JPH07247456A - Readily solvent-recoverable printing ink composition - Google Patents

Abstract

PURPOSE:To obtain the subject printing ink composition containing a polyurethane resin as a binder and a specified composition of a mixed solvent, excellent in stability, fluidity, color development, adhesion, etc., and suitable for flexible packaging gravure almost in a single solvent system. CONSTITUTION:This printing ink composition is prepared by blending (A) a binder composed of a polyurethane resin with (B) a mixed solvent composed of (i) 89.5 to 95.5wt.% ester solvent (e.g. ethyl acetate), (ii) 0.5 to 5wt.% water and (iii) <=10wt.% alcoholic solvent (e.g. methanol). As the component (A), a polyurethane resin synthesized by reacting a polyol of ethylene glycol, etc., with an excessive amount of a diisocyanate compound and lengthening the chain of the resultant terminal NCO group-containing prepolymer in the solvent (B) is preferably used. In addition, the component (A) has recommendably 5000 to 100000 molecular weight, 15 to 60wt.% resin solid content and 50 to 100000CPS (25 deg.C) viscosity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nearly single-solvent, easy-solvent recoverable printing ink composition, which is preferably used for flexible packaging gravure.

[0002]

2. Description of the Related Art In recent years, the destruction of the ozone layer in the stratosphere,
Problems related to air pollution such as damage to agricultural products and destruction of forest resources due to acid rain in the lower stratosphere, and adverse effects on human bodies due to photochemical oxidants are becoming more serious. In particular,
In the gravure printing industry, which uses a large amount of organic solvents, it is necessary to comply with the hydrocarbon emission regulations of local governments, the recent fire fire law, and the revision of the Occupational Safety and Health Act. There is growing interest.

A single solvent type ink is preferred for solvent recovery, and among polyurethane resins having no urea bond, those which are soluble in a ketone type or ester type single solvent are commercially available. However, these polyurethane resins usually have low performance such as fluidity, color developability, and adhesiveness for a general-purpose ink for gravure printing for flexible packaging that uses various types of pigments, and are industrially stable. I can not use it.

Generally, a urea bond is introduced into a polyurethane resin skeleton in order to improve performances such as fluidity, color developability and adhesiveness. A polyurethane resin having a urea bond is a ketone type or an ester type. It is insoluble in a single solvent, and it is essential to use a polar solvent such as alcohol. However, the presence of a large amount of alcohol has a drawback that it is not preferable for solvent recovery (especially steam desorption) in terms of solvent separation, wastewater treatment, and cost because the alcohol dissolves in water.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing ink composition which is almost a single solvent system and is easy to recover the solvent.

[0006]

That is, the present invention is a printing ink composition using a polyurethane resin as a binder, wherein the solvent is 89.5 to 95.5% by weight of an ester solvent,
Provided is a solvent-recoverable printing ink composition comprising 0.5 to 5.0% by weight of water and 10.0% by weight or less of an alcohol solvent.

The printing ink composition of the present invention uses a small amount of water in combination with an ester solvent and has a low alcohol content, so that it is excellent in solvent recovery. Examples of the ester solvent include ethyl acetate, isopropyl acetate, butyl acetate and isobutyl acetate. The amount of water in the total amount of the solvent is 0.5 to 5.0% by weight, particularly preferably 3.0 to 4.
5% by weight. If the amount of water is less than 0.5% by weight, the required amount of alcohol solvent will increase and the amount of water will be 5.0% by weight.
If the amount is larger, the stability, fluidity and color developability of the resulting ink will be poor.

As the alcohol solvent, methanol,
Examples thereof include ethanol, isopropyl alcohol, n-propanol and the like. The amount of the alcohol solvent in the total amount of the solvent is 10% by weight or less, and the smaller the range in which the polyurethane resin can be dissolved, the better. If the amount of the alcohol solvent exceeds 10% by weight, the solvent recoverability becomes poor. Water and an alcohol solvent are added at the time of synthesizing the polyurethane resin (at the time of chain extension or after the chain extension) and / or at the time of ink preparation.

