JP5728749B1 - Printing ink - Google Patents

Abstract

[PROBLEMS] There is no brown change when mixed with nitrified cotton resin, and both printing suitability such as plate fogging and alcohol bleed resistance in an ester / alcohol solvent system are compatible, and further, blocking resistance, adhesion, laminate strength, Providing printing inks that contain polyurethane resin that also has printing properties such as motility. SOLUTION: By using a polyurethane resin in which both diphenylmethane diisocyanate and isophorone diisocyanate are essential components as organic diisocyanate and the synthesis parameters are controlled, there is no brown change when mixed with nitrified cotton resin and it is relatively soluble. It has been found that in a weak ester / alcohol solvent system, it is possible to design a printing ink using a polyurethane resin that achieves both excellent printability and printed physical properties. [Selection figure] None

Description

 The present invention relates to a printing ink, and more particularly to a printing ink containing a polyurethane resin that does not cause browning when used in combination with a nitrified cotton resin and is excellent in various printability and print physical properties.

Gravure printing and flexographic printing are used for soft packaging materials used in foods and daily necessities to add beauty and functionality. Various resins are used in printing inks used for these depending on the application. In particular, polyurethane resins are widely used because the toughness and flexibility of the coating film can be appropriately adjusted by selecting an organic polyol, an organic diisocyanate, and the like. Furthermore, the printability and physical properties of the print are improved by extending the chain with an organic diamine and forming a polyurethane resin containing a urea bond.

On the other hand, a nitrified cotton resin is used in combination with a polyurethane resin because it has excellent rigidity and re-dissolvability and good color of printing ink. However, in the case of such a printing ink, when it has an amino group at the terminal of the polyurethane resin, there is a problem that browning of the printing ink or printed matter occurs with time when mixed with the nitrified cotton resin.

For example, Patent Documents 1 and 2 do not mention the brown color change of the printing ink over time, and an amino group is included at the terminal of the polyurethane resin, so that the brown color of the printing ink changes over time.

Furthermore, from the viewpoint of environmental protection and legal regulations, printing inks that use ester / alcohol solvent systems that exclude aromatic solvents and ketone solvents are desired and research and development are underway. Since the solvent power is lower than that of aromatic or ketone solvents, the printability is poor, and conversely, it is a work that increases the solvent power in ester / alcohol solvents. There are still many issues, such as poor physical properties.

For example, Patent Documents 2 to 3 use only diphenylmethane diisocyanate as the organic diisocyanate of the polyurethane resin, and Patent Documents 4 to 6 use only isophorone diisocyanate as the organic diisocyanate of the polyurethane resin. And the problem of alcohol bleed resistance remain.

Japanese Patent No. 4882206 Special table 2011-503334 gazette Japanese Patent No. 3166543 JP 2002-294128 A Japanese Patent Laid-Open No. 2004-204048 JP 2006-306979 A

 The present invention has no brown change when mixed with nitrified cotton resin, and is compatible with printing suitability such as plate fogging and alcohol bleed resistance in an ester / alcohol solvent system, and further, blocking resistance, adhesion, laminate strength, An object of the present invention is to provide a printing ink containing a polyurethane resin having printing properties such as resistance to fringing.

 As a result of intensive studies in view of the above circumstances, the present inventors have used nitrified cotton by using a polyurethane resin that uses both diphenylmethane diisocyanate and isophorone diisocyanate as organic diisocyanates as essential components and has controlled synthesis parameters. Enables the design of printing inks that use polyurethane resin that achieves both excellent printability and physical properties in an ester / alcohol solvent system that does not change brown color when mixed with a resin and has a relatively weak dissolving power. And found the present invention.

That is, the present invention is a printing ink characterized by containing the following polyurethane resins (1) to (4) and a nitrified cotton resin :
The solid content weight ratio of the said polyurethane resin and the said nitrifying cotton resin is polyurethane resin / nitrating cotton resin = 1 / 9-6 / 4, It is related with printing ink characterized by the above-mentioned .
(1) A polyurethane resin obtained by reacting a urethane prepolymer (C) having an isocyanate group at the terminal obtained by reacting an organic polyol (A) and an organic diisocyanate (B) with an organic diamine (D). It is.
(2) The molar ratio [NCO] / [OH] in the reaction between the hydroxyl group of the organic polyol (A) and the isocyanate group of the organic diisocyanate (B) is [NCO] / [OH] = 1.25 to 2.50. It is.
(3) The organic diisocyanate (B) is isophorone diisocyanate and diphenylmethane diisocyanate, and the molar ratio of isophorone diisocyanate and diphenylmethane diisocyanate is isophorone diisocyanate / diphenylmethane diisocyanate = 9/1 to 1/9.
(4) The amine value of the polyurethane resin is less than 0.1 mgKOH / g.

