JPS6231976B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for encapsulating a hydrophobic substance, and more particularly to a method for producing microcapsules having a hydrophobic substance as a core material and a means for forming a complex coacervate covering the core material. Conventional methods for microencapsulating hydrophobic substances include complex coacervation method, simple coacervation method, salt coacervation method, interfacial polymerization method, in situ polymerization method, submerged drying method, and orifice method. Many methods are known, including the powder bed method, air suspension method, and electrostatic coalescence method, but the most representative method is the complex coacervation method described in U.S. Patent No. 2,800,457. It is. This method involves (1) ionizing a first sol of a hydrophilic colloid (e.g. gelatin) in water, and mixing oil into the solution and a second sol having an opposite charge to the first sol to form an O/W emulsion. forming process, (2)
A step of causing coacervation by adding water or adjusting pH to cause coacervate droplets to adhere around the oil droplets; (3) cooling the coacervate droplets to below the gelling point of the first sol (e.g. gelatin) to form a gel; (4) Adjusting the pH to alkaline side (e.g. 7~
11) and then adding a hardening agent. In other words, this complex coacervation method uses two types of colloidal substances with opposite charges,
For example, the electrical interaction between a positively charged first colloid material such as gelatin, casein, albumin, or fibrinogen and a positively charged second colloid material such as gum arabic, carboxymethyl cellulose, or cellulose phthalate is utilized. This forms a complex coacervate that becomes the capsule wall membrane. However, since this method of forming complex coacervate uses a hydrophilic substance as a raw material, it is necessary to make the hydrophilic substance insoluble in water by adding a curing agent as shown in step (4) above. Moreover, even with this treatment, not only is it not possible to form a sufficient hydrophobic coating, but also a step of cooling the coacervate droplets to gel them is required. The present invention provides a novel method for encapsulating hydrophobic substances that overcomes the above-mentioned drawbacks of complex coacervation methods. That is, in the encapsulation method of the present invention, a hydrophobic substance is emulsified and dispersed in an aqueous solution of an anionic (or cationic) surfactant, and then an aqueous dispersion of an amphoteric hydrophobic resin having an isoelectric point is added to the alkaline side (cationic side). After adding the hydrophobic substance to the complex coacervate of the surfactant and the amphoteric hydrophobic resin, the pH of the liquid is made acidic (or alkaline if the liquid is cationic). It is characterized by being coated with. According to the present invention, hydrophobic substances that could not be used in conventional complex coacervation methods, such as hydrophobic liquids, resins, waxes, etc., can be used as core substances, and the gelation of coacervates can be improved. There is no need for a cooling process for water insolubilization or a curing process for water insolubilization. To carry out the present invention, if the hydrophobic substance is a solid, the solid is first ground into particles of approximately 3 to 100 μm, or if it is a liquid, it is placed in an aqueous solution of an anionic (or cationic) surfactant. Stir thoroughly to emulsify and disperse. When the hydrophobic substance is a liquid, emulsification and dispersion are carried out so that the droplet diameter in the dispersion liquid is about 3 to 100 μm, as in the case of a solid substance. Next, after making the pH of this aqueous dispersion alkaline with caustic soda, etc. (if cationic, make it acidic with hydrochloric acid, etc.), add an aqueous dispersion of an amphoteric hydrophobic resin having an isoelectric point to make it anionic. Alternatively, a system is formed in which a hydrophobic substance is dispersed in both dispersions of a cationic surfactant and an amphoteric hydrophobic resin. After that, add acids such as hydrochloric acid to this system to lower the pH to about 4 to 7 (if the system is cationic, add an alkali such as caustic soda to raise the pH to 9 to 10), and it becomes stable with surfactants. Complex coacervation occurs between the dispersion of the hydrophobic substance and the amphoteric hydrophobic resin dispersion, and a coacervate film of the amphoteric hydrophobic resin is formed around the hydrophobic substance as a core, forming microcapsules. Becomes the prototype. Next, the microcapsules are dried by a method such as spray drying to form a product. As described above, in the present invention, the conventional complex coacervation method can be employed as is, except for the cooling process for gelling the coacervate and the curing process for making the coacervate water insoluble. The hydrophobic substance used as the core material of the microcapsule in the present invention may be either solid or liquid as long as it is insoluble in water and does not react with water or the constituent substances of the capsule wall membrane.
