JPS6116500B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing microcapsules having a hydrophobic substance as a core material, and more particularly to a method for producing microcapsules characterized by means of forming a complex coacervate coating covering the hydrophobic substance.

Conventional methods for microencapsulating hydrophobic substances include complex coacervation method, simple coacervation method, salt coacervation method, interfacial polymerization method, in situ polymerization method, submerged drying method, and orifice method. Although many methods are known, such as powder bed method, air suspension method, and electrostatic coalescence method, the most representative method is the complex coacervation method described in US Pat. No. 2,800,457.

This method consists of (1) ionizing a first sol of a hydrophilic colloid in water, and mixing oil into the hydrophilic sol and solution, which have an opposite charge to the first sol;
The process of forming an emulsion, (2) adding water or
A process in which coacervation is caused by pH adjustment and coacervate droplets are attached around the oil droplets,
It consists of (3) the step of cooling the coacervate droplets to a temperature below the gelatin point to gelatinize them, and (4) the step of adjusting the pH to the alkaline side (for example, 7 to 11) and adding a hardening agent. That is, the above-mentioned complex coacervation method uses two colloidal substances with opposite charges, such as a positively charged colloidal substance such as gelatin, casein, albumin, or fibrinogen, and a positively charged colloidal substance such as gum arabic, carboxymethylcellulose, or cellulose phthalate. Complex coacervate, which becomes the capsule wall membrane, is formed by utilizing electrical interaction with negatively charged colloidal substances.

However, since this method of forming complex coacervate uses a hydrophilic substance as a material, it is difficult to make the hydrophilic substance water-insoluble by adding a curing agent as shown in step (4) above. Not only is this treatment necessary, but it is not possible to form a sufficient hydrophobic coating, it also requires a step of cooling and gelling the coacervate droplets.

The present invention provides a method for producing microcapsules using a novel hydrophobic substance as a core material, which eliminates the above-mentioned drawbacks of the complex coacervation method.

That is, the gist of the present invention is to provide a method for producing microcapsules having a hydrophobic substance as a core material by a complex coacervation method, in which the hydrophobic substance is formed into an emulsion of a hydrophobic resin or a hydrophobic rubber, or a wax emulsion. and a complex coacervate produced by the use of an amphoteric surfactant.

According to the present invention, hydrophobic resins, hydrophobic rubbers, and waxes, which could not be used conventionally, can be used as coating materials in the complex coacervation method. No curing process is required for insolubilization.

In the present invention, the core substance of the microcapsule may be a solid substance as long as it is insoluble in water and does not react with water or the constituent substances of the capsule wall membrane.
It can be any liquid. Various organic and inorganic materials can be used as the solid material for the core material.
For example, pharmaceutical products including growth hormones and vitamins, cosmetics, pigments, dyes, color formers, fluorescent bleaches,
Various textile treatment agents, fillers, waxes, fertilizers, plant conditioners, adhesives, fragrances and other gradient-producing substances,
These include photochemicals, water-insoluble metal oxides (eg, magnetic oxides), and water-insoluble salts.

The liquid substance for the core material is emulsifiable, and includes a liquid organic substance alone, a liquid or solid organic substance dissolved in a suitable organic solvent, and the like.
In general, it is preferable that the liquid substance for the core substance has a high boiling point or is difficult to volatilize. However, according to the invention it is also possible to encapsulate liquids with low boiling points. Liquid substances include, in particular, petroleum compartment distillates such as kerosene and naphtha, linear or branched paraffins (including their halides), aromatic hydrocarbons (including their halides), such as benzene, toluene and xylene. Alkylbenzene, fluorobenzene, trichlorobenzene, benzine chloride,
benzine chloride and similar bromine compounds, alkylated di- and polyphenyls, hydrogenated terphenyls such as dodecahydroterphenyl and hexahydroterphenyl, chlorinated diphenyls, vegetable oils such as corn oil, These include soybean oil, olive oil, coconut oil, balm oil, castor oil, peanut oil, rapeseed oil, sunflower oil, hempseed oil, linseed oil, cottonseed oil, fish oil, animal oils such as whale oil, mineral oil, and silicone oil.

