JPS60238140A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To enhance the strength and compactness of a wall film, by emulsifying and dispersing a hydrophobic core substance into an acidic aqueous solution of specific anionic high-molecular electrolyte to form a capsule wherein a wall film of an amino resin is formed around the core substance. CONSTITUTION:A hydrophobic core substance is emulsified and dispersed into an acidic aqueous solution of a water-soluble polymer comprising an anionic ternary copolymer consisting of 9-92mol% of acrylic acids, 3-87mol% of acrylamide and 4-26mol% of acrylonitrile. Next, a film comprising an amino resin is formed around the hydrophobic core substance to obtain a microcapsule. The use amount of the aformentioned ternary copolymer is usually 1-80pts.wt. to 100pts. wt. of the hydrophobic substance. As the aforementioned hydrophobic core substance, animal oils such as fish oil or lard, vegetable oils such as soybean oil or linseed oil and mineral oils such as petroleum or kerosine are designated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing microcapsules, particularly to a method for producing microcapsules having a monolayer of amino resin.

Microcapsules have the function of temporarily protecting the core substance, which is originally unstable, to make it stable, and releasing it instantly or gradually when necessary. It was developed by To8CR for carbonless paper, and has already been used in this field by B.
We have a track record of more than 0 years.

In recent years, the manufacturing technology of microcapsules has progressed significantly, and attempts have been made to apply them to pharmaceuticals, agricultural chemicals, fragrances, cosmetics, foods, dyes, etc., and now they are widely used in the fields of gods as well as carbonless paper. There is.

Generally, methods for producing microcapsules include physical methods,
Mechanical methods, physicochemical methods, and chemical methods are known, and are appropriately selected and used 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 are limited. On the other hand, with physicochemical and chemical methods, it is easy to control the capsule particle size arbitrarily, particles as small as several microns can be easily produced, and capsules with a dense wall membrane can be obtained. It is used over a wide range.

As a physicochemical method, the coacervation method using gelatin as a membrane material is known and is currently applied in the widest range of fields, but because it uses gelatin, a natural product, as a membrane material, it is expensive and expensive. It has drawbacks such as being easily attacked by pressure and 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 uses hydrophobic monomers and hydrophilic monomers,
An interfacial polymerization method in which a polymerization reaction occurs at the interface between a hydrophobic core substance and an aqueous phase to form a wall film of polyamide, epoxy resin, polyurethane, polyurea, etc., and an interfacial polymerization method in which a wall film of polyamide, epoxy resin, polyurethane, polyurea, etc. It is legal to carry out a polymerization reaction to form a wall film of amine resin or the like around the core material in -5 itu '71.

Since the interfacial polymerization method uses highly reactive or highly toxic materials such as isocyanates, acid chlorides, and epoxy compounds as membrane materials, it is difficult to control the one-coat reaction, and substances with active hydrogen cannot be used as core materials. In addition, it has drawbacks such as the high cost of the membrane material itself. I'm busy with this
-5 In the itu polymerization method, most of the materials that form synthetic resins, such as acrylic ester resins, amino resins, and polyester resins, are used as membrane materials, and among them, amine resins are cheap and easy to obtain; It has the advantage that a special catalyst is not particularly required during the polymerization reaction, and the polymerization reaction can be carried out in a relatively short time.

As described above, the 1n-5 itu polymerization method is easier to handle than the interfacial polymerization method, and is therefore more practical. Many inventions have been filed, such as JP-A-58-84881 and JP-A-54-49984.

However, although the capsule wall membrane obtained by this method has excellent water resistance, it is poor in density, cannot sufficiently emulsify and disperse the core material, and is difficult to efficiently and stably form the polycondensate around the core material. It has drawbacks such as being difficult to deposit.

The present invention relates to an encapsulation method using the in-5 itu 9 method. Methods of using melamine formaldehyde resin or urea formaldehyde resin as the membrane material are described, for example, in Japanese Patent Publications No. 87-12880 and Japanese Patent Publication No. 44-8.
It is already known as described in Japanese Patent Publication No. 495, Japanese Patent Publication No. 47-48166, etc. However, as mentioned above, these methods require efficient and stable deposition of the polycondensate of amino resin around the hydrophobic core material, and also have drawbacks such as insufficient emulsification and dispersion of the core material. was there.

