JPS6140213A - Production of microcapsule containing liquid active substance - Google Patents

Abstract

PURPOSE:To obtain diretly the titled microcapsule having a film containing a surface active agent, showing improved water dispersibility, capable of releasing even an unstable active substance sustainedly, by dissolving a specific polymer, a liquid active substance, and a surface active substance in an organic solvent, subjecting the solution to spray drying. CONSTITUTION:A polymer, a liquid active substance, and surface active agent are dissolved in an organic solvent, the solution is sprayed from a nozzle into very small liquid droplets, the solvent is dried, and the active substance is sealed in the film of the polymer, to give the titled microcapsule containing the surface active agent in the film. The polymer used dissolves the liquid active substance in a limited solubility, especially in 0.01-2wt%. The organic solvent used has higher volatility (e.g., methylene chloride, etc.) than the active substance. The microcapsule is formed in a gas, water is not admixed, and the liquid active subtance has good stability. The microcapsule has improved dispersibility, and is useful as a spray agent or wettable powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing microcapsules containing a liquid active substance, and in particular to a method for producing microcapsules that have excellent dispersibility in a dispersion medium such as water, and that can control the liquid active substance in a substantially constant manner. The present invention relates to a method for producing microcapsules containing liquid active substances which can be released at a controlled rate.

Various methods are already known in which microcapsules are obtained by encapsulating an active substance or a solution of an active substance that is liquid at room temperature within a film made of a polymer. A typical method is an in-liquid drying method that uses a polymer from the beginning as a film-forming substance. The method is as follows. For example, if the active substance is water-soluble, first dissolve the film-forming polymer in an organic solvent with a boiling point lower than that of water, and add the aqueous solution of the active substance to this polymer solution to form a W2O type primary Form an emulsion. Next, this emulsion is added with stirring to an aqueous solution containing protective colloid substances such as gelatin and surfactants to form a (Wlo)/W type secondary emulsion, which is then heated and depressurized. By removing the organic solvent, a film is formed on the polymer and the active substance is encapsulated within the film.

This method is described, for example, in US Pat. No. 3,523,906.

On the other hand, when the active substance is provided as a water-insoluble oily substance or oily solution, the active substance or its oily solution is first mixed with a hydrophobic film-forming polymer that is less compatible with the active substance or its oily solution. , and an organic solvent that can dissolve both of them and has a boiling point lower than that of water and is hardly soluble in water, and this solution is added to an aqueous solution containing a protective colloid substance such as gelatin or a surfactant. Disperse to form an O/W type emulsion. Thereafter, the organic solvent is removed by heating, reducing pressure, etc. to obtain microcapsules. This method is described, for example, in U.S. Pat.
No. 0,304.

The above-mentioned methods all have the advantage that microcapsules can be obtained in a dispersed state in water, so that they can be applied by a so-called spraying method, for example, when the active substance contained in the microcapsules is a pesticide. However, in its production, the film-forming polymer is determined depending on whether the active substance to be encapsulated in the microcapsules is oil-based or water-based, as described above, and its selectable surroundings are Not only is it narrow, but it also requires a lot of effort to make a second emulsion or a second emulsion, and furthermore, the second emulsion is not always well formed.

Further, the solvent used is limited to one that is water-insoluble or has water WAR properties, and therefore it takes a long time to remove this solvent.

In order to solve the drawbacks of the above-mentioned submerged drying method, it is also known to produce microcapsules by a spray drying method.

This method is described, for example, in US Pat. No. 3.1) 1,407. However, microcapsules obtained by spray drying methods, including this method,
Because of its poor dispersibility in aqueous media, it is not suitable for application as a dispersion in which microcapsules are dispersed in water, such as a spray agent as described above or a wettable powder.

On the other hand, in recent years, as pest control methods that do not cause environmental pollution, the so-called mass trapping method, in which insects are attracted to traps and killed by slowly releasing insect sex pheromones into the atmosphere, and the so-called mass trapping method, in which males detect females However, so-called disturbance methods that disrupt mating behavior are attracting attention. Of course, microcapsules produced by the submerged drying method described above can be used to some extent for sustained release of pheromones, but since many pheromones have unsaturated bonds or aldehyde groups, they are generally chemically It is unstable and easily transforms into a different substance that does not have the desired effect in the microcapsule under environmental conditions, thus allowing the pheromone to retain its effective attracting and disturbing effects over a long period of time. , it is difficult to achieve sustained release. In particular, according to the above-mentioned submerged drying method, microcapsule formation is performed in water, so in the case of pheromones that are normally subjected to microencapsulation as an oily substance or an oily solution, water gets mixed into the microcapsules, and the water Not only is there the problem that oxygen dissolved in this water accelerates the deterioration of the pheromones, but there is also the problem that the pheromones are lost in the water.

