Liquid printing ink composition, and printed materials and laminates using the same.

Abstract

The object of the present invention is to provide a liquid ink composition that has excellent adhesion and lamination strength, and furthermore, can maintain stable adhesion and lamination strength over a long period of time. [Solution] A liquid ink composition containing a polyurethane resin and a solvent, wherein the main component of the solvent is an organic solvent, and the pH of the liquid ink composition is 7.0 to 9.0.

Description

[Technical Field]

[0001] The present invention relates to a liquid printing ink composition that can be used as a gravure ink or flexographic ink, and to printed materials and laminates using the same. [Background technology]

[0002] Gravure inks and flexographic inks are widely used to impart aesthetic appeal and functionality to substrates. When gravure-printed or flexographic substrates are used as packaging materials, particularly food packaging, lamination is commonly applied. In this case, various substrates and lamination processes are used depending on the type of contents and intended use.

[0003] In recent years, packaging materials have become increasingly diverse, and the requirements for the adhesion of printing inks to the printing substrate and resistance to blocking (the phenomenon where the ink film migrates to the non-printed surface when an ink-printed film is stored in a rolled-up state) are becoming stricter year by year, including from the perspective of improving work efficiency. Furthermore, from the perspective of both the hygiene of the printing process and the harmfulness of the packaging materials, there is a need to restrict the use of aromatic solvents such as toluene and ketone-based solvents such as methyl ethyl ketone. For example, Patent Document 1 discloses the use of ethylene glycol-containing polyurethane resin as an ink that exhibits excellent lamination strength and boil / retort resistance even when using organic solvents that do not contain aromatic organic solvents.

[0004] However, among the films used in film packaging, there is a growing trend towards high-performance films with various barrier properties. These high-performance films have inorganic or organic barrier coatings applied to their surfaces, and when these high-performance films are used as the base material for gravure printing or flexographic printing, the adhesion between the film base material and the ink is often impaired compared to general films. Therefore, printing inks with high lamination strength for various films are desired. Furthermore, printing inks with high lamination strength are desired in both extruded lamination, which is manufactured by melt-extruding molten polyolefins, and dry lamination, which involves laminating a plastic film onto the printed surface via an adhesive. Furthermore, gravure inks have the problem of degrading performance over time. In recent years, due to the effects of global warming, gravure inks are increasingly exposed to high temperatures during transportation and storage, increasing the risk of performance degradation. As a result, maintaining stable quality over the long term has become more difficult than ever before. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-94411 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a liquid ink composition that has excellent adhesion and lamination strength, and furthermore, can maintain stable adhesion and lamination strength over a long period of time. [Means for solving the problem]

[0007] As a result of diligent research to solve the aforementioned problems, the inventors have found that controlling the pH of the ink in a liquid ink composition is effective in solving the problems.

[0008] In other words, the present invention relates to a liquid ink composition containing a polyurethane resin and a solvent, wherein the main component of the solvent is an organic solvent, and the pH of the liquid ink composition is 7.0 to 9.0.

[0009] Furthermore, the present invention relates to a liquid ink composition containing a polyurethane resin and a solvent, wherein the main component of the solvent is an organic solvent, and the pH of the liquid ink composition is 7.0 to 9.0, and is used to print a printed material on a substrate.

[0010] Furthermore, the present invention relates to a laminate or packaging body that includes a printed material obtained by printing a liquid ink composition containing a polyurethane resin and a solvent, wherein the main component of the solvent is an organic solvent, and the pH of the liquid ink composition is 7.0 to 9.0 on a substrate. [Effects of the Invention]

[0011] The present invention provides a liquid ink composition that achieves excellent adhesion and laminate strength both initially and over time. The liquid ink composition of the present invention can achieve excellent laminate strength in both extrusion lamination and dry lamination. [Modes for carrying out the invention]

[0012] (Definition of terms) In the present invention, the liquid printing ink composition refers to a liquid ink applied to a printing method using a printing plate, such as a gravure ink or a flexographic ink, and is preferably a gravure ink or a flexographic ink. Furthermore, the liquid printing ink of the present invention does not contain any active energy curable components, that is, it is an active energy ray nonreactive liquid ink.

[0013] In the following description, all "inks" refer to "printing inks". Also, all "parts" refer to "parts by mass", "total ink volume" refers to the total volume of the ink including all volatile components such as organic solvents, and "non-volatile component amount of the ink" refers to the solid component remaining as a coating film when made into an ink coating film, indicating the total amount of only the non-volatile components without including volatile components.

[0014] The present invention is a laminate ink composition for flexible packaging mainly containing a binder resin containing a polyurethane resin and an organic solvent, and the pH of the liquid ink composition is 7.0 to 9.0. By adjusting the pH of the liquid ink composition to 7.0 to 9.0, physical properties such as adhesion and laminate strength can be stabilized both initially and over time. Preferably, the pH of the liquid ink composition is preferably 7.5 to 8.9, more preferably 7.5 to 8.7, and even more preferably 7.8 to 8.5. When the pH of the liquid ink composition is less than 7.0 or exceeds 9.0, the urethane resin in the ink composition is likely to undergo hydrolysis, and sufficient adhesion and laminate physical properties cannot be obtained as a liquid ink composition. It is preferable to control the pH of the liquid ink composition within the above range because high quality can be maintained. During printing, when the pH of the liquid ink composition that has been stored for a long time has decreased, it may be adjusted to the above range and used before the pH of the liquid ink becomes less than 7.0.

[0015] (Polyurethane resin) Known polyurethane resins can be used as the polyurethane resin used in the liquid ink composition of the present invention. The polyurethane resin of the present invention is preferably a compound having a polyisocyanate compound and a polyol component (for example, containing at least a polyester polyol) as reaction raw materials. In other words, the polyurethane resin of the present invention has a structure in which constituent units derived from a polyisocyanate compound and constituent units derived from a polyester polyol are chemically bonded directly or indirectly. As will be described later, the polyurethane resin may also use polyester polyol and polyether polyol as reaction raw materials as the polyol component. That is, the preferred polyurethane resin of this embodiment may be a compound using a polyisocyanate compound, a polyester polyol, and a polyether polyol as reaction raw materials.

[0016] <Polyisocyanate compounds> The polyisocyanate compound used as a reaction raw material for the polyurethane resin of the present invention is preferably a compound having two or more isocyanate groups, and more preferably a diisocyanate compound. Examples of such polyisocyanate compounds include various known aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates that are commonly used in the production of the above-mentioned known polyurethane resins. As the polyisocyanate compound, isocyanate compounds similar to the above-mentioned organic diisocyanate compound (a1) can be used, for example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzylu isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, and 2,2,4-trimethylhexamethylene Examples include diisocyanates, lysine diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dimeryl diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanate-methyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, m-tetramethylxylylene diisocyanate, 4,4-diphenylmethane diisocyanate, tolylene diisocyanate, bis-chloromethyl-diphenylmethane-diisocyanate, 2,6-diisocyanate-benzyl chloride, and dimer diisocyanates obtained by converting the carboxyl groups of dimer acids to isocyanate groups. These diisocyanate compounds can be used individually or in combination of two or more.

[0017] In the reaction raw materials for the polyurethane resin of the present invention, the proportion of the polyisocyanate compound is preferably 1% to 40% by mass, and more preferably 5% to 30% by mass, based on the total amount of the reaction raw materials (100% by mass). Furthermore, the content of the polyisocyanate compound constituent units in the polyurethane resin is preferably in the range of 1% to 40% by mass, more preferably in the range of 5% to 30% by mass, relative to the urethane resin. If the polyisocyanate compound content is 1% by mass or more, a tough ink film can be obtained. If it is 40% by mass or less, a flexible ink film can be obtained.

[0018] <Polyester Polyol> The reaction raw materials for the polyurethane resin of the present invention preferably contain at least a polyester polyol. Furthermore, if necessary, the reaction raw materials may further contain a polyether polyol and / or a polyol used in combination. In one embodiment of the urethane resin of this embodiment, when polyester polyol and polyether polyol are used as part of the reaction raw materials, it is preferable that the mass proportion of polyester polyol is large in the total mass of the polyester polyol and polyether polyol. In the reaction raw materials for the polyurethane resin of the present invention, the total proportion of the polyester polyol and the polyether polyol is preferably 40% to 99% by mass, and more preferably 50% to 95% by mass, based on the total amount of the reaction raw materials (100% by mass). In the reaction raw materials for the polyurethane resin of the present invention, the proportion of polyester polyol is preferably 40% to 95% by mass, and more preferably 50% to 95% by mass, based on the total amount of reaction raw materials (100% by mass). In other words, it is preferable that the polyol structure of the polyurethane resin has constituent units derived from polyester polyol, as this improves the lamination strength. Furthermore, it is preferable that it also has constituent units derived from polyether polyol, as this improves the dispersibility and fluidity of the ink, and also improves adhesion.

