JPH06345997A - Aqueous pigment dispersion and water-base coating composition containing the same - Google Patents

Abstract

PURPOSE:To obtain an aqueous pigment dispersion which gives a coating film excellent in gloss, tinting strength and water resistance and is excellent in fluidity and storage stability by mixing a pigment, a specified pigment dispersant and an aqueous resin each in a specified amount with water. CONSTITUTION:This pigment dispersion contains: 100 pts.wt. pigment (e.g. copper phthalocyanine); 0.1-50 pts.wt. pigment dispersant formed by neutralizing a resin containing an acidic functional group (e.g. an acrylic acid/styrene copolymer resin) with a basic pigment derivative represented by the formula P-[X-(CH2)m-N(R1, R2)]n [ wherein P is a residue of at least one organic coloring matter group selected from azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, anthrapyrimidine, anstanthrone, indanthrone, etc.; X is direct linkage or a divalent bonding group; R1 and R2 are each H, (substituted)alkyl, aryl or a heterocyclic ring optionally containing O or N; and (m) and (n) are each 1 to 4] preferably to a degree of neutralization of 60-300%; 5-200 pts.wt. aqueous rein (e.g. acrylic resin); and water.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] The present invention is excellent in gloss, tinting strength and water resistance of a film when used in a water-based paint or ink.
The present invention relates to an aqueous pigment dispersion having good fluidity and storage stability.

[0002]

2. Description of the Related Art Conventionally, in paints, printing inks, etc.,
Dispersants have been used to enable pigments to fully function as colorants. This is because when manufacturing paints, printing inks, etc., there is a pigment dispersion process that consumes a large amount of energy. If a dispersant is not used, the dispersion time will become longer and production efficiency will decrease, or dispersion after dispersion will occur. This is because stability becomes worse. On the other hand, in recent years, paints and printing inks using a water-based resin containing water as a diluent have been demanded from the viewpoints of preventing air pollution and saving expensive organic solvents. As the water-based resin, water-based acrylic resin, water-based epoxy resin, water-based polyester resin, water-based urethane resin, etc. have been used.

Conventionally, the effect of the pigment dispersant has been well obtained for the dispersion of the pigment in the system using the organic solvent. That is, by adsorbing a pigment derivative on the surface of a pigment, an adsorbing point and a binding point are formed on a pigment having a small adsorbing point, and a resin is adsorbed on the pigment to improve the dispersion efficiency and dispersion stability. In order to maximize the excellent dispersion effect of the pigment derivative, the pigment derivative is dissolved in a solvent and an anchor part having a structure similar to or the same as the pigment used is adsorbed on the pigment surface, and the substituent of the tail part is It is necessary to generate strong hydrogen bonds and ionic bonds with the polymer in the vehicle to be used, and use these as adsorption points to promote resin adsorption.

In a system using an organic solvent, there is no problem in dissolving the pigment derivative in the solvent, which is the first condition to bring out the effect of the pigment derivative, and an optimum pigment dispersant is selected from various pigment derivatives. It was possible to However, in a system using water, since the polarity of water is much higher than that of an organic solvent, the pigment derivative cannot exhibit a sufficient dispersion effect, and there are some problems in the method of use. Specifically, since the pigment derivative has a large pigment skeleton as an anchor, it has low solubility in an aqueous system. Therefore, as in the case of using it in an organic solvent system, in the method of simultaneously adding the pigment and the resin at the time of dispersion, the pigment derivative is highly aggregated, and it was necessary to increase the addition amount of the pigment derivative in order to obtain the dispersion effect. .