In order to improve these shortcomings, Special Publication No. 16949/1983, 4? 1986-1968-6881, JP-A-5B-8488
No. 2, JP-A No. 58-84888 discloses ethylene/maleic anhydride copolymer, methyl vinyl ethyl/maleic anhydride copolymer, polyacrylic acid, etc. as an anionic polymer electrolyte which is a system modifier. The method used has been published. This method improved the emulsifying and dispersing properties of the hydrophobic core substance, improved the strength and density of the capsule wall membrane, and made it possible to obtain a highly concentrated capsule slurry in a short time, but the viscosity of the capsule slurry was high. However, the particularly effective ethylene/maleic anhydride copolymer and methyl vinyl ether/maleic anhydride copolymer require a long time to dissolve.

Also, JP-A-64-49984, JP-A-55-471
No. 89 and JP-A-55-15660 disclose the use of styrene/maleic anhydride copolymer or its combination with vinyl acetate/anhydride play/acid copolymer or ethylene/maleic anhydride copolymer. (・ru. In this method, the emulsifying and dispersing properties of the core substance are further improved, and a stable, low-viscosity, and highly concentrated capsule slurry can be obtained. However, the styrene/maleic anhydride copolymer precipitates when T)H is low. Because this happens,
There is a drawback that it cannot be used in the urea-formaldehyde system, which is often subjected to a polycondensation reaction at a low pH, and it also has a drawback that it cannot be used in a method for removing residual formaldehyde that removes unreacted residual formaldehyde at a low pH.

Furthermore, JP-A-56-51288 announces the use of styrene sulfonic acid polymers such as polystyrene sulfonic acid and acrylic acid/styrene sulfonic acid copolymers as mono-anionic polymer electrolytes in melamine formaldehyde systems. ing.

Since styrene sulfonic acid-based polymers are stable at low pH, polycondensation reactions in urea-formaldehyde systems or low pH
Although it has become possible to treat unreacted formaldehyde with H, styrene sulfonic acid-based polymers foam a lot during dissolution, causing problems in workability, and when used in urea-formaldehyde-based polymers, even slight changes in reaction conditions cause the entire system to coagulate. There are drawbacks to doing so.

Therefore, the present inventors developed a method for producing microcapsules that does not have the above-mentioned drawbacks by (1) maintaining good emulsification dispersibility of the hydrophobic core substance (, r21 and stability of the emulsion), and (8) encapsulating Due to the simple process and short reaction time, (
4) Excellent wall membrane strength, density, water resistance, and heat resistance (
5) As a result of repeated research aimed at improving the manufacturing method of microcapsules that yield capsule slurry with high concentration and low viscosity, a water-soluble terpolymer copolymer of acrylic acids, acrylamide, and acrylonitrile was developed. The present inventors have discovered that the above-mentioned objective can be achieved extremely effectively using a polymeric polymer, and have completed the present invention.

That is, the method for producing microcapsules according to the present invention is characterized in that an acrylic acid/acrylamide/acrylonitrile terpolymer is used as an anionic polymer electrolyte, and a hydrophobic core is added to an acidic aqueous solution of the terpolymer. After the substance is emulsified and dispersed, a polycondensate of amino resin is formed and deposited around the core substance to form a capsule mucus.

The acrylic acid/acrylamide/acrylonitrile terpolymer according to the present invention can be easily produced as an aqueous solution, so it can be easily produced in the form of a conventional ethylene/maleic anhydride copolymer,
Unlike methyl vinyl ether/maleic anhydride copolymer, it does not have the problem of requiring a long time for dissolution, and also has excellent workability without foaming seen in styrene sulfonic acid polymers. Furthermore, unlike 1-styrene/maleic anhydride copolymer, it does not precipitate even in low pH ranges and can exist stably. It can be used in a method for manufacturing capsules, and is also effective in a method for removing residual formaldehyde carried out at low pH. Therefore, according to the present invention, in both cases of melamine formaldehyde type or urea formaldehyde type,
An emulsion of a hydrophobic core material that is stable and uniform in particle size can be obtained, and it also promotes the formation of capsule wall membranes with excellent density and density in a short time and efficiently, resulting in capsules with excellent quality such as water resistance. can be obtained at high concentration and low viscosity. The five excellent effects are that the acrylic acid/acrylamide/acrylonitrile terpolymer of the present invention itself has high emulsifying and dispersing power and has excellent protective colloid ability, and that the j4@ compound of amino resin It is thought that this is because it has the ability to efficiently form and deposit around the core substance, but its detailed function is not clear.

