AU2018373094B2 - Aqueous liquid ink and printed article - Google Patents

Abstract

The present invention addresses the problem of providing an aqueous liquid ink which exhibits adhesion to a base material, blocking resistance, redissolution properties, and a high printing density, and which is also capable of achieving high water resistance (boil retort properties). 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 a polyol (b1-1) having acid groups and a polyether polyol (b1-2). The content of alicyclic structures included in the urethane resin (B1) is in the range of 1,000-5,000 mmol/kg inclusive. The basic compound (C) includes 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 isocyanate containing 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. 8

53641)

[0004]

Also proposed is a water-based printing ink composition

for lamination. This ink composition is made with a water

based 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).

[0004A]

Throughout this specification the word "comprise", or

variations such as "comprises" or "comprising", will be

understood to imply the inclusion of a stated element,

integer or step, or group of elements, integers or steps,

but not the exclusion of any other element, integer or step,

- 2A

or group of elements, integers or steps.

[0004B]

Any discussion of documents, acts, materials, devices,

articles or the like which has been included in the present

specification is not to be taken as an admission that any or

all of these matters form part of the prior art base or were

common general knowledge in the field relevant to the

present disclosure as it existed before the priority date of

each of the appended claims.

Citation List

Patent Literature

[00051

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

[00061

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 good dispersion

of pigment(s) therein and resolubility, i.e., the ability of

a dried coating of an aqueous printing ink, for example on a

gravure plate, to dissolve again in the ink, 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 may be insufficient in

terms of the prevention of blocking and resolubility. The

water-based printing ink composition for lamination

described in PTL 2 may be lacking in resolubility and,

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 combines

adhesion to substrates, freedom from blocking, resolubility,

and high print density and also achieves high waterproofness

(boilability/retortability). 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 for laminated packaging materials), a printed article that can withstand even boiling and retort treatment.

Solution to Problem

[00081

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.

[00091

That is, the present invention relates to an aqueous

liquid ink that contains a colorant (A), a binder having an

acid group (B), basic compounds (C), and an aqueous medium

(D). The binder having an acid group (B) contains a

urethane resin (B1) that is a product of reaction between

polyols (bl) including a polyol having an acid group (bl-1)

and a polyether polyol (bl-2) and a polyisocyanate (b2), and

the alicyclic structure content of the urethane resin (B1)

is 1,000 mmol/kg or more and 5,000 mmol/kg or less in the

total amount of the urethane resin (B1). The basic compounds (C) include 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

adhesiveness, anti-blocking properties, resolubility, and

high print density but also has high waterproofness

(boilability/retortability).

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), basic compounds (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 29

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 non

leafing, 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 (B1) that is a product of reaction between polyols

(bl) including at least one polyol having an acid group (bl

1) and at least one polyether polyol (bl-2) and at least one

polyisocyanate (b2).

[0018]

The acid value of the urethane resin (B1) 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 25 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 (B1), such as the polyol having an acid group (bl-1).

[0019]

The urethane resin (B1), moreover, contains an

alicyclic structure. By virtue of containing an alicyclic

structure, the urethane resin (B1) helps reduce blocking of

printed articles. Examples of alicyclic structures include

saturated C3 to C10 (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

(B1) is 1,000 mmol/kg or more in the total amount of the

urethane resin (B1), preferably 1,300 mmol/kg or more, more preferably 1,800 mmol/kg or more, and 5,000 mmol/kg or less, preferably 3,000 mmol/kg or less, more preferably 2,500 mmol/kg or less.

As mentioned herein, the proportion of alicyclic

structures in the urethane resin (B1) is a calculation based

on the total mass of the polyols (b1), polyisocyanate (b2),

and all other raw materials used to produce the urethane

resin (B1) 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 alicyclic structure may be contained in the polyols

(b1) 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 (b1) 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.

[0022]

The acid group in the polyol having an acid group (bl

1) 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.

[0023]

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.

[0024]

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 low

molecular-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 5

sulfoisophthalic acid, sulfoterephthalic acid, 4

sulfophthalic acid, and 5-(4-sulfophenoxy)isophthalic acid.

