AU2018373095A1 - Aqueous liquid ink and printed article - Google Patents

Abstract

The present invention addresses the problem of providing an aqueous liquid ink which exhibits fundamental characteristics as an aqueous liquid ink (adhesion to a base material, blocking resistance, a high printing density, and the like), and which also exhibits high water resistance (boil retort properties) and solvent resistance. This aqueous liquid ink includes a colouring agent (A), a binder (B) having acid groups, a basic compound (C), and an aqueous medium (D). The binder (B) having acid groups includes a urethane resin (B1) which is a reaction product of a polyisocyanate (b2), and a polyol (b1) including at least one from among a polyol (b1-1) having acid groups, a polyester polyol (b1-2), and a polycarbonate polyol (b1-3). The content of alicyclic structures in the urethane resin (B1) is at least 1,000 mmol/kg. The basic compound (C) includes at least one from among a basic metal compound (C1) and an organic amine (C2).

Description

DESCRIPTION Title of Invention: AQUEOUS LIQUID INK AND PRINTED ARTICLE Technical Field [0001]

The present invention relates to an aqueous liquid ink that can be used for water-based printing, and to a printed article printed using an aqueous liquid ink. Background Art [0002]

Gravure printing and flexography are widely used to give esthetics and functionality to printed material. In recent years, the printing ink industry has faced a growing demand for a turn to aqueous printing inks as they are viewed as a solution to problems with solvent-based printing inks, such as environmental issues including air pollution, occupational health and safety concerns including organic solvent poisoning, and dangers including ignition and explosion, and also from the perspectives of operational safety and hygiene, environmental protection, the reduction of residual solvents in packaging, etc. Indeed, aqueous printing inks have been increasingly used in commercial printing, for example of wrapping paper and paper-made containers such as cardboard boxes. [0003]

As an example of such an aqueous printing ink, a surface-printing water-based ink for packaging has been proposed. This ink contains, as a binder, a water-based polyurethane resin obtained by reacting an isocyanatecontaining polymer with a polyhydrazide compound and a polyamine compound other than the polyhydrazide compound and making the resulting polyurethane resin water-soluble by neutralizing an organic solution of the resin with a deionized water containing aqueous ammonia (e.g., see PTL 1: Japanese Unexamined Patent Application Publication No. 853641) . [0004]

Also proposed is a water-based printing ink composition for lamination. This ink composition is made with a waterbased polyurethane resin obtained by reacting an organic diisocyanate compound with a polymeric diol compound containing a particular polycarbonate diol and with a chain extender and making the resulting resin water-based by adding water and trimethylamine (e.g., see PTL 2: Japanese Unexamined Patent Application Publication No. 5-171091). Citation List Patent Literature [0005]

PTL 1: Japanese Unexamined Patent Application Publication No. 8-53641

PTL 2: Japanese Unexamined Patent Application

Publication No. 5-171091 Summary of Invention Technical Problem [0006]

Aqueous printing inks, however, are slow to dry compared with solvent-based inks. Besides the essential performance attributes of adhesion to plastic substrates and freedom from blocking, requirements include, for example, good dispersion of pigment(s) therein, and it is difficult to improve print density while fulfilling all of these. For example, the surface-printing water-based ink for packaging described in PTL 1 and the water-based printing ink composition for lamination described in PTL 2 may be lacking in essential performance for use as aqueous liquid inks. Moreover, the water-based printing ink composition for lamination described in PTL 2, occasionally but notably, is by no means one that can withstand long-run printing. [0007]

Made under these circumstances, the present invention is aimed at providing an aqueous liquid ink that meets essential performance requirements for use as an aqueous liquid ink (adhesion to substrates, freedom from blocking, high print density, etc.) and also combines high waterproofness (boilability/retortability) and resistance to solvents. By virtue of combining these performance attributes, the ink can provide, when used as an aqueous liquid ink (in particular, an aqueous liquid ink for printing on laminated packaging materials), a printed article that can withstand even boiling and retort treatment.

Solution to Problem [0008]

After extensive research to solve the above problem, the inventors found that the problem can be solved with the use of a binder for water-based flexo inks that contains a urethane resin that has an acid group neutralized with basic compounds including a basic metal compound and an organic amine. The present invention was completed on the basis of these findings. [0009]

That is, the present invention relates to an aqueous liquid ink that contains a colorant (A), a binder having an acid group (B), at least one basic compound (C), and an aqueous medium (D). The binder having an acid group (B) contains a urethane resin (Bl) that is a product of reaction between polyols (bl) including at least one selected from the group consisting of a polyol having an acid group (bl-1) and a polyester polyol (bl-2) and a polycarbonate polyol (bl-3) and a polyisocyanate (b2), and the alicyclic structure content of the urethane resin (Bl) is 1,000 mmol/kg or more in the total amount of the urethane resin (Bl) . The basic compound (C) includes at least one selected from the group consisting of a basic metal compound (Cl) and an organic amine (C2).

Advantageous Effects of Invention [0010]

According to the present invention, there can be provided an aqueous liquid ink that not only has essential performance attributes for use as an aqueous liquid ink (adhesiveness, anti-blocking properties, high print density, etc.) but also combines high waterproofness (boilability/retortability) and high resistance to solvents. Description of Embodiments [0011]

An aqueous liquid ink according to the present invention contains at least one colorant (A), a binder having an acid group (B), at least one basic compound (C), and at least one aqueous medium (D). [0012]

The colorant (A) can be one or two or more colorants. Examples include pigments, such as organic or inorganic pigments, and dyes. Colorants used in, for example, inks, paints, and recording agents are preferred.

