JP2890977B2 - Printing ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is particularly useful as a coating for printing inks, and more particularly for coating various plastic films, plastic sheets or synthetic resin molded articles.
In particular, the present invention relates to a printing ink that has excellent adhesion to substrates such as polypropylene, polyester, and nylon, has a one-pack specification, and has excellent boil resistance and retort resistance.

[0002]

2. Description of the Related Art As printing ink compositions used for plastics, especially for plastic films such as polypropylene, polyester and nylon, there are two-part printing ink compositions containing a linear polyurethane resin soluble in an organic solvent as a main binder. A two-pack type using a mixture of a linear polyurethane resin soluble in an organic solvent and a polyisocyanate compound as a main binder is used, and is used depending on the type and use of a printing medium. Of these, the one-pack type printing ink composition has good adhesion to plastics and suitability for lamination to plastic films, but is adequate for applications requiring high resistance such as boil sterilization and retort sterilization. There was a disadvantage that it could not be done.

[0003] In addition, although the two-pack type can sufficiently cope with applications requiring high resistance, a polyisocyanate compound is added to a component containing a linear polyurethane resin and mixed immediately before use from the viewpoint of storage stability. However, there are drawbacks in that the operation is complicated, that the remaining meat lacks stability, and that it is difficult to reuse the remaining meat. In order to improve these drawbacks, various one-part inks having boiling and retort suitability have been proposed in recent years. However, storage stability of the ink, print suitability, anti-blocking property, general-purpose use for various films have been proposed. Two-component type that combines a one-component type ink and a polyisocyanate-based curing agent depending on the application, because it does not have the performance required for industrial printing inks, such as properties such as properties, boiling, retort suitability, etc. At present, ink is used properly.

[0004]

The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, the present invention has been mainly directed to polyurethane resins containing a carbodiimide group (-N = C = N-) in the molecule. The printing ink used as a binder is
The present inventors have found that they exhibit excellent adhesiveness to plastic films such as polyester, nylon, and polypropylene, have good resistance to boiling and retorting, and are also excellent in storage stability, and have completed the present invention.

[0005]

That is, the present invention provides a printing ink comprising a polyurethane resin containing a carbodiimide group in a molecule as a main binder. The content of the carbodiimide group in the polyurethane resin is preferably in the range of 5.0 × 10 ⁻⁵ to 3.0 × 10 ⁻³ gram equivalent per 1 g of the solid content of the polyurethane resin. When the content is less than 5.0 × 10 ^-5 gram equivalent, it is difficult to obtain physical properties such as boil resistance and retort resistance, and when the content is more than 3.0 × 10 ^-3 gram equivalent, the viscosity stability with time of the polyurethane resin solution. Decreases,
Printing inks using this polyurethane resin tend to thicken and gel.

A polyurethane resin containing a carbodiimide group in a molecule is generally obtained by reacting a polymer polyol, a diisocyanate compound, a chain extender and the like, and the method of introducing the carbodiimide group is not limited at all. However, for example, the following method can be used. That is, by using a compound having at least one carbodiimide group and at least one isocyanate group as part or all of the diisocyanate compound component, the carbodiimide group can be introduced into the polyurethane resin, but a uniform polyurethane resin solution is easily obtained. From this viewpoint, it is preferable to use a compound having two isocyanate groups represented by the following general formula (1).

[0007]

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(Wherein, R represents an alkyl, cycloalkyl, aryl, aralkyl, alkaryl, or heterocyclic group which may have a substituent, n represents an integer of 1 or more, and R may be the same or different. Good.)

Compounds having at least one carbodiimide group and one or more isocyanate groups can be prepared by known methods, for example, by di- or triisocyanate compounds in a non-reactive organic solvent with a suitable catalyst such as 3-methyl-1-phenyl- It is obtained by a method in which isocyanate is carbodiimidated by heating in the presence of 2-phosphorate-1-oxide and performing a condensation reaction accompanied by decarbonation.

The diisocyanate compound, which is a raw material of the compound having at least one carbodiimide group and at least one isocyanate group, is an aromatic diisocyanate, an aliphatic diisocyanate, an alicyclic diisocyanate, or a mixture thereof. Isocyanate, 4,4-diphenylmethane diisocyanate, 4,4-
Diphenyldimethylmethane diisocyanate, 4,4-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-
Phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane -4,4-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, dimeryl diisocyanate, and the like.

