JP7698963B2 - Aqueous dispersion of polyurethane resin for inkjet printing - Google Patents

Description

The present invention relates to an aqueous polyurethane resin dispersion for inkjet printing.

Polyurethane resins have excellent flexibility, chemical resistance, and mechanical strength, and are therefore widely used as binder resins for paints, printing inks, adhesives, etc. In recent years, there has been an increasing need for water-dispersed polyurethane resins that emit less VOC during the drying process due to environmental considerations, and the addition of water-dispersed polyurethane resins to printing inks has been considered.
In particular, use in inkjet inks for low-absorption or non-absorption recording media is expected in the future, and such applications require high levels of image color development and fastness (abrasion resistance, light fastness, ozone gas resistance, water fastness, etc.).
In printed matter printed with pigment ink containing a pigment as a coloring material, the pigment component is likely to localize on the surface of the recording medium, resulting in high color development. The pigment remains on the surface of the recording medium due to evaporation and penetration of the vehicle components that occur during and after the ink is attached to the recording medium. However, since the pigment, which is the coloring material, is likely to be present on the surface of the recording medium, the adhesion and abrasion resistance of the ink film are particularly important for pigment ink. In order to improve these properties of recording with pigment ink, the addition of urethane resin to the ink has been considered (Patent Document 1).

JP 2016-81826 A

However, non-permeable recording media include polar recording media having many polar groups such as polyethylene terephthalate (PET) and nylon, and low-polarity recording media having few polar groups such as polypropylene (OPP). For both of these recording media, the ink film is still not sufficient in terms of ink that can provide excellent properties such as adhesion.
An object of the present invention is to provide an aqueous polyurethane resin dispersion which is resistant to blocking and has excellent adhesion (lamination strength) to non-permeable recording media.

The inventors have made extensive investigations and have arrived at the present invention. That is, the present invention is an aqueous polyurethane resin dispersion for inkjet inks, which contains water and a polyurethane resin (U) obtained by reacting a polyol component with a polyisocyanate component, in which the polyurethane resin (U) is a polyurethane resin having a carboxyl group and/or a carboxylate anion group, the polyol component is a polyol component containing polytetramethylene ether glycol, the weight ratio of the polytetramethylene ether glycol is 10 to 70% by weight based on the total weight of the polyol component and the polyisocyanate component, the polyisocyanate component is a polyisocyanate component containing isophorone diisocyanate, the weight ratio of the isophorone diisocyanate is 25 to 70% by weight based on the total weight of the polyol component and the polyisocyanate component, the acid value of the polyurethane resin (U) is 15 to 40 mgKOH/g, and the content of urea groups in the polyurethane resin (U) is 0.45 mol/kg or less.

The present invention makes it possible to provide an aqueous dispersion of polyurethane resin that is resistant to blocking and has excellent adhesion (lamination strength) to non-permeable recording media.

The aqueous polyurethane resin dispersion of the present invention contains water and a polyurethane resin (U) obtained by reacting a polyol component with a polyisocyanate component.
The polyurethane resin (U) is preferably contained in the polyurethane resin aqueous dispersion as polyurethane resin particles made of the polyurethane resin (U). The polyurethane resin particles are the solid content in the dispersion in which the polyurethane resin particles are dispersed in a dispersion medium. A dispersion in which the dispersion medium is mainly water is called an aqueous dispersion.

The polyurethane resin (U) in the present invention can be obtained by reacting a polyol component with a polyisocyanate component.

The polyol component in the present invention contains polytetramethylene ether glycol as an essential component from the viewpoint of adhesion to recording media, particularly polypropylene (OPP) films and polyethylene terephthalate (PET) films.

The polytetramethylene ether glycol may be used alone or in combination with other polyol components, and may be used alone or in combination with two or more kinds. The polytetramethylene ether glycol is not particularly limited, but examples thereof include polytetramethylene ether glycol and polytetramethylene ether glycol modified with 3-methyl-tetrahydrofuran.
Specific examples of such polytetramethylene ether glycols include PTMG1000 [poly(oxytetramethylene) glycol having Mn=1000, manufactured by Mitsubishi Chemical Co., Ltd.], PTMG2000 [poly(oxytetramethylene) glycol having Mn=2000, manufactured by Mitsubishi Chemical Co., Ltd.], PTMG3000 [poly(oxytetramethylene) glycol having Mn=3000, manufactured by Mitsubishi Chemical Co., Ltd.], PTGL2000 [modified poly(oxytetramethylene) glycol having Mn=2000, manufactured by Hodogaya Chemical Co., Ltd.], and PTGL3000 [modified poly(oxytetramethylene) glycol having Mn=3000, manufactured by Hodogaya Chemical Co., Ltd.]. In the present invention, "Mn" means number average molecular weight.

The weight ratio of polytetramethylene ether glycol is 10 to 70% by weight, preferably 35 to 70% by weight, and more preferably 45 to 70% by weight, based on the total weight of the polyol component and the polyisocyanate component, from the viewpoints of adhesion to recording media, particularly OPP films, and blocking resistance.

Other polyol components other than those mentioned above are not particularly limited, but examples include high molecular weight diols (A) other than polytetramethylene ether glycol, diols (B) having carboxyl groups and/or carboxylate anion groups, and low molecular weight polyols (C).

In addition, since the polyurethane resin (U) is a polyurethane resin having a carboxyl group and/or a carboxylate anion group, it is preferable that the polyol component contains a diol (B) having a carboxyl group and/or a carboxylate anion group, from the viewpoint of introducing a carboxyl group and/or a carboxylate anion group into the polyurethane resin (U).

The polymer diol (A) is not particularly limited, but examples thereof include polyether polyols other than polytetramethylene ether glycol, polycarbonate polyols, polyester polyols, and polyolefin polyols.

Polyether polyols other than polytetramethylene ether glycol are not particularly limited, but examples include aliphatic polyether diols and aromatic polyether diols.

Examples of aliphatic polyether diols include adducts of alkylene oxides (hereinafter abbreviated as AO) having 2 to 12 carbon atoms to aliphatic polyhydric alcohols having 2 to 20 carbon atoms, and specific examples include polyoxyalkylene glycols (polyethylene glycol, etc.), polyoxypropylene glycols (polypropylene glycol, etc.), and polyoxyethylene/propylene glycol copolymers.

Commercially available aliphatic polyether diols include Sannix PP-2000 [polyoxypropylene glycol with Mn=2000, manufactured by Sanyo Chemical Industries, Ltd.].

The aromatic polyether diol is not particularly limited, but examples thereof include diols having a bisphenol skeleton such as ethylene oxide (hereinafter abbreviated as EO) adducts of bisphenol A (2 mole EO adducts of bisphenol A, 4 mole EO adducts of bisphenol A, 6 mole EO adducts of bisphenol A, 8 mole EO adducts of bisphenol A, 10 mole EO adducts of bisphenol A, and 20 mole EO adducts of bisphenol A, etc.) and propylene oxide (hereinafter abbreviated as PO) adducts of bisphenol A (2 mole PO adducts of bisphenol A, 3 mole PO adducts of bisphenol A, and 5 mole PO adducts of bisphenol A, etc.), and EO or PO adducts of resorcin.

The polycarbonate polyol is not particularly limited, but examples include polycarbonate polyols produced by condensing one or more polyhydric alcohols having 2 to 20 carbon atoms with a low molecular weight carbonate compound (for example, dialkyl carbonates having an alkyl group with 1 to 6 carbon atoms, alkylene carbonates having an alkylene group with 2 to 6 carbon atoms, and diaryl carbonates having an aryl group with 6 to 9 carbon atoms) while causing a dealcoholization reaction.

Such polycarbonate polyols are not particularly limited, but examples thereof include polyhexamethylene carbonate diol, polypentamethylene carbonate diol, 3-methyl-5-pentane carbonate diol, polytetramethylene carbonate diol, and poly(tetramethylene/hexamethylene) carbonate diol (diols obtained by condensing 1,4-butanediol and 1,6-hexanediol with a dialkyl carbonate while causing a dealcoholization reaction, etc.).

