JP2002012798A - Method of manufacturing aqueous recording fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an aqueous inkjet printer recording fluid composed of a solid coloring compound containing a pigment and a resin which finely disperses the pigment particles and improves ease of its attachment to rolls upon kneading, and an aqueous inkjet printer recording fluid. SOLUTION: The method of manufacturing an aqueous inkjet printer recording fluid comprises adding a water-soluble organic solvent to be used in an aqueous recording fluid, preferably a water-soluble organic solvent having a boiling point of >=100 deg.C, more preferably propylene glycol monopropyl ether upon kneading a solid coloring compound to conduct the kneading.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an aqueous recording liquid in which a pigment is dispersed, and more particularly to an aqueous recording liquid suitable for printing on a porous recording material such as paper, In particular, the present invention relates to a method for producing an aqueous recording liquid that is effective when used as an ink for ink jet recording in which ink droplets are ejected from fine nozzles for recording.

[0002]

2. Description of the Related Art A recording liquid using a pigment as a coloring agent has an advantage that the recording liquid is superior to a recording liquid using a dye as a coloring agent. However, the dye-based recording liquid, which is a dissolving system, has excellent stability over time, whereas the pigment-based recording liquid, which is a dispersion system, has poor stability over time due to sedimentation of the pigment.

In recording on a transparent original such as an OHP film processed for an aqueous recording liquid, a dye recording liquid has high transparency and shows vivid coloration, whereas a pigment recording liquid does not. It also has disadvantages and disadvantages in that light scattering by the pigment particles occurs, resulting in low transparency and poor coloring.

In order to solve these drawbacks of the pigment-based recording liquid, it is necessary to disperse the pigment particles in the recording liquid as finely as possible, and various dispersion methods have been proposed. Among them, the method for producing a dispersion of colored fine particles for jet ink and jet ink disclosed in JP-A-11-80633 has a kneading step of obtaining a solid colored compound, while having excellent dispersion stability, high transparency and vivid coloration. In, depending on the formulation, the compound is easy to stick to the roll,
There has been a demand for a manufacturing method in which sticking to a roll is less likely to occur and which has improved workability during manufacturing.

[0005]

The problem to be solved by the present invention is to improve the ease of adhering the compound to a roll in the process of producing a solid colored compound comprising a pigment and a resin, and to improve the pigment particles. An object of the present invention is to provide a method for producing a finely dispersible aqueous recording liquid.

[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 relates to a method for producing an aqueous recording liquid containing pigment, resin, water-soluble organic solvent and water as essential components by using a solid coloring compound containing a pigment and a resin. Kneading is performed by adding the same water-soluble organic solvent as one component of the water-soluble organic solvent used in the aqueous recording liquid, preferably with a water-soluble organic solvent having a boiling point of 100 ° C. or more, and more preferably the aqueous recording liquid. The present invention provides a method for producing an aqueous recording liquid, wherein propylene glycol monopropyl ether is used as a water-soluble organic solvent used for kneading a solid coloring compound.

Here, the water-soluble organic solvent used in the aqueous recording liquid refers to a water-soluble organic solvent which is blended as one of the main components of the aqueous recording liquid when the aqueous recording liquid is produced from a solid coloring compound. A solvent, which is used in a manufacturing process such as a kneading process and does not mean a water-soluble organic solvent remaining in an aqueous recording liquid. In addition, the same water-soluble organic solvent here means that it is sufficient to use the same water-soluble organic solvent as the kneading with at least one water-soluble organic solvent contained in the aqueous recording liquid. When several water-soluble organic solvents are used, it does not mean that a water-soluble organic solvent mixture having the same composition as the mixture is used for kneading.

More preferably, however, all the water-soluble organic solvents having a temperature of 100 ° C. or higher used for kneading the solid coloring compound, if not the same composition as the water-soluble organic solvent mixture used in the aqueous recording liquid, are used. Is preferably selected from the water-soluble organic solvents used in the aqueous recording liquid, and more preferably contains propylene glycol monopropyl ether.
When only one kind of water-soluble organic solvent is used for kneading, it is most preferable that it is propylene glycol monopropyl ether, and that propylene glycol monopropyl ether is used in the aqueous recording liquid.

[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 in which the resin is heated and melted. And finally taken out as a solid kneaded material (solid colored compound). Although the ratio of the resin to the pigment is not particularly limited, it is generally kneaded with 10 to 500 parts by weight of the pigment per 100 parts by weight of the resin.