[0019] The polyester polyol in this embodiment is preferably a compound obtained by dehydration condensation or polymerization of a low molecular weight polyol and a polycarboxylic acid or an anhydride thereof. The lamination strength of the polyester polyol can be further increased by introducing ester groups to increase the cohesive energy.

[0020] As the low molecular weight polyol mentioned above, various known compounds having two or more hydroxyl groups that are commonly used in the production of known polyester polyols can be used. For example, one or more compounds may be used in combination as the polyester polyol. Specifically, as the low molecular weight polyol, for example, glycols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol; 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-butanediol, 1,3-butanediol, 2-butyl-2- Branched glycols such as ethyl-1,3-propanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-isopropyl-1,4-butanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-ethyl-1,6-hexanediol, 3,5-heptanediol, and 2-methyl-1,8-octanediol can be used; glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, sorbitol, etc. can also be used. It is preferable to use a polyester polyol that is reacted with two or more diols and a polycarboxylic acid as the reaction raw materials. Furthermore, in order to maintain a good balance between initial and long-term adhesion and laminate strength, it is preferable to use polyester polyols that combine ethylene glycol with one or more diols having three or more carbon atoms. Preferably, the diols having three or more carbon atoms used in combination with ethylene glycol include 1,2-propylene glycol, neopentyl glycol, 1,3-propylene glycol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 1,4-butanediol. By using ethylene glycol as a low-molecular-weight polyol component in polyester polyols, the number of crosslinking points in the resin can be increased, improving the laminate strength and adhesion. From the viewpoint of suppressing the rate of amine value reduction and maintaining a better balance of physical properties, the mass ratio of ethylene glycol to other low molecular weight polyols is preferably (ethylene glycol):(other low molecular weight polyols) = 2:8 to 5:5. On the other hand, since ethylene glycol has shorter side chains and is more susceptible to hydrolysis than diols with 3 or more carbon atoms, if the proportion of ethylene glycol in the low molecular weight polyol component exceeds 50% by mass, adhesion and laminate strength tend to decrease over time.

[0021] As the polycarboxylic acid or anhydride thereof mentioned above, various known polycarboxylic acids commonly used in the production of known polyester polyols can be used. In addition, one or more compounds may be used in combination as the polycarboxylic acid or anhydride thereof. Specifically, for example, polycarboxylic acids having 6 or fewer carbon atoms and 2 or more carboxyl groups, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid and anhydrides of these acids; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid and anhydrides of these acids; aliphatic dicarboxylic acids such as pimelic acid, suberic acid, azelaic acid, sebacic acid, and dimer acid; tricarboxylic acids such as trimellitic acid and its anhydride; benzenetetracarboxylic acid, benzenepentacarboxylic acid, benzenehexacarboxylic acid and anhydrides of these acids can be used.

[0022] Furthermore, the polyester polyol may be any known polyester polyol commonly used in the production of polyurethane resins, such as cyclic ester compounds, including polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, and poly(β-methyl-γ-valerolactone), or one or more compounds may be used in combination.

[0023] The polyester polyol preferably has a number average molecular weight of 1,000 to 8,000, more preferably 1,400 to 7,000, and even more preferably 1,800 to 6,000.

[0024] In this invention, the number-average and weight-average molecular weights are those measured by gel permeation chromatography (GPC) under the following conditions. Measurement device: High-speed GPC device (HLC-8220GPC manufactured by Tosoh Corporation) Columns: The following columns manufactured by Tosoh Corporation were used, connected in series.

[0025] "TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mmI.D. x 30cm) x 1 Detector: RI (Differential Refractometer) Column temperature: 40℃ Eluent: Tetrahydrofuran (THF) Flow rate: 1.0mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass) Standard samples: Calibration curves were prepared using the following standard polystyrene samples. [Standard polystyrene] TSKgel Standard Polystyrene A-500, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene A-1000, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene A-2500, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene A-5000, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-1, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-2, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-4, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-10, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-20, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-40, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-80, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-128, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-288, manufactured by Tosoh Corporation. TSKgel Standard Polystyrene F-550, manufactured by Tosoh Corporation.

[0026] The content of the constituent units of polyester polyol is preferably in the range of 40% to 85% by mass, more preferably in the range of 50% to 80% by mass, relative to the polyurethane resin. When the polyester polyol content is 40 parts by mass or more per 100 parts by mass of polyurethane resin, the solubility of the polyurethane resin in ketone, ester, and alcohol-based solvents is ensured, and adhesion on the high-performance barrier film is good. Furthermore, the resolubility of the ink film in the solvent is good, improving the tone reproducibility of printed materials. When the content is 85 parts by mass or less, the ink film has appropriate flexibility, which tends to result in good blocking resistance.

[0027] <Polyether polyol> The polyurethane resin of the present invention may contain a polyether polyol as a reaction material. As the polyether polyol, which is an optional component of the reaction material, various polyether polyols commonly used in the production of known polyurethane resins can be used, and one or more types may be used in combination. For example, polyether polyols of polymers or copolymers of methylene oxide, ethylene oxide, propylene oxide, tetrahydrofuran, etc. Specifically, known and commonly used ones such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol may be used. By including a polyether polyol, adhesion, especially on high-performance barrier films, is greatly improved, resulting in superior blocking resistance and lamination strength.

[0028] The polyether polyol preferably has a number-average molecular weight of 100 to 3500. If the number-average molecular weight of the polyether polyol is less than 100, the polyurethane resin film tends to become hard, reducing its adhesion to the polyester film. If the number-average molecular weight is greater than 3500, the resulting resin film tends to become brittle, reducing the blocking resistance of the ink film.

[0029] In the reaction raw materials for the polyurethane resin of the present invention, the proportion of polyester polyol is preferably 40% to 95% by mass, and more preferably 50% to 95% by mass, based on the total amount of reaction raw materials (100% by mass). When the reaction raw material (II) contains polyether polyol (b3), it is preferable that the constituent units of polyether polyol (b3) are contained in an amount of 1% to 40% by mass relative to the urethane resin (B). If the polyether polyol is 1 part by mass or more per 100 parts by mass of urethane resin (B), the solubility of the urethane resin (B) in ketone, ester, and alcohol-based solvents is ensured, and adhesion on the high-performance barrier film is improved. Furthermore, the resolubility of the ink film in the solvent is improved, and the tone reproduction of the printed material is enhanced. If the amount is 40 parts by mass or less, the ink film has appropriate flexibility, which tends to result in good blocking resistance.

[0030] The reaction raw material for the polyurethane resin of the present invention may further contain a co-op polyol as needed. As the polyol used in the polyurethane resin used in the ink composition for flexible packaging lamination of the present invention, various known polyols commonly used in the production of polyurethane resins can be used, and one or more may be used in combination. For example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaestritol, etc. Examples include saturated or unsaturated low molecular weight polyols (1); polycarbonate polyols obtained by reacting the low molecular weight polyols with, for example, dimethyl carbonate, diphenyl carbonate, ethylene carbonate, phosgene, etc. (2); polybutadiene glycols (3); glycols obtained by adding ethylene oxide or propylene oxide to bisphenol A (4); and acrylic polyols (4) obtained by copolymerizing one or more hydroxyethyl acrylates, hydroxypropyl acrylates, hydroxybutyl acrylates, etc., or their corresponding methacrylic acid derivatives, etc., with, for example, acrylic acid, methacrylic acid, or their esters.

[0031] Furthermore, the reaction raw materials for urethane resin may contain amine compounds such as chain extenders. Examples of such amine compounds include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, as well as amines having a hydroxyl group in their molecule, such as dialkylamines including 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypyropyrethylenediamine, di-2-hydroxypyropyrethylenediamine, cyclohexylamine, di-2-hydroxypropylethylenediamine, and di-n-butylamine. By including the above amine compounds in the reaction raw materials for urethane resin, it becomes easier to introduce urea bonds into the urethane resin. Furthermore, because the urea bonds within the urethane resin have a low degree of rotational freedom at the molecular structure of the urea bond portion, it becomes easier to ensure high rigidity of the entire composition. Therefore, the urethane resin of this embodiment, by having both urethane bonds and urea bonds, tends to have improved rigidity and elongation performance. For this reason, it is preferable that the polyurethane resin of the present invention has urea bonds in order to exhibit good boil resistance, retort resistance, and blocking resistance.

