JPS61118133A - Manufacture of microcapsule - Google Patents

Abstract

PURPOSE:To enhance the maintainability of the core substance of a capsule by coating the hydrophobic core substance incorporated with an initial oil-soluble melamine-formaldehyde condensate with a hydrophilic aldehydic resin-forming material. CONSTITUTION:An initial oil-soluble melamine-formaldehyde condensate having 40-100% formaldehyde substitution degree, 80-100% alkylation degree, and a 1-3 mean carbon number C alkyl group is incorporated to prepare a hydrophobic core substance. A hydrophilic aldehydic resin-forming material incorporated into water or a hydrophilic medium is condensed and polymerized, and the product is coated on the hydrophobic core substance to manufacture a microcapsule. The initial oil-soluble melamine-formaldehyde condensate contg. hexamethoxyhexamethylol melamine is preferable used.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a novel method for producing microcapsules containing a hydrophobic core material. In particular, the present invention relates to a method for easily producing capsules that have excellent retention of capsule core materials.

"Prior Art" In recent years, microcapsule technology has made remarkable progress, and the fields of use of these microcapsules are extremely wide and diverse, including pressure-sensitive copying paper.

Various methods are known for manufacturing microcapsules, such as core cell basic method, interfacial polymerization method, and 1n-situ polymerization method.Among them, microcapsules having aldehyde polycondensation resin as a wall film are generally water resistant, Due to its excellent solvent resistance, various encapsulation methods have been proposed. Patent No. 3016308, Japanese Patent Publication No. 47-51714, Japanese Patent Application Publication No. 48-57892, Japanese Patent Application Publication No. 51-9079, Japanese Patent Application Publication No. 52-66878, Japanese Patent Application Publication No. 53-84881, Japanese Patent Application Publication No. 53-84882 , JP-A-53-84883, JP-A-54-25277,
JP 54-49984, JP 54-53679, JP 54-8' 5184, JP 54-135185, JP 54-107881,
JP-A-55-8856, JP-A-55-15660,
JP-A-55-47139, JP-A-55-51431, JP-A-55-67329, JP-A-55-92135
No., JP-A-55-132631, JP-A-55-152
No. 546, JP-A-56-51238, JP-A-56-7
No. 8626, JP-A-56-102934, JP-A-56
-1) No. 5634, JP-A-56-155636, JP-A-57-1) 0332, JP-A-57-135038, JP-A-57-147429, and the like.

However, in spite of the fact that a large number of encapsulation methods have been developed and proposed, these methods still require improvement because they are associated with any of the following disadvantages.

■ The physical properties of the water-soluble polymer used as an emulsifier for the core substance, such as the degree of polymerization, molecular weight distribution, copolymerization ratio, degree of modification, etc., are easily affected by subtle changes, and on an industrial scale using materials with different lofts. It is easy to account for variations in quality such as film strength during the preparation of the film.

■ Subtle differences in capsule preparation conditions can easily cause differences in the quality of capsules, so high-precision equipment is required to control this for industrialization.

■ The process is complicated.

■ In order to prevent capsule particle agglomeration during film formation, strong stirring is required to maintain a constant yield, and if the hydrophobic core substance has the property of being easily sheared with low stirring, encapsulation may be performed while maintaining the emulsified particle size. difficult to do.

(2) If the emulsifier used has poor emulsification stability, giant oil droplets are likely to form, which causes spot stains when applied to pressure-sensitive copying paper.

■ The system tends to thicken during film formation, and the film material has a weak tendency to deposit on the surface of the core material, so it is necessary to use a large amount of dilution water to promote deposition, and high concentration paint is not obtained.

(2) The deposition efficiency of the film agent on the surface of the core material is poor, making it impossible to obtain sufficient inclusion retention properties.

(2) If the film material deposited on the surface of the core substance is in the form of a mixture of an aldehyde polycondensation resin having water resistance and a polymer compound having poor water resistance, only 9 cells with poor water resistance can be obtained.

