JP6394298B2 - Alcohol-soluble printing ink binder - Google Patents

Description

  The present invention relates to a printing ink binder for a plastic film, and more particularly to an alcohol-soluble printing ink binder mainly composed of a polyurethane resin.

  In recent years, with the diversification of packages and the advancement of packaging technology, various plastic films have been developed as packaging materials, and those suitable for packages are appropriately selected and used. By the way, when a plastic film is used as a packaging material, printing is performed for decoration or surface protection of the plastic film, but the applied printing ink has good adhesion to these various plastic films. Is desired.

  Conventionally, polyurethane is often used as a binder for printing ink used for printing ink. In general, printing inks with polyurethane as a binder have excellent adhesion to polyester films and nylon (NY) films, but they adhere to polyethylene (PE) and polypropylene (PP) films, which are general purpose films. The power is insufficient. For this reason, when printing on a PE film or PP film, a toluene type printing ink in which a chlorinated polypropylene-based resin is blended with polyurethane has been used to supplement the adhesive strength.

However, an environmentally friendly ink is desired, and an ink that does not use an aromatic solvent such as toluene in the printing ink is desired. As a solvent for such a non-aromatic solvent type printing ink (generally called “non-toluene type printing ink”), a non-aromatic solvent such as methyl ethyl ketone or ethyl acetate is often used as a main solvent. However, since the chlorinated polypropylene resin hardly dissolves in the ink, there is a problem that sufficient adhesiveness cannot be obtained with respect to the polyethylene (PE) film or the polypropylene (PP) film.
As a countermeasure for this, for example, Patent Document 1 discloses a binder for printing ink mainly containing polyurethane obtained by reacting a polymer diol, a diisocyanate compound and a chain extender, as a component of the polymer diol, 2 , 4-dialkyl-1,5-pentanediol is disclosed, and a printing ink binder is disclosed.

In addition, aromatic solvents such as toluene, ketone solvents such as methyl ethyl ketone, and ester solvents such as ethyl acetate have been mixed and used as printing ink solvents. From the environmental and safety perspectives, aromatic solvents, There is a growing demand for printing inks that contain as little ketone and ester solvents as possible, and alcoholic solvents are attracting attention. In particular, effective utilization of bioethanol that has a low environmental impact is desired in recent years.
However, since alcohol solvents have lower solvency than aromatic solvents, ketone solvents, and ester solvents, printability is slightly inferior. In addition, when a resin soluble in an alcohol solvent is used, other physical properties such as adhesion and blocking resistance may be inferior.

JP 2000-26882 A

  The present invention also provides a binder for printing ink that is soluble in alcohol without deteriorating physical properties such as adhesion and blocking resistance between the plastic film and the printing ink when used as a binder for printing ink. It is.

  The present inventors have intensively studied to solve the above problems. As a result, it has been found that printing inks using polyurethane resins having specific constituents as printing ink binders are soluble in alcoholic solvents and do not deteriorate physical properties such as adhesion and blocking resistance. The present invention has been completed.

  Specifically, the alcohol-soluble printing ink binder of the present invention comprises a urethane prepolymer obtained by reacting a polymer polyol and a polyisocyanate compound in a solvent-free system, and a chain extender in an alcohol solvent. A binder for an alcohol-soluble printing ink comprising a polyurethane resin obtained by reaction, wherein when the polymer polyol and the polyisocyanate compound are reacted, the moles of isocyanate group (NCO) and hydroxyl group (OH) Ratio of NCO / OH = 2.4 to 3.2, a urethane prepolymer obtained by reacting, and the amine value of the polyurethane resin is 5.0 to 15.0 mgKOH / g, and the alcohol solvent. Is an alcohol-soluble printing ink binder characterized by having an ethanol content of 60% by mass or more It is intended to provide.

  Furthermore, it is the above-mentioned binder for alcohol-soluble printing ink, in which the polymer polyol used has a number average molecular weight of 500 to 4,000.

