycol can be suitably used.

[0050] Alternatively, products using biomass raw materials, distinguished by their biomass plasticity as defined by ISO 16620 or ASTM D6866, are also available. In the atmosphere, 10 12 Radioactive carbon-14C is present at a rate of one molecule per unit, and this rate does not change even in atmospheric carbon dioxide. Therefore, this rate remains unchanged even in plants that fix carbon dioxide through photosynthesis. For this reason, plant-derived resins contain radioactive carbon-14C. In contrast, fossil fuel-derived resins contain almost no radioactive carbon-14C. By measuring the concentration of radioactive carbon-14C in the resin using an accelerator mass spectrometer, the proportion of plant-derived resin in the resin, i.e., the biomass plastic content, can be determined. Examples of plant-derived low-density polyethylene that are biomass plastics with a biomass plastic content of 80% or more, preferably 90% or more, as defined by ISO 16620 or ASTM D6866, include Braskem's product names "SBC818," "SPB608," "SBF0323HC," "STN7006," "SEB853," and "SPB681," and films using these as raw materials can be suitably used.

[0051] For example, as an alternative to conventional polyolefin films using petroleum-based raw materials, biomass polyolefin films such as biomass polyethylene films and biomass polyethylene-polypropylene films, which contain ethylene resins made from biomass-derived ethylene glycol, are also known. The ethylene-based resin is not particularly limited except for the use of ethylene glycol derived from the biomass mentioned above as part of the raw materials. Examples include ethylene homopolymers, copolymers of ethylene and α-olefins with ethylene as the main component (ethylene-α-olefin copolymers containing 90% by mass or more of ethylene units), and these can be used individually or in combination of two or more. The α-olefin constituting the copolymer of ethylene and α-olefin is not particularly limited, and examples include α-olefins having 4 to 8 carbon atoms, such as 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene. Known polyethylene resins such as low-density polyethylene resin, medium-density polyethylene resin, and linear low-density polyethylene resin can be used. Among these, linear low-density polyethylene resin (LLDPE) (a copolymer of ethylene and 1-hexene, or a copolymer of ethylene and 1-octene) is preferred from the viewpoint of making it even less likely for damage such as punctures or tears to occur when the films rub against each other, and has a density of 0.910 to 0.925 g / cm³. 3 A linear low-density polyethylene resin is more preferable.

[0052] The biomass film may be a laminate formed by stacking multiple biomass films, or it may be a laminate formed by combining a conventional petroleum-based film with a biomass film.

[0053] The above-mentioned plastic substrate may be subjected to some kind of surface treatment, such as physical treatments like corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, or flame treatment, or chemical treatments such as oxidation treatment using chemicals, or other treatments.

[0054] The above-mentioned plastic substrate can be manufactured using conventionally known film formation methods such as extrusion, casting, T-die, cutting, and inflation methods. It may be an unstretched film, or, from the viewpoint of film strength, dimensional stability, and heat resistance, it may be stretched in one or two axes using a tenter method, tubular method, etc.

[0055] The above-mentioned plastic substrate may contain additives as needed. Specifically, plastic compounding agents and additives such as elastomers, lubricants, crosslinking agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, and pigments may be added to improve or modify properties such as processability, heat resistance, weather resistance, mechanical properties, dimensional stability, oxidation resistance, slipperiness, mold release properties, flame retardancy, mold resistance, electrical properties, and strength. The amount of additives added should be adjusted within a range that does not affect other properties or recyclability.

[0056] The film thickness of the above-mentioned plastic substrate is not particularly limited and can be appropriately selected within the range of 0.1 to 300 μm from the viewpoint of moldability and transparency. Preferably, it is in the range of 0.3 to 100 μm. If the film thickness of the substrate is 0.1 to 300 μm, good strength and processing stability can be obtained.

[0057] On the above-mentioned plastic substrate, there may be other layers, such as a coating layer that provides functions such as mold release and antistatic properties, a barrier resin layer that provides barrier properties, or a heat-resistant resin layer that provides heat resistance. In this case, the other layer may be located between the plastic substrate and the primer layer, between the primer layer and the printing layer, or on the outermost surface of the printed material, i.e., the surface of the printed material on the plastic substrate side and / or the surface on the printing layer side.

[0058] <Print layer> The printed layer is a layer on which characters, figures, symbols, or other desired patterns are printed, and is formed by printing ink. There are no particular limitations on the printing ink or printing method, and known printing inks and printing methods can be used. Depending on the medium used, printing inks include water-based inks, organic solvent-based inks, UV inks, etc. As for the printing ink that forms the printed layer of the present invention, water-based inks or organic solvent-based inks are preferred from the viewpoint of adhesion to the plastic substrate, conformability when the plastic substrate shrinks, and prevention of ink cracking.

[0059] The printing methods described above often utilize printing inks that employ gravure printing, flexographic printing, lithographic offset printing, and inkjet recording printing, which are commonly used for the films used as the substrate. In addition, printing inks that combine these printing methods with curing methods using active energy rays such as ultraviolet (UV), LED, or electron beam (EB), or curing methods using heat are also used. Specifically, examples include gravure printing inks and flexographic printing inks (in some industries, gravure printing inks and flexographic printing inks are referred to as liquid printing inks), UV-curable inks for lithographic offset printing, electron beam-curable inks for lithographic offset printing, UV-curable inks for inkjet recording printing, and electron beam-curable inks for inkjet recording printing.

[0060] The ink may contain a coloring agent as an essential component, or it may be a so-called clear ink or varnish that substantially does not contain a coloring agent. Furthermore, the printing layer may consist of multiple layers. Specifically, it may be a white printing layer - a color printing layer, a white printing layer - a white printing layer - a color printing layer, a white printing layer - a color printing layer - a clear / varnish printing layer, a white printing layer - a white printing layer - a color printing layer - a clear / varnish printing layer, and so on. The following describes the liquid printing inks most commonly used for printing on film.

[0061] (Liquid printing ink) Liquid printing inks are used as gravure printing inks and flexographic printing inks, and are broadly classified into organic solvent-type liquid printing inks, which use organic solvents as the main solvent, and aqueous liquid printing inks, which use water as the main solvent. As the printing ink for forming the printed layer of the present invention, organic solvent-type liquid printing inks and aqueous liquid printing inks are preferred.

[0062] (Organic solvent-based liquid printing ink) Organic solvent-based liquid printing inks are produced by dispersing a mixture containing a binder resin, organic solvent medium, dispersant, defoamer, etc., in a disperser to obtain a pigment dispersion. The resulting pigment dispersion is then mixed with resin, organic solvent medium, and, if necessary, leveling agents and other additives, and stirred. Dispersers commonly used in the production of gravure and flexographic printing inks include bead mills, Eiger mills, sand mills, gamma mills, and attritors.

[0063] The viscosity of the above-mentioned organic solvent-type liquid printing ink is preferably in the range of 10 mPa·s or higher from the viewpoint of preventing pigment sedimentation and ensuring appropriate dispersion, and 1000 mPa·s or lower from the viewpoint of workability during ink manufacturing and printing, whether used as a gravure printing ink or a flexographic printing ink. The above viscosity was measured at 25°C using a Tokimec-type B viscometer.

[0064] The viscosity of the ink can be adjusted by appropriately selecting the type and amount of raw materials used, binder resin, pigment, organic solvent, etc. Furthermore, the viscosity of the ink can also be adjusted by controlling the particle size and particle size distribution of the pigment in the ink.

[0065] The above-mentioned organic solvent-type liquid printing ink exhibits excellent adhesion to various substrates and can be used for printing on paper, synthetic paper, thermoplastic resin films, plastic products, steel plates, etc. It can be used as an ink for gravure printing using gravure printing plates made by electronic engraving or the like, or for flexographic printing using flexographic printing plates made by resin plates or the like.

[0066] The film thickness of the liquid printing ink formed using the above-mentioned organic solvent-type liquid printing ink by gravure printing or flexographic printing is, for example, 10 μm or less, preferably 5 μm or less.

[0067] (Binder resin (A)) Examples of binder resins (A) used in the above-mentioned organic solvent-type liquid printing inks include cellulose resins such as nitrated cotton, cellulose acetate propionate (CAP) and cellulose acetate butyronate (CAB), polyamide resins, urethane resins, acrylic resins, vinyl chloride-vinyl acetate copolymer resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, polyvinyl chloride resins, polyester resins, alkyd resins, rosin resins, rosin-modified maleic acid resins, ketone resins, cyclic rubbers, chlorinated rubbers, polyvinyl butyral resins, and petroleum resins.

[0068] Among these, cellulose resins, polyamide resins, urethane resins, acrylic resins, vinyl chloride resins, and polyvinyl butyral resins are preferred. In particular, it is preferable that the binder resin contains at least two types of resins. Preferably, the combination is selected from urethane resin / vinyl chloride resin, urethane resin / cellulose resin, polyamide resin / cellulose resin, acrylic resin / cellulose resin, vinyl chloride resin / cellulose resin, and urethane resin / polyvinyl butyral resin, and it is preferable that the two resins together make up 80 to 100% by mass of 100% by mass of the binder resin (A), and more preferably 90 to 100% by mass.

[0069] Furthermore, the mass ratio of urethane resin / vinyl chloride resin, urethane resin / cellulose resin, polyamide resin / cellulose resin, acrylic resin / cellulose resin, and vinyl chloride resin / cellulose resin is preferably 95 / 5 to 20 / 80. More preferably, the mass ratio is 90 / 10 to 50 / 50. This combination provides excellent basic performance characteristics desired in coating agents, such as abrasion resistance, blocking resistance, heat resistance, and oil resistance.

[0070] (Hardening agent) Additionally, a hardener may be used in combination with the binder resin (A). A general-purpose hardener for gravure printing inks using organic solvents can be used as the hardener, but isocyanate-based hardeners are the most commonly used. From the viewpoint of curing efficiency, the amount of isocyanate compound added is preferably in the range of 0.3% to 10.0% by mass relative to the liquid printing ink solid content, and more preferably in the range of 1.0% to 7.0% by mass.

[0071] The binder resin (A) is preferably in the range of 0.15 to 50% by mass relative to the liquid printing ink, and most preferably in the range of 1 to 40% by mass.

[0072] (Organic solvents) There are no particular restrictions on the organic solvent used in organic solvent-based liquid printing inks; any known organic solvent can be used. Generally, ethyl acetate, propyl acetate, isopropanol, and n-propanol are often used, considering both the hygiene of the printing process and the toxicity of the materials.

[0073] (Coloring agent) Organic solvent-based liquid printing inks contain colorants and can be used as liquid printing inks containing colorants for design printing and other purposes to impart aesthetic appeal. Examples of colorants include inorganic pigments, organic pigments, and dyes used in general inks, paints, and recording agents, with pigments being preferred.

[0074] Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, anthraquinone pigments, anthancerone pigments, dianthaquinonyl 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, chromophthal yellow, chromophthal red, phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone magenta, quinacridone red, indanthrone blue, pyrimidine yellow, thioindigobordeaux, thioindigomagenta, perylene red, perinone orange, isoindolinone yellow, aniline black, diketopyrrolopyrrole red, and daylight fluorescent pigments. Both unacidified and acidified pigments can be used.

[0075] Examples of inorganic pigments include white inorganic pigments such as titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, litsubone, antimony white, and gypsum. Among inorganic pigments, the use of titanium dioxide is particularly preferred. Titanium dioxide is white and is preferred in terms of coloring power, opacity, chemical resistance, and weather resistance, and from the viewpoint of printing performance, titanium dioxide that has been treated with silica and / or alumina is preferred. Examples of inorganic pigments other than white include aluminum particles, mica, bronze powder, chrome vermilion, lead yellow, cadmium yellow, cadmium red, ultramarine, Prussian blue, red iron oxide, yellow iron oxide, iron black, and zircon. Aluminum is available in powder or paste form, but it is preferred to use it in paste form from the viewpoint of handling and safety, and the use of leafing or non-leafing is appropriately selected from the viewpoint of brightness and density.

[0076] The above-mentioned pigments are preferably included in an amount sufficient to ensure the concentration and coloring power of the liquid printing ink, i.e., 1 to 60% by mass relative to the total mass of the liquid printing ink, or 10 to 90% by mass in terms of solid content weight ratio in the liquid printing ink. Furthermore, these pigments can be used individually or in combination of two or more types.

