JPS6257645A - Production of microcapsule - Google Patents

Abstract

PURPOSE:To form the dense wall of a microcapsule by forming an amino- aldehyde wall film on the surface of a hydrophobic core material in a system prepd. by dispersing or emulsifying the core material into an aq. acidic soln. contg. a specific water soluble anionic hihg-polymer material. CONSTITUTION:The system dispersed or emulsified with the hydrophobic core material in the aq. acidic soln. contg. the water soluble anionic hihg-polymer material contg. an acrylamide/aralkyl sulfonic acid and/or the salt thereof as an essential monomer is prepd. The amino/aldehyde resin is then formed as the wall film on the surface of the hydrophobic core material in the system to produce the microcapsule. A multi-element copolymer of 2-acrylamide-2-phenyl propane sulfonic acid, acrylic acid and/or methacrylic acid and acrylonitrile is adequate as the above-mentioned water soluble anionic hihg-polymer material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing microcapsules. More specifically, a method for producing microcapsules having a melamine-formaldehyde resin film obtained by an in-situ polymerization method will be described.

[Conventional technology]

Microcapsules have been studied in a wide variety of fields, including recording materials such as pressure-sensitive recording paper, pharmaceuticals, fragrances, pesticides, adhesives, foods, adhesives, dyes, solvents, rust preventives, liquid crystals, and health foods. Many of them have reached the practical application or practical testing stage.

In particular, many techniques have already been proposed for the microencapsulation of hydrophobic substances (oils and solids), and among these, the coacervation method (phase separation method) using gelatin is mainly used for pressure-sensitive copying paper. Produced on a commercial scale.

However, regarding complex coacervation microcapsules using gelatin and anionic polymer electrolyte, (1) In principle, it is difficult to obtain microcapsule liquid with a high solid content concentration of 20% or more. , transportation costs, and when used in pressure-sensitive copying paper, a large amount of water must be evaporated, so there is great room for improvement in terms of work speed and energy costs.

(2) Since the capsule membrane material is a natural product, there are large fluctuations in quality and price.

(3) It cannot withstand long-term storage because it has a tendency to rot and agglomerate.

However, there has been a strong demand for improvements in terms of quality and cost of pressure-sensitive copying paper. As an improved technique to meet such requirements, Japanese Patent Application Laid-open Nos. 51-9079 and 53
In No. 84881 and the like, a high-concentration microencapsulation method using urea formaldehyde resin or melamine formaldehyde resin as a membrane material by an in-3 in-itu polymerization method was proposed, and various improved techniques have been proposed since then.

Among these proposals, JP-A-53-8488 is an example of a method using melamine-formaldehyde resin as a membrane material.
No. 1 received the anionic polymer electrolysis award for ethylene maleic anhydride copolymer, methyl vinyl ether maleic anhydride copolymer, polyacrylic acid, propylene maleic anhydride copolymer, butadiene maleic anhydride copolymer, and acetic acid. A method using a vinyl maleic anhydride copolymer is disclosed. However, these polymers require a high temperature and a long time to dissolve, and the resulting microcapsule slurry has a high viscosity, so it is difficult to obtain a capsule slurry with a high solids content by the above method.

JP-A Nos. 54-49984 and 55-47+39 disclose styrene-maleic acid copolymers or copolymers of styrene-maleic acid copolymers and other maleic acid copolymers as anionic polymers. An example of a microencapsulation method using a system in which a styrene-maleic acid copolymer is used in combination has been disclosed;
It takes a long time at high temperature while adding alkali to melt, and
At a pH as low as below, polymer precipitation causes system thickening and dispersion failure. Therefore, formaldehyde removal cannot be performed on the acidic side, and a relatively high viscosity microcapsule slurry is obtained. .

JP-A-56-58536 describes compounds having a phenyl group/or a sulfonic acid group that does not contain a sulfophenyl group [specifically, sulfoethyl (meth)acrylate, sulfopropyl (meth)acrylate, maleimide-N-ethane sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid] or a copolymer solution with C1-C3 alkyl acrylate, hydroxy C2-C4 alkyl acrylate, and N-vinylpyrrolidone. A method has been proposed in which, after the core material is emulsified and dispersed, a melamine-formaldehyde precondensate is added continuously or in small amounts depending on the condensation rate. However, in such a method, as described in Specification 1, when the core material is oily, a melamine-formaldehyde precondensate is added, and the dispersion system before the capsule wall is formed is unstable. Therefore, unless strong shear stress is present, that is, under intense stirring conditions, it is difficult to set the emulsion particle size to a desired size because oil droplets tend to coalesce and form a particle size.

