JPS60190228A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To obtain a capsule having good quality, by allowing a surfactant to be present in an acidic aqueous solution of an acrylic acid/styrenesulfonic acid/ acrylonitrile three-component copolymer. CONSTITUTION:An aqueous solution of an anionic three-component copolymer consisting of 5-85mol% of acrylic acids, 1-50mol% of styrenesulfonic acids and 5-80mol% of acrylonitrile is obtained. After a nonionic surfactant such as sorbitan fatty acid ester is allowed to be present in said aqueous anionic three- component copolymer solution, a hydrophobic core substance to be encapsulated is emulsified and dispersed in said aqueous solution. Next, aldehyde is added under stirring and reaction is performed at 30-95 deg.C for 0.5-6hr to form a capsule wall film. Thereafter, cooling and/or pH-adjustment are performed if necessary to complete encapsulation.

Description

[Detailed description of the invention] The present invention relates to a cell manufacturing method.

In recent years, with the remarkable progress in manufacturing technology, microcapsules have been applied to pharmaceuticals, agriculture, fragrances, cosmetics, foods, and dyes, and are now widely used in various fields including pressure-sensitive copying paper. There is.

Generally, methods for producing microcapsules include physical methods,
Mechanical methods, four methods, physicochemical methods, and chemical methods are known, and are selected and used as appropriate depending on the purpose.

With physical and mechanical methods, the particle size of the capsules obtained is large and the density of the wall membrane is insufficient, so the uses of microcapsules produced by these methods are limited. On the other hand, with physicochemical methods and chemical methods, it is easy to control the particle size of capsules arbitrarily, and it is
It is used over a wide range of areas because it can be easily manufactured even to a small degree, and capsules with a dense wall membrane can be obtained. As a physicochemical method, the coacervation method using gelatin as a membrane material is known.
Currently, it is applied in the widest range of fields, but since gelatin, a natural product, is used as the membrane material, it is expensive and
It has disadvantages such as being easily attacked by microorganisms, the produced capsules having poor water resistance, difficulty in obtaining a highly concentrated capsule slurry, and the encapsulation process being complicated. The chemical method involves a polymerization reaction between a hydrophobic monomer and a hydrophilic monomer at the interface between a hydrophobic core substance and an aqueous phase to form polyamide,
An interfacial polymerization method in which a wall film such as epoxy resin, polyurethane, or polyurea is formed, and an in-method in which a wall film such as an amino resin is formed around the core material by polymerizing only one of the hydrophobic core material or the aqueous phase. -Situ polymerization method polymerization agent.

Since the interfacial polymerization method uses highly reactive or highly toxic materials such as incyanates, acid chlorides, and epoxy compounds as membrane materials, it is difficult to control the polymerization reaction, and substances with active hydrogen cannot be used as core materials. It has drawbacks such as the high cost of the membrane material itself. On the other hand, in − s
The itu polymerization method is easier to handle than the interfacial polymerization method, so it is more practical.
No. 95, Special Publication No. 1972-28165, Special Publication No. 1977-
No. 16049, JP-A-58-84881, JP-A-54
- Many inventions such as No. 49984 have been filed. i
Most of the materials used to form synthetic resins, such as acrylic ester resins, amino resins, and polyester resins, are used as membrane materials for n-situ polymerization.Among them, amine resins are cheap and easily available. It has the advantages of not requiring any special catalyst during the polymerization reaction, and that the polymerization reaction can be carried out in a relatively short time. However, although the capsule wall membrane obtained by this method has excellent water resistance, it has poor density, and it is difficult to emulsify and disperse the core material sufficiently. Moreover, it also has drawbacks such as difficulty in depositing it stably.

Generally, microcapsules have a particle size of several microns to 100 microns, but when the particle size becomes large, they are exposed to external physical forces and the capsules break off and turn brown, so they are usually pressure sensitive. A few microns to 20 microns for applications such as copy paper, adhesives, fragrances, etc.
A moderate amount is considered practical.

