JP4614023B2 - Pigment dispersing apparatus and pigment dispersing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pigment dispersion apparatus, a pigment dispersion method, and a colored resin particle dispersion production method capable of dispersing while reducing pressure. More specifically, the present invention relates to a dispersion device and a manufacturing method for a pigment of pigment ink for inkjet recording and a colored resin particle dispersion.
[0002]
[Prior art]
Ink jet recording inks are roughly classified into oil-based inks and water-based inks, but oil-based inks have problems in terms of odor and toxicity, and water-based inks are becoming mainstream.
[0003]
However, many of the conventional water-based inks have a drawback that water resistance and light resistance are poor because a water-soluble dye is used as a colorant. In addition, since the dye is dissolved at the molecular level, printing on so-called plain paper such as copy paper commonly used in offices causes bleeding called wrinkle-like feathering, which causes a significant decrease in print quality. .
[0004]
Various so-called water-based pigment inks have been proposed in the past to improve the above-mentioned drawbacks. For example, resin-dissolved inks in which carbon black or organic pigments are dispersed using a water-soluble resin as a binder / dispersant. Various resin-dispersed inks containing a colorant as polymer latex or microcapsules have been proposed.
[0005]
As water-based pigment inks for jet printers, colorant particles dispersed in a fine particle size as much as possible are required. As a specific example of a resin-soluble water-based ink, Japanese Patent No. 2512861 discloses (a) a pigment and Filling a 2-roll mill with a polymeric dispersant; (b) grinding to obtain a dispersion of pigment and polymeric dispersant; and (c) dispersing the pigment dispersion in an aqueous carrier medium A method for preparing an aqueous pigmented ink-jet ink having improved properties is disclosed in JP-A-3-153775 as follows: a) Solid pigment preparation b containing a pigment and a carboxyl group-containing polyacrylic resin b A water-based ink composition for ink jet printing has been proposed which contains a) an organic solvent dilutable with water c) a wetting agent d) water.
[0006]
Resin-dispersed water-based inks have the advantages of relatively little increase in viscosity due to water evaporation of the ink and excellent water resistance. Specifically, JP-A-58-45272 discloses an ink composition containing a urethane polymer latex containing a dye, and JP-A-62-95366 discloses a method in which a polymer and an oily dye are dissolved in a water-insoluble organic solvent. Furthermore, an ink containing a dye encapsulated in polymer particles by evaporating the solvent after mixing with an aqueous solution containing a surfactant and emulsifying is proposed. Japanese Patent Application Laid-Open No. Sho 62-254833 discloses an organic solvent for encapsulation. A method for producing an aqueous suspension of colorant by reducing the interfacial tension between water and water to 10 dynes or less has been proposed. In JP-A-1-170672, a recording liquid containing a macroencapsulated dye is similarly used. Has been proposed.
[0007]
However, although these techniques are effective for finer pigments, the dispersion stability of the dispersed colorant and the ejection stability from the nozzles are not always sufficient, and the printing quality is not always good.
[0008]
As means for improving the ejection stability of ink, known is a method under reduced pressure (vacuum) and / or ultrasonic treatment. Specifically, the recording liquid disclosed in JP-A-06-184479 is identified as an aqueous medium. A method in which at least one azo dye is sufficiently mixed and dissolved, pressure-filtered with a Teflon filter having a pore size of 1 μm, and degassed with a vacuum pump and an ultrasonic cleaner, Japanese Patent Laid-Open No. 06-25574 Ink jet printer inks include inks containing a finely dispersed three-phase suspension consisting of a continuous liquid phase, a discontinuous phase and a solid phase, specifically, for example, a solid phase consisting of a pigment such as carbon black. Stirring a hydrophilic phase containing triethanolamine, an emulsifying aid and water as an emulsifier in a hydrophobic phase containing a fine dispersion dispersed in oleic acid and an sorbitan monostearate as an emulsifying aid After the addition, the obtained suspension is subjected to ultrasonic treatment to obtain the above-mentioned three-phase suspension, and the recording liquid treatment method disclosed in Japanese Patent Application Laid-Open No. 09-286943 includes at least a dispersant, an aqueous liquid. A method of performing ultrasonic treatment and vacuum defoaming treatment after preparing and purifying an aqueous pigment-based recording liquid composed of a medium, a pigment, and water is disclosed.
[0009]
However, these technologies do not have the pigment dispersion effect of the ultrasonic wave itself, and the pigment dispersion stability and jet stability from the nozzle are small because the effect of finer pigment, improvement of wetting, and defoaming effect are small. However, the print quality was not always good.
[0010]
On the other hand, as a general pigment dispersion method, a coloring material for paint as disclosed in JP-A-61-163970 and as a method for producing the same, the pigment is wet treated with a solution containing a resin for paint, and the pigment is dispersed in the solution. Thereafter, a method of obtaining a coating colorant having excellent optical properties of the coating film by drying and solidifying and coating the pigment surface with a coating resin is disclosed in Japanese Patent Application Laid-Open No. 62-192471. In the manufacturing method, the pigment dispersibility is greatly improved by instantaneous vacuum drying of the dispersion in which the pigment is uniformly dispersed in the resin solution dissolved in the solvent by the wet disperser, and the hiding property and smoothness are excellent. A method for obtaining a powder coating material has been proposed and can be applied as a method for producing ink for ink jet recording. However, in order to solidify the dispersion once, a redispersion step is necessary. Wetting to dispersion medium Discharge stability of insufficient ink is insufficient.
[0011]
In addition, in the method for producing a magnetic paint disclosed in Japanese Patent Application Laid-Open No. 09-12933, a kneading step of kneading the magnetic paint using a continuous biaxial kneader is performed by kneading the kneading part of the kneader in a vacuum atmosphere. However, in the apparatus configuration of this manufacturing method, magnetic powder and paint resin are melt-kneaded, and wet-kneading is impossible.