Commercially available polycarbonate polyols include Nipporan 980R [polycarbonate polyol with Mn=2000 using 1,6-hexanediol, manufactured by Nippon Polyurethane Industry Co., Ltd.], Duranol T6002 [polycarbonate polyol with Mn=2000 using 1,6-hexanediol, manufactured by Asahi Kasei Chemicals Corporation], ETERNACOLL UH-300 [polycarbonate polyol with Mn=3000 using 1,6-hexanediol, manufactured by Ube Industries, Ltd.], ETERNACOLL UH-200 [polycarbonate polyol with Mn=2000 using 1,6-hexanediol, manufactured by Ube Industries, Ltd.], ETERNACOLL UM-90 (1/3) [polycarbonate polyol with Mn=900 using 1,4-cyclohexanedimethanol/1,6-hexanediol=1/3 (molar ratio), manufactured by Ube Industries, Ltd.], Duranol G4672 [polycarbonate polyol with Mn=2000 using 1,4-butanediol/1,6-hexanediol=70/30 (molar ratio), manufactured by Asahi Kasei Chemicals Corporation], Duranol T5652 [polycarbonate polyol having Mn=2000 using 1,5-pentanediol/1,6-hexanediol=50/50 (molar ratio), manufactured by Asahi Kasei Chemicals Corporation], T4672 [polycarbonate polyol having Mn=2000 using 1,4-butanediol/1,6-hexanediol, manufactured by Asahi Kasei Chemicals Corporation], Kuraray Polyol C-2090 [polycarbonate polyol having Mn=2000 using 3-methyl-1,5-pentanediol/1,6-hexanediol=90/10 (molar ratio), manufactured by Kuraray Co., Ltd.], Kuraray Polyol C-3090 [polycarbonate polyol having Mn=3000 using 3-methyl-1,5-pentanediol/1,6-hexanediol, manufactured by Kuraray Co., Ltd.], and Kuraray Polyol Examples include C-2050 [polycarbonate polyol with Mn=2000 using 3-methyl-1,5-pentanediol/1,6-hexanediol = 50/50 (molar ratio), manufactured by Kuraray Co., Ltd.].

Polyester polyols are not particularly limited, but examples include condensation type polyester polyols, polylactone polyols, and castor oil-based polyols.

The condensation type polyester polyol is not particularly limited, but examples thereof include polyester polyols obtained by dehydration condensation of polycarboxylic acids having 4 to 20 carbon atoms and polyhydric alcohols having 2 to 20 carbon atoms, and polyester polyols obtained by dehydration condensation of ester-forming derivatives of polycarboxylic acids having 4 to 20 carbon atoms and polyhydric alcohols having 2 to 20 carbon atoms.

Here, the 2-20 polyhydric alcohol is not particularly limited, but examples thereof include dihydric alcohols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methylpentanediol, diethylene glycol, neopentyl glycol, 1,4-bis(hydroxymethyl)cyclohexane, 1,4-bis(hydroxyethyl)benzene, and 2,2-bis(4,4'-hydroxycyclohexyl)propane, trihydric alcohols such as glycerin and trimethylolpropane, and tetrahydric to octahydric alcohols such as pentaerythritol, diglycerin, α-methylglucoside, sorbitol, xylitol, mannitol, dipentaerythritol, glucose, fructose, and sucrose.

In addition, examples of polycarboxylic acids having 4 to 20 carbon atoms or ester-forming derivatives thereof include, but are not limited to, aliphatic dicarboxylic acids (succinic acid, adipic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, etc.), alicyclic dicarboxylic acids (dimer acid, etc.), aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, etc.), trivalent or higher polycarboxylic acids (trimellitic acid, pyromellitic acid, etc.), their anhydrides (succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, etc.), their acid halides (adipic acid dichloride, etc.), their low molecular weight alkyl esters (dimethyl succinate, dimethyl phthalate, etc.), and mixtures thereof.

The polylactone polyol is not particularly limited, but for example, it is a polyaddition product of lactone to the polyhydric alcohol having 2 to 20 carbon atoms, and examples of the lactone include lactones having 4 to 12 carbon atoms (for example, γ-butyrolactone, γ-valerolactone, and ε-caprolactone).
Specific examples of polylactone polyols include polycaprolactone diol, polyvalerolactone diol, and polycaprolactone triol.

The castor oil-based polyol is not particularly limited, but includes, for example, modified castor oil in which castor oil is modified with a polyol or an alkylene oxide having 2 to 12 carbon atoms (hereinafter abbreviated as AO). Modified castor oil can be produced by transesterification of castor oil and a polyol and/or by addition of AO. Examples of castor oil-based polyols include castor oil, trimethylolpropane-modified castor oil, pentaerythritol-modified castor oil, and EO adducts of castor oil (addition mole number 4 to 30 moles), etc.

AO having 2 to 12 carbon atoms is not particularly limited, but examples include EO, PO, 1,2-, 2,3- or 1,3-butylene oxide, tetrahydrofuran, 3-methyl-tetrahydrofuran, α-olefin oxide, styrene oxide, and epihalohydrin (epichlorohydrin, etc.).

The polyolefin polyol is not particularly limited, but examples thereof include polybutadiene polyol, hydrogenated polybutadiene polyol, polyisoprene polyol, hydrogenated polyisoprene polyol, and hydroxyl-modified polyolefins obtained by reacting amino alcohols with acid-modified polyolefins obtained by modifying polyolefins with unsaturated (poly)carboxylic acids (anhydrides), as described in, for example, JP 2018-076428 A.

Commercially available polyolefin polyols include, but are not limited to, the NISSO-PB G series [polybutadiene polyols, manufactured by Nippon Soda Co., Ltd.], the Poly bd series [polybutadiene polyols, manufactured by Idemitsu Kosan Co., Ltd.], the NISSO-PB GI series [hydrogenated polybutadiene polyols, manufactured by Nippon Soda Co., Ltd.], Polytail H [hydrogenated polybutadiene polyols, manufactured by Mitsubishi Chemical Corporation], the Poly ip series [polyisoprene polyols, manufactured by Idemitsu Kosan Co., Ltd.], and the EPOL series [hydrogenated polyisoprene polyols, manufactured by Idemitsu Kosan Co., Ltd.].

The diol (B) having a carboxyl group and/or a carboxylate anion group is not particularly limited, and examples thereof include a diol (b1) having one carboxyl group, a diol (b2) having two or more carboxyl groups, and a salt obtained by neutralizing the above diol with a neutralizing agent described below.
The diol (b1) having one carboxyl group is not particularly limited, but examples thereof include 2,2'-dimethylolpropionic acid, 2,2'-dimethylolbutanoic acid, 2,2'-dimethylolbutyric acid, and 2,2'-dimethylolvaleric acid.

The diol (b2) having two or more carboxyl groups is not particularly limited, but examples thereof include tartaric acid.

Neutralizing agents for diols (b1) and (b2) are not particularly limited, but examples include ammonia, amine compounds having 1 to 20 carbon atoms, and alkali metal hydroxides (sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.).

Here, the amine compound having 1 to 20 carbon atoms is not particularly limited, but examples thereof include primary amines such as monomethylamine, monoethylamine, monobutylamine, monoethanolamine, and 2-amino-2-methyl-1-propanol, secondary amines such as dimethylamine, diethylamine, dibutylamine, diethanolamine, and N-methyldiethanolamine, and tertiary amines such as trimethylamine, triethylamine, dimethylethylamine, and triethanolamine.

Among these, from the viewpoint of the drying property of the resulting polyurethane resin aqueous dispersion and the water resistance of the resulting film, preferred are amine compounds with low vapor pressure at 25°C, more preferably ammonia, monomethylamine, monoethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine and dimethylethylamine.

Among the diols (B) having a carboxyl group and/or a carboxylate anion group, preferred are diols (b1) having one carboxyl group and salts of (b1) neutralized with a neutralizing agent, and more preferred are 2,2'-dimethylolpropionic acid, 2,2'-dimethylolbutanoic acid, salts of 2,2'-dimethylolpropionic acid neutralized with a neutralizing agent, and salts of 2,2'-dimethylolbutanoic acid neutralized with a neutralizing agent.

