JPH02972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing microcapsule particles having a uniform particle size distribution containing core particles produced using an electroemulsification method.

Microcapsule particles are polymer containers with sizes ranging from several microns to hundreds of microns, and are currently used in carbonless copying paper, fast-acting and slow-acting paper, and are used to protect the contents and control the release of the contents. It has been commercialized as a chemical agent, catalyst, and rust preventive agent, but these are only a small part of its wide range of useful value, and future developments are expected.

In order to microencapsulate conventional substances,
First, a dispersion emulsification step (first step) in which the existing substance is divided into small particles and an encapsulation step (second step) in which a coating is applied are required. For example, to make uniform microcapsule particles, the core material is uniformly atomized by using a large amount of emulsifier in advance, high-speed mechanical stirring, ultrasonic vibration, etc. Alternatively, in that state, the material that will become the wall film is fixed in the dispersion medium containing the core material, and if necessary, interfacial polymerization method, phase separation method, etc.
A cooling method is used to form a wall film, and in some cases, the capsule wall is further strengthened chemically or physically to form a stable wall. However, in the past, the essential condition of using a large amount of emulsifier in the first step caused the emulsifier to remain on the surface layer of the core material in the second step, which caused the adhesion between the core material and the wall film to deteriorate during microencapsulation. As a result, the force is greatly reduced and single particles formed only from the wall material are produced as by-products, it is difficult to obtain microcapsule particles with desired uniform particle size and good so-called monodispersity. Furthermore, the expression of expected functions is adversely affected. For this reason, before the microencapsulation step, the atomized core material is generally pretreated by washing with water or by removing the emulsifier using electrodialysis, a semipermeable membrane, an ion exchange resin, or the like. However, the microencapsulated particles produced using this method suffer from a decrease in yield and a rise in production cost due to the complexity of the working process, and there are many problems that are extremely difficult to implement.

As a result of intensive research in view of the existing problems, the inventors of the present invention have overcome the above-mentioned problems by a method that was completely unthinkable in the past. That is, the present invention provides microcapsule particles having a uniform particle size using an electroemulsification method. Specifically, in the present invention, a core material that is melted by heating,
It is atomized into the air from the atomizing head to which a high voltage of 2KV to 200KV is applied, and is caused to fly through an electric field to generate core particles. It includes a shell material for micro-encapsulating the generated core particles. Covered with media. The present invention relates to a method for producing microcapsule particles, characterized in that they are collected on a grounded surface to be coated facing an atomizing head, and the collected core particles are covered with a shell material to form microcapsules.

As described in the Examples below, waxes are preferred as the core material, and styrene-acrylate copolymer is preferred as the shell material.

Fine particles having a uniform particle size obtained by the electroemulsification method as described above are supplied into a medium containing a shell material that forms a uniform thin film without directly producing a defective film, so that the appearance of microcapsule particles is Manufactured continuously. Furthermore, in the present invention,
By applying a voltage, it is possible to prevent the material from flying up and obtain microcapsule particles with a high yield.

In a specific embodiment of the present invention, a high positive or negative voltage is applied to the core material under conditions where the amount of emulsifier is much smaller or not present at all during core formation, and at the same time, mechanical This is carried out by transferring uniformly atomized droplets into a grounded wall material or a dispersion medium containing the wall material while the core material is made to fly in an electric field. That is, the surface to be coated facing the atomizing head is coated with a medium containing a shell material for microencapsulation, and the generated core material particles are caused to fly to the surface to be coated covered with the medium. According to
It is also possible to carry out the first step of forming the core material particles and the second step of forming the shell in good succession. As a result, microcapsule particles are obtained in which little or no emulsifier is present in the resulting microcapsule particles.