The method of the present invention is carried out mainly according to the following steps. That is, an acidic aqueous solution of an acrylic acid/acrylamide/acrylonitrile terpolymer is prepared. If necessary, adjust the pH within the acidic range. The hydrophobic core substance to be encapsulated is emulsified and dispersed in this aqueous solution. The amino compound, which is a capsule wall forming material, may be added either before or after emulsification and dispersion. This amine compound may be used after forming an initial condensate with the aldehyde to be added next. Examples of those that have already formed an initial condensate include a melamine resin initial condensate aqueous solution (trade name: Milbenresin 5M-800, manufactured by Showa Kobunshi Co., Ltd.), and a urea resin initial condensate aqueous solution (trade name: Thermotie).
8I (SP, manufactured by Showa Kobunshi Co., Ltd.), etc. If necessary, adjust the pT.Next, add aldehyde while continuing stirring.Addition of aldehyde is not necessary when using an amino resin initial condensate.After rising, hold for a certain period of time to form a capsule wall film. . Then cool and/or cool as necessary.
Alternatively, pH adjustment is performed to complete encapsulation.

The acrylic acid/acrylamide/acrylonitrile terpolymer used in the present invention preferably has a size of 50 to 200,000 cps, preferably 100 to 10,000 cps, when expressed in terms of the viscosity of an aqueous solution. However, the viscosity referred to here is usually 15 to 25% non-volatile content, p
This is a value measured using a B-type viscometer at 80° C. for an aqueous solution of the anionic terpolymer according to the present invention obtained in an acidic state in which H is usually 1 to 4. If the viscosity is less than 50 cps, the emulsifying dispersion power and protective effect during capsule formation will be insufficient, and the
If it is higher than 0.00 cps, it becomes difficult to handle and the resulting capsule slurry also has a high viscosity, which is generally not preferable. In addition, the copolymerization ratio of the terpolymer is 9 to 92 mol% of acrylic acids, 8 to 87 mol% of acrylamide,
Acrylonitrile is preferably 4 to 26 mol%, preferably acrylic acids are 12 to 84 mol%, and acrylamide is 6 mol%.
~80 mol%, preferably 9 to 22 mol% of acrylonitrile. If the acrylic acid content is less than 9 mol %, emulsifying dispersion power and emulsified particle stability will be lacking, and if it is more than 92 mol %, the obtained capsule slurry will have a high viscosity.

If the acrylamide content is less than 8 mol%, emulsifying and dispersing power is lacking,
The emulsification rate becomes slow and the encapsulation reaction takes time, and if the amount exceeds 87 mol%, the system during the encapsulation process tends to become unstable and aggregation is likely to occur. If the acrylonitrile content is less than 4 mol %, it will lack emulsifying dispersion power and emulsified particle stability similar to acrylic acid, and if it is more than 26 mol %, the terpolymer will become insoluble in water.

Acrylic acids may be in a free form, or some of the carboxyl groups in the molecule may form a salt.

Typical salts include, for example, sodium salts, potassium salts, and ammonium salts. Among acrylic acids, acrylic acid is particularly preferably used.

The acrylic acid/acrylamide/acrylonitrile terpolymer used in the present invention can be prepared, for example, by mixing these eight types of monomers in water with hydrogen peroxide, potassium persulfate, ammonium persulfate, benzoyl peroxide, and cumene oxide. , cyclohexane peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, etc., by methods known to those skilled in the art. Note that when the copolymerization ratio of acrylonitrile is low, the aqueous solution sometimes becomes cloudy (.); Because it is transparent, it can be used without any problem in the production of microcapsules.
The desired effect can be obtained. Further, the terpolymer can be mixed and dissolved in water at a moderate ratio. The amount of the terpolymer used in the hydrophilic encapsulation medium is generally 1 to 80 parts by weight per 100 parts by weight of the hydrophobic core material. , viscosity, capsule particle size, etc. However, if the amount used is small, agglomeration may occur in the system during the encapsulation process, and if the amount used is too large, the viscosity of the resulting capsule slurry will increase, making it difficult to obtain good capsules. The amount is preferably 8 to 25 parts by weight.