[0077] Organic solvent-based liquid printing inks may also contain, as needed, waxes, chelating crosslinking agents, extender pigments, leveling agents, defoamers, plasticizers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, etc.

[0078] (Water-based liquid printing ink) The above-mentioned aqueous liquid printing ink is produced by dispersing a mixture of pigment, water alone, or an organic solvent miscible with water (sometimes referred to as an aqueous medium), a pigment dispersant, an antifoaming agent, etc., in a disperser to obtain a pigment dispersion. The aqueous liquid printing ink is then produced by adding an aqueous resin, water, or an organic solvent miscible with water, and, if necessary, additives such as a leveling agent, to the obtained pigment dispersion and stirring and mixing. Dispersers commonly used in the production of gravure and flexographic printing inks include bead mills, Eiger mills, sand mills, gamma mills, attritors, etc.

[0079] When the above-mentioned water-based liquid printing ink is used as a flexographic ink, its viscosity should be 7 to 25 seconds at 25°C using a Zaan Cup #4 manufactured by Rigosha, and more preferably 10 to 20 seconds. Furthermore, the surface tension of the obtained flexographic ink at 25°C is preferably 25 to 50 mN / m, and more preferably 33 to 43 mN / m. The lower the surface tension of the ink, the better the wettability of the ink to the substrate such as film. However, if the surface tension is below 25 mN / m, the ink tends to spread, causing adjacent halftone dots in the midtone areas to connect easily, which can lead to staining of the printed surface called dot bridging. On the other hand, if the surface tension exceeds 50 mN / m, the wettability of the ink to the substrate such as film decreases, which can easily cause repelling.

[0080] On the other hand, when the above-mentioned water-based liquid printing ink is used as a gravure ink, its viscosity should be 7 to 25 seconds at 25°C using a Zaan Cup #3 manufactured by Rigosha, and more preferably 10 to 20 seconds. Furthermore, the surface tension of the obtained gravure ink at 25°C is preferably 25 to 50 mN / m, and more preferably 33 to 43 mN / m, similar to flexographic inks. The lower the surface tension of the ink, the better the wettability of the ink to the substrate such as film. However, if the surface tension falls below 25 mN / m, the ink tends to spread, causing adjacent halftone dots in the midtone areas to connect, which can easily lead to smudging on the printed surface, known as dot bridging. Conversely, if the surface tension exceeds 50 mN / m, the wettability of the ink to the substrate such as film decreases, which can easily cause repelling.

[0081] The viscosity of the ink can be adjusted by appropriately selecting the type and amount of raw materials used, binder resin, pigment, organic solvent, etc. Furthermore, the viscosity of the ink can also be adjusted by controlling the particle size and particle size distribution of the pigment in the ink.

[0082] The above-mentioned aqueous liquid printing ink exhibits excellent adhesion to various substrates and can be used for printing on paper, synthetic paper, thermoplastic resin films, plastic products, steel plates, etc. The film thickness of the aqueous liquid printing ink formed using the above-mentioned aqueous liquid printing ink by gravure printing or flexographic printing is, for example, 10 μm or less, preferably 5 μm or less.

[0083] (Water-based resin) Examples of aqueous resins used in the above-mentioned aqueous liquid printing inks include water-soluble or water-dispersible urethane resins, polyester resins, acrylic resins, urethane-acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, etc., which can be used individually or in combination of two or more. There are no particular limitations on the method for making these resins aqueous, and conventionally known methods can be used. Examples include, but are not limited to, a method of neutralizing the acid groups present in these resins with a neutralizing agent, a method of graft polymerizing ethylenically unsaturated monomers containing acid groups into these resins and then neutralizing them with a neutralizing agent, and a method of polymerizing ethylenically unsaturated monomers in an aqueous solvent using an aqueous resin having acid groups as a polymer emulsifier. Furthermore, the aqueous resin may have a core-shell structure. When dissolving or dispersing aqueous resins in aqueous solvents, a homogenizer or the like may be used as needed.

[0084] Examples of neutralizing agents include amine compounds such as ammonia, triethylamine, N,N-dimethylethanolamine, and monoethanolamine; non-volatile amine compounds such as triethylenediamine, diethanolamine, triethanolamine, diethylenetriamine, and diazabicyclooctene; metal hydroxides such as lithium hydroxide, potassium hydroxide, and sodium hydroxide; metal chlorides such as potassium chloride and sodium chloride; and metal sulfides such as copper sulfate. From the viewpoint of VOC reduction, it is preferable to use non-volatile compounds such as non-volatile amine compounds, metal hydroxides, metal chlorides, and metal sulfides.

[0085] When dispersing the aqueous resin in the aqueous solvent described later, an emulsifier may be used in combination. Examples of emulsifiers include nonionic emulsifiers such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene sorbitol tetraoleate, and polyoxyethylene-polyoxypropylene copolymer; anionic emulsifiers such as fatty acid salts such as sodium oleate, alkyl sulfate esters, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, and sodium alkyldiphenyl ethersulfonates; and cationic emulsifiers such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts.

[0086] The acid value of the aqueous resin is preferably 10 mg KOH / g or more and 300 mg KOH / g or less, and more preferably 10 mg KOH / g or more and 120 mg KOH / g or less. If the acid value is 10 mg KOH / g or more, the abrasion resistance, water abrasion resistance, and scratch resistance of the laminate can be improved when a curing agent is added. The acid value referred to here indicates the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 gram of resin. Furthermore, while there are no particular restrictions on the glass transition temperature of the aqueous resin, it is preferably in the range of -30 to 130°C, and more preferably in the range of -30°C to 55°C. If the Tg is -30°C or higher, the strength of the printed layer is maintained and the water-resistant friction properties of the laminate do not decrease. If it is 55°C or lower, the compatibility with other printed layers does not decrease, and the abrasion resistance, water-resistant friction properties, and scratch resistance of the laminate tend to be well maintained. Furthermore, the glass transition temperature (Tg) mentioned above refers to the so-called calculated glass transition temperature.

[0087] The weight-average molecular weight of the above-mentioned aqueous resin is preferably in the range of 5,000 to 1,500,000. If the weight-average molecular weight is 5,000 or higher, the heat resistance of the resin printing layer tends to not decrease, and the abrasion resistance and water abrasion resistance of the laminate tend to be maintained. If it is 1,500,000 or lower, the laminate tends to have both substrate adhesion and scratch resistance.

[0088] The content of the aqueous resin is arbitrary, but as an example, it is preferable to have 5% or more by mass in terms of solid content relative to the total mass of the aqueous liquid printing ink, and 70% or less by mass from the viewpoint of appropriate ink viscosity and work efficiency during ink manufacturing and printing, and more preferably in the range of 5 to 50% by mass. If the content is 5% by mass or more, the ink film strength will not decrease, and substrate adhesion, water friction resistance, etc. will be maintained well. Conversely, if it is 50% by mass or less, the decrease in coloring power can be suppressed, and high viscosity can be avoided, thus preventing a decrease in workability.

[0089] (aqueous medium) The aqueous medium may be water, or water mixed with a monohydric alcohol solvent such as ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, or 2-methyl-2-propanol; Polyhydric alcohol-based solvents such as ethylene glycol, 1,3-propanediol, propylene glycol, 1,2-butanediol, 1,4-butanediol, pentylene glycol, 1,2-hexanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, and glycerin;

[0090] Glycol ether solvents such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether;

[0091] Lactam-based solvents such as N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, and ε-caprolactam; Hydrophilic solvents such as formamide, N-methylformamide, N,N-dimethylformamide, Idemitsu Equamid M-100, Equamid B-100, and other amide solvents may be used in combination. These hydrophilic solvents may be used alone or in combination of two or more.

[0092] By using these hydrophilic solvents in combination, the wettability of the substrate and the drying properties of the water-based liquid printing ink (poor drying of the ink coating) can be controlled. In order to balance with VOC reduction, the content of the hydrophilic solvent is preferably 10% by mass or less of the total amount of water-based liquid printing ink, and more preferably 5% by mass or less.

[0093] (Coloring agent) Water-based liquid printing inks contain colorants and can be used as liquid printing inks containing colorants for design printing and other purposes to impart aesthetic appeal. Examples of colorants include inorganic pigments, organic pigments, and dyes used in general inks, paints, and recording agents, with pigments being preferred. Pigments similar to those used in organic solvent-type liquid printing inks can be used. Furthermore, if no colorant is included, the ink becomes a transparent printing layer after printing and can be used as a colorless transparent ink (in this technical field, it is commonly called an overcoat varnish or OP varnish because it is used to print a solid color on the outermost layer of a color printing layer to protect the color printing layer. In this invention, it may be referred to as OP varnish hereafter).

[0094] Organic pigments such as yellow, magenta, cyan, and black are preferably blended in a ratio of 5 to 30% by weight relative to the total mass of the water-based liquid printing ink. In the case of white titanium dioxide, it is preferable to blend it in a ratio of 10 to 60% by weight relative to the total mass of the water-based liquid printing ink.

[0095] The average particle size of the pigment is preferably in the range of 1 to 300 nm, and more preferably in the range of 50 to 150 nm. The pigment is preferably included in an amount sufficient to ensure the concentration and coloring power of the water-based liquid printing ink, i.e., 1 to 60% by weight relative to the total weight of the ink composition, or 10 to 90% by weight relative to the solid content of the ink composition. These pigments can be used individually or in combination of two or more types.

[0096] (Pigment-dispersed resin) Water-based liquid printing inks may contain a pigment dispersion resin for dispersing pigments. Any water-soluble resin can be used as the pigment dispersion resin, as long as it maintains the stability of the ink and has pigment dispersion ability. Examples of such pigment dispersion resins include polyvinyl alcohol, polyvinylpyrrolidone (commercial products such as ISP's K-30, K-60, K-90, etc.), polyethylene glycol, poly(meth)acrylic acid, (meth)acrylic acid-(meth)acrylate alkyl ester copolymer, styrene-(meth)acrylic acid-(meth)acrylate alkyl ester copolymer, styrene-(meth)acrylic acid copolymer, maleic acid-(meth)acrylate alkyl ester copolymer, styrene-maleic acid copolymer, styrene-maleic acid-(meth)acrylate alkyl ester copolymer, styrene-maleic acid half-ester copolymer, vinylnaphthalene-(meth)acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinylpyrrolidone-(meth)acrylate alkyl ester copolymer, vinylpyrrolidone-styrene copolymer, vinylpyrrolidone-vinyl acetate copolymer, and vinyl acetate-croton Water-soluble vinyl copolymers such as acid copolymers, vinyl acetate-(meth)acrylic acid copolymers, vinyl acetate-crotonic acid copolymers, polyvinyl sulfonic acid, sodium polyvinyl sulfonate, polystyrene sulfonic acid, sodium polystyrene sulfonate (e.g., Polinas PS-1, Polinas PS-5, manufactured by Tosoh Corporation), styrene sulfonic acid-maleic acid copolymers, polyitaconic acid, polyhydroxyethyl (meth)acrylate, poly(meth)acrylamide, (meth)acrylamide-(meth)acrylic acid copolymers, polyvinyl methyl ether, methyl vinyl ester, and carboxyvinyl polymer; water-soluble polyurethane resins obtained by polyaddition reaction of polyisocyanate and polyol, in which the entire resin is water-soluble by the introduction of hydrophilic groups; and water-soluble polyester resins obtained by polycondensation reaction of polycarboxylic acid and polyol, in which the entire resin is water-soluble by the introduction of hydrophilic groups.Cellulose derivatives such as methylcellulose, ethylcellulose, propylcellulose, ethylmethylcellulose, hydroxyalkylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, alkali metal carboxymethylcellulose, alkali metal cellulose sulfate, and cellulose graft polymers; polypeptides such as polyglutamic acid and polyaspartic acid; etc., can be used individually or in combination of two or more.

[0097] In particular, (meth)acrylic acid-(meth)acrylic acid alkyl ester copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid alkyl ester copolymer, styrene-(meth)acrylic acid copolymer, maleic acid-(meth)acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene-maleic acid-(meth)acrylic acid alkyl ester copolymer, and styrene-maleic acid half-ester copolymer are preferred from the viewpoint of excellent pigment adsorption capacity and dispersion stability. Furthermore, these resins may be synthesized by solution polymerization or bulk polymerization with a radical initiator, or commercially available products may be used.

