JP3482133B2 - Recording liquid, method for producing recording liquid, and method for using recording liquid - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording liquid, and a pigment-containing recording liquid suitable for use in ballpoint pens and marking pens.

[0002]

2. Description of the Related Art The ink jet recording method produces less noise and does not require special fixing on plain paper.
Various types have been actively studied because of the capability of high-speed recording.

In these ink jet recording methods, the recording liquid (recording ink) used has physical properties such as viscosity and surface tension within appropriate ranges, and does not clog fine discharge ports (orifices). Various characteristics are required, such as providing a recorded image with a clear color tone and a sufficiently high density, and preventing physical property changes or precipitation of solid contents during storage.

In addition to these characteristics, the recording liquid can perform recording without limiting the type of recording medium represented by paper, and has a high fixing speed on the recording medium.
It is also required to have various properties such as excellent water resistance, solvent resistance, light resistance and abrasion resistance, and giving an image with excellent resolution.

Since the recording liquid applied to the ink jet recording method is basically composed of a pigment as a recording material and its solvent (dispersion medium), various characteristics of the above recording liquid are as follows. It largely depends on the properties inherent to the pigment. Therefore, selecting a pigment so that the recording liquid has the above-mentioned various properties is an extremely important technique in the future technical field.

[0006] In particular, the solubility and dispersibility of the pigment in the solvent are important, and the pigment must have sufficient solubility and dispersibility in water and also in a wetting agent generally composed of an organic solvent. It is the basis for maintaining good anti-clogging property and maintaining the pigment dissolution stability and dispersion stability.

Among these pigments, the black pigment is in great demand. As such a black pigment, carbon black particles are often used in recording liquids because they are inexpensive.

However, in the conventional recording liquid using carbon black particles as the black pigment, when the dispersion stability is determined with the carbon black particles having a small particle size, the carbon black particles themselves are hydrophobic, so that they easily aggregate. It has a disadvantage that the above various characteristics cannot be sufficiently satisfied.

Therefore, in order to avoid the above inconvenience,
It is considered to make the pigment hydrophilic, that is, to modify the pigment. Thus, as a method for modifying the pigment, for example, in JP-A-6-145545, 3 g of the azo pigment is dissolved in 50 g of sulfuric acid grade 1 and stirred for 4 hours to sulfonate the azo pigment to form an azo pigment. A method of making a pigment hydrophilic to modify it is disclosed.

[0010]

However, when the above-mentioned conventional modifying method is used for carbon black particles used as a black pigment, it has a problem that the pigment itself is discolored by a long-term acid treatment. Instead, the amount of chemicals (sulfuric acid) used for the oxidation treatment is enormous (15 to 20 times by weight) as compared with the amount of the obtained modified pigment, resulting in an increase in waste liquid treatment cost and treatment. Since it is a batch system and continuous processing is impossible, there is a problem in that the manufacturing cost is increased and the cost is increased.

Further, in the above-mentioned conventional modification method, when treating the fine particles of submicron order or less, it is said that the stable treatment of the individual particles makes it easy for the fine particles to easily aggregate. Difficult because of its drawbacks.

As described above, since the recording liquid prepared by the above-mentioned conventional reforming method cannot be made into a uniform and comparatively small particle size in a short time and at a low cost with a simple device and operation, it is stable in storage. And the jetting stability when used in the inkjet recording method, and the problem that it is difficult to satisfy both the recording property such as the water resistance and the light resistance in which bleeding is suppressed when recording on a recording medium. Have a point.

The present invention has been made in view of the above-mentioned problems of the prior art, and has a relatively small particle size and a uniform size in a short time and at low cost with a simple device and operation, and also has a dissolution stability. An object of the present invention is to provide a recording liquid including pigment particles having excellent dispersion stability, a method for producing the recording liquid, and a method for using the recording liquid.

[0014]

In order to solve the above-mentioned problems, the recording liquid of the present invention holds pigment particles having an average particle diameter of 10 nm to 20 μm in a solvent containing water, and the pigment particles have a surface on the surface thereof. , better to so that the oxidation treatment unit is provided.
The oxidation treatment part immerses (suspends) the pigment particles in an acidic liquid such as an aqueous nitric acid solution and rapidly boils / vaporizes the acidic liquid (nucleate boiling with the pigment particles as nuclei) to make the surface of the pigment particles hydrophilic. It is formed by a chemical treatment. In the above recording liquid, a plurality of pigment particles having different sizes may be used.

The solvent contains water as a main component, and it is desirable to use water alone or a mixture of water and various water-soluble organic solvents. Examples of the water-soluble organic solvent include methyl alcohol, ethyl alcohol, n
-Propyl alcohol, isopropyl alcohol, n-
C1-4 such as butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol
Alkyl alcohols, amides such as dimethylformamide and dimethylacetamide, ketones or keto alcohols such as acetone and diacetone alcohol, ethers such as tetrahydrofuran and dioxane, polyalkyl glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol , Propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, and the like, alkylene glycols containing 2 to 6 carbon atoms, glycerin, ethylene Polyglycol, methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether, etc. Lower alkyl ethers of alcohols, 2-pyrrolidone, pyrrole, nitrogen-containing heterocyclic ketones such as pyridine.

Among them, among water-soluble organic solvents, polyhydric alcohols of polyalkyl glycols and alkylene glycols, lower alkyl ethers of polyhydric alcohols,
Nitrogen-containing heterocyclic ketones are preferred, especially alkylene glycols containing 2 to 6 carbon atoms. Polyhydric alcohols are particularly preferable because they have a large wetting effect of preventing clogging of the nozzles due to the evaporation of water in the recording liquid and the deposition of the pigment as the recording material.

The content of hydrophilic particles having hydrophilicity by having an oxidation treatment portion and the content of a solvent in the recording liquid are appropriately set depending on the purpose of the recording liquid and the kind of hydrophilic particles or solvent used. The content of the hydrophilic particles is usually 0.01% by weight, though not particularly limited.
Within the range of 20% by weight, more preferably 0.1% by weight
It is in the range of 10% by weight, and the content of the solvent is in the range of 60% by weight to 99.9% by weight, more preferably in the range of 70% by weight to 99.9% by weight.

Further, for the purpose of suppressing bleeding when recording on a recording medium such as paper using the above recording liquid, ammonium polyacrylate and / or vinyl alcohol is further added to the above recording liquid. You may mix | blend the copolymer with acrylic acid.

The content (blending amount) of ammonium polyacrylate is in the range of 0.3% by weight to 10% by weight, more preferably in the range of 1% by weight to 10% by weight. If the content (blending amount) of ammonium polyacrylate is less than 0.3% by weight, the effect of suppressing bleeding cannot be expected. On the other hand, when the content (blending amount) of ammonium polyacrylate is more than 10% by weight, further improvement of the bleeding suppression effect in proportion to the increase of the addition amount is not observed, and a part of the added ammonium polyacrylate is Not only becomes wasteful and economically disadvantageous, but also increases the viscosity of the recording liquid, resulting in deterioration of the function of the recording liquid, which is not preferable.

The content (blending amount) of the copolymer of vinyl alcohol and acrylic acid in the recording liquid is in the range of 1% by weight to 10% by weight, and more preferably 3% by weight to.
It is within the range of 10% by weight.