Specifically, for example, Japanese Patent Application Laid-Open No. 51-9079
No., JP-A-53-84882, JP-A-53-8488
No. 3, JP-A No. 54-536.79 and JP-A No. 54-8
No. 5184, JP-A-53-84881, and JP-A-54
The method of forming a urea formaldehyde resin film or a melamine formaldehyde resin film in a hydrophobic monomer unit and maleic anhydride or polyacrylic acid as shown in No. 49984 is accompanied by the above-mentioned drawbacks (1), (2), and (2).

Also, JP-A-54-85185, JP-A-54-1078
81 and JP-A-55-132631, a method for forming a formaldehyde resin film in carboxy-modified polyvinyl alcohol, gum arabic, polyvinyl alcohol with a degree of saponification of 95% or more, and JP-A-55-132631.
The method of forming an aminoaldehyde resin film in anion-modified polyvinyl alcohol or cation-modified polyvinyl alcohol as shown in No. 92135 and JP-A No. 57-1) No. 0332 has the above-mentioned drawbacks (1), (2), (2), and (2). accompanying.

On the other hand, a method has also been proposed in which a hydrophobic core material contains an aldehyde polycondensation resin material, and after emulsification, polycondensation is performed to form a capsule membrane.
Examples thereof include Japanese Patent Publication No. 4-27257, Japanese Patent Publication No. 45-20885, and Japanese Patent Publication No. 52-18671.

Although these encapsulation methods rarely have the disadvantages (1) to (3) mentioned above, they have better retention of inclusions compared to capsules obtained by polymerizing and depositing a membrane material from water or a hydrophilic medium. The microcapsules were quite poor in quality and were completely impractical as microcapsules for pressure-sensitive copying paper, which particularly requires good retention.

"Problems to be Solved by the Invention" The object of the present invention is to provide capsules (easily and stably) with excellent retention of capsule core substances in a method for producing microcapsules having aldehyde polycondensation resin as a wall membrane. The purpose of this is to provide a method for producing microcapsules by coating a hydrophobic core material with a hydrophilic aldehyde-based resin-forming material. This is achieved by containing a soluble melamine-formaldehyde precondensate.

"Means for Solving the Problems" The present invention provides a method for producing microcapsules in which a hydrophilic aldehyde resin-forming material contained in water or a hydrophilic medium is polycondensed to coat a hydrophobic core substance. ,
The degree of formaldehyde substitution in the hydrophobic core material is 40 to 10.
0%, alkylation degree 80-100%, hydrophobicity degree 4-9,
Oil-soluble melamine whose alkyl group has an average carbon number of 1 to 3.
This is a method for producing microcapsules characterized by containing a formaldehyde initial condensate.

"Function" The oil-soluble melamine-formaldehyde initial condensate used in the present invention may be one that dissolves in the hydrophobic core material, and its formaldehyde substitution degree, alkylation degree, hydrophobicity degree, etc. may be adjusted as appropriate depending on the core material. The range of average carbon number of the alkyl group is adjusted.

Incidentally, a melamine resin initial condensate having a hydrophobicity degree of 5 to 7 is preferably used because a particularly good capsule can be obtained, and a melamine resin initial condensate containing hexamethoxyhexamethylol melamine as a main component is the most preferable among them. used.

In addition, the degree of formaldehyde substitution in the present invention is a value indicating the percentage of active hydrogen possessed by the amino group of melamine that is substituted by nor-5-ol group, alkoxymethylol group, and himethylene group, and is expressed by the following formula. expressed.

In addition, the degree of alkylation is a value indicating what percentage of the methylol group is alkoxylated, and is expressed by the following formula.The degree of hydrophobicity is the total number of carbon atoms in all alkyl groups per melamine residue. .

Further, the average carbon number of the alkyl group is a value indicating the average carbon number of the alcohol used for alkylation.