Furthermore, the present invention relates to a printing ink, wherein the polyurethane resin has a weight average molecular weight of 40,000 to 80,000.

 Furthermore, this invention relates to the printed matter formed by printing printing ink on a plastic film using a printing machine.

 Furthermore, this invention relates to the laminated body formed by laminating printed matter and a base material through an adhesive agent.

 The present invention makes it possible to provide a printing ink using a polyurethane resin that does not change brown color when mixed with nitrified cotton and has excellent printability and print properties.

Hereinafter, the printing ink of the present invention will be described. The printing ink of the present invention contains a polyurethane resin. The polyurethane resin is obtained by reacting an organic polyol (A) with an organic diisocyanate (B) containing both isophorone diisocyanate and diphenylmethane diisocyanate, and a urethane prepolymer (C) having an isocyanate group at the terminal, and an organic diamine as a chain extender. Obtained by reacting (D). That is, first, as a prepolymer reaction, an organic polyol (A) and an organic diisocyanate (B) are used, and if necessary, an inert solvent for the isocyanate group is used, and if necessary, a temperature of 10 to 100 ° C. using a catalyst. To produce a urethane prepolymer (C) having an isocyanate group at the terminal, and then react the urethane prepolymer and the organic diamine (D) at 10 to 80 ° C. as a chain extension reaction. The end points of the prepolymer reaction and chain extension reaction are determined by viscosity measurement, NCO peak by IR measurement, amine value measurement by titration, and the like.

In the present invention, various known polyester polyols, polyether polyols and the like can be used as the organic polyol (A), and one or more of them may be used in combination. Examples of the polyester polyol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2methyl-1,3-propanediol, 2ethyl-2butyl-1,3propanediol, and 1,3-butane. Diol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene Saturated or unsaturated low molecular weight polyols such as glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, and pentaerythritol Kind , Adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, speric acid, azelaic acid, sebacic acid, trimellitic acid, pyromellitic acid Polyester polyols obtained by dehydration condensation or polymerization of these polyhydric carboxylic acids or their anhydrides, cyclic ester compounds such as polycaprolactone, polyvalerolactone, poly (β-methyl-γ-valerolactone), etc. And polyester polyols obtained by ring-opening polymerization of lactones. Examples of polyether polyols include polymers or copolymers such as methylene oxide, ethylene oxide, propylene oxide, and tetrahydrofuran. The polyester polyol and the polyether polyol are preferably those having a branched structure.

In the polyurethane resin of the present invention, when considering the compatibility between the solubility in an ester / alcohol solvent and various printed physical properties for various plastic films, an important factor is the formation of urethane bond and urea bond hard segments. Organic diisocyanate (B).

 In the present invention, the organic diisocyanate (B) includes both isophorone diisocyanate and diphenylmethane diisocyanate, and may be expressed as IPDI and MDI, respectively. Diphenylmethane diisocyanate is preferably 3,3-diphenylmethane diisocyanate or 4,4-diphenylmethane diisocyanate, and 3,3-diphenylmethane diisocyanate and 4,4-diphenylmethane diisocyanate may be mixed and used.

 Since diphenylmethane diisocyanate is an aromatic isocyanate having two aromatic rings in the molecule, compared to aliphatic isocyanates and alicyclic isocyanates, it is more resistant to alcohol, so in ester / alcohol solvent based printing inks. It can be said that the organic diisocyanate easily balances printing suitability such as plate fog and alcohol bleed resistance.

  The organic diamine (D) as a chain extender in the present invention is ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4′-diamine, 2-hydroxyethylethylenediamine, 2-hydroxyethyl, etc. Propyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypyrroleethylenediamine, di-2-hydroxypyrroleethylenediamine, Amines having a hydroxyl group in the molecule such as di-2-hydroxypropylethylenediamine can also be used. These chain extenders can be used alone or in admixture of two or more, and isophoronediamine is particularly preferred.