Microcapsules with a particle size of 4 to 5 μm or less are sufficiently small and are excellent in terms of resistance to breakage during handling, but their manufacturing method is difficult and has been considered industrially difficult. That is, 4
In order to produce microcapsules having a particle size of ~5μ or less, it is necessary to make the hydrophobic core material sufficiently small at the time of emulsification and dispersion, but for this purpose it must be able to withstand mechanical forces. Along with this, it is difficult to think that applying a strong mechanical force for a long period of time, even though it requires a lot of energy, will have a positive effect on the emulsified particles.

In the interfacial polymerization method, as the particle size decreases, the surface area increases, so at the interface between the hydrophobic core material and the aqueous phase, hydrophobic
This increases the amount of contact between the hydrophilic monomer and the reaction rate, making it difficult to use it industrially. In addition, the coacervation method has the disadvantage that when the particles become small, they cause aggregation during coacervation, and it is difficult to obtain capsules with a high concentration.

As a means to solve these problems, in -5 itu
Many methods of producing microcapsules using the oxidation method have been studied, and various anionic polymer electrolytes have been announced as system modifiers in order to improve emulsification dispersibility and produce good capsules.

For example, Japanese Patent Publication No. 54-1.6949, Japanese Patent Publication No. 58-8
No. 4881, JP-A-58-84882, JP-A-58-
No. 84888 discloses a method of using ethylene/maleic anhydride copolymer, methyl vinyl ether/maleic anhydride copolymer, polyacrylic acid, etc. as an anionic polymer electrolyte as a system modifier. With this method, the emulsification dispersibility of the hydrophobic core material has been improved compared to the conventional method, and it has become possible to obtain a highly concentrated capsule slurry, but it takes time to emulsify and disperse, and there are problems with emulsion stability. The resulting capsule slurry has a high viscosity, and it takes a long time to dissolve particularly effective ethylene/maleic anhydride copolymers and methyl vinyl ether/maleic anhydride copolymers.

The present inventors have developed a method for producing microcapsules that does not have the above-mentioned drawbacks. (8) and maintains the stability of the emulsion, (4) the encapsulation process is simple and requires a short reaction time, (5)
) Excellent wall membrane strength, water resistance, heat resistance, and denseness, (6
) As a result of research aimed at establishing a method for manufacturing microcapsules that would yield capsule slurry with high concentration and low viscosity, we discovered that acrylic acids/styrene sulfonic acids/acrylonitrile terpolymer was used as an anionic polymer electrolyte. It has been discovered that the above object can be achieved very effectively by using surfactant 1 in combination with surfactant 1, and the present invention has been completed.

Acrylic acids / styrene sulfonic acids / which are system modifiers
Even when the acrylonitrile terpolymer is used alone, a stable emulsion of the hydrophobic core substance with uniform particle size can be obtained, and it also promotes the formation of a capsule wall film with good occlusion effect and excellent density in a short time. , capsules with excellent quality such as water resistance can be obtained.

That is, acrylic acids / styrene sulfonic acids / acrylonitrile terpolymer alone can also be used alone, for example, in the aforementioned Japanese Patent Publication Nos. 16949-1981, 84881-1981, 84882-1982, and 4) Showa 5) 1-848
System modifiers such as ethylene/maleic anhydride copolymer, methyl vinyl ether/maleic anhydride copolymer and polyacrylic acid described in No. 88, JP-A-54-49984
Modified IL+ systems such as styrene/maleic anhydride co-tetrapolymer, combination system of styrene/maleic anhydride copolymer and vinyl acetate/maleic anhydride copolymer, etc. described in Although better capsules can be obtained than the capsules obtained using system modifiers such as polystyrene sulfonic acid, acrylic acid/styrene sulfonic acid copolymer, etc. described in JP-A No. 56-51288, still To obtain capsules with a size of 5μ or less, a certain amount of time is required for emulsification.

According to the present invention, by allowing a surfactant to exist in the acidic aqueous solution of acrylic acid @/styrene sulfonic acids/acrylonitrile ternary copolymerization, acrylic acids/styrene sulfonic acids/acrylonitrile ternary copolymerization is possible. In addition to obtaining capsules that are as good as or better than when using it alone, it also exhibits a progressively better effect on emulsification and dispersion.
An emulsion of 4 to 5 μm or less can be obtained by emulsification for a short time, and the particle size distribution is uniform, and the encapsulation process is good, that is, good capsules can be produced in which no unencapsulated core substance (free oil) remains.