[0032] Furthermore, monovalent active hydrogen compounds can be used as end-capping agents to stop the reaction of polyurethane resins. Examples of such compounds include dialkylamines such as di-n-butylamine, amines having a hydroxyl group in their molecule such as monoethanolamine and diethanolamine, and alcohols such as ethanol and isopropyl alcohol. In addition, when it is particularly desirable to introduce carboxyl groups into the polyurethane resin, amino acids such as glycine and L-alanine can be used as reaction stoppers. These end-capping agents can be used individually or in combination of two or more.

[0033] In the urethane resin (B) of this embodiment, it is preferable that the reaction raw material contains a biomass-derived raw material. The urethane resin of this embodiment is a compound that reacts with a polyisocyanate compound and at least a polyester polyol and optionally a polyether polyol as reaction raw materials, but the biomass in the reaction raw material may be any material. Preferably, at least one or more components or raw materials constituting the polyester polyol and / or polyether polyol are biomass. More specifically, "at least one or more raw materials constituting the polyester polyol are biomass" means that at least a portion of the total carbon atoms constituting the polyester polyol contains carbon atoms derived from biomass. Furthermore, if the polyester polyol is a compound obtained by dehydration condensation or polymerization of a low molecular weight polyol and a polycarboxylic acid or its anhydride, then it means that the low molecular weight polyol and / or polycarboxylic acid or its anhydride is biomass (in other words, the total carbon atoms in the low molecular weight polyol and / or polycarboxylic acid or its anhydride contain carbon atoms derived from biomass). Similarly, for at least one component or raw material constituting a polyether polyol to be biomass, it means that at least a portion of the total carbon atoms constituting the polyether polyol contains carbon atoms derived from biomass. Biomass refers to organic resources derived from plants and animals that can be recycled into energy or material (for example, agricultural, forestry, and fishery products or parts thereof, rice straw, rice husks, food waste, livestock excrement, or wood chips), excluding fossil fuels such as petroleum and coal. For example, when a polyester polyol is composed of biomass, it is preferable that the polycarboxylic acid or its anhydride, which is a raw material for the polyester polyol, contains carbon atoms derived from biomass.

[0034] The polyurethane resin used in the liquid ink composition of the present invention is obtained by reacting a polyol, a polyisocyanate, a chain extender, and optionally a monovalent active hydrogen compound, as described above. For example, a polyester polyol and a combined polyol is reacted with a diisocyanate compound in a proportion that results in an excess of isocyanate groups to obtain a prepolymer of terminal isocyanate groups. The resulting prepolymer is then reacted with a chain extender and / or a chelating agent in a suitable solvent, i.e., an ester solvent such as ethyl acetate, propyl acetate, or butyl acetate, which are commonly used as solvents for liquid inks; a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone; an alcohol solvent such as methanol, ethanol, isopropyl alcohol, or n-butanol; a hydrocarbon solvent such as toluene, xylene, methylcyclohexane, or ethylcyclohexane; or a mixture thereof, in a two-step method, or in a one-step method, in which the polyester polyol and a combined polyol, a diisocyanate compound, a chain extender, and / or a chelating agent are reacted in a suitable solvent from among the above. Among these methods, the two-stage method is preferred for obtaining a uniform polyurethane resin (A). Furthermore, when producing polyurethane resin (A) by the two-stage method, it is preferable to react the chain extender and / or end-capping agent in such a ratio (equivalent ratio) that the total amino groups are 1 / 0.9 to 1.3. If the equivalent ratio of isocyanate groups to amino groups is less than 1 / 1.3, the chain extender and / or end-capping agent may remain unreacted, which may cause the polyurethane resin to yellow or produce an odor after printing.

[0035] The weight-average molecular weight of the polyurethane resin (A) obtained in this manner is preferably in the range of 15,000 to 150,000. More preferably, it is in the range of 20,000 to 130,000. If the weight-average molecular weight of the polyurethane resin (A) is 15,000 or more, the blocking resistance of the resulting ink composition, the strength and oil resistance of the printed film, etc., will not be reduced. If it is 150,000 or less, the viscosity of the resulting ink composition will not become too high, and there will be no problems with manufacturing or work efficiency. The weight-average molecular weight of the polyurethane resin (A) is the value obtained by measuring it in the same way as the number-average molecular weight of the polyester polyol.

[0036] While polyurethane resins can be used without particular limitations as long as they have the aforementioned compositions, those containing active hydrogen-containing functional groups, such as hydroxyl groups, primary or secondary amino groups, are preferred because they facilitate smooth crosslinking between the polyurethane resin and the blocked isocyanate, resulting in a stronger printing ink layer. Even if the polyurethane resin does not contain active hydrogen-containing functional groups, similar results can be obtained by heating the ink layer at a high temperature.

[0037] The amine value of the polyurethane resin is preferably 0.5 mgKOH / g or more and 1.5 mgKOH / g or less. If the amine value is less than 0.5 mgKOH / g, the initial adhesion and laminate strength tend to be low. On the other hand, if the amine value is higher than 1.5 mgKOH / g, the pH of the ink shifts to the alkaline side, making the polyurethane resin more susceptible to hydrolysis, which makes it difficult to obtain stability of the physical properties over time. The amine value of the polyurethane resin is more preferably 0.6 mgKOH / g or more, and even more preferably 0.8 mgKOH / g or more. On the other hand, the amine value of the polyurethane resin is more preferably 1.3 mgKOH / g or less, and even more preferably 1.1 mgKOH / g or less.

[0038] The urethane bonding concentration of the polyurethane resin is preferably 0.6 mmol / g or higher, more preferably 0.7 mmol / g or higher, and even more preferably 0.8 mmol / g or higher. When the urethane bonding concentration is 0.6 mmol / g or higher, the extruded laminate strength is particularly excellent. On the other hand, the upper limit of the urethane bonding concentration is preferably 2.5 mmol / g, and more preferably 2.0 mmol / g. The urethane bonding concentration can be calculated using the following formula (1).

[0039] Urethane bond concentration = {(W1 × OH1 + W2 × OH2 + ... + W i ×OH i )×1000} / (56100×S) Equation (1) In equation (1), the following applies to each of them: 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 solids

[0040] Furthermore, the polyurethane resin has urea bonds, and it is preferable that the urea bond concentration in the polyurethane resin (A) is 1.5 mmol / g or less. If the urea bond concentration is within this range, the boil resistance and retort resistance of the ink film can be improved without reducing the extrusion lamination strength. The preferred range for the urea bond concentration is 0.1 to 1.2 mmol / g, and more preferably 0.2 to 1.0 mmol / g. The urea bond concentration referred to here can be calculated using the following formula (1). Urea bond concentration={(X1 / M1+X2 / M2+···+X i / M i )×2-(W1×OH1+W2×OH2+···+W i ×OH i ) / 56100}×1000 / S formula (1) In formula (1), the symbols are as follows: X1: Weight of diisocyanate compound 1 M1: Molecular weight of diisocyanate compound 1 X2: Weight of diisocyanate compound 2 M2: Molecular weight of diisocyanate compound 2 X i : Weight of diisocyanate compound i M i : Molecular weight of diisocyanate compound i 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

[0041] The content of the polyurethane resin used in the liquid ink composition of the present invention relative to the total amount of the composition is preferably 4% by mass or more with respect to the total amount of the composition from the viewpoint of sufficiently ensuring the adhesion of the ink to the printed body, and preferably 35% by mass or less from the viewpoints of appropriate ink viscosity and work efficiency during ink production and printing. More preferably, it is in the range of 5 to 20% by mass. Also, the ratio of the polyurethane resin to the total resin solid content of the liquid printing ink is preferably in the range of 30 to 100% by mass, and more preferably in the range of 40 to 90% by mass. Only one kind of polyurethane resin may be used, or two or more kinds may be used in combination.

[0042] (Other resins) Furthermore, the liquid ink composition of the present invention may contain other known resins in addition to the polyurethane resin. Examples of other resins include resins selected from vinyl chloride-vinyl acetate copolymer resins, cellulose resins, polyester resins, rosin resins, acrylic resins, polyamide resins, chlorinated polypropylene resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, alkyd resins, polyvinyl chloride resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyral resins, and petroleum resins. The content of other resins that can be used in combination with polyurethane resins is preferably 0.5 to 40% by weight, and more preferably 5 to 30% by weight, relative to the total weight of the ink.

