Laminate

Abstract

To provide a laminate in which an adhesion property of a printing layer is excellent, detachment of the printing layer from a base material is easily performed by dissolving or swelling a primer layer by treatment with an aqueous solution, and recycling of the base material is easily performed.SOLUTION: There is provided a laminate, comprising: a base material; a primer layer (A) containing a vinyl-based copolymer (a) having an acid value of 100 mgKOH / g or more and 300 mgKOH / g or less and a glass transition temperature (Tg) of 25°C or more and 120°C or less; and a printing layer (B) containing an acrylic-based copolymer (b) having a solubility parameter of 19.7 [J / cm3]1 / 2 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate having a substrate, a primer layer, and a printed layer. More specifically, the present invention relates to a laminate in which the printed layer has excellent adhesiveness and the printed layer can be easily removed from the substrate by dissolving or swelling the primer layer through treatment with an aqueous solution, thereby facilitating recycling of the substrate. [Background technology]

[0002] Traditionally, plastics have been disposed of by landfilling or incineration. However, in recent years, it has become increasingly difficult to secure landfill sites, and the greenhouse gases emitted during incineration contribute to global warming. Furthermore, waste discarded or dumped in the ocean breaks down into submicron-sized fragments (microplastics) in seawater and floats there. These microplastics are prone to adsorbing pollutants such as polychlorinated biphenyls, which can accumulate in the bodies of fish and shellfish as they are ingested, leading to bioaccumulation and raising concerns about their impact on human health. To address these issues, efforts are being made to recycle plastics.

[0003] One of the applications of plastics is packaging materials and containers for food and other products, many of which are printed on their surfaces. Plastic products with printed layers on their surfaces are often discarded without being collected because they can cause discoloration during recycling. Therefore, there is a strong demand for a method to recycle plastic products with printed layers on their surfaces.

[0004] As a method for recycling plastic products having a printed layer printed on the surface, Patent Documents 1 and 2 describe a method in which a primer layer made of an acrylic resin or a styrene-maleic acid resin is provided on a plastic substrate, and the printed layer printed on the primer layer is removed using a basic aqueous solution. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-131484 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-084670 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the methods described in Patent Documents 1 and 2 have the problem that the adhesion between the primer layer and the printed layer, or between the substrate and the primer layer, is low, and the printed layer peels off during use.

[0007] The present invention aims to provide a laminate that has excellent adhesiveness of the printed layer, and that can be easily detached from the substrate by dissolving or swelling the primer layer through treatment with an aqueous solution, thereby facilitating recycling of the substrate. [Means for solving the problem]

[0008] That is, the present invention is summarized as follows: [1] to [5]. [1] A substrate, a primer layer (A) containing a vinyl copolymer (a) having an acid value of 100 mg KOH / g or more and 300 mg KOH / g or less and a glass transition temperature (Tg) of 25 ° C or more and 120 ° C or less, and a solubility parameter of 19.7 [J / cm 3 ] 1 / 2 and a printed layer (B) containing the above acrylic copolymer (b). [2] The printed layer (B) has a solubility parameter of 20.1 [J / cm 3 ] 1 / 2 The laminate according to [1], which contains the above acrylic copolymer (b). [3] The laminate according to [1] or [2], in which the primer layer (A) and the printing layer (B) are laminated in this order on a substrate. [4] The laminate according to any one of [1] to [3], wherein the acid value of the vinyl copolymer (a) is 151 mgKOH / g or more and 250 mgKOH / g or less. [5] The laminate according to any one of [1] to [4], wherein the glass transition temperature (Tg) of the vinyl copolymer (a) is 40°C or higher and 90°C or lower. [Effects of the Invention]

[0009] According to the present invention, a laminate can be provided which has excellent adhesion of the printed layer, and in which the printed layer can be easily detached from the substrate by dissolving or swelling the primer layer through treatment with an aqueous solution, thereby facilitating recycling of the substrate. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the present invention, "(meth)acrylic" is a general term for "acrylic" and "methacrylic." "(Meth)acrylate" is a general term for "acrylate" and "methacrylate."

[0011] The laminate of the present invention comprises a substrate, a primer layer (A) containing a vinyl copolymer (a) having an acid value of 100 mgKOH / g or more and 300 mgKOH / g or less and a glass transition temperature (Tg) of 25°C or more and 120°C or less, and a polymer having a solubility parameter of 19.7 [J / cm 3 ] 1 / 2 The printing layer (B) contains the above acrylic resin.

[0012] Examples of the substrate include polyethylene film or sheet (PE), unstretched polypropylene film or sheet (CPP), oriented polypropylene film or sheet (OPP), ethylene-vinyl acetate copolymer film or sheet (EVA), ethylene-vinyl alcohol copolymer film or sheet (EVOH), polyvinyl chloride film or sheet (PVC), polyethylene terephthalate film or sheet (PET), amorphous polyethylene terephthalate film or sheet (A-PET), glycol-modified polyethylene terephthalate film or sheet (G-PET), polycarbonate film or sheet, polybutylene terephthalate resin film or sheet (PBT), unstretched nylon film or sheet, biaxially oriented nylon film or sheet, polyvinylidene chloride film or sheet, polyvinyl alcohol film or sheet, polystyrene film or sheet, acrylic film or sheet, and polylactic acid film or sheet (PLA). Also included are vapor-deposited substrates, in which metals such as aluminum, gold, silver, copper, nickel, zinc, titanium, cobalt, indium, and chromium are vapor-deposited on the surface of the substrate. Furthermore, the surface of the substrate may be subjected to a surface treatment such as corona treatment or plasma treatment to improve adhesion. The substrate may be a single layer or two or more layers. In the case of two or more layers, the layers may be the same or different types. In the case of two or more layers, an adhesive layer may be provided to laminate the layers.

[0013] Among these, polyethylene film or sheet (PE), unstretched polypropylene film or sheet (CPP), oriented polypropylene film or sheet (OPP), polyethylene terephthalate film or sheet (PET), amorphous polyethylene terephthalate film or sheet (A-PET), and glycol-modified polyethylene terephthalate film or sheet (G-PET) are preferred because they are easy to recycle.

[0014] The primer layer (A) contains a vinyl copolymer (a) having an acid value of 100 mgKOH / g or more and 300 mgKOH / g or less and a glass transition temperature (hereinafter also referred to as "Tg") of 25°C or more and 120°C or less.

