JP2965838B2 - Aqueous printing ink composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous printing ink composition containing an aqueous polyurethane dispersion having an active amino group capable of easily reacting with various reactive groups and a crosslinking agent.

[0002]

2. Description of the Related Art Resins such as polyurethane, polyamide, nitrocellulose and polyester are used as binders in printing inks used for various plastic films and metal foils. These resins are used alone or in combination and dissolved in an organic solvent. In this organic solvent type ink, the binder itself has water resistance, and by obtaining a crosslinked ink film using an isocyanate compound or an epoxy compound, excellent physical properties such as solvent resistance and chemical resistance are obtained. Has been expressed.

[0003]

However, these printing inks have a risk of fire due to an organic solvent.
It has the problem of polluting the atmosphere. It is not preferable from the viewpoint of resource saving. Therefore, development of water-based printing inks having excellent physical properties such as solvent resistance, chemical resistance, and water resistance in place of these organic solvent-based inks has been actively conducted.

In water-based printing inks, styrene-maleic acid copolymer resin, styrene-acrylic copolymer resin, acrylic resin and the like are generally used as a binder. However, when printing is performed using an aqueous ink using a binder composed of these resins, it has been pointed out that physical properties such as water resistance, solvent resistance, and chemical resistance of the printed matter are extremely low in practical use. ing.

[0005] In order to obtain sufficient physical properties such as solvent resistance, chemical resistance and water resistance, an epoxy compound is added to an aqueous printing ink.
It is known that a certain degree of physical properties can be obtained by adding a crosslinking agent such as a carbodiimide compound and drying and then crosslinking the ink film. However, because the crosslinking between the functional groups of these aqueous binders and these crosslinking agents is weak,
At present, sufficient solvent resistance, chemical resistance, and water resistance are not obtained.

On the other hand, aqueous urethane binders have been proposed because of their excellent flexibility and adhesiveness to various materials. However, since the conventional aqueous urethane binder is basically an aqueous dispersion of thermoplastic urethane, it is insufficient in solvent resistance, chemical resistance, water resistance, etc. as described above, and further performance At present, improvement is desired.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and an object of the present invention is to provide an aqueous printing having excellent properties such as solvent resistance, chemical resistance, and water resistance. It is to provide an ink composition.

[0008]

The aqueous printing ink composition of the present invention is characterized by containing a polyurethane aqueous dispersion having an active amino group and a crosslinking agent. The aqueous polyurethane dispersion used in the present invention can be produced by the following method.

That is, the aqueous printing ink composition of the present invention comprises a compound having two or more active hydrogen atoms and an alicyclic compound.
The urethane prepolymer having an isocyanate group at the molecular end obtained by the reaction of the above with an organic polyisocyanate is dispersed in water, and then at least two 1
It is obtained by adding and reacting a polyamine having a primary amino group and at least one secondary amino group in one molecule. At that time, (terminal NCO of urethane prepolymer
Group) / (primary amino group of polyamine) molar ratio is 1/1
It is in the range of 1 / 0.7.

The aqueous polyurethane dispersion obtained by the above-mentioned method has a secondary amino group introduced into the polyurethane skeleton as an active amino group (in some cases, a primary amino group is also introduced into the polyurethane skeleton). ), Whereby a cross-linking reaction occurs at a low temperature when a cross-linking agent such as an epoxy or melamine is used in combination, and as a result, the physical properties of the polyurethane aqueous dispersion are remarkably improved.

Hereinafter, the aqueous polyurethane dispersion used in the present invention will be described in more detail. The urethane prepolymer having an isocyanate group at the molecular terminal used herein is obtained by reacting a compound having two or more active hydrogen atoms with an excess amount of an organic polyisocyanate in the presence or absence of a solvent. Can be

The above-mentioned compound having two or more active hydrogen atoms is a compound having two or more hydroxy groups at a molecular terminal or in a molecule and generally known polyether, polyester, polycarbonate, polyetherester, polythioether. And polyol compounds such as polyacetal, polybutadiene and polysiloxane. The molecular weight of the compound having two or more active hydrogen atoms is preferably in the range of 300 to 5,000.