  By using the printing ink binder of the present invention having the above-described configuration, it is possible to provide a printing ink binder that is soluble in alcohol without deteriorating physical properties such as adhesion and blocking resistance of the printing ink.

  According to the present invention, it is soluble in alcohol that is excellent in adhesion, blocking resistance and re-dissolvability to various plastic films such as polyester, nylon (NY), polyethylene (PE), polypropylene (PP) as printed materials. The printing ink binder and the printing ink composition using the same can be provided.

  In the present invention, as the polymer polyol, conventionally known polymer polyols generally known for polyurethane resins can be used. For example, polyether polyols such as polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran, etc .; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl -1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, octanediol, Saturated and unsaturated various known low molecular glycols such as 1,4-butynediol and dipropylene glycol, alkyl glycidyl ethers such as n-butyl glycidyl ether and 2-ethylhexyl glycidyl ether, glycidyl ether versatate Monocarboxylic acid glycidyl esters such as tellurium, dimer diol obtained by reducing dimer acid, adipic acid, maleic acid, fumaric acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonic acid , Polyester polyols obtained by dehydration condensation of dibasic acids such as glutaric acid, pimelic acid, azelaic acid, sebacic acid and suberic acid, and acid anhydrides and dimer acids corresponding to these, and ring-opening polymerization of cyclic ester compounds High molecular polyols such as polyester polyols, polycarbonate polyols, polybutadiene glycols, and glycols obtained by adding ethylene oxide or propylene oxide to bisphenol A. These polymer polyols may be used alone or in combination of two or more.

  Of the polymer polyols used, in the case of polymer polyols obtained from glycols and dibasic acids, a part of the glycols can be substituted with the following various polyols. Examples of various polyols include glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaerythritol and the like.

In the present invention, the number average molecular weight of the polymer polyol is preferably 500 to 4,000 in view of the performance of the printing ink resin of the present invention. More preferably, the number average molecular weight is 700 to 3,000. When the number average molecular weight is 500 or more, the printability is good. When the number average molecular weight is 4,000 or less, the solubility in an alcohol solvent, the drying property and the blocking resistance are good.
The number average molecular weight in the present invention is a value determined by polystyrene conversion by gel permeation chromatography (GPC). For measurement of GPC, using tetrahydrofuran as a solvent at a flow rate of 1.0 ml / min, Hitachi Chemical's HPLC packed columns “GL-A160-S”, “GL-A150-S”, and “GL-A130-S” are connected. A differential refractometer was used as the detector.

In the present invention, the alcohol solvent is, for example, methanol, ethanol, 1-propanol, 1-butanol, 2-methyl-1-propanol, etc. as primary alcohol, 2-propanol, 2-propanol as secondary alcohol, etc. Examples of tertiary alcohol include aliphatic alcohols having 1 to 7 carbon atoms such as 2-methyl-2-propanol and 2-methyl-2-butanol. Further, modified alcohols classified as industrial alcohols, for example, 85% by mass ethanol mixed with 15% by mass of methanol and 2-propanol can be used.
Among these various alcohols, the content of ethanol having a low environmental load and high volatility needs to be 60% by mass or more. These alcohol solvents may be used in combination of two or more, but are preferably used alone because the solvent can be easily recovered and reused.
Moreover, the ethanol of this invention can use the bioethanol produced by fermenting and distilling sugarcane, corn and the like.

  In the present invention, various known polyisocyanates that are aromatic, aliphatic or alicyclic can be used as the polyisocyanate compound. For example, 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3- Phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4- Trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate Isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and the carboxyl group of dimer acid were converted to isocyanate groups. A typical example is dimer isocyanate. These polyisocyanate compounds may be used alone or in combination of two or more.

  In the present invention, various known chain extenders can be used. Examples thereof include ethylenediamine, propylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, isophoronediamine, dicyclohexylmethane-4,4′-diamine, dimer diamine and the like. In addition, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, etc. Examples thereof include diamines having a hydroxyl group, glycols described in the section of the polyester polyol, and other glycols. These chain extenders may be used individually by 1 type, and may use 2 or more types together.