Examples of the amine resin forming the capsule wall include urea, methylol urea, thiourea, alkyl urea, ethylene urea, melamine, methylol melamine, benzoguanamine,
Obtained by polycondensing one or more amine compounds selected from acetoguanamine, etc., and one or more aldehydes selected from formaldehyde, acetaldehyde, glutaraldehyde, no(laformaldehyde, crotonaldehyde, be/zaldehyde, etc.) Refers to resins, used in the form of their 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 mineral oils such as oils, toluene, xylene, etc., synthetic oils such as alkyl-substituted diphenylalkanes, alkyl-substituted naphthalenes, diphenylethanes, diptyl phthalates, methyl salicylate, etc. are used. These hydrophobic liquids can be used by appropriately mixing and dissolving medicines, agricultural chemicals, fragrances, foods, dyes, catalysts, etc., depending on the use and purpose of the microcapsules.

The pH during emulsification should be in the acidic range of 2 to 7 (・.

For this purpose, use a suitable acid or alkali if necessary.
Adjust H. Although it is not necessary to specify a specific temperature, it is generally preferable to adjust the temperature to 80 to 50°C, since the higher the temperature, the more uniform the particle size of the emulsified particles becomes.

In the encapsulation reaction, it is desirable to adjust the reaction temperature to 80 to 95°C, preferably 40 to 85°C, particularly preferably 50 to 80°C, taking into account the polycondensation conditions of the amino resin. The time required for the reaction varies depending on various factors such as reaction volume and reaction container, but is usually about 0.1 to 6 hours. In addition, the pH of the system only needs to be acidic, preferably 1
It is preferable to adjust it to 6.5 to 6.5, particularly 2 to 5.5.

In order to keep the pH of this yarn at 4tf acidic, acid catalysts commonly used in the production of amine resins such as formic acid, acetic acid, citric acid, oxalic acid, hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, and ammonium chloride can be used. However, it is also possible to utilize the acid groups of the acrylic acid/acrylamide/acrylonitrile terpolymer used in the present invention.

In addition to the above-mentioned acids, basic substances such as alkali metal hydroxides, aqueous ammonia, triethanolamine, etc. can be used to separately adjust the pH to a desired value. Since the properties of the resulting capsule wall film are greatly influenced by the encapsulation reaction conditions described above, such as temperature, pH, and heating rate, the reaction conditions may be adjusted as appropriate depending on the type of capsule wall forming substance and the intended use of the capsule. Set. Regarding stirring,
In order to avoid impairing the quality of the resulting capsules, it is preferable to perform uniform stirring to the extent that no foaming occurs. After holding for a certain period of time and completing encapsulation, if necessary, as a post-treatment, for example, alkali metal Adjust the pH of the system with a basic substance such as Suizun II/Todoroki Soeteshi L II I/n-〒Gichitsuba, or use chemicals such as sodium sulfite, formamide, hydroxylamine hydrochloride, urea, and ethylene urea. The unreacted aldehyde remaining in the system is removed by a method such as addition of water or 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 carbonless paper, which is the most commonly used microcapsule, but the present invention is not limited to the examples only, and capsules for other uses may be similarly prepared. I can do it. Further, unless otherwise specified, parts and percentages in the examples are based on weight.

Further, although a 10% aqueous sodium hydroxide solution or 10% hydrochloric acid was used to adjust the pH, the present invention is not limited to these.

Example 1 An aqueous anionic terpolymer solution was prepared according to the following procedure.

After stirring, 608 parts of water was placed in a fifth flask equipped with a thermometer and a reflux condenser, and the temperature was raised to 80°C.

256 parts of water was added to 240 parts of acrylic acid aqueous solution (80%), 24 parts of acrylamide, and 24 parts of acrylonitrile, and the volume of the homogeneous monomer aqueous solution was put into a flask. Subsequently, 82 parts of a 1% aqueous solution of potassium persulfate was added. When the internal temperature of the flask began to rise and reached 88°C, the remainder of the monomer aqueous solution (8/4 of the total amount) was added to 1% aqueous solution of potassium persulfate. .5
Continuously dripped into the flask over time. At the time when the dropping was completed, 80 minutes later, and 1 hour later, 8 parts each of a 1% aqueous solution of potassium persulfate (24 parts in total) were charged into the flask. The flask internal temperature was maintained at 85 to 88°C, and the above series of operations were performed in a nitrogen stream.

