Aqueous overprint varnish composition, and laminate

Abstract

To provide an aqueous overprint varnish composition which can suppress winding blocking, and enables formation of a varnish layer excellent in laminate strength to a resin layer formed by extrusion lamination.SOLUTION: An aqueous overprint varnish composition contains styrene-acrylic resin emulsion having a glass transition temperature of 55°C to 130°C, a wax, and an aqueous medium.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous overprint varnish composition and a laminate.

Background Art

[0002] For paper products used in food and beverage containers, in order to impart durability to the base material due to environmental problems (such as reducing solvent odor and solvent reduction), after printing an aqueous printing ink composition on the paper base material, a method of laminating molten polyethylene with an extrusion laminator to obtain an extrusion laminate has been carried out (see, for example, Patent Document 1).

[0003] When using the conventional method as described above, there are problems such as roll contamination caused by the aqueous printing ink composition during printing and back transfer (winding blocking) during storage of the printed matter until extrusion lamination (lamination of the resin layer) is performed on the printed layer formed by the solvent-based printing ink composition. In response to such problems, a method of coating a solvent-based overprint varnish composition having lamination suitability on the printed layer formed by the aqueous printing ink composition has been used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Furthermore, from the perspective of environmental problems, there has been a demand for an aqueous overprint varnish composition having lamination suitability instead of a solvent-based overprint varnish composition having lamination suitability for the overprint varnish composition.

[0006] Therefore, an object of the present invention is to provide an aqueous overprint varnish composition that has little solvent odor, can suppress winding blocking, and can form a varnish layer excellent in laminate strength with respect to a resin layer formed by extrusion lamination.

Means for Solving the Problems

[0007] The inventors of the present invention have found that all of the above-described problems can be solved by using an aqueous overprint varnish composition containing a styrene-acrylic resin emulsion having a specific glass transition temperature, wax, and an aqueous medium, and have completed the present invention.

[0008] That is, the present invention is an aqueous overprint varnish composition containing a styrene-acrylic resin emulsion having a glass transition temperature of 55°C to 130°C, wax, and an aqueous medium.

[0009] In the aqueous overprint varnish composition of the present invention, the styrene-acrylic resin emulsion preferably has an acid value of 50 mg / KOH or more. Further, the content of the styrene-acrylic resin emulsion is preferably 65% by mass to 85% by mass in terms of solid content based on the total solid content of the aqueous overprint varnish composition. Further, the aqueous overprint varnish composition preferably further contains an alkali-soluble resin. Further, the aqueous overprint varnish composition preferably further contains an aqueous rosin-based resin. Further, the aqueous overprint varnish composition is preferably used for the varnish layer of a laminate including at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order. Further, the present invention is a laminate including at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order, and the varnish layer is also a laminate formed by the aqueous overprint varnish composition of the present invention.

Effects of the Invention

[0010] The present invention can provide an aqueous overprint varnish composition capable of suppressing winding blocking and forming a varnish layer excellent in laminate strength with respect to a resin layer formed by extrusion lamination.

Mode for Carrying Out the Invention

[0011] <Aqueous Overprint Varnish Composition> The aqueous overprint varnish composition of the present invention contains a styrene-acrylic resin emulsion having a glass transition temperature of 55°C to 130°C, wax, and an aqueous medium.

[0012] In the aqueous overprint varnish composition of the present invention, by using a styrene-acrylic resin emulsion having a relatively high glass transition temperature (55°C to 130°C) as a main binder, a hard coating film can be obtained, winding blocking can be suppressed, and a varnish layer excellent in laminate strength with respect to a resin layer formed by extrusion lamination can be formed. However, the present invention may not be construed as being limited to the above mechanism. Hereinafter, each component will be described in detail.

[0013] (Styrene-Acrylic Resin Emulsion) The aqueous overprint varnish composition of the present invention contains a styrene-acrylic resin emulsion.

[0014] The styrene-acrylic resin emulsion is, for example, a resin emulsion obtained by emulsion polymerization of a monomer composition containing a styrene monomer, an acrylic monomer, and, if necessary, other copolymerizable monomers. At least one kind of the styrene-acrylic resin emulsion may be used, or two or more kinds may be used in combination.