In addition, in the present invention, the average number of nuclei represented by the average number of melamine residues contained in one molecule of the initial condensate is 1 to 1.
0. More preferably, an initial condensate having a number of 1 to 5 is used.

In the present invention, when such an oil-soluble melamine-formaldehyde initial condensate is dissolved in a hydrophobic core material, when the initial condensate used has insufficient solubility or has a high viscosity, and when the initial condensate is dissolved in a hydrophobic core material, When the viscosity of the hydrophobic core substance is high, it is possible to heat the hydrophobic core substance or to use a polar solvent or a low boiling point solvent together. Examples of low boiling point solvents used for this include n-pentane, methylene chloride, etc. , ethylene chloride, carbon disulfide,
Acetone, methyl acetate, chloroform, methyl alcohol, tetrahydrofuran, n-hexane, carbon tetrachloride,
Ethyl acetate, ethyl alcohol, n-propyl alcohol, 1so-propyl alcohol, n-butyl alcohol, 1so-butyl 7) L/cole, t-butyl alcohol, n-pentyl alcohol, methyl ethyl ketone,
Examples include benzene, toluene, xylene, ethyl ether and petroleum ether.

As the polar solvent, dioxane, cyclohexanone, methyl isobutyl ketone, dimethylformamide, etc. are used.

The amount of the oil-soluble melamine-formaldehyde initial condensate varies depending on the type and amount of the hydrophobic core substance and hydrophilic aldehyde-based resin forming material used, the particle size of the capsule, its intended use, etc. I can't decide, but
0.0% in terms of melamine per 100 parts by weight of the hydrophobic core material.
It is preferably 1 part by weight or more and 20 parts by weight or less, particularly preferably 0.1 part by weight or more and 5 parts by weight or less.

In addition, when the hydrophobic core substance used is a solid,
For this purpose, the solid is dispersed in an initial condensate or a low boiling point solvent in which the initial condensate is dissolved, and then emulsified in water or a hydrophilic medium.

The hydrophilic aldehyde-based resin forming material used in the present invention includes, for example, a combination of at least one member of amines or phenols and at least one member of aldehydes. It is added in the form of a substance.

Examples of the amines include urea, urea, alkyl urea, ethylene urea, acetoguanamine, benzoguanamine, melamine, guanidine, dicyandiamide, biuret, and cyanamide, and examples of the phenols include phenol, cresol, xylenol, resorcinol, and hydroquinone. , pyrocatechol, pyrogallol, etc. Examples of aldehydes include formaldehyde,
Examples include acetaldehyde, paraformaldehyde, hexamethylenetetramine, geltaraldehyde, glyoxal, and furfural. In addition, the initial condensate may be the above-mentioned amines.

In addition to the initial condensate of at least one compound belonging to phenols and at least one aldehyde, hydrophilic ones such as alkylated products such as methylated products, partially alkylated products, or anion, cation, or nonionic modified products thereof are used. selected.

Note that these modifiers include, for example, sulfamic acid,
Anion modifiers such as sulfanilic acid, glycolic acid, glycine, acidic sulfites, sulfonic acid phenols, taurine, diethylenetriamine, triethylenetetramine,
Examples include cationic modifiers such as tetraethylenepentamine and dimethylaminoethanol, and nonionic modifiers such as ethylene glycol and diethylene glycol.

As the hydrophilic aldehyde-based resin forming material, various materials can be used as mentioned above, but among them, melamine-formaldehyde initial condensate, urea-melamine-formaldehyde initial condensate, or methylated products thereof,
This is preferable because a dense film can be obtained.

In addition, the blending amount of the hydrophilic aldehyde resin forming material is
It depends on the type of hydrophobic core material used, the intended use of the capsule, the amount of the oil-soluble melamine-formaldehyde initial condensate, etc. - although it cannot be determined generally.
It is preferably 0.5 parts by weight or more and 40 parts by weight or less, particularly preferably 2 parts by weight or more and 20 parts by weight or less, in terms of amine compound or fetool compound, based on 100 parts by weight of the hydrophobic core material.

