JPH0925431A - Aqueous pigment dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new low-viscosity aqueous pigment dispersion, having a low yield point and good in dispersion and storage stabilities by blending a pigment with a pigment dispersing agent and water and further water-insoluble solid fine particles. SOLUTION: This aqueous pigment dispersion consists essentially of (A) a pigment (preferably having 0.1-1μm average particle diameter measured by a centrifugal sedimentation method, etc.), (B) a pigment dispersing agent (e.g. a water-soluble amino resin or an alkyd resin), (C) water-soluble solid fine particles and (D) water (preferably deionized water). The component (C) is inorganic fine solid particles having <=50mg/l solubility in water at 20 deg.C and the average particle diameter of (1/2) to (1/20) that of the component (A) and preferably fine particles capable of providing a transparent dispersion having >=90% total light transmittance when dispersing the fine particles at 50wt.% concentration in water. For example, fine titanium oxide particles, etc., are concretely cited. Furthermore, the amounts of the components used are preferably 10-70wt.% component (A) based on the dispersion, 1-3wt.% component (B) based on the component (A) and 5-250 pts.wt. component (C) based on 100 pts.wt. component (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel water-based pigment dispersion, and more specifically, a novel water-based pigment dispersion excellent in dispersion stability capable of preventing aggregation between particles of the same kind and particles of different kinds in an aqueous paint. It relates to a pigment dispersion.

[0002]

2. Description of the Related Art Conventionally, water-based paints or water-based inks are composed of a pigment, a pigment dispersant, and water as essential components. However, it is difficult to disperse pigments during the production of water-based paints or water-based inks. Agglomeration and settling of pigments during storage,
It is known that undesired phenomena such as a decrease in coloring effect on the coated surface, flooding (color separation), floating (floating), decrease in gloss, and discoloration with time occur. Various improvements have been attempted for the purpose of solving these problems. For example, (1) a method of dispersing a pigment using a wetting agent such as a nonionic, cationic or anionic surfactant or an aliphatic polycarboxylic acid as an auxiliary agent, (2) a pigment affinity substance and a medium affinity A method of dispersing using an amphipathic substance combined with a volatile substance,
(3) A method of reducing the surface tension with a surfactant such as an alkyl silicone to prevent the occurrence of floating is known.

However, the above-mentioned known methods cannot sufficiently improve the above-mentioned drawbacks, and conversely, the adverse effects of the above-mentioned additives found in the conventional methods, that is, deterioration of coating film performance or coating film state. The actual situation is that secondary adverse effects such as

[0004]

The inventors of the present invention have excellent storage stability in which the stability of the dispersion liquid is not hindered by the various components present in the paint without deteriorating the paint film performance or the paint film state. As a result of intensive studies to obtain an aqueous pigment dispersion, it was found that the above-mentioned problems can be solved by further adding water-insoluble solid fine particles to an aqueous pigment dispersion comprising a pigment, a dispersant and water. The present invention has been completed.

Thus, according to the present invention, there is provided an aqueous pigment dispersion liquid containing a pigment, a pigment dispersant, water-insoluble solid fine particles and water as essential components.

The pigment used in the dispersion of the present invention can be any of those commonly used in paints, inks, plastics and the like. For example, as an inorganic pigment,
Carbon black, aluminum powder, etc. which are mainly composed of simple elements, Zn, Pb, Ti, Sb, Cd, F
e, As, Mg, Al, Ba, Ca, Si, Co, Cr
Oxides, sulfates, sulfides, chromates, silicates, etc.
Hydroxides, carbonates and the like can be mentioned, and as the organic pigment,
From natural dye pigments, nitroso pigments, nitro pigments, azo pigments, phthalocyanine pigments, basic dye pigments, quinacridone red, quinacridone violet, perylene red, perylene scarlet, dioxane violet, isoindolinone yellow, etc. At least one pigment selected is included. The average particle size of these pigments in the dispersion is usually in the range of 0.2 to 5 μm, particularly preferably 0.1 to 1 μm, when measured by the centrifugal sedimentation method or the light scattering method. The amount of these pigments used is 80% by weight of the pigment dispersion liquid.
Below, it is particularly preferable to be in the range of 10 to 70% by weight, and if it exceeds 80% by weight, it may become difficult to handle due to thickening.

The pigment dispersant used in the dispersion liquid of the present invention is a substance which is used to loosen the pigment and exhibits adsorptivity to the pigment, and its kind is not particularly limited.
Various conventionally known water-soluble resins, for example, water-soluble amino resins, alkyd resins, acrylic resins, melamine resins, polyester resins, polyether resins, epoxy resins, polyurethane resins, fluororesins, silicone resins, fiber-based resins At least one resin selected from a phenol resin, a xylene resin, a toluene resin, a vinyl chloride resin and the like can be used. Further, various conventionally known surfactants can also be used as the pigment dispersant. The amount of the pigment dispersant used is not particularly limited, but in order to obtain a fine pigment dispersion, it is generally preferably 1% by weight or more, and particularly preferably 1 to 3% by weight based on the above pigment. . Further, when a pigment having a relatively large specific surface area such as carbon black is used as the pigment, a large amount of the pigment dispersant is used, and when a pigment having a relatively small specific surface area such as titanium oxide is used, the pigment is dispersed. The dispersant can be used to a small extent.

