JP2898817B2 - Aqueous pigment dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention relates to aqueous pigment dispersions used in the colorant industry. More particularly, the present invention relates to an aqueous pigment dispersion liquid useful for producing aqueous flexographic inks, aqueous paints, aqueous inks for writing instruments, etc. using pigments.

[0002]

2. Description of the Related Art Conventionally, in the colorant industry, various aqueous resins are used as dispersants to disperse pigments, and are marketed as such as colorants or mixed with various aqueous resin liquids to form aqueous paints and aqueous inks. Used in manufacturing. Conventionally, as a water-soluble resin as a dispersant, an acrylic resin having a carboxyl group introduced therein, a styrene-acryl resin, a styrene-maleic acid resin, a rosin-modified maleic resin, and the like have been used.

[0003]

Problems to be Solved by the Invention As to inks and paints, aqueous types are preferable in various aspects. However, when these inks and paints are dried, since the latent heat of vaporization of water is larger than the latent heat of vaporization of the solvent, they are the same. In the case of nonvolatile components, there is a problem that aqueous paints and aqueous inks dry more slowly than solvent-based paints. Therefore, it is desirable that the water-based paint or the water-based ink has a higher concentration (that is, less water content) than the solvent-based paint or the ink, and therefore various measures have been taken. In order to obtain a high-concentration aqueous paint, it is desirable to use a water-dispersed resin. However, in order to prepare a coating using a water-dispersible resin, the pigment must first be sufficiently dispersed. The dispersion of the pigment is usually performed in a water-soluble resin,
In order to increase the pigment content even slightly, the degree of polymerization of the water-soluble resin must be reduced. If the degree of polymerization of the water-soluble resin is reduced, there is a problem that the physical properties of the coating film deteriorate. This is the same for the water-based flexographic ink. The same is true for the water-based ink for writing implements. If the pigment concentration is to be increased, the rub resistance of the written matter is deteriorated. Accordingly, an object of the present invention is to provide an aqueous pigment dispersion liquid having a low viscosity and a high pigment content, a good pigment dispersibility, and excellent writing resistance and a coating film having excellent friction resistance.

[0004]

The above object is achieved by the following invention. That is, the present invention provides an aqueous pigment dispersion comprising a water-soluble resin, a pigment, and water, wherein the water-soluble resin is a water-soluble resin having an acid value of 87 to 200 and comprising a tetrabasic acid and a specific diol. The specific diol is an ethylene oxide additive and / or propylene oxide additive of bisphenol A and / or a polycondensate of the additive with phthalic acid.

[0005]

A water-soluble resin comprising a tetrabasic acid and a specific diol, wherein the specific diol is an addition product of ethylene oxide and / or propylene oxide of bisphenol A and / or a condensation product of the addition product and phthalic acid. By using a water-soluble resin, which is a polymer, as a dispersant for pigments, an aqueous pigment dispersion having low viscosity, high pigment content, good pigment dispersibility, and excellent writing and coating properties with excellent friction resistance can be obtained. Can be provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The dispersant used in the present invention is a water-soluble resin comprising a tetrabasic acid and a specific diol, wherein the specific diol is an ethylene oxide additive and / or propylene oxide additive of bisphenol A and / or the additive. And phthalic acid. As the tetrabasic acid constituting the dispersant, pyromellitic acid, naphthalenetetracarboxylic acid, biphenyltetracarboxylic acid, benzophenonetetracarboxylic acid and the like, and further derivatives thereof, for example,
Acid anhydrides, acid halides, lower alcohol esters and the like can be used. Pyromellitic acid is particularly preferred as the tetrabasic acid. The above tetrabasic acid is used for polycondensation and for making the obtained polyester resin water-soluble, and it is necessary that gelation does not occur due to polycondensation and that a carboxyl group for water-solubility is left. It is.

