JP5057501B2 - Microcapsule manufacturing method, microcapsule and display medium using the same - Google Patents

Description

The present invention relates to a method for producing a microcapsule and a microcapsule produced thereby. More specifically, the present invention relates to a method for producing a microcapsule that forms a film with a specific hydrophilic colloid and a compound having a carbodiimide group (hereinafter sometimes referred to as a carbodiimide compound) at the time of producing the microcapsule.
The present invention further relates to a display / recording material such as a magnetic display medium comprising such microcapsules.

  Conventionally, microcapsules have been applied to various uses, and many proposals have been made regarding their production methods. For example, a complex coacervation method, which is one of the microencapsulation methods applied industrially, produces microcapsules by the following treatment example.

(1) A core substance (oil-based substance) is dispersed in an aqueous solution containing a film substance (polycation) to obtain an O / W emulsion in which oil droplets are dispersed in the aqueous solution.
(2) A polyanion is added to the emulsion and mixed, and an acid is added to adjust the pH to about 3-5. As a result, coacervation occurs and a coacervate film is formed.
(3) The film of coacervate droplets is gelled at a low temperature, and a curing agent is further added to cure (crosslink and / or modify) the film.

  Aldehydes such as formaldehyde and glutaraldehyde are generally used as a curing agent for the microcapsule film by such a method. However, although aldehydes are effective curing agents, it is not preferable to use them from the viewpoints of toxicity and environmental considerations. Both formaldehyde and glutaraldehyde have been designated as PRTR Class 1 Designated Chemical Substances. In particular, formaldehyde has been suspected as a causative substance of sick house syndrome in recent years, and volatile organic compounds (hereinafter referred to as VOCs). It is positioned as a substance subject to emission control. For this reason, various studies have been made on curing agents that can replace aldehydes.

On the other hand, compounds having a carbodiimide group have been proposed as coating materials, paints, adhesives and the like as curable resin compositions (Patent Documents 1 to 3). The carbodiimide group can react with active hydrogen such as carboxyl group, amino group and hydroxyl group.
Many patents have been filed for gelatin related to biochemistry, such as immobilized enzymes and pharmaceutical applications. In addition, there are examples of application to the surface effect and functionality of thermoplastic fine particles, but only proposals for surface modification and functional addition of these fine particles, microcapsule capsules containing functional materials inside It is not membrane modification.
These patent documents and the like do not exemplify gelatin, gelatin does not correspond to the thermoplastic resin, and the prior art has no proposal relating to the present invention.

  Further, in applications such as the coating, the reaction is performed at a relatively high temperature. The reaction in the present invention is carried out at a relatively low temperature and can be carried out in water. Moreover, the reaction in water required by this invention must be processed at the temperature below a prescription | regulation by the property, and requires special conditions. This is because a gel-like hydrophilic colloid film that does not have heat resistance before curing readily dissolves in water at a temperature above the gel point. The reaction of the carbodiimide compound in the prior art is not a reaction in water but a dried / cured product, and there is no suggestion regarding the present invention.

Further, a magnetic display medium using a microcapsule and a heat-sensitive recording material have been studied (Patent Document 4). However, these materials use microcapsules manufactured by a conventional method, and microcapsules containing harmful aldehydes are generally used.
Japanese Patent Laid-Open No. 10-316930 JP 2003-268118 A JP 2004-75710 A JP 2001-75510 A

  The present invention prepares microcapsules that can obtain heat resistance, strength, and transparency without using aldehydes that have been used in the past, and that are particularly suitable for display media such as magnetic display media. The present invention intends to provide a method for producing a capsule.