A chain extender may be added to the compound having two or more active hydrogen atoms, if necessary. Specific examples of the chain extender include low molecular weight 1,4-
Butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, ethylene glycol,
Neopentyl glycol, diethylene glycol, trimethylolpropane, cyclohexanedimethanol and the like can be mentioned.

On the other hand, the alicyclic organic polyisocyanate
Dicyclohexylmethane diisocyanate
G, isophorone diisocyanate, hydrogenated xylylenediene
Isocyanates and mixtures thereof. What
In addition, to the alicyclic organic polyisocyanate,
Diisocyanate, diphenylmethane diisocyanate
G, naphthalene diisocyanate, xylylene diisocyanate
Anate, hexamethylene diisocyanate, tetrame
Aromatic or aliphatic such as tyl xylylene diisocyanate
A polyisocyanate may be added as needed.

The reaction between the above-mentioned compound having two or more active hydrogen atoms and an excess amount of an organic polyisocyanate is carried out by a conventionally known one-stage or multi-stage isocyanate polyaddition reaction at a temperature of 50 to 120 ° C. Do it below.

In the above method, if necessary, a reaction controlling agent such as phosphoric acid, adipic acid, benzoyl chloride, a reaction catalyst such as dibutyltin dilaurate, stannas octoate, triethylamine, and an organic solvent which does not react with an isocyanate group are used. It may be added at the reaction stage or after the completion of the reaction.

Examples of the organic solvent include acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, ethyl acetate, toluene, xylene and the like. It is possible not to use an organic solvent, but if a solvent is used for dilution due to the viscosity of the urethane prepolymer, it is recovered in the final stage.

Further, in the above polyaddition reaction method, if necessary, a stabilizer such as an antioxidant or an ultraviolet absorber can be added at the reaction stage or after completion of the reaction.

The urethane prepolymer thus obtained has a terminal isocyanate group content of 3 to 0.3% by weight.
Is particularly preferable, and 2-1% by weight is particularly preferable. When the content of the terminal isocyanate group is 3% by weight or more, emulsification is destructed in the reaction step with a polyamine to be described later to cause gelation, or the obtained polyurethane emulsion composition has poor product stability and aging stability. Becomes When the content of terminal isocyanate groups is 0.3% by weight or less, the amount of active amino groups introduced by the reaction with a polyamine described below is reduced, and the crosslinking effect of the melamine-based or epoxy-based crosslinking agent is reduced. Is not exhibited.

Next, the urethane prepolymer obtained above is dispersed in water and emulsified. In this dispersion, when the urethane prepolymer itself has dispersibility, it is directly added to water. When the urethane prepolymer does not have self-dispersibility, the following three methods can be adopted as a treatment method performed before dispersing in water. That is, (1) In the urethane prepolymer preparation step, a carboxyl group-containing polyol component, for example, a carboxyl group by a reaction of an organic polyisocyanate with dimethylolpropionic acid or the like is previously introduced into the molecule, and the carboxyl group is then introduced into the molecule. A method in which the group is neutralized with a basic compound such as triethylamine, trimethylamine, diethanol monomethylamine, dimethylethanolamine, caustic soda, caustic potassium, etc., and converted into carboxyl salts; (2) in the urethane prepolymer preparation step, A method in which a urethane prepolymer containing oxyethylene chains in the molecule in an amount of 5% by weight or more is prepared in advance, and a nonionic surfactant having an HLB value of 6 to 18 is added and mixed at 50 ° C. or less after the preparation of the urethane prepolymer. (However, the amount of nonionic surfactant used is It is preferably 15% by weight or less based on the urethane prepolymer in consideration of the emulsification dispersibility and the water resistance of the ink film). 5
%, Preferably 30 to 5%, of an aqueous solution of a sodium or potassium salt such as aminoethanesulfonic acid and aminoacetic acid at 5 to 50 ° C, preferably 20 to 40 ° C, for 60 minutes.

These processing operations are unnecessary when the urethane prepolymer itself has dispersibility as described above.

