JPH05212273A - Production of microcapsule - Google Patents

Abstract

PURPOSE:To obtain a microcapsule capable of easily controlling the grain to a minute diameter and having a relatively sharp distribution of the grain diameters when a hydrophobic substance is microcapsuled by in situ polycondensation. CONSTITUTION:A hydrophobic substance contg. the divalent or more metal salt of an alkylbenzenesulfonic acid is emulsified and dispersed in a soln. of a water-soluble polymer in an aq. medium, and the dispersion is microcapsuled by an amino plastomer shell forming component.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing microcapsules containing a hydrophobic substance.

[0002]

2. Description of the Related Art Microcapsules are used in many fields such as recording materials such as pressure-sensitive recording paper and heat-sensitive recording paper, agricultural chemicals, pharmaceuticals, fragrances, liquid crystals and adhesives, and many methods have been proposed. Has been done. Typical microencapsulation methods include coacervation method, interfacial polymerization method,
The in-situ polymerization method and the like are known. Urea /
Microcapsules obtained by in-situ polycondensation method using formaldehyde initial polycondensate etc. are physically,
Many have excellent chemical properties and have been particularly well studied. Such a microcapsule is disclosed in, for example, JP-A-54.
-53679, Japanese Patent Publication No. 60-2100, Japanese Patent Publication No. 59-35258, Japanese Patent Publication No. 60-12904.
JP-A No. 60-216838 and the like. The method of making microcapsules disclosed herein is primarily concerned with the use of water-soluble polymers in in situ polymerization processes. The water-soluble polymer is mainly used for controlling the particle size and preventing the particles from aggregating, and shows good results for the production of microcapsules having a particle size of about 5 to 30 μm.

However, even when such a water-soluble polymer is used, it is difficult to control the fine particle size,
In particular, microcapsules having a particle size of 5 μm or less cannot be easily obtained by using various homogenizers or ultrasonic waves.

[0004]

DISCLOSURE OF THE INVENTION The present invention makes it possible to easily obtain a fine particle size when a hydrophobic substance is microencapsulated by an in-situ condensation polymerization method using an aminoplast-based shell-forming component as a shell-forming component. It is an object of the present invention to provide a method for producing microcapsules which can be controlled to a desired value and have a relatively sharp particle size distribution.

[0005]

The present invention emulsifies and disperses a hydrophobic substance containing a divalent or higher valent metal salt of alkylbenzene sulfonic acid in an aqueous medium in which a water-soluble polymer is dissolved, and forms an aminoplast-based shell. The present invention relates to a method for producing microcapsules, which comprises microencapsulating the ingredients. By this method, even when microcapsules having a particle size of 5 μm or less are produced, those having a relatively sharp particle size distribution can be manufactured.

In the production method of the present invention, a divalent or higher valent metal salt of alkylbenzene sulfonic acid is dissolved in a hydrophobic substance to be microencapsulated, and this solution is emulsified and dispersed in an aqueous medium in which a water-soluble polymer is dissolved. ..

The divalent or higher valent metal salt of alkylbenzene sulfonic acid used in the present invention is used as an emulsifier for a hydrophobic substance to be microencapsulated, and the length of the alkyl group is the optimum length for emulsifying the hydrophobic substance. May be used alone or in combination. It is preferably about C _{1 to} C ₃₀ , particularly preferably about C _{8 to} C ₁₃ . The alkyl group may be linear or branched. The chain length of the alkyl group is C ₃₀
If it exceeds, the emulsification dispersibility deteriorates and the stability of the particles deteriorates. As the divalent or higher valent metal salt, any of zinc salt, calcium salt, magnesium salt, and aluminum salt is preferably used, and calcium salt is particularly preferable.

The amount of the divalent or higher-valent metal salt of alkylbenzenesulfonic acid used is preferably 0.01 to 50 parts by weight, based on 100 parts by weight of the hydrophobic substance to be microencapsulated.
It is more preferably 0.1 to 10 parts by weight. The amount of divalent or higher metal salt of alkylbenzene sulfonic acid used is 0.0
If the amount is less than 1 part by weight, the effect is not exhibited, and if the amount exceeds 50 parts by weight, the emulsion stability is adversely affected.

Other surfactants for controlling the emulsified state, nonionic surfactants of the polyalkylene oxide addition ether type, such as polyoxyethylene alkylphenyl ethyl, polyoxyethylene alkyl ether, polyoxyethylene phenylphenol, poly An appropriate amount of oxyethylene polyhydric alcohol fatty acid ester or the like may be blended and used.

Examples of the water-soluble polymer used in the present invention include acrylic acid polymers and (meth) acrylic acid copolymers (acrylic acid esters such as methyl acrylate, acrylic acid amides, acrylonitrile, 2-methylpropane sulfone). Acid, styrene sulfonic acid, vinyl acetate, etc.), maleic acid copolymer (styrene, ethylene,
Examples thereof include copolymers of propylene, methyl vinyl ether, vinyl acetate, isobutylene, butadiene and the like with maleic acid), carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, gelatin, gum arabic starch derivative, polyvinyl alcohol and the like. A water-soluble salt of an acrylic acid polymer, an acrylic acid copolymer, or a maleic acid copolymer is particularly preferable.