The present invention, in order to solve the above problems, a process for the preparation of microcapsules according to Complex coacervation method, a basic film material gelatin, the polymer compound having a carbodiimide group The basic coating material in water The microcapsules and the like of the present invention were completed by characterizing the formation of microcapsules by curing (crosslinking and / or modification, the same applies hereinafter).
That is, the present invention
"1. A method of manufacturing a microcapsule according to Complex coacervation method, a basic film material gelatin, forming a film of the microcapsules by the base coating material is cured by a polymer compound having carbodiimide groups A method for producing a microcapsule, characterized in that:
2. The method for producing a microcapsule according to claim 1 , wherein the polymer compound having a carbodiimide group is a polymer compound having film-forming properties.
3. Preparation of microcapsules according to claim 1 or 2 wherein the gelatin is pI = 8.0 or more.
4). The microcapsule according to any one of claims 1 to 3, wherein the reaction at the time of hardening is an acidic region of pH = 3 to 5 and is treated at a temperature not higher than a gel point of gelatin. Manufacturing method.
5. Microcapsules obtained by the process according to any one of claims 1 to 4.
6). A display medium obtained by arranging a plurality of microcapsules according to claim 5 including at least a display element as a core substance. ".

According to the present invention, microcapsules having heat resistance, strength, and transparency can be prepared as VOCs and without using highly harmful aldehydes that can cause sick house syndrome.
Further, it is not always necessary to adjust the pH to the alkaline region when the microcapsule film is cured, and it is possible to avoid phenomena such as thickening of the microcapsule dispersion, aggregation of the microcapsules, and swelling of the microcapsule film.
For the same reason, since microcapsules can be prepared in a wide pH range from acidic to alkaline, it is suitable for microencapsulation of substances that are easily affected by pH.
In addition, when a polymer, particularly a film-forming polymer, is used as the curing agent, the curing agent itself has a film property, so that the coating material is cured, and at the same time, a double coating with the curing agent itself occurs, and the inclusion is retained. Ability can be improved.
By using the microcapsules obtained by this method, it is possible to obtain a display medium that does not contain harmful substances and has excellent resolution.

Manufacturing method of microcapsule The manufacturing method of the microcapsule according to the present invention includes forming a microcapsule by using a hydrophilic colloid having a carboxyl group as a basic coating material and curing the basic coating material with a compound having a carbodiimide group. It is characterized by.
Here, the hydrophilic colloid indicates a molecular colloid or the like that exists in a solvent and can be coordinated around a core substance to form an emulsion.
For example, hydrophilic colloids having a carboxyl group include water-soluble proteins such as gelatin and albumin, natural polymer substances such as starch, agar, and gum arabic, synthetic cellulose ethers such as carboxymethylcellulose and carboxymethylhydroxyethylcellulose, and polyvinylmethyl. Synthetic polymer compounds such as ether / maleic anhydride copolymer and carboxyl group-modified polyvinyl alcohol can be used, and one or more of them can be used in combination. Among them, a water-soluble protein having gelling property is preferable for use as a basic film substance. Further, gelatins such as alkali-treated gelatin and acid-treated gelatin are preferable, and among them, acid-treated gelatin is most suitable.

  In addition, carbodiimide groups can react with active hydrogens such as carboxyl groups, amino groups, and hydroxyl groups, and can react with both carboxyl groups and amino groups of gelatin. The carbodiimide compound is extremely useful, and is preferable because it can exert a crosslinking action on both functional groups.

The method of the present invention will be described as an example using the complex coacervation method according to the order of the manufacturing steps as follows.
First, a core material (oil-based substance) is dispersed in an aqueous solution containing a carboxyl group-containing hydrophilic colloid, that is, a basic film material, thereby forming an O / W emulsion in which oil droplets are dispersed in the aqueous solution.

  The core substance to be used is arbitrarily selected according to the target microcapsule. For example, a pressure-sensitive adhesive, an adhesive, a color material, and the like can be given. In addition, an element of a display medium, for example, an oily substance containing fine magnetic particles of a magnetic display medium as a dispersion, an electrophoretic particle used in electronic paper, an inverted particle such as a twist ball, an oily substance containing liquid crystal, or the like by heating A heat-sensitive recording material that changes color can also be used. In addition, foods, pharmaceuticals, quasi drugs, fragrances, detergents and the like that are immiscible with water can be used as the core substance.