Examples of organic pigments include pigments such as azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine-azo, diketopyrrolopyrrole, and isoindoline pigments.

[0013]

Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, and mica. Shiny pigments produced by coating glass flakes or lump flakes as a base material with a metal or metal oxide (Metashine; Nippon Sheet Glass Co., Ltd.) can also be used. [0014]

By color index name, examples include:

C.I. Pigment Yellow 1, 3, 12, 13, 14, 17, 42, 74, and 83;

C.I. Pigment Orange 16;

C.I. Pigment Red 5, 22, 38, 48:1, 48:2, 48:4, 49:1, 53:1, 57:1, 63:1, 81, and 101;

C.I. Pigment Violet 19 and 23;

C.I. Pigment Blue 23, 15:1, 15:3, 15:4, 17:1, 18, 27, and 2 9

C.I. Pigment Green 7, 36, 58, and 59;

C.I. Pigment Black 7; and

C.I. Pigment White 4, 6, and 18.

[0015]

For cyan ink, C.I. Pigment Blue 15:3 (copper phthalocyanine) is preferred. For yellow ink, C.I. Pigment Yellow 83 is preferred in terms of cost and light fastness. For magenta ink, C.I. Pigment Red 57:1 is preferred. For white, black, gold/silver, and pearl inks, titanium oxide, carbon black, aluminum, and mica, respectively, are preferred in terms of cost and tinctorial strength. Aluminum is in powder or paste form, but preferably is used in paste form for the sake of ease of handling and safety. As for which type of aluminum to use, leafing or nonleafing, an appropriate type is selected considering brightness felt and density. [0016]

To ensure sufficient density and tinctorial strength of the ink, the total percentage of the pigment(s) is preferably 1% by mass or more in the total amount of the ink, preferably 50% by mass or less. [0017]

The binder having an acid group (B) contains a urethane resin (Bl) that is a product of reaction between polyols (bl) including at least one selected from the group consisting of at least one polyol having an acid group (bl1) and at least one polyether polyol (bl-2) and at least one polycarbonate polyol (bl-3) and at least one polyisocyanate (b2) .

[0018]

The acid value of the urethane resin (Bl) is preferably 3 mg KOH/g or more, more preferably 5 mg KOH/g or more, preferably 40 mg KOH/g or less, more preferably 30 mg KOH/g or less. As used herein, an acid value refers to a theoretical calculation based on the amount of, for example, acid group-containing compounds used to produce the urethane resin (Bl), such as the polyol having an acid group (bl-1). [0019]

The urethane resin (Bl), moreover, contains an alicyclic structure. By virtue of containing an alicyclic structure, the urethane resin (Bl) helps reduce blocking of printed articles. Examples of alicyclic structures include saturated C3 to CIO (preferably C4 to C8) monocyclic structures, such as the cyclobutyl ring, the cyclopentyl ring, the cyclohexyl ring, the cycloheptyl ring, the cyclooctyl ring, and the propylcyclohexyl ring; and saturated C5 to C20 (preferably C7 to C12) bridged cyclic structures, such as the tricyclo[5.2.1.0.2.6]decyl structure, the bicyclo[4.3.0]nonyl structure, the tricyclo[5.3.1.1]dodecyl structure, the propyltricyclo[5.3.1.1]dodecyl structure, the norbornyl structure, the isobornyl structure, the dicyclopentanyl structure, and the adamantyl structure. Of these, saturated monocyclic structures are particularly preferred, and the cyclohexyl ring structure is more preferred. [0020]

The alicyclic structure content of the urethane resin (Bl) is 1,000 mmol/kg or more in the total amount of the urethane resin (Bl), preferably 1,200 mmol/kg or more, more preferably 1,500 mmol/kg or more, preferably 5,000 mmol/kg or less, more preferably 3,000 mmol/kg or less, even more preferably 2,500 mmol/kg or less.

As mentioned herein, the proportion of alicyclic structures in the urethane resin (Bl) is a calculation based on the total mass of the polyols (bl), polyisocyanate (b2), and all other raw materials used to produce the urethane resin (Bl) and the amount of substance of alicyclic structures in the compound(s) containing an alicyclic structure used to produce the urethane resin (A) (polyol(s) having an alicyclic structure (bl-3) and/or polyisocyanate (s) having an alicyclic structure) . [0021]

The urethane resin (Bl), furthermore, may contain an aromatic ring. If the urethane resin (Bl) contains an aromatic ring, its amount is preferably 0 mmol/kg or more in the total amount of the urethane resin (Bl), more preferably 500 mmol/kg or more, even more preferably 1,000 mmol/kg or more, preferably 4,000 mmol/kg or less, more preferably 3,000 mmol/kg or less, even more preferably 2,500 mmol/kg or less . [0022]

The alicyclic structure may be contained in the polyols (bl) or may be contained in the polyisocyanate (b2). The ratio between the alicyclic structure content, by the number of moles, derived from the polyisocyanate (b2) and that from the polyols (bl) is 0 or more, preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.2 or more, preferably 10 or less, more preferably 8 or less, even more preferably 5 or less. [0023]

The acid group in the polyol having an acid group (bl1) can be, for example, a carboxy or sulfonic acid group. The polyol having an acid group (bl-1) can be, for example, at least one polyol having a carboxy group or at least one polyol having a sulfonic acid group. [0024]

The polyol having a carboxy group can be one or two or more of such polyols. Examples include hydroxy acids, such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid; and polyester polyols having a carboxy group. Polyester polyols having a carboxy group can be obtained by reacting a hydroxy acid with polycarboxylic acids. [0025]