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 kneading temperature is usually in the range of 5 to 200 ° C., and each resin has an optimum melting state capable of realizing good pigment dispersion. Can be adjusted. When the temperature rises due to self-heating, the temperature may be adjusted by cooling the kneading device.

Although a solid colored compound can be obtained by mixing and kneading only the resin and the pigment, a kneading aid is preferably added in order to obtain a more dispersed state because the compound is easily stuck to a roll. 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 and methyl ethyl ketone; alcohol solvents such as methanol, ethanol and isopropyl alcohol; chlorine solvents such as chloroform and methylene chloride; and aromatic solvents such as benzene and toluene. Group solvents, and the like. Among these, they are appropriately selected and used according to the characteristics of the resin.

[0015] These organic solvents have the advantage that they have a low boiling point, so they are easily volatilized and hardly remain in solid coloring compounds. On the other hand, their composition changes every moment due to volatilization from the resin / pigment mixture during kneading. Therefore, there is a problem that it is difficult to keep the melted state of the resin optimal 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 the application of the organic solvent having a high boiling point improved the workability in the kneading step and, at the same time, made the obtained aqueous recording liquid fine. A combination of a low-boiling organic solvent and a high-boiling organic solvent that dissolve a conventionally used resin has been particularly effective.

However, an organic solvent having a high boiling point is difficult to volatilize, so that it tends to remain in a solid coloring compound, and is mixed in a finally obtained aqueous recording liquid. Therefore, the effect on the recording liquid such as impairing the dispersion stability or causing aggregation and gelation is taken into consideration, and the incorporation of an organic solvent having a high boiling point adversely affects the properties required for the use of the aqueous recording liquid. , The high boiling organic solvent to be used must be selected.

On the other hand, the aqueous recording liquid of the present invention contains a water-soluble organic solvent as an essential component. When a water-soluble organic solvent, which is an essential component of an aqueous recording liquid, is applied as a high-boiling organic solvent to be added during kneading of a solid coloring compound, the recording liquid is a component of the aqueous recording liquid even if it remains in the solid coloring compound. This is very preferable because there is no adverse effect on the characteristics required for the application. Here, from the viewpoint of preventing volatilization during kneading, the boiling point of the water-soluble organic solvent is preferably 100 ° C. or higher. Of course, if it is a trace amount, it is also possible to use in combination the kneading step of a water-soluble organic solvent not used in the aqueous recording liquid, but preferably only one selected from the water-soluble organic solvents used in the aqueous recording liquid. It is more desirable to use.

The kind and amount of the water-soluble organic solvent which is an essential component of the aqueous recording liquid and which is added at the time of kneading the solid coloring compound, and the low-boiling organic solvent which dissolves the resin conventionally used as a mixing aid. Since the type and amount of the solvent are determined by the type and characteristics of the resin, the type and the operating conditions of the kneading apparatus, it is necessary to appropriately select and apply the optimum conditions in each combination, but the solvent is also used simultaneously with the aqueous recording liquid. The amount of the high-boiling water-soluble organic solvent used is in the range of 0.1 to 40% by weight based on the total weight of the resin and the pigment, and the amount of the low-boiling water-soluble organic solvent is about 5 to 40% by weight. It may be adjusted to the optimum condition within the range of.

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 the aqueous recording liquid of the present invention is applied to ink for inkjet recording in which ink droplets are ejected from fine nozzles for recording, it is preferable to use two rolls.

An example of a method for producing an aqueous recording liquid from a solid coloring compound is disclosed in JP-A-11-8063.
Although described in Japanese Patent Publication No. 3, various methods including the method of the present publication can be adopted. For example, after dissolving the solid coloring compound in an organic solvent, water is added dropwise with stirring to convert the solvent into an aqueous phase, pigment fine particles encapsulated in the resin are prepared, and after removing the solvent, a water-soluble organic solvent or A method for obtaining an aqueous recording liquid by adding other additives. 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.

When the aqueous recording liquid of the present invention is applied to an ink for ink-jet recording in which ink droplets are ejected from fine nozzles for recording, the following method is particularly preferred.

