Manufacturing method of laminate

Abstract

To provide a method for producing a laminate which has excellent production efficiency without requiring aging, can meet the requirements for a wide variety of products, small lots and short delivery times and has excellent performance stability with a uniform amount of adhesive applied even when applied over a long period of time.SOLUTION: There is provided a method for producing a laminate which comprises: a step 1 of forming an adhesive layer by applying a hot-melt adhesive containing an aqueous emulsion on a printed layer and / or on a base material 2 of a printed matter having a base material 1 and a printed layer by an on-demand application method; and a step 2 of bonding the printed layer and the base material 2 of the printed matter through the adhesive layer obtained in the step 1.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a laminate suitable for use as a packaging material for foods, medicines, cosmetics, detergents, miscellaneous goods, etc., and more particularly to a method for producing a laminate simply and easily without residence time and without aging. [Background technology]

[0002] Composite laminates formed by laminating various plastic films in multiple layers are widely used as packaging materials for foods, clothing, cosmetics, miscellaneous goods, etc. Such laminates are generally produced by forming a printed layer on a plastic film to produce a printed film, and then laminating the resulting printed film with another plastic film using an adhesive. The printing layer is generally formed by gravure printing, flexographic printing, or on-demand printing such as inkjet printing. The adhesive used for lamination is primarily a two-component reactive adhesive that reacts a polyol component with a polyisocyanate component to form a urethane adhesive layer. However, because the two-component reactive adhesive requires the polyol component and polyisocyanate component to be mixed in advance, the urethane reaction begins immediately after mixing, causing the viscosity to increase. As a result, the viscosity exceeds the range of viscosity that can be applied over time, resulting in a problem of limited usable time (pot life). Furthermore, adhesives that have exceeded their usable time and become unusable must be discarded, and improvements were desired from the perspective of environmental impact. Furthermore, laminates obtained using the above-mentioned two-component reactive adhesive require an aging period to harden the adhesive, resulting in poor production efficiency. Therefore, there has been a demand for a method for producing laminates that does not require aging (hereinafter also referred to as aging-less).

[0003] To address these problems, Patent Document 1 discloses a method of obtaining a laminate by separately inkjet printing a polyol component and a polyisocyanate component that constitute a solvent-free adhesive onto a printed layer formed by inkjet printing, and then laminating the resulting material.

[0004] Patent Document 2 discloses a method for producing a packaging material without requiring curing, in which a heat-activatable laminating material containing a heat-activatable polymer selected from a copolymer of an alkylene monomer and an acrylic acid or methacrylic acid monomer, a copolymer of an alkylene monomer and an alkyl acrylate or alkyl methacrylate, a polyurethane, an ionomer, a copolymer of an alkylene monomer, a maleic anhydride-modified polyalkylene, and an acid-modified polyolefin is used to bond the printed surface of a flexible substrate having a printed layer to another flexible substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-098285 [Patent Document 2] Special Publication No. 2018-530454 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the laminate described in Patent Document 1 requires an aging step to harden the adhesive, and does not solve the problem of eliminating the aging step, which aims to further improve production efficiency. Furthermore, the method described in Patent Document 2 forms an adhesive layer by gravure coating, and as water evaporates from the gravure cylinder, the dried adhesive does not redisperse, easily clogging the cylinder, making it difficult to maintain a constant coating amount. For example, if adhesive is applied continuously by gravure coating for about six hours, the amount of adhesive applied decreases due to cylinder clogging, resulting in a problem where the amount applied at the end is less than at the start of application. As a result, the adhesive cannot be applied in the desired amount, resulting in poor appearance and poor laminate strength. Therefore, an object of the present invention is to provide a method for producing a laminate that does not require aging, has excellent production efficiency, can meet demands for high-mix, small-lot production, and short delivery times, and has excellent performance stability with a uniform amount of adhesive applied even when applied over a long period of time. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following embodiments, and have thus completed the present invention.

[0008] An embodiment of the present invention relates to a method for producing a laminate having at least a substrate 1, a printed layer, an adhesive layer, and a substrate 2 in this order, the method including: step 1 of forming an adhesive layer by applying a heat-fusible adhesive containing an aqueous emulsion onto the printed layer and / or onto the substrate 2 of a printed matter having the substrate 1 and the printed layer using an on-demand application method; and step 2 of bonding the printed layer of the printed matter to the substrate 2 via the adhesive layer obtained in step 1.

[0009] Another embodiment of the present invention relates to a method for producing the laminate, wherein the printed layer is a layer formed using a liquid electrophotographic method or an inkjet method.

[0010] Another embodiment of the present invention relates to the method for producing the laminate, wherein the ink-jet ink used in the ink-jet method is a water-based ink or a UV ink.