When a copolymer of vinyl alcohol and acrylic acid is used instead of ammonium polyacrylate, if the content of the copolymer is less than 1% by weight,
The effect of suppressing bleeding cannot be expected. On the other hand, when the content (blending amount) of the copolymer is more than 10% by weight, further improvement of the bleeding suppressing effect in proportion to the increase of the addition amount is not observed, and a part of the added copolymer is Not only is it wasteful and economically disadvantageous, but the viscosity of the recording liquid increases, and this leads to deterioration of the functions of the recording liquid, which is not desirable.

In the present invention, by using a poly (ammonium polyacrylate) and / or a copolymer of vinyl alcohol and acrylic acid as a component of the recording liquid, the permeability of the recording liquid into the recording medium is reduced and the bleeding occurs. Reduce
You may do it . Generally, when the permeability is low, the drying property is low, but the above-mentioned ammonium polyacrylate,
Also, the copolymer of vinyl alcohol and acrylic acid can suppress bleeding while maintaining the drying property.

In the present invention, the recording liquid may further contain a water-soluble dye as a colorant. Specifically, CI (Color Index) Direct B
lack 2,4, 17, 19, 22, 32, 38, 51, 56, 62, 71, 74,
77, 105, 108, 112, 154, etc. are used alone or in combination. In addition, CI Direc as a blue dye
tBlue 1, 2, 6, 8, 15, 22, 25, 71, 86, 98, 108, 19
CI Direct as a red dye such as 2, 199, 201, 237
Red 1, 11, 37, 52, 75, 81, 99, 227, 220 etc., CIA
cid Red 87, 92, 94, 115, 154, 131, 186, 254, etc., and yellow dye CI Direct Yellow 12, 27, 33, 50,
86, 110, 157, CI Acid Yellow 7, 17, 23, 29,
42, 99 and the like may be mixed. When the recording liquid further contains a water-soluble dye, the color tone of transparency and glossiness can be improved, and these color tones can be finely changed, so that the field of use can be expanded.

The recording liquid of the present invention prepared from such components has recording properties (signal responsiveness, stability of droplet formation during ejection, ejection responsiveness, long-term continuous recording property,
Discharge stability after long-term recording suspension), storage stability, fixability to a recording medium, light resistance of a recorded image, weather resistance, water resistance, etc. are all well balanced and excellent. In order to further improve such characteristics, various conventionally known additives may be further added and contained.

As such additives, antiseptics, antifungal agents, pH adjusting agents, rust preventives, surface tension adjusting agents, viscosity adjusting agents,
An ultraviolet absorber, an infrared absorber, etc. can be mentioned.
A solubilizer may be added to the recording liquid of the present invention.
By adding nitrogen-containing heterocyclic ketones as a solubilizing agent, the solubility or dispersibility of the hydrophilic particles in a solvent can be improved.

When applied to an ink jet type in which a recording liquid is ejected by the action of thermal energy, thermal physical property values may be applied.

The recording liquid of the present invention has excellent characteristics suitable for ink jet recording, but is a recording ink for writing instruments such as ballpoint pens and marking pens for recording on a recording medium such as paper. Can also be preferably used.

In order to solve the above-mentioned problems, the above-mentioned method for producing a recording liquid comprises suspending pigment particles in an acidic liquid to obtain a suspension solution, and then rapidly suspending the suspension solution to a temperature of 700K.
In heated, by rapid boiling and vaporization of the acid liquid pigment particles suspended in an acidic solution as the core, the pigment particles in the suspension by nucleate boiling as nuclei, the phase change at the boiling Due to the rapid expansion of the volume by separating the aggregated pigment particles, the surface of the pigment particles, to form an oxidation treatment portion to prepare hydrophilic particles, the hydrophilic particles, water and,
It is characterized in that it is dispersed in a solvent containing ammonium polyacrylate and / or a copolymer of vinyl alcohol and acrylic acid.

In the above-mentioned method for producing the recording liquid, the acidic liquid in the suspension obtained by suspending the raw material particles of the pigment in the acidic liquid is heated to a temperature of 10 K or higher, more preferably 20 K, with respect to the boiling point of the acidic liquid. It is preferable to heat and vaporize at the above temperature. By the above method, the acidic liquid can be heated or vaporized more reliably, and the surface-modified hydrophilic particles can be obtained more efficiently.

In the above method, the acidic liquid preferably contains a volatile liquid having a latent heat of vaporization equal to or lower than that of water. The volatile liquid is latent heat of vaporization of water [41 kJ / mo
1 (373K)], which has a smaller latent heat of vaporization than that of liquid at room temperature, such as ethyl alcohol [39kJ]
/ Mol (352K)].

According to the above method, since the liquid acidic liquid can be quickly vaporized by containing the volatile liquid and the dispersion of the aggregated pigment particles can be more surely performed, the surface can be modified more efficiently. It is possible to obtain the hydrophilic particles thus treated.

In the above method, the volatile liquid may be a vaporization accelerator that promotes vaporization of the acidic liquid. The vaporization accelerator may be any substance that easily foams and vaporizes by heating, and examples thereof include ethyl alcohol, freon gas, hydrogen peroxide solution, carbon dioxide gas, liquefied carbon dioxide gas, and liquid nitrogen.

According to the above method, since the acidic liquid can be vaporized more quickly and the aggregated pigment particles can be more surely dispersed by containing the vaporization accelerator, the hydrophilic particles can be more efficiently produced. It becomes possible to obtain.

In the above method, it is desirable to disperse the pigment particles of the suspension in the suspension. According to the above method, the pigment particles are more uniformly dispersed in the suspension, whereby each aggregated pigment particle can be reduced, and the aggregated size of each aggregated pigment particle can also be reduced. With relatively small and uniform hydrophilic particles,
It can be manufactured more stably.

In the above method, the suspension is preferably heated in advance. According to the above method, since the temperature rise Δt required for nucleate boiling and vaporization of the acidic liquid in the suspension can be reduced, nucleate boiling and vaporization can be accelerated. From this,
In the above method, the rate of change in volume expansion during nucleate boiling or vaporization can be increased, and the dispersed pigment particles can be efficiently dispersed. Therefore, the particle diameter is relatively small, and hydrophilic particles that are uniform are more preferable. It can be manufactured stably.

In the above method, the suspension is preferably in the form of liquid drops. In the above method, by forming a droplet,
Nucleate boiling and vaporization of the acidic liquid in the suspension can be facilitated, and for example, the power supply for heating can be reduced, and the cost can be reduced.

The pigment particles according to the present invention are fine particles which are solid at room temperature and pressure, and when immersed in an acidic liquid,
It is a particle that has stability without causing a change in basic structure such as decomposition or polymerization, and can be imparted with hydrophilicity such as a functional group, for example, a carboxyl group, that is, a particle into which a hydrophilic group can be introduced. .

The above-mentioned particles are not particularly limited, but particles such as titanium oxide and pigments are mentioned, and black pigments such as carbon black particles are particularly preferable. In the present invention, “normal temperature / normal pressure” means 20 ° C. and 1 atm.