A preferred method for synthesizing a water-soluble resin used as a dispersant in the present invention is a method in which ring-opening is added using pyromellitic anhydride, and it is desirable that the reaction is performed under conditions that do not cause a dehydration reaction. Diols are the basis of the dispersant used in the present invention. The hydrophilicity (acid value), hardness, strength and pigment dispersibility of the water-soluble resin according to the present invention are determined by the choice of diol. The diols for the purpose of the present invention are bisphenol A adducts of ethylene oxide and / or propylene oxide and / or polycondensates of these adducts with phthalic acid. Further, phthalic acid includes orthophthalic acid, isophthalic acid and terephthalic acid, and terephthalic acid is particularly desirable. The ratio of the use of pyromellitic anhydride and the above diol is determined by the molecular weight of the obtained water-soluble resin. The molecular weight which can be used is approximately 1,500 to 8,000, preferably 2,000 to 7,000. If the molecular weight is less than 1,500, the abrasion resistance of the written matter or the coating film is weak, and if the molecular weight exceeds 8,000, the viscosity of the dispersion becomes too high, which does not meet the object of the present invention.

The selection of the diol is determined by the hydrophilicity (acid value) of the resulting water-soluble resin. Used in the present invention
The preferred acid value of the water-soluble resin is from 87 to 200. When the dispersant of the present invention is used in an aqueous flexographic ink, the higher the acid value of the resin, the better. For example, a condensation polymer of 5 mol of pyromellitic anhydride and 6 mol of an adduct of bisphenol A with 2 mol of propylene oxide (acid value 1)
80) is suitable. For aqueous inks for writing instruments and aqueous jet printing inks, those having a slightly higher acid value are preferred. For example, 4 mol of pyromellitic anhydride, 2 mol of a condensation polymer of 2 mol of bisphenol A ethylene oxide adduct and 1 mol of terephthalic acid, and 3 mol of 2 mol of bisphenol A ethylene oxide adduct are added. (Acid value 132) is suitable. Further, a material having a slightly lower acid value is suitable for dispersing a pigment for an aqueous paint. For example, a condensation polymer (acid value 87) of 3 mol of pyromellitic anhydride, 4 mol of a condensation polymer of 2 mol of an addition of propylene oxide of bisphenol A and 1 mol of terephthalic acid is suitable.

The acid value can also be changed by carrying out a post-treatment such as esterification of the carboxylic acid of the resulting water-soluble resin with a monoalcohol or acylation with an amine. As the polycondensation conditions of the acid component and the diol component, it is desirable to flow nitrogen gas at a temperature of 140 to 170 ° C. for 4 to 10 hours. If necessary, a solvent can be used. It is desirable that the solvent be water-soluble and have no active hydrogen. The water-soluble resin used as a dispersant in the present invention can be dissolved in water as an ammonium salt, an amine salt, or an alkali metal salt. After the polycondensation reaction is completed, the polycondensation reaction may be taken out, cooled, pulverized, and then dissolved in water and a neutralizing agent, or, after the polycondensation reaction is completed, neutralized in the same reaction vessel and added with water. It may be taken out as an aqueous solution. When the solution is taken out as an aqueous solution, the solution is cooled to 100 ° C. or less, and then the neutralizing agent and water are added. When the solution is cooled to 100 ° C. or less, the viscosity of the solution increases. The solvent at this time may have active hydrogen.

In the above-mentioned polycondensation reaction, a tribasic acid, for example, trimellitic acid or a dibasic acid, for example, phthalic acid or another alcohol can be added as long as the object of the present invention is not impaired. The water-soluble resin thus obtained has good film strength (rub resistance) despite its low molecular weight, and also has excellent pigment dispersibility. When a pigment is dispersed using the water-soluble resin, a pigment dispersion having a high pigment content, a low viscosity and a good dispersion can be obtained. By using this aqueous pigment dispersion, a high concentration aqueous flexographic ink,
Water-based paints, water-based inks for writing instruments with high concentration and high friction resistance, jet printing inks, etc. can be obtained. For dispersing the pigment using the water-soluble resin as a dispersant, a conventional method using a carboxy-type water-soluble resin can be used as it is.

