阅读说明：本技术 水性油墨 (Water-based ink ) 是由 王悦 佐藤阳 原口辰介 德江洋 芹泽昌史 于 2019-04-25 设计创作，主要内容包括：本发明提供一种颜料的分散性高、所得到的涂膜的平滑性和光泽度高的水性油墨。本发明的水性油墨是包含颜料、展色剂和水的水性油墨,所述水性油墨包含碱可溶型树脂(I)和复合树脂(II)作为所述展色剂,所述复合树脂(II)是氨基甲酸酯聚合物(e)和丙烯酸聚合物(f)的复合树脂。(The invention provides a water-based ink which has high pigment dispersibility and high smoothness and glossiness of an obtained coating film. The aqueous ink of the present invention is an aqueous ink containing a pigment, a vehicle and water, the aqueous ink containing an alkali-soluble resin (I) and a composite resin (II) as the vehicle, the composite resin (II) being a composite resin of a urethane polymer (e) and an acrylic polymer (f).)

1. An aqueous ink comprising a pigment, a vehicle and water,

the water-based ink comprises alkali-soluble resin I and composite resin II as the vehicle,

the composite resin II is a composite resin of a urethane polymer e and an acrylic polymer f.

2. The aqueous ink according to claim 1, wherein the composite resin II is an emulsion type resin.

3. The aqueous ink according to claim 1 or 2, wherein the alkali-soluble resin I is a neutralization product of a copolymer I' with an alkali,

the copolymer I' has a monomer unit derived from a styrene derivative a and a monomer unit derived from a vinyl compound b having an acid group.

4. The aqueous ink according to claim 3, wherein the copolymer I' further has a monomer unit derived from methyl methacrylate c.

5. The aqueous ink according to claim 4, wherein the copolymer I' further has a monomer unit derived from a vinyl-based monomer d other than the monomer unit derived from the styrene derivative a, the monomer unit derived from the acid group-containing vinyl compound b, and the monomer derived from methyl methacrylate c.

6. The aqueous ink according to claim 5,

relative to the mass of the copolymer I', in 100 mass%,

the content ratio of the monomer unit derived from the styrene derivative a is 5 to 30% by mass,

the content ratio of the monomer unit derived from the acid group-containing vinyl compound b is 4 to 20% by mass,

the content of the monomer unit derived from methyl methacrylate c is 5 to 70% by mass,

the content of the monomer unit derived from the vinyl monomer d is 10 to 70% by mass.

7. The aqueous ink according to claim 5 or 6, wherein the vinyl monomer d comprises an alkyl (meth) acrylate having an alkyl group with 4 to 15 carbon atoms.

8. The aqueous ink according to claim 5 or 6, wherein the vinyl monomer d comprises an alkyl (meth) acrylate having an alkyl group with 4 to 6 carbon atoms.

9. The aqueous ink according to claim 5 or 6, wherein the vinyl monomer d comprises an alkyl (meth) acrylate having an alkyl group with 7 to 10 carbon atoms.

10. The aqueous ink according to claim 8, wherein the vinyl monomer d further comprises an alkyl (meth) acrylate having an alkyl group with 7 to 10 carbon atoms.

11. The aqueous ink according to any one of claims 3 to 10, wherein the secondary transition temperature of the copolymer I' is 10 to 150 ℃.

12. The aqueous ink according to any one of claims 3 to 11, wherein the weight average molecular weight of the copolymer I' is 5000 to 30000.

13. The aqueous ink according to any one of claims 3 to 12, wherein the copolymer I' has an acid value of 35 to 200 mgKOH/g.

14. The aqueous ink according to any one of claims 3 to 13, wherein the mass ratio of the copolymer I 'to the composite resin II, i.e., the mass of the copolymer I' per the mass of the composite resin II, is 5/95 to 95/5.

15. The aqueous ink according to any one of claims 1 to 14, wherein the aqueous ink is an ink for gravure printing.

Technical Field

The invention relates to water-based ink.

The present application claims priority based on Japanese application No. 2018-087623, 4/27 in 2018, the contents of which are incorporated herein by reference.

Background

As a composition for a pigment-containing aqueous ink, for example, patent document 1 describes a composition obtained by mixing an aqueous solution of a vinyl polymer with an aqueous dispersion of a polyurethane polymer.

Patent document 2 describes a composition produced by allowing a polyurethane polymer to exist in the polymerization process of a vinyl monomer.

Disclosure of Invention

Problems to be solved by the invention

However, the water-based ink obtained by adding a pigment to the composition described in patent document 1 tends to decrease the smoothness and glossiness of the obtained coating film.