  Further, a reaction terminator may be used for the chain extension reaction. Examples of the reaction terminator include dialkylamines such as di-n-butylamine, monoethanolamine, diethanolamine, 2-amino-2-methyl-1-propanol, tri (hydroxymethyl) aminomethane, 2-amino. Amines having a hydroxyl group such as 2-ethyl-1,3-propanediol can also be used. Furthermore, monoamine type amino acids such as glycine, alanine, glutamic acid, taurine, aspartic acid, aminobutyric acid, valine, aminocaproic acid, aminobenzoic acid, aminoisophthalic acid, sulfamic acid and the like can also be mentioned.

In the polyurethane resin in the present invention, the molar ratio [NCO] / [OH] in the reaction between the hydroxyl group of the organic polyol (A) and the isocyanate group of the organic diisocyanate (B) is [NCO] / [OH] = 1.25. 2.50. If [NCO] / [OH] = 1.25 or less, the number of hard segment bonds, particularly the number of urea bonds decreases, resulting in poor blocking resistance, and if it exceeds 2.50, the number of hard segment bonds increases. Adhesion and laminate strength are inferior.

  The molar ratio of isophorone diisocyanate and diphenylmethane diisocyanate in the polyurethane resin in the present invention is isophorone diisocyanate / diphenylmethane diisocyanate = 9/1 to 1/9. When isophorone diisocyanate / diphenylmethane diisocyanate = 10/0, all of the isophorone rings are introduced into the urethane bond sites, resulting in poor alcohol bleed resistance. In the case of isophorone diisocyanate / diphenylmethane diisocyanate = 0/10, two rigid aromatic rings are similarly introduced into the urethane bond site, and the plate fogging property is remarkably inferior, and at the same time, the resistance to swelling is also inferior.

The polyurethane resin in the present invention has an amine value of less than 0.1 mgKOH / g in view of brown color change when mixed with nitrified cotton resin. When the amine value is 0.1 mgKOH / g or more, when mixed with nitrified cotton resin, a brown color changes with time of the printing ink or printed matter.

  The weight average molecular weight of the polyurethane resin in the present invention is preferably 40,000 to 80,000. When the weight average molecular weight is less than 40,000, the alcohol bleed resistance and blocking resistance tend to be poor. When the weight average molecular weight is more than 80000, the plate fogging property, adhesion, and laminate strength tend to be inferior.

  The organic solvent used for the polyurethane resin in the present invention includes a mixed solvent of an ester solvent and an alcohol solvent. Examples of ester solvents include ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and alcohol solvents include methanol, ethanol, n-propanol, isopropanol, It is preferable to use a known solvent such as an alcohol solvent such as n-butanol, propylene glycol monoethyl ether, propylene glycol monomethyl ether.

  A catalyst can also be used for the prepolymer reaction. Examples of catalysts that can be used include tertiary amine catalysts such as triethylamine and dimethylaniline; metal catalysts such as tin, zinc, bismuth and zirconium. These catalysts are usually used in the range of 0.001 to 1 mol% with respect to the polyol.

  The printing ink of the present invention can be produced by dissolving and / or dispersing a colorant, a resin, or the like in an organic solvent. Specifically, a pigment dispersion in which a colorant is dispersed in an organic solvent with a polyurethane resin and / or other resin as required is manufactured, and the resulting pigment dispersion is polyurethane resin and / or other resin. A printing ink can be produced by blending an organic solvent and additives as required.

It is preferable to use a nitrified cotton resin in addition to the polyurethane resin in the printing ink of the present invention. Although the polyurethane resin can be dispersed alone, it is preferable to use a nitrified cotton resin in order to disperse the pigment more stably.
By dispersing with nitrified cotton resin, the color developability also tends to be good. Further, by including the nitrified cotton resin, the plate fogging property, the alcohol bleed resistance, and the blocking resistance tend to be good.

  The nitrified cotton resin used in the printing ink of the present invention is usually called nitrocellulose, and is obtained by a known method such as esterification of purified natural cellulose with a mixed acid and substitution of a hydroxyl group in the cellulose with a nitrate group. Can do. In general, a nitrifying resin has high coating strength, elastic modulus, and surface hardness, so that it is used in various applications. Further, solubility can be selected by nitrogen content, and solution viscosity can be selected by degree of polymerization. The nitrogen content in the present invention refers to the weight percent of nitrogen atoms in the resin, and becomes a larger numerical value as the amount of cellulose hydroxyl groups substituted with nitrate groups increases. In the case of industrial nitrified resins, those with a nitrogen content of 10.7 to 12.2 are lined up, but the nitrified cotton resin in the present invention has a nitrogen content of 10.7 to 11.5. A low nitrogen content type called L type is preferred because of its high affinity for alcohol solvents. The nitrified cotton resin used in the present invention is not limited to L cotton or L type, and is slightly inferior in affinity to alcohol solvents, but is nitrogen in that it can exhibit high pigment dispersibility and color developability. A high nitrogen content type called H cotton or H type having a minute content of 11.5-12.2 can be used as required. The average degree of polymerization of the nitrified cotton resin in the present invention is preferably 30 to 150. If the average degree of polymerization of the nitrified cotton resin is 30 or less, the toughness of the film cannot be ensured and the alcohol bleed resistance and blocking resistance are inferior. On the other hand, when the average degree of polymerization of the nitrified cotton resin exceeds 150, the resin solution and the viscosity of the used printing ink are remarkably increased, which makes designing difficult.

