JP2006003705A - Method for manufacturing master batch used for electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a master batch which can be dispersed into the main resin of toner with low shear force during mixing with the main resin of the toner and is superior in the dispersibility of a coloring agent. <P>SOLUTION: The manufacturing method has a process of coating a resin material by a chemical technique on the surface of a pigment particle, which is the coloring agent and has a process of mechanically and electrically flocculating the pigment particles within a dispersion liquid of the included resin particulates, and the master batch is generated as a solid by settling the resin particles within the dispersion liquid. Since the master batch is composed of the pigment coated with the resin, aggregate of the pigment particles does not exist and the pigment particles separate easily at the resin particulate boundaries, including the pigments during mixing with the main resin of the toner and therefore the dispersion in the main resin of the toner is made possible with a low shear force. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a master batch for an electrophotographic toner.

  In the conventional method, a toner used in an apparatus to which an electrophotographic method is applied is manufactured by melting and kneading a colorant such as a pigment together with a binder resin, and then cooling, pulverizing, and classifying the resulting resin kneaded product. The method was general.

  As a method for uniformly dispersing the pigment as the colorant in the binder resin, a part of the binder resin and the pigment as the colorant are melt-kneaded in a separate step, cooled, and then pulverized to obtain a master batch. There is a method in which a toner is manufactured by manufacturing, kneading this master batch again with the remaining binder resin, and crushing and classifying the cooled resin.

  In other masterbatch manufacturing methods, the binder resin is melted with an organic solvent, and the pigment, which is a colorant, is pulverized and dispersed in the resulting resin solution, and then the masterbatch is manufactured by removing the organic solvent. A method has been proposed (for example, Patent Document 1). In this method, when the organic solvent is removed, the organic solvent is unevenly distributed in the resin solution, and the resin concentration is different in the resin solution. The pigment uniformly dispersed in the resin solution has a problem that it aggregates due to the gradient of the resin concentration generated in the resin solution and the dispersibility is lowered.

  Further, a method has been proposed in which a water-insoluble colorant is pulverized and dispersed in an aqueous medium, and then the aqueous medium is removed and replaced with a resin (for example, Patent Document 2). However, in this method, the dispersion liquid in which the pigment is dispersed is filtered to disperse the solid matter of the aqueous medium and the pigment, and the solid matter is kneaded in the binder resin, but the solid matter is formed. The colorant has high cohesiveness, and in order to pulverize this aggregation again, it is necessary to set a high shearing force in the binder resin when kneaded with the binder resin. In order to crush and uniformly disperse, the binder resin must be kneaded so that a high shearing force is generated. As a result, the molecular weight of the binder resin is reduced, and this decrease in the amount of the binder resin There is a problem of deteriorating the mechanical strength.

Further, the present applicant previously proposed a method using a phase inversion emulsification method in which a resin to be coated is dissolved in a solvent, colorant particles are dispersed in the prepared resin solution, and colorant particles are encapsulated with the resin. (Patent No. 2004-71094). In this method, the organic solvent is unevenly distributed in the resin solution as described above, and there is a problem that a concentration gradient of the resin concentration occurs in the resin solution, and a high shear force is required at the time of kneading. As a result, the molecular weight of the binder resin There is no problem that the mechanical strength of the binder resin is deteriorated.
JP-A-3-72371 JP-A-6-130724

  However, in the method in which the colorant particles are encapsulated with a resin, kneading is required when forming the toner. Accordingly, the toner main resin has a considerable share and is subjected to mechanical stress. As a result, the molecular weight of the binder resin is lowered, and the mechanical strength of the binder resin is deteriorated. An object of the present invention is to provide a method for producing a masterbatch capable of being dispersed in a toner main resin with a low shear force when mixed with a toner main resin, and having excellent colorant dispersibility. .

