JPH06100817A - Binder for flexographic ink - Google Patents

Abstract

PURPOSE:To improve the adhesion to a plastic film by using as the main component a soln. of a polyurethane resin obtd. by reacting a specific high-molecular polyol component, a diisocyanate compd., and a chain extender. CONSTITUTION:A high-molecular polyol component is obtd. by mixing 30-70wt.% polypropylene glycol and/or polytetramethylene glycol having a mol.wt. of 700-2,500 with 70-30wt.% poly(beta-methyl-delta-valerolactone) diol having a mol. wt. of 700-2,500. A polyurethane resin having a number-average mol.wt. of 5,000-100,000 is obtd. by reacting this polyol component with isophorone diisocyanate in an equivalent ratio of OH group/NCO group of (1:1.2) to (1:4) in the presence of a chain extender. The objective binder having a solid resin content of 15-60 wt.% and a viscosity of 50-10,000cP is obtd. by dissolving this resin in a solvent contg. 75wt.% or higher isopropanol and/or ethanol.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a binder for flexographic printing inks.

[0002]

2. Description of the Related Art In flexographic printing, a plate material is rubber or plastic, plate making is easy, and the total cost required for printing is lower than that of gravure printing. Liner paper, heavy wrapping paper,
Widely used in light wrapping paper, etc.). Further, when a CI (Center Impression Drum) type flexographic printing machine is used, the registration accuracy is better than that of gravure printing, so that it is also suitable for printing on a flexible substrate such as a plastic film. However, since the plate material is rubber or plastic, there is a limitation in the solvent used, for example, a ketone solvent such as methyl ethyl ketone having a high dissolving power or toluene,
Aromatic solvents such as xylene cannot damage the plate and cannot be used. Therefore, a mixed solvent having alcohol such as isopropyl alcohol or ethanol as a main solvent and ester solvent such as ethyl acetate as an auxiliary solvent is widely used. Similarly, the binder used in flexographic printing is also limited, and only alcohol-soluble resins such as nitrocellulose and acrylic resins have been used so far. However, these do not have sufficient adhesion to polyethylene or polypropylene film, and in order to compensate for this, tackifiers such as polyamide, alkyd, and rosin ester resin have been added, but they are unsatisfactory, and in the printing film. It has the disadvantage that it also contains a large amount of residual solvent. Therefore, a binder having good solubility in the mixed solvent, excellent adhesion to a plastic substrate, and a small amount of residual solvent after printing has been desired.

On the other hand, in the field of gravure printing inks, a polyurethane resin has been favored as a resin having excellent adhesion to a plastic film and having a small residual solvent amount after printing, but the resin has a high polarity and is stable. In order to obtain such a resin solution, it is necessary to use a solvent having a high dissolving power (ketone-based, aromatic-based, ester-based solvent, etc.) as a main solvent. Therefore, the polyurethane resin cannot be used as a binder for flexographic printing ink. Japanese Patent Sho 58-
6754 discloses polyurethane having excellent solubility in ester solvents and alcohol solvents, but it is a polyurethane for gravure ink using ethyl acetate as a main solvent, and a binder for flexographic printing ink. Not applicable.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a binder for flexographic printing ink which has excellent adhesion to various plastic films as printed materials and has an extremely small residual solvent amount after printing. Intended.

[0005]

In view of the above technical background, the inventors of the present invention have conducted extensive studies to solve the problems of the prior art, and as a result, used a combination of specific polymer diols and a diisocyanate compound. By using isophorone diisocyanate for the present invention, a polyurethane resin having good solubility that can be used as a binder for flexographic printing ink has been found, and the present invention has been completed.

That is, the present invention relates to a binder for flexographic printing ink containing a polyurethane resin solution obtained by reacting (A) a polymer polyol, (B) a diisocyanate compound and (C) a chain extender as a main component,
As (A) high molecular weight polyol, (a-1) molecular weight 70
0 to 2500 polypropylene glycol and / or polyoxytetramethylene glycol and (a-2) poly (β-methyl-δ-valerolactone) diol having a molecular weight of 700 to 2500 are (a-1) / (a- 2) = 3
Used at 0/70 to 70/30 (weight% basis), (B)
The present invention relates to a binder for flexographic printing ink, which comprises a polyurethane resin containing isophorone diisocyanate as a diisocyanate compound and diamine as an essential component as a (C) chain extender.

