JPH0732871B2 - Microcapsule manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for producing microcapsules having yeast as a microcapsule film.

(B) Conventional Technology A microcapsule is one in which a liquid, a solid, or a gas is encapsulated as fine particles having a size of 1 μm to several hundreds of μm, and the surroundings are uniformly covered with a thin film. In addition, microcapsules containing colored dyes, pharmaceuticals, agricultural chemicals, fragrances, feed materials, food materials, etc. are industrially commercialized.

By forming a thin film on the outside of a substance with a certain property, the microcapsule can also contain that property at the same time, and if the film is destroyed when necessary, the encapsulated substance can be taken out. .

Conventionally known methods for producing microcapsules include: (1) Coacervation method using gelatin (US Pat. Nos. 2,800,457 and 2,800,458 etc.) (2) Forming a film from the outer phase (aqueous phase) in situ method (Japanese Patent Publication No. 36-9168, No. 47-23165, JP-A-48-57892,
No. 51-9907, No. 54-49984, No. 54-25277, etc.) (3) An interfacial polymerization method utilizing a film-forming reaction between an internal phase and an external phase is known as an effective method.

In addition, US Pat. No. 4,001,480 discloses a method of encapsulating a substance soluble in a lipid in a fungus having a lipid content of 40 to 60%.

Further, in JP-A-58-107189, a method for increasing the lipid content of a growth microorganism is used, in which the lipid content recovered from the medium is 10 wt.
% Or more growing microorganisms (eg, oil-forming yeasts, brewer's yeasts, etc.) selected from organic substances for increasing lipids (eg, aliphatic alcohols, esters, aromatic hydrocarbons, hydrogenated aromatic hydrocarbons) A microbial capsule obtained by encapsulating a liquid to be a heart substance soluble in these lipid-increasing organic substances after the liquid is contained.

(C) Problems to be Solved by the Invention In the encapsulation method described above, microcapsules having a dense film excellent in protective power of the inclusion are obtained, and are widely applied industrially, It is also true that it has a number of problems regarding manufacturing. That is, in the coacervation method (1), there are problems that the pH, temperature and time operations involved in the reaction are complicated, and that the encapsulation process requires a long time.

The in situ method (2) and the interfacial polymerization method (3) are suitable for encapsulation of unstable substances or substances that are easily thermally denatured because a highly reactive coating substrate is reacted at a relatively high temperature. It has drawbacks such as emptiness.

In addition, the microencapsulation method using microorganisms uses a natural product, and part of the organism as a raw material, and the encapsulation mechanism is completely different from the conventional method. However, looking at the examples in these patent specifications, the amount of the hydrophobic liquid that can be encapsulated by the initially added yeast (membrane material) is relatively small compared to the method currently used industrially, Moreover, it has a drawback that encapsulation requires a long time if a large amount is to be ingested.

Further, based on these proposals, the present inventors prepared microcapsules using microorganisms, manufactured pressure-sensitive copying paper, and compared the color developability by writing with a typewriter. Coacervation method and (2) in
Probably because of the higher physical strength of the film part compared to the microcapsules obtained by the in situ method, a relatively low color density despite the same amount of dye smeared on the resulting sheet. However, it was difficult to obtain a large number of copies.

INDUSTRIAL APPLICABILITY The present invention makes it possible to rapidly ingest a large amount of hydrophobic liquid per unit cell amount in a microencapsulation method utilizing microorganisms, and yet, it is a film that is rich in robustness during normal handling or included. It is intended to provide a method for producing microcapsules having a film that can be efficiently destroyed when a substance is desired to be taken out.

(D) Means for Solving the Problem The inventors of the present invention have conducted studies to solve the above-mentioned problems of the encapsulation method using a microorganism, and have found that the following method can solve the problem.

That is, it has become possible to solve the above-mentioned problems by treating yeast in an alkaline aqueous solution in the method for producing microcapsules in which a hydrophobic liquid is encapsulated in yeast.

More specifically, the cell wall of the microcapsules obtained by the present invention is a glucan, mannan, a physically and chemically relatively strong film composed of a chitin layer,
The present inventors have studied various methods of controlling the strength of the cell wall without impairing the protective function of the encapsulating material to be provided as microcapsules, and the yeast is heated and stirred in an alkaline aqueous solution for a predetermined time. After that, by mixing with a hydrophobic liquid to be encapsulated and performing an encapsulation operation, it becomes possible to rapidly encapsulate a large amount of hydrophobic liquid, and by changing the treatment conditions in an alkaline aqueous solution, microcapsules can be obtained. It became possible to freely control the physical strength and sustained release of

The pH of the alkaline aqueous solution used in the present invention is preferably 9.0 to 13.0, and more preferably 10.0 to 12.0. A pH higher than this is not preferable because it has been found that the protective function of the microcapsules is significantly reduced.

The treatment time is 1 hour or longer, preferably 3 hours or longer.

The treatment temperature is empirically determined depending on the pH and ionic strength of the system, but it is 20 ° C or higher and 100 ° C or lower, preferably 30 ° C or higher and 60 ° C or lower.