The present invention has been made to solve the various problems described above, and has a wide range of selection of film-forming substances for encapsulating liquid active substances. Not only can the microcapsules obtained have excellent dispersibility in water, but they can also be effectively used even when the liquid active substance is an unstable pheromone with unsaturated bonds or aldehyde groups. It is an object of the present invention to provide a method for producing microcapsules using a spray drying method that allows sustained release over a long period of time while retaining activity.

The method for producing liquid active substance-containing microcapsules according to the present invention involves combining a polymer, an active substance that is liquid at room temperature and having limited solubility in the polymer at room temperature, and a surfactant. Both the surfactant and the polymer can be dissolved in an alkaline solvent that is more volatile than the above-mentioned active substance, and this solution is sprayed from a nozzle in the form of minute droplets, and from these droplets the above-mentioned Obtained by the method of the present invention, which is characterized in that the solvent is evaporated to dryness to obtain microcapsules in which the liquid active substance is encapsulated within the film of the polymer and the film contains a surfactant. Because microcapsules contain surfactants in their walls, they have improved wettability and poor dispersibility in water, and are therefore suitable for application as sprays or wettable powders. be.

In the present invention, liquid active substances refer to volatile substances that are liquid at room temperature and have chemical or physiological activities such as pesticide activity, attractant activity, repellent activity, and aromatic activity;
Including water-based. As a specific example of such a liquid active substance, for example, as an agricultural chemical active substance, Nale
d), insecticides such as Diazinon, Sumithion, fungicides such as β-propiolactone,
Triethylene glycol monohexyl ether, N, N
- Repellents such as diethyl-m-toluamide, dodecyl acetate, Z-1) -tetradecenyl acetate, Z-
9-dodecenyl acetate, Z-7-eicosene-1)
-one, Z-1)-hexadecenal, Z-1)-octadecenal, Z-9-tetradecenal, Z-1)1
-Tetrazonal Z1) -Tetrazonal Z,
Attractants such as pheromones or pheromone-like compounds such as Z, Z-9,12,15-octadecatrienal, esters, ethers, aldehydes, etc. derived from limonene, benzyl alcohol, hydrocarbons having 1+6 to 16 carbon atoms, etc. Mention may be made of aroma active substances and the like.

The microcapsules according to the invention contain a surfactant in the film. Here, the surfactant is appropriately selected from nonionic surfactants, anionic surfactants, and cationic surfactants depending on the type and properties of the liquid active substance.

For example, nonionic surfactants include polyalkylene glycol ethers such as polyethylene glycol alkyl ether, polyethylene glycol alkyl phenyl ether, and polyethylene glycol polypropylene glycol ether, polyalkylene glycol esters such as polyethylene glycol fatty acid ester, and polyethylene glycol polypropylene glycol ester. Preferred specific examples include sorbitan fatty acid ester, glycerin fatty acid ester,
Sucrose esters and the like are also preferably used.

Preferred examples of the anionic surfactant include polyoxyethylene alkyl ether phosphate, polyethylene glycol alkyl ether sulfate ammonium salt, alkyl sulfate, dialkyl sulfosuccinate sodium salt, and sodium alkyl hanzene sulfonate. can be mentioned.

In the present invention, nonionic and anionic surfactants are preferred, and nonionic surfactants are particularly preferably used because of their excellent ability to stably retain liquid active substances. The amount of surfactant used is usually suitably from 0.1 to 20% by weight, preferably from 1 to 15% by weight, based on the total amount of active substance and surfactant.

In the present invention, it is necessary for the polymer for forming the film of the microcapsules to have a limited solubility with respect to the liquid active substance used. Limited solubility refers to the number of parts by weight of liquid active material that can be dissolved, and limited solubility refers to the number of parts by weight of liquid active material that can be dissolved.
It means that the active substance is dissolved only in a range of 5 parts by weight or less per 0 parts by weight. In particular, in the present invention, a polymer capable of dissolving a liquid active substance in a range of 0.01 to 2 parts by weight is preferably used.

Such polymers are appropriately selected depending on the liquid active substance used, and specific examples include polysulfone,
Polyether sulfone, polycarbonate, polystyrene, poly(meth)acrylate ester including polymethyl methacrylate, polyphenylene oxide, polyphenylene sulfide, polyamide, polyester, polyvinylidene chloride, polyvinylidene fluoride, cellulose ester, regenerated cellulose, polyurethane, polyvinyl alcohol , polyvinyl chloride, polyvinyl acetate,
One or more of ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polystyrene-bolybucdiene block copolymer, etc. Mention may be made of mixtures of.

