JPH0427426A - Microcapsule and production thereof - Google Patents

Abstract

PURPOSE:To microencapsulate a chemically and/or physically unstable core material by using capsule walls formed by aggregating colloidal fine particles with an electrolyte. CONSTITUTION:A core material is added to a hydrosol contg. colloidal fine particles in water as a dispersive medium, they are dispersed in an oily medium and the colloidal fine particles in the resulting emulsion are aggregated with an electrolyte to produce microcapsules. The core material used is not especially limited and may be selected among various materials such as dyes, pigments, pharmaceuticals, agricultural chemicals, perfume, chemical products, adhesives, enzyme and fungi. The core material is usually added by 0.1-50wt.% of the amt. of the hydrosol. Any solvent known as a hydrophobic solvent may be used as an org. solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel microcapsule and a method for producing the same.

[Conventional technology]

Many methods have been reported regarding the production of microcapsules, among which physicochemical and chemical methods include complex coacervation method, simple coacervation method, interfacial polymerization method, and in5 method.
The itu polymerization method and the like are known. These methods do not require the use of special equipment, can produce capsules with any particle size ranging from 1 micron or less to several millimeters, and are dependent on the properties of the capsule membrane. It is used in many fields because of its advantages such as being able to control density and precision.

[Problem to be solved by the invention]

However, in the coacervation method, the most common capsule membrane material is gelatin-gum arabic, a natural polymer, but it has poor water resistance, high cost, and is difficult to obtain a highly concentrated capsule liquid. It has disadvantages such as the complicated process. On the other hand, interfacial polymerization method and in 5
Chemical production methods such as the itu polymerization method have high reactivity of the raw materials for the capsule membrane, so they may react with the core material contained therein, or the core material may be exposed to strong acid or alkalinity, so this method is not always satisfactory. Not.

[Means to solve the problem]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems.

That is, the present invention provides: (1) Microcapsules containing a core substance in a capsule membrane obtained by agglomerating colloidal fine particles using an electrolyte.

(2) A core substance is added to a dispersion (hydrosol) of colloidal fine particles using water as a dispersion medium, and this is dispersed in an oily medium to form an emulsion. A water-soluble core substance is added to a suspension or a dispersion (hydrosol) of colloidal particles using water as a dispersion medium, and this is dispersed in an oily medium to form a W/O emulsion. The method described in (2).

(4) The emulsion is obtained by dispersing an oil-soluble core substance in a dispersion (hydrosol) of colloidal particles using water as a dispersion medium to obtain an O/W type emulsion, which is further dispersed in an oily medium, 0/W
/O-type emulsion according to the method described in (2) above.

(5) A water-insoluble powder core material is dispersed in an emulsion or a dispersion (hydrosol) of colloidal fine particles using water as a dispersion medium, and this is dispersed in an oily medium to form a W(S)/O type. It relates to the method described in (2) above, which is an emulsion.

In the dispersion (hydrosol) of colloidal fine particles using water as a dispersion medium used in the present invention, the particle size of the colloidal fine particles is usually 5 to 1/O00n, preferably 1/O to 500n.
It is nm. Hydrosols include, for example, sols of metals such as gold, silver, and platinum, sols of metal oxides such as silicon oxide, zirconium oxide, aluminum oxide, iron oxide, copper oxide, zinc oxide, and chromium oxide, and arsenic sulfide. Examples include sols of metal sulfides such as zinc sulfide and lead sulfide, sols of other silver halides, barium sulfate, and ferric hydroxide, sols of fine particles made of organic polymers, and sols of mixtures thereof. The inorganic sol is manufactured by a known method such as a flocculation method or a peptization method. In addition, organic sols include, for example, styrene,
It is produced by polymerizing methyl (meth)acrylate, vinyl acetate, vinyl chloride, vinylidene chloride, etc., singly or as a mixture, using a known emulsion polymerization method. The solid content concentration of the hydrosol is not particularly limited as long as it can be easily dispersed when dispersing the hydrosol in an oily medium, and is usually 5 to 50% by weight.

Next, a core material is mixed or dispersed in the hydrosol.