[0011] Another embodiment of the present invention relates to the method for producing the laminate, wherein the on-demand coating method is at least one method selected from the group consisting of an inkjet method, a dispenser method, and a spray method. [Effects of the Invention]

[0012] The present invention makes it possible to provide a method for producing a laminate that does not require aging, has excellent production efficiency, can meet the demands of high-mix, small-lot production, and short delivery times, and has excellent performance stability with a uniform amount of adhesive applied even when applied over a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention is a method for producing a laminate having at least a substrate 1, a printed layer, an adhesive layer, and a substrate 2 in this order, characterized by comprising: step 1 of forming an adhesive layer by applying a heat-sealing adhesive containing an aqueous emulsion onto the printed layer and / or onto substrate 2 of a printed matter having substrate 1 and a printed layer using an on-demand application method; and step 2 of bonding the printed layer of the printed matter to substrate 2 via the adhesive layer obtained in step 1. By using a heat-sealing adhesive containing a water-based emulsion and forming an adhesive layer using an on-demand coating method that does not require a plate, it is possible to obtain a laminate that does not require residence time for aging, has excellent production efficiency, and can meet the demands of a wide variety of products, small lots, and short delivery times.It is also possible to obtain a laminate with a uniform coating amount and little fluctuation in performance, even when coating is carried out continuously for long periods of time. The present invention will be described in detail below.

[0014] <Process 1> Step 1 is a step of forming an adhesive layer by applying a heat-sealable adhesive containing an aqueous emulsion onto the printing layer of a printed matter having a substrate 1 and a printing layer, and / or onto substrate 2 using an on-demand application method. The on-demand application method refers to supplying an adhesive on demand and applying it to a substrate, and refers to a method that allows for application of "what is needed, when it is needed, and in the amount needed." Examples of such methods include an application method that uses a digital printing machine that directly outputs digital data without requiring a process such as plate making, and at least one method selected from the group consisting of an inkjet (IJ) method, a dispenser method, and a spray method is preferably used. The coating method may be one method alone or two or more methods may be combined.

[0015] In step 1, the heat-sealing adhesive is applied onto the printing layer of a printed matter having a substrate 1 and a printing layer, and / or onto substrate 2. That is, the heat-sealing adhesive may be applied only onto the printing layer, only onto substrate 2, or both onto the printing layer and substrate 2.

[0016] When a heat-fusible adhesive is applied to a printed layer (described later), the heat-fusible adhesive may be applied continuously after the printed layer is formed without being wound up into a roll, or may be applied after the printed material is wound up into a roll. When the printed material is wound up into a roll, the problem of blocking of the printed layer occurs, but when the printed material is formed after the printing layer is formed without being wound up into a roll, the problem of blocking can also be solved, which is preferable.

[0017] In the present invention, the thickness of the adhesive layer to be formed can be appropriately selected depending on the required performance, and is preferably in the range of 1 to 10 μm. The adhesive layer may be patterned or may be formed solidly (over the entire surface).

[0018] [Heat-fusible adhesive] The heat-fusible adhesive used in the present invention may contain an aqueous emulsion and have heat-fusible properties. Examples of such aqueous emulsions include aqueous emulsions of vinyl acetate resin, ethylene-vinyl acetate resin, vinyl chloride resin, acrylic resin, polyamide resin, cellulose resin, or olefin resin. From the viewpoint of excellent emulsion stability, the resin forming the emulsion is preferably a vinyl acetate resin, an ethylene-vinyl acetate resin, a vinyl chloride resin, an acrylic resin, or an olefin resin.

[0019] When the substrate 1 and substrate 2 described below are made of a poorly adhesive non-polar polyolefin resin substrate such as crystalline polyethylene or polypropylene, the resin that forms the aqueous emulsion is preferably an olefin resin from the viewpoint of improving adhesiveness. Furthermore, the use of polyolefin substrates as substrates 1 and 2 also makes it possible to improve material recyclability by forming the laminate into a mono-material packaging material, so it is preferable to use an olefin resin.

[0020] The shape of the aqueous emulsion particles in the heat-fusible adhesive is not particularly limited as long as they can bond substrate 1 and substrate 2 as an adhesive component, and they may be flat, amorphous, etc., but are usually spherical or granular. The particle size of the aqueous emulsion is preferably in the range of 0.01 to 1 μm from the viewpoint of suitable use in an inkjet system, a dispenser system, or a spray system. Within this range, stable discharge is possible, and the coating amount can be kept stable even during long-term continuous coating. In this specification, the particle size of an aqueous emulsion means the size of the oil phase dispersed in water, and means the number average particle size measured in accordance with JIS Z 8828:2019.

[0021] From the viewpoint of fully exhibiting the heat resistance and adhesiveness of the adhesive layer, the minimum film formation temperature (MFT) of the aqueous emulsion is preferably in the range of −10 to 25° C., more preferably −5 to 20° C. By setting it within this range, the adhesive strength to the substrate and adhesive layer will be good, and heat resistance such as heat seal strength when used as a packaging material and adhesive strength after boiling sterilization treatment will also be good.