The polyurethane resin used as the binder is not particularly limited, but it is obtained, for example, by chain-extending a prepolymer having an isocyanate group at the terminal, which is obtained by reacting a polymer polyol with an excess diisocyanate compound. It is a thing. As the polymer polyol for obtaining the polyurethane resin, various ones generally known as a polymer polyol component of polyurethane can be used. For example, polyether polyols such as polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran and the like: ethylene glycol, diethylene glycol, triethylene glycol,
1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1,6- Hexanediol, octanediol, 1,
Well-known saturated and unsaturated low-molecular-weight glycols such as 4-butynediol and dipropylene glycol, alkyl glycidyl ethers such as n-butyl glycidyl ether and 2-ethylhexyl glycidyl ether, and monocarboxylic acids such as versatic acid glycidyl ester Acid glycidyl esters and adibic acid, maleic acid, fumaric acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid,
Polyester polyols obtained by dehydration condensation of dibasic acids such as azelaic acid, sebacic acid, suberic acid, etc. or their corresponding acid anhydrides, dimer acids, etc .: Polyester polyols obtained by ring-opening polymerization of cyclic ester compounds Group: Others Polycarbonate polyols, polybutadiene glycols, glycols obtained by adding ethylene oxide or propylene oxide to bisphenol A, and the like.

In the case of polymer polyols obtained from glycols and dibasic acids among the above polymer polyols, up to 5 mol% of the glycols can be replaced with the following various polyols. For example, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, bentaerythritol and the like can be mentioned. The molecular weight of the polymer polyol is appropriately determined in consideration of the solubility, drying property, blocking resistance, etc. of the resulting polyurethane, and is usually about 700 to 5000, preferably 10
It is recommended to set it within the range of 00 to 4000. If the molecular weight is less than 700, the printability tends to decrease with the decrease in solubility, and if it exceeds 5,000, the drying property and blocking resistance tend to decrease.

As the diisocyanate compound, various known aromatic, aliphatic or alicyclic diisocyanates can be used. For example, 1,5-naphthylene diisocyanate, 4,4-diphenylmethane diisocyanate, 4,4-diphenyldimethylmethane diisocyanate,
4,4-Dibenzylisocyanate, 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, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexanediisocyanate, m- Tetramethyl xylylene diisocyanate and dimers - dimer diisocyanate which a carboxyl group of the acid was converted into an isocyanate group as a representative example.

A prepolymer having an isocyanate group at both ends of the polymer polyol (preferably a free isocyanate value) is obtained by reacting the polymer polyol with a diisocyanate compound at a ratio such that an isocyanate group becomes excessive.
0.5-10%). The conditions for reacting the high-molecular polyol and the diisocyanate compound are not particularly limited except that the isocyanate group is excessive, but the hydroxyl group /
It is preferable that the equivalent ratio of the isocyanate group is within the range of 1 / 1.2 to 1/3. A polyurethane resin is obtained by chain extension of the obtained prepolymer with a chain extender. When the chain is extended with the chain extender or after the chain is extended, a reaction terminator may be used if necessary.

The chain extension is carried out in a mixed solvent consisting of 89.5 to 95.5% by weight of an ester solvent, 0.5 to 5.0% by weight of water and 10.0% by weight or less of an alcohol solvent,
It is preferable because a polyurethane resin having a urea bond can be stably synthesized. When the prepolymer is reacted with the chain extender and, if necessary, the reaction terminator, the free isocyanate group at both ends of the prepolymer is
When equivalent, the total equivalent of amino groups in the chain extender and the reaction terminator is preferably in the range of 0.5 to 1.3. When the total equivalent of amino groups is less than 0.5, the drying property, blocking resistance, and film strength are not sufficient, and when it exceeds 1.3, the chain extender and the reaction terminator remain unreacted, and the printed matter has an odor. It becomes easy to remain.

As the chain extender, various known amines can be used. Examples thereof include ethylenediamine, propylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, isophoronediamine, dicyclohexylmethane-4,4-diamine and the like. In addition, in the molecule of 2-hydroxyethylethylenediamine, di-2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, etc. Representative examples thereof include diamines having a hydroxyl group and dimer diamines obtained by converting the carboxyl group of dimer acid into an amino group. Examples of the reaction terminator include dialkylamines such as di-n-butylamine.

The molecular weight of the polyurethane resin obtained as described above is preferably in the range of 5,000 to 100,000. When the molecular weight is less than 5000, the drying property of the printing ink using this as a binder, blocking resistance, film strength and oil resistance are poor, and when it exceeds 100000, the viscosity of the polyurethane resin solution increases. , The gloss of printing ink tends to decrease. The concentration of the resin solid component of the polyurethane resin is not particularly limited and is appropriately determined in consideration of workability during printing. Practically, the resin solids concentration is 15-60% by weight, and the viscosity is 50-100,000 cps (25 ° C)
Is preferred.