In addition, the aqueous ink obtained by adding a pigment to the composition described in patent document 2 has insufficient dispersibility of the pigment.

The invention aims to provide a water-based ink which has high pigment dispersibility and high smoothness and glossiness of an obtained coating film.

Technical scheme for solving problems

The present invention has the following aspects.

[1] An aqueous ink comprising a pigment, a vehicle and water,

the aqueous ink comprises alkali-soluble resin (I) and composite resin (II) as the color-spreading agent,

the composite resin (II) is a composite resin of a urethane polymer (e) and an acrylic polymer (f).

[2] The aqueous ink according to [1], wherein the composite resin (II) is an emulsion type resin.

[3] The aqueous ink according to [1] or [2], wherein the alkali-soluble resin (I) is a neutralization product of a copolymer (I') with an alkali,

the copolymer (I') has a monomer unit derived from a styrene derivative (a) and a monomer unit derived from an acid group-containing vinyl compound (b).

[4] The aqueous ink according to [3], wherein the copolymer (I') further has a monomer unit derived from methyl methacrylate (c).

[5] The aqueous ink according to [4], wherein the copolymer (I') further has a monomer unit derived from a vinyl-based monomer (d) other than the monomer unit derived from the styrene derivative (a), the monomer unit derived from the acid group-containing vinyl compound (b) and the monomer derived from methyl methacrylate (c).

[6] The aqueous ink according to [5], wherein,

with respect to the mass (100 mass%) of the copolymer (I'),

the content ratio of the monomer unit derived from the styrene derivative (a) is 5 to 30% by mass,

the content ratio of the monomer unit derived from the vinyl compound (b) containing an acid group is 4 to 20% by mass,

the content of the monomer unit derived from methyl methacrylate (c) is 5 to 70% by mass,

the content of the monomer unit derived from the vinyl monomer (d) is 10 to 70% by mass.

[7] The aqueous ink according to [5] or [6], wherein the vinyl monomer (d) contains an alkyl (meth) acrylate having an alkyl group with 4 to 15 carbon atoms.

[8] The aqueous ink according to [5] or [6], wherein the vinyl monomer (d) contains an alkyl (meth) acrylate having an alkyl group with 4 to 6 carbon atoms.

[9] The aqueous ink according to [5] or [6], wherein the vinyl monomer (d) contains an alkyl (meth) acrylate having an alkyl group with 7 to 10 carbon atoms.

[10] The aqueous ink according to [8], wherein the vinyl monomer (d) further contains an alkyl (meth) acrylate having an alkyl group with 7 to 10 carbon atoms.

[11] The aqueous ink according to any one of [3] to [10], wherein the secondary transition temperature of the copolymer (I') is 10 to 150 ℃.

[12] The aqueous ink according to any one of [3] to [11], wherein the weight average molecular weight of the copolymer (I') is 5000 to 30000.

[13] The aqueous ink according to any one of [3] to [12], wherein the acid value of the copolymer (I') is 35 to 200 mgKOH/g.

[14] The aqueous ink according to any one of [3] to [13], wherein the mass ratio of the copolymer (I ') to the composite resin (II) [ mass of copolymer (I')/mass of composite resin (II) ] is 5/95 to 95/5.

[15] The aqueous ink according to any one of [1] to [14], wherein the aqueous ink is an ink for gravure printing.

Effects of the invention

The water-based ink of the present invention has high pigment dispersibility, and the obtained coating film has high smoothness and glossiness.

Detailed Description

In the present specification and claims, "(meth) acrylate" means a generic term of acrylate and methacrylate. "(meth) acrylic acid" refers to the generic term of acrylic acid and methacrylic acid. "(meth) acryloyl" refers to the generic term acryloyl and methacryloyl.

"monomer unit" means a structural unit derived from a monomer constituting a polymer.

The aqueous ink of the present invention comprises a pigment, a vehicle and water.

(pigment)

The pigment contained in the aqueous ink of the present invention is a colorant, and may be either an inorganic pigment or an organic pigment, or may be both of them.

Examples of the inorganic pigment include titanium oxide, red iron oxide, and extender pigments. Examples of the organic pigment include azo-based, polycyclic and lake pigment-based organic pigments.

The content of the pigment contained in the water-based ink of the present invention varies depending on the type of the pigment, and is preferably 10 to 1000 parts by mass in the case of 100 parts by mass of the vehicle, more preferably 20 to 1000 parts by mass in the case of the inorganic pigment, and more preferably 10 to 600 parts by mass in the case of the organic pigment, for example, 20 to 60 parts by mass and more preferably 30 to 40 parts by mass in the case of titanium oxide.

