JPH0515772A - Manufacturing method of microcapsules - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing microcapsules in which inorganic fine particles as a core substance can be effectively promoted by a coating substance used for encapsulation. [Structure] Inorganic fine particles are added to an organic solvent solution of a copolymer obtained by copolymerization of (meth) acrylic acid and another vinyl monomer copolymerizable with the (meth) acrylic acid. This produces an emulsified dispersion. The (meth) acrylic acid of the copolymer in this dispersion is neutralized, the obtained neutralized product of the copolymer is crosslinked to use the inorganic substance as the core substance, and the crosslinked product of the neutralized copolymer is the coating substance. To obtain microcapsules.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing microcapsules containing inorganic pigments such as titanium oxide and various inorganic fine particles such as silica, alumina and glass frit as core materials.

[0002]

2. Description of the Related Art A microcapsule is a container (capsule) in which microscopic units are enclosed, and various substances are contained therein. By destroying the capsule, the internal core substance is released or the encapsulated core substance is encapsulated. It has a lot of usefulness because it can be used in a wide variety of ways, such as slowly releasing it.

Generally, methods for producing microcapsules using an inorganic substance as a core substance and a polymer substance as a coating substance include a physicochemical method such as a coacervation method and an air drying method or a liquid drying method. Physical methods are known. The coacervation method, which is known as a physicochemical method, is a combination of an organic solvent that is easily soluble in the polymer that constitutes the coating material, and an organic solvent that is insoluble in the polymer, and forms microcapsules by phase separation. To do.

The air drying method in the physical method includes
There are rolling fluid coating method and spray drying method. On the other hand, the rolling fluid coating method uses a methylene chloride solution prepared by dissolving a polymer substance such as an epoxy resin or a methyl methacrylate resin while suspending a powder serving as a core substance, for example, fine particles such as glass, in the air. It is a method of spraying fine particles to prepare microcapsules. The other spray-drying method is to disperse a powder as a core substance in a methylene chloride solution in which a coating substance made of a polymer substance is dissolved, and spray the dispersion liquid into the air to instantaneously volatilize the solvent. It is a method of coating powder.

[0005]

There are merits and demerits to each of the above-mentioned methods for producing microcapsules. On the other hand, in the coacervation method, the most common means is to use harmless gelatin having excellent film-forming ability as a coating material or gelatin-gum arabic to generate coacervate droplets. In order to cause the separation to generate the microcapsules, it is necessary to strictly set the conditions such as the concentration of the coating substance and the temperature. On the other hand, methods such as air drying as a physical method require a device for spraying the liquid.

In general, these known methods focus on the production of microcapsules, and give little consideration to the utilization of the obtained microcapsules.
Therefore, when only the core substance is used, the fact is that no consideration is given to the fact that the coating substance contributes to the utilization of the core substance to promote the utilization of the core substance.

In view of such a current situation, the inventors of the present invention have considered the use of microcapsules containing inorganic fine particles as a core substance.
As a result of earnest research tests for the purpose of producing new microcapsules, the inorganic fine particles as the core substance can be more effectively promoted by the coating substance used for the encapsulation, which has led to the completion of the present invention. .

[0008]

In order to achieve the above object, the method for producing microcapsules of the present invention is (meth) acrylic acid and other vinyl-based monomers copolymerizable with the (meth) acrylic acid. To the organic solvent solution of the copolymer obtained by the copolymerization with, the inorganic fine particles as the core substance are added to form an emulsified dispersion liquid, and the (meth) copolymer of the copolymer in the dispersion liquid is generated.
It is possible to obtain a microcapsule in which the acrylic acid content is neutralized and the obtained copolymer neutralized product is crosslinked to use the inorganic fine particles as a core substance and the crosslinked product of the copolymer neutralized product as a coating substance. It is a feature.

In the present invention, examples of the inorganic fine particles as the core substance include inorganic pigments such as titanium oxide, silica, alumina and glass frit.

The copolymer obtained by the copolymerization of (meth) acrylic acid dissolved in an organic solvent and another vinyl monomer copolymerizable with the (meth) acrylic acid is (meth) acrylic acid. And an alkyl ester of (meth) acrylic acid, for example, methyl, ethyl, butyl of (meth) acrylic acid,
Preference is given to using copolymers by copolymerization with esters such as 2-ethylhexyl. The mixing ratio of (meth) acrylic acid and the other copolymerizable Birni-based monomer is not particularly limited, but (meth) acrylic acid, which is a monomer having a functional group, is generally in a small amount (5% by weight). The following) is good.

Toluene, xylene, etc. can be used as the organic solvent for dissolving such a copolymer. To the organic solvent solution of this copolymer, the inorganic fine particles as the core substance are added to form an emulsified dispersion, but before the addition of the core substance, or after the addition of the surface active agent in the organic solvent solution. It is preferable to add an agent, whereby an emulsified dispersion liquid in which the core substance is uniformly dispersed can be obtained.