[0012]
In general, it is known that pigment dispersion is performed under reduced pressure, but a pigment dispersion apparatus capable of performing pigment dispersion continuously and efficiently has not been known.
[0013]
[Problems to be solved by the invention]
The problem to be solved by the present invention is a pigment that enables an ink composition using a pigment as a colorant, which has excellent dispersion stability with fine particle size, and enables stable jetting and excellent print quality in ink jet recording. An object of the present invention is to provide a dispersing device, a pigment dispersing method, and a colored resin particle manufacturing method.
[0014]
[Means for Solving the Problems]
As a result of intensive studies in order to solve the above problems, the present inventors have solved the present invention. That is, the present invention provides the following inventions.
[0015]
(1) Pigment dispersing device
It is possible to depressurize the part where the solid pigment is dispersed in the liquid medium, having at least a container having a structure capable of depressurization and a dispersion mechanism for passing and dispersing the mixture of the solid pigment and the liquid medium through the moving media group. A mechanism for continuously circulating the mixture between the vessel and the dispersion mechanism until the solid pigment is stably dispersed in the liquid medium. A pigment dispersion apparatus comprising mediamil.
[0016]
(2) Pigment dispersion method
It is possible to depressurize the part where the solid pigment is dispersed in the liquid medium, having at least a container having a structure capable of depressurization and a dispersion mechanism for passing and dispersing the mixture of the solid pigment and the liquid medium through the moving media group. In order to stably disperse the solid pigment in the liquid medium by using a pigment dispersing apparatus including the mediamyl which disperses the solid pigment in the liquid medium, the mixture is circulated and the solid pigment is stabilized in the liquid medium under reduced pressure. A pigment dispersion method characterized by dispersing.
[0017]
Hereinafter, the present invention will be described in order.
[0018]
The pigment dispersion apparatus of the present invention is a pigment dispersion apparatus in which at least a part where dispersion is performed has a decompression structure and is a media mill through which the dispersion continuously passes, preferably a dispersion supply and / or recovery tank The pigment dispersion device is configured to perform decompression from the beginning.
[0019]
The pigment dispersing apparatus of the present invention has at least the following configuration.
{Circle around (1)} A container having a structure capable of depressurization for containing a mixture of a liquid medium (corresponding to a dispersion medium) and a solid pigment.
(2) It has a dispersion mechanism for passing and dispersing between moving media groups, and has a media mill for dispersing the solid pigment in the liquid medium, enabling the portion where the solid pigment is dispersed in the liquid medium to be decompressed.
(3) A mechanism for continuously circulating the mixture (1) between the container (1) and the dispersion mechanism until the solid pigment is stably dispersed in the liquid medium.
[0020]
The greatest feature of the pigment dispersing apparatus of the present invention is that it has both the above (1) and (3).
[0021]
As the media mill which is a preferred dispersing apparatus of the present invention, any of the known and conventional bead mills and ball mills can be used. For example, the passing type is classified according to an introduction to dispersion technology (Nikkan Kogyo Shimbun; written by Masumi Koishi and Taiichi Tsuritani). Mills (sand mills, continuous attritors, pearl mills, Molinex) and their deformation mills (Dryswerke DCP mills, Mitsui Mining SC mills, Inoue Spike mills, Shinmaru Enterprises dyno mills ECM, Asada Tekko nano mills Etc.).
[0022]
These are dispersing devices that grind and disperse the pigment by utilizing the grinding shear force of the dispersed media (ball or bead). In the present invention, these are used so that they can be performed under reduced pressure.
[0023]
Among them, the dispersion mechanism including a moving media group through which a mixture of a solid pigment and a liquid medium passes has a rotatable rotor having an outer wall through a minute gap on the inner wall of the vessel, An annular media mill that is filled so that the media can be moved, rotates the rotor, and allows the mixture of the solid pigment and the liquid medium to pass through the dispersion mechanism in a substantially plug flow. Is particularly preferred.
[0024]
In order to make the mixture of the solid pigment and the liquid medium into a stable solid pigment dispersion, in order to make the mixture substantially plug flow, in addition to the above, for example, a rotation and impact force is applied to the media on the rotor surface. It is preferable to form a groove so that the projection and the median are returned in the direction opposite to the flow direction of the mixture.
[0025]
It is preferable to provide a cooling structure in at least a part of the apparatus so that the mixture of the solid pigment and the liquid medium or the solid pigment dispersion can be cooled. Specifically, a cooling jacket is provided inside the rotor or the outer wall of the vessel so as not to come into direct contact with the mixture of the solid pigment and the liquid medium or the solid pigment dispersion, and a coolant such as cooling water is passed through. It is preferable to adjust the temperature during dispersion. Hereinafter, such a particularly preferred media mill is referred to as a spike mill.
[0026]
A small gap between the rotor and the vessel of the media mill is filled with a media for dispersion. Existing dispersion media can be used for the dispersion of the present invention. The finer the media diameter, the higher the density, and the higher the rotation speed, the higher the pigment grinding ability. The dispersed media is preferably glass beads, ceramic beads, steel balls, stainless balls, cross-linked resin beads, and the like. In order to make the pigment into fine particles, beads having a diameter as small as possible are preferable. These media are not allowed to flow out of the media.
[0027]
In the present invention, a container having a structure capable of depressurization for containing a mixture of a solid pigment and a liquid medium is provided. However, a supply container for supplying a mixture of the solid pigment and the liquid medium and / or the solid pigment is supplied to the liquid medium. It has a collection container that collects the stably dispersed pigment dispersion, and the pressure is reduced from at least one of them.
[0028]
That is, in the present invention, there are a case where the supply container and the recovery container are the same and only one is used as a dual-purpose container, and a case where both the supply container and the recovery container are used separately. In the former case, it is preferable that the pressure is reduced from this single combined container, and in the latter case, the pressure is reduced so that the pressure of the recovery container becomes negative with respect to the pressure of the supply container.