The core material used in the present invention can be any material that can be ejected with a nozzle or bell into a medium containing shell material while applying a voltage. In general, substances that exhibit a liquid or suspended/dispersed state upon discharge are effective, such as polyester resins; polyester-based urethane polymers;
Polyester-based alkyd resin; typical examples include trimellitic acid ester of polycaprolactone, rosin ester, modified rosin ester, reaction product of isopropylidene diphenoxypropanol and adipic acid, reaction product of isopropylidene phenoxypropanol and sebacic acid, etc. Various modified polyester resins used; typical examples include polyethylene wax, carnauba wax, castor wax, rice wax, Syuratu wax, Zazor wax, amide wax, Montan wax, microcrystalline wax, ceresin wax, paraffin wax, and ozokerite. Waxes to be used; behenic acid amide, stearic acid amide, palmitic acid amide, lauric acid amide, erucic acid amide, braidic acid amide, oleic acid amide, elaidic acid amide, methylene bisbehenic acid amide, methylene bis stearic acid amide , methylenebisoleic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisoleic acid amide, octamethylenebiserucic acid amide, monoalkylolamide, polyamide produced from dimerized linoleic acid and diamine or polyamine, dicarboxylic acid Polyamide resins typified by reaction products of and linear diamine; polyvinyl acetate, ethylene-vinyl acetate copolymer, polyisobutylene, polystyrene, dodecyl acrylate
Styrene copolymer, polyurethane elastomer,
Examples include epoxy resin, epoxidized phenol formaldehyde resin, and acrylic resin. Further, the above resins may be used alone or as a mixture depending on the case. Since these core materials are atomized in a molten or dispersed state, they must have a sufficiently low melt viscosity, and generally have a softening temperature of 5 to 50%.
Softening temperature is about 200℃, especially preferably 30~150℃
It is preferable that the degree of

Furthermore, in the above resin, magnetic powder, coloring pigments, dyes, water-miscible solvents, charge control agents, curing agents,
Additives such as flow regulators and stabilizers may be dispersed or dissolved.

All known dyes and pigments can be used as coloring agents, such as carbon black, iron black, nigrosine, benzidine yellow, quinacridone, rhodamine B, and phthalocyanine blue. The amount of pigment added is appropriately adjusted depending on the type of pigment used and the degree of coloring. Generally, in order to reduce the viscosity of the core material, the amount of pigment added is 80% by weight or less, preferably 70% by weight or less, particularly preferably 30 to 60% by weight based on the resin.

The magnetic powder can be any substance that becomes magnetized when placed in a magnetic field, and generally includes powders of ferromagnetic metals such as iron, cobalt, and nickel, or compounds such as magnetite, hematite, and ferrite. The content of this magnetic powder is 10 to 80% by weight, preferably 30 to 60% by weight based on the weight of the core material.

Other core materials used in the present invention include corn oil, castor oil, mineral oil, fats and oils represented by cod liver oil, fragrances, rust preventives, liquid crystal substances, vitamins,
Examples include minerals and nutrients, pharmaceuticals, lubricants such as polytetrafluoroethylene, and plasticizers such as dicyclohexyl phthalate. The additives used vary greatly depending on the purpose of use, but are generally 20 to 200% by weight, preferably 25 to 100% by weight. In this case, if too many additives are used, the viscosity becomes too high, making it difficult to pulverize by spraying, and the pumping pressure becomes too high, causing problems. The above substances are used by adding a solvent or heating as necessary.

As the shell material used in the present invention, any material that is liquid at room temperature and soluble or dispersible in water and organic and inorganic solvents can be used. Furthermore, a portion of the shell material used in the present invention can be added to the core material.

Examples of the shell material include polystyrene, polymonochlorostyrene, styrene-methacrylate copolymer, styrene-acrylate copolymer, styrene-maleic acid copolymer, polycarbonate, polyether, low molecular weight polyethylene,
Polyester, fumarate polyester resin, methyl acrylate-methacrylic acid copolymer, polyamide, gelatin, polypropylene, polyurethane, epoxy resin, polyvinyl alcohol, rosin, ethyl cellulose, paraffin, carboxymethyl cellulose, silica, gum arabic,
Tristearin, polyacrylamide, polybutadiene, polyisoprene, silicone resin, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, benzylcellulose, cellulose, acetobutyrate, 5-ethyl-2-vinylpyridine-acrylic Methyl acid-methacrylic acid copolymer, 2-methyl-5-vinylpyridine-methacrylic acid copolymer, vinylpyridine-styrene copolymer, polyvinylpyrrolidone, vinylpyrrolidone-vinyl acetate copolymer, phthalic acid chloride, phthalic acid bromide , aromatic dicarboxylic acid halides such as terephthalic acid chloride and terephthalic acid bromide, and polyamines represented by ethylenediamine, diethylenetriamine, and triethylenetetramine. The above-mentioned compounds are supplied onto the surface of the device in a solubilized or dispersed state in water and an organic or inorganic solvent, either alone or in the form of a copolymer, or in some cases in the form of a mixture.