Water is added to the urethane prepolymer which has been subjected to the above-mentioned processing operations (1), (2) or (3), or in the case of a urethane prepolymer having self-dispersibility, these treatments are not carried out. Water is added, and the mixture is emulsified using an emulsifying and dispersing device such as a homomixer and a homogenizer. When performing this operation, the emulsification and dispersion temperature is preferably low, in order to suppress the reaction between the terminal isocyanate group of the urethane prepolymer and water, and is preferably 5 to 40 ° C, preferably 5 to 30 ° C, and particularly preferably 5 to 20 ° C. What is necessary is just to emulsify in the range of ° C.

After the urethane prepolymer is emulsified in water as described above, a polyamine is added thereto, and the terminal isocyanate group of the urethane prepolymer is reacted with the polyamine in an emulsified dispersion system to carry out a polyamine chain extension reaction. As a result, an active amino group-containing polyurethane emulsion composition according to the present invention is obtained.

The polyamine added above has at least two primary amino groups and at least one 2 amino group in the same molecule.
A polyamine having a secondary amino group, and specific examples thereof include diethylenetriamine, triethylenetetramine,
Dipropylene triamine and the like.

The amount of the polyamine used may be such that the molar ratio of (terminal NCO group of urethane prepolymer) / (primary amino group of polyamine) is in the range of 1/1 to 1 / 0.7. . When this molar ratio is smaller than 1/1 (the number of moles of the primary amino group is large), effective increase in the molecular weight tends to be inhibited. On the other hand, the molar ratio is 1 / 0.7
Greater than (small number of primary amino groups)
In this method, the amount of active amino groups to be introduced is reduced, and as a result, even when a crosslinking agent is used in combination with the obtained aqueous polyurethane dispersion, the effect of improving the physical properties by the crosslinking reaction itself is reduced.
On the other hand, when the molar ratio is larger than 1 / 0.7, the emulsion composition is not preferred because the viscosity of the emulsion composition, gelation, and the like occur.

In the polyamine chain elongation reaction in the emulsified dispersion system, an emulsified dispersion device such as a homomixer or a homogenizer is used to carry out a uniform reaction.
The reaction temperature is 5 to 40 ° C., preferably 5 to 30 ° C., particularly preferably 5 to 40 ° C., in view of gelation caused by emulsification destruction due to rapid reaction or local reaction, and stability of the product and stability over time. Is in the range of 5-20 ° C, and usually 10
Perform the polyamine chain extension reaction for ~ 120 minutes.

In the above-mentioned polyamine chain extension reaction, the primary amino group in the polyamine molecule has a faster reaction rate with respect to the isocyanate group, so that it selectively acts on the chain extension reaction. The site of the secondary amino group will be introduced into the polyurethane skeleton structure.

In order to effectively carry out the reaction between the isocyanate group of the urethane prepolymer and the polyamine and to suppress the side reaction between water and the isocyanate group, phosphoric acid,
Hydrochloric acid, benzoyl chloride and the like can be added.

When an organic solvent is contained in the finally obtained emulsified dispersion, if necessary, the organic solvent is distilled off under reduced pressure at 30 to 70 ° C. to be used in the aqueous printing ink composition of the present invention. An aqueous dispersion of the active amino group-containing polyurethane is obtained.

Further, examples of the crosslinking agent used in the aqueous printing ink composition of the present invention include a water-soluble or water-dispersible crosslinking agent. Specific examples include epoxy-based and melamine-based ones. Examples of these crosslinking agents include, as epoxy-based crosslinking agents, glycerol polyglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol Examples include polyglycidyl ethers of aliphatic polyhydric alcohols such as diglycidyl ether. Examples of the melamine-based crosslinking agent include a methylated melamine resin alkylated with methanol and a mixed etherified melamine resin alkylated with two or more alcohols.

In the aqueous printing ink composition of the present invention containing the active amino group-containing polyurethane aqueous dispersion and these crosslinking agents, in order to carry out a crosslinking reaction at a low temperature, an epoxy is used as the crosslinking agent. Systems are preferred.

[0032]

The aqueous printing ink composition of the present invention contains a polyurethane aqueous dispersion containing an active amino group in the polyurethane skeleton and a crosslinking agent such as an epoxy-based or melamine-based crosslinking agent. Therefore, the active amino group easily cross-links with these cross-linking agents to form a strong ink film.