[0098] Examples of commercially available products include BASF's JONCRYL67, JONCRYL678, JONCRYL586, JONCRYL611, JONCRYL683, JONCRYL690, JONCRYL57J, JONCRYL60J, JONCRYL61J, JONCRYL62J, JONCRYL63D, JONCRYLHPD-96J, JONCRYL501J, JONCRYL PDX-6102, and Big Chemie's DYSPERBYK180, DYSPERBYK Examples include 187, DYSPERBYK190, DYSPERBYK191, DYSPERBYK194, DYSPERBYK2010, DYSPERBYK2015, DYSPERBYK2090, DYSPERBYK2091, DYSPERBYK2095, DYSPERBYK2155, SOLSPERSE41000 from Lubrizol, and SMA1000H, SMA1440H, SMA2000H, SMA3000H, SMA17352H from Sartomer.

[0099] It is preferable to use the pigment dispersion resin in an amount of 10 to 60 parts by mass in terms of solid content per 100 parts by mass of pigment. If the amount of pigment dispersion resin is less than 10 parts by mass per 100 parts by mass of pigment, the pigment dispersion stability will decrease, which may worsen the dispersion stability and storage stability of the water-based liquid printing ink. On the other hand, if the amount of pigment dispersion resin exceeds 60 parts by mass per 100 parts by mass of pigment, the viscosity of the water-based liquid printing ink will increase significantly, which may adversely affect the storage stability of the ink. In addition, poor drying of the coating film may occur and the amount of components leached into water will increase, which may also reduce the physical properties of the coating film (substrate adhesion, water friction resistance, blocking resistance).

[0100] Water-based liquid printing inks may contain waxes and film-forming emulsions to provide coating durability. Suitable waxes include animal and plant-based waxes such as beeswax, lanolin wax, whale wax, candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil; mineral waxes such as montane wax, ozogenite, ceresin, paraffin wax, microcrystalline wax, and petrolatum; liquid paraffin, natural paraffin, synthetic paraffin, petroleum-based waxes; synthetic hydrocarbon waxes such as Fischer-Tropsch wax, polyethylene wax, ethylene-propylene copolymer wax, oxidized polyethylene wax, and oxidized polypropylene wax; modified waxes such as montane wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives; hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives; and polytetrafluoroethylene wax. Polyethylene wax is preferred due to its balance of static and dynamic friction properties.

[0101] These waxes may be used individually or in combination of two or more, and it is preferable that the total amount of these waxes added is 0.5 to 5% by mass of the total amount of ink. If the total amount of wax added is 0.5% by mass or more of the total amount of ink, abrasion resistance, water abrasion resistance, and scratch resistance can be maintained. If the total amount of wax added is 5% by mass or less of the total amount of ink, adhesion to the substrate, abrasion resistance, water abrasion resistance, and scratch resistance can be maintained.

[0102] Examples of film-forming emulsions include resin emulsions that form films at a glass transition temperature of 10°C or lower. Specifically, these include acrylic resin emulsions, water-soluble styrene-acrylic resin emulsions, water-soluble styrene-maleic acid resin emulsions, and water-soluble styrene-acrylic maleic acid resin emulsions. Emulsions obtained by copolymerizing a water-soluble acrylic resin as a polymer emulsifier with a styrene monomer, an alkyl ester of (meth)acrylic acid, etc., can be preferably used.

[0103] Water-based liquid printing inks may contain surface modifiers to adjust their leveling properties to the substrate. Examples of surface modifiers include, but are not limited to, Surfinol 104E, 104H, 104A, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, PSA-336, 61, 2502, Dynol 604, 607 from Nisshin Chemical Co., Ltd., and BYK-381, 3441, 302, 307, 325, 331, 333, 342, 345, 346, 347, 348, 349, 378, 3455 from Bic Chemie Co., Ltd. Among these, acetylene-based surfactants and / or alcohol alkoxylate-based surfactants are preferred. Commercially available examples include alkylene oxide-modified acetylene glycol surfactants such as Surfinol 61, 82, and 104 (all manufactured by Evonik), and alkylene oxide-modified acetylene glycol surfactants such as Surfinol 420, 440, 465, 485, TG, 2502, Dynol 604, and 607 (all manufactured by Evonik), Surfinol SE, MD-20, Olfin E1004, E1010, PD-004, EXP4300, PD-501, PD-502, and SPC (all manufactured by Nisshin Chemical Industry Co., Ltd.), and Acetyleneol EH, E40, E60, E81, E100, and E200 (all manufactured by Kawaken Fine Chemical Co., Ltd.). Among these, alkylene oxide-modified acetylene glycol surfactants are preferred. Furthermore, specific examples of alcohol alkoxylate surfactants include alcohol ethoxylates and alcohol polyethoxylates, and a commercially available example is DYNWET800 (manufactured by Bic Chemie Japan). Furthermore, other acrylic polymer-based surfactants (e.g., Polyflow WS-314 manufactured by Kyoeisha Chemical Co., Ltd.) or modified silicone-based surfactants (e.g., Polyflow KL-401 manufactured by Kyoeisha Chemical Co., Ltd.) may be used as needed.

[0104] The total amount of surface modifiers added is preferably 0.1 to 1% by mass of the total ink volume. These surface modifiers may be used individually or in combination of two or more. If the total amount of surface modifiers added is 0.1% by mass or more of the total ink volume, the wettability with the substrate will be improved and adhesion to the substrate will be maintained. If the total amount of surface modifiers added is 1% by mass or less of the total ink volume, the abrasion resistance, water abrasion resistance, and scratch resistance will not be reduced.

[0105] Water-based liquid printing inks may contain various additives to improve drying properties, such as extender pigments like calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay, and talc; inorganic fine particles and adhesive resins (acrylic resin, vinyl acetate resin) to provide anti-slip properties; defoamers to provide anti-foaming properties; and basic compounds such as caustic soda to provide resolubility.

[0106] (Hardening agent) In water-based liquid printing inks, a curing agent that can react with an acid may be used in combination. The curing agent that can react with an acid is not particularly limited, and any known curing agent that can be used in an aqueous medium can be used. Examples include epoxy curing agents, carbodiimide curing agents, oxazoline curing agents, and so on.

[0107] The epoxy curing agent is not particularly limited as long as it is a compound having at least one epoxy group. Examples of epoxy curing agents include epoxy resins such as bisphenol A diglycidyl ether, modified bisphenol A diglycidyl ether, novolac glycidyl ether, glycerin polyglycidyl ether, and polyglycerin polyglycidyl ether.

[0108] The carbodiimide-based curing agent is not particularly limited as long as it is a compound having at least one carbodiimide group (-N=C=N-). A polycarbodiimide compound having at least two or more carbodiimide groups is preferred as the carbodiimide-based curing agent.

[0109] The oxazoline-based curing agent is not particularly limited as long as it is a compound having an oxazoline skeleton. Specific examples of oxazoline-based curing agents include the Epocross series manufactured by Nippon Shokubai Co., Ltd. The epoxy compounds include diglycidyl ether of bisphenol A and its oligomers, diglycidyl ether of hydrogenated bisphenol A and its oligomers, diglycidyl orthophthalate, diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl p-oxybenzoate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, diglycidyl succinate, diglycidyl adipicate, diglycidyl sebacate, ethylene glycol diglycidyl ether, and diglycidyl propylene glycol. Examples include diglycidyl ethers, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether and polyalkylene glycol diglycidyl ethers, trimellitic acid triglycidyl ester, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidylpropylene urea, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, and triglycidyl ethers of glycerol alkylene oxide adducts.

[0110] The amount of curing agent added is preferably 0.1 to 10.0% by mass, and more preferably in the range of 0.5 to 9.0% by mass, based on the solid content of the total ink. If the additive amount is 0.1% by mass or more, the curing effect is obtained, while if it is 10.0% by mass or less, the substrate adhesion, abrasion resistance, and water abrasion resistance tend to be maintained.

[0111] Water-based liquid printing inks may also contain, as needed, chelating crosslinking agents, defoamers, plasticizers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, etc. In particular, they often contain fatty acid amides such as oleamide, stearamide, and erucamide to provide abrasion resistance and slipperiness, silicone-based and non-silicone defoamers to suppress foaming during printing, and various pigment dispersants to improve pigment wetting.

[0112] (Biomass liquid printing ink) In liquid printing inks, it is preferable to use liquid printing inks made from plant-derived raw materials, taking into consideration the creation of a sustainable circular society (sustainability) that should be developed in a sustainable manner. Examples of plant-derived raw materials include cellulose acetate propionate resin and nitrated cotton resins, polyamide resins using dimer acids or polymerized fatty acids derived from natural oils such as soybean oil, palm oil, and rice bran oil, as well as polycarboxylic acids such as succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, dimer acid, glutaric acid, and malic acid, as well as polyols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, pentylene glycol, 1,10-dodecanediol, dimer ol, and isosorbide, and polyisocyanates such as 1,5-pentamethylene diisocyanate and dimer isocyanate. Biomass polyurethanes synthesized from these plant-derived raw materials and rosin resins are also available.

[0113] Commercially available products can also be used as biomass liquid printing inks. Examples of commercially available products include inks listed by the Japan Organic Resources Association.

[0114] (Formation of the printed layer) In this invention, a printed material is obtained by printing a liquid printing ink onto a substrate to form a printed layer. Typically, the ink is applied to the substrate using a gravure or flexographic printing method, and the printed layer is obtained by drying and fixing it in an oven. The drying temperature is usually around 40 to 60°C.

[0115] Flexographic printing is a type of relief printing that primarily uses resin plates as printing plates (relief plates), and employs a fine-mesh engraved roll called an anilox roll to supply ink to the printing plate. The anilox roll receives ink from a chamber-type doctor and applies it to the printing plate, offering the advantage of uniform ink transfer to the plate.

[0116] Specifically, ink is applied to the surface of an anilox roll having partitions and numerous openings surrounded by the partitions. A doctor is pressed against the surface of the anilox roll to scrape off the ink present on the top surface of the partitions and fill the recessed openings with ink. Next, a flexographic plate is pressed against the anilox roll to transfer the ink present in the recessed areas of the anilox roll to the raised areas (pattern areas) of the printing plate. Then, the plate is brought into contact with a substrate to transfer the ink present in the pattern areas of the plate to the substrate on which a primer layer has been formed, thereby obtaining a printed product.

[0117] Furthermore, a rotary printing method may be combined. For example, in the manufacturing method of a rotary printed product, a liquid printing ink is used for rotary printing on the surface of a rolled film that has a primer layer formed on it. After printing, processes such as lamination, slitting (cutting off the unnecessary parts of the width), and bag making (cutting and heat sealing to make bags) can be carried out. By rotary printing liquid printing ink onto a rolled film, high-speed printing is possible, resulting in excellent productivity. There are two types of web printing: gravure web printing and flexographic web printing. Either method is acceptable, but this document will focus on flexographic web printing. In this document, "web printing" refers to both gravure web printing and flexographic web printing.

[0118] In flexographic web printing, ink is supplied directly from a container that holds liquid printing ink, or via an ink supply pump, to an anilox roller having a textured surface. The ink supplied to this anilox roller is transferred to the printing plate surface through contact with the raised parts of the plate surface, and then finally transferred to the substrate film through contact between the plate surface and the substrate film, thereby forming the image and / or characters.

[0119] When using water-based flexographic printing inks, the ink drying speed is slightly inferior to that of solvent-based flexographic printing inks, so it is preferable to keep the ink film thickness as thin as possible. From this viewpoint, it is preferable to supply as little ink as possible to the anilox roller. On the other hand, since a thinner film thickness tends to result in lower print density, the pigment concentration of the water-based flexographic printing ink used should be controlled as appropriate. Specifically, an appropriate print density can be obtained if the pigment concentration of the water-based flexographic printing ink is 1 to 5% by weight higher than that of the solvent-based flexographic printing ink.