Therefore, a method in which a pigment derivative is previously slurry-blended with a pigment in an aqueous solvent and dispersed with a resin, or a method in which a pigment derivative is previously slurry-blended with an aqueous resin and then dispersed with a pigment, We investigated how to effectively use the pigment derivative, but problems such as determining the proper amount of the pigment derivative added and examining the usage method depending on the type of pigment derivative occurred. In other words, the pigment derivative is agglomerated in an aqueous system, and it is difficult to effectively use the pigment derivative. That is, the low solubility of the pigment derivative in water poses a problem. Further, when the amount of the pigment derivative added is large, there is a drawback that the coating performance such as water resistance and corrosion resistance is deteriorated due to the hydrophilic functional group of the pigment derivative remaining in the coating.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive research on effective dispersion using conventional pigment derivatives, and as a result, neutralized acidic functional group-containing resins with basic pigment derivatives. The present inventors have found that a pigment dispersant formed by adsorbing a resin in the pigment adsorbs the resin in an aqueous system, and thus the present invention has been accomplished. The pigment dispersant of the present invention is dissolved or finely dispersed in an aqueous system, and its anchor portion is adsorbed to the pigment while the amount of the pigment derivative used is small. Then, the tail portion of the pigment derivative is made to act on the adsorption with the resin, and the resin adsorption is promoted.

[0007]

The present invention provides a pigment dispersant containing 0.1 to 50 parts by weight of a pigment and an acidic functional group-containing resin neutralized with a basic pigment derivative represented by the following general formula (1).
An aqueous pigment dispersion containing 1 part by weight, 5 to 200 parts by weight of an aqueous resin, and water is provided. _{P- [X- (CH 2) m} -N (R 1, R 2)] n Formula (1) (wherein, P is an azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, anthrapyrimidine pyridinium Ji system , Ansanthrone, indanthrone, flavanthrone, pyranthrone, perylene, perinone, thioindigo, diketopyrrolopyrrole, isoindolinone, isoindoline, quinophthalone Dye residue, X is a direct bond or a divalent bond group, R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group which may have a substituent, an aryl group, or a nitrogen atom for R ₁ and R _2. Or a heterocycle which may contain an oxygen atom, m is an integer of 1 to 4, and n is an integer of 1 to 4, respectively.)

Examples of the acidic functional group-containing resin include acrylic resin, urethane resin and polyester resin, and acrylic resin is particularly preferable. The acid value of the acidic functional group-containing resin is preferably 5 to 95. When the acid value is less than 5, the pigment dispersant becomes poorly dispersed, and when the acid value exceeds 95, the water resistance of the film cannot be obtained when the aqueous pigment dispersion of the present invention is used in paint or ink. Furthermore, it is preferable that the acidic functional group-containing resin has a weight average molecular weight of 30,000 to 200,000 because of its properties as an aqueous dispersion.

The acidic functional group-containing resin is, for example, an alcohol solvent such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol or n-butanol, or a water such as ethylene glycol or diethylene glycol mono- or dialkyl ether. Using miscible organic solvent,
It is obtained by heating and mixing an acidic functional group-containing monomer and, if necessary, a monomer having no acidic functional group, and polymerizing with a polymerization initiator. The polymerization initiator is dissolved in an organic solvent and added at a constant rate to the heated monomer solution. The addition time is
It is selected in the range of 0.5 to 12 hours.

As the acidic functional group-containing monomer, a carboxyl group-containing monomer is preferable, and acrylic acid, propiolic acid, methacrylic acid, alkenyl monocarboxylic acid,
Crotonic acid, tiglic acid, oleic acid, docosenoic acid, sorbic acid, farnesyl acetic acid, maleic acid, fumaric acid,
At least one selected from itaconic acid and alkenyl-substituted succinic acid is used.

As the monomer having no acidic functional group,
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, (meth ) 2-Ethylhexyl acrylate, Dodecyl (meth) acrylate, (Meth)
(Meth) acrylic acid alkyl esters such as cetyl acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, vinyltoluene, α-
Styrene monomer such as methyl styrene, vinyl acetate,
Vinyl propionate, (meth) acrylamide, acrylonitrile, vinyl stearate, divinylbenzene,
Diisopropenylbenzene, acrylic acetate, diallyl adipate, dimethyl itaconate, diethyl mariate, acrylic alcohol, vinyl chloride, vinylidene chloride, ethylene and the like are used.

Further, a monomer having a hydroxyl group or an amide group in at least a part thereof, specifically, ethylene glycol mono (meth) acrylate, diethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, propylene glycol mono ( (Meth) acrylate, dipropylene glycol mono (meth) acrylate, glycerin mono or di (meth) acrylate, trimethylolpropane mono or di (meth) acrylate, pentaerythritol mono or di or tri (meth) acrylate, N-methylol ( It is also possible to use (meth) acrylamide, (meth) acrylic amine, and the like.