In addition, the melamine-formaldehyde precondensate was gradually added to
If the system is not charged carefully, the entire system may gel or agglomerated particles may be formed, which is not preferable from the viewpoint of workability. Moreover, according to this method, microcapsules with a high solid content exceeding 50 wt% cannot be obtained.

JP-A No. 56-155636 discloses that although it itself does not have dispersion stability for the core material at acidic pH, it imparts dispersion stability to the liquid material that becomes the core material through interaction with the melamine-formaldehyde initial condensate. An aqueous medium is prepared containing a polymer forming a substance and a melamine-formaldehyde precondensate, and after this dispersion stable substance is formed, a core material is added to form a stable dispersion, and an acid A method has been proposed in which a melamine-formaldehyde initial condensate is condensed using a catalyst to form a capsule wall membrane.

However, in this method, in order to form a dispersion-stable material for the core material between the melamine-formaldehyde initial condensate and the polymer, partial condensation is carried out at low temperature for a long time before the presence of the core material. After that, it is necessary to emulsify and disperse the core material, raise the temperature, and condense the core material.If the partial condensation conditions of the melamine-formaldehyde initial condensate in the presence of the polymer are not controlled to Ii[, the emulsion stability will be poor and the particles will be Capsules with irregular diameters may be obtained, or the capsules may tend to thicken significantly. Additionally, problems remained in terms of work process management. Further, with this method, it is not possible to obtain a microcapsule slurry having a solid content of 55 wt% or more.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for producing microcapsules having dense microcapsule walls.

Broadly speaking, it is an object of the present invention to provide a method for producing microcapsules that provides a microcapsule slurry that has low viscosity despite a high solids concentration and has excellent pH stability.

(Means for Solving the Problems) The above object of the present invention is achieved by the following method for producing microcapsules.

In a system in which a hydrophobic core material is dispersed or emulsified in an acidic aqueous solution containing an anionic water-soluble polymer, an amino-aldehyde resin film is formed on the surface of the hydrophobic core material as a wall film to form microcapsules. In the production, acrylamide is used as the anionic water-soluble polymer component.
A method for producing microcapsules, characterized by using a polymeric substance containing aralkyl sulfonic acid and/or its salt as an essential monomer.

The acrylamide-aralkyl sulfonic acid used in the present invention has the general formula CI) (wherein, Rle R3 represents a hydrogen atom or a lower alkyl group, and R2 represents a C1 to C4 alkylene group).
In the present invention, the compound is used in the form of an acid form, or an alkali metal salt such as Na, K, Cs, or Li, an ammonium salt, or a lower amine salt.

Specific examples of acrylamide-aralkylsulfonic acid include 2-acrylamido-2-phenylpropanesulfonic acid, 2-acrylamido-2-phenylbutanesulfonic acid, 2-acrylamido-2-(p-tolyl)propanesulfonic acid, and 3-acrylamido-2-phenylbutanesulfonic acid. Acrylamide-3 phenylpropanesulfonic acid, 2-acrylamide-2-phenylethanesulfonic acid, 2-acrylamide-2(2',4''-
Examples include, but are not limited to, compounds such as dimethylphenyl)ethanesulfonic acid.

The production of the microcapsules of the present invention uses the above-mentioned polymer using acrylamide-aralkylsulfonic acid, and among these acrylamide-aralkylsulfonic acids, 2-acrylamido-2-phenylpropanesulfonic acid is industrially It is also preferable from the viewpoint of workability.

Such acrylamide-aralkyl sulfonic acid may be polymerized alone or copolymerized with other vinyl monomers. As a method for polymerizing acrylamide-aralkyl sulfonic acid, known ionic polymerization method or radical polymerization method may be used. is used.

Vinyl monomers used in the copolymerization of acrylamide-aralkylsulfonic acid include acrylic acid, methacrylic acid, acrylonitrile, methacrylaterile, styrene, vinyltoluene, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxymethyl acrylate, and hydroxyl. Ethyl methacrylate, acrylamide, methacrylamide, methylol acrylamide, etc. are used. The polymer composition of the acrylamide aralkyl sulfonic acid used is changed as appropriate depending on the manufacturing conditions of the microcapsules, the core material, etc. Among these, (1) ease of obtaining raw material monomers;
2-acrylamide-2-phenylpropanesulfonic acid-acrylic acid from the viewpoints of (2) copolymerizability, and (3) excellent emulsifying and dispersing effects on non-polar and polar oily substances, which are usually the core materials of capsules. Acid-acrylonitrile terpolymer is most preferably used.