The amount of the water-soluble polymer used is 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the aqueous medium.
It is preferably parts by weight and the viscosity of the aqueous medium is 5 to 1000. When the amount of the water-soluble polymer used is 0.1 parts by weight or less, the emulsion stability is insufficient and stable particles cannot be obtained. Further, when the amount exceeds 20 parts by weight, the wall material does not deposit well on the surface of the core substance, which makes encapsulation difficult.

The aminoplast-type shell forming component used in the present invention is a melamine / formaldehyde prepolymer, a urea / formaldehyde prepolymer, an alkylated methylolurea alkylated methylolmelamine, an N-alkylmelamine / formaldehyde prepolymer, and guanamine. / Formaldehyde prepolymer, alkylurea / formaldehyde prepolymer, alkylene urea / formaldehyde prepolymer, etc. are exemplified. Particularly preferred shell-forming components are the former four.

The aminoplast-based shell-forming component is 1 to 20 with respect to 100 parts by weight of the hydrophobic substance to be microencapsulated.
0 parts by weight, more preferably 10 to 60 parts by weight is used. Two
If it exceeds 100 parts by weight, the particles tend to aggregate during the reaction.

The hydrophobic substance to be microencapsulated in the present invention is not particularly limited. Hydrophobic substances of interest, such as dyes, pesticides, pharmaceuticals, fragrances, adhesives, oil-soluble vitamins, fish oils, vegetable oils, mineral oils, catalysts, cosmetics which are liquids themselves, and solid or liquid hydrophobic substances Examples include various substances such as a hydrophobic solution in which is dissolved or dispersed in a hydrophobic solvent. As the hydrophobic solvent, toluene, xylene, aromatic solvent such as methylnaphthalene, kerosene, aliphatic hydrocarbon such as liquid paraffin, cyclohexane, cyclopentane, alicyclic hydrocarbon such as decalin,
Examples thereof include ester compounds such as dibutyl phthalate, dioctyl phthalate, and dibutyl adipate.

When the hydrophobic substance is a solid, it may be dissolved in a hydrophobic organic solvent which can be dissolved before use.
Alternatively, it may be used by dissolving it in a hydrophobic wax that melts at the shell forming temperature, or by dispersing it in a hydrophobic organic solvent.

In order to produce microcapsules by the method of the present invention, first, a metal salt of divalent or higher valent alkylbenzene sulfonic acid is dissolved in a hydrophobic substance, and this is mixed with an acidic aqueous solution of a polymer, and a commercially available homogenizer is used. Alternatively, emulsification and dispersion are performed using ultrasonic waves or the like. Alkylbenzenesulfonic acid 2
By the emulsifying action of a metal salt having a valency or more, it is possible to obtain emulsified dispersed particles having a smaller particle diameter than before. The size of these emulsified dispersed particles depends on the particle size of the desired microcapsule, but is usually 1 to 100 μm, and more generally 1 to 100 μm.
Adjust to 30 μm. In particular, when the divalent or higher valent metal salt of alkylbenzenesulfonic acid of the present invention is used, it can be adjusted to 1 to 5 μm. Next, an aminoplast-based shell-forming component is added and the pH is adjusted with stirring to produce microcapsules by a conventional method.

When the aminoplast-based shell-forming component is a urea / formaldehyde prepolymer, this component may be gradually or at once added to the system, or the raw material urea may be previously dissolved in an aqueous medium, Thereafter, formaldehyde may be gradually or once added to the system. The same applies to other shell-forming components.

In the present invention, in order to carry out the reaction quickly, the microencapsulation is preferably carried out under acidic conditions, that is, the pH of the system is 2.0 to 6.8, more preferably 3.0 to.
Perform at 6.0. The conditions of the system may be appropriately adjusted depending on the type of aminoplast-based shell-forming component to be used. For example, in the case of a melamine / formaldehyde prepolymer or an alkylated methylolmelamine, pH 4.0 to 5.5, urea / formaldehyde prepolymer. For goods, pH 2.0 to 4.5
Is appropriate.

The shell-forming component adjusts the pH of the system to 3.0 to 6.8 and is heated to 30 to 80 ° C. to polycondense on the surface of the dispersed particles of the hydrophobic substance to form a shell. During this period, the system is maintained in a uniform emulsified and dispersed state by stirring.

The present invention will be described in more detail with reference to the following examples. Microcapsules having a hydrophobic component of toluene and a shell-forming component of melamine / formaldehyde initial polycondensate were produced in the following manner, and the particle size was measured.

[0021]

Example 1 Hydrophobic microcapsule material 50 parts of toluene and 2 parts of calcium dodecylbenzenesulfonate were mixed.

Aqueous medium Scripset # 520 (styrene / maleic anhydride copolymer; manufactured by Monsanto Co.) was mixed with 30 parts by weight of a 20% aqueous solution of a partial sodium salt and 120 parts by weight of water to prepare an aqueous medium.

