JP2002012810A - Solid colored compound and method for reducing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a solid colored compound comprising a pigment and a resin with an acid value and intended for producing printing liquids for ink-jet printers, designed to ameliorate the compound's tending to stick on the roll under kneading operation and more finely disperse the pigment particles therein, and to obtain such a solid colored compound by the above method. SOLUTION: This method for producing a solid colored compound involves adding a glycol ether, preferably propylene glycol monopropyl ether, to the kneading system for the compound to carry out a kneading operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid coloring compound comprising a pigment and a resin having an acid value, and a method for producing the same. The production method of the present invention provides a solid coloring compound in which a pigment is finely dispersed. The aqueous dispersion of colored resin particles obtained from the solid colored compound of the present invention is finely divided and is particularly preferable as a coloring agent for aqueous recording liquids such as inks for ink jet printers.

[Prior art]

[0002] A solid coloring compound in which a pigment is dispersed in a resin is used as a coloring agent for various plastic molded products, sheets, toners for electrophotography, printing inks and the like. In the case of coloring a solid such as a molded product, a resin that is highly compatible with various resins as a dispersion medium, and in the case of coloring a solution such as a printing ink, with a variety of solvents, respectively. When used, a solid colored compound can be obtained by dispersing the pigment at a higher concentration than the actual use concentration.

[0003] Pigment dispersion at a high concentration can give a high shear force to the pigment, so that fine dispersion is possible.
The pigment once dispersed in the resin can be relatively easily dispersed when the solid coloring compound is secondarily dispersed and colored in various resins and solvents. Therefore, obtaining a solid colored compound that is a good primary dispersion is extremely important in terms of application of the dispersion thereafter.

[0004] In particular, for application to applications where transparency is required for colored objects such as plastic sheets, electrophotographic toners, printing inks, etc.
The pigment in the solid color compound must be finely dispersed.

[0005]

An object of the present invention is to improve the ease of sticking of a compound to a roll in the process of producing a solid colored compound comprising a pigment and a resin having an acid value. Another object of the present invention is to provide a solid colored compound in which pigment particles are finely dispersed and a method for producing the same, while improving the properties.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have accomplished the present invention. That is, the present invention provides the following inventions.

[0007] A solid coloring compound comprising a pigment and a resin having an acid value, wherein a glycol ether is added and kneaded, and a method for producing the same.

[0008] The solid colored compound wherein the glycol ether is a propyl ether, and a method for producing the same.

The above-mentioned solid colored compound wherein the propyl ether is propylene glycol monopropyl ether, and a method for producing the same.

[0010] A solid colored compound can be obtained by dispersing a pigment in a resin. Specifically, using a conventionally known kneading device such as a roll, kneader, or bead mill, the pigment is uniformly dispersed in the resin in a semi-solid state in which the resin is swollen with a solution or a solvent, or in a state where the resin is heated and melted. And finally taken out as a solid kneaded material (solid colored compound).

The kneading of the solid coloring compound is carried out by charging a resin and a pigment which have been mixed in advance into a kneading apparatus. At this time, the resin / pigment mixture self-heats due to heating by the kneading device or shearing force received from the kneading device, and the temperature rises. At this time, the resin is in a molten state, and the pigment is crushed by the shearing force received from the kneading device and dispersed in the resin. The ratio of the resin to the pigment is not particularly limited, but generally 10 to 500 parts by weight of the pigment is kneaded per 100 parts by weight of the resin.

[0012] The kneading temperature is usually in the range of 5 to 200 ° C. Each resin has an optimal melting state in which a good pigment dispersion can be achieved, and the heating temperature of the kneading device may be adjusted to achieve this state. When the temperature rises due to self-heating, the temperature may be adjusted by cooling the kneading device.

A solid colored compound can be obtained by mixing and kneading only a resin and a pigment. However, since the compound is likely to stick to a roll, it is preferable to add a kneading aid in order to obtain a better dispersion state. . As a kneading aid, an organic solvent having a low boiling point that dissolves the resin is generally used.