Examples of low-molecular-weight polyols include C1-10

alkanediols, such as ethylene glycol, propylene glycol, 1,4

butanediol, 1,6-hexanediol, and neopentyl glycol; and C2-10

polyether polyols, such as diethylene glycol.

[0025]

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).

[0026]

The polyether polyol (bl-2) can be, for example,

polymer(s) 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).

[0027]

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.

[0028]

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.

[0029]

For the sake of compatibility with, for example,

pigments, the number-average molecular weight of the

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).

[0030]

The total percentage of the polyol having an acid group

(bl-1) and polyether polyol (bl-2) 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.

[0031]

Preferably, the polyols (bl) further include at least

one polyol having an alicyclic structure (bl-3).

The polyol having an alicyclic structure (bl-3) 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 1,3 adamantanediol; unsaturated diols having an alicyclic structure, such as 1,1'-bicyclohexylidenediol; and saturated trials having an alicyclic structure, such as cyclohexanetriol. The number-average molecular weight of the polyol having an alicyclic structure (bl-3) is preferably 100 or more and 500 or less.

[0032]

If a polyol having an alicyclic structure (bl-3) 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.

[0033]

The total percentage of the polyol having an acid group

(bl-1), polyether polyol (bl-2), and polyol having an

alicyclic structure (bl-3) 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.

[0034]

The polyols (bl) may include extra polyols (bl-4).

Examples of extra polyols include polyester polyols, low

molecular-weight polyols (e.g., with a molecular weight of or more and 300 or less), polycarbonate polyols, and polyolefin polyols.

[00351

Examples of polyester polyols include polyester polyols

resulting from esterification of a low-molecular-weight

polyol (e.g., a polyol having a molecular weight of 50 or

more and 300 or less) and a polycarboxylic acid; polyester

polyols resulting from ring-opening polymerization of a

cyclic ester compound, such as e-caprolactone; and polyester

polyols that are copolymers thereof.

[00361

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-1,3

propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5

pentanediol, 1,4-cyclohexanediol, 1,6-hexanediol, and

cyclohexanedimethanol.

[0037]

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.

[00381

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, 1,5

pentanediol, 1,6-hexanediol, 3-methyl-1,5-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.

[00391

Examples of polycarbonate polyols include products of

reaction between a carbonate and a polyol; and products of

reaction between phosgene and bisphenol A or any similar

compound.

[0040]

Examples of carbonates include methyl carbonate,

dimethyl carbonate, ethyl carbonate, diethyl carbonate,

cyclocarbonates, and diphenyl carbonate.

[0041]

Examples of polyols that can react with carbonates 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

,000 or less), such as polyether polyols (e.g.,

polyethylene glycol and polypropylene glycol) and polyester

polyols (e.g., polyhexamethylene adipate).

[0042]

Examples of polyolefin polyols include polyisobutene

polyols, hydrogenated polybutadiene polyols, and

hydrogenated polyisoprene polyols.

[0043]

The percentage of extra polyols (bl-4) is preferably

% by mass or less in the polyols (b1), 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.

In particular, the percentage of polyester polyols is

preferably 10% by mass or less in the polyols (b1), more

preferably 5% by mass or less, even more preferably 3% by

mass or less, in particular 1% by mass or less.

[0044]

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.

[0045]

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.

[0046]

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 (b1)

[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.

[0047]

In the production of the urethane resin (B1), at least

one chain extender may optionally be used.

[0048]

The chain extender can be one or two or more extenders.

Examples include polyamines, hydrazine compounds, and other

compounds having an active hydrogen atom.

[0049]

Examples of polyamines include diamines, such as

ethylenediamine, 1,2-propanediamine, 1,6

hexamethylenediamine, piperazine, 2,5-dimethylpiperazine,

isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'

dimethyl-4,4'-dicyclohexylmethanediamine, 1,4

cyclohexanediamine, N-ethylaminoethylamine, and N

methylaminopropylamine; diamines having a hydroxy group,

such as N-hydroxymethylaminoethylamine, N

hydroxyethylaminoethylamine, and N

hydroxypropylaminopropylamine; triamines, such as

diethylenetriamine and dipropylenetriamine; and tetramines,

such as triethylenetetramine. Of these, ethylenediamine is

particularly preferred.