When the content of the pigment in the aqueous ink is not less than the lower limit, the coating film formed from the aqueous ink can be sufficiently colored, and when the content is not more than the upper limit, the aggregation of the pigment can be easily prevented.

(spreading agent)

The vehicle contained in the water-based ink of the present invention contains an alkali-soluble resin (I) and a complex resin (II).

The alkali-soluble resin (I) is not particularly limited as long as it is an alkali-soluble resin, and is preferably a neutralized product of a copolymer (I') having a monomer unit derived from a styrene derivative (a) and a monomer unit derived from an acid group-containing vinyl compound (b) and a base.

The composite resin (II) is a composite resin which is a composite of the urethane polymer (e) and the acrylic polymer (f).

As the vehicle, vehicles other than the alkali-soluble resin (I) and the composite resin (II) may be contained.

< alkali-soluble resin (I) >

The alkali-soluble resin (I) is, for example, a neutralized product of a copolymer (I') having an acid group because it has a monomer unit derived from a vinyl compound (b) having an acid group and a base.

In this case, the copolymer of the alkali-soluble resin (I) which forms a salt by neutralizing the copolymer (I') has improved water solubility and can be dissolved in water. The acid groups of the copolymer (I') need not be completely neutralized, and the neutralization rate is preferably 30% or more, more preferably 70% or more. Here, the neutralization ratio is a ratio (%) of the number of moles of acid groups neutralized with a base to the number of moles of all acid groups in the copolymer (I').

[ copolymer (I') ]

The copolymer (I') is a copolymer having a monomer unit (hereinafter also referred to as "monomer (a) unit") derived from a styrene derivative (a) (hereinafter also referred to as "monomer (a)") and a monomer unit (hereinafter also referred to as "monomer (b) unit") derived from a vinyl compound (b) having an acid group (hereinafter also referred to as "monomer (b)").

The copolymer (I') may have a monomer unit derived from methyl methacrylate (c) (hereinafter also referred to as "monomer (c)") (hereinafter also referred to as "monomer (c) unit") in addition to the monomer (a) unit and the monomer (b) unit.

The copolymer (I ') may have, in addition to the monomer (a) unit and the monomer (b) unit, a monomer unit derived from a vinyl monomer (d) (hereinafter also referred to as "monomer (d)") other than the monomer (a) and the monomer (b) which is copolymerizable with the monomer (a) and the monomer (b) (when the copolymer (I') further contains the monomer (c) unit, a monomer unit derived from a vinyl monomer other than the monomer (a), the monomer (b) and the monomer (c) (hereinafter also referred to as "monomer (d) unit") which is copolymerizable with the monomer (c) is also included).

The copolymer (I') may have both the monomer (c) unit and the monomer (d) unit in addition to the monomer (a) unit and the monomer (b) unit.

The monomer (a) unit imparts gloss to a coating film of the aqueous ink. In addition, the monomer (a) unit contributes to improvement of compatibility of the alkali-soluble resin (I) with the composite resin (II).

Specific examples of the monomer (a) include styrene, α -methylstyrene, and p-methylstyrene.

The monomer (a) may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

Among the monomers (a), styrene is preferred from the viewpoint of ease of polymerization in the production of the copolymer (I').

The monomer unit derived from the monomer (b) imparts an acid group to the copolymer (I').

The monomer (b) is, for example, a vinyl compound having an acid group such as a carboxylic acid or a sulfonic acid, and specific examples thereof include monobasic acids such as acrylic acid, methacrylic acid, and crotonic acid; dibasic acids such as fumaric acid, maleic acid, and itaconic acid; anhydrides of these monobasic and dibasic acids; and partial esters of these dibasic acids.

The monomer (b) may be used alone in 1 kind or in combination of 2 or more kinds.

Among the monomers (b), monomers having a carboxylic acid are preferable from the viewpoint of water solubility of the alkali-soluble resin (I). Among the monomers having carboxylic acid, methacrylic acid and acrylic acid are preferable.

The monomer (c) unit contributes to the increase in hardness of the alkali-soluble resin (I). Therefore, the aqueous ink containing the alkali-soluble resin (I) having a monomer (c) unit can improve the hardness of the ink coating film.

The monomer (d) unit is used for adjusting the physical properties and characteristics of the polymer (I) depending on the amount or kind thereof. The monomer (d) is a monomer copolymerizable with the monomer (a), the monomer (b) and, if necessary, the monomer (c), and is a monomer other than the monomer (a), the monomer (b) and the monomer (c).

Specific examples of the monomer (d) include alkyl (meth) acrylates having an alkyl group having 2 to 18 carbon atoms, hydroxyalkyl (meth) acrylates, glycol di (meth) acrylates, alkylamino (meth) acrylates, other (meth) acrylates, and vinyl monomers other than (meth) acrylates.