The encapsulation rate here means the degree to which the core material is encapsulated, and its evaluation is as follows, taking a carbonless paper capsule as an example.

That is, when the resulting capsule slurry is applied to a carbonless bottom paper, the bottom paper develops color if unencapsulated core material (free oil) is present. The degree of color development determines the encapsulation level. If emulsion dispersion is poor and there is a large amount of remaining free oil, the encapsulation rate will be poor, so the quality of the encapsulation rate is related to the emulsion dispersion power.Conversely, knowing the encapsulation rate can improve the emulsion dispersion power. be able to evaluate the degree of

These excellent effects are due to the effects of the acrylic acids/styrene sulfonic acids/acrylonitrile terpolymer itself, as well as the emulsion dispersion and emulsion stabilization abilities of the surfactant. This is thought to be due to the fact that it exists without interfering with the quality of the capsule.

The method of the present invention is carried out mainly according to the following steps. νU First, an acidic aqueous solution containing an anionic polymer electrolyte is prepared. If necessary, adjust the pH within the acidic range. A surfactant is mixed into this aqueous solution to emulsify and disperse the hydrophobic substance to be encapsulated. The amino compound, which is a capsule wall film forming material, may be added either before or after emulsification and dispersion. This amino compound may be used after forming an initial condensate with the aldehyde to be added next. For those that have already formed an initial condensate,
For example, melamine resin initial condensate aqueous solution (commercial resin product name MIL <""7y"J-8o o, Showa Kobunshi Center), urea resin initial condensate aqueous solution (product name Thermotite 8)
H4F (manufactured by Showa Kobunshi), etc. Adjust pH if necessary. Next, while stirring, aldehyde is added (addition of aldehyde is not necessary when using an amino resin initial condensate), and after raising the temperature, it is held for a certain period of time to form a capsule wall film. Thereafter, cooling and/or PA sub-adjustment is performed as necessary to complete encapsulation.

The surfactant used in the present invention is preferably a nonionic surfactant. For example, sorbitan laurate monoester, sorbitan palmitate monoester, sorbitan stearate monoester, sorbitan oleate monoester, polyoxyethylene sorbitan laurate monoester, polyoxyethylene sorbitan palmitate monoester, polyoxyethylene sorbitan Stearic acid monoester, polyoxyethylene sorbitan oleic acid monoester, etc. Use of surfactants
hk is preferably about 0-OR to 1 weight percent, preferably about 0.1 to 0.5 weight percent, based on the hydrophobic core material.

The acrylic acids/styrene sulfonic acids/acrylonitrile terpolymer used in the present invention preferably has a size of about 50 to 200,000 cps, preferably about 100 to 10,000 cps when expressed in terms of the viscosity of an aqueous solution. However, the viscosity referred to here usually has a solid content of about 15 to 2.
This is a value measured using a B-type viscometer at 80° C. for an anionic ternary covalent aqueous solution according to the present invention obtained in an acidic state with a market weight of 5% and a pn of usually about 1 to 4. Viscosity is approximately 50 cps
The following are generally unfavorable because they lack emulsifying dispersion power and retaining action during capsule formation, and at temperatures above about 200,000 cps, they become difficult to handle and the resulting capsule slurry also becomes highly viscous. In addition, the copolymerization ratio of the terpolymer is about 5 to 85 mol% of acrylic acids,
Styrene sulfonic acids are preferably about 1 to 50 mol%, acrylonitrile is about 5 to 80 mol%, preferably acrylic acids are about 10 to 80 mol%, styrene sulfonic acids are about 8 to 45 mol%, and acrylonitrile is about 15 to 80 mol%. 60 mol% is good. If the acrylic acid content is less than about 5 mol %, emulsifying dispersion power and stability of emulsified particles will be lacking, and if it is more than about 85 mol %, the resulting capsule slurry will have a high viscosity.

