JP2005325190A - Emulsion composition for water-based printing ink and water-based printing ink using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous printing ink excellent in adhesion to various plastic films and the like and pigment dispersion stability.
SOLUTION: (A) a polymer polyol having Mn = 500 to 10,000, (B) a chain extender, (C) a compound containing a carboxyl group and an active hydrogen group, (D) an organic polyisocyanate, (E) An emulsion composition for aqueous printing ink of polyurethane-based polymer obtained by reacting a neutralizing agent, wherein (D) the organic polyisocyanate contains (D1) allophanate-modified polyisocyanate, It solves with the emulsion composition for water-based printing inks, and the water-based printing ink using the same.
[Selection figure] None

Description

  The present invention relates to an emulsion composition used for a vehicle of an aqueous printing ink excellent in adhesion and printability and an aqueous printing ink using the same.

  Conventionally, in the field of printing inks, organic solvent-based ones have been mainstream. However, in recent years, aqueous printing inks have been directed from the viewpoints of air pollution prevention, regulations under the Fire Service Act, occupational safety and health, and the like. The performance of such water-based printing ink largely depends on the characteristics of the resin used as a vehicle. Resins in which carboxylates are introduced into the molecular chain, such as polyester resins, acrylic resins, polyurethane resins, etc. have been proposed. ing. In particular, polyurethane resins are widely used in organic solvent-based printing inks because of their good adhesion to various plastic films. However, polyurethane resins for aqueous printing inks are inferior to organic solvent-based ones in performance, and various studies have been made.

  For example, Patent Document 1 discloses an aqueous printing ink using an aqueous emulsion of a polyurethane resin using polycarbonate diol. Patent Document 2 discloses a binder for aqueous printing ink using an aqueous emulsion of a polyurethane resin into which nonionic and anionic hydrophilic groups are introduced.

Japanese Patent Laid-Open No. 5-171091 JP-A-6-346012

  In water-based emulsions, the resin is not dissolved in water, so to apply an organic solvent-based printing system to a system using printing ink of an aqueous emulsion as it is, poor drying, poor ink adhesion, ink Problems such as cracking of the film may occur.

  The aqueous printing ink using the emulsion composition of the present invention has good adhesion to various plastic films and metal foils, and has an appropriate viscosity, and therefore has excellent pigment dispersion stability. Further, those using a specific allophanate-modified polyisocyanate have a smaller average particle size, and therefore have better plate clogging properties.

  An object of this invention is to provide the water-based printing ink excellent in the adhesiveness to various plastic films etc., pigment dispersion stability, etc.

  That is, this invention is shown by the following (1)-(3).

(1) (A) a polymer polyol having a number average molecular weight of 500 to 10,000, (B) a chain extender, (C) a compound containing a carboxyl group and an active hydrogen group, (D) an organic polyisocyanate, (E) An emulsion composition for aqueous printing ink of polyurethane-based polymer obtained by reacting a neutralizing agent, wherein (D) the organic polyisocyanate contains (D1) allophanate-modified polyisocyanate, Emulsion composition for aqueous printing ink.

(2) (D1) The emulsion composition for aqueous printing inks according to (1), wherein the allophanate-modified polyisocyanate is obtained by reacting hexamethylene diisocyanate with a monool having 1 to 6 carbon atoms. Stuff.

(3) A water-based printing ink using the emulsion composition of (1) or (2).

  The number average molecular weight of the polymer polyol (A) used in the emulsion composition of the present invention is 500 to 10,000, preferably 1,000 to 5,000. Moreover, 2-4 are preferable and, as for the average functional group number of this (A) polyol, 2-3 are still more preferable. When the number average molecular weight of the polymer polyol is less than the lower limit, the ink film tends to be too hard. On the other hand, if the upper limit is exceeded, the blocking resistance tends to be insufficient. The number average molecular weight of the polymer polyol is calculated from the average number of functional groups and the terminal group weight determined by the terminal group determination method.

Examples of the polymer polyol used in the present invention include polyester polyol, polyamide ester polyol, polyether polyol, polyether ester polyol, polycarbonate polyol, polyolefin polyol, animal and plant polyol.
The polymer polyol (A) preferred in the present invention is a polyester polyol when importance is attached to adhesion, and is a polyether polyol or polycarbonate polyol when importance is attached to water resistance.