[0029]
In addition, it is preferable to provide an ultrasonic transmission mechanism in a part of the container in that a stable dispersion can be obtained in a shorter time when the same media mill is operated under the same operating conditions.
[0030]
A mechanism for continuously circulating a mixture of the solid pigment and the liquid medium is provided between the containers and the dispersion mechanism until the solid pigment is stably dispersed in the liquid medium. Specifically, this mechanism can be provided by providing tubes and connecting them. Of course, it is also possible to provide a jacket in this piping portion so as to adjust the temperature during dispersion in the same manner as described above, and it is preferable to actually do so.
[0031]
For example, degassing may be performed to reduce the pressure in the portion where the media diamyl is dispersed. If the vessel and the pipe are connected to each other, for example, a mixture of a solid pigment and a liquid medium may be put in, and the pressure may be reduced from above the vessel having a depressurizable structure.
[0032]
The dispersion temperature and pressure for carrying out the pigment dispersion method of the present invention are not particularly limited and may be appropriately selected. As the dispersion temperature, the entire circulation system is 1 to 20 ° C., preferably 1 The circulating system pressure is 1 to 500 mmHg, preferably 1 to 100 mmHg. In the case of obtaining a pigment dispersion for water-based ink for ink jet recording, the circulation system in which the dispersion is performed has a temperature of 1 to 5 in that the printing density is higher and stable, and the ejection stability in long-term continuous printing is better. It is particularly preferable that the pressure is 1 to 100 mmHg at 10 ° C.
[0033]
Using such a pigment dispersion apparatus, the mixture is repeatedly circulated until a stable solid pigment dispersion is obtained, thereby dispersing the solid pigment in the liquid medium. In order to obtain a stable dispersion, it is necessary to perform sampling under various conditions in the middle of the circulation in advance, find conditions that maintain the required stability, and then carry out under the optimum conditions. preferable. In general, it is preferable to perform processing until the dispersion stability becomes constant and becomes saturated.
[0034]
Next, the pigment dispersion apparatus of this invention is demonstrated using drawing. FIG. 1 shows a pigment dispersion apparatus 1A having a decompression structure in which the supply tank and the recovery tank of the present invention are the same. The black arrow indicates the flow direction of the mixture with the liquid medium of the solid pigment, and the white arrow indicates the flow direction in the jacket (described later) through which the liquid medium for maintaining the apparatus at a constant temperature is passed (hereinafter referred to as the flow direction). , And so on.)
[0035]
This apparatus corresponds to a container having a depressurizable structure, which is a supply container / collection container provided with a deaeration pump (not shown) corresponding to a deaeration element and a deaeration port 6 that needs to be depressurized. And a pipe 7 for connecting the tank 4 and the media mill, which is a mechanism for continuously circulating a mixture of the liquid medium of the media pigment and the media pigment. In actual use, the deaeration pump and the deaeration port 6 are connected by a pipe to bring the system into a depressurized state.
[0036]
An ultrasonic oscillator 5 corresponding to an ultrasonic transmission mechanism is provided on a side portion inside the tank 4. On the other hand, a pipe 4 on the side for supplying a mixture of the tank 4 and a liquid medium of a solid pigment is provided. A jacket is provided outside to keep the circulation system at a constant temperature. The lower part of the tank 4 is connected to the inlet (inlet port) of the media mill by a pipe 7. On the contrary, the outlet (discharge port) of the media mill is connected by a pipe 7 so as to be returned to the tank 4 and thereby circulates.
[0037]
When supplying the mixture of the solid pigment and the liquid medium more stably to the inlet of the media mill, although not shown, a supply pump may be provided.
[0038]
The media mill includes a vessel and the rotor 3, and has a minute gap between the vessel wall 2 and the outer wall of the rotor 3, and the gap is filled with the dispersed media. This rotor is annular and rotates about its axis. When the mixture of the solid pigment and the liquid medium is introduced from the inlet of the media mill through the pipe 7 and passed through this gap, the rotor 3 rotates. The media group moves, and the shearing force causes dispersion of the solid pigment into the liquid medium, so that the dispersion state is more stable than the inlet, and is discharged to the pipe 7 from the outlet (discharge port) of the media mill. It has become. The surface of the rotor 3 is provided with irregularities so that the momentum based on the rotation and impact force of the media is increased and, as a result, a large shearing force acts on the mixture.
[0039]
Similarly, a jacket is provided outside the vessel so that the temperature inside the system can be kept constant even when passing through a minute gap.
[0040]
By doing so, it becomes possible to circulate and disperse the mixture or a dispersion liquid still having insufficient dispersion stability while reducing the pressure.
[0041]
FIG. 2 shows a pigment dispersion apparatus 1B having a decompression structure, which has both the supply container and the recovery container of the present invention separately. This apparatus 1B has a supply tank 4A corresponding to the supply container and a recovery tank 4B corresponding to the recovery container, and each tank has a deaeration port 6 and an ultrasonic oscillator 5 as in the apparatus 1A. Each is provided. Further, a pressure control valve 8 is provided in a part of the pipe 7 connecting the tank 4A and the media mill, and a switching valve 9 is provided in a part of the pipe 7 connecting the tanks 4A and 4B.
[0042]
In the case of this apparatus 1B, the pressure of the recovery tank 4B is negative with respect to the pressure of the supply tank 4A, that is, 4B is higher in pressure than the tank 4A. It is preferable to disperse the solid pigment in the liquid medium.
[0043]
Specifically, when the supply tank 4A and the recovery tank 4B are individually installed as described above, the supply tank 4A side is set to normal pressure or reduced pressure, and further, the recovery tank 4B is set against the pressure of the supply tank 4A. By making the pressure of the negative pressure, it is possible to disperse under reduced pressure in the dispersion part in the media mill. Valves 8 and 9 are used for pressure adjustment at this time.