  In the present invention, when the polyurethane resin and the nitrified cotton resin are used in combination, the solid content weight ratio of the polyurethane resin and the nitrified cotton resin is preferably polyurethane resin / nitrified cotton resin = 1/9 to 6/4. When the amount of nitrified cotton resin is greater than polyurethane resin / nitrated cotton resin = 1/9, the coating film becomes too tough, and the adhesiveness, laminate strength, and resistance to abrasion tend to be poor. When there are more polyurethane resins than polyurethane resin / nitrified cotton resin = 6/4, the coating tends to be flexible, and alcohol bleeding resistance and blocking resistance tend to be poor.

  In addition to polyurethane resin and nitrified cotton resin, the printing ink of the present invention can be used in combination with resins used in general inks, paints, recording agents and the like. For example, polyurethane resin, vinyl chloride-vinyl acetate copolymer resin, chlorinated polypropylene resin, ethylene-vinyl acetate copolymer resin, vinyl acetate resin, polyamide resin, acrylic resin, polyester resin, alkyd resin, polyvinyl chloride resin, ketone resin Cyclized rubber, chlorinated rubber, rosin, rosin derivative, butyral, petroleum resin and the like. The resins can be used alone or in admixture of two or more. The resin content (in terms of solid content) is preferably 4 to 25% by weight, more preferably 6 to 20% by weight, based on the total weight of the ink.

In the printing ink of the present invention, an inorganic colorant and an organic colorant can be used as the colorant. Examples of the inorganic colorant include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, aluminum hydroxide, chromium oxide, silica, carbon black, aluminum, mica (mica), and the like. From the viewpoint of coloring power, hiding power, chemical resistance, and weather resistance, titanium oxide is preferable for the white colorant, and titanium oxide having a basic pigment surface is more preferable. Aluminum is in the form of powder or paste, but is preferably used in the form of paste from the viewpoint of handling and safety, and whether to use leafing or non-leafing is appropriately selected from the viewpoint of brightness and concentration. Barium sulfate, calcium carbonate, and aluminum hydroxide are called extender pigments and are used as extenders to improve fluidity, strength, and optical properties. On the other hand, examples of the organic colorant include organic pigments and dyes used in general inks, paints, and recording agents. Examples thereof include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, dictopyrrolopyrrole, and isoindoline. Indigo ink is copper phthalocyanine, and transparent yellow ink is C.I. I. Pigment No Yellow 83 is preferably used.

  The colorant is preferably contained in an amount sufficient to ensure the density and coloring power of the printing ink, that is, in a proportion of 1 to 50% by weight with respect to the total weight of the printing ink. These colorants can be used alone or in combination of two or more.

  The particle size distribution of the pigment in the pigment dispersion is adjusted by appropriately adjusting the size of the grinding media of the disperser, the filling rate of the grinding media, the dispersion treatment time, the discharge speed of the pigment dispersion, the viscosity of the pigment dispersion, and the like. be able to. As the disperser, generally used, for example, a roller mill, a ball mill, a pebble mill, an attritor, a sand mill and the like can be used.

  The solvent used in the printing ink of the present invention also includes a mixed solvent of an ester solvent and an alcohol solvent, like the polyurethane resin. Examples of ester solvents include ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and alcohol solvents include methanol, ethanol, n-propanol, isopropanol, It is preferable to use a known solvent such as an alcohol solvent such as n-butanol, propylene glycol monoethyl ether, propylene glycol monomethyl ether.