As the alkaline substance used in the present invention, inorganic salts such as sodium hydroxide, calcium hydroxide, sodium silicate, and potassium hydroxide, organic nitrogen compounds such as ammonia, monoethanoldiamine, ethylenediamine, and diethylenetriamine are used, but are not particularly limited. It is not done.

At the time of treatment, various organic solvents, dispersants, preservatives and the like can be added.

In practice of the present invention, the following steps are basically performed.

Step of preparing yeast dispersion liquid Step of treating yeast with alkaline aqueous solution Preparation of hydrophobic liquid and mixing with yeast dispersion liquid Encapsulation process with heating and stirring Here and step may be performed at the same time It is possible.

In addition, if necessary, it is possible to incorporate washing, dehydration, and drying steps of yeast. The yeast used in the present invention is a general term for microorganisms that grow by budding or division. Specifically, Saccharomyces cerevisiae of the genus Saccharomyces
visiae) Saccharomyces rouxii Saccharomyces curlsbergensis
ces carlsbergensis) Candida utilis of the genus Candida (Candida utilis) Candida tropicallis (Candida lypolytica) Candida flaveri can be used.

There are various shapes of yeast such as oval, spherical, lemon-shaped, columnar, and oval depending on the type of yeast, but spherical,
A shape such as an oval shape or an oval shape is preferable. The particle size is preferably 1 to 20 μm. These yeasts used in the present invention may be in a raw state, a dried state or a dead state.

In these yeasts, intracellular tissues such as enzymes and proteins soluble in water or polar solvents, amino acid components, sugars and nucleic acid components are present, but in the present invention, these intracellular components (yeast It is also possible to use a yeast residue after extracting (also referred to as an extract) by various methods.

These yeasts or yeast residues are dispersed in an aqueous solution using a suitable dispersant.

As used in the present invention, the hydrophobic liquid encapsulated in yeast can be used as long as it is a substantially water-insoluble liquid or a liquid that becomes a liquid by heating, cottonseed oil, soybean oil,
Corn oil, olive oil, castor oil, fish oil, various fatty acids,
Oily liquids extracted from animals and plants such as various steroids, and especially when used for pressure-sensitive copying paper, paraffin oil, chlorinated paraffin, chlorinated diphenyl, dibutyl phthalate, dioctyl phthalate, dibutyl maleate, o-dichloro. Examples thereof include benzene, alkylated naphthalenes such as diisopropylnaphthalene, 1-phenyl-1-xylylethane and the like. If necessary, dyes, fragrances, pharmacologically active substances, food materials, feed materials, etc. are dissolved or dispersed in these hydrophobic liquids, and the resulting microcapsules are used for cosmetics, pharmaceuticals, foods, feeds, in addition to pressure-sensitive copying paper.
Used for agricultural chemicals. The substance can also be used alone as long as it is a hydrophobic liquid that is immiscible with the water-soluble liquid.

The mixing of the hydrophobic liquid and the yeast acid-diluting liquid is usually performed by adding the hydrophobic liquid to the yeast dispersion liquid. In this case, the hydrophobic liquid may be added to the yeast dispersion liquid as it is, but in order to allow the yeast to exist in a more uniform state, it is dispersed in an aqueous solution containing an appropriate emulsifier and emulsified. It is preferable to add after the state.

The temperature in the encapsulation process is not particularly limited,
It is preferably 20 to 70 ° C. The time is required to be 1 hour or more, but can be appropriately changed depending on the amount of the encapsulated hydrophobic liquid and the encapsulation temperature.

If necessary during the encapsulation process, the dissolution promoter, enzyme agent, emulsifier, catalyst, hardener, pH regulator, preservative,
It is also possible to add various deterioration inhibitors and the like.

(E) Examples Hereinafter, the present invention will be described in detail with reference to Examples. In addition,
The invention is not limited to the examples.

The yeast weights shown in Examples and Comparative Examples are all weights in a dry state.

Example 1 [Elution process of intracellular components] 10 g of ethanol was added to 100 g of a dispersion liquid containing commercially available baker's yeast (10 g of live yeast [Saccharomyces cereviche] manufactured by Kanegafuchi Chemical Industry Co., Ltd.), and then in a rotary shaker. At a temperature of 40 ℃
The mixture was shaken for 24 hours under the conditions described above to elute the water-soluble components in the cells outside the cells. After separating the eluate from the yeast residue by centrifugation, the total amount of the eluate was evaporated in a drier at 105 ° C to leave 6.0 g of non-volatile components, which was 40 wt% of the initial weight of yeast. It was possible to confirm that% had eluted.

[Alkali treatment step] After centrifuging the yeast dispersion liquid to remove the filtrate, the residue is redispersed in 100 g of phosphoric acid-hydroxy sodium hydroxide buffer adjusted to pH 10.0 and heated at 50 ° C for 3 hours. Stir processing was performed.