[0022] The glass transition temperature (Tg) of the aqueous emulsion is preferably in the range of −50 to 100° C., more preferably −20 to 50° C. By setting the temperature within this range, stress is alleviated when an external load such as deformation is applied to the laminate, and peeling of the adhesive layer can be prevented.

[0023] The heat-fusible adhesive may further contain additives such as antioxidants, ultraviolet absorbers, antifungal agents, plasticizers, and lubricants, as needed, and may also contain crosslinking agents such as carbodiimide compounds and oxazoline compounds to improve heat resistance. In particular, when the laminate is used for applications requiring boiling resistance, retort resistance, and water resistance, it is preferable to contain a crosslinking agent such as the above-mentioned carbodiimide compound or oxazoline compound. Alternatively, the aqueous emulsion itself may be a carbodiimide compound or oxazoline compound. Unlike isocyanate compounds, carbodiimide compounds and oxazoline compounds do not react with moisture in the air to increase viscosity, and are therefore suitable for use in long-term application of heat-fusible adhesives. In addition, as a coating method for these, it is preferable to separate a heat-fusible adhesive containing a carbodiimide compound or an oxazoline compound and a heat-fusible adhesive not containing the compound, and coat each of them on a substrate. When coating two types of heat-fusible adhesives, the two adhesives may be coated on one substrate, or each adhesive may be coated on both substrates. By separating them into two liquids, the viscosity of the heat-fusible adhesive does not change, and stable coating of the adhesive becomes possible.

[0024] In step 1, the above-mentioned heat-fusible adhesive is applied onto the printed layer of a printed matter having a substrate 1 and a printed layer, and / or onto the substrate 2.

[0025] [Base material 1] The substrate 1 used in the present invention is not particularly limited, and a film-like or sheet-like plastic substrate that is generally used for packaging materials can be used. These may also be laminated. Examples of plastic substrates include films of thermoplastic resins and thermosetting resins, preferably thermoplastic resin films, such as polyolefin resins, polyester resins, polyamide resins, polystyrene resins, vinyl chloride resins, vinyl acetate resins, AS resins, ABS resins, acrylic resins, acetal resins, polycarbonate resins, cellulose resins, and cellulose-based plastics.

[0026] More specifically, polyolefin resin films such as polyethylene (PE) and biaxially oriented polypropylene (OPP); polyester resin films such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polylactic acid (PLA); polystyrene resin films; polyamide resin films such as nylon 6 and poly-p-xylylene adipamide (MXD6 nylon); polycarbonate resin films; polyacrylonitrile resin films; polyimide resin films; cellophane films; multilayers or mixtures thereof (e.g., nylon 6 / MXD6 / nylon 6, nylon 6 / ethylene-vinyl alcohol copolymer / nylon 6); etc. Among these, those having mechanical strength and dimensional stability are preferred. The plastic substrate may contain additives such as antistatic agents and ultraviolet protection agents as required, and may be provided with a vapor-deposited layer of silica, alumina, or the like.

[0027] When the substrate 1 is a laminate of multiple substrates, the substrates are preferably laminated together via an adhesive layer, and may have a metal foil layer such as aluminum foil. The method for forming the adhesive layer is not limited, and it can be formed by a known method using a known adhesive.

[0028] The thickness of the substrate 1 is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less, and even more preferably 10 μm or more and 50 μm or less. The surface of the substrate 1 may be subjected to a corona treatment or a low-temperature plasma treatment. The substrate 1 may also have a coating layer such as an anchor coating or a primer coating to improve adhesion to a printing layer, which will be described later.

[0029] [Print layer] The printed layer is a layer on which any desired printed pattern such as letters, numbers, pictures, figures, symbols, designs, etc. is formed for decoration, indication of contents, indication of expiration date, indication of manufacturer, seller, etc., or for imparting aesthetic appeal, and includes solid printed layers. The printed layer can be formed using conventionally known pigments or dyes, for example, it can be formed using printing ink containing a colorant such as a pigment or dye. The method for forming the printed layer is not limited, and examples thereof include gravure printing, flexographic printing, screen printing, offset printing, offset gravure, liquid electrophotography (LEP), and inkjet printing. If necessary, air blowing, heating, drying under reduced pressure, ultraviolet irradiation, etc. may be performed. The printing ink used to form the printed layer is not particularly limited, and for example, solvent-based ink, water-based ink, UV-curable ink, two-component curable ink, and toner ink can be used.

[0030] From the viewpoint of saving materials and shortening delivery lead times, the printing layer is preferably a layer formed on the substrate 1 by on-demand printing, and specific methods include, for example, a liquid electrophotographic method or an inkjet method. In either method, a digitally printed layer is patterned on the substrate 1 without a plate.

[0031] That is, step 1 may include a step of forming a print layer using a liquid electrophotographic method or an inkjet method. After applying the wet toner or inkjet ink to the substrate 1, a step (drying / curing step) may be carried out to dry or cure the inkjet ink on the substrate 1. When a water-based ink is used as the inkjet ink, it is preferable that the printed layer contains volatile components (water and a water-soluble organic solvent) from the viewpoint of increasing affinity with the heat-fusible adhesive described below and obtaining a laminate with excellent adhesive strength without aging.

