JP3204525B2 - Manufacturing method of microcapsules - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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, repellents, fragrances, liquid crystals, and adhesives. Proposed. A typical microencapsulation method is an in-situ radical polymerization method. This method is described in, for example, Japanese Patent Publication No. Sho 42-26524,
No. 51234. These methods use a water-soluble polymer such as a cellulose derivative or a colloidal inorganic substance when dispersing a hydrophobic substance containing a radical polymerizable simple substance in an aqueous medium, and depending on this system, a particle diameter of usually 5 to 30 μm is used. Is obtained.

[0003] The particle size of the microcapsules produced by the above-mentioned method is relatively large, and it is extremely difficult to obtain an arbitrary particle size, particularly a fine particle size of 5 µm or less. In order to produce microcapsules of 5 μm or less, it is necessary to make the emulsification of oil droplets finer by mechanical force, but this requires a large amount of energy for a long time.

[0004]

The present invention relates to a microcapsule comprising a polymer whose core component is a hydrophobic substance and whose shell component is a radical polymerizable monomer.
It is an object of the present invention to provide a method for producing microcapsules, which can easily control a fine particle diameter when producing by a situ radical polymerization method and have a relatively sharp particle diameter distribution.

[0005]

That is, the present invention relates to a method for preparing a hydrophobic substance containing at least a divalent or higher valent metal salt of alkylbenzene sulfonic acid, at least one radical polymerizable monomer and a polymerization initiator in an aqueous medium. The present invention relates to a method for producing microcapsules, which comprises emulsifying and dispersing the resulting emulsion and heat-polymerizing the obtained emulsion to form microcapsules.

According to the method for producing microcapsules of the present invention, a divalent or higher valent metal salt of alkylbenzenesulfonic acid is dissolved in a hydrophobic substance containing a radical polymerizable monomer, and this solution is emulsified and dispersed in an aqueous medium.

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 an optimum length for emulsifying the hydrophobic substance. May be used alone or as a mixture. C _{1 to} C ₃₀ , especially C ₈ to
About C ₁₃ are preferred. The alkyl group may be linear or branched. When the chain length of the alkyl group exceeds _C30 , the emulsification and dispersibility deteriorate, and the stability of the particles deteriorates.

[0008] Examples of the divalent or higher valent metal salts include zinc salts, calcium salts, magnesium salts and aluminum salts, and calcium salts are particularly preferred.

The amount of the divalent or higher valent metal salt of alkylbenzene sulfonic acid is preferably 0.01 to 50 parts by weight, more preferably 0.1 to 10 parts by weight, per 100 parts by weight of the hydrophobic substance to be microencapsulated. . If it is used in an amount of more than 50 parts by weight, the stability of the emulsion will deteriorate. If the amount is less than 0.01 parts by weight, the effect cannot be exhibited.

To control the emulsification state, other surfactants, for example, polyalkylene oxide-added ether type nonionic surfactants, for example, polyoxyethylene alkylphenyl ether, polyoxyethylene phenyl ether, polyoxyethylene phenylphenol ,
An appropriate amount of polyoxyethylene polyhydric alcohol fatty acid ester or the like may be blended.

The radical polymerizable monomer serving as the shell wall component of the present invention includes a nitrile monomer such as acrylonitrile, methacrylonitrile, β, β-dimethylacrylonitrile, crotononitrile, especially acrylonitrile and / or methacrylonitrile. Nitriles and the like; (meth) acrylic monomers such as acrylates, methacrylates, ethyl acrylates, itaconic esters, maleates, crotonates or neutralized products of these acids, especially methacrylic acid Esters and the like;
Vinyl monomers, monomer vinyl acetate, styrene, vinyl toluene, methyl styrene, pinyl pyridine, vinyl alkyl ether, vinyl pyrrolidone, vinyl chloride, vinylidene chloride; amide monomers such as acrylamide, methacrylamide, N- Methylol acrylamide and the like; crosslinkable monomers such as divinylbenzene, ethylene di (meth) acrylate, polyethylene di (meth) acrylate, N, N-methylene (bis) acrylamide, triacrylformal, polyvalent metal salt of (meth) acrylic acid (M
g, Ca, Zn, Al, etc.), especially divinylbenzene, ethylenedi (meth) acrylate, and the like.