Examples of the polymerization initiator include inorganic peroxide compounds such as potassium or ammonium persulfate, hydrogen peroxide and percarbonate, which are radicals which generate radicals under the conditions of the polymerization reaction, and acyl peroxides (for example, peroxides). Organic peroxides such as benzoyl oxide), alkylhydroperoxides (eg tertiary butyl hydroperoxide, p-menthahydroperoxide), dialkyl peroxides (eg tertiary butyl peroxide), azo compounds (eg azobis) Isobutyronitrile)
Etc. are used. Inorganic and organic peroxide compounds can be used as a redox catalyst in combination with a reducing agent. Examples of the reducing agent include sodium sulfite and acidic sodium sulfite.

The pigment derivative of the present invention has the general formula
The pigment derivative having a basic group represented by (1) is used.
X in the general formula (1) may be a direct bond or a divalent linking group. -C as the divalent linking group
_{H 2 NH -, - SO 2} NH -, - CH 2 NHCO -, -
_{CH 2 NHCOCH 2 NH -, -} CONH- , etc. are preferable.

The above acidic functional group-containing resin is replaced by the above general formula (1)
The pigment dispersant of the present invention can be obtained by neutralizing with a basic pigment derivative represented by The neutralization rate of the resin containing an acidic functional group is preferably 60 to 300%. If the neutralization rate is less than 60%, the effect of the resin will be large, and the effect of the pigment derivative will not be obtained. If it exceeds 300%, the effect of the pigment derivative will be too large, and the dispersant composed of the pigment derivative and the resin will be dispersed in water. The properties and water resistance are reduced, and neither effect as a pigment dispersant can be obtained.

As a neutralization method, there is a method in which a basic pigment derivative is gradually added to an acidic functional group-containing resin solution while heating the resin solution, if necessary, and mixed and stirred. At this point, the pigment derivative and the resin are in the form of a paste to a solution, and the dispersant may be used in this state. Alternatively, after that, water is gradually added, and when mixed and stirred, most of it becomes a slurry state as a salt insoluble in water, so adjust the pH to near neutral, and filter and wash to form a paste. The pigment dispersant may be used as it is, or may be further dried and pulverized to be powdered.

The acidic functional group-containing resin solution may use only water as a solvent, but if necessary, ethyl alcohol,
An alcohol solvent such as isopropyl alcohol, n-propyl alcohol, n-butanol or a water-miscible organic solvent such as a mono- or dialkyl ether of ethylene glycol or diethylene glycol may be mixed up to 50% by weight in the aqueous solvent. it can. When the acidic functional group-containing resin is neutralized with the basic pigment derivative, the acidic functional group may be partially neutralized with a basic substance such as amine or ammonia. The neutralization rate at this time is preferably less than 40%.

The basic substance is preferably a substance which volatilizes during the heat drying or heat curing step after coating or printing an aqueous paint or aqueous ink produced using the aqueous pigment dispersion of the present invention. The first of these is
, Secondary and tertiary amine compounds such as methylamine, ethylamine, butylamine, dimethylamine,
Diethylamine, dibutylamine, trimethylamine,
Examples include triethylamine, tributylamine, ethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-aminoethylethanolamine, N-methyldiethanolamine, and ammonium hydroxide.

100 parts by weight of pigment, 0.1 to 50 of the above pigment dispersant
By mixing and dispersing parts by weight, 5 to 200 parts by weight of the aqueous resin and water, the aqueous pigment dispersion of the present invention can be obtained.
If the amount of the above-mentioned pigment dispersant used is less than 0.1 part by weight, the pigment dispersing effect due to the pigment derivative cannot be obtained, and even if it is used in excess of 50 parts by weight, the effect of the amount used cannot be obtained.

As the water-based resin, an acrylic copolymer system,
Styrene-acrylic acid copolymer system, styrene-maleic acid copolymer system, alkyd-based, epoxy-based, polyester-based, urethane-based water-dispersible resin and water-soluble resin are used, but especially acrylic copolymer-based water is used. Dispersible resins and water-soluble resins are preferred. The amount of the aqueous resin used is 5 to 200 parts by weight in terms of solid content based on 100 parts by weight of the pigment. If the amount is less than 5 parts by weight, the pigment will not be completely dispersed,
If the amount is more than the amount by weight, the dispersion stability becomes poor and separation or the like occurs over time.