In the case of producing a printing ink composition, various pigments, ester solvents, water and alcohol solvents are added to polyurethane resin, and if necessary, antiblocking agents, additives such as plasticizers, and ink fluidity. And a surfactant for improving the dispersibility, or a resin compatible with the polyurethane resin is used in combination within a range where thickening and gelation do not occur over time, and ordinary printing such as ball mill, attritor, and sand mill is performed. Knead using an ink manufacturing device.

Resins that can be used in combination include nitrified cotton, chlorinated polyethylene, chlorinated polypropylene, chlorinated polyolefins such as chlorinated ethylene / propylene, chlorosulfonated polyolefins, ethylene / vinyl acetate copolymers or chlorinated or chlorsulfone thereof. Compounds, maleic acid resins, vinyl chloride / vinyl acetate copolymers and the like. When producing printing ink using the polyurethane resin solution obtained by using water and alcohol solvent together during polyurethane resin synthesis (during chain extension or after chain extension), print without limitation It is not necessary to add water and alcohol solvents during ink production.

[0018]

The present invention is described in detail below with reference to examples, but the present invention is not limited to these examples. The parts and% in the examples and comparative examples represent parts by weight and% 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 1000 parts of a polycaprolactone diol having a molecular weight of 2000 and 223 parts of isophorone diisocyanate, and at 90 ° C. under a nitrogen stream. The reaction was carried out for 6 hours. Then, this was cooled to 50 ° C., 80 parts of isophoronediamine, 9.6 parts of di-n-butylamine, 3020 parts of ethyl acetate and 46 parts of water were added and reacted at 50 ° C. for 3 hours with stirring to give a solid content of 30%. A polyurethane resin solution (A) having a viscosity of 5000 cps at 25 ° C. and a molecular weight of 40,000 was obtained. Next, a mixture of 40 parts of the polyurethane resin solution (A), 30 parts of titanium oxide, 29.5 parts of ethyl acetate and 0.5 part of water was kneaded to prepare a white printing ink (a).

[Example 2] Polyurethane resin solution (A) 40
Parts, 30 parts of titanium oxide, 24.9 parts of ethyl acetate, 4.6 parts of isopropyl alcohol (hereinafter referred to as IPA), and 0.5 parts of water were kneaded to prepare a white printing ink (b).

Example 3 The same reactor as in Example 1 was charged with 1000 parts of polycaprolactone diol having a molecular weight of 2000 and 233 parts of isophorone diisocyanate, and the reaction was carried out at 90 ° C. for 6 hours under a nitrogen stream. Then this is 50 ℃
Cooled to 80 parts isophoronediamine, 9.6 parts di-n-butylamine, 2802 parts ethyl acetate, 131 parts IPA and water.
Add 131 parts and react under stirring at 50 ° C for 3 hours to obtain a solid content.
A polyurethane resin solution (B) having a viscosity of 900 cps at 25 ° C. and a molecular weight of 40,000 at 30% was obtained. Next, polyurethane resin solution (B) 40 parts, titanium oxide 30 parts, ethyl acetate 27.4 parts, IP
A white printing ink (c) was prepared by kneading a mixture of 1.3 parts of A and 1.3 parts of water.

[Comparative Example 1] In the same reactor as in Example 1, 1211 parts of polycaprolactone diol having a molecular weight of 2000 and 102 parts of isophorone diisocyanate were charged and reacted at 90 ° C for 6 hours under a nitrogen stream. Then this is 50 ℃
After cooling to 3064 parts of ethyl acetate and stirring, a polyurethane resin solution (C) having a solid content of 30%, a viscosity at 25 ° C. of 500 cps and a molecular weight of 4000 was obtained. Next, a mixture of 40 parts of the polyurethane resin solution (C), 30 parts of titanium oxide and 30 parts of ethyl acetate was kneaded to prepare a white printing ink (d).