In addition, pigment dispersants, leveling agents, surfactants, antifoaming agents, waxes, silane coupling agents, plasticizers, titanium chelates, light stabilizers, infrared absorbers, ultraviolet absorbers, fragrances, as necessary Additives such as flame retardants can also be included. Waxes are added for the purpose of improving heat resistance, oil resistance and friction resistance, and include various known waxes such as polyolefin wax and paraffin wax. Titanium chelate is used as a cohesive strength improver. The titanium chelate has a Ti—O—C type bond in one molecule, and specific examples thereof include titanium chelates such as titanium alkoxide and titanium acylate. Typical examples of the titanium chelate include titanium alkoxides such as tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, tetrastearyl titanate, triethanolamine titanate, titanium acetyl acetate, Mention may be made of titanium chelates such as titanium ethyl acetoacetate, titanium lactate, octylene glycol titanate, titanium tetraacetylacetonate. Among these, chelate-type titanium organic compounds generally require heating to complete the crosslinking reaction, but are hardly hydrolyzed at room temperature and have excellent stability and are suitable for use in inks. In particular, those having an amine in the molecule can be preferably used. Titanium chelate contributes to the intermolecular or intramolecular crosslinking of the resin by having an alkoxy group in one molecule.

  In the case where bubbles or unexpectedly large particles are included in the ink, it is preferably removed by filtration or the like in order to reduce the quality of the printed matter. A conventionally well-known filter can be used.

  The viscosity of the ink produced by the above method is in the range of 10 mPa · s or more from the viewpoint of preventing the pigment from settling and being appropriately dispersed, and 1000 mPa · s or less from the viewpoint of workability efficiency during ink production or printing. Is preferred. In addition, the said viscosity is a viscosity measured at 25 degreeC with the Tokimec B-type viscometer.

  The printing ink in the present invention can be used in known printing methods such as gravure printing and flexographic printing, and can be applied to back printing applications and front printing applications. For example, it is diluted with a diluting solvent to a viscosity and concentration suitable for printing, and is supplied to each printing unit alone or mixed. Gravure and flexographic printing are preferable.

  Base materials to which the printing ink of the present invention can be applied include polyolefins such as polyethylene or polypropylene, polyethylene terephthalate, polyesters such as polycarbonate or polylactic acid, polystyrene resins such as polystyrene, AS resin or ABS resin, nylon, polyamide, polychlorinated. There are various films of vinyl and polyvinylidene chloride, cellophane, paper, aluminum foil, etc., or a film or sheet made of a composite material thereof. These substrates may be subjected to vapor deposition coating treatment and / or coating treatment such as polyvinyl alcohol on the surface of a metal oxide, for example, GL- manufactured by Toppan Printing Co., Ltd. in which aluminum oxide is vapor deposited on the substrate surface. Examples include AE and IB-PET-PXB manufactured by Dai Nippon Printing Co., Ltd. Further, those treated with additives such as an antistatic agent and an ultraviolet ray inhibitor, and those obtained by subjecting the surface of the substrate to corona treatment or low temperature plasma treatment can be used as necessary.

  The printed matter in the present invention can be obtained by applying the printing ink using the above printing method, and drying and fixing it by drying with an oven. The drying temperature is usually about 40 to 60 ° C.

  When the printed material in the present invention is used for surface printing, it can be made into a final product by printing on the applicable substrate. In particular, for surface printing applications, in order to maintain the cosmetics of the packaging material itself and to ensure the resistance to the contents, a technique of using a wax or the like as needed and sliding the surface of the printed material may be used.

  When the printed matter in the present invention is used for back printing, at least one layer of lamination can be applied via an adhesive to form a laminate. There are various processing methods for laminating, but typical examples include (1) extrusion laminating method (EL), (2) dry laminating method (DL), and the like.

  (1) The extrusion laminating method is a method in which a thermoplastic resin is melted on the printing surface of the obtained printed matter and extruded from a slit-like die called a T die into a film shape and laminated on a substrate. is there. In many cases, an anchor coating agent is applied in advance to the printed surface of a printed material and then laminated. It is also possible to extrude the molten resin onto the printed surface of the printed material and bond the sealant from another unwinder. As the anchor coating agent, an imine-based, butadiene-based, or isocyanate-based anchor coating agent can be used. Specific examples include EL-420 (imine type), EL-452 (butadiene type), EL-530A / B (isocyanate type), EL-540 / CAT-RT32 (isocyanate type), manufactured by Toyo Morton. It is done. As the molten resin, low density polyethylene, polypropylene, ethylene-vinyl acetate copolymer and the like can be used. Specific examples include Novatec LD LC600A (low density polyethylene) manufactured by Nippon Polyethylene. Examples of the sealant include the above-mentioned various films, cellophane, paper, aluminum foil and the like used for the substrate, or a film or sheet made of a composite material thereof. Specific examples include TUX-FCD (LLDPE) manufactured by Mitsui Chemicals, Inc., Cello Co., Ltd., FCMN (CPP) manufactured by Phutamura Chemical Co., Ltd., and Diastar (VMPET) manufactured by Reiko.

