Flexographic Ink for Solvent-Type Lamination and Its Use

Abstract

To provide flexographic ink which has good plate tangling property in flexographic printing, and is excellent in laminate strength in extrusion laminate processing.SOLUTION: Flexographic ink for solvent type laminate contains an urethane resin, wherein the urethane resin includes a structural unit derived from polyether polyol and / or a structural unit derived from aliphatic diol, and has urethane bond concentration of 2.6 or more and 5.0 or less (mmol / g).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a flexographic ink for solvent-based laminates, printed matter thereof, and laminates.

Background Art

[0002] Flexographic inks are widely used as pattern prints for the purpose of imparting cosmetic and functional properties to printed objects. In recent years, however, demands for printing inks have diversified year by year, including the diversity of packaging materials, the sophistication of packaging technologies, and efforts to address the environment from the perspective of regulatory aspects represented by organic solvents.

[0003] Among flexographic inks, inks used particularly for the printing layer of laminate laminates often use urethane resins in order to maintain and improve laminate strength. This is because urethane resins can be freely designed into coatings ranging from hard and tough coatings to flexible and elastic coatings by selecting isocyanates, polyols, etc.

[0004] As methods for producing laminate laminates, there are extrusion lamination methods, dry lamination methods, and solventless lamination methods. From the perspective of running costs, extrusion lamination methods are often used for light packaging materials such as snack foods. In the production, an anchor layer, a melt-adhesive olefin resin, and a sealant base material are laminated on the printed matter. Generally, it is difficult to obtain strong laminate strength with this lamination structure.

[0005] Hitherto, it has been known that the adhesiveness and laminate strength in plastic base materials such as OPP films, PET films, and NY films are improved in printing inks using urethane resins mainly composed of polyester polyols and vinyl chloride copolymer resins (Patent Documents 1 and 2).

[0006] In the above printing ink, while ester-based organic solvents are widely used, the resin plates used in flexographic printing have low resistance to such ester-based solvents, and problems such as swelling of the plates during long-run printing and easy occurrence of density changes in printed matter have existed. Furthermore, printing inks using urethane resins mainly composed of the above polyester polyol do not have sufficient solubility in alcohol-based solvents. Therefore, ink deposition on relief plates, resulting in a printing defect called plate clogging, still cannot be resolved.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a flexographic ink having good plate clogging resistance in flexographic printing and excellent laminating strength in extrusion lamination and the like.

Means for Solving the Problems

[0009] As a result of intensive studies, the inventors of the present application have found that the above problems can be solved by using the flexographic ink for solvent-based lamination described below, and have thus completed the present invention.

[0010] That is, the present invention is a flexographic ink for solvent-based lamination containing a urethane resin and a solvent, wherein the urethane resin contains structural units derived from polyether polyol and / or structural units derived from aliphatic diol, and the urethane bond concentration is 2.6 or more and 5.0 or less (mmol / g), and relates to a flexographic ink for solvent-based lamination.

[0011] Further, the present invention relates to a flexographic ink for solvent-based lamination, wherein the urethane resin contains a structural unit derived from a polyether polyol and a structural unit derived from an aliphatic diol, and the mass ratio of the structural unit derived from the polyether polyol to the structural unit derived from the aliphatic diol is 5:95 to 95:5.

[0012] Further, the present invention relates to a flexographic ink for solvent-based lamination, wherein the aliphatic diol has a branched structure.

[0013] Further, the present invention relates to a flexographic ink for solvent-based lamination, which further contains at least one selected from the group consisting of a cellulose resin, a polyvinyl acetal resin, and a rosin resin.

[0014] Further, the present invention relates to a flexographic ink for solvent-based lamination, which further contains a chelating crosslinking agent and / or a plasticizer.

[0015] Further, the present invention relates to a flexographic ink for solvent-based lamination, wherein the solvent contains an ester-based organic solvent and an alcohol-based organic solvent, and the mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is 60:40 to 5:95.

[0016] Further, the present invention relates to a printed matter having a printing layer made of the above-mentioned flexographic ink for solvent-based lamination on a substrate 1.

[0017] Further, the present invention relates to a laminate having an adhesive layer and a substrate 2 in this order on the printing layer of the above-mentioned printed matter.

Advantages of the Invention

[0018] According to the present invention, it has become possible to provide a flexographic ink having good plate adhesion in flexographic printing and excellent lamination strength in extrusion lamination processing and the like.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail with examples. However, the matters described below are examples or representative examples of the embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist thereof.

[0020] The present invention is a flexographic ink for solvent-based laminates containing a urethane resin. Part or all of the urethane resin contains structural units derived from polyether polyol and / or aliphatic diol, and the urethane bond concentration is 2.6 or more and 5.0 or less (mmol / g). By containing the urethane resin, it has the effect of imparting appropriate solubility and flexibility. As a result, it is considered to contribute to the improvement of properties such as printability and laminate strength.

[0021] In this specification, "flexographic ink" may sometimes be simply referred to as "ink" or "printing ink", which are synonymous. The layer formed from the flexographic ink is referred to as a "printing layer" or an "ink film".

[0022] (Urethane resin) The urethane resin is preferably contained in the total mass of the ink in an amount of 3 to 25% by mass, more preferably 5 to 22% by mass, as the mass of the non-volatile component. In addition, two or more kinds of urethane resins can be mixed and used in the ink of the present invention.