The acrylic copolymer water-dispersible resin is, for example, 50 to 80% by weight of a (meth) alkyl ester-modified monomer, 5 to 30% by weight of an acid functional group-containing monomer, and other monomers in an aqueous medium containing an emulsifier. Weight average molecular weight of 5,000 obtained by adding 0 to 20% by weight of a mixture and emulsion polymerization.
It is a resin with ~ 300,000 and an acid value of 1 ~ 200. A high molecular weight dispersant may be used instead of or in combination with the emulsifier. The acrylic copolymer-based water-dispersible resin and water-soluble resin can also be obtained by neutralizing the carboxylic acid incorporated in the resin with amine, ammonia or the like and dispersing it in the aqueous dispersion. For example, it can be obtained by neutralizing an acrylic copolymer resin having a free carboxylic acid polymerized in a hydrophilic organic solvent with an organic amine and adding water.

As the method for producing the aqueous pigment dispersion of the present invention, for example, 1) a pigment composition obtained by previously mixing a pigment and a pigment dispersant is added to an aqueous resin solution or dispersion and dispersed. ) Gradually add and disperse the pigment and the pigment dispersant to the aqueous resin solution or dispersion, and 3) mix the dispersion obtained by previously dispersing the pigment and the pigment dispersant in the aqueous resin solution or dispersion. 4) A method in which a pigment is dispersed in an aqueous resin solution or dispersion and then a pigment dispersant is added to the obtained dispersion.

In the method of 1) above, the desired effect can be obtained by simply mixing the pigment powder and the pigment dispersant, but the kneader, roll mill, attritor, super mill, various pulverizers, etc. Solution, or by adding a solution containing a pigment dispersant to a suspension system of the pigment in water or a water-miscible organic solvent to deposit the pigment dispersion on the surface of the pigment, or to dissolve the water-miscible organic solvent. Even better results can be obtained by performing a close mixing method such as co-dissolving the solvent, the pigment, and the pigment dispersant and coprecipitating with a poor solvent such as water. In the above methods 2) to 4), a disperser, a high speed mixer, a homomixer, a kneader, a roll mill, a sand mill, an attritor or the like can be used as a dispersing machine to disperse the pigment well.

The aqueous medium used in the aqueous resin solution or dispersion may be only water, but in some cases, alcohol solvents such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butanol and the like. A water-miscible organic solvent such as ethylene glycol or a mono- or dialkyl ether of diethylene glycol can be mixed up to 50% by weight in the aqueous medium.

[0025]

EXAMPLES The present invention will be described below with reference to examples. In the examples, “part” means “part by weight” and “%” means “% by weight”. Synthesis Examples 1 to 3 of the acidic functional group-containing resin used for the pigment dispersant are shown below. (Synthesis Example 1) 100 parts of n-butyl cellosolve was placed in a reaction vessel and heated to 100 ° C. Next, a mixture having the following composition was added dropwise over about 3 hours. The reaction was performed under a nitrogen atmosphere. Acrylic acid 10 parts Styrene 90 parts While keeping the reaction temperature at 100 ° C and stirring the reaction solution,
0.5 part of azobisisobutyronitrile was added to the above mixture and added dropwise. Azobisisobutyronitrile after dropping
0.1 part was added, and the reaction was carried out for 2 hours while maintaining the temperature at 100 ° C. An acidic functional group-containing resin solution A (nonvolatile content: 50%) having a weight average molecular weight of 70,000 and an acid value of 80 was obtained.