In the recording liquid according to the present invention, hydrophilic particles whose surface has been modified, for example, surface-modified by introducing hydrophilic groups, are dispersed more uniformly (average particle size is 10 nm).
To 20 μm, preferably 20 nm to 10 μm, and more preferably 40 nm to 5 μm).

When the pigment particles are dipped and suspended in the acidic liquid, the pigment particles may be heated by a heater or the like, if necessary, near the boiling point of the acidic liquid and / or stirred by a stirring blade or the like. May be dispersed as much as possible. Further, it is expected that the higher the stirring strength is, the more the dispersion of the pigment particles progresses, but it is not particularly limited.

The hydrophilic particles obtained by the above method are
After collecting, it is washed with ultrapure water or the like, if necessary. This makes it possible to produce hydrophilic particles from which impurities have been removed. The hydrophilic particles washed with water may be dried, if necessary, to such an extent that the hydrophilic particles can be prevented from aggregating with each other. Whether or not the impurities contained in the hydrophilic particles have been removed may be determined using, for example, the pH of the cleaning liquid as a guide. The method of collecting hydrophilic particles, the method of washing with water, and the method of drying are not particularly limited.

As described above, in the method for producing hydrophilic particles according to the present invention, a suspension obtained by immersing and suspending hydrophobic pigment particles in an acidic liquid is heated while being conveyed, more preferably the particles are suspended. This is a method in which the pigment particles that easily aggregate are dispersed by heating so as to rapidly nucleate as nuclei, and at the same time, the surface of the pigment particles is modified by oxidation of an acidic liquid to impart a hydrophilic group.

Therefore, in the above method, unlike the conventional method in which the particles are oxidized while being stirred by using a stirring device such as a stirring blade, the risk of the particles being charged by friction or the like is avoided. In addition, the above-mentioned production method can modify the surface of the pigment particles by a simple device and operation in a short time.

Further, in the above method, even if the pigment particles are agglomerated, an external force due to a rapid volume expansion due to nucleate boiling, for example, a volume expansion of 1000 times when water is vaporized is utilized. Secondary particles, which are aggregated pigment particles, are dispersed in the primary particles, and hydrophilic particles having a small particle size and high dispersibility can be stably obtained.

For example, since the hydrophilic particles obtained by the above method are imparted with hydrophilicity by, for example, introducing a hydrophilic group (oxidized portion) to the surface of the pigment particles, the wettability with water is improved. Has been improved. Specifically, for example, hydrophilic particles have a carboxyl group (oxidized portion) on the surface of the hydrophilic particles by the above-mentioned oxidation treatment.
Has been introduced, the wettability with respect to water is improved.

The hydrophilic particles obtained by the above method are
For example, when the particles are pigment particles composed of a pigment having hydrophobicity, it can be used in various applications such as paints, printing inks (ink-jet recording inks, recording inks for ballpoint pens and marking pens), toners (developer), etc. It is preferably used.

[0047]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows an embodiment of the present invention.
The following is a description with reference to FIG.

As shown in FIG. 1, the recording liquid according to the present invention has hydrophilic particles 42b suspended and held in a solvent 14 containing water. The hydrophilic particles 42 b are obtained by oxidizing the surface of the pigment particles 42, and the hydrophilic groups (oxidized portions) 12 such as carboxyl groups are provided on the surfaces of the pigment particles 42.

As the pigment particles 42, black pigments such as carbon black particles, which are hydrophobic and have a small particle diameter (average particle diameter of 10 nm to 20 μm), are preferable. Such hydrophilic particles 42b are manufactured, for example, by the particle surface oxidation device shown in FIG.

First, the particle surface oxidizer (hereinafter referred to as “manufacturing device”) 1 will be described. The manufacturing device 1 includes a particle suspension unit 2, a particle supply unit 3, a particle oxidizing unit 4, a diluent gas introducing unit 5, and One liquid processing section 6, two respective particle collecting sections 7a,
7b, an optical measuring unit 8, a second liquid processing unit 9, and the like, and by heating the hydrophobic pigment particles 42 while conveying them, the hydrophilic groups 12 by oxidation are introduced to the surfaces of the pigment particles 42. The hydrophilic particles 42b thus prepared can be continuously and stably manufactured.

As shown in FIG. 3, the optical measuring section 8 includes a light source 8a, a lens 8b, and transparent plates 8e and 8e inside a housing 8h.
f, the photodetector 8g and the like are provided. The light emitted from the light source 8a is scattered and dimmed by the pigment particles (droplets) 42 introduced into the housing 8h, so that the amount of light changes.

As a result, the optical measuring unit 8 can measure the particle diameter and number concentration of the pigment particles 42 and the liquid droplets based on the signal output from the light detecting unit 8g according to the amount of incident light. ing. By measuring the particle diameter and the particle number concentration using the optical measuring unit 8, the manufacturing process of the hydrophilic particles 42b can be controlled.

The optical measuring unit 8 is constructed so as to measure the particle size by using the photodialysis / scattering method.
The measuring method is not particularly limited, and for example, an X-ray transmission method, a sedimentation method, a laser diffraction / scattering method, a photon correlation method utilizing dynamic scattering, or the like can be adopted. In addition to the optical measurement method, an image processing analysis method using an optical microscope or an electron microscope can be adopted. The number concentration can be determined by, for example, a light transmission method.

The particle suspension unit 2 shown in FIG. 2 is provided with a cylindrical or prismatic container 21. The container 21 contains water or a mixed liquid of water and an azeotropic compound of water (hereinafter, simply abbreviated as water) and a suspension 22 in which particles are mixed and suspended. By adjusting the pressure and flow rate of the inert gas 23 supplied into the closed container 21, the suspension 22 supplied from the particle suspension unit 2 to the particle oxidation unit 4 via the particle supply unit 3 is adjusted. The liquid volume can be controlled.

In the container 21 of the particle suspension unit 2, for example, a stirring device such as a magnetic stirrer or an ultrasonic vibration device is installed as the particle dispersion device 24. The particle dispersion device 24 prevents the particles in the suspension 22 in the container 21 from aggregating or disperses the agglomerated particles to a certain extent by dispersion by stirring or vibration. The particle suspension unit 2 is connected to the particle oxidation unit 4 via the particle supply unit 3 so that the suspension 22 can be supplied.

The particle oxidizing section 4 has a tube 41 into which the suspension 22 is introduced and an electric furnace (heating section) 44 as a heating member for heating the inside of the tube 41. Particle oxidation part 4
In Fig. 4, when the suspension flowing in the pipe 41 from the bottom to the top is rapidly heated while being conveyed in the pipe 41 which has been preheated by the electric furnace 44, as shown in Fig. 4, The particles of the suspension 22 are rapidly changed to a preheating flow, a bubbling flow, a turbulent flow, and a vaporization flow, and flow toward the carry-out port 46 from the introduction port 45 shown in FIG. It can be heated while being transported to.