[0015] The acid value of the vinyl copolymer (a) is 100 mgKOH / g or more and 300 mgKOH / g or less. If the acid value is equal to or more than the lower limit, the printed layer is easily detached by an aqueous solution. If the acid value is equal to or less than the upper limit, sufficient adhesion to the printed layer can be imparted. From the viewpoint of detachment and adhesion of the printed layer, the acid value of the vinyl copolymer (a) is more preferably 130 mgKOH / g or more and 280 mgKOH / g or less, and even more preferably 151 mgKOH / g or more and 250 mgKOH / g or less.

[0016] The weight-average molecular weight (hereinafter also referred to as "Mw") of the vinyl copolymer (a) is preferably 5,000 or more and 100,000 or less, more preferably 10,000 or more and 50,000 or less. Within the above range, the higher the weight-average molecular weight, the more sufficient cohesive force can be imparted to the primer layer (A), improving the adhesion between the substrate and the primer layer (A), and thereby imparting sufficient adhesion to the printed layer. Within the above range, the lower the weight-average molecular weight, the more easily the printed layer is detached by an aqueous solution. In this specification, the term "weight average molecular weight" refers to the weight average molecular weight in terms of polystyrene measured by the GPC-LS method (Gel Permeation Chromatography-Light Scattering Method: GPC-light scattering method).

[0017] The glass transition temperature (Tg) of the vinyl copolymer (a) is 25°C or higher and 120°C or lower. If the Tg is equal to or higher than the lower limit, sufficient cohesive strength can be imparted to the primer layer (A), improving the adhesion between the substrate and the primer layer (A), thereby imparting sufficient adhesion to the printed layer. If the Tg is equal to or lower than the upper limit, the printed layer is more likely to be detached by an aqueous solution. From the viewpoints of adhesion and detachment of the printed layer, the Tg of the vinyl copolymer (a) is more preferably 40°C or higher and 90°C or lower. In this specification, the term "glass transition temperature (Tg)" refers to a value calculated by the Fox formula shown below in equation (1).

[0018]

number

[0019] Wi: mass fraction of monomer i Tgi: Tg (°C) of the homopolymer of monomer i For the Tg of a homopolymer, the values described in "Polymer Handbook, 4th Edition, John Wiley & Sons" can be used.

[0020] The vinyl copolymer (a) may have any structure such as a random copolymer, a graft copolymer, a block copolymer, a linear copolymer, or a branched copolymer.

[0021] Examples of the vinyl copolymer (a) include vinyl polymers having structural units derived from a vinyl compound having at least one acid group. The ratio of structural units derived from a vinyl compound having an acid group to all structural units in the vinyl copolymer (a) is such that the acid value of the vinyl copolymer (a) is 100 mg KOH / g or more and 300 mg KOH / g or less, preferably 130 mg KOH / g or more and 280 mg KOH / g or less, and more preferably 151 mg KOH / g or more and 250 mg KOH / g or less. Within this range, the solubility of the vinyl copolymer (a) in aqueous solutions is good.

[0022] Specific examples of the vinyl compound having an acid group include vinyl compounds having a carboxyl group or a sulfo group. Specific examples of vinyl compounds having a carboxyl group include monobasic acids such as acrylic acid, methacrylic acid, crotonic acid, mono(2-(meth)acryloyloxyethyl) succinate, and ω-carboxy-polycaprolactone mono(meth)acrylate; dibasic acids such as fumaric acid, maleic acid, and itaconic acid; and partial esters of the above dibasic acids. Specific examples of vinyl compounds having a sulfo group include vinylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid.

[0023] As the vinyl compound having an acid group, a vinyl compound having a carboxyl group is preferred, and (meth)acrylic acid is more preferred, in terms of improving the solubility of the vinyl copolymer (a) in an aqueous solution. The vinyl copolymer (a) is preferably an acrylic copolymer. That is, the vinyl copolymer (a) preferably has an acid group (carboxyl group) derived from a vinyl compound having a carboxyl group, and more preferably has an acid group (carboxyl group) derived from (meth)acrylic acid. The vinyl compound having an acid group may be used alone or in combination of two or more.

[0024] From the viewpoint of adhesion to the substrate or the printed layer, the vinyl copolymer (a) preferably has a structural unit derived from a monomer other than a vinyl compound having at least one acid group. From the viewpoint of adhesion to the substrate or the printed layer, the monomer other than a vinyl compound having an acid group is preferably a (meth)acrylate or a (meth)acrylamide derivative, more preferably a (meth)acrylate.

[0025] Examples of the (meth)acrylate include alkyl (meth)acrylates having a linear or branched hydrocarbon skeleton, alkyl (meth)acrylates having an alicyclic skeleton, (meth)acrylates having a glycidyl group, (meth)acrylates having an aromatic ring, (meth)acrylates having a cyclic ether, (meth)acrylates having an amino group, (meth)acrylates having a phosphoric acid group, hydroxyalkyl (meth)acrylates, hydroxy (meth)acrylates having an aromatic ring, hydroxypolyalkylene oxide (meth)acrylates, bifunctional (meth)acrylates having two polymerizable double bonds, and trifunctional or higher functional (meth)acrylates having three or more polymerizable double bonds.

[0026] Specific examples of alkyl(meth)acrylates having a linear or branched hydrocarbon skeleton include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, i-propyl(meth)acrylate, n-butyl(meth)acrylate, i-butyl(meth)acrylate, t-butyl(meth)acrylate, n-pentyl(meth)acrylate, i-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-octyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, isostearyl(meth)acrylate, and 4-t-butylcyclohexyl(meth)acrylate.

[0027] Specific examples of alkyl(meth)acrylates having an alicyclic skeleton include cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, adamantyl(meth)acrylate, tricyclodecanyl(meth)acrylate, dicyclopentadienyl(meth)acrylate, and dicyclopentanyl(meth)acrylate. Specific examples of the (meth)acrylate having a glycidyl group include glycidyl (meth)acrylate and hydroxybutyl (meth)acrylate glycidyl ether.

[0028] Specific examples of (meth)acrylates having an aromatic ring include phenoxy(meth)acrylate, benzyl(meth)acrylate, phenyl(meth)acrylate, phenoxyethyl(meth)acrylate, phenoxypolyethylene glycol(meth)acrylate, nonylphenol EO adduct (meth)acrylate, and o-biphenyloxyethyl(meth)acrylate.

[0029] A specific example of the (meth)acrylates having a cyclic ether is tetrahydrofurfuryl (meth)acrylate. Specific examples of (meth)acrylates having an amino group include N-dimethylaminoethyl (meth)acrylate and N-diethylaminoethyl (meth)acrylate.