It was then cooled. The analytical values of the obtained acrylic acid/acrylamide/acrylonitrile terpolymer aqueous solution were: non-volatile content 20.5%, T) H8.25, and viscosity 480 cps.
(80°C, type B viscosity needle).

80 parts of acrylic acid obtained by the above method, acrylic 7511
Non-volatile component zO consisting of 0 parts and 10 parts of acrylonitrile
80 parts of a 15% terpolymer water-soluble polymer (copolymerization ratio in molar ratio: 77.179.8/1B, 1) aqueous solution was added to 70 parts of water with stirring, and the pH was adjusted to 4.6. The encapsulated hydrophilic medium was prepared.

Meanwhile, add 728,710 parts and 25 parts of 87% formalin to 6 parts of water.
5 parts, the pH was adjusted to 9 under stirring, and the mixture became transparent in about 20 minutes when heated to 60° C. to obtain a melamine formaldehyde initial condensate. Separately, 4 parts of crystal violet lactone (CVL) and 2 parts of benzoyl leucomethylene blue (BLMB) were added to 100 parts of alkyldiphenylethane (trade name Hysol 5AS-296, Japan Petrochemical Exhibition) and dissolved by heating at 90°C for 20 minutes with stirring. The mixture was cooled to room temperature to obtain a hydrophobic core material. 100 parts of this core material was mixed with 100 parts of the encapsulated hydrophilic medium at a temperature of 40°C, and the mixture was mixed with 9000 parts of the core material using a homomixer (manufactured by Tokushu Kika).
When emulsified for 4 minutes at rpm, the average particle size was 4.0.
An O/W emulsion containing μ particles was obtained.

Melamine formaldehyde initial condensate prepared previously 10
After adjusting the pH of 0 part to 4.5, it was heated to 40°C, added to this emulsion, and heated to 60°C while stirring. 2
After holding for a period of time, the temperature of the system was cooled to 26°C, and the pH was adjusted to 8°C.
, 5, average particle size 4, θμ, viscosity 210cps
A capsule slurry having a good value (80° C., B-type viscometer) was obtained. Note that there was no particular foaming during the preparation of the encapsulated hydrophilic medium and during the encapsulation process, and the workability was good.

Example B A commercially available aqueous solution of initial condensate as a melamine formaldehyde initial condensate (trade name: Milbenresin 8M-800,
An encapsulation reaction was carried out in the same manner as in Example 1, except that a capsule slurry (manufactured by Showa Kobunshi) was used to produce a capsule slurry. The obtained capsule slurry had an average particle size of 8.
7μ, viscosity 190cps (80℃, B type viscometer),
It was of good quality.

Example 8 61S parts of acrylic acid produced in the same manner as in Example 1,
Consisting of 85 parts of acrylamide and 10 parts of acrylonitrile, nonvolatile content 21.2%, viscosity 860 CT) 8 (8
0°C, Type B viscometer), terpolymer water-soluble polymer with pH 8.85 (copolymerization ratio is 62.6/24.4 in mol%)
/ IB, 1) The use of an aqueous solution and the commercially available aqueous initial condensate solution as a melami/formaldehyde initial condensate (trade name: Milbenresin 5M-800, Showa Kobunshi 1)
! An encapsulation reaction was carried out in the same manner as in Example 1, except that a capsule slurry was produced. The obtained capsule slurry had an average particle size of 4.1μ and a viscosity of 1
It was 0 cps (80°C, Type B viscometer) and was of good quality.

Composed of 50 parts of acrylic acid, 40 parts of acrylamide and 10 parts of acrylonitrile produced in the same manner as in Example 1, non-volatile content zO 09%, viscosity 83!0 cps (80
℃, Type B viscometer), terpolymer water-soluble polymer with pH 8.65 (copolymerization ratio is 48.0/88.9 in mole%)
/ 1B, 1) Same as Example 1 except that an aqueous solution was used and a commercially available aqueous initial condensate solution (trade name Milbenresin 5M-5OO, manufactured by Showa Kobunshi) was used as the melamine formaldehyde initial condensate. The encapsulation reaction was carried out by the method to produce capsule slurry. The obtained capsule slurry had an average particle size of 4 Jμ and a viscosity of 880c.
ps (80°C, Type B viscometer), and was of good quality.