[0044]
At this time, if a supply pump for supplying the mixture of the solid pigment and the liquid medium to the inlet of the media mill is provided, the load on the pump can be greatly reduced. Become. The mixture of the solid pigment and the liquid medium received in the supply tank 4A is once returned to normal pressure and then returned to the recovery tank, and is circulated and repeatedly dispersed again until the dispersion stability of the solid pigment in the liquid medium is saturated. Although it is possible to perform the dispersion, it is possible to continue the dispersion without returning to the normal pressure by returning the dispersion liquid to the supply tank with a suction pump having a pressure equal to or higher than that of the recovery tank 4B.
[0045]
At this time, it is preferable that the media mill is provided with a valve structure for generating pressure loss on the supply side of the dispersion portion, or the above deformation mill in which the cross-sectional area of the dispersion portion is small and large pressure loss is generated in the dispersion portion.
[0046]
In the case of the apparatus of FIG. 2, the mixture of the solid pigment filled in the tank 4A and the liquid medium is supplied into the vessel of the media mill by the pressure difference between the tank 4A and the tank 4B, but the pressure control valve 8 is throttled. Thus, the negative pressure in the vessel can be controlled. At this time, the switching valve 9 between the tank 4A and the tank 4B is closed.
[0047]
When the dispersion liquid of the mixture is collected in the tank 4B, the pressure control valve 8 is closed, and when the switching valve 8 is opened by reversing the pressure reduction of the tanks 4A and 4B, the mixture is transferred from the tanks 4A to 4B. Moving. By repeating the same operation for the mixture of the solid pigment and the liquid medium, it is possible to repeat the path dispersion. By repeating this process until the dispersion stability is saturated and a stable dispersion is obtained, the dispersion stability of the mixture is further improved.
[0048]
In the case of circulation dispersion, the flow rate or the processing amount of the mixture in the media mill can be determined by the supply amount provided with a supply pump. In the pass method, the processing amount can be determined by the difference in the degree of pressure reduction between the tanks 4A and 4B. However, depending on the structure of the media mill, the processing amount may increase as the rotor speed increases. For example, the SC mill has a suction effect due to the generation of negative pressure accompanying the rotation of the rotor, so that the throughput increases as the rotor speed increases. However, in the spike mill structure suitable as a media mill in the present invention, the suction force accompanying rotation does not work, so the pressure difference becomes the dominant factor.
[0049]
As a pigment dispersion apparatus of the present invention, a pigment dispersion apparatus in which an ultrasonic oscillator is installed at least in a part of the recovery tank 4B further improves the dispersion stability of a dispersion liquid subjected to a vacuum dispersion treatment by a media mill. The apparatus 1B is shown in a preferred form in which an ultrasonic oscillator is provided in both tanks 4A and 4B.
[0050]
Further, in order to keep the circulation system of the pigment dispersing apparatus of the present invention at a constant temperature, or to avoid excessive heating of the mixture of the solid pigment and the liquid medium or the stable dispersion due to the dispersion, The pigment dispersion apparatus of the present invention in which at least a part of the pipe and the tank has a cooling structure can also prevent evaporation of volatile components in the mixture of the solid pigment and the liquid medium or the stable dispersion due to the reduced pressure.
[0051]
This jacket structure is preferably installed as wide as possible where the mixture of solid pigment and liquid medium or stable dispersion comes into contact. Also, dew condensation and freezing of parts of the apparatus and mechanical strength decrease due to cooling. It is preferable to take measures to prevent this from occurring.
[0052]
In the present invention, the portion where the dispersion of the solid pigment into the liquid medium is performed, which has a container having at least a structure capable of depressurization and a dispersion mechanism for passing and dispersing the mixture of the solid pigment and the liquid medium between the moving media groups. In order to stably disperse the solid pigment in the liquid medium using a pigment dispersing apparatus comprising a mediamyl which disperses the solid pigment in the liquid medium, the mixture is circulated and the solid pigment is circulated under reduced pressure. Disperse stably in a liquid medium.
[0053]
In the present invention, a mixture, which is a treatment liquid to be dispersed, is prepared using a solid pigment and a liquid medium as essential components.
[0054]
The solid pigment used in the pigment dispersion method of the present invention is not particularly limited, and any known and commonly used pigment can be used. For example, inorganic pigments such as carbon black, titanium black, titanium white, zinc sulfide, bengara, etc. , Phthalocyanine pigments, monoazo and disazo pigments, organic pigments such as phthalocyanine pigments, quinacridone pigments, isoindoline pigments, perylene pigments and imidazolone pigments.
[0055]
In addition to the solid pigment and the liquid medium, the mixture can contain a resin and a resin neutralizer. As the liquid medium, a liquid medium containing at least a resin having an acid value, water, and a base is preferably used.
[0056]
The resin used in the pigment dispersion method of the present invention is not particularly limited, and publicly known and public ones can be used, and various resins can be used without being limited to natural resins or synthetic resins. ) Acrylic resin, polyester resin, polyurethane resin and the like.
[0057]
More preferable resins of the present invention include resins having an acid value, and resins having a water-soluble or water-dispersible acid value in combination with a base. The acid value of the preferred resin is 10 to 200, and the molecular weight is 1000 or more and 100,000 or less. A particularly preferred resin composition is a copolymer of (meth) acrylic acid and at least one monomer selected from the group consisting of styrene, substituted styrene, and (meth) acrylic acid ester.
[0058]
Examples of the base used in the present invention include alkali metal hydroxides such as sodium hydroxide (caustic soda), potassium hydroxide and lithium hydroxide, basic substances such as ammonia, triethylamine and morpholine, triethanolamine and diethanolamine. , N-methyldiethanolamine and other alcohol amines can be used, and these may be used alone or in combination. The amount of the base to be used may be set to an appropriate neutralization rate in consideration of dispersibility with respect to the acid group of the resin, for example, ink jet aptitude.