The constituents of the polyurethane resin which is the main binder of the present invention are as follows. First, at least one of polypropylene glycol having a molecular weight of 700 to 2500 and polyoxytetramethylene glycol having a molecular weight of 700 to 2500 is used as the polymer polyol component (A).
Poly (ether diol) (hereinafter referred to as component (a-1)); poly (β-methyl-) having a molecular weight of 700 to 2500
δ-valerolactone) diol (hereinafter referred to as component (a-2)) is essential.

The component (a-1) is a polymer obtained by ring-opening polymerization of propylene oxide or tetrahydrofuran. Specifically, for example, propylene oxide or tetrahydrofuran is a low molecular weight compound such as ethylene glycol or butanediol. Examples thereof include those obtained by ring-opening polymerization with a polyhydric alcohol. In the present invention, it is not possible to use other polyether diols. For example, ethylene oxide adduct of bisphenol A,
When a propylene oxide adduct corresponding to this is used, the solubility of the polyurethane resin solution is lowered and the object of the present invention cannot be achieved.

The component (a-2) is β-methyl-δ.
-A polymer obtained by ring-opening polymerization of valerolactone, specifically, by ring-opening polymerization of β-methyl-δ-valerolactone with a low molecular weight dihydric alcohol such as ethylene glycol or butanediol. You can get what you get.

The molecular weight of the above-mentioned polymer polyol component (A) must be in the range of 700 to 2500 for both the component (a-1) and the component (a-2). If the molecular weight is less than 700, the polarity will be too strong and the solubility will decrease, while if it exceeds 2,500, the solubility, drying property and blocking resistance will tend to be decreased, both of which are not preferred.

In the present invention, in addition to the limitation of the various constituents in the polymer polyol component (A), the proportion of the constituents used is also limited. That is, the component (a-
The use ratio of 1) and the component (a-2) is (a-1) / (a
-2) = 30/70 to 70/30 (weight% basis) must be in the range. This is because the stability of the obtained polyurethane resin solution is poor outside this range.

As the diisocyanate compound which is another constituent of the polyurethane resin of the present invention, only isophorone diisocyanate can be used. With diisocyanates other than isophorone diisocyanate, polyurethane resins having satisfactory solubility cannot be obtained.

As the chain extender, diamine is an essential component. Typical examples thereof include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4 ′.
-Examples include diamines. Also, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2
Diamines having a hydroxyl group in the molecule, such as -hydroxypropylethylenediamine and di-2-hydroxypropylethylenediamine, can be similarly used. In combination with diamine, low molecular weight glycols having a side chain and having 3 to 10 carbon atoms can also be used. Specifically, 1,2-propylene glycol, 1,3-butylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,
2-diethyl-1,3-propanediol and the like can be mentioned.

A chain length terminator can also be used if necessary. Representative examples thereof include dialkylamines such as di-n-butylamine, dihydroxyalkylamines such as diethanolamine, and alcohols such as ethanol and isopropyl alcohol.

As the method for producing the polyurethane resin of the present invention, first, a polymer polyol component and isophorone diisocyanate are reacted under conditions of excess isocyanate groups to prepare a prepolymer having isocyanate groups at both ends of the polymer polyol. Then, a two-step method of reacting it with a chain extender and, if necessary, a chain length terminating agent in a suitable solvent, and a high molecular weight polyol component, isophorone diisocyanate, a chain extender and a chain length terminating agent as necessary. Although any one-step method in which the reaction is carried out at once in a suitable solvent can be adopted, the former method is preferable for the purpose of obtaining a uniform polymer solution. In these production methods, as a solvent used, ethanol and isopropyl alcohol are used as a main solvent, and in combination therewith, an alcohol solvent such as methanol and n-butanol, and / or ethyl acetate, butyl acetate and the like are used. An ester solvent is used.

When the polyurethane resin used in the present invention is produced by the two-step method, the conditions for reacting the high molecular weight polyol component and isophorone diisocyanate are not limited, except that they are in excess of isocyanate. The base is equivalent ratio of 1 / 1.2 to 1/4
It is preferable that the reaction is performed within the range. In addition, the conditions for reacting the obtained prepolymer with a chain extender and, if necessary, a chain length terminating agent are as follows when the free isocyanate group at the end of the prepolymer is 1 equivalent,
The total equivalent of active hydrogen capable of reacting with the isocyanate group in the chain extender is preferably in the range of 0.5 to 2.0 equivalents (particularly, when the active hydrogen is an amino group, 0.5 to 2.0).
It should be in the range of 1.3 equivalents). When the amount of active hydrogen is less than 0.5 equivalent, the drying property, blocking resistance and film strength are not sufficient, and when the amount of active hydrogen exceeds 2.0 equivalents, the chain extender remains unreacted. It remains, and odor tends to remain after printing.

