JPH02139030A - Manufacture of microcapsule - Google Patents

Abstract

PURPOSE:To minimize generation of an encapsulated core material by introducing vapor directly into an emulsification dispersant and forming a microcapsule with a heating process when the surface of a hydrophobic oily liquid is covered with a synthesized polymer wall film. CONSTITUTION:A hydrophobic oily liquid is emulsified and dispersed in a hydrophilic liquid in the presence of an emulsifier, and a synthesized polymer wall film is formed on the surface of a liquid droplet to cover the surface of the hydrophobic oily liquid. In this case, vapor is directly introduced into the dispersed liquid when the surface of the hydrophobic oily film is covered with the synthesized polymer wall film, and then the dispersed liquid is thermally processed. If heated vapor is directly introduced into the capsulated dispersed liquid and the liquid is heated, the temperature is increased in a short time and uniformly, so that no giant or flocculated capsules generate, and capsules with sufficient wall strength can be formed efficiently.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method for manufacturing microcapsules encapsulating a hydrophobic oily liquid, and particularly to a method for industrially and extremely efficiently manufacturing microcapsules having a synthetic polymer wall. It's about how to do it.

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

Various methods are known for producing microcapsules, such as coacervation, interfacial polymerization, and 1n-situ polymerization, but the encapsulation method of the present invention is particularly suitable for interfacial polymerization and 1n-situ polymerization. This is related to the improvement of.

The interfacial polymerization method is an encapsulation method in which a synthetic polymer wall M such as polyurea or polyurethane is formed at the interface between a hydrophobic liquid and a hydrophilic liquid. A method for obtaining capsules having a polyurea wall by reacting with polyurea and amines is described.

For a similar encapsulation method, see Japanese Patent Publication No. 47-43740.
No., Special Publication No. 49-45133, Special Publication No. 52-1350
No. 8, JP-A-56-10489, JP-A-56-158
No. 36, JP-A-58-40142, JP-A-62-19
Various proposals have been made in No. 3641, Japanese Unexamined Patent Publication No. 63-1) No. 6736, etc.

In addition, a method for manufacturing capsules having an aminoaldehyde polycondensed resin wall film by a 1n-situ polymerization method is described, for example, in JP-A-53-84881, in which melamine and formaldehyde are combined in the presence of an ethylene/maleic anhydride copolymer. A method for obtaining capsules by reacting is described.

Regarding the encapsulation method using similar 1n-situ polymerization method, JP-A-55-92135, JP-A-56-512
No. 38, JP-A-56-58536, JP-A-56-10
No. 2934, JP-A-57-56293, JP-A-58-
No. 8689, JP-A No. 68045, JP-A No. 60-
216838, JP 60-238140, JP 61-1) 138, JP 61-25635, JP 621451, JP 62-19238, JP 62-56778, Various proposals have been made in Japanese Unexamined Patent Publication No. 62-277146, etc.

``Problems to be Solved by the Invention'' However, the polyurea/polyurethane wall capsules and aminoaldehyde resin wall capsules that have been proposed and used in large numbers have the following problems, so improvements still need to be made. There is room left.

In other words, the polyvalent isocyanate compound used in the interfacial polymerization method is highly reactive and therefore easily reacts with compounds having active hydrogen, such as water. The overall viscosity increases significantly, and in some cases, the entire system may gel, resulting in a capsule wall that is not dense and has poor heat resistance and light resistance. Furthermore, if the stability of the emulsion is poor, there is a risk that giant capsules or agglomerated capsules with a size of several hundred micrometers will be produced.

On the other hand, when aminoaldehyde resin wall capsules obtained by the 1n-situ polymerization method are used, for example, in pressure-sensitive copying paper, the colorless basic dye that is the core material may become colored, or the aminoaldehyde resin wall capsules on the surface of the core material may become colored. The resin is not deposited sufficiently, resulting in capsules with poor heat resistance, moisture resistance, solvent resistance, etc., and problems such as formation of giant capsules and unencapsulated core material remaining in the system. .

Therefore, the purpose of the present invention is to improve the above-mentioned problems,
An object of the present invention is to provide a method for industrially and extremely efficiently producing microcapsules having excellent properties.