The polyol having a sulfonic acid group can be one or two or more of such polyols. Examples include polyester polyols that are products of reaction between a dicarboxylic acid having a sulfonic acid group or its salt and a lowmolecular-weight polyol (e.g., with a molecular weight of 100 or more and 1000 or less) . Examples of dicarboxylic acids having a sulfonic acid group include 5sulfoisophthalic acid, sulfoterephthalic acid, 4sulfophthalic acid, and 5-(4-sulfophenoxy) isophthalic acid. Examples of low-molecular-weight polyols include Cl-10 alkanediols, such as ethylene glycol, propylene glycol, 1,4butanediol, 1,6-hexanediol, and neopentyl glycol; and C2-10 polyether polyols, such as diethylene glycol. [0026]

The number-average molecular weight of the polyol having an acid group (bl-1) is preferably 100 or more, preferably 2000 or less, more preferably 1000 or less.

As mentioned herein, number-average and weight-average molecular weights are polystyrene-equivalent values measured by gel permeation chromatography (GPC). [0027]

The polyester polyol (bl-2) can be, for example, polyester polyol(s) resulting from esterification of a lowmolecular-weight polyol (e.g., a polyol having a molecular weight of 50 or more and 300 or less) and a polycarboxylic acid; polyester polyol(s) resulting from ring-opening polymerization of a cyclic ester compound, such as εcaprolactone; and/or polyester polyol(s) that is copolymer(s) thereof. [0028]

Examples of low-molecular-weight polyols include polyols having a relatively low molecular weight (e.g., a molecular weight of 50 or more and 300 or less), such as ethylene glycol, diethylene glycol, 1,2-propylene glycol, dipropylene glycol, neopentyl glycol, 2-butyl-2-ethyl-l,3propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-l,5pentanediol, 1,4-cyclohexanediol, 1,6-hexanediol, and cyclohexanedimethanol. [0029]

Examples of polycarboxylic acids include aliphatic polycarboxylic acids, such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid; aromatic polycarboxylic acids, such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; and anhydrides or ester-forming derivatives of such aliphatic and aromatic polycarboxylic acids. [0030]

For the sake of compatibility with, for example, pigments, the number-average molecular weight of the polyester polyol (bl-2) is preferably 500 or more, more preferably 1,000 or more, preferably 4,000 or less, more preferably 3,000 or less.

[0031]

The polycarbonate polyol (bl-3) can be, for example, product(s) of reaction between a carbonate and a polyol; and/or product(s) of reaction between phosgene and a polyol or similar compound. [0032]

Examples of carbonates include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonates, and diphenyl carbonate. [0033]

Examples of polyols that can react with carbonates and phosgene include the polyols listed above as examples of low-molecular-weight polyols; and high-molecular-weight polyols (with a weight-average molecular weight of 500 or more and 5,000 or less), such as polyether polyols (e.g., polyethylene glycol and polypropylene glycol) and polyester polyols (e.g., polyhexamethylene adipate). In particular, polyols containing an aromatic ring are preferred. [0034]

For the sake of compatibility with, for example, pigments, the number-average molecular weight of the polycarbonate polyol (bl-3) is preferably 500 or more, more preferably 1,000 or more, preferably 4,000 or less, more preferably 3,000 or less. [0035]

In the polyols (bl), the percentage of the polycarbonate polyol (bl-3) in the total of the polyester polyol (bl-2) and polycarbonate polyol (bl-3) is preferably 0% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, preferably 100% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less. [0036]

Preferably, the polyols (bl) include at least a polycarbonate polyol (bl-3). In the polyols (bl), the percentage of the polycarbonate polyol (bl-3) is preferably 0% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, preferably 100% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less. [0037]

The total percentage of the polyol having an acid group (bl-1), polyester polyol (bl-2), and polycarbonate polyol (bl-3) is preferably 60% by mass or more in the polyols (bl), more preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more and may be 95% by mass or less. [0038]

Preferably, the polyols (bl) further include at least one polyol having an alicyclic structure (bl-4).

The polyol having an alicyclic structure (bl-4) can be one or two or more of such polyols. Examples include saturated diols having an alicyclic structure, such as cyclobutanediol, cyclopentanediol, 1,4-cyclohexanediol, cycloheptanediol, cyclooctanediol, butylcyclohexanediol, cyclohexanedimethanol, hydroxypropylcyclohexanol, dicyclohexanediol, hydrogenated bisphenol A, and 1,3adamantanediol; unsaturated diols having an alicyclic structure, such as 1,1'-bicyclohexylidenediol; and saturated triols having an alicyclic structure, such as cyclohexanetriol. The number-average molecular weight of the polyol having an alicyclic structure (bl-4) is preferably 100 or more and 500 or less. [0039]

If a polyol having an alicyclic structure (bl-4) is used, its percentage is preferably 0% by mass or more in the total amount of the polyols (bl) for reduced blocking of printed articles, more preferably 5% by mass or more, preferably 40% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less. [0040]

The total percentage of the polyol having an acid group (bl—1), polyester polyol (bl-2), polycarbonate polyol (bl3), and polyol having an alicyclic structure (bl-4) is preferably 70% by mass or more in the polyols (bl), more preferably 80% by mass or more, even more preferably 90% by mass or more.