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, an aqueous dispersion of colored resin particles having the pigment surface coated with the resin can be obtained. To the aqueous dispersion of the colored resin particles microencapsulated with the resin thus obtained, a water-soluble organic solvent essential for the aqueous recording liquid was added, mixed, and filtered with a filter to obtain the aqueous recording liquid of the present invention. Obtainable. As an ink for ink jet recording, an organic solvent that is a good solvent for the resin present in the suspension of the solid coloring compound, and when the remaining of the organic solvent that is the admixing aid is not preferable, the ratio of water in the solvent composition is adjusted. What is necessary is just to completely remove by distillation in the step of raising the temperature. The beadless dispersion device used here is preferably a collision-type dispersion device in which suspensions or pigment particles in a suspension collide with each other at a high liquid pressure to perform dispersion. Specifically, a nanomizer is used. (Manufactured by Nanomizer Co., Ltd.) or the like is used.

The composition of the suspension of the solid coloring compound and the ratio of water in the solvent composition to be changed after redispersion are appropriately determined according to each solid coloring compound since the optimum range varies depending on the individual solid coloring compound. Although it is necessary, when the colorant suspension is prepared from the solid coloring compound, the total of the pigment and the resin is 10 to 40 in the total suspension.
The optimum amount may be appropriately adjusted from about 20% by weight, about 20 to 70% by weight of ion exchange water, and about 5 to 40% by weight of an organic solvent which is a good solvent for the resin. The total of the pigment and the resin in the final aqueous recording liquid is about 0.5 to 20% by weight in the total aqueous recording liquid, the total of the water-soluble organic solvents is about 3 to 50% by weight, and the amount of water is also 20 to 98%. Although it is about weight%, it is adjusted to a quantity suitable for each ink suitability from about the range of these usage amounts.

A water-soluble organic solvent essential for an aqueous recording liquid, which can be used as a high-boiling organic solvent at the time of kneading a solid coloring compound, is used as an agent for imparting permeability to a recording material and an anti-drying agent when water is evaporated. ,ethylene glycol,
Polyhydric alcohols such as propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and glycerin;
Pyrrolidones such as N-methyl-2-pyrrolidone and 2-pyrrolidone; amides; ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether; and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. No.

When the aqueous recording liquid of the present invention is applied to an ink for ink jet recording in which ink droplets are ejected from fine nozzles for recording, propylene glycol monopropyl ether is preferred as a water-soluble organic solvent.

The resin 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. Among them, a resin having an acid value is preferable, and a particularly preferable range of the acid value is 1
0 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 aqueous recording liquid of the present invention is applied to an ink for inkjet recording in which ink is ejected from a fine nozzle for recording, at least one resin selected from the group consisting of styrene, substituted styrene, and (meth) acrylic acid ester is used as the resin. A copolymer of a monomer and (meth) acrylic acid is preferred. The molecular weight range in this case is 1000
It is preferably from 100,000 to 100,000.

The pigment used in the present invention may be appropriately selected from known and publicly used pigments in consideration of the tint, use, and compatibility with the resin. Examples thereof include inorganic pigments such as carbon black, titanium black, 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 water used in the present invention preferably has a purity higher than that of ion-exchanged water from the viewpoint of preventing impurities from being mixed.

The aqueous recording liquid of the present invention contains a resin, a pigment, a water-soluble organic solvent and water as essential components.
Various additives represented by preservatives and pH adjusters can also be used. The type and amount of the additive may be appropriately selected according to the use of the aqueous recording liquid.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes the following inventions and embodiments. 1. Using a solid coloring compound containing a pigment and a resin, in a manufacturing method for obtaining an aqueous recording liquid containing pigment, resin, a water-soluble organic solvent, and water as essential components, kneading of the solid coloring compound is used for the aqueous recording liquid. A method for producing an aqueous recording liquid, comprising adding the same water-soluble organic solvent as one of the water-soluble organic solvents to be used. 2. A water-soluble organic solvent used for an aqueous recording liquid,
2. The method for producing an aqueous recording liquid according to the above 1, wherein the water-soluble organic solvent used for kneading the solid coloring compound is a water-soluble organic solvent having a boiling point of 100 ° C. or higher. 3. 2. The method for producing an aqueous recording liquid according to the above 1, wherein the water-soluble organic solvent used for the aqueous recording liquid and the water-soluble organic solvent used for kneading the solid coloring compound is propylene glycol monopropyl ether. 4. Using a solid coloring compound containing a pigment and a resin, in a production method of obtaining an aqueous recording liquid containing pigment, resin, a water-soluble organic solvent, and water as essential components, the kneading of the solid coloring compound is carried out with an aqueous solution having a boiling point of 100 ° C or more. A method for producing an aqueous recording liquid, wherein a water-soluble organic solvent is used and the water-soluble organic solvent is all selected from the water-soluble organic solvents used in the aqueous recording liquid.