``Means for Solving the Problems'' The present invention emulsifies and disperses a hydrophobic oily liquid in a hydrophilic liquid in the presence of an emulsifier, forms a synthetic polymer wall film at the droplet interface, and produces a hydrophobic oily liquid. A method for producing microcapsules that envelops a surface, which is characterized by directly introducing water vapor into the dispersion liquid and heating it when enveloping the surface of a hydrophobic oily liquid with a synthetic molecular wall film. This is a method for producing microcapsules.

"Operation" The method of the present invention is a method in which water vapor is directly introduced into the dispersion liquid and heated when the surface of the hydrophobic oily liquid is covered with a synthetic polymer wall film as described above. The encapsulation step is not particularly limited, and may be prepared according to various methods as described above.

For example, capsule dispersions having polyurea and/or polyurethane walls are usually prepared by emulsifying and dispersing a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid containing an emulsifier.

Examples of emulsifiers include polyvinyl alcohol, anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, gelatin, gum arabic, carboxymethylcellulose, polyacrylamide, hydroxyethylcellulose, methylcellulose, ethylcellulose, cellulose acetobutyrate, hydroxymethylcellulose, polyvinylpyrrolidone, montmorillonite, and lignin. Sulfonic acid, polystyrene sulfonic acid and its copolymers, hydrolysates of maleic anhydride copolymers, polyacrylic acid and its copolymers, polymethacrylic acid and its copolymers, polyacrylamidomethylpropanesulfonic acid and its copolymers One or more types of polymers and salts thereof are used.

Examples of polyvalent isocyanates include m-phenylene diisocyanate, p-phenylene diisocyanate, 2
．． 6-) lylene diisocyanate, 2.4-) lylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-isocyanate, 3
, 3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4
'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, 4
, 4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1゜2-diisocyanate, butylene-1,2-diisocyanate, ethyridine diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1, 4-diisocyanate, isophorone diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethyridine diisothiocyanate, dimethylsilyl diisocyanate, vinylmethylsilyl isocyanate,
Diisocyanates or diisothiocyanates such as 4-isocyanatemethyl-1,8-octamethylene diisocyanate, lysine diisocyanate, bis(isocyanatemethyl)cyclohexane, dicyclohexylmethane diisocyanate, trimethylhexamethylene diisocyanate, 4.4', 4'-1- Riphenylmethane triisocyanate, toluene-2゜4.6-1 diisocyanate, tris(isocyanate phenyl) thiophosphate, methylsilyl triisocyanate, vinylsilyl triisocyanate, phenyldilyl triisocyanate, octadecylsilyl triisocyanate, methoxysilane triisocyanate Isocyanate, butoxysilane triisocyanate, octylsilane triisocyanate, 2,
6-diycyanatecaproic acid-β-isocyanate ethyl ester, 2,6-diycyanatecaproic acid-γ-diisocyanate propyl ester, 2,6-diycyanatecaproic acid-2-methyl-β-incyanate ester, Hexamethylene diisocyanate 3
Triisocyanates such as polymethylene polyphenylisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, tetraisocyanate silane, hexamethylene diisocyanate and isophorone diisocyanate. polyvalent isocyanates such as biuret-type polyisocyanates containing groups, and these polyvalent isocyanates [to be converted into compounds having hydrophilic groups such as polyvalent amines, polyvalent carboxylic acids, polyvalent thiols, polyvalent hydroxy compounds, and epoxy compounds. Examples include those added.

Hydrophobic liquids include, for example, cottonseed oil, hydrogenated cuphenyl, hydrogenated terphenyl RM fi1, alkyl biphenyl, alkylnaphthalene, diarylalkane, kerosene, paraffin, naphthenic oil, dibasic acid esters such as phthalate esters, etc. Alternatively, one or more synthetic hydrophobic liquids are used.

The amount of the isocyanate compound added to the hydrophobic liquid is from 0.02 to 100 parts by weight of the hydrophobic liquid.
A range of 60 parts by weight is effective, more preferably 0.
The amount is adjusted within the range of 0.03 to 40 parts by weight.