Example 5 80 parts of the acrylic acid/acrylamide/acrylonitrile terpolymer water-soluble polymer aqueous solution having a nonvolatile content of 20.6% obtained in Example 1 was added to 70 parts of water with stirring. Furthermore, 10 parts of urea and 1.4 parts of resorcin were added and dissolved. T of this water-soluble polymer water bath solution containing urea and resorcinol.
) H was adjusted to 13.6 to obtain an encapsulated hydrophilic medium. Separately, add 4 parts of crystal violet lactone and 2 parts of benzoyl leucomethylene blue to 1 part of alkyldiphenylethane (trade name: Hysol SAS 296.8 manufactured by Seki Kagaku).
00 parts, heated and dissolved at 90°C for 20 minutes with stirring,
The mixture was cooled to room temperature to obtain a hydrophobic core material. This core substance 10
0 part was mixed with 100 parts of the encapsulated hydrophilic medium in a Yamaga oven at 45°C, and the mixture was mixed using a homo mixer (manufactured by Tokushu Kika).
When emulsified for 8 minutes at 000 rpm, a 0/v type emulsion containing particles with an average particle size of 4.1 μm was obtained. Next, add 27 parts of 87% formalin and stir while stirring.
The temperature was raised to 60°C. After carrying out the encapsulation reaction at 60° C. for 2 hours, the temperature of the system was cooled to 20° C., the pH was adjusted to 8.5, and a capsule slurry was produced. The obtained capsule slurry had an average particle size of 4.1μ and a viscosity of 480 cps (
It was found to be of good quality as measured at 80°C (B-type viscometer).

Example 6 A commercially available aqueous solution of an initial condensate as a urea-formaldehyde initial condensate (trade name: Thermotite 8H8P).

A capsule slurry was produced by carrying out an encapsulation reaction in the same manner as in Example 5, except that the same method as in Example 5 was used, except for using the same method as in Example 5. The obtained capsule slurry had an average particle size of 8.9μ.
The product had a viscosity of 420 cps (80° C., B-type viscometer) and was of good quality.

Comparative Example l As an anionic polymer electrolyte aqueous solution, 20 parts of ethylene/maleic anhydride copolymer (trade name EMA81, manufactured by Monsanto) was dissolved in 80 parts of water to make an aqueous solution with a non-volatile content of 20%. The encapsulation reaction was carried out in the same manner as in Example 1, except that a commercially available aqueous solution of the initial condensate (trade name Milbenregi 78M-800, Showa Kobunshi fA) was used as the melamine formaldehyde initial condensate. A capsule slurry was produced. The obtained capsule slurry had an average particle size of 5.8μ and a viscosity of 2000 cps.
(80℃, B-type viscometer), which resulted in a high viscosity.
It took 8 hours.

Comparative Example 2 A partial sodium salt of polystyrene sulfonic acid (trade name VER8A Tl2) was used as an anionic polymer electrolyte aqueous solution.
20 parts of O3, -)-Shof (manufactured by Rusl'-chi Co., Ltd.) and 8 parts of water.
0 parts to make an aqueous solution with a non-volatile content of 20%.
-800, manufactured by Showa Kobunshi Co., Ltd.) was used, but the encapsulation reaction was carried out in the same manner as in Example 1 to produce a capsule slurry. The obtained capsule slurry has an average particle size of 5.4 μ, a viscosity of 2500 cps (80°C, B-type viscometer), and a size of 1.5 μm (80°C, B-type viscometer). At this time, a large amount of foaming was observed, so the mixture was left for about 1 hour until the foam disappeared, and then encapsulation was performed.

Comparative Example 8 A partial sodium salt of polystyrene sulfonic acid (trade name VER8A"rL") was used as an anionic polymer electrolyte aqueous solution.
The encapsulation reaction was carried out in the same manner as in Example 6, except that 20 parts of 500 (manufactured by National Starch) were dissolved in 80 parts of water to make an aqueous solution containing 20% non-volatile matter. The inside of the system agglomerated and no capsules were obtained.

The capsule slurries obtained in the above Examples and Comparative Examples were evaluated for the following items: 0 fil Particle size: Capsules measured by Coulter Counter TA-, II type particle size analyzer (manufactured by Coulter Electronics) K The average particle size of is shown as the particle size at r10% volume point. It is considered that the smaller the average particle size, the stronger the emulsifying power.

(1!+ Viscosity 2) The viscosity of the capsule slurry at 80°C was measured using a B-type viscometer.