The number average molecular weight of the polyurethane resin obtained as described above is preferably in the range of 5,000 to 100,000. If the molecular weight is less than 5000, the printing ink using this as a binder is inferior in the drying property, blocking resistance, film strength and oil resistance, while if it exceeds 100,000, the viscosity of the polyurethane resin solution increases. Or the gloss of the printing ink tends to decrease.

The concentration of the resin solid content of the polyurethane resin solution obtained as described above is not particularly limited and is appropriately determined in consideration of workability at the time of printing and is usually about 15 to 60% by weight. Also, the viscosity is usually 50 to 10,000 cP
Practically suitable is about / 25 ° C. In the solvent composition of the polyurethane resin solution, 75% by weight or more of the total weight of the solvent is isopropyl alcohol and / or ethanol, and the remaining 25% by weight or less is isopropyl alcohol such as methanol or n-butanol and an alcohol solvent other than ethanol and And / or an ester solvent such as ethyl acetate or butyl acetate.

To produce the flexographic printing ink composition of the present invention using the polyurethane resin of the present invention, a colorant, a solvent and, if necessary, an interface for improving ink fluidity and surface film are added to the polyurethane resin. An activator and a wax may be appropriately mixed and kneaded by using an ordinary ink manufacturing device such as a ball mill, an attritor, or a sand mill. Further, nitrocellulose, polyamide, acrylic resin, rosin ester and the like may be blended within the range not departing from the performance of the present invention. In the solvent composition of the ink composition using the binder for printing ink of the present invention, 75 wt% or more of the total weight of the solvent is isopropyl alcohol and / or ethanol, and the remaining 25 wt% or less is methanol and n-. It is preferable to use isopropyl alcohol such as butanol and an alcohol solvent other than ethanol and / or ester solvent such as ethyl acetate and butyl acetate.

[0020]

EXAMPLES The present invention will be described in detail below with reference to production examples, examples and comparative examples, but the present invention is not limited to these examples. In the examples, all parts and% are by weight unless otherwise specified.

Production Example 1 350 parts of polypropylene glycol having a molecular weight of 2000 and 650 parts of poly (β-methyl-δ-valerolactone) diol were placed in a round bottom flask equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas introducing tube. Isophorone diisocyanate 2
77.5 parts were charged and reacted under a nitrogen stream at 130 ° C. for 6 hours to form a prepolymer having a free isocyanate value of 4.68%. To this, 517 parts of ethyl acetate was added to prepare a uniform solution of a urethane prepolymer. Then, 1794.5 parts of the above urethane prepolymer solution was added in the presence of a mixture consisting of 97.3 parts of isophorone diamine and 2084 parts of isopropyl alcohol, and then reacted at 50 ° C. for 3 hours. The polyurethane resin solution A thus obtained is
The resin solid content concentration was 35%, and the viscosity was 900 cP / 25 ° C. The polyurethane resin solution A had good solution stability even after being left at 0 ° C. for 1 month, and no precipitates or crystals were formed.

Production Example 2 In the same round bottom flask as in Production Example 1, 500 parts of polyoxytetramethylene glycol having a molecular weight of 2000 and molecular weight of 2 were added.
Of poly (β-methyl-δ-valerolactone) diol (500 parts) and isophorone diisocyanate (222 parts) were charged and reacted under a nitrogen stream at 130 ° C. for 6 hours to give a prepolymer having a free isocyanate value of 3.44%. Ethyl acetate (487 parts) was added to obtain a uniform solution of urethane prepolymer. Then, isophorone diamine 62.8
Part, 10.9 parts of di-n-butylamine and 1955 parts of isopropyl alcohol in the presence of a mixture of 1709 parts of the above urethane prepolymer solution, then 5 parts
The reaction was carried out at 0 ° C for 3 hours. The polyurethane resin solution B thus obtained had a resin solid content concentration of 35% and a viscosity of 63%.
It was 0 cP / 25 ° C. The polyurethane resin solution B is
Even after standing at 0 ° C. for 1 month, its solution stability was good and no precipitate or crystal was formed.