[0050]

Examples of hydrazine compounds include hydrazine,

N,N'-dimethylhydrazine, 1,6-hexamethylenebishydrazine,

succinic dihydrazide, adipic dihydrazide, glutaric dihydrazide, sebacic dihydrazide, isophthalic dihydrazide,

$-semicarbazidopropionic hydrazide, 3 semicarbazidopropyl

carbazate, and semicarbazido-3-semicarbazidomethyl-3,5,5

trimethylcyclohexane.

[0051]

Examples of other compounds having an active hydrogen

include glycols, such as ethylene glycol, diethylene glycol,

triethylene glycol, propylene glycol, 1,3-propanediol, 1,3

butanediol, 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.

[0052]

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.

[0053]

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.

[0054]

The urethane resin (B1) can be produced by reacting the

polyols (b1) and the polyisocyanate (b2), optionally with

chain extender(s). The reaction between the polyols (b1)

and the polyisocyanate (b2) may be done in the presence of

at least one organic solvent. Preferably, the polyols (b1)

and the polyisocyanate (b2) are allowed to react at a

temperature of 500C or more and 1500C or less.

[0055]

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.

[0056]

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 (B1).

[0057]

The percentage of the urethane resin (B1) is preferably

% 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.

[0058]

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 (B1) in the aqueous medium (D) (making the ink water

based) 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

compounds (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.

[0059]

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.

[00601

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 polyoxyethylene

polyoxypropylene 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.

[0061]

The basic compounds (C) include 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.

[0062]

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.

[0063]

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))

[0064]

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.

[00651

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.

[00661

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-n propyl ether, and ethyl carbitol; and amide solvents, such as N-methyl-2-pyrrolidone.

[0067]

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

% 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.

[0068]

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.

[00691

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.

[0070]

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.

[0071]

The viscosity of the aqueous liquid ink is preferably 7

seconds or more as a measurement taken at 250C 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.

[0072]

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.

[0073]

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.

[0074]

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 compounds

(C), a dispersant as described above, and at least a subset

or part of the aqueous medium (D).

[0075]

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.

[0076]

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 non

oriented 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

[0077]

The following describes the present invention in detail

by examples and comparative examples.

[0078]

(Synthesis Example 1: Preparation of Binder (1))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 195 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 145 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 28 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 203 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 2.2 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 12.0 parts by mass of

% by mass aqueous ammonia were added to neutralize some or all of the carboxy groups in the urethane prepolymer, and the mixture was stirred thoroughly with 726 parts by mass of water and 9.2 parts by mass of an 80% aqueous solution of hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (1) was obtained with a

non-volatile content of 40% by mass.

For this binder (1), the proportion of alicyclic

structures in the urethane resin was 2115 mmol/kg, and the

acid value was 28 mg KOH/g.

[0079]

(Synthesis Example 2: Preparation of Binder (2))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 194 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 144 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 28 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 202 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 6.5 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 9.3 parts by mass of 25%

by mass aqueous ammonia were added to neutralize some or all

of the carboxy groups in the urethane prepolymer, and the mixture was stirred thoroughly with 727 parts by mass of water and 9.1 parts by mass of an 80% aqueous solution of hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (2) was obtained with a

non-volatile content of 40% by mass.

For this binder (2), the proportion of alicyclic

structures in the urethane resin was 2103 mmol/kg, and the

acid value was 28 mg KOH/g.

[00801

(Synthesis Example 3: Preparation of Binder (3))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 193 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 143 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 28 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 201 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 10.8 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 6.6 parts by mass of 25%

by mass aqueous ammonia were added to neutralize some or all

of the carboxy groups in the urethane prepolymer, and the

mixture was stirred thoroughly with 728 parts by mass of water and 9.1 parts by mass of an 80% aqueous solution of hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (3) was obtained with a

non-volatile content of 40% by mass.

For this binder (3), the proportion of alicyclic

structures in the urethane resin was 2092 mmol/kg, and the

acid value was 28 mg KOH/g.

[0081]

(Synthesis Example 4: Preparation of Binder (4))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 192 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 142 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 28 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 200 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 15.1 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 3.9 parts by mass of 25%

by mass aqueous ammonia were added to neutralize some or all

of the carboxy groups in the urethane prepolymer, and the

mixture was stirred thoroughly with 729 parts by mass of

water and 9.0 parts by mass of an 80% aqueous solution of hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (4) was obtained with a

non-volatile content of 40% by mass.