The above-mentioned core substance is in the form of particles of about 3 to 100 μm depending on the solid or liquid state, or in the form of particles of about 3 to 100 μm.
Microcapsules are formed by forming droplets with a particle size of about 100μ. The above-mentioned solid particles and droplets can be obtained by adding a predetermined amount of a core substance to a solution containing an amphoteric surfactant and thoroughly mixing and stirring the mixture. At this time, it is necessary to adjust the pH of the system to 4-7.

The amphoteric surfactant is preferably of the betaine type, imidazoline type, β-alanine type, or α-imino type. Such amphoteric surfactants are commercially available products such as Amibol D (manufactured by NICCA Chemical Co., Ltd.), Amogen K, Amogen 8 (manufactured by Daiichi Kogyo Seiyaku KK), Amorfuen (manufactured by Tokai Oil Industries KK), and Alfamine P (manufactured by Miyoshi Chemical Co., Ltd.). KK), Anphotite AK,
Amphotite DF (manufactured by Marubishi Yushi Chemical Co., Ltd.), Amphorin B (manufactured by Aoki Yushi Kogyo KK), Amphorex (manufactured by Miyoshi Yushi Kogyo KK), Itzbol
133T (Ichimansha Yushi Kogyo KK), (MY Soft BAT
(manufactured by Yoshimura Yushi Kagaku KK), Eleganol C (manufactured by Meisei Chemical Industry KK), Eleton L100, Ereton L1000
(manufactured by Tokai Yushi Kogyo KK), Ogamin C (manufactured by Kenseido Kagaku Kogyo KK), Obanol (manufactured by Toho Kagaku Kogyo KK)
(Manufactured by Aoki Yushi Kogyo Co., Ltd.)
Manufactured by KK) Safanol NW (Sanyo Oil Industry KK)
), Syurincar H (manufactured by Yoshimura Yushi Kagaku KK), Seroner No. 8 (manufactured by Takemoto Yushi Kagaku KK), Softamine KS
(manufactured by Chukyo Yushi KK), Softner TS (manufactured by Marubishi Yushi Chemical Co., Ltd.), Sofbon AK (manufactured by Takemoto Yushi KK), Dacrotux LEN (manufactured by Tokai Yushi Kogyo KK), Dabrol (manufactured by Yoshimura Yushi Kagaku KK), Tsuhaar (manufactured by Nakamura Chemical Co., Ltd.) industry
(manufactured by KK), Twitterter 40 (manufactured by Ichisha Yushi Kogyo KK)
), Disper (manufactured by Meisei Kagaku Kogyo KK), and Trimin (manufactured by Kyoeisha Yushi Kagaku Kogyo).

Next, after dispersing the core material in a solution containing an amphoteric surfactant, a hydrophobic resin or hydrophobic rubber emulsion or wax emulsion is added and mixed, and the pH of the system is adjusted to 9 to 9 with caustic soda or the like.
Keep it at 10.

Examples of the hydrophobic resin emulsion include emulsions of ethylene, styrene, acrylic, and vinyl acetate resins.
As the hydrophobic rubber emulsion, either natural rubber or synthetic rubber emulsion can be used. A good wax emulsion is a microcrystalline wax emulsion. In short, any emulsion can be used within the above range as long as it is based on a hydrophobic substance and emulsified with an anionic surfactant. Commercially available emulsions include, for example, natural rubber emulsions.
SP-17, SP-818, SP-82, SP-91 (Nanyo Kasei
Made by KK, a polymer made of natural rubber grafted with acrylic), VSR as a styrenic emulsion
0561, JSR 2108, JSR 0650, JSR 0651, JSR
0602 (manufactured by Japan Synthetic Rubber Co., Ltd., styrene-butadiene copolymer), 722Plastc Pigment XD8557-01,
XD-8557-02 (manufactured by Dow Chemical Company), C-72, B-85, E-581 as acrylic emulsion,
HA-16, AC-22 (manufactured by Nippon Acrylic Co., Ltd., acrylic acid ester emulsion), E-3923A, 103A (manufactured by Toho Chemical Co., Ltd.) as a polyethylene emulsion, Nopco 1245M (manufactured by San Nopco Co., Ltd.) as a microcrystalline wax, Cellosol 966
(manufactured by China Communist Party Oil & Fats KK).