  The present invention includes a step (1) of preparing a resin solution by dissolving a resin that coats the pigment particle surface in an organic solvent, and mixing the pigment into the resin solution, and the pigment particles are refined in the resin solution. A step (2), a step (3) in which the resin solution is made into a liquid enemy of fine particles in an aqueous medium, and then converted into a deorganic solvent, and a resin containing a pigment dispersed in the aqueous medium And (4) separating and drying the fine particles from the aqueous medium.

  In the step (3), the pigment particle surface is coated with a resin in an aqueous medium from a resin solution, such as a coacervation method, a submerged drying method, an interfacial polymerization method, or a phase inversion emulsification method. Any method may be used as long as it is a method. In the present invention, a phase inversion emulsification method is used.

  In the step (4), the coated pigment is solidified by separating the fine particles coated with the resin obtained in the step 3 by using a centrifugal separation method. Separate as a thing.

  In the present invention, a water-insoluble resin is dissolved in an organic solvent, and in the obtained resin solution, finely divided pigment particles as a resin colorant are dispersed in the resin solution. The coated pigment particles having a resin material deposited on the surface are used as a master batch. In particular, pigment particles coated with a resin are highly dispersed in a dispersion by an aggregation process, and since pigment particles are coated with a resin, an aggregate of pigment particles is not formed, When mixing with the main resin material of the electrophotographic toner, it is not necessary to disperse the aggregates of the pigment particles in the toner main resin, and the pigment particles are not in contact with the toner main resin material. Since the material and the highly wettable resin material are in contact with each other, the material diffuses into the toner main resin material, so that the toner main resin material can be mixed with a low shear force.

  Embodiments according to the present invention will be described in detail with reference to the drawings.

  In the method for producing a masterbatch of the present invention, the pigment that is a colorant may be a pigment made of metal, regardless of whether it is an inorganic pigment or an organic pigment.

  As the organic pigment, for example, a phthalocyanine pigment such as phthalocyanine blue, an insoluble azo pigment such as benzidine yellow, or the like can be used.

  Examples of inorganic pigments include natural products such as mica and ocher, chromates such as yellow lead, zinc yellow and barium yellow, ferrocyanides such as bitumen, sulfates such as barium sulfate, lead sulfate and strontium sulfate, zinc Hana, titanium white, benkara, iron black, oxides such as chromium oxide, hydroxides such as aluminum hydroxide, silicates such as calcium silicate, carbonates such as calcium carbonate and magnesium carbonate, carbon such as carbon black Examples of the pigment made of metal include metal powder such as aluminum powder.

  The resin material which comprises a masterbatch is a water-insoluble resin material, and if it is a water-insoluble thing, it will not specifically limit.

  In this embodiment, a polyester resin is used as the water-insoluble resin, and ethyl acetate is used as the water-insoluble organic solvent.

  In addition, polyester resin and ethyl acetate are part of the combination of each material, and other than polyester resin, polyolefin-based or styrene-based, for example, polystyrene, poly-p-chlorostyrene, etc. can be used. is there.

  The organic solvent is not particularly limited as long as it is water-insoluble and can dissolve the resin material used for the fine particles. For example, toluene, benzene, THF (tetrahydrofuran) or the like may be used. A solvent such as ethyl acetate in which a minute amount is soluble in water may be used, but it is preferable to use a solvent whose solubility is 20% or less.

(Embodiment 1)
The process of the masterbatch manufacturing method of this invention is demonstrated using FIG.

  FIG. 1 is a flowchart of Step 1 to Step 4.

(Step 1: Resin solution preparation step)
The coating resin material that coats the pigment surface, which is a colorant, may be any resin that is highly dispersible with the electrophotographic toner resin material.

  Further, since the colorant surface is coated, a resin excellent in optical properties is desirable, and the same kind of resin material as the main resin is preferable from the viewpoint of affinity with the resin.

  In particular, in terms of visible light transmittance, a polyester-based resin is excellent in optical characteristics, and in the present embodiment, the polyester resin is used as the colorant coating resin material 10. As the organic solvent 11 for dissolving the polyester resin, ethyl acetate was employed. If the concentration of the resin material 10 in the resin solution 12 is adjusted in the range of 5% by weight to 50% by weight, the surface of the pigment particles 20 as the colorant can be coated. It is more preferable to use the one adjusted by weight%.

