Aqueous ink and laminate

Abstract

To provide aqueous ink from which a film excellent in adhesion, blocking resistance of films, wet friction resistance, and whitening suppression during heat shrinkage can be obtained.SOLUTION: There are provided aqueous ink which contains a binder resin, a curing agent and an aqueous solvent, wherein the binder resin contains aqueous (meth)acrylic emulsion and an alkali-soluble type water-soluble resin, a mass ratio of nonvolatile components of the aqueous (meth)acrylic emulsion to the alkali-soluble type water-soluble resin is 10 / 90 to 90 / 10, and a glass transition temperature (Tg) of the aqueous (meth)acrylic emulsion is -30 to 60°C; and a laminate using the same.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to aqueous ink and a laminate.

Background Art

[0002] Gravure ink and flexographic ink are widely used for the purpose of imparting cosmetic properties and functional properties to a printing object of a flexible packaging film.

[0003] Specifically, for example, in the packaging of products, for decoration and surface protection, these gravure inks and flexographic inks are printed on the front side (the side that does not come into contact with the product to be packaged) of a plastic film serving as a base material, and not printed on the back side (the side that comes into contact with the product to be packaged). A printed matter having a simple configuration (referred to as a front printing method) is used.

[0004] Also, in the case of body wrap labels and shrink labels for PET bottles, generally, a top coat varnish for imparting a film damage prevention function is printed on the outer surface side, and a printing layer for decoration and a varnish layer for imparting blocking prevention to the PET bottle are provided on the inner surface side. Since the inks and top coat varnishes for the above-described front printing are directly exposed to the outside or come into direct contact with other members, strong film physical properties are required during the handling of products.

[0005] In recent years, from the perspective of sustainability based on the worsening of air pollution due to VOCs and the global expansion such as global warming, in response to the movement to convert to non-petroleum resources, adding labor safety and hygiene and further flammability and explosiveness, the spread of so-called aqueous ink in which the organic solvent in the ink is replaced with water is expected. Under such circumstances, various studies on aqueous ink applicable to inks and top coat varnishes for front printing are being advanced (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Here, for a film made of ink, in addition to the adhesion to the substrate, various film physical properties (blocking resistance between films, water friction resistance, suppression of whitening during heat shrinkage) are required. However, conventional aqueous inks had room for improvement in terms of satisfying all of these requirements.

[0008] Therefore, an object of the present invention is to provide an aqueous ink capable of obtaining a film excellent in adhesion, blocking resistance between films, water friction resistance, and suppression of whitening during heat shrinkage. Another object of the present invention is to provide a laminate having an ink layer excellent in adhesion, blocking resistance between films, water friction resistance, and suppression of whitening during heat shrinkage as a film.

MEANS FOR SOLVING THE PROBLEMS

[0009] That is, the present invention relates to an aqueous ink containing a binder resin, a curing agent, and an aqueous solvent, wherein the binder resin contains an aqueous (meth)acrylic emulsion and an alkali-soluble water-soluble resin, and the mass ratio of the non-volatile content of the aqueous (meth)acrylic emulsion to the alkali-soluble water-soluble resin is aqueous (meth)acrylic emulsion / alkali-soluble water-soluble resin = 10 / 90 to 90 / 10, and the glass transition temperature (Tg) of the aqueous (meth)acrylic emulsion is -30 to 60°C.

[0010] The present invention also relates to a laminate including a heat-shrinkable film and a varnish layer provided on the heat-shrinkable film, wherein the varnish layer is a printed layer of the aqueous ink according to claim 1 or 2.

EFFECTS OF THE INVENTION

[0011] According to the present invention, it is possible to provide an aqueous ink capable of obtaining a film excellent in adhesion, blocking resistance between films, water friction resistance, and whitening suppression during heat shrinkage. Further, according to the present invention, it is possible to provide a laminate having an ink layer excellent in adhesion, blocking resistance between films, water friction resistance, and whitening suppression during heat shrinkage as a film.

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention (hereinafter sometimes referred to as "the present embodiments") will be described in detail. However, the present invention is not limited to the following description and can be variously modified and implemented within the scope of the gist.

[0013] (Aqueous Ink) The aqueous ink of the present invention contains a binder resin, a curing agent, and an aqueous solvent. The binder resin contains an aqueous (meth)acrylic emulsion and an alkali-soluble water-soluble resin, and the mass ratio of the non-volatile components of the aqueous (meth)acrylic emulsion and the alkali-soluble water-soluble resin is aqueous (meth)acrylic emulsion / alkali-soluble water-soluble resin = 10 / 90 to 90 / 10, and the glass transition temperature (Tg) of the aqueous (meth)acrylic emulsion is 0 to 60°C. In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0014] (Binder Resin) The aqueous ink of the present invention contains an aqueous (meth)acrylic emulsion and an alkali-soluble water-soluble resin as a binder resin.

[0015] (Aqueous (meth)acrylic emulsion) The aqueous (meth)acrylic emulsion used in the present invention is not particularly limited, and a known and commercially available aqueous (meth)acrylic emulsion can be used.

[0016] ((Meth)acrylic resin) The (meth)acrylic resin contained in the aqueous (meth)acrylic emulsion is not particularly limited, and examples thereof include a homopolymer or copolymer of (meth)acrylate and a copolymer obtained by copolymerizing (meth)acrylate and a vinyl monomer copolymerizable therewith. Further, it is preferably a copolymer having an acid value for the purpose of imparting water dispersibility and water solubility. In the present invention, "(meth)acrylate" refers to either one or both of acrylate and methacrylate, and "(meth)acrylic" refers to either one or both of acrylic and methacrylic.