[0023] The urethane resin in the present invention is preferably obtained by reacting a polyether polyol and / or an aliphatic diol with a polyisocyanate to obtain a urethane polymer having terminal isocyanate groups, and then reacting the urethane polymer with an alcohol or a polyamine. The mass ratio of the structural unit derived from the polyether polyol to the structural unit derived from the aliphatic diol is preferably 5:95 to 95:5, more preferably 90:10 to 25:75, and even more preferably 80:20 to 40:60. This is for improving the laminating suitability and the plate entanglement property. Also, the weight average molecular weight of the urethane resin is preferably 2000 to 90000, more preferably 4000 to 70000 or 4000 to 55000. This is because it can achieve both the laminating strength and the plate entanglement performance during flexographic printing.

[0024] In addition, in the above, the case where the aliphatic diol is a polyether polyol is excluded. The aliphatic diol refers to a substituted or unsubstituted alkanediol (alkylene glycol).

[0025] The urethane resin may contain a structural unit derived from a polyol other than those described above (other polyols). Examples of other polyols include polyester polyols (including polylactone polyols), polycarbonate polyols, polyolefin polyols, castor oil polyols, hydrogenated castor oil polyols, and the like. Preferably, it is a polyester polyol. This is because it can ensure solubility in ester solvents and alcohol solvents.

[0026] (polyether polyol) Suitable examples of the polyether polyol include polymers or copolymers such as methylene oxide, ethylene oxide, propylene oxide, and tetrahydrofuran. These can be used alone or in admixture of two or more thereof. More specifically, it preferably includes polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytrimethylene glycol, and copolymers thereof, and still more preferably includes polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0027] The polyether polyol may be used alone or in combination of two or more. The number average molecular weight of the polyether polyol is preferably from 200 to 5000, more preferably from 200 to 4000, in order to ensure blocking resistance and solubility.

[0028] (Aliphatic diol) The aliphatic diol excludes the case where it is a polyether polyol. The aliphatic diol refers to a substituted or unsubstituted alkanediol (alkylene glycol), and the alkanediol preferably has 2 to 10 carbon atoms. For example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 3,3,5-trimethylpentanediol, 2,4-diethyl-1,5-pentanediol, 1,12-octadecanediol, 1-monoglyceride, 2-monoglyceride, 1-monoglycerin ether, 2-monoglycerin ether, dimer diol, hydrogenated dimer diol, etc. are preferably exemplified.

[0029] Among the above aliphatic diols, aliphatic diols having a branched structure are preferred, and 2-butyl-2-ethyl-1,3-propanediol (hereinafter also referred to as BEPG), 2-methyl-1,3-propanediol (hereinafter also referred to as MPO), 3-methyl-1,5-pentanediol (also referred to as MPD), neopentyl glycol (also referred to as NPG), 1,2-propylene glycol (hereinafter also referred to as PG), 2,4-diethyl-1,5-pentanediol, 1,3-butanediol, dipropylene glycol and the like are preferably mentioned. Among them, it is preferably at least one diol having a selected structure selected from MPO, MPD, BEPG, NPG, PG, 2,4-diethyl-1,5-pentanediol, and it is more preferable to use NPG and / or BEPG, and it is particularly preferable to use BEPG. This is because the laminate strength and blocking property are improved.

[0030] As the above polyisocyanate, diisocyanate is preferable, and as such a compound, various known aromatic, aliphatic or alicyclic diisocyanates can be used. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanate obtained by converting the carboxyl group of dimer acid into an isocyanate group are cited as typical examples. These can be used alone or in admixture of two or more. Among them, isophorone diisocyanate, tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate are preferable, and 4,4'-diphenylmethane diisocyanate is more preferable from the viewpoint of lamination suitability.

[0031] The above polyamine is preferably an organic diamine. Examples of such diamines include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, etc. Amines having a hydroxyl group in the molecule, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypyrropyethylethylenediamine, and di-2-hydroxypyrropyethylethylenediamine, can also be used. These organic diamines can be used alone or in combination of two or more, and isophoronediamine is preferred. Further, polyfunctional amines having 3 or more amino groups, such as diethylenetriamine, iminobispropylamine: (IBPA, 3,3'-diaminodipropylamine), N-(3-aminopropyl)butane-1,4-diamine: (spermidine), 6,6-iminodihexylamine, 3,7-diazanonane-1,9-diamine, N,N'-bis(3-aminopropyl)ethylenediamine, etc., can also be used in combination with the above organic diamines.

[0032] (Urethane bond concentration) The urethane bond concentration is, for example, a value calculated by the calculation method described in JP-A-2016-130297.

[0033] Urethane bond concentration ={(W1×OH1 + W2×OH2 + ··· + W i ×OH i )×1000} / (56100×S) Formula (1) In Formula (1), each is as follows. W1: Weight of polyol 1 OH1: Hydroxyl value of polyol 1 W2: Weight of polyol 2 OH2: Hydroxyl value of polyol 2 W i : Weight of polyol i OH i : Hydroxyl value of polyol i S: Weight of urethane resin solid content

[0034] For simplicity, when the isocyanate group is in excess, it can be understood as the number of moles of hydroxyl groups modified (urethane-bonded) by the isocyanate group, and when the hydroxyl group is in excess, it is the number of moles of isocyanate groups modified by the hydroxyl group. For example, the urethane bond concentration refers to the value represented by the following formula. · When (NCO molar equivalent / OH molar equivalent) > 1 Formula (1) Urethane bond concentration (mmol / g) = Total number of moles of hydroxyl groups (mmol) / Total solid content (g) Here, the total number of moles of hydroxyl groups refers to the total number of moles of hydroxyl groups possessed by the polymer polyol, aliphatic diol, and other polyols used in the reaction to form urethane. Also, the total solid content refers to the total mass of the non-volatile components that become the polyurethane resin. · When (NCO molar equivalent / OH molar equivalent) < 1 Formula (2) Urethane bond concentration (mmol / g) = Total number of moles of isocyanate groups (mmol) / Total solid content (g) Here, the total number of moles of isocyanate groups refers to the total number of moles of isocyanate groups possessed by the polyisocyanate used in the reaction to form urethane.