  As the basic film material, a gelable hydrophilic colloid having an isoionic point as a polycation is used, and a water-soluble protein is generally used. More specifically, gelatin, agar, casein, soybean protein, collagen, albumin and the like can be mentioned. Of these, gelatin such as acid-treated gelatin and alkali-treated gelatin is preferred, and acid-treated gelatin is most preferred.

  In order to disperse the core substance in the aqueous solution containing the basic film substance, a method such as stirring and ultrasonic irradiation can be used by adding the core substance to the aqueous solution. The concentrations of the core substance and the film substance are arbitrarily selected depending on the properties and shapes required for the target microcapsules. Further, the size of the core material droplet obtained by the dispersion is related to the size of the microcapsule finally obtained. The size of the microcapsules is selected according to the purpose, and the size of the droplets of the emulsion is substantially reflected as the particle size of the microcapsules. The final size of the microcapsules is specifically, oil droplets corresponding to a sphere equivalent diameter of generally 0.1 to 3000 μm, preferably 0.1 to 2000 μm, more preferably 0.1 to 1000 μm. Disperse as follows.

  Subsequently, a polyanion is mixed into the obtained O / W emulsion to make it uniform, and then the pH is acidified to form a coacervate film.

  The polyanion to be used is selected as necessary, and specific examples include gum arabic, sodium carboxymethylcellulose, sodium alginate, sodium polyvinylbenzenesulfonate, polyvinylmethylether / maleic anhydride copolymer, and the like. Of these, gum arabic and sodium carboxymethyl cellulose are preferably used.

  After mixing the polyanions, the pH of the emulsion is adjusted to acidic, for example, pH = 3-5, preferably 4-5. The acid used at this time is preferably selected from those that do not impair the properties of the core material and the coating material, and those that do not inhibit the curing reaction. In general, organic acids such as acetic acid, citric acid, succinic acid, oxalic acid, lactic acid and salicylic acid, and inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid are used.

The emulsion on which the coacervate film is formed is subsequently cooled in order to gel the film. Usually, the emulsion is cooled to 5 to 25 ° C., preferably 5 to 10 ° C. to gel the film.
In order to cure the gelled film, a curing agent is subsequently mixed into the emulsion. Although it is possible to cure with conventionally known aldehydes such as formaldehyde and glutaraldehyde, it is not preferable to use them from the viewpoint of toxicity and consideration of the environment.
Therefore, in the present invention, a compound having a carbodiimide group having a low toxicity and environmental burden is used as a curing agent in place of aldehydes. Such a so-called carbodiimide compound is a compound having a carbodiimide group as shown in (Chemical Formula 1), and can be obtained by combining one or more isocyanate compounds.
(Chemical formula 1)
-N = C = N-

For example, hexamethylene diisocyanate (HDI), hydrogenated xylylene diisocyanate (H ₂ XDI), xylylene diisocyanate (XDI), 2,2,4-trimethylhexamethylene diisocyanate (TMHDI), 1,12-diisocyanate dodecane (DDI) , Norbornane diisocyanate (NBDI), 2,4-bis- (8-isocyanate octyl) -1,3-dioctylcyclobutane (OCDI), 4,4′-dicyclohexylmethane diisocyanate (HMDI), tetramethylxylylene diisocyanate (TMXDI), Examples thereof include isophorone diisocyanate (IPDI) and the like, and these can be obtained by subjecting one or more of these compounds to a deoxygenation condensation reaction.

As an example of such a compound, the carbodiimide compounds described in Patent Document 1, Patent Document 3, and the like can be exemplified.
Specific examples that are commercially available include Carbodilite V-02, Carbodilite V-02-L2, Carbodilite V-04, Carbodilite V-06, Carbodilite E-02, Carbodilite E-02, Carbodilite V-01, Carbodilite V-01 -03, Carbodilite V-05, Carbodilite V-07, Carbodilite V-09 (all manufactured by Nisshinbo Industries, Inc.) and the like.