[0032] (Liquid electrophotography (LEP) method) Electrophotographic printing is applied in a variety of fields, including copiers, point-of-sale printers, facsimiles, and small-run printers. Toners used in electrophotographic printing are broadly divided into dry toner and liquid toner, with liquid toner being used in what is called liquid electrophotography. Compared to dry toner, liquid toner has less toner particle scattering and can be made finer, making it suitable for high-precision printing. Hewlett-Packard's Indigo is a well-known LEP-based digital printing device.

[0033] When forming a printing layer using the LEP method, usable liquid toners include those exemplified in WO 2016 / 074716. The liquid toner may contain, for example, a colorant such as a pigment or dye, an ionic compound for charging the toner, a resin composition such as an acrylic resin, a solvent, and other additives.

[0034] (Inkjet (IJ) method) The inkjet method is a method of ejecting inkjet ink directly onto a substrate to create a pattern. An example of an inkjet printing device is the Fujifilm Inkjet Digital Press. Examples of inkjet inks include water-based inks, solvent-based inks, and UV inks, and can be selected appropriately depending on the application. Among these, water-based inks are preferred because they offer high material selection, reduce environmental impact, and can enhance the effectiveness of water-based emulsions used as thermal adhesives. UV inks are also preferred because they offer extremely high production efficiency and enable printing in a small space.

[0035] If necessary, a step (fixing step) may be carried out in which a printed layer made of a liquid toner or IJ ink is fixed onto the substrate 1. Specific examples include a heating and pressurizing method using a roller, drum, conveyor, film, or the like; a pressurizing method using a pressure roller, or the like; and a heating method using hot air, infrared rays, microwaves, or the like. The above-mentioned drying and curing steps may be carried out in combination with the fixing step for the printed layer. When using a water-based ink as the IJ ink and carrying out both the drying and curing steps and the fixing step, it is preferable to carry out the fixing step after the drying and curing step, since this allows for the production of a laminate that has excellent adhesive strength and image quality without aging.

[0036] The thickness of the printed layer is not particularly limited, but is generally adjusted to within the range of 0.1 to 10 μm, more preferably 0.5 to 5 μm, and even more preferably 1 to 3 μm. The thickness of the printed layer can be changed appropriately depending on the design.

[0037] The laminate used in the present invention may have a primer layer disposed between the substrate 1 and the printed layer to improve adhesion between the substrate 1 and the printed layer. The primer layer may be patterned or may be formed solid (overall). The thickness of the primer layer may be within a range that does not affect the visibility of the printed layer from the substrate 1 side, and is preferably approximately 0.02 to 2 μm. The primer layer may be formed using, for example, a urethane-based primer composed of an acrylic polyol and a polyisocyanate, a polyethyleneimine-based primer, or a polyamide-based primer.

[0038] [Base material 2] Examples of the substrate 2 used in the present invention include the substrates listed above as the substrate 1 as well as sealant substrates, and may be a laminate obtained by laminating these substrates. Examples of sealant substrates include polyethylenes such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), acid-modified polyethylene, non-oriented polypropylene (CPP), acid-modified polypropylene, copolymerized polypropylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid ester copolymer, ethylene-(meth)acrylic acid copolymer, and ionomer. The substrate 2 is preferably a sealant substrate containing polyolefin. The substrate 2 may contain additives such as antistatic agents and ultraviolet protection agents as needed, and may be provided with a vapor-deposited layer of aluminum, silica, alumina, or the like.

[0039] The thickness of the substrate 2 is not particularly limited, and is preferably 10 μm to 150 μm, more preferably 20 μm to 70 μm, taking into consideration processability into packaging containers, heat sealing properties, etc. The substrate 2 may be provided with unevenness with a height difference of about several μm to impart slipperiness and tearability to the packaging material. The surface of the substrate 2 may be subjected to corona treatment or low-temperature plasma treatment. Furthermore, a sealant layer may be provided on the outermost layer of the substrate 2, and the sealant layer may be either a heat sealant layer or a cold sealant layer.

[0040] <Process 2> Step 2 is a step of bonding the printed layer of the printed matter to the substrate 2 via the adhesive layer obtained in step 1. The method for bonding the printed layer of the printed material and the substrate 2 is not particularly limited and can be appropriately selected from known methods. A preferred example of such a method is a method using a hot nip roll. An adhesive layer made of a heat-fusible adhesive is melted by the hot nip roll, bonded together, and then allowed to cool and solidify, bonding the laminate film made of at least the substrate 1 / printed layer to the substrate 2 via the adhesive layer.