When an epoxy-based crosslinking agent is used in combination,
A cross-linking reaction between the active amino group and the epoxy group of the cross-linking agent occurs in the air-dry state. By the cross-linking reaction between the active amino group and the cross-linking agent, an ink film having further improved physical properties such as water resistance, solvent resistance, and adhesion resistance is obtained as compared with a conventional polyurethane emulsion having no functional group. be able to.

[0034]

The aqueous printing ink composition of the present invention is constituted as described above, and has remarkable effects as described below.

That is, since the active amino group is positively introduced into the skeleton of the polyurethane in the aqueous printing ink composition of the present invention, a known crosslinking agent such as an epoxy-based crosslinking agent may be added. A crosslinking reaction occurs at about room temperature drying to form a strong ink film. Further, since the polyurethane in the aqueous printing ink composition is easily crosslinked by a crosslinking agent, an ink film can be formed without passing through a heating operation.

[0036]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to these. In addition, “parts” and “%” in Synthesis Examples, Examples, Comparative Synthesis Examples, Comparative Examples, and the like described below indicate parts by weight and% by weight, respectively, unless otherwise specified.

<Synthesis Example 1> 350 parts of polyester polyol (butylene adipate, molecular weight: 2,000), 10.1 parts of trimethylolpropane, 35 parts of polyethylene glycol (molecular weight: 600), and a random copolymer of PO (propylene oxide) / EO (ethylene oxide) 35 parts of polymerized polyether polyol (PO / EO = 30/70,
Molecular weight 3400), and 1,4-butanediol 78.
3 parts were added to and dissolved in 400 parts of methyl ethyl ketone, and 310 parts of isophorone diisocyanate was added at a system temperature of 5 parts.
Added at 0 ° C. Thereafter, 0.05 parts of dibutyltin dilaurate was added, and the temperature was gradually increased to 75 ° C. in the system. At the stage where the reaction was carried out at 75 ° C. for 60 minutes, 0.05 part of dibutyltin dilaurate was further added. Thereafter, the reaction was continued and cooled at the time of 75 ° C./200 minutes,
The temperature in the system was set to 50 ° C. The free isocyanate group of the urethane prepolymer after cooling to 50 ° C. was 2.0% (based on solid type).

Next, at a system temperature of 45 ° C., 80 parts of a polyoxyethylene allylphenol ether type nonionic surfactant (HLB = 15), which is an ethylene oxide adduct of distyrenated phenol, was added and mixed for 10 minutes. . Then, the contents in the system were removed using a homomixer for 300 minutes.
The mixture was stirred at 0 rpm at a high speed, and 1300 parts of distilled water was gradually added thereto, and then emulsification was performed at a system temperature of 30 ° C. for 20 minutes.

After the temperature in the system was further cooled to 20 ° C., an aqueous solution of diethylenetriamine in which 18 parts of diethylenetriamine was dissolved in 130 parts of distilled water (molar ratio of terminal NCO group of urethane prepolymer / primary amino group of diethylenetriamine = 1/0. 9) was added. Keep the temperature in the system between 20 and 2
The stirring was continued at 3000 rpm for 60 minutes using a homomixer while controlling the temperature at 5 ° C. Next, the solvent used, methyl ethyl ketone, was recovered under reduced pressure (warm bath 40 ° C.) by an evaporator. As described above, the active amino group-containing polyurethane emulsion composition of the present invention was prepared.

The obtained active amino group-containing polyurethane emulsion composition was analyzed.

The results are shown in Table 1. The amount of active amino groups contained was determined by precisely weighing 10 parts of the emulsion and adding N-methyl-2.
It was dissolved in 300 parts of pyrrolidone and determined by titration with hydrochloric acid using bromophenol blue as an indicator. That is,
The number of KOH mg equivalent to the carboxyl group required to neutralize 1 g of the sample was determined by Am · V (amine value) (unit: KOH
mg / g).

[0042]

[Table 1]

<Synthesis Example 2> Polycarbonate polyol (polycarbonate of 1,6 hexane, molecular weight 200
0) To 255 parts, 7.0 parts of trimethylolpropane and 57.0 parts of 1,4-butanediol were added, and 290 parts of methyl ethyl ketone was added and dissolved.