[0043] (Vinyl chloride vinyl acetate copolymer resin) While any known vinyl chloride vinyl acetate copolymer resin can be used without particular limitations, it is preferable that it is a vinyl chloride vinyl acetate copolymer resin having hydroxyl groups, and more preferably a vinyl chloride vinyl acetate copolymer resin having hydroxyl groups having a hydroxyl value of 50 to 200 mg KOH / g and a vinyl chloride component content ratio of 80 to 95% by weight in the copolymer resin.

[0044] A hydroxyl-containing vinyl chloride vinyl acetate copolymer resin can be obtained by two methods. One method involves copolymerizing vinyl chloride monomer, vinyl acetate monomer, and vinyl alcohol in appropriate proportions. The other method involves copolymerizing vinyl chloride and vinyl acetate, followed by partial saponification of the vinyl acetate. The properties of the resin film and the resin dissolution behavior of the hydroxyl-containing vinyl chloride vinyl acetate copolymer resin are determined by the monomer ratios of vinyl chloride, vinyl acetate, and vinyl alcohol. Specifically, vinyl chloride imparts toughness and hardness to the resin film, vinyl acetate imparts adhesion and flexibility, and vinyl alcohol imparts good solubility in polar solvents.

[0045] Furthermore, regarding the monomer ratio of the vinyl chloride vinyl acetate copolymer resin having hydroxyl groups, for example, a ratio of 80 to 95 parts by mass of vinyl chloride per 100 parts by mass of vinyl chloride vinyl acetate copolymer resin having hydroxyl groups is preferable as it provides a good balance between blocking resistance and adhesion. If the ratio is 80 parts by mass or more, the toughness of the resin film can be maintained and blocking resistance can be ensured. If it is 95 parts by mass or less, the resin film will not become too hard and adhesion will not easily decrease. In addition, the hydroxyl value obtained from vinyl alcohol is preferably 50 to 200 mg KOH / g. If it is 50 mg KOH / g or more, solubility in polar solvents is good and printability is easily stabilized. If it is 200 mg KOH / g or less, lamination suitability can also be maintained well.

[0046] When vinyl chloride vinyl acetate copolymer resin is used in combination, it is preferably in the range of 1 to 30% by mass, and more preferably in the range of 5 to 20% by mass, relative to the total resin solids content of the liquid printing ink (the proportion of resin excluding pigment from the amount of non-volatile components of the ink).

[0047] In the present invention, it is preferable that the solid content mass ratio of polyurethane resin and vinyl chloride vinyl acetate copolymer resin is in the range of (polyurethane resin):(vinyl chloride vinyl acetate copolymer resin) = 100:0 to 65:35. This is because if the proportion of vinyl chloride vinyl acetate copolymer resin is high, the initial pH of the liquid ink composition shifts to the acid side, and the laminate properties deteriorate both initially and over time. For this reason, a liquid printing ink that does not contain vinyl chloride vinyl acetate copolymer resin may be used, but if vinyl chloride vinyl acetate is included, it is preferable that (polyurethane resin):(vinyl chloride vinyl acetate copolymer resin) = 95:5 to 65:35, and more preferably 90:10 to 70:30.

[0048] (Rosin-based resin) The rosin-based resin is not particularly limited as long as it has a rosin skeleton, but rosin-modified maleic acid resin, rosin ester, rosin phenol, polymerized rosin, etc. are preferred. The softening point (measured by the ring-ball method) is preferably 90 to 200°C. <Rosin-modified maleic acid resin> Rosin-modified maleic acid resins are alkyd resins obtained by reacting a polyhydric alcohol such as glycerin, pentaerythritol, or ethylene glycol with an adduct formed by the Diels-Alder reaction between rosin and maleic acid. The acid value is determined by the ratio of the polyhydric alcohol reacted with the rosin-maleic acid adduct and the degree of esterification. In addition to polyhydric alcohols, polybasic acids may also be used to create a structure in which long-chain alkyd resins are bonded to a rosin skeleton.

[0049] Examples of polyhydric alcohols used to react with the adduct of rosin and maleic acid include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, trimethylolpropane, glycerin, pentaerythritol, and sorbitol. Polybasic acids used as raw materials for alkyd resins along with these polyhydric alcohols include phthalic anhydride, terephthalic acid, isophthalic acid, adipic acid, maleic acid, itaconic acid, succinic acid, and sebacic acid.

[0050] Furthermore, for example, a compound having a carbon-carbon unsaturated double bond, such as maleic acid, may be used as a raw material for the above-mentioned alkyd resin, and a styrene monomer may be reacted with it to produce a rosin-modified styrene-maleic acid resin, which is also included in rosin-modified maleic acid resin.

[0051] It is preferable that the rosin-modified maleic acid resin is contained in an amount of 0% by mass or more and less than 3% by mass relative to the total mass of the liquid ink composition. If the amount of rosin-modified maleic acid added is 3.0% by mass or more, the initial pH of the liquid ink composition will be lower, and the laminate strength will decrease both initially and over time. When rosin-modified maleic acid is added, the amount of rosin-modified maleic acid added is more preferably 0.1% by mass or more and 2.0% by mass or less, and even more preferably 0.2% by mass or more and 1.5% by mass or less, relative to the total mass of the liquid ink composition.

[0052] (Chlorinated polypropylene resin) Chlorinated polyolefin resins are resins obtained by introducing chlorine atoms into polyolefins. As polyolefins, resins consisting of copolymers or homopolymers of α-olefin-based unsaturated hydrocarbons such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene can be used. Examples of such copolymers include propylene-α-butene copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, ethylene-1-butene copolymer, polyethylene, and poly-4-methyl-1-pentene. Chlorinated polyolefins are produced by methods such as solution chlorination, which involves dissolving polyolefins in an organic solvent such as carbon tetrachloride and chlorinating them; chlorination, which involves chlorinating polyolefins in an aqueous suspension state; and chlorination, which involves chlorinating polyolefins in a mass state. Furthermore, chlorinated polyolefins may also be acid-modified chlorinated polyolefin resins in which α,β-unsaturated carboxylic acids and / or their derivatives and chlorine are introduced into the polyolefin. Furthermore, as a method for producing the acid-modified chlorinated polyolefin, for example, a polyolefin may be acid-modified with an α,β-unsaturated carboxylic acid and / or its derivative to obtain an acid-modified polyolefin, which may then be dissolved in a chlorine-based solvent such as chloroform, and chlorine gas may be blown in to introduce chlorine into the acid-modified polyolefin.

[0053] Examples of the α,β-unsaturated carboxylic acids and / or derivatives thereof include fumaric acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, itaconic acid, itaconic anhydride, aconitic acid, aconitic anhydride, hymic anhydride, (meth)acrylic acid, (meth)acrylic acid esters, and the like.

[0054] In liquid ink compositions, the chlorinated polyolefin often used has a chlorine content of 5 to 50% by mass. A typical example of the chlorinated polyolefin is chlorinated polypropylene resin. The chlorinated polypropylene resin often has a degree of chlorination of 30 to 45% by mass (the mass percentage of chlorine atoms in the chlorinated polypropylene resin) and a weight-average molecular weight of 5,000 to 50,000.

[0055] It is preferable that the chlorinated polypropylene resin is contained in the liquid ink composition in an amount of 0% by mass or more and less than 3.0% by mass relative to the total mass. If the amount of chlorinated polypropylene resin added is 3.0% by mass or more, the pH of the liquid ink composition shifts to the acid side, and the lamination strength over time decreases. In addition, the effects of chlorine compounds may cause the doctor blade and printing plate to oxidize more easily during printing, which may lead to premature deterioration of the printing equipment. When chlorinated polypropylene resin is added, the amount of chlorinated polypropylene resin added is preferably 0.05% by mass or more and 1.0% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the total mass of the liquid ink composition.

[0056] (Polyvinyl butyral resin) The liquid ink composition of the present invention may also preferably contain polyvinyl butyral resin in addition to the polyurethane resin. In particular, when designing a liquid ink composition using a resin that does not contain chlorine atoms from an environmental perspective, it is preferable to use polyvinyl butyral resin. There are no particular limitations on the polyvinyl butyral resin, and any known resin can be used. Generally, a reaction product obtained by acetalizing polyvinyl alcohol with butyraldehyde by a known reaction can be used.

