JPS5825496B2 - Microcapsule Seihou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for the preparation of microcapsules, which is based on a concept significantly different from the known microencapsulation methods by phase separation from aqueous systems.

A microencapsulation method is known in which a water-soluble polymer is used as a capsule wall material, and a concentrated phase of the polymer is phase-separated around a core particle by some means to form a capsule wall. ing.

These can be classified into the following four types.

One of them is the so-called complex coacervation method, which utilizes the fact that when the pH of a mixed system of two types of aqueous solutions, polycation colloid and polyanionic colloid, is adjusted, electrical interaction occurs and phase separation occurs.
Coacervation): Another is that when a non-solvent that is not an electrolyte for the polymer that is miscible with water is added to an aqueous solution of a water-soluble polymer, for example,
When ethanol is added to an aqueous gelatin solution, the so-called simple core cell vanecon method utilizes the phenomenon that the concentrated polymer phase initially separates into droplets.
Another method is to change the pH of the aqueous solution system by taking advantage of the fact that some polymers in an aqueous solution decrease their solubility and precipitate on either the alkaline side or the acidic side depending on their structure. A method of precipitating and insolubilizing the polymer in the system, that is, p
Polymer insolubilization coacervation method using H; and another method utilizes the salting-out-like effect that occurs when electrolyte salts are added to an aqueous solution of a water-soluble polymer, such as when an aqueous gelatin solution undergoes phase separation with sodium sulfate. This is the so-called salt coacervation method that causes coacervation.

The above-mentioned complex core-cell vane-con method has the drawback that the microcapsules cannot be separated from the system unless the formed capsule wall membrane is made water-insoluble, for example, by formalin, and also requires complicated and difficult-to-control pH adjustment operations. There are disadvantages and the operation takes a long time.

Another drawback is that it can only be operated with dilute solutions, resulting in poor productivity.

In addition, the above-mentioned simple coacervation method has the limitation that the core substance must be insoluble in both water and a non-solvent (non-electrolyte), and furthermore, it is difficult to control the particle size of the capsule. There is a flaw that there is.

Furthermore, the above-mentioned pH-based polymer insolubilization core cell venion method has the disadvantage that the structures of usable polymers are limited, and in addition, the encapsulation rate is too fast and the pH adjustment operation must be performed very carefully and gradually. (There is a cumbersome and disadvantageous operational flaw in that it cannot be used.

In addition, in the above-mentioned salt coacervation method, since a considerable amount of electrolyte salts are present in the system, there is a disadvantage that desalination from the formed wall film is required after encapsulation. Another drawback is that it is difficult to control the particle size of the capsules, and the capsules often aggregate to form agglomerates.

The present inventor has overcome the disadvantages and deficiencies of the conventional methods as described above in an operationally advantageous manner, and has achieved a method that allows for easy operation, easy particle size adjustment, no fear of agglomerate formation, and a method that can be used on the rear wall of coacervation. We are conducting research to develop a method that can provide excellent microcapsules with good quality reproducibility at low cost, without the need for membrane curing means or membrane desalination on the back wall of the core cell vane, and with shortened operation time. I proceeded.

As a result, (b) a hydrophilic sol that has the action of forming a metal bond with alkaline earth metal ions and trivalent metal ions to form a gel and has a wall film forming ability; and (a) alkaline earth metal ions. The aqueous solution system containing the above-mentioned components (b) and (d), which contain a product-generating water-soluble compound and which originally undergoes a chemical bonding reaction in an aqueous medium to form an aqueous medium-insoluble metal salt, is further added with (a) A hydrophilic sol that does not form metal bonds with valence metal ions, has the effect of suppressing the formation of metal bonds between other hydrophilic sol and alkaline earth metal ions, and has wall film forming ability, and (e) alkali. Earth metal ions are hydrophilic metals that do not form metal bonds or do not gel even if they do, and have the ability to gel by forming metal bonds with trivalent metal ions and have the ability to form a wall film. The aqueous medium system in which the sol is dissolved forms an extremely stable system, and a stable oil-in-water type (in the present invention refers to the hydrophobic core substance type in water) emulsion in which hydrophobic core substance particles are dispersed. It has been discovered that by adding a trivalent metal ion-generating water-soluble compound (e) to the microcapsules, the above-mentioned improvements can be achieved and excellent microcapsules can be produced.

Therefore, an object of the present invention is to provide a method for manufacturing microcapsules that can achieve the above-mentioned improvements by a method different from conventional sweeping methods.

Many other objects and advantages of the present invention will become more apparent from the following description.