[0030] Specific examples of (meth)acrylates having a phosphate group include 2-(meth)acryloyloxyethyl acid phosphate, 2-(meth)acryloyloxyethyl acid phosphate monoethanolamine salt, diphenyl((meth)acryloyloxyethyl)phosphate, (meth)acryloyloxypropyl acid phosphate, 3-chloro-2-acid phosphooxypropyl (meth)acrylate, acid phosphooxypolyoxyethylene glycol mono(meth)acrylate, and acid phosphooxypolyoxypropylene glycol (meth)acrylate.

[0031] Specific examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,2-dihydroxyethyl (meth)acrylate, 1,2-dihydroxypropyl (meth)acrylate, 1,2-dihydroxybutyl (meth)acrylate, 1,2-dihydroxy-5-ethylhexyl (meth)acrylate, 1,1-dihydroxyethyl (meth)acrylate, 1,1-dihydroxypropyl (meth)acrylate, 1,1-dihydroxybutyl (meth)acrylate, 1,2,3-trihydroxypropyl (meth)acrylate, 1,2,3-trihydroxybutyl (meth)acrylate, 1,1,2-trihydroxypropyl (meth)acrylate, and 1,1,2-trihydroxybutyl (meth)acrylate. A specific example of the aromatic ring-containing hydroxy(meth)acrylates is 2-hydroxy-3-phenoxypropyl(meth)acrylate.

[0032] Specific examples of hydroxypolyalkylene oxide (meth)acrylates include hydroxypolyethylene oxide mono(meth)acrylate, hydroxypolypropylene oxide mono(meth)acrylate, hydroxy(polyethylene oxide-polypropylene oxide) mono(meth)acrylate, hydroxy(polyethylene oxide-propylene oxide) mono(meth)acrylate, hydroxy(polyethylene oxide-polytetramethylene oxide) mono(meth)acrylate, and hydroxy(polyethylene oxide-tetramethylene oxide) mono(meth). hydroxy(polypropylene oxide-polytetramethylene oxide) mono(meth)acrylate, hydroxy(polypropylene oxide-polytetramethylene oxide) mono(meth)acrylate, 1,2-dihydroxypolyethyl oxide (meth)acrylate, 1,2-dihydroxypolypropylene oxide (meth)acrylate, polyhydroxyalkyl (meth)acrylate, 1,2,3-trihydroxypropylene glycol (meth)acrylate, 1,1,2-trihydroxypropylene glycol (meth)acrylate.

[0033] Specific examples of bifunctional (meth)acrylates having two polymerizable double bonds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, and propylene oxide-modified bisphenol. Examples of the di(meth)acrylate include A-type di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,6-hexanediol ethylene oxide-modified di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid-modified neopentyl glycol di(meth)acrylate, and isocyanuric acid ethylene oxide-modified diacrylate.

[0034] Specific examples of trifunctional or higher (meth)acrylates having three or more polymerizable double bonds include trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, ethoxylated glycerin tri(meth)acrylate, glycerin polyglycidyl ether poly(meth)acrylate, isocyanuric acid ethylene oxide modified tri(meth)acrylate, ε-caprolactone modified tris-(2-acryloxyethyl)isocyanurate, ethylene Examples of the acrylate include ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tetra(meth)acrylate, succinic acid-modified pentaerythritol tri(meth)acrylate, tripentaerythritol acrylate (e.g., "Viscoat #802" manufactured by Osaka Organic Chemical Industry Co., Ltd.), and dendrimer acrylate (e.g., "STAR-501" manufactured by Osaka Organic Chemical Industry Co., Ltd.).

[0035] From the viewpoint of solubility in aqueous solutions, the (meth)acrylate is preferably at least one of alkyl (meth)acrylates having a linear or branched hydrocarbon skeleton with 8 or less carbon atoms and alkyl (meth)acrylates having an alicyclic skeleton, and more preferably at least one of methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. One (meth)acrylate may be used alone, or two or more may be used in combination.

[0036] Specific examples of the (meth)acrylamide derivative include (meth)acrylamide, (meth)acrylamide diacetone acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and (meth)acryloylmorpholine. One (meth)acrylamide derivative may be used alone, or two or more may be used in combination.

[0037] The vinyl copolymer (a) may contain, as a constituent unit derived from a monomer other than a vinyl compound having an acid group, a constituent unit derived from a monomer other than a (meth)acrylate or a (meth)acrylamide derivative. Examples of other monomers include aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and chlorostyrene; vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, α-cyanoacrylate, dicyanovinylidene, and fumaronitrile; polyfunctional monomers such as divinylbenzene, divinylnaphthalene, and divinyl ether; vinyl monomers such as vinyl acetate and vinyl propionate; and conjugated diene monomers such as 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, and chloroprene. One type of other monomer may be used alone, or two or more types may be used in combination.

[0038] From the viewpoint of solubility in aqueous solutions, the proportion of (meth)acrylate-derived structural units in the vinyl copolymer (a) is preferably 40% by mass or more, more preferably 60% by mass or more, based on all structural units.

[0039] The method for producing the vinyl copolymer (a) is not particularly limited, and examples thereof include known methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. From the viewpoints of ease of synthesis, handling, and solubility in water, suspension polymerization is preferred. The polymerization temperature in producing the vinyl copolymer (a) is not particularly limited, but is preferably -100°C or higher and 250°C or lower, more preferably 0°C or higher and 200°C or lower, from the viewpoint of ease of control of the polymerization rate.

[0040] A chain transfer agent or a radical polymerization initiator can be used in the polymerization for producing the vinyl copolymer (a). Examples of the chain transfer agent include hydrogen, mercaptans, α-methylstyrene dimer, terpenoids, and cobalt chain transfer agents. One type of chain transfer agent may be used alone, or two or more types may be used in combination.

[0041] Specific examples of suitable mercaptans used as chain transfer agents include n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan, n-hexyl mercaptan, 2-ethylhexyl thioglycolate, 2-ethylhexyl-3-mercaptopropionate, methoxybutyl-3-mercaptopropionate, and pentaerythritol tetrakis(3-mercaptopropionate). The amount of the chain transfer agent added may be adjusted appropriately depending on the type of the agent so that the weight average molecular weight of the vinyl copolymer (a) reaches a desired value.

[0042] Examples of the radical polymerization initiator include organic peroxides and azo compounds. One type of radical polymerization initiator may be used alone, or two or more types may be used in combination.