Note that polyvalent amines may be added to the hydrophilic liquid depending on the desired capsule quality.
Any compound having two or more Nl2 or Nl2 groups in its molecule and capable of being dissolved or dispersed in a hydrophilic liquid forming a continuous layer can be used. Specific substances include, for example, diethylenetriamine, triethylenetetramine, ■
, aliphatic polyvalent amines such as 3-propylene diamine and hexamethylene diamine, adducts of aliphatic polyvalent amines with varnish compounds, alicyclic polyvalent amines such as piperazine, etc.
3.9-bis-aminopropyl-2°4, 8. 10
Examples include heterocyclic diamines such as -tetraoxaspiro-(5,5)undecane.

The amount of the polyvalent amine to be added is appropriately determined depending on the type and amount of the polyvalent isocyanate used, the desired strength of the capsule wall film, etc., but it is not more than 0.000% based on 100 parts by weight of the polyvalent ixyanate. It is desirable to adjust the amount within a range of about 1 to 200 parts by weight, more preferably about 1 to 100 parts by weight.

On the other hand, a capsule dispersion having an aminoaldehyde polycondensation resin wall is also prepared by a conventional method, and various anionic, nonionic, cathine, or amphoteric water-soluble polymers are used as emulsifiers.

As an anionic polymer, for example, -〇〇〇-5o=
Natural polymers such as gum arabic, carrageenan, sodium alginate, pectic acid, gum tragacanth, almond gum, agar, etc., having -0PO-1- groups, carboxymethylcellulose, sulfated cellulose, sulfated methylcellulose, carboxymethylated starch, phosphorus Oxidized starch, semi-synthetic polymers such as ligninsulfonic acid, maleic anhydride (including hydrolyzed) copolymers, acrylic acid,
Methacrylic acid-based or crotonic acid-based polymers and copolymers, vinylbenzenesulfonic acid-based or 2-acrylamido-2-methyl-propanesulfonic acid-based polymers and copolymers, and parts of such polymers and copolymers. Examples include synthetic polymers such as amides or partially esterified products, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, and phosphoric acid-modified polyvinyl alcohol.

More specifically, maleic anhydride copolymers (including hydrolyzed ones) include methyl vinyl ether-maleic anhydride copolymers, ethylene-maleic anhydride copolymers, and vinyl acetate-maleic anhydride copolymers. Polymer, methacrylamide-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, etc., and examples of acrylic acid copolymer, methacrylic acid copolymer, or crotonic acid copolymer include acrylic acid copolymer, methacrylic acid copolymer, and crotonic acid copolymer. Methyl acrylate-acrylic acid copolymer (hereinafter referred to 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,
Examples include copolymers of acrylamide-acrylic acid, acrylamide-methacrylic acid, methacrylamide-acrylic acid, methacrylamide-methacrylic acid, vinyl acetate-crotonic acid, vinylbenzenesulfonic acid, or 2-acrylamide-2-methyl. - Propanesulfonic acid copolymers include methyl acrylate-vinylhenzenesulfonic acid (or its salt) copolymer, vinyl acetate-vinylbenzenesulfonic acid copolymer, acrylamide-vinylbenzenesulfonic acid copolymer, Examples include acryloylmorpholine-vinylbenzenesulfonic acid copolymer, vinylpyrrolidone-vinylbenzenesulfonic acid copolymer, and vinylpyrrolidone-2-acrylamide-2-methyl-propanesulfonic acid copolymer.

Examples of nonionic polymers include semi-synthetic polymers such as hydroxyethylcellulose, methylcellulose, pullulan, soluble starch, and oxidized starch having -OH groups, and synthetic polymers such as polyvinyl alcohol, and examples of cationic polymers include Examples include cation-modified polyvinyl alcohol. Furthermore, examples of amphoteric polymers include gelatin and the like.

The aminoaldehyde resin used to cover the surface of the hydrophobic core material is obtained by polycondensing one or more amines such as urea and melamine with one or more aldehydes such as formaldehyde, geltaraldehyde, and furfural. It may be modified with glycine, sulfamic acid, methanol, etc. These are preferably used in the form of an initial condensate in view of the density of the capsule wall, but they may also be used in the form of a hexamer.