At this time, as shown in FIG. 5, the suspension liquid 22 in the pipe 41 causes nucleate boiling with the pigment particles 42 as nuclei and vaporization of the acid liquid 43 in the acidic liquid 43, so that each pigment particle Four
The agglomerated particles 42a of No. 2 are dispersed into individual single pigment particles 42 by the rapid volume expansion during nucleate boiling or vaporization, and the acidic liquid 43 around the pigment particles 42 is rapidly nucleated and vaporized. By doing so, the pigment particles 42 are boiled by the acidic liquid 43 around the pigment particles 42, the surfaces of the pigment particles 42 are rapidly oxidized, and the hydrophilic particles 42b having the hydrophilic groups 12 are generated. . It is further preferable that the suspension liquid 22 transported to the pipe 41 is in the form of droplets.

On the other hand, the inner wall of the pipe 41 has a water repellent portion 19 made of a water repellent (liquid repellent) material, as shown in FIG. As the water repellent material, for example, fluororesin, flushing glass having a roughened surface, or the like is used.

Further, the inner wall of the pipe 41 is formed, for example, in the shape of a cylinder, in which the central axis of the pipe 41 is inclined at an angle θ with respect to the horizontal direction as shown in FIG. For this reason,
In such a particle oxidation part 4, the suspension 2 attached to the inner wall
2 flows into the storage portion 47 (liquid recovery portion) provided below, so that the inside of the pipe 41 can be prevented from being blocked by the suspension liquid 22.

At the carry-out port 46 of the particle oxidizing section 4, the hydrophilic particles 42b and the acidic liquid 43 produced in the particle oxidizing section 4 are discharged.
The mixture of the vaporized gas is diluted with a clean inert gas (for example, nitrogen gas), and the hydrophilic particles 42.
b is gas-transported by the vaporized gas and the inert gas and introduced into the first liquid processing unit 6.

Further, in the step of oxidizing the surface of the above-mentioned particles, there is a case where a sufficient amount of hydrophilic groups cannot be imparted in one oxidation step. Therefore, in the manufacturing apparatus 1, the particle suspension unit 2 and the particles described above are provided for the subsequent stage of the particle extraction port of the particle collection unit 7 provided between the first liquid processing unit 6 and the second liquid processing unit 9. The process of newly connecting the supply unit 3, the particle oxidation unit 4, and the first liquid treatment unit 6 and oxidizing the surface of the hydrophilic particles 42b obtained in the previous stage again may be repeated.
That is, a plurality of sets of the particle suspension unit 2, the particle supply unit 3, the particle oxidation unit 4 and the first liquid treatment unit 6 shown in FIG. 2 may be connected in series with each other.

At this time, the acidic liquid 43 used in the subsequent step
It is also possible to use a concentration different from that of the former stage. By using the acidic liquids 43 having different concentrations, it is possible to arbitrarily control the amount of hydrophilic groups on the surface of the hydrophilic particles 42b.

The surface of the particles may be oxidized by using a chemical different from the previously treated acidic liquid 43, for example, an acidic compound liquid such as sulfuric acid aqueous solution. In this case, as described above, a plurality of manufacturing sections including the particle suspension section 2, the particle supply section 3, the particle oxidation section 4 and the first liquid processing section 6 are used by being connected to each other in series. The acidic liquid 43 charged in 2 is replaced with a desired acidic compound liquid in advance. This makes it possible to easily manufacture the hydrophilic particles 42b each having a hydrophilic group of a different component or a functional group provided on the surface thereof.

The mixture of the vaporized gas of the hydrophilic particles 42b and the acidic liquid 43 produced by the treatment in the particle oxidizing section 4 is further diluted with the clean diluent gas introduced from the diluent gas introducing section 5 to obtain the first liquid. It is conveyed to the processing unit 6. As the diluent gas, an inert gas having a low reactivity with the obtained hydrophilic particles 42b and the vaporized gas of the generated acidic liquid 43, for example, nitrogen gas is preferable.

The clean diluent gas is obtained by removing dust and the like from an inert gas by a trapping member such as a filter (eg, HEPA filter, ULPA filter, bag filter). By thus diluting the mixture with a diluting gas, it is possible to prevent the treated hydrophilic particles 42b from aggregating with each other.

The first liquid processing section 6 has a first cooling section (cooling section) 61 and a first drying section 62 into which the gas-transported mixture of the hydrophilic particles 42b, the vaporized gas and the inert gas is successively introduced. Is equipped with. The first cooling unit 61 is provided with a pipe portion 61a into which the mixture is introduced and a cooling member 61b for cooling the pipe portion 61a. Cooling member 61b
Is equipped with, for example, a Peltier element, so that the vaporized gas can be almost recovered in the first cooling unit 61 by cooling the inside of the pipe portion 61a, that is, the mixture by the Peltier effect.

The cooling member 61b may have a structure corresponding to a desired cooling temperature and is not particularly limited. For example, the introduced mixture may be cooled using an organic solvent (refrigerant) cooled by liquid nitrogen, water, dry ice, or the like, or helium, which has a relatively high thermal conductivity.

In the first liquid treatment section 6, the mixture obtained by diluting the mixture from the particle oxidation section 4 is cooled to reduce the saturated vapor amount of the vaporized gas,
The relative humidity is lowered, and the vaporized acidic liquid 43 is liquefied and collected. In order to accelerate the drying of the transport gas atmosphere containing the treated hydrophilic particles 42b, the dilution gas introducing part 5 is provided.
The diluted gas may be passed through a desiccant to dehumidify it.

As shown in FIG. 6, the inner wall of the tube portion 61a is
Similar to the inner wall of the particle oxidation portion 4, it has a water repellent portion 19 formed of a water repellent material, and as shown in FIG. 2, is formed in, for example, a cylindrical tube inclined at an angle θ with respect to the horizontal direction. Has been done. Therefore, the acidic liquid 43 attached to the inner wall of the pipe portion 61a by condensation is stored in the storage portion (liquid recovery portion) 61.
Since it flows into c and is collected, the inside of the pipe part 61a is prevented from being blocked and continuous operation is enabled.

After the above cooling treatment, if necessary, the acid solution 43 may be recovered by introducing it into the first drying section 62. The first drying section 62 has a structure in which its particle transport pipe is exposed to a processing space filled with a desiccant, and can further dry the hydrophilic particles 42b and remove the acidic liquid 43. .

The hydrophilic particles 42b carried out from the first liquid processing section 6 are collected (collected) by the first particle collecting section 7a. Examples of the collection method include a cleaning dust collection method using water as a collection medium and a filter cloth dust collection method using a bag filter or the like. The recovered hydrophilic particles 42b are, if necessary,
It is washed with ultrapure water or the like by a washing device (not shown).
As a result, hydrophilic particles 42b from which impurities have been removed are obtained. If necessary, the hydrophilic particles 42b washed with water are dried to such an extent that the hydrophilic particles 42b do not aggregate.

The transport gas from which the hydrophilic particles 42b have been almost removed is further introduced into the second liquid processing section 9, and is cooled to a very low temperature (250 K by the second cooling section 91 of the second liquid processing section 9).
The residual acidic liquid 43 is liquefied and recovered (collected) by cooling the saturated vapor amount to a certain degree), and is further dehumidified by passing through the second drying unit 92 and exhausted. It is processed. The second cooling unit 91 and the second drying unit 92 are configured similarly to the first cooling unit 61 and the first drying unit 62 described above. One of the cooling unit and the drying unit may be arranged in the first liquid processing unit 6 and the second liquid processing unit 9, but it is more preferable to include both of them.