For this binder (4), the proportion of alicyclic

structures in the urethane resin was 2080 mmol/kg, and the

acid value was 28 mg KOH/g.

[0082]

(Synthesis Example 5: Preparation of Binder (5))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 191 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 142 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 28 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 199 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 19.2 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 1.3 parts by mass of 25%

by mass aqueous ammonia were added to neutralize some or all

of the carboxy groups in the urethane prepolymer, and the

mixture was stirred thoroughly with 730 parts by mass of

water and 9.0 parts by mass of an 80% aqueous solution of

hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (5) was obtained with a

non-volatile content of 40% by mass.

For this binder (5), the proportion of alicyclic

structures in the urethane resin was 2069 mmol/kg, and the

acid value was 28 mg KOH/g.

[00831

(Synthesis Example 6: Preparation of Binder (6))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 269 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 102 parts by mass of isophorone diisocyanate, 24

parts by mass of 2,2-dimethylolpropionic acid, and 3.5 parts

by mass of neopentyl glycol were allowed to react in 204

parts by mass of methyl ethyl ketone to give an organic

solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 2.0 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 10.8 parts by mass of

% by mass aqueous ammonia were added to neutralize some or

all of the carboxyl groups in the urethane prepolymer, and

the mixture was stirred thoroughly with 726 parts by mass of

water and 6.4 parts by mass of an 80% aqueous solution of

hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was eliminated. In this way, binder (6) was obtained with a non-volatile content of 40% by mass.

For this binder (6), the proportion of alicyclic

structures in the urethane resin was 1142 mmol/kg, and the

acid value was 25 mg KOH/g.

[0084]

(Synthesis Example 7: Preparation of Binder (7))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 268 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 100 parts by mass of isophorone diisocyanate, 22

parts by mass of 2,2-dimethylolpropionic acid, and 5.6 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 204 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 1.8 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 10.0 parts by mass of

% by mass aqueous ammonia were added to neutralize some or

all of the carboxyl groups in the urethane prepolymer, and

the mixture was stirred thoroughly with 726 parts by mass of

water and 6.3 parts by mass of an 80% aqueous solution of

hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (7) was obtained with a non-volatile content of 40% by mass.

For this binder (7), the proportion of alicyclic

structures in the urethane resin was 1222 mmol/kg, and the

acid value was 23 mg KOH/g.

[00851

(Synthesis Example 8: Preparation of Binder (8))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 252 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 110 parts by mass of isophorone diisocyanate, 8.7

parts by mass of 2,2-dimethylolpropionic acid, and 26 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 204 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 0.7 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 4.0 parts by mass of 25%

by mass aqueous ammonia were added to neutralize some or all

of the carboxyl groups in the urethane prepolymer, and the

mixture was stirred thoroughly with 726 parts by mass of

water and 7.0 parts by mass of an 80% aqueous solution of

hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (8) was obtained with a

non-volatile content of 40% by mass.

For this binder (8), the proportion of alicyclic

structures in the urethane resin was 1683 mmol/kg, and the

acid value was 9 mg KOH/g.

[00861

(Synthesis Example 9: Preparation of Binder (9))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 115 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 181 parts by mass of isophorone diisocyanate, 17

parts by mass of 2,2-dimethylolpropionic acid, and 85 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 205 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group (binder having an acid group).

Then 1.4 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 7.9 parts by mass of 25%

by mass aqueous ammonia were added to neutralize some or all

of the carboxyl groups in the urethane prepolymer, and the

mixture was stirred thoroughly with 727 parts by mass of

water and 2.2 parts by mass of an 80% aqueous solution of

hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (9) was obtained with a

non-volatile content of 40% by mass.

For this binder (9), the proportion of alicyclic structures in the urethane resin was 3511 mmol/kg, and the acid value was 18 mg KOH/g.

[0087]

(Comparative Synthesis Example 1: Preparation of Binder

(10))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 196 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 145 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 28 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 204 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group.