The number average molecular weight of the polyurethane resin containing a carbodiimide group in the molecule is preferably in the range of 5,000 to 150,000. When the number average molecular weight is less than 5,000, a printing ink using this as a binder is inferior in drying properties and blocking resistance, and hardly obtains physical properties such as film strength, boiling resistance and retort properties. On the other hand, when it exceeds 150,000, the viscosity of the polyurethane resin solution increases, which is not preferable in terms of storage stability and printability of the ink.

Also, hydroxyl groups,
It has various functional groups such as amino group, carboxyl group, etc.
Also, especially when it contains a carboxyl group,
Since it reacts with the mixed carbodiimide group, it shows a specific behavior as compared with the case where it contains another functional group or contains no functional group other than the carbodiimide group. That is, the carbodiimide group equivalent is excessive relative to the carboxyl group equivalent in the polyurethane resin, and contains a carboxyl group and a carbodiimide group as long as the viscosity is not significantly increased during the production or storage of the polyurethane resin solution. When a printing ink containing a polyurethane resin as a main binder is used, a printed matter having particularly excellent heat resistance, oil resistance and the like can be obtained by a reaction between a carboxyl group and a carbodiimide group.

The amount of carboxyl groups which may be contained in the polyurethane resin varies depending on the equivalent carbodiimide group, but the acid value of the polyurethane resin is 0.1 to 20 KOH mg.
/ g is preferred. If the amount of the carboxyl group in the polyurethane resin is too large, a reaction between the carboxyl group and the carbodiimide group occurs during the production or storage of the polyurethane resin solution or during storage when the ink is used as a printing ink, and the resin solution or the printing ink is It may cause thickening or gelation, which is not preferable in terms of storage stability.
Further, the carbodiimide group is consumed, and the effect of the present invention is reduced or lost, which is not preferable.

Specific examples of the above-mentioned polymer polyol include:
For example, polyether polyols such as polymers or copolymers such as ethylene oxide, propylene oxide, and tetrahydrofuran; ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol,
4-butanediol, neopentyl glycol, pentanediol, hexanediol, octanediol, 1,4-
Saturated and unsaturated low molecular weight glycols such as butynediol, diethylene glycol, triethylene glycol, and dipropylene glycol; and alkyl glycidyl ethers such as n-butyl glycidyl ether and 2-ethylhexyl glycidyl ether; and monomers such as versatic acid glycidyl ester Carboxylic acid glycidyl esters and adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid,
Polyester polyols obtained by dehydrating and condensing dibasic acids such as malonic acid, glutaric acid, pimelic acid, speric acid, azelaic acid, sebacic acid, dimer acid or anhydrides thereof; ring-opening polymerization of cyclic ester compounds Polyester polyols obtained; other polycarbonate polyols, polybutadiene glycols,
Various known polymer polyols generally used in the production of polyurethane, such as glycols obtained by adding ethylene oxide or propylene oxide to bisphenol A, may be mentioned.

[0015] Of these polymer polyols,
When a polymer polyol obtained from a glycol and a dibasic acid is used, up to 5 mol% of the glycol can be replaced with the following various polyols. That is, for example, glycerin, trimethylolpropane,
Trimethylolethane, 1,2,6-hexanetriol, 1,
It may be replaced by a polyol such as 2,4-butanetriol, sorbitol, pentaerythritol and the like.

The molecular weight of the high molecular polyol is appropriately determined in consideration of the solubility, drying property, blocking resistance and the like of the obtained polyurethane resin, but is usually preferably in the range of 500 to 3,000, more preferably 700 to 3,000. A range of 2500 is preferred. If the molecular weight is less than 500, the printability tends to be inferior due to the decrease in solubility, and if it exceeds 3000, the drying property and the anti-blocking property tend to decrease. These polymer polyols may be used alone or in combination of two or more.