The acrylamide aralkylsulfonic acid polymer used in the present invention is used in the form of an aqueous solution when producing microcapsules. These are 20% aqueous solution (pH 4.0,
3 to IO0,000 cps at 25° C.), more preferably 10 to 10,000 cps. The viscosity of a 20wt% aqueous solution is 3cps
It is difficult to produce the following copolymers with relatively small molecular weights;
In addition, if the slurry is too high or more than 0.000 cps, the resulting microcapsule slurry will have a high viscosity, making it unsuitable for the production of high solid content microcapsules. The aqueous solution of anionic polymer electrolyte (copolymer) used for
No clouding, precipitation, or significant thickening tendency is observed in any pH range of 14. Therefore, large viscosities such as aqueous solutions of maleic acid copolymer (hydrolyzate of ethylene maleic anhydride copolymer) There is no pH dependence, and when the pH is increased, there is no significant viscosity change (increase) of the copolymer aqueous solution or the microcapsule slurry obtained using the copolymer solution, making it extremely easy to handle.

Furthermore, when applying the microcapsules of the present invention to pressure-sensitive copying paper, which is one specific use, the coating is generally applied to the support as a neutral to weakly alkaline paint, so viscosity changes due to pH increases are avoided. The fact that there is no such thing is extremely convenient from the viewpoint of coating work.

The amount of the water-soluble polymer used in the present invention is 0.2-15 wt% of the microcapsule production system, the fis of the water-soluble polymer used, the capsule membrane forming starting material used, and the type of core material to be encapsulated. , or 1-5W for microcapsule production, although it varies depending on the capsule production conditions etc.
In addition to the water-soluble polymer of the present invention, which is generally used in an amount of about t%, other anionic water-soluble polymers such as ethylene maleic anhydride copolymer, methyl vinyl ether maleic anhydride copolymer, Polyacrylic acid, styrene maleic anhydride copolymer, vinyl acetate maleic anhydride copolymer,
It is also possible to use a styrene sulfonic acid polymer or copolymer, anion-modified poval, gum arabic, cellulose derivatives, etc. in combination as appropriate.

The substances that form the amino-aldehyde resin film are:
For example, urea and formaldehyde, urea-formaldehyde initial condensates and their modified products (methylolurea, methylated methylol urea, or their low molecular weight polycondensates, etc.), melamine and formaldehyde, melamine-formaldehyde initial condensates (methylolated melamine, methylated methylol (melamine or a low molecular weight polycondensate thereof), a urea-melamine-formaldehyde initial condensate, etc. are used, but the present invention is not limited to these examples.

The ratio of the above amino-aldehyde resin film-forming material to the core material to be microencapsulated is generally 1 by weight.
:2 to 1:20, but it varies depending on the type of material used as the core material or the use.

The microcapsule core material used in the present invention is
It is a liquid or solid that is immiscible with water and is substantially inert to water. Preferred core materials include:
Examples of hydrophobic liquids include partially hydrogenated terphenyl, chlorinated paraffin, diallylalkane, alkylnaphthalene, dibenzylbenzene derivative,
Alkylbenzenes, paraffins, cycloparaffins, and various esters such as phthalic acid, azidoic acid, citric acid, myristic acid, trimellitic acid, sebacic acid, stearic acid, benzoic acid, phosphoric acid, silicon-containing Compounds such as nitrobenzene, dimethylaniline, dimethyl-p-toluidine, and the like. Further examples include liquid crystal substances (cholesteric liquid crystal, chiral nematic liquid crystal). Furthermore, a hydrophobic liquid in which a water-insoluble solid substance is dissolved can also be used as the core material.

Preferred applications of the microcapsules of the present invention for pressure-sensitive copying paper include phthalide derivatives, fluoran derivatives, azaphthalide derivatives, acylleucophenothiazine derivatives, leukotriarylmethane derivatives, icoidolylmethane derivatives, and suthrobilane derivatives. or phthalimidine derivatives dissolved in a hydrophobic high-boiling solvent such as alkylnaphthalene, diallylalkane, or partially hydrogenated terphenyl is used.

A detailed outline of the microencapsulation process of the present invention is as follows.

1) Preparing an anionic polymer electrolyte aqueous solution, 2) Emulsifying or dispersing a core substance in an anionic electrolyte aqueous solution, 3) Adding an amino-aldehyde wall film-forming substance, 4) Amino-aldehyde resin microcapsule formation step by film formation, and 5) treatment step of residual formalin (if necessary) Of course, in these steps, a step of changing the pH and temperature of the system at any point as necessary is also possible. It is inclusive.