The compound having a carbodiimide group is preferably a polymer compound, and more preferably a polymer compound having film-forming properties.
When a film-forming polymer compound is used as a curing agent, effects such as further improvement of the strength of the microcapsule film and improvement of the holding ability of the inclusion can be obtained. This is presumed to be because the curing agent itself has film-forming properties, so that the coating substance is cured, and at the same time, a double coating is formed by the curing agent itself, thereby strengthening the microcapsule film.
Here, the film-forming property means having a film-like film-forming property when a solution of a polymer compound having a carbodiimide group alone is applied and evaporated to dryness.
In addition to further improving the strength of the capsule film, it is possible to obtain favorable effects such as improvement in sealing performance, flexibility and flexibility.

  After the coating is cured in this way, the desired microcapsules can be obtained by operations such as filtration, decantation, dehydration, liquid separation, and drying as necessary.

  When an uncured gel film is subjected to a curing reaction in an aqueous solution, there is a problem in setting the treatment temperature to be higher than the gel point of the basic film material. This is because a gel film that does not have heat resistance before curing readily dissolves in water at a temperature above its gel point. In addition, there is a problem that the microcapsules tend to aggregate at a temperature near the gel point. In particular, it is very difficult to dispose the basic film material at an arbitrary position and shape with respect to the periphery of the core material (encapsulated material) like a microcapsule and to desire curing while maintaining the state. For example, the general gel point of an aqueous gelatin solution, which is a kind of basic film material, is around 25 ° C.

  In the present invention, a carbodiimide compound, particularly a polymer compound, and if necessary, a carbodiimide compound having film-forming properties is used as a curing agent, and the film can be cured in water by selecting appropriate reaction conditions. Utilization has made it possible to cure suitable microcapsules.

  Carbodiimide compounds react with all hydrophilic colloids having carboxyl groups to give microcapsules having a cured film. Hydrophilic colloids having carboxyl groups are hydrophilic colloids having amino groups as well as carboxyl groups. Further, it may have active hydrogen including a hydroxyl group. Since the reactivity with the carbodiimide group is high in the carboxyl group, followed by the amino group and the hydroxyl group, a hydrophilic colloid having a carboxyl group is more preferable.

Specific appropriate reaction conditions are shown below.
Curing with a carbodiimide compound in the complex coacervation method needs to be performed after separating the uncured basic film substance (gelatin) microcapsule from the adjustment liquid and washing the microcapsule several times with water. If such an operation is not performed, sufficient curing cannot be achieved. This is because when microcapsules are prepared by the complex coacervation method, polyanions necessary for coacervation and undeposited (dissolved) basic coating substance (gelatin) molecules are present in the aqueous solution in which the microcapsules are dispersed. Is considered to exist. As the polyanion, a compound having a carboxyl group (such as gum arabic or carboxymethyl cellulose) is generally used. In addition, the basic film substance (gelatin) molecule naturally has a carboxyl group.
That is, in the microcapsule dispersion in this state, as a carboxyl group-containing component that can react with the carbodiimide group,
a) Basic film substance molecules in dissolved state (gelatin, etc.)
b) Dissolved polyanion molecules (gum arabic, carboxymethyl cellulose, etc.)
c) Dispersed basic film material gel (gelatin gel, etc.)
Can be said to exist. This is because it is presumed that it is necessary to remove dissolved a) and b) in order to efficiently react the dispersed basic film material (gelatin gel) with the carbodiimide compound.

As the hydrophilic colloid having a carboxyl group, a water-soluble protein is preferable, and gelatin is particularly preferable. In particular, those having a pI (isoionic point) of 8.0 or more are desirable, and acid-treated gelatin is more preferred.
In the present invention, the measured value of pI is a value obtained by treating an aqueous gelatin solution with an ion exchange resin and then measuring the pH of the aqueous gelatin solution at 35 ° C., but other commonly used pI (isoionic point: Isoionic point) measurements and equivalents can also be used.
A carbodiimide compound forms a hardened film on gelatin in general and can obtain a suitable microcapsule. However, a microcapsule using gelatin having a pI of less than 8.0 (for example, alkali-treated gelatin) has a pI of 8 The heat resistance tends to be inferior compared to the case of using gelatin of 0.0 or more (for example, acid-treated gelatin).
pI represents an isoionic point of gelatin or the like, which can be said to indicate the amount of acid amide bond, carboxyl group and amino group of the basic film substance (gelatin) molecule.
Gelatin having a high pI shows that the acid amide bond of the amino acid side chain is not deamidated and cleaved in the extraction process from collagen, and remains a lot. Since the carbodiimide group can react with both a carboxyl group and a functional group having an amino group active hydrogen, the functional group of the basic coating material may be any of a carboxyl group, an amino group, a hydroxyl group, and the like. When there are abundant cross-linking points, it is considered preferable that the basic film material itself has a strong structure. Therefore, when gelatin in which many acid amide bonds of amino acid side chains remain is used, a more stable microcapsule is obtained. It is estimated that it is easy to obtain.