[0035] <Urea bond concentration> The urea bond concentration refers to the value represented by the following formula. After synthesizing a prepolymer having a terminal isocyanate group under the condition of (NCO molar equivalent / OH molar equivalent) > 1 above and then chain-extending it with polyamine, when the polyurethane resin has an amino group at the terminal, it is represented by the following formula (3). Formula (3) Urea bond concentration (mmol / g) = [Total number of moles of isocyanate groups (mmol) - Total number of moles of hydroxyl groups (mmol)] / Total solid content (g) After synthesizing a prepolymer having terminal isocyanate groups under the condition of (NCO molar equivalent / OH molar equivalent) > 1 and then chain-extending with a polyamine, when the polyurethane resin has isocyanate groups at its terminals, it is represented by the following formula (4). Formula (4) Urea bond concentration (mmol / g) = (total number of amino group moles (mmol)) / total solid content (g) Here, the total number of amino group moles refers to the total number of moles of amino groups in the polyamine used to react with the prepolymer having terminal isocyanate groups to form urea bonds.

[0036] The urethane resin in the present invention preferably has a urethane bond concentration of 2.6 or more and 5.0 or less (mmol / g), more preferably 2.8 or more and 4.5 or less (mmol / g), and still more preferably 3.0 or more and 4.2 or less (mmol / g). This is because these compositions result in good lamination strength and plate adhesion performance during flexographic printing.

[0037] The urethane resin in the present invention preferably has a urea bond concentration of 1.0 or less (mmol / g), 0.7 or less (mmol / g), or 0.5 or less (mmol / g). (The term "or less" includes the case of 0.0 (mmol / g).) This is for improving plate adhesion.

[0038] The urethane resin may or may not have a urea bond. The production method in the case of having a urea bond is not particularly limited, but when the number of isocyanate groups in the prepolymer having terminal isocyanate groups obtained by reacting a polyol and / or an aliphatic diol and a polyisocyanate is set to 1, the total quantity of amino groups in the chain extender and the reaction terminator is preferably in the range of 0.2 to 1.5.

[0039] The terminal groups in the urethane resin refer to, for example, if the structure of the urethane resin is a linear structure, both ends of the linear structure are called terminal groups, and if the structure of the urethane resin is a branched structure, the end portions including the ends of the branches are also called terminal groups. Although the terminal group is not particularly limited, among others, the terminal group is preferably an alkyl group and / or a hydroxyl group. When having a hydroxyl group, the hydroxyl value of the urethane resin is preferably 0.1 to 35 mgKOH / g, and more preferably 0.5 to 20 mgKOH / g. When having an alkyl group as the terminal group, the number of carbon atoms is preferably 1 to 10, more preferably 1 to 8, and still more preferably 1 to 5. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tertiary butyl group, a pentyl group, a hexyl group, etc.

[0040] As one embodiment, in order to introduce a hydroxyl group and an alkyl group to the terminal of the urethane resin, after reacting a polyol with a polyisocyanate to obtain a urethane prepolymer having terminal isocyanate groups, a method of using a polymerization terminator to introduce a terminal structure derived from the polymerization terminator can be mentioned, etc. When it is desired to introduce an alkyl group to the isocyanate terminal after the reaction, it is preferable to use a monoalcohol as the polymerization terminator, and monoalcohols having 1 to 8 carbon atoms such as ethanol, isopropanol, normal propanol, butanol and hexanol are suitable. In addition, when having a plurality of carbon atoms and there are structural isomers, those structural isomers are also included. In order to introduce a hydroxyl group to the terminal of the urethane resin, it is preferable to use a diol or an amino alcohol as the polymerization terminator. Examples of the diol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, etc. Preferably mentioned. Examples of the amino alcohol include 2-ethanolamine, 4-butanolamine, 3-propanolamine, etc., and amino alcohols having 1 to 8 carbon atoms are suitable. In addition, when having a plurality of carbon atoms and there are structural isomers, those structural isomers are also included. Also, in the case of reacting the above polyol with a polyisocyanate, a method of obtaining a urethane resin having a hydroxyl group at the terminal by making the hydroxyl value of the polyol excessive is also preferably mentioned.

[0041] (Cellulose resin) The cellulose resin is preferably obtained by reacting natural cellulose with nitric acid to substitute three hydroxyl groups in the six-membered ring of the anhydroglucopyranose group in natural cellulose with nitrate groups to form a nitrate ester. The weight average molecular weight is preferably from 10,000 to 100,000, more preferably from 10,000 to 80,000. This is because the strength of the ink film is improved, and the solubility in solvents, the low-temperature stability of the ink, and the compatibility with the combined resin are improved. Further, the nitrogen content in the cellulose resin is preferably 10.5 to 12.5% by mass. This is because it has a high affinity for alcohol solvents and good flexographic printing suitability. In addition, cellulose acetate propionate and cellulose acetate butyrate are also preferably used. The cellulose resin is preferably contained in the total ink mass in an amount of 0.5 to 15% by mass, more preferably 1.5 to 12% by mass, as the total mass of the non-volatile components.