Microencapsulation The above materials and an aqueous medium are mixed and mixed with stirring using a homomixer (made by Tokushu Kika Kogyo Co., Ltd.) at 10,000 rpm for 2 minutes,
An emulsified dispersion was obtained. Separately, 13% by weight of 37% formalin,
A mixture of 5 parts by weight of melamine and 33 parts by weight of water,
The pH was adjusted to 9.0 with stirring, and the reaction was carried out at 60 ° C. for about 20 minutes to obtain a transparent melamine / formaldehyde prepolymer.
This was added to the above emulsified dispersion and reacted at 60 ° C. for 3 hours while stirring at 250 rpm. Subsequently, in order to remove residual formalin, the pH of the system was adjusted to 4.0, and the reaction was continued at 80 ° C. for 2 hours.

Results Microcapsules with an average particle size of 3 μm were obtained.

[0025]

Example 2 Microcapsules were prepared in the same manner as in Example 1 except that 50 parts of the fragrance Jasmine No. 39591 (manufactured by Nagahirodo Honten Co., Ltd.) was used instead of the toluene of Example 1. Results Microcapsules with an average particle size of 2.5 μm were obtained.

[0026]

Example 3 In place of toluene in Example 1, 50 parts of terthion (isobornyl thiosiaacetate; manufactured by Nippon Terpene Co., Ltd.), and Aron A-10H (polyacrylic acid; Toa Co., Ltd.) in place of Scriptset # 520. Synthetic Co., Ltd.)
Microcapsules were prepared in the same manner as in Example 1 except that 30 parts by weight of a 20% aqueous solution was used. Results Microcapsules with an average particle size of 2 μm were obtained.

[0027]

Comparative Example 1 Microcapsules were prepared in the same manner as in Example 1 except that 2 parts of Rheodor SP-L10 (sorbitan monolaurate; manufactured by Kao Corporation) was used instead of the calcium dodecylbenzenesulfonate of Example 1. Prepared. Results Microcapsules with an average particle size of 6 μm were obtained.

[0028]

Example 4 Hydrophobic microcapsule material 50 parts of toluene and 2 parts of calcium dodecylbenzenesulfonate were mixed.

Aqueous medium script set # 520 (styrene / maleic anhydride copolymer; manufactured by Monsanto) 30 parts by weight of a 20% aqueous solution of a partial sodium salt, 12 parts by weight of urea, 30% of formalin 37%
The pH of an aqueous solution containing 2 parts by weight and 120 parts by weight of water is 2
The one adjusted to 3.2 using an aqueous solution of N sodium hydroxide was used.

Microencapsulation The above materials and an aqueous medium are mixed and mixed with a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at 10000 rpm for 2 minutes, and then reacted at 60 ° C. for 3 hours while stirring at 250 rpm. Microencapsulation was performed.

Results Microcapsules having an average particle size of 3.5 μm were obtained.

[0032]

Example 5 Instead of the urea and 37% formalin of Example 4, 30 parts by weight of Euramine P6300 (methylated methylol melamine; manufactured by Mitsui Toatsu Chemicals, Inc.) was used to prepare a p of an aqueous solution.
Microcapsules were prepared in the same manner as in Example 4 except that H was 4.2. Results Microcapsules with an average particle size of 3.2 μm were obtained.

[0033]

Example 6 Microcapsules were prepared in the same manner as in Example 4 except that 50 parts of di (2-ethyl-hexyl) phthalate (DOP) was used instead of toluene in Example 4. Results Microcapsules with an average particle size of 2.0 μm were obtained.

[0034]

According to the method for producing a microcapsule of the present invention, when a hydrophobic substance is microencapsulated by an in-situ polycondensation method using an aminoplast-based shell-forming component as a shell-forming component, it is easy to form fine particles. It is possible to obtain microcapsules whose diameter can be controlled and whose particle size distribution is relatively sharp.

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Claims (5)

[Claims] 1. A hydrophobic substance containing a divalent or higher-valent metal salt of alkylbenzene sulfonic acid is emulsified and dispersed in an aqueous medium in which a water-soluble polymer is dissolved, and this is microencapsulated with an aminoplast-based shell-forming component. A method for producing a microcapsule, comprising: 2. The method for producing microcapsules according to claim 1, wherein the alkyl group of the divalent or higher-valent metal salt of alkylbenzenesulfonic acid is C _{8 to} C ₁₃ . 3. The method for producing microcapsules according to claim 1, wherein the divalent or higher valent metal salt of alkylbenzenesulfonic acid is a calcium salt. 4. The method for producing microcapsules according to claim 1, wherein the water-soluble polymer is selected from the group consisting of acrylic acid polymers, acrylic acid copolymers, and maleic acid copolymers. 5. The micro according to claim 1, wherein the aminoplast-based shell-forming component is selected from the group consisting of urea / formaldehyde initial polycondensate, melamine / formaldehyde initial polycondensate, alkylated methylol urea and alkylated methylol melamine. Capsule manufacturing method.