These monomers are generally used in combination of two or more in accordance with desired properties. The amount of monomer used is about 5 to 95 parts by weight, more preferably 20 to 80 parts by weight, per 100 parts by weight of all components to be microencapsulated. If the amount is more than 95 parts by weight, the number of capsules of non-inclusions can be increased.

The size of the microcapsules can be adjusted to an average particle size of 0.1 to 10 μm, more preferably 0.5 to 5 μm. The method of microencapsulation is not limited, and various methods can be adopted. Specifically, a hydrophobic substance containing a divalent or higher valent metal salt of alkylbenzene sulfonic acid, a monomer, a catalyst, and the like are mixed in advance, or if necessary, other additives such as a solvent and a plasticizer are blended. May be added to an aqueous medium containing a water-soluble polymer and / or colloidal inorganic fine particles, if desired, and dispersed particles may be prepared using a homomixer, ultrasonic waves or the like, and then reacted by heating.

The reaction temperature is selected depending on the type of the monomer, but is preferably about 30 to 150 ° C. Further, the reaction may be performed under pressure. The pressure at that time is 0.1 to 10 kg / cm ²
Is appropriate.

In the present invention, the hydrophobic substance to be microencapsulated is not particularly limited. Hydrophobic substances of interest, such as dyes for pressure-sensitive recording paper, pesticides,
Pharmaceuticals, insecticides, repellents, fragrances, solvents, adhesives, oil-soluble vitamins, fish oils, vegetable oils, silicone oils, liquid crystals, flame retardants, catalysts, etc., which are themselves liquids and solid or liquid hydrophobic Examples include a hydrophobic solution in which a substance is dissolved or dispersed in a hydrophobic solvent. Examples of the hydrophobic solvent include aromatic hydrocarbons such as toluene, xylene and methylnaphthalene, aliphatic hydrocarbons such as kerosene and liquid paraffin, and alicyclic hydrocarbons such as cyclohexane, cyclopentane and decalin.

Examples of the water-soluble polymer include polyvinyl alcohol, cellulose derivatives, acrylic acid polymers, acrylic acid copolymers, and water-soluble nylons. By adding the water-soluble polymer to the aqueous medium, the emulsion dispersion stability is increased, and stable particles are obtained, so that the particle size of the microcapsules can be more easily controlled.

The amount of the water-soluble polymer used is preferably 0.01 to 100 parts by weight, more preferably 0.1 to 100 parts by weight, per 100 parts by weight of the aqueous medium.
It is 1 to 10 parts by weight.

As the colloidal inorganic fine particles, kaolin clay, calcined clay, sericite, talc, bentonite,
Examples include white carbon, colloidal antimony, silica fine particles, alumina fine particles, titanium oxide fine particles, calcium carbonate, dolomite powder, calcium sulfate, barium sulfate and the like. By adding the colloidal inorganic fine particles to the aqueous medium, the emulsification dispersion stability of the hydrophobic particles can be increased, and good microcapsules can be produced.

The amount of the colloidal inorganic fine particles used in the present invention is 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight, per 100 parts by weight of the aqueous medium.

As a catalyst which is an initiator for radical polymerization, organic peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, 2,2-bis (t
-Butylperoxy) barate, di-t-butyl peroxide, dicumyl peroxide, octanoyl peroxide, benzoyl peroxide and the like; azo compounds such as 2,2-azobis (2,4-dimethylvaleronitrile),
2,2-azobis (2-methylbutyronitrile), 1,1-
Azobis (cyclohexyl-1-carbonitrile) and the like are exemplified.

The amount of the catalyst used is 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the monomer.

An electrolyte such as sodium chloride, potassium chloride or ammonium chloride may be added to the aqueous medium for the purpose of suppressing the solubility of the hydrophobic substance or the polymerizable monomer in water. The amount of these electrolytes used is 100
0-100 parts by weight per part by weight, more preferably 0-50 parts by weight
Parts by weight. Hereinafter, the present invention will be described in more detail with reference to Examples.

In the following manner, microcapsules whose shell wall component was an acrylonitrile / methyl methacrylate copolymer were prepared, and the particle size was measured.

[0024]

EXAMPLE 1 Hydrophobic microcapsule material hexane 450 parts by weight of acrylonitrile 58 parts by weight,
10 parts by weight of methyl methacrylate, perloyl IPP-
1.5 parts by weight of 50 (diisopropyl peroxydicarbonate; manufactured by NOF Corporation) and 4.5 parts by weight of calcium dodecylbenzenesulfonate were mixed.