[0015] Examples of the styrene monomer include styrene, α-methylstyrene, β-methylstyrene, 2,4-dimethylstyrene, α-ethylstyrene, α-butylstyrene, 4-methoxystyrene, vinyltoluene, and the like.

[0016] Examples of the acrylic monomer include acrylic esters and methacrylic esters such as acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate; acrylic ester derivatives and methacrylic ester derivatives such as 3-ethoxypropyl acrylate, 3-ethoxybutyl acrylate, and hydroxyethyl methacrylate; aryl acrylates and aralkyl acrylates such as phenyl acrylate and benzyl acrylate; and monoacrylic esters of polyhydric alcohols such as diethylene glycol, triethylene glycol, and glycerin. In the present specification, "(meth)acrylate" means acrylate and / or methacrylate.

[0017] Examples of the other monomers include unsaturated aliphatic carboxylic acids having a radically polymerizable unsaturated bond such as maleic acid, itaconic acid, and crotonic acid; dialkyl maleates and monoalkyl maleates such as dimethyl maleate and monomethyl maleate; and esters such as vinyl acetate.

[0018] From the viewpoint of suitably imparting laminate strength to the resin layer formed by extrusion lamination, the ratio of the styrene monomer to all the monomers of the styrene-acrylic resin emulsion is preferably 40% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more.

[0019] The styrene-acrylic resin emulsion may have a core-shell structure. Note that the shell part is formed of a component having a structural unit having a carboxyl group such as (meth) acrylic acid, a component derived from a styrene-based monomer, and a component derived from an acrylic-based monomer, and the core part is preferably formed of a component derived from an acrylic-based monomer and a component derived from a styrene-based monomer.

[0020] The above styrene-acrylic resin emulsion has a glass transition temperature of 55°C to 130°C. By being within the above range of the glass transition temperature, winding blocking can be suppressed. The above glass transition temperature is preferably 60°C or higher, more preferably 70°C or higher, still more preferably 80°C or higher, and particularly preferably 85°C or higher. In this specification, the "glass transition temperature" may be measured using a thermal analysis apparatus such as a differential scanning calorimeter (DSC), but when the following Wood's equation can be applied, it is preferably the theoretical glass transition temperature obtained by the following Wood's equation. Wood's equation: 1 / Tg = W1 / Tg1 + W2 / Tg2 + W3 / Tg3 + ······ + W n / Tg n (In the formula, Tg is the theoretical glass transition temperature of the resin; Tg1 to Tg n are the glass transition temperatures of the respective homopolymers of monomers 1, 2, 3 ··· n constituting the copolymer of the resin; W1 to W n represent the polymerization fractions of the respective monomers 1, 2, 3 ··· n of the resin. However, the glass transition temperature in Wood's equation is in absolute temperature.)

[0021] The above styrene-acrylic resin emulsion preferably has an acid value of 50 mg / KOH or more. By being within the above range of the acid value, laminate strength for a resin layer formed by extrusion lamination can be suitably imparted. In this specification, the "acid value" is the theoretical acid value obtained arithmetically by calculating the number of mg of potassium hydroxide theoretically required to neutralize 1 g of the above resin.

[0022] The content of the above styrene - acrylic resin emulsion is preferably 65% to 85% by mass in terms of solid content based on the total solid content of the aqueous overprint varnish composition. When the content of the above styrene - acrylic resin emulsion is within the above range, the laminating strength with respect to the resin layer formed by extrusion lamination can be preferably imparted.

[0023] The content of the above styrene - acrylic resin emulsion is more preferably 67% by mass or more, still more preferably 70% by mass or more, and particularly preferably 72% by mass or more in terms of solid content based on the total solid content of the aqueous overprint varnish composition. Also, the content of the above styrene - acrylic resin emulsion is more preferably 82% by mass or less, still more preferably 80% by mass or less, and particularly preferably 78% by mass or less in terms of solid content based on the total solid content of the aqueous overprint varnish composition.

[0024] As the method for producing the above styrene - acrylic resin emulsion, for example, known methods such as suspension polymerization and emulsion polymerization may be appropriately selected.