The water-insoluble solid fine particles used in the dispersion of the present invention have a solubility in water of 50 mg / l or less at 20 ° C. and are smaller than the average particle size of the pigment used, and generally 1/1 of the average particle size of the pigment. Inorganic or organic, preferably inorganic solid fine particles having an average particle size in the range of 2 to 1/20, and when the solid fine particles are dispersed in water at a concentration of 50% by weight, the solid fine particles are substantially It is intended to give a transparent dispersion (total transmittance of light of 90% or more), and such solid fine particles generally have a particle size of 0.1 μm or less, particularly 0.01 to 0.05 μm as measured by an electron microscope. It can have an average particle size within the range. Specific examples of such water-insoluble solid fine particles include, for example, MT-10.
0S, MT-500B (above, Teikoku Kako Co., Ltd.), TTO
-55 (manufactured by Ishihara Sangyo Co., Ltd.) and other commercially available titanium oxide microparticles; alumina oxide C (manufactured by Nippon Aerosil Co., Ltd.) and other commercially available alumina microparticles;
Varifine BF-1, BF-20 and BF-21
(Above, manufactured by Onahama Sakai Chemical Co., Ltd.) and other commercially available barium sulfate fine particles; Elosil # 200, # 380 and R-972 (all manufactured by Nippon Aerosil Co., Ltd.), colloidal silica water sol (Catalyst Chemical Co., Ltd.) Silica fine particles marketed under the trade name such as; Neolite SA-200
B, TPS-2 and S (all manufactured by Takehara Chemical Industry Co., Ltd.),
Calcium carbonate fine particles marketed under the trade name of Toyofine (manufactured by Toyo Denka Kogyo Co., Ltd.); Ferric oxide marketed under the trade names of Transoxide Red 5201 and 5202 (above, manufactured by Dainichi Seika Co., Ltd.) Examples thereof include fine particles.

The amount of the water-insoluble solid fine particles used in the present invention can be experimentally determined according to the type, the type of pigment, the amount used, etc., but generally 5 to 400 per 100 parts by weight of the pigment. A suitable range is parts by weight, especially 5 to 250 parts by weight.

The water-insoluble solid fine particles play a very important role in stabilizing the dispersion of the present invention. Although its mechanism of action is not necessarily clear, in the water-based pigment dispersion of the present invention, the water-insoluble solid fine particles are adsorbed on the pigment surface to increase the pigment aggregation inhibiting ability, and as a result, the storage stability of the water-based pigment dispersion is improved. It is speculated that it will significantly improve.

Examples of water that can be used as the dispersion medium in the present invention include deionized water, tap water, ground water, and industrial water. Deionized water is preferred from the viewpoint of storage stability.

In the present invention, a water-soluble organic solvent may be used in combination if necessary. As the kind of the water-soluble organic solvent, a pigment that is soluble in water and is contained in the pigment dispersion liquid,
It is not particularly limited as long as it does not react with the pigment dispersant and the solid fine particles, and examples thereof include methanol, ethanol, isopropyl alcohol, hexylene glycol, diethylene glycol monobutyl ether, acetone, diacetone alcohol, cellosolve, methyl cellosolve, butyl cellosolve, carbitol. Acetate, methyl cellosol acetate, propylene glycol monomethyl ether, isopropyl glycol, 3-methyl-3-methoxybutanol and the like can be mentioned, and the amount thereof is preferably 20% by weight or less with respect to water.

The water-based pigment dispersion liquid of the present invention is a fine pigment dispersion liquid which can be easily obtained by mixing the above-mentioned pigment, pigment dispersant, water-insoluble solid fine particles and water and dispersing the mixture by a method known per se. Can be obtained. Examples of the dispersing device that can be used at that time include a paint shaker,
Roll mill, colloid mill, ball mill, sand mill,
Attritor etc. are mentioned.

[0014]

The aqueous pigment dispersion of the present invention has a low viscosity, a low yield value, and good dispersion stability and storage stability.

[0015]

The present invention will be described in more detail with reference to the following examples. "Parts" and "%" in the examples are "parts by weight" and "% by weight", respectively.

Production Example 1 Production of Pigment Dispersant Methyl methacrylate 43 parts n-Butyl acrylate 27 parts Hydroxypropyl acrylate 15 parts Polyoxyethylene methacrylate 10 parts Acrylic acid 5 parts Azobisisobutyronitrile 2 parts A mixture of 120 ° C. After dripping into 100 parts of butyl cellosolve and reacting for 5 hours, 4.5 parts of dimethylaminoethanol were added at 90 ° C., solid content 50%, Gardner viscosity Z6.
A pigment dispersant of

Example 1 20 parts of copper phthalocyanine blue, which is a blue pigment, and 40 parts of the pigment dispersant obtained in Production Example 1 were placed in a 450 cc dispersion container.
Part, butyl cellosolve 10 parts and deionized water 11
0 part was charged and sufficiently mixed, 300 parts of glass beads having a diameter of 1 mm were further added, and the mixture was dispersed for 2 hours using a pent shaker to obtain a dispersion liquid (A-1).