Examples of the alkyl (meth) acrylate having an alkyl group with 2 to 18 carbon atoms include ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate.

Examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate.

Examples of the diol di (meth) acrylate include ethylene glycol di (meth) acrylate, butylene glycol (meth) acrylate, and the like.

Examples of the alkylamino (meth) acrylate include dimethylaminoethyl (meth) acrylate.

Examples of the other (meth) acrylic acid esters include dimethylaminoethyl (meth) acrylate methyl chloride salt, cyclohexyl (meth) acrylate, allyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycidyl (meth) acrylate, and the like.

Examples of the vinyl monomer other than the (meth) acrylate ester include vinyl acetate, vinyl propionate, and (meth) acrylonitrile.

The monomer (d) may be used alone in 1 kind or in combination of 2 or more kinds.

The monomer (d) preferably contains an alkyl (meth) acrylate having an alkyl group with 4 to 15 carbon atoms. When the copolymer (I') has an alkyl (meth) acrylate unit, the greater the number of carbon atoms in the alkyl group of the alkyl (meth) acrylate, the more the compatibility of the alkali-soluble resin (I) with the composite resin (II) tends to be improved. Further, the hardness of the alkali-soluble resin (I) tends to be increased as the number of carbon atoms in the alkyl group of the alkyl (meth) acrylate is smaller. For these reasons, the copolymer (I') preferably contains alkyl (meth) acrylate units having an alkyl group of 4 to 15 carbon atoms.

Among these, in the production of the aqueous ink, the monomer (d) is more preferably an alkyl (meth) acrylate having an alkyl group with 4 to 6 carbon atoms, from the viewpoint of improving the solubility of the alkali-soluble resin (I) in water.

In addition, from the viewpoint of further improving the dispersibility of the pigment in the aqueous ink, the monomer (d) is more preferably an alkyl (meth) acrylate having an alkyl group with 7 to 10 carbon atoms.

The monomer (d) more preferably contains both an alkyl (meth) acrylate having an alkyl group with 4 to 6 carbon atoms and an alkyl (meth) acrylate having an alkyl group with 7 to 10 carbon atoms.

When an alkyl (meth) acrylate having an alkyl group with 4 to 6 carbon atoms and an alkyl (meth) acrylate having an alkyl group with 7 to 10 carbon atoms are used together, the smoothness and gloss of the coating film of the water-based ink can be further improved.

When the copolymer (I') has the monomer (a) unit, the monomer (b) unit, the monomer (c) unit, and the monomer (d) unit, the preferable content ratio of each monomer unit is as follows.

The content of the monomer (a) unit in the copolymer (I ') is preferably 5 to 30% by mass, more preferably 8 to 20% by mass, based on 100% by mass of the copolymer (I').

When the content ratio of the monomer (a) unit is not less than the lower limit, the glossiness of the ink coating film can be further improved.

Further, if the content ratio of the monomer (a) unit is not more than the upper limit, the water solubility of the alkali-soluble resin (I) can be further improved.

The content ratio of the monomer (b) unit in the copolymer (I ') is preferably 4 to 20% by mass, more preferably 7 to 18% by mass, based on 100% by mass of the copolymer (I').

When the content ratio of the monomer (b) unit is not less than the lower limit, the water solubility of the alkali-soluble resin (I) can be further improved.

When the content ratio of the monomer (b) unit is not more than the upper limit, the smoothness and glossiness of the ink coating film can be further improved.

The content ratio of the monomer (c) unit in the copolymer (I ') is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, based on 100% by mass of the copolymer (I').

If the content ratio of the monomer (c) unit is not less than the lower limit, the hardness of the alkali-soluble resin (I) can be further improved.

When the content ratio of the monomer (c) unit is not more than the upper limit, the water solubility of the alkali-soluble resin (I) can be further improved.

The content ratio of the monomer (d) unit in the copolymer (I ') is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, based on 100% by mass of the copolymer (I').

When the content ratio of the monomer (d) unit is within the above range, the effect of having the monomer (d) unit can be sufficiently exhibited, and the effects of having the monomer (a) unit, the monomer (b) unit and the monomer (c) unit can be sufficiently exhibited.

Examples of the copolymer (I') include the following:

a styrene-acrylic resin obtained by copolymerizing a monomer mixture containing styrene as a monomer (a), (meth) acrylic acid as a monomer (b), and (meth) acrylic acid esters as monomers (c) and (d);

a styrene-maleic acid-acrylic resin obtained by copolymerizing a monomer mixture containing styrene as a monomer (a), maleic anhydride and (meth) acrylic acid as a monomer (b), and (meth) acrylic acid ester as a monomer (c) and a monomer (d);

a styrene-maleic acid resin obtained by copolymerizing a monomer mixture containing styrene as a monomer (a) and maleic anhydride as a monomer (b); and the like.