[0057] The weight-average molecular weight of the polyvinyl butyral resin is preferably 5,000 to 60,000, more preferably 6,000 to 50,000, and even more preferably 7,000 to 40,000. By setting the weight-average molecular weight of the polyvinyl butyral resin within the above range, an ink with an excellent balance of fluidity and dispersibility can be obtained.

[0058] The glass transition temperature (hereinafter sometimes referred to as Tg) of polyvinyl butyral resin is preferably in the range of 50°C to 120°C, more preferably in the range of 55°C to 115°C, and more preferably in the range of 60°C to 110°C. In the present invention, the glass transition temperature is obtained by measurement using a differential scanning calorimeter.

[0059] The hydroxyl group content of the polyvinyl butyral resin is preferably in the range of 10 to 30% by mass, and more preferably in the range of 15 to 25% by mass. By setting the hydroxyl group content of the polyvinyl butyral resin within the above range, an ink with an excellent balance of fluidity and dispersibility can be obtained.

[0060] Furthermore, the amount of acetyl groups in the polyvinyl butyral resin is preferably 10% by mass or less, and more preferably 8% by mass. By setting the amount of acetyl groups in the polyvinyl butyral resin within the above range, an ink with an excellent balance of fluidity and dispersibility can be obtained.

[0061] The polyvinyl butyral resin content (solid content of polyvinyl butyral resin) is preferably 0.1 to 5% by mass, more preferably 0.1 to 4.0% by mass, and most preferably 0.2 to 3.0% by mass, relative to the total mass of the liquid ink composition. Adding 0.1% by mass or more of polyvinyl butyral resin tends to maintain the adhesion and transferability of the ink film, while keeping the total at 5% by mass or less maintains the lamination strength, boil resistance, and retort resistance of the ink. Furthermore, the lower limit of the weight ratio of total resin solids in the ink is preferably 0.1% by mass, more preferably 0.2% by mass, and most preferably 0.3% by mass. Furthermore, the upper limit of the weight ratio of total resin solids in the ink is preferably 45% by mass, preferably 40% by mass, preferably 30% by mass, preferably 20% by mass, more preferably 15% by mass, and most preferably 10% by mass.

[0062] (Organic solvents) The liquid ink composition of the present invention is an oil-based ink in which the main component of the solvent is an organic solvent. The main component refers to the component that is present in the largest amount in the solvent, and preferably the proportion of the organic solvent in the solvent is 50% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. The organic solvent may also be 100% by mass. Examples of organic solvents include aromatic organic solvents, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as ethyl acetate, n-propyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate, and alcohol solvents such as n-propanol, inopropanol, n-butanol, and propylene glycol monomethyl ether. These can be used individually or in mixtures of two or more. In recent years, from the viewpoint of the working environment, it has become desirable to avoid using aromatic solvents such as toluene and xylene, and ketone solvents.

[0063] (water) The liquid printing ink of the present invention may also contain water as a volatile component along with the organic solvent. By adding water, the drying properties of the ink can be controlled, and in gravure printing in particular, the characteristic gradient areas with low ink transfer can be reproduced beautifully. The amount of water added is preferably in the range of 0.3 to 10% by mass of the total ink composition, from the viewpoint of good printability. If the amount of water added is 0.3% by mass or more, the reproducibility of the gradient areas tends to be good without reducing the ink drying suppression effect. If the amount of water added is 10% by mass or less of the total ink composition, the decrease in ink stability can also be suppressed. Furthermore, by adding water in this way, it is possible to reduce the amount of organic solvent components used, which contributes to environmental friendliness. Water may be added to the organic solvent in advance to make a water-containing organic solvent, or a specific amount may be added separately.

[0064] (Coloring agent) Examples of colorants include organic and inorganic pigments and dyes commonly used in inks, paints, and recording materials. Examples of organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, dicutopyrrolopyrrole, and isoindoline pigments. For blue ink, copper phthalocyanine is preferable, and for transparent yellow ink, CIPigment No. Yellow 83 is preferable from the standpoint of cost and lightfastness.

[0065] Examples of inorganic pigments include carbon black, titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, and mica. Additionally, luminous pigments (MetaShine; Nippon Sheet Glass Co., Ltd.) coated with metal or metal oxide on a base material of glass flakes or bulk flakes can be used. From the standpoint of cost and coloring power, titanium dioxide is preferred for white inks, carbon black for black inks, aluminum for gold and silver inks, and mica for pearl inks. Titanium dioxide preferably has a treatment layer containing at least alumina and / or silica on its surface. In titanium dioxide surface-treated with alumina and / or silica, silica is generally used to adjust the acid-base state of the titanium dioxide surface and to impart durability to the resulting ink / paint film, while alumina is used to improve the wettability of titanium dioxide during dispersion. Surface treatment methods for titanium dioxide include aqueous treatment and gas-phase treatment. Aluminum is available in powder or paste form, but it is preferable to use it in paste form for ease of handling and safety reasons. Whether to use leafing or non-leafing aluminum is selected as appropriate from the standpoint of brightness and density.

[0066] The colorant should preferably be included in an amount sufficient to ensure the ink's concentration and coloring power, i.e., in a ratio of 1 to 50% by weight relative to the total weight of the ink. Furthermore, the colorant can be used alone or in combination of two or more types.

[0067] (Other additives) The present invention may further include, as necessary, a combination resin, extender pigment, pigment dispersant, leveling agent, defoamer, wax, plasticizer, infrared absorber, ultraviolet absorber, fragrance, flame retardant, and the like.

[0068] To stably disperse pigments in an organic solvent, the resin alone can be used for dispersion, but a dispersant can also be used in combination to further stabilize the dispersion of the pigments. As dispersants, surfactants such as anionic, nonionic, cationic, and amphoteric surfactants can be used. Examples include comb-structured polymer compounds obtained by adding polyester to polyethyleneimine, or alkylamine derivatives of α-olefin maleic acid polymers. Specifically, examples include the Solspers series (ZENECA), Ajisper series (Ajinomoto), and Homogenol series (Kao). The BYK series (BIK Chemie) and EFKA series (EFKA) can also be used as appropriate. From the viewpoint of ink storage stability, the dispersant is preferably included in the ink at a concentration of 0.05% by mass or more relative to the total weight of the ink, and from the viewpoint of lamination suitability, at a concentration of 5% by mass or less, and more preferably in the range of 0.1 to 2% by mass. In particular, in the present invention, it is preferable to use dispersants having an amine value such as DISPERBYK-106, DISPERBYK-108, DISPERBYK-180, DISPERBYK-2008, DISPERBYK-2022, SOLSPERSE-13300, SOLSPERSE-13400, SOLSPERSE-24000GR, SOLSPERSE-24000SC, SOLSPERSE-33000, SOLSPERSE-73000, and SOLSPERSE-M387. By using a dispersant containing an amine value, the pH of the ink composition can be adjusted by shifting it towards the alkaline side. Furthermore, even when using a dispersant with an acid value, by designing the amine value in the polyurethane resin to be high, or by adjusting the amount of raw materials that shift the pH to the acidic side, such as rosin resin, chlorinated polypropylene, and vinyl chloride vinyl acetate copolymer resin, and controlling the pH within the range of 7.0 to 9.0, it is possible to create a liquid ink composition in which adhesion and laminate properties do not deteriorate initially or over time. Examples of dispersants with acid value include SOLSPERSE-3000, SOLSPERSE-21000, DISPERBYK-106, DISPERBYK-111, and DISPERBYK-2096. The liquid ink composition of the present invention preferably contains a dispersant containing an amine value in an amount of 0.1% by mass or more and 1.0% by mass or less relative to the total mass of the ink. If the content of the dispersant containing an amine value exceeds 1.0% by mass, the laminate strength tends to decrease. In order to adjust the pH of the liquid ink composition and maintain the laminate strength, it is more preferable that the content of the dispersant containing an amine value be 0.2% by mass or more and 0.9% by mass or less, and even more preferable that be 0.3% by mass or more and 0.8% by mass or less.

[0069] The liquid ink composition of the present invention can be manufactured by dissolving and / or dispersing a resin, a colorant, etc., in an organic solvent. Specifically, a pigment dispersion can be manufactured by dispersing a pigment in an organic solvent with a polyurethane resin, and then, if necessary, other compounds can be added to the obtained pigment dispersion to manufacture the ink.