  In the present embodiment, the concentration of the resin material 10 in the resin solution 12 is adjusted to 20% by weight.

(Process 2: Pigment refinement process)
The pigment particles 20 as a colorant are added to the resin solution 12 produced in step 1 while stirring the resin solution 12. During the addition, a dispersion stabilizer may be added to the resin solution 12.

  In the present embodiment, carbon black is used for the pigment particles 20. The resin solution 12 mixed with the carbon black is put into a bead mill apparatus, and the carbon black is wet pulverized while circulating the resin solution 12 in the bead mill apparatus until the target particle size is reached. Carbon black was refined.

  The method using the bead mill apparatus is merely an example, and a ball mill, an attritor, or the like may be used as long as it is a mechanical pulverization apparatus. In addition, as a treatment method, a batch method in which the resin solution is circulated in the bead mill apparatus until the target particle size is reached is used. Good.

(Process 3: Coating process)
In this step, the resin solution 31 in which the finely divided pigment particles 20 obtained in the step 2 are dispersed is deposited on the surface of the pigment particles 20 with the organic solvent 11 using a chemical method. This is the process of coating.

  As a method for coating the pigment surface, any method can be used as long as it is a method in which a resin solution is coated with a resin in an aqueous medium, such as a coacervation method, a submerged drying method, an interfacial polymerization method, and a phase inversion emulsification method. May be.

  In the present embodiment, the surface of the pigment particles 20 is coated with a polyester resin using a phase inversion emulsification method.

  With respect to the resin solution 31 in which the carbon black produced in the step 2 is dispersed, the aqueous medium as an aqueous phase is within the range of a weight ratio of surfactant to distilled water of 0.3 to 1.0% by weight. A surfactant solution is prepared as follows. When the volume of the resin solution 21 is 1 times, the surfactant solution is dispersed from the resin solution 31 by adding the amount of the surfactant solution 5 times or more, preferably 8 times or more to the resin solution 31. As a result, a dispersion liquid is obtained in which the liquid droplets of the resin solution 31 are dispersed in the aqueous medium. In order to remove the organic solvent in the fine droplets from the resin solution 31, the aqueous medium is heated from the outside to vaporize the organic solvent in the aqueous medium, and the solvent is removed from the fine droplets. Coating is performed by precipitating a polyester resin dissolved in an organic solvent on the surface of the carbon black particles.

  FIG. 2 shows the measurement result of the particle size distribution of the carbon black particles coated with the polyester resin using the phase inversion emulsification method. By using the phase inversion emulsification method, fine pigment particles coated with a resin having a sharp particle size distribution can be obtained.

(Process 4: Aggregation / sedimentation / separation / drying process)
This step is performed by precipitating and agglomerating the resin fine particles 30 made of a polyester resin material covering the surface of the carbon black particles, which are the pigment particles 20 dispersed in the aqueous medium obtained in the step 3, In this step, after solidifying in an aqueous medium, only the aqueous medium is discarded to extract the polyester resin particles, that is, the master batch 40 that covers the surface of the pigment particles 20.

  Note that the aqueous medium remaining in the extracted solid is removed by leaving it in a dryer.

  In this step, the zeta potential generated on the surface of the fine particles 30 dispersed in the aqueous medium was measured with respect to the fine particles 30 in which the surface of the pigment particles 20 produced in the step 3 was coated with a resin. In order to adjust the hydrogen ion concentration of the aqueous medium in the aqueous medium in which the fine particles 30 are dispersed so that the zeta potential is minimized, a dilute solution of NaOH (sodium hydroxide) or NaCl (sodium chloride) is used. Sequentially added. FIG. 3 shows the measurement results of the pH concentration and the zeta potential at that time.