[0017] Examples of (meth)acrylates and vinyl monomers copolymerizable with (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-pentafluoropropyl (meth)acrylate, perfluorocyclohexyl (meth)acrylate, glycidyl (meth)acrylate, allyl glycidyl ether, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, (meth)acrylamide, N-monoalkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isobutoxymethyl (meth)acrylamide, 2-aziridinylethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, acrolein, diacetone (meth)acrylamide, acetoacetoxyethyl (meth)acrylate, etc. The (meth)acrylate may be used alone or in combination of two or more.

[0018] Examples of vinyl monomers include vinyl monomers such as vinyl acetate, vinyl propionate, vinyl versatate, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, (meth)acrylonitrile, styrene, α-methylstyrene, divinylstyrene, isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone, etc. The polymerizable unsaturated group-containing compound may be a single species or a combination of two or more species.

[0019] In addition, for the purpose of introducing one or more acidic groups selected from the group consisting of a carboxyl group and a carboxylate group in which the carboxyl group is neutralized by a basic compound, (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, β-(meth)acryloyloxyethyl hydrogen succinate, β-(meth)acryloyloxyethyl hydrogen phthalate, etc. A copolymer having an acid value can be obtained by copolymerizing a (meth)acrylic monomer having a carboxyl group. When introducing an acidic group, although it will be described in detail later, it is preferable to appropriately adjust the monomer amount so that the acid value falls within a desired range.

[0020] Also, the (meth)acrylic resin may be reacted with a self-crosslinking component. That is, the (meth)acrylic resin may be self-crosslinking. Examples of the self-crosslinking component include isocyanate compounds, epoxy compounds, amine compounds, melamine compounds, hydrazine compounds, aldehyde compounds, oxazoline compounds, etc.

[0021] (Meta)acrylic resins can be produced, for example, by polymerizing various monomers in the temperature range of 50°C to 180°C, more preferably 80°C to 150°C, in the presence of a polymerization initiator. Examples of the polymerization method include bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. Also, the (meta)acrylic resin in the case of a copolymer may be a random copolymer, block copolymer, graft copolymer, etc. from the viewpoint of its polymerization mode. When obtained by the above bulk polymerization or solution polymerization, the (meta)acrylic resin into which an acidic group has been introduced can be neutralized with a neutralizing agent such as an alkali after polymerization, and the solvent can be replaced with an aqueous medium to obtain an aqueous emulsion.

[0022] (Meta)acrylic resins may be and are preferably emulsions that form a core-shell type. The above core-shell type emulsion refers to a state in which the first polymer is dispersed in an aqueous medium by the second polymer, and usually, the second polymer exists on the outermost part of the resin particles to form a shell part, and a part or all of the first polymer often forms a core part.

[0023] The glass transition temperature (Tg) of the above aqueous (meta)acrylic emulsion is characterized by being -30 to 60°C. By being in this range, the effects of the present invention can be maximally exerted, which is preferable. Among them, the glass transition temperature (Tg) is more preferably -10°C or higher, further preferably 0°C or higher, still more preferably 20°C or higher, and more preferably 40°C or lower.

[0024] In the present invention, the glass transition temperature (Tg) refers to the so-called calculated glass transition temperature and refers to the value calculated by the following method. (Equation 1) 1 / Tg(K)=(W1 / T1)+(W2 / T2)+···(Wn / Tn) (Equation 2) Tg(°C)=Tg(K)-273 In Formula 1, W1, W2, ···, Wn represent the mass % of each monomer with respect to the total mass of the monomers used in the production of the polymer, and T1, T2, ···, Tn represent the glass transition temperatures (K) of the homopolymers of the respective monomers. Note that the values of T1, T2, ···, Tn are those described in the Polymer Handbook (Fourth Edition, edited by J. Brandrup, E.H. Immergut, and E.A. Grulke). Also, for monomers whose glass transition temperatures of the homopolymers are not described in the above Polymer Handbook, the glass transition temperatures were measured by a differential scanning calorimeter "DSCQ-100" (manufactured by TA Instrument) using a method compliant with JIS K7121. Specifically, for the polymer from which the solvent was completely removed by vacuum suction, the heat quantity change was measured in the range of -100 °C to +200 °C at a heating rate of 20 °C / min, and the point where a straight line equidistant in the vertical axis direction from the extended straight line of each baseline intersects the curve of the stepwise change portion of the glass transition was defined as the glass transition temperature.

[0025] The acid value (also referred to as "AV") of the above aqueous (meth)acrylic emulsion is preferably 0 mgKOH / g to 100 mgKOH / g. By being in this range, it is preferable as the effects of the present invention can be maximally exerted. The acid value of the above (meth)acrylic resin (A) is more preferably 15 mgKOH / g or more, and more preferably 60 mgKOH / g or less, and even more preferably 40 mgKOH / g or less. In the present invention, the acid value indicates the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 g of the resin.

[0026] In the present invention, the above (meth)acrylic resin (A) is preferably an acrylic resin (i.e., a resin obtained by polymerizing substantially only (meth)acrylate monomers) or a styrene-acrylic resin (i.e., a resin obtained by copolymerizing styrene monomers and (meth)acrylate monomers), and more preferably a styrene-acrylic resin.

[0027] (Alkali-soluble water-soluble resin) The alkali-soluble water-soluble resin used in the present invention is not particularly limited, and a publicly available alkali-soluble water-soluble resin can be used. Among them, from the viewpoint of compatibility with the above aqueous (meth)acrylic emulsion, it is preferable to use a (meth)acrylic resin. As the (meth)acrylic resin, the same resin as the above aqueous (meth)acrylic emulsion can be used.

