JPH01184035A - Production of microencapsulated fine particle - Google Patents

Abstract

PURPOSE:To form a microcapsulated particle having a porous capsule film by agitating and treating both base particles having specified number average particle diameter and minor particles having number average particle diameter not larger than 1/5 of particle diameter of the base particle in an air flow at high velocity, by supplying these minor particles to those base particles with a specified method. CONSTITUTION:Both base particles having 1-200mum number average particle diameter and minor particles which have number average particle diameter not larger than 1/5 of particle diameter of the base particle and are utilized for formation of a coating layer are agitated and treated in an air flow at high velocity. In this case, microencapsulated fine particles are produced by supplying all parts or one part of the minor particles continuously or intermittently and successively into an air flow and agitating them at high velocity and forming the coating layer of the minor particles on the surfaces of the base particles. The kind of the used minor particles can be properly selected with the intention of modifying the surfaces of the base particles. When imparting conductivity to the base particles consisting of polymer particles, metallic powder such as Ni and Cu besides carbon black can be used as the minor particles.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a method for producing microencapsulated fine particles. The present invention relates to a method for producing microencapsulated fine particles in which the surface of the particles is uniformly modified.

These microencapsulated fine particles can be used in a wide range of fields such as paints, electronic materials, electrophotography, biochemical carriers, cosmetics, pharmaceuticals, and catalysts.

(Prior art) As a method for modifying the particle surface, the surface of the inorganic particle is treated with a surfactant, a silane coupling agent, a titanium coupling agent, etc. to improve the lipophilicity of the particle surface, and the oil layer of the particle is A method of improving the dispersibility of polymer particles, and a method of imparting conductivity to polymer particles by applying metal plating to the surface of the polymer particles are known. However, these methods only achieve the single purpose of making the particle surface lipophilic or imparting conductivity, and in the case of metal plating of polymer particles, the metal that can be used for plating is Ni.

There was a drawback that it was limited to Au, Cu, Sn, etc.

Therefore, recently, a method has been proposed to modify the particle surface using the so-called mechanochemical effect (chemical equipment,
March 1986 issue, p27-33). According to this method, child particles for coating having a predetermined particle size ratio are electrostatically attached to the mother particles, and by vigorously mixing them in a ball mill or automatic mortar, the child particles are embedded in the mother particles and immobilized. By doing so, it is attempted to modify the particle surface and make it composite.

However, according to the surface modification method using the mechanochemical effect described above, since the mother particles and child particles are mixed using a ball mill or an automatic mortar, the mother particles may crack or the particles may fuse together. Therefore, it is not possible to uniformly cover the coating layer made of child particles.

The present inventors conducted extensive studies to solve the above problems, and found that the number average particle diameter is 1 to 200 μm and the number average particle diameter is 115 or less of the number average particle diameter of the base particle. We learned that microencapsulated fine particles consisting of a mother particle as a core material and a coating layer formed on the surface of the mother particle can be obtained by stirring the child particles of the coating layer forming material at high speed in an air stream. I want to apply for a patent.Patent application 1986-255
484 and Japanese Patent Application No. 62-87727).

(Problems to be Solved by the Invention) However, although these methods reliably provide a thicker coating layer than the conventional microencapsulation method, the coating layer on the particle surface tends to be somewhat uneven. there were. For this reason, when these microencapsulated fine particles are used, for example, as a toner for electrophotography, fogging may occur in images.

(Means for Solving the Problems) The present invention provides base particles having a number average particle diameter of 1 to 200 μm, and coating layer forming particles having a number average particle diameter of 115 or less of the number average particle diameter of the base particles. A method for producing microencapsulated fine particles in which a coating layer of child particles is formed on the surface of a mother particle by subjecting child particles to a high-speed stirring process in an air flow, the method comprising The present invention relates to a method for producing microencapsulated particles, characterized by supplying continuously or intermittently.

The present invention will be explained in detail below.

The number average particle diameter of the base particles used in the present invention is 1 to 200.
μm, preferably 1 to 100 μm, more preferably 2
~50 μm. If the number average particle diameter is less than 1 μm, the collision energy generated by high-speed agitation of the particles will be insufficient, making it difficult to form a coating layer, and the particles will aggregate, causing individual particles to become independent and forming a coating layer on their surfaces. It becomes difficult to form. - On the other hand, if the number average particle diameter exceeds 200 μm, the characteristics as fine particles will be lost.