[0120] A roll of thermoplastic resin film is a roll of film cut to a specified width, and is different from sheet-fed paper, which is pre-cut into individual sheets. It is a film used for web printing. The width of the film is appropriately selected based on the width of the printing plate of the web printing press and the width of the image (pattern) portion of the gravure plate. In this invention, a roll of film with a pre-formed desorption primer layer can be used. Furthermore, when layering colors using multiple colors of rotary printing inks, there are no particular restrictions on the order in which they are printed.

[0121] When performing surface printing, it is common practice to print white ink first, followed by the colored inks, as needed. If there are multiple colored inks, they can be printed in the order of, for example, yellow, magenta, cyan, and black, but this is not particularly limited. In surface printing configurations, abrasion resistance and water resistance can be improved by applying an overcoat agent to the printed surface of the web-printed material as needed. When the substrate is white, for example, paper substrates and thermoplastic resin films with white pigments kneaded into them, printing with colored inks only is also possible as needed.

[0122] Furthermore, when performing reverse printing, it is common practice to first print the colored ink on the rolled film, followed by the white ink. If there are multiple colored inks, for example, they can be printed in the order of black, cyan, magenta, and yellow, but there are no particular restrictions. In addition, large-format printing presses can use spot colors in addition to the basic colors mentioned above. That is, large-format printing presses have multiple printing units that correspond to 5 to 10 colors, and each printing unit is equipped with one color of ink, allowing for the simultaneous overlay printing of 5 to 10 colors. Printed materials obtained by reverse printing can be used as is, or an anchor coating agent and adhesive can be applied to the printed surface of the rotary printed material obtained by the above method, and if necessary, after drying, they can be laminated by bonding them with a film or the like.

[0123] The printed material of the present invention has excellent ink detachment properties, making it suitable for forms where the printed layer is the outermost layer. In the above-mentioned front-printed and back-printed materials, the printed material has a liquid printing ink printed layer on the surface that becomes the outermost layer during distribution, or the printed material has the printed layer on the inner side that comes into direct contact with the product, as these are preferable as they allow the effects of the present invention to be maximized.

[0124] (Gas barrier resin layer) (Gas barrier resin layer A) One example of a gas barrier resin layer is a gas barrier resin layer A, which can be obtained by applying a gas barrier coating agent containing a vinyl alcohol-based polymer and an aqueous solvent using a known coating method to form a coating film. Specific examples of vinyl alcohol polymers include polyvinyl alcohol, ethylene vinyl alcohol, and polyvinyl butyral. Vinyl alcohol polymers may also have reactive functional groups other than hydroxyl groups, such as acetoacetyl groups, carboxyl groups, anionic carboxyl groups, sulfonic acid groups, and anionic sulfonic acid groups. These may be used individually or in combination of two or more.

[0125] Vinyl alcohol-based polymers have excellent gas barrier properties, so a degree of saponification of 90% or more is preferable, and preferably 95% or more. It may also be 100%. The degree of saponification can be measured by FTIR using, for example, a Nicolet 5700FTIR spectrometer controlled by OMNIC software.

[0126] The gas barrier coating agent constituting the gas barrier resin layer A may further contain additives such as layered inorganic compounds, crosslinking agents that react with the functional groups of vinyl alcohol polymers, adhesion enhancers, inorganic fillers, defoamers, stabilizers (antioxidants, heat stabilizers, UV absorbers, etc.), plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, and leveling agents.

[0127] The amount of gas barrier coating agent that constitutes the gas barrier resin layer A is adjusted as appropriate depending on the desired degree of gas barrier performance, but as an example, it is 0.1 g / m². 2 ~5.0g / m 2 More preferably 0.3 g / m 2 ~2.0g / m 2 That is the case.

[0128] Commercially available gas barrier coating agents can be used to constitute the gas barrier resin layer A. Examples include Exevia (registered trademark) from Sumitomo Chemical, the SunBar (registered trademark) series from Sun Chemical, the Takelac WPB (registered trademark) series from Mitsui Chemicals, and LG-OX from Tokyo Ink Co., Ltd.

[0129] (Gas barrier resin layer B) In addition, as an example, the gas barrier resin layer is composed of a vinyl alcohol-based polymer, a water-soluble polymer having a hydroxyl group such as polyvinylpyrrolidone, starch, methylcellulose, carboxymethylcellulose, sodium alginate, etc., and Si(OR 1 )4, or R 2 Si(OR 3 )3 (where OR 1 and OR 3 represent hydrolyzable groups, and R 2 represents an organic functional group), or a silicon compound represented by a hydrolyzate of the silicon compound, and a gas barrier resin layer B that can also be obtained by coating a gas barrier coating agent containing one or more of them and an aqueous solvent by a known coating method to form a coating film is exemplified.

[0130] Since the water-soluble polymer used in the present invention can impart good gas barrier properties, it is preferable to use a vinyl alcohol-based polymer. Preferable specific examples of the vinyl alcohol-based polymer include polyvinyl alcohol, ethylene vinyl alcohol, polyvinyl butyral, etc. It may be used alone or in combination of two or more. From the viewpoint of the balance between gas barrier properties and adhesion, it is more preferable to use either or both of polyvinyl alcohol and ethylene vinyl alcohol in combination.

[0131] The Si(OR 1 )4 or R 2 Si(OR 3 )3 used in the present invention (where OR 1 and OR 3 represent hydrolyzable groups, and R 2Examples of silicon compounds represented by (where represents an organic functional group), or hydrolysates of said silicon compounds, include tetraalkoxysilanes such as tetraethyl silicate (Si(OC2H5)4) (hereinafter sometimes referred to as TEOS), tetramethyl silicate, etc.; trialkoxysilanes such as trimethoxymethylsilane, triethoxymethylsilane, trimethoxyvinylsilane, etc.; dialkoxysilanes such as dimethoxydimethylsilane, diethoxydimethylsilane, etc.; monoalkoxysilanes such as methoxytrimethylsilane, ethoxytrimethylsilane, etc., or hydrolysates or partial hydrolysates thereof.

[0132] TEOS is preferred because it is relatively stable in aqueous solvents after hydrolysis. 2 Si(OR 3 )3 contains R 2 The group is preferably a vinyl group, epoxy group, acryloyl group, methacryloxy group, ureido group, or isocyanate group.

[0133] When the water-soluble polymer is a vinyl alcohol-based polymer, the ratio of the mass of the vinyl alcohol-based polymer to the mass of the total solids in the mixed solution is preferably 20% by mass or more and 50% by mass or less, and more preferably 25% by mass or more and 40% by mass or less. The inclusion of 20% by mass or more of PVA maintains the flexibility of the coating film. Therefore, the formation of the coating film is easy. Furthermore, the inclusion of 50% by mass or less of the vinyl alcohol-based polymer makes it possible to have sufficient barrier properties.

[0134] The gas barrier resin layer may contain other components. These other components may include other water-soluble polymers (e.g., sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, dextrin, chitosan, chitin, methylcellulose, hydroxyethylcellulose, etc.), as well as fragrances, rust inhibitors, colorants, fillers, defoamers, UV absorbers, fluorescent whitening agents, liquid paraffins, bittering components (e.g., denatonium benzoate, etc.).

[0135] The thickness of the gas barrier resin layer B is preferably selected from a range of, for example, 0.05 μm to 30 μm.

[0136] (Gas barrier resin layer C) Furthermore, a gas barrier resin layer C can also be obtained by applying a gas barrier coating agent containing a polyester polyol, which is a reaction product of an acid component containing an ortho-orienting polycarboxylic acid or a meta-orienting polycarboxylic acid and a polyol component, an isocyanate compound, and an organic solvent, using a known coating method to form a coating film.

[0137] (Acid component: ortho-directing polycarboxylic acid or meta-directing polycarboxylic acid) Examples of ortho-directing polycarboxylic acids used in the synthesis of polyester polyols include orthophthalic acid or its acid anhydride, naphthalene 2,3-dicarboxylic acid or its acid anhydride, naphthalene 1,2-dicarboxylic acid or its acid anhydride, anthraquinone 2,3-dicarboxylic acid or its acid anhydride, and 2,3-anthracenecarboxylic acid or its acid anhydride. These compounds may have substituents on any carbon atom of the aromatic ring. Furthermore, examples of meta-directing polycarboxylic acids used in the synthesis of polyester polyols include isophthalic acid and 1,3-naphthalenedicarboxylic acid. These compounds may have substituents on any carbon atom of the aromatic ring.

[0138] In addition, the polycarboxylic acid may contain other known polycarboxylic acids other than the ortho-directing polycarboxylic acid or meta-directing polycarboxylic acid. When the polycarboxylic acid contains polycarboxylic acids other than ortho-directing polycarboxylic acid or meta-directing polycarboxylic acid, it is preferable that the proportion of ortho-directing polycarboxylic acid or meta-directing polycarboxylic acid to the total amount of polycarboxylic acid is 40 to 100% by mass.

[0139] (Polyol component) The polyol component polyhydric alcohol used in the synthesis of polyester polyols preferably includes dihydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol, and trihydric alcohols such as glycerol, trimethylolethane, and trimethylolpropane. Among these, the inclusion of ethylene glycol and glycerol is more preferable. The inclusion of glycerol is particularly preferable. Glycerol is preferably contained in the polyol component of polyol (A) at a concentration of 10 to 100% by mass. Other known polyhydric alcohols may also be used in combination. Furthermore, the polyester polyol may be a single type, or a combination of multiple polyol types may be used. The polyester polyol may also be a polyester polyurethane polyol obtained by urethane elongation through reaction with a diisocyanate compound.

[0140] The hydroxyl value of the polyester polyol is preferably between 20 mg KOH / g and 250 mg KOH / g. Furthermore, if the polyester polyol has an acidic group, the acid value is preferably 200 mg KOH / g or less.

[0141] (Isocyanate compounds) The isocyanate compounds used in the present invention can be conventionally known compounds without particular limitation, and include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, or trimers of these isocyanate compounds, and adducts obtained by reacting an excess amount of these isocyanate compounds with low molecular weight active hydrogen compounds such as ethylene glycol, propylene glycol, metaxylylene alcohol, 1,3-bishydroxyethylbenzene, 1,4-bishydroxyethylbenzene, trimethylolpropane, glycerol, pentaerythritol, erythritol, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, metaxylylenediamine and their alkylene oxide adducts, various polyester resins, polyether polyols, polyamides, and other high molecular weight active hydrogen compounds. Alternatively, a polyester polyisocyanate obtained by reacting a polyester polyol with a diisocyanate compound in an isocyanate excess ratio of hydroxyl groups to isocyanate groups may be used. Blocked isocyanates may also be used. These can be used individually or in combination of two or more.

[0142] The isocyanate compound preferably has an aromatic ring or an aliphatic ring. Having an aromatic ring or an aliphatic ring can be expected to improve the gas barrier properties and blocking resistance of the coating film.

[0143] Furthermore, the polyisocyanate compound may also contain a known epoxy compound in combination with the polyisocyanate compound. When using an epoxy compound, a commonly known epoxy curing accelerator may be added as appropriate to the extent that the objectives of the present invention are not impaired, in order to accelerate curing.

[0144] Furthermore, it is preferable to use a compound having an active hydrogen group in combination with the polyisocyanate compound. Examples of active hydrogen groups in the compound having an active hydrogen group include hydroxyl groups, amino groups, imino groups, carboxylic acids, urea groups, or SH groups. Among these, hydroxyl groups, amino groups, or SH groups are preferred. Among these, compound (C) having a hydroxyl group as the active hydrogen group is preferred, and isosorbide, tris(2-hydroxyethyl) isocyanurate, trimethylolpropane, dipentaerythritol, and 1,4-cyclohexanedimethanol are preferred.

[0145] The amount of the compound having the active hydrogen group is preferably 0.5% by mass or more and 20% by mass or less relative to the solid content of the gas barrier layer. Within this range, it is expected that winding blocking during coating will be prevented, good adhesion to the substrate and improved gas barrier properties of the coating film will be achieved. The amount is more preferably 1% by mass or more and 15% by mass or less, and most preferably 2% by mass or more and 8% by mass or less.