  As this polyester polyol, known phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, kurtaconic acid, azelaic acid, Sebacic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromuconic acid, α-butyl-α-ethylglutaric acid, α, β-diethyl One or more of dicarboxylic acids or anhydrides such as succinic acid, maleic acid, fumaric acid and the like, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexane All, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol , Cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, dimer acid diol, ethylene oxide and propylene oxide adducts of bisphenol A, bis (β-hydroxyethyl) benzene, xylylene glycol, glycerin, trimethylol It can be obtained from a polycondensation reaction with one or more low molecular polyols such as propane and pentaerythritol. Furthermore, there are lactone-based polyester polyols obtained from ring-opening polymerization of cyclic ester (so-called lactone) monomers such as ε-caprolactone, alkyl-substituted ε-caprolactone, δ-valerolactone, and alkyl-substituted δ-valerolactone. Further, a low molecular polyol such as hexamethylene diamine, isophorone diamine, monoethanol amine or the like may be used as a part of the low molecular polyol. In this case, a polyester-amide polyol is obtained.

  As the polyether polyol, active hydrogen groups such as low molecular polyols used in the above-mentioned polyester polyol, low molecular polyamines such as ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, and xylylenediamine are used. Starting from a compound having 2 or more, preferably 2 to 3, alkylene oxides such as ethylene oxide, propylene oxide and butylene oxide, alkyl glycidyl ethers such as methyl glycidyl ether, and aryl glycidyl such as phenyl glycidyl ether It can be obtained by addition polymerization by a known method from a single or mixture of cyclic ether monomers such as ethers and tetrahydrofuran.

  The polycarbonate polyol is obtained from a dealcoholization reaction or a dephenol reaction between one or more low molecular diols or low molecular triols from the above-mentioned polyester polyol source and ethylene carbonate, diethyl carbonate, or diphenyl carbonate. In addition, the transesterification product of the above-mentioned polycarbonate polyol and polyester polyol can also be used suitably.

  Examples of polyether ester polyols include copolyols obtained from the aforementioned polyether polyols and the aforementioned dicarboxylic acids. Further, there are those obtained by reacting the aforementioned polyester or polycarbonate with epoxide or cyclic ether.

  Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

  Examples of animal and plant-based polyols include castor oil-based polyols and silk fibroin.

  Moreover, if it has a number average molecular weight of 500 to 10,000 and an average of one or more active hydrogen groups in one molecule, in addition to dimer acid polyol, hydrogenated dimer acid polyol, epoxy resin, Active hydrogen group-containing resins such as polyamide resin, polyester resin, acrylic resin, rosin resin, urea resin, melamine resin, phenol resin, coumarone resin, and polyvinyl alcohol can also be used as the polymer polyol.

  (B) The chain extender used in the present invention includes low molecular polyols, monoethanolamine, diethanolamine, N-methyldiethanolamine, N-phenyldipropanolamine, which are used for obtaining the above-described polyester polyol and polyether polyol. Amino alcohols such as The chain extender preferred in the present invention is an aliphatic polyol, alicyclic polyol, aliphatic polyamine, or alicyclic polyamine having 2 to 15 carbon atoms.

  Examples of the compound containing a carboxyl group and an active hydrogen group used in the present invention include dimethylolpropionic acid, dimethylolbutanoic acid, a reaction product of polyamine and acid anhydride, dimethylolpropionic acid and dimethylolbutane. Examples include lactone adducts using an acid as an initiator. Preferred compounds (C) containing a carboxyl group and an active hydrogen group in the present invention are dimethylolpropionic acid and dimethylolbutanoic acid.

  The (D) organic polyisocyanate used in the present invention is one in which (D1) allophanate-modified polyisocyanate is an essential constituent. (D1) The allophanate-modified polyisocyanate is obtained by allophanating the above-mentioned organic diisocyanate and a hydroxyl group-containing compound in the presence of an allophanate-forming catalyst. The (D1) allophanate-modified polyisocyanate preferred in the present invention is obtained from hexamethylene diisocyanate and a monool having 1 to 6 carbon atoms, and the particularly preferred (D1) allophanate-modified polyisocyanate is from hexamethylene diisocyanate and isopropyl alcohol. The allophanate-modified polyisocyanate obtained.