[0033]

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 weight”.

The details of the operations common to each embodiment after the preparation of the solid coloring compound are as follows.

<Preparation of Colorant Suspension> Ion-exchanged water as water, methyl ethyl ketone as an organic solvent which is a good solvent for a resin, triethanolamine as a base, and isopropyl alcohol as a hydrophilic organic solvent as an admixture. Was charged into a melting pot and mixed using a paddle blade. 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 parts Isopropyl alcohol 4.7 parts Glycerin 2.2 parts Total 53.6 Department

<Preparation of Colorant Particle Dispersion> 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,
The whole amount of ion-exchanged water was dropped at a rate of 5 ml per minute.

<Preparation of aqueous recording liquid> From the aqueous dispersion of colored resin particles obtained through the above steps, methyl ethyl ketone,
Isopropyl alcohol was removed by distillation. Using a rotary evaporator for distillation, the aqueous dispersion of colored resin particles was heated to 70 ° C., distilled under reduced pressure, and concentrated until the solid content became 20% by weight.

Glycerin, propylene glycol monopropyl ether, and ion-exchanged water were added to the concentrated aqueous dispersion of colored resin particles, and the mixture was stirred to uniformity. The mixture was filtered through a Teflon (registered trademark) filter having a pore size of 1 μm. I got

Aqueous recording liquid composition Colored resin particle aqueous dispersion 30.0 parts Ion-exchanged water 55.0 parts Glycerin 10.0 parts Propylene glycol monopropyl ether 5.0 parts Total 100.0 parts

The particle size of the aqueous recording liquid was determined using Microtrack UP.
The particle size was measured using an A particle size analyzer (manufactured by Leads and Northrup). The sample was appropriately diluted with ion-exchanged water to a measurable concentration.

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 solid coloring compound during kneading had good workability without sticking to the 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, an aqueous recording liquid was obtained by the above-described method.

The volume average particle diameter of the obtained recording liquid was 182 n.
m.

(Example 2) The sheet-shaped solid coloring compound obtained in Example 1 was 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, an aqueous recording liquid was obtained by the above-described method.

The volume average particle diameter of the obtained recording liquid is 158 n.
m, which was more finely divided 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, an aqueous recording liquid was obtained by the above-described method.

The volume average particle diameter of the obtained recording liquid was 402 n.
m.

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.

[0051]

According to the method for producing an aqueous recording liquid of the present invention, it is possible to improve the workability in the process of producing a solid colored compound comprising a pigment and a resin and to provide an aqueous recording liquid capable of finely dispersing pigment particles. Becomes

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Claims (4)

[Claims] 1. A method for producing an aqueous recording liquid comprising a pigment, a resin, a water-soluble organic solvent and water as essential components by using a solid coloring compound containing a pigment and a resin, wherein the kneading of the solid coloring compound is performed by: A method for producing an aqueous recording liquid, comprising adding the same water-soluble organic solvent as one of the water-soluble organic solvents used for the aqueous recording liquid. 2. A water-soluble organic solvent used for an aqueous recording liquid, wherein the water-soluble organic solvent used for kneading a solid coloring compound is a water-soluble organic solvent having a boiling point of 100 ° C. or higher. The method for producing an aqueous recording liquid according to claim 1, wherein 3. The aqueous recording medium according to claim 1, wherein the water-soluble organic solvent used for the aqueous recording liquid and the water-soluble organic solvent used for kneading the solid coloring compound is propylene glycol monopropyl ether. Liquid production method. 4. A method for producing an aqueous recording liquid comprising a pigment, a resin, a water-soluble organic solvent and water as essential components by using a solid coloring compound containing a pigment and a resin. A method for producing an aqueous recording liquid, wherein a water-soluble organic solvent having a temperature of 100 ° C. or higher is used, and all of the water-soluble organic solvents are selected from the water-soluble organic solvents used in the aqueous recording liquid. .