  In the present invention, as a method for producing a polyurethane resin, first, a urethane prepolymer having isocyanate groups (NCO) at both ends prepared by reacting a polymer polyol and a polyisocyanate compound in a solvent-free system is prepared. Either the two-stage method of reacting the compound with a chain extender in an alcohol solvent or the one-stage method of reacting each component at one time can be adopted. For the purpose of obtaining a uniform polymer solution, the former method is used. (Two-stage method) is preferred.

The molar ratio of isocyanate group (NCO) to hydroxyl group (OH) when reacting the polymer polyol and the polyisocyanate compound is preferably in the range of NCO / OH = 2.4 to 3.2, more preferably The NCO / OH molar ratio is in the range of 2.45 to 2.8.
If the molar ratio of NCO / OH is 2.4 or more, the urethane resin obtained by reacting using this is excellent in adhesion and blocking resistance. On the other hand, when the molar ratio of NCO / OH is 3.2 or less, the viscosity of the urethane prepolymer does not increase, and synthesis without a solvent becomes easy.

  In the above reaction, in order to accelerate the reaction, an amine catalyst (triethylamine, N-ethylmorpholine, triethylenediamine, etc.), which is a catalyst used in a usual urethane reaction, if necessary, a tin-based catalyst (dibutyltin dilaurate, dioctyltin dilaurate) , Tin octylate, etc.), titanium-based catalysts (tetrabutyl titanate, etc.) may be used. In addition, the usage-amount of a catalyst is 0.1 mass% or less normally with respect to a polyurethane resin.

In the present invention, the polyurethane resin preferably has a primary or secondary amino group in the molecular chain, and its amine value is 5.0 to 15.0 mgKOH / g, preferably 7.0 to 11.0 mgKOH / g. It is. By setting the amine value within the above range, it is possible to impart good adhesion to a surface treatment (corona treatment, etc.) polypropylene (PP) film.
The amine value in the present invention is determined by the following method.
As a sample amount Sg, 0.5 to 10 g of a polyurethane resin having an amino group in a molecular chain is precisely weighed. To a precisely weighed sample, 50 mL of an organic solvent in which methyl ethyl ketone (MEK) and isopropyl alcohol (IPA) are mixed at a volume ratio of 1: 1 is added and dissolved. Bromocresol green is added as an indicator to the obtained solution, and titration is performed with 0.1 mol / L hydrochloric acid (titer: f). The point at which the color of the solution changed from green to yellow was taken as the end point, and the amine value was calculated from the titration (AmL) at this time according to the following formula.
Amine value [mg KOH / g] = (A × f × 5.611) / S
Furthermore, the number average molecular weight of the polyurethane resin is usually in the range of 5,000 to 100,000. If the number average molecular weight is 5000 or more, the drying property, blocking resistance, film strength, etc. of the printing ink using this as a vehicle are good. On the other hand, if it is 100,000 or less, the viscosity of the polyurethane resin increases, and the gloss of the printing ink does not decrease. In addition, the measuring method of a number average molecular weight is a value determined by polystyrene conversion by GPC.
Further, the resin solid content concentration of the polyurethane resin is not particularly limited, but may be appropriately determined in consideration of the workability at the time of ink production, and is usually 15 to 60% by mass, and the viscosity is 50 to 10,000 mPa · s. It is practically preferable to adjust to the range of / 25 ° C.
In addition, in the present invention, if necessary, in addition to the polyurethane resin that is the main component of the present invention, the following resins may be used in combination as subcomponents. Examples thereof include polyurethane resins other than the present invention, polyamide, nitrocellulose, polyacrylic acid ester, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, rosin resin, and ketone resin.