Further, within the range not deviating from the performance of the polyurethane resin of the present invention, a part of the high molecular polyol is replaced with low molecular polyols, for example, various low molecular polyols used for producing the high molecular polyol. In this case, the amount of the low-molecular polyol used is preferably 20% by weight or less, more preferably 10% by weight or less. When the amount of the low molecular polyol used exceeds 20% by weight, the solubility in a diluting solvent and the adhesion of the obtained printing ink to a plastic film are reduced. In particular, when a carboxyl group is to be introduced into the polyurethane resin, a polyester polyol obtained by ring-opening polymerization of a cyclic ester compound with dimethylol propionic acid or the like is used as the high molecular polyol, or the low molecular polyol is used as the low molecular polyol. Dimethylolpropionic acid or the like may be used.

As the isocyanate compound, aromatic,
Various known aliphatic or alicyclic diisocyanates can be used. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3- Phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4- Trimethylhexamethylene diisocyanate, cyclohexane-
1,4-diisocyanate, xylylene diisocyanate,
Isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate,
Typical examples thereof include 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexanediisocyanate, m-tetramethylxylylene diisocyanate, and dimer isocyanate obtained by converting a carboxyl group of dimer acid into an isocyanate group.

As the chain extender, various known amines can be used. For example, ethylenediamine, propylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, isophoronediamine, dicyclohexylmethane-4,4′-diamine and the like can be mentioned. Others, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-
Diamines having a hydroxyl group in the molecule such as hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, and dimerdiamine in which a carboxyl group of dimer acid is converted to an amino group And the like are also typical examples.

Further, a reaction terminator can be used.
Examples of such a reaction terminator include dialkylamines such as di-n-butylamine and alcohols such as ethanol and isopropyl alcohol. Furthermore, when it is desired to introduce a carboxyl group into the polyurethane resin, an amino acid such as glycine or L-alanine can be used as a reaction terminator.

The method for producing the polyurethane resin is not particularly limited. For example, a polymer polyol, a compound having at least one carbodiimide group and at least one isocyanate group, and if necessary, a diisocyanate compound containing an excess of isocyanate groups may be used. And a prepolymer having isocyanate groups at both ends of a high molecular polyol (preferably a free isocyanate value of 0.5 to 10).
%), And then add this to a chain extender in a suitable solvent,
Further, a two-stage method of reacting with a reaction terminator, if necessary, may be mentioned. The two-stage method is a preferable production method in that a uniform polymer solution is easily obtained.

A polymer polyol, a compound having at least one carbodiimide group and at least one isocyanate group,
The conditions for reacting the diisocyanate compound, if necessary, are not particularly limited except that the isocyanate group is excessive, but the equivalent ratio of hydroxyl group / isocyanate group is not limited.
It is preferably within the range of 1 / 1.2 to 1/3. Further, the conditions for reacting the obtained prepolymer with a chain extender and, if necessary, a reaction terminator are not particularly limited, but 1 equivalent of a free isocyanate group having both ends of the prepolymer is used. In this case, the total equivalent of the amino groups in the chain extender and the reaction terminator is preferably in the range of 0.5 to 1.30. If the total equivalent weight of the amino group is less than 0.5, the drying property, the blocking resistance, and the film strength are not sufficient, and 1.30.
If the amount becomes excessive, the chain extender and the reaction terminator remain unreacted, and the odor tends to remain on the printed matter.

Examples of the solvent used in the above-mentioned production method include aromatic solvents such as benzene, toluene, and xylene, which are well known as solvents for printing inks.
Methanol, ethanol, isopropanol, alcohol solvents such as n-butanol, acetone, methyl ethyl ketone, ketone solvents such as methyl isobutyl ketone, ethyl acetate, ester solvents such as butyl acetate, and the like,
These are used alone or in a mixture of two or more.

In the case of producing a printing ink, various pigments and the above-mentioned solvent are added to the above-mentioned polyurethane resin containing a carbodiimide group, and additives such as an anti-blocking agent and a plasticizer, if necessary, ink fluidity and dispersibility. A surfactant for improving the viscosity, or a nitrified cotton, a chlorinated polyethylene, a chlorinated polypropylene, a chlorinated ethylene / Chlorinated polyolefins such as propylene, chlorsulfonated polyolefins, ethylene / vinyl acetate copolymers, or chlorinated or chlorsulfonated products thereof, maleic acid resins, vinyl chloride / vinyl acetate copolymers, and resins such as polyurethanes, Uses normal printing ink production equipment such as ball mills, attritors, and sand mills Kneaded Te.