The secondary transition temperature, i.e., the glass transition temperature, of the copolymer (I') is preferably 10 to 150 ℃, more preferably 20 to 110 ℃, and further preferably 25 to 60 ℃.

The secondary transition temperature of the copolymer (I') was determined by Differential Scanning Calorimetry (DSC).

If the secondary transition temperature of the copolymer (I') is not less than the lower limit, the viscosity of the ink coating film is lowered, and therefore the stain resistance and blocking resistance of the printed matter tend to be improved.

If the secondary transition temperature of the copolymer (I') is not higher than the upper limit, the ink coating film becomes soft and the adhesion to the printed matter tends to be improved.

The secondary transition temperature of the copolymer (I ') can be adjusted, for example, by the composition of the monomer units constituting the copolymer (I').

The weight average molecular weight of the copolymer (I') is preferably 5000 to 30000, more preferably 6000 to 25000, and further preferably 6000 to 10000.

The weight average molecular weight of the copolymer (I') is a value measured by Gel Permeation Chromatography (GPC) and determined using standard polystyrene having a known molecular weight.

If the weight average molecular weight of the copolymer (I') is not less than the lower limit, the strength of the ink coating film tends to be improved.

If the weight average molecular weight of the copolymer (I') is not more than the upper limit, the compatibility of the alkali-soluble resin (I) with the composite resin (II) tends to be improved.

The average molecular weight of the copolymer (I') can be adjusted by, for example, appropriately adding a chain transfer agent such as n-dodecylmercaptan, 1-octylmercaptan, 2-ethylhexyl thioglycolate or the like during polymerization.

The acid value of the copolymer (I') is preferably 35 to 200mgKOH/g, more preferably 40 to 150mgKOH/g, and still more preferably 50 to 100 mgKOH/g.

The acid value of the copolymer (I') is: to the aqueous solution of the copolymer (I ') was added dropwise potassium hydroxide (KOH) dissolved in ethanol, and titration was carried out based on the color change point of phenolphthalein, to obtain a value represented by mg of KOH necessary for neutralizing 1g of the copolymer (I').

When the acid value of the copolymer (I') is not less than the lower limit, the water solubility of the copolymer (I) is further improved.

When the acid value of the copolymer (I') is not more than the above upper limit, the compatibility of the alkali-soluble resin (I) with the composite resin (II) and the water resistance of the coating film tend to be further improved.

The acid value of the copolymer (I ') increases as the content ratio of the monomer (b) unit in the copolymer (I') increases.

The copolymer (I') can be produced by polymerizing the monomer (a) and the monomer (b) and, if necessary, the monomer (c) and the monomer (d).

As a polymerization method for producing the copolymer (I'), various polymerization methods such as a suspension polymerization method, a solution polymerization method, a bulk polymerization method, and the like can be applied. Among these polymerization methods, the suspension polymerization method is preferable.

When the suspension polymerization method is applied, it is possible to easily produce alkali-soluble resin (I) having excellent pigment dispersibility and excellent compatibility with composite resin (II).

[ alkali ]

Examples of the base used for the neutralization for producing the copolymer (I') of the alkali-soluble resin (I) include organic metal hydroxides, ammonia, amine compounds, morpholine and the like.

Examples of the organic metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.

Examples of the amine compound include triethylamine, propylamine, diethylamine, tripropylamine, dibutylamine, pentylamine, 1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol, 2-diethylaminoethanol, 1-amino-2-propanol, 2-amino-1-propanol, 3-amino-1-propanol, 1-dimethylamino-2-propanol, 3-dimethylamino-1-propanol, 2-propylamine, ethoxypropylamine, aminobenzyl alcohol, and the like.

Among the bases, ammonia and amine compounds are preferable from the viewpoint of being easily volatilized at the time of drying and being less likely to remain in the ink coating film after drying.

The alkali can be used alone in 1, also can be used simultaneously in more than 2.

< composite resin (II) >

The composite resin (II) is a polymer obtained by compounding a urethane polymer (e) (hereinafter also referred to as "polymer (e)") and an acrylic polymer (f) (hereinafter also referred to as "polymer (f)").

The polymer (e) and the polymer (f) are compounded in the sense that the polymer (e) adheres to the polymer (f).

For example, a polymer in which the polymer (e) and the polymer (f) are compounded can be obtained by polymerizing a (meth) acrylic monomer in the presence of the polymer (e) to form the polymer (f) and simultaneously adhering the polymer (f) to the polymer (e).