[0043] Specific examples of organic peroxides used as radical polymerization initiators include t-butyl peroxypivalate, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, cyclohexanone peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate.

[0044] Specific examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyrate) dimethyl, and 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile).

[0045] As the radical polymerization initiator, benzoyl peroxide, lauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile) are preferred because of their good polymerizability. In terms of good polymerizability, the amount of radical polymerization initiator added is preferably 0.0001 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the total of the monomers used.

[0046] The primer layer (A) may contain components other than the vinyl copolymer (a) as long as they do not impair adhesion to the substrate. Because the printed layer is more easily detached by an aqueous solution, the content of the vinyl copolymer (a) relative to the total mass of the primer layer (A) is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Examples of components other than the vinyl copolymer (a) include leveling agents, thixotropic agents, organic or inorganic fine particles, viscosity modifiers, antistatic agents, antioxidants, antifouling agents, slip agents, refractive index modifiers, antifoaming agents, polyaromatic vinyl compounds such as polystyrene, polyester polymers, polyurethane polymers, alkyd polymers, epoxy polymers, and cellulose polymers such as nitrocellulose, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate.

[0047] The method for laminating the primer layer (A) on the substrate is not particularly limited, and known methods can be used. For example, there are methods such as (Method 1) in which a film containing the vinyl copolymer (a) is produced in advance and then bonded to the substrate by lamination or coextrusion, (Method 2) in which a raw material containing the vinyl copolymer (a) is extruded onto the substrate using a T-die or the like to obtain a laminate, and (Method 3) in which a resin liquid containing the vinyl copolymer (a) is applied to the substrate by various coating methods such as gravure printing or spray coating, and then dried.

[0048] The organic solvent used in the method 3 is not particularly limited as long as it is an organic solvent that can at least either dissolve or disperse the vinyl copolymer (a). Examples of the organic solvent include aromatic hydrocarbons such as toluene (boiling point 110.6°C), xylene (boiling point 144°C), Swazol #1000 (manufactured by Maruzen Petrochemical Co., Ltd., boiling point 150°C or higher), and Sorbets #150 (manufactured by Exxon Chemical Co., Ltd., boiling point 190°C to 210°C); alicyclic hydrocarbons such as cyclohexane (boiling point 80.7°C) and methylcyclohexane (boiling point 101°C); ketones such as methyl ethyl ketone (boiling point 79.6°C), methyl isobutyl ketone (116.2°C), and diisobutyl ketone (boiling point 168°C); ethyl acetate (boiling point 77.1°C), i-propyl acetate (boiling point 89°C), and the like. esters such as ethanol (boiling point 78.3°C), isopropyl alcohol (boiling point 82°C), n-propyl alcohol (boiling point 97.2°C), n-butanol (boiling point 117°C), and cyclohexanol (boiling point 161°C); glycol-based solvents such as propylene glycol monomethyl ether (boiling point 121°C) and ethylene glycol monobutyl ether (boiling point 171°C); and aliphatic hydrocarbons such as Myisoper E (manufactured by Exxon Chemical Co., Ltd., boiling point 114°C) and mineral turpentine (boiling point 150°C to 280°C). Among these, esters, ketones, and alcohols are preferred from the viewpoint of at least one of the solubility and dispersibility of the vinyl copolymer (a). The organic solvents can be used alone or in combination of two or more. Drying conditions can be adjusted as appropriate, taking into account the boiling point of the solvent used and the heat resistance temperature of the substrate, such as temperature and time.

[0049] The thickness of the primer layer (A) is not particularly limited, but is, for example, preferably from 0.1 μm to 10 μm, more preferably from 0.1 μm to 8 μm, and even more preferably from 1 μm to 5 μm. When the thickness of the primer layer (A) is within the above range, the printing layer is easily detached by an aqueous solution.

[0050] The printed layer (B) has a solubility parameter (Sp value, hereinafter also referred to as "Sp value") of 19.7 [J / cm 3 ] 1 / 2 The acrylic copolymer (b) is as described above.

[0051] The Sp value of the acrylic copolymer (b) is 19.7 (J / cm 3 ) 1 / 2 If the Sp value is equal to or greater than 20.1 (J / cm), sufficient adhesiveness can be imparted to the printed layer (B). In order to impart sufficient adhesiveness to the printed layer (B), the Sp value of the acrylic copolymer (b) is set to 20.1 (J / cm). 3 ) 1 / 2 The upper limit of the Sp value of the acrylic polymer (b) is not particularly limited, but as a guideline, it is 22.5 (J / cm 3 ) 1 / 2 The following are included:

[0052] Here, the solubility parameter is determined by substituting the Sp value (Sp(Ui)) of the monomer unit constituting the polymer into formula (1). Sp(Ui) can be determined by the Fedors method described in Polymer Engineering and Science, Vol. 14, 147 (1974). The Sp values (Sp(Ui)) of representative monomer units are shown below.

[0053]

number

[0054] <Sp value of representative monomer units (Sp(Ui))> Methyl methacrylate: 20.32 (J / cm 3 ) 1 / 2 Ethyl methacrylate: 19.89 (J / cm 3 ) 1 / 2 n-Butyl methacrylate: 19.33 (J / cm 3 )1 / 2 i-Butyl methacrylate: 18.96 (J / cm 3 ) 1 / 2 2-Ethylhexyl methacrylate: 18.50 (J / cm 3 ) 1 / 2 Isobornyl methacrylate: 19.61 (J / cm 3 ) 1 / 2 Methacrylic acid: 25.65 (J / cm 3 ) 1 / 2 n-Butyl acrylate: 19.99 (J / cm 3 ) 1 / 2 Styrene: 20.09 (J / cm 3 ) 1 / 2 2-Hydroxyethyl methacrylate: 27.56 (J / cm 3 ) 1 / 2

[0055] The acrylic copolymer (b) has a structural unit derived from at least one (meth)acrylic acid ester monomer. Examples of the (meth)acrylic acid ester monomer include the above-mentioned (meth)acrylates and (meth)acrylamide derivatives, as well as (meth)acrylates having a carboxyl group, such as acrylic acid, methacrylic acid, mono(2-(meth)acryloyloxyethyl) succinate, and ω-carboxy-polycaprolactone mono(meth)acrylate.

[0056] From the viewpoint of adhesion, the (meth)acrylate is preferably at least one of alkyl (meth)acrylates having a linear or branched hydrocarbon skeleton with 8 or less carbon atoms and alkyl (meth)acrylates having an alicyclic skeleton, and more preferably at least one of methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. One (meth)acrylate may be used alone, or two or more may be used in combination.