[0041]

The polyols (bl) may include extra polyols (bl-5). Examples of extra polyols include polyether polyols, lowmolecular-weight polyols (e.g., with a molecular weight of 50 or more and 300 or less), and polyolefin polyols. [0042]

Examples of polyether polyols (bl-2) include polymers produced by addition polymerization of an alkylene oxide performed using one or two or more compounds having two or more groups bearing an active hydrogen atom (-NH- or -OH) as initiator (s) . [0043]

Examples of initiators include compounds having two hydroxyl groups, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and bisphenol A; and compounds having three hydroxyl groups, such as glycerol, trimethylolethane, and trimethylolpropane. [0044]

Examples of alkylene oxides include epoxide compounds, such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, and epichlorohydrin; and C4 or larger (preferably C4-6, in particular C4) cyclic ethers, such as tetrahydrofuran .

[0045]

For the sake of compatibility with, for example, pigments, the number-average molecular weight of a polyether polyol is preferably 500 or more, more preferably 1,000 or more, preferably 4,000 or less, more preferably 3,000 or less .

As mentioned herein, number-average molecular weights represent values measured by gel permeation chromatography (GPC) . [0046]

Low-molecular-weight polyols can be polyols having a molecular weight of roughly 50 or more and 300 or less. Examples include C2 to C6 aliphatic polyols, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5pentanediol, 1,6-hexanediol, 3-methyl-l,5-pentanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, and 1,3-butanediol; polyols containing an alicyclic structure, such as 1,4-cyclohexanediol and cyclohexanedimethanol; and polyols containing an aromatic structure, such as bisphenol compounds, e.g., bisphenol A and bisphenol F, and their alkylene oxide adducts.

[0047]

Examples of polyolefin polyols include polyisobutene polyols, hydrogenated polybutadiene polyols, and hydrogenated polyisoprene polyols. [0048]

The percentage of extra polyols (bl-5) is preferably 50% by mass or less in the polyols (bl), more preferably 40% by mass or less, even more preferably 30% by mass or less, further preferably 20% by mass or less, in particular 10% by mass or less.

[0049]

The polyisocyanate (b2) can be one or two or more polyisocyanates. Examples include aromatic polyisocyanates, such as 4,4'-diphenylmethane diisocyanate, 2,4'diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate; aliphatic polyisocyanates, such as hexamethylene diisocyanate and lysine diisocyanate; and polyisocyanates having an alicyclic structure, such as cyclohexane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate . [0050]

Preferably, the polyisocyanate (b2) includes a polyisocyanate having an alicyclic structure. The percentage of the polyisocyanate having an alicyclic structure is preferably 50% by mass or more in the polyisocyanate (b2), more preferably 80% by mass or more, even more preferably 90% by mass or more, preferably 100% by mass or less. [0051]

The proportion of the number of equivalents, by the number of moles, of isocyanate groups in the polyisocyanate (b2) to that of hydroxyl groups in the polyols (bl) [isocyanate groups/hydroxyl groups] is preferably 0.8 or more, more preferably 0.9 or more, preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less . [0052]

In the production of the urethane resin (Bl), at least one chain extender may optionally be used. [0053]

The chain extender can be one or two or more extenders. Examples include polyamines, hydrazine compounds, and other compounds having an active hydrogen atom. [0054]

Examples of polyamines include diamines, such as ethylenediamine, 1,2-propanediamine, 1,620 hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'dimethyl-4,4'-dicyclohexylmethanediamine, 1,4cyclohexanediamine, N-ethylaminoethylamine, and Nmethylaminopropylamine; diamines having a hydroxy group, such as N-hydroxymethylaminoethylamine, Nhydroxyethylaminoethylamine, and Nhydroxypropylaminopropylamine; triamines, such as diethylenetriamine and dipropylenetriamine; and tetramines, such as triethylenetetramine. Of these, ethylenediamine is particularly preferred. [0055]

Examples of hydrazine compounds include hydrazine, N,N'-dimethylhydrazine, 1,6-hexamethylenebishydrazine, succinic dihydrazide, adipic dihydrazide, glutaric dihydrazide, sebacic dihydrazide, isophthalic dihydrazide, β-semicarbazidopropionic hydrazide, 3 semicarbazidopropyl carbazate, and semicarbazido-3-semicarbazidomethyl-3,5,5trimethylcyclohexane. [0056]

Examples of other compounds having an active hydrogen include glycols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3butanediol, 1,4-butanediol, hexamethylene glycol, saccharose, methylene glycol, glycerol, and sorbitol;

phenols, such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone, and water.

[0057]

If the chain extender is, for example, polyamine (s), the ratio between the number of equivalents of amino groups and that of isocyanate groups in the polyamine(s) [amino groups/isocyanate groups] is preferably 1.2 or less, more preferably in the range of 0.3 or more and 1 or less. [0058]

For improved durability of printed articles, the weight-average molecular weight of the urethane resin (A) is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 20,000 or more, preferably 500,000 or less, more preferably 200,000 or less, even more preferably 100,000 or less. Increasing the weight-average molecular weight not only helps improve the durability of printed articles, but also helps reduce, for example, blocking caused by incomplete drying. Ensuring the weight-average molecular weight is moderately small helps reduce, for example, incomplete transfer and resolubility of the ink. [0059]

The urethane resin (Bl) can be produced by reacting the polyols (bl) and the polyisocyanate (b2), optionally with chain extender(s). The reaction between the polyols (bl) and the polyisocyanate (b2) may be done in the presence of at least one organic solvent. Preferably, the polyols (bl) and the polyisocyanate (b2) are allowed to react at a temperature of 50°C or more and 150°C or less.