[0070] The particle size distribution of pigments in a pigment dispersion can be adjusted by appropriately adjusting the size of the grinding media in the disperser, the packing density of the grinding media, the dispersion processing time, the discharge speed of the pigment dispersion, and the viscosity of the pigment dispersion. Commonly used dispersers such as roller mills, ball mills, pebble mills, attritors, and sand mills can be used.

[0071] If the ink contains air bubbles or unexpectedly large particles, these can degrade the quality of the printed material, so it is preferable to remove them by filtration or other means. Conventional filters can be used.

[0072] The viscosity of the ink produced by the above method is preferably in the range of 10 mPa·s or higher from the viewpoint of preventing pigment sedimentation and ensuring appropriate dispersion, and 1000 mPa·s or lower from the viewpoint of workability during ink production and printing. The above viscosity was measured at 25°C using a Tokimec Type B viscometer.

[0073] The viscosity of the ink can be adjusted by appropriately selecting the type and amount of raw materials used, such as polyurethane resin, colorants, and organic solvents. Furthermore, the viscosity of the ink can also be adjusted by controlling the particle size and particle size distribution of the pigments in the ink.

[0074] The pH of the liquid ink composition of the present invention can be measured using a commercially available pH meter. Examples of pH meters include the Horiba F-74 desktop pH meter.

[0075] In the liquid ink composition of the present invention, when a colorant is used, there are five basic process colors (yellow, red, cyan, black, and white) and three extra-process gamut colors (red (orange), grass (green), and purple), depending on the type of colorant used. Furthermore, transparent yellow, peony, vermilion, brown, gold, silver, pearl, and a nearly transparent medium for adjusting color density (including extender pigments as needed) are prepared as base colors. For boil and retort inks, appropriate selections are made considering the migration properties and heat resistance of the pigments. The base inks for each hue are diluted with a diluent solvent to a viscosity and concentration suitable for gravure printing or flexographic printing, and supplied to each printing unit either individually or in mixtures.

[0076] (Printed material) The printed material of the present invention is a printed material having a printed layer formed by printing the liquid printing ink of the present invention onto a substrate. The liquid printing ink of the present invention has excellent adhesion to various substrates and can be used for printing on paper, synthetic paper, thermoplastic resin film, plastic products, steel plates, etc. It is useful as an ink for gravure printing using gravure printing plates such as electronic engraving intaglio plates, or for flexographic printing using flexographic printing plates such as resin plates, but excludes inks for inkjet systems that eject ink from inkjet nozzles without using plates.

[0077] In other words, while inkjet inks form printed materials by direct adhesion of ink droplets ejected from a nozzle onto the substrate, the liquid printing ink of the present invention first adheres and transfers the printing ink to a printing plate or printing pattern, then the ink alone is again adhered to the substrate, and dried as necessary to form a printed material.

[0078] The film thickness of the printing ink formed by gravure printing or flexographic printing using the liquid printing ink of the present invention is, for example, 10 μm or less, preferably 5 μm or less.

[0079] Examples of the aforementioned substrates include films and laminates made of thermoplastic resins such as polyamide resins like nylon 6, nylon 66, and nylon 46; polyester resins such as polyethylene terephthalate (hereinafter sometimes referred to as PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; biodegradable resins such as polyhydroxycarboxylic acids like polylactic acid, and aliphatic polyester resins such as poly(ethylene succinate) and poly(butylene succinate); polyolefin resins such as polypropylene and polyethylene; polyimide resins; polyarylate resins; or mixtures thereof. Among these, films made of polyester, polyamide, polyethylene, and polypropylene are particularly suitable.

[0080] Furthermore, it is preferable to use a film formed from a material containing biomass-derived components as the base material. Biomass films are sold by various companies, and publicly known sheets, such as those listed in the biomass certified product list of the Japan Organic Resources Association, can also be used.

[0081] These films may be laminated films made by stacking multiple films, for example, a laminate made by stacking biomass films, or a laminate of conventional petroleum-based films and biomass films.

[0082] These base films may be unstretched or stretched films, and their manufacturing methods are not limited. Furthermore, the thickness of the base film is not particularly limited, but is usually within the range of 1 to 500 μm.

[0083] Furthermore, these base films may have a vapor-deposited layer of metal such as aluminum, or metal oxides such as silica or alumina, or they may use metal foil, or they may be coated with a barrier film containing a gas barrier layer such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, or vinylidene chloride, or they may be coated with polyvinyl alcohol or the like. By using such films, a laminate with even higher barrier properties against water vapor, oxygen, alcohol, inert gases, volatile organic compounds (fragrances), etc. can be obtained. The liquid printing ink of the present invention also exhibits excellent adhesion to films with vapor-deposited layers or various coating treatments.

[0084] The print can be produced using known printing methods such as gravure printing and flexographic printing, but gravure printing is particularly preferred.

[0085] The above printing method, that is, after the printing ink is first brought into contact with and transferred to a printing plate or printing pattern, only the ink is brought into contact with the substrate again, and if necessary, it is dried or cured in an oven to fix it, thereby obtaining a printed material. The film thickness of the printing ink formed by gravure printing or flexographic printing using the liquid printing ink of the present invention is, for example, 10 μm or less, preferably 5 μm or less.

[0086] The printed material of the present invention can preferably use the above-described liquid ink composition as a front-printing ink, a back-printing ink, or a laminating ink on a film substrate. When used as a front-printing ink, a separate overprint varnish layer may be provided. The overprint varnish does not need to contain a colorant, or various pigments may be used for coloring purposes. On the other hand, when used as a back-printing ink, a separate anchor coat varnish layer may be provided. In addition to the printing layer using the liquid ink composition of the present invention, other printing layers containing a colorant may be provided.

[0087] In particular, the liquid printing ink of the present invention is preferable for use as a laminating ink because it has excellent lamination strength.

[0088] (Laminated structure) The laminate of the present invention is obtained by bonding together a plurality of substrates, and at least one of the substrates has a printed layer of the liquid printing ink of the present invention. The substrates can be bonded together with an adhesive or laminated by extrusion lamination.

[0089] More specifically, the configuration of the laminate is as follows: (1) Base film 1 / Printing layer / Adhesive layer 1 / Sealant film (2) Substrate film 1 / Printing layer / Adhesive layer 1 / Metal vapor deposition unstretched film (3) Base film 1 / Printing layer / Adhesive layer 1 / Metal vapor-deposited stretched film (4) Transparent vapor-deposited stretched film / Printed layer / Adhesive layer 1 / Sealant film (5) Substrate film 1 / Printing layer / Adhesive layer 1 / Substrate film 2 / Adhesive layer 2 / Sealant film (6) Substrate film 1 / Printing layer / Adhesive layer 1 / Metal vapor-deposited stretched film / Adhesive layer 2 / Sealant film (7) Substrate film 1 / Printing layer / Adhesive layer 1 / Transparent vapor-deposited stretched film / Adhesive layer 2 / Sealant film (8) Substrate film 1 / Printing layer / Adhesive layer 1 / Metal layer / Adhesive layer 2 / Sealant film (9) Substrate film 1 / Printing layer / Adhesive layer 1 / Substrate film 2 / Adhesive layer 2 / Metal layer / Adhesive layer 3 / Sealant film (10) Substrate film 1 / Printing layer / Adhesive layer 1 / Metal layer / Adhesive layer 2 / Substrate film 2 / Adhesive layer 3 / Sealant film Examples include, but are not limited to, the above. Note that the above "base film 1 / and printing layer" corresponds to the above printed material having a white printing layer and a color printing layer on a film base. In addition, although the above configurations (1) to (10) describe a configuration in which the printing layer is provided on the side of the base film 1 that is on the side of the adhesive layer 1, the printing layer may also be provided on the side (surface) of the base film 1 opposite to the adhesive layer 1, or the printing layer may be provided on the base film 2.

[0090] Examples of base film 1 used in composition (1) include OPP film, PET film, nylon film (hereinafter also referred to as Ny film), etc. Furthermore, base film 1 may be coated for purposes such as improving gas barrier properties or ink receptivity when providing the printing layer described later. Examples of commercially available coated base film 1 include K-OPP film and K-PET film. Examples of sealant films include CPP film and LLDPE film.

[0091] Examples of base film 1 used in configurations (2) and (3) include OPP film and PET film. As the unstretched metal-deposited film, a VM-CPP film obtained by depositing a metal such as aluminum onto a CPP film can be used, and as the stretched metal-deposited film, a VM-OPP film obtained by depositing a metal such as aluminum onto an OPP film can be used.