[0042] (Polyvinyl acetal resin) The polyvinyl acetal resin is obtained by reacting polyvinyl alcohol with an aldehyde such as butyraldehyde and / or formaldehyde for acetal cyclization, and preferably contains vinyl alcohol units, vinyl acetate units and acetal ring groups. The polyvinyl acetal resin preferably contains 60 to 90% by mass of acetal rings, 5 to 30% by mass of vinyl alcohol units, and 0.5 to 10% by mass of vinyl acetate units. More preferably, it is a polyvinyl butyral resin having a butyral ring as the acetal ring. The weight average molecular weight of the polyvinyl acetal resin is preferably from 10,000 to 100,000, more preferably from 10,000 to 80,000. The glass transition point of the polyvinyl acetal resin is preferably from 50 to 80°C, more preferably from 60 to 75°C.

[0043] (Rosin resin) A rosin resin refers to a resin having as a main component structural units derived from rosin acids (for example, abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, dehydroabietic acid). Here, the main component means 50% by mass or more. The rosin acid or rosin resin may be hydrogenated. Preferably, the rosin resin is at least one selected from the group consisting of rosin-modified phenol resins, rosin ester resins, rosin-modified maleic acid resins, and polymerized rosin resins. The acid value of the rosin resin is preferably 5 to 350 mgKOH / g, more preferably 20 to 350 mgKOH / g, and still more preferably 60 to 320 mgKOH / g. The softening point of the rosin resin is preferably 60 to 180 °C, more preferably 80 to 160 °C. In this specification, the softening point is a measured value by the ring and ball method and can be measured in accordance with JIS K2207.

[0044] As the rosin resin, a rosin ester which is an ester condensation resin of a low molecular weight polyol having a molecular weight of 1,000 or less and rosin acid is preferable. The low molecular weight polyol preferably has 2 to 4 hydroxyl groups in one molecule (hereinafter may be abbreviated as 2 to 4 functional) and a molecular weight of 50 to 500. Examples of such low molecular weight polyols include bifunctional low molecular weight polyols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,10-decanediol; trifunctional low molecular weight polyols such as glycerin, trimethylolpropane; tetrafunctional low molecular weight polyols such as erythritol, pentaerythritol; are preferably used. Among them, trifunctional and / or tetrafunctional low molecular weight polyols are preferable. The weight average molecular weight of the rosin ester is preferably 500 to 2,000, more preferably 500 to 1,500.

[0045] (Other resins) Within the scope not impairing the effects of the present invention, resins other than those described above may be included, for example, acrylic resin, polyamide resin, chlorinated rubber, cyclized rubber, vinyl chloride, vinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyester resin, ketone resin, ethylene-vinyl acetate resin, ethylene-vinyl alcohol resin, styrene-maleic acid resin, casein, alkyd resin.

[0046] (Chelating crosslinking agent) In the present invention, in order to improve the lamination suitability and blocking resistance, it is preferable to use a chelating crosslinking agent. As the chelating crosslinking agent, an organic titanium compound having a Ti-O-C type bond in one molecule is preferable. Specifically, titanium chelates such as titanium alkoxide and titanium acylate can be mentioned. It is preferable to use a titanium chelate. Representative examples of the titanium chelate include titanium alkoxides such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, tetramethyl titanate, tetrastearyl titanate, triethanolamine titanate, titanium acetylacetate, titanium ethyl acetoacetate, titanium lactate, octylene glycol titanate, titanium tetraacetylacetonate and other titanium chelates. Among these, the organic titanium compounds that are titanium chelates generally require heating to complete the crosslinking reaction, but hydrolysis hardly occurs at room temperature, and they are excellent in stability and suitable for use in inks, and can be preferably used. The chelating crosslinking agent is preferably contained in the total mass of the ink in an amount of 0.1 to 8% by mass, and more preferably 0.5 to 5% by mass.

[0047] (Plasticizer) In the present invention, it is preferable to use a plasticizer. This is because the flexibility of the ink film is improved, thereby enhancing the lamination suitability and plate wrapping property. Specifically, examples thereof include citrate esters, castor oil fatty oils, phthalate esters, polyesters, epoxidized vegetable oils, phosphate esters, and sulfonamides. Among them, citrate esters, epoxidized vegetable oils, phosphate esters, and sulfonamides are preferable, and citrate esters are more preferable. In addition, the plasticizer is preferably contained in an amount of 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, and even more preferably 0.8 to 5% by mass based on the total mass of the ink.

[0048] (Other additives) The ink of the present invention may also contain additives such as a leveling agent, an antifoaming agent, wax, a silane coupling agent, a light stabilizer, silica particles, an infrared absorber, an ultraviolet absorber, a fragrance, a flame retardant, and a curing agent, as necessary.

[0049] (Pigment) The ink preferably contains a pigment, but the pigment used is not particularly limited. Any of organic pigments, inorganic pigments, and extender pigments can be used. Among inorganic pigments, those containing titanium oxide are preferable, and among extender pigments, silica, barium sulfate, kaolin, clay, calcium carbonate, magnesium carbonate, etc. are preferable. Among organic pigments, those composed of organic compounds and organometallic complexes are preferably used. When containing a white pigment such as titanium oxide, it is preferably 10 to 80% by mass, and still more preferably 30 to 60% by mass based on the total mass of the ink. When containing an organic pigment or other colored pigments other than the white pigment, it is preferably 5 to 50% by mass, and still more preferably 10 to 40% by mass based on the total mass of the ink.

[0050] (Organic pigment) Examples of the organic pigment include, but are not limited to, the following pigments: soluble azo pigments, insoluble azo pigments, azo pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, anthraquinone pigments, ansanthrone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, azomethine azo pigments, flavanthrone pigments, diketopyrrolopyrrole pigments, isoindoline pigments, indanthrone pigments, carbon black pigments, etc.