If the core substance is a water-soluble substance, only mixing is required; if it is an oil-soluble substance or a water-insoluble powdered substance, it must be dispersed. The core material is not particularly limited, and various materials such as dyes, pigments, pharmaceuticals, agricultural chemicals, fragrances, chemical products, adhesives, enzymes, and bacterial cells can be used. For example, in the case of a water-soluble core material such as a water-soluble dye, the core material is mixed and dissolved in a hydrosol. In the case of an oil-soluble core material such as olive oil, the core material is dispersed in a hydrosol to form an 0/W type dispersion. The stability of the dispersion at this time is important and is greatly involved in the inclusion rate of the core substance. That is, if the stability of the dispersion is poor, the inclusion rate of the core substance will be poor, and in some cases, encapsulation may not be possible at all. It is preferable to use a dispersant to stabilize the dispersion. The dispersant used may be a known surfactant or polymer dispersant that stabilizes the O/W type emulsion. however,
The microparticles in the hydrosol must not aggregate during dispersion. Examples include fatty acid salts, alkyl sulfate salts, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene sorbitan fatty acid esters, polyvinyl alcohol, and carboxymethyl cellulose. Further, in the case of a water-insoluble powdery core material such as carbon black or magnetic iron, the water-insoluble powdery core material is dispersed in a hydrosol in the same manner as in the case of an oil-soluble core material. At this time, the combination must be such that the fine particles in the hydrosol are not aggregated into a powdery core substance. For example, the surface charges of the fine particles in the hydrosol and the powdery core material are the same.

Further, a treatment may be applied to adsorb a dispersant or the like onto the surface of the powdery core material so that the powdery core material itself does not aggregate in the hydrosol. A hydrosol in which the core substance is dissolved or dispersed as described above is called a primary dispersion.

The ratio of the core material to the hydrosol in this second-order dispersion is not particularly limited (as long as a dispersion can be formed).

Usually, the core material is used in an amount of 0.1 to 50% by weight based on the hydrosol. Furthermore, the ratio of the core material to the fine particles in the hydrosol is not particularly limited, or should be adjusted depending on the intended use of the capsules since it affects the film thickness of the resulting capsule particles. Next, this -ash dispersion is further dispersed in an organic solvent (oil-based medium) containing a dispersant, and if the core material is a water-soluble material, a W/O emulsion is obtained, or if the core material is a powdered core material, a W/O type emulsion is obtained. If the core substance or oil-soluble substance is used, make it a 0/W/O type emulsion. These emulsions are called secondary dispersions.

The organic solvent used here can be any solvent that is generally known as a hydrophobic solvent.For example, as an aliphatic solvent, C0 to C+□ hydrocarbons, especially n-hexane, n- Common examples include butane, n-octane, etc., benzene, toluene, xylene, etc. as aromatic solvents, and chloride as halide solvents.
Chloroform, dichloromethane, tetrachloromethane,
Examples include mono- or dichlorobenzene. These solvents may be used alone or as a mixed solvent of two or more. The amount of organic solvent used is such that the emulsion obtained is W2O type,
It is not limited as long as it is W(S)/O type or 0/W/O type, and it may normally be 25% by volume or more, preferably 40 to 90% by volume of the emulsion. As dispersants, nonionic surfactants such as polyoxyethylene sorbitan triolate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monostearate can be used. sorbitan triolate, sorbitan monooleate, sorbitan tristearate, sorbitan monostearate, sorbitan monopalmitate, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, (hydrogenated) soybean lecithin, (hydrogenated) Phospholipids such as egg yolk lecithin, and JP-A-1983-13
Examples include polymeric dispersants disclosed in Japanese Patent No. 5501.

These dispersants may be used alone (or two or more types may be used in combination.The amount of these dispersants used is 0% to the primary dispersion.
．． 01 to 30% by weight is preferred, particularly 0.2 to 20% by weight.