[0060]

The organic solvent can be one or two or more solvents. Examples include ketone solvents, such as acetone and methyl ethyl ketone; ether solvents, such as tetrahydrofuran and dioxane; ester solvents, such as ethyl acetate and butyl acetate; nitrile solvents, such as acetonitrile; and amide solvents, such as dimethylformamide and N-methylpyrrolidone. [0061]

As an attempt at safety and/or reducing environmental burdens, the organic solvent may be partially or completely removed, for example by vacuum distillation, during or after the production of the urethane resin (Bl). [0062]

The percentage of the urethane resin (Bl) is preferably 90% by mass or more in the binder having an acid group (B), more preferably 95% by mass or more, even more preferably 99% by mass or more, in particular 100% by mass. [0063]

The binder having an acid group (B) may be dispersed beforehand in the aqueous medium (D), described later herein. An example of a method for dispersing the urethane resin (Bl) in the aqueous medium (D) (making the ink waterbased) is to prepare the binder having an acid group (B) (binder (B) preparation step), mix the resulting binder having an acid group (B) with at least a subset of the basic compound (C), described later herein (neutralization step), and mix the resulting mixture with the aqueous medium (D) to make a liquid dispersion (dispersion step).

If chain extender(s) is used, the chain extender(s) may be added in the binder (B) preparation step or may be added after the dispersion step. [0064]

For the sake of resolubility of the aqueous ink, reduced blocking of printed articles, improved print density, and adhesion to substrates, the percentage of the binder having an acid group (B) is preferably 10% by mass or more in the liquid dispersion, more preferably 20% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less. [0065]

During the process of making the ink water-based, an emulsifier may optionally be used. During the aqueous dissolution or aqueous dispersion, a homogenizer or similar machinery may optionally be used.

Examples of emulsifiers include nonionic emulsifiers, such as polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styryl phenyl ether, polyoxyethylene sorbitol tetraoleate, and polyoxyethylenepolyoxypropylene copolymers; anionic emulsifiers, such as sodium oleate and other fatty acid salts, alkyl sulfates, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonate, polyoxyethylenealkyl sulfates, sodium alkanesulfonates, and sodium salts of alkyl diphenyl ether sulfonic acids; and cationic emulsifiers, such as salts of alkylamines, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts. In particular, anionic or nonionic emulsifiers are preferred in terms of storage stability. [0066]

The basic compound (C) includes at least one selected from the group consisting of a basic metal compound (Cl) and an organic amine (C2).

Examples of basic metal compounds (Cl) include metal hydroxides, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide; metal chlorides, such as sodium chloride and potassium chloride; and metal sulfates, such as copper sulfate . [0067]

Examples of organic amines (C2) include ammonia; primary amines, such as monoethanolamine; tertiary amines, such as triethylamine and diethylethanolamine; and cyclic amines, such as morpholine.

Preferably, the basic compound (C) includes at least an organic amine (C2). [0068]

The proportion represented by the formula below is preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.05 or more and is 0.3 or less, preferably 0.25 or less, more preferably 0.2 or less, even more preferably 0.15 or less. Ensuring this proportion is in these ranges leads to good boilability/retortability.

The number of moles of the basic metal compound (Cl) x the valency of the basic metal compound (Cl) / {(the number of moles of the organic amine (C2) x the valency of the organic amine (C2) + (the number of moles of the basic metal compound (Cl) x the valency of the basic metal compound (Cl)) } [0069]

The basic metal compound (Cl) and organic amine (C2) may be in salt form with the acid group in the binder having an acid group (B) in the aqueous liquid ink. Neutralization of the acid group in the binder having an acid group by the basic compound (Cl) and organic amine (Cl) helps improve the aqueous dispersibility of the binder. [0070]

The basic compound (C) content is preferably 0.01 parts by mass or more per 100 parts by mass of the binder having an acid group (B), more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, preferably 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 4 parts by mass or less . [0071]

For the aqueous medium (D), examples include water; at least one hydrophilic organic solvent; and a mixture of water and at least one hydrophilic organic solvent. In terms of safety and addition to the environment, water or a mixture of water and at least one hydrophilic organic solvent is preferred.

The hydrophilic organic solvent can be one or two or more of such solvents, preferably water-miscible one(s) . Examples include alcohol solvents, such as methanol, ethanol, n-propanol, and 2-propanol; ketone solvents, such as acetone and methyl ethyl ketone; polyhydric alcohol solvents, such as ethylene glycol, diethylene glycol, propylene glycol, polyalkylene glycols, and glycerol; ether solvents, such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-npropyl ether, and ethyl carbitol; and amide solvents, such as N-methyl-2-pyrrolidone.

[0072]

If the aqueous medium (D) includes water and hydrophilic organic solvent(s), the percentage of water is preferably 80% by mass or more in the aqueous medium (D), more preferably 85% by mass or more, even more preferably 90% by mass or more. For example, the percentage of water may be 100% by mass or less, and even a percentage of 95% by mass or less is acceptable. [0073]

The aqueous liquid ink according to the present invention may further contain auxiliaries. The auxiliaries may alternatively be the following ones, which are used on an as-needed basis: waxes for imparting, for example, abrasion resistance and sliding smoothness, such as paraffin waxes, polyethylene waxes, and carnauba wax; fatty acid amide compounds, such as oleic acid amide, stearic acid amide, and erucic acid amide; silicone or non-silicone antifoams for controlling foaming during printing; dispersants, etc. [0074]

For dispersants, nonionic dispersants are preferred.

The acid value of a dispersant is preferably 30 mg KOH/g or less, more preferably 25 mg KOH/g or less, even more preferably 20 mg KOH/g or less. For example, the acid value may be 1 mg KOH/g or more, or may even be 3 mg KOH/g or more.