[0057] The acrylic copolymer (b) may contain, as a constituent unit derived from a monomer other than the (meth)acrylic acid ester monomer, a constituent unit derived from another monomer.

[0058] Examples of other monomers include aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and chlorostyrene; cyanide vinyl monomers such as acrylonitrile, methacrylonitrile, α-cyanoacrylate, dicyanovinylidene, and fumaronitrile; polyfunctional monomers such as divinylbenzene, divinylnaphthalene, and divinyl ether; vinyl monomers such as vinyl acetate and vinyl propionate; conjugated diene monomers such as 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, and chloroprene; dibasic acids such as fumaric acid, maleic acid, and itaconic acid; and vinyl compounds having a sulfo group such as partial esters of these dibasic acids, vinyl sulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid. These other monomers may be used singly or in combination.

[0059] From the viewpoint of adhesion, the proportion of structural units derived from (meth)acrylic acid ester monomers in the acrylic copolymer (b) is preferably 50% by mass or more, more preferably 75% by mass or more, based on all structural units.

[0060] The weight-average molecular weight of the acrylic copolymer (b) is preferably 5,000 to 200,000, more preferably 10,000 to 150,000, and even more preferably 15,000 to 100,000. Within the above range, the higher the weight-average molecular weight, the better the cohesive strength of the printed layer (B), thereby imparting sufficient adhesiveness to the printed layer. Within the above range, the lower the weight-average molecular weight, the better the printability.

[0061] The acrylic copolymer (b) may have any structure such as a graft copolymer or a block copolymer.

[0062] The glass transition temperature (Tg) of the acrylic copolymer (b) is preferably 20°C or higher and 100°C or lower, more preferably 30°C or higher and 90°C or lower, and even more preferably 40°C or higher and 80°C or lower. If the Tg is equal to or higher than the lower limit, fusion between the laminates of the present invention can be prevented when the laminate is stored in a roll or in a stack of multiple laminates. If the Tg is equal to or lower than the upper limit, flexibility can be imparted to the printed layer (B), and therefore sufficient adhesiveness can be imparted to the printed layer (B).

[0063] The acid value of the acrylic copolymer (b) is preferably less than 100 mgKOH / g, more preferably 50 mgKOH / g or less, and even more preferably 10 mgKOH / g or less. The lower limit of the acid value may be 0 mgKOH / g, but is preferably 1 mgKOH / g or more. If the acid value is equal to or greater than the lower limit, the printing layer is more likely to be detached by an aqueous solution. If the acid value is equal to or less than the upper limit, adhesion to the primer layer is improved.

[0064] The method for producing the acrylic copolymer (b) is not particularly limited, but may be the same method as that for the vinyl copolymer (a) described above.

[0065] The method for laminating the printed layer (B) on the substrate or on the primer layer (A) of the substrate on which the primer layer (A) has been laminated is not particularly limited, but examples thereof include a method in which an ink (B') containing the acrylic copolymer (b) is prepared and this ink (B') is printed by a known printing method. That is, from the viewpoint of the design of the printed layer (B), it is preferable that the printed layer (B) is a dried or cured product of the ink (B') containing the acrylic copolymer (b).

[0066] The ink (B') can be produced by at least one of dissolving and dispersing the acrylic copolymer (b) together with a colorant, etc., as required, in an organic solvent.

[0067] The content of the acrylic copolymer (b) relative to the total mass of the nonvolatile components of the ink (B') is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 23% by mass or more. An example of an upper limit is 90% by mass or less. If the content is equal to or greater than the lower limit, better adhesion to the primer layer can be achieved. Examples of nonvolatile components other than the acrylic copolymer (b) include colorants, which will be described later.

[0068] The ink (B') may contain other polymers besides the acrylic copolymer (b) to the extent that the adhesion to the substrate is not impaired. The other polymers are not particularly limited, but examples thereof include polyaromatic vinyl compounds such as polystyrene, polyester resins, polyurethane resins, alkyd resins, epoxy resins, and cellulose-based resins such as nitrocellulose, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate.

[0069] Ink (B') may contain a colorant. Hues containing colorants include, for example, the five basic process colors, including white, yellow, crimson, indigo, and black, and the three process gamut colors, red (orange), grass green, and purple. Other base colors include transparent yellow, peony, vermilion, brown, gold, silver, pearl, and a nearly transparent medium (containing an extender pigment, if necessary) for adjusting color density. Other inks can be mixed with the white ink, and organic pigments, inorganic pigments, and dyes can also be mixed as necessary.

[0070] Examples of white inorganic pigments that can be used in the ink (B') include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, and silica. Titanium oxide is preferably used as the pigment for white ink in terms of coloring power, hiding power, chemical resistance, and weather resistance. Examples of inorganic pigments other than white pigments include carbon black, aluminum, and mica.

[0071] Examples of colored colorants that can be used in ink (B') include organic and inorganic pigments and dyes that are commonly used in inks, paints, and recording materials. Examples of organic pigments that can be used in combination include azo-based, phthalocyanine-based, anthraquinone-based, perylene-based, perinone-based, quinacridone-based, thioindigo-based, dioxazine-based, isoindolinone-based, quinophthalone-based, azomethine azo-based, dicetpyrrolopyrrole-based, and isoindoline-based pigments. Copper phthalocyanine is preferably used for indigo ink, and CI Pigment No. Yellow 83 is preferably used for clear yellow ink from the standpoints of cost and lightfastness.

[0072] In order to ensure the density and coloring strength of the ink, the colorant is preferably contained in an amount of 1 to 50% by mass relative to the total mass of the ink. These colorants can be used alone or in combination of two or more types.

[0073] To stably disperse the pigment in an organic solvent, the acrylic copolymer (b) alone can be used, but a dispersant can also be used in combination to further stably disperse the pigment. Anionic, nonionic, cationic, amphoteric surfactants can be used as dispersants. From the viewpoint of ink storage stability, the dispersant is preferably contained in the ink in an amount of 0.05% by mass or more relative to the total mass of the ink. Furthermore, from the viewpoint of printability, the dispersant is preferably contained in the ink in an amount of 5% by mass or less. Furthermore, from the viewpoint of ink storage stability and printability, the dispersant is more preferably contained in the ink in an amount of 0.1 to 2% by mass.