Examples of such organic solvents include ketone solvents such as acetone, dimethyl ketone and methyl ethyl ketone, alcohol solvents such as methanol, ethanol and isopropyl alcohol, chlorine solvents such as chloroform and methylene chloride, benzene and toluene. And other aromatic solvents. Among these, they are appropriately selected and used according to the characteristics of the resin.

However, these organic solvents have an advantage that they have a low boiling point, so that they are easily volatilized and hardly remain in a solid coloring compound. Has changed,
There is a problem that it is difficult to keep the resin in the optimum molten state for dispersion.

This problem is due to the high volatility of the organic solvent added as a dispersing agent, and various organic solvents are studied based on the presumption that it can be solved by changing to an organic solvent having a high boiling point or by using it in combination. did. As a result, it was confirmed that when glycol ether was used as the organic solvent having a high boiling point, the workability in the kneading step was improved and, at the same time, fine particles of the obtained solid colored compound were obtained. A combination of a low boiling organic solvent that dissolves a conventionally used resin and a glycol ether has been particularly effective.

Examples of the glycol ether used in the present invention include methyl ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether, propylene glycol monomethyl ether and dipropylene glycol monomethyl ether; Ethyl ethers such as ethylene glycol monoethyl ether and diethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monopropyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether Propyl ethers such as ether, butyl ethers such as ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, and ethylene glycol Hexyl ethers such as monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol mono 2-ethylhexyl ether, diethylene glycol mono 2-ethylhexyl ether; phenyl ethers such as ethylene glycol monophenyl ether and propylene glycol monophenyl ether; ethylene glycol Dimethyl ethers such as dimethyl ether, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether; diethyl ethers such as ethylene glycol diethyl ether and diethylene glycol diethyl ether; dibutyl ethers such as ethylene glycol dibutyl ether and diethylene glycol dibutyl ether; ethylene glycol monoallyl ether; ethylene Glycol t-butyl ether and the like.

Among the glycol ethers, propyl ethers are preferred, and propylene glycol monopropyl ether is most preferred.

The type and amount of glycol ether used,
The type and amount of the low-boiling organic solvent used for dissolving the resin are determined by the type and characteristics of the resin, the ratio of the pigment to the resin, the type of the kneading device, and the operating conditions, and thus are not necessarily determined.
As a guide of the amount of use, the glycol ether is in the range of 0.1% to 40% and the low boiling point solvent is in the range of 5% to 40% based on the total mass of the resin and the pigment.

In the case where the pigment is finely dispersed in the resin, it is preferable to perform the dispersion under a high shearing force. What is necessary is just to employ the dispersing means. When applying the solid colored compound of the present invention to an aqueous dispersion of colored resin particles, it is preferable to use two rolls.

The resin having an acid value used in the present invention may be appropriately selected in consideration of the type, molecular weight range, use of dispersion, compatibility with the pigment, and the like. As the type of resin, various resins can be used from among natural resins and synthetic resins. A particularly preferred acid value range is from 10 to 280.

Examples of the resin include a styrene resin, an acrylic resin, a polyester resin, and a polyurethane resin. The resin may be a permanently crosslinked resin having no heat dependency, or may have a reversible crosslink that is crosslinked at room temperature but becomes non-crosslinked by heat. When the solid colored compound of the present invention is applied to an aqueous dispersion of colored resin particles, and further to an aqueous recording liquid for an ink jet printer, at least one selected from the group consisting of styrene, substituted styrene, and (meth) acrylate as a resin. A copolymer of one monomer and (meth) acrylic acid is preferred. In this case, the molecular weight range is preferably from 1,000 to 100,000.

The pigment used in the present invention may be appropriately selected from known pigments in consideration of the color, use, and compatibility with the resin. Examples include carbon black, titanium black,
Examples include inorganic pigments such as titanium white, zinc sulfide, and red iron oxide, phthalocyanine pigments, azo pigments such as monoazo and disazo pigments, and organic pigments such as quinacridone pigments.