Preferably, the acid value of the dispersant is smaller than that of the binder having an acid group (B). The difference between the acid value of the binder having an acid group (B) and that of the dispersant is, for example, 1 mg KOH/g or more, more preferably 3 mg KOH/g or more, preferably 30 mg KOH/g or less, more preferably 20 mg KOH/g or less. [0075]

The dispersant content is preferably 40 parts by mass or more per 100 parts by mass of the colorant (A), more preferably 50 parts by mass or more, even more preferably 60 parts by mass or more, preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 75 parts by mass or less.

The dispersant content is preferably 10 parts by mass or more per 100 parts by mass of the binder having an acid group (B) , more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less. [0076]

The viscosity of the aqueous liquid ink is preferably 7 seconds or more as a measurement taken at 25°C using a Rigo Zahn cup #4, more preferably 10 seconds or more, preferably seconds or less, more preferably 20 seconds or less.

In millipascal-seconds, the viscosity is preferably 70 (mPa-s) or more at 25°C, more preferably 100 (mPa-s) or more, preferably 350 (mPa-s) or less, more preferably 250 (mPa-s) or less. [0077]

The surface tension of the aqueous liquid ink is preferably 25 mN/m or more, more preferably 33 mN/m or more, preferably 50 mN/m or less, more preferably 43 mN/m or less. Ensuring the surface tension of the ink is moderately high helps reduce dot bridging (type of dirt on the print surface that occurs when adjacent dots in halftone-dot areas join together) while maintaining wettability of the ink on substrates. Ensuring the surface tension of the ink is moderately small helps increase the wettability of the ink on substrates and thereby reduce repellence. [0078]

The aqueous liquid ink according to the present invention can be produced using equipment that is common in the production of gravure and flexographic inks, such as an Eiger mill, a sand mill, a gamma mill, or an attritor. [0079]

In the preparation of the aqueous liquid ink according to the present invention, a precursory composition (milled base ink) may be prepared to ensure uniformity. The precursory composition is prepared by mixing together the colorant (A), at least part of the binder having an acid group (B), at least a subset or part of the basic compound (C), a dispersant as described above, and at least a subset or part of the aqueous medium (D). [0080]

The aqueous liquid ink according to the present invention is superior in adhesion to different substrates; can be used for printing on paper, synthetic paper, thermoplastic resin films, plastic products, sheet steel, etc.; is a useful ink for gravure printing, in which an electronically engraved or similar gravure plate is used, or for flexography, in which a resin or similar flexographic plate is used; and, at the same time, is not an ink for inkjet printing, in which ink is ejected from inkjet nozzles without using a plate. That is, with an inkjet ink, ink droplets ejected from nozzles adhere directly to a substrate and form a printed article. With the aqueous liquid ink according to the present invention, the printing ink is once attached/transferred to a printing plate or printing pattern, and then only the ink is attached again, to a substrate this time, optionally followed by drying, to make a printed article.

The thickness of a film of printing ink formed by gravure printing or flexography using the aqueous liquid ink according to the present invention is, for example, 10 pm or less, preferably 5 pm or less.

[0081]

Examples of substrates include films of thermoplastic resins, such as polyamide resins, e.g., nylon 6, nylon 66, and nylon 46, polyester resins, e.g., polyethylene terephthalate (PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate, polyhydroxycarboxylic acids, e.g., polylactic acid, biodegradable resins, e.g., poly(ethylene succinate), poly(butylene succinate), and other aliphatic polyester resins, polyolefin resins, e.g., PP and polyethylene, polyimide resins, polyarylate resins, and mixtures thereof as well as a stack of such films, but in particular, polyester, polyamide, polyethylene, and polypropylene films are suitable for use. These substrate films may be nonoriented films or oriented films and are not limited to a particular production process. The thickness of the substrate film is not critical either, but usually it only needs to be in the range of 1 to 500 pm.

Preferably, the print surface of the substrate film has been treated with a corona discharge. There may be a deposited coating of silica or alumina, for example, on the print surface.

EXAMPLES [0082]

The following describes the present invention in detail by examples and comparative examples. [0083] (Synthesis Examples 1 to 10 and Comparative Synthesis Examples 1 to 3: Preparation of Binders (1) to (13))

In a nitrogen-purged vessel equipped with a thermometer, a nitrogen inlet tube, and a stirrer, the polyols (bl) specified in Table 1 and the polyisocyanate (b2) specified in Table 1 were allowed to react in methyl ethyl ketone to give an organic solution of a urethane prepolymer having a terminal isocyanate group (binder having an acid group).

Then the basic compound (C) or aqueous solution of a basic compound (C) specified in Table 1 was added to neutralize some or all of the carboxy groups in the urethane prepolymer, and the mixture was stirred thoroughly with water and the aqueous solution of a chain extender specified in Table 1, giving an aqueous dispersion of urethane resin. Then the dispersion was aged, and the solvent was eliminated. In this way, binders (1) to (13) were obtained with a non-volatile content of 40% by mass.