A variety of organic and inorganic materials can be used as the hydrophobic solid material. For example, pharmaceuticals, cosmetics, pigments, dyes, coloring agents, fluorescent bleaches, various textile treatment agents, fillers, waxes, resins, rubber, fertilizers, plant conditioners,
Examples include adhesives, fragrances and other odor-producing substances, photochemicals, metal oxides (e.g. magnetic oxides), salts, etc. In addition, hydrophobic liquid substances include liquid organic substances alone,
Alternatively, a solution in which a liquid or solid organic substance is dissolved in a hydrophobic organic solvent may be used. It should be noted that these hydrophobic liquid substances are generally preferably those with a high boiling point or those that are difficult to volatilize, but those with a low boiling point can also be used. Specific examples of hydrophobic liquid substances include petroleum compartment fractions such as kerosene and naphtha, linear or branched paraffins and their halides, aromatic hydrocarbons and their halides (e.g. benzene; toluene, xylene, etc.). alkylbenzenes such as fluorobenzene, trichlorobenzene, chlorobenzene, dichlorobenzene and similar brominated benzenes; alkylated di- and polyphenyls; hydrogenated terphenyls such as dodecahydroterphenyl, hexahydroterphenyl. ; chlorinated terphenyl; chlorinated diphenyl); vegetable oils such as corn oil, soybean oil, olive oil, coconut oil, palm oil, castor oil, peanut oil, rapeseed oil, sunflower oil, hempseed oil, linseed oil, cottonseed oil ;Animal oils such as fish oil and whale oil;Mineral oils;
Silicone oil etc. Examples of anionic surfactants include Emar A, Emar 10, Emar 40, Emarl (manufactured by Kao Soap), Ripal C-40, Riponol PS-M, Riponol F-150, Riponol LE-158, Riponol LF, and Riponol LS-. 103, Lipomin OS, Liporan TE (manufactured by Lion Oil), Honol, Honoralin, Homosol EP, Honsparder (manufactured by Takemoto Oil), Nitsusan Erectol #100, Nitsusan Erectol #300, Nitsusan Soluble Het, Nitsusan Kali Soap, Nitsusan These include Industrial Soap S, Nitsusan Mintretsukiss (manufactured by Nippon Oil & Fats), etc. In addition, the cationic surfactants include Nitsusan Cation AB, Nitsusan Cation PB, Nitsusan Cation BB, Nitsusan Cation M ₂ -100, Nitsusan Dispanol CT, Nitsusan Amine 12A, and Nitsusan Vecx AB-7 (all manufactured by NOF). , Lipomin CP, Lipomin OHK (manufactured by Lion Oil)
etc. ^An example of an aqueous dispersion of an amphoteric hydrophobic resin having ^an isoelectric _point is a latex or emulsion (A.
Homla et al., J. Colloid Interface Sic 59 , [1]
123-134 (1977)). Such amphoteric polystyrene latex can be prepared, for example, by mixing 100 ml of ion-exchanged water whose pH has been adjusted to 1 with concentrated hydrochloric acid, 0.5 g of N.N-diethylaminoethyl methacrylate (DEAM), 0.5 g of methacrylic acid (MA) and 10 ml of styrene monomer in a nitrogen stream for 100 ml of ion-exchanged water. It can be produced by refluxing for a minute, stirring and reacting at 70°C for 2 hours, and dialyzing the reaction product using ion exchange to remove unreacted monomers and electrolyte. The MA/DEAM ratio of the amphoteric polystyrene latex thus obtained is 1:1.