Then 13.3 parts by mass of 25% by mass aqueous ammonia

was added to neutralize some or all of the carboxy groups in

the urethane prepolymer, and the mixture was stirred

thoroughly with 725 parts by mass of water and 9.2 parts by

mass of an 80% aqueous solution of hydrazine, giving an

aqueous dispersion of urethane resin. Then the dispersion

was aged, and the solvent was eliminated. In this way,

binder (10) was obtained with a non-volatile content of 40%

by mass.

For this binder (10), the proportion of alicyclic

structures in the urethane resin was 2120 mmol/kg, and the acid value was 28 mg KOH/g.

[00881

(Comparative Synthesis Example 2: Preparation of Binder

(11))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 196 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 145 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 28 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 204 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group.

Then 20 parts by mass of triethylamine was added to

neutralize some or all of the carboxyl groups in the

urethane prepolymer, and the mixture was stirred thoroughly

with 725 parts by mass of water and 9.2 parts by mass of an

% aqueous solution of hydrazine, giving an aqueous

dispersion of urethane resin. Then the dispersion was aged,

and the solvent was eliminated. In this way, binder (11)

was obtained with a non-volatile content of 40% by mass.

For this binder (11), the proportion of alicyclic

structures in the urethane resin was 2120 mmol/kg, and the

acid value was 28 mg KOH/g.

[00891

(Comparative Synthesis Example 3: Preparation of Binder

(12))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 191 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 141 parts by mass of isophorone diisocyanate, 26

parts by mass of 2,2-dimethylolpropionic acid, and 27 parts

by mass of 1,4-cyclohexanedimethanol were allowed to react

in 198 parts by mass of methyl ethyl ketone to give an

organic solution of a urethane prepolymer having a terminal

isocyanate group.

Then 21.3 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide was added to neutralize some

or all of the carboxyl groups in the urethane prepolymer,

and the mixture was stirred thoroughly with 730 parts by

mass of water and 8.9 parts by mass of an 80% aqueous

solution of hydrazine, giving an aqueous dispersion of

urethane resin. Then the dispersion was aged, and the

solvent was eliminated. In this way, binder (12) was

obtained with a non-volatile content of 40% by mass.

For this binder (12), the proportion of alicyclic

structures in the urethane resin was 2064 mmol/kg, and the

acid value was 28 mg KOH/g.

[00901

(Comparative Synthesis Example 4: Preparation of Binder

(13))

In a nitrogen-purged vessel equipped with a

thermometer, a nitrogen inlet tube, and a stirrer, 296 parts

by mass of polyoxytetramethylene glycol (a molecular weight

of 2000), 82 parts by mass of isophorone diisocyanate, 17

parts by mass of 2,2-dimethylolpropionic acid, and 3.6 parts

by mass of neopentyl glycol were allowed to react in 205

parts by mass of methyl ethyl ketone to give an organic

solution of a urethane prepolymer having a terminal

isocyanate group.

Then 1.4 parts by mass of a 50% by mass aqueous

solution of potassium hydroxide and 7.6 parts by mass of 25%

by mass aqueous ammonium were added to neutralize some or

all of the carboxyl groups in the urethane prepolymer, and

the mixture was stirred thoroughly with 727 parts by mass of

water and 3.4 parts by mass of an 80% aqueous solution of

hydrazine, giving an aqueous dispersion of urethane resin.

Then the dispersion was aged, and the solvent was

eliminated. In this way, binder (13) was obtained with a

non-volatile content of 40% by mass.

For this binder (13), the proportion of alicyclic

structures in the urethane resin was 917 mmol/kg, and the

acid value was 17 mg KOH/g.

[0091]

Examples 1 to 9 and Comparative Examples 1 to 4

Binders (1) to (13), obtained in Synthesis Examples 1

to 9 and Comparative Synthesis Examples 1 to 4, 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

(250C) as measured with a Zahn cup #4 (Rigo). The inks

obtained were respectively named aqueous liquid inks of

Examples 1 to 9 and Comparative Examples 1 to 4.

[0092]

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.

[0093]

[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

[0094]

[Total Amounts in the Aqueous Liquid Inks (blue) (excluding

water for viscosity adjustment)]

FASTOGEN BLUE LA5380 cyan pigment (DIC) 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

[0095]

The aqueous liquid inks of Examples 1 to 9 and

Comparative Examples 1 to 4 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.