[0041] Thus, the present invention forms an adhesive layer formed from a heat-sealable adhesive containing an aqueous emulsion and formed by an on-demand coating method, so that the amount of the heat-sealable adhesive used is minimized, and there is no need for a residence time due to aging, resulting in excellent production efficiency. In addition, it can meet the requirements of multi-variety, small-lot, and short-delivery-time. Furthermore, by applying a heat-sealable adhesive containing an aqueous emulsion using an on-demand coating method, a laminate with a uniform thickness of the adhesive layer and excellent performance stability can be manufactured even in a long-time coating process, which is useful in the field of packaging materials.

Example

[0042] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the Examples and Comparative Examples, "parts" and "%" mean "parts by mass" and "mass%" unless otherwise specified.

[0043] <Preparation of IJ Ink> (Aqueous Ink Set P1) 〔Preparation of Pigment Dispersions 1C, 1M, 1Y, 1K) 20 parts of C.I. Pigment Blue 15:3, 20 parts of a varnish (solid content 25%) of a coloring agent dispersion resin (a water-soluble resin containing styrene, acrylic acid, and stearyl methacrylate as constituent units in a mass ratio of 25:40:35, having a weight average molecular weight of 25,000 and an acid value of 185 mgKOH / g), and 60 parts of water were charged into a mixing container and then thoroughly mixed with a stirrer. Then, this dispersion was carried out using a dyno mill (bead mill manufactured by Shinmaru Enterprises Co., Ltd.) with a volume of 0.6 L filled with zirconia beads having a diameter of 0.5 mm to obtain a cyan pigment dispersion (referred to as pigment dispersion 1C). In addition, except that the pigments were changed to C.I. Pigment Red 122, C.I. Pigment Yellow 14, and carbon black, respectively, magenta, yellow, and black pigment dispersions (referred to as pigment dispersions 1M, pigment dispersions 1Y, and pigment dispersions 1K, respectively) were obtained in the same manner as pigment dispersion 1C.

[0044] 〔Preparation of Binder Resin 1〕 A reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer was charged with 72.4 parts of 2-butanone and purged with nitrogen gas. After heating the reaction vessel to 80°C, a mixture of 4.5 parts of methacrylic acid, 5.0 parts of 2-hydroxyethyl methacrylate (an ethylenically unsaturated monomer having a hydroxyl group), 90.5 parts of methyl methacrylate, and 12 parts of V-601 (a polymerization initiator manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 2 hours to carry out the polymerization reaction. After the addition was completed, the reaction was continued for another 3 hours at 80°C, after which 0.6 parts of V-601 was added, and the reaction was continued for another 2 hours at 80°C to obtain a hydrosol solution of binder resin 1. The weight-average molecular weight of the binder resin 1 was measured using a GPC (Tosoh Corporation, HLC-8120GPC) equipped with a TSKgel column (Tosoh Corporation) and an RI detector, using THF as the developing solvent, and was found to be approximately 7,000. After cooling the binder resin 1 solution to 50°C, 4.7 parts of dimethylaminoethanol was added for neutralization, followed by the addition of 140 parts of water. The reaction vessel was then heated to 78°C or higher, and 2-butanone was distilled off by azeotropy with water. The solid content was then adjusted to 30% with water, yielding a varnish of binder resin 1 (solid content 30%). The acid value and hydroxyl value of binder resin 1 calculated from the resin's constituent units were 29.3 mg KOH / g and 21.6 mg KOH / g, respectively. The glass transition temperature (Tg) measured using a DSC (PerkinElmer, DSC6000) was 103°C.

[0045] [Preparation of Water-Based Ink Set P1] 20 parts of the pigment dispersion 1C, 21 parts of the binder resin 1 varnish (30% solids), 25 parts of 1,2-propanediol, 1 part of Surfynol 465 (an acetylene-based surfactant manufactured by Shin-Etsu Chemical Co., Ltd.), 0.1 parts of Proxel GXL (a preservative manufactured by LONZA), and 32.9 parts of water were sequentially added to a mixing vessel. The contents of the mixing vessel were then heated to 50°C and mixed with a stirrer for 1 hour. The mixture was then filtered using a depth filter with a pore size of 1 μm to remove coarse particles, yielding a cyan water-based ink (referred to as ink 1C). In addition, magenta, yellow, and black water-based inks (referred to as Ink 1M, Ink 1Y, and Ink 1K, respectively) were obtained in the same manner as Ink 1C described above, except that Pigment Dispersion 1M, Pigment Dispersion 1Y, and Pigment Dispersion 1K were used as the pigment dispersions. The four color inks, Ink 1C, Ink 1M, Ink 1Y, and Ink 1K, prepared in this manner were used as water-based ink set P1.