  The allophanate-modified polyisocyanate obtained from hexamethylene diisocyanate and monool having 1 to 6 carbon atoms has a molecular structure having a side chain having 1 to 6 carbon atoms. For this reason, the polyurethane resin using this has improved the adhesiveness with respect to various plastic films, especially polyolefin-type films, such as polyethylene and a polypropylene, compared with the polyurethane resin which does not use this. In addition, the plate clogging property is improved because the polyurethane resin has an effect of preventing aggregation between molecules. In order to effectively exhibit such an effect, a secondary alcohol is preferable to a primary alcohol and further a tertiary alcohol is preferable to a primary alcohol if the carbon number is constant (for example, in the case of butanol, normal butanol <isobutanol < Tertiary butanol). However, when obtaining allophanate-modified polyisocyanates, secondary alcohols are preferable to tertiary alcohols, and primary alcohols are more preferable to secondary alcohols from the viewpoint of reactivity. For this reason, secondary alcohols are balanced and the most preferred is isopropanol.

  In the present invention, an organic polyisocyanate other than the allophanate-modified polyisocyanate can be used together. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, diphenyldimethylmethane diisocyanate, dibenzyl diisocyanate, naphthylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpe Aliphatic diisocyanates such as tan-1,5-diisocyanate, 2,2,4-trimethylhexahylene-1,6-diisocyanate, 2,4,4-trimethylhexahylene-1,6-diisocyanate, isophorone diisocyanate, There are alicyclic diisocyanates such as cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated trimethylxylylene diisocyanate. These organic diisocyanates can be used alone or in a mixture. Furthermore, modified products such as these adduct-modified products, carbodiimide-modified products, allophanate-modified products (excluding those mentioned above), burette-modified products, uretdione-modified products, uretoimine-modified products, and isocyanurate-modified products can be used. In this case, it is preferable that (D1) allophanate-modified polyisocyanate is 25% by mass or more based on the whole (D) organic polyisocyanate. When there are too many organic polyisocyanates other than (D1), since the intermolecular force of the obtained polyurethane resin is too large, it will aggregate and the plate-clogging property will fall easily.

  Examples of the (E) neutralizing agent used in the present invention include ammonia, ethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-phenyldiethanolamine, monoethanolamine, dimethyl Organic amines such as ethanolamine, diethylethanolamine, morpholine, N-methylmorpholine, 2-amino-2-ethyl-1-propanol, alkali metals such as lithium, potassium and sodium, inorganics such as sodium hydroxide and potassium hydroxide Examples include alkalis, but in order to improve the weather resistance and water resistance after drying, those having high volatility that are easily dissociated by heat are preferable, and ammonia, trimethylamine, and triethylamine are preferable. These neutralizing agents can be used alone or in a mixture of two or more.

  Note that (D) the neutralizing agent forms a salt with the carboxylic acid introduced into the polyurethane polymer. The amount of carboxylate introduced is 0.05 to 1.5 mmol / g in the polyurethane polymer, preferably 0.1 to 1.3 mmol / g. When the amount of carboxylate introduced is less than the lower limit, the polyurethane polymer does not disperse well in water. When the upper limit is exceeded, the water resistance of the polyurethane polymer after drying is insufficient. The pH of the emulsion is preferably from 5.5 to 10.5, more preferably from 6 to 10. When the pH is less than 5.5, the water dispersibility of the polyurethane polymer is insufficient. On the other hand, when the pH exceeds 10.5, the molecular cleavage of the polymer may occur over time due to the hydrolysis reaction.

  The polyurethane polymer in the present invention introduces a carboxylate as a hydrophilic group in the molecular chain in order to give water dispersibility, but if necessary, sulfonate, phosphate, phosphone Anionic polar groups other than carboxylates such as acid salts and the like, cationic polar groups such as quaternary ammonium salts, and nonionic polar groups such as ether groups may be introduced.

  In the present invention, when synthesizing a polyurethane-based polymer, a reaction terminator can be used as necessary. Examples of the reaction terminator include monoalcohols and monoamines. In some cases, aminoalcohols can also serve as the reaction terminator. Monoisocyanates such as phenyl isocyanate, butyl isocyanate, cyclohexyl isocyanate and the like can also be used as a reaction terminator.