[0028] In the present invention, it is preferable that the above (meth)acrylic resin (A) is an acrylic resin (that is, a resin obtained by polymerizing substantially only (meth)acrylate monomers) or a styrene-acrylic resin (that is, a resin obtained by copolymerizing a styrene monomer and a (meth)acrylate monomer), and more preferably a styrene-acrylic resin.

[0029] In the present invention, the (meth)acrylic resin may be one reacted with a self-crosslinking component. That is, the (meth)acrylic resin may be a self-crosslinking type. Examples of the self-crosslinking component include isocyanate compounds, epoxy compounds, amine compounds, melamine compounds, hydrazine compounds, aldehyde compounds, oxazoline compounds, and the like.

[0030] The glass transition temperature (Tg) of the above alkali-soluble water-soluble resin preferably ranges from 10 to 130 °C so that the effects of the present invention can be maximally exerted. Among them, the glass transition temperature (Tg) is more preferably 20 °C or higher, further preferably 30 °C or higher, still more preferably 50 °C or higher, and more preferably 80 °C or lower.

[0031] Also, the acid value of the above alkali-soluble water-soluble resin is preferably 40 mgKOH / g to 240 mgKOH. By being in this range, the effects of the present invention can be maximally exerted, which is preferable. Among them, the acid value is more preferably 40 mgKOH / g or higher, and more preferably 60 mgKOH / g or lower, still more preferably 100 mgKOH / g or lower.

[0032] (Mass ratio) In the present invention, it is characterized in that the mass ratio of the non-volatile content of the aqueous (meth)acrylic emulsion and the alkali-soluble water-soluble resin is such that aqueous (meth)acrylic emulsion / alkali-soluble water-soluble resin = 10 / 90 to 90 / 10. By setting it within this range, the effects of the present invention can be maximally exerted. Among these, the mass ratio is preferably in the range of 30 to 70, and most preferably in the range of 70 to 30.

[0033] (Aziridine-based curing agent) The aqueous ink of the present invention may be used in combination with a curing agent. As the curing agent, among others, an aziridine-based curing agent is preferable. An aziridine-based curing agent is a compound having an aziridine group. More specifically, for example, trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-(2-methylaziridine)propionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), and N,N'-toluene-2,4-bis(1-aziridinecarboxamide) etc. may be mentioned. The aziridine-based curing agent may be used alone or in combination of two or more.

[0034] Also, as the aziridine-based curing agent, commercially available products can be used. Examples of commercially available products of aziridine-based curing agents include "PZ-33" manufactured by Nippon Shokubai Co., Ltd., "DZ-22E" manufactured by Nippon Shokubai Co., Ltd., "XL-706" manufactured by Stahl, and "SU-125F" manufactured by Meisei Chemical Industry Co., Ltd. etc.

[0035] In the aqueous ink of the present invention, it is necessary that the amount of the non-volatile content of the aziridine-based curing agent with respect to 100 parts by mass of the non-volatile content of the binder resin is 2.0 parts by mass or more and 11.0 parts by mass or less. If the above amount is less than 2.0 parts by mass, there is a risk that the five properties cannot be achieved, especially there is a risk that at least one of heat resistance, water friction resistance, and alcohol resistance cannot be improved. Further, if the above amount exceeds 11.0 parts by mass, there is a risk that the five properties cannot be achieved, especially there is a risk that improvement of shrinkage suitability cannot be achieved. And from the same viewpoint as above, the amount of the non-volatile content of the aziridine-based curing agent with respect to 100 parts by mass of the non-volatile content of the binder resin is preferably 5.0 parts by mass or more, more preferably 7.0 parts by mass or more, and preferably 10.0 parts by mass or less, and more preferably 9.0 parts by mass or less.

[0036] Incidentally, when the binder resin and the aziridine-based curing agent are used in the preparation of the aqueous ink, they are often in a state of being dispersed in a solvent. Therefore, in order to calculate the mass ratio of the non-volatile content described above, it is important to know the NV value (Nonvolatile content) of each of the binder resin and the aziridine-based curing agent. It is important to grasp. Incidentally, "non-volatile content" (Non-Volatile, NV) is sometimes generally referred to as "solid content".

[0037] (Aqueous solvent) Examples of the aqueous solvent used in the present embodiment include water alone or an organic solvent miscible with water. Examples of the organic solvent include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-propyl alcohol; polyhydric alcohols such as propylene glycol and glycerin; ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monon-propyl ether, and ethyl carbitol; and the like. The aqueous solvent may be a single type or a combination of two or more types.

[0038] (Pigment) In addition to the above, the aqueous ink of the present invention can contain various pigments. Examples of pigments include inorganic pigments and organic pigments from the perspective of materials, and black pigments, blue pigments, green pigments, red pigments, purple pigments, yellow pigments, orange pigments, brown pigments, etc. from the perspective of coloring. The aqueous ink containing these pigments can be used as an ink for so-called black-and-white printing or color printing. However, since the aqueous ink of the present invention can exhibit tough film physical properties that can withstand contact with the outside, it is preferably a topcoat varnish that does not contain pigments (that is, a colorless and transparent ink used for solid printing on the outermost surface of the color printing layer for the purpose of protecting the color printing layer).

[0039] (Surfactant) In addition to the above, the aqueous ink of the present invention can further contain a surfactant. As the above surfactant, an acetylene-based surfactant and an alcohol alkoxylate-based surfactant are preferable. These surfactants may be used alone or in combination of two or more.