[0025]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” means “parts by weight” and “%” means “% by weight”. Example 1 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube was charged with a molecular weight of 2,000 obtained from adipic acid and 3-methyl-1,5-pentanediol.
A diisocyanate compound solution having 100 parts of a polyester diol of the formula and hexamethylene diisocyanate as raw materials and having one carbodiimide group [in the general formula (2), R: hexamethylene, n: 1, a 50% solids ethyl acetate solution] 58 The reaction was conducted at 85 ° C. for 6 hours under a nitrogen stream. Then, 8.2 parts of isophoronediamine, di-n-
0.97 parts of butylamine, 117 parts of toluene, 117 parts of methyl ethyl ketone and 59 parts of isopropyl alcohol were added, and the mixture was reacted at 50 ° C. for 3 hours with stirring.
A carbodiimide group-containing polyurethane resin solution (A) having a viscosity of 210 cps and a molecular weight of 40,000 was obtained.

The obtained polyurethane resin solution (A) was mixed with 2
After placing in a 00 ml glass sample bottle and left at 40 ° C. for 1 week, the storage stability was evaluated. Table 1 shows the results. …: No increase in viscosity or gelation is observed as compared to immediately after production. Δ: No gelation, but an increase in viscosity is observed as compared to immediately after production. ×: Gelling as compared to immediately after production. Next, a mixture of 40 parts of the obtained carbodiimide group-containing polyurethane resin solution (A), 30 parts of titanium oxide, 15 parts of toluene and 15 parts of methyl ethyl ketone was kneaded to prepare a white printing ink.

Further, the viscosity of the obtained printing ink was adjusted with a mixed solvent of toluene, methyl ethyl ketone and isopropyl alcohol (weight ratio 60:30:10), and the printing plate depth 35 μm.
m Print on corona-treated polyester film (PET) and corona-treated nylon film (NY) with a gravure proofing machine equipped with a m-gravure plate, and dry at 40 ° C to 50 ° C.
Printed matter was obtained. About the obtained printed matter, heat resistance, adhesiveness, extrusion lamination strength, dry lamination strength,
Boil suitability and retort suitability were evaluated. Table 1 shows the results. The evaluation was performed by the following test method.

1) Heat resistance Pressure was applied with a heat seal bar (2 kg / cm ² , 1 second) while the ink surface of the PET print was in contact with a 9 μ aluminum foil.
Immediately thereafter, the ink surface was peeled off from the aluminum foil, and the heat sealing temperature when the ink surface could be peeled off without resistance was determined according to the following criteria. 5: At 200 ° C, the ink surface and the aluminum foil peel off without resistance. 4: At 180 ° C, the ink surface and the aluminum foil peel off without resistance. 3: At 160 ° C, the ink surface and the aluminum foil peel off without resistance. 2: At 140 ° C, the ink surface and the aluminum foil peel off without resistance. 1: The ink surface is removed on aluminum foil at 120 ° C or peel resistance is high.

2) Adhesion After the printed matter was allowed to stand for one day, a cellophane tape was stuck on the printing surface, and the appearance of the printed film when this was rapidly peeled was visually judged. The criteria were as follows. A: The printed film did not come off at all. …: 80% or more of the printed film remained on the film. Δ: 50% to 80% of the print film remained on the film. X: 50% or less of the printed film remained on the film. 3) Extrusion (EL) laminating strength Using an isocyanate-based anchor coating agent on the printed matter, laminating molten polyethylene with an extruding laminator, aging at 40 ° C for 2 days, and 3 days after lamination, the sample was 15 mm wide. And the T-peel strength was measured.

4) Dry (DL) Laminating Strength A CPP (unstretched polypropylene) film is laminated by a dry laminating machine using a urethane-based adhesive on the printed matter, and aged at 40 ° C. for 3 days. The peel strength was measured by the method described above. 5) Suitability for boil and retort After dry lamination of the above-mentioned NY printed matter, the laminate is made into a bag, a mixture of water / salad oil is put as the contents, and after sealing, the suitability for boil is 100 ° C, 30 minutes, retort suitability. After heating at 120 ° C. for 30 minutes, the presence or absence of laminar floating was visually judged by appearance. The criteria were as follows. …: There is no lami floating. Δ: Delamination was found in a very small portion, or blisters were generated, albeit slightly. X: Delamination occurred on the entire surface.