[0146] (Other ingredients) The gas barrier resin layer C may also contain, in addition to known plate-like inorganic compounds, low molecular weight organic compounds that react with oxygen, such as acid anhydrides, hindered phenols, vitamin C, vitamin E, organophosphorus compounds, gallic acid, and pyrogallol, as well as transition metal compounds such as cobalt, manganese, nickel, iron, and copper, and inorganic fillers such as silica, alumina, aluminum flakes, and glass flakes. If inorganic materials are used, dispersants, stabilizers (antioxidants, heat stabilizers, UV absorbers, etc.), plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, leveling agents, slip enhancers, etc.

[0147] (Gas barrier resin layer D) Furthermore, a gas barrier resin layer D can also be obtained by applying a gas barrier coating agent containing a heteroatom compound having dehydration condensation properties, a polymer having a carboxyl group, and an organic solvent using a known coating method to form a coating film.

[0148] (Heteroatom compounds with dehydration condensation properties) The heteroatom compounds having dehydration condensation properties used in this invention are compounds that undergo dehydration condensation when in contact with a compound having a hydroxyl group, and which have a heteroatom in their structure. Examples of these heteroatom compounds having dehydration condensation properties include phosphoric acid, sulfuric acid, and nitric acid. These may be used individually or in combination. Preferably, the amount of the heteroatom compound having dehydration condensation properties added to the gas barrier resin layer is 10 parts by mass or less.

[0149] (A polymer containing a carboxyl group) Examples of polymers having carboxyl groups used in the present invention include polymers of polymerizable unsaturated monomers having carboxyl groups, and copolymers of polymerizable unsaturated monomers having carboxyl groups and general-purpose polymerizable unsaturated monomers. Examples of polymerizable unsaturated monomers having a carboxyl group include unsaturated carboxylic acids such as (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, crotonic acid, itaconic acid, maleic acid, or fumaric acid; monoesters (half-esters) of various unsaturated dicarboxylic acids such as monomethyl itaconic acid, mono-n-butyl itaconic acid, monomethyl maleic acid, mono-n-butyl maleic acid, monomethyl fumarate, and mono-n-butyl fumarate with saturated monohydric alcohols; monovinyl esters of various saturated dicarboxylic acids such as monovinyl adipate or monovinyl succinate; addition reaction products of various saturated polycarboxylic acid anhydrides such as succinic anhydride, glutaric anhydride, phthalic anhydride, or trimellitic anhydride with various hydroxyl group-containing vinyl monomers; and various monomers obtained by addition reactions of the aforementioned carboxyl group-containing monomers with lactones.

[0150] The acid value of the polymer having the carboxyl group is preferably 50 to 800 mgKOH / g, as this improves barrier performance. The carboxyl group polymer used in this invention is not particularly limited in terms of molecular weight, but a weight-average molecular weight of 300 to 1,000,000 is preferred from the viewpoint of good film formation properties. Particularly preferred is 500 to 500,000.

[0151] Furthermore, it is preferable that the gas barrier resin layer D has an adjacent resin layer containing a polyvalent metal compound. Here, "adjacent" means that at least a portion of the resin layers are in direct contact with each other.

[0152] Examples of polyvalent metal compounds included in the resin layer include zinc compounds, magnesium compounds, calcium compounds, manganese compounds, iron compounds, cobalt compounds, nickel compounds, and copper compounds, with zinc compounds, magnesium compounds, and calcium compounds being particularly preferred. These metal compounds may be used individually or in combination of two or more, and among them, zinc oxide, magnesium oxide, and calcium oxide are preferred. These polyvalent metal compounds are preferably included in the resin layer containing the polyvalent metal compounds in an amount of 40 to 90 parts by mass.

[0153] In addition to the polyvalent metal compound, the resin layer containing the polyvalent metal compound preferably also contains ethyl cellulose resin, polyether polyurethane polyol resin, polyester polyol resin, and polyurethane polyol resin in order to stably coat the polyvalent metal compound. The resin is preferably contained in the resin layer containing the polyvalent metal compound in an amount of 10 to 60 parts by mass.

[0154] Furthermore, it is preferable that the gas barrier resin layer D has an adjacent layer containing aluminum oxide, silicon oxide, or silicon nitride, etc. These adjacent layers are formed by depositing a compound selected from the group consisting of aluminum oxide, silicon oxide, and silicon nitride by processes such as vapor deposition, sputtering, and CVD. These layers may be formed on a base film such as polyethylene terephthalate (PET) resin film, polypropylene (PP) resin film, polybutylene terephthalate (PBT) resin film, nylon (NY) resin film, or biomass film. These base films may be films manufactured by various known processes such as biaxially oriented films, stretched films, or unstretched films, or films that have undergone various surface treatments as needed.

[0155] The gas barrier resin layer D should be applied in an amount of 0.01 to 100 g / m² after drying. 2 Preferably, 0.1 to 50 g / m 2 More preferably, 0.5-3 g / m 2 That is particularly preferable.

[0156] (Heat-resistant resin layer) The heat-resistant resin layer is a coating layer of a heat-resistant coating agent (hereinafter sometimes simply referred to as a heat-resistant coating agent). Commercially available heat-resistant coating agents can be used. Examples of such products include SUNSYSFS241 from Sun Chemical Co., Ltd., DH-004 / DH-HARDENERP-60 from DIC Corporation, and ThermaGloss463 from Michaelman Corporation.

[0157] Furthermore, heat-resistant coating agents containing compounds having a cellulose skeleton, benzene ring skeleton, isocyanuric ring skeleton, or alicyclic skeleton, for example, whose homopolymer glass transition temperature (hereinafter sometimes referred to as Tg) is 100°C or higher, are also preferred. Specifically, examples include polyester resins having a benzene ring such as nitrated cotton, cellulose acetate, cellulose propionate, and cellulose butyrate, phthalic acid, naphthalenedicarboxylic acid, and ethylene oxide (hereinafter sometimes referred to as EO) adduct of bisphenol A, and / or alicyclic skeletons such as cyclopentanediol and dimethylol tricyclodecane; or urethane resins bonded with aromatic isocyanates such as diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, and naphthalenediisocyanate, alicyclic isocyanates such as isophorone diisocyanate and norbornene diisocyanate, and / or isocyanurol triisocyanate, and / or polyols and / or tris(2-hydroxyethyl) isocyanurate. Polyisocyanates using the aforementioned isocyanates may also be used as curing agents. Furthermore, compounds having a benzene ring and an unsaturated double bond, such as styrene and phenoxydiethylene glycol acrylate, and / or compounds having an alicyclic structure and an unsaturated double bond, such as isobornyl acrylate and dicyclopentanyl acrylate, and radical copolymers such as (meth)acrylate can also be preferably used. In addition, resins with a low Tg may be mixed in to improve adhesion to the olefin film. The total amount of the cellulose skeleton, benzene ring skeleton, isocyanuric ring skeleton, and alicyclic skeleton of the aforementioned compounds is preferably 20 to 90% by mass of the solid content of the heat-resistant coating layer. Preferably, it is 30 to 80% by mass.

[0158] Furthermore, the heat-resistant coating agent may be colored. There are no particular limitations on the coloring agent, and examples include inorganic pigments, organic pigments, and dyes used in general inks, paints, and recording agents, such as those used in the printing layer described later. Pigments are preferred among these. Among inorganic pigments, titanium dioxide is particularly preferred. Titanium dioxide is white and is preferred in terms of coloring power, opacity, chemical resistance, and weather resistance, and from the viewpoint of printing performance, titanium dioxide that has been treated with silica and / or alumina is preferred. Aluminum is in powder or paste form, but it is preferred to use it in paste form in terms of handling and safety, and whether to use leafing or non-leafing aluminum is appropriately selected in terms of brightness and density.

[0159] Furthermore, the heat-resistant coating agent preferably uses inorganic fine particles such as alumina, magnesia, titania, zirconia, and silica (quartz, fumed silica, precipitated silica, anhydrous silicic acid, fused silica, crystalline silica, ultrafine amorphous silica, etc.) as aggregate because they have excellent heat resistance. Alternatively, boron nitride, aluminum nitride, aluminum oxide, titanium oxide, magnesium oxide, zinc oxide, silicon oxide, etc. are preferred because they have excellent thermal conductivity. The inorganic fine particles may be used individually or in combination of multiple types. The shape of the silica nanoparticles is not particularly limited; spherical, hollow, porous, rod-shaped, plate-shaped, fibrous, or irregularly shaped nanoparticles can be used. For example, commercially available hollow silica nanoparticles include "SiliNax" manufactured by Nippon Steel Mining Co., Ltd.

[0160] The primary particle size of the inorganic fine particles is preferably in the range of 5 to 200 nm. If it is 5 nm or larger, the inorganic fine particles in the dispersion will be well dispersed, and if the diameter is within 200 nm, the strength of the cured product will be good. More preferably it is 10 nm to 100 nm. The inorganic fine particles can be blended in a ratio of 5 to 90% by weight relative to the total solid content of the heat-resistant coating agent and the inorganic fine particles, and the blending amount can be adjusted as needed depending on the purpose. In particular, a ratio of 20% by mass or more is preferred.

[0161] The heat-resistant coating agent may contain waxes, silicone additives, and organic beads to prevent damage to the coated film, prevent blocking during lamination, and provide processability during bag making after lamination. Specifically, waxes such as amide wax, polypropylene wax, polyethylene wax, paraffin wax, carnauba wax, and rice wax, ethylene oxide (EO) adducts of dimethylsiloxane, silicone additives such as silicone-modified products, and organic beads made of acrylic, nylon, urethane, or epoxy can be added.

[0162] There are no particular restrictions on the solvent used in the heat-resistant coating agent; it can be used alone or in a mixture of two or more. Furthermore, defoaming agents and leveling agents may be used to make the coating process more effective.

[0163] The amount of heat-resistant resin layer applied is selected appropriately depending on the application, but the amount applied after drying is typically between 0.01 and 100 g / m². 2 Preferably, 0.1 to 50 g / m 2 More preferably, 0.5-3 g / m 2 That is particularly preferable.

[0164] <Recycling Methods> The recycling method in this invention involves immersing a printed material, which is laminated in the order of a plastic substrate, a delamination primer layer, and a printed layer, in an alkaline aqueous solution, which is a delamination treatment solution, to delaminate the other layers (particularly the printed layer) provided on the plastic substrate. Delamination refers to the separation of the plastic substrate from the other layers by the delamination primer layer swelling or slightly dissolving and peeling off due to the delamination treatment solution. The delaminated plastic substrate can be used as recycled plastic.

[0165] The desorption process involves immersing the printed material in an alkaline aqueous solution while stirring or ultrasonically vibrating it at a liquid temperature of 40 to 90°C. Heating, stirring, and ultrasonic vibration may be performed simultaneously. The immersion time is within 60 minutes, more preferably within 30 minutes, more preferably within 20 minutes, and even more preferably within 15 minutes. The temperature of the alkaline aqueous solution is preferably 40°C or higher, more preferably 50°C or higher. The temperature is preferably 100°C or lower, and more preferably 90°C or lower. It is also preferable to perform stirring and ultrasonic vibration simultaneously. The desorption primer layer of the present invention is resistant to alkaline aqueous solutions at low temperatures (below 40°C), and even if an alkaline aqueous solution such as a cleaning agent solution comes into contact with the printed material unintentionally in daily life, the coating film consisting of the printed layer will not detach from the printed material. Therefore, a recycling method is preferred in which the printed layer is detached from the plastic substrate by immersion in an alkaline aqueous solution at 40°C or higher.

[0166] The alkaline aqueous solution used in the desorption process is not limited, but sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium bicarbonate aqueous solution, potassium bicarbonate aqueous solution, sodium dihydrogen carbonate aqueous solution, potassium dihydrogen carbonate aqueous solution, etc. are preferred. The sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium bicarbonate aqueous solution, potassium bicarbonate aqueous solution, sodium dihydrogen carbonate aqueous solution, potassium dihydrogen carbonate aqueous solution, etc. are preferably aqueous solutions with a concentration of 0.001% to 10% by mass, preferably 0.005% to 5% by mass, preferably 0.01% to 3% by mass, preferably 0.05% to 1.5% by mass, and more preferably 0.1% to 0.5% by mass. Furthermore, the pH of the alkaline aqueous solution is preferably 9.0 or higher, and more preferably 10.0 or higher. The desorption primer layer of the present invention is suitable for recycling because it can be easily desorbed by heating even in low-concentration, low-pH alkaline aqueous solutions.