  Specific monoalcohols used as the reaction terminator include methanol, ethanol, propanol, isopropanol, 2-ethylhexanol and the like. Monoamines include primary amines such as ethylamine, propylamine, and butylamine, and secondary amines such as diethylamine and dibutylamine. Examples of amino alcohols include monoethanolamine and diethanolamine.

  The polyurethane polymer used in the present invention can be produced by a one-shot method in which reaction is performed in an atmosphere containing excess active hydrogen, or by reacting an active hydrogen compound (particularly a polymer polyol) with an organic diisocyanate in excess of an isocyanate group, A base terminal prepolymer is synthesized and then synthesized by a known method such as a prepolymer method in which an active hydrogen compound (particularly a chain extender) is reacted. In addition, after reacting the polyurethane polymer in an organic solvent compatible with water, water is added and then the organic solvent is removed, or the polymer is synthesized without using a solvent, and is forcibly dispersed or dissolved in water. Can also be obtained. In addition, the salt formation time of the carboxylic acid introduced into the polyurethane polymer and the (D) neutralizing agent may be before or after the urethanization reaction.

  In the case of the one-shot method, the isocyanate group / active hydrogen group molar ratio is 0.5 to less than 1, preferably 0.8 to less than 1. When it is less than 0.5, the molecular weight of the polyurethane polymer is too small, so that the durability is insufficient. In the case of 1 or more, gelation tends to occur when a polymer is synthesized.

  In the case of the prepolymer method, the molar ratio of isocyanate group / active hydrogen group during synthesis of the prepolymer is 1.1 to 5.0, preferably 1.2 to 4.0. When it is less than 1.1, the molecular weight of the prepolymer becomes too large and it is difficult to proceed to the subsequent reaction step. If it exceeds 5.0, the adhesion is poor.

  The total of the urethane group concentration and the urea group concentration of the polyurethane polymer used in the present invention is 1.0 to 3.0 mmol / g, preferably 1.3 to 2.7 mmol / g. When urea groups are not present in the polymer, the urethane group concentration is 1.0 to 3.0 mmol / g, preferably 1.3 to 2.7 mmol / g. When the sum of the urethane group concentration and the urea group concentration is less than the lower limit, the strength of the ink film tends to be insufficient. Moreover, when exceeding an upper limit, the adhesiveness of an ink film tends to become inadequate.

  When using an organic solvent, examples of usable organic solvents include toluene, xylene, swazol (aromatic hydrocarbon solvent manufactured by Cosmo Oil Co., Ltd.), and Solvesso (aromatic hydrocarbon solvent manufactured by Exxon Chemical Co., Ltd.). Aromatic solvents such as hexane, aliphatic hydrocarbon solvents such as hexane, cycloaliphatic hydrocarbon solvents such as isophorone, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl acetate , Ester solvents such as isobutyl acetate, glycol glycols such as ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol 3-methyl-3-methoxybutyl acetate, ethylene glycol ethyl-3-ethoxypropionate Non-solvents such as ethylene glycol dimethyl ether, diethylene glycol dibutyl ether, glycol ether solvents such as propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, ether solvents such as tetrahydrofuran and dioxane, N-methylpyrrolidone, hexamethylphosphoramide, etc. Examples include protic polar solvents. The said solvent may contain 1 type (s) or 2 or more types.

  As the reaction catalyst for synthesizing the isocyanate group-terminated prepolymer or polyurethane polymer used in the present invention, a known so-called urethanization catalyst can be used. Specific examples include organic metal compounds such as dioctyltin dilaurate, organic amines such as triethylenediamine, and salts thereof. The reaction temperature during urethanization is 10 to 100 ° C, preferably 30 to 80 ° C.

  The number average molecular weight of the polyurethane polymer thus obtained is preferably 5,000 or more, and particularly preferably 10,000 or more. When the number average molecular weight of the polyurethane polymer is less than 5,000, durability is poor. In the present invention, the number average molecular weight of the polymer is measured by a gel permeation chromatography (GPC) method using a polyethylene glycol calibration curve.

  The average particle size of the polyurethane emulsion is 100 nm or less, preferably 80 nm or less. When the average particle diameter exceeds the upper limit, the water-based ink using this emulsion tends to clog the plate. The average particle diameter is a value obtained by analyzing a value measured by a dynamic light scattering method by a cumulant method.