The anionic electrolyte used in the present invention has a wide pH range,
It exhibits extremely stable emulsifying and dispersing properties for the core material over a temperature range, and even when an amino-aldehyde film-forming substance is added, there is almost no tendency for thickening or growth of particles due to coalescence or aggregation of the core material particles. It has extremely good workability.

For emulsifying and dispersing the core substance, an emulsifying machine such as a homomixer, homogenizer, ultrasonic homogenizer, Waring blender, flow jet mixer, in-line mill, etc. is appropriately selected and used depending on the purpose. The preferred particle size of the emulsified dispersion varies depending on the use of the microcapsules, but as a specific example, when used for pressure-sensitive copying paper, the average particle size is about 2 to 8 μm, and many coarse microcapsule particles are present. This is undesirable because weak pressure causes scumming due to destruction of the microcapsules.

Furthermore, another embodiment of the method for manufacturing microcapsules of the present invention includes a manufacturing method (B) using the following steps.

1) Step of preparing an aqueous solution of anionic polymer electrolyte 2) Step of adding and mixing an amino-aldehyde film-forming substance 3) Step of adding a core material and emulsifying and dispersing it 4) Forming microcapsules by forming an amino-aldehyde resin film Formation step 5) (required (accordingly) processing step for residual formalin) In this manufacturing method, compared to the above-mentioned manufacturing method,
Depending on the core material used, the effect of shortening the time required for emulsification and narrowing the particle size distribution width of emulsified droplets may be obtained.

In either method, the microcapsule film forming reaction by polycondensation of the water-soluble melamine-formaldehyde wall film-forming material is carried out at a temperature of 40 to 90°C after the formation of an emulsified dispersion of the core material.
The reaction is carried out at a temperature of preferably 50 DEG to 80 DEG C. and a pH of 3.0 to 6.5, preferably 4.0 to 5.5, for 1 to 10 hours. Generally, empty microcapsule wall films are formed using melamine formaldehyde resin by storing them under the above conditions for about 1 to 2 hours. When used in such applications, microcapsules with a higher degree of crosslinking and excellent solvent resistance stability can be obtained by reacting under somewhat harsh conditions, for example, at 70° C. or higher for a long time. There is also no problem in using a reaction accelerator such as an ammonium salt of an acid (for example, ammonium chloride) during the formation of microcapsules.

After the formation of the microcapsule wall, if it is sanitary necessary to remove or reduce the remaining free formaldehyde, use urea, ethylene urea, sulfites, sugars, ammonia, amines, formamide, hydroxyalkyl (hydrochloric acid) salts, sulfates, phosphates), melamine, compounds with active methylene groups, hydroxyalkylamines,
Residual formalin can be removed by converting formaldehyde into a harmless form by adding acrylamide, an acrylamide-based polymer, a copolymer, etc. and under appropriate reaction conditions.

〔Effect of the invention〕

As mentioned above, the microcapsule liquid of the present invention has no agglomeration tendency in a wide H range and exhibits a low and stable viscosity value, so it can easily respond to a wide range of formaldehyde treatment conditions and is generally used as a binder or other The viscosity does not change even under weakly alkaline conditions when mixed with other materials and applied to a support such as paper, so coating workability is also extremely good.

By using the method for producing microcapsules of the present invention, microcapsules with an ultra-high solid concentration exceeding 60 wt% solid content can be produced on an industrial scale as a slurry with a very low viscosity, which has been previously desired but could not be achieved. be able to obtain it. This greatly improves the volumetric efficiency of capsule manufacturing equipment, and significantly improves capsule manufacturing and transportation costs. By making it possible to reduce the viscosity and high concentration of capsule slurry, it has become possible to apply capsule slurry with a higher solids content than before, and as a result, the energy required to remove water during coating drying has been significantly reduced. high speed coating is possible. Furthermore, in addition to coating methods using air knife coaters and bar coaters, which have not been widely used in the past, coating methods such as blade coaters and gravure coaters suitable for high-speed application of higher concentration paints are now possible, as well as water-based flexo inks. It also makes it possible to achieve high density printing, and it is possible to achieve zero printing on the entire surface or in parts using a printing method that was previously impossible to obtain.
8 paper can be put to practical use.