Media used in the present invention include amides such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone, methyl propyl ketone, diethyl ketone, cyclohexanone, ethers such as dioxane, tetrahydrofuran, ethyl ether, ethylene glycol diethyl ether, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethylene glycol monoethyl acetate Ester, esters such as glycol diacetate, alcohols such as n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, cyclohexanol, benzyl alcohol, chlorine-substituted hydrocarbons such as methylene chloride, β, β'-dichlorodiethyl ether, etc. nitromethane,
These include nitro compounds such as nitroethane. These solvents are added in an amount of 1 to 100% by weight, preferably 5 to 50% by weight, based on the resin.

The present invention optionally includes a crosslinking agent, a polymerization initiator,
A coloring agent, a charge control agent, a curing agent, a flow regulator, a stabilizer, etc. may be added.

The amount of the shell material used in the present invention can be selected within a wide range in order to exhibit good electrophotographic properties. Generally, the shell material is added so that the thickness of the shell material forming film is 1/1000 to 10 times, preferably 1/500 to 1/50 times the core material particle size.

In the present invention, methods for producing core particles include a two-fluid nozzle equipped with a high voltage generator, a pressurized nozzle, and a rotating disk type bell. Preferably, in order to atomize the molten core material, a two-fluid nozzle or a rotating disk-type bell having a plurality of micro-machined grooves in the atomizing head of the bell, which are opened adjacently so that the injection directions are parallel or intersecting, is used. At this time, the core material to be discharged is prepared in advance from a commonly used homo mixer, disperser, roll mill, sand mill, etc.
Thoroughly kneaded using a ball mill, sentry mill, or sassmeyer mill.

The pressure at which the core material is transferred to the atomizing head consisting of a nozzle or bell can be arbitrarily adjusted to obtain the desired particle size. When using a two-fluid nozzle, the pressure is generally 1 to 100Kg/cm2, preferably ²
The core material is transferred at a pressure of ~10 Kg/cm ² and a hot air pressure of about 5 to 50 Kg/cm ² . When using a rotating disc type bell, it is generally fed at a transfer rate of 1 to 200 g/min, preferably 20 to 100 g/min. Although it depends on the core material used for the rotary disc bell, it is generally maintained at 1,000 to 100,000 rpm, preferably 5,000 to 50,000 rpm. Pumps used for transfer include centrifugal, reciprocating, and rotary pumps that can maintain a constant continuous flow with little pulsation, such as volito pumps, turbo pumps, propeller pumps,
gear pump, screw pump, partition plate pump,
Magnetic pumps, lab pumps, diaphragm pumps, bellows pumps, Banton pumps, etc. are preferred.

The high voltage applied to the nozzle or bell in the present invention is generally 2-200KV, preferably 40-90KV
is used. The above applied voltage also depends on the material used, but if the applied voltage is lower than the above range, the particles will not be sufficiently atomized, and if the applied voltage is higher than the above range, the atomization effect will be saturated, and the effect of increasing the voltage will be reduced. Not expressed.

In the present invention, microcapsules are produced by flying the core material, which has been atomized in advance using an atomizing head, into a medium containing the shell material on a grounded surface to be coated. The grounded surface to be coated and the energized atomizing head must be kept at a distance that does not cause dielectric breakdown. In the present invention, the distance between the atomizing head to which voltage is applied and the surface to be coated usually depends on the applied voltage, but when the applied voltage is 80 KV, it is 50 to 500 mm, preferably 100 to 500 mm. They are installed 200mm apart. Microcapsule particles obtained in the present invention can be cooled or filtered as they are to obtain microencapsulated particles.