If the content of styrene sulfonic acids is less than about 1 mol%, the emulsification rate will be slow and the encapsulation reaction will take time; if it is more than about 50 mol%, the system during the encapsulation process will tend to become unstable and agglomeration will easily occur. . If the acrylonitrile content is less than about 5 mol %, the emulsifying dispersion power and the stability of emulsified particles will be lacking like acrylic acids, and if it is more than about 80 mol %, the terpolymer will not be bathable in water. The use of a surfactant, which is a feature of the present invention, improves emulsifying and dispersing power, especially for systems with a low copolymerization ratio of acrylic acids, systems with a low copolymerization ratio of styrene sulfonic acids, or systems with a low copolymerization ratio of acrylonitrile. It is effective for

Styrene sulfonic acids may remain as free acids,
Some or all of the sulfonic acid groups in the molecule may form a salt. Typical salts include, for example, sodium salts, potassium salts, and ammonium salts.The ternary acrylic acid/styrene sulfonic acid/acrylonitrile ternary combination used in the present invention can be prepared by, for example, combining 8 parts of these single digits in water. , hydrogen peroxide, potassium persulfate, ammonium peroxide, benzoyl peroxide, cumene peroxide, cyclohexane peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide, azobisbutyronitrile, etc. It is produced by a method known to those skilled in the art by radical polymerization using a catalyst such as. In addition, for products with a high copolymerization ratio of acrylonitrile, the aqueous solution may be cloudy depending on the product, but the terpolymer may be mixed with a small amount of basic substances such as alkali metal hydroxides. , can be mixed and dissolved with water in various proportions. The amount of the terpolymer to be used in the hydrophilic encapsulation medium is the hydrophobic encapsulation medium.

The amount is generally about 1 to 80 parts by weight based on Kurumadobu, but it is appropriately selected depending on the concentration and viscosity of the capsule slurry to be produced, the particle size of the capsules, etc. However, if the amount used is small, agglomeration may occur in the system during the encapsulation process, and conversely, if the amount used is too large, the viscosity of the resulting capsule slurry may become sieved.
Since it becomes difficult to obtain good capsules, the amount used is preferably about 8 to 25 times.

Examples of amino resins forming the capsule wall include urea, methylol urea, thiourea, alkyl urea, ethylene urea, melamine, methylol melamine, benzoguanamine,
A resin obtained by polycondensing one or more amino compounds selected from acetoguanamine, etc., and one or more aldehydes selected from formaldehyde, acetaldehyde, daltaraldehyde, paraformaldehyde, crotonaldehyde, benzaldehyde, etc. , used in the form of the respective monomers or precondensates.

Hydrophobic core substances to be encapsulated include, for example, fish oil, animal oils such as lard oil, vegetable oils such as soybean oil, linseed oil, peanut oil, castor oil, corn oil, etc., petroleum, kerosene, gasoline, naphtha, paraffin. Hydrophobic liquids such as oil, mineral oils such as toluene, xylene, etc., synthetic oils such as alkyl-substituted diphenyl alkanes, alkyl-substituted naphthalenes, diphenylethane, dibutyl phthalate, methyl salicylate, etc. are used. These hydrophobic liquids can be used by appropriately mixing and dissolving medicines, lk drugs, fragrances, foods, dyes, catalysts, etc., depending on the use and purpose of the microcapsules.

The pH during emulsification may be in the acidic range of about 2 to 7. For this purpose, if necessary, adjust the pH using a suitable acid or alkali.
A I guess. Although the temperature does not need to be particularly specified, it is generally preferable to adjust the temperature to about 80 to 50'' CKP!Im because the higher the temperature, the more uniform the particle size of the emulsified particles becomes.

The encapsulation reaction takes into consideration the polycondensation conditions of the amino resin.
It is desirable to adjust the reaction temperature by about 80-95"C, preferably about 40-85"C, particularly preferably about 50"C.
~80°C. The time required for the reaction varies depending on factors such as reaction capacity and reactor, but is usually about 0.5 to 6 hours. Further, the pHFi of the system may be adjusted as long as it is acidic, preferably about 1 to 6.5, more preferably about 2 to 5.5.