The low molecular weight polyol (C) may be a polyhydric alcohol having 2 to 20 carbon atoms.
Examples of the polyhydric alcohol having 2 to 20 carbon atoms include the same as those mentioned above.

The number average molecular weight (Mn) of the polyol components other than the low molecular weight polyol (C) is preferably 300 or more, more preferably 300 to 10,000, and particularly preferably 500 to 6,000, from the viewpoint of the mechanical properties of the polyurethane resin (U). The Mn of the polyol in the present invention is measured by gel permeation chromatography (GPC) using polyethylene glycol as the standard. However, the Mn of the low molecular weight polyol is a calculated value from the chemical formula.

The number average molecular weight (Mn) of the polyol component in the present invention can be measured by gel permeation chromatography, for example, under the following conditions.
Apparatus: "Waters Alliance 2695" [manufactured by Waters]
Column: "Guardcolumn Super H-L" (1 column), "TSKgel Super H2000, TSKgel Super H3000, TSKgel Super H4000 (all manufactured by Tosoh Corporation) connected together (1 column each)"
Sample solution: 0.25% by weight tetrahydrofuran solution Solution injection amount: 10 μl
Flow rate: 0.6ml/min Measurement temperature: 40℃
Detector: Refractive index detector Reference material: Standard polyethylene glycol

The polyisocyanate component in the present invention contains isophorone diisocyanate as an essential component from the viewpoint of adhesion to recording media, particularly OPP films and PET films. Isophorone diisocyanate (hereinafter also referred to as IPDI) may be used alone or in combination with other polyisocyanate components, and one type may be used alone or two or more types may be used in combination.

From the viewpoint of adhesion to the OPP film and blocking resistance, the weight ratio of isophorone diisocyanate is 25 to 70% by weight, preferably 25 to 40% by weight, and more preferably 28 to 35% by weight, based on the total weight of the polyol component and the polyisocyanate component.

The polyisocyanate components other than the above-mentioned isophorone diisocyanate are not particularly limited, but examples thereof include aromatic polyisocyanates having 8 to 26 carbon atoms and having two or more isocyanate groups, aliphatic polyisocyanates having 4 to 22 carbon atoms, alicyclic polyisocyanates having 8 to 18 carbon atoms, aromatic aliphatic polyisocyanates having 10 to 18 carbon atoms, and modified products of these polyisocyanates. The polyisocyanate components may be used alone or in combination of two or more kinds.

Examples of aromatic polyisocyanates having 8 to 26 carbon atoms include, but are not limited to, 1,3- or 1,4-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate (hereinafter, tolylene diisocyanate is abbreviated as TDI), crude TDI, 4,4'- or 2,4'-diphenylmethane diisocyanate (hereinafter, diphenylmethane diisocyanate is abbreviated as MDI), crude MDI, polyaryl polyisocyanate, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 1,5-naphthalene diisocyanate, 4,4',4"-triphenylmethane triisocyanate, and m- or p-isocyanatophenylsulfonyl isocyanate.

Examples of aliphatic polyisocyanates having 4 to 22 carbon atoms include, but are not limited to, ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (hereinafter abbreviated as HDI), dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate.

Alicyclic polyisocyanates having 8 to 18 carbon atoms are not particularly limited, but examples include 4,4'-dicyclohexylmethane diisocyanate (hereinafter abbreviated as hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexene-1,2-dicarboxylate, and 2,5- or 2,6-norbornane diisocyanate. 4,4'-dicyclohexylmethane diisocyanate is also called methylenebis-4,4'-cyclohexylene diisocyanate.

The aromatic aliphatic polyisocyanate having 10 to 18 carbon atoms is not particularly limited, but examples include m- or p-xylylene diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate.

The modified polyisocyanate is not particularly limited, but examples thereof include modified polyisocyanates such as those mentioned above (modified polyisocyanates containing urethane groups, carbodiimide groups, allophanate groups, urea groups, biuret groups, uretdione groups, uretoimine groups, isocyanurate groups, or oxazolidone groups; those containing 8 to 33% by weight, preferably 10 to 30% by weight, and particularly 12 to 29% by weight of free isocyanate groups), modified MDI (urethane-modified MDI, carbodiimide-modified MDI, trihydrocarbyl phosphate-modified MDI, etc.), urethane-modified TDI, biuret-modified HDI, isocyanurate-modified HDI, and isocyanurate-modified IPDI.

When the above polyol component and polyisocyanate component are reacted to obtain polyurethane resin (U), a chain extender and a reaction terminator may be used to control the molecular weight.

The chain extender is not particularly limited, but examples thereof include water, aliphatic polyamines having 2 to 36 carbon atoms [alkylenediamines such as ethylenediamine and hexamethylenediamine; poly(n=2-6) alkylene (carbon number 2-6) poly(n=3-7) amines such as diethylenetriamine, dipropylenetriamine, dihexylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine], alicyclic polyamines having 6 to 20 carbon atoms (1,3- or 1,4-diaminocyclohexane, 4,4'- or 2,4'-dicyclohexylmethanediamine, and isopropyl alcohol, etc.), and cyclohexane-1,1-dimethylethyl alcohol. Examples of suitable chain extenders include aromatic polyamines having 6 to 20 carbon atoms (1,3- or 1,4-phenylenediamine, 2,4- or 2,6-tolylenediamine, 4,4'- or 2,4'-methylenebisaniline, etc.), heterocyclic polyamines having 3 to 20 carbon atoms (2,4-diamino-1,3,5-triazine, piperazine, and N-aminoethylpiperazine, etc.), hydrazine or a derivative thereof (dibasic acid dihydrazide, such as adipic acid dihydrazide, etc.), and amino alcohols having 2 to 20 carbon atoms (e.g. ethanolamine, diethanolamine, 2-amino-2-methylpropanol, and triethanolamine). One type of chain extender may be used alone, or two or more types may be used in combination.

The reaction terminator is not particularly limited, but examples thereof include monoalcohols having 1 to 20 carbon atoms (methanol, ethanol, butanol, octanol, decanol, dodecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, etc.), and monoamines having 1 to 20 carbon atoms (mono- or di-alkylamines such as monomethylamine, monoethylamine, monobutylamine, dibutylamine, monooctylamine, etc., and mono- or di-alkanolamines such as monoethanolamine, diethanolamine, diisopropanolamine, etc.). One type of reaction terminator may be used alone, or two or more types may be used in combination.

The acid value of the polyurethane resin (U) in the present invention is 15 to 40 mgKOH/g, preferably 15 to 30 mgKOH/g, from the viewpoints of the dispersion stability of the polyurethane resin aqueous dispersion, the viscosity of the printing ink, and the water resistance of the dried resin film. If the acid value is 15 mgKOH/g or more, the polyurethane resin (U) has good dispersion stability in the polyurethane resin aqueous dispersion, and is less likely to cause clogging even at high temperatures. On the other hand, if the acid value is 40 mgKOH/g or less, the polyurethane resin is less likely to swell in water, and the printing ink is less likely to thicken. Furthermore, the water resistance of the resulting recorded matter can be maintained at a good level.

The acid value of the polyurethane resin (U) can be changed, for example, by adjusting the content of the skeleton derived from the diol (B) (an acid group-containing polyol such as dimethylolpropionic acid) having a carboxyl group and/or a carboxylate anion group.

The acid value of polyurethane resin (U) can be measured by the method described in JIS K 0070:1992 (potentiometric titration method).

The number average molecular weight (Mn) of the polyurethane resin (U) in the present invention is preferably 10,000 to 1,000,000 from the viewpoint of the blocking resistance and adhesion of the polyurethane resin (U).

The number average molecular weight (Mn) of the polyurethane resin (U) can be measured by the same method as the number average molecular weight (Mn) of the polyol component described above.