  (2) The dry laminating method is a method in which an adhesive is diluted to an appropriate viscosity with an organic solvent, applied to the printed surface of the obtained printed matter, dried and then pressure-bonded with a sealant for lamination. As the adhesive, a two-component type of polyol / isocyanate is mainly used. Specifically, TM-250HV / CAT-RT86L-60, TM-550 / CAT-RT37, TM-314 / CAT-14B manufactured by Toyo Morton Co., Ltd. Etc. Examples of the sealant include the above-mentioned various films, cellophane, paper, aluminum foil and the like used for the substrate, or a film or sheet made of a composite material thereof. Specifically, there are TUX-FCD (LLDPE) manufactured by Mitsui Chemicals Tosero Co., Ltd., ZK93KM (CPP) manufactured by Toray Industries, Inc., Dialeraster (VMPET) manufactured by Reiko, 2203 (VMPP) manufactured by Toray Industries, Inc., and the like.

The laminate obtained by the above method becomes a packaging bag by heat-sealing the sealant surfaces. Therefore, a film for imparting heat sealability is used for the sealant that hits the innermost side in the packaging bag. For example, polyolefin such as unstretched polyethylene or polypropylene can be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples. In the present invention, “parts” and “%” represent “parts by weight” and “% by weight” unless otherwise noted.

  The hydroxyl value was acetylated with an excess of an acetylating reagent and the amount of hydroxyl group in 1 g of resin calculated by back titrating the remaining acid with alkali was converted to mg of potassium hydroxide. The value is a value obtained according to JIS K0070. The molecular weight was determined as a polystyrene-converted molecular weight by measuring the molecular weight distribution using a GPC (gel permeation chromatography) apparatus. Tetrahydrofuran was used as a measurement solvent for GPC. The amine value is the number of mg of potassium hydroxide equivalent to the equivalent of hydrochloric acid required to neutralize the amino group contained in 1 g of resin. The method for measuring the amine value is as follows.

[Method for measuring amine value]
Weigh accurately 5-10 g of sample. (Sample amount: S (weight of solid content) g) Toluene 25 mL and n-butanol 25 mL are added to a precisely weighed sample and sufficiently dissolved. 30 mL of methanol is added thereto, and potentiometric titration is performed with a 0.1 mol / L aqueous hydrochloric acid solution (titer: f). The amine value was calculated | required by the following (Formula 1) using the titration amount (AmL) at this time.

Formula 1
Amine value = (A × f × 0.1 × 56.108) / S [mgKOH / g]

[Synthesis of polyurethane resin]
[Synthesis Example 1]
In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 257.86 parts of poly (1,2-propylene glycol) having a number average molecular weight of 2000 (hydroxyl value 56.1 mgKOH / g), Charge 18.01 parts of isophorone diisocyanate, 20.27 parts of diphenylmethane diisocyanate, 0.03 part of tin (II) 2-ethylhexanoate, and 200 parts of ethyl acetate, and react at 90 ° C. for 3 hours under a nitrogen stream. 496.14 parts of polymer solution were obtained. Next, a mixture of 3.86 parts of isophorone diamine, 280 parts of isopropyl alcohol and 220 parts of ethyl acetate was gradually added to the resulting solution of the terminal isocyanate prepolymer at room temperature, and then reacted at 50 ° C. for 1 hour. A polyurethane resin (PU01) having a solid content of 30.0%, a weight average molecular weight of 78000, and an amine value not detected (less than 0.1 mgKOH / g) was obtained.

[Synthesis Examples 2 to 12]
Polyurethane resins (PU02 to PU12) were obtained in the same manner as in Synthesis Example 1 with the charging ratios shown in Table 1. The following raw materials were used for the synthesis.
PPG2000: poly (1,2-propylene glycol) (number average molecular weight 2000)
IPDI: isophorone diisocyanate MDI: diphenylmethane diisocyanate IPDA: isophorone diamine

[Example 1]
30 parts of titanium oxide ("TITONE R45M" manufactured by Sakai Chemical), 20 parts of nitrified cotton resin A (L cotton, 30% solid content "DLX-5-8" manufactured by Nobel Enterprises), ethyl acetate / isopropyl alcohol mixed solvent (weight) 10 parts of 50/50) was mixed with stirring and kneaded in a sand mill, and then 10 parts of nitrified cotton resin A, 20 parts of polyurethane resin (PU01), and 10 parts of ethyl acetate / isopropyl alcohol mixed solvent (weight ratio 50/50) were stirred. The white printing ink (W01) was obtained by mixing. Furthermore, 20 parts each of a diluted solvent of ethyl acetate / isopropyl alcohol = 50/50 by weight ratio was mixed with 100 parts of this white printing ink to obtain a white diluted printing ink for evaluation.