[0025] (Wax) The aqueous overprint varnish composition of the present invention contains wax.

[0026] Examples of the above wax include polyethylene wax, polypropylene wax, Fischer - Tropsch wax, carnauba wax, paraffin wax, microcrystalline wax, and the like. The above wax can be used alone or in combination of two or more.

[0027] From the viewpoint of the abrasion resistance of the coating film (varnish layer), the above wax is preferably polyethylene wax.

[0028] From the perspective of improving the abrasion resistance of the formed coating film, the wax is preferably wax particles.

[0029] From the perspective of suitably improving the abrasion resistance of the formed coating film, the average particle diameter of the wax particles is preferably 1 to 10 μm, and more preferably 2 to 5 μm. The average particle diameter is the average particle diameter measured by the Coulter counter method. As the measuring instrument, a commercially available measuring instrument can be appropriately selected and used.

[0030] Examples of commercially available products of the wax include Chemparl W100, W200, W300, W310, W306, W400, W410, W500, W800, etc. (all manufactured by Mitsui Chemicals, Inc.).

[0031] The content of the wax is preferably 0.5% by mass to 7% by mass in terms of solid content based on the total solid content of the aqueous overprint varnish composition. The content of the wax is more preferably 0.7% by mass or more, and even more preferably 0.8% by mass or more in terms of solid content based on the total solid content of the aqueous overprint varnish composition. Also, the content of the wax is more preferably 5% by mass or less, and even more preferably 3% by mass or less in terms of solid content based on the total solid content of the aqueous overprint varnish composition.

[0032] (Aqueous medium) The aqueous overprint varnish composition of the present invention contains an aqueous medium. In addition, components other than the solid content of the resin emulsion, wax, alkali-soluble resin, and aqueous rosin resin described above are also aqueous media.

[0033] The aqueous medium can contain a water-soluble organic solvent in addition to water within a range that does not affect the performance of the aqueous overprint varnish composition of the present invention.

[0034] As the above water-soluble organic solvent, it is preferably an alcohol and / or a polyhydric alcohol-based solvent. Specifically, methanol, ethanol, propanol, butanol, hexanol, octanol, decanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monooctyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, dibutyl glycol, glycerin, etc. may be mentioned. The above water-soluble organic solvent can be used alone or in combination of two or more.

[0035] As the content of the above water-soluble organic solvent, it is preferably 1.5% by mass to 7.5% by mass based on the total mass of the aqueous medium.

[0036] From the viewpoint of printing drying properties, the content of the above aqueous medium is preferably 60.0% by mass to 80.0% by mass based on the total mass of the aqueous overprint varnish composition.

[0037] (Alkali-soluble resin) The aqueous overprint varnish composition of the present invention preferably further contains an alkali-soluble resin. By containing the alkali-soluble resin, re-dissolvability can be suitably imparted.

[0038] As the alkali-soluble resin, for example, a resin containing one or more anionic groups such as a carboxyl group, a sulfonic acid group, and a phosphonic acid group (-P(=O)(OH2)) is preferable. The alkali-soluble resin can be used alone or in combination of two or more.

[0039] Examples of the alkali-soluble resin include a polyimide resin, a polyimide precursor, a polybenzoxazole resin, a polybenzoxazole precursor, a cardo resin, a styrene (meth)acrylate resin, an epoxy (meth)acrylate resin, a polysiloxane resin, a novolak resin, a (meth)acrylic resin, a polyurethane resin, and a polyester resin.

[0040] The alkali-soluble resin preferably has an acid value of 100 mgKOH / g or more and 300 mgKOH / g or less, more preferably 150 mgKOH / g or more, and still more preferably 200 mgKOH / g or more.

[0041] The alkali-soluble resin preferably has a glass transition temperature of 100°C or more, more preferably 125°C or more, and still more preferably 150°C or more.

[0042] The weight average molecular weight of the alkali-soluble resin is preferably 5,000 or more, more preferably 8,000 or more. From the viewpoint of enhancing solubility, the weight average molecular weight of the alkali-soluble resin is preferably 100,000 or less, more preferably 50,000 or less.