A second particle collecting section 7b is provided between the second cooling section 91 and the second drying section 92. In the second particle collecting section 7b, the hydrophilic particles 42b are collected (collected) again by the same collecting method as described above. By disposing the second particle collecting portion 7b, the efficiency of collecting the hydrophilic particles 42b having a hydrophilic group whose surface is oxidized can be improved, and the hydrophilic particles 42b can be collected more reliably.

With such a structure, it is possible to suppress the obtained hydrophilic particles 42b from scattering into the surrounding environment, and it is possible to process and discharge the used transport gas in a safer state. . It should be noted that the first particle collecting portion 7a and the second particle collecting portion 7b may be further provided in plural numbers as needed.

Further, in each of the tubular processing parts of the particle oxidation part 4, the first liquid processing part 6, and the second liquid processing part 9, the central axis thereof is at an angle θ (0 ° <θ ≦
90 °, more preferably 70 ° ≦ θ ≦ 90 °), and they are preferably arranged in parallel with each other. By arranging in this way, the expansion due to the vaporization of the acidic liquid 43 in the particle oxidation part 4 can be effectively used for the production and transportation of the hydrophilic particles 42b, and the device configuration can be simplified and the required floor area can be reduced. Since the number can be reduced, the device configuration can be downsized, that is, space can be saved.

Next, regarding the particle surface oxidation method for manufacturing the hydrophilic particles 42b, the manufacturing apparatus 1 is used,
An example of performing the oxidation treatment under predetermined conditions is shown in FIG. 7 and FIG.
A description will be given based on the flowchart.

First, as shown in FIG. 7, the particles are suspended in an acidic liquid (step 1, hereinafter, step is abbreviated as S),
Then, the obtained suspension is more uniformly dispersed by, for example, applying ultrasonic vibration (S2).

Next, the temperature of the particle oxidization section 4 is heated to a specified value, for example, 700 K (S3), and the above suspension is introduced into the particle oxidization section 4 whose temperature has been increased as described above, to oxidize the particles. In Part 4, while transporting the suspension, the acidic liquid of the suspension is rapidly boiled and vaporized to cause nucleate boiling with the particles in the suspension as nuclei, and the volume due to the phase change at that time is generated. The agglomerated particles are separated by the rapid expansion of the particles, and the surfaces of the particles are rapidly heated in the presence of an acidic liquid, whereby the surfaces of the particles are oxidized and hydrophilic particles 42b are formed (S4). ).

Along with the above-mentioned oxidation treatment (S4), the hydrophilic particles 42b are conveyed by the expansion of the vaporized gas of the acidic liquid (S).
5) Subsequently, the mixture of the hydrophilic particles 42b and the vaporized gas carried out from the particle oxidation unit 4 is diluted with a diluent gas which is an inert gas, and the mixed gas containing the hydrophilic particles 42b is gas-transported. Yes (S6).

Then, as shown in FIG. 8, by cooling the mixed gas (S7), the acidic liquid is condensed and recovered from the mixed gas (S8). Subsequently, the mixed gas is dehumidified with a desiccant (S9), and then the hydrophilic particles 42b are collected from the mixed gas (S10).

Next, the transport gas after the hydrophilic particles 42b are collected is cooled to an extremely low temperature (S11), and the remaining acidic liquid and hydrophilic particles 42b are respectively collected (S12). , Further dehumidified and exhausted (S1
3).

As described above, the hydrophilic particles 4 according to the present invention
The manufacturing method and manufacturing apparatus of 2b are 10 nm to 20 μm.
For a hydrophobic particle having a small particle size, such as having an average particle size within the range, which easily aggregates, a suspension 22 is prepared by immersing and dispersing the above particle in an acidic liquid 43 in order to impart hydrophilicity. A method and an apparatus for oxidizing the surface of particles with an acidic liquid 43 while dispersing aggregated particles by rapidly heating and boiling (vaporizing) while transporting in one direction along a straight line or a curved line Is.

Therefore, in the present invention, unlike the conventional method in which the particles are oxidized while being dispersed by using a stirring device such as a stirring blade, the possibility that the particles are charged due to friction during stirring is avoided. Further, in the present invention, since the hydrophilic particles 42b obtained by utilizing the expansion of the acidic liquid by the vaporized gas can be transported (transported), the apparatus and the operation can be simplified and the treatment can be performed in a short time, and the cost can be reduced.

Further, in the above-mentioned structure and method, the external force due to the volume expansion is utilized even for the agglomerated particles.
Hydrophilic particles 4 with small particle size, which suppress aggregation and have high dispersibility
2b can be stably obtained.

As a result, in the present invention, the obtained hydrophilic particles 42b are not charged, and in a short time and at low cost with a simple device and operation, the particle size is relatively small and uniform. The hydrophilic particles 42b can be stably manufactured.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples unless it exceeds the scope of the claims. The properties of the recording liquids obtained in the examples and comparative examples shown below were measured by the following methods.

A) Jetting stability The recording liquid is put into an ink tank of an ink jet apparatus having a glass nozzle having a diameter of 30 μm, jetted once, and then stopped, and is left as it is for 3 days, 7 days, 14 days, 30 days.
After leaving it at room temperature for days, 60 days and 90 days,
Re-injection was performed and it was examined whether or not the nozzle was clogged. The maximum number of days left for re-injection without causing clogging was evaluated.

B) Storage stability The recording liquid was sealed in a Pyrex test tube and kept at 0 ° C and 50 ° C.
After standing at ℃ for 1 month, the presence or absence of precipitate was examined.
The amount of precipitation was evaluated in four grades: no precipitate, almost no precipitate, small quantity of precipitate, and large quantity of precipitate.

C) Water resistance After ink-jet recording on high-quality paper using the above-mentioned ink-jet device and drying, the recorded high-quality paper is dipped in water, and when the recorded traces are bleeding or the density is lowered, x, Those that did not change were evaluated as ◯.

D) Bleeding Using the above-mentioned ink jet device, ink jet recording was carried out on a high-quality paper, and the occurrence of the bleeding of the ink recorded on this high-quality paper was visually evaluated in four levels. In this evaluation, the larger the number, the less bleeding.

E) Color and color tone Color and color tone were evaluated visually. Using the color and tone of the hydrophilic particles 42b obtained in Reference Example as a standard, compared with the above-mentioned color and tone, those with improved transparency are ○○, those that do not change are ○, and those that are inferior are ×. Indicated.

[0092] in [Reference Example] Hereinafter, with <br/> in Reference Example is a specific example relating to the above embodiment will be described with reference to the flowchart shown in FIGS. First, 2 g of carbon black particles having a particle diameter of 0.02 μm (hereinafter abbreviated as CB particles) were mixed with 100 ml of an aqueous nitric acid solution (nitric acid concentration 1.1 N) as the acidic liquid 43 as shown in FIG. , Suspension 22 was prepared (S21).

After that, CB particles are dispersed in the suspension 22 while applying ultrasonic vibration to the suspension 22 by means of a particle dispersion device 24 that generates ultrasonic vibration, and a more uniform suspension 22 is obtained. (S22). On the other hand, the particle oxidation part 4
Was heated to 700 K using the electric furnace 44 (S
23).