As the base particles used in the present invention, both organic substances and Ja-free substances can be used as long as they satisfy the above conditions, and they can be selected as appropriate depending on the purpose of use of the microencapsulated fine particles as the final product. Can be done.

A typical example of the organic substance is a synthetic resin (polymer).

As the synthetic resin, vinyl polymers are particularly preferred, and the vinyl monomers used for their production include aromatic vinyl monomers such as styrene, α-methylstyrene, halogenated styrene, and divinylbenzene, vinyl acetate,
Vinyl esters such as vinyl propionate, unsaturated nitriles such as acrylonitrile, methyl acrylate,
Ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate,
Examples include ethylenically unsaturated carboxylic acid alkyl esters such as lauryl acrylate, lauryl methacrylate, ethylene glycol diacrylate, and ethylene glycol dimethacrylate. This vinyl polymer may be a homopolymer or a copolymer consisting of two or more types of monomers selected from the above vinyl monomers. In addition, the above vinyl monomers, conjugated diolefins such as butadiene and isoprene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide, 2-hydroxyethyl acrylate Copolymers with copolymerizable monomers such as , 2-hydroxyethyl methacrylate, diallyl phthalate, allyl acrylate, and allyl methacrylate can also be used.

Polymer particles having a number average particle diameter within the specific range of the present invention can be easily obtained, for example, by emulsion polymerization, soap-free polymerization, suspension polymerization, or crushing of the polymer bulk of the vinyl monomers described above.

In particular, when microencapsulated fine particles having a uniform particle size are required, base particles having a uniform particle size may be used.
The swelling polymerization method described in the Journal of Polymer Science Polymer Letter Edition (J,
Polym, Sci.

The polymerization method described in Polymer Letter Ed, ) or the polymerization method previously proposed by the present inventors (
It can be easily manufactured according to JP-A-61-215602, JP-A-61-215603, and JP-A-61-251504. For example, particles having a number average particle size Sn of 1 to 100 μm, preferably 1 to 25 μm, and a particle size in the range of Sn±20% account for 70% by weight or more, preferably 80% by weight or more of the total1, and more preferably 90% by weight. % or more, microencapsulated fine particles having a uniform particle size can be obtained.

In addition to the above-mentioned polymer particles, the base particles of the present invention may also include pharmaceuticals, agricultural chemicals, foods, fragrances, dyes, pigments, metal powders, toner particles, etc. having a number average particle diameter in the range of 1 to 200 μm. can.

Furthermore, if porous particles or hollow particles absorb or adsorb a fine powder of a liquid substance or solid substance and then use these particles as base particles, microencapsulated fine particles containing the liquid substance or solid substance can be obtained. It will be done. In addition, absorption or adsorption of the above-mentioned substance in the present invention means absorption, adsorption, or adhesion on the particle surface and inner pores, and this absorption and adsorption can be carried out by conventionally known methods.

The number average particle diameter of the particles in the present invention was determined by randomly measuring the particle diameters of 1000 particles on an electron micrograph. In addition, in the case of acicular particles such as some dyes,
The particle size was defined as the average value of the major axis and the minor axis, and in the case of amorphous particles such as wax, the average value of the maximum diameter and the minimum diameter was defined as the particle diameter.

The child particles for forming the coating layer used in the present invention have a number average particle diameter of 115 or less, preferably 1/10 or less, more preferably 1/20 or less of the number average particle diameter of the mother particle.

The number average particle diameter of the child particles is 115 the number average particle diameter of the mother particle.
If it exceeds 100%, it will not be possible to form a uniform and sufficiently thick coating layer on the surface of the base particles.

The type of child particle used in the present invention can be appropriately selected depending on the purpose of surface modification of the mother particle, but for example, when the mother particle is a polymer particle and conductivity is to be imparted to it,
In addition to carbon black, child particles include nickel, copper,
Various metal powders such as aluminum and iron, inorganic materials such as copper iodide and ruthenium oxide, and conductive polymers such as polyacetylene, polypyrrole, and polyethylene can be used. Conversely, if the base particles are conductive and you want to increase their electrical resistance and give them chargeability through surface modification,
As child particles it is advisable to use polymer particles, preferably thermoplastic polymer particles.

The thermoplastic polymer particles can be appropriately selected from the above-mentioned vinyl polymers depending on the purpose.

Further, when the purpose of surface modification of the mother particles is to color the particles, the following pigments can be used as child particles for coloring.