Next, 260 parts of isophorone diisocyanate and 0.01 part of dibutyltin dilaurate were added thereto at a system temperature of 50 ° C., and the mixture was gradually heated to a system temperature of 75 ° C.
For 180 minutes to obtain a urethane prepolymer containing 5.0% of free isocyanate groups (based on solid content). Next, dimethylolpropionic acid 26.5 was added thereto.
Parts and methyl ethyl ketone 120 parts, dibutyltin dilaurate 0.07 part was added, and triethylamine 9.9 parts was further added. This was gradually heated, and the reaction was carried out at a system temperature of 75 ° C. for 120 minutes. When the system temperature was further cooled to 50 ° C., 1.99% of free isocyanate groups (to solid type) and carboxyl groups Was obtained.

Next, 9.9 parts of triethylamine was added thereto at a system temperature of 50 ° C. to neutralize the remaining carboxyl groups. Thereafter, 900 parts of distilled water was gradually added, and the mixture was stirred at 3000 rpm using a homomixer, and emulsification was performed at a system temperature of 25 ° C for 20 minutes.

Next, an aqueous solution of diethylenetriamine (13.3 parts of diethylenetriamine) dissolved in 80 parts of distilled water (molar ratio of terminal NCO groups of urethane prepolymer / primary amino groups of diethylenetriamine = 1 / 0.9) was added to the system at a temperature of 25%. At 25 ° C., and mixed by stirring at 25 ° C. for 60 minutes.
Thereafter, methyl ethyl ketone as a solvent to be used was recovered under reduced pressure (water bath 40 ° C.) by an evaporator. Thus, an active amino group-containing polyurethane emulsion composition was obtained.

The active amino group-containing polyurethane emulsion composition was analyzed, and the results are shown in Table 1. The amount of amino group contained was measured in the same manner as in Synthesis Example 1.

<Comparative Synthesis Examples 1 and 2> A urethane prepolymer was prepared and emulsified in the same manner as in Synthesis Examples 1 and 2, and then ethylenediamine was used in the same molar amount instead of adding diethylenetriamine used in the Synthesis Examples. In addition, the mixture was stirred and mixed in the same manner as in Synthesis Examples 1 and 2, and the solvent used was recovered to obtain polyurethane emulsions of Comparative Synthesis Examples 1 and 2 according to the prior art. These polyurethane emulsions were analyzed, and the results are shown in Table 1. The amount of amino group contained was measured in the same manner as in Synthesis Example 1.

In Synthesis Examples 1 and 2, the polyamine to be added to the emulsified and dispersed urethane prepolymer has at least two primary amino groups and at least one secondary amino group.
Having in the molecule, and the polyamine,
It is added so that the molar ratio of (terminal NCO group of urethane prepolymer) / (primary amino group of polyamine) is in the range of 1/1 to 1 / 0.7.

Thus, each amino group (1
Grade, secondary) and isocyanate group,
The reaction between the primary amino group and the isocyanate group proceeds selectively and preferentially reacts. As a result, the secondary amino group portion of the polyamine remains and is introduced into the polyurethane skeleton,
Therefore, it is considered that the obtained polyurethane emulsion composition contains an active amino group.

On the other hand, in Comparative Synthesis Examples 1 and 2, a conventional polyurethane emulsion containing no active amino group is obtained. This is because the terminal NCO group of the urethane prepolymer and all amino groups (primary and secondary) of the polyamine participate in the reaction for increasing the molecular weight.

Next, printing inks were prepared using the polyurethane emulsion compositions of Synthesis Examples 1 and 2 of the present invention, and the adhesion, solvent resistance and water resistance of the ink film of each printing ink were evaluated. Printing inks were prepared in the same manner using the conventional polyurethane emulsions of Comparative Synthesis Examples 1 and 2, and the ink films were similarly evaluated.

(Preparation of Printing Ink) <Examples 1 and 2, Reference Examples 1 and 2> 100 parts of each of the active amino group-containing polyurethane emulsion compositions prepared in Synthesis Examples 1 and 2 were added with a pigment, Lionol Blue FG73, to 100 parts.
No. 30 (trade name, manufactured by Toyo Ink Mfg. Co., Ltd.) was mixed and kneaded so that the resin solid content / pigment = 2/1. These were used as the aqueous printing inks of Reference Examples 1 and 2.