The content of urea groups in the polyurethane resin (U) in the present invention is 0.45 mol/kg or less. If the content of urea groups is more than 0.45 mol/kg, coarse particles are likely to be generated, which leads to poor stability of the ink viscosity over time and clogging of the inkjet head when used in an inkjet ink. Furthermore, the inclusion of urea groups improves adhesion (lamination strength). The content of urea groups in the polyurethane resin (U) is preferably 0.3 mol/kg or less, and from the viewpoint of blocking resistance, is more preferably 0.1 to 0.3 mol/kg.

The content of urethane groups in the polyurethane resin (U) in the present invention is preferably 1.0 to 10 mol/kg, more preferably 1.5 to 8.0 mol/kg, and even more preferably 1.8 to 6.0 mol/kg. By having the content of urethane groups within the above range, the generation of coarse particles is suppressed, and adhesion tends to be further improved.

The contents of urethane groups and urea groups in the present invention can be calculated from the composition of the raw materials charged, and can also be measured by the following analytical method, if necessary.
<Method for measuring urea group and urethane group content>
The urea group and urethane group contents are calculated from the N atom content quantified by a nitrogen analyzer [ANTEK7000 (manufactured by Antec)] and the ratio of urethane group and urea group quantified by 1H-NMR. The 1H-NMR measurement is performed according to the method described in "Structural Study of Polyurethane Resin by NMR: Takeda Laboratory Report 34 (2), 224-323 (1975)". That is, when an aliphatic isocyanate is used by measuring 1H-NMR, the weight ratio of urea group and urethane group is measured from the ratio of the integral amount of hydrogen derived from urea group at a chemical shift of about 6 ppm to the integral amount of hydrogen derived from urethane group at a chemical shift of about 7 ppm, and the urethane group and urea group contents are calculated from the weight ratio, the above-mentioned N atom content, and the allophanate group and biuret group contents. When an aromatic isocyanate is used, the weight ratio of the urea group to the urethane group is calculated from the ratio of the integral amount of hydrogen derived from the urea group at a chemical shift of about 8 ppm to the integral amount of hydrogen derived from the urethane group at a chemical shift of about 9 ppm, and the urea group content is calculated from this weight ratio and the above-mentioned N atom content.

The urethane group content of the polyurethane resin (U) in the present invention can be calculated by the following method: It was calculated from the charged composition of the raw materials by the following calculation formula (1) or (2).
Calculation formula (1):
In the case where the content (mol) of isocyanate groups in the raw material - the content (mol) of hydroxyl groups in the raw material < 0, the content (mol/kg) of urethane groups = the content (mol) of isocyanate groups in the raw material / the resin solid content (kg)
Calculation formula (2):
When the isocyanate group content (mol) in the raw material - the hydroxyl group content (mol) in the raw material > 0, the urethane group content (mol/kg) = the hydroxyl group content (mol) in the raw material / resin solid content (kg)

The urea group content of the polyurethane resin (U) in the present invention can be calculated by the following method: It was calculated from the charged composition of the raw materials by the following calculation formula (3) or (4).
Calculation formula (3):
In the case where isocyanate group content (mol) in raw material - hydroxyl group content (mol) in raw material - amino group content (mol) of chain extender > 0, urea group content (mol/kg) = amino group content (mol) of chain extender + {[isocyanate group content (mol) in raw material - hydroxyl group content (mol) in raw material - amino group content of chain extender] x 1/2} / resin solid content (kg)
Calculation formula (4):
Isocyanate group content (mol) in raw material - hydroxyl group content (mol) in raw material - amino group content (mol) of chain extender < 0 Urea group content (mol/kg) = [Isocyanate group content (mol) in raw material - hydroxyl group content (mol) in raw material] / resin solid content (kg)

The storage modulus G' at 50°C of the film obtained by drying the polyurethane resin aqueous dispersion of the present invention at 105°C for 3 hours is preferably 0.9 to 80 MPa, more preferably 1 to 60 MPa, and even more preferably 3 to 30 MPa, from the viewpoints of blocking resistance and adhesion to a recording medium.

In the present invention, the storage modulus G' of the polyurethane resin (U) can be measured by the following method. The storage modulus G' at 50°C of a film obtained by drying the aqueous polyurethane resin dispersion at 105°C for 3 hours was measured using the following viscoelasticity measuring device.
Apparatus: MCR92 (manufactured by Anton Paar)
Jig: 8 mm parallel plate Frequency: 11 Hz
Distortion rate: 0.5%
Heating rate: 5°C/min. Start of heating: 20°C.
End of temperature rise: 120°C
Preparation of a film by drying an aqueous polyurethane resin dispersion: 10 parts of an aqueous polyurethane resin dispersion was poured into a polypropylene mold of 10 cm × 20 cm × 0.1 cm, in an amount such that the film thickness after evaporation of water would be 200 μm, and the film was dried at room temperature overnight and at 105° C. for 3 hours in a circulating air dryer, and then cut into a size of 1 cm × 1 cm to prepare a measurement sample.

In terms of adhesion, it is preferable that the polyurethane resin (U) in the polyurethane resin aqueous dispersion of the present invention exists as polyurethane resin particles. In addition, in terms of blocking resistance of an image obtained from an ink using the polyurethane resin aqueous dispersion, it is preferable that the polyurethane resin particles in the polyurethane resin aqueous dispersion contain an ink blocking inhibitor (E) within the same particle.

Anti-blocking agent for ink (E) is an additive that is added to inkjet ink for the purpose of preventing problems such as printed characters or images sticking to the unprinted back side when the front side of a printed material printed with inkjet ink overlaps with the unprinted back side of the next printed material, or when a printed material is stored in a rolled up state. It is an additive that has the function of roughening the ink coating surface to reduce the contact area, or of migrating to the ink coating surface to form a protective layer on the surface.

The ink anti-blocking agent (E) can be used as an aqueous dispersion containing polyurethane resin particles in the polyurethane resin aqueous dispersion and (E) in the same particle, but it can also be used by blending it with the polyurethane resin aqueous dispersion or printing ink as an aqueous dispersion separate from the polyurethane resin particles, and if the ink anti-blocking agent (E) is water-soluble, it can be blended by dissolving it in the aqueous medium of the polyurethane resin aqueous dispersion or printing ink, or these can be used in combination. From the viewpoint of not impairing the dispersion stability of the aqueous dispersion of the resin and pigment, it is preferable to use it as an aqueous dispersion containing polyurethane resin particles and the ink anti-blocking agent (E) in the same particle.

Anti-blocking agents for inks (E) are not particularly limited, but examples include polyolefin waxes, natural waxes, aliphatic alcohols having 30 to 50 carbon atoms, fatty acids having 30 to 50 carbon atoms, fluorine-based compounds, silicone-based compounds, aliphatic amides, and polyoxyethylene compounds.

Examples of polyolefin waxes include, but are not limited to, (co)polymers of olefins (such as ethylene, propylene, 1-butene, isobutylene, 1-hexene, 1-dodecene, 1-octadecene, and mixtures thereof) [including those obtained by (co)polymerization and thermally degradable polyolefins], oxides of olefin (co)polymers with oxygen and/or ozone, maleic acid modified products of olefin (co)polymers [such as maleic acid and its derivatives (maleic anhydride, monomethyl maleate, monobutyl maleate, dimethyl maleate, etc.) modified products], copolymers of olefins and unsaturated carboxylic acids [(meth)acrylic acid, itaconic acid, maleic anhydride, etc.] and/or unsaturated carboxylic acid alkyl esters [(meth)acrylic acid alkyl esters (alkyl having 1 to 18 carbon atoms) and maleic acid alkyl esters (alkyl having 1 to 18 carbon atoms), etc.], and Sasol wax.

Natural waxes are not particularly limited, but examples include carnauba wax, montan wax, paraffin wax, and rice wax.

There are no particular limitations on the aliphatic alcohol having 30 to 50 carbon atoms, but examples include triacontanol, etc.

Fatty acids having 30 to 50 carbon atoms are not particularly limited, but examples include triacontane carboxylic acid.

The fluorine-based compound is not particularly limited, but examples thereof include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride.