[0059]
The liquid medium is a dispersion medium in which the solid pigment is to be dispersed, and examples thereof include water and / or an organic solvent.
[0060]
As the organic solvent used in the pigment dispersion method of the present invention, a water-soluble organic solvent capable of dissolving the above-described resin is used. For example, ketone solvents such as acetone, dimethyl ketone and methyl ethyl ketone, alcohols such as methanol, ethanol and isopropyl alcohol are used. The solvent may be selected according to the resin such as a solvent, an ester solvent such as ethyl acetate, a glycol ether solvent such as ethylene glycol monomethyl ether or ethylene glycol dimethyl ether, an amide or the like. These solvents are preferably those that dissolve or disperse the resin alone or in combination.
[0061]
In the case of general pigment dispersion, particularly when an organic solvent is mainly used as a dispersion medium, the dispersion medium easily penetrates into the pigment and can sufficiently wet the pigment. On the other hand, in the case of water or a liquid medium mainly composed of water, it is difficult to wet the pigment even if a mill having a strong grinding power is used.
[0062]
When a mixture of at least a solid pigment and a liquid medium is dispersed using the pigment dispersion apparatus of the present invention, the pigment fine particles are wetted very efficiently by the resin, organic solvent, surfactant, etc. constituting the liquid medium. It will be.
[0063]
In order to stably disperse a solid pigment in water or a liquid medium mainly composed of water, there is a method using a surfactant or the like. In many cases, such problems occur.
[0064]
The pigment dispersion apparatus and the pigment dispersion method of the present invention are suitable for stably dispersing a solid pigment in water or a dispersion medium mainly composed of water without using a surfactant.
[0065]
By using a combination of a resin having an acid value and a base as described above, a solid pigment can be dispersed without using a surfactant, and a pigment dispersion having excellent dispersion stability can be obtained. I can do it.
[0066]
In the pigment dispersion method of the present invention, when the mixture containing the solid pigment is under reduced pressure during dispersion by the media mill, the dispersion medium comprising at least an acid value resin, water, and a base is obtained by the dispersion apparatus of the present invention. It penetrates into the new pigment surface generated with the grinding of the pigment very efficiently, and as a result, the solid pigment surface gets wet. At this time, when dispersing at a higher degree of vacuum, cooling according to the degree of vacuum should be performed so that the composition of the pigment dispersion does not change by suppressing the volatilization of the dispersion medium component having a low boiling point such as water. preferable.
[0067]
When a mixture of at least a solid pigment and water or a liquid medium mainly composed of water is dispersed using the pigment dispersing apparatus of the present invention, the pigment fine particles can form a dispersion medium, for example, a resin having an acid value. It gets wet very efficiently by organic solvents and bases.
[0068]
As a result, the pigment fine particles in the obtained pigment dispersion are more excellent in dispersion stability by being completely wetted with the dispersion medium. When this pigment dispersion is used, for example, in ink for ink jet recording, stable ink ejection and vivid and excellent print quality are possible.
[0069]
When the above operation is performed using a liquid medium containing at least an acid value resin, water, and a base as a liquid medium, a part of the resin is not adsorbed on the fine particles of the solid pigment and is not contained in the dispersion medium. Although it is often dissolved, the surface of the fine particles of the solid pigment in the liquid medium can be coated with the resin by adding a poor solvent for the resin.
[0070]
As the poor solvent for the resin, it is preferable to use water and / or a water-soluble organic solvent that does not dissolve the resin. This may be water alone or an aqueous solution of the water-soluble organic solvent.
[0071]
In the pigment dispersion method of the present invention, the organic solvent that acts as a poor solvent for the resin is, in addition to water, a polyvalent such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and glycerin. There are water-soluble organic solvents such as alcohols or their alkyl ethers and their aqueous solutions.
[0072]
The ratio of water to the water-soluble organic solvent in the pigment dispersion method of the present invention is not particularly defined as long as the effect of the present invention is achieved, but the weight ratio of water / organic solvent is 10/1 to 1/1. A small amount is preferred.
[0073]
As a result of the operation described above, the pigment fine particles in the obtained pigment dispersion are extremely excellent in dispersion stability by being completely covered with the resin in addition to being completely wetted with the dispersion medium. When this pigment dispersion is used in ink for ink jet recording, it enables more stable ink ejection and more vivid and superior printing quality.
[0074]
In particular, a liquid medium containing at least a resin having an acid value, water, a water-soluble organic solvent capable of dissolving the resin, the amount of which is controlled so that the resin is self-dispersible, and a base, By the pigment dispersing apparatus and the pigment dispersing method of the present invention, the resin that has become self-water-dispersible strongly coats the surface of the pigment fine particles, and as a poor solvent, only water or a water-soluble organic solvent that does not dissolve the resin is used. By adding a liquid medium mainly composed of water, such as an aqueous solution, the resin partially dissolved in the liquid medium further coats the surface of the pigment fine particles to form a so-called microcapsule and a highly stable colored resin particle dispersion. Become. In the present invention, the colored resin particle dispersion comprising the microcapsules is also referred to as a pigment dispersion.
[0075]
When this colored resin particle dispersion is used in ink for ink jet recording, it exhibits the most excellent characteristics, and more stable discharge of ink and vivid and excellent print quality are possible.
[0076]
In the pigment dispersion method of the present invention, pre-dispersion or post-processing dispersion by other dispersion means may be performed on the mixture of the solid pigment and the liquid medium or the pigment dispersion before and after dispersion by the pigment dispersion apparatus of the present invention. it can.
[0077]
For the mixture of the solid pigment and the liquid medium in the above pigment dispersion method and the pigment dispersion, a dispersant, a plasticizer, an antioxidant, an ultraviolet absorber, etc. may be used as an additive, if necessary. These may be added at any step of the pigment dispersion method of the present invention.