[0040] Specific examples of the acetylene-based surfactant include 2,5-dimethyl-3-hexyne-2,5-diol, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,5-dimethyl-1-hexyne-3-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3-hexyne-2,5-diol, 2-butyn-1,4-diol, etc. These acetylene-based surfactants may be used alone or in combination of two or more.

[0041] In addition, examples of commercially available products of acetylene-based surfactants include commercially available products of alkylene oxide non-modified acetylene glycol-based surfactants and commercially available products of alkylene oxide-modified acetylene glycol-based surfactants. Examples of commercially available products of alkylene oxide non-modified acetylene glycol-based surfactants include Surfynol 61, 82, 104 (all manufactured by Air Products). Examples of commercially available alkylene oxide-modified acetylene glycol surfactants include Surfynol 420, 440, 465, 485, TG, 2502, Dynol 604, 607 (all manufactured by Air Products); Surfynol SE, MD-20, Olfin E1004, E1010, PD-004, EXP4300, PD-501, PD-502, SPC (all manufactured by Nissin Chemical Industry Co., Ltd.); Acetylenol EH, E40, E60, E81, E100, E200 (all manufactured by Kawaken Fine Chemicals Co., Ltd.); and the like. Among them, as the acetylene surfactant, an alkylene oxide-modified acetylene glycol surfactant is preferred.

[0042] Specific examples of the alcohol alkoxylate surfactant include alcohol ethoxylate, alcohol polyethoxylate, etc. Examples of commercially available alcohol alkoxylate surfactants include "BYK-DYNWET800" (manufactured by BYK). These alcohol alkoxylate surfactants may be used alone or in combination of two or more.

[0043] In addition to the above-mentioned surfactants, if necessary, an acrylic polymer surfactant (for example, "Polyflow WS-314" manufactured by Kyoeisha Chemical Co., Ltd.) and a modified silicone surfactant (for example, "Polyflow KL-401" manufactured by Kyoeisha Chemical Co., Ltd.) may also be used.

[0044] When the aqueous ink of the present invention contains a surfactant, the total proportion of the surfactant in the total amount of the aqueous ink is preferably 0.1% by mass or more and 3.0% by mass or less. If the above proportion is 0.1% by mass or more, the wettability of the substrate can be enhanced and the effect of maintaining the adhesion to the substrate can be obtained. Further, if the above proportion is 3.0% by mass or less, the abrasion resistance, water abrasion resistance, and scratch resistance can be maintained well. From the same viewpoint, the above proportion is more preferably 1.0% by mass or less.

[0045] (Wax) In addition to the above, the aqueous ink of the present invention can further contain wax. As the wax, hydrocarbon wax is preferable. Specifically, examples of the wax include liquid paraffin, natural paraffin, synthetic paraffin, microcrystalline wax, polyethylene wax, fluorocarbon wax, ethylene-propylene copolymer wax, tetrafluoroethylene resin wax, Fischer-Tropsch wax, and the like. These waxes may be used alone or in combination of two or more. Among them, polyethylene wax is preferable as the wax.

[0046] When the aqueous ink of the present invention contains wax, the total proportion of the wax in the total amount of the aqueous ink is preferably 0.5% by mass or more and 5.0% by mass or less. If the above proportion is 0.5% by mass or more, the effect of maintaining water and abrasion resistance can be obtained. Also, if the above proportion is 5.0% by mass or less, good adhesion to the substrate, water and abrasion resistance, and antiblocking properties can be maintained.

[0047] (Other components) In addition to the above, the aqueous ink of the present invention can contain an appropriate amount of other components such as general-purpose resins other than the above binder resin, extender pigments, lubricants (such as oleic acid amide, stearic acid amide, erucic acid amide), pigment dispersants, leveling agents, antifoaming agents (such as silicone-based antifoaming agents, non-silicone-based antifoaming agents), plasticizers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, and the like, as required.

[0048] (Method for producing aqueous ink) The method for manufacturing the aqueous ink of the present invention is not particularly limited. For example, after dispersing a mixture added with an aqueous solvent, an antifoaming agent, etc., a binder resin, an aqueous solvent, an aziridine-based curing agent, and additives such as a surfactant as required are added and stirred and mixed to obtain an aqueous ink. In the above-mentioned dispersion and stirring and mixing, dispersers such as a bead mill, an Eiger mill, a sand mill, a gamma mill, an attritor, etc., which are generally used in the production of inks for flexographic printing or gravure printing, can be used.

[0049] Also, as described later, the aqueous ink of the present invention is preferably used for flexographic printing or gravure printing.

[0050] When the aqueous ink of the present invention is used for flexographic printing or gravure printing, that is, when the aqueous ink of the present invention is used as a flexographic ink or a gravure ink, its viscosity may be 7 to 25 seconds at 25 °C when using a RK Print Coat Instruments Zahn Cup #4, and more preferably 10 to 20 seconds. Also, the surface tension of the ink at 25 °C is preferably 25 to 50 mN / m. The lower the surface tension of the ink, the better the wettability of the ink to a substrate such as a film. However, when the surface tension is less than 25 mN / m, due to the wetting spread of the ink, adjacent dots in the halftone dot portion tend to be easily connected. And this tends to cause contamination of the printed surface called dot bridging. On the other hand, when the surface tension exceeds 50 mN / m, the wettability of the ink to a substrate such as a film decreases, which tends to cause repelling. From the same viewpoint, the surface tension of the ink at 25 °C is more preferably 33 mN / m or more, and more preferably 43 mN / m or less.

[0051] (Laminate) The laminate of the present invention includes a substrate and an ink layer provided on the substrate, and is characterized in that the ink layer is a printed layer of the above-mentioned aqueous ink. That is, the laminate of the present invention is obtained by printing the above-mentioned aqueous ink on a substrate.