The silicone compound is not particularly limited, but examples thereof include lecithin, silicone oil, silicone wax, etc., and examples of the silicone oil include linear silicone oil, cyclic silicone oil, and modified silicone oil.
The chain silicone oil is not particularly limited, but examples thereof include linear dimethyl silicone oils such as tetradecamethylhexasiloxane, hexadecamethylheptasiloxane, and docosamethyldecasiloxane, and branched dimethyl silicone oils such as methyltris(trimethylsiloxy)silane and tetrakis(trimethylsiloxy)silane.
The cyclic silicone oil is not particularly limited, but examples thereof include decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, hexadecamethylcyclooctasiloxane, and octadecamethylcyclononasiloxane.
The modified silicone oil is not particularly limited, but examples thereof include alkyl-modified silicones, aryl-modified silicones such as phenyl-modified silicones and aralkyl-modified silicones, carboxylate-modified silicones, alkylene-modified silicones, and polyether-modified silicones.

The aliphatic amides are not particularly limited, but examples thereof include saturated fatty acid monoamides such as lauric acid amide and stearic acid amide, unsaturated fatty acid monoamides such as oleic acid amide, saturated fatty acid bisamides such as methylene bisstearic acid amide and ethylene biscapric acid amide, unsaturated fatty acid bisamides such as ethylene bisoleic acid amide and hexamethylene bisoleic acid amide, substituted amides such as N-stearyl stearic acid amide and N-oleyl oleic acid amide, aromatic bisamides such as methylol stearic acid amides, methylol amides such as methylol behenic acid amide, N,N-distearyl isophthalic acid amide and metaxylylene bisstearic acid amide, branched amides such as N,N'-2-hydroxyethyl stearic acid amide and N,N'-ethylene bisoleic acid amide, and alkanolamides such as coconut oil fatty acid monoethanolamide and lauric acid monoethanolamide.

Polyoxyethylene compounds are not particularly limited, but examples include polyoxyethylene alkyl ethers, polyoxyethylene alkenyl ethers, polyoxyethylene mono fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.

The polyoxyethylene alkyl ether is not particularly limited, but examples thereof include polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene behenyl ether, and the like.
The polyoxyethylene alkenyl ether is not particularly limited, but examples thereof include polyoxyethylene tetradecenyl ether, polyoxyethylene hexadecenyl ether, and polyoxyethylene octadecenyl ether.
The polyoxyethylene monofatty acid ester is not particularly limited, but examples thereof include polyoxyethylene monolaurate, polyoxyethylene monomyristate, polyoxyethylene monopalmitate, and polyoxyethylene monostearate.
The polyoxyethylene sorbitan fatty acid ester is not particularly limited, but examples thereof include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monoisostearate, polyoxyethylene sorbitan distearate, and polyoxyethylene sorbitan tristearate.

As the blocking inhibitor (E) for ink, from the viewpoint of blocking resistance and compatibility with polyurethane resin, silicone compounds, aliphatic amides and polyoxyethylene compounds are preferred, silicone oil and polyoxyethylene alkyl ether are more preferred, silicone oil is even more preferred, modified silicone oil is particularly preferred, and polyether modified silicone is most preferred.

When the polyurethane resin particles contain an anti-blocking agent for ink (E), from the viewpoint of blocking resistance and adhesion to a recording medium, the polyurethane resin particles preferably contain 0.1 to 10% by weight of the anti-blocking agent for ink (E) based on the weight of the polyurethane resin (U), more preferably 0.5 to 5% by weight, and even more preferably 0.5 to 3% by weight.

The volume average particle size (Dv) of polyurethane resin particles measured by light scattering measurement method is preferably 10 to 80 nm, more preferably 20 to 60 nm. If (Dv) is 10 nm or more, the viscosity of the polyurethane resin aqueous dispersion is appropriate and the handling properties are good, and if it is 80 nm or less, the dispersion stability is good.

The volume average particle diameter (Dv) can be controlled by the content of carboxyl groups and/or carboxylate anion groups, the amount of neutralizing agent and dispersing agent, as well as the type and dispersing conditions of the dispersing machine used in the dispersing step.
The volume average particle diameter (Dv) can be measured using a light scattering particle size distribution measuring device ("LA950 V2" manufactured by Horiba, Ltd.).

From the viewpoint of the water resistance of the dried film obtained from the polyurethane resin aqueous dispersion of the present invention, it is preferable that the polyurethane resin aqueous dispersion of the present invention is a self-emulsifying aqueous dispersion that does not use a dispersant (H).

Dispersants (H) used when dispersing polyurethane resin (U) in an aqueous medium include nonionic surfactants (h1), anionic surfactants (h2), cationic surfactants (h3), amphoteric surfactants (h4) and other emulsifying dispersants (h5). (H) may be used alone or in combination of two or more types.

The nonionic surfactant (h1) is not particularly limited, but examples thereof include AO-added nonionic surfactants and polyhydric alcohol-type nonionic surfactants. Examples of AO-added types include EO adducts of aliphatic alcohols having 10 to 20 carbon atoms, EO adducts of phenol, EO adducts of nonylphenol, EO adducts of alkylamines having 8 to 22 carbon atoms, and EO adducts of polyoxypropylene glycol. Examples of polyhydric alcohol types include fatty acid (8 to 24 carbon atoms) esters of polyhydric (3 to 8 or more) alcohols (2 to 30 carbon atoms) (e.g., glycerin monostearate, glycerin monooleate, sorbitan monolaurate, sorbitan monooleate, etc.) and alkyl (4 to 24 carbon atoms) poly (polymerization degree 1 to 10) glycosides.

The anionic surfactant (h2) is not particularly limited, but examples thereof include ether carboxylic acids or salts thereof having a hydrocarbon group having 8 to 24 carbon atoms [sodium lauryl ether acetate and (poly)oxyethylene (number of moles added: 1 to 100) sodium lauryl ether acetate, etc.]; sulfate esters or ether sulfate esters and salts thereof having a hydrocarbon group having 8 to 24 carbon atoms [sodium lauryl sulfate, (poly)oxyethylene (number of moles added: 1 to 100) sodium lauryl sulfate, (poly)oxyethylene (number of moles added: 1 to 100) triethanolamine lauryl sulfate and (poly)oxyethylene (number of moles added: 1 to 100) sodium coconut oil fatty acid monoethanolamide sulfate, etc.]; sulfonates having a hydrocarbon group having 8 to 24 carbon atoms [sodium dodecylbenzenesulfonate, etc.]; sulfosuccinates having one or two C14 hydrocarbon groups; phosphates or ether phosphates and their salts having a hydrocarbon group with 8 to 24 carbon atoms [sodium lauryl phosphate and (poly)oxyethylene (molar number added: 1 to 100) sodium lauryl ether phosphate, etc.]; fatty acid salts having a hydrocarbon group with 8 to 24 carbon atoms [sodium laurate and triethanolamine laurate, etc.]; and acylated amino acid salts having a hydrocarbon group with 8 to 24 carbon atoms [sodium methyl coconut taurate, sodium coconut sarcosine, triethanolamine coconut sarcosine, triethanolamine N-coconut acyl-L-glutamate, sodium N-coconut acyl-L-glutamate, sodium lauroyl methyl-β-alanine, etc.].

The cationic surfactant (h3) is not particularly limited, but examples thereof include quaternary ammonium salt type [stearyl trimethyl ammonium chloride, behenyl trimethyl ammonium chloride, distearyl dimethyl ammonium chloride, lanolin fatty acid aminopropyl ethyl dimethyl ammonium ethyl sulfate, etc.] and amine salt type [stearic acid diethyl aminoethyl amide lactate, dilauryl amine hydrochloride, oleyl amine lactate, etc.].

Examples of amphoteric surfactants (h4) include, but are not limited to, betaine-type amphoteric surfactants [coconut oil fatty acid amidopropyl dimethylaminoacetate betaine, lauryl dimethylaminoacetate betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, lauryl hydroxysulfobetaine, and lauroyl amidoethyl hydroxyethyl carboxymethyl betaine hydroxypropyl sodium phosphate, etc.] and amino acid-type amphoteric surfactants [sodium β-lauryl aminopropionate, etc.].