[0074] The organic solvent that can be used in the ink (B') is not particularly limited as long as it can dissolve and / or disperse the acrylic resin (b) and the other components, and can also dissolve and / or disperse the other components. Examples of suitable organic solvents include aromatic hydrocarbons such as toluene (boiling point 110.6°C), xylene (boiling point 144°C), Swazol #1000 (manufactured by Maruzen Petrochemical Co., Ltd., boiling point 150°C or higher), and Sorbets #150 (manufactured by Exxon Chemical Co., Ltd., boiling point 190°C to 210°C); alicyclic hydrocarbons such as cyclohexane (boiling point 80.7°C) and methylcyclohexane (boiling point 101°C); ketones such as methyl ethyl ketone (boiling point 79.6°C), methyl isobutyl ketone (boiling point 116.2°C), and diisobutyl ketone (boiling point 168°C); and ethyl acetate (boiling point 77.5°C). Examples of suitable solvents include esters such as propylene glycol monomethyl ether acetate (boiling point 146°C), isopropyl acetate (boiling point 89°C), n-propyl acetate (boiling point 96.6°C), i-butyl acetate (boiling point 118°C), n-butyl acetate (boiling point 126°C), and propylene glycol monomethyl ether acetate (boiling point 146°C); alcohols such as ethanol (boiling point 78.3°C), isopropyl alcohol (boiling point 82°C), n-propyl alcohol (boiling point 97.2°C), n-butanol (boiling point 117°C), and cyclohexanol (boiling point 161°C); glycol-based solvents such as propylene glycol monomethyl ether (boiling point 121°C) and ethylene glycol monobutyl ether (boiling point 171°C); and aliphatic hydrocarbons such as MISOPER E (manufactured by Exxon Chemical Co., Ltd., boiling point 114°C) and mineral turpentine (boiling point 150°C to 280°C). Among these, esters, alcohols, and ketones are preferred because of their low environmental impact due to volatile emissions. The organic solvents may be used alone or in combination of two or more.

[0075] To the ink (B'), as needed, conductive agents such as carbon black and ferrite; luminescent agents such as inorganic fillers, lubricants, plasticizers, organic peroxides, aluminum paste and mica; various stabilizers such as antioxidants, ultraviolet absorbers, weathering stabilizers, radiation resistant agents and heat stabilizers; and auxiliary additives such as surface conditioners, crosslinking agents, curing catalysts and pigment anti-settling agents can be added by a general compounding method.

[0076] The method for producing the ink (B') is not particularly limited, and the ink (B') can be produced by a known method. For example, the ink can be produced by dispersing a pigment in an organic solvent with a polymer and the dispersant to produce a pigment dispersion, and then blending other compounds, etc., as necessary, with the obtained pigment dispersion. The particle size distribution of the pigment in the pigment dispersion can be adjusted by appropriately adjusting the size of the grinding media of the disperser, the packing ratio of the grinding media, the dispersion treatment time, the discharge speed of the pigment dispersion, the viscosity of the pigment dispersion, etc. As the disperser, a commonly used device such as a roller mill, a ball mill, a pebble mill, an attritor, a sand mill, or a planetary mixer can be used. If the ink (B') contains air bubbles or unexpectedly large particles, these particles will deteriorate the quality of the printed matter, so it is preferable to remove them by filtration, etc. Conventional filters can be used.

[0077] The viscosity of the ink (B') produced by the above method is preferably 10 mPa·s or more in order to prevent pigment sedimentation and to adequately disperse the pigment. Furthermore, the viscosity of the ink (B') is preferably in the range of 5000 mPa·s or less in order to improve workability during ink production and printing. The viscosity is measured at 25°C using a Brookfield viscometer.

[0078] The viscosity of the ink (B') can be adjusted by appropriately selecting the types and amounts of raw materials used, such as polymers, colorants, and organic solvents, and can also be adjusted by adjusting the particle size and particle size distribution of the pigment in the ink (B').

[0079] The ink (B') can be used in known printing methods such as gravure printing, flexographic printing, and offset printing.

[0080] The printed layer (B) may be a single layer or a laminate. The thickness of the printed layer (B) is not particularly limited, but is preferably 0.3 μm to 20 μm, more preferably 0.4 μm to 15 μm, and even more preferably 0.5 μm to 10 μm. Within the above range, both the adhesiveness of the printed layer and its detachment by an aqueous solution can be satisfied.

[0081] The laminate of the present invention preferably has a primer layer (A) and a printed layer (B) laminated on a substrate in this order, which allows the printed layer to be easily removed by dissolving or swelling the primer layer through treatment with an aqueous solution, facilitating recycling of the substrate.

[0082] A basic aqueous solution is preferred as the aqueous solution used to dissolve or swell the primer layer. The use of a basic aqueous solution allows the printing layer to be easily removed. The basic compound used in the basic aqueous solution is not particularly limited, and examples include metal hydroxides such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; metal carbonates such as sodium carbonate; and volatile amino compounds such as ammonia, triethylamine, propylamine, diethylamine, tripropylamine, dibutylamine, amylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 2-diethylaminoethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 1-dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-propylaminoethanol, ethoxypropylamine, aminobenzyl alcohol, and morpholine. The basic compounds may be used alone or in combination. As the basic compound, metal hydroxides and metal carbonates are preferred, and sodium hydroxide and potassium hydroxide are more preferred, since the printed layer can be easily removed.

[0083] The amount of basic compound in the aqueous solution is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and even more preferably 1 to 10% by mass, based on the total mass of the aqueous solution. If the amount is above the lower limit, the primer layer can be dissolved or swelled by treatment with the aqueous solution, allowing the printed layer to be easily removed, facilitating recycling of the substrate. If the amount is below the upper limit, deterioration of the substrate due to the basic compound can be prevented, allowing recycling without deteriorating the quality of the substrate.

[0084] Examples of methods for treating the laminate of the present invention with an aqueous solution include immersing the laminate, either as is or after cutting and crushing, in an aqueous solution or spraying the aqueous solution on the laminate. In view of the fact that the printed layer detaches from the substrate in a short time, the method of treating the laminate with an aqueous solution preferably involves immersing the laminate, after cutting and crushing, in an aqueous solution.

[0085] The temperature of the aqueous solution during immersion is preferably 15°C or higher, more preferably 20°C or higher, and even more preferably 25°C or higher. Furthermore, the temperature of the aqueous solution during immersion is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower. As long as the temperature of the aqueous solution during immersion is within the above-mentioned range, the higher the temperature, the more likely the printed layer will detach from the substrate in a shorter time. As long as the temperature during immersion is within the above-mentioned range, the lower the temperature, the more likely it is that the substrate will be prevented from deteriorating, allowing the substrate to be recycled without deteriorating in quality.

