JPS6338375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a highly concentrated pigment dispersion by a flushing method.

Conventional methods for producing high-concentration pigment dispersions include dispersing powdered pigments into a vehicle using a dispersing machine such as a three-roll mill or ball mill, or kneading a wet cake of pigment, which is formed as fine precipitates in an aqueous system, with a vehicle using a kneader or the like. Flushing methods in which pigments are kneaded in a machine and transferred and dispersed in a vehicle are well known.

In general, the flushing method attempts to perform the steps of drying, pulverizing, and dispersing the pigment in a vehicle in one step, and is intended to simplify the work and facilitate the dispersion of the pigment when forming it into a paint.

When a wet cake of pigment is kneaded in a vehicle and flushed, even after separating the mixed water, the amount of water dissolved and dispersed in the highly concentrated pigment dispersion remains
20% remains.

Several studies aimed at reducing the amount of water remaining have also been reported. For example, a method of increasing hydrophobicity by adsorbing a surfactant onto the surface of the raw pigment and fixing it with metal ions, an anionic or cationic surfactant in the pigment, and a cationic or anionic surfactant opposite to the pigment in the vehicle. A method using a surface treatment agent, such as adding a surface treatment agent to facilitate flushing through a chemical reaction between the two, and a method using an acidic additive, an alkaline additive, or an activator such as an amine or an amine substitute as a flushing aid. etc. are examples.

However, although the above-mentioned treatment methods may lower the viscosity of the highly concentrated pigment dispersion, improve the gloss, and improve the hue, there is a limit to the amount of water remaining.

A commonly used method for removing residual water is heating or vacuum distillation under heating. However, when water is removed from a highly concentrated pigment dispersion by such a method, some of the pigment particles form aggregates even if the polarity of the pigment surface and the solvent composition in the vehicle are appropriate. If a high concentration pigment dispersion contains a small amount of pigment aggregates, it not only causes a decrease in tinting power and gloss, but also deteriorates the finish of the coating film. Furthermore, even when used as printing ink, the rate of ink transfer to paper decreases, resulting in poor quality of printed matter. To improve this, it is necessary to mechanically redisperse the aggregates using three rolls or the like, which complicates the process.

The inventors of the present invention have conducted research on methods for preventing the formation of pigment aggregates that cause such drawbacks, and as a result have found that, regardless of the amount of remaining water, a uniform, high-concentration pigment dispersion that does not contain pigment aggregates due to water removal. I succeeded in gaining a body.

In the present invention, after kneading a wet cake and a vehicle to remove free water, a broken aromatic hydrocarbon and a lower alcohol are added and mixed, and then the remaining water and the added aromatic hydrocarbon are mixed under reduced pressure while heating. The present invention relates to a method for producing a highly concentrated pigment dispersion, which is characterized by removing pigments and lower alcohols.

The present invention will be specifically explained as follows. After water separation obtained by flushing, one type of alcohol and a solvent in an amount greater than the amount necessary to azeotropically remove the total water content are added and stirred to form a uniform slurry, and then Remove water under reduced pressure and heat (below 90°C) while stirring gently. The highly concentrated pigment dispersion obtained in this way does not contain aggregates of pigment particles and has a high coloring power.
It has excellent gloss and clear hue, making it ideal for paints and inks.

The pigment used in the present invention may be hydrophobic itself, or may have a surface made hydrophobic by surface treatment. Examples include carbon black, insoluble azo pigments, phthalocyanine pigments, quinacridone pigments, titanium dioxide pigments, isoindolinone pigments, yellow lead, iron oxide, barium sulfate, and the like.

The resin in the vehicle can be selected depending on the purpose and form of the product, and examples thereof include thermoplastic resins such as rosin-modified maleic acid resins, rosin-modified phenolic resins, alkyd resins, vinyl chloride resins, and acrylic resins.

The solvent in the vehicle may be one type or a mixture of two or more types depending on the resin used and the purpose. Furthermore, when the purpose is to obtain a highly concentrated pigment dispersion containing a solvent with high solubility in water, such as n-butanol, ethyl acetate, etc., it is desirable to add these solvents after flushing.
The alcohol added when removing water from the water-containing pigment dispersion after flushing includes methanol, ethanol, isopropanol, n-
butanol etc. The amount of alcohol added varies depending on the water content, but it is 25 parts by weight per 100 parts by weight of the pigment.
It is preferably about 500 parts by weight. Furthermore, depending on the resin used, two or more types of alcohol may be used in combination to improve compatibility with water.