  The binder of the present invention thus obtained is appropriately blended with a colorant, a solvent, and, if necessary, a surfactant, a wax and other additives for improving the ink fluidity and the ink surface film. A printing ink composition can be produced by kneading using a normal ink production apparatus such as a lighter or a sand mill. In addition, it is preferable to mix | blend the compounding quantity of the binder of this invention in a printing ink composition so that the resin solid content may be 3-20 mass% in a printing ink composition.

  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. Parts and% are based on mass.

[Example 1] (Synthesis of polyurethane resin A)
In a round bottom flask equipped with a stirrer, a thermometer and a nitrogen gas inlet tube, 1,000 parts of polypropylene glycol (trade name: Exenol 2020 manufactured by Asahi Glass Co., Ltd.) having a number average molecular weight of 2,000 and isophorone diisocyanate (manufactured by Sumika Bayern Urethane) Product name: Desmodur I) 277 parts were charged and reacted in a nitrogen stream at 105 ° C. for 3 hours in a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 4.9%.
Next, 1,000 parts of the urethane prepolymer was added to a mixture consisting of 118.8 parts of isophoronediamine (manufactured by BASF Japan) and 1,119 parts of ethanol (manufactured by Wako Pure Chemical Industries), and reacted at 65 ° C. for 3 hours. .
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin A) had a resin solid content concentration of 50% and a viscosity of 1,420 mPa · s / 25 ° C. The amine value of the polyurethane resin was 11.2 mgKOH / g.
The molar ratio of isocyanate group (NCO) to hydroxyl group (OH) was 2.5.

[Example 2] (Synthesis of polyurethane resin B)
A device similar to that of Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as Example 1) and 333 parts of isophorone diisocyanate (same as Example 1) were charged in a round bottom flask. The reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours in a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 6.29%.
Next, 1,000 parts of the urethane prepolymer was added to a mixture consisting of 147.1 parts of isophoronediamine (same as in Example 1) and 1,402 parts of ethanol (same as in Example 1), and reacted at 65 ° C. for 3 hours. I let you.
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin B) had a resin solid content concentration of 45% and a viscosity of 600 mPa · s / 25 ° C. The amine value of the polyurethane resin was 11.1 mgKOH / g.
The molar ratio of isocyanate groups to hydroxyl groups was 3.0.

[Example 3] (Synthesis of polyurethane resin C)
The same apparatus as in Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as Example 1) and 277 parts of isophorone diisocyanate (same as Example 1) were charged in a round bottom flask. The reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours under a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 4.9%.
Next, 1,000 parts of the urethane prepolymer was added to a mixture comprising 125.3 parts of isophoronediamine (same as in Example 1) and 921 parts of ethanol (same as in Example 1), and reacted at 65 ° C. for 3 hours. .
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin C) had a resin solid content concentration of 55% and a viscosity of 320 mPa · s / 25 ° C. The amine value of the polyurethane resin was 14.9 mgKOH / g.
The molar ratio of isocyanate groups to hydroxyl groups was 2.5 as in Example 1.

[Example 4] (Synthesis of polyurethane resin D)
The same apparatus as in Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as Example 1) and 277 parts of isophorone diisocyanate (same as Example 1) were charged in a round bottom flask. The reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours under a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 4.9%.
Next, 1,000 parts of the urethane prepolymer was added to a mixture comprising 108.3 parts of isophoronediamine (same as in Example 1) and 1,662 parts of ethanol (same as in Example 1), and reacted at 65 ° C. for 3 hours. I let you.
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin D) had a resin solid content concentration of 40% and a viscosity of 8,400 mPa · s / 25 ° C. The amine value of the polyurethane resin was 5.1 mgKOH / g.
The molar ratio of isocyanate groups to hydroxyl groups was 2.5 as in Example 1.