At this time, in order to maintain the pH of the system acidic, for example, formic acid, acetic acid, citric acid, oxalic acid, hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, etc.
Acid catalysts commonly used in the production of amino resins such as ammonium chloride can be used, but acid groups of the acrylic acids/styrene sulfonic acids/acrylonitrile terpolymer used in the present invention can also be used. In addition, the desired p
In addition to the above-mentioned acids, basic substances such as alkali metal hydroxides, aqueous ammonia, triethanolamine, etc. can be used to adjust the HK. Since the aforementioned encapsulation reaction conditions, such as temperature, pH, temperature increase rate, etc. have a very large effect on the properties of the resulting capsule wall, the reaction conditions should be adjusted as appropriate depending on the type of capsule wall forming substance and the intended use of the capsule. Set. Regarding stirring, it is preferable to carry out uniform stirring to the extent that foaming does not occur so as not to impair the quality of the obtained capsules.

After holding for a certain period of time and completing encapsulation, the pH of the system may be adjusted with a basic substance such as alkali metal hydroxide, aqueous ammonia, or triethanolamine, or For example, unreacted aldehyde remaining in the system is removed by adding chemicals such as sodium sulfite, formamide, hydroxylamine hydrochloride, urea, and ethylene urea, or by methods such as steam distillation.

The method of the present invention will be explained in more detail below with reference to Examples.

In the examples, the method of the present invention will be described for the case of pressure-sensitive copying paper, where microcapsules are most often used, but the present invention is not limited to the examples only, and capsules for other uses can be similarly prepared. be able to. In addition, unless otherwise specified, parts and percentages in examples are based on weight. In addition, to adjust the pH, use a 10% aqueous sodium hydroxide solution or
Although 0% hydrochloric acid was used, the present invention is not limited thereto.

Example 1 40 parts of acrylic acid, 40 parts of sodium styrene sulfonate
30 parts of the aqueous solution was added to 70 parts of water with stirring, and the pH was adjusted to 4.5 U.
h 7 foil cut o Ws stal violet lactone (OV
L) 4-part tobenzoylleucomethylene blue (BI, M
B') 2 parts') Add to 100 parts of alkyldiphenylethane (trade name 5AS29 (!, manufactured by Yakushiki Kagaku), heat and dissolve at 90°C for 20 minutes with stirring, cool to room temperature, and dissolve hydrophobic forgotten item 1. (100 parts of this core material was mixed with 100 parts of the encapsulated hydrophilic medium at a temperature of 40°C,
Furthermore, 0.15 parts of polyoxyethylene sorbitan oleate monoester (trade name: Rheodor TW-0106 manufactured by Kao Seiken) was added as a nonionic surfactant, and the mixture was heated at 9000 rpm using a homomixer (manufactured by Tokushu Kika). When emulsified for 8 minutes, an 0/W type emulsion containing particles with an average particle size of 8.6 μm was obtained. Separately, a melamine resin pre-condensed milben resin compound aqueous solution (K!n shoulder N wing 100, manufactured by Showa Kobunshi Co., Ltd., N
1) Mix 15 parts of (80%) with 80 parts of water,
After adjusting to H'f4.5, the temperature was raised to 40°C. This first light condensate water bath solution was added to the emulsion, and the temperature was raised to 60"C while stirring. After 2 hours of encapsulation reaction, the temperature of the system was cooled to 25°C, and the pH was adjusted to 8. Capsule slurry was produced by adjusting the concentration to .5.

Example 2 Polyoxyethylene sorbicun stearic acid, monoester (trade name Rheodol T) was used as a nonionic surfactant.
A capsule slurry was produced by carrying out an encapsulation reaction in the same manner as in Example 1, except that W-8120 (manufactured by Kao Sekiken) was used.

Example 8 Sorbitan lauric acid monoester (trade name: Rheodol 5P-LIO) as a nonionic surfactant.

A capsule slurry was produced by carrying out an encapsulation reaction in the same manner as in Example 1, except for using the same method as in Example 1.

Example 4 An encapsulation reaction was carried out in the same manner as in Example 1, except that sorbitan stearate triester (trade name Rheodol 5P-880, manufactured by Kao Soap) was used as a nonionic surfactant, and a capsule slurry was prepared. was manufactured.

Example 5 Example 1 except that 22.5 parts of acrylic acid, 67.5 parts of sodium styrene sulfonate, and 10 parts of acrylonitrile were used (mol% 37.8:31L6:22.6). Capsule slurry was produced by carrying out the encapsulation reaction in the same manner as above.