Next, the colloidal fine particles in the obtained secondary dispersion are aggregated using an electrolyte to obtain the microcapsules of the present invention. Examples of methods for performing this aggregation include adding a secondary dispersion into an electrolyte aqueous solution, or adding an electrolyte aqueous solution into a secondary dispersion. The electrolyte is preferably one that is not particularly limited or does not cause problems when the obtained capsule particles are applied. for example,
Alkali metals, alkaline earth metals, iron, co/silt, nickel, copper, zinc, aluminum, chlorides, bromides, ammonium chloride, tetramethylammonium chloride, polyacrylic acid, polystyrene sulfonic acid, chitosan, etc. There are polymer electrolytes. In particular, it is preferable to use an electrolyte that generates multivalent ions having a charge opposite to that of the colloidal particles. The amount of electrolyte used should be sufficient to aggregate colloidal particles (S
5 to 50% by weight (however, 0.1 to 5% by weight for polymer electrolytes) of an electrolyte aqueous solution to the secondary dispersion (as long as it is above the critical coagulation concentration called Chulze-Hardy's law). It is preferable to use 500% by volume.

The temperature at which the method of the present invention is carried out is not particularly limited as long as it does not damage the dispersion system, and it can usually be carried out at 20 to 70°C.

When adding the secondary dispersion into the electrolyte aqueous solution or when adding the electrolyte aqueous solution into the secondary dispersion, the rate of addition is not particularly limited as long as the rate does not break the emulsion state.

In this way, the microcapsules of the present invention are obtained in the form of a slurry. When making powdered microcapsules from this, there are no particular restrictions on the method, and any conventional method can be used. For example, it can be obtained by washing a capsule particle slurry with alcohol and water, separating solid and liquid by suction filtration, and drying. In addition, powdery fine particles can be obtained directly by a spray drying method or the like.

The particle size of the capsule particles obtained in the present invention is determined by the dispersion conditions of the secondary dispersion, and particles having a particle size of 1 μm to 500 μm are usually obtained. That is, capsule particles having a desired particle size can be obtained by selecting the type and amount of the dispersant used and the stirring conditions (diameter of the stirring blade, rotation speed, etc.).

According to the method of the present invention, under mild conditions and with easy operation,
Moreover, desired microcapsules can be obtained in a short time and in high yield.

〔Example〕

The number in parentheses after the amount obtained in the examples indicates the proportion of the colloidal fine particles used that became a capsule membrane.

Example 1 A dye (
Blue No. 2) 20mg dissolved in 0.2g of sorbitan triolate and 48ml of chloroform in which 2.0g of polyoxyethylene sorbitan monooleate was dissolved.
Disperse at 9000 rpm using a homogenizer,
30 seconds) Prepare a W/O emulsion. Next, 75 ml of a 20 wt % calcium chloride aqueous solution was placed in a 300-mm round bottom flask equipped with a stirrer, and the above emulsion was added dropwise over about 5 minutes while stirring. Continue stirring at room temperature for 30 to 60 minutes. 20 ml of methanol is added to the resulting slurry of capsule particles (microcapsules) and filtered with suction to separate the capsule particles, followed by drying. Particles with a blue appearance were obtained.

The average particle size was 5 μm and the yield was 2.9 g (90%).

Example 2 Limonene (fragrance) 8- in which 0.16 g of polyoxyethylene sorbitan triolate was dissolved in 16 mg of colloidal silica (SiO□, Snowtex 01 particle size/O ~ 20 nm, solid content concentration 20%) was dispersed. A W-type emulsion is prepared (-separated dispersion). Furthermore, the above primary dispersion was dispersed using a homogenizer in 64 ml of chloroform in which 0.2 g of sorbitan triolate and 2.0 g of polyoxyethylene sorbitan monooleate were dissolved.
prn, 30 seconds) Prepare an O/W/O emulsion (secondary dispersion). This was placed in a 300 ml round bottom flask equipped with a stirrer, and while stirring, 24 yd of an Owt% calcium chloride aqueous solution was added dropwise at room temperature over about 5 minutes. Continue stirring at room temperature for 15 to 30 minutes.

20 ml of methanol is added to the resulting slurry of seven turnip particles, filtered with suction to remove capsule particles, and dried. Capsule particles containing limonene were obtained, and the average particle size was 1.
At 6 μm, the yield was 8.7 g (85.3%).