[Encapsulation process] Next, in 20 g of an aqueous solution of 0.5 wt% nonionic surfactant (Tao80, trade name, manufactured by Kao Atlas) as an emulsifier, 3-N-methylcyclohexylamino- was added as a hydrophobic liquid.
High-boiling point hydrophobic liquid containing 1.1 g of 6-methyl-7-anilinofluorane (black coloring dye manufactured by Shin Nisso Chemical Co., Ltd., trade name PSD-150) (manufactured by Nippon Petrochemical, trade name Hysol SAS N-29)
6) Add 22 g with vigorous stirring to obtain an average particle size of 8 μm.
To obtain an emulsified liquid of a hydrophobic liquid. This emulsion was added to the yeast residue dispersion liquid treated with an alkaline aqueous solution, and then shaken in a rotary shaker at a temperature of 50 ° C. and a stirring speed of 200 rpm for 3 hours. As a result, all of the hydrophobic liquid was encapsulated in yeast and microencapsulation was completed. When this microcapsule dispersion was applied as it was to a high quality paper having a basis weight of 40 g / m ² with a bar coat at a smearing amount of about 5 g / m _2, an excellent paper for pressure-sensitive copying paper with good color development was obtained.

Example 2 A 10% aqueous solution of 0.5% Alon T-40 (manufactured by Toagosei Kagaku Kogyo, 40% sodium polyacrylate solution) prepared by adjusting the pH of the commercial baker's yeast 10 g used in Example 1 to 12.0 with sodium hydroxide.
The mixture was added to 100 g, and heated and stirred at 40 ° C. for 6 hours.
After the treatment, remove the filtrate by centrifugation and then
After adjusting the total amount to 100 g with a 0.5% Aron T-40 aqueous solution, the pH was adjusted to 7.0 with acetic acid to prepare a yeast dispersion liquid. Hereinafter, microcapsules were obtained in the same manner as in Example 1. By smearing the obtained microcapsules on a high-quality paper having a basis weight of 40 g / m ² , an upper paper for pressure-sensitive copying paper with good color development was obtained.

Comparative Example 1 In Example 1, when an emulsified liquid of a hydrophobic liquid was added to the yeast residue dispersion liquid without performing the alkali treatment step and encapsulation was performed in the same manner, all the added aqueous semen liquid was included. It took about 6 hours. Further, using this microcapsule, an upper sheet for pressure-sensitive copying paper was obtained in the same manner as in Example 1.

Comparative Example 2 The yeast residue that had undergone the elution treatment step in the alkaline treatment step of Example 1 was centrifuged to have a pH of 6.0 as a post-treatment solution.
Re-dispersed in 100 g of phosphoric acid-sodium hydroxide buffer
The mixture was heated and stirred at 50 ° C. for 3 hours.

When this yeast dispersion liquid was used for encapsulation for about 6 hours in the same manner as in Example 1, a large amount of emulsified particles that could not be completely encapsulated in the yeast cells were found in the obtained yeast dispersion liquid. Existed.

Using this dispersion as it was, an upper paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1.

The coloring property of the upper paper for pressure-sensitive copying paper and the fastness of the microcapsules obtained in the above Examples and Comparative Examples were evaluated and compared by the following methods.

Color development: 15 kg / cm with the upper paper facing the lower paper for commercial pressure-sensitive copying paper (Mitsubishi NCR paper super product N-40 manufactured by Mitsubishi Paper Mills)
Color is passed by passing it once between a pair of rolls to which pressure is applied, and the color density of the color-developed portion after 1 hour is measured by a commercially available color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd. color differential meter ND-101P ) Was used for the measurement. (The smaller the value, the higher the color density.) Robustness: Overlay the upper paper and the same lower paper used in the color development test with the coated surfaces facing each other, and apply a light load of 5 kg / cm ^2. The reflectance of the lower paper surface was measured after leaving it in an atmosphere of 105 ° C for 12 hours. (The larger the evaluation value, the better the fastness of the microcapsule film. In other words, the poorer the fastness of the film, the microcapsules are destroyed during the heat treatment and the encapsulated dye is transferred to the opposite lower sheet. As a result, a low reflectance is obtained.) The numerical value was determined by using the value obtained by the following formula.

Table 1 shows the results of evaluation of each sheet based on the above measuring method.

(F) Effect of the Invention As shown in the present invention, by treating yeast serving as a wall material of microcapsules in an alkaline aqueous solution,
A large amount of the ingested hydrophobic liquid can be encapsulated more quickly than when the above operation is not performed.

Further, when the present invention is applied to microcapsules for pressure-sensitive paper, it is possible to obtain color development and film fastness comparable to those of conventionally known microencapsulation methods. .

As described above, the present invention is a quality and industrially superior means as a microencapsulation method using a microorganism.

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Claims (2)

[Claims] 1. A method for producing a microcapsule comprising a yeast cell in which a hydrophobic liquid is encapsulated, wherein the yeast is treated in an alkaline aqueous solution. 2. The method for producing microcapsules according to claim 1, wherein the pH of the alkaline aqueous solution is in the range of 9.0 to 13.0.