[0051] As the hue of the organic pigment, at least one selected from the group consisting of black pigments, blue pigments, green pigments, red pigments, purple pigments, yellow pigments, orange pigments, and brown pigments is preferable. Further, at least one or two or more selected from the group consisting of black pigments, blue pigments, red pigments, and yellow pigments are preferable. Specific examples of the organic pigment are indicated by the C.I. number of the Color Index International (abbreviation: C.I.). Preferably, C.I. Pigment Red 57:1, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, C.I. Pigment Red 146, C.I. Pigment Red 242, C.I. Pigment Yellow 83, C.I. Pigment Yellow 14, C.I. Pigment Orange 38, C.I. Pigment Orange 13, C.I. Pigment Yellow 180, C.I. Pigment Yellow 139, C.I. Pigment Red 185, C.I. Pigment Red 122, C.I. Pigment Red 178, C.I. Pigment Red 149, C.I. Pigment Red 144, C.I. Pigment Red 166, C.I. Pigment Violet 23, C.I. Pigment Violet 37, C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:6, C.I. Pigment Green 7, C.I. Pigment Orange 34, C.I. Pigment Orange 64, C.I. Pigment Black 7, and it is preferable to use one or more of them.

[0052] Examples of the inorganic pigment include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, aluminum particles, mica, bronze powder, chrome vermilion, lead yellow, cadmium yellow, cadmium red, ultramarine, cobalt blue, red iron oxide, yellow iron oxide, iron black, etc. Aluminum has a leafing type or a non-leafing type, and the non-leafing type is preferable.

[0053] (Titanium oxide pigment) In the present invention, as the titanium oxide pigment, any of anatase type, rutile type, and brookite type crystal structures may be used. Among them, the rutile type titanium oxide is preferably used because of good pigment dispersibility. In the industrial production of titanium oxide, rutile ore or ilmenite ore (FeTiO3) is used as a raw material. The main production methods include two types: the chlorine method and the sulfuric acid method, and either method may be used. In addition, in order to improve printability, the titanium oxide pigment is preferably surface-treated. In particular, it is preferably surface-treated with at least one metal selected from Si, Al, Zn, Zr, and their oxides.

[0054] Also, the oil absorption amount measured by the measurement method specified in JIS K5101 is preferably 14 to 35 ml / 100 g, and more preferably 17 to 32 ml / 100 g. Further, the average particle diameter (median particle diameter) measured by a transmission electron microscope is preferably 0.2 to 0.3 μm. Also, a plurality of types of titanium oxide pigments may be used in combination. In the flexographic ink of the present invention, in addition to the titanium oxide pigment, other inorganic pigments and organic pigments can be further used in combination.

[0055] (Organic solvent) The flexographic ink preferably contains an organic solvent. The organic solvent can be appropriately used such as an alcohol-based organic solvent, an ester-based organic solvent, a glycol-based organic solvent, etc., and is preferably a mixed solvent. The organic solvent is preferably contained in the total mass of the flexographic ink in an amount of 30 to 85% by mass. As the alcohol-based organic solvent, ethanol, isopropyl alcohol, n-propyl alcohol, n-butanol, isobutanol, etc. are preferable, and as the ester-based organic solvent, ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, etc. are preferable. As the glycol ether-based organic solvent, ethylene glycol mono n-butyl ether, propylene glycol monopropyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, etc. are preferable. The mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is preferably 60:40 to 5:95, more preferably 50:50 to 15:85, and even more preferably 40:60 to 25:75. By setting this mass ratio, the resin plate used for the flexographic ink can be prevented from being eroded, and good plate-making property can be obtained.

[0056] (Manufacturing method of flexographic ink) The flexographic ink in the present invention can be produced, for example, by first stirring and mixing organic pigments, urethane resins, other resins, organic solvents, etc. in a stirring mixer in advance, and then subjecting the mixture to a pigment dispersion process using a disperser such as a bead mill, and mixing a chelating crosslinking agent and a plasticizer into the obtained dispersion. General dispersers are used in the production of the pigment dispersion. For example, a roller mill, ball mill, pebble mill, attritor, bead mill (such as a sand mill, gamma mill, etc.) can be used. Among them, production by a bead mill disperser such as a sand mill is preferred.

[0057] (Flexographic printing) In the packaging material of the present invention, the printed layer obtained by the flexographic printing method has the characteristics of low film thickness and high concentration, is excellent in the reproducibility of fine characters and sharp color reproduction, and also has less solvent discharge during printing compared to gravure printing, and is effective from the perspective of environmental consideration. Flexographic printing is a printing method in the field of packaging material printing and is a relief printing method. The method for forming the flexographic printing layer may be a known method. For example, in the doctor chamber method, two-roll method, ink pot method, etc., ink is supplied from the ink supply part to the anilox roll, and then the ink is transferred to the convex part of the printing plate made of resin or rubber, and this ink is transferred to the printing object passing between the impression cylinder to form the flexographic printing layer. Examples of the plate include a photosensitive resin plate that utilizes ultraviolet curing by a UV light source or an elastomer material plate that uses a direct laser engraving method. Regardless of the method for forming the image part of the flexographic plate, those with a screening line number of 75 lpi or more are used. As an anilox roll, a ceramic anilox roll with cell engraving, a chrome-plated anilox roll, etc. can be used. In order to obtain a printed matter with excellent dot reproducibility, an anilox roll having a line number of 5 times or more, preferably 6 times or more, the number of plate lines used for printing is used. For example, when the number of plate lines used is 75 lpi, an anilox of 375 lpi or more is required, and when the number of plate lines is 150 lpi, an anilox roll of 750 lpi or more is required. Regarding the anilox capacity, it is a capacity of 1 to 10 cc / m 3 of capacity, preferably 2 to 9 cc / m 3 of an anilox roll. In order to obtain the characteristics of the packaging material of the present invention, the flexographic printing layer preferably uses a plate of 80 to 175 lpi and an anilox roll of 200 to 1400 lpi. As the form of the obtained flexographic printing layer, the film thickness is preferably 0.5 to 10 μm, and more preferably 1 to 8 μm.