Other emulsifying dispersants (h5) are not particularly limited, but examples thereof include polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose, carboxyl group-containing (co)polymers such as sodium polyacrylate, and emulsifying dispersants having urethane groups or ester groups described in U.S. Pat. No. 5,906,704 [for example, polycaprolactone polyol and polyether diol linked with polyisocyanate].

The dispersant (H) may be added at any time after the urethanization reaction of the polyurethane resin (U), before the water dispersion process of the polyurethane resin (U), during the water dispersion process, or after the water dispersion process. From the viewpoint of the dispersibility of the polyurethane resin (U) and the stability of the aqueous dispersion, however, it is preferable to add the dispersant (H) before or during the water dispersion process.

Methods for producing the aqueous polyurethane resin dispersion of the present invention include, for example, the following methods [1] and [2].

[1] A method in which a polyol component, a polyisocyanate component, and optionally a chain extender and a reaction terminator are reacted in one or more stages in the presence or absence of an organic solvent (S) to produce a polyurethane resin (U), and the carboxyl groups are converted into salts using a neutralizing agent as necessary, and the resulting product is dispersed in an aqueous medium, and the organic solvent (S) is then distilled off as necessary.

[2] A method in which a polyol component and a polyisocyanate component are reacted in one or more stages in the presence or absence of an organic solvent (S) to produce a urethane prepolymer (P) having an isocyanate group, and then, if necessary, the carboxyl groups in the prepolymer (P) are converted into salts using a neutralizing agent and dispersed in an aqueous medium, and a chain extender and/or a reaction terminator are reacted with the isocyanate groups in the prepolymer (P), and the organic solvent (S) is distilled off if necessary.

Of methods [1] and [2], method [2] is preferred from the viewpoints of dispersion stability of polyurethane resin (U) and mechanical strength of the dried film.

The reaction temperature when producing the polyurethane resin (U) in method [1] and the urethane prepolymer (P) in method [2] is preferably 60 to 120°C, more preferably 60 to 110°C, and particularly preferably 60 to 100°C, from the viewpoint of suppressing side reactions. The production time can be appropriately selected depending on the equipment used, but is generally preferably 1 minute to 100 hours, more preferably 3 minutes to 30 hours, and particularly preferably 5 minutes to 20 hours.

The organic solvent (S) is selected from solvents that are substantially non-reactive with an isocyanate group, and examples thereof include ketone-based solvents (e.g., acetone and methyl ethyl ketone), ester-based solvents [e.g., ethyl acetate, dibasic acid ester (DBE)], ether-based solvents (e.g., tetrahydrofuran), amide-based solvents (e.g., N,N-dimethylformamide and N-methylpyrrolidone), aromatic hydrocarbon-based solvents (e.g., toluene), etc. These organic solvents (S) may be used alone or in combination of two or more.
In the present invention, the aqueous medium means water or a mixture of water and the organic solvent (S).

The organic solvent (S) is preferably an organic solvent having a boiling point of less than 100° C., such as acetone, methyl ethyl ketone, ethyl acetate, and tetrahydrofuran.
If an organic solvent having a boiling point of 100° C. or higher is used, it becomes difficult to completely remove the organic solvent from the aqueous medium, and the organic solvent remains in the aqueous dispersion, which is not preferable because the organic solvent is generated during drying. In addition, the organic solvent tends to remain in the film, which is not preferable because the mechanical properties of the film change over time.

From the viewpoints of odor, stability over time, environmental impact, and safety, the content of the organic solvent (S) in the polyurethane resin aqueous dispersion is preferably 1% by weight or less, more preferably 0.8% by weight or less, and particularly preferably 0.5% by weight or less, based on the weight of the polyurethane resin aqueous dispersion.

In the urethanization reaction in the above methods [1] and [2], a known urethanization catalyst or the like can be used as necessary to promote the reaction. The amount of the urethanization catalyst added is preferably 0.001 to 3% by weight, more preferably 0.005 to 2% by weight, and particularly preferably 0.01 to 1% by weight, based on the weight of the polyurethane resin (U) or prepolymer (P).
It is.

Examples of urethane catalysts include metal catalysts [tin-based catalysts (trimethyltin laurate, trimethyltin hydroxide, dimethyltin dilaurate, dibutyltin diacetate, dibutyltin dilaurate, stannous octoate, and dibutyltin maleate, etc.), lead-based catalysts (lead oleate, lead 2-ethylhexanoate, lead naphthenate, and lead octenate, etc.), cobalt-based catalysts (cobalt naphthenate, etc.), bismuth-based catalysts (bismuth tris(2-ethylhexanoate), etc.) and mercury-based catalysts (phenylmercury propionate, etc.)], amine catalysts [triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkene {1 , 8-diazabicyclo[5.4.0]-7-undecene}, etc.; carbonates or organic acid salts (formates, etc.) of dialkylaminoalkylamines {dimethylaminoethylamine, dimethylaminopropylamine, diethylaminopropylamine, dibutylaminoethylamine, dimethylaminooctylamine, dipropylaminopropylamine, etc.} or heterocyclic aminoalkylamines [2-(1-aziridinyl)ethylamine, 4-(1-piperidinyl)-2-hexylamine, etc.], etc.; N-methylmorpholine, N-ethylmorpholine, triethylamine, diethylethanolamine, dimethylethanolamine, etc.], and mixtures of two or more of these.

The apparatus for dispersing the polyurethane resin (U) or its organic solvent solution in the above method [1], and the urethane prepolymer (P) or its organic solvent solution in the above method [2] in water is not particularly limited, but it is preferable to use a rotary dispersion mixer, ultrasonic disperser, or kneader, and among these, a rotary dispersion mixer with particularly excellent dispersion ability is even more preferable.

Examples of rotary dispersion mixers include mixers with typical stirring blades such as Maxblend and helical blades, TK Homomixer (manufactured by Primix Corporation), Clearmix (manufactured by M Technique Corporation), Filmix (manufactured by Primix Corporation), Ultra Turrax (manufactured by IKA Corporation), Ebara Milder (manufactured by Ebara Corporation), Cavitron (manufactured by Eurotech), and Biomixer (manufactured by Nippon Seiki Co., Ltd.).

The solids concentration (content of components other than volatile components) of the polyurethane resin aqueous dispersion is preferably 20 to 65% by weight, and more preferably 25 to 55% by weight, from the viewpoint of ease of handling of the polyurethane resin aqueous dispersion. The solids concentration can be obtained by thinly spreading about 1 g of the aqueous dispersion on a Petri dish, weighing it, and then heating it at 130°C for 45 minutes using a circulating constant temperature dryer, and then weighing it and calculating the ratio (percentage) of the remaining weight after heating to the weight before heating.

From the viewpoint of ease of handling, the viscosity of the aqueous polyurethane resin dispersion at 25°C is preferably 5,000 mPa·s or less, and more preferably 1,000 mPa·s or less. The viscosity can be measured using a BL type viscometer.

From the viewpoint of dispersion stability, the pH of the polyurethane resin aqueous dispersion at 25°C is preferably 2 to 12, and more preferably 4 to 10. The pH can be measured using a pH Meter M-12 [manufactured by Horiba, Ltd.].

The polyurethane resin aqueous dispersion of the present invention is an aqueous polyurethane resin dispersion for inkjet inks, and is preferably used as an inkjet ink because it provides good adhesion to a recording medium. Furthermore, it is preferably used as an inkjet ink for printing on flexible packaging from the viewpoints of image adhesion (lamination strength) and blocking resistance. Flexible packaging printing refers to printing on packaging materials made of flexible materials. Examples of packaging materials include thin and flexible materials such as plastic film, aluminum foil, and paper, and these materials may be used alone or in combination. Packaging materials printed on flexible packaging are used, for example, as bags for food, medicine, etc.

The printing ink (L) containing the polyurethane resin aqueous dispersion contains, in addition to the polyurethane resin aqueous dispersion, a colorant, a moisturizer, a penetrant, water, and other additives.

Colorants include dyes and pigments.
The dye is not particularly limited, and reactive dyes, vat dyes, naphthol dyes, sulfur dyes, direct dyes, acid dyes, metal complex dyes, disperse dyes, cationic dyes, and the like can be selected depending on the medium used.