In the present invention, the hydrophilic aldehyde resin-forming material is used before or during emulsification of the hydrophobic core substance.
Furthermore, although it can be added to the system at any stage after emulsification, it is desirable to add it after the polymerization of the oil-soluble melamine-formaldehyde initial condensate has partially progressed.

In the present invention, it is not necessary to use an emulsifier as long as the hydrophobic core material containing the oil-soluble melamine-formaldehyde initial condensate can be emulsified in water or a woody medium. It is preferable to use the emulsifier, and anionic, nonionic, cationic, or amphoteric polymer or low-molecular emulsifiers can be used.

As the anionic polymer, both natural and synthetic polymers can be used, for example -000''.

Examples include natural polymers such as gum arabic, carrageenan, sodium alginate, pectic acid, gum tragacanth, almond gum, and agar, carboxymethyl cellulose, sulfated cellulose, and sulfuric acid. Semi-synthetic polymers such as hydrogenated methyl cellulose, carboxymethyl starch, phosphorylated starch, lignin sulfonic acid, maleic anhydride (including hydrolyzed) copolymers, acrylic acid, methacrylic acid, or crotonic acid polymers. Polymers and copolymers, vinylbenzenesulfonic acid-based or 2-acrylamide-2-methyl-
Synthetic polymers such as propane sulfonic acid polymers and copolymers, partial amides or partial esters of such polymers and copolymers, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl alcohol, etc. Examples include molecules.

More specifically, maleic anhydride-based (including hydrolyzed) copolymers include methyl vinyl ether-maleic anhydride copolymer, ethylene, maleic anhydride copolymer, and vinyl acetate-maleic anhydride copolymer. Examples include a polymer, an isobutylene-maleic anhydride copolymer, a styrene-maleic anhydride copolymer, and the like.

Examples of acrylic acid copolymers, methacrylic acid copolymers, or crotonic acid copolymers include methyl acrylate.
Acrylic acid copolymer (hereinafter abbreviated as "copolymer") Ethyl acrylate-acrylic acid, Methyl acrylate-methacrylic acid, Methyl methacrylate-acrylic acid, Methyl methacrylate-methacrylic acid, Methyl acrylate-acrylamide -acrylic acid, acrylonitrile-acrylic acid, acrylonitrile-methacrylic acid, hydroxyethyl acrylate-acrylic acid, hydroxyethyl methacrylate-methacrylic acid, vinyl acetate-acrylic acid, vinyl acetate-methacrylic acid, acrylamide-acrylic acid,
Examples include copolymers of acrylamide-methacrylic acid, methacrylamide-acrylic acid, methacrylamide-methacrylic acid, and acetic acid and nyl-crotonic acid.

Examples of vinylbenzenesulfonic acid copolymers or 2-acrylamido-2-methyl-propanesulfonic acid copolymers include methyl acrylate-vinylbenzenesulfonic acid (or salts thereof) copolymers, and vinyl acetate-vinylbenzenesulfonic acid copolymers. Polymer, acrylamide-vinylbenzenesulfonic acid copolymer, acryloylmorpholine-vinylbenzenesulfonic acid copolymer, vinylpyrrolidone-vinylbenzenesulfonic acid copolymer, vinylpyrrolidone-2-acrylamide-2-methyl-propanesulfonic acid copolymer Examples include polymers.

As the nonionic polymer, both natural and synthetic polymers can be used, and examples thereof include those having an -OH group.

Specific nonionic semi-synthetic polymers include hydroxyethyl cellulose, methyl cellulose, pullulan (non-crystalline, easily water-soluble polymer made from starch by microbial fermentation method), soluble starch, oxidized Examples include starch, and synthetic products include polyvinyl alcohol.