[0058] (Printing press) Examples of flexographic printing presses include CI type multicolor flexographic printing presses and unit type multicolor flexographic printing presses. Examples of ink supply methods include chamber method and two-roll method, and an appropriate printing press can be used.

[0059] (Base material 1) The flexographic ink of the present invention is printed on the base material 1 to become a printed matter. As a base material to which the flexographic ink of the present invention can be applied, there are polyethylene, polypropylene and other polyolefin base materials, polycarbonate base materials, polyester base materials (such as polyethylene terephthalate and polylactic acid), polystyrene base materials, polystyrene-based base materials such as AS resin or ABS resin, polyamide base materials, polyvinyl chloride base materials, various base materials of polyvinylidene chloride, cellophane base materials, paper base materials or aluminum foil base materials, etc., or films or sheets made of these composite materials. Among them, polyester base materials and polyamide base materials having a high glass transition temperature are preferably used.

[0060] The above-mentioned base material may be subjected to vapor deposition coating treatment and / or coating treatment such as polyvinyl alcohol on the surface. For example, GL-AE manufactured by Toppan Printing Co., Ltd. with aluminum oxide vapor-deposited on the surface of the base material, IB-PET-PXB manufactured by Dai Nippon Printing Co., Ltd., etc. can be mentioned. Furthermore, those treated with additives such as antistatic agents and ultraviolet inhibitors as necessary, or those with the surface of the base material subjected to corona treatment or low-temperature plasma treatment can also be used.

[0061] (Base material 2) Examples of the base material 2 are the same as those of the base material 1, and they may be the same or different. It is preferably a thermoplastic base material (which may be referred to as a sealant), and a non-stretched polyethylene base material, a non-stretched polypropylene base material, a non-stretched polyester base material, etc. are preferred.

[0062] In the present invention, "for lamination" means a usage form which is a laminate having the base material 1, a printing layer formed from the ink of the present invention, and the base material 2 in this order, and a form which is a laminate having the base material 1, the printing layer, the adhesive layer, and the base material 2 in this order is more preferred.

[0063] (Laminate) The laminate of the present invention is obtained by providing an adhesive layer on the printing layer of a printed matter printed with flexographic ink and laminating (bonding) it with the base material 2. Representative examples of the lamination process include extrusion lamination, dry lamination, non-solvent lamination method, etc. Extrusion lamination is a method in which an anchor coat agent is applied on the printing layer of a printed matter and a molten polyethylene resin, a molten polypropylene resin, etc. are extruded and simultaneously laminated by bonding with the base material. The dry lamination method and the non-solvent lamination method are methods in which an adhesive is applied and dried on the printing layer of a printed matter and heat-pressed and laminated with a sealant. The difference between the dry lamination method and the non-solvent lamination method lies in whether or not they contain an organic solvent or other volatile media.

Examples

[0064] Hereinafter, the present invention will be described in detail with reference to examples. However, the following embodiments are merely examples of the present invention, and the present invention is not limited to these examples. In the present invention, parts and % represent parts by mass and mass %, respectively, unless otherwise noted. Note that Examples 21, 24, and 29 are reference examples.

[0065] <Measurement method of number average molecular weight (Mn) and mass average molecular weight (Mw)> The number average molecular weight (Mn) and mass average molecular weight (Mw) were determined by the GPC (gel permeation chromatography) method. The molecular weight distribution was measured using "Shodex GPC System-21" manufactured by Showa Denko KK, and the molecular weight in terms of polystyrene was determined. The measurement conditions are shown below. Column: A plurality of the following columns were connected in series and used. TSKgel SuperAW2500 manufactured by Tosoh Corporation, TSKgel SuperAW3000 manufactured by Tosoh Corporation, TSKgel SuperAW4000 manufactured by Tosoh Corporation, TSKgel guard column SuperAWH manufactured by Tosoh Corporation Detector: RI (differential refractometer), Measurement conditions: Column temperature 40 °C, Eluent: Tetrahydrofuran Standard substance: Polystyrene Flow rate: 0.5 mL / min

[0066] <Measurement method of hydroxyl value> It was determined according to the method described in JIS K0070.

[0067] [Synthesis Example 1] (Synthesis of urethane resin P1) Into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 20 parts of ethyl acetate, 16 parts of polypropylene glycol with a number average molecular weight of 1000 (hereinafter also abbreviated as PPG), 10 parts of 2-butyl-2-ethyl-1,3-propanediol (hereinafter also abbreviated as BEPG), 24 parts of 4,4'-diphenylmethane diisocyanate (hereinafter also abbreviated as 4,4-MDI), and 0.003 part of tin 2-ethylhexanoate were charged, and the reaction was carried out at 80 °C for 3 hours under a nitrogen stream. Then, 5 parts of ethyl acetate and 25 parts of isopropanol (hereinafter also abbreviated as IPA) were added and cooled to obtain a urethane resin P1 solution with a solid content of 50% and a mass average molecular weight of 14000.