According to the method of the present invention, in addition to the hydrophilic sol (b) and the water-soluble compound (d), the hydrophilic sol (a) and (c)
Not only can a stable emulsion be obtained by forming an oil-in-water emulsion in which hydrophobic core material particles are dispersed in a system in which In addition, the rapid formation of metal salts insoluble in aqueous media is moderately controlled, and the combination of the hydrophilic sol (b) and the alkaline earth metal ion-generating water-soluble compound (a), and the combination of the hydrophilic sol (c) and the trivalent sol In combination with the metal ion-forming water-soluble compound (e), the inevitable formation of large gelled insoluble metal salts is inhibited.

Although the theoretical details of this inhibition mechanism are not yet clear, it is presumed that the above-mentioned two types of insoluble metal salt forming reactions interact with each other in some way.

As a result of such moderately controlled coacervation, the disadvantages and all the deficiencies of the various types of microencapsulation methods described above can be advantageously overcome with easy operation, and excellent quality microcapsules can be obtained. It has good reproducibility and can be provided at low cost.

Furthermore, with conventionally known devices and operations such as the orifice method, fine microcapsules such as those obtained by the method of the present invention cannot be provided.

Furthermore, if you simply want to adjust phase separation, it should be possible to use stabilizers such as various phosphates and organic acid salts that have been tried in conventional phase separation methods, but these stabilization The agent does not exhibit a usable stabilizing effect in the process of the present invention, and its use would lead to disadvantageous prolongation of operating time and requirement for additional processing to remove the stabilizer.
It often only comes with disadvantages.

In the method of the present invention, a sol that does not form metal bonds with polyvalent metal ions dissolved in an aqueous medium, has the effect of suppressing the formation of metal bonds between other hydrophilic sol and alkaline earth metal ions, and has a wall Hydrophilic sol (a) having film-forming ability includes: gelatin; gelatin derivatives, such as gelatin adducts with dicarboxylic acids such as succinic acid and maleic acid; gum arabic; methyl cellulose; polyvinyl alcohol; starch; starch without carboxyl groups. Derivatives include, for example, alkyl or arylalkyl derivatives of starch such as isopropyl, ethyl, benzyl, etc.; dextrin; hydroxyethyl cellulose; albumin.

These can be used singly or in combination.

Further, as the hydrophilic sol (b) which has the action of forming a metal bond with an alkaline earth metal ion and a trivalent metal ion to form a gel, and has a wall film forming ability, sodium alginate;
Potassium alginate; polyacrylic acid; sodium polyacrylate
Salts or salts; polyacrylamide partial hydrolyzate salts, such as Na salts; low pectic acid metkynated products;
Dextran and its sulfate; milk casein:
Examples include polyethyleneimine.

These can also be used alone or in combination.

Furthermore, a hydrophilic sol (c) which does not form an alkaline earth metal bond or does not gel even if it does form, has an effect of forming a metal bond with trivalent metal ions, and has a wall film forming ability. Specific examples include carboxymethyl cellulose Na salt or salt; carboxyethyl cellulose; carboxymethyl hydroxyethyl cellulose; carboxymethyl starch; hydrophilic starch derivatives having a carboxyl group such as carboxyethyl starch, and polyvinyl alkyl ether-non-maleic acid copolymers. Examples include salts of ammonium and Na1.

In the method of the present invention, examples of the alkaline earth metal ion-forming water-soluble compound (d) that is dissolved in the aqueous medium together with the hydrophilic sols (a), (b), and (c) include Mg++ , CA++, Sr±+, Ba++, and other water-soluble compounds that can generate divalent metal ions.

The degree of water solubility can be selected as appropriate, and it should be water soluble to the extent that divalent metal ions can be formed in an amount that gives a gelling effect to the hydrophilic sol (b) in cooperation with trivalent metal ions. available.

For example, about 0.1g for 100g of water (0°C)
It is possible to use water-soluble products with a certain degree of water solubility or higher.

Specific examples of these water-soluble compounds (d) include Ca-1+ calcium hydroxide, calcium halide (e.g. calcium chloride), calcium nitrate, calcium citrate, calcium acetate, calcium lactate, calcium adipate, Mg++ magnesium halide. (e.g. magnesium chloride), magnesium nitrate, magnesium citrate,
Magnesium acetate, magnesium lactate, magnesium cyclamate, magnesium adipate, Ba±10 Barium hydroxide, barium halide, (e.g. barium chloride), barium nitrate, barium acetate, Sr+10 Strontium hydroxide, strontium halide (e.g. strontium chloride) ), strontium nitrate, etc.