Examples of cationic polymers include cation-modified polyvinyl alcohol, and examples of amphoteric polymers include gelatin.

Examples of low-molecular emulsifiers include anionic, cationic, nonionic, and amphoteric ones, but anionic ones are preferred, and among them, organic sulfuric acids having a total carbon number of 1 to 14 are preferred. Or L of organophosphoric acid
i'', Ha'', K'', NH4+ salts are preferred, specifically sodium vinylsulfonate, sodium benzenesulfonate, sodium benzenesulfinate, p-
Sodium toluenesulfonate, p-) Sodium toluenesulfinate, Sodium p-vinylbenzenesulfonate, Sodium p-1-amylbenzenesulfonate,
Naphthalene-α-sodium sulfonate, Naphthalene-β
-Sodium sulfonate, 2-methylnaphthalene-6-sodium sulfonate, 2,6-dimethylnaphthalene-8
-sodium sulfonate, sodium 2゜6-dimethylnaphthalene-3-sulfonate, sodium 1-naphthol-4-sulfonate, sodium benzene-m-disulfonate, funnel oil, sodium diphenylphosphate, sodium phenylphosphonate, Examples include sodium di-n-butyl phosphate and sodium di-i-7 milphosphate.

In the present invention, the above-mentioned high-molecular or low-molecular emulsifiers may be used alone or in combination, but preferred are high-molecular emulsifiers, and among these, polymers or copolymers composed of anionic monomer units are preferred. , a copolymer of an anionic monomer unit and a hydrophobic heptamer unit is preferable, and a copolymer of acrylic acid and an acrylic ester, especially an acrylic acid-methyl acrylate copolymer, can easily stabilize emulsified particles. Preferably used for 8
I can stay.

In addition, the emulsifier as mentioned above is added in water or a hydrophilic medium at a concentration of 0.1
It is preferable to contain % or more, and it is easy to prepare an emulsion.
It is more preferable to contain 1% or more from the viewpoint of stabilizing the emulsion. The upper limit of the amount used is determined by the viscosity of the system, the capsule preparation device, etc., but is generally kept at 20% or less.

In the present invention, so-called acid catalysts commonly used in the field of aminoaldehyde resin production, such as formic acid, acetic acid, citric acid, oxalic acid, para-toluenesulfonic acid, hydrochloric acid, and sulfuric acid, are used to maintain the reaction system acidic. .

The reaction conditions in the present invention vary depending on the type of initial condensate used and the intended use of the capsules, and are not generally determined, but are preferably at 40°C or higher for 1 hour or more, particularly preferably at 60°C or higher.
It is preferable to maintain it for at least 1 hour, especially for at least 3 hours, under conditions of 0°C or higher.In particular, when this is used as microcapsules for pressure-sensitive copying paper, the temperature is 70°C or higher or the pH is 6.0 or lower. , maintained at 60°C or higher for 2 hours or more.Deaf people are preferred.

In the present invention, the hydrophobic core substance to be encapsulated in the microcapsules is not particularly limited, but the following substances are exemplified.

Animal oils such as fish oil, lard oil, etc., vegetable oils such as olive oil, peanut oil, linseed oil, soybean oil, castor oil, etc., mineral oils such as petroleum, kerosene, xylene, toluene, etc., alkyl-substituted diphenylalkanes, alkyl-substituted naphthalene, biphenylethane, methyl salicylate, diethyl adipate, di-n-propyl adipate,
Synthetic oils such as di-n-butyl adipate, di-methyl phthalate, diethyl phthalate, di-n-propyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate, etc. A solution in which an electron-donating color former, an electron-accepting color developer, a ligand compound, an organic metal salt, etc. are dissolved in a water-insoluble or substantially water-insoluble liquid or the above-mentioned synthetic oil;
Water-insoluble metal oxides and salts, fibrous materials such as cellulose or asbestos, water-insoluble synthetic polymeric materials, minerals, pigments, glasses, fragrances, flavoring agents, fungicidal compositions, Physiological compositions, fertilizer compositions.