The organic solvent used in the method of the present invention must be capable of dissolving all of the liquid active substance, surfactant, and polymer used, and must be more volatile than the above-mentioned active substance. The surfactant is appropriately selected depending on the type of surfactant, but specifically, lower aliphatic halogenated hydrocarbons such as methylene chloride, chloroform, and carbon tetrachloride, lower aliphatic alcohols such as methanol and ethanol, and In addition to the acetic acid ester, one or a mixture of two or more of acetonitrile, acetone, ethyl ether, tetrahydrofuran and the like can be mentioned. Preferably, lower aliphatic halogenated hydrocarbons such as methylene chloride are used.

The total amount of liquid active substance, surfactant, and polymer is usually 1.0% based on the weight of the solution in which they are dissolved in an organic solvent. ．． 0 to 50% by weight is suitable, preferably 1.
5-43% by weight. The ratio of the liquid active substance to the polymer is preferably selected such that the liquid active substance weighs 5 to 70% by weight based on the total amount thereof.

If the liquid active substance is sensitive to oxidation and unstable, for example pheromones or pheromone-like compounds having unsaturated bonds or aldehyde groups, along with a surfactant, if necessary, Antioxidants can be used. Similarly to the surfactant, the antioxidant is preferably used in an amount of 0.1 to 20% by weight, preferably 1 to 15% by weight, based on the total amount of active substance and antioxidant.

Examples of antioxidants include phenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol and alkylated bisphenols, and phosphoric acid antioxidants such as trisnonylphenyl phosphite and triphenyl phosphite. agents, imidazole-based antioxidants such as 2-mercaptobenzimidazole, thiodipropionate-based antioxidants such as distearyl-3,3'-thiodipropionate, diallyl-3,3''-thiodipropionate, Amine antioxidants such as nonylated diphenylamine, N,N'-diallyl-p-phenylenediamine, n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, etc. Propionate antioxidants and the like can be used alone or as a mixture of two or more.

According to the method of the present invention, a liquid active substance, a surfactant, a polymer, and, if necessary, an antioxidant are dissolved in an organic solvent as described above, and this solution is sprayed through a small hole in a nozzle. , the solvent was evaporated to dryness to obtain microcapsules.

Polymer, surfactant, liquid active substance and, if necessary,
A solution containing a dissolved antioxidant is sprayed in the form of minute droplets from a small nozzle hole, and the organic solvent is evaporated from the droplets at room temperature, but if necessary, it may be heated. Good too. It may also be evaporated under reduced pressure. The diameter of the nozzle small hole depends on the particle size of the target microcapsule, but is usually 0.1 to 1 i+++, preferably 0.4 to 1
A material with a diameter of about 0.8 tm is used. In this way, as the organic solvent evaporates from the spray-formed droplets, a phase separation occurs between the active substance and the polymer, since the liquid active substance has only limited solubility in the polymer. occurs, the polymer forms a film, and the liquid active substance and surfactant are encapsulated within this polymer film, and the surfactant is also included in the polymer film to form microcapsules. In this case, there is no problem in that a part of the surfactant is encapsulated in the polymer film together with the active substance. Usually, the microcapsules obtained in this way have a particle size of about 1 to 200 μm, and the thickness of the film is usually 1/10 to 1/100 of the particle size.

According to the method of the present invention, since the formation of microcapsules is carried out in gas, water does not get mixed into the microcapsules unlike in the case of the above-mentioned submerged drying method, so that the liquid active substance is not deteriorated. The microcapsules are stably maintained over a long period of time without any turbidity, and the film contains a surfactant, which increases the wettability of the microcapsule surface to water, resulting in excellent dispersibility in water. Therefore, the microcapsules obtained according to the present invention are suitable for application as a spray or a wettable powder.

Furthermore, the polymer for forming the film is arbitrary as long as the solubility of the liquid active substance therein is low, and the organic solvent used also dissolves the surfactant together with the above polymer and liquid active substance, and further, The choice is free as long as it is more volatile than the liquid active substance. In particular, according to the conventional underwater drying method, when the liquid active substance is oil-based, a water-soluble polymer must be used as a film-forming substance, but according to the present invention, when the liquid active substance is oil-based, Also, oil-soluble polymers can be used.

Furthermore, according to the microcapsules obtained in this way, the liquid active substance has limited solubility in the polymer forming the film, so that the liquid active substance in the film can diffuse into the film polymer. It is released into the ambient atmosphere at a controlled and substantially constant rate, with reduced oxidation, and can therefore be suitably used as a so-called sustained release device for active substances.

1 The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Polysulfone (Union Carbide P-1700)
) After dissolving 4 g in methylene chloride loO+nl,
Z-7-eicosene-1), a type of insect attractant
0.3 ml of anionic surfactant polyethylene glycol alkyl ether sulfate ammonium salt (Hytenol N17 manufactured by Daiichi Kogyo Seiyaku) were added and dissolved to obtain a homogeneous solution. This solution is sprayed at room temperature as droplets with a diameter of 30 to 40 μΦ from a nozzle with small holes, and the solvent is evaporated to dryness, containing about 40% by weight of the active substance and about 5% by weight of the above-mentioned surfactant. Microcapsules were obtained.