[0078]
Thus, according to the present invention, a pigment dispersion having a desired particle size can be obtained, but the average particle size range is usually 0.01 to 1 μm. When the dispersion is finally used, for example, as an ink jet recording liquid, the average particle diameter may be on the order of submicrons (less than 1 μm).
[0079]
The pigment dispersion obtained in this way can be used as it is, but if the dispersion stability of pigment particles or colored resin particles is poor due to the coexisting organic solvent, the storage stability is further improved. In order to improve safety against fire or pollution, it is preferable to further remove the solvent.
[0080]
In this operation, the resin is composed of a resin having an acid value, water, a water-soluble organic solvent capable of dissolving the resin, a base, and a water-soluble organic solvent that does not dissolve water and / or the resin. After coating the solid pigment in the liquid medium with the above resin, coating the solid pigment and stably dispersing in the liquid medium, remove at least the water-soluble organic solvent that can dissolve the resin from the liquid medium. Can be implemented.
[0081]
The colored resin particle dispersion containing submicron-order pigment microcapsules obtained by the pigment dispersion method of the present invention exhibits inkjet suitability excellent in dispersion stability and jetting characteristics when used as an aqueous ink for inkjet recording.
[0082]
When the finally obtained colored resin particle dispersion is used as a water-based ink for ink jet recording, the liquid medium has a purity higher than that of ion-exchanged water in each step of the present invention or all of the additional steps. It is preferable to have.
[0083]
When the dispersion obtained above is used as an ink for inkjet recording, it is preferable that an anti-drying agent is present in the ink in order to prevent the ink from drying. The drying inhibitor may be added directly to the pigment dispersion or the colored resin particle dispersion.
[0084]
Such an anti-drying agent has an effect of preventing the ink from drying at the jet nozzle opening of the ink jet, and usually has a boiling point equal to or higher than the boiling point of water. As such an anti-drying agent, any conventionally known ones can be used. For example, polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and glycerin. Or their alkyl ethers.
[0085]
The amount of the anti-drying agent used varies depending on the type, but is usually appropriately selected from the range of 1 to 150 parts by weight per 100 parts by weight of water.
[0086]
In particular, when the method of the present invention is applied to a method for producing a water-based ink for ink-jet recording, a water-solubility exhibiting a penetrability-imparting effect as a penetrability-imparting agent for allowing the ink to penetrate better into paper as required Additives such as organic solvents, water-soluble resins, pH adjusters, surfactants for dispersion, defoaming, and paper penetration, preservatives, and chelating agents can be added.
[0087]
In particular, when the method of the present invention is applied to a method for producing a water-based ink for ink-jet recording, the obtained dispersion can be used as a water-based ink as it is, but is usually passed through a filter having a desired particle size. It is filtered and used as a water-based ink for ink jet recording in which only particles smaller than the nozzle diameter of the ink jet recording apparatus are dispersed in a liquid medium. Therefore, for this application, it is preferable to avoid adding additives after the final filtration.
[0088]
The colored resin particles comprising the pigment microcapsules obtained by the pigment dispersion method of the present invention are excellent in color development and dispersion stability in the state of dispersion or in the state of dried solid and powder. In addition to recording water-based inks, it can be applied to writing instrument inks, paints, color filters, and toners.
[0089]
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes the following embodiments.
1. It is possible to depressurize the part where the solid pigment is dispersed in the liquid medium, having at least a container having a structure capable of depressurization and a dispersion mechanism for passing and dispersing the mixture of the solid pigment and the liquid medium through the moving media group. A mechanism for continuously circulating the mixture between the vessel and the dispersion mechanism until the solid pigment is stably dispersed in the liquid medium. A pigment dispersion apparatus comprising mediamil.
[0090]
2. The dispersion mechanism including a moving media group through which a mixture of a solid pigment and a liquid medium passes has a rotatable rotor having an outer wall through a minute gap on the inner wall of the vessel, and the media is located in the minute gap. 2. The pigment dispersion apparatus according to 1 above, which is filled so as to be movable, rotates the rotor, and allows the mixture of the solid pigment and the liquid medium to pass through the dispersion mechanism in a substantially plug flow.
[0091]
3. In order to make the mixture of the solid pigment and liquid medium substantially plug flow, the rotor surface is provided with protrusions that apply rotation and impact force to the media and a groove so that the media is returned in the direction opposite to the flow direction of the mixture. 3. The pigment dispersion apparatus as described in 2 above.
[0092]
4). A supply container for supplying a mixture of a solid pigment and a liquid medium and / or a recovery container for recovering a pigment dispersion in which the solid pigment is stably dispersed in the liquid medium are provided, and the pressure is reduced from at least one of them. The pigment dispersion apparatus of said 1-3.
[0093]
5). 5. The pigment dispersion apparatus according to 4 above, wherein the supply container and the recovery container are the same.
[0094]
6). 5. The pigment dispersion apparatus as described in 4 above, wherein both the supply container and the recovery container are provided separately, and the pressure of the recovery container is negative with respect to the pressure of the supply container.
[0095]
7). 7. The pigment dispersion apparatus according to 1 to 6 above, wherein an ultrasonic wave transmission mechanism is provided in a part of the container.
[0096]
8). 8. The pigment dispersion apparatus according to any one of 1 to 7 above, wherein at least a part of the apparatus is provided with a cooling structure so that the dispersion liquid can be cooled.
[0097]
9. It is possible to depressurize the part where the solid pigment is dispersed in the liquid medium, having at least a container having a structure capable of depressurization and a dispersion mechanism for passing and dispersing the mixture of the solid pigment and the liquid medium through the moving media group. In order to stably disperse the solid pigment in the liquid medium by using a pigment dispersing apparatus including the mediamyl which disperses the solid pigment in the liquid medium, the mixture is circulated and the solid pigment is stabilized in the liquid medium under reduced pressure. A pigment dispersion method characterized by dispersing.