Regarding the dispersion of the pigment using the water-soluble resin in the present invention, any known pigments such as organic pigments and inorganic pigments can be used. For example, organic pigments include phthalocyanine, azo, anthraquinone, perinone / perylene, indigo / thioindigo, isoindolinone, azomethine, azomethineazo, dioxazine, quinacridone, aniline black, triphenyl Methane type, carbon black type and the like can be mentioned, and as inorganic pigments, titanium oxide type, iron oxide type, iron hydroxide type, chromium oxide type, spinel type fired pigment, lead chromate type and the like can be mentioned. For dispersing the pigment using the above water-soluble resin, a water-soluble solvent can be used if necessary. For example, carbon number 1
And alcohols having 1 to 3 carbon atoms, such as ethylene glycol monoether, diethylene glycol monoether, propylene glycol monoether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol, diethylene glycol, and propylene glycol.

The disperser has no problem except that it is water-based, and a disperser using glass or zircon beads or a ceramic ball mill can be used. Rustless steel ball mills can also be used with great care. or,
The water-soluble resin and pigment taken out as a solid, a kneader,
It can be kneaded with a Banbury mixer or a mixing roll to form a color chip, which can be dissolved in water and a neutralizing agent.

Next, the present invention will be described more specifically with reference to examples. In the following, “parts” or “%” means “parts by weight” or “% by weight” unless otherwise specified.

Example 1 1209.6 parts of bisphenol A to which 2 mol of propylene oxide had been added, 349.2 parts of dimethyl terephthalate and 0.5 part of tetra-n-butoxytitanium were placed in a reaction vessel and heated at 210 ° C. in a nitrogen stream. Stir for 10 hours. Fifteen
After cooling to 0 ° C., 294.3 parts of pyromellitic anhydride and 434.7 parts of diethylene glycol dimethyl ether were added.
Stir for hours. Further, 434.3 parts of ethylene glycol monobutyl ether is added and stirred. 80 reaction mixture
After cooling to 0 ° C., a mixed solution of 163.9 parts of 28% aqueous ammonia and 1,574.1 parts of water was added, and the mixture was stirred well. Cool and take out to obtain water-soluble resin liquid-1. Dissolve 100 parts of the water-soluble resin liquid-1 in 431 parts of water, and add 9 parts of 28% ammonia water. 360 parts of solvent-stable copper phthalocyanine blue is added to this solution, stirred, and dispersed by a horizontal bead mill to obtain Pigment Dispersion-1 of the present invention. To 100 parts of a white acrylic emulsion paint (for exterior: glossy), 5 parts of the above-mentioned pigment dispersion liquid-1 was added,
When the paint obtained by stirring was applied to a slate plate by brush application, a clear blue color was obtained without a decrease in gloss or color separation.

Example 2 360 parts of an aqueous alkyd resin (resin content 50%, butyl cellosolve 20%, water 30%; water dilution dispersion type) 360 parts, rutile type titanium dioxide pigment 250 parts, water 330 parts and water-soluble melamine crosslinking agent 60 parts Is dispersed using a sand mill to obtain white paint-2. 650 parts of petiole were replaced with water-soluble resin liquid-1 17
0 part and 180 parts of water, and dispersed in the pigment dispersion liquid 2 of the present invention.
And To 370 parts of the above-mentioned white paint-2, 30 parts of the above-mentioned pigment dispersion liquid-2 were added and stirred to obtain colored paint-2.
Apply the above colored paint-2 to a tin plate with an applicator.
After coating to a thickness of 6 μm / wet and air-drying,
The coated plate was baked for 0 minutes. This coated plate had a beautiful light brown color, and the surface condition of the coating film was good.

Example 3 150 parts of the water-soluble resin liquid-1 was dissolved in 520 parts of water.
30 parts of 8% ammonia water and 300 parts of carbon black are added and stirred. This is dispersed by a horizontal bead mill to obtain Pigment Dispersion-2 of the present invention. 90 parts of acrylic resin emulsion for paint (MFT 15 ° C.), 5 parts of the above-mentioned pigment dispersion-2, thickener (nonionic activator type) 0.0
2 parts, 4.98 parts of water, and 3 parts of Texanol (a film-forming auxiliary) were mixed and stirred to obtain a paint. The paint showed no loss of gloss in a one month storage stability test at 50 ° C. When the paint was applied to a steel plate (32 μm / dry), the paint had good gloss and did not swell in a one-week water resistance test. The paint is most suitable as a black paint for chassis.