Production Example 3 In the same round bottom flask as in Production Example 1, 600 parts of polypropylene glycol having a molecular weight of 1000 and poly (β-methyl-δ-valerolactone) diol 400 having a molecular weight of 2000 were prepared.
And isophorone diisocyanate 355.2 parts were charged and reacted at 130 ° C. for 6 hours under a nitrogen stream to form a prepolymer having a free isocyanate value of 4.94%. To this, 545 parts of ethyl acetate was added to prepare a uniform solution of urethane prepolymer. And Then, 66.1 parts of isophorone diamine,
1900.2 parts of the above urethane prepolymer solution was added in the presence of a mixture of 27.2 parts of 2-hydroxyethylethylenediamine and 2196 parts of ethanol, and then reacted at 50 ° C. for 3 hours. The polyurethane resin solution C thus obtained had a resin solid content concentration of 35% and a viscosity of 700 cP / 25 ° C. Polyurethane resin solution C
The solution had good solution stability even after being left at 0 ° C. for 1 month, and no precipitates or crystals were formed.

Production Example 4 In the same round bottom flask as in Production Example 1, 500 parts of polyoxytetramethylene glycol having a molecular weight of 2000 and a molecular weight of 2 were added.
Of poly (β-methyl-δ-valerolactone) diol (500 parts), neopentyl glycol (30 parts) and isophorone diisocyanate (350 parts) were charged and reacted under a nitrogen stream at 130 ° C. for 6 hours to give a free isocyanate value of 4.6.
A 5% prepolymer was prepared, and 559 parts of ethyl acetate was added thereto to prepare a uniform solution of urethane prepolymer. Then, 1939 parts of the above urethane prepolymer solution was added in the presence of a mixture of 58.6 parts of isophoronediamine, 28.0 parts of 2-hydroxyethylethylenediamine, 38.8 parts of di-n-butylamine and 2237 parts of isopropyl alcohol. Then, the mixture was reacted at 50 ° C. for 3 hours. The polyurethane resin solution D thus obtained had a resin solid content concentration of 35% and a viscosity of 1300 cP / 25 ° C. The polyurethane resin solution D had good solution stability even after being left at 0 ° C. for 1 month, and no precipitates or crystals were formed.

Production Example 5 In a round bottom flask similar to that of Production Example 1, poly (β-methyl-δ-valerolactone) diol 100 having a molecular weight of 2000 was added.
0 part and 222 parts of isophorone diisocyanate were charged and reacted under a nitrogen stream at 130 ° C. for 6 hours to obtain a prepolymer having a free isocyanate value of 3.44%. To this, 483 parts of ethyl acetate was added to obtain a uniform solution of a urethane prepolymer. did. Then, 1705 parts of the above urethane prepolymer solution was added in the presence of a mixture of 63.0 parts of isophoronediamine and 1948 parts of isopropyl alcohol, and then the mixture was reacted at 50 ° C. for 3 hours. The polyurethane resin solution E thus obtained had a resin solids concentration of 35.
%, The viscosity was 1100 cP / 25 ° C. The polyurethane resin solution E was inferior in solution stability and a resin precipitate was already formed after 1 day at 0 ° C.

Production Example 6 A round-bottomed flask similar to that used in Production Example 1 was charged with 1000 parts of polyoxytetramethylene glycol having a molecular weight of 2000 and 222 parts of isophorone diisocyanate and reacted at 130 ° C. for 6 hours under a nitrogen stream to give a free isocyanate value of 3 ．
43% prepolymer and ethyl acetate 483
Parts were added to obtain a uniform solution of urethane prepolymer. Then, 1705 parts of the above urethane prepolymer solution was added in the presence of a mixture of 62.7 parts of isophorone diamine and 1947.5 parts of isopropyl alcohol, and then the mixture was reacted at 50 ° C. for 3 hours. The polyurethane resin solution F thus obtained had a resin solid content concentration of 35% and a viscosity of 850 cP / 25 ° C. Polyurethane resin solution F
Had poor solution stability and had already formed a resin precipitate after 1 day at 0 ° C.