[0167] Furthermore, the above-mentioned alkaline aqueous solution may contain a water-soluble organic solvent. Examples of water-soluble organic solvents include 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 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, which can be used individually or in combination of two or more.

[0168] The content of the water-soluble organic solvent in the above alkaline aqueous solution is preferably 0.01% to 20% by mass, and more preferably 0.1% to 10% by mass.

[0169] Furthermore, the above-mentioned alkaline aqueous solution may contain a water-insoluble organic solvent. Specific examples of water-insoluble organic solvents include alcohol-based solvents such as n-butanol, 2-butanol, isobutanol, and octanol; aliphatic hydrocarbon-based solvents such as hexane, heptane, and n-paraffin; aromatic hydrocarbon-based solvents such as benzene, toluene, xylene, and alkylbenzene; halogenated hydrocarbon-based solvents such as methylene chloride, 1-chlorobutane, 2-chlorobutane, 3-chlorobutane, and carbon tetrachloride; ester-based solvents such as methyl acetate, ethyl acetate, and butyl acetate; ketone-based solvents such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; and ether-based solvents such as ethyl ether and butyl ether. These can be used individually or in combination of two or more.

[0170] Furthermore, the above-mentioned alkaline aqueous solution preferably contains a surfactant. Examples of surfactants include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, and among these, cationic surfactants are preferred.

[0171] As the cationic surfactant, a cationic surfactant with a quaternary ammonium skeleton is preferred, and more preferably, it contains a cationic surfactant with a quaternary ammonium skeleton containing at least one compound represented by general formula (3a).

[0172] R1-N+(R2R3)-R4(3a) (In general formula (3a), R1 represents a linear or branched alkyl group or a linear or branched alkenyl group, and the -CH2- in the alkyl group or alkenyl group may be substituted with -C(=O)-, -NH-, or -C(=O)-NH-; R2 and R3 represent a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkenyl group; R4 represents a hydrogen atom, a linear or branched alkyl group, a linear or branched alkenyl group, or a phenyl group, and the terminal -CH3 in the alkyl group or alkenyl group may be substituted with a carboxyl group or a phenyl group.) In general formula (3a), R1 is preferably a long-chain alkyl or alkenyl group in order to further enhance the deleacing properties of the ink. Specifically, it is preferably an alkyl or alkenyl group having 8 to 30 carbon atoms, preferably an alkyl group having 10 to 25 carbon atoms, and preferably an alkyl or alkenyl group having 12 to 22 carbon atoms. The alkyl or alkenyl group may be linear or branched, but it is preferably linear, and more preferably a linear alkyl group.

[0173] R1 may have at least one -CH2- in the alkyl or alkenyl group substituted with -C(=O)-, -NH-, or -C(=O)-NH-. In particular, it is preferable that at least one -CH2- in the alkyl or alkenyl group is substituted with -C(=O)-NH- or -NH-C(=O), and it is preferable that one -CH2- in the alkyl group is substituted with -C(=O)-NH- or -NH-C(=O), and it is more preferable that R1 has an amidopropyl skeleton.

[0174] R2 and R3 preferably represent a linear or branched alkyl group or a linear or branched alkenyl group, and more preferably a linear or branched alkyl group. In particular, they preferably represent a linear alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.

[0175] R4 preferably represents a linear or branched alkyl group, a linear or branched alkenyl group, or a phenyl group, and more preferably a linear or branched alkyl group. Furthermore, the terminal -CH3 in the alkyl group or alkenyl group is preferably substituted with a carboxyl group or a phenyl group.

[0176] The number of carbon atoms in R4 is preferably 1 to 8, preferably 1 to 5, preferably 1 to 3, and more preferably 1 or 2.

[0177] When R4 represents a methyl group, it is preferable that R2 and R3 also represent methyl groups, and that general formula (3a) represents an alkyltrimethylammonium skeleton.

[0178] Furthermore, if R4 represents an ethyl group, it is preferable that the terminal -CH3 in the ethyl group is substituted with a carboxyl group or a phenyl group. In other words, it is preferable that R4 represents -CH2-(C(=O))OH or a benzyl group.

[0179] The compound represented by general formula (3a) is preferably a cationic surfactant with a quaternary ammonium skeleton represented by general formula (3a-1).

[0180] CnH2n+1N+(CH3)2R4(3a-1) (In general formula (3a-1), n ​​represents the average number of moles added, and R4 has the same meaning as R4 in general formula (3a).) In general formula (3a-1), the number of carbon atoms represented by n is preferably 8 or more. A higher number of carbon atoms, such as 8 or more, is preferable as it improves ink desorption properties. Specific examples of carbon atoms include the octyl group with 8 carbon atoms, the nonyl group with 9 carbon atoms, the decyl group with 10 carbon atoms, the undecyl group with 11 carbon atoms, the lauryl group with 12 carbon atoms, the tridecyl group with 13 carbon atoms, the myristyl group with 14 carbon atoms, the pentadecyl group with 15 carbon atoms, the cetyl group with 16 carbon atoms, the oleyl group with 18 carbon atoms, and the stearyl group.

[0181] The preferred group of R4 is the same as in general formula (3a).

[0182] These quaternary ammonium skeleton cationic surfactants are preferably quaternary ammonium skeleton salts that form a salt with a halogen, preferably with Cl-, more preferably with Br-, and even more preferably with I-. Quaternary ammonium skeleton salts that form a salt with a halogen are thought to improve the desorption properties of the ink by promoting hydrolysis of the ink film through the nucleophilic action of the halogen.

[0183] Among these, alkyltrimethylammonium chloride type, dialkyldimethylammonium chloride type, and alkylbenzalkonium chloride type compounds are preferred.

[0184] Specific products corresponding to general formula (3a) or (3a-1) include, from NOF Corporation: Nissan Cation MA, Nissan Cation SA, Nissan Cation BB, Nissan Cation FB, Nissan Cation PB-300, Nissan Cation ABT2-500, Nissan Cation AB, Nissan Cation AB-600, Nissan Cation VB-M Flake, Nissan Cation VB-F, Nissan Cation 2-DB-500E, Nissan Cation 2-DB-800E, Nissan Cation 2ABT, Nissan Cation 2-OLR, Nissan Cation F2-50R, Nissan Cation M2-100R; from Daiichi Kogyo Co., Ltd.: Kachiogen TML, Kachiogen TMP, Kachiogen TMS, Kachiogen DDM-PG, Kachiogen BC-50, Kachiogen TBB; and from Kao Corporation: Cotamin 24P, Cotamin 86P Concentrate, Cotamin Examples include Min 60W, Cotamin 86W, Sanizol C, and Sanizol B-50. Lion Corporation products include Lipoguard C-50, Lipoguard T-28, Lipoguard T-30, Lipoguard T-50, Lipoguard T-800, Lipoguard 16-29, Lipoguard 16-50E, Lipoguard 18-63, Lipoguard 22-80, Lipoguard CB-50, Lipoguard 210-80E, Lipoguard 2C-75, Lipoguard 2HP-75, and Li Examples include, but are not limited to, Lipoguard 2HP Flake, Lipoguard 2HT-75, Lipoguard 2HT Flake, Lipoguard 20-75L, Lipoguard 41-50, TMAC-50, TPAH-40, TBAB-50A, TBAB-100A, TBAH-40, Lipoguard PH-100, BTMAC-50, BTMAC-100A, BTEAC-50, BTEAC-100A, BTBAC-50A, etc.

[0185] Furthermore, the cationic surfactant may contain at least one compound represented by a primary or secondary alkanolamine skeleton, or at least one compound represented by a monoalkanolamine skeleton. The primary monoalkanolamine is preferably a lower alkanol having 1 to 4 carbon atoms, specifically monoethanolamine, 2-aminoisobutanol, etc., while the secondary monoalkanolamine is N-methylethanolamine, 2-ethylaminoethanol, isopropanolamine, etc., but other substances may also be used as appropriate. Furthermore, these monoalkanolamine compounds can be used individually or in combination of two or more as appropriate, and can also be used mixed with water.

[0186] These cationic surfactants of the monoalkanolamine skeleton are preferably in the form of monoalkanolamine salts that form a salt with a halogen, and more preferably with Cl-.

[0187] Examples of anionic surfactants include alkylbenzene sulfonates, alkylphenyl sulfonates, alkylnaphthalene sulfonates, higher fatty acid salts, sulfate salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, and polyoxyethylene alkyl ether phosphates. Specific examples of these include dodecylbenzene sulfonate, isopropylnaphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenyl sulfonate, and dibutylphenylphenol disulfonate.

[0188] 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, alkyl alkanolamides, acetylene glycols, oxyethylene adducts of acetylene glycols, polyethylene glycol polypropylene glycol block copolymers, etc. Among these, polyoxyethylene nonylphenyl ethers, polyoxyethylene octylphenyl ethers, polyoxyethylene dodecylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylolamides, acetylene glycols, oxyethylene adducts of acetylene glycols, and polyethylene glycol polypropylene glycol block copolymers are preferred.

[0189] Other surfactants that can be used include silicone-based surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; and biosurfactants such as spicrispolic acid, rhamnolipid, and lysolecithin.

[0190] These surfactants can be used individually or in mixtures of two or more types. When surfactants are 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, relative to the total amount of the alkaline aqueous solution.

[0191] (Antifoaming agent) The defoaming solution may contain an antifoaming agent. During immersion, stirring and crushing of the substrate may generate a large amount of foam, and if foam remains, it may overflow during the plastic film recovery process. Also, if a large amount of foam is incorporated into the defoaming solution during substrate crushing, the substrate may not be crushed to the desired size.

[0192] Commonly used defoaming agents include water-soluble organic solvents and nonionic surfactants with low HLB values ​​in the range of 1 to 3. However, silicone compounds are particularly preferred due to their high defoaming ability. Among these, emulsion-type and self-emulsifying silicone compounds are preferred.

[0193] The defoaming agent may be used alone or in combination of two or more types. In step 1, the amount of the defoaming agent in the usable cleaning solution is preferably in the range of 0.01 to 5% by weight, more preferably in the range of 0.02 to 4% by weight, and even more preferably in the range of 0.03 to 3% by weight.

[0194] The target printed material is immersed in an alkaline aqueous solution, which is heated to a liquid temperature of 40-90°C or subjected to ultrasonic vibration, for example, in a processing tank. There are no particular limitations on the heating method for adjusting the liquid temperature, and known heating methods such as those using heat rays, infrared rays, or microwaves can be employed. For ultrasonic vibration, for example, an ultrasonic transducer can be attached to the processing tank and ultrasonic vibrations can be applied to the hot water or alkaline aqueous solution.

[0195] While stirring is not mandatory when immersing printed materials in an alkaline aqueous solution, it is optional, but stirring allows for more efficient swelling. It is preferable to keep the stirring speed low enough to prevent foaming without the need for an antifoaming agent. The stirring method is not particularly limited, and known methods can be used. For example, methods include mechanically stirring the dispersion of printed materials contained in the processing tank with stirring blades, using ultrasound, using a device that can shake the container, using a wet crusher, stirring with water using a water pump, and bubbling with an inert gas such as nitrogen gas. These methods may be used in combination to efficiently remove the material.

[0196] The immersion time for the printed material in the alkaline aqueous solution depends on the composition of the printed material, but is generally in the range of 1 minute to 48 hours. In this invention, it is not necessary for the printed layer of the printed material to be 100% completely detached from the substrate, but it is preferable that 60% or more by mass of the printed layer be detached, more preferably 70% or more by mass, even more preferably 80% or more by mass, and particularly preferably 90% or more by mass. Furthermore, the removal rate of the detachment primer layer when washed with water and dried is preferably 90% or more by mass, more preferably 95% or more by mass, and even more preferably 98% or more by mass.

[0197] In the desorption process, the film substrate may be immersed in the alkaline aqueous solution once or in several stages. That is, the film substrate may be recovered after one immersion, or it may be recovered after several immersions. Furthermore, if multiple immersions are performed in the desorption process, the concentration of the alkaline aqueous solution may be changed. In addition, known processes such as washing with water and drying may be added as appropriate during the desorption process.

[0198] Furthermore, the alkaline aqueous solution promotes the detachment of the plastic substrate by coming into contact with the interface between the primer layer and other layers from the edges of the printed material. Therefore, it is preferable that the primer layer is exposed in the cross-section. For this reason, it is more preferable to include a step of fragmenting the printed material by cutting or crushing.