[0092] Examples of transparent vapor-deposited stretched films used in configuration (4) include films obtained by vapor-depositing silica or alumina onto OPP film, PET film, nylon film, etc. Films with a coating applied to the vapor-deposited layer may also be used for purposes such as protecting the inorganic vapor-deposited layer of silica or alumina. Examples of sealant films are the same as those in configuration (1).

[0093] Examples of base film 1 used in composition (5) include PET film. Examples of base film 2 include nylon film. Examples of sealant film are the same as those in composition (1).

[0094] The base film 1 of composition (6) is the same as that of compositions (2) and (3). Examples of metal-deposited stretched films include VM-OPP films and VM-PET films, which are obtained by depositing metal such as aluminum onto OPP films or PET films. Examples of sealant films are the same as those of composition (1).

[0095] Examples of the base film 1 in composition (7) include PET film. Examples of the transparent vapor-deposited stretched film include the same as in composition (4). Examples of the sealant film include the same as in composition (1).

[0096] Examples of the base film 1 in composition (8) include PET film. Examples of the metal layer include aluminum foil. Examples of the sealant film include those the same as in composition (1).

[0097] Examples of base film 1 in configurations (9) and (10) include PET film. Examples of base film 2 include nylon film. Examples of metal layers include aluminum foil. Examples of sealant film are the same as those in configuration (1).

[0098] (adhesive layer) For the adhesive layer, any known adhesive for film lamination can be used as appropriate. Furthermore, when laminating by extrusion lamination, any known anchor coating agent for extrusion lamination can be used as an adhesive aid as appropriate. Using gas barrier materials as these adhesives and anchor coating agents allows for the creation of laminates with particularly excellent barrier properties.

[0099] Particularly preferred as an adhesive with excellent gas barrier properties is 3 g / m². 2 The oxygen barrier property of the cured coating film of the adhesive applied with (solid content) is 300 cc / m². 2 Water vapor barrier capacity of 120 g / m² or less than / day / atm 2 This refers to products that satisfy at least one of the following conditions: / day or less. Examples of commercially available products include the "PASLIM" series such as PASLIM VM001 and PASLIM J350X from DIC Corporation, and "Maxive" from Mitsubishi Gas Chemical Company.

[0100] The adhesive layer is not particularly limited and can be made from known materials, but it is preferable that it contains a cured product of a polyol and an isocyanate compound. If these polyols and / or isocyanate compounds contain biomass-derived components, a laminate with a high biomass content can be made, thereby reducing the environmental burden.

[0101] In addition, the adhesive may contain other additives such as adhesion promoters, acid anhydrides, compounds with oxygen-scavenging properties, tackifiers, gas barrier adhesives, stabilizers (antioxidants, heat stabilizers, UV absorbers, etc.), plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, and crystal nucleating agents. These various additives may be added beforehand to either the polyol composition (A) or the polyisocyanate composition (B), or to both, or they may be added when mixing the polyol composition (A) and the polyisocyanate composition (B).

[0102] Furthermore, the gas barrier adhesive used may be either solvent-based or solvent-free. When the gas barrier adhesive used is solvent-based, the adhesive of the present invention is applied to the printed layer surface printed on the first substrate using a roll such as a gravure roll, the organic solvent is evaporated by heating in an oven or the like, and then the other substrate is bonded to obtain the laminate of the present invention. It is preferable to perform an aging treatment after lamination. The aging temperature is preferably room temperature to 80°C, and the aging time is preferably 12 to 240 hours.

[0103] If the gas barrier adhesive used is solvent-free, the adhesive of the present invention, which has been preheated to approximately 40°C to 100°C, is applied to the printed layer surface printed on the first substrate using a roll such as a gravure roll, and then the other substrate is immediately bonded to obtain the laminate of the present invention. It is preferable to perform an aging treatment after lamination. The aging temperature is preferably room temperature to 70°C, and the aging time is preferably 6 to 240 hours.

[0104] When using a gas barrier adhesive as an adhesion aid, the adhesion aid of the present invention is applied to the printed layer surface printed on the first substrate using a roll such as a gravure roll, the organic solvent is evaporated by heating in an oven or the like, and then the laminate of the present invention is obtained by laminating with a molten polymer material using an extruder. As the polymer material to be molten, polyolefin resins such as low-density polyethylene resin, linear low-density polyethylene resin, and ethylene-vinyl acetate copolymer resin are preferred. The aging temperature is preferably room temperature to 70°C, and the aging time is preferably 6 to 240 hours.

[0105] The amount of gas barrier adhesive to be applied should be adjusted as needed. For solvent-based adhesives, for example, the solid content should be 1 g / m². 2 More than 10g / m 2 Preferably 2 g / m 2 More than 5g / m 2 Adjust the following: For solvent-free adhesives, the adhesive application amount is, for example, 1 g / m². 2 More than 5g / m 2 Preferably 1 g / m 2 More than 3g / m 2 The following applies:

[0106] When using adhesive as an adhesion aid, the application amount is adjusted as needed, but one example is 0.03 g / m². 2 More than 2g / m 2 The following is the (solid content).

[0107] (Laminated structure, other layers) The laminate of the present invention may be used alone or may further contain other films or substrates. In addition to the stretched film, unstretched film, and transparent vapor-deposited film mentioned above, porous substrates such as paper, wood, and leather may also be used as other substrates. The adhesive used when bonding the other substrates may be a gas barrier adhesive as described above, or it may not be.

[0108] <Packaging material> The printed materials and laminates of the present invention can be used as multilayer packaging materials for the purpose of protecting food, pharmaceuticals, and other products. When used as multilayer packaging materials, the layer configuration may change depending on the contents, usage environment, and usage method.

[0109] The packaging material of the present invention can be obtained, for example, by using the laminate of the present invention, overlapping the sealant film surfaces of the laminate facing each other, and then heat-sealing the peripheral edges. Methods for making the bag include folding or overlapping the laminate of the present invention so that the inner layer surfaces (sealant film surfaces) face each other, and then heat-sealing the peripheral edges in forms such as side seal type, two-side seal type, three-side seal type, four-side seal type, envelope seal type, gusset seal type, pleated seal type, flat-bottom seal type, square-bottom seal type, gusset type, and other heat-seal types. The packaging material of the present invention can take various forms depending on the contents, usage environment, and usage. Self-standing packaging materials (standing pouches) are also possible. Heat sealing can be performed using known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high-frequency sealing, and ultrasonic sealing.

[0110] Products using the packaging material of the present invention are manufactured by filling the contents into the packaging material through its opening and then heat-sealing the opening. The applications of the packaging material are not particularly limited, but it can be suitably used for food packaging, pharmaceuticals, sanitary products, cosmetics, electronic materials, building materials, industrial materials, etc. It can also be used as packaging material for cigarettes, disposable hand warmers, medicines, supplements, intravenous fluid packs, vacuum insulation materials, etc. [Examples]

[0111] The present invention will be further described in detail by examples. Hereinafter, "parts" and "%" will be based on mass. Blank spaces in the table indicate that the ingredient was not included.

[0112] [Synthesis of polyurethane resin Pu-a] A polyester polyol consisting of neopentyl glycol, ethylene glycol, and sebaciac acid (the mass ratio of neopentyl glycol to ethylene glycol is shown in Table 1) and isophorone diisocyanate were charged into a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube. The mixture was reacted at 100°C for 20 hours under a nitrogen stream to produce a urethane prepolymer, to which ethyl acetate was added to obtain a homogeneous solution of the urethane prepolymer. Next, the urethane prepolymer solution was added to a mixture consisting of isophorone diamine, monoethanolamine, ethyl acetate, and isopropyl alcohol, and the mixture was stirred at 45°C for 5 hours to obtain polyurethane resin solution Pu-a. The obtained polyurethane resin solution Pu-a had a resin solids content concentration of 30.0% by mass.

[0113] [Synthesis of polyurethane resins Pu-b to Pu-f] Polyurethane resin solutions Pu-b to Pu-f were obtained in the same manner as for polyurethane resin Pu-a, except that the dicarboxylic acids and diols listed in Table 1 were used as polyester polyols. The resin solids content concentration was 30.0% by mass.