[0046] (UV ink set P3) [Preparation of pigment dispersions 3C, 3M, 3Y, 3K] 20 parts of CI Pigment Blue 15:4, 4 parts of Solsperse 32000 (a colorant dispersion resin manufactured by Lubrizol Corporation), 75.5 parts of phenoxyethyl acrylate, and 0.1 parts of dibutylhydroxytoluene (a polymerization inhibitor) were added to a mixing vessel and thoroughly mixed with a stirrer. A 0.6 L Dynomill (a bead mill manufactured by Shinmaru Enterprises) filled with 0.5 mm diameter zirconia beads was then used for main dispersion, yielding a cyan pigment dispersion (referred to as Pigment Dispersion 3C). In addition, magenta, yellow, and black pigment dispersions (referred to as Pigment Dispersion 3M, Pigment Dispersion 3Y, and Pigment Dispersion 3K, respectively) were obtained in the same manner as Pigment Dispersion 3C, except that the pigments were changed to CI Pigment Red 122, CI Pigment Yellow 14, and carbon black, respectively.

[0047] [Preparation of UV ink set P3] 10 parts of the pigment dispersion 3C, 40 parts of 2-(2-vinyloxyethoxy)ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), 31.9 parts of phenoxyethyl acrylate, 1 part of dipropylene glycol diacrylate, 6 parts of OMNIRAD 819 (a polymerization initiator manufactured by IGM Resins), 6 parts of OMNIRAD TPO H (a polymerization initiator manufactured by IGM Resins), 4.9 parts of KAYACURE DETX-S (a sensitizer manufactured by Nippon Kayaku Co., Ltd.), 0.1 parts of BYK-UV3500 (a siloxane-based surfactant manufactured by BYK), and 0.1 parts of dibutylhydroxytoluene were sequentially added to a mixing vessel. Next, the mixing vessel was heated to 50°C and mixed with a stirrer until the polymerization initiator was dissolved. The mixture was then filtered using a depth type filter with a pore size of 1 μm to remove coarse particles, thereby obtaining a cyan UV ink (referred to as ink 3C). In addition, magenta, yellow, and black UV inks (referred to as Ink 3M, Ink 3Y, and Ink 3K, respectively) were obtained in the same manner as Ink 3C described above, except that Pigment Dispersion 3M, Pigment Dispersion 3Y, and Pigment Dispersion 3K were used as the pigment dispersions. The four color inks, Ink 3C, Ink 3M, Ink 3Y, and Ink 3K, prepared in this manner were designated as UV ink set P3.

[0048] <Preparation of heat-fusible adhesive> (Thermal adhesive J1) 400 parts of an acrylic resin emulsion, Plextol R100 (manufactured by Synthomer, solid content 62%, average particle size 0.4 μm, MFT 0°C, Tg 13°C), was mixed with 185 parts of isopropyl alcohol and 655 parts of water to obtain a heat-fusible adhesive J1 with a solid content of 20%.

[0049] (Thermal adhesive J2) 400 parts of Sumikaflex-401HQ, an EVA emulsion (manufactured by Sumitomo Chemical Co., Ltd., solid content 55%, average particle size 0.8 μm, MFT 0°C, Tg -18°C), were mixed with 154 parts of propylene glycol and 546 parts of water to obtain a heat-fusible adhesive J2 with a solid content of 20%.

[0050] (Thermal adhesive J3) 800 parts of a polyolefin emulsion, Zaixen-AC (manufactured by Sumitomo Seika Chemicals, solid content 30%, average particle size 0.2 μm, MFT 20°C, Tg 85-95°C), was mixed with 57 parts of isopropyl alcohol and 343 parts of water to obtain a heat-fusible adhesive J3 with a solid content of 20%.

[0051] (Heat-fusible adhesive J4) 800 parts of an oxazoline-based emulsion, Epocross K-2020E (manufactured by Nippon Shokubai Co., Ltd., solid content 40%, average particle size 0.5 μm, MFT 14°C, Tg 0°C), were mixed with 100 parts of isopropyl alcohol and 700 parts of water to obtain a heat-fusible adhesive J4 with a solid content of 20%.

[0052] <Preparation of two-component curing adhesive> (Polyol component A1) 98 parts of Sannix PP-200 (manufactured by Sanyo Chemical Industries, Ltd.) and 2 parts of Sannix GP-250 (manufactured by Sanyo Chemical Industries, Ltd.) were mixed to obtain a polyol component A1.

[0053] (Polyisocyanate component B1) Polymeric MDI Millionate MR-100 (manufactured by Tosoh) was used as polyisocyanate component B1.

[0054] <Production of laminate> Example 1 A 12 μm-thick polyethylene terephthalate (PET) film was unwound at a speed of 30 m / min. A Kyocera printhead (KJ4B-1200 model, design resolution 1200 dpi) was used to print an image on the film, consisting of 5 cm x 5 cm solid patches with a 100% coverage, adjacent to each other. The printing conditions were a frequency of 20 kHz, 1200 x 1200 dpi, and a drop volume of 2.5 pL. After printing, the film was passed through a drying box generating hot air at 70°C at the same speed to form a printed layer. After forming the printed layer, the thermal adhesive J1 was applied onto the printed layer without winding using an inkjet coating method, and the solvent was dried in a drying oven. The inkjet head used was KJ4B-0300 (manufactured by Kyocera). The amount of thermal adhesive applied at the start of application was 2.7 g / m. 2 (solid content equivalent). Next, without winding, a linear low density polyethylene (LLDPE) film having a thickness of 100 μm was continuously pressed onto the film using nip rolls at 100° C. to obtain a laminate having a structure of PET / printed layer / adhesive layer / LLDPE. The production of the above laminate was continued for 6 hours, and a laminate immediately after the start of production and a laminate at the end of production (after 6 hours of coating) were obtained.