[0043] The weight average molecular weight can be measured by gel permeation chromatography (GPC). As an example, using Water 2690 (manufactured by Waters) as the GPC apparatus, PLgel, 5 μm, MIXED-D (manufactured by Polymer Laboratories) as the column, tetrahydrofuran as the developing solvent, a column temperature of 25°C, a flow rate of 1 milliliter per minute, an RI detector, a sample injection concentration of 10 milligrams per milliliter, and an injection volume of 100 microliters, chromatography can be performed and it can be determined as the weight average molecular weight in terms of polystyrene.

[0044] As the alkali-soluble resin, it is preferable to use a resin obtained by neutralizing part or all of the acid value of an alkali-soluble resin having an acid value of 100 mgKOH / g or more and 300 mgKOH / g or less with a basic compound and dissolving it in water.

[0045] Examples of the basic compound include ammonia, organic amines, alkali metal hydroxides, etc. Specifically, examples of the organic amine include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. Among them, from the viewpoints of coating film physical properties and redissolvability, it is desirable to use a combination of volatile and non-volatile basic compounds.

[0046] From the viewpoint of imparting redissolvability, the content of the alkali-soluble resin is preferably 5% by mass to 20% by mass in terms of solid content based on the total solid content of the aqueous overprint varnish composition.

[0047] (aqueous rosin-based resin) The aqueous overprint varnish composition of the present invention preferably further contains an aqueous rosin-based resin. By containing the above aqueous rosin-based resin, the biomass component ratio can be improved, contributing to the formation of a recycling-oriented society and the reduction of greenhouse gas emissions.

[0048] The above aqueous rosin-based resin may be an aqueous rosin-based resin with an acid value of 0 mgKOH / g and / or 0 to 350 mgKOH / g, and may be either an emulsion or water-soluble.

[0049] The acid value of the above aqueous rosin-based resin emulsion is 0 mgKOH / g and / or 0 to 150 mgKOH / g, and the acid value of the above water-soluble rosin-based resin is 100 to 350 mgKOH / g.

[0050] As the above aqueous rosin-based resin emulsion, those obtained by dispersing rosin derivatives such as rosin esters and rosin, which are made of materials obtained by extraction from plants or the like, as fine particles in water in the presence of a low molecular weight emulsifier can be used. Specific examples include Harieaster SK218NS, SK370N, SK385NS, SK501NS manufactured by Harima Kasei Co., Ltd., Snowpack XW-2442, XW-2551, XW-2561, XW-2582, SE780G, 100G manufactured by LAWTER, and Super Ester NS-121, NS-100H, E-865NT manufactured by Arakawa Chemical Industries, Ltd.

[0051] As the above water-soluble rosin-based resin, those obtained by neutralizing part or all of the acid value of a rosin-based resin having an acid value of 100 to 350 mgKOH / g with a basic compound and dissolving it in water are used. Specific examples include Tespol 150, 154, 158 manufactured by Hitachi Chemical Co., Ltd., Harimac T-80 manufactured by Harima Kasei Co., Ltd., Harieaster MSR-4, AS-5, and Markid 31, 32, 33 manufactured by Arakawa Chemical Industries, Ltd.

[0052] Examples of the basic compound include ammonia, organic amines, alkali metal hydroxides, etc. Specifically, examples of the organic amine include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. Among them, from the viewpoints of coating film physical properties and redissolvability, it is desirable to use a combination of volatile and non-volatile basic compounds.

[0053] From the viewpoint of performance, the aqueous rosin-based resin is preferably an aqueous rosin-based resin emulsion.

[0054] From the viewpoint of improving the biomass component content, the content of the aqueous rosin-based resin is preferably 1% by mass to 25% by mass in terms of solid content based on the total solid content of the aqueous overprint varnish composition.

[0055] (Others) The aqueous overprint varnish composition of the present invention may contain various additives such as a polymerization inhibitor, a sensitizer, a pigment, a pigment dispersant / resin for pigment dispersion, a surfactant, an organic solvent, an ultraviolet absorber, an antioxidant, an antifoaming agent, a preservative improver, a fungicide, a rust preventive, a thickener, a humectant, and a pH adjuster. The content of the above additives is about 0.1 to 5% by mass based on the total mass of the aqueous overprint varnish composition.