In general, the microcapsules obtained by the method of the present invention have extremely high heat resistance stability, which, combined with an unprecedentedly high concentration, makes it necessary for drying processes such as spray drying to handle them as powder capsules. This makes it possible to significantly reduce thermal energy and improve work efficiency. Furthermore, the microcapsules obtained by the method of the present invention have solvent extraction resistance such that the core substance is not extracted even when mixed with wood-philic polar solvents such as alcohol and ketones. Microcapsules based on water slurry are easy to use, and unlike microcapsules obtained by conventionally proposed in-3 intu polymerization methods, the system does not tend to agglomerate or thicken due to the addition of polar solvents. , a variety of water-based inks, such as water-based flexo ink, water-based gravure ink, and water-based screen ink suitable for partial printing of microcapsules, is unprecedented and outstanding, and unexpected from conventionally disclosed technology. It is extremely effective.

〔Example〕

The present invention will be explained in detail with reference to Examples below.

Examples] 0.2 mol of 2-acrylamido-2-phenylpropanesulfonic acid (hereinafter abbreviated as APPS), 0 acrylic acid
．． 5 mol of acrylonitrile and 0.3 mol of acrylonitrile, a 20% aqueous solution of a pale yellow APPS copolymer (
A) was obtained (average molecular weight 300,000, viscosity 430 cps by aqueous GPC).

Microencapsulation was performed using this aqueous solution (A) in the following manner. 30 parts of aqueous solution (A) was diluted with water to make 92.4 parts, and the core material was added to an aqueous solution (pH 4.0) containing 3.0% by weight of Nostalgic violet lactone and 0.8 parts by weight of benzoyl leucomethylene blue. I%
Alkylnafucrene (Kureha Chemical Co., Ltd.) dissolved in MCll
Add 130 parts of 3 J) and mix and emulsify with a homomixer (manufactured by Tokushu Kika) at a rotation speed of 1100 m.
After 0 minutes, a stable OZW type emulsion with an average particle size of 3.5 μm was obtained. After adding 24.4 parts of methylated methylolmelamine resin aqueous solution (non-volatile content 80 wt%, Mitsui Toatsu Chemical "Euramint 34") with stirring, the system was heated to 60°C.
The temperature was raised to 2 hours, and the mixture was combined for 2 hours, and then cooled to complete the microencapsulation.

The resulting microcapsule slurry contains a very high solids content of 63 wt% and has a viscosity of 550 at 25°C.
It was cps. To remove residual formaldehyde in the slurry, add 28% ammonia water to pH 8.5.
As a result, the formalin odor disappeared and there was no aggregation tendency.
The microcapsule slurry of the present invention, in which a microcapsule slurry with a good viscosity of 50 cps was obtained, is useful for pressure-sensitive copying paper.

Example 2 The microcapsule slurry obtained in Example 1 was diluted with water, and the relationship between solid content and viscosity was investigated.

The viscosity of each sample was measured using a B total viscometer at 25°C.

Example 3 36 parts of the 20% aqueous anionic water-soluble polymer solution (A) prepared in Example 1 was diluted with 84 parts of water to adjust the pH to 4.1. To this was added 36 parts of a methylated methylolmelamine aqueous solution containing 80% nonvolatile content, and the mixture was stirred to prepare a homogeneous aqueous solution. In the aqueous solution, 3-diethylamino-
Add 144 parts of phenylxylylethane (Japan Petrochemical Co., Ltd. "Hisol 5AS-296") in which 4.0% by weight of 6-methyl-7-anilinofluorane and 0.5% by weight of crystal violet lactone were dissolved, and mix it with a homomixer. When the mixture was emulsified using IIooorpm, a stable 0/W type emulsion with an average particle size of 3.5 μm was obtained in 3 minutes. This emulsion had low viscosity and excellent emulsion stability. Note that the above steps are performed at a temperature of 2
It was carried out at 5°C. Next, remove the homomixer and slowly raise the temperature of the system to 70°C while stirring slowly.
Capsule wall formation was carried out at 70° C. for 1 hour. Next, 50% acetic acid was added to adjust the pH to 4.5, and then 1
A time reaction was performed. After that, the microcapsule slurry of this example was cooled and microcapsules were completed at 60w.
It contained a high solids content of t% and a low viscosity of 110 cps. Take 100 parts of the microcapsule slurry thus obtained, add 1,710 parts of urea to the methylated methylolmelamine used, and adjust the pH with acetic acid.
After setting the pH to 3.0, the temperature was raised and the reaction was carried out at 70°C for 1 hour to remove residual formaldehyde.Finally, the pH was raised to 9.5 with a 20% aqueous solution to obtain a microcapsule slurry with no formalin odor. Ta. Even in the formalin removal step, no tendency towards thickening and aggregation was observed. In addition, almost no coloring of the capsule slurry was observed, and the pressure-sensitive copying paper obtained using this microcapsule slurry also exhibited a good hue without background stains, and when combined with CF paper, a black colored image was provided.