[0052] Examples of the base material include thermoplastic resin films, paper, synthetic paper, steel plates, aluminum foils, wood, woven fabrics, knitted fabrics, non-woven fabrics, gypsum boards, wooden boards, and the like. Among these, as the base material, paper, synthetic paper, thermoplastic resin films, and the like are preferable. Further, the base material may be a combination of multiple types of the above-mentioned materials. For example, a laminated base material in which paper and a thermoplastic resin film are laminated, a laminated base material in which a thermoplastic resin film and an aluminum foil are laminated, and the like may be used. In the case of a combination of multiple types, the lamination method is not particularly limited, and a general one-component adhesive, two-component adhesive, or the like may be used for adhesion, or a laminated base material bonded by extrusion molding may be used if there are multiple thermoplastic resin films.

[0053] The thermoplastic resin film is not particularly limited. For example, polyamide resins such as nylon 6, nylon 66, and nylon 46; polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; biodegradable resins typified by polyhydroxycarboxylic acids such as polylactic acid, aliphatic polyester resins such as poly(ethylene succinate) and poly(butylene succinate); polyolefin resins such as polypropylene (PP) and polyethylene; polyimide resins; polyarylate resins; or films made of thermoplastic resins such as mixtures thereof, and laminated films in which a plurality of these are laminated are also included. Among these, as the thermoplastic resin film, films made of polyester, polyamide, polyethylene, and polypropylene are preferable.

[0054] These thermoplastic resin films may be either unstretched films or stretched films, and their manufacturing methods are not particularly limited. Also, the thickness of the thermoplastic resin film as the base material is not particularly limited, but usually it may be in the range of 1 to 500 μm. Further, it is preferable that the surface of the thermoplastic resin film to be printed is subjected to corona discharge treatment. In this case, the adhesion can be further improved. Furthermore, silica, alumina, etc. may be vapor-deposited on the surface of the thermoplastic resin film to be printed, or a gas barrier coating layer such as an oxygen gas barrier layer may be laminated.

[0055] In order to maximize the effects of the present invention, it is preferable to use a base material that is a constituent material of the shrink label, and it is preferable to use a thermoplastic resin film that shrinks by heat treatment. Among them, it is preferable to use a heat-shrinkable thermoplastic resin film (referred to as a heat-shrink film) having high mechanical strength and chemical strength and good printability. Examples of such heat-shrink films include stretched polyester-based films, shrinkable polyvinyl chloride films, shrinkable polystyrene films, shrinkable polyethylene terephthalate films, shrinkable polypropylene films, and the like. The surface to be the printed surface may be untreated or may be subjected to surface treatments such as plasma treatment, corona treatment, radiation treatment, and silane coupling treatment. The thermoplastic resin film may have a single-layer structure or a multilayer structure. Furthermore, aluminum vapor deposition or transparent vapor deposition may be performed on the thermoplastic resin film.

[0056] Examples of the paper as the base material include kraft paper, liner paper, art paper, coated paper, carton paper, and the like. Also, the structure of the synthetic paper is not particularly limited and may be either a single-layer structure or a multilayer structure. Examples of the multilayer structure include a two-layer structure of a base material layer and a surface layer, a three-layer structure in which surface layers exist on the front and back surfaces of the base material layer, and a multilayer structure in which another resin film layer exists between the base material layer and the surface layer. Each layer of the multilayer structure may or may not contain inorganic or organic fillers. Also, a microporous synthetic paper having a large number of fine voids can be used.

[0057] In this embodiment, an aqueous ink is printed on a substrate to provide a printed layer, thereby obtaining a printed matter. In this regard, usually, the ink is applied to the substrate using a printing method such as gravure printing or flexographic printing, and is dried and fixed by drying with an oven to obtain a printed layer. The drying temperature is usually about 40 to 60°C.

[0058] The thickness of the printed layer of the above-mentioned aqueous ink is not particularly limited, and can be appropriately determined in consideration of various factors such as the ink drying property and running cost during the formation of the printed layer.

[0059] The printed layer of the above-mentioned aqueous ink is preferably formed using a printing method such as flexographic printing or gravure printing. Both flexographic printing and gravure printing are a type of rotary printing, and a printed layer with good properties can be formed. In addition, flexographic printing and gravure printing are preferable in terms of high-speed printing suitability, printing reproducibility, etc.

[0060] Flexographic printing is a type of relief printing. It mainly uses a rubber plate as a printing plate (relief plate), and a finely meshed engraved roll called an anilox roll is used for the part that supplies ink to the printing plate. The anilox roll plays a role of receiving ink from a chamber doctor and applying ink to the printing plate, and has the advantage that the ink can be uniformly transferred to the printing plate through the anilox roll.

[0061] Specifically, ink is applied to the surface of an anilox roll having a large number of partition walls and openings surrounded by the partition walls, a doctor is pressed against the surface of the anilox roll, the ink existing on the top surface of the partition walls of the anilox roll is scraped off, and the ink is filled into the recesses which are the openings. Subsequently, a flexographic plate is pressed against the anilox roll to transfer the ink existing in the recesses of the anilox roll to the convex portions (pattern portions) of the printing plate, and then the plate is brought into contact with the substrate to transfer the ink existing in the pattern portions of the plate to the substrate, thereby obtaining a printed matter.

[0062] In addition, a rotary printing method may be combined. For example, when performing rotary printing using a thermoplastic resin film as a substrate, rotary printing is performed on the surface of the wound thermoplastic resin film using water-based ink. After printing, processes such as lamination, slitting (cutting unnecessary parts of the width portion), and bag making (cutting and heat-sealing into bags) can be performed. By performing rotary printing of water-based ink on the wound thermoplastic resin film, high-speed printing is possible and productivity is excellent.