Pigments include inorganic pigments (e.g. white pigments, black pigments, gray pigments, red pigments, brown pigments, yellow pigments, green pigments, blue pigments, purple pigments and metallic pigments) and organic pigments (e.g. natural organic pigments, synthetic organic pigments, nitroso pigments, nitro pigments, pigment dye-type azo pigments, azo lakes made from water-soluble dyes, azo lakes made from sparingly soluble dyes, lakes made from basic dyes, lakes made from acid dyes, xanthan lakes, anthraquinone lakes, pigments from vat dyes and phthalocyanine pigments).

Among these coloring materials, pigments are preferred. The coloring materials may be used alone or in combination of two or more.
The content of the coloring material is preferably 50% by weight or less, more preferably 30% by weight or less, based on the weight of the printing ink (L).

Humectants include, but are not limited to, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, polyethylene glycols with Mn of 2,000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, glycerin, mesoerythritol, pentaerythritol, 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone. One type of humectant may be used alone, or two or more types may be used in combination.

The penetrating agent is not particularly limited, but examples thereof include glycol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monobutyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol monobutyl ether, etc.) and aliphatic diols having 4 to 8 carbon atoms (1,2-alkyl diols such as 1,2-pentanediol and 1,2-hexanediol, and 1,3 acetylene glycol-based surfactants; acetylene alcohol-based surfactants; ether-based surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyalkylene alkyl ether; ester-based surfactants such as polyoxyethylene oleic acid, polyoxyethylene oleic acid ester, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; silicone-based surfactants such as dimethylpolysiloxane; and fluorine-based surfactants such as fluorine alkyl esters and perfluoroalkyl carboxylates. The penetrating agents may be used alone or in combination of two or more.

The water is not particularly limited, but examples include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as ultrapure water from which ionic impurities have been removed as much as possible. In addition, the use of water sterilized by ultraviolet irradiation or the addition of hydrogen peroxide can prevent the growth of bacteria and fungi when the inkjet ink composition is stored for a long period of time.

Other additives include chelating agents, preservatives, and pH adjusters. Examples of chelating agents include ethylenediaminetetraacetate (EDTA), ethylenediamine nitrilotriacetate, hexametaphosphate, pyrophosphate, and metaphosphate.

Preservatives include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, and 1,2-dibenzylthiazolin-3-one.

Examples of pH adjusters include potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, potassium carbonate, sodium carbonate, and sodium bicarbonate.

The recording medium used in printing with the printing ink (L) is not particularly limited, but examples include non-permeable recording media and permeable recording media.

Non-permeable recording media include, but are not limited to, resin media such as polycarbonate, rigid PVC, flexible PVC, polystyrene, expanded polystyrene, polymethyl methacrylate, polypropylene, polyethylene, polyethylene terephthalate, and nylon, as well as metal substrates such as glass and stainless steel.

Examples of permeable recording media include, but are not limited to, paper media such as fine paper, art paper, coated paper, and cast-coated paper.

Among these, from the viewpoint of adhesion, non-permeable recording media are preferred as recording media for the printing ink (L), and resin media are more preferred. Furthermore, from the viewpoint of adhesion (lamination strength) and blocking resistance, resin media are suitable for printing on flexible packaging.

Flexible packaging printing refers to printing on flexible recording media such as resin film, either alone or in laminated layers, and printed materials produced by flexible packaging printing are used to package food, daily necessities, etc.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. In the following, "parts" refers to parts by weight unless otherwise specified.

<Production Example 1>
A reaction apparatus equipped with a stirrer, reflux tube, and heater was charged with 150 parts of methyl hydrogen silicone oil (number average molecular weight 1500, functional group equivalent weight 500 g/mol), 150 parts of an ethylene oxide 12 mole adduct of allyl alcohol, and 100 parts of isopropanol as an organic solvent for reaction, and 0.15 ml of _a 1 mol solution of _H2PtCl6 in isopropanol was charged as a catalyst. After heating under reflux for 1 hour, the isopropanol was distilled off under reduced pressure at 110°C to obtain a polyether modified silicone with a number average molecular weight of 3000.

Example 1
A simple pressurized reaction apparatus equipped with a stirrer and a heater was charged with 67.6 parts of PTMG2000 [manufactured by Mitsubishi Chemical Corporation] as polytetramethylene ether glycol, 2.8 parts of 1,4-butanediol as a low molecular weight diol, 4.5 parts of 2,2-dimethylolpropionic acid as a polyol component having a carboxyl group on the side chain, 25.1 parts of isophorone diisocyanate as a polyisocyanate component, and 54 parts of methyl ethyl ketone as a reaction organic solvent, and the mixture was stirred at 70° C. for 12 hours to carry out a urethanization reaction, producing a methyl ethyl ketone solution of a urethane prepolymer (P1) having an isocyanate group.
Next, 3.4 parts of triethylamine as a neutralizing agent was added to the methyl ethyl ketone solution of the obtained urethane prepolymer (P1) to homogenize it, and then 263 parts of ion-exchanged water as an aqueous medium was added while stirring at 200 rpm to disperse the polyurethane prepolymer in water. The obtained dispersion was heated to 50°C and stirred for 4 hours to carry out a chain extension reaction with water, and further heated to 60°C under reduced pressure to distill off methyl ethyl ketone. Then, water was added to adjust the solid content concentration to 30% by weight to obtain an aqueous polyurethane resin dispersion (Q-1).

Example 2
An aqueous polyurethane resin dispersion (Q-2) was obtained in the same manner as in Example 1, except that the amounts of the raw materials used were changed to those shown in Table 1.

<Examples 3 to 11>
The same procedure as in Example 1 was repeated except that the raw materials and amounts used were changed to those shown in Table 1, and a chain extender shown in Table 1 was added after dispersing the polyurethane prepolymer in water, to obtain aqueous polyurethane resin dispersions (Q-3 to Q-11).

Example 12
A simple pressurized reaction apparatus equipped with a stirrer and a heater was charged with 16.0 parts of PTMG2000 [manufactured by Mitsubishi Chemical Corporation] as polytetramethylene ether glycol, 17.8 parts of polycarbonate diol ETERNACOLL UH-200 [manufactured by Ube Industries, Ltd.], 12.2 parts of 1,4-butanediol as a low molecular weight diol, 4.5 parts of 2,2-dimethylolpropionic acid as a polyol component having a carboxyl group on the side chain, 47.6 parts of isophorone diisocyanate as a polyisocyanate component, and 54 parts of methyl ethyl ketone as a reaction organic solvent, and the mixture was stirred at 70° C. for 12 hours to carry out a urethanization reaction, producing a methyl ethyl ketone solution of a urethane prepolymer (P12) having an isocyanate group.
Next, 8.0 parts of the polyether-modified silicone obtained in Production Example 1 as an ink blocking inhibitor and 3.4 parts of triethylamine as a neutralizing agent were added to the methyl ethyl ketone solution of the obtained urethane prepolymer (P12), and the mixture was homogenized, and then 262 parts of ion-exchanged water as an aqueous medium was added while stirring at 200 rpm to disperse the polyurethane prepolymer in water. 6.3 parts of a 10 wt% aqueous solution of ethylenediamine as a chain extender was added to the obtained dispersion, which was heated to 50°C and stirred for 4 hours to carry out an extension reaction, and further heated to 60°C under reduced pressure to distill off the methyl ethyl ketone. Then, water was added to adjust the solid content concentration to 30 wt%, thereby obtaining an aqueous polyurethane resin dispersion (Q-12) containing an ink blocking inhibitor in the same particle.

<Examples 13 and 14>
Aqueous polyurethane resin dispersions (Q-13, Q-14) were obtained in the same manner as in Example 1, except that the raw materials and amounts used were changed to those shown in Table 1.

<Comparative Examples 1 to 6>
Aqueous polyurethane resin dispersions (Q'-1) and (Q'-6) were obtained in the same manner as in Example 1, except that the raw materials and amounts used were changed to those shown in Table 1.