Preparation of Aqueous Medium An aqueous medium was prepared by mixing 600 parts by weight of water and 113 parts by weight of Snowtex S (colloidal silica; manufactured by Nissan Chemical Industries, Ltd.).

Microencapsulation The above materials and an aqueous medium were mixed, stirred and mixed at 10,000 rpm for 2 minutes using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and reacted at 55 ° C. for 6 hours.

As a result, microcapsules having a particle size distribution of 1 to 5 μm and an average particle size of 3 μm were obtained. In the above and the following examples and comparative examples, the particle size distribution and the average particle size were measured using “Heros and Rhodos system” (manufactured by Nippon Laser Co., Ltd.).

[0028]

Example 2 Microcapsules were produced in the same manner as in Example 1 except that 450 parts by weight of diethyltoluamide was used instead of hexane. Result Microcapsules having a particle size distribution of 1 to 5 μm and an average particle size of 2 μm were obtained.

[0029]

Example 3 A fragrance Jasmine No. was used in place of hexane of Example 1. Microcapsules were produced in the same manner as in Example 1 except that 450 parts by weight of 39591 (manufactured by Eikodo Head Office) was used. Result Microcapsules having a particle size distribution of 1 to 5 μm and an average particle size of 3 μm were obtained.

[0030]

Example 4 Snowtex 20L (colloidal silica; manufactured by Nissan Chemical Industries, Ltd.) in place of Snowtex S of Example 1
113 parts by weight of terthion (isobornyl thioacetate; manufactured by Nippon Terpene Co., Ltd.) 450 instead of hexane
Microcapsules were produced in the same manner as in Example 1 except that parts by weight were used. Result Microcapsules having a particle size distribution of 1 to 3 μm and an average particle size of 2 μm were obtained.

[0031]

Example 5 Microcapsules were prepared in the same manner as in Example 1 except that 450 parts by weight of di (2-ethyl-hexyl) phthalate (DOP) was used instead of hexane. Result Microcapsules having a particle size distribution of 1 to 5 μm and an average particle size of 3 μm were obtained.

[0032]

Comparative Example 1 Microcapsules were produced in the same manner as in Example 1 except that calcium dodecylbenzenesulfonate was removed from the hydrophobic microcapsule material of Example 1. Result Microcapsules having a particle size distribution of 1 to 30 μm and an average particle size of 15 μm were obtained.

Comparative Example 2 In the step of the hydrophobic microcapsule material of Example 1, calcium dodecylbenzenesulfonate was added in an amount of 4.
Microcapsules were prepared in the same manner as in Example 1, except that 4.5 parts by weight of sodium dodecylbenzenesulfonate was used instead of 5 parts by weight. The obtained microcapsules had a wide particle size distribution with a particle size distribution of 1 to 20 μm and an average particle size of 10 μm.

[0033]

According to the method for producing microcapsules of the present invention, microcapsules in which the core component is a hydrophobic substance and the shell wall component is composed of a polymer having a radical polymerizable monomer as a main polymer component can be obtained in situ. In the production by the radical polymerization method, it is possible to easily control the fine particle size and obtain microcapsules having a relatively sharp particle size distribution.

Claims (7)

(57) [Claims] 1. An emulsion obtained by emulsifying and dispersing a hydrophobic substance containing at least a divalent or higher valent metal salt of alkylbenzenesulfonic acid, at least one radically polymerizable monomer and a polymerization initiator in an aqueous medium. A method for producing microcapsules, wherein the liquid is heated and polymerized to form microcapsules. 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 alkyl. 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 according to claim 1, wherein the aqueous medium contains an aqueous solution of a water-soluble polymer. 5. The water-soluble polymer is polyvinyl alcohol,
The method according to claim 4, wherein the method is selected from the group consisting of a cellulose derivative, an acrylic acid polymer, an acrylic acid copolymer and water-soluble nylon. 6. The method for producing microcapsules according to claim 1, wherein the aqueous medium contains colloidal inorganic fine particles. 7. The colloidal inorganic fine particles are silica fine particles,
The method for producing microcapsules according to claim 6, wherein the method is selected from the group consisting of alumina fine particles and titanium oxide fine particles.