[0096]

The resulting printed articles were tested for resolubility, freedom from blocking, and adhesion to substrate for each type of film. The ink transfer was checked on the basis of print density.

[0097]

[Test Item 1: Boilability/Retortability (resistance to hot

water)]

The ink side of the printed article made with a corona

treated 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/m 2 , 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 pm) was placed thereon, and the

resulting stack was aged at 400C for 5 days, giving three

layer 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 three

grades.

0: No signs of delamination.

0: Only a very few small delamination blisters.

A: Medium-sized delamination blisters are observed in

part.

x: Signs of delamination, whether large or small, are

observed throughout.

[00981

[Test Item 2: Resolubility]

One drop of distilled water was put on the ink coating

side of the printed article with a dropper and wiped away

with gauze quickly. Resolubility was graded on the basis of

the time after the wiping until the coating dissolved and

disappeared.

0: The coating dissolves in less than 3 seconds after

the drop of water is put thereon.

0: The coating dissolves in 3 seconds or more and less

than 5 seconds after the drop of water is put thereon.

A: The coating dissolves in 5 seconds or more and less

than 7 seconds after the drop of water is put thereon.

x: It takes 7 seconds or more to dissolve the coating.

[00991

[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 400C conditions for 12 hours under a load of

2 Kgf/cm , 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.

0: No transfer to the non-printed side.

0: Setoff transfer is observed, although as small as

less than 5%.

A: 5% or more to less than 20% setoff transfer is

observed.

x: 20% or more setoff transfer is observed.

[0100]

[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.

0: No print coating is removed.

0: 80% or more and less than 90% of the print coating

remained on the film.

A: 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.

[0101]

[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.

0: Ink transfer is good; the cyan density of the

printed article is 1.9 or more.

A: 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.

[0102]

It xG G x G)QQ0Q -a E a) 2:x

E 0

x x x 0 O O

0oo o 0 0oo o 000o oo00o oo

x ow 0 oo 00 0o o

C14oo0000 0o

0 o o000o o

0 0o0 mo EOH -H - O zOW -W - O E m0 0C 00)

c 0

0 0)

0 0EC Z). 0) U) a, 0 a

() a, _0

[0103]

By using the aqueous liquid ink according to the

present invention, one can provide an aqueous liquid ink

that combines adhesion to substrates, freedom from blocking,

resolubility, and high print density and also achieves high

waterproofness (boilability/retortability). By virtue of

combining these performance attributes, the ink can provide

a printed article that can withstand even boiling and retort

treatment.

Claims (4)

1. [Claim 1]

   An aqueous liquid ink comprising a colorant (A), a

   binder having an acid group (B), basic compounds (C), and an

   aqueous medium (D), wherein:

   the binder having an acid group (B) contains a urethane

   resin (B1) that is a product of reaction between polyols

   (bl) including a polyol having an acid group (bl-1) and a

   polyether polyol (bl-2) and a polyisocyanate (b2);

   a percentage of the urethane resin (B1) is 90% by mass

   or more in the binder (B);

   an alicyclic structure content of the urethane resin

   (B1) is 1,000 mmol/kg or more and 5,000 mmol/kg or less in a

   total amount of the urethane resin (B1);

   the basic compounds (C) include a basic metal compound

   (Cl) and an organic amine (C2);

   a proportion represented by the following formula is

   0.5 or less:

   the number of moles of the basic metal compound (Cl) x

   a valency of the basic metal compound (Cl) / {(the number of

   moles of the organic amine (C2) x a valency of the organic

   amine (C2) + (the number of moles of the basic metal

   compound (Cl) x the valency of the basic metal compound

   (C1))}; and

   an acid value of the urethane resin (B1) is 3 mg KOH/g or more and 40 mg KOH/g or less.
2. [Claim 2]

   The aqueous liquid ink according to Claim 1, wherein

   the polyols (bl) further include 0% to 20% by mass polyol

   having an alicyclic structure (bl-3).
3. [Claim 3]

   The aqueous liquid ink according to Claim 1 or 2,

   wherein the ink has a surface tension of 25 mN/m or more and

   mN/m or less at 25°C.
4. [Claim 4]

   A printed article comprising a print made using an

   aqueous liquid ink according to any one of Claims 1 to 3.