For the binders (1) to (13) obtained, the alicyclic structure content and aromatic ring content of the urethane

- 33 resin and the acid value are presented in Table 1. [0084]

- 34 [Table 1]

Comparative Synthesis Example	CO	(13)	CM CO			258			co		107			co co		ID	40	066	34
CM	(12)	cn I-			279		r-			96					CD	40	1182	20
v—	(11)	27					29		198	147	45				CD	40	2120	co CM
Synthesis Example	o T-	(10)	Ί-		92	184		00			100			co		in	40	1157	CO T-
σ>	(6)	CO t—	125		166		Tt			92			27		CD	o Tt	1016	14
co	co	Ί-			250		23			110			22		CO	40	1485	co T-
Γ.	(z)	25				CO CM	co Ί-			145			23		CO	40	1659	26
cd	(9)	co T-			o co CM		CM Ί—			93		co T-			CO	40	1218	CD T-
ID	(S)	σ>			290		15			86	T*“				CM	40	1170	10
Ct	(4)	20		224			14			141			co		CD	40	1747	CM
CO	(e)	19		228			18			135		Ί—			'Ct	40	1787	20
CM	(2)	13	197				'Ct			148			19		ct	40	co CM	14
T“	X	15	231				35			119		CO T-				40	1918	1“
	Binder No.	2,2-Dimethylolpropionic acid	Polyester polyol 1	Polyester polyol 2	Polycarbonate polyol 1	Polycarbonate polyol 2	1,4-Cyclohexanedimethanol	Neopentyl glycol	Polyether polyol 1	Isophorone diisocyanate	50% by mass aqueous solution of potassium hydroxide	25% by mass aqueous ammonia	Dimethylethanolamine	Triethylamine	80% by mass aqueous solution of hydrazine	licyclic structure content (mmol/kg)	Aromatic ring content (mmol/kg)	Acid value (mg KOH/g)
Ί- -Q^	CM X)	CO X> ·>—X	(wq)	(9-i.q)	Basic metal compound (C1)	Organic amine (C2)
Polyols (b1)	Polyisocyanate (b2)	Basic compound (C)	Chain extender	<

Unit: parts by mass

[0085]

In Table 1, polyester polyol 1 represents an aliphatic polyester polyol (Daicel Corporation L212AL; numberaverage molecular weight, 1,250), polyester polyol 2 represents an aromatic polyester polyol (an aromatic polyester polyol produced by reacting 13.1 parts by mass of ethylene glycol, 22.0 parts by mass of neopentyl glycol, 18.5 parts by mass of terephthalic acid, 18.5 parts by mass of isophthalic acid, and 7.9 parts by mass of acrylic acid in the presence of 0.03 parts by mass of monobutyltin oxide; number-average molecular weight, 1,000), polycarbonate polyol 1 represents a polycarbonate polyol (Ube Industries, Ltd. ETERNACOLL UH-200; number-average molecular weight, 2,000), polycarbonate polyol 2 represents a polycarbonate polyol (Ube Industries, Ltd. ETERNACOLL UH-100; numberaverage molecular weight, 1000), and polyether polyol 1 represents a polytetraethylene glycol (number-average molecular weight, 2,000) . [0086] Examples 1 to 10 and Comparative Examples 1 to 3

Binders (1) to (13), obtained in the Synthesis Examples and Comparative Synthesis Examples, were each stirred and mixed well in accordance with the formula below. The resulting mixtures were milled in a bead mill to give milled base inks. The resulting milled base inks were respectively mixed with another 10 parts by mass of binders (1) to (13) and another 4 parts by mass of water, giving aqueous blue printing inks. The viscosity of the resulting printing inks was adjusted with water to be 16 seconds (25°C) as measured with a Zahn cup #4 (Rigo). The inks obtained were respectively named aqueous liquid inks of Examples 1 to 10 and Comparative Examples 1 to 3. [0087]

The surface tension of the resulting aqueous liquid inks was checked by measuring their surface tension at 25°C. The measurement of the surface tension was based on the Wilhelmy method and performed using Kyowa Interface Science Co., Ltd. DY-300 automatic surface tensiometer. [0088] [Formula of the Milled Base Inks]

FASTOGEN BLUE LA5380 cyan pigment (DIC) 15 parts by mass

Binder for aqueous flexographic inks 40 parts by mass Nonionic pigment dispersant (BYK)10 parts by mass Isopropyl alcohol 3 parts by mass Water 8 parts by mass Silicone antifoam (BYK) 0.2 parts by mass [0089]

[Total Amounts in the Aqueous Liquid Inks (blue) (excluding water for viscosity adjustment)]

FASTOGEN BLUE LA5380 cyan pigment (DIG) 15 parts by mass

Binder for aqueous flexographic inks 50 parts by mass Nonionic pigment dispersant (BYK)10 parts by mass Isopropyl alcohol 3 parts by mass Water 12 parts by mass Silicone antifoam (BYK) 0.2 parts by mass [0090]

The aqueous liquid inks of the Examples and Comparative Examples were applied to the corona-treated polyethylene terephthalate (PET) film (Toyobo Co., Ltd. ESTER E5102; thickness, 12 pm) and corona-treated biaxially oriented polypropylene (OPP) film (Toyobo Co., Ltd. PYLEN P2161; thickness, 20 pm) specified in Table 1 using Flexiproof 100 test printer (Testing Machines, Inc.) to print a 240-mm long by 80-mm wide solid image. The printed image was dried using a hair dryer, giving printed articles. [0091]

The resulting printed articles were tested for boilability/retortability, resistance to solvents, freedom from blocking, and adhesion to substrate for each type of film. The ink transfer was checked on the basis of print density. [0092] [Test Item 1: Boilability/Retortability (resistance to hot water)]

The ink side of the printed article made with a coronatreated polyethylene terephthalate (PET) film was coated with DICDRY LX-500/KW-75 urethane-based dry-lamination adhesive (DIC) to a coating density of 3.5 g/m², dried, and then laminated with aluminum foil (hereinafter AL; Toyo Aluminum Kogyo K.K., Aluminum Foil C, 15 pm) using a dry laminator (DIC Engineering), giving two-layer laminate 1. Then the AL of laminate 1 was likewise coated with the adhesive, cast polypropylene film (hereinafter R-CPP; Toray Plastic Films ZK-75, 50 gm) was placed thereon, and the resulting stack was aged at 40°C for 5 days, giving threelayer composite laminate 2.