Example 3 Zirconia sol (ZrO2, NZS-3OA, Yasan Kagaku Co., Ltd., particle size 95 nm, solid content concentration 35%) 16 m
Disperse 2 g of Red No. 226 (organic pigment) into g using an ultrasonic disperser. The dispersion was mixed with 0.6 sorbitan monopalmitate.
g, 48 methylene chloride in which 60 mg of soybean lecithin was dissolved
Using a homogenizer on m1, disperse at 9000 rpm.
, 30 seconds) Prepare a W (S)/O type emulsion. Transfer this to a 300mJ round bottom flask equipped with a stirrer, and add 24yd of 15wt% sodium sulfate aqueous solution without stirring.
is added dropwise over about 5 minutes at room temperature. Continue stirring at room temperature for 15 to 30 minutes. 20 ml of methanol is added to the obtained capsule particle slurry, and the slurry is suction-filtered to separate the capsule particles and dried. Red capsule particles were obtained with an average particle size of 9 μm and a yield of 7.2 g (95%).

Example 4 Styrene latex particle size 120 nm, solid content concentration 30
%) Disperse 1 g of carbon black in 15 yards using an ultrasonic disperser. The dispersion was mixed with 0.1 g of polyoxyethylene sorbitan monooleate and 0.5 g of sorbitan triolate.
(8000 rpm, 20 seconds) to prepare a W (S)/O type emulsion. Add this to 300 ml with a stirrer
% aluminum sulfate aqueous solution was added dropwise over about 5 minutes at room temperature while stirring. Continue stirring at room temperature for 15 to 30 minutes.

Twenty minutes of methanol is added to the obtained capsule particle slurry, and the capsule particles are separated by suction filtration and dried.

Black styrene capsule particles were obtained with an average particle size of 22 μm and a yield of 4.9 g (89%).

Example 5 Colloidal silica (SiO□, Snowtex 0, particle size /O~20nm, solid content concentration 20%) 7.5yd, styrene latex (manufactured in-house, 35nm, /O%) 7.5m
lGm polyoxyethylene sorbitan monooleate 20
Disperse 1 g of soybean oil with a homogenizer (9000 rpm, 20 seconds) to prepare an 0/W emulsion (-ash dispersion). The -ash dispersion was dispersed in hexane 45rILI in which 0.1 g of polyoxyethylene sorbitan monostearate and 0.5 g of sorbitan triolate were dissolved using a homogenizer (7000 rpm, 20 seconds) O/
Prepare a W/O emulsion (secondary dispersion). The secondary dispersion was placed in a 300-mm round bottom flask equipped with a stirrer, and without stirring, 30 ml of an Owt% aluminum sulfate aqueous solution was added.
Add 1 dropwise over about 5 minutes. Continue stirring at room temperature for 15 to 30 minutes. 20 ml of methanol is added to the obtained capsule particle slurry, and the capsule particles are separated by suction filtration and dried. Capsule particles of a styrene/silica composite capsule membrane containing soybean oil were obtained, with an average particle diameter of 26 μm and a yield of 2.6 g (80%).

Example 6 Zirconia sol (NZS-30A, particle size 95 nm,
solid content concentration 35%) lOm/, alumina sol (colloidal alumina/O0, particle size 420 nm, solid content concentration 1)
5%) Dissolve 1.0 g of isothurin in 6 m (!) to make a mixed solution with colloidal particles. Add the mixed solution to 60 ml of methylene chloride in which 0.1 g of soybean lecithin and 0.5 g of polyoxyethylene sorbitan monopalmitate are dissolved.
Disperse at 9000 rpm using a homogenizer,
30 seconds) Prepare a W/O emulsion. The emulsion was placed in a 300 ml round bottom flask equipped with a stirrer, and without stirring, 30 ml of an Owt% aqueous sodium sulfate solution was added to about 5 ml of aqueous solution of sodium sulfate.
Add dropwise over several minutes at room temperature. Continue stirring at room temperature for 15 to 30 minutes.

Twenty minutes of methanol is added to the obtained capsule particle slurry, and the capsule particles are separated by suction filtration. The cake of capsule particles obtained here is thoroughly washed with water and freeze-dried. Fine particles containing insulin were obtained, the average particle size of which was 15 μm, and the yield was 4.9 g (90%).