[0055] (Examples 2 and 3) A laminate immediately after the start of production and a laminate at the end of production were obtained in the same manner as in Example 1, except that the heat-fusible adhesive in Example 1 was changed to the adhesive shown in Table 1.

[0056] Example 4 In Example 1, the ink was changed to UV ink set P3, a Kyocera head (KJ4A-RH model, design resolution 600 dpi) was used as the IJ head, and UV irradiation was performed using an ultraviolet exposure device (GEW 240 W / cm metal halide lamp) instead of a drying box. Except for this, a laminate immediately after the start of production and a laminate at the end of production were obtained in the same manner as in Example 1.

[0057] Example 5 In Example 1, the method for forming the printed layer was changed to gravure printing, and LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) was printed all over a 12 μm thick polyethylene terephthalate film to form a 1 μm thick printed layer. Except for this, a laminate immediately after the start of production and a laminate at the end of production were obtained in the same manner as in Example 1.

[0058] Example 6 In Example 1, the method for forming the printed layer was changed to a flexographic printing method, and a 1 μm-thick printed layer was formed by printing Aquaecol white ink (manufactured by Toyo Ink Co., Ltd.) all over the surface of a 12 μm-thick polyethylene terephthalate film. Except for this, a laminate was obtained immediately after the start of production and a laminate at the end of production in the same manner as in Example 1.

[0059] Example 7 In Example 1, a laminate immediately after the start of production and a laminate at the end of production were obtained in the same manner as in Example 1, except that the 12 μm thick polyethylene terephthalate film was changed to a 12 μm thick MDO PE Film (HDPE, manufactured by Windmiller).

[0060] Example 8 In Example 1, the method of applying the heat-fusible adhesive was changed to a spray coating method using an air spray coater, and in the same manner as in Example 1, laminates were prepared immediately after the start of production and at the end of production.

[0061] Example 9 In Example 5, a heat-sealable adhesive was applied to a 100 μm thick linear low-density polyethylene film, and then the film was continuously bonded to a 12 μm thick polyethylene terephthalate film on which a printed layer had been formed without being wound up. Except for this, a laminate was obtained immediately after the start of production and at the end of production in the same manner as in Example 5.

[0062] Example 10 In Example 5, the adhesive applied to the printed layer was changed to the heat-sealing adhesive J3 (application amount 2.5 g / m 2 On the other hand, the heat-fusible adhesive J4 was applied to a linear low-density polyethylene film having a thickness of 100 μm by inkjet coating, and the solvent was dried in a drying oven to obtain a coating amount of 0.2 g / m 2 A process for forming an adhesive layer of 1000 sq m (converted to solid content) was added, and then the adhesive layers of both films were continuously bonded to each other without being wound up, in the same manner as in Example 5, to obtain a laminate immediately after the start of production and a laminate at the end of production.

[0063] Example 11 In Example 1, after the printing layer was formed, it was once wound up into a roll. A laminate was obtained in the same manner as in Example 1, except that a rolled printed film was used, by applying a heat-fusible adhesive and pressing with a linear low-density polyethylene having a thickness of 100 μm. The process from application of the fusion adhesive to pressure bonding with the linear low-density polyethylene was continued for 6 hours, to obtain a laminate immediately after the start of production and a laminate at the end of production.

[0064] Example 12 In Example 1, the printing layer formation method was changed to a liquid electrophotographic method, and cyan ink was printed all over the surface of a 12 μm thick polyethylene terephthalate film using HP Indigo 8000 to form a 1 μm thick printing layer. Except for this, a laminate immediately after the start of production and a laminate at the end of production were obtained in the same manner as in Example 1.

[0065] (Comparative Example 1) LP Bio white ink (manufactured by Toyo Ink Co., Ltd.) was printed over the entire surface of a 12 μm thick polyethylene terephthalate sheet by gravure printing to form a printed layer with a thickness of 1 μm. After forming the printed layer, without rewinding, polyol component A1 was continuously ejected from a first inkjet head onto the entire surface of the printed layer using an inkjet coating method, followed by polyisocyanate component B1 from a second inkjet head. Both the first and second inkjet heads were KJ4C-0360 (manufactured by Kyocera). The reactive adhesive was applied in such a manner that the ratio of A1 to B1 was 1 / 1 (mass ratio), and the total amount of A1 and B1 at the start of application was 3.5 g / m. 2 (solid content equivalent). Next, without winding, a linear low-density polyethylene having a thickness of 100 μm was continuously pressed with nip rolls at 50° C. to obtain a laminate having a structure of PET / printed layer / adhesive layer / LLDPE. The production of the above laminate was continued for 6 hours, and a laminate immediately after the start of production and a laminate at the end of production were obtained.