[0068] [Synthesis Examples 2 to 16] (Synthesis of Urethane Resins P2 to P16) Urethane resins P2 to P16 were obtained by the same procedure as in Synthesis Example 1, except that the raw materials and charging ratios shown in Table 1 were used. The abbreviations shown in the table represent the following. · NPG / AdA: A polyester polyol that is a condensate of neopentyl glycol and adipic acid, with a number average molecular weight of 400 · PPG: Polypropylene glycol (those with number average molecular weights of 3,000, 1,000, and 200 were used.) · PEG: Polyethylene glycol with a number average molecular weight of 1,000 · PTMG: Polytetramethylene ether glycol with a number average molecular weight of 1,000 · 1,3PD: 1,3-propanediol · PG: 1,2-propylene glycol · MPO: 2-methyl-1,3-propanediol · NPG: Neopentyl glycol · TDI: Toluene diisocyanate · IPDI: Isophorone diisocyanate · IPDA: Isophorone diamine · AEA: N-(2-aminoethyl)ethanolamine

[0069] [Synthesis Example 17] (Synthesis of Urethane Resin P17) Into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 20 parts of ethyl acetate, 16 parts of polypropylene glycol with a number average molecular weight of 1000, 10 parts of 2-butyl-2-ethyl-1,3-propanediol, 23.5 parts of 4,4'-diphenylmethane diisocyanate, and 0.003 parts of tin 2-ethylhexanoate were charged, and the reaction was carried out at 80 °C for 3 hours under a nitrogen stream. Then, 5 parts of ethyl acetate was added and cooled to obtain a solution of a terminal isocyanate prepolymer. Next, 0.5 part of isophoronediamine (hereinafter also abbreviated as IPDA) was gradually added to the obtained solution of the terminal isocyanate prepolymer at room temperature, and then the reaction was carried out at 50 °C for 1 hour. Thereafter, 25 parts of isopropanol was added and cooled to obtain a urethane resin P15 solution having a solid content of 50% and a mass average molecular weight of 52000.

[0070] [Synthesis Example 18] (Synthesis of urethane resin P18) A urethane resin P18 was obtained in the same manner as in Synthesis Example 17, except that the raw materials and the charging ratios described in Table 1 were used.

[0071] [Comparative Synthesis Examples 1 to 3] (Synthesis of urethane resins PP1 to PP3) Urethane resins PP1 to PP3 were obtained in the same manner as in Synthesis Example 1, except that the raw materials and the charging ratios described in Table 1 were used.

[0072] [Table 1]

[0073] [Example 1] (Production of ink S1) 20 parts of a urethane resin P1 solution, 15 parts of C.I. Pigment Blue 15:4 (manufactured by Toyo Color Co., Ltd.: LIONOL BLUE FG-7400-G), 10 parts of a cellulose resin solution (manufactured by Inaba Sangyo Co., Ltd.: DHX4-6, nitrogen content 10.5 - 12.5% by mass, weight average molecular weight 22000) (solid content 50%, ethyl acetate / IPA = 50 / 50), and 10 parts of ethyl acetate were mixed and dispersed with a bead mill for 20 minutes to obtain a pigment dispersion. To the obtained pigment dispersion, 33 parts of IPA, 1 part of tetra-isopropyl titanate, and 1 part of tributyl acetyl citrate were stirred and mixed to obtain flexographic ink S1.

[0074] [Examples 2 - 29] (Production of Inks S2 - S29) Flexographic inks S2 - S29 were obtained in the same manner as in Example 1, except that the raw materials and formulations shown in Table 2 were changed. · Polyvinyl acetal resin solution: Mobiltal B20H manufactured by Kuraray Co., Ltd., solid content 50%, (ethyl acetate / IPA = 50 / 50), weight average molecular weight approximately 23000, vinyl alcohol unit 18 - 21% by mass, glass transition temperature 64°C · Rosin resin solution: Marukid No33 manufactured by Arakawa Chemical Industries, Ltd., solid content 50%, ethyl acetate / IPA = 50 / 50)

[0075] [Comparative Examples 1 - 3] (Production of Inks SS1 - SS3) Flexographic inks SS1 - SS3 were obtained in the same manner as in Example 1, except that the raw materials and formulations shown in Table 2 were changed.

[0076]

Table 2

[0077] [Production of Printed Matter Using Ink S1] The viscosity of Ink S1 was adjusted by dilution to a viscosity of 14 seconds (at 25 °C) in a Zahn cup #4 (manufactured by Separate Company) using a mixed solvent of n-propyl acetate / n-propyl alcohol = 30 / 70. Then, using a flexographic printing proofing machine equipped with a flexographic plate (150 LPI) and an anilox roll (120 LPI, 3.0 cc / m2), printing was performed on the corona-treated surface of a one-sided corona-treated polypropylene (OPP) film (Pyren P2161 manufactured by Toyobo Co., Ltd.) at a speed of 50 m / min, and drying was carried out at 50 - 60 °C to obtain an OPP print using Ink S1.

[0078] [Production of Prints Using Inks S2 - S29 and Inks SS1 - SS3] Except for using Inks S2 - S29 and Inks SS1 - SS3, OPP prints using Inks S2 - S29 and Inks SS1 - SS3 were obtained in the same manner as the example of the print using Ink S1 above.

[0079] The following evaluations were performed using the inks and prints obtained in the above examples and comparative examples. The evaluation results are shown in Table 2.