Black pigment carbon black, acetylene black, lamp black, aniline black, magnetite yellow pigment yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S1 Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Penzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake Brown Pigment Red Yellow Lead, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Palcan Orange, Indanthrene Brilliant Orange RK, Benzidine Orange G, Indanthrene Brilliant Orange GK Red Pigment Red Garla, Cadmium Red, Red Lead, Mercury Cadmium Sulfide, Permanent Red 4R, Lysol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin rake,
Rhodamine Lake B, Alizarin Lake, Brilliant Carmine JB Purple Pigment Manganese Purple, Fast Violet B, Methyl Violet Lake Blue Pigment Dark Blue, Cobalt Blue, Alkaline Blue Lake, Metal Phthalocyanine Blue, Phthalocyanine Blue Partially Chlorinated Compound, Fast Sky Blue, Indanthrene Blue-B
C Green pigment chrome green, chromium oxide, pigment green B,
Malachite green lake, final yellow green white pigment zinc white, titanium oxide, antimony white, zinc sulfide extender pigment pallite powder, barium carbonate, clay, silica, white carbon, talc, alumina white The purpose is to control the chargeability of the base particles. In this case, various dyes such as nigrosine, methylene blue, rose bengal, quinoline yellow, and ultra blue can be used as the child particles for forming the coating layer.

In addition, when the purpose is to impart magnetism to the base particles,
As the child particles for forming the coating layer, in addition to cobalt, iron, and nickel, iron oxide and various ferrites can be used.

Furthermore, depending on the purpose, various functional materials such as fluorescent substances and hydroxyapatite can be used as child particles for forming the coating layer.

The above-mentioned child particles for forming the coating layer are not limited to a single column, and two or more types can be used in combination. especially,
When using a material that is difficult to melt, such as an inorganic material, it is preferable to use a mixture of the inorganic material particles and thermoplastic polymer particles, since this facilitates the formation of a coating layer. It is also possible to repeatedly perform surface modification of the same base particle two or more times to provide two or more coating layers. In this case, if the types of child particles are changed for each coating layer, they will easily adhere to each other due to triboelectric charging, making it easier to form the coating layer.

In order to modify the surface of the mother particle by forming or immobilizing the child particles on the surface of the mother particle by the method of the present invention, the mother particle and the child particles are placed in a container equipped with a stirring blade at high speed with a stirring blade in an air stream. Stir. This high-speed agitation process causes particles to collide with each other or particles with blades or the wall of the container, generating local impact energy on the particle surface, and this energy melts the mother particle surface or child particles or stretches the child particles. A coating layer is formed on the surface of the base particle.

In the method of the present invention, as described above, the mother particles and child particles are stirred at high speed in an air stream. This treatment in the air stream prevents the fusion of the mother particles and separates the individual mother particles used. By forming and fixing child particles on the surface to form a uniform coating layer, the surface of the mother particle can be modified. In addition,
If a ball mill or a powder mill is used as in the conventional method, the degree of fusion of particles increases, which is undesirable.

The peripheral speed of the stirring blade in the method of the present invention is 15 m/sec or more, preferably 30 m/sec or more, more preferably 40 m/sec or more.
The speed is 150m/sec. If the peripheral speed of the stirring blade is lower than 15 m/sec, sufficient energy cannot be obtained to form the coating layer. The upper limit of the circumferential speed of the stirring blade is not particularly limited, but it is naturally determined from the viewpoints of the equipment to be used, energy efficiency, and the like.

In the method of the present invention, if a large amount of the above-mentioned mother particles and child particles are introduced into a container equipped with stirring blades and stirred at high speed, collisions between the particles or between the particles and the blades or the wall surface will occur more than necessary, and the desired coating layer will not be formed. or high-speed stirring becomes difficult, so the total weight of the mother particles and child particles is 1! It is preferable to use it at a concentration of 10 to 100 g, preferably 20 to 70 g. If the total weight of both particles is less than 10 g, the frequency of collisions between the particles is low, and the collision energy necessary for forming the coating layer cannot be obtained. On the other hand, if the total weight of both particles exceeds 100 g, fusion of the base particles occurs, coating layer forming fine particles having a uniform particle size cannot be obtained, and adhesion to the inner wall of the device occurs, which is not preferable.

In the method of the present invention, as described above, the mother particles and child particles are stirred at high speed in an air stream, but at the beginning of the treatment, only the mother particles or a part of the mother particles and child particles are transferred to the processing device. After that, the child particles or the remaining child particles are continuously or intermittently supplied while the high speed stirring process is continued to form a coating layer.