Production Example 7 (The polyurethane resin in Production Example 1 of JP-B-58-6754 was produced with a solvent composition of isopropyl alcohol / ethyl acetate = 80/20). A round-bottomed flask similar to that of Production Example 1 had a molecular weight of 1900. Was charged with 655 parts of propylene oxide adduct of bisphenol A, 345 parts of polyethylene adipate diol having a molecular weight of 2000 and 230 parts of isophorone diisocyanate, and the mixture was heated to 130 ° C. under a nitrogen stream.
Was reacted for 6 hours to form a prepolymer having a free isocyanate value of 3.53%, and 487 parts of ethyl acetate was added thereto to prepare a uniform solution of the urethane prepolymer. Then, 1717 parts of the above urethane prepolymer solution was added in the presence of a mixture of 65.5 parts of isophorone diamine and 1963.9 parts of isopropyl alcohol, and then the mixture was reacted at 50 ° C. for 3 hours. The polyurethane resin solution G thus obtained has a resin solid content concentration of 35% and a viscosity of 1000 c.
It was P / 25 degreeC. Polyurethane resin solution F was inferior in solution stability and a resin precipitate had already formed after 1 day at 0 ° C.

Production Example 8 (Polyurethane resin represented by Vehicle F of JP-B-58-6754 was prepared with a solvent composition of isopropyl alcohol / ethyl acetate = 80/20). 1500 parts of polypropylene glycol, 500 parts of polyethylene adipate diol having a molecular weight of 1500, and isophorone diisocyanate 2
95.8 parts were charged and reacted at 130 ° C. for 6 hours under a nitrogen stream to form a prepolymer having a free isocyanate value of 4.31%. 520.7 parts of ethyl acetate was added to this to prepare a uniform solution of urethane prepolymer. . Then 89.2 parts of isophorone diamine and isopropyl alcohol 209
1816.5 parts of the above urethane prepolymer solution was added in the presence of a mixture of 9.5 parts and then at 50 ° C. for 3 hours.
Reacted for hours. The polyurethane resin solution H thus obtained had a resin solid content concentration of 35% and a viscosity of 1200 cP.
/ 25 ° C. Polyurethane resin solution H was inferior in solution stability and a resin precipitate had already formed after 1 day at 0 ° C.

Examples 1 to 4 Phthalocyanine blue 10 parts Polyurethane resin solutions A to D obtained in Production Examples 1 to 50 50 parts Ethyl acetate 5 parts Isopropyl alcohol 35 parts Mixtures of the above composition were each kneaded with a paint shaker, A blue printing ink was prepared. To the obtained indigo printing ink, 5 parts of ethyl acetate and 35 parts of isopropyl alcohol were further added to adjust the viscosity.
Indigo blue ink was made. The indigo ink of Comparative Example 1 is a conventional nitrified cotton polyamide type flexo ink. Corona discharge treated nylon film (NY), polyethylene terephthalate (PET) film, corona discharge treated polypropylene film (OPP), corona discharge treated by using a rubber roller equipped with 165 lines of anilox roller for these five indigo printing inks. The color was spread on a polyethylene film (PE).

(Cellophane Tape Adhesion Test) One day after the color development, cellophane adhesive tape was adhered to the color development surface, and the state of the ink film when strongly peeled off was evaluated as follows. ◎ −−−−− There is no abnormality on the ink film. ->---> 80% or more of the ink film remained. Δ ----- 50% or more of the ink film remained. Less than 50% of the x ------ ink film remains.

(Residual solvent test) After one day of color development, 300 cm ² of each color development product was placed in a 300 ml Erlenmeyer flask and sealed, and then kept at 140 ° C. for 10 minutes, and then the gas in the flask was quantified by gas chromatography. .

[0032]

[Table 1]

[0033]

According to the present invention, a binder for flexographic printing ink having good solubility in a low-solubility mixed solvent, excellent adhesion to a plastic substrate, and a small amount of residual solvent after printing is obtained. It has a great effect that it can be done.

Claims (2)

[Claims] 1. A binder for flexographic printing ink comprising a polyurethane resin solution obtained by reacting a polymer polyol (A), a diisocyanate compound (B) and a chain extender (C) as a main component, wherein the polymer (A) As the polyol, (a-1) polypropylene glycol and / or polyoxytetramethylene glycol having a molecular weight of 700 to 2500, and (a-2) a molecular weight of 700 to 250.
0 of poly (β-methyl-δ-valerolactone) diol, (a-1) / (a-2) = 30/70 to 70/3
0 (% by weight), (B) diisocyanate compound is isophorone diisocyanate, (C)
A binder for flexographic printing ink, which comprises a polyurethane resin containing diamine as an essential component as a chain extender as a main component. 2. The binder for flexographic printing ink according to claim 1, wherein isopropyl alcohol and / or ethanol is contained as a solvent component in the binder in an amount of 75% by weight or more based on the total weight of the solvent.