[0199] The method for shredding plastic film is not particularly limited and can be carried out by known methods. Furthermore, shredding may be performed in an air atmosphere without the presence of solvents or other liquids, or in water or a washing solution. When shredding is performed in an air atmosphere, a dry shredder can be used. When shredding is performed in water or a washing solution, a wet shredder capable of simultaneous shredding and pumping can be used. Using a wet shredder allows for efficient shredding of printed plastic film.

[0200] There are no particular restrictions on the longest side of the crushed substrate, but in the case of a surface-printed configuration in which the ink layer or coating layer is on the surface of the plastic substrate, it is preferably 1 mm to 50 mm, more preferably 1 mm to 30 mm, and more preferably 1 mm to 20 mm.

[0201] (Recycling equipment) The plastic substrate or crushed substrate can be recovered layer by layer. In the separated liquid, the separated plastic substrate and residues such as printing ink and primer layers are suspended or dissolved. After removing these from the liquid, they can be separated using known methods such as flotation. The equipment and methods for recovering the substrate and crushed substrate are not particularly limited, but for example, filters, centrifuges, automatic scraping bar screens, inclined wire screens, and rotary drum screens can be used.

[0202] Furthermore, it is preferable to perform a final wash by stirring the recovered substrate in a rinsing solution to remove any remaining detached materials such as ink that have re-adhered to the single-layer plastic film. By removing the small amount of ink fragments remaining on the film surface, the quality of the recycled pellets can be greatly improved. There are no particular restrictions on the rinsing solution, and the aforementioned desorption treatment solution can be used as is, but it is preferable that it contains an appropriate amount of organic solvent. As for the organic solvent, it is preferable that it contains one or more types of water-soluble alcohols or water-soluble solvents with a flash point of 21°C or higher, and it is preferable that the cleaning solution contains a so-called water-soluble solvent including alcohols. The equipment and methods for stirring in the rinsing solution are not particularly limited, and known methods can be used. Specifically, examples include devices equipped with a motor with stirring blades that can stir the cleaning solution in a container, devices equipped with an ultrasonic generator, devices that can shake the container, wet crushers, kneaders, etc.

[0203] (Recovery and reuse of the desorption treatment liquid) The desorption liquid used in the desorption process is fed into one or more recycling machines selected from filters, centrifugal separators, and ultrafilters to recover it, and after removing solid material, it can be reused. Water, rinsing liquid, etc., can also be reused in the same way. It is also possible to continuously operate the reuse processes for water, desorption liquid, rinsing liquid, etc., while wet crushing is being performed, separating solid material from water, washing liquid, and rinsing liquid.

[0204] (Drying of plastic separation) The recovered material from the separated and recovered substrate is dried (film pieces) by one or more methods selected from vacuum heating drying, hot air drying, and pressure compression drying in order to remove residual moisture. As a pretreatment for producing the recycled pellets described later, briquettes may be produced after or during the drying of the recovered film pieces using a pressure compressor such as a press dewatering machine manufactured by Nippon Seam Co., Ltd., a pellet mill manufactured by Oike Iron Works Co., Ltd., or an Elcom Stella or briquette machine. When the plastic film is crushed into a powder using a grinder as a wet crusher, the crushed material is crushed to about 10 to 500 μm, and since the density of the crushed material is high, the pressure compression process can be omitted. The density varies depending on the materials that make up the crushed material, but a higher density is preferable because it is easier to handle when put into a kneader. Specifically, a dry weight of 0.03 kg or more is preferred, 0.05 kg or more is more preferred, 0.2 kg or more is even more preferred, and 0.3 kg or more is even more preferred.

[0205] (Recycled pellet production) Dried film pieces or briquettes are fed into single-screw and twin-screw extruders to produce recycled pellets. When film pieces are fed directly into the extruder without a pressurization process, a phenomenon called bridging, where ink fragments clog the feed port, is likely to occur. To avoid bridging, the film pieces may be pressurized in the feeder section or pushed in with air. Alternatively, to avoid bridging, the extruder body may use twin screws that rotate in opposite directions, or a side feeder may be used to push the pieces in. The kneader conditions are not particularly limited, but it is preferable to operate at 180-260°C to avoid significantly degrading the resin performance before recycling. The printed material of the present invention can be recycled as a recycled plastic product via the recycled pellets using the above recycling method. [Examples]

[0206] The present invention will be described in more detail below with reference to examples. In the following examples, parts, parts by mass, and % all represent mass percent.

[0207] (Synthesis of acrylic resin) [Synthesis Example 1: Preparation of Acrylic Resin (Polymer a1) for the Shell Part] A reaction vessel was equipped with a stirrer, thermometer, dropping funnel, and reflux tubing, and 60.0 parts by mass of n-propyl acetate was charged. The reaction vessel was heated to 90°C while being stirred under a nitrogen atmosphere. Meanwhile, 25.0 parts by mass of methyl methacrylate, 61.0 parts by mass of n-butyl acrylate, 14.0 parts by mass of acrylic acid, and 1.0 part by mass of azobisisobutyronitrile were dissolved in 40.0 parts by mass of n-propyl acetate and added dropwise over 4 hours using a dropping funnel. After the addition was complete, the reaction was allowed to continue for another 6 hours. After the reaction was complete, the mixture was cooled, and the resulting acrylic resin solution was neutralized by adding 8.0 parts by mass of 30% by mass of aqueous ammonia. Deionized water was then added, and the solvent was replaced while heating to obtain an aqueous solution of acrylic resin (a1) with a solid content of 50% by mass. The acid value was 109 mgKOH / g, the Tg was -12.0 °C, and the weight-average molecular weight was 16,000.

[0208] [Synthesis Example 2: Preparation of Core-Shell Type (Meth)Acrylic Emulsion (No. 1)] A reaction vessel containing 39.5 parts by mass of the acrylic resin aqueous solution (a1) prepared in Synthesis Example 1 was equipped with a stirrer, thermometer, dropping funnel, and reflux duct, and 230.0 parts by mass of deionized water was added. The reaction vessel was heated to 75°C while being stirred under a nitrogen atmosphere. Subsequently, 15.5 parts by mass of n-butyl methacrylate, 5.0 parts by mass of 2-ethylhexyl methacrylate, 39.5 parts by mass of 2-ethylhexyl acrylate, and 3.3 parts by mass of 30% ammonium persulfate were added dropwise over 4 hours using a dropping funnel. After the addition was complete, the reaction was carried out for a further 6 hours to obtain a core-shell type acrylic emulsion (No. 1) with a solid content of 40% by mass. The acid value was 42 mg KOH / g, the Tg was -22°C, and the weight-average molecular weight was 1,200,000.

[0209] [Synthesis Example 3: Preparation of Solution-Type (Meth)acrylic Resin (No. 16)] A reaction vessel was equipped with a stirrer, thermometer, dropping funnel, and reflux tube, and 65.0 parts by mass of n-propyl acetate was charged. The reaction vessel was heated to 90°C while being stirred under a nitrogen atmosphere. Meanwhile, 10.0 parts by mass of methyl acrylate, 20.0 parts by mass of n-butyl acrylate, 45.0 parts by mass of methyl methacrylate, 15.0 parts by mass of 2-ethylhexyl methacrylate, 10.0 parts by mass of acrylic acid, and 1.6 parts by mass of azobisisobutyronitrile were dissolved in 35.0 parts by mass of n-propyl acetate and added dropwise over 4 hours using a dropping funnel. After the addition was complete, the reaction was allowed to continue for another 6 hours. After the reaction was complete, the mixture was cooled, and 10.0 parts by mass of 30% by mass of ammonia water was added to the resulting acrylic resin solution to neutralize it. Deionized water was then added, and solvent replacement was performed while heating to obtain a solution-type acrylic resin (No. 16), which is an aqueous solution of acrylic resin with a solid content of 30% by mass. The acid value was 42 mgKOH / g, the Tg was 79°C, and the weight-average molecular weight was 10,000.

[0210] Acrylic emulsions No. 1-6, No. 8-15, and No. 20-27, and acrylic resins No. 17-19 were prepared by appropriately changing the type and amount of radically polymerizable unsaturated monomers to achieve the acid values ​​and Tg listed in Table 1, using the same method as described above. For acrylic emulsion No. 7, Seikoh PMC's acrylic core-shell emulsion resin "Hyros-X·QE-2128" was used.

[0211] [Table 1]

[0212] [Alkaline solubility] The alkali solubility of the (meth)acrylic resin obtained above was evaluated using the following procedure. To 100g of a 2% by mass sodium hydroxide aqueous solution heated to 70°C, 3g of resin component was added as solid content. After stirring for 5 minutes, the solution was left standing at 70°C for 1 day. After 1 day, the solution was adjusted to room temperature (25°C), and the NTU (Nephelometric Turbidity Unit) was measured using a Lovibond TB 300 IR turbidimeter (Tintmaker). The solution was also filtered using Whatman FILTER PAPER No. 1 (cytiva), and the undissolved resin component and precipitates due to the room temperature adjustment were visually inspected. If the turbidity is 50 NTU or higher, or if there are undissolved particles, the resin component is determined to be alkali-insoluble. If the turbidity is less than 50 NTU, and there are no undissolved resin components or precipitates due to exposure to room temperature, the resin component is determined to be alkali-soluble.

[0213] [Preparation of primer composition] Primer composition 1 was prepared as follows: Using acrylic resin 1, it was diluted with isopropyl alcohol (IPA) / water = 30 / 70 to a solid content of 20%, and 1 part of Surfinol 420 was added to 100 parts by mass of the dilution to prepare primer composition 1. Primer compositions 2 to 27 were prepared using the corresponding acrylic resins 2 to 27 in the same manner as the preparation method for primer composition 1.

[0214] [Preparation of solvent-based ink 1] A mixture of 37 parts by mass of N-propyl acetate (n-propyl acetate), 10 parts by mass of ethyl acetate, 11 parts by mass of blue pigment, 10 parts by mass of industrial nitrate H1 / 2 solution (nitrocellulose, 70% solids, viscosity 9.0-14.9% at a solution concentration of 25.0% according to JIS K-6703, manufactured by Taihei Chemical Products Co., Ltd., adjusted to 50% solids with IPA), 6 parts by mass of isopropyl alcohol, 1 part by mass of dispersant, 20 parts by mass of acrylic resin "Acridic WCL-1419 manufactured by DIC Corporation, weight-average molecular weight 35,000", and 5 parts by mass of cellulose acetate propionate (total of 100 parts) was kneaded to prepare a blue liquid printing ink. To 100 parts by mass of the obtained mixture, 42 parts by mass of IPA / EtAc mixed solvent (isopropyl alcohol / ethyl acetate = 50 / 50 (parts by mass / parts by mass)) was added to a Zahn cup #3 (manufactured by Rigosha) for approximately 15 seconds (25°C) to prepare solvent-based ink 1.

[0215] [Preparation of solvent-based ink 2] A mixture of 40 parts by mass of N-propyl acetate (n-propyl acetate), 10 parts by mass of ethyl acetate, 11 parts by mass of blue pigment, 3 parts by mass of vinyl chloride resin (vinyl chloride-vinyl acetate copolymer resin), 6 parts by mass of isopropyl alcohol, 1 part by mass of dispersant, and 29 parts of urethane resin (product name: Barnock ECL-341, weight-average molecular weight 85,000) (total of 100 parts) was kneaded to prepare a blue liquid printing ink. To 100 parts by mass of the obtained mixture, 42 parts by mass of IPA / EtAc mixed solvent (isopropyl alcohol / ethyl acetate = 50 / 50 (parts by mass / parts by mass)) was added to prepare solvent-based ink 2 by heating it in a Zahn cup #3 (manufactured by Rigosha) for about 15 seconds (25°C).