[0056] The aqueous overprint varnish composition of the present invention is preferably used for the varnish layer of a laminate comprising at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order. The aqueous overprint varnish composition of the present invention can suppress winding blocking and can form a varnish layer having excellent laminate strength with respect to the resin layer formed by extrusion lamination, and thus can be suitably used for the above applications.

[0057] (Manufacturing method) The aqueous overprint varnish composition of the present invention can be manufactured by using the above-described various materials and various known dispersion and kneading apparatuses.

[0058] <Laminate> The laminate of the present invention includes at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order, and the varnish layer is formed of the aqueous overprint varnish composition of the present invention.

[0059] The laminate of the present invention can suppress winding blocking and has a varnish layer excellent in laminate strength with respect to the resin layer formed by extrusion lamination, and thus can be suitably used for, for example, containers for food and beverages.

[0060] (Paper base material) The laminate of the present invention includes a paper base material layer.

[0061] The paper base material layer is not particularly limited, and a known paper base material mainly composed of pulp can be used.

[0062] The thickness of the paper base material layer is not particularly limited and may be appropriately selected according to the application.

[0063] (Printing layer) The laminate of the present invention includes a printing layer.

[0064] The printing layer is not particularly limited, and a known ink composition can be used, but it is preferable to use a printing layer formed of a known aqueous ink composition.

[0065] The method for forming the printing layer is not particularly limited, and a known aqueous ink composition may be printed using a known printing method such as gravure printing or flexographic printing.

[0066] (Varnish layer) The laminate of the present invention includes a varnish layer.

[0067] The varnish layer is formed by the aqueous overprint varnish composition of the present invention described above.

[0068] The method for forming the varnish layer is not particularly limited, and the aqueous overprint varnish composition of the present invention may be printed using a known method such as a roll coating method using a gravure cylinder or the like, a doctor knife method, an air knife / nozzle coating method, a bar coating method, a spray coating method, a dip coating method, and a coating method combining these methods.

[0069] The varnish layer can suppress winding blocking. The above winding blocking can be evaluated by the following two types of tests.

[0070] On a paper base material layer (non-coated cup base paper 200 g, manufactured by Nippon Paper Industries Co., Ltd.), a printing layer (Eco Print No. 800 blue, manufactured by Sakata Inx Corporation) is printed using a gravure printing machine (manufactured by Toshiba Corporation) at a printing speed of 80 m / min, a printing pressure of 2.2 t, a printing plate: Helio 150 - 200 LPI full solid, and drying conditions: 80°C, 80 cm 3 / min to form a printing layer. Next, an aqueous overprint varnish composition is spread on the above printing layer using a bar coater (No. 6 linear 0.15 mm) to form a varnish layer of 6 - 7.5 WETg / m 2 to produce a test laminate. After producing the test laminate, it is cut into pieces of 5 cm × 4 cm to produce test pieces. On the varnish layer side of the above test piece, a backing material [the back side (paper base material side) of the above laminate] is overlaid, and pressure is applied under the conditions of a load of 10 kg / cm 2 , environmental conditions: 40°C / 90% RH, and time: 12 hours. Thereafter, the surface of the backing material overlaid with the varnish layer is visually confirmed.

[0071] After producing a laminate in the same manner as the above test, it is cut into pieces of 5 cm × 4 cm to produce test pieces. Over the varnish layer of the test piece, the application material [the back side (paper base material side) of the laminate] was overlapped, and a local pressure portion was provided in a state of being fastened with a gem clip (width 7 mm, length 28 mm), load: 10 kg / cm 2 (With respect to the size of the test piece), pressurization is performed under the environmental conditions of 23 °C / 50% RH and for a time of 12 hours. After that, visually check the surface that was overlapped with the varnish layer of the application material.

[0072] In any of the above two types of tests, when no contamination is confirmed on the surface overlapped with the varnish layer of the application material, it is judged that winding blocking can be suppressed.

[0073] (Extrusion laminate resin layer) The laminate of the present invention includes an extrusion laminate resin layer.