The aqueous dispersion of colored resin particles obtained from the solid colored compound of the present invention is finely divided and is suitable as a coloring agent for aqueous recording liquids such as inks for ink jet printers. The dispersibility of the pigment in the solid coloring compound greatly affects the particle diameter of the pigment and the microcapsule in the ink of the ink for a jet printer. According to the method of the present invention, the particle size of the pigment particles in the compound can be made extremely small, so that the pigment particles in the ink using the compound or the pigment microencapsulated with the resin can also be reduced in particle size.

As a method for obtaining an aqueous dispersion of colored resin particles from a solid colored compound, various known methods can be employed. For example, a method in which a solid colored compound is dissolved in an organic solvent, water is added dropwise with stirring to convert the solvent into an aqueous phase, and the solvent is removed to obtain an aqueous dispersion of colored resin particles. A method in which a pigment in a solid coloring compound is dispersed in an aqueous recording liquid medium by neutralizing an acid group of a resin with an alkali is exemplified.

Among them, the following method is particularly preferable.

When the organic solvent and water and the base, and the water and the organic solvent, which are good solvents for the resin, are not mixed, a solid coloring compound is added to a solvent containing an organic solvent as a mixing aid, and the mixture is mixed and stirred. A suspension of the coloring compound is obtained. After re-dispersing the obtained suspension with a beadless dispersion device,
The ratio of water in the solvent composition is increased by adding water or distilling off the organic solvent. Through the above steps, the pigment surface is coated with the resin, and a microencapsulated aqueous dispersion of colored resin particles can be obtained. If the organic solvent that is a good solvent for the resin present in the suspension of the solid coloring compound and the residual organic solvent that is a miscible additive is not preferable, complete distillation is performed in the step of increasing the proportion of water in the solvent composition. You just have to remove it.

The beadless dispersion apparatus used here is preferably a collision-type dispersion apparatus that performs dispersion by causing high-pressure liquid pressure to collide suspensions or pigment particles in the suspension. Is a Nanomizer (Nanomizer Co., Ltd.)
And the like are used. To the aqueous dispersion of the colored resin particles obtained in this manner, a water-soluble organic solvent essential for the aqueous recording liquid is added, mixed, and filtered through a filter. Aqueous recording liquid.

The composition of the solid coloring compound suspension and the ratio of water in the solvent composition to be changed after redispersion may be appropriately determined according to each solid coloring compound.
As a quantitative guide, when the colorant suspension is prepared from the solid coloring compound, the total of the pigment and the resin is about 10 to 40% by weight of the total suspension, the ion exchange water is about 20 to 70% by weight, 5 to 4 organic solvents that are good solvents for the resin
It is about 0% by weight, and the optimum quantity may be appropriately adjusted from these.

[0030]

Next, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited to these examples. In the following examples, “parts” means “parts by mass”.

In this example, since it is difficult to directly measure the particle size of the pigment in the solid coloring compound, an aqueous dispersion of colored resin particles is prepared from the solid coloring compound by the following method, and the particle size is compared. Dispersibility was evaluated based on the particle size.

The details of the operations common to the embodiments are as follows.

Ion-exchanged water is used as the water, methyl ethyl ketone is used as the organic solvent which is a good solvent for the resin, triethanolamine is used as the base, and isopropyl alcohol is used as the hydrophilic organic solvent which is used as the admixture. And mixed. After the solvent became homogeneous, a solid coloring compound was added and stirred for 2 to 3 hours to obtain a colorant suspension.

Colorant suspension composition Solid coloring compound 9.5 parts Ion-exchanged water 25.5 parts Methyl ethyl ketone 10.7 parts Triethanolamine 1.0 part Isopropyl alcohol 4.7 parts Glycerin 2.2 parts Total 53.6 Department

A high shearing force was applied to the obtained colorant suspension using a Nanomizer (manufactured by Nanomizer Co., Ltd.), which is a beadless dispersion device. The operating pressure of the Nanomizer was 98 MPa.

Nanomizer-treated colorant suspension 5
Glycerin 8% aqueous solution (glycerin 8
Parts, ion-exchanged water 92 parts) to increase the ratio of water in the solvent composition. By this operation, the resin component dissolved in the suspension can be adsorbed on the pigment surface. At that time, while slowly stirring the colorant suspension,
A 8% aqueous glycerin solution was dropped at a rate of 5 ml / min.