[0066] (Comparative Example 2) In Example 12, except that the method of applying the heat-fusible adhesive was changed to gravure application, the same procedures as in Example 12 were carried out to obtain a laminate immediately after the start of production and a laminate at the end of production. The gravure cylinder used for gravure coating is a 110-line grating type, and the amount of heat-fusible adhesive applied is 2.5 g / m at the start of coating. 2 (solid content equivalent).

[0067] <Evaluation of laminate> The obtained laminate (immediately after the start of production and at the end of production (after 6 hours of coating)) was evaluated as follows without aging. The results are shown in Table 1.

[0068] [Adhesive strength] Immediately after the start of production and at the end of production, the laminate was cut into test pieces 15 mm wide and 300 mm long. Based on JIS K6854, an Instron tensile tester was used to measure the T-peel strength [N / 15 mm] between substrate 1 and substrate 2 at a peel rate of 300 mm / min under an environment of 20°C and 65% relative humidity. The measurement was performed five times, and the average value was taken as the adhesive strength. The obtained adhesive strength was evaluated according to the following criteria. A: Adhesion strength is 1.0N / 15mm or more (good) B: Adhesive strength is 0.6N / 15mm or more and less than 1.0N / 15mm (usable) C: Adhesive strength is less than 0.6N / 15mm (unusable)

[0069] [Amount of application] The amount of heat-sealing adhesive applied (g / m) to the laminate immediately after the start of production and at the end of production was measured. 2 ) was calculated from the difference in mass between a 10 cm x 10 cm piece of the laminate before and after wiping off the heat-fusible adhesive layer with a solvent.

[0070] [Boil resistance] Immediately after the start of production, the laminate was pressed for 1 second using a 150°C heat seal bar, and then immersed in 98°C warm water for 60 minutes. The state of delamination (peeling) was visually inspected and evaluated according to the following criteria: A indicates that it can be used for boiling applications; B indicates that it cannot be used for boiling applications, but can be used for non-boiling applications. A: No peeling B: Peeling

[0071] [Table 1]

[0072] The abbreviations in Table 1 are as follows: PET: Futamura Chemical Co., Ltd. biaxially oriented polyester film "FE2001", thickness 12 μm LLDPE: Mitsui Chemicals Tocello linear low-density polyethylene film "TUX-FC-D", thickness 100 μm HDPE: Windmill biaxially oriented high density polyethylene film "MDO PE Film", thickness 12 μm

[0073] According to the results in Table 1, the laminate produced by the production method of the present invention did not show a decrease in the amount of heat-fusible adhesive applied even after continuous application for as long as 6 hours. Therefore, there was no decrease in adhesive strength due to long-term production, and the laminate had excellent stability during production. In Example 10, two liquid components, a heat-sealing adhesive containing an oxazoline-based emulsion and a heat-sealing composition containing a polyolefin-based emulsion, were used, and these were applied separately and then bonded together, thereby improving heat resistance and water resistance, and making it possible to use the product in applications that require subsequent processes such as boiling sterilization. On the other hand, Comparative Example 1 corresponds to Patent Document 1, and sufficient adhesive strength was not obtained without aging. Furthermore, polyisocyanate component B1 hardened due to reaction with moisture in the air in the nozzle of the inkjet head, making it impossible to carry out continuous, stable coating. In Comparative Example 2, which corresponds to Patent Document 2, the emulsion contained in the heat-fusible adhesive dried on the gravure cylinder and did not redisperse, causing clogging. As a result, when the adhesive was applied continuously for 6 hours, the amount of the adhesive applied was reduced and the adhesive strength was poor.

Claims

1. A method for producing a laminate for packaging material having at least a substrate 1, a printing layer, an adhesive layer, and a substrate 2 in this order, comprising: Step 1: forming an adhesive layer by applying a heat-fusible adhesive containing an aqueous emulsion onto the printed layer of a printed material having a substrate 1 and a printed layer and / or onto the substrate 2 by an on-demand application method; and Step 2: bonding the printed layer of the printed matter to a substrate 2 via the adhesive layer obtained in step 1; Including, The substrate 1 is a thermoplastic resin film, The thickness of the adhesive layer is 1 to 10 μm, The substrate 2 is a sealant substrate having heat sealing properties. A method for manufacturing a laminate for packaging.

2. The method for producing a laminate for packaging materials according to claim 1, wherein the printed layer is a layer formed using a liquid electrophotographic method or an inkjet method.

3. The method for producing a laminate for packaging material according to claim 2, wherein the ink-jet ink used in the ink-jet method is a water-based ink or a UV ink.

4. 4. The method for producing a laminate for packaging material according to claim 1, wherein the on-demand coating method is at least one method selected from the group consisting of an inkjet method, a dispenser method, and a spray method.

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