  For the measurement, a laser zeta electrometer ELS8000 manufactured by Otsuka Electronics Co., Ltd. was used.

  FIG. 3 shows that the zeta potential on the surface of the fine particles 30 decreases with the change in pH concentration. This result is only a result obtained by the combination of the materials in the present embodiment, and a suitable agent for adjusting the hydrogen ion concentration may be selected and used according to the resin material to be used.

  By controlling the pH of the water-soluble medium, the value of the zeta potential on the surface of the fine particles 30 can be reduced, and the electric repulsive force acting between the fine particles 30 can be reduced, so that the fine particles 30 can be easily aggregated. It becomes.

  The master batch for electrophotography produced in Step 1 to Step 4 described in this embodiment is composed of fine particles of polyester resin containing carbon black, and the carbon black is locally contained within the master batch 40. The carbon black can be obtained as a solid in a state where the carbon black is uniformly dispersed throughout the master batch 40.

  The coated pigment is separated as a solid by separating the aqueous medium and the fine particles from the aggregated and settled fine particles using a centrifugal separation method.

  The aqueous medium and the pigment fine particles 30 are separated by rotating the centrifuge at a high speed of 2000 rpm to 5000 rpm with respect to the solution in which the fine particles are aggregated and settled.

  The solid matter of the coated pigment particles extracted by the centrifuge is slightly left in the aqueous medium. By leaving it in a dryer for 24 hours, the remaining aqueous medium in the solid matter is completely removed. Can be removed.

(Embodiment 2)
The steps of the master batch production method of the present invention are shown in a flowchart in FIG.

  Since the manufacturing method of the 1st resin microparticle which includes the pigment is produced using the process 1-the process 3 of Embodiment 1, it is not described here.

  Each step will be described in detail below.

(Step 5: Preparation of resin solution of second resin material)
In the present embodiment, a polyester resin is used as the second resin material 50. However, the second resin material 50 is not particularly limited to the polyester resin, and may be any resin material that is water-insoluble and soluble in an organic solvent. For example, polyolefin, styrene, polystyrene, poly p-chlorostyrene, or the like may be used.

  The organic solvent is not particularly limited. For example, toluene, benzene, THF (tetrahydrofuran) or the like may be used. A solvent such as ethyl acetate in which a minute amount is soluble in water may be used, but it is preferable to use a solvent whose solubility is 20% or less.

  As the water-soluble medium, distilled water is used, and a surfactant prepared by adjusting a cationic polymer material at a weight ratio of 0.1 to 1.0% by weight is used as the aqueous medium.

  In this embodiment, the polyester resin of the second resin material was dissolved with ethyl acetate to produce a resin solution of the second resin material. The resin concentration of the second resin material in the second resin material solution is adjusted to 20% by weight.

(Step 6: Fine particle step of second resin)
This step is a step of precipitating and miniaturizing the second resin material of the second resin solution prepared in step 5.

  With respect to the second resin solution 52 produced in the step 5, as an aqueous medium that is an aqueous phase, the interface is set so that the weight ratio of the surfactant and distilled water is within the range of 0.3 to 1.0% by weight. Make an activator solution. Assuming that the volume of the second resin solution 52 is 1 time, the amount of the surfactant solution is 5 times or more, preferably 8 times or more, by adding a volume of the second resin solution 52 to the second resin solution 52. A phase transition is made from the solution 52 to the aqueous medium in which the surfactant is dispersed, and a dispersed solution in which the fine droplets of the second resin solution 52 are dispersed in the second aqueous medium is obtained. In order to remove the organic solvent in the fine droplets of the dispersion solution, the second aqueous medium is heated from the outside. As a result, the organic solvent is vaporized in the second aqueous medium, and the solvent is removed from the minute droplets.

  A solution 61 in which the resin particles 60 of the second resin material are dispersed in the prepared second aqueous medium is charged into a bead mill device, and the dispersion solution 61 is circulated in the bead mill device until the target particle size is obtained. The resin particles 60 were wet pulverized and the resin particles 60 were refined in the dispersion solution 61.