In order to more specifically explain the method of the present invention, examples will be described below with reference to its application to the field of pressure-sensitive copying paper, but the present invention is of course not limited thereto. Further, unless otherwise specified, parts and % in the examples represent parts by weight and % by weight, respectively.

"Example" Example 1 Microcapsule IL 5 parts of crystal violet lactone and 100 parts of alkylnaphthalene (trade name: KMC oil, manufactured by Kureno Kagaku Co., Ltd.)
7 parts of an initial condensate containing hexamethoxyhexmethylol melamine as a main component (trade name: Cymel 350, manufactured by Mitsui Toatsu Chemical Co., Ltd.) was added and mixed into the solution obtained by heating and dissolving 125°C of the solution. A phase liquid was obtained.

Separately, polyacrylic acid (trade name Aron A-IQH, manufactured by Toagosei Chemical Industry Co., Ltd.) was placed in a stirring mixing container equipped with a heating device.
200 parts of a 1.25% aqueous solution of was added thereto, and a 20% aqueous sodium hydroxide solution was added thereto to adjust the pH to 4.7, thereby preparing an aqueous medium for capsule production. After heating this aqueous medium to 80° C., the above-mentioned heated internal phase liquid was added thereto with stirring, and emulsified and dispersed at 80° C. so that the average particle size was 6.0 μm.

Separately, melamine 10
part and 30 parts of a 37% formaldehyde aqueous solution, and
After stirring for 15 minutes at ℃ to prepare a water-soluble melamine-formaldehyde initial condensate, this liquid was emulsified and dispersed at 40°C.
After a few minutes, it was added to the above emulsion. This system was then heated to 85°C.
The temperature was further increased to 95° C. and maintained at this temperature for 2 hours.

Next, 0.05N-
Hydrochloric acid was gradually added over 5 hours to adjust the pH of the system to 3.6, and then 10 parts of urea and 1 part of acidic sodium sulfite were added as treatment agents for deformaldehyde treatment, and then the pH of the system was adjusted to 3.6 at 95°C. After holding for a period of time, a milky white capsule dispersion was obtained.

120 parts of wheat starch powder was added to the obtained capsule dispersion,
Add and mix 20 parts of gelatinized starch, add water to make a solid content concentration of 25% to make a capsule coating solution, and coat it on a 40 g/ld base paper with an air knife coater so that the solid content becomes 4 g/rrr. did.

', 65 parts of aluminum hydroxide, 20 parts of zinc oxide, 3.5-
Mixture of zinc di(α-methylbenzyl)salicylate and α-methylstyrene/styrene copolymer (melt ratio 80/
20) Add 20 parts (solid content) of carboxy-modified styrene-butadiene copolymer latex to a dispersion obtained by grinding 15 parts of polyvinyl alcohol aqueous solution (solid content) and 300 parts of water in a ball mill for 24 hours. In addition, the prepared color developer coating liquid was smeared onto the coated surface of the above-mentioned coated paper using an air knife coater so that the solid content was 5 g/cd to prepare a single pressure-sensitive copying paper.

When printed on the single pressure-sensitive copying paper obtained as described above using a typewriter without ribbon, a clear colored image was obtained. Separately, this copy paper was treated at 100° C. for 3 hours, but no stains were observed on the sheet, indicating that it had good core material retention.

Example 2 A capsule dispersion was prepared in the same manner as in Example 1, except that 3 parts of an initial condensate (Cymel 350) containing hexamethoxyhexamemethylolmelamine as the main component was added and mixed to form an internal phase liquid. However, as a result of similarly preparing and evaluating a single pressure-sensitive copying paper, it was found to have good core substance retention.