[0216] [Preparation of solvent-based ink 3] A mixture of 20 parts by mass of N-propyl acetate (n-propyl acetate), 10 parts by mass of ethyl acetate, 38 parts by mass of white pigment, 10 parts by mass of polyvinyl butyral resin, 6 parts by mass of isopropyl alcohol, 1 part by mass of dispersant, 10 parts by mass of urethane resin (product name: Barnock ECL-341, weight-average molecular weight 85,000), and 5 parts by mass of cellulose acetate propionate (total 100 parts) was kneaded to prepare a white liquid printing ink. To 100 parts by mass of the resulting mixture, 42 parts by mass of IPA / EtAc mixed solvent (isopropyl alcohol / ethyl acetate = 50 / 50 (parts by mass / parts by mass)) was added to a Zahn cup #3 (manufactured by Rigosha) for about 15 seconds (25°C) to prepare solvent-based ink 3.

[0217] [Preparation of water-based ink 1] A mixture of 20 parts by mass of core-shell type acrylic emulsion "Hyros X-436" manufactured by Seikoh PMC (based on solid content), 40 parts by mass of titanium dioxide, 1 part by mass of Surfinol 420, 5 parts by mass of polyethylene wax, 3 parts by mass of n-propanol, 0.1 parts by mass of defoamer, 0.6 parts by mass of aqueous ammonia, and 30.3 parts by mass of water (totaling 100 parts by mass) was kneaded to prepare a white aqueous ink 1. The viscosity of the obtained aqueous ink 1 was confirmed to be 16 seconds (25°C) using a Zahn cup #4 (manufactured by Rigosha).

[0218] [Production of printed materials] (Example 1) The printed material used in Example 1 was prepared as follows. The base film used was OPP film (Toyobo Co., Ltd.'s "Pyrene P2161 20μm"). The desorption primer layer was prepared as follows: Primer composition 1 was printed onto a substrate film that had been corona-discharged on one side, using a gravure printing press (manufactured by DIC Engineering Co., Ltd.) equipped with a gravure plate having a plate depth of 22 μm. The resulting coating was dried at room temperature for one day. The printed layer was prepared as follows: Solvent-based ink 1 was printed using a gravure printing press (manufactured by DIC Engineering Co., Ltd.) equipped with a gravure plate having a plate depth of 22 μm. The resulting print was dried at room temperature for one day. This resulted in obtaining the printed material of Example 1, which was laminated with a substrate, a primer layer, and a printing layer.

[0219] (Examples 2-228, Comparative Examples 1-96) Printed materials for Examples 2-228 and Comparative Examples 1-96 were prepared in the same manner as in Example 1, except that the base film, desorption primer layer, and printing layer were changed as shown in the table. Note that the base film used in the table is "Space Clean S-7053 40μm" manufactured by Toyobo Co., Ltd. for s-PET, and "Hybrid Styrene Sheet Film 40μm" for HyOPS.

[0220] <Method for detaching printed materials> The following delamination tests were performed on the printed materials of Examples 1 to 228 and Comparative Examples 1 to 96.

[0221] <Evaluation of detachability> <<Alkaline solution>> Desorption tests were conducted under the following conditions, and the ease of desorption under each condition was compared. • Desorbing properties 1: 1.5% by mass of sodium hydroxide, no surfactant, 85°C, pH 13.2 • Desorbing properties 2: 1.5% by mass of sodium hydroxide, no surfactant, 55°C, pH 13.2 • Desorption properties 3: 0.5% by mass of sodium hydroxide, no surfactant, 55°C, pH 13.0 • Desorbing properties 4: 0.1% by mass of sodium hydroxide, no surfactant, 55°C, pH 12.3 • Desorbing properties 5: 1.5% by mass of sodium hydroxide, no surfactant, 30°C, pH 13.2 • Desorbing properties 6: 1.5% by mass of sodium hydroxide, 0.3% by mass of nonionic surfactant, 30°C, pH 13.2 • Desorbing properties 7: 0.5% by mass of sodium hydroxide, 0.3% by mass of nonionic surfactant, 55°C, pH 13.0 • Desorbing properties 8: 0.1% by mass of sodium hydroxide, 0.3% by mass of nonionic surfactant, 55°C, pH 12.3 • Desorbing properties 9: 1.5% by mass of sodium hydroxide, 0.3% by mass of nonionic surfactant, 30°C, pH 13.2 • Desorbing properties 10: 0.005% by mass of sodium hydroxide, 0.3% by mass of cationic surfactant, 55°C, pH 10.5

[0222] <<Detachment Test Conditions>> The printed material was cut to a size of 20 mm x 20 mm to obtain test specimens. The test specimens were immersed in the solution and stirred with a stirrer. After stirring and confirming the desorption state, we also checked whether the coating film would detach by rubbing the printed material with our fingers. The delamination properties of the ink coating under the above conditions were evaluated according to the following evaluation criteria. [Evaluation Criteria] Complete detachment of the ink coating was confirmed by stirring for 5 minutes and 15 seconds or less. After stirring for 4:15-30 minutes, complete removal of the ink coating was confirmed. After stirring for 3:30 to 60 minutes, complete removal of the ink coating was confirmed. After 2 minutes and 60 minutes of stirring, partial detachment of the ink coating was observed. When rubbed with a finger, approximately 50-100% of the coating detached. After 1:60 minutes of stirring, the detachment of the ink coating was not confirmed. Rubbing with a finger revealed approximately 0-50% detachment. While a practical level of 3 or higher is preferable for the above evaluation results, a level of 2 is also sufficient to contribute to recycling, therefore, a level of 2 or higher can be considered an acceptable level. As an exception, in the evaluation under the condition of detachability 5, alkali resistance at room temperature is evaluated, so 1 is the most preferable, and 3 or less is a practical level.

[0223] [Adhesion] For the printed materials of Examples 1 to 228 and Comparative Examples 1 to 96, cellophane tape (manufactured by Nichiban Co., Ltd.) was applied to the printed surface, then the tape was quickly peeled off, and the condition of the printed surface was visually evaluated. (Evaluation Criteria) 5: The printed film does not peel off from the film at all. 4: As the area ratio of the printed film, less than 15% peels off from the film. 3: As the area ratio of the printed film, less than 30% peels off from the film. 2: As the area ratio of the printed film, less than 50% peels off from the film. 1: As the area ratio of the printed film, 50% or more peels off from the film.

[0224] 〔Abrasion resistance〕 For the printed matters of Examples 1 to 228 and Comparative Examples 1 to 96, on the printed surface, using black high-quality paper for the friction paper and a commercially available academic society type friction fastness tester, evaluation was carried out under the conditions of a load of 500 g and 100 reciprocations. (Evaluation criteria) 5: The rubbed black high-quality paper is not colored at all. 4: The rubbed black high-quality paper is colored very thinly. 3: The rubbed black high-quality paper is colored thinly but within the practical range. 2: The rubbed black high-quality paper is colored. 1: The rubbed black high-quality paper is colored darkly.

[0225] 〔Scratch resistance〕 For the printed matters of Examples 1 to 228 and Comparative Examples 1 to 96, the printed surface was rubbed 20 times back and forth with a fingernail, and the peeling state of the ink was visually evaluated. (Evaluation criteria) 5: The printed film does not peel off from the film at all. 4: As the area ratio of the printed film, less than 15% peels off from the film. 3: As the area ratio of the printed film, less than 30% peels off from the film. 2: As the area ratio of the printed film, less than 50% peels off from the film. 1: As the area ratio of the printed film, 50% or more peels off from the film.

[0226] 〔Blocking resistance〕 For the printed materials of Examples 1-228 and Comparative Examples 1-96, the printed surfaces were placed together and left for one day under the conditions of a blocking tester with a pressure of 0.5 MPa, a temperature of 50°C, and a humidity of 80%, before being peeled apart. The resistance during peeling and the state of surface peeling were evaluated. (Evaluation Criteria) 5: When peeling the printed surfaces apart, they separate without resistance, and there are no particular problems with the surface. 4. There is some resistance when peeling the printed surfaces apart, but the surface itself is fine. 3: When peeling the printed surfaces apart, there is some resistance, indicating that they are slightly stuck together. 2: When peeling the printed surfaces apart, there is resistance, and you can see that the surfaces are sticking together. 1: When peeling the printed surfaces apart, there is considerable resistance, indicating that the surfaces are strongly adhered to each other.

[0227] [Suitability for contraction] Primer-coated materials 1 to 27, each coated with primer compositions 1 to 27 on a substrate, were partially fixed to a stainless steel plate, immersed in 90°C hot water for 20 seconds to shrink, and then dried. The haze value of the dried coating was measured using a turbidimeter "NDH5000" (manufactured by Nippon Denshoku Industries, Ltd.). The method of coating the primer compositions was the same as the method for preparing a desorption primer layer in the production of printed materials. Haze value = Diffuse transmittance (DF) / Total light transmittance (TT) 5: Haze value between 0% and less than 10% 4: Haze value between 10% and less than 20% 3: Haze value between 20% and less than 40% 2: Haze value between 40% and less than 60% 1: Haze value 60% or higher A rating of 3 or higher is practically preferable. A rating of 4 or higher is even more preferable.

[0228] [Table 2]

[0229] [Table 3]

[0230] Table 4

[0231] Table 5

[0232] Table 6

[0233] Table 7

[0234] Table 8

[0235] Table 9

[0236] Table 10

[0237] As shown in the table, printed materials containing a desorption primer layer formed by the desorption primer compositions of the present invention in Examples 1 to 228 were found to have desorption performance at high temperatures and low alkali concentrations, and alkali resistance at low temperatures. Furthermore, it was found that the desorption primer compositions of the present invention can exhibit adhesion, abrasion resistance, scratch resistance, blocking resistance, and shrinkage suitability equivalent to conventional inks. In particular, printed materials (Examples 1 to 48) having a primer layer formed by primers 1 to 4 containing (meth)acrylic resin with an acid value of 10 to 50 mg KOH / g and a glass transition temperature (Tg) of -30 to 20°C showed excellent desorption, alkali resistance, adhesion, abrasion resistance, scratch resistance, blocking resistance, and shrinkage suitability. On the other hand, printed materials (Comparative Examples 1-24) having a primer layer formed by primers 20-21 containing (meth)acrylic resin with an acid value of less than 10 mg KOH / g did not exhibit delamination performance regardless of alkali concentration or liquid temperature. Printed materials (Comparative Examples 25-48) having a primer layer formed by primers 22-23 containing (meth)acrylic resin with a glass transition temperature (Tg) of less than -30°C had no problems with delamination and alkali resistance, but exhibited particularly poor abrasion resistance, scratch resistance, and blocking resistance. Printed materials (Comparative Examples 49-72) having a primer layer formed by primers 24-25 containing (meth)acrylic resin with a glass transition temperature (Tg) exceeding 90°C had no problems with delamination and alkali resistance, but exhibited particularly poor adhesion. Printed materials (Comparative Examples 73-96) having a primer layer formed by primers 26-27 containing (meth)acrylic resin with an acid value exceeding 90 mg KOH / g had poor alkali resistance at low temperatures.

Claims

1. A recycling method for recovering a plastic substrate from which the printed layer has been detached, from a printed material laminated in the order of at least a plastic substrate, a detachment primer layer, and a printed layer, The aforementioned desorption primer layer is formed by a desorption primer composition, The aforementioned desorption primer composition contains at least a (meth)acrylic resin and an aqueous solvent mainly composed of water. The (meth)acrylic resin has an acid value of 10 to 90 mgKOH / g and a glass transition temperature of -30°C to 0°C. The printed material is immersed in an alkaline aqueous solution to separate the printed layer from the plastic substrate. The aforementioned alkaline aqueous solution is an alkaline aqueous solution of sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium dihydrogen carbonate, or potassium dihydrogen carbonate, and has a concentration of 0.001% by mass to 0.5% by mass or less. The temperature of the aforementioned alkaline aqueous solution is 40°C or higher. Recycling methods.

2. The (meth)acrylic resin has an acid value of 10 to 50 mgKOH / g. The recycling method according to claim 1.

3. The (meth)acrylic resin is a homopolymer or copolymer of (meth)acrylate. The recycling method according to claim 1.

4. The (meth)acrylic resin is a (meth)acrylic resin emulsion having a core-shell structure. The recycling method according to claim 1.

5. The recycling method according to claim 1, wherein the (meth)acrylic resin is contained in an amount of 50% or more relative to the total solid content in the composition.

6. The aforementioned desorption primer composition does not contain a coloring agent. The recycling method according to claim 1.

7. The aforementioned plastic substrate is a shrinkable film. The recycling method according to claim 1.

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