[Example 5] (Synthesis of polyurethane resin E)
The same apparatus as in Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as Example 1) and 277 parts of isophorone diisocyanate (same as Example 1) were charged in a round bottom flask. The reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours under a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 4.9%.
Next, 118.8 parts of isophorone diamine (same as in Example 1), industrial alcohol (a mixture of 85.5% ethanol + 14.5% methanol and 2-propanol, trade name: Solmix AP manufactured by Nippon Alcohol Sales Co., Ltd.) -1) 1,000 parts of the urethane prepolymer was added to a mixture consisting of 1,119 parts and reacted at 65 ° C. for 3 hours.
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin E) had a resin solid content concentration of 50% and a viscosity of 2,500 mPa · s / 25 ° C. The amine value of the polyurethane resin was 11.2 mgKOH / g.
The molar ratio of isocyanate groups to hydroxyl groups was 2.5 as in Example 1.

[Example 6] (Synthesis of polyurethane resin F)
A device similar to that of Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as Example 1) and 333 parts of isophorone diisocyanate (same as Example 1) were charged in a round bottom flask. The reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours in a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 6.29%.
Then, 147.1 parts of isophorone diamine (same as Example 1), 60% ethanol (same as Example 1) and 40% 2-propanol (made by Wako Pure Chemical Industries) 40% mixed solvent 1,402 parts 1,000 parts of the urethane prepolymer were added and reacted at 65 ° C. for 3 hours.
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin F) had a resin solid content concentration of 45% and a viscosity of 610 mPa · s / 25 ° C. The amine value of the polyurethane resin was 11.1 mgKOH / g.
The molar ratio of isocyanate groups to hydroxyl groups was 3.0 as in Example 2.

[Comparative Example 1] (Synthesis of polyurethane resin G)
The same apparatus as in Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as in Example 1) and 222 parts of isophorone diisocyanate (same as in Example 1) were charged in a round bottom flask. Then, the reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours in a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 3.43%.
Next, 1,000 parts of the urethane prepolymer was added to a mixture comprising 88.1 parts of isophoronediamine (same as in Example 1) and 712 parts of ethanol (same as in Example 1), and reacted at 65 ° C. for 3 hours. .
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin G) had a resin solid content concentration of 55% and a viscosity of 1,020 mPa · s / 25 ° C. The amine value of the polyurethane resin was 11.3 mgKOH / g.
The molar ratio of isocyanate groups to hydroxyl groups was 2.0.

[Comparative Example 2] (Synthesis of polyurethane resin H)
The same apparatus as in Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as Example 1) and 277 parts of isophorone diisocyanate (same as Example 1) were charged in a round bottom flask. The reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours under a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 4.9%.
Next, 1,000 parts of the urethane prepolymer was added to a mixture comprising 106.5 parts of isophoronediamine (same as in Example 1) and 1,660 parts of ethanol (same as in Example 1), and reacted at 65 ° C. for 3 hours. I let you.
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin H) had a resin solid content concentration of 40% and a viscosity of 13,200 mPa · s / 25 ° C. The amine value of the polyurethane resin was 4.0 mgKOH / g.
The molar ratio of isocyanate group to hydroxyl group was 2.5, as in Example 1.

[Comparative Example 3] (Synthesis of polyurethane resin I)
The same apparatus as in Example 1 was prepared, and 1,000 parts of polypropylene glycol having the number average molecular weight of 2,000 (same as Example 1) and 277 parts of isophorone diisocyanate (same as Example 1) were charged in a round bottom flask. The reaction was carried out in a nitrogen stream at 105 ° C. for 3 hours under a solvent-free system to produce a urethane prepolymer having a free isocyanate content of 4.9%.
Next, 1,000 parts of the urethane prepolymer was added to a mixture consisting of 127.2 parts of isophoronediamine (same as in Example 1) and 922 parts of ethanol (same as in Example 1), and reacted at 65 ° C. for 3 hours. .
The polyurethane resin thus obtained (hereinafter referred to as polyurethane resin I) had a resin solid content concentration of 55% and a viscosity of 200 mPa · s / 25 ° C. The amine value of the resin was 16.0 mgKOH / g.
The molar ratio of isocyanate group to hydroxyl group was 2.5, as in Example 1.