Example 4 Na salt of 2-acrylamido-2-phenylpropanesulfonic acid (hereinafter abbreviated as APPS-Na) 0.35
A 20% aqueous solution (B) of an anionic water-soluble polymer having a monomer composition of 0.2 mol% of methacrylic acid and 0.45 mol% of vinylpyrrolidone was prepared according to the method for producing a copolymer in Example 1. I got it. The average molecular weight of the aqueous solution (B) by GPC was 140,000, and the viscosity was 1200 cps. 50 parts of aqueous solution CB), 10 parts of urea, 1 part of resorcinol, and 250 parts of water are mixed well, and the pH is adjusted to 3.3 using a 20% aqueous NaOH solution. Next, phenylxylylethane (Japan Petrochemical Co., Ltd. "Hysol 5AS-29
Add 200 parts of
pm) Emulsified using 7i, average particle size of 3 minutes 4.0u
A stable emulsion of ○/W type was obtained. Add 25 parts of formalin (37% formaldehyde aqueous solution) to the system. The system was heated to 60° C. with stirring, and then kept at this temperature for 4 hours while stirring to complete microencapsulation with a dense wall film of urea-formaldehyde resin around the core material. Ta. Cool and stir under stirring.
The formaldehyde odor of the system disappeared by gradually adding % ammonia water and adjusting the pH to 8.5.The microcapsule slurry of this example had a solid content of 43 wt% and a solid content of 60%.
It has a low viscosity of cps. In this microcapsule slurry, almost no viscosity change was observed between the pH at the time of condensation (3,3) and the pH after formaldehyde removal (8,5). This microcapsule slurry was useful for pressure sensitive copying paper.

Comparative Example 1 50 parts of ethylene maleic anhydride copolymer was heated and dissolved in 450 parts of water to make a 10% aqueous solution (CD)! Obtained. Aqueous solution (D)
Mix 100 parts and 200 parts of water, 10% Na0HA
The pH was raised to 4.0 with J solution. Into this, 200 parts of the same core material as in Example 1 was emulsified using a homomixer to obtain a stable O/W type emulsion.

While stirring, 60 parts of methylated methylolmelamine (Mitsui Toatsu's Neelamine T-530J) having a solid content of 50% is added thereto, and the mixture is stirred and kept warm at 55° C. for 2 hours to complete microencapsulation.

Although this microcapsule slurry has a solid content concentration of 42.9 wt%, the viscosity of the system increases significantly with the formation of a wall film due to the condensation of the melamine formaldehyde initial condensate. Although the slurry had no tendency to agglomerate, it exhibited a high viscosity of 7400 cps and almost lost its fluidity.

Comparative Example 2 Solid content of finished microcapsule liquid lFr35wt%
Microencapsulation was completed in the same manner as in Comparative Example except that the water content was adjusted so that

The obtained microcapsule slurry had a pH of 4 after cooling.
8 showed a viscosity of 250 cps. To remove residual formalin, add 28% ammonia water to adjust the pH to 8.5.
After one adjustment, the formaldehyde odor completely disappeared, but the microcapsule slurry thickened to 670 cp.
It showed a viscosity of s, and a large viscosity-leaf dependence was observed, requiring sufficient attention to +)H management during coating work.

Comparative Example 3 2.5 parts of styrene-maleic anhydride copolymer (Monsanto "Sufrivset-520J") and vinyl acetate maleic anhydride copolymer (Nippon Nyukazai rDisrol H-
12 Unneutralized J) 2.5 parts were dissolved under heating while adjusting the pH to 5.0 using a dilute NaOH aqueous solution to obtain aqueous solution 1.
00 copies. It took 4 hours to completely dissolve (heating at 90°C). Microcapsules were then carried out in a constant temperature water bath at 55°C.

100 parts of the above styrene-maleic anhydride copolymer and vinyl acetate-maleic anhydride aqueous solution and 17.5 parts of water.
10 parts of the same core material used in Example 1.
After emulsifying and dispersing 0 part with a homomixer, add methylated methylolmelamine 80% aqueous solution (Neelamine T-33)
After 12.5 parts of the mixture was added and the mixture was combined for 2 hours, it was cooled to complete the capsule membrane formation. The resulting microcapsule slurry contained 50 wt% solids and had a viscosity of 620 cps. In order to remove residual formalin, the mixture was heated to 60°C again, 3 parts of a 40 wt% urea aqueous solution lFr was added, and the pH was adjusted to 4.0 with acetic acid, but the entire mixture thickened and became impossible to stir, resulting in the addition of urea, etc. It was not possible to use the method of removing residual formaldehyde on the acidic side.