[Examples 2 to 11] [Comparative Examples 1 to 6]
White printing inks (W02 to 17) were obtained in the same manner as in Example 1 with the charging ratio shown in Table 2. The following nitrified cotton was used. However, the nitrified cotton resin and the polyurethane resin in Table 2 represent the solid content weight.
Nitrified cotton resin A: L cotton, solid content 30% “DLX-5-8” manufactured by Nobel Enterprises Nitrified cotton resin B: H cotton, solid content 30% “DHX-5-8” manufactured by Nobel Enterprises Co., Ltd. Examples In No. 11, polyurethane resin is also used for the meat paste, and nitrified cotton resin is not included. On the other hand, Comparative Example 6 does not contain a polyurethane resin. Moreover, the white dilution printing ink for evaluation was also obtained by the same operation as Example 1.

First, brown change with time was evaluated using the obtained polyurethane resin and nitrified cotton resin.

[Brown change]
50 g of polyurethane resin (PU01-12) was mixed with 50 g of nitrified cotton resin (A or B), and allowed to stand for 24 hours under a constant temperature condition of 40 ° C., and the hue change of the mixed solution was visually evaluated.
○: Hue change is not recognized. (More than this is a practical level)
Δ: Hue change is recognized.
X: A clear hue change and state abnormality are recognized.

Plate fogging and alcohol bleed resistance were evaluated using the white diluted printing ink.

[Print fogging]
NBR (nitrile butadiene rubber) rubber cylinder 80Hs impression cylinder, blade thickness 60μm (base material thickness 40μm, one side ceramic layer thickness 10μm), ceramic plating doctor blade, Toyo FPP Co., Ltd. chromium hardness 1050Hv White diluted printing ink is set on a gravure printing machine manufactured by Fuji Machine Industry Co., Ltd. with an electronic engraving plate (stylus angle of 120 degrees, 200 lines / inch), and idling is performed at a doctor pressure of 2 kg / cm ² and a rotation speed of 100 m / min. Then, it was dried on a corona-treated surface of a corona-treated OPP film (FOR # 20, manufactured by Futamura Chemical Co., Ltd.) at a printing speed of 100 m / min with a printing pressure of 2 kg / cm ² and hot air at 60 ° C. . This printed matter was pasted on black paper, and the amount of ink attached to the blank portion (non-image area) was visually evaluated according to the following criteria.
A: No ink transfer was observed in the non-image area.
○: Slight ink transfer was observed in the non-image area. (More than this is a practical level)
Δ: Ink transfer was observed in a large area of the non-image area.
X: Ink transfer was observed over the entire non-image area.

[Alcohol bleed resistance]
The white diluted printing ink is printed on a corona-treated OPP film (Furmura Chemical Co., FOR # 20) by a gravure proofing machine equipped with a 35 μm gravure printing plate, dried at 40-50 ° C., and then in-line isopropyl alcohol The coating was dried at 40 to 50 ° C., and the appearance such as bleed marks was observed.
A: There was no appearance defect on the printed matter.
○: Some unevenness was observed in the printed matter. (More than this is a practical level)
Δ: Thin bleed marks were observed on the printed matter.
X: Bleed marks were clearly observed on the printed matter.

  The white diluted printing ink is printed on a corona-treated PET film (Toyobo Co., Ltd., E5100 # 12) at a speed of 100 m / min with a center drum type 6-color flexo printing machine “SOLOFLEX” manufactured by Windmill & Helshire Co. It dried at 70 degreeC and the printed matter was obtained. As an anilox roll, 350 lines / cm is used, and as a printing cylinder, DuPont's “Syrel DPU thickness 1.14 mm” is made into a solid plate, and a double-sided tape “DF 7382T thickness 0.50 mm made by Toyo Ink Co., Ltd.” ”Was used. Using the obtained printed matter, evaluation of blocking resistance, adhesion, DL laminate strength, and resistance to frying was performed.