(Synthesis Example 2) Using a mixture having the following composition,
In the same manner as in Synthesis Example 1, weight average molecular weight 150,000, acid value 65
To obtain a resin solution B containing an acidic functional group (50% non-volatile content). Methacrylic acid 10 parts Ethyl acrylate 40 parts Methyl methacrylate 40 parts Styrene 10 parts

(Synthesis Example 3) Using a mixture having the following composition,
In the same manner as in Synthesis Example 1, weight average molecular weight 40,000, acid value 26
To obtain a resin solution C containing an acidic functional group (50% nonvolatile content). Methacrylic acid 4 parts Butyl methacrylate 16 parts 2-Hydroxyethyl methacrylate 80 parts

(Production Examples 1 to 12 of Pigment Dispersant) Pigment dispersants having the compositions shown in Table 1 were produced as follows. The acidic functional group-containing resin solution was heated to 100 ° C, the pigment derivative was gradually added while stirring and mixing, and the mixture was stirred at 100 ° C for 30 minutes. Water was gradually added, and the mixture was stirred at 70 ° C. for 30 minutes, adjusted to pH 7 with triethylamine, filtered, washed with water and dried to obtain a pigment dispersant. However, the pH was not adjusted if the pH exceeded neutrality.

[0029]

[Table 1]

[Examples 1 to 14 and Comparative Examples 1 to 18] Table 2
And 12.5 parts of pigment, pigment dispersant, acrylic resin solution (solid content 20%), 20 parts of ion-exchanged water and 150 parts of 3 mmφ alumina beads are placed in a 225 ml glass container and dispersed for 3 hours with a paint conditioner. Then, an aqueous pigment dispersion was prepared and the fluidity was evaluated. The results are shown in Tables 2 and 3. Then, 37.5 parts of the acrylic resin and 4.3 parts of a methylated melamine resin (“Cymel 303” manufactured by Mitsui Cyanamid Co., Ltd.) were added and mixed to obtain a water-based paint. The resulting water-based paint was color-developed on a glass substrate with a 4 mil film applicator and baked at 140 ° C. for 30 minutes to form a film, and gloss and water resistance were evaluated. The results are shown in Tables 2 and 3.

[0031]

[Table 2]

[0032]

[Table 3]

The evaluation was carried out by the following method. (1) Fluidity The viscosity of the obtained pigment dispersion was measured at 6 rpm using a B type viscometer. (2) Gloss The gloss was measured with a digital variable angle gloss meter at 20 ° gloss. (3) Water resistance Immersed in distilled water at 20 ° C for 2 days and visually inspect the coated surface.
◯: Good Δ: Normal ×: Inferior The evaluation was performed in 3 stages.

As is clear from Tables 2 and 3, the pigment dispersions of the present invention show good dispersibility and excellent water resistance which cannot be obtained by conventional pigment derivatives. That is, according to the present invention, the acidic functional group-containing resin undergoes a salt-forming reaction with a pigment derivative having low solubility in water (the pigment derivative chemically bonds with a part of the resin), so that the pigment derivative is dissolved in the water-soluble resin. It is possible to obtain paints and inks that are finely dispersed and in which pigments are highly dispersed.

[0035]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a coating material, an ink or the like in which a pigment is highly dispersed and which has good fluidity and storage stability. Paints and inks containing the aqueous pigment dispersion of the present invention form a film having excellent gloss, tinting strength and water resistance.

Claims (3)

[Claims] 1. A pigment dispersant obtained by neutralizing 100 parts by weight of a pigment, a resin containing an acidic functional group with a basic pigment derivative represented by the following general formula (1), 0.1 to 50 parts by weight, and an aqueous resin of 5 to 200. An aqueous pigment dispersion comprising parts by weight and water. _{P- [X- (CH 2) m} -N (R 1, R 2)] n Formula (1) (wherein, P is an azo, phthalocyanine, quinacridone, anthraquinone, dioxazine, anthrapyrimidine pyridinium Ji system , Ansanthrone, indanthrone, flavanthrone, pyranthrone, perylene, perinone, thioindigo, diketopyrrolopyrrole, isoindolinone, isoindoline, quinophthalone Dye residue, X is a direct bond or a divalent bond group, R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group which may have a substituent, an aryl group, or a nitrogen atom for R ₁ and R _2. Or a heterocycle which may contain an oxygen atom, m is an integer of 1 to 4, and n is an integer of 1 to 4, respectively.) 2. The pigment dispersant is obtained by neutralizing an acidic functional group-containing resin having an acid value of 5 to 95 with a basic pigment derivative to a neutralization rate of 60 to 300%. Aqueous pigment dispersion. 3. An aqueous coating composition comprising the aqueous pigment dispersion according to claim 1 or 2.