Comparative Example 4 (Based on Example 1 of JP-A-56-58536) After stirring and dissolving 40 parts of 2-acrylamide F-2-methylpropanesulfonic acid in 160 parts of water, 5.0% of P)I was dissolved in 20% NaOH aqueous solution. Adjust to 0 and 10 of ammonium persulfate.
% aqueous solution and 0.8 part of a 10% sodium bisulfite aqueous solution were added and polymerized under adiabatic conditions at 25°C (
20% of the Na salt of poly-(2-acrylamido-2-methyl-propanesulfonic acid) with a viscosity of 430 cps.
wt% aqueous solution (D)! Obtained.

[4-11 Microencapsulation (carried out in a constant temperature water bath at 60°C) 25 parts of the aqueous solution (D) and 85 parts of water were mixed with stirring, and the pH was adjusted to 4.0 with acetic acid. 100 parts of the same core material as in Example 1 was added to the system, and emulsified and dispersed for 20 minutes using a homomixer. The obtained O/W type emulsion has poor emulsification stability, and as soon as stirring is stopped, the oil droplets coalesce, so it is necessary to constantly apply strong shearing force to maintain the oil droplets in minute size. Moreover, it was very difficult to control the size of the emulsified droplets.When 30 parts of a 50% aqueous solution of methylated methylolmelamine (Neilamine P-6+00J manufactured by Mitsui Toatsu Chemical Co., Ltd.) was added to the system under 0-strong stirring, the system rapidly increased. After 5 minutes of viscosity, the entire mixture became agglomerated into a gel.

[4-21 It has the same composition as [4-1], but after carefully dropping methylated methylolmelamine (Neilamine P-6100) under strong stirring over a period of 2 hours to avoid gelation of the system. The reaction was further carried out for 2 hours to complete the encapsulation. Due to the poor emulsion stability with respect to oil, the resulting microcapsules contained many coarse particles and aggregated particles, which was inconvenient for use in pressure-sensitive copying paper unless they were passed through a sieve.

The average particle diameter was 7.4 μ, the solid content was 50 wt%, and the viscosity was 350 cps.

Comparative Example 5 (Based on JP-A-58-14949 Example 1) Styrene sulfonic acid sodium salt (Toyo Soda "Svinomer-3S")
J) (purity 85%) 8.4 parts dissolved in 161.3 parts of 598% acrylic acid and human O
6.5 parts of xyethyl methacrylate (HEMA) was added, stirred to form a homogeneous aqueous solution, and kept at 40°C. Radical polymerization was started by adding 12.9 parts of a 10% aqueous solution of ammonium persulfate and 4.0 parts of a 10% aqueous solution of sodium bisulfite salt, and the internal temperature was raised to 65° C. in 330 minutes. The polymerization was completed by further heating at 70° C. for 30 minutes to obtain an anionic water-soluble polymer aqueous solution (E) with a solid content of 20 wt%. The viscosity of this product was 4800 CI)S at 25°C.

[5-11 Microphone 0 encapsulation with melamine formaldehyde resin (carried out in a constant temperature water bath at 60°C) 32.5 parts of polymer aqueous solution (E) was stirred and mixed with 125.1 parts of water, and the mixture was mixed with 10% NaOH aqueous solution to pH 2.0. 4 to 4
．． Raised to 0. Same core material 13 as used in Example 1
0 parts was added and emulsified for 20 minutes using a homomixer to obtain an O/W type emulsion. Emulsion stability is somewhat insufficient, and if snow is crushed as it is, the droplet size tends to increase due to coalescence of oil droplets. 80% methylated methylolmelamine under stirring
When 16.25 parts of % aqueous solution [Neelamine P-6300] was added and condensation was carried out, the entire system gelled after 10 minutes and no microcapsules were obtained.