  The viscosity of the polyurethane emulsion at 25 ° C. is 2,000 mPa · s or less, preferably 50 to 1,000 mPa · s, when the solid content is 30% by mass. If the viscosity exceeds the upper limit, it is difficult to make an ink or print.

  In the polyurethane emulsion of the present invention, additives and auxiliaries commonly used in aqueous systems can be used as necessary. For example, pigments, antiblocking agents, dispersion stabilizers, viscosity modifiers, leveling agents, antigelling agents, light stabilizers, antioxidants, UV absorbers, inorganic and organic fillers, plasticizers, lubricants, antistatic agents Further, a reinforcing material, a catalyst and the like can be added.

  The polyurethane emulsion of the present invention can be used by blending with other resin emulsions. For example, acrylic emulsion, polyester emulsion, polyolefin emulsion, latex and the like.

  The water-based printing ink of the present invention includes the above-described polyurethane-based emulsion, coloring components such as pigments and dyes, and other resins as necessary, water for adjusting solid content and viscosity, isopropanol for adjusting surface tension, Organic solvents such as N-methylpyrrolidone, antiblocking agents, dispersion stabilizers, thixotropic agents, antioxidants, UV absorbers, antifoaming agents, thickeners, dispersants, surfactants, catalysts, fillers, lubricants And an additive such as an antistatic agent and a plasticizer, which are blended and obtained using a ball mill, a sand grind mill or the like. Moreover, you may add and use a hardening | curing agent just before application | coating as needed. Specific examples of the curing agent include self-emulsifying polyisocyanate-based curing agents such as Aquanate 100 and 200 manufactured by Nippon Polyurethane Industry.

  Next, although the Example and comparative example of this invention are demonstrated in detail, this invention is not limited to these Examples. Unless otherwise specified, “%” in the examples means “% by mass”.

[Synthesis of polyurethane emulsion]
Example 1
Capacity with stirrer, thermometer, nitrogen seal tube and condenser: A 2 L reactor was charged with 100 g of DMFDG, 141.6 g of polyol-1 and 21.0 g of DMBA, and uniformly mixed at 100 ° C. Thereafter, 117.8 g of ALP-1 and 0.03 g of DOTDL were charged and reacted at 80 ° C. for 3 hours. Next, 14.3 g of TEA was charged to neutralize the carboxyl group. The isocyanate content at this time was 1.81%. Thereafter, 570 g of water was charged to cause inversion. Immediately after the phase transfer, a chain extension reaction was carried out by adding amine water consisting of 30 g of water, 4.8 g of EDA, and 0.5 g of MEA in advance. The reaction was terminated when the presence of isocyanate groups was no longer confirmed by FT-IR, and polyurethane emulsion PU-1 was obtained. The solid content of PU-1 was 30.0%, the viscosity at 25 ° C. was 280 mPa · s, the pH was 9.7, and the average particle size was 19 nm.

Examples 2-5, Comparative Examples 1-2
In the same reactor as in Example 1, the raw materials shown in Tables 1 and 2 were charged and reacted in the same procedure as in Example 1 to obtain polyurethane emulsions PU-2 to PU-6. However, for Examples 4 and 5 and Comparative Example 2, a reactor having a capacity of 3 L was used. The synthesis results are shown in Tables 1 and 2. In addition, since PU-7 became paste-like, subsequent evaluation was not performed.

[Film properties]
P-1 to 6 were cast and dried to prepare a dry film having a thickness of about 100 μm, and various physical properties were measured. The measurement results are shown in Tables 1 and 2.
Drying conditions: 50 ° C x 2 hours

In Examples 1-5, Comparative Examples 1-2, and Tables 1-2, DMFDG:
Dipropylene glycol dimethyl ether polyol-1:
Polyester polyol obtained from mixed diol and mixed dicarboxylic acid Number average molecular weight = 2,000
Mixed diol → ethylene glycol / neopentyl glycol = 1/9 (molar ratio)
Mixed dicarboxylic acid → adipic acid / isophthalic acid = 1/1 (molar ratio)
DMBA:
2,2-dimethylolbutanoic acid ALP-1:
Allophanate-modified polyisocyanate Hexamethylene diisocyanate / isopropanol = 2/1 (molar ratio)
Isocyanate content = 21.2%
ALP-2:
Allophanate-modified polyisocyanate Hexamethylene diisocyanate / methanol = 2/1 (molar ratio)
Isocyanate content = 22.8%
HDI:
Hexamethylene diisocyanate IPDI:
Isophorone diisocyanate DOTDL:
Dioctyltin dilaurate TEA:
Triethylamine EDA:
Ethylenediamine MEA
Monoethanolamine

