JP2649796B2 - Method for producing sustained-release microcapsules - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling the amount of core substance released from microcapsules.

2. Description of the Related Art Microcapsules are microscopic bodies having a structure in which a core material is covered with a wall film, and are used as coating materials for pressure-sensitive copying paper, pharmaceuticals, agricultural chemicals, fragrances, adhesives, enzymes, pigments, dyes, It is widely applied as an encapsulant for solvents and the like.

As a method for producing this microcapsule, a non-water-miscible solvent containing a hydrophobic monomer is finely dispersed in water containing a hydrophilic monomer, and a polymerization reaction is performed at an interface between the non-water-miscible solvent and water. To form a wall film,
A so-called interfacial polymerization method, a hydrophobic polymer solution is introduced in a finely dispersed state into a coagulating liquid and cured to form a wall film,
A so-called in-situ polymerization method in which a core material is introduced into a medium in a differentially dispersed state, and a monomer contained in either the core material or the medium is polymerized to form a wall film. A so-called coacervation method is known in which a non-solvent of a water-miscible polymer is added to an aqueous solution of a water-soluble polymer in which a core substance is finely dispersed to form a polymer coating on the surface of the core substance.

Examples of the material of the wall film formed by these methods include gelatin, gum arabic, polyamide, polyurethane, polyester, polysulfonamide, polyurea, polysulfonate, polycarbonate, epoxy resin, urea-formaldehyde resin, melamine-formaldehyde. There are resins and the like.

By the way, in recent years, as the use field of microcapsules has expanded, the required characteristics have been increasing.
For example, there is a property that the core substance in the microcapsule is gradually released and the required effect is continuously exhibited, that is, a so-called sustained release property.

However, there has been no known method for imparting sustained-release properties to the wall membrane. Thus, in order to obtain a sustained-release microcapsule, a microcapsule having a wall membrane having a different solubility or a thickness of the wall membrane is not considered. A plurality of different microcapsules had to be prepared and mixed and used, but this required a great deal of labor and expense and was not practically feasible.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a method for controlling the release amount of a core substance of a microcapsule according to the purpose of use.

Means for Solving the Problems The present inventors have conducted various studies in order to develop a method for controlling the amount of core substance released from microcapsules. A simple method of containing a compatible liquid material, and changing the content, distribution ratio to the hydrophobic core material, and reaction conditions for forming the wall film, adjusts the tightness of the wall film to form the microparticles. They found that the amount of core substance released from the capsule could be controlled, and based on this finding, completed the present invention.

That is, the present invention disperses a hydrophobic core material in an aqueous medium, and then forms a wall film around the core material to produce microcapsules. A liquid material that is compatible with both the medium and the hydrophobic core material is contained, and the content is changed in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the hydrophobic core material, and the hydrophobic core is changed. It is an object of the present invention to provide a method for controlling a core substance release amount of produced microcapsules, characterized in that the density of a wall film is adjusted by changing a distribution ratio to a substance and a reaction condition for forming a wall film.

 Hereinafter, the present invention will be described in detail.

The method for forming microcapsules in the method of the present invention is not particularly limited, and may be arbitrarily selected from conventional methods such as interfacial polymerization, in-liquid curing coating, in-situ polymerization, and coacervation. can do. In this case, it is necessary to use a hydrophobic substance as the core substance and an aqueous medium as a medium for finely dispersing the core substance. Examples of such core materials include non-water-miscible solvents, oil-based inks, water-insoluble pharmaceutical ingredients, water-insoluble pesticide ingredients, water-insoluble adhesives, and the like. Examples of the material constituting the wall film of the microcapsule include gelatin, gum arabic, polyamide, polyurethane, polyester, polysulfonamide, polyurea, polysulfonate, polycarbonate, epoxy resin, urea-formaldehyde resin, melamine-formaldehyde resin, and the like. Among them, a reaction product of a partially hydrolyzed styrene-maleic anhydride copolymer with an alkali and a methylolated melamine or a styreneolated urea is particularly preferred.

In the method of the present invention, it is necessary to include a liquid material that is compatible with both the core material and the aqueous medium in which the core material is finely dispersed in the core material when forming the microcapsules.

When a liquid film is formed around the hydrophobic core material, the liquid material elutes from the core material into the aqueous medium to regulate the tightness of the wall film.

Examples of such liquid substances include polyhydric alcohols, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, and water-soluble epoxy compounds.

In the method of the present invention, it is important to change the content of the liquid substance in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the hydrophobic core substance, and to change the distribution ratio to the hydrophobic core substance. It is important to change the reaction conditions for forming the wall film.

According to a preferred embodiment of the method of the present invention, the aforementioned liquid substance is added to the hydrophobic core substance, and this mixture is finely dispersed in an aqueous medium as appropriate to form a wall film around the core substance.
At this time, since the liquid substance in the hydrophobic core substance is soluble in the aqueous medium, the liquid substance is diffused and released from the finely dispersed core substance into the aqueous medium, and the tightness of the formed wall film is adjusted. Therefore, the amount of elution from the core substance can be controlled by appropriately selecting the type and amount of the liquid substance,
The properties of the wall membrane can be controlled.