Among them, melamine-formaldehyde resins whose main starting materials are melamine and formaldehyde, and melamine-urea-formaldehyde resins whose main starting materials are melamine, urea, and formaldehyde are excellent in the uniformity and physical strength of the capsule wall membrane. It is particularly preferably used because capsules with good core material retention properties can be obtained.

When preparing a capsule dispersion comprising an aminoaldehyde polycondensation resin wall film, the polycondensation reaction is carried out by adjusting the capsule manufacturing system to an acidic range, preferably pH 3 to 6.

Therefore, in the method of the present invention, when the surface of the hydrophobic oily liquid of the capsule production system thus prepared is covered with a synthetic molecular wall film, heat treatment is performed by directly introducing water vapor into the dispersion liquid. administered.

Even with conventional encapsulation methods, heating the capsule manufacturing system accelerates the reaction and produces a dense capsule wall.
The capsule dispersion is heated to a temperature of about 50 to 100°C, but in the conventional method, the capsule dispersion is heated by circulating a heat medium or water vapor through the jacket or coiled pipe of the reaction tank, so it takes a long time to raise the temperature. However, the stability of the emulsion is affected on the inner wall surface of the reaction tank, resulting in defects that tend to produce giant capsules or agglomerated capsules. Further, even if sufficient stirring is performed, deposits tend to adhere to the walls of the tank, which poses a problem for continuous production of capsules on an industrial scale.

However, since the method of the present invention involves directly introducing heating steam into the capsule dispersion to heat it, the temperature can be raised rapidly within a short period of time.1. Since the temperature is raised uniformly, there is almost no generation of giant capsules or agglomerated capsules, and capsules with sufficient wall strength can be efficiently obtained. In addition, there is no deposit on the walls of the reaction tank, making it possible to produce capsules with extremely high industrial efficiency.

Of course, there is little coloring of the dispersion observed in the aminoaldehyde polycondensation resin wall capsules, and almost no unencapsulated core material is observed. In the preparation of aminoaldehyde polycondensation resin wall capsules, after the capsules have been cured, steam evaporation may be continued to remove residual formaldehyde, if necessary.

Thus, according to the method of the present invention, by simply mixing the capsule-forming materials and providing simple reaction conditions, the wall resin is efficiently deposited on the surface of the capsule core material, resulting in heat resistance, temperature resistance,
Capsules with excellent solvent resistance etc. are formed.

The microcapsules prepared by the method of the present invention are
Various pharmaceuticals, fragrances, paints, pesticides, adhesives, liquid crystals, foods,
It is suitable for encapsulating rust preventive agents, toners, etc., and is particularly useful for applications such as printing ink and pressure-sensitive copying paper.

"Example" In order to explain the present invention more specifically, examples for preparing microcapsules for pressure-sensitive copying paper will be described below, but the present invention is of course not limited to these. do not have. In addition, "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Diisopropylnaphthalene (trade name 1K-1) in which 7 parts of polymethylene polyphenyl polyisocyanate (trade name: Millionate MR400, manufactured by Nippon Polyurethane Industries, Ltd.), 4 parts of hexamethylene diisocyanate, and 5 parts of crystal violet lactone were dissolved. 3. Manufactured by Kureha Chemical Co.)
105 parts of polyvinylbenzenesulfonic acid (trade name, VER
The mixture was added to 200 parts of a 5% aqueous solution of SA-Tl2O3 (manufactured by NSC) and emulsified and dispersed.

Next, 1 part of diethylenetriamine was added, heated steam was blown directly into the system while stirring, and the temperature was raised to 95°C.
After being kept as it was for 1 hour, it was cooled to obtain a capsule dispersion.

There was no occurrence of deposits on the reaction vessel, and capsule dispersions could be repeatedly prepared in a stable manner.

Example 2 A 35% aqueous solution (25°C,
p+1)1.9. viscosity 400 cps) 30 parts water 170 parts
The mixture was prepared with acetic acid to give a pi of 4.8, and the resulting mixture was used as a hydrophilic medium for capsule production.

To this was added 105 parts of diisopropylnaphthalene (trade name: Ni-1) 3, manufactured by Kureha Chemical Co., Ltd., in which 5 parts of crystal violet lactone was dissolved, and the mixture was emulsified and dispersed so that the average particle size was 5 μm.