The polymer (e) is a urethane polymer obtained by reacting a polyol with a polyisocyanate. That is, the polymer (e) is a reaction product of a polyol and a polyisocyanate.

The polyol is an organic compound having 2 or more hydroxyl groups per molecule, and various polyols including known polyols can be used.

Specific examples of the polyol include low molecular weight polyols having a number average molecular weight of 500 or less, polyether diols, polyester polyols, polyether polyols, polycarbonate polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, polyacrylate polyols, and the like.

Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, hexanediol, and cyclohexanedimethanol.

Examples of the polyether diol include polyols obtained by addition polymerization of at least 1 of the low molecular weight polyols with ethylene oxide, propylene oxide, tetrahydrofuran, and the like.

Examples of the polyester polyol include polyols obtained by polycondensation of at least 1 of the low-molecular-weight polyols with dicarboxylic acids such as adipic acid, sebacic acid, itaconic acid, maleic anhydride, terephthalic acid, and isophthalic acid.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polycaprolactone polyol, polytetramethylene ether polyol, and the like.

The polyhydric alcohol may be used alone in 1 kind or in combination of 2 or more kinds.

The polyisocyanate is an organic compound having 2 or more isocyanate groups per molecule, and various polyisocyanates including known ones can be used.

Specific examples of the polyisocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

Examples of the aliphatic polyisocyanate include ethylene diisocyanate, tetramethylene diisocyanate, Hexamethylene Diisocyanate (HDI), dodecamethylene diisocyanate, 1,6, 11-undecane triisocyanate, 2, 4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2, 6-diisocyanatomethylhexanoate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2, 6-diisocyanatohexanoate.

Examples of the alicyclic polyisocyanate include isophorone diisocyanate (IPDI), 4' -dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis (2-isocyanatoethyl) -4-cyclohexene-1, 2-dicarboxylate, 2, 5-norbornane diisocyanate, 2, 6-norbornane diisocyanate and the like.

Examples of the aromatic polyisocyanate include 1, 3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, 2, 4-Toluene Diisocyanate (TDI), 2, 6-toluene diisocyanate, 4 ' -diphenylmethane diisocyanate (MDI), 2, 4-diphenylmethane diisocyanate, 4 ' -diisocyanate biphenyl, 3 ' -dimethyl-4, 4 ' -diisocyanatodiphenylmethane, 1, 5-naphthalene diisocyanate, 4 ', 4 ″ -triphenylmethane triisocyanate, m-isocyanatobenzenesulfonyl isocyanate, and p-isocyanatobenzenesulfonyl isocyanate.

The polyisocyanate may be used alone in 1 kind or in combination of 2 or more kinds.

The polymer (f) is a polymer having a structural unit derived from a (meth) acrylic monomer.

The (meth) acrylic monomer is a monomer having a (meth) acryloyl group.

Examples of the (meth) acrylic monomer include alkyl (meth) acrylates, hydroxyalkyl (meth) acrylates, and (meth) acrylic acids.

Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate.

Examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate.

Examples of the (meth) acrylic acid include acrylic acid and methacrylic acid.

The (meth) acrylic monomer may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The polymer (f) may have a radical polymerizable monomer unit other than the monomer unit derived from the (meth) acrylic monomer.

The radical polymerizable monomer is a monomer having a radical polymerizable group. The radical polymerizable group means a group including a radically polymerizable carbon-carbon unsaturated double bond, a radically polymerizable carbon-carbon unsaturated triple bond, a radically ring-opening polymerizable ring, and the like.

Examples of the radical polymerizable monomer other than the (meth) acrylic monomer include aromatic vinyl compounds such as styrene, and vinyl cyanide compounds such as acrylonitrile. The radical polymerizable monomer unit other than the monomer unit derived from the (meth) acrylic monomer in the polymer (f) is preferably 30% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less.

The content ratio of the polymer (e) to the polymer (f) in the composite resin (II) is preferably 10 to 900 parts by mass, more preferably 30 to 300 parts by mass, and still more preferably 50 to 200 parts by mass, based on 100 parts by mass of the polymer (e).

When the content of the polymer (f) is within the above range relative to 100 parts by mass of the polymer (e), the properties of each component can be sufficiently exhibited, and the improvement of the pigment dispersibility, the smoothness of the coating film and the gloss can be further facilitated.

The composite resin (II) is preferably an aqueous dispersion dispersed in water, i.e., an emulsion type resin.

Examples of the method for producing the aqueous dispersion of the composite resin (II) include the methods described in jp 2010-163612 a and the like.