The composition of each raw material in Table 1 is as follows.
PTMG2000: Polytetramethylene ether glycol with Mn = 2,000 [manufactured by Mitsubishi Chemical Corporation]
PTMG1000: Polytetramethylene ether glycol with Mn = 1,000 [manufactured by Mitsubishi Chemical Corporation]
Sannix PP-2000: Polyoxypropylene glycol with Mn=2,000 [manufactured by Sanyo Chemical Industries, Ltd.]
ETERNACOLL UH-200: Polycarbonate diol with Mn=2,000 [manufactured by Ube Industries, Ltd.]

<Production of Printing Inks (L-1) to (L-14) and (L'-1) to (L'-6)>
2.7 parts of the polyurethane resin aqueous dispersions (Q-1) to (Q-14) or (Q'-1) to (Q'-6) obtained in Examples 1 to 14 or Comparative Examples 1 to 6, 25 parts of a pigment [carbon black aqueous dispersion {"Aqua-Black 162" manufactured by Tokai Carbon Co., Ltd., solid content concentration 20% by weight}], 10 parts of propylene glycol as a moisturizing agent, 1.0 part of 1,2-hexanediol as a penetrating agent, 1.0 part of 2-pyrrolidone, and 63 parts of water were charged into a container and mixed for 10 minutes to prepare printing inks (L-1) to (L-14) and comparative printing inks (L'-1) to (L'-6).

<Method for evaluating adhesion of printing ink>
Printing inks (L-1) to (L-14) and comparative printing inks (L'-1) to (L'-6) were applied to a polypropylene film (OPP) [Toyobo Co., Ltd. "Pylen P-2161" (thickness 30 μm)] and a polyester film (PET) [Toyobo Co., Ltd. "Espet E-5102" (thickness 12 μm)] with a bar coater so that the thickness after drying was 1 μm, and then dried at 90 ° C. for 10 minutes to prepare test pieces in which polyurethane resin was applied onto each resin film. In accordance with JIS K5600-5-6, a cutter knife was used to make 1 mm wide cuts on the dried film surface of the printing ink of the prepared test pieces so that 100 (10 × 10) squares were made, and a peeling test was performed with a transparent pressure-sensitive adhesive tape, and the number of squares remaining on the recording medium film was counted. The more the number of remaining squares, the better the adhesion of the printing ink.

<Method for evaluating blocking resistance and adhesion (lamination strength) of printing ink>
Printing inks (L-1) to (L-14) and comparative printing inks (L'-1) to (L'-6) were printed on the entire surface of a polypropylene film (OPP) [Toyobo Co., Ltd. "Pylen P-2161" (thickness 30 μm)] and a polyester film (PET) [Toyobo Co., Ltd. "Espet E-5102" (thickness 12 μm)] by the inkjet method, and then dried at 90 ° C for 10 minutes. An inkjet printer [Seiko Epson Co., Ltd. PX-105] was used for printing. However, for the comparative printing inks (L'-4 to L'-6), clogging of the ink head nozzle was confirmed during printing, and printing on the entire surface was not possible, so evaluation of adhesion (lamination strength) and blocking resistance was discontinued.

<Blocking resistance>
After printing ink was applied to the entire surface of a resin film, a piece of 4 cm x 8 cm was cut out and the printed surface of this sample was placed together with the untreated side of an unprinted film of the same size. The film was then peeled off at 50°C for 24 hours and a pressure of 7 kg/cm2 was applied, and the degree of peeling of the printed surface and the resistance were observed when the film was peeled off.
5 points: No peeling of the ink was observed from the printed matter, and no resistance was felt when peeling.
4 points: No peeling of the ink from the printed matter was observed, but there was resistance when peeling.
3 points: Peeling of the ink was observed from the print, but it was less than 10% of the entire printed surface.
2 points: Ink peeling occurred on 10% or more but less than 50% of the total printed area.
1 point: Ink peeling occurred on more than 50% of the printed area.
A score of 3 or more is a practical level.

<Adhesion (lamination strength)>
After printing ink was applied to the entire surface of the resin film, a PE film ["T.U.X HC-E" (thickness 25 μm) manufactured by Mitsui Chemicals Tohcello Inc.] was laminated as a sealant film using a laminating adhesive [Polybond AY-651A/AY-651C two-liquid type manufactured by Sanyo Chemical Industries, Ltd.], and after curing for 24 hours at 40°C, the tensile strength was measured using an Instron type tensile tester (Autograph manufactured by Shimadzu Corporation).

The lamination conditions were as follows:
Adhesive: AY-651A/AY-651C/ethyl acetate = 6.7/1/9.3 (solid content approx. 30%)
Application: Apply adhesive to the ink surface with bar coater #7 Drying conditions: 10 seconds with hot air from a dryer (approximately 80°C) Bonding: Bond the sealant film with a lamination tester [manufactured by Tester Sangyo Co., Ltd.]. (Lamination pressure: 0.1 MPa, 1 rotation, room temperature)
Curing: 40°C, 24 hours. The conditions for measuring adhesive strength are as follows.
Sample: 15 mm wide Peel speed: 50 mm/min

<Ink Viscosity>
In the present invention, the printing ink viscosity was measured using the following measuring device and conditions.
Apparatus: MCR92 (manufactured by Anton Paar)
Jig: 50 mm cone plate Shear rate: 200 1/s
Measurement temperature: 25℃

<Printing ink permeability>
100 g of printing ink was filtered by a vacuum filtration method, and the amount of ink passed until the filter was clogged was measured. When the entire amount of ink was passed through, the amount of ink passed through was taken as 100 g.
Filter: MF-Millipore SMWP04700
Filtration pressure: 50 kPa

The polyurethane resin aqueous dispersion of the present invention is an aqueous polyurethane resin dispersion for inkjet inks, and is useful as an ink raw material for printing on recording media such as resin media such as polycarbonate, hard PVC, soft PVC, polystyrene, expanded polystyrene, polymethyl methacrylate, polypropylene, polyethylene, polyethylene terephthalate, and nylon; paper media such as fine paper, art paper, coated paper, and cast coated paper; and inorganic media such as glass and stainless steel.

Claims (6)

An aqueous polyurethane resin dispersion for an ink-jet ink, comprising a polyurethane resin (U) obtained by reacting a polyol component with a polyisocyanate component, and water,
The polyurethane resin (U) is a polyurethane resin having a carboxyl group and/or a carboxylate anion group,
the polyol component is a polyol component containing polytetramethylene ether glycol,
The weight ratio of the polytetramethylene ether glycol is 10 to 70% by weight based on the total weight of the polyol component and the polyisocyanate component,
The polyisocyanate component is a polyisocyanate component containing isophorone diisocyanate,
The weight ratio of the isophorone diisocyanate is 25 to 70% by weight based on the total weight of the polyol component and the polyisocyanate component,
The polyurethane resin (U) has an acid value of 15 to 30 mgKOH/g;
The polyurethane resin aqueous dispersion has a urea group content of 0.15 to 0.45 mol/kg . The polyurethane resin aqueous dispersion according to claim 1, wherein the storage modulus G' at 50°C of the film obtained by drying the polyurethane resin aqueous dispersion at 105°C for 3 hours is 0.9 to 80 MPa. 3. The polyurethane resin aqueous dispersion according to claim 1, wherein the polyurethane resin (U) is contained in the polyurethane resin aqueous dispersion as polyurethane resin particles made of the polyurethane resin (U), and the polyurethane resin particles in the polyurethane resin aqueous dispersion contain the ink anti-blocking agent (E) within each particle . The polyurethane resin aqueous dispersion according to claim 3, wherein the polyurethane resin particles contain 0.1 to 10% by weight of the ink blocking inhibitor (E) based on the weight of the polyurethane resin (U). The polyurethane resin aqueous dispersion according to claim 3 or 4, wherein the ink blocking inhibitor (E) is a polyether-modified silicone. The polyurethane resin aqueous dispersion according to any one of claims 1 to 5, wherein the polyurethane resin (U) is contained in the polyurethane resin aqueous dispersion as polyurethane resin particles made of the polyurethane resin (U), and the volume average particle diameter of the polyurethane resin particles measured by a light scattering measurement method is 10 to 80 nm.