Example 4 700 parts of pyromellitic anhydride, 1,232 parts of a 2-mol additive of propylene oxide of bisphenol A, and 700 parts of diethylene glycol dimethyl ether were charged into a reaction vessel, and heated to 165 ° C. in a nitrogen stream.
Stir at 6 ° C for 6 hours. Cool to 90 ° C and add
A mixed liquid of 13 parts and 385 parts of 28% aqueous ammonia was added, stirred, cooled, and taken out to obtain a water-soluble resin liquid-4.
To 400 parts of water, 70 parts of the above water-soluble resin liquid-4 and 12 parts of 28% ammonia water were added and stirred, and 300 parts of permanent carmine 2B was added and stirred, and dispersed with a horizontal bead mill. 4 and 150 parts of water are added and stirred to obtain a dispersion liquid-4. 48.8 parts of an acrylic styrene emulsion resin (resin content 47%) using a water-soluble acrylic resin as a protective colloid, 50 parts of the above dispersion-4, and 1.2 parts of a low molecular weight polyethylene emulsion were mixed and stirred to obtain an aqueous flexo. Ink-4. When the aqueous flexo ink-4 was used to print on a cardboard liner paper, a beautiful printed matter was obtained. The printed matter was tested with a Gakushin type friction tester using a liner paper as a test paper under a load of 200 g.
When a rub test was performed, discoloration was slight.

Example 5 Bisphenol A ethylene oxide 2 mol additive 6
16 parts, 194 parts of dimethyl terephthalate and tetra-n-
0.4 parts of butoxytitanium are put in a reaction vessel and reacted by stirring at 170 ° C. for 10 hours in a nitrogen stream. The reaction mixture was cooled to 150 ° C., and 462 parts of an ethylene oxide 2 mol of bisphenol A, 428 parts of pyromellitic anhydride and diethylene glycol dimethyl ether 43 were added.
After adding 5.5 parts and heating once to 165 ° C, the mixture is stirred at 150 ° C for 6 hours in a nitrogen stream. Cool to 85 ° C,
A mixed liquid of 242.8 parts of 28% ammonia water and 1,934.7 parts of water was added, and the mixture was stirred well and taken out to obtain a water-soluble resin liquid-5. Water 308 parts, ethylene glycol 80
, 8 parts of aqueous ammonia and 80 parts of a water-soluble resin liquid-5 are mixed well, and 320 parts of copper phthalocyanine blue (solvent unstable type) is added thereto, stirred and dispersed by a horizontal bead mill. 2,048 parts of water and 160 of water-soluble resin liquid-4
Parts, 176 parts of ethylene glycol and 16 parts of 28% aqueous ammonia were added, stirred, and ultra-centrifuged to remove coarse particles to obtain dispersion liquid-5. Dispersion-5 has a viscosity of 3.
The pH was as low as 5 cps and the pH was 9.1. I stuffed this in a ballpoint pen and wrote it on Kent paper.
Writing fast did not fade. Further, the written portion was subjected to a friction test using a Gakushin-type friction tester. As a result, good results were obtained with little white paper contamination.

[0018]

As described above, the aqueous pigment dispersion of the present invention has a low viscosity and a high solid content, is resistant to friction, and is suitable as a coloring agent for aqueous flexographic inks, aqueous inks for writing instruments, aqueous inks for jet printing or aqueous paints. I have.

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Claims (3)

(57) [Claims] 1. An aqueous pigment dispersion comprising a water-soluble resin, a pigment and water, wherein the water-soluble resin has an acid value of 87-2.
00, a water-soluble resin comprising a tetrabasic acid and a specific diol, wherein the specific diol is an ethylene oxide adduct and / or propylene oxide adduct of bisphenol A and / or a condensation product of the adduct and phthalic acid. An aqueous pigment dispersion, which is a polymer. 2. The aqueous pigment dispersion according to claim 1, wherein the tetrabasic acid is pyromellitic acid. 3. The water-soluble resin having a molecular weight of 1,500 to 8,
The aqueous pigment dispersion according to claim 1, which has a molecular weight of 000.