Then, the inside of the container 21 containing the suspension 22 is pressurized at a pressure of 0.5 kgf / cm ² with clean nitrogen gas from which dust has been removed by an air filter or the like, to thereby suspend the suspension 22. While being introduced into the particle oxidizer 4 and transported, the particles were subjected to an oxidation treatment to obtain hydrophilic particles 42b (S24).

At this time, the suspension 22 introduced into the tube 41 through the inlet 45 of the particle oxidizing unit 4 is rapidly heated to about 700 K, so that the CB particles in the suspension 22 are suspended as nuclei. The nitric acid aqueous solution in the suspension 22 was nucleated and vaporized in the tube 41.

As a result, in the particle oxidation unit 4,
By the expansion of the nitric acid aqueous solution due to vaporization, the suspension 22 is conveyed from the inlet 45 toward the outlet 46 and CB particles are dispersed (including aggregating particles into single particles), while the CB particles are being dispersed. The hydrophilic particles 42b having a carboxyl group as a hydrophilic group were obtained by subjecting the surface of No. 1 to the surface treatment with nitric acid.

Then, by the expansion of the vaporized gas of the acidic liquid,
After carrying out the mixture of the hydrophilic particles 42b and the vaporized gas from the particle oxidizing part 4 (S25), a clean gas such as nitrogen gas is introduced as a diluent gas from the diluent gas introducing part 5 into the mixture, and the mixture is nitrogenized. Diluted with gas.
The mixed gas thus diluted was gas-transported to the first liquid processing section 6 by the diluted gas and the vaporized gas contained in the mixed gas (S26).

Then, regarding the above-mentioned mixed gas, FIG.
As shown in FIG. 4, the nitric acid aqueous solution (acidic solution) part which has been vaporized by being introduced into the cooled (273K) pipe part 61a in the first cooling part 61 of the first liquid processing part 6 and cooled (S27). Is almost liquefied and collected (recovered) and removed (S28),
Next, it was dehumidified and dried in the first drying section 62 (S29).
After that, in the first particle collecting portion 7a, the hydrophilic particles 42b (particle diameter 0.02 μm) contained therein are mixed with the mixed gas.
Were collected (S30).

Next, with respect to the transport gas from the first particle collecting section 7a in which most of the hydrophilic particles 42b are removed,
Further, by being introduced into the second cooling unit 91 cooled to an extremely low temperature of 250 K (S31), the amount of saturated vapor is reduced by cooling, and the nitric acid aqueous solution remaining in the transport gas is collected and removed. Further, the hydrophilic particles 42b remaining in the second particle collecting portion 7b were collected (S32) (particle diameter 0.02 μm).

After that, the transport gas is passed through the second drying section 92 to be dehumidified and exhausted (S33), thereby completing the surface oxidation treatment of the CB particles. Collected hydrophilic particles 42
Regarding b, the impurities were removed by washing with ultrapure water. The obtained hydrophilic particles 42b had the same black color as before the reaction.

Next, the hydrophilic particles 42b, which were CB particles subjected to the surface oxidation treatment, and the CB particles before the treatment, were respectively put into pure water and stirred to examine the wettability of each particle. As a result, the CB particles before treatment were not wet with pure water and remained on the water surface. On the other hand, the hydrophilic particles 42b were wet with pure water and dispersed / floated in water. As a result, the treated hydrophilic particles 42b, which are pigment particles subjected to surface oxidation treatment by the above-mentioned method, are wetted as compared with the CB particles before treatment due to the surface being oxidized and a carboxyl group being imparted. It was confirmed that the sex is improved.

Pure water was added to the hydrophilic particles 42b obtained above so that the compounding ratio of the hydrophilic particles 42b was 1% by weight, and an ultrasonic disperser (manufactured by Sharp, trade name: ut-1) was added.
05) was dispersed and suspended for 10 minutes. Then, the dispersion liquid is filtered through a 0.5 μm membrane filter, and the filtrate is used as a black ink (1) as a recording liquid according to the present invention.
Was produced. The black ink (1) had a good color without discoloration. Moreover, various characteristics of this black ink (1) were measured by the above-mentioned measuring methods a) to e). The results are shown in Table 1.

[0103]

[Table 1]

Example 1 As components, the hydrophilic particles 42b described in Reference Example , ammonium polyacrylate, diethylene glycol, glycerol, and a surfactant (manufactured by Nikko Chemical, trade name: BT-7) were added to pure water. Was added and stirred to disperse and dissolve the above components in pure water. The surfactant is a colorless transparent liquid of an ether type nonionic surfactant having a secondary alkyl ether.

Hydrophilic particles 42 in this dispersion solution
The mixing ratio of b, ammonium polyacrylate, diethylene glycol, glycerol, and the surfactant is
1% by weight, 1% by weight, 7.5% by weight, 2.5
% By weight, 1% by weight. Then, the dispersion solution was filtered in the same manner as in Reference Example , and the filtrate was used to prepare a black ink (2) as a recording liquid according to the present invention.

The black ink (2) had a good color without discoloration. The black ink (2) was inkjet-recorded on a high-quality paper and dried to evaluate the drying property of the black ink (1) by the drying time. The drying time of the black ink (2) was ) Was almost the same. Moreover, various characteristics of this black ink (2) were measured by the above-mentioned measuring methods a) to e). The results are shown in Table 1.

Comparative Example 1 In Example 1 , the hydrophilic particles 42b were treated with untreated CB.
A comparative black ink (A) was produced in the same manner as in Example 1 except that the particles were replaced. The various measuring methods a) to e) described above for the characteristics of the black ink (A) for comparison.
It was measured by. The results are shown in Table 1.

Example 2 A copolymer of vinyl alcohol and acrylic acid (produced by Kuraray Co., Ltd., trade name: Crustomer AP-2) was used in place of the ammonium polyacrylate used in Example 1 .
A black ink (3) as a recording liquid according to the present invention was produced by the same method as in Example 1 except that 2) was added so as to be 3.0% by weight.

The black ink (3) had a good color without discoloration. Further, the dryness of the black ink (3) with respect to the black ink (1) was evaluated by the same method as in Example 1. The drying time of the black ink (3) was almost the same as that of the black ink (1). Met. Moreover, various characteristics of this black ink (3) were measured by the above-mentioned measuring methods a) to e). The results are shown in Table 1.

Comparative Example 2 In Example 2 , the hydrophilic particles 42b were treated with untreated CB.
A comparative black ink (B) was prepared in the same manner as in Example 2 except that the particles were replaced. The various measuring methods a) to e) for the characteristics of the comparative black ink (B) are described above.
It was measured by. The results are shown in Table 1.

Example 3 As components, the hydrophilic particles 42b described in Reference Example , CI Direct Black 108 as water-soluble dye, ammonium polyacrylate, diethylene glycol, glycerol, and a surfactant (manufactured by Nikko Chemical Co., Ltd., product Name: BT-
Pure water was added to 7), and the mixture was irradiated with ultrasonic waves and stirred with a homogenizer to disperse and dissolve the above components in pure water.