The weight ratio of the mother particles and child particles supplied to the processing equipment at the beginning of the stirring process varies depending on the particle diameters and particle size ratios of the mother particles and child particles, and their compositions, but - most preferably - 100 parts by weight of the mother particles. The amount is 0 to 40 parts by weight, preferably 30 parts by weight or less, and more preferably 20 parts by weight or less, based on the child particles. If the amount of child particles used is 50 parts by weight or more, all of the child particles will not be able to cover the surface of the mother particle, and unintended coarse particles are likely to be formed due to aggregation of the child particles. The thickness of the coating layer of each child particle differs from particle to particle, and even in a single particle, the coating layer becomes non-uniform depending on its location.

There are no particular restrictions on the method of supplying the child particles that are additionally added during the high-speed stirring process, but there are two methods: a continuous addition method that continuously supplies the child particles at a constant rate, and an intermittent method that supplies the child particles intermittently in several batches. There are ways to add it.

In any of these methods, in the stirring device immediately after additional child particles are added, the mother particles 1 during high-speed stirring are
00 parts by weight of uncoated child particles (
The amount of child particles added must be controlled so that the amount of child particles that do not contribute to the coating of the mother particles does not exceed 50 parts by weight, preferably 30 parts by weight or less, and more preferably 20 parts by weight or less. Must be.

As long as this condition is satisfied, the final ratio of the mother particle component to the child particle component is not particularly limited.

By supplying the child particles continuously or intermittently in this way, the child particles formed on the surface of the mother particle can be reduced, compared to the conventional method in which all the components of the child particles are added before the stirring process. The thickness of the coating layer became uniform, and individual differences in film thickness between particles and differences in film thickness between parts of a single particle became almost negligible.

Furthermore, by processing the child particles while sequentially supplying them, it is possible to form a film of a large amount of the child particles on the surface of the mother particle, compared to the case where the mother particle and child particles are treated at once. A thick coating layer can now be obtained.

Note that the number of child particles is not limited to one type, and may be a mixture of several types. Furthermore, the type of additional child particles can be changed depending on the timing of addition. With this, it is also possible to form microencapsulated fine particles with a multilayer structure in a single film forming process.

When child particles of the same type are encapsulated singly or in combination with child particles of the same composition, the child particles that cover the surface of the mother particle and the child particles that are further coated are the same, so that the particles gradually Electrostatic repulsion occurs due to charging, and when the weight ratio of the mother particle to child particle reaches approximately 1=1, it becomes difficult to form any more coating layer. However, by changing the composition of the child particles constituting the coating layer as described above, such electrostatic repulsion between the child particles is reduced, making it possible to form a thicker coating layer.

In the present invention, there are no particular restrictions on the method of introducing the child particles into the apparatus during high-speed stirring processing, but for example, the child particles may be introduced using a rotary valve device, using a piston cylinder device, or being entrained in the air flow used for stirring processing. For example, the following means can be exemplified.

In addition, in the present invention, it is preferable to crush the mother particles and/or child particles in advance using a jet mill apparatus, as this enables more uniform film formation.

This crushing treatment must be performed on particles that have a large cohesive force and are likely to cause secondary aggregation, and is usually effective when performed on child particles that are small in particle size and are likely to agglomerate. The crushing treatment using a jet mill is preferably carried out to the extent that the size of 90% by weight or more of the child particles (including aggregates) is smaller than the number average particle diameter of the mother particles. 1 of the number average particle diameter of the base particles
It is preferable to carry out the process until the particle size becomes smaller than /2, and to the extent that 90% by weight or more of the base particles are not secondary agglomerated and are in the state of single particles.

The crushing treatment using a jet mill may be performed after mixing the mother particles and child particles, or may be performed separately on the mother particles and child particles and then mixing them. It may be performed only for either the child particle or the mother particle of the type.

Any type of jet mill device can be used as long as it can break up secondary agglomerated particles through collisions between particles or collision plates in a jet stream using high-pressure gas. .

Specific examples of jet mill devices include those called jet mills, jet-o-mizers, micronizers, magic mills, and torosto mills.