[0074] Examples of the extrusion laminate resin layer include resin layers containing polyolefin, PLA, etc. Among them, from the viewpoint of laminate adhesion strength, it is preferably polyolefin.

[0075] The thickness of the extrusion laminate resin layer can be arbitrary depending on the application, but is usually preferably 5 μm to 300 μm.

[0076] The method for obtaining the extrusion laminate resin layer is not limited, and an extrusion lamination method of laminating a molten polymer, which is a conventionally known method, may be used. The above laminate strength can be evaluated by the following test. The above winding blocking can be evaluated by the following two types of tests

[0077] The above varnish layer is excellent in laminate strength with respect to the resin layer formed by extrusion lamination.

[0078] After forming the varnish layer by the same method as the above test, on the above varnish layer, a resin (Sumika Sen L705, manufactured by Sumitomo Chemical Co., Ltd.) was extrusion laminated using a laminator (manufactured by Okazaki Machinery Co., Ltd.) under the conditions of a resin temperature of 365 ° C (310 ° C directly under the T-die) and a winding speed of 50 m / min to form an extrusion laminated resin layer (film thickness: 20 μm), and a laminate was produced. After leaving the above laminate for 3 days, it is cut into a width of 15 mm. Thereafter, using a peel tester (manufactured by Yasuda Seiki Co., Ltd.), the T-peel strength is measured at a tensile speed of 300 mm / min with respect to the extrusion laminated resin layer side. If the adhesive strength is 150 g / 15 mm or more, it is judged that the lamination strength is excellent, and if it is 200 g / 15 mm or more, it is judged that the lamination strength is particularly excellent.

[0079] (Method for manufacturing laminate) As the method for manufacturing the laminate of the present invention, the above paper substrate may be prepared, and each layer may be laminated on the paper substrate by the formation methods of the respective layers described above.

[0080] The following matters are disclosed in this specification.

[0081] The present disclosure (1) is an aqueous overprint varnish composition containing a styrene-acrylic resin emulsion having a glass transition temperature of 55 ° C to 130 ° C, a wax, and an aqueous medium. The present disclosure (2) is the aqueous overprint varnish composition according to the present disclosure (1), wherein the acid value of the styrene-acrylic resin emulsion is 50 mg / KOH or more. The present disclosure (3) is the aqueous overprint varnish composition according to the present disclosure (1) or (2), wherein the content of the styrene-acrylic resin emulsion is 65% by mass to 85% by mass in terms of solid content based on the total solid content of the aqueous overprint varnish composition. The present disclosure (4) is the aqueous overprint varnish composition according to any one of the present disclosures (1) to (3), further containing an alkali-soluble resin. The present disclosure (5) is further an aqueous overprint varnish composition according to any one of the present disclosures (1) to (4) containing an aqueous rosin resin. The present disclosure (6) is an aqueous overprint varnish composition according to any one of the present disclosures (1) to (5) used for the varnish layer of a laminate including at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order. The present disclosure (7) is a laminate including at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order, wherein the varnish layer is formed of the aqueous overprint varnish composition according to any one of the present disclosures (1) to (6).

Examples

[0082] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples only. Unless otherwise specified, “%” means “mass %” and “part” means “part by mass”.