  The reaction between the carbodiimide compound and the basic film material is r. t. Progress even under conditions. However, as in general organic reactions, it is desirable to advance the reaction by heating as much as possible. For this reason, it is possible to secure the reaction temperature and to perform a desired treatment in a shorter time by using a basic film substance having a gel point as high as possible.

  In addition, although this example demonstrated by the complex coacervation method, the similar effect can be acquired also by other microcapsule manufacturing methods, such as a simple coacervation method and an orifice method.

Microcapsule The microcapsule according to the present invention is a film formed by curing a basic film substance, which is a hydrophilic colloid having a carboxyl group, with a compound having a carbodiimide group in water. Is obtained.

  The microcapsules according to the present invention can be used for various applications by selecting a core material and a coating material. Specific examples include uses for pressure-sensitive adhesives, adhesives, coloring materials, foods, pharmaceuticals, quasi drugs, fragrances, cleaning agents, and the like. In these applications, since it is necessary to consider toxicity, it is preferable not to use toxic aldehydes such as formaldehyde and glutaraldehyde as the material of the microcapsules. Also, display media, toys, stationery, and the like are not preferable because volatilization of formaldehyde, which is a VOC, and accidents due to incorrect usage are assumed. That is, it is preferable that the film does not substantially contain aldehydes having high toxicity that can cause VOC and sick house syndrome, which are substances subject to emission control. Furthermore, a display medium or a recording material can be formed using the microcapsules according to the present invention. For example, by using an oily substance containing fine magnetic particles as a dispersion as a core substance, it can be used as an element of a magnetic display medium. Further, if a thermosensitive color-changing substance that changes color by heating is used as a core substance, an element of a thermosensitive recording material can be obtained. In particular, a reversible thermosensitive recording material is formed by using, as a heat-sensitive color-changing substance, a substance that can be colored, decolored and decolored by heat, for example, a combination of an electron-accepting compound and an electron-donating color-forming compound. It can also be made.

Magnetic display media and thermosensitive recording materials using microcapsules are already known (for example, Patent Document 4). However, aldehydes are often used to harden protein films in the manufacturing method of microcapsules used therefor. The use of such aldehydes is not preferred from the viewpoint of toxicity and environment, and a carbodiimide compound is preferred as a curing agent to be replaced with aldehydes.
In order to use microcapsules as a display medium or a recording material, microcapsules are usually arranged on a support. However, if a gap corresponding to a swollen film thickness occurs between the core materials of microcapsules, the resolution and contrast may be reduced. It becomes. Normally, when curing with aldehydes, the pH is adjusted to alkaline as a reaction condition, specifically, pH = 9 or more. At this time, the microcapsule film may swell due to the pH adjusted to alkaline. is there. However, since the microcapsules according to the present invention can perform the curing reaction in an acidic region, swelling associated with pH change can be avoided. For this reason, since the core substances can be arranged at high density, it is possible to provide a magnetic display medium and a heat-sensitive recording material that are excellent in resolution and contrast and substantially free of harmful aldehydes.

  The microcapsules according to the present invention that can be used for the above-mentioned applications can be produced, for example, by the above-described method for producing microcapsules. The microcapsule has an appropriate size selected according to its use, but generally has a sphere equivalent diameter of 0.1 to 3000 μm, preferably 0.1 to 2000 μm. Among them, the magnetic display medium is preferably 50 to 1000 μm, and the thermosensitive recording material is preferably 0.1 to 10 μm. An appropriate thickness is selected according to the application.