[0098]
10. 10. The pigment dispersion method according to 9 above, wherein a liquid medium containing at least an acid value resin, water, and a base is used as the liquid medium.
[0099]
11. A liquid medium containing at least a resin having an acid value, water, and a base is added as a liquid medium, a poor solvent for the resin is added, and the solid pigment in the liquid medium is coated with the resin, so that the solid pigment 10. The pigment dispersion method as described in 9 above, wherein the fine particle surface is coated and stably dispersed in a liquid medium.
[0100]
12 The liquid medium is composed of a resin having an acid value, water, a water-soluble organic solvent capable of dissolving the resin, and a base, and the poor solvent for the resin is a water-soluble organic solvent that does not dissolve water or the resin. Or the pigment dispersion method of 11.
[0101]
13. A poor solvent for the resin, wherein the liquid medium is composed of a resin having an acid value, water, a water-soluble organic solvent capable of dissolving the resin, and a base, and an aqueous solution of water or a water-soluble organic solvent that does not dissolve the resin. In addition, after the solid pigment in the liquid medium is coated with the resin, and the solid pigment is coated and stably dispersed in the liquid medium, at least the water-soluble organic solvent capable of dissolving the resin is removed from the liquid medium. 11. The pigment dispersion method according to 11.
[0102]
The present invention includes the following preferred embodiments.
(1) A pigment dispersion apparatus in which at least a portion where dispersion is performed has a decompression structure and is a media mill through which the dispersion continuously passes, preferably, the decompression is performed from the supply and / or recovery tank of the dispersion. When the supply tank and the recovery tank are the same supply and recovery tank and the decompression line is installed in the tank, or when the supply tank and the recovery tank are installed separately, the supply tank side is set to normal pressure or decompression, Furthermore, the recovery tank pressure is set to a negative pressure relative to the supply tank pressure.
[0103]
(2) Pigment dispersion method
At least the dispersion portion where the dispersion is performed is made by using a media mill having a decompression structure (preferably a decompression line to the supply and recovery tank of the spike mill) while reducing the pressure, and a pigment and a resin base having an acid value (preferably Pigment dispersion using an aqueous solution containing caustic soda).
[0104]
(3) Colored resin particle dispersion manufacturing method
At least the dispersion part where dispersion is performed is a base of a resin having a pigment and an acid value (preferably a resin, preferably while reducing pressure using a media mill having a reduced pressure structure (preferably reduced pressure from a supply and recovery tank of a spike mill). Pigment dispersion is carried out using an aqueous solution containing caustic soda) and methyl ethyl ketone in an equivalent amount less than the equivalent of the acid value. Water, which is a poor solvent, is added dropwise to the obtained pigment dispersion while stirring under reduced pressure, and then methyl ethyl ketone is distilled off to obtain a suitable colored resin particle dispersion among pigment dispersions.
[0105]
A preferred embodiment of the present invention will be described as an example where it is applied to an ink for ink jet recording.
[0106]
An ink adjusting agent is added to the obtained pigment dispersion (preferably colored resin particle dispersion) to adjust the concentration and physical properties, followed by filtration to obtain an aqueous ink for inkjet recording. The above operation is preferably performed under reduced pressure.
[0107]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following examples, “part” represents “part by mass”.
[0108]
Example 1
20 parts of carbon black and 10 parts of styrene-acrylic acid-methacrylic acid resin (styrene / acrylic acid / methacrylic acid = 77/10/13; molecular weight 7400 / acid value 160), 200 parts of water, 1 part of caustic soda, It put into the mixed solution and stirred for 3 hours using a dispersion stirrer at room temperature to obtain a preliminary dispersion.
[0109]
Prepare a spike mill manufactured by Inoue Seisakusho using zirconia beads with a diameter of 0.3 mm as dispersion media. Place the pre-dispersed liquid obtained above in the supply and recovery tank and cool the tank and the entire pipe to 5 ° C. Then, the pressure was reduced to 30 mmHg and continuous dispersion was performed for 8 hours to obtain a black colored resin particle dispersion containing pigment microcapsules as the pigment dispersion. In dispersing the pigment, the apparatus was configured as shown in FIG.
[0110]
100 parts of the obtained black dispersion was added to an aqueous solution consisting of 20 parts of diethylene glycol, 5 parts of propylene glycol propyl ether and 75 parts of water while stirring, and stirred at 30 mmHg for 4 hours, using a 0.5 μm filter. Then, filtration under reduced pressure was performed to obtain a water-based ink for inkjet recording.
[0111]
The microcapsules in the obtained water-based ink have an average particle size of 0.09 μm, exhibit stable dispersion over a long period without aggregates, and printing using a thermal jet ink jet printer is stable. The obtained printed matter showed high blackness without bleeding. The obtained printed matter was not disturbed in characters and the printing density was high.
[0112]
(Example 2)
20 parts of carbon black and 20 parts of styrene-acrylic acid-methacrylic acid resin (styrene / acrylic acid / methacrylic acid = 77/10/13; molecular weight 50,000 / acid value 160), 210 parts of water, 35 parts of glycerin, It put into the mixed solution of 8 parts of triethanolamine, 90 parts of methyl ethyl ketone, and 40 parts of isopropyl alcohol, and it stirred at room temperature for 4 hours using the dispersion stirrer, and obtained the preliminary dispersion liquid.
[0113]
Prepare a spike mill manufactured by Inoue Seisakusho using zirconia beads with a diameter of 0.3 mm as dispersion media. Place the pre-dispersed liquid obtained above in the supply and recovery tank and cool the tank and the entire pipe to 5 ° C. Then, the pressure was reduced to 30 mmHg and continuous dispersion was performed for 8 hours to obtain a black colored resin particle dispersion containing pigment microcapsules as the pigment dispersion. In dispersing the pigment, the apparatus was configured as shown in FIG.