The resulting laminate 2 was shaped into a 120 mm x 120 mm pouch, and 70 g of simulated food, a mixture of vinegar, salad oil, and Bolognese meat sauce in a 1:1:1 weight ratio, was sealed in the pouch. After 30 minutes of retort sterilization of the pouch with steam at 135°C, the delamination of the ink coating was evaluated in four grades .

®: No signs of delamination.

O: Only a very few small delamination blisters.

Δ: Medium-sized delamination blisters are observed in part.

x: Signs of delamination, whether large or small, are observed throughout.

[0093]

[Test Item 2: Resistance to Solvents]

The printed article prepared was rubbed ten times with a cotton swab soaked in ethanol, and the erasure of the print was graded. A commercially available laminate with a best-before date inkjet-printed thereon was used as a reference standard. The criteria for grading were as follows .

®: A good result; none of the print was erased.

O: A good result; 80% or more of the print was left.

Δ: 50% of the print was erased.

x: 100% of the print was erased.

[0094]

[Test Item 3: Freedom from Blocking]

The film was cut to a 4 cm x 4 cm size, and the cut pieces were put on top of one another with the printed side of the printed article on the non-printed side. The stack was left under 40°C conditions for 12 hours under a load of 5 Kgf/cm², then the pieces of film were separated, and the ink transfer (setoff) to the non-printed side was visually assessed on the basis of the percentage area (%) of setoff.

®: No transfer to the non-printed side.

O: Setoff transfer is observed, although as small as less than 5%.

Δ: 5% or more to less than 20% setoff transfer is observed.

x: 20% or more setoff transfer is observed. [0095] [Test Item 4: Adhesion to the Substrate]

Adhesive tape (Nichiban, 12-mm wide) was attached to the printed side of a printed article that had been aged for one day. An end of the tape was pulled off at right angles to the surface of the print, and the appearance was visually assessed on the basis of the percentage of the remaining print coating.

®: No print coating is removed.

O: 80% or more and less than 90% of the print coating remained on the film.

Δ: 50% or more and less than 80% of the print coating remained on the film.

x: Only less than 50% of the print coating remained on the film.

[0096]

[Test Item 5: Ink Transfer]

Ink transfer was graded on the basis of the solid density of the printed article measured using X-Rite SpectroEye densitometer.

O: Ink transfer is good; the cyan density of the printed article is 1.9 or more.

- 41 Δ: Ink transfer is intermediate; the cyan density of the printed article is 1.6 or more and less than 1.9.

x: Ink transfer is poor; the cyan density of the printed article is less than 1.6. [0097]

- 42 [Table 2]

Comparative Example	co	Tf CM	X	O	<	X	<	©	O	O	O
CM	Binder synthesis failed
	co CM	X	X	X	©	©	©	©	O	O
Example	o I-	o co	o	O	O	©	©	©	O	O	O
σ>	CO	O	o	O	O	O	©	©	O	O
00	CM CO	o	o	o	©	©	©	©	O	O
	o co	o	o	o	©	©	©	©	O	O
co	CM CO	o	o	o	©	©	©	©	o	O
in	CO rt	o	o	o	o	©	©	©	o	O
st	00 CM	o	Θ	©	©	©	©	©	o	O
co	CM	o	©	©	©	©	©	©	o	O
CM	CO	o	o	o	©	©	©	©	o	O
V“	CM CO	o	o	o	©	©	©	©	o	O
	Surface tension (mN/m)	Boilability/Retortability	Ethanol	Alkali	1— LU CL	CL CL O	1— LU CL	OPP	LU CL	OPP
Resistance to solvents	Freedom from blocking	Adhesion to substrate	Ink transfer

[0098]

By using the aqueous liquid ink according to the present invention, one can provide an aqueous liquid ink that meets essential performance requirements for use as an aqueous liquid ink (adhesion to substrates, freedom from blocking, high print density, etc.) and also combines high waterproofness (boilability/retortability) and resistance to solvents. By virtue of combining these performance attributes, the ink can provide a printed article that can withstand even boiling and retort treatment.

Claims (5)

1. CLAIMS [Claim 1]

   An aqueous liquid ink comprising a colorant (A), a binder having an acid group (B), at least one basic compound (C), and an aqueous medium (D), wherein:

   the binder having an acid group (B) contains a urethane resin (Bl) that is a product of reaction between polyols (bl) including at least one selected from the group consisting of a polyol having an acid group (bl-1) and a polyester polyol (bl-2) and a polycarbonate polyol (bl-3) and a polyisocyanate (b2);

   an alicyclic structure content of the urethane resin (Bl) is 1,000 mmol/kg or more in a total amount of the urethane resin (Bl); and the basic compound (C) includes at least one selected from the group consisting of a basic metal compound (Cl) and an organic amine (C2).
2. [Claim 2]

   The aqueous liquid ink according to Claim 1, wherein an acid value of the binder having an acid group (B) is 3 mg KOH/g or more and 40 mg KOH/g or less.
3. [Claim 3]

   The aqueous liquid ink according to Claim 1 or 2, wherein the polyols (bl) further include 20% by mass or less polyol having an alicyclic structure (bl-4).
4. [Claim 4]

   The aqueous liquid ink according to any one of Claims 1 to 3, wherein the ink has a surface tension of 25 mN/m or more and 50 mN/m or less at 25°C.
5. [Claim 5]

   A printed article comprising a print made using an aqueous liquid ink according to any one of Claims 1 to 4.