One of the main uses of the microencapsulated fine particles obtained by the method of the present invention is as a toner for developing electrostatic images used in electrophotography. When producing this toner, particles having a number average particle size Sn of 1 to 30 μm, preferably 1 to 15 μm, and a particle size in the range of Sn ± 20% are
Polymer particles usually selected from vinyl polymers are used as mother particles, and have a particle size distribution that accounts for 0% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more. A mixture is used in which coloring particles such as carbon black and the polymer particles are mixed at a ratio of 0.1 to 100 parts by weight, preferably 0.3 to 10 parts by weight of polymer particles per 1 part by weight of coloring particles. is preferable. In addition, fine particles such as a charge control agent such as nigrosine or chromium-containing dye, a fixing property control agent such as polyethylene wax or polypropylene wax, or a magnetism imparting agent such as magnetite are mixed and used as part of the child particles to improve the performance of the toner. It can also be adjusted.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited by these.

Example 1 By the method described in Japanese Patent Publication No. 57-24369, the monomer composition was styrene/butyl acrylate, the glass transition temperature was 50°C, the molecular weight Mn = 16,000, and Mw = 4.6.
10,000 polymer particles were produced. These particles have a number average particle size (Sn) of 7 μm and a particle size distribution in which particles with a particle size in the range of 5.6 to 8.4 μm account for 95% by weight (the standard deviation of the particle size is 5% of the particle diameter), and the particles were extremely uniform in particle size.

The particles were washed with water and dried, and 100 g of the obtained particle powder was used as a base particle.

On the other hand, emulsion polymerization was carried out using sodium dodecylbenzenesulfonate as an emulsifier and sodium persulfate as a polymerization initiator, and Sn was 0.08 μm, the composition was p-MMA/butyl acrylate, the glass transition temperature was 50°C, and Mn was 3. 9
Polymer particles with Mw=58,000 and Mw=58,000 were obtained. The particles were coagulated with calcium chloride, washed with water, and dried to obtain 10 g of polymer particles, which were used as child particles. Further, this child particle is referred to as a polymer child particle (A).

Furthermore, 10 g of carbon black '#40J (manufactured by Mitsubishi Kasei Corporation) having a number average particle diameter of 0.01 μm was mixed as second child particles with the previous mother particles and polymer child particles (A) in a Henschel mixer. . This mixture has an internal volume of 4! Hybridizer rNH8-1 type (manufactured by Nara Kikai Seisakusho Co., Ltd.) was used to perform high-speed stirring for 3 minutes at room temperature with a blade circumferential speed of 78 m/s, and after 2 minutes, further polymer particle particles ( A) and carbon black (1 each)
The mixture obtained by mixing 0 g in a Henschel mixer was put into the inlet of the machine, the inlet valve was opened for a short time, and the mixture was introduced into the machine through the air flow entrainment rod, followed by high-speed stirring for 3 minutes to form microcapsules. A powder of fine particles was obtained.

When the powder thus obtained was rubbed between slide glasses and observed under an optical microscope, it was found that the coating layer did not fall off and that the film formation was sufficient. The microencapsulated fine particles were uniform particles with a number average particle size of 7.1 μm and no coarse particles. Furthermore, it was confirmed that these particles were perfectly spherical, and there was no difference in blackness between the particles, and that the adhesion and film formation of carbon black and polymer child particles were uniform.

Comparative Example 1 In Example 1, the amount of particles introduced into the hybridizer at the start of the high-speed stirring process was 100 g of mother particles, 20 g of polymer child particles (A), and 20 g of carbon black.
A powder of microencapsulated fine particles was obtained in the same manner as in Example 1, except that high-speed stirring treatment was performed for 6 minutes without additionally introducing child particles during the treatment. When this powder was rubbed between slide glasses and observed under an optical microscope, the coating layer did not fall off and the film formation was sufficient. However, this powder has different blackness depending on the particle,
There was a mixture of light black particles and dark black particles. In addition, there were also coarse particles of 10 to 30 μm, which were estimated to have been agglomerated with child particles without being completely formed on the surface of the mother particles.

Example 2 Mixture 20 of polymer child particles (A) and carbon black
Example 1 except that the additional addition of g was repeated 4 times every 3 minutes.
Similarly, polymer child particles (
A total of 100 g of A) and carbon black was subjected to a high-speed stirring treatment to obtain a powder of microencapsulated fine particles.9 The obtained microencapsulated fine particles had a number average particle diameter of 10.
The particles had uniform particle diameters of 0 μm and a standard deviation of particle diameters of 6% of the average particle diameter.

When observed using an optical microscope, there was no difference in blackness between the particles.
All particles had uniform blackness.

Moreover, no coarse particles were observed.