Average particle size measuring device:
Otsuka Electronics Co., Ltd. Electrophoretic light scattering system ELS-800

Physical property measurement items:
Tensile test A sample was prepared by punching with a No. 4 dumbbell of JIS K6301 (1995).
Tensile property measuring device:
Tensilon UTA-500 manufactured by Orientec Co., Ltd.
Measurement conditions: Tensile speed = 200 mm / min, measurement temperature = 25 ° C.

[Ink conversion test]
Examples 6 to 10, Comparative Example 3
A white ink was prepared with the following composition. These inks were used for printing on various substrates, and the ink performance in the print samples was evaluated. The evaluation results are shown in Table 3.
(Ink formulation)
Ink formulation (PU-1 to 3, 6)
Emulsion composition 26.7g
Titanium white 32.0g
17.3g of water
Isopropanol 4.0g
Ink formulation (PU-4, 5)
Emulsion composition 80.0g
Titanium white 32.0g
The mixture having the above composition was kneaded for 2 hours with a paint shaker using the same amount of glass beads as the dispersion medium. Next, the paste was filtered to prepare a water-based printing ink evaluation sample.

Each test method in Table 3 is as follows.
Pigment dispersion stability After mixing for 48 hours after mixing with ink, check for pigment precipitation, etc.

(Printing conditions)
Ink: White ink printer prepared above: Simple gravure printer equipped with gravure plate Printing speed: 20 m / min Ink thickness: Ink thickness 1 μ (dry)
Printing substrate: Corona-treated stretched polyester film (20 μm thick)
(Polyethylene terephthalate (PET) film)
(Evaluation item)
Plate clogging property After printing, a mixed solvent of isopropanol / water = 1/1 (mass ratio) is dropped on a gravure roll of a simple gravure printing machine in a washing bottle to observe whether ink can be washed off from the gravure roll.
Evaluation ○: Easily washed away ×: Adhesiveness that cannot be washed away simply by dropping the mixed solvent Immediately after printing and after standing overnight after printing, a cellophane tape is affixed to the printed surface, and this is rapidly applied I peeled it off.
Evaluation A: 90% to 100% of the printed film remained.
○: 70% to 80% of the printed film remained.
Δ: 50% to 70% of the printed film remained.
X: Only 50% or less of the printed film remained.
Rubbing test After printing and standing overnight, the appearance of the printed surface was rubbed with absorbent cotton soaked in water and evaluated by the number of rubbing times when the surface condition was rough for the first time.

Examples 1-4 using 25 mass% or more of allophanate-modified polyisocyanate in the isocyanate component were excellent in various performances such as pigment dispersion stability and adhesion to various plastic films. In Example 5, since the allophanate-modified polyisocyanate was less than 25% by mass in the isocyanate component, the plate clogging property and final adhesion were slightly inferior to those of other examples. On the other hand, PU-6 using a single IPDI for the organic polyisocyanate resulted in inferior adhesion to the examples. This seems to be because the aggregation of urethane groups could not be inhibited because there was no allophanate group. In addition, PU-7 using a single HDI as an organic polyisocyanate was not evaluated since the emulsion obtained from the ease of arrangement of HDI became a paste.

Claims (3)

  (A) a polymer polyol having a number average molecular weight of 500 to 10,000, (B) a chain extender, (C) a compound containing a carboxyl group and an active hydrogen group, (D) an organic polyisocyanate, (E) a neutralizer. The aqueous printing ink is an emulsion composition for aqueous printing inks of polyurethane-based polymer obtained by reacting, wherein the (D) organic polyisocyanate contains (D1) allophanate-modified polyisocyanate. Emulsion composition.   (D1) The emulsion composition for aqueous printing inks according to claim 1, wherein the allophanate-modified polyisocyanate is obtained by reacting hexamethylene diisocyanate with a monool having 1 to 6 carbon atoms. An aqueous printing ink using the emulsion composition according to claim 1.