  The method using the bead mill apparatus is merely an example, and a ball mill, an attritor, or the like may be used as long as it is a mechanical pulverization apparatus. In addition, as a treatment method, a batch method in which the resin solution is circulated in the bead mill apparatus until the target particle size is reached is used. Good.

(Step 7: Mixing of dispersion)
In this step, a dispersion solution 61 in which the resin fine particles 60 not including the pigment prepared in Step 6 are dispersed and a dispersion 32 in which the resin fine particles 30 including the pigment prepared in Steps 1 to 3 are dispersed are dispersed. It is a process of mixing.

(Process 8: Aggregation / extraction process)
This step is a step of aggregating the fine particles in the dispersion solution 70 prepared in step 7. The surface of the resin fine particles 60 produced in Step 5 to Step 6 is attached with the cationic polymer material used as the surfactant, and the surface of the fine particles 60 exhibits basicity. The surface of the resin fine particles 30 containing the pigment uses a surfactant of an anionic polymer material, which is electrically neutral, but is a mixed dispersion solution due to the basicity of the polyester resin itself. In 70, the resin fine particles start to adhere to each other. Due to the adhesion between the resin fine particles, the ratio of solids increases, and the particles settle in the dispersion by gravity. As a result of the sedimentation, the resin fine particles 30 containing the pigment and the resin fine particles 60 not containing the pigment form solids so as to be adjacent to each other, and the pigment particles as the colorant are uniformly dispersed inside the solid used as the master batch. .

  The master batch produced in this step has high dispersibility of pigment particles inside the master batch, and does not require high shear when mixing with the main resin of the toner. It becomes possible to achieve high dispersion in the resin.

Master batch manufacturing flowchart Size distribution of resin-coated carbon black particles obtained by phase inversion emulsification method PH concentration and zeta potential in the dispersion Master batch manufacturing flowchart

Explanation of symbols

DESCRIPTION OF SYMBOLS 10- Resin material 11- Organic material 12- Resin solution 20- Pigment particle 30- Resin fine particle containing the pigment 31- Dispersion solution 32- Dispersion solution 40- Masterbatch 50- Resin material 52- 2nd resin material solution 60-Resin fine particles of second resin material 61-Dispersion solution 70-Mixed solution 80-Masterbatch

Claims (5)

A step (1) of preparing a resin solution by dissolving a resin for coating the pigment particle surface in an organic solvent;
Step (2) of mixing pigment particles in the resin solution and making the pigment particles fine in the resin solution;
A step (3) of making the resin solution into droplets of fine particles in an aqueous medium and then desolvating the organic solvent;
And a step (4) of separating and drying the resin fine particles containing the pigment particles dispersed in the aqueous medium from the aqueous medium.   The master batch production method according to claim 1, wherein the step (3) uses a phase inversion emulsification method.   The master batch manufacturing method according to claim 1, wherein the step (4) uses a centrifugal separation method.   4. In the step (4), a solvent for controlling a hydrogen ion concentration is added to a dispersion in which resin particles encapsulating the pigment are dispersed, and the resin fine particles encapsulating the pigment are aggregated. The masterbatch manufacturing method as described. A step (1) of preparing a first resin solution by dissolving a resin for coating the pigment particle surface in an organic solvent;
Mixing a pigment in the first resin solution, and refining the pigment particles in the resin solution (2);
After the first resin solution is made into droplets of fine particles in the first aqueous medium, the resin fine particles formed by coating the surface of the prepared pigment particles are dispersed by the step (3) of removing the organic solvent. A first dispersion,
A step (5) of preparing a second resin solution by dissolving a resin for coating the pigment particle surface in an organic solvent;
After the second resin solution is made into droplets of fine particles in the second aqueous medium, the resin fine particles not containing the prepared pigment are dispersed by the step (6) of removing the organic solvent. The masterbatch manufacturing method characterized by mixing and aggregating the dispersion liquid.

Images