[0086] The immersion time is preferably 30 seconds to 6 hours, more preferably 1 minute to 3 hours, and even more preferably 3 minutes to 2 hours. As long as the immersion time is within the above range, the longer the immersion time, the more thoroughly the printed layer is detached from the substrate, making it easier to recycle the substrate. Furthermore, as long as the immersion time is within the above range, the shorter the immersion time, the more effectively the substrate is prevented from being deteriorated by the basic compound, allowing the substrate to be recycled without deteriorating in quality.

[0087] In order to ensure sufficient detachment of the printed layer from the substrate, the amount of the aqueous solution used during immersion is preferably 1,000 to 1,000,000 times the total mass of the laminate. The aqueous solution may be stirred during immersion.

[0088] Methods for recycling the substrate after removing the printed layer from the substrate by treating the laminate with an aqueous solution include, but are not limited to, recovering, washing, and drying the substrate, processing it into pellets using an extruder or the like, and reusing it as a recycled polymer. [Example]

[0089] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0090] <Measurement of weight average molecular weight (Mw)> The weight-average molecular weight was measured using a Tosoh high-speed GPC system, model HLC-8320GPC (detector: RI detector). Two Tosoh TSKgel SuperHZM-M (4.6 mm ID x 15 cm L) columns and one Tosoh TSKgel HZ2000 (4.6 mm ID x 15 cm L) columns were connected together. The eluent was tetrahydrofuran (containing the stabilizer dibutylhydroxytoluene), with a flow rate of 0.35 mL / min, an inlet temperature of 40°C, an oven temperature of 40°C, and an RI detector temperature of 40°C. A 10 μL sample was injected, adjusted with tetrahydrofuran to a polymer concentration of 0.2% by mass.

[0091] <Method for measuring the acid value of a polymer> The acid value of the polymer was measured as follows. Approximately 0.2 g (WA (g)) of the polymer sample to be measured was weighed and placed in a side-arm Erlenmeyer flask. 10 mL of propylene glycol monomethyl ether (PGM) was added to dissolve the sample. After dissolution, 10 mL of toluene, 20 mL of ethanol, and a few drops of phenolphthalein solution were added, and the sample was titrated with a 0.02 N potassium hydroxide aqueous solution (KOH aqueous solution). The titer was designated LB (mL), and the titer of the KOH aqueous solution was designated p. A blank measurement was also performed in the same manner. The titer was designated LC (mL), and the acid value was calculated according to the following formula: Acid value (mgKOH / g) = {(LB-LC) × 0.02 × 56.11 × p} / WA

[0092] Synthesis Examples 1 to 11: Synthesis of Acrylic Polymers (a-1 to a-11) A polymerization reactor equipped with a stirrer, condenser, and thermometer was charged with 145 parts by mass of deionized water, 0.10 parts by mass of sodium sulfate (NaSO), and 1 part by mass of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) as a dispersant, and the resulting mixture was stirred to prepare a homogeneous aqueous solution. The (meth)acrylic monomer a, chain transfer agent, and radical polymerization initiator shown in Table 1 were added to the resulting aqueous solution to prepare a dispersion. The atmosphere inside the polymerization reactor was thoroughly purged with nitrogen, and the resulting dispersion was heated to 80°C with continued stirring and maintained there for 2 hours. It was then further heated to 90°C and maintained there for 1 hour, yielding a suspension containing a granular polymer. The resulting suspension was filtered through a filter cloth, and the filtrate was washed with deionized water, dehydrated, and dried at 40°C for 16 hours to obtain particulate acrylic polymers (a-1 to a-11). The weight-average molecular weight, acid value, hydroxyl value, and glass transition temperature (Tg) of the acrylic polymers (a-1 to a-11) are shown in Table 1. The hydroxyl value was calculated from the composition of the raw materials.

[0093] Synthesis Examples 12 to 16: Synthesis of Acrylic Polymers (b-1 to b-5) A polymerization apparatus equipped with a stirrer, condenser, and thermometer was charged with 145 parts by mass of deionized water, 0.10 parts by mass of sodium sulfate (NaSO), and 1 part by mass of polyvinyl alcohol (saponification degree 80%, polymerization degree 1,700) as a dispersant, and the resulting mixture was stirred to prepare a uniform aqueous solution. The (meth)acrylic monomer a, chain transfer agent, and radical polymerization initiator shown in Table 1 were added to the resulting aqueous solution to prepare a dispersion. The atmosphere inside the polymerization apparatus was thoroughly purged with nitrogen, and the resulting dispersion was heated to 80°C with continued stirring and maintained there for 2 hours, then further heated to 90°C and maintained there for 1 hour, yielding a suspension containing a granular polymer. The resulting suspension was filtered through a filter cloth, and the filtrate was washed with deionized water, dehydrated, and dried at 40°C for 16 hours to obtain particulate acrylic polymers (b-1 to b-5). Table 2 shows the weight average molecular weight, acid value, glass transition temperature (Tg), and solubility parameter (Sp value) of the acrylic polymers (b-1 to b-5).

[0094] The numerical values for each component in Tables 1 and 2 represent parts by mass.

[0095] [Table 1]

[0096] [Table 2]

[0097] The abbreviations listed in Tables 1 and 2 are as follows: MMA: Methyl methacrylate (Mitsubishi Chemical Corporation, Acryester M) nBMA: n-butyl methacrylate (manufactured by Mitsubishi Chemical Corporation, Acryester B) iBMA: i-butyl methacrylate (Mitsubishi Chemical Corporation, Acryester IB) MA: Methyl acrylate (Mitsubishi Chemical Corporation) EA: Ethyl acrylate (Mitsubishi Chemical Corporation) nBA: n-butyl acrylate (Mitsubishi Chemical Corporation) St: Styrene (Mitsubishi Chemical Corporation) MAA: methacrylic acid (manufactured by Mitsubishi Chemical Corporation, methacrylic acid) HEMA: 2-hydroxyethyl methacrylate (Mitsubishi Chemical Corporation, Acryester HO) AMBN: 2,2'-azobis-2-methylbutyronitrile (Otsuka Chemical Co., Ltd.) nDM: n-dodecyl mercaptan (Chevron Phillips Chemical Company)

[0098] (Production Example 1: Production of Ink (B'-1)) A polymer solution was prepared by dissolving 17 g of acrylic polymer (b-1) in 41.4 g of ethyl acetate. 24 g of titanium oxide (manufactured by Ishihara Sangyo Kaisha, Ltd., product name: CR-90) and 30 g of glass beads were added to the polymer solution in this order, and the mixture was mixed and stirred to prepare a premix. This premix was kneaded and dispersed in a sand mill for 1 hour to obtain a pigment paste. 17.6 g of isopropyl alcohol was added to the pigment paste, which was then thoroughly stirred and filtered through a 100-mesh filter cloth to produce ink (B'-1).