Examples are shown below. Parts are parts by weight.

[Example 1] Polyethylene resin 100 parts Ethylene-vinyl acetate copolymer 20 parts Magnetite 80 parts The above mixture was heated at 120°C for 2 hours using a homomixer.
The molten material subjected to time-kneading treatment is supplied to the bell section at a discharge rate of 50 g/min using a metering gear pump equipped with a heating pot and a heating tube. The bell uses a G bell (manufactured by Landsburg) with finely processed grooves.
Atomization was carried out at 30,000 rpm and an applied voltage of -80 KV. On the other hand, styrene-acrylic acid ethyl ester copolymer
20 parts Diethylaminoethyl methacrylate resin 3 parts A solution prepared by dissolving the above mixture in DMF is supplied to the surface to be coated at a rate of 3/min. The obtained microcapsules were collected, filtered, and dried to obtain microencapsulated particles. When measuring the particle size distribution using a Coulter counter, the volume average particle size
It was found that particles having a particle size of 10.9 μm, 6.35 μm to 20.2 μm comprised 92% by weight of the total particles.

[Example 2] Polyethylene resin 100 parts Ethylene-vinyl acetate copolymer 20 parts Magnetite 80 parts The above mixture was heated at 120°C for 2 hours using a homomixer.
The time-kneaded molten material is supplied to the bell section at a discharge rate of 50 g/min using a metering gear pump equipped with a heating pot and a heating tube. The bell uses a G bell (manufactured by Landsburg) with finely processed grooves.
Atomization was carried out at 30,000 rpm and an applied voltage of -80 KV. On the other hand, styrene-acrylic acid ethyl ester copolymer
20 parts Methyl methacrylate resin 3 parts A solution prepared by dissolving the above mixture in DMF is supplied to the surface to be coated at a rate of 3/min. The obtained microcapsules were collected, filtered, and dried to obtain microencapsulated particles. When measuring the particle size distribution using a Coulter counter, the volume average particle size
It was found that 89% by weight of the total particles were comprised of particles having a particle size of 10.2 μm, between 6.35 μm and 20.2 μm.

[Example 3] Polyethylene resin 100 parts Ethylene-vinyl acetate copolymer 20 parts Tin oxide 80 parts The above mixture was heated at 120°C using a homomixer for 2
The molten material subjected to time-kneading treatment is supplied to the bell section at a discharge rate of 50 g/min using a metering gear pump equipped with a heating pot and a heating tube. The bell uses a G bell (manufactured by Landsburg) with micro-machined grooves.
Atomization was carried out at 30,000 rpm and an applied voltage of -80 KV. On the other hand, styrene-acrylic acid ethyl ester copolymer
20 parts Methyl methacrylate resin 3 parts Diethylaminoethyl methacrylate resin 1 part A solution prepared by dissolving the above mixture in DMF is supplied to the surface to be coated at a rate of 3/min. The obtained microcapsules were collected, filtered, and dried to obtain microcapsule particles. When the particle size distribution was measured using a Coulter counter, the volume average particle diameter was 10.9 μm.
Those with a particle size between 6.35μ and 20.2μm account for all particles.
It was found that it contained 85% by weight.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a device applicable to the present invention. 1... Rotating bell, 2... Mounted object, 3... Drain valve, 4... Collection tank, 5... Dispersoid tank, 6...
Gear pump, 7...Air turbine motor, 8
... Dispersion medium supply pump, 9 ... Supply hose, 10
...Dispersion medium tank.

Claims (1)

[Claims] 1. Core material melted by heating is atomized into the air from an atomization head to which a high voltage of 2KV to 200KV is applied, and is caused to fly in an electric field to generate core material particles, Collecting the generated core material particles on a grounded surface to be coated facing the atomizing head, which is coated with a medium containing a shell material for microencapsulation;
A method for producing microcapsule particles, which comprises covering collected core material particles with a shell material to microcapsule them. 2. The method for producing microcapsule particles according to claim 1, wherein the core material is a wax and the shell material is a styrene-acrylate copolymer.