Hydrophilic particles 42 in this dispersion solution
b, CI Direct Black 108, ammonium polyacrylate, diethylene glycol, glycerol, and
The blending ratio of the surfactant is 1% by weight and 0.1, respectively.
% By weight, 2.0% by weight, 7.5% by weight, 2.5% by weight,
It is 1% by weight. Then, the dispersion solution was filtered in the same manner as in Reference Example, and the filtrate was used to prepare a black ink (4) as a recording liquid according to the present invention.

The black ink (4) had a good color without discoloration. In addition, of this black ink (4),
When the drying property with respect to the black ink (1) was evaluated by the same method as in Example 1 , the drying time of the black ink (4) was almost the same as that of the black ink (1). In addition, the various characteristics of this black ink (4) are measured by the above-mentioned measuring methods a).
To e). The results are shown in Table 1.

[Comparative Example 3] CI Direct Black 108 was used as a water-soluble dye as a component.
, Ammonium polyacrylate, diethylene glycol, glycerol, and surfactant (manufactured by Nikko Chemical Co., Ltd., trade name: BT-7) were added with pure water, irradiated with ultrasonic waves, and stirred and dissolved by a homogenizer. .

CI Direct Black in this solution
The compounding ratios of 108, ammonium polyacrylate, diethylene glycol, glycerol and the surfactant are 1% by weight, 0.05% by weight, 7.5% by weight, 2.5% by weight and 1% by weight, respectively. . Then, the dispersion solution was filtered in the same manner as in the reference example, and the filtrate was used as a comparative black ink (C). The characteristics of the comparative black ink (C) were measured by the above-described measuring methods a) to e). The results are shown in Table 1.

[0116] As Example 4 components, hydrophilic particles 42b described in Reference Example (particle diameter 0.02 [mu] m), a CB particles subjected to the same treatment as in Reference Example hydrophilic particles 42b (particle size 0. 12 μm), ammonium polyacrylate, diethylene glycol, glycerol, and a surfactant (manufactured by Nikko Chemical Co., Ltd., trade name: BT-7) are added with pure water and stirred to disperse and dissolve the above components in pure water. It was

Hydrophilic particles 42 in this dispersion solution
b (particle diameter 0.02 μm), hydrophilic particles 42b (particle diameter 0.12 μm), ammonium polyacrylate, diethylene glycol, glycerol, and a surfactant, the compounding ratios of 0.8% by weight and 0. 2% by weight,
1% by weight, 7.5% by weight, 2.5% by weight and 1% by weight. Then, the dispersion solution was filtered in the same manner as in Reference Example, and the filtrate was used as a recording liquid according to the present invention to prepare a black ink (5).

The black ink (5) had a good color without discoloration. In addition, when this black ink (5) was inkjet-recorded on a high-quality paper and dried, the dryness of the black ink (1) was evaluated by the drying time. The drying time of the black ink (5) was ) Was almost the same. Further, various characteristics of this black ink (5) were measured by the above-mentioned measuring methods a) to e). The results are shown in Table 1.

[0119] Comparative Example 4 hydrophilic particles 42b (particle size 0 used in Example 4.
02 μm), hydrophilic particles 42b (particle diameter 0.12 μm)
Instead of untreated CB particles (particle diameter 0.02 μm),
A black ink (D) for comparison was prepared in the same manner as in Example 4 except that untreated CB particles (particle diameter 0.12 μm) were used. The characteristics of this comparative black ink (D) were measured by the above-mentioned measuring methods a) to e). The results are shown in Table 1.

The black inks obtained in Examples 1 , 2 , 3 , and 4 and Comparative Example 3 were filled in a ball-point pen or a marking pen as a water-based ink for writing instruments to obtain stability over time. A test and a water resistance test were conducted.

The stability test with the passage of time was carried out according to Example 1 , Example 2 ,
The ballpoint pens or marking pens filled with the respective black inks obtained in Example 3 , Example 4 and Comparative Example 3 were left sideways for 15 days or 30 days, and then JIS P32 was used.
Observe the state of handwriting when writing on 01 Writing Paper A,
No problem was evaluated as ◯, and a case where a blur was generated was evaluated as x.

In the water resistance test, a ball-point pen or a marking pen filled with each black ink obtained in Example 1 , Example 2 , Example 3 , Example 4 and Comparative Example 3 was used,
Writing was performed on the writing paper A of JIS P3201, and after 30 seconds, the writing paper was immersed in water, and when the handwriting was blurred or the density of the handwriting was decreased, x was evaluated, and when not changed, it was evaluated as o. The results are shown in Table 2.

[0123]

[Table 2]

From the results of Examples 1 to 4 and Comparative Examples 1 to 3 shown in Table 1, the black ink (recording liquid) obtained in this example has no discoloration, and the conventional pigment was used. It can be seen that, as compared with the recording used, it has excellent storage stability and jetting stability, and also has good water resistance.

From the results of Examples 1 and 2 , when the black ink contains a copolymer of ammonium polyacrylate or vinyl alcohol and acrylic acid, bleeding does not occur without lowering the drying property. It turns out that less recording can be done.

Furthermore, from the results of Example 3 , it can be seen from the results of Example 4 that the color tone is improved by using the hydrophilic particles 42b of the present invention as a colorant in combination with the water-soluble dye.
Recording with less bleeding is performed by using in combination each hydrophilic particle 42b from at least two types of pigment particles having different sizes (size ratio, small pigment particles: large pigment particles = 1: 2 to 10). You can see that

Further, when only the water-soluble dye of Comparative Example 3 was used as the colorant, the water-soluble dye was dissolved in water.
It has excellent storage stability and jetting stability, but low water resistance and bleeding.

However, if the hydrophilic particles 42b obtained in this example are used as a coloring agent, storage stability and jetting stability similar to those of a water-soluble dye can be obtained, and the water resistance and the bleeding are excellent. It is understood that the suppressed black ink (recording liquid) can be obtained.

Further, as is clear from the results of Table 2, the recording liquid of the invention of the present application shows that good results are obtained even when used in a ballpoint pen or a marking pen.

In the above description, the suspension 22 is introduced into the particle oxidation part 4 as it is to obtain the hydrophilic particles 42b, but the introduction method is not particularly limited.
For example, the suspension 22 may be introduced into the particle oxidation unit 4 in a droplet state having a particle size of, for example, about 10 μm to 20 μm. In this case, since it is in the droplet state, the heating efficiency can be improved, so that the nucleate boiling and vaporization in the tube 41 in the nitric acid aqueous solution can be speeded up, and the hydrophilic particles 42b.
The production of can be speeded up.

Moreover, in the above structure, the suspension 22 and the droplets of the suspension 22 in the container 21 are preheated to a temperature near the boiling point of the suspension 22 by a heater or the like, if necessary. You can leave it. With this configuration, the acidic liquid 43 of the suspension 22 can be nucleated and vaporized more quickly, and the production of the hydrophilic particles 42b can be made more efficient.

Further, in the above description, the manufacturing apparatus 1 capable of continuously manufacturing the hydrophilic particles 42b has been described as an example, but the specific structure of the manufacturing apparatus is the same as the above-exemplified structure. It is not limited only. The apparatus for producing the hydrophilic particles 42b according to the present invention may have a configuration capable of producing the hydrophilic particles 42b in a batch system.