[0063] Note that as the rotary printing, gravure printing and flexographic printing are mentioned as described above, and either method can be adopted. However, for printing with the water-based ink of the present invention, it is preferable to use the flexographic printing method. Therefore, hereinafter, flexographic printing will be described in detail. Note that in this specification, rotary printing means gravure printing and flexographic printing, and inkjet printing and silk screen printing methods, which are other printing methods, are not included.

[0064] In flexographic printing, the water-based ink is supplied directly from a container storing the water-based ink or via an ink supply pump or the like to an anilox roller having an uneven shape on its surface. The water-based ink supplied to this anilox roller is transferred to the printing plate surface by contact with the convex portions of the printing plate surface, and further transferred to the thermoplastic resin film by contact between the printing plate surface and the thermoplastic resin film, thereby forming a pattern and / or characters.

[0065] When using water-based ink, since the ink drying property is slightly inferior to that of solvent-based flexographic printing ink, it is preferable that the film thickness of the ink is as thin as possible. From this viewpoint, it is preferable that the amount of ink supplied to the anilox roller is as small as possible. On the other hand, when the film thickness becomes thin, the printing density tends to become thin, so it is preferable to appropriately control the concentration of the pigment in the water-based ink used. Specifically, when the concentration of the pigment in the water-based ink is increased by 1 to 5% by weight compared to the concentration of the solvent-based flexographic printing ink, an appropriate printing density can be obtained.

[0066] A wound thermoplastic resin film is a roll-shaped thermoplastic resin film aligned to a specified width, which is a film for rotary printing different from single-sheet paper where each sheet is pre-separated. The width of the film is appropriately selected based on the plate width of the rotary printing machine to be used and the width of the image (pattern) part of the gravure plate. When overlapping colors using rotary printing inks of multiple colors, the order of printing is not particularly limited.

[0067] When performing surface printing, it is common to first print white ink if necessary and then print color ink. When there are multiple color inks, for example, they can be printed in the order of yellow, magenta, cyan, and black, but it is not particularly limited. In the case of the configuration of surface printing, the aqueous ink of the present invention is applied as an overcoat on the printing surface of the rotary printed matter.

[0068] When the color of the base material is white, that is, for example, in the case of a paper base material or a thermoplastic resin film kneaded with a white pigment, printing with only color ink is also possible if necessary.

[0069] When performing reverse printing, it is common to first print color ink on the wound thermoplastic resin film and then print white ink. When there are multiple colors of color ink, for example, they can be printed in the order of black, cyan, magenta, and yellow, but it is not particularly limited. In addition, in a large printing machine, special colors and the like can be used in addition to the above primary colors. That is, a large printing machine has a plurality of printing units corresponding to 5 to 10 colors, each printing unit is equipped with one color of ink, and 5 to 10 colors of overprinting can be performed at once. The printed matter obtained by reverse printing may be used as it is, or an anchor coating agent, an adhesive, etc. may be applied to the printing surface of the obtained rotary printed matter, and after drying if necessary, it can be laminated with a film or the like to form a laminate.

[0070] And the ink layer (printing layer) in the laminate of the present invention has tough film physical properties that can withstand contact with the outside, and is particularly excellent in blocking resistance and water friction resistance, so it is preferably located on the outermost layer. Therefore, in the laminate of the present invention, an intermediate ink layer may be further provided between the base material and the ink layer. Such an intermediate ink layer can be a printing layer of any ink, and may be only one layer, or two or more layers. Further, the intermediate ink layer may be a color ink layer appropriately containing coloring materials such as pigments based on the desired design. The manufacturing method of the intermediate ink layer is not particularly limited either, and for example, it can be manufactured in the same manner as the printing layer of the aqueous ink of the present invention described above.

[0071] The laminate of the present invention has excellent adhesion regardless of the type of base material such as a plastic film, and in addition to the physical properties described in the examples, it also has excellent coating film strength, particularly abrasion resistance and scratch resistance, so it is suitable for the form in which the printing layer is the outermost layer. Therefore, in the case of a front-printed product or a back-printed product, a printed product having a printing layer of the aqueous ink of the present invention on the surface that becomes the outermost layer during distribution can preferably exhibit the effects of the present invention to the maximum extent. The laminate of the present invention can be applied to various uses such as plastic labels (including shrink labels and body-wrapped labels) for beverage and food bottles, integrated packages, and exterior packages. In particular, the laminate of the present invention is preferably used as a heat-shrinkable film in the above-mentioned various uses.

Examples

[0072] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. In the examples, "parts" represents "parts by mass" and "%" represents "% by mass".