Example 0 7 17.5'dR, 52.5 parts of sodium styrene sulfonate and 80 parts of acrylonitrile, the number of moles was 22.8: 24.0: 58
．． 2) Capsule slurry was produced by conducting an encapsulation reaction in the same manner as in Example 1, except that an aqueous solution was used.

Example 7 Comprised of 52.5 parts of acrylic acid, 17.5 parts of sodium styrene sulfonate (and 80 parts of acrylonitrile) with a viscosity of 580 cps (80"
C.

The joint bid is 52.8: 6.2: 41.0 in mole%.
) An encapsulation reaction was carried out in the same manner as in Example 1 except that an aqueous solution was used to produce a capsule slurry.

Example 8 Molecules were prepared from 67.5 parts of acrylic acid, 22.5 parts of sodium styrene sulfonate, and 10 parts of acrylonitrile (copolymerization ratio was 76.0:8.8:15.2 in mol%)
) An encapsulation reaction was carried out in the same manner as in Example 1 except that an aqueous solution was used to produce a capsule slurry.

Example 9 A urea resin initial condensate aqueous solution (trade name Thermotite 8H8P + manufactured by Showa Kobunshi Co., Ltd., solid and non-interpolated content: 80%) was used as the capsule wall film forming substance, and the pH during emulsification and encapsulation reaction was adjusted. The encapsulation reaction was carried out in the same manner as in Example 1, except that the respective values were adjusted to 8.5, and a capsule slurry was produced. The solid content concentration of the terpolymer water-soluble polymer aqueous solution was 16.9%.

Comparative example l No nonionic surfactant and emulsification time of 4
The encapsulation reaction was carried out in the same manner as in Example 1, except that the capsule slurry was produced. The solid content of the water-soluble polymer aqueous solution combined with ternary components is 16.
It was 9%.

Comparative Example 2 Ethylene/maleic anhydride copolymer (trade name EMA l
The encapsulation reaction was carried out in the same manner as in Comparative Example 1, except that 20 parts of L l (manufactured by Monsando) were dissolved in 80 parts of water to make an aqueous solution with an At'rTr content of 20%. 50 parts of capsule slurry was prepared.

Comparative Example 8 Partial sodium salt of polystyrene sulfonic acid (product name V
ER3A TL 500, manufactured by National Starch) 2
A capsule slurry was produced by carrying out an encapsulation reaction in the same manner as in Comparative Example 1, except that 0 part was dissolved in 80 parts of water to make an aqueous solution with a volatile content of zO%. ' The capsule slurries obtained in the above Examples and Comparative Examples were evaluated for their characteristics with respect to the following items.

(z1 particle size: The average particle size of capsules measured by Coulter Counter TA-II Model Particle Size Measurement 8 (Coulter Electronics Co., Ltd., M) is expressed as the particle size at 50% volume point. If the average particle size is small, It is considered to have strong emulsifying power.

(2) Viscosity = The viscosity of the capsule slurry at 25°C was measured using a B-type viscometer.

(8) Encapsulation rate: The term encapsulation rate here refers to the evaluation of the degree of color development on the coated surface after 50 parts of capsule slurry was poured onto a carbonless base paper and dried. That is, 50 parts of water was added to 50 parts of the obtained capsule slurry, and the mixture was coated on a commercially available carbonless base paper (trade name: Micro Chemical Paper NW 400, manufactured by Daio Paper Co., Ltd.) so that the dry bizo cloth had a length of 417 m. We compared the color of the cloth surface after drying. [Phase] If the cloth surface is pure white, all the core substance has been encapsulated, but if the coated surface turns blue, it means that 1 ft of emulsion is in the capsule slurry. If there is a core material containing insufficient dye, it will remain unencapsulated.

That is, the encapsulation name is a measure of the emulsifying power.

(4) Color development: 50 parts of water was added to 50 parts of capsule slurry, and further 5 parts of cellulose powder and 10 parts of 10% oxidized starch aqueous solution were mixed and dispersed to adjust the capsule color. The dry coating amount of this capsule color is 401 copies on m2 of base paper! J/m" with a wire bar and dried to create a carbonless top paper. This top paper was coated with a commercially available carbonless bottom paper (trade name: Micro Chemical Paper NW 400, manufactured by Daio Paper Co., Ltd.) The prints were printed using a typewriter, and the chromaticity was evaluated.