Then, CB particles were suspended in nitric acid aqueous solutions having various different concentrations, and the same treatment as in Reference Example and Example 1 was performed. The influence of the amount of carboxyl groups formed on the surface of the particles 42b was examined.

When the nitric acid concentration was 0 N (zero), no carboxyl group was added, but the nitric acid concentration was 0.4
At 4 N and 1.1 N, the carboxyl groups provided on the surfaces of the hydrophilic particles 42b are 0.0071 g equivalent and 0.00725 g equivalent, respectively, and the amount of carboxyl groups on the surface increases as the nitric acid concentration increases. It was found that the concentration gradually increased and increased with the concentration of nitric acid. When the wettability of each hydrophilic particle 42b obtained at each nitric acid concentration with water was examined, the nitric acid concentration was 0.44 N
All concentrations of 1.1N were good.

Generally, in industrial processes, the lower the concentration of nitric acid, the more advantageous 1) the material cost can be reduced, 2) the treatment cost of the acid solution 43 can be reduced, and 3) the complexity of equipment can be reduced. Therefore, the nitric acid concentration is preferably as low as possible in the range where effective hydrophilicity is obtained for the obtained hydrophilic particles 42b.

In each of the above-mentioned embodiments and examples, the liquid containing nitric acid as a modifier is used as an acidic liquid to introduce a carboxyl group on the particle surface. However, the present invention is not limited to this. Even when the surface of each small particle is modified by heating with a modifier capable of introducing a functional group such as a hydroxyl group, an amino group, a nitro group, or an ammonium group by heating. Similarly, the method and apparatus of the present invention can be used.

In each of the above-mentioned embodiments and examples, the acidic substance (modifying agent) used is a liquid at room temperature, but any substance soluble in water or a volatile liquid as a solvent may be used. , For example, as the acidic substance, acetic acid, citric acid,
Tartaric acid or the like can also be used.

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

Recording liquid of the present invention according to the present invention may also contain a port Riakuriru ammonium 0.3% by weight or more. According to the above configuration, even if plain paper is used as a recording medium for recording with the recording liquid, it is possible to prepare a recording liquid that has good drying properties and can perform recording with less blurring.

The recording liquid of the present invention may further contain 1% by weight or more of a copolymer of vinyl alcohol and acrylic acid. Even if plain paper is used as a recording medium for recording with the recording liquid, it is possible to produce a recording liquid that has good drying properties and can perform recording with less bleeding.

[0148]

[0149]

[0150]

In the method for producing a recording liquid of the present invention, the pigment particles are suspended in an acidic liquid to obtain a suspension solution, and the suspension solution is rapidly heated to a temperature of 700 K to form an acidic liquid. By rapidly boiling and vaporizing the acidic liquid with the suspended pigment particles as the core, the pigment particles in the suspension are nucleated as nuclei, and due to the rapid expansion of the volume due to the phase change during the boiling, Agglomerated pigment particles are separated, and an oxidized portion is formed on the surface of the pigment particles to prepare hydrophilic particles. The hydrophilic particles are treated with water, ammonium polyacrylate and / or vinyl alcohol and acrylic acid. It is a method of dispersing in a solvent containing a copolymer of.

Therefore, in the above-mentioned method, the suspension is heated or vaporized while being conveyed to prevent charging of the particles, and the particle size is relatively small with a simple operation in a short time at low cost. It is possible to produce uniform hydrophilic particles.

From the above, it is possible to prevent discoloration of the obtained hydrophilic particles and to obtain hydrophilic particles having a relatively small particle size and uniform, since the above method can be produced in a short time. Therefore, when the recording liquid is used as an inkjet recording liquid, the recording liquid has excellent storage stability, good ejection stability, and good water resistance.

Further, in the above-mentioned method, the vaporized acidic liquid can be easily recovered in high purity by condensation, so that the recovered acidic liquid can be reused again and can be easily continuously produced, resulting in cost increase. It also has the effect of suppressing

[Brief description of drawings]

FIG. 1 is a schematic view of a recording liquid according to the present invention.

FIG. 2 is a schematic diagram showing an embodiment of a particle surface oxidation apparatus for producing hydrophilic particles in the recording liquid.

FIG. 3 is a schematic diagram of an optical measurement unit in the particle surface oxidation device.

FIG. 4 is a view showing a particle oxidation part of the particle surface oxidation device.
It is explanatory drawing which shows a mode that a suspension changes phase, while being conveyed.

5A and 5B are explanatory views showing a state of nucleate boiling in the suspension, where FIG. 5A is a diagram showing a state in which agglomerated particles composed of four particles are dispersed during nucleate boiling, and FIG. It is an explanation showing how agglomerated particles consisting of three particles are dispersed during nucleate boiling, and (c) is an explanation showing how agglomerated particles consisting of two particles are dispersed during nucleate boiling.

FIG. 6 is a schematic cross-sectional view of each inner wall of a particle oxidation part and a first cooling part in the particle surface oxidation device.

FIG. 7 is the first half of a flowchart showing the steps of the particle surface oxidation method used in the particle surface oxidation apparatus.

FIG. 8 is the latter half of the above flowchart.

FIG. 9 is the first half of a flowchart showing the steps of the method for oxidizing the surface of a particle described in Reference Example relating to the hydrophilic particles.

FIG. 10 is the latter half of the above flowchart.

[Explanation of symbols]

12 Hydrophilic group (oxidized part) 14 solvent 22 suspension 42 pigment particles 42b hydrophilic particles 43 Acid solution

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B41M 5/00 B41J 3/04 101Y (56) References JP-A-9-194775 (JP, A) JP-A-10-7968 ( JP, A) JP 10-237349 (JP, A) JP 2000-70704 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 11 / 00-11 / 20 C09C 1/00-3/12

Claims (2)

(57) [Claims] 1. Pigment particles are suspended in an acidic liquid to obtain a suspension solution, and the suspension solution is rapidly heated to a temperature of 700K ,
By rapidly boiling and vaporizing the acidic liquid with the pigment particles suspended in the acidic liquid as nuclei, the pigment particles in the suspension are nucleated as nuclei, and the volume change due to the phase change during the boiling Due to the expansion, the aggregated pigment particles are separated, and an oxidation treatment portion is formed on the surface of the pigment particles to prepare hydrophilic particles. The hydrophilic particles are mixed with water and 0.3% by weight or more of polyacrylic acid. A method for producing a recording ink, which comprises dispersing in a solvent containing ammonium. 2. The pigment particles are suspended in an acidic liquid to obtain a suspension solution, and the suspension solution is rapidly heated to a temperature of 700K ,
By rapidly boiling and vaporizing the acidic liquid with the pigment particles suspended in the acidic liquid as nuclei, the pigment particles in the suspension are nucleated as nuclei, and the volume change due to the phase change during the boiling Due to the expansion, the aggregated pigment particles are separated, and at the surface of the pigment particles, an oxidation treatment portion is formed to adjust hydrophilic particles, and the hydrophilic particles are mixed with water and 1% by weight or more of vinyl alcohol and acrylic acid. A method for producing a recording ink, which comprises dispersing in a solvent containing a copolymer of