[Adjustment of printing ink]
A mixture of 35 parts of titanium white (rutile type), 35 parts of binder resin of 9 types of synthesized polyurethane resins A to I, and 30 parts of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) was kneaded to obtain the white base ink. Prepared. To 100 parts of this white base ink, 20 parts of ethanol (same as above) was added to adjust the viscosity to prepare 9 points of white printing ink.

[Sample preparation]
The nine white printing inks thus obtained were subjected to a discharge treatment surface of a corona discharge treatment nylon (NY) film, a polyethylene terephthalate (PET) film, and 2 using a gravure printing machine (rotary coater, manufactured by RK Print Coat Instruments). It printed on the single side | surface of the axial stretch polypropylene (OPP), and it dried at 80 degreeC, and obtained the printing film. The obtained printed film was subjected to the following test.

〔Adhesiveness〕
The print film was allowed to stand for 24 hours, and then a cellophane tape was affixed to the print surface, and the appearance of the print film when peeled rapidly at an angle of 90 ° was visually observed and evaluated. The evaluation results are shown in Table 1.
○: More than 80% of the printed film remained on the film.
Δ: 50 to 80% of the printed film remained on the film.
X: 50% or less of the printed film remained in the film.

[Blocking resistance]
The printing surface of the printing film is folded so that it is on the inside, a load of 2.0 N (200 gf) / cm ² is applied, and the adhesion state of the printing surface after being left at 40 ° C. for 24 hours is visually observed. Evaluated by criteria.
○: 0% or more to less than 20% of the contact area.
Δ: Adhesion of 20% to less than 50% of the contact area.
X: Adherence of 50% or more of the contact area.

(Ethyl acetate resistance)
The obtained 7 white printing inks were printed on one side of a biaxially oriented polypropylene (OPP) film using a small desktop printer (Kurabo GP-2), and then printed on the printed side with ethyl acetate. The surface was observed visually.
○: More than 80% of the printed film remained on the film.
Δ: 50 to 80% of the printed film remained on the film.
X: 50% or less of the printed film remained in the film.

As shown in Table 1, in the printing inks using the printing ink binders of Examples 1 to 6 of the present invention, the adhesion to various films and the blocking resistance were good. Also, the ethyl acetate resistance is good.
However, in the printing ink using the polyurethane resin G of Comparative Example 1 in which the molar ratio of hydroxyl group to isocyanate group is 2.0, the adhesion to various films is good, but the blocking resistance is inferior. The blocking resistance was evaluated as “x” with adhesion of 50% or less of the contact area.
Next, in the printing ink using the polyurethane resin H of Comparative Example 2 having an amine value of 4.0 mgKOH / g, the adhesiveness to various films was inferior in “Δ˜ ×”.
On the other hand, in the printing ink using the polyurethane resin I of Comparative Example 3 having an amine value of 16.0 mgKOH / g, the adhesiveness, blocking resistance, and ethyl acetate resistance were all inferior in “Δ” or “x”. .

Claims (3)

Comprising a polyurethane resin obtained by reacting a urethane prepolymer comprising by reacting a polymeric polyol with a polyisocyanate compound under solvent-free with a chain extender and under an alcohol solvent, the alcohol-based solvent, a A binder for alcohol-soluble printing ink,
The polymer polyol consists only of polyether polyol,
The urethane prepolymer reacts in a molar ratio of isocyanate group (NCO) to hydroxyl group (OH) when the polymer polyol and polyisocyanate compound are reacted, and NCO / OH = 2.4 to 3.2. It is a urethane prepolymer,
The amine value of the polyurethane resin is 5.0-15.0 mg KOH / g,
The alcohol-based binder for alcohol-soluble printing ink, wherein the alcohol solvent has an ethanol content of 60% by mass or more. The alcohol-soluble printing ink binder according to claim 1, wherein the polymer polyol has a number average molecular weight of 500 to 4,000. The alcohol-soluble printing ink binder according to claim 1 or 2, wherein the alcohol solvent comprises only primary alcohol or only primary alcohol and secondary alcohol.