In the method of the present invention, the hydrophilic sol (
Forming an oil-in-water emulsion in which hydrophobic core material particles are dispersed in an aqueous medium in which a), (b), and (c) and the divalent metal ion-producing water-soluble compound (d) as described above are dissolved. .

The formation of the emulsion described above can be carried out in various addition orders.

For example, the hydrophilic sols (b) and (c) and the alkaline earth metal ion-producing water-soluble compound (d) can be added in any order and combination to a system in which the hydrophilic sol (a) is present. .

Preferably, the hydrophilic sols (a), (b) and (c) are dissolved in an aqueous medium in any order or together, and after the addition of the hydrophobic core material to this system or together with the hydrophobic core material, the alkali An earth metal ion-generating water-soluble compound (d) is added.

These additions are preferably carried out under stirring conditions.

The amount of water is usually determined by the hydrophilic sols (a), (b) and (c).
from about 5 to about 25 times the total weight, preferably about 1
It is about 0 to about 20 times the amount.

In addition, the proportions of the hydrophilic sols (a), (b) and (c) can be appropriately changed depending on the type of these sols used, their combination, the desired concentration of these sols in the oil-in-water emulsion, etc. The hydrophilic sol (b) is used in an amount of about 5 to about 20 parts by weight, and the hydrophilic sol (c) is used in an amount of about 5 to about 20 parts by weight, relative to 100 parts by weight of the hydrophilic sol (a).

Also, an alkaline earth metal ion-generating water-soluble compound (d)
The amount used can be appropriately changed depending mainly on the amount of hydrophilic alcohol (b) used.

Usually, 1 mol of hydrophilic sol (b) as metal ions,
The amount is about 4 mol ions, preferably about 1 to 1 mol ions.

The amount of the hydrophobic core substance to be used can be appropriately selected depending on the type thereof, the use of the formed microcapsules, the purpose of microencapsulation, etc.

Usually about 80 to about 500%, preferably about 100 to 4%, based on the total weight of hydrophilic sols (a), (b) and (c).
It is about 00%.

The formation of the above oil-in-water emulsion consists of a hydrophilic sol (a)
The reaction can be carried out at any temperature that does not cause thermal gelation, and is usually carried out at room temperature, although a suitable superheating temperature may be employed if desired.

Also, if the core substance is a very volatile substance, cooling conditions can also be employed.

As the hydrophobic core substance, any substance that is immiscible with water and forms a liquid phase under oil-in-water emulsion forming conditions can be used;
Examples include various medicinal substances, fragrances, food additives, dyes, agricultural chemicals, and the like.

In the method of the present invention, a trivalent metal ion-producing water-soluble compound (e) is added to the oil-in-water emulsion formed as described above.

The addition is usually carried out under stirring conditions.

The addition is preferably done in portions or continuously and gradually, but if desired, it can be added all at once under sufficient stirring conditions.

The above compound (e) can be added in the form of a finely divided solid, or can be added as an aqueous solution.

The amount of the trivalent metal ion-generating water-soluble compound (e) added is:
It can be changed appropriately depending mainly on the amount of the hydrophilic sol (c) used, and usually about 1 h mol ion per 1 mole of the hydrophilic sol (e) as metal ions, preferably about 1 to 1 h It is on the order of moles and ions.

The above trivalent metal ions include Fe 10sho, A I ++
Specific examples of these include aluminum chloride, aluminum nitrate, aluminum sulfate,
Examples include sodium alum AINa(5O4)2, potassium alum AIK(SO2)2, aluminum alum, ferric chloride, and the like.

The microcapsules formed can be easily separated by any liquid-solid phase separation means and do not require special means, although spray drying means can be utilized if desired.

The advantages of the present invention are as follows.

1. This can be achieved by forming a stable system in a solution system that would normally cause a chemical bonding reaction in an aqueous medium to form an insoluble metal salt in the aqueous medium, and then disrupting this system while controlling it appropriately. However, a small amount of the phase separation inducing agent used in this system is enough to achieve the purpose.

2. All of the hydrophilic sol and polyvalent metal ion-producing water-soluble compounds used in the stable solution system can be selected from the range of food additives, so there is no need to completely remove them.

3. The wall film can be formed by using multiple types of hydrophilic nols and polyvalent metal ions that have the effect of forming metal bonds, and hydrophilic sols that have the ability to form wall films, and by varying the proportions of their usage. The release function of the core substance can be freely adjusted without making it water-insoluble through formalin denaturation.

4. Since the microencapsulating agent such as a wall agent and a polyvalent metal ion can be selected from food additives, it can be used for a wide range of applications.