From the aqueous dispersion of colored resin particles obtained through the above steps, methyl ethyl ketone and isopropyl alcohol were removed by distillation. Using a rotary evaporator for distillation, the aqueous dispersion of colored resin particles was heated to 70 ° C. and distilled under reduced pressure.

The particle size of the obtained aqueous dispersion of colored resin particles was measured using a Microtrac UPA particle size analyzer (Leeds and
(Manufactured by Northrup). The sample was appropriately diluted with ion-exchanged water to a measurable concentration. In order to obtain an aqueous dispersion for an ink jet printer from the aqueous dispersion of colored resin particles of the present invention, after concentrating the solid content to about 20% by weight, ion-exchanged water, glycerin, ethylene A high-boiling water-soluble organic solvent such as glycol is added, the mixture is stirred to be uniform, and filtered through a Teflon (registered trademark) filter having a pore size of about 1 μm.

Example 1 C.I. I. Pigment Red 254 as a resin having an acid value and a styrene-acrylic acid-methacrylic acid resin (styrene / acrylic acid / methacrylic acid = 77/10/13; molecular weight 5)
And an acid value of 160), and kneaded with a two-roll mill to form a bulk mixture containing 8 parts of propylene glycol monopropyl ether and 12 parts of methyl ethyl ketone. Since the lump mixture self-generated heat during kneading, the lump mixture was cooled while flowing cooling water.

The workability of the solid coloring compound during kneading was good without sticking to a roll, and a sheet-like solid coloring compound in which most of methyl ethyl ketone had evaporated was obtained. The obtained solid coloring compound was pulverized to a size of about 4 to 5 mm. Thereafter, a colored resin particle dispersion was obtained by the above-described method.

The average particle size of the obtained aqueous dispersion of colored resin particles was 181 nm.

(Example 2) The sheet-like solid coloring compound obtained in Example 1 was further crushed into an appropriate size such that it could be put on two rolls, and kneaded again. The solid coloring compound during the kneading had good workability without sticking to the roll. The obtained solid coloring compound was pulverized to a size of about 4 to 5 mm. Thereafter, a colored resin particle dispersion was obtained by the above-described method.

The obtained aqueous dispersion of colored resin particles had an average particle diameter of 159 nm, and was further finer than the recording liquid of Example 1.

Comparative Example 1 40 parts of the same pigment as in Example 1
A lump mixture obtained by adding 20 parts of methyl ethyl ketone to 40 parts of the same resin was kneaded with two rolls under the same conditions as in Example 1. The solid coloring compound stuck to the roll, and the workability was very poor. The obtained solid coloring compound was pulverized to a size of about 4 to 5 mm. Thereafter, a colored resin particle dispersion was obtained by the above-described method.

The resulting aqueous dispersion of colored resin particles had an average particle size of 400 nm.

Comparative Example 2 The sheet-shaped solid colored compound of Comparative Example 1 was kneaded again in the same manner as in Example 2.
The solid colored compound did not wind well on the rolls and could not be kneaded.

[0047]

According to the method for producing a solid colored compound of the present invention, the workability is improved as shown by the fact that kneading with a roll can be performed twice, and the particle size of the aqueous dispersion of colored resin particles is improved. As is clear from the above, a solid coloring compound in which pigment particles can be finely dispersed can be provided. The solid coloring compound thus produced is particularly preferable as a compound for producing an ink for an ink jet printer.

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Claims (6)

[Claims] 1. A solid coloring compound comprising a pigment and a resin having an acid value, wherein a glycol ether is added and kneaded. 2. The solid coloring compound according to claim 1, wherein the glycol ether is a propyl ether. 3. The solid coloring compound according to claim 2, wherein the propyl ether is propylene glycol monopropyl ether. 4. A method for producing a solid colored compound comprising a pigment and a resin having an acid value, wherein a glycol ether is added and kneaded. 5. The method for producing a solid colored compound according to claim 4, wherein the glycol ether is a propyl ether. 6. The method for producing a solid colored compound according to claim 5, wherein the propyl ether is propylene glycol monopropyl ether.