[0073] 〔Preparation of Resin A〕 A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux pipe was charged with 60.0 parts by mass of n-propyl acetate. While stirring under a nitrogen atmosphere, the temperature was raised to 90 °C. On the other hand, 32.5 parts by mass of methyl methacrylate, 20.0 parts by mass of ethyl methacrylate, 15.0 parts by mass of n-butyl methacrylate, 10.0 parts by mass of isobutyl methacrylate, 15.0 parts by mass of 2-ethylhexyl acrylate, 7.5 parts by mass of acrylic acid, and 1.0 part by mass of azobisisobutyronitrile were dissolved in 40.0 parts by mass of n-propyl acetate and dropped using a dropping funnel over 4 hours. After completion of the dropping, the reaction was further carried out for 6 hours. After completion of the reaction, cooling was performed, and 8.0 parts by mass of 30% aqueous ammonia was added to the obtained acrylic resin solution for neutralization. Further, ion-exchanged water was added and solvent substitution was carried out while heating to obtain an aqueous solution of an acrylic resin having a solid content of 55%. The above resin had an acid value of 58 mgKOH / g and a Tg of 52 °C. Thereafter, 121.2 parts by mass of the above aqueous solution of the acrylic resin was charged into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux pipe, and 195.5 parts by mass of ion-exchanged water was added. While stirring under a nitrogen atmosphere, the temperature was raised to 75 °C. Subsequently, using a dropping funnel, 40.0 parts by mass of methyl methacrylate, 20.0 parts by mass of butyl acrylate, 25.0 parts by mass of ethyl methacrylate, 15.0 parts by mass of 2-ethylhexyl acrylate, and 3.5 parts by mass of 30% ammonium persulfate were dropped over 4 hours. After completion of the dropping, the reaction was further carried out for 6 hours to obtain a core-shell type acrylic emulsion (resin A) having a solid content of 40%. Resin A had an acid value of 23 mgKOH / g and a Tg of 32 °C.

[0074] [Preparation of Resin B, Resin C, Resin D, Resin E, Resin F, Resin G, Resin H, Resin I, and Resin J] Regarding Resin B, Resin C, Resin D, Resin E, Resin F, Resin G, Resin H, Resin I, and Resin J, in the preparation of the above acrylic emulsion (resin A), the conditions were appropriately changed so that the values of Tg and acid value shown in Table 1 were obtained, and they were prepared.

[0075] [Preparation of Resin a] 80.0 parts by mass of methyl triglycol was charged into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux tube. While stirring under a nitrogen atmosphere, the temperature was raised to 90 °C. Next, using two dropping funnels, 40.0 parts of lauryl methacrylate, 23.0 parts of ethyl methacrylate, 16.0 parts of 2-ethylhexyl acrylate, and 21.0 parts of acrylic acid were dropped from one over 4 hours. From the other, 5.0 parts of azobisisobutyronitrile was dissolved in 10.0 parts of methyl isobutyl ketone and dropped over 4.5 hours. After completion of the dropping, the reaction was further carried out for 4 hours. After completion of the reaction, cooling was performed, and 8.0 parts by mass of 30% aqueous ammonia was added to 55 parts of the obtained acrylic resin solution for neutralization. Further, ion-exchanged water was added and solvent substitution was carried out while heating to obtain an acrylic-soluble water-soluble resin having a solid content of 21%. Resin a had an acid value of 164 mgKOH / g and a Tg of 30 °C.

[0076] [Preparation of Resin b, Resin c, Resin d, Resin e, Resin f, Resin g, and Resin h] For Resin b, Resin c, Resin d, Resin e, Resin f, Resin g, and Resin h, in the preparation of the above-described alkali-soluble water-soluble resin (Resin a), the conditions were appropriately changed so as to obtain the Tg and acid value shown in Table 1, respectively, and they were prepared.

[0077] [Preparation of Aqueous Ink and Laminate] In each example, an aqueous ink was prepared according to a conventional method with the formulation shown in Table 1. On the other hand, as a substrate, a corona-treated polystyrene heat-shrinkable film (BonSet BS55S, thickness 50 μm, manufactured by Takiron Shiaei Co., Ltd.) was prepared, and as a printing apparatus, a Flexoproof100 test printing machine (manufactured by Testing Machines, Inc., anilox 200 lines / inch) was prepared. Then, a solid pattern of 240 mm in length and 80 mm in width of the aqueous ink of each example was printed at a printing speed of 100 m / min using the anilox roll and resin plate of this test printing machine. Next, the obtained printed matter was aged at 25 °C for 24 hours to obtain a printed ink laminate.

[0078] The following evaluations were performed on the obtained laminate.

[0079] (Substrate adhesion) A cellophane tape was attached to the surface of the ink layer of the laminate. Then, the cellophane tape was quickly peeled off, and the degree of peeling of the ink layer (film) from the substrate at that time was visually observed and evaluated according to the following criteria. Note that the evaluation result of 4.5 is the case where the evaluation results of 4 and 5 are mixed at the same level among multiple evaluations. The practical level is 4 or higher. 5: No peeling of the ink layer 4: The peeling area of the ink layer is more than 0% and less than 10% of the printing area 3: The peeling area of the ink layer is 10% or more and less than 30% of the printing area 2: The peeling area of the ink layer is 30% or more and less than 75% of the printing area 1: The peeling area of the ink layer is 75% or more of the printing area

[0080] (Blocking resistance) Two laminates were prepared, and their printing surfaces of the ink layers were put together and left standing at 40 °C and 80% humidity under a load of 5 kg / cm 2 for 1 day. Then, it was peeled off by hand, and the presence or absence of peeling resistance and the degree of transfer of the ink layer (film) at that time were visually observed and evaluated according to the following criteria. Note that the evaluation result of 4.5 is the case where the evaluation results of 4 and 5 are mixed at the same level among multiple evaluations. The practical level is 4 or higher. 5: No transfer of the ink layer, no peeling resistance 4: No transfer of the ink layer, but there is peeling resistance 3: The transfer amount of the ink layer is less than 10% of the printing area, and there is peeling resistance 2: The transfer amount of the ink layer is 10% or more and less than 50% of the printing area, and there is peeling resistance 1: The transfer amount of the ink layer is 50% or more of the printing area, and there is peeling resistance