  The present invention will be described below with reference to various examples.

Example 1
Maintaining the temperature of the system at 40 ° C., 10 mass% acid-treated gelatin aqueous solution (Nippi Co., Ltd. AP-200 pI: 8.92) While stirring 60 parts by mass, 40 ° C. warm water (ion exchange water) 80 parts by mass 80 parts by mass of isoparaffin (Isopar M manufactured by Esso Chemical Co., Inc.) were added in order and emulsified and dispersed to form an O / W emulsion. Furthermore, 60 mass parts of 1.25 mass% carboxymethylcellulose aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd. cellogen F-7A) was mixed as a polyanion, and it was made uniform. 10% by mass hydrochloric acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust the pH to 4.6 to form a coacervate film. The emulsion was gradually cooled to 5 ° C. while stirring to gel the film, and kept at 30 min / 5 ° C. for stabilization. The cooled microcapsule dispersion was transferred to a separatory funnel and allowed to stand to separate into a microcapsule layer and a dispersion layer. Ion exchange water cooled to 5 ° C. was added to the separated microcapsule layer, and after stirring and washing, the microcapsule layer and the dispersion layer were separated again. After repeating this operation several times, the washed microcapsule dispersion was transferred to a beaker and stirred. The temperature of the system was raised to 25 ° C., and 21.3 parts by mass of carbodiimide polymer compound (Carbodilite V-02-L2 manufactured by Nisshinbo Industries, Ltd.) was adjusted to pH 4 with 10% by mass hydrochloric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.). The one adjusted to 0.0 was added. Add 10 mass% hydrochloric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) to adjust the pH to 4.0, and continue stirring for 65 hours while maintaining the system temperature at 25 ° C. A liquid was obtained. The obtained microcapsules were mononuclear microcapsules having no heat swell and heat resistance.

Examples 2-4
Microcapsules were produced in the same manner as in Example 1 except that the gelatin type was changed to that shown in Table 1.

Example 5
Microcapsules were produced in the same manner as in Example 1 except that the gelatin species were changed to those shown in Table 1 and the pH during the formation of the coacervate film was changed from 4.6 to 4.3.

Example 6
Microcapsules were produced in the same manner as in Example 1 except that the gelatin species were changed to those shown in Table 1 and the pH during the formation of the coacervate film was changed from 4.6 to 4.2.

Example 7
Keeping the temperature of the system at 40 ° C., 10 mass% acid-treated gelatin aqueous solution (Nippi Co., Ltd. AP-200 pI: 8.76) While stirring 60 parts by mass, 40 ° C. warm water (ion exchange water) 80 parts by mass 80 parts by mass of isoparaffin (Isopar M manufactured by Esso Chemical Co., Inc.) were added in order and emulsified and dispersed to form an O / W emulsion. Furthermore, 60 mass parts of 1.25 mass% carboxymethylcellulose aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd. cellogen F-7A) was mixed as a polyanion, and it was made uniform. 10% by mass hydrochloric acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust the pH to 4.6 to form a coacervate film. The emulsion was gradually cooled to 5 ° C. while stirring to gel the film, and kept at 30 min / 5 ° C. for stabilization. The cooled microcapsule dispersion was transferred to a separatory funnel and allowed to stand to separate into a microcapsule layer and a dispersion layer. Ion exchange water cooled to 5 ° C. was added to the separated microcapsule layer, and after stirring and washing, the microcapsule layer and the dispersion layer were separated again. After repeating this operation several times, the washed microcapsule dispersion was transferred to a beaker and stirred. The temperature of the system was raised to 25 ° C., and 8 parts by mass of sulfonic acid-modified polyvinyl alcohol (Goseiran L3266 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added and completely dissolved. Carbodiimide polymer compound (Nisshinbo Co., Ltd. Carbodilite V-02-L2) 21.3 parts by mass was added, and triethanolamine (Wako Pure Chemical Industries, Ltd. reagent) was added to adjust the pH to 9.0. did. While maintaining the temperature of the system at 25 ° C., stirring was continued for 65 hours to obtain a microcapsule dispersion having a cured film. The obtained microcapsules were mononuclear microcapsules having heat resistance.
The pH was measured with a glass electrode type hydrogen ion concentration meter (HM-30S manufactured by Toa DKK Corporation).