[5-2] Microcapsulation with urea formaldehyde resin (conducted in a constant temperature water bath at 60°C) 9.88 parts of polymer aqueous solution (E) + 138.23 parts were mixed with stirring, 6.63 parts of urea, and 0 resorcinol. Add and dissolve .93 parts, and adjust the pH to Fr2.75 with 10% NaOH aqueous solution.
It was raised from 3.40 to 3.40. To this was added 117 parts of the same core material used in Example 2, and the mixture was emulsified for 20 minutes using a homomixer.
/W type emulsion was obtained, but the emulsion was colored deep reddish-purple due to its strong acidity. 37 under stirring
After adding 17.2 parts of % formalin and reacting for 3 hours, microencapsulation was completed and the mixture was cooled. The resulting microcapsule slurry had a solids content of 45 wt% and 250 c
It had a viscosity of ps. However, this slurry was extremely colored reddish-purple, and the coloring did not disappear even if it was made alkaline with NaOH or the like, and the surface of the pressure-sensitive paper coated with this capsule slurry was also highly colored and was not practical.

Example 5 69 parts of the aqueous solution (A) obtained in Example 1 was added to 17 parts of water.
It was diluted with 5 parts and the po was adjusted to 4.3 with 10% aqueous NaOH. To this aqueous solution, 67.5 parts of an 80% aqueous solution of methylated methylolmelamine was added with stirring, and then 1 part by weight of crystal violet lactone as a core material, 2 parts by weight of Suphenol A, and 30 parts by weight of lauric acid were mixed and heated. 270 parts of the melted composite acid was added and emulsified by mixing 1 liter at 1000 rpm for 10 minutes using a homomixer. The temperature of the system was then raised to 60° C. while stirring, alignment was carried out for 2 hours, and then cooled to room temperature to complete microencapsulation.

The obtained microcapsules are disclosed in Japanese Patent Application Laid-Open No. 53-12858.
It is useful as a microcapsule for thermochromic ink proposed in No. 8, which develops and fades at a temperature of about 42°C.

Example 6 The same procedure as in Example 5 was carried out except that the core material was changed to N,N-dimethyl-p-toluidine. The dried powder obtained by spray drying the obtained microcapsules is effective as a curing agent for anaerobic adhesives for fixing bolts in automobiles.

Example 7 The same procedure as in Example 5 was carried out except that the core material was replaced with the same one as in Example 1. The resulting microcapsule slurry is useful for aqueous flexographic microcapsule spot inks.

70 parts of the microcapsule slurry of this example, and styrene maleic anhydride copolymer [Arayo Kagaku Alastair 7]
00) Ethanol 100 dissolved in 300 wt%
An alcohol-water flexographic ink was obtained by mixing the two parts. The ink was a milky white, low viscosity slurry with a viscosity of 15 seconds in Zahn Cup Well 3. This ink was partially printed on high-quality paper using a test flexographic printing machine to obtain pressure-sensitive copy paper spot-on paper. When partially printing with this ink, it dries quickly and there is no problem with the drying speed, and the viscosity and concentration of the ink can be freely adjusted using ethanol. When the spot-printed surface was combined with a commercially available pressure-sensitive copying paper, CF paper, a clear blue colored image was obtained on the CF surface.

Example 8 The same procedure as in Example 1 was carried out except that 2-acrylamido-2(2°,4′-dimethylphenyl)ethanesulfonic acid was used in the same molar amount instead of 2-acrylamido-2-phenylpropanesulfonic acid. Microencapsulation was performed.

Furthermore, 28% ammonia water was added in the same manner as in Example 1 to remove formalin, and a good microcapsule slurry having a viscosity of 720 cps was obtained. This microcapsule slurry is useful for pressure sensitive copying paper.

Claims (4)

[Claims] (1) In a system in which a hydrophobic core substance is dispersed or emulsified in an acidic aqueous solution containing an anionic water-soluble polymer substance, an amino-aldehyde resin film is formed as a wall film on the surface of the hydrophobic core substance to form a microorganism. When manufacturing capsules,
A method for producing microcapsules, characterized in that the anionic water-soluble polymer substance is a polymer substance containing acrylamide-aralkyl sulfonic acid and/or its salt as an essential monomer. (2) The acrylamide-aralkyl sulfonic acid is
The method according to claim 1, which is 2-acrylamido-2-phenylpropanesulfonic acid and/or a salt thereof. (3) The anionic water-soluble polymer substance includes (a) 2-acrylamido-2-phenylpropanesulfonic acid, (b
) acrylic acid and/or methacrylic acid and (c
) The method according to claim 1, wherein the copolymer is a multicomponent copolymer of acrylonitrile. (4) Claims in which the amino-aldehyde resin film is substantially a melamine-formaldehyde resin film obtained from melamine and formaldehyde, methylolmelamine or a low molecular weight condensate thereof, or alkylated methylolmelamine or a lower condensate thereof. The method described in paragraph 1.