Example 2 A diisocyanate compound solution containing 100 parts of polycaprolactone diol having a molecular weight of 2,000 and isophorone diisocyanate and having one carbodiimide group was prepared in the same reactor as in Example 1 [in the general formula (2) R: isophorone, n: 1, 50% solids in ethyl acetate solution] 80 parts, and put under nitrogen stream
The reaction was performed at 85 ° C. for 6 hours. Then isophorone diamine
8.2 parts, di-n-butylamine 0.97 parts, toluene 123 parts,
123 parts of methyl ethyl ketone and 62 parts of isopropyl alcohol are added, and the mixture is reacted at 50 ° C. for 3 hours with stirring.
I got In the same manner as in Example 1, the storage stability of the obtained polyurethane resin solution (B) was evaluated, and an ink was further prepared and printed, and evaluated. Table 1 shows the results.

Example 3 A diisocyanate compound solution having three carbodiimide groups using 100 parts of polycaprolactone diol having a molecular weight of 2,000 and m-tetramethylxylylene diisocyanate as raw materials was prepared in the same reaction apparatus as in Example 1. In (2), R: m-tetramethylxylylene, n: 3, 50% solids in ethyl acetate solution]
169 parts were charged and reacted at 85 ° C. for 6 hours under a nitrogen stream. Then, 8.2 parts of isophoronediamine, 0.97 parts of di-n-butylamine, 147 parts of toluene, 1 part of methyl ethyl ketone
47 parts and 73 parts of isopropyl alcohol were added and reacted at 50 ° C. for 3 hours with stirring to obtain a polyurethane resin solution (C) containing a carbodiimide group having a solid content of 30%, a viscosity at 25 ° C. of 230 cps and a molecular weight of 40,000. . The storage stability of the obtained polyurethane resin solution (C) was evaluated in the same manner as in Example 1, and an ink was further prepared and printed.
evaluated. Table 1 shows the results.

Example 4 In the same reactor as in Example 1, 100 parts of a polyesterdiol having a molecular weight of 2,000 obtained from adipic acid and 3-methyl-1,5-pentanediol, and 100 parts of hexamethylene diisocyanate were used as raw materials. 80 parts of a diisocyanate compound solution having one group [in the general formula (2), R: hexamethylene, n: 1, a 50% solids ethyl acetate solution] is charged and reacted at 85 ° C. for 6 hours under a nitrogen stream. I let it. Next, 129 parts of toluene and 2.5 parts of dimethylolpropionic acid were added, and reacted at 50 ° C. for 6 hours with stirring.
11.2 parts, 1.7 parts of di-n-butylamine, 129 parts of methyl ethyl ketone and 64 parts of isopropyl alcohol were added and reacted under stirring at 50 ° C. for 3 hours. A carbodiimide group having a solid content of 30%, a viscosity of 520 cps at 25 ° C. and a molecular weight of 55,000 was added. And a polyurethane resin solution (D) containing a carboxyl group. The acid value of the polyurethane resin is 6.7 K
OH mg / g. In the same manner as in Example 1, the storage stability of the obtained polyurethane resin solution (D) was evaluated. Further, an ink was prepared and printed, and the evaluation was performed. Table 1 shows the results.

Comparative Example 1 The same reactor as in Example 1 was charged with 100 parts of a polyester diol having a molecular weight of 2,000 obtained from adipic acid and 3-methyl-1,5-pentanediol and 22 parts of isophorone diisocyanate. The reaction was carried out at 85 ° C. for 6 hours under a stream of air. Then, 8.2 parts of isophoronediamine, 1.3 parts of di-n-butylamine, and 1 part of toluene
30 parts, 130 parts of methyl ethyl ketone and 62 parts of isopropyl alcohol were added and reacted at 50 ° C. for 3 hours with stirring. The solid content was 30%, the viscosity at 25 ° C. was 550 cps, and the molecular weight was 5
1,000 polyurethane resin solutions (E) were obtained. Example 1
In the same manner as in the above, the storage stability of the obtained polyurethane resin solution (E) was evaluated, an ink was further prepared, printed, and evaluated. Table 1 shows the results.