[0083] The materials used when preparing the aqueous overprint varnish compositions of the examples and comparative examples are as follows. The glass transition temperature and acid value were determined by the methods described in this specification. <Aqueous resin emulsion> Aqueous resin emulsion 1 (styrene-acrylic resin emulsion, solid content 40 mass%, glass transition temperature 98°C, acid value 50 mgKOH / g) Aqueous resin emulsion 2 (styrene-acrylic resin emulsion, solid content 40 mass%, glass transition temperature 60°C, acid value 60 mgKOH / g) Aqueous resin emulsion 3 (styrene-acrylic resin emulsion, solid content 40 mass%, glass transition temperature 86°C, acid value 112 mgKOH / g) Aqueous resin emulsion 4 (styrene-acrylic resin emulsion, solid content 40 mass%, glass transition temperature 123°C, acid value 200 mgKOH / g) Water-based resin emulsion 5 (styrene-acrylic resin emulsion, solid content 40% by mass, glass transition temperature 117 °C, acid value 84 mgKOH / g) Water-based resin emulsion 6 (styrene-acrylic resin emulsion, solid content 40% by mass, glass transition temperature -4 °C, acid value 59 mgKOH / g) Water-based resin emulsion 7 (styrene-acrylic resin emulsion, solid content 40% by mass, glass transition temperature 14 °C, acid value 36 mgKOH / g) Water-based resin emulsion 8 (styrene-acrylic resin emulsion, solid content 40% by mass, glass transition temperature 40 °C, acid value 71 mgKOH / g) Water-based resin emulsion 9 (styrene-acrylic resin emulsion, solid content 40% by mass, glass transition temperature 53 °C, acid value 53 mgKOH / g) <Alkali-soluble resin> Alkali-soluble resin 1 (styrene-acrylic resin varnish, solid content 25% by mass, glass transition temperature 155 °C, acid value 240 mgKOH / g) Alkali-soluble resin 2 (styrene-acrylic resin varnish, solid content 25% by mass, glass transition temperature 107 °C, acid value 210 mgKOH / g) <Water-based rosin resin> Water-based rosin resin emulsion (product name: Harister SK-218NS, manufactured by Harima Kasei Co., Ltd., solid content 50% by mass) <Wax> Wax (polyethylene wax, solid content 40% by mass, average particle diameter 4 μm (Coulter counter method)) <Water-based medium> Purified water

[0084] <Preparation of water-based overprint varnish composition> (Examples 1 to 11, Comparative Examples 1 to 4) Each material was stirred and mixed in the blending amounts shown in Table 1 to prepare a water-based overprint varnish composition. In Table 1, the glass transition temperature is described as "Tg".

[0085]

Table 1

[0086] <Fabrication of the laminate> (Examples 1 - 11, Comparative Examples 1 - 4) On a paper base material layer (200 g non - coated cup base paper, manufactured by Nippon Paper Industries Co., Ltd.), using a gravure printing machine (manufactured by Toshiba Corporation), a printing layer (Ecopino Blue 800, manufactured by Sakata Inx Corporation) was printed under the conditions of printing speed: 80 m / min, printing pressure: 2.2 t, printing plate: Helio 150 - 200 LPI full solid, drying conditions: 80°C, 80 cm 3 / min to form a printing layer. Next, an aqueous overprint varnish composition was spread on the above - mentioned printing layer using a bar coater (NO.6 linear 0.15 mm) to form a varnish layer of 6 - 7.5 WETg / m 2 . Thereafter, a resin (Sumicasen L705, manufactured by Sumitomo Chemical Co., Ltd.) was extrusion - laminated on the above - mentioned varnish layer using a laminator (manufactured by Okazaki Machinery Co., Ltd.) under the conditions of resin temperature 365°C (310°C directly below the T - die), winding speed 50 m / min to form an extrusion - laminated resin layer (film thickness 20 μm) and fabricate a laminate. Note that in each of the examples and comparative examples, the corresponding aqueous overprint varnish compositions were used.

[0087] (Comparative Example 5) On a paper base material layer (200 g non - coated cup base paper, manufactured by Nippon Paper Industries Co., Ltd.), using a gravure printing machine (manufactured by Toshiba Corporation), a printing layer (Ecopino Blue 800, manufactured by Sakata Inx Corporation) was printed under the conditions of printing speed: 80 m / min, printing pressure: 2.2 t, printing plate: Helio 150 - 200 LPI full solid, drying conditions: 80°C, 80 cm 3 / min to form a printing layer. Thereafter, a resin (Sumicasen L705, manufactured by Sumitomo Chemical Co., Ltd.) was extrusion - laminated on the above - mentioned printing layer using a laminator (manufactured by Okazaki Machinery Co., Ltd.) under the conditions of resin temperature 365°C (310°C directly below the T - die), winding speed 50 m / min to form an extrusion - laminated resin layer (film thickness 20 μm) and fabricate a laminate.