Example 3 The same procedure as in Example 1 was carried out, except that an aqueous solution of a copolymer of acrylic acid and methyl acrylate in a molar ratio of 85:15 was used instead of an aqueous solution of polyacrylic acid (Aron A-10H) as an emulsifier. A capsule dispersion was prepared, and a single pressure-sensitive copying paper was similarly prepared and evaluated. As a result, it had good core material retention.

Example 4 Trimethylolmelamine i, 1) 14.9 parts of a 37% formalin aqueous solution was diluted with water to 100
%, and then P H6 with 0.1 N-NaOH aqueous solution.
23.1 parts of melamine was added, and the temperature was gradually raised to 75° C. while stirring to completely dissolve the melamine. Then, after holding at 75°C for 5 minutes,
The mixture was rapidly cooled to 0° C., stirring was stopped, and the mixture was allowed to stand for one day and night, and white crystals were precipitated.

The crystals were filtered, washed several times with methanol, and air-dried to obtain 25.7 parts of trimethylolmelamine crystals.

Amount of triethoxytrimethylolmelamine 1 Add 25.7 parts of trimethylolmelamine and 300 parts of ethanol into a separable flask equipped with a reflux condenser, and heat to 78°C.
While stirring, 5 parts of 1N-HCl was added to dissolve the trimethylolmelamine crystals. 78℃ for 30 minutes after dissolution
5 parts of 1N-NaOH aqueous solution was added.

Next, this was cooled, filtered to remove trace impurities, concentrated under reduced pressure at a temperature of 55°C to 60 parts, added with 30 parts of xylene, further concentrated under reduced pressure to 40 parts, and triethoxytrimethylol. A xylene solution of melamine was obtained.

Preparation of microcapsules - Oil-soluble melamine-formaldehyde Instead of Cymel 350, a xylene solution of triethoxytrimethylolmelamine prepared as described above was used as the solid content of 7.
A capsule dispersion was prepared in exactly the same manner as in Example 1, except that a portion of the capsule dispersion was used, and a single pressure-sensitive copying paper was similarly prepared and evaluated. As a result, the core material was good, although slightly inferior to that in Example 1. It was found that it has retention properties.

Example 5 170 parts of a 1.8% aqueous solution of a styrene-maleic anhydride copolymer (trade name Suflibuset 520, manufactured by Monsando) was added to a stirring mixing container equipped with a heating device, and 0.0
．． 6 A capsule dispersion was prepared in the same manner as in Example 1, except that 2N-acetic acid was added to adjust the pH to 4.8 to prepare an aqueous medium for capsule production. As a result of preparation and evaluation, it was found that it had good core substance retention.

"Function" According to the present invention, microcapsules with excellent retention of capsule core substances can be easily and stably produced.

Patent applicant: Kanzaki Paper Co., Ltd. or

Claims (5)

[Claims] (1) In a method for producing microcapsules in which a hydrophilic aldehyde-based resin-forming material contained in water or a hydrophilic medium is polycondensed to cover a hydrophobic core substance, the degree of formaldehyde substitution in the hydrophobic core substance is 40-100%
A method for producing microcapsules, which comprises containing an oil-soluble melamine-formaldehyde initial condensate having a degree of alkylation of 80 to 100%, a degree of hydrophobicity of 4 to 9, and an alkyl group having an average carbon number of 1 to 3. (2) The production method according to claim (1), wherein the oil-soluble melamine-formaldehyde initial condensate is an initial condensate containing hexamethoxyhexamethylolmelamine. (3) The hydrophilic aldehyde resin forming material is melamine.
The manufacturing method according to claims (1) and (2), which is at least one of a formaldehyde initial condensate and a urea-melamine-formaldehyde initial condensate. (4) Claim No. 1 in which water or a hydrophilic medium contains as an emulsifier at least one of a polymer or copolymer composed of anionic monomer units, and a copolymer of anionic monomer units and hydrophobic monomer units. )
- The manufacturing method described in (3). (5) The manufacturing method according to claim (4), wherein the emulsifier is an acrylic acid-methyl acrylate copolymer.