[0114] [Table 1]

[0115] (Preparation of vinyl chloride vinyl acetate copolymer resin solution) A vinyl chloride vinyl acetate copolymer resin containing hydroxyl groups, used in combination with polyurethane resin (resin monomer composition in weight percent: vinyl chloride / vinyl acetate / vinyl alcohol = 92 / 3 / 5, hydroxyl value (mgKOH) = 64), was prepared as a 15% solution with ethyl acetate, and this was used as the vinyl chloride vinyl acetate copolymer resin solution.

[0116] (Chlorinated polypropylene resin) As the chlorinated polypropylene resin, Superclon 360T (manufactured by Nippon Paper Industries Co., Ltd.) was prepared as a 50% solution with ethyl acetate, and this was used as the chlorinated polypropylene resin solution (degree of chlorination 32%, weight-average molecular weight 12000). (Maleic acid-modified rosin resin) As the maleic acid-modified resin, Marquid No. 33 (Arakawa Chemical Industries, Ltd.), with a solid content of 100%, was dissolved in ethyl acetate to a 50% solution, and this was used as the maleic acid-modified rosin resin solution. (Ester gum rosin resin) As the ester gum rosin resin, ester gum HP (Arakawa Chemical Industries, Ltd.), which has a solid content of 100%, was prepared as a 50% solution with ethyl acetate, and this was used as the ester gum rosin resin solution.

[0117] [Example 1] A mixture of 30 parts of the obtained polyurethane resin solution Pu-a, 15 parts of a hydroxyl-containing vinyl chloride vinyl acetate copolymer resin solution (15% solution), 1.0 part of a maleic acid-modified rosin resin solution (50% solution), 0.5 parts of an amine-containing dispersant A, 1.0 part of a chlorinated polypropylene resin solution (50% solution), 35 parts of titanium dioxide, and 17.5 parts of ethyl acetate was kneaded to prepare a printing ink.

[0118] [Examples 2-16, Comparative Examples 1-7] Printing inks for Examples 2-16 and Comparative Examples 1-7 were prepared in the same manner as in Example 1, using the formulations shown in Tables 2-4.

[0119] (Amine value) The amine values ​​shown in Tables 2 to 4 represent the equivalent amount of hydrochloric acid and the equivalent amount of potassium hydroxide required to neutralize the amino groups contained in 1 g (non-volatile content) of polyurethane resin sample, and were measured in accordance with JIS K 0070. Specifically, 0.5 to 2 g of the sample was accurately weighed (sample solid content: S g). 50 mL of a methanol / methyl ethyl ketone = 60 / 40 (mass ratio) mixed solution was added to the accurately weighed sample and dissolved. Bromophenol blue was added to the resulting solution as an indicator, and the resulting solution was titrated with a 0.2 mol / L ethanolic hydrochloric acid solution (titer: f). The endpoint was defined as the point where the color of the solution changed from green to yellow, and the titration volume (A mL) at this point was used to determine the amine value using the following formula. Amine value = (A × f × 0.2 × 56.108) / S [mgKOH / g] The initial amine value was measured before ink preparation, while the amine value after one year was measured after storage at room temperature for one year.

[0120] [Table 2]

[0121] [Table 3]

[0122] [Table 4]

[0123] In Tables 2 to 4, Amine value-containing dispersant A: DISPERBYK-2008 Acid group-containing dispersant A: DISPERBYK-111 Titanium dioxide: R-780, manufactured by Ishihara Sangyo Co., Ltd.) I used it.

[0124] (pH of the ink) The pH of each printing ink obtained was measured using a Horiba F-74 desktop pH meter. A Horiba pH electrode 9681S-10D was used as the electrode. Note that the initial pH was measured after ink preparation, and the pH after one year was measured after storing the ink at room temperature for one year after preparation. The results are shown in Tables 5-7.

[0125] The viscosity of the obtained printing ink was adjusted with ethyl acetate in a Zahn cup #3 (manufactured by Rigosha) for 16 seconds (25°C). The ink was then printed onto biaxially oriented polypropylene film (hereinafter referred to as OPP) and nylon film (ON-RT (15μm), manufactured by Unitika Ltd., hereinafter referred to as NY), which had been corona-treated on one side, using a gravure proofing machine equipped with a gravure plate with a plate depth of 35μm. The prints were dried at 40-50°C to obtain the printed materials. Furthermore, the printed materials were obtained using the ink after adjustment and the ink after adjustment and storage at room temperature for one year. The obtained printed materials were evaluated by measuring adhesion, extrusion lamination strength, and dry lamination strength. The results are shown in Table 3. The evaluation was performed using the following test method.

[0126] (Adhesion) After leaving the above printed material for one day, cellophane tape (Nichiban brand, 18mm wide) was applied to the printed surface, and the appearance of the printed film was visually assessed when the tape was rapidly peeled off. The assessment criteria were as follows: 5: The printed coating did not peel off at all. (Best result) 4: More than 80% of the printed coating remained on the film. 3: 40-80% of the printed film remained on the film. 2: 10-40% of the printed coating remained on the film. 1: Less than 10% of the printed coating remained on the film. (Worst case)

[0127] (Extruded lamination strength) Apply 0.1 g / m² of polyethyleneimine-based anchor coating agent to OPP printed materials. 2After coating, molten polyethylene was laminated to a thickness of 40 μm using an extrusion laminating machine to obtain a laminated product. The laminate film was then cut to a width of 15 mm, and a 90-degree peel test was performed at a tensile speed of 50 mm / min.

[0128] (Dry lamination strength) In the aforementioned OPP printed material, a dry laminating machine (manufactured by DIC Engineering) was used to coat the printed surface of the printed material with a urethane-based dry laminating adhesive, DIC Dry LX-703VL / KR-90 (manufactured by DIC), and an unstretched polypropylene film (hereinafter, R-CPP: ZK-207 70μm manufactured by Toray Synthetic Film Co., Ltd.) was laminated onto the adhesive-coated surface. After that, the laminate was aged at 40°C for 5 days to obtain the laminated material.

[0129] Similarly, in a printed material from New York, a dry laminating machine (manufactured by DIC Engineering) was used to coat the printed surface of the printed material with a urethane-based dry laminating adhesive, DIC Dry LX-703VL / KR-90 (manufactured by DIC), and an unstretched low-density polyethylene film (hereinafter referred to as LLDPE: TUX-HC 60μm manufactured by Mitsui Chemicals Tohcello Co., Ltd.) was laminated onto the adhesive-coated surface. The laminated material was then aged at 40°C for 5 days to obtain the laminated product.

[0130] The resulting laminate was cut into 15mm wide strips, and a peel test was performed at a tensile speed of 300mm / min at a 90-degree angle.

[0131] [Table 5]

[0132] [Table 6]

[0133] [Table 7]

Claims

1. A liquid ink composition containing a polyurethane resin and a solvent, The main component of the aforementioned solvent is an organic solvent. The pH of the liquid ink composition is 7.0 to 9.

0. Liquid ink composition.

2. The liquid ink composition contains a dispersant with an amine value in an amount of 0.1% by mass or more and 1.0% by mass or less relative to the total mass of the liquid ink composition. The liquid ink composition according to claim 1.

3. It contains vinyl chloride vinyl acetate copolymer resin, The solid content mass ratio of polyurethane resin to vinyl chloride acetate is polyurethane resin:vinyl chloride acetate = 100:0 to 65:

35. The liquid ink composition according to claim 1 or 2.

4. The liquid ink composition contains 0% by mass or more and less than 3% by mass of rosin-modified maleic acid resin based on the total mass of the composition. The liquid ink composition according to claim 1 or 2.

5. The liquid ink composition contains 0% to less than 3% by mass of chlorinated polypropylene resin based on the total mass. The liquid ink composition according to claim 1 or 2.

6. The amine value of the polyurethane resin is 0.4 or more and less than 1.

5. The liquid ink composition according to claim 1 or 2.

7. The aforementioned polyurethane resin is reacted using at least a polyester polyol and a polyisocyanate compound as reaction materials. The aforementioned polyester polyol is reacted using two or more diols and a polycarboxylic acid as raw materials. The liquid ink composition according to claim 1 or 2.

8. As the aforementioned diol, ethylene glycol and one or more diols having three or more carbon atoms are used. The liquid ink composition according to claim 7.

9. The mass ratio of the ethylene glycol to the diol having 3 or more carbon atoms is 2:8 to 5:

5. The liquid ink composition according to claim 8.

10. A liquid ink composition according to claim 1 or 2 for use in flexible packaging lamination.

11. A printed article obtained by printing the liquid ink composition according to claim 1 or 2 onto a substrate.

12. A laminate or packaging comprising the printed material described in claim 11.

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