[0114]
While stirring under reduced pressure at 30 mmHg to the resulting black dispersion, a mixed solution of 30 parts of glycerin and 210 parts of water was added dropwise at a rate of 5 ml / min, and then methyl ethyl ketone and isopropyl alcohol were distilled off using a rotary evaporator. Concentration was performed to obtain a final black colored resin particle dispersion having a carbon black content of 8%.
[0115]
To 100 parts of the resulting aqueous dispersion, 20 parts of glycerin, 5 parts of propylene glycol propyl ether and 75 parts of water were added, stirred at 30 mmHg for 4 hours, filtered under reduced pressure using a 0.5 μm filter, and water-based for inkjet recording Ink was used.
[0116]
The microcapsules in the obtained water-based ink have an average particle size of 0.09 μm, show stable dispersion over a long period without agglomerates, and continuous printing using a piezoelectric inkjet printer is stable. The obtained printed matter showed no blackness and high blackness, and was excellent in water and light resistance.
[0117]
【The invention's effect】
The pigment dispersion obtained by the pigment dispersion method using the dispersion apparatus of the present invention and the colored resin particle dispersion obtained by the colored resin particle production method have a fine particle size, extremely excellent dispersion stability, and are water-based for inkjet recording. When applied to ink, it has excellent dispersion stability and enables stable inkjet ejection characteristics and excellent print quality.
[Brief description of the drawings]
FIG. 1 is a media mill having a decompression structure in which a supply tank and a recovery tank of the present invention are the same.
FIG. 2 is a media mill having a pressure reducing structure in which the pressure of the recovery tank becomes negative with respect to the pressure of the supply tank of the present invention.
[Explanation of symbols]
1A Dispersing device A
1B Dispersing device B
2 Vessel wall
3 Rotor
4 tanks
5 Ultrasonic oscillator
6 Degassing mouth
7 pipes
8 Pressure control valve
9 Switching valve

Claims (10)

It is possible to depressurize the part where the solid pigment is dispersed in the liquid medium, having at least a container having a structure capable of depressurization and a dispersion mechanism for passing and dispersing the mixture of the solid pigment and the liquid medium through the moving media group. was, and a Mejiamiru dispersing the solid pigment in a liquid medium until the solid pigment is stably dispersed in a liquid medium, between the container and the dispersing mechanism, a mechanism for circulating the mixture continuously, the vacuum Possible containers include a supply container that supplies a mixture of a solid pigment and a liquid medium, and a recovery container that collects a pigment dispersion in which the solid pigment is stably dispersed in the liquid medium, and the pressure is reduced from at least one of them. A pigment dispersing apparatus comprising a media mill , wherein the recovery container pressure is negative relative to the supply container pressure .   The dispersion mechanism including a moving media group through which a mixture of a solid pigment and a liquid medium passes has a rotatable rotor having an outer wall through a minute gap on the inner wall of the vessel, and the media is located in the minute gap. 2. The pigment dispersion apparatus according to claim 1, wherein the pigment dispersion apparatus is filled so as to be movable, rotates the rotor, and allows the mixture of the solid pigment and the liquid medium to pass through the dispersion mechanism in a substantially plug flow.   In order to make the mixture of the solid pigment and the liquid medium substantially plug flow, a protrusion is provided on the rotor surface that gives rotation and impact force to the media and a groove so that the media is returned in the direction opposite to the flow direction of the mixture. The pigment dispersion apparatus according to claim 2 formed. Pigment dispersing apparatus according to claim 1 to 3, wherein the part provided with the ultrasonic wave transmission mechanism of the container. The dispersion so as to be cooled, at least the pigment dispersion according to claim 1-4, wherein a portion of which is provided a cooling structure of the apparatus. It is possible to depressurize the part where the solid pigment is dispersed in the liquid medium, having at least a container having a structure capable of depressurization and a dispersion mechanism for passing and dispersing the mixture of the solid pigment and the liquid medium through the moving media group. In order to stably disperse the solid pigment in the liquid medium by using a pigment dispersion apparatus containing mediamyl which disperses the solid pigment in the liquid medium, the mixture is circulated and the solid pigment is stabilized in the liquid medium under reduced pressure. As a container that can be dispersed and depressurized, it has both a supply container that supplies a mixture of a solid pigment and a liquid medium, and a recovery container that collects a pigment dispersion in which the solid pigment is stably dispersed in the liquid medium. A pigment dispersion method, wherein pressure is reduced from any one of the two so that the pressure in the recovery container becomes negative relative to the pressure in the supply container . The pigment dispersion method according to claim 6 , wherein a liquid medium containing at least a resin having an acid value, water, and a base is used as the liquid medium. A liquid medium containing at least a resin having an acid value, water, and a base is added as a liquid medium, a poor solvent for the resin is added, and the solid pigment in the liquid medium is coated with the resin, so that the solid pigment The pigment dispersion method according to claim 6, wherein the fine particle surface is coated and stably dispersed in a liquid medium. The liquid medium comprises a resin having an acid value, water, a water-soluble organic solvent capable of dissolving the resin, and a base, and the poor solvent for the resin is a water-soluble organic solvent that does not dissolve water or the resin. The pigment dispersion method according to 7 or 8 . A poor solvent for the resin, wherein the liquid medium is composed of a resin having an acid value, water, a water-soluble organic solvent capable of dissolving the resin, a base, and an aqueous solution of water or a water-soluble organic solvent that does not dissolve the resin. in addition, by coating the solid pigment in a liquid medium in the resin, after stabilize dispersed in a liquid medium by coating the solid pigment claim 7 to be removed from the liquid medium at least a resin dissolvable water-soluble organic solvent Or the pigment dispersion method of 8 .

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