(5) An upper paper was prepared in the same manner as for the pressure smash stain two-color test, and overlaid with a commercially available carbonless lower paper (Micro Chemical Vapor NW 40'0 Daio Paper Co., Ltd.), about 1. A static pressure of 5 kg/c+n2 was applied, and the colored stains on the developer-coated surface of the lower paper were compared. Naturally, if the capsule film strength is weak or if the capsule particle size distribution is poor and there are coarse particles, the amount of colored stains will increase.

(6) Prepare clay paper in the same manner as for the moisture resistance dichromatic test, and hold it in constant temperature and humidity conditions at 40°C and 90% relative humidity.
After being left for a week, the prints were combined with a commercially available carbonless paper (Micro Chemical Paper NW 400, manufactured by Daio Paper Co., Ltd.) for 16 minutes, printed using a typewriter, and compared with those printed during the color development test.

If the moisture resistance is poor, the color density will be lower than that printed during the color development test, and the difference between the two will be large; however, as the moisture resistance improves, the difference disappears, and it can be said that the capsule is a good capsule.

The results of the above evaluation are summarized in Table 1 below.

As is clear from Table 1 above, when comparing Examples 1 to 9 and Comparative Example 1, Comparative Example 1 had an emulsification time of 4.7 minutes with an emulsification time of 4 minutes.
However, in Examples j to 9, by using a surfactant, which is a feature of the present invention, capsules of 4 μ or less were obtained with an emulsification time of 8 minutes, and the viscosity was lower than that of Comparative Example 1. Good capsules were also obtained for encapsulation. In addition, other qualities such as color development, pressure color development stain, and moisture resistance were all in comparison (+11, 4th grade or higher).

On the other hand, capsules according to Comparative Examples 2 and 8 were found in Comparative Example 1.
Despite the same emulsification conditions, the particle size is over 5μ, the Ml size distribution is wide, and the viscosity is 2000cp.
q or higher, the encapsulation strength, pressure color staining, and moisture resistance were all poor, and the practical usability was poor. Therefore, according to the present invention, microcapsules having unique characteristics can be manufactured by IQ, which is extremely useful in the world.

Procedural amendment April 13, 1982 1. Indication of the case 1988 Patent Application No. 4: 4086 No. 2. Title of the invention: Manufacturing of microcapsules! Method 3: Relationship with the case of the person making the amendment Patent applicant Daio Paper Co., Ltd. Showa Kobunshi Co., Ltd. 1. "Solid content" in Line 15 of Specification No. 18R is corrected to "Non-volatile content".

Claims (1)

[Scope of Claims] L A microcapsule in which a hydrophobic core substance is emulsified and dispersed in an acidic aqueous solution of an acrylic acid/styrene sulfonic acid/acrylonitrile terpolymer, and then a capsule having an amino resin as a wall is formed. A method for producing microcapsules at tA, characterized in that a surfactant is present in the acidic aqueous solution. 2. The method for producing microcapsules according to claim 1, wherein the amino resin is a melamine formaldehyde resin. & Particular t1 - The method for producing microcapsules according to claim 1, wherein the amino resin is a urea formaldehyde resin. 4. The method for producing microcapsules according to claim 1, wherein the interfacial agent is a nonionic surfactant. Rev. Claim 4. The method for producing microcapsules according to claim 4, wherein the nonionic surfactant is a sorbitan fatty acid ester. a. A method for producing microcub capsules according to claim 4. 7.% In the method for producing microcapsules according to claim 1, the copolymerization ratio of the terpolymer consisting of acrylic acids, styrene sulfonic acids, and acrylonitrile is 5 to 85 mol% of acrylic acids, Styrene sulfonic acids 1 to 50 mol%, acrylonitrile 5 to 80 mol%
A method for producing microcapsules characterized by: & In the method for producing microcapsules according to claim 1, acrylic acids/styrenesulfonic acids/
Acrylonitrile terpolymer is hydrophobic core material 100m
A method for producing microcapsules, characterized in that the ratio is '1 to 30 JJt ff+ parts per 1 t part.