[0088] <Blocking Resistance (Rewinding Blocking) Test 1> In the laminate, for Examples 1 to 11 and Comparative Examples 1 to 4, the laminate at the stage of forming the varnish layer was cut into 5 cm × 4 cm to prepare test pieces. In the laminate, for Comparative Example 5, the laminate at the stage of forming the printing layer was cut into 5 cm × 4 cm to prepare test pieces. On the varnish layer side of the above test piece (printing layer in Comparative Example 5), the backing material [the back side (paper base material side) of the above laminate] was overlaid, and pressure was applied under the conditions of load: 10 kg / cm 2 , environmental conditions: 40°C / 90% RH, time: 12 hours. After that, the surface overlaid with the varnish layer of the backing material (printing layer in Comparative Example 5) was visually confirmed and evaluated according to the following criteria. The results are shown in Table 2. (Evaluation Criteria) 〇: No contamination was confirmed. ×: Contamination was confirmed.

[0089] <Blocking Resistance (Rewinding Blocking) Test 2> In the laminate, for Examples 1 to 11 and Comparative Examples 1 to 4, the laminate at the stage of forming the varnish layer was cut into 5 cm × 4 cm to prepare test pieces. In the laminate, for Comparative Example 5, the laminate at the stage of forming the printing layer was cut into 5 cm × 4 cm to prepare test pieces. On the varnish layer side of the above test piece (printing layer in Comparative Example 5), the backing material [the back side (paper base material side) of the above laminate] was overlaid, and a local pressure part was provided in a state of being fastened with a zem clip (width 7 mm, length 28 mm), and pressure was applied under the conditions of load: 10 kg / cm 2 , environmental conditions: 23°C / 50% RH, time: 12 hours. After that, the surface overlaid with the varnish layer of the backing material (printing layer in Comparative Example 5) was visually confirmed and evaluated according to the following criteria. The results are shown in Table 2. (Evaluation Criteria) 〇: No contamination was confirmed. ×: Contamination was confirmed.

[0090] <Extrusion Lamination Strength Test> After leaving the produced laminate to stand for 3 days, it was cut into a width of 15 mm. Thereafter, using a peel tester (manufactured by Yasuda Seiki Co., Ltd.), the T-peel strength was measured at a tensile speed of 300 mm / min with respect to the extrusion laminate resin layer side, and evaluation was performed according to the following criteria. The results are shown in Table 2. (Evaluation Criteria) ◎: 200 g / 15 mm or more 〇: 150 g / 15 mm or more and less than 200 g / 15 mm ×: Less than 150 g / 15 mm

[0091]

Table 2

[0092] As shown in Tables 1 and 2, the varnish layer formed of the styrene-acrylic resin emulsion, wax, and aqueous medium containing an aqueous medium having a glass transition temperature of 55°C to 130°C can suppress winding blocking, and it was confirmed that the laminate strength with respect to the resin layer formed by extrusion lamination is excellent. It was confirmed.

Industrial Applicability

[0093] The aqueous overprint varnish composition of the present invention can suppress winding blocking and can form a varnish layer excellent in laminate strength with respect to the resin layer formed by extrusion lamination. Therefore, for example, it can be suitably used for the varnish layer of containers for food and beverages.

Claims

1. A styrene-acrylic resin emulsion having a glass transition temperature of 55°C to 130°C, a wax, and an aqueous medium, an aqueous overprint varnish composition.

2. The aqueous overprint varnish composition according to Claim 1, wherein the styrene-acrylic resin emulsion has an acid value of 50 mg / KOH or more.

3. The aqueous overprint varnish composition according to Claim 1 or 2, wherein the content of the styrene-acrylic resin emulsion is 65% by mass to 85% by mass in terms of solid content based on the total solid content of the aqueous overprint varnish composition.

4. The aqueous overprint varnish composition according to Claim 1 or 2, further containing an alkali-soluble resin.

5. The aqueous overprint varnish composition according to Claim 1 or 2, further containing an aqueous rosin resin.

6. The aqueous overprint varnish composition according to Claim 1 or 2, which is used for the varnish layer of a laminate comprising at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order.

7. A laminate comprising at least a paper base material layer, a printing layer, a varnish layer, and an extrusion laminate resin layer in this order, wherein the varnish layer is formed of the aqueous overprint varnish composition according to Claim 1 or 2.

Images