In carrying out the flushing of the present invention, aromatic hydrocarbons such as benzene, toluene, and xylene are used, and the kneading machines used include commonly used two-roll machines, kneaders, crushers, etc. A material capable of kneading a high viscosity liquid substance is used.

As for the device for removing the water in the dispersion, if it is capable of heating and reducing pressure, it may be used as is, but another device capable of reducing pressure, heating, and stirring may be used.

The highly concentrated pigment dispersion obtained by the present invention is
To provide a well-dispersed paint or ink using only a simple stirring machine.

The present invention will be specifically described below based on Examples. In the examples, percentages and percentages indicate parts by weight and percentages by weight.

Example 1 Quinacridone pigment press cake (water content 80%,
CI46500) 225 parts (pigment content: 45 parts) Acrylic resin vehicle for paint (solid content: 50%)
90 parts (solid content: 45 parts) The above composition was kneaded using a grinder until the water was completely precipitated (about 10 minutes), and 142 parts of the precipitated water was separated and removed. Next, the obtained dispersion was transferred to a stirring device capable of heating and reducing pressure, and 110 parts of xylene and n-
80 parts of butanol was added and stirred until a homogeneous system was obtained.

After the system becomes homogeneous, the temperature is 60~70℃ and the pressure is 100℃.
Remaining water was removed while stirring gently within a range of ~120 mmHg to obtain a highly concentrated pigment dispersion.

A paint obtained by mixing 15 parts of this dispersion, 20 parts of an acrylic resin vehicle for paints (solid content 50%), 10 parts of a melamine resin vehicle for paints (60% solids), and 10 parts of thinner for acrylic vehicles. No aggregates of pigment particles were observed inside. Furthermore, the coating film obtained with this paint had good gloss, high tinting power, and good dispersibility.

Example 2 Quinacridone pigment press cake (water content 80%,
CI46500) 2250 parts (pigment content 450 parts) Phthalkyd resin vehicle for paints (solid content 60 parts)
%) 750 parts (solid content 450 parts) The above composition was kneaded with a kneader until the water was completely precipitated (about 15 minutes), 1430 parts of precipitated water was separated and removed, and 1300 parts of xylene and 300 parts of ethanol were added. and stirred until a homogeneous mixture was obtained. After a homogeneous system was obtained, remaining water was removed while gently stirring at a temperature of 45 to 75°C and a pressure of 100 to 120 mmHg to obtain a highly concentrated pigment dispersion.

It was obtained by mixing 10 parts of this dispersion, 18 parts of a phthalkyd resin vehicle for paints (solid content 60%), 12 parts of a melamine resin vehicle for paints (50% solids), and 16 parts of a thinner for phthalkyd vehicles. No aggregates of pigment particles were observed in the paint.

Furthermore, the coating film obtained with this paint had good gloss, high tinting power, and good dispersibility.

Example 3 Isoindolinone yellow pigment press cake (water content 70.6%) 1530 parts (pigment content 450 parts) Phthalkyd resin vehicle for paint (solid content 60
%) 750 parts (solid content 450 parts) The above composition was kneaded with a kneader until the water was completely precipitated (about 15 minutes), 710 parts of precipitated water was separated and removed, and 1000 parts of xylene and 200 parts of ethanol were added. and stirred until a homogeneous mixture was obtained. After a homogeneous system was obtained, remaining water was removed while gently stirring at a temperature of 45 to 75°C and a pressure of 100 to 120 mmHg to obtain a highly concentrated pigment dispersion.

A mixture of 20 parts of this dispersion, 37 parts of a phthalkyd resin vehicle for paints (solid content 60%), 25 parts of a melamine resin vehicle for paints (50% solids), and 32 parts of thinner for phthalkyd vehicles was obtained. No aggregates of pigment particles were observed in the paint.

Furthermore, the coating film obtained with this paint had good gloss, high tinting power, and good dispersibility.

Claims (1)

[Scope of Claims] 1. After kneading a wet pigment cake and a vehicle to remove free water, an aromatic hydrocarbon and a lower alcohol are added and mixed therein, and then the remaining water is mixed with the remaining water under reduced pressure while heating. A method for producing a highly concentrated pigment dispersion, characterized by removing added aromatic hydrocarbons and lower alcohols. 2. The manufacturing method according to claim 1, in which xylene is used as the aromatic hydrocarbon. 3. The manufacturing method according to claim 1 or 2, in which methanol, ethanol, isopropanol, or n-butanol is used as the lower alcohol. 4. The manufacturing method according to claim 1, 2 or 3, wherein the heating temperature is 90°C or lower.