Example 7 3 ml of diazinon (insecticide) in which 0.3 g of polyoxyethylene sorbitan triolate was dissolved in colloidal silica (SiO2, Snowtex 0, particle size lO ~ 20 nm, solid content concentration 20%) was dispersed in O/ A W-type emulsion is prepared (-ash dispersion). Furthermore, using a homogenizer, the above primary dispersion was dispersed in 90 ml of chloroform in which 0.3 g of sorbitan triolate and 2.0 g of polyoxyethylene sorbitan monooleate were dissolved.
0 rpm, 30 seconds) Prepare a 0/W/O type emulsion (
secondary dispersion). This was placed in a 500 ml round bottom flask equipped with a stirrer, and while stirring, 50 ml of an Owt% aqueous calcium chloride solution was added dropwise at room temperature over about 5 minutes.

Continue stirring at room temperature for 15 to 30 minutes. 20 mj of methanol is added to the obtained capsule particle slurry and filtered by suction to separate the capsule particles, followed by drying. Capsule particles containing diazinon were obtained, and the average particle size was 18μ.
The yield was 8 g (88°9%).

Example 8 50 mg of dye (red/No. 6) was dissolved in 16 mj' of colloidal silica (SiO□, Snowtex 01 particle size 1O ~ 20 nm, solid content concentration 20%), and 0.2 g of sorbitan triolate and polyoxy Chloroform 48 in which 2.0 g of ethylene sorbitan monooleate was dissolved
Disperse using a homogenizer at 9000 rpm.
, 30 seconds) Prepare a W/O emulsion. Transfer this to a 300-mm round bottom flask equipped with a stirrer, and add 24 ml of a 5.4 wt% ammonium chloride aqueous solution to about 5 mL without stirring.
Add dropwise over several minutes at room temperature. Continue stirring at room temperature for 30 to 60 minutes. 20mj7 of methanol is added to the obtained slurry of capsule particles, and the capsule particles are separated by suction filtration and dried. Particles with a red appearance were obtained.

The average particle size was 12 μm and the yield was 3 g (90%).

Example 9 Styrene latex (particle size 120 nm, solid content concentration 3
Disperse 5 g of an aqueous pigment (H) Micron-K, blue, solid content concentration 20%) in 0%) 20-. The dispersion was dispersed in hexane 45 in which 0.1 g of polyoxyethylene sorbitan monooleate and 0.5 g of sorbitan triolate were dissolved using a homogenizer at 8000 rpm.
Sec) Prepare a W (S)/O type emulsion. This was placed in a 300 rnl round bottom flask equipped with a stirrer, and while stirring, 30 ml of a 0.5 wt % chitosan aqueous solution was added dropwise at room temperature over about 5 minutes. Continue stirring at room temperature for 15 to 30 minutes. 20 ml of methanol is added to the obtained capsule particle slurry, and the capsule particles are separated by suction filtration and dried. Blue styrene capsule particles were obtained with an average particle size of 22 μm and a yield of 6 g (85.7%).

〔Effect of the invention〕

The microcapsules of the present invention can be prepared under mild conditions as described above.
Furthermore, since it can be produced with easy operations and does not use chemically active raw materials, even chemically and/or physically unstable core substances can be encapsulated. Depending on the purpose of use, the capsule membrane can be freely selected from inorganic, organic, and inorganic/organic composites.

Patent applicant: Nippon Kayaku Co., Ltd.

Claims (1)

[Claims] 1. Microcapsules containing a core substance in a capsule membrane obtained by agglomerating colloidal fine particles using an electrolyte. 2. Add a core substance to a dispersion (hydrosol) of colloidal fine particles using water as a dispersion medium, disperse this in an oily medium to form an emulsion, and transfer the colloidal fine particles in the emulsion to an electrolyte. A method for producing microcapsules characterized by aggregation using. 3. The emulsion is made by adding a water-soluble core substance to a dispersion (hydrosol) of colloidal particles using water as a dispersion medium, and dispersing this in an oily medium to form a W/O emulsion. The method according to claim 2. 4. The emulsion is made by dispersing an oil-soluble core substance in a dispersion (hydrosol) of colloidal particles using water as a dispersion medium to obtain an O/W type emulsion, which is further dispersed in an oily medium, /W/
3. The method according to claim 2, wherein the method is an O-type emulsion. 5. The emulsion is made by dispersing a water-insoluble powdery core substance in a dispersion (hydrosol) of colloidal fine particles using water as a dispersion medium,
3. The method according to claim 2, wherein this is dispersed in an oily medium to form a W(S)/O type emulsion.