Application Example 1
10 mass% acid while maintaining the temperature of the system at 40 ° C. with 88 parts by mass of a plastic dispersion obtained by mixing fine particle magnetic substance and isoparaffin (Isopar M manufactured by Esso Chemical Co., Ltd.) as main components as a core substance. An S / O / W emulsion obtained by emulsifying and dispersing an aqueous solution containing 60 parts by mass of a processed gelatin aqueous solution (AP-200pI: 8.92 manufactured by Nippi Corporation) and 80 parts by mass of warm water (ion exchange water) at 40 ° C. Formed. Furthermore, 60 mass parts of 1.25 mass% carboxymethylcellulose aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd. cellogen F-7A) was mixed as a polyanion, and it was made uniform. 10% by mass hydrochloric acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust the pH to 4.6 to form a coacervate film. The emulsion was gradually cooled to 5 ° C. while stirring to gel the film, and kept at 30 min / 5 ° C. for stabilization. The cooled microcapsule dispersion was transferred to a separatory funnel and allowed to stand to separate into a microcapsule layer and a dispersion layer. Ion exchange water cooled to 5 ° C. was added to the separated microcapsule layer, and after stirring and washing, the microcapsule layer and the dispersion layer were separated again. After repeating this operation several times, the washed microcapsule dispersion was transferred to a beaker and stirred. The temperature of the system was raised to 25 ° C., 21.3 parts by mass of a carbodiimide polymer compound (Nisshinbo Co., Ltd. Carbodilite V-02-L2) was added with 10 mass% hydrochloric acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.), pH 4. What was adjusted to 0 was added. Add 10 mass% hydrochloric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) to adjust the pH to 4.0, and continue stirring for 65 hours while maintaining the system temperature at 25 ° C. A liquid was obtained. The obtained microcapsules were mononuclear microcapsules having no heat swell and heat resistance.
The obtained microcapsule dispersion was applied to a PET film having a thickness of 125 μm as a support to form a magnetic display medium. The obtained magnetic display medium had sufficient resolution.

The present invention provides a method for producing a microcapsule and a microcapsule produced thereby, and can be used for, for example, a pressure-sensitive adhesive, an adhesive, a coloring material, and the like depending on a core material to be used. In addition, an element of a display medium, for example, an oily substance containing fine magnetic particles of a magnetic display medium as a dispersion, an electrophoretic particle used in electronic paper, an inverted particle such as a twist ball, an oily substance containing liquid crystal, or the like by heating If a heat-sensitive recording material that changes color is used as a core substance, it can also be used for display / recording materials such as magnetic display media. In addition, foods, pharmaceuticals, quasi drugs, fragrances, cleaning agents, and the like that are immiscible with water can be used as a core substance and can be used.

Claims (6)

A method of manufacturing a microcapsule according to Complex coacervation method, a basic film material gelatin, the basic film material, forming a film of the microcapsules by curing by a polymeric compound having a carbodiimide group A method for producing a microcapsule, which is characterized. The method for producing a microcapsule according to claim 1 , wherein the polymer compound having a carbodiimide group is a polymer compound having film-forming properties. Preparation of microcapsules according to claim 1 or 2 wherein the gelatin is pI = 8.0 or more. The microcapsule according to any one of claims 1 to 3, wherein the reaction at the time of hardening is an acidic region of pH = 3 to 5 and is treated at a temperature not higher than a gel point of gelatin. Manufacturing method. Microcapsules obtained by the process according to any one of claims 1 to 4. A display medium obtained by arranging a plurality of microcapsules according to claim 5 including at least a display element as a core substance.