A system is formed in which a core material is dispersed in a dispersion of a hydrophobic resin or hydrophobic rubber emulsion or wax emulsion and an amphoteric surfactant, and then acetic acid, hydrochloric acid, etc. are added to bring the pH of the system to 4. When the temperature is lowered to about 7, complex coacervation occurs between the emulsion of the hydrophobic substance stabilized by the anionic surfactant and the amphoteric surfactant, and this coacervate is formed with the core substance as the nucleus. and finally surround it and settle down. As a result, a coacervate film is formed around the core material, which becomes the prototype of the microcapsule.

That is, in the present invention, the conventional complex coacervation method can be employed as is, except for the cooling process for gelling the coacervate and the curing process for making the coacervate insoluble in water.

Example 1 (Encapsulation of castor oil) 1 g of the alkyl betaine type surfactant MY Soft (manufactured by Yoshimura Yukagaku Kogyo KK) was dissolved as a solid content in the ion-exchanged water from 1, and then 30 g of castor oil was added and emulsified with a homomixer. Disperse and adjust the particle size to 30-50μ, then add caustic soda to adjust the pH of this system.
was set at 8.5 to 9.5. To this dispersion, 10 g of styrene-butadiene emulsion (0602 Latex Emulsion, manufactured by Japan Synthetic Rubber Co., Ltd.) was added as a solid content.
The pH was adjusted to 8.5-9.5 with 1N caustic soda.

Next, a 1% acetic acid aqueous solution was added dropwise to lower the pH to 5 to 5.5, and complex coacervate droplets of styrene emulsion and alkyl betaine were attached around the castor oil droplets to obtain a castor oil core-containing capsule slurry. . The capsules were spray-dried using a spray dryer to obtain castor oil-containing capsule powder. The spray dryer conditions are: inlet temperature 150°C, outlet temperature 80-90°C, and atomizer pressure 3.8-4.5.

Example 2 (Encapsulation of ferrite) The alkyl betaine type surfactant Seroner TS (manufactured by Takemoto Yushi Co., Ltd.) was added as a solid content to the ion-exchanged water of 1.
1 g was dissolved, and then 30 g of ferrite (triferric tetroxide manufactured by Toda Kogyo Co., Ltd.) was added and dispersed with a homomixer, and 1N caustic soda was added so that the pH of the system was 8.5 to 9.5. Add polyethylene wax emulsion 3924A (manufactured by Toho Chemical Co., Ltd.) to this dispersion.
Add 10g of solid content and dissolve with 1N caustic soda.
Adjusted the pH to 8.5-9.5.

Next, add 1% acetic acid solution dropwise to adjust the pH to 5.5-6.5.
The complex coacervate droplets of polyethylene and alkyl betaine formed a capsule wall around the ferrite.

This slurry having capsule walls was spray-dried under the same conditions as in Example 1 to obtain ferrite-containing capsule powder.

Example 3 (Encapsulation of wet toner) 30g of concentrated toner for Ricoh DT-1200 was mixed with alanine-type amphoteric surfactant Ribomin SA (Lion Oil).
(manufactured by KK) was dissolved in an aqueous solution 1 containing 1 g of solid content, and then emulsified and dispersed using a homomixer, and the size of the droplets was adjusted to 10 to
Polystyrene latex after adjusting to 20μ
Add 5g of Plastic Pigment 722 (manufactured by Dow Chemical Company) as a solid content, and add 1N caustic soda to pH 8.5 to 9.5.
Adjusted to.

Next, add 1% acetic acid solution dropwise to adjust the pH to 4.5-5.5.
A capsule film was formed in which coacervate droplets of Ribomin SA and polystyrene latex were precipitated around the concentrated toner droplets. This slurry having a capsule coating was spray-dried under the same conditions as in Example 1 to obtain a liquid toner core-containing capsule powder.

Claims (1)

[Claims] 1. In a method for producing microcapsules having a hydrophobic substance as a core material by a complex coacervation method, the hydrophobic substance is mixed with a hydrophobic resin or hydrophobic rubber emulsion or wax emulsion and an amphoteric surfactant. A method for producing microcapsules having a hydrophobic substance as a core material, characterized in that the microcapsules are coated with a complex coacervate produced by use of a hydrophobic substance.