Example 3 After mixing 1000 g of the mother particles used in Example 1, 100 g of polymer child particles (A) used in Example 1, and $40,100 g of carbon black in a Henschel mixer, a jet mill rPJM-100SP type was used (Japan Pneumatic Kogyo ■) was used for crushing. 12 of these
0g was charged into a hybridizer NH8-1 type equipped with a rotary valve device at the input port, and the circumferential speed of the blade was set to 90.
High-speed stirring treatment was carried out at m/sec for 3 minutes.

Then, 10 g of polymer particles (B) of styrene-butyl methacrylate copolymer (glass transition temperature: 55° C., number average particle size: 0.15 μm) were added through the rotary valve, and high-speed stirring was continued for an additional 3 minutes. This additional addition of polymer child particles (B) was repeated twice to obtain a powder of microencapsulated fine particles. The obtained microencapsulated fine particles have a uniform particle size with a number average particle size of 8.0 μm and a standard deviation of particle size of 6% of the average particle size, and have a black color whose surface is coated with a polymer layer. It was a particle. In addition, the electrical resistance value of the powder is 2X10160-c
m, the blow-off charge amount was -35; uc/g, and the toner could function as a negatively chargeable toner.

When this toner was used in a copying test using a copying machine rFT-4045J (manufactured by Ricoh Co., Ltd.), there was no fogging, a high resolution of 10 lines/mm was obtained, and the gradation was good. Furthermore, good images were obtained even after a long run test of 30,000 sheets.

Comparative Example 2 100g of base particles used in Example 1, carbon black #
4010 g, polymer child particles (A) Log, and 30 g of polymer child particles (B) used in Example 3 were thoroughly mixed together using a Henschel mixer, and then stirred at high speed for 12 minutes using a hybridizer, model NHS-1. processed.

The obtained particles had a number average particle diameter of 8.0 μm, a standard deviation of the particle diameter was 12% of the average particle diameter, and the film formation state was good, but there was a difference in blackness between the particles. It was something. The electrical resistance value of this powder is 4X1011Ω・c
m, the blow-off charge amount was 4 μC/g, and the electrical properties as a toner were insufficient.

Example 4 In Example 3, 30 g of polymer child particles (B) were put into the machine at once in the child particle addition stage, and the high-speed stirring process was carried out for 9
A powder of microencapsulated fine particles was obtained in the same manner as in Example 3, except that the treatment was carried out for a minute.

The obtained particles had a number average particle diameter of 8.1 μm, a standard deviation value of the particle diameter of 6% of the average particle diameter, and film formation on the particle surface was good. The electrical resistance value of this powder is 1×1016
The blow-off charge amount of Ω·CrII was -26 μC/g. Using this powder as toner, the copier FT-40
When a copying test was conducted with 45, a high resolution of 10 lines/order was obtained, and the quality was practical as a toner, but there was some fog in the copied image.

The reason for this fogging is that in this toner particle, although the first stage carbon black was uniformly formed on the base particles by sequential addition, the second stage
This is thought to be due to the fact that the coating layer became non-uniform because the film was formed by using only the polymer child particles in the step at once.

(Effects of the Invention) According to the present invention, by continuously or intermittently supplying all or part of the child particles during a high-speed stirring process, it is possible to uniformly form a film using the child particles on the surface of the mother particle. can.

As a result, the thickness of the coating layer between particles and on a single particle becomes uniform, and variations in particle performance are reduced, so that particles with good properties can be obtained.

Furthermore, in the present invention, particles with a multilayer structure can be obtained in a single process by simply changing the type of child particles added during the stirring process, greatly improving productivity.

The microencapsulated fine particles obtained by the present invention are
It can be used in a wide range of fields including paints, electronic materials, electrophotography, biochemical carriers, cosmetics, pharmaceuticals, and catalysts. In particular, in the field of electrophotography, it can be effectively used as a toner that is free from fog, has high resolution, and produces good images.

Agent: Patent attorney Michie Fuse (2 others)

Claims (1)

[Claims] (1) base particles having a number average particle diameter of 1 to 200 μm;
A coating layer of the child particles is formed on the surface of the mother particle by high-speed stirring treatment in an air stream with child particles for forming a coating layer whose number average particle diameter is 1/5 or less of the number average particle diameter of the mother particle. A method for producing microencapsulated fine particles, the method comprising: supplying all or part of the child particles continuously or intermittently during high-speed stirring treatment.