[Blocking resistance]
The printed matter of the PET film is sampled to 4 cm × 4 cm, and the non-printed surface of the unprinted PET film having the same size as the printed surface of this sample is put together and pressurized at 10 kgf for 12 hours at 50 ° C. When peeled, the ink was removed and the resistance was observed.
A: No ink transfer was observed from the printed material, and there was no resistance when peeled.
◯: No transfer of ink was observed from the printed matter, but there was a feeling of resistance at the time of peeling. (More than this is a practical level)
Δ: Ink transfer from the printed material was observed in an area of less than 30%.
X: Ink transfer from the printed matter was observed in an area of 30% or more.

[Adhesion]
A cellophane tape (made by Nichiban, width 12 mm) was affixed to the printed matter of the PET film and rubbed strongly with the thumb five times, and then the cellophane tape was gradually pulled apart and abruptly pulled halfway to examine the degree of peeling of the ink film.
◎: No peeling of ink is observed even when pulled apart slowly or abruptly ○: No peeling of ink is observed even when pulled slowly, but when peeled off suddenly, the ink peeling is less than 20% Admitted. (More than this is a practical level)
Δ: Ink peeling was not observed even when pulled slowly, but ink peeling was observed in an area of 20% or more when pulled away abruptly.
Δ ×: Ink peeling with an area of up to about 50% was observed even when slowly separated.
X: Most ink peeling was recognized even if it pulled away slowly.

[DL laminate strength]
A polyester-based adhesive “TM-314 / CAT-14B” (manufactured by Toyo Morton Co., Ltd.) is applied to the printed matter of the PET film, and CPP (manufactured by Nippon Polychem Co., Ltd.) is pasted on the coated surface as a sealant. Was aged for 48 hours to obtain a laminate. The ink part in the laminated product was cut at a width of 15 mm and peeled between the ink surface and the molten resin layer, and the peel strength was measured with an Intesco 2.01 million tensile tester. In addition, 1.0N / 15mm or more shall be a practical use level.

[Scratch resistance]
The degree to which the ink film was taken when the printed surfaces of the printed matter of the PET film were rubbed together was examined.
A: The ink film was not removed at all even after rubbing 30 times or more. ○: When the ink film was rubbed about 30 times, it was recognized in an area of less than 10% of the ink film. (More than this is a practical level)
Δ: Taken off in an area of less than 30% of the ink film when rubbed about 30 times.
[Delta] x: When it was rubbed about 30 times, it was observed that the area was less than 50% of the ink film.
X: When rubbed about 30 times, it was observed that the ink film was almost entirely removed.

  The evaluation results are summarized in Table 2. The polyurethane resin used in Examples 1-11 does not cause a brown color change when mixed with a nitrified cotton resin, and the printing inks of Examples 1-11 are ester / alcohol solvent based compared to Comparative Examples 1-6. In the printing ink, it is possible to provide a printing ink that can ensure various plate physical properties such as plate fogging and alcohol bleeding resistance, blocking resistance, adhesion, DL laminate strength, and resistance to fringing.

Claims (4)

A printing ink comprising the following polyurethane resins (1) to (4) and a nitrified cotton resin ,
A printing ink, wherein a solid content weight ratio between the polyurethane resin and the nitrified cotton resin is polyurethane resin / nitrified cotton resin = 1/9 to 6/4.
(1) A polyurethane resin obtained by reacting a urethane prepolymer (C) having an isocyanate group at the terminal obtained by reacting an organic polyol (A) and an organic diisocyanate (B) with an organic diamine (D). It is.
(2) The molar ratio [NCO] / [OH] in the reaction between the hydroxyl group of the organic polyol (A) and the isocyanate group of the organic diisocyanate (B) is [NCO] / [OH] = 1.25 to 2.50. It is.
(3) The organic diisocyanate (B) is isophorone diisocyanate and diphenylmethane diisocyanate, and the molar ratio of isophorone diisocyanate and diphenylmethane diisocyanate is isophorone diisocyanate / diphenylmethane diisocyanate = 9/1 to 1/9.
(4) The amine value of the polyurethane resin is less than 0.1 mgKOH / g. 2. The printing ink according to claim 1, wherein the polyurethane resin has a weight average molecular weight of 40,000 to 80,000. A printed matter obtained by printing the printing ink according to claim 1 or 2 on a plastic film using a printing machine. A laminate obtained by laminating the printed matter according to claim 3 and a substrate with an adhesive.