Next, a water-soluble epoxy crosslinking agent (triglycidyl ether of glycerin) was added to the aqueous printing inks of Reference Examples 1 and 2 so that the (active amino group) / (epoxy group) molar ratio was 1/1. To obtain the aqueous printing inks of Examples 1 and 2, respectively.

<Comparative Examples 1 to 4> Lionol Blue FG7330 (Toyo Ink Manufacturing Co., Ltd.
Was mixed and kneaded in the same manner as in Examples 1 and 2. These were used as the aqueous printing inks of Comparative Examples 1 and 2.

Next, the same amount of the same water-soluble epoxy crosslinking agent as in Examples 3 and 4 was mixed with the aqueous printing inks of Comparative Examples 1 and 2, respectively, to obtain aqueous printing inks of Comparative Examples 3 and 4.

(Evaluation of physical properties of ink film) The aqueous printing inks of Examples 1 to 4 and Comparative Examples 1 to 4 were coated on a corona discharge-treated surface of a stretched polypropylene film having a thickness of 20 μm by corona discharge so as to have a thickness of 5 μm. And then apply 4
The specimen was left standing in a 0 ° C. dryer for 24 hours to prepare a test piece. Evaluate the adhesion, solvent resistance and water resistance of the printing surface of each test piece,
Table 2 shows the results. The test method and evaluation criteria are as follows.

[0058]

[Table 2]

<Adhesion> A peel test of a test piece was performed using Nichiban cellotape. The evaluation criteria are as follows.

◎ No peeling even when separated suddenly ○ Adhesive strength intermediate between ◎ and △ △ Peeling when rapidly separated, but not peeling when gradually separated × Peeling even when gradually separated <Solvent resistance> Apply ethanol to the printed surface of the test piece,
After 30 minutes, the surface condition was determined by rubbing with absorbent cotton (using a Gakushin type fastness tester). The evaluation criteria are as follows.

○ The ink film is retained even after 30 times △ The ink film disappears after 10 to 30 times × The ink film disappears after 10 times or less <Water resistance> The test piece is immersed in 60 ° C. warm water for 30 minutes After that, the surface condition of the ink film was determined. The evaluation criteria are as follows.

○ Transparent and clear print color △ Partially whitened and partially unclear print color × White and unclear print color From Table 2, the active amino group-containing polyurethanes of Examples 1 and 2 are contained. As is clear from comparison with the inks of Reference Examples 1 and 2, the water-based printing ink has improved adhesiveness, hot water resistance and solvent resistance at about room temperature when an epoxy-based crosslinking agent is used in combination. You can see that there is. This is considered to be due to a crosslinking reaction between the active amino group of the active amino group-containing polyurethane and the epoxy group of the crosslinking agent at room temperature or higher.

On the other hand, in the polyurethane emulsion paints of the prior arts of Comparative Examples 1 to 4, even if an epoxy-based crosslinking agent is used in combination, almost no improvement or change in physical properties is observed at about room temperature drying. This is considered to be because the co-crosslinking with the epoxy crosslinking agent is weak in the polyurethane emulsion according to the prior art.

The modification of the ink film by the active amino group-containing polyurethane emulsion composition and the epoxy-based crosslinking agent in Examples 1 and 2 is due to the crosslinking of the two and is considered to be integrated.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-114496 (JP, A) JP-A-5-132567 (JP, A) JP-A-5-320361 (JP, A) 279562 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 11/00-11/20

Claims (1)

(57) [Claims] An urethane prepolymer having an isocyanate group at a molecular end obtained by reacting a compound having two or more active hydrogen atoms with an alicyclic organic polyisocyanate is dispersed in water, at least A polyamine having two primary amino groups and at least one secondary amino group in one molecule may have a molar ratio of (terminal NCO group of the urethane prepolymer) / (primary amino group of the polyamine). 2 obtained by adding and reacting in a range of 1/1 to 1 / 0.7.
An aqueous printing ink composition comprising: an aqueous dispersion of a polyurethane having a secondary active amino group; and a crosslinking agent for crosslinking the secondary active amino group .