[0099] (Production Example 2: Production of Ink (B'-2)) Ink (B'-2) was produced in the same manner as in Production Example 1, except that the acrylic polymer was changed to acrylic polymer (b-2).

[0100] (Production Example 3: Production of Ink (B'-3)) Ink (B'-3) was produced in the same manner as in Production Example 1, except that the acrylic polymer was changed to acrylic polymer (b-3).

[0101] (Production Example 4: Production of Ink (B'-4)) Ink (B'-4) was produced in the same manner as in Production Example 1, except that the acrylic polymer was changed to acrylic polymer (b-4).

[0102] (Production Example 5: Production of Ink (B'-5)) Ink (B'-5) was produced in the same manner as in Production Example 1, except that the acrylic polymer was changed to acrylic polymer (b-5).

[0103] (Examples 1 to 12, Comparative Examples 1 to 3) The print layer adhesion and print layer detachability were evaluated according to the following methods. The results are shown in Table 3.

[0104] (Method for evaluating print layer adhesion) A 10% polymer solution prepared by dissolving the acrylic polymer shown in Table 3 in methyl ethyl ketone / isopropyl alcohol = 2 / 1 (mass ratio) was applied to a substrate (PET film, Futamura Chemical Co., Ltd., FE2001, 100 μm thick, corona-treated surface) using a bar coater to a thickness of 2 μm after drying to form a primer layer. Subsequently, the ink shown in Table 3 was applied to the primer layer using a bar coater to a film thickness of 6 μm after drying to form a printed layer, thereby obtaining a laminate. Using the resulting laminate, a peel test of the printed layer from the substrate using Cellophane Tape (registered trademark) was conducted. The state of the film surface after the peel test was visually observed, and the print layer adhesion was evaluated using the following evaluation criteria. (Evaluation criteria) A: Printing layer remaining area 90% or more B: Remaining area of printed layer is 70% or more but less than 90% C: Remaining printed area is 50% or more but less than 70% D: Remaining area of printed layer is 10% or more but less than 50% E: Less than 10% of the printed layer remains

[0105] (Method for evaluating print layer detachability) A 10% polymer solution prepared by dissolving the acrylic polymer shown in Table 3 in a 2 / 1 (mass ratio) mixture of methyl ethyl ketone and isopropyl alcohol was applied to a substrate (PET film, Futamura Chemical Co., Ltd., FE2001, 100 μm thick, corona-treated surface) using a bar coater to a thickness of 2 μm after drying to form a primer layer. Subsequently, the ink shown in Table 3 was applied to the primer layer using a bar coater to a thickness of 6 μm after drying to form a printed layer, thereby obtaining a laminate. The resulting laminate was cut into a 2 cm x 2 cm piece and placed in a 50 mL beaker containing 10 g of 2% aqueous sodium hydroxide solution at 25°C. The mixture was then stirred at 100 rpm using a stirrer, and the time until the printed layer completely detached from the substrate was measured. The detachability of the printed layer was evaluated using the following criteria. (Evaluation criteria) A: The printed layer was completely removed within 30 minutes. B: The printed layer completely detaches within 30 to 60 minutes. C: The printed layer has not completely detached even after 60 minutes, but the detached area of the printed layer is 50% or more. D: The printed layer has not completely detached even after 60 minutes, but the detached area of the printed layer is 10% or more but less than 50% E: The printed layer is not completely detached even after 60 minutes, and the detached area of the printed layer is less than 10%.

[0106] [Table 3]

[0107] As shown in Table 3, in Examples 1 to 12, the primer layer contained a vinyl copolymer (a) having an acid value of 100 mgKOH / g or more and 300 mgKOH / g or less and a glass transition temperature of 25°C or more and 120°C or less, and the printing layer (B) contained a vinyl copolymer (a) having a solubility parameter of 19.7 [J / cm 3 ] 1 / 2 Since the acrylic copolymer (b) described above was contained, the printed layer had excellent adhesiveness, and the printed layer could be easily removed by treatment with an aqueous solution.

[0108] On the other hand, in Comparative Example 1, in which the glass transition temperature of the acrylic polymer contained in the primer layer was as low as 8°C, the adhesion and detachability of the printed layer were poor. Furthermore, in Comparative Example 2, in which the acid value of the acrylic polymer contained in the primer layer was as low as 97.7, the detachability of the printed layer was poor when treated with an aqueous solution. Furthermore, the solubility parameter of the acrylic copolymer (b) contained in the printed layer (B) was 19.1 [J / cm 3 ] 1 / 2 In Comparative Example 3, which had a low adhesion of 1000 kJ / cm, the adhesiveness of the printed layer was poor. [Industrial Applicability]

[0109] The laminate of the present invention has excellent adhesion of the printed layer, and the printed layer can be easily removed from the substrate by treating it with an aqueous solution to dissolve or swell the primer layer, making it easy to recycle the substrate. Therefore, it can be suitably used in fields such as packaging materials and packaging containers, and is therefore extremely important industrially.

Claims

1. A substrate, a primer layer (A) containing a vinyl copolymer (a) having an acid value of 100 mgKOH / g or more and 300 mgKOH / g or less and a glass transition temperature (Tg) of 25°C or more and 120°C or less, and a solubility parameter of 19.7 [J / cm ３ ] １／２ and a printed layer (B) containing the acrylic copolymer (b) described above.

2. The printed layer (B) has a solubility parameter of 20.1 [J / cm ３ ] １／２ The laminate according to claim 1, comprising the acrylic copolymer (b) above.

3. The laminate according to claim 1 or 2, wherein the primer layer (A) and the printed layer (B) are laminated in this order on a substrate.

4. The laminate according to any one of claims 1 to 3, wherein the vinyl copolymer (a) has an acid value of 151 mgKOH / g or more and 250 mgKOH / g or less.

5. The laminate according to any one of claims 1 to 4, wherein the vinyl copolymer (a) has a glass transition temperature (Tg) of 40°C or higher and 90°C or lower.

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