[0081] (Water rubbing resistance) A canakin soaked in water was applied to the formation surface of the ink layer of the laminate, and friction was applied 100 times with a load of 200 g using a Kagaku-Shinkou type friction fastness tester. The degree of peeling of the ink layer (film) at this time was visually observed and evaluated according to the following criteria. The practical level is 4 or more. 5: No peeling of the ink layer 4: The peeled area of the ink layer is more than 0% and less than 10% of the printed area 3: The peeled area of the ink layer is 10% or more and less than 50% of the printed area 2: The peeled area of the ink layer is 50% or more and less than 70% of the printed area 1: The peeled area of the ink layer is 70% or more of the printed area

[0082] (Shrinkage suitability (whitening during heat shrinkage)) The laminate was cut into a size of 20 cm × 10 cm, immersed in hot water at 90 °C for 30 seconds, and shrunk to a size of 10 cm × 10 cm. Then, the printed surface of the ink layer was measured with a haze meter using the haze value. The practical level is 4 or more. 5: Haze value less than 30 4: Haze value 30 or more and less than 40 3: Haze value 40 or more and less than 50 4: Haze value 50 or more and less than 60 5: Haze value 60 or more

[0083] The aqueous ink compositions of the examples and comparative examples, and the evaluation results are shown in Tables 1 to 3. Note that the blank spaces represent non-formulation.

[0084]

Table 1

[0085]

Table 2

[0086]

Table 3

[0087] In each table, for each binder resin, the glass transition temperature (Tg, unit: °C), acid value (AV, unit: mgKOH / g), and the ratio of non-volatile content (NV value, unit: mass%) are also shown.

[0088] Details of each component other than the binder resin in each table are as follows.

[0089] Defoaming agent: Organically modified polysiloxane emulsifier (manufactured by Evonik, "TEGO (registered trademark) Formax1488") Surface conditioner: Alcohol alkoxylate (manufactured by BYK, "BYK-DYNWET800") Wax: Polyethylene wax (manufactured by BYK, "AQUACER531") Silicone-based additive: Silicon emulsion (manufactured by Evonik, "Tego Glide490") Aziridine-based curing agent: "PZ-33" manufactured by Nippon Shokubai Co., Ltd., NV value: 100 mass%

[0090] From each table, in the examples according to the present invention, good evaluation results are obtained in all of substrate adhesion, blocking resistance, water friction resistance, and shrinkage suitability. In addition to the adhesion to the substrate, it can be seen that the various durability is excellent.

[0091] On the other hand, in the comparative examples, poor evaluation results were obtained in at least one of substrate adhesion, blocking resistance, water friction resistance, and shrinkage suitability.

[0092] The reason is as follows. In Comparative Example 1, since only an aqueous (meth)acrylic emulsion was used as the binder resin and no alkali-soluble water-soluble resin was used, flexibility could not be imparted to the coating film after two-component curing and it was too hard, so it is considered that the shrinkage suitability deteriorated. In Comparative Example 2, since only an alkali-soluble water-soluble resin was used as the binder resin and no aqueous (meth)acrylic emulsion was used, the affinity for water increased and it is considered that the water resistance friction and blocking properties under high humidity (humidity 80%) deteriorated. In Comparative Examples 3 and 4, since the glass transition temperature of the aqueous (meth)acrylic emulsion used as the binder resin was too high, the flexibility of the coating film was impaired and it is considered that the shrinkage suitability deteriorated. In Comparative Example 5, since the glass transition temperature and acid value of the alkali-soluble water-soluble resin used as the binder resin were too high, the affinity for water increased and the flexibility of the coating film was impaired, so it is considered that the water resistance friction and shrinkage suitability deteriorated.

[0093] According to the present invention, it is possible to provide an aqueous ink capable of obtaining a film excellent in substrate adhesion, blocking resistance, water resistance friction, and shrinkage suitability. Further, according to the present invention, it is possible to provide a laminate including an ink layer excellent in adhesion, blocking resistance, water resistance friction, and shrinkage suitability as a film.

Claims

1. Containing a binder resin, a curing agent, and an aqueous solvent, The binder resin contains an aqueous (meth)acrylic emulsion and an alkali-soluble water-soluble resin, The mass ratio of the non-volatile content of the aqueous (meth)acrylic emulsion to the alkali-soluble water-soluble resin is aqueous (meth)acrylic emulsion / alkali-soluble water-soluble resin = 10 / 90 to 90 / 10, An aqueous ink characterized in that the glass transition temperature (Tg) of the aqueous (meth)acrylic emulsion is -30 to 60°C.

2. The aqueous ink according to claim 1, wherein the acid value of the aqueous (meth)acrylic emulsion is 0 mgKOH / g to 100 mgKOH / g.

3. The aqueous ink according to claim 1 or 2, wherein the glass transition temperature (Tg) of the alkali-soluble water-soluble resin is 10 to 130°C.

4. The aqueous ink according to claim 1 or 2, wherein the acid value of the alkali-soluble water-soluble resin is 40 mgKOH / g to 230 mgKOH / g.

5. The aqueous ink according to claim 1 or 2, wherein the curing agent is an aziridine-based curing agent.

6. The aqueous ink according to claim 1 or 2, wherein at least one of the aqueous (meth)acrylic emulsion and the alkali-soluble water-soluble resin is a styrene acrylic resin.

7. The aqueous ink according to claim 1 or 2, wherein at least one of the aqueous (meth)acrylic emulsion and the alkali-soluble water-soluble resin contains a self-crosslinking component.

8. The aqueous ink according to claim 1 or 2, which is used for flexographic printing or gravure printing.

9. A laminate comprising a heat-shrinkable film and a varnish layer provided on the heat-shrinkable film, wherein the varnish layer is a printed layer of the aqueous ink according to claim 1 or 2.

10. The laminate according to claim 9, further comprising an intermediate ink layer between the shrinkable film and the varnish layer.

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