Comparative Example 2 1120 parts of a polycaprolactone diol having a molecular weight of 2000 and 156.2 parts of isophorone diisocyanate were charged in the same reactor as in Example 1 and reacted at 90 ° C. for 6 hours in a nitrogen stream. Then this is 50
After cooling to ℃, add 39.4 parts of di-n-butylamine and 3064 parts of ethyl acetate and react with stirring for 3 hours at 50 ℃, solid content 30%, viscosity at 25 ℃ 600cps, molecular weight 40,000 polyurethane resin solution ( D) got. Next, a mixture of 40 parts of the polyurethane resin solution (D), 30 parts of titanium oxide and 30 parts of ethyl acetate was kneaded to prepare a white printing ink (e).

Comparative Example 3 The same reactor as in Example 1 was charged with 1000 parts of polycaprolactone diol having a molecular weight of 2000 and 223 parts of isophorone diisocyanate, and reacted at 90 ° C. for 6 hours under a nitrogen stream. Then this is 50 ℃
After cooling to 80 parts of isophorone diamine, 9.6 parts of di-n-butylamine, 2926 parts of ethyl acetate and 138 parts of IPA, the mixture is reacted under stirring at 50 ° C for 3 hours, solid content 30%, 25 ° C.
A polyurethane resin solution (E) having a viscosity of 50,000 cps and a molecular weight of 40,000 was obtained. Next, polyurethane resin solution (E) 40
Parts, 30 parts titanium oxide, 28.7 parts ethyl acetate and IPA
1.3 parts of the mixture was kneaded to prepare a white printing ink (f).

Comparative Example 4 Polyurethane resin solution (E) 40
Parts, titanium oxide 30 parts, ethyl acetate 13.9 parts and IPA1
A white printing ink (g) was prepared by kneading 6.1 parts of the mixture. Comparative Example 5 Polyurethane resin solution (E) 40 parts, titanium oxide 30 parts, ethyl acetate 24.6 parts, IPA 1.3 parts and water 4.1
Part of the mixture was kneaded to prepare a white printing ink (h).

The resulting ink was evaluated for stability over time, fluidity, color development and solvent recovery. The evaluation results are shown in Table 1. The evaluation was based on the following method. (1) Temporal stability The obtained white printing ink was put in a 200 ml glass sample bottle, and the storage stability was evaluated after 1 week at 40 ° C. The judgment value of the evaluation result is as follows. ○ …… No thickening or gelation was observed compared to immediately after production. △ ・ ・ ・ Compared to immediately after production, gelation does not occur, but an increase in viscosity is observed. × ・ ・ ・ Gelified compared to immediately after production. (2) Fluidity The fluidity of the ink was visually judged. The judgment value of the evaluation result is as follows. ○ …… Excellent △ …… Normal × …… Inferior

(3) Color developability A white printing ink is applied to the treated surface of a corona-treated polyester film (“Ester E5100” manufactured by Toyobo Co., Ltd., thickness: 15 μm) with a Meyer bar # 4, and the appearance of the coated product is made to have a density and gloss. A comprehensive evaluation was made in terms of transparency. The judgment value of the evaluation result is as follows. ○ …… Excellent △ …… Normal × …… Inferior (4) Solvent recovery The evaluation was performed by the amount of alcohol contained in the ink. ◎ …… Excellent ○ …… Excellent △ …… Normal × …… Inferior － …… Not evaluated because of poor inkability

[0027]

[Table 1]

[0028]

Industrial Applicability According to the present invention, a printing ink composition having excellent stability, fluidity, color development, adhesiveness and the like, and having a substantially single solvent type, can be easily recovered.

Claims (3)

[Claims] 1. A printing ink composition comprising a polyurethane resin as a binder, wherein the solvent comprises 89.5 to 95.5% by weight of an ester solvent, 0.5 to 5.0% by weight of water and 10.0% by weight or less of an alcohol solvent. The easy-solvent recoverable printing ink composition according to claim 1. 2. The easy-solvent recoverable printing ink composition according to claim 1, wherein the polyurethane resin has a urea bond. 3. A prepolymer having an isocyanate group at the terminal, which is obtained by reacting a high-molecular polyol with an excess of a diisocyanate compound, is prepared by adding 89.5 to 95.5% by weight of an ester solvent, 0.5 to 5.0% by weight of water and 10.0% by weight. The solvent-recoverable printing ink composition according to claim 1 or 2, wherein the binder is a polyurethane resin obtained by chain extension in a mixed solvent of the following alcohol solvents.