[0012]

The method for producing microcapsules of the present invention uses inorganic fine particles as the core substance.
Acrylic acid was added to an organic solvent solution of a copolymer obtained by copolymerization of the vinyl-based monomer copolymerizable with the (meth) acrylic acid, and the copolymer in the emulsified dispersion was formed. To neutralize the (meth) acrylic acid content of the polymer and crosslink the obtained neutralized product of the copolymer to form microcapsules,
The obtained microcapsules are those in which the surface of the core substance is surrounded and bound by a coating substance composed of a crosslinked product of the copolymer neutralized product. Therefore, the coating material finally composed of the crosslinked product of the neutralized copolymer which is surrounded and bound to the core material,
Since the inorganic fine particles are bonded to each other by heat fusion to form a kind of binder, for example, when the core substance of this microcapsule is bound to the surface of another substance by heating, the coating substance is melted by heating, It is possible to effectively promote the binding of the inorganic fine particles to each other and the binding to other substances. In addition, when the inorganic fine particles that are substantially the core substance are melted and used by heating at a higher temperature, the coating substance melted by the high temperature heating is evenly melted into the molten inorganic fine particles to give a gloss or gloss. It is possible to form a layer of fine inorganic particles.

[0013]

EXAMPLES Hereinafter, examples of production of microcapsules containing inorganic fine particles as a core substance by the method for producing microcapsules of the present invention will be described in detail with reference to examples.

Example 1 Toluene was added 2% by weight of Aron S-1045 (trade name of acrylic copolymer manufactured by Toagosei Kagaku Kogyo Co., Ltd.) to prepare a mixed solution having a total amount of 200 g. As an activator, 35 g of Emulgen 109P (trade name of a surfactant of Kao Corporation; the same applies hereinafter) was added and completely dissolved to obtain an organic solvent solution of a copolymer. To this organic solvent solution, 100 g of glass frit was added and uniformly dispersed by stirring to prepare an emulsified dispersion liquid. 4% caustic soda solution was added to this dispersion to add Aron S
The acrylic acid content in -1045 was completely neutralized. At that time, since the heat of neutralization occurs, the liquid temperature is kept at 20 ° C., and 100 g of a 1% calcium chloride aqueous solution prepared in advance is added all at once to the dispersion liquid to crosslink the neutralized product of the copolymer. Then, microcapsules containing glass frit as a core substance were formed. The microcapsules produced by filtering the dispersion are separated and washed with warm water at a temperature of 40 ° C.
Aron S on the surface of the glass frit by air drying
Dried microcapsules having a film formed of a crosslinked product of the neutralized product of -1045 were obtained.

Example 2 Toluene was added 2% by weight of a copolymer of methacrylic acid to form a mixed solution having a total amount of 200 g. To this mixed solution, 35 g of Emulgen 109P was added as a surfactant, which was completely added. An organic solvent solution of the copolymer was obtained by dissolving.
To this organic solvent solution, 100 g of silica powder was added and uniformly dispersed by stirring to prepare an emulsified dispersion liquid. A 10% aqueous solution of caustic soda was added to this dispersion to completely neutralize the acrylic acid content in the acrylic acid copolymer, and 100 g of a 1% calcium chloride aqueous solution was added all at once to the dispersion to obtain a copolymer in the dispersion. The neutralized product was crosslinked to form microcapsules containing silica as a core substance. The dispersion is filtered to separate the generated microcapsules,
The microcapsules were washed with warm water at a temperature of 37 ° C. and air-dried to obtain dry microcapsules on the surface of which silica powder was formed a coating film of a crosslinked product of a neutralized methacrylic acid copolymer.

[0016]

The method for producing the microcapsules of the present invention comprises:
Inorganic fine particles are added to an organic solvent solution of a copolymer (meth) obtained by copolymerization of (meth) acrylic acid and another vinyl monomer copolymerizable with (meth) acrylic acid. An emulsified dispersion is generated, the (meth) acrylic acid content of the copolymer in this dispersion is neutralized, and the neutralized product of this copolymer is crosslinked to use the inorganic fine particles as the core substance, It is possible to easily and inexpensively manufacture microcapsules having a crosslinked product of a neutralized product of the coalescence as a coating material.

In the microcapsules obtained by the method of the present invention, a reliable coating film is formed on the surface of the inorganic fine particles which are the core substance, and the formed coating substance binds to the core substances when the microcapsules are used. Alternatively, it can effectively contribute to the binding of the core substance to other substances, or the addition of gloss to the layer of the inorganic fine particles by heating and melting.

Claims (2)

[Claims] 1. A core substance in an organic solvent solution of a copolymer obtained by copolymerization of (meth) acrylic acid and another vinyl monomer copolymerizable with the (meth) acrylic acid. By adding inorganic fine particles to form an emulsified dispersion liquid, neutralizing the (meth) acrylic acid content of the copolymer in the dispersion liquid, and cross-linking the obtained copolymer neutralized product. A process for producing a microcapsule, which comprises using inorganic fine particles as a core substance and a cross-linked product of the copolymer neutralized product as a coating substance. 2. The method for producing microcapsules according to claim 1, wherein the dispersion is produced by adding a surfactant to an organic solvent solution containing a core substance.