[Comparative Example 2] In the same reactor as in Example 1, polycaprolactone diol 100 having a molecular weight of 2,000 was added.
Part, a diisocyanate compound solution having 22 parts of isophorone diisocyanate and hexamethylene diisocyanate as raw materials and having one carbodiimide group [in the general formula (2), R: hexamethylene, n: 1, a 50% solids ethyl acetate solution] 1.8 parts, 6 at 85 ° C under nitrogen flow
Allowed to react for hours. Then 8.2 parts of isophoronediamine,
0.97 part of di-n-butylamine, 122 parts of toluene, 122 parts of methyl ethyl ketone and 61 parts of isopropyl alcohol are added, and the mixture is reacted under stirring at 50 ° C. for 3 hours.
A polyurethane resin solution (F) having a viscosity of 410 cps at 25 ° C. and a molecular weight of 45,000 and containing a carbodiimide group was obtained.
In the same manner as in Example 1, the storage stability of the obtained polyurethane resin solution (F) was evaluated, an ink was further prepared, printed, and evaluated. Table 1 shows the results.

Comparative Example 3 A carbodiimide was prepared in the same reactor as in Example 1 by using 100 parts of a polyester diol having a molecular weight of 2,000 obtained from adipic acid and 3-methyl-1,5-pentanediol and 100 parts of hexamethylene diisocyanate as raw materials. 234 parts of a diisocyanate compound solution having one group [in the general formula (2), R: hexamethylene, n: 1, a 50% solids ethyl acetate solution] was charged and reacted at 85 ° C. for 6 hours under a nitrogen stream. I let it. Then, toluene 210
And 20 parts of dimethylolpropionic acid, and the mixture was reacted under stirring at 50 ° C. for 6 hours.
33 parts, di-n-butylamine 5.1 parts, methyl ethyl ketone
Add 210 parts and 105 parts of isopropyl alcohol and react under stirring at 50 ° C. for 3 hours. Polyurethane resin solution (G) having a solid content of 30%, a viscosity of 470 cps at 25 ° C. and a molecular weight of 48,000 and containing a carbodiimide group and a carboxyl group (G) I got The acid value of the polyurethane resin is 35 KO
Hmg / g. When the storage stability of the obtained polyurethane resin solution (G) was evaluated in the same manner as in Example 1, the polyurethane resin solution (G) was gelled after being left at 40 ° C. for one week, and was not suitable for a binder for printing ink. [Comparative Example 4] A reaction apparatus similar to that in Example 1 was charged with a molecular weight of 500.
Of polycaprolactone diol and m-tetramethylxylylene diisocyanate as raw materials, a diisocyanate compound solution having 10 carbodiimide groups (in the general formula (2), R: m-tetramethylxylylene, n: 10 50% ethyl acetate solution] 449 parts were charged and reacted at 85 ° C for 6 hours under a nitrogen stream. Next, 8.2 parts of isophoronediamine, 0.97 parts of di-n-butylamine, 152 parts of toluene, 152 parts of methyl ethyl ketone and 76 parts of isopropyl alcohol are added, and the mixture is reacted with stirring at 50 ° C. for 3 hours. Viscosity 800cps, molecular weight
A polyurethane resin solution (H) containing 52,000 carbodiimide groups was obtained. When the storage stability of the obtained polyurethane resin solution (H) was evaluated in the same manner as in Example 1, the polyurethane resin solution (H) was gelled after being left at 40 ° C. for one week, and was not suitable for a binder for printing ink.

[0037]

[Table 1]

[0038]

According to the present invention, it has excellent one-part adhesiveness to various plastic films such as polyester, nylon, polyethylene, and polypropylene used as a printing material, storage stability, and lamination processing. It is possible to provide a printing ink having excellent properties such as suitability, boilability, and retort suitability.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 11/00-11/20 C09D 175/00-175/16

Claims (2)

(57) [Claims] 1. A printing ink comprising a polyurethane resin containing a carbodiimide group in a molecule as a main binder. 2. The polyurethane resin has a resin solid content of 1 g.
2. The printing ink according to claim 1, wherein the printing ink contains 5.0 × 10 ^{-5 to} 3.0 × 10 ^-3 gram equivalent of carbodiimide groups per gram.