(8) Encapsulation rate: What is the encapsulation rate here?
After coating the carbonless paper treatment capsule slurry and drying it, the degree of color development on the coated surface was evaluated. That is, 50 parts of water was added to 50 parts of the obtained capsule slurry.
A commercially available carbonless paper (trade name: Micro Chemical Paper NW40c, manufactured by Daio Paper Co., Ltd.) was applied so that the dry coating amount of K was 49/rn2 K, and the color of the coated surface after drying was compared. If the coated surface is pure white, all the core material is encapsulated (good encapsulation rate), but if the coated surface turns blue, there is core material containing dye in the capsule slurry that is not sufficiently emulsified and dispersed. This means that it remains unencapsulated (the encapsulation rate is poor).

That is, the encapsulation rate is a measure of emulsification dispersion power.

(4) Color development: Capsule color was adjusted by adding 50 parts of capsule slurry and 50 parts of water, and further mixing and dispersing 6 parts of cellulose bag and 10 parts of 10% oxidized starch aqueous solution. This capsule color was applied to 40'/Q base paper using a wire bar so that the dry coating amount was 4 to 2, and dried to produce a carbonless top paper. This is paper
.

Commercially available bottom paper (product name: microchemical pen-NW)
40c (manufactured by Daio Paper Co., Ltd.) and printed using a typewriter to evaluate color development.

(5) An upper paper was prepared in the same manner as for the pressure smash stain two-color test, and it was overlaid with a commercially available lower paper (trade name: Micro Chemical Paper NW-40 parts %, manufactured by Daio Paper Co., Ltd.) to yield approximately 1.6 kfl. /am'' static pressure was applied, and the color development stains on the developer surface of the lower paper were compared.Of course, if the capsule film strength is weak or the capsule particle size distribution is poor and there are coarse particles, the color development will be worse. There will be more dirt.

(6) Moisture resistance: The upper paper was prepared in the same manner as for the color development test, and was kept at 40°C and 90% relative humidity in a constant humidity state.
After being left for a week, it was printed on a commercially available carbonless base paper (trade name: Microchemical Peno: -NW400 manufactured by Daio Paper Co., Ltd.) using a typewriter, and compared with that 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, this 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, all the capsules according to the present invention have a small average particle size of 8.7 to 4.2μ, and the viscosity of the capsule slurry is as low as 190 to 480 cps.
The encapsulation rate was excellent, and the capsules had good color development and moisture resistance, and were of good quality with little color staining due to pressure. On the other hand, the capsules according to the comparative example had a large average particle size of 5 microns or more, the viscosity of the capsule slurry was high, the moisture resistance was poor, and there was a lot of colored staining due to pressure, and the quality could not be said to be good. Furthermore, in Comparative Example 8, the entire system agglomerated during the encapsulation process, and no capsules were obtained. Therefore, the present invention can produce microcapsules that are excellent in all properties, and is extremely useful industrially.

Claims (1)

[Scope of Claims] 1. Microcapsules in which a hydrophobic core substance is emulsified and dispersed in an acidic aqueous solution of an anionic polymer %I membrane, and then a capsule having an amino resin as a wall membrane is formed around the core substance. A method for producing microcapsules, wherein the anionic polymer electrolyte is an anionic terpolymer water-soluble polymer composed of acrylic acids, acrylamide, and acrylonitrile. Higashi A method for producing microcapsules according to claim 1, wherein the amine resin is a melamine formaldehyde resin. & The method for producing microcapsules according to claim 1, wherein the amine resin is a urea formaldehyde resin. 4% In the method for producing microcapsules according to claim 1, the copolymerization ratio of the anionic terpolymer water-soluble polymer is 9 to 92 mol% of acrylic acids and 8 to 87 mol% of acrylamide. , a method for producing microcapsules containing 4 to 26 mol% of acrylonitrile. (5) In the method for producing microcapsules according to claim 1, the amount of the anionic terpolymer water-soluble polymer is 1 to 80 parts by weight based on 100 parts by weight of the hydrophobic core substance. Production method. a. The method for producing microcapsules according to claim 1, wherein the acidic aqueous solution of the anionic terpolymer water-soluble polymer has a viscosity of 50 to 200,000 cps. I. The method for producing microcapsules according to claim 6, wherein the acidic aqueous solution of the anionic terpolymer water-soluble polymer has a viscosity of 100 to 10,000 cps.