Next, 25 parts of methylated methylolmelamine initial condensate (trade name: Beckamine APM, manufactured by Dainippon Ink Chemical Co., Ltd.) was added, and while stirring was continued, heated steam was blown directly into the system to raise the temperature to 95°C. After being kept as it was for 1 hour, it was cooled to obtain a milky white capsule dispersion.

There was no occurrence of deposits on the reaction vessel, and a capsule dispersion liquid could be stably prepared.

Comparative Example 1 The same emulsion as in Example 1 was placed in a reaction vessel equipped with a shell and a jacket, and the temperature of the system was raised to 95°C by passing steam through the jacket, maintained for 1 hour, and then cooled. A capsule dispersion was obtained.

A large amount of deposits were observed on the inner wall of the reaction vessel, and it was not possible to continuously prepare a capsule dispersion without washing.

Comparative Example 2 An emulsion exactly the same as in Example 1 was placed in a reaction vessel with a jacket, and the temperature of the system was raised to 95°C by passing hot water at 95°C through the jacket, and the temperature was maintained at that temperature for 1 hour. , and cooled to obtain a capsule dispersion.

Adherence was observed on the inner wall of the reaction vessel, and it was not possible to stably and repeatedly prepare a capsule dispersion.

Comparative Example 3 The same emulsion as in Example 2 was placed in a reaction vessel with a jacket, and the temperature of the system was raised to 95°C by passing water vapor through the jacket, maintained for 1 hour, and then cooled to disperse capsules. I got the liquid.

The capsule dispersion was slightly blue colored. A large amount of deposits were observed on the inner wall of the reaction vessel, and it was not possible to continuously prepare a capsule dispersion without washing.

Comparative Example 4 The same emulsion as in Example 2 was placed in a reaction vessel with a jacket, the temperature of the system was raised to 95°C by passing hot water at 95°C through the jacket, and the temperature was maintained at that temperature for 1 hour. , and cooled to obtain a capsule dispersion.

Adherence was observed on the inner wall of the reaction vessel, and it was not possible to stably prepare a capsule dispersion.

The capsule dispersion thus obtained was diluted to a concentration of 30%, applied to the surface of a CF plate using a wire bar No. 18 (product name: KS Copy Bright, manufactured by Kanzaki Paper Industries), and dried. . The following performance comparison tests were conducted using this paper and each capsule dispersion, and the results are listed in Table 1.

[Core material retention]

The test paper was treated at 120° C. for 5 hours, and the degree of color development on the coated surface was measured using a Macbeth densitometer (filter: Visual). The better the core substance retention, the lower the color density on the coated surface (smaller the numerical value).

[Unencapsulated core material]

When the capsule dispersion liquid is applied to the CF surface of the lower paper and dried, if there is a hydrophobic core material that is not encapsulated, it will appear as spot-like stains, so the number of spot-like stains existing on an area of 15 cm x 25 cm was measured. .

[Giant capsules, aggregates]

The capsule dispersion was processed through a 200 mesoscreen and the weight of the residue was expressed as a percentage (%) of the total weight of the capsules.

Table 1 "Effects" As is clear from the results in Table 1, the microcapsules obtained by the method of the present invention have less occurrence of unencapsulated core material, giant capsules, and aggregates, and have good core material retention. It was an excellent capsule. Furthermore, capsules could be continuously and stably manufactured on an industrial scale without any deposits on the reaction tank.

Claims (3)

[Claims] (1) A method for producing microcapsules in which a hydrophobic oily liquid is emulsified and dispersed in a hydrophilic liquid in the presence of an emulsifier, and a synthetic polymer wall film is formed at the droplet interface to enclose the surface of the hydrophobic oily liquid. A method for producing microcapsules, characterized in that when the surface of a hydrophobic oily liquid is covered with a synthetic polymeric wall film, water vapor is directly introduced into the dispersion liquid for heating treatment. (2) The manufacturing method according to claim (1), wherein the synthetic polymer wall film is a polyurea or polyurethane wall film. (3) The manufacturing method according to claim (1), wherein the synthetic polymer wall film is an aminoaldehyde polycondensation resin wall film.