Specifically, a (meth) acrylic monomer and, if necessary, a radical polymerizable monomer other than the (meth) acrylic monomer are added to the aqueous dispersion of the polymer (e) to perform radical polymerization, thereby forming a polymer (f), and a composite resin (II) is obtained.

As the aqueous dispersion of the polymer (e), a commercially available polyurethane resin emulsion may be used, or an aqueous dispersion of the polymer (e) may be prepared by producing the polymer (e).

Examples of the method for producing the polymer (e) include a method in which a polyol and a polyisocyanate are reacted in an ether such as dioxane. In the above reaction, a urethanization catalyst such as dibutyltin dilaurate may be used.

The aqueous dispersion of the polymer (e) can be prepared by emulsifying the polymer (e).

Examples of the method for emulsifying the polymer (e) include a method in which a carboxyl group is introduced into the polymer (e) and dispersed in water; a method of dispersing the polymer (e) in water using an emulsifier.

It is also possible to introduce a carboxyl group into the polymer (e) and disperse the polymer (e) in water using an emulsifier to obtain an aqueous dispersion of the polymer (e).

The emulsifier may be any of an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant.

The amount of the emulsifier added is preferably 0.05 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the total monomers.

The emulsifier can be used singly or in combination of 1 or more than 2.

In the aqueous dispersion of the polymer (e), the polymer (e) is in the form of particles. The volume average particle diameter of the polymer (e) particles contained in the aqueous dispersion of the polymer (e) is preferably 30nm or more.

When the volume average particle diameter of the polymer (e) particles is not less than the lower limit, the viscosity of the aqueous dispersion decreases and the fluidity increases.

On the other hand, the volume average particle diameter of the polymer (e) particles is preferably 300nm or less, more preferably 150nm or less. When the volume average particle diameter of the polymer (e) particles is not more than the above upper limit, the average particle diameter of the resulting composite resin (II) can be prevented from becoming coarse, and the storage stability can be improved.

The solid content of the aqueous dispersion of the polymer (e) is preferably 10 to 70% by mass, more preferably 25 to 60% by mass.

If the solid content of the aqueous dispersion of the polymer (e) is not less than the lower limit, the solid content of the aqueous ink can be easily increased.

If the solid content of the aqueous dispersion of the polymer (e) is not more than the upper limit, the viscosity of the aqueous ink can be easily reduced.

When the polymer (e) is produced in the presence of an organic solvent, the organic solvent is preferably removed from the aqueous dispersion.

To the aqueous dispersion of the polymer (e) obtained, a (meth) acrylic monomer and, if necessary, a radically polymerizable monomer other than the (meth) acrylic monomer are added to carry out radical polymerization.

The method of adding the monomer to the polymer (e) may be a method of adding the monomer at once, a method of adding the monomer continuously, or a method of adding the monomer sequentially.

In the radical polymerization, a radical polymerization initiator is added and heated to polymerize the monomer. The polymerization forms a polymer (f), and a composite resin (II) in which the polymer (e) and the polymer (f) are combined is obtained.

As the radical polymerization initiator, known radical polymerization initiators such as azo compounds, persulfates, organic peroxides, and the like can be used without limitation. The amount of the radical polymerization initiator added is preferably 0.01 to 5 parts by mass, and preferably 0.05 to 2 parts by mass, based on 100 parts by mass of the total monomers.

The heating temperature is usually set to be in the range of 30 to 90 ℃.

As described above, when the (meth) acrylic monomer is added to the aqueous dispersion of the polymer (e) and polymerized, the polymer (f) can be formed by polymerizing the (meth) acrylic monomer in the presence of the polymer (e) and can be brought into close contact with the polymer (e). Therefore, the composite resin (II) which is a composite of the polymer (e) and the polymer (f) can be easily obtained.

< ratio of copolymer (I') to composite resin (II) >

The vehicle preferably contains the alkali-soluble resin (I) and the composite resin (II) in such a manner that the mass ratio of the copolymer (I ') to the composite resin (II) [ mass of the copolymer (I')/mass of the composite resin (II) ] is 5/95 to 95/5, and more preferably 20/80 to 65/35.

If the mass ratio of the copolymer (I ') to the composite resin (II) is not less than the lower limit, that is, if the copolymer (I') is contained in a certain amount or more, the pigment dispersibility is further improved.

When the mass ratio of the copolymer (I') to the composite resin (II) is not more than the upper limit, that is, the composite resin (II) is contained in a certain amount or more, the strength of the coating film is increased, and the compatibility of the alkali-soluble resin (I) with the composite resin (II) is further improved.

< other vehicle >

The other vehicle is a polymer other than the alkali-soluble resin (I) and the composite resin (II).