Then, 20 parts of solid fine particles of barium sulfate "BF-20" (trade name, manufactured by Onahama Sakai Chemical Co., Ltd.) were placed in a 450 cc dispersion container, and 4 parts of the pigment dispersant obtained in Production Example 1 were used.
0 parts, 10 parts butyl cellosolve and 1 part deionized water
10 parts of the mixture was charged and sufficiently mixed, 300 parts of glass beads having a diameter of 1 mm were further added, and the mixture was dispersed for 2 hours using a pent shaker to obtain a dispersion liquid (B-1).

Thereafter, 160 parts of the above dispersion liquid (A-1) and 30 parts of the above dispersion liquid (B-1) were placed in a 450 cc dispersion container.
One part was charged and thoroughly mixed, 300 parts of glass beads having a diameter of 1 mm were added, and the mixture was dispersed for 2 hours using a pent shaker to obtain a dispersion liquid (P-1).

Example 2 32 parts of quinacridone red which is a red pigment and 34 parts of the pigment dispersant obtained in Production Example 1 were placed in a 450 cc dispersion container.
10 parts of butyl cellosolve and 102 parts of deionized water were charged and mixed sufficiently, 300 parts of glass beads having a diameter of 1 mm were further added, and the mixture was dispersed for 2 hours using a paint shaker to obtain a dispersion liquid (A-2).

Next, 32 parts of barium sulfate "BF-21" (trade name, manufactured by Onahama Sakai Chemical Co., Ltd.), which are solid fine particles, were placed in a 450 cc dispersion container, and 3 parts of the pigment dispersant obtained in Production Example 1 were used.
4 parts, 10 parts butyl cellosolve and 1 part deionized water
02 parts were charged and sufficiently mixed, 300 parts of glass beads having a diameter of 1 mm were added, and the mixture was dispersed for 2 hours using a paint shaker to obtain a dispersion liquid (B-2).

Then, 101 parts of the above dispersion liquid (A-2) and 81 parts of the above dispersion liquid (B-2) were placed in a 450 cc dispersion container.
Parts were charged and mixed well, 300 parts of glass beads having a diameter of 1 mm were added, and the mixture was dispersed for 2 hours using a paint shaker to obtain a dispersion liquid (P-2).

Example 3 A 450 cc dispersion container was charged with 8 parts of carbon black, which is a black pigment, 48 parts of the pigment dispersant obtained in Preparation Example 1 and 130 parts of deionized water, and they were mixed thoroughly and further with a diameter of 1 mm. 300 parts of glass beads were added and dispersed using a paint shaker for 2 hours to obtain a dispersion liquid (A-3).

Next, silicon dioxide "Erosil R-972" (trade name,
(Manufactured by Nippon Aerosil Co., Ltd.), 48 parts of the pigment dispersant obtained in Production Example 1, 10 parts of butyl cellosolve and 120 parts of deionized water are thoroughly mixed, and further the diameter is 1 mm.
300 parts of the glass beads of was added and dispersed using a paint shaker for 2 hours to obtain a dispersion liquid (B-3).

Then, 109 parts of the above dispersion liquid (A-3) and 38 parts of the above dispersion liquid (B-3) were placed in a 450 cc dispersion container.
Parts were charged and mixed well, 300 parts of glass beads having a diameter of 1 mm were added, and the mixture was dispersed for 2 hours using a paint shaker to obtain a dispersion liquid (P-3).

Comparative Example 1 The dispersion liquid (A-1) of Example 1 was used as a sample.

Comparative Example 2 The dispersion (A-2) of Example 2 was used as a sample.

Comparative Example 3 The dispersion (A-3) of Example 3 was used as a sample.

Table 1 shows the results of characteristic evaluation of the dispersions of Examples 1 to 3 and Comparative Examples 1 to 3. Table-1
The test conditions in are as follows.

(* 1) Viscosity of dispersion liquid: The viscosity behavior of the dispersion liquid was measured by Rheometer MR-300 (produced by Rheology Co., Ltd.).
The viscosity at a shear rate of 100 sec ^{-1 was} measured in poise.

(* 2) Casson Yield Value of Dispersion Liquid: The Casson yield value when the viscosity behavior of the dispersion liquid was measured by Rheometer MR-300 (manufactured by Rheology Co., Ltd.) was shown.

(* 3) Storage stability of dispersion liquid: The dispersion liquid was put in a test tube, plugged with an actual plug, and stored for one month at 40 ° C., and the state of the dispersion liquid was visually observed. It evaluated by the standard of. ◯: Good ×: Separation / sedimentation is observed

[0033]

[Table 1]

Claims (1)

[Claims] 1. A water-based pigment dispersion liquid containing a pigment, a pigment dispersant, water-insoluble solid fine particles and water as essential components.