(The isoelectric point IEP is PH7.2). Three MA/DEAM ratios of 1:1, 2:1, and 5:1 were obtained using the same procedure.
Different types of amphoteric polystyrene latexes (isoelectric points of 7.2, 5.5, and 4.2, respectively) were prepared. Examples are shown below. Example 1 The anionic surfactant Emal A [the main component has the general formula ROSO ₃ Na (R=C ₁₁ ~
Sodium salt of higher alcohol sulfonic acid ester represented by _C17 ) was dissolved in solid content of 1 g, then 30 g of castor oil was added and emulsified and dispersed with a homomixer to adjust the particle size to 30 to 50μ, and then 1N- NaOH
The solution was added to adjust the PH to 8.5-9.5. To this dispersion, 10g of solid content of amphoteric polystyrene latex with an isoelectric point of 4.2 was added, and the pH was further adjusted with 1N-NaOH.
Adjusted to 8.5-9.5. Next, a 1% acetic acid aqueous solution was added dropwise to lower the pH to 5 to 5.5, and complex coacervate droplets of Emar A and polystyrene latex were attached around the castor oil to obtain a castor oil core capsule slurry. This slurry was spray-dried using a spray dryer to obtain capsule powder. The spray dryer conditions are inlet temperature 150℃, outlet temperature 80-90℃, and atomizer pressure 3.8℃.
~4.5Kg/ ^cm2 . Example 2 Add the anionic surfactant Liponol F-150 to the ion-exchanged water in step 1 [the main component has the general formula ROSO ₃ NH ₄
(Ammonium salt of higher alcohol sulfonic acid ester represented by R=C ₁₁ to _{C 17} )] in solid content of 1 g
After dissolving, 30 g of ferrite (triiron tetroxide manufactured by Toda Kogyo Co., Ltd.) was added and dispersed using a homomixer, and a 1N NaOH solution was added thereto to adjust the pH to 8.5 to 9.5. To this dispersion, 10 g of solid content of amphoteric polystyrene latex with an isoelectric point of 7.2 was added, and 1N-NaOH
The pH was adjusted to 9-10 with the solution. Next, a 1% acetic acid aqueous solution was added dropwise to lower the pH to 5.5 to 6.5, and complex coacervate droplets of Liponol F-150 and amphoteric polystyrene latex were precipitated around the ferrite. The obtained capsule slurry was spray-dried under the same conditions as in Example 1 to obtain a ferrite-containing capsule powder. Example 3 30g of concentrated toner for Ricoh's electrophotographic copying machine DT-1200 was mixed with anionic surfactant homosol EP.
[The main component is the general formula

[Formula] (Sodium salt of dialkyl sulfosuccinate represented by R=C ₃ to _{C 7} )] was emulsified and dispersed in aqueous solution 1 in which 1 g of solid content was dissolved using a homomixer, and the size of the droplets was adjusted to 10 to 10%.
After adjusting the pH to 20μ, 5g solid content of amphoteric polystyrene latex with an isoelectric point of 5.5 was added, and the pH was adjusted to 8.5 to 9.5 with 1N NaOH solution. Next, a 1% aqueous acetic acid solution was added dropwise to lower the pH to 5 to 5.5, and complex coacervate droplets of homosol EP and amphoteric polystyrene latex were precipitated around the concentrated toner droplets. The obtained capsule slurry was spray-dried under the same conditions as in Example 1 to obtain a core-containing capsule powder of a concentrated toner (toner for wet development).

Claims (1)

[Claims] 1. A hydrophobic substance is emulsified and dispersed in an aqueous solution of an ionic surfactant, an aqueous dispersion of an amphoteric hydrophobic resin having an isoelectric point is added to this, and the pH of the system is then changed to create a coacelvation. A method for encapsulating hydrophobic substances, which is characterized by