[0080] [Extrusion Lamination Strength] On the printing layer of the OPP film prints of Inks S1 - S29 (examples) and SS1 - SS3 (comparative examples) obtained in the above examples and comparative examples, a methanol solution with a solid content of 1 mass% of an imine-based anchor coating agent (EL420 manufactured by Toyo Morton Co., Ltd.) was applied. Using an extrusion lamination machine (manufactured by Musashino Kikai Co., Ltd.), molten polyethylene (LC600A manufactured by Nippon Polyethylene Co., Ltd.) was extruded at 320 °C at a line speed of 100 m / min and laminated with a thickness of 20 μm. At the same time, CPP (FCMN film thickness 20 μm manufactured by Futamura Chemical Co., Ltd.) was laminated in the same manner to obtain a laminate. After the lamination process, the laminate was cut into pieces with a length of 150 mm and a width of 15 mm, opened at the ink / OPP film interface, and the lamination strength in the 90° direction was measured using a tensile testing machine.

[0081] (Evaluation Criteria) 5: 1.2 N / 15 mm or more (excellent) 4: Above 1.0 N / 15 mm and less than 1.2 N / 15 mm (good) 3: Above 0.8 N / 15 mm and less than 1.0 N / 15 mm (acceptable) 2: Above 0.5 N / 15 mm and less than 0.8 N / 15 mm (unacceptable) 1: Less than 0.5 N / 15 mm (inferior) Note that the practical level is 3 - 5.

[0082] [Blocking resistance] The obtained printed matter was cut into a size of 4 cm × 4 cm. The printed surface of the cut sample was overlapped with the untreated surface of a polypropylene film with a thickness of 20 μm and the same size to form a test piece. A load of 10 kgf was applied to the test piece in an atmosphere of a temperature of 40°C and a relative humidity of 80%. After 48 hours, the films were peeled off, and the peeling state of the ink from the printed surface was visually judged.

[0083] (Evaluation criteria) 5: The ink film does not peel off and there is no peeling resistance 4: The ink film does not peel off and the peeling resistance is small 3: The peeled area of the ink film is 1% or more and less than 5% 2: The peeled area of the ink film is 5% or more and less than 50% 1: The peeled area of the ink film is 50% or more Note that the practical level is 3 - 5.

[0084] [Plate entanglement property] In the above Examples and Comparative Examples, inks S1 to S29 (Examples) and SS1 to SS3 (Comparative Examples) were diluted and adjusted in a mixed solvent of n-propyl acetate / n-propyl alcohol = 30 / 70 so that the viscosity in a Zahn cup #4 (manufactured by Rika Shakai) was 14 seconds (at 25 °C). Then, using a flexographic printing proofing machine equipped with a flexographic plate (150 LPI) and an anilox roll (1200 LPI, 3.0 cc / m2), printing was performed on the corona-treated surface of a one-sided corona-treated polypropylene (OPP) film (Pyren P2161 manufactured by Toyobo Co., Ltd.) at a speed of 50 m / min. The test was carried out using a flexographic plate having a halftone dot gradation pattern, and the unevenness of the printed matter in the highlight (dot area 5% or more and 10% or less) printing part when printing for 30 minutes was visually evaluated. 5: There is no unevenness in the highlight printing area. 4: The uneven area in the highlight printing area is less than 5%. 3: The uneven area in the highlight printing area is 5% or more and less than 25%. 2: The uneven area in the highlight printing area is 25% or more and less than 50%. 1: The uneven area in the highlight printing area is 50% or more. The practical level is 3 to 5.

[0085] From the above results, when using the flexographic ink for solvent-based lamination of the present invention, the problems of the present application could be achieved. Further, when using a urethane resin containing a structural unit derived from polyether polyol and / or aliphatic diol and having a urethane bond concentration of 2.6 or more and 5.0 or less (mmol / g), excellent results were obtained for the extrusion lamination strength, blocking resistance, and plate clogging property.

Claims

1. A flexographic ink for solvent-based lamination containing a binder resin and a solvent, wherein the binder resin includes a urethane resin and at least one selected from the group consisting of a cellulose-based resin, a polyvinyl acetal resin, and a rosin resin, the urethane resin includes a structural unit derived from a polyether polyol and / or a structural unit derived from an aliphatic diol, and the urethane bond concentration is 2.6 or more and 5.0 or less (mmol / g), the solvent includes an ester-based organic solvent and an alcohol-based organic solvent, and a mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is 60:40 to 5:

95. The flexographic ink for solvent-based lamination.

2. The solvent-based flexographic ink according to Claim 1, wherein the content of the urethane resin is 66.6% by mass or more in 100% by mass of the binder resin.

3. A flexographic ink for solvent-based lamination containing a urethane resin and a solvent, wherein the urethane resin includes a structural unit derived from a polyether polyol and / or a structural unit derived from an aliphatic diol, the urethane bond concentration is 2.6 or more and 5.0 or less (mmol / g), and the urea bond concentration is 0.3 or less (mmol / g), the solvent includes an ester-based organic solvent and an alcohol-based organic solvent, and a mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is 60:40 to 5:

95. The flexographic ink for solvent-based lamination.

4. The urethane resin includes a structural unit derived from a polyether polyol and a structural unit derived from an aliphatic diol, and a mass ratio of the structural unit derived from the polyether polyol to the structural unit derived from the aliphatic diol is 5:95 to 95:

5. The flexographic ink for solvent-based lamination according to Claims 1 to 3.

5. The flexographic ink for solvent-based lamination according to any one of Claims 1 to 4, wherein the aliphatic diol has a branched structure.

6. Furthermore, the flexographic ink for solvent-based lamination according to any one of Claims 1 to 5, which contains a chelating crosslinking agent and / or a plasticizer.

7. A printed matter having a printing layer made of the flexographic ink for solvent-based lamination according to any one of Claims 1 to 6 on a substrate 1.

8. A laminate having an adhesive layer and a substrate 2 in this order on the printing layer of the printed matter according to Claim 7.

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