5. In the conventional microencapsulation method based on phase separation from an aqueous solution, it is necessary to make the material insoluble in water by denaturing the wall membrane, etc., but in the method of the present invention, it is taken out in a surface-dried state without any denaturation treatment. In addition, there is no trouble with the core substance caused by the modifier, and there are no restrictions on use, and a complicated process for removing the modifier is unnecessary.

6. By appropriately designing the type and amount of hydrophilic sol that has the effect of forming metal bonds with polyvalent metal ions, it can be manufactured to any size with good reproducibility.

7. Strict adjustment of pH control, temperature, concentration conditions, etc. is not required at all, and it is possible to operate from a concentrated solution, which makes the operation itself easy and does not require a long time, making it possible to produce a wide variety of products on an industrial scale. Production is possible.

8. Since it can be dried without drying up by heating such as spray drying, it is possible to microcapsule volatile components and substances that are easily denatured by heat as core substances in their raw state. .

Examples will be shown below to more specifically explain the method according to the present invention.

Example 1 10 g of gelatin as hydrophilic sol (a) (gelatin used here does not need to be limited in raw material manufacturing method or quality such as jelly strength, freezing point, viscosity isoelectric point, etc., and gelatin from acid treatment to alkali treatment can be used) In addition, it can be used in a wide range from low jelly strength of 100 blooms or less to high jelly strength of 300 blooms or more) and gum arabic3. 200ml of water-soluble polymer sol containing OI
70 g of fragrance lemon oil is emulsified and dispersed therein as a hydrophobic core substance.

On the other hand, a mixed polymer sol containing 1.5 g of carboxymethyl cellulose and sodium as the hydrophilic sol (c) and 0.5 g of sodium alginate as the hydrophilic sol (b) was prepared, and this was added to the perfume emulsion dispersion. Disperse into minutes.

Next, under stirring, calcium chloride II as an alkaline earth metal ion-forming water-soluble compound was dissolved in a small amount of water.
Mix and disperse in the emulsion.

At this point, no formation of calcium alginate jelly was observed.

Next, 3 g of aluminum sulfate (16-18 hydrate) as a trivalent metal ion-producing water-soluble compound was added to a small amount of water (50
When the monthly amount of the gel is added to the emulsified mixture under stirring, phase separation occurs, and the whole becomes a finely dispersed suspension of gel.

Further stirring is continued for about 30 minutes and left at room temperature to obtain individually compact flavored lemon microcapsules (mainly occupied by roughly spherical ones in the range of about 20-250μ).

This product can be used as it is in a suspended state, and can be used by drying it properly after suctioning the tears with lachrymal paper or the like.

Example 2 200ml of 10% gelatin aqueous solution as hydrophilic sol (a)
1. 10% sodium polyacrylate aqueous solution 30T/ll as hydrophilic sol (b), 20% as hydrophilic sol (a)
Mix 50rrLl of gum arabic.

Next, 701rL of lavender oil was used as a hydrophobic core substance.
1 and emulsify and disperse.

Further, 20 ml of a 5% sodium alginate aqueous solution as a hydrophilic sol (b) and 50 ml of a 3% sodium carboxymethyl cellulose aqueous solution as a hydrophilic sol (c) are added and dispersed.

To this emulsion, 10TrLl of a 10% aqueous calcium chloride solution as an alkaline earth metal ion-generating water-soluble compound is added under stirring and mixed and dispersed.

Subsequently, as a trivalent metal ion-generating water-soluble compound, 5
% aluminum sulfate (16-18 hydrate) aqueous solution 50ml
By gradually dropping the solution, gelation is effected, and finally approximately spherical fine particles having a size of about 30 to 300 microns are suspended.

This material can be used for various purposes by dehydrating and redispersing, drying, or as it is by any method.

Claims (1)

[Scope of Claims] 1 a. Does not form metal bonds with polyvalent metal ions, has the effect of suppressing the formation of metal bonds between other hydrophilic sol and alkaline earth metal ions, and has wall film forming ability. What is an alkaline earth metal ion?B A hydrophilic sol that has the action of forming a metal bond with an alkaline earth metal ion and a trivalent metal ion to form a gel and has a wall film forming ability.C What is an alkaline earth metal ion? A hydrophilic sol that does not form metal bonds or does not gel even if it does, has the ability to gel by forming metal bonds with trivalent metal ions, and has the ability to form a wall film, and (d) alkaline earth. A microcapsule characterized in that a water-soluble compound capable of producing trivalent metal ions is added to an oil-in-water emulsion in which hydrophobic core material particles are dispersed in an aqueous medium dissolving a water-soluble compound capable of producing similar metal ions. manufacturing method.