Note that the solubility of Z-7-eicosen-1)-one in polysulfone is 0.5 part.

The above-mentioned liquid active substance-containing microcapsules were left in an open atmosphere at 30°C, and the amount of active substance released over time was determined from the weight loss per 100+ng of microcapsules.

The results are shown in the drawing. The active substance is released from the microcapsules at a nearly constant rate.

For comparison, microcapsules were prepared in exactly the same manner as above except that no surfactant was contained. In order to evaluate the dispersibility of the above-mentioned microcapsules for the present invention and comparison in water, a 0.1% by weight aqueous solution of each microcapsule was prepared, and after standing for 1 minute, the light transmittance by light with a wavelength of 61 Onm was was measured.

As a result, the light transmittance was 10% because the microcapsules according to the present invention were uniformly dispersed in water. However, in the case of comparative microcapsules, the light transmittance reached 98% because the microcapsules aggregated and floated on the ice surface.

Example 2 4 g of the same polysulfone as in Example 1 was added to 100 g of methylene chloride.
After dissolving in m1, Z-1), which is a type of insect attractant
- 4 ml of tetradecenyl acetate and 0.4 g of nonionic surfactant polyethylene glycol oleyl ether (Neugen ETI20, manufactured by Daiichi Kogyo Seiyaku ■) were added and dissolved to obtain a homogeneous solution. This solution was sprayed as droplets with a diameter of 30 to 40 μm from a nozzle with small holes in a temperature atmosphere of 80°C, and as in Example 1, about 40% by weight of the active substance and about 5% by weight of the surfactant were mixed. Microcapsules containing the same were obtained.

Note that the solubility of Z-1)-tetradecenyl acetate in polysulfone is 0.8 parts.

The amount of active substance released from this microcapsule was investigated under the same conditions as in Example 1, and is shown in the figure.

As in Example 1, the active substance is released from the microcapsules at an approximately constant rate.

For comparison, microcapsules were prepared in exactly the same manner as above except that no surfactant was contained. A 0.1% by weight aqueous solution of each of the above-mentioned microcapsules for the present invention and for comparison was prepared, and Example 1
As a result of measuring the light transmittance in the same manner as above, it was 10% for the microcapsules according to the present invention and 98% for the comparative microcapsules.

Example 3 Cellulose acetate (Eastman Kodak CA-4
35-753) was dissolved in 100 ml of methylene chloride, and then 0.25 ml of Z-1)-hexadecenal, a type of insect attractant, and the nonionic surfactant polyethylene glycol phenyl ether (Daiichi Kogyo Seiyaku ■) were dissolved. Neugen EA102) 0.25g and antioxidant 2.6-
0.25 g of di-t-butyl-4-methylphenol was added and dissolved to obtain a homogeneous solution. 80% of this solution
Diameter 30~4 from a nozzle with a small hole in a temperature atmosphere of ℃
It was sprayed as droplets of 0μ to obtain microcapsules containing about 35% by weight of active substance, about 5% by weight of surfactant, and 5% by weight of antioxidant in the same manner as in Example 1.

The solubility of Z-1)-hexadecenal in the cellulose acetate is 0.6 part.

The figure shows the amount of active substance released from this microcapsule, which was investigated under the same conditions as in Example 1.

As in Example 1, the active substance is released from the microcapsules at an approximately constant rate.

For comparison, microcapsules were prepared in exactly the same manner as above except that no surfactant was contained. O, I, and weight% aqueous solutions of the microcapsules of the present invention and comparative microcapsules were prepared, and the light transmittance was measured in the same manner as in Example 1. As a result, in the case of the microcapsules according to the present invention, the light transmittance was 10%, In the case of microcapsules by comparison, it was 98%.

[Brief explanation of the drawing]

The figure is a graph showing the amount of active substance released from liquid active substance-containing microcapsules according to the invention. Target 1flJ (○) Procedural amendment (voluntary) July 4, 1981

Claims (1)

[Claims] (1) A polymer, an active substance that is liquid at room temperature that has limited solubility in the polymer at room temperature, and a surfactant; all of these active substances, the surfactant, and the polymer are dissolved. The active substance is dissolved in an organic solvent that is more easily volatile than the active substance, and this solution is sprayed in the form of minute droplets from a nozzle, and the solvent is evaporated from the droplets to dryness, thereby forming a film of the polymer. 1. A method for producing microcapsules containing a liquid active substance, which comprises obtaining microcapsules in which the liquid active substance is encapsulated and the coating contains a surfactant.