Next, a preferred embodiment of the present invention will be described by taking, as an example, a case where the wall material is a reaction product of a partially hydrolyzed styrene-maleic anhydride copolymer with an alkali and a methylolated melamine or a methylolated urea. To explain, first, a styrene-maleic anhydride copolymer is dispersed in an aqueous medium, a desired amount of alkali is added thereto, and the mixture is maintained at a temperature of 20 to 100 ° C. and hydrolyzed until a desired hydrolysis rate is reached. The aqueous solution of this partial hydrolysis is adjusted to a concentration of 0.5 to 20% by weight. Next, a hydrophobic core substance in which a required amount of a liquid substance is dissolved is added thereto, and the mixture is emulsified or dispersed by high-speed stirring or ultrasonic waves for a required time. The amount of the core substance at this time is suitably about 5 to 50 times the partial hydrolyzate of the styrene-maleic anhydride copolymer based on the weight, and
The time required for emulsifying or dispersing the hydrophobic core material is usually 1 to 30 in consideration of the partition ratio of the liquid material to the aqueous medium and the hydrophobic core material, the desired properties of the wall film, and the like.
In the range of minutes.

Next, an aqueous solution of methylolated melamine or methylolated urea was added to the aqueous solution containing the partial hydrolyzate of the styrene-maleic anhydride copolymer and the core substance, and had a pH of 3 to
7. React with stirring at 40-90 ° C for 30-180 minutes. In this case, an acid such as citric acid can be used for pH adjustment, if necessary. The amount of methylolated melamine or methylolated urea is 10 to 1 per 100 parts by weight of the partially hydrolyzed styrene-maleic anhydride copolymer.
It is selected within the range of 00 parts by weight.

By this reaction, a wall film composed of a reaction product of a partial hydrolyzate of a styrene-maleic anhydride copolymer and a methylolated melamine or a methylolated urea is formed around the core substance. The tightness is controlled by the liquid substance, and the amount of elution from the core material can be controlled.

Effect of the Invention According to the method of the present invention, the characteristics of the wall membrane can be arbitrarily adjusted so that the release amount, release time, timing, etc. of the core substance (active ingredient) in the capsule can be controlled as desired. For example, sustained-release microcapsules can be easily produced.

Examples Next, the present invention will be described in more detail with reference to Examples.
The invention is not limited in any way by these examples.

In this example, the tightness of the wall film of the microcapsules was evaluated by solvent resistance. The solvent resistance of the microcapsules was determined as follows.

That is, after adding 20 cc of a solvent to 0.5 g of the dry capsule and treating it in an ultrasonic cleaner (25 ° C.) for 30 hours, the amount of the core substance extracted in the solvent is quantified by liquid chromatography, and the solvent resistance is determined. It was shown as% of the total amount of the substance. The smaller the value, the better the solvent resistance.

Note that two types of solvents, ethanol and tetrahydrofuran, were used.

Comparative Example 1 100 g of a script set 520 [trade name, manufactured by Monsanto Co., styrene-maleic anhydride copolymer (molar ratio 1: 1)] and 0.17 mol of sodium hydroxide were heated in water to form a styrene-maleic anhydride copolymer. 5% by weight of partial hydrolyzate of polymer
After emulsifying and dispersing 300 g of dimethyl phthalate in 300 g of the aqueous solution for 2 minutes, stir the mixture in a water bath at 60 ° C and keep the temperature in the emulsified dispersion to add melamine resin (Sumirog Resin).
(607 Syrup, manufactured by Sumitomo Chemical Co., Ltd.) was added and reacted for 2 hours to obtain a capsule slurry.

The capsules were taken out and the solvent resistance was determined. The results are shown in Table 1.

Comparative Example 2 Isopropyl naphthalene (KMC-113, manufactured by Kureha Chemical Co., Ltd.)
A solution of terephthalic acid chloride 13 g dissolved in 120 g,
The emulsion was emulsified in 300 g of a 2% by weight aqueous solution of polyvinyl alcohol for 2 minutes. Then, while stirring into this emulsion,
An aqueous solution in which 4 g of sodium carbonate and 8 g of diethylenetriamine were dissolved in 80 g of water was gradually added, and the mixture was reacted for 24 hours to obtain a capsule.

The capsule was taken out and the solvent resistance was determined. The results are shown in Table 2.

Examples 1 and 2 In Comparative Example 1, dimethyl phthalate was added to a water-soluble epoxy compound (Denacol EX 61, manufactured by Nagase Kasei Kogyo Co., Ltd.).
1) A capsule was obtained by treating in the same manner as in Comparative Example 1 except that 1 g was dissolved as a core substance and the emulsification time was 5 minutes (Example 1) and 10 minutes (Example 2). Was. The solvent resistance of these capsules was determined, and the results are shown in Table 1.

Examples 3 and 4 In Comparative Example 2, 1 g of a water-soluble epoxy compound (Denacol EX 611) was further added to isopropyl naphthalene, and the emulsification time was changed to 5 minutes (Example 3) and 10 minutes (Example 4). A capsule was obtained in the same manner as in Comparative Example 2 except for the above. The solvent resistance of these capsules was determined, and the results are shown in Table 2.

Claims (1)

(57) [Claims] (1) dispersing a hydrophobic core material in an aqueous medium, and then forming a wall film around the core material to manufacture microcapsules; And a liquid substance that is compatible with both the hydrophobic core substance and the content thereof.
It is characterized in that it changes in the range of 0.1 to 20 parts by weight with respect to 0 parts by weight, and that the partitioning ratio of the hydrophobic core substance and the reaction conditions for forming the wall film are changed to adjust the tightness of the wall film. To control the amount of core substance released from the resulting microcapsules.