Examples of the other vehicle include natural resins such as acrylic resin, casein resin, and shellac resin which do not contain a unit of the monomer (a). Examples of the other vehicle include emulsion type resins other than the composite resin (II), and colloidal dispersion type resins.

Other vehicles may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

(solvent)

The aqueous ink of the present invention contains water. In the aqueous ink of the present invention, water is used as the solvent, but a solvent other than water may be contained.

Examples of the solvent other than water include an alcohol-based solvent, a glycol-based solvent, and a carbitol-based solvent.

The solvent other than water may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

When a solvent other than water is used, the content of the solvent other than water is preferably 3 to 60% by mass, more preferably 5 to 50% by mass, based on 100% by mass of the total solvent.

If the content ratio of the solvent other than water is not less than the lower limit, the dispersibility of the vehicle in the aqueous ink can be further improved.

If the content of the solvent other than water is not more than the upper limit, the material is said to be aqueous.

(adjuvant)

The aqueous ink of the present invention may also contain adjuvants other than a solvent containing a pigment, a vehicle and water.

Examples of the auxiliary agent include an antifoaming agent such as a silicone resin, a lubricant such as a polyethylene wax, a leveling agent such as a surfactant, a pigment dispersant for further improving the dispersibility of the pigment, and an antiseptic agent.

(method for producing Water-based ink)

The water-based ink of the present invention is produced by mixing a pigment, a vehicle and water.

An example of the method for producing the aqueous ink of the present invention includes a method including the following varnish production step, pigment dispersion step, and product finishing step. However, the method for producing the aqueous ink of the present invention is not limited to the following production method.

< varnish production Process >

The varnish production step includes mixing the copolymer (I'), an aqueous alcohol solution and a base to produce a water-soluble varnish.

In this step, the copolymer (I') is neutralized with an alkali to form an alkali-soluble resin (I), and the alkali-soluble resin (I) is dissolved in water. The aqueous solution of the alkali-soluble resin (I) is referred to as a water-soluble varnish. The mixing may be carried out with or without heating.

The concentration of the water-soluble varnish is preferably 20 to 40% by mass in view of the viscosity at which the pigment slurry becomes easy to handle in the pigment dispersion step described later.

The pH of the water-soluble varnish is preferably 6 to 9, and the alkali-soluble resin (I) can be stably dissolved.

< pigment Dispersion step >

The pigment dispersion step includes mixing of a pigment and a water-soluble varnish and kneading of a premix obtained using a disperser to produce a premix.

The coagulated pigment is dispersed by kneading to produce a pigment slurry in which the copolymer (I') is adsorbed on the surface of the pigment.

Examples of the dispersing machine used in kneading include a bead mill, a sand mill, a ball mill, an attritor, a roll mill, and the like.

< finishing Process of product >

The product finishing process comprises mixing of the pigment slurry with an aqueous dispersion of the composite resin (II) for the manufacture of an aqueous ink.

In the product finishing step, a diluent containing at least one of water and an organic solvent may be added as necessary to adjust the solid content concentration of the aqueous ink.

When the aqueous ink contains an auxiliary agent, the auxiliary agent is appropriately mixed in the finishing step of the product. However, the auxiliary agent may be mixed in a step prior to the product finishing step.

(use of Water-based ink)

The aqueous ink of the present invention is printed on the surface of a printed matter such as a resin film, a resin molded product, and paper. The printed matter is colored by forming an ink coating film by printing.

Examples of the printing method include a gravure printing method, an offset printing method, a flexographic printing method, an inkjet printing method, a spray coating method, a roll coating method, a bar coating method, an air knife coating method, a casting method, a brush coating method, and a dip coating method.

The aqueous ink of the present invention can be suitably used for gravure printing. That is, the water-based ink of the present invention is preferably an ink for gravure printing.

The drying conditions after the formation of the ink coating film may be appropriately selected depending on the printing method and the like.

For example, when gravure printing is performed on a resin film, the film is preferably dried at a temperature of 20 to 60 ℃ for 10 seconds to 10 hours.

When ammonia or an amine compound is used as the base of the copolymer (I), the base is easily volatilized at the time of drying after the ink coating film is formed. Therefore, the ink coating film formed from the aqueous ink containing the alkali-soluble resin (I) and the composite resin (II) becomes a coating film containing the copolymer (I') and the composite resin (II).

(Effect)

The aqueous ink of the present invention contains an alkali-soluble resin (I) and a composite resin (II) as a vehicle, the composite resin (II) being a composite resin of a polymer (e) and a polymer (f).

According to the water-based ink of the present invention, the dispersibility of the pigment can be improved, and the smoothness and glossiness of the obtained ink coating film can be improved.