JP2006061826A - Production method of microcapsule, microcapsule, and magnetic display medium using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microcapsule with little coating swelling without using aldehydes and a method of producing the microcapsule. <P>SOLUTION: The production method is employed for producing a microcapsule having a protein coating which employs a complex coacervation method and at the time of setting the coacervated coating, it is carried out in co-presence of water-soluble polymer compound having an electric conductivity of 0.005-1.2 S/m in form of an aqueous 10 wt.% solution or a water-soluble polymer compound selected from polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and their mixtures. The microcapsule contains one of the above-mentioned water-soluble polymer compound in the coating. The microcapsule is useful for a magnetic display medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for producing a microcapsule and a microcapsule produced thereby. More specifically, a method for producing a microcapsule using a complex coacervation method, in which a specific water-soluble polymer compound is allowed to coexist during the production of the microcapsule, and a protein is identified as a film. The present invention relates to a microcapsule containing the water-soluble polymer compound.
The present invention further relates to a recording material such as a magnetic display medium comprising such a microcapsule.

  Conventionally, microcapsules have been applied to various uses, and many proposals have been made regarding their production methods. Among them, the complex coacervation method is one of the microencapsulation methods applied industrially.

A general complex coacervation method is to produce microcapsules by the following process.
(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. A typical example is transglutaminase (Patent Documents 1 to 3). However, according to the study of the present inventors, the coacervation of the protein film and the gelation of the coacervate film need to be performed in the acidic region, that is, at a low pH, whereas the curing reaction of transglutaminase has a pH of 5-9. It is necessary to carry out at a relatively high pH. In such a high pH region, the protein film significantly swells, and consequently, the shape of the capsule is distorted due to volume expansion, the capsule dispersion is thickened during the manufacturing process, the processability after encapsulation is reduced, and the core substance retention capacity is reduced. Such problems may occur.

  Techniques for preventing such swelling of the film have also been studied (Patent Document 4 or 5). These methods are examples using the salting-out method, which is a kind of orifice method or simple coacervation method, and in order to suppress swelling of the film when the film is cured by transglutaminase, phosphates and metaphosphates are used. In addition, electrolytes such as sulfates and acetates coexist. The simple coacervation method emulsifies and disperses the core material in a solution in which the film material is dissolved in a good solvent, and then decreases the solubility of the film material by adding a poor solvent such as salt or the film material, thereby surrounding the core material. In this method, a wall film is formed. On the other hand, the complex coacervation method is a method for forming a wall film by an electrical interaction using a polycation and a polyanion as a coating substance, and thus is greatly different as a production method. In addition, when the electrolyte as described above is used, it may be necessary to remove the electrolyte (desalting step) prior to the use of the microcapsules. That is, when the microcapsules are used as a display medium such as a magnetic display medium or a heat-sensitive recording material, when the microcapsules are applied and arranged on the support, the microcapsule dispersion is directly applied to the support and dried. The dissolved salt or the like is precipitated as a solid in the display medium and may adversely affect the visibility as the display medium. In such a case, it is common to remove the salt by a desalting step. Furthermore, the complex coacervation method is not necessarily a suitable method because it needs to be added after film formation.

  In order to enable the complex coacervation method to be performed in a wide pH range, a method using a nonionic water-soluble polymer compound as an additive has been studied (Patent Document 6). In this method, various types of nonionic water-soluble polymer compounds are added, but there is no mention of suppression of swelling when the film is cured.

On the other hand, magnetic display media and heat-sensitive recording materials using microcapsules have been studied (Patent Document 7). However, these materials use microcapsules manufactured by a conventional method, and microcapsules containing harmful aldehydes are generally used.
Japanese Patent Laid-Open No. 10-249184 Japanese Patent Laid-Open No. 02-086741 JP 05-292899 A JP 09-248137 A JP 2000-079337 A JP-A-57-171432 JP 2001-0775510 A

  The present invention intends to provide a method for producing a microcapsule which does not use a highly harmful aldehyde which has been conventionally used and which is suitable for a display medium such as a magnetic display medium and has a small film swelling. It is.

  The method for producing a microcapsule according to the present invention uses a complex coacervation method to produce a microcapsule having a protein film, and the electrical conductivity when the aqueous solution is 10% by weight is 0.005 to 1.2 S / m is a water-soluble polymer compound.

  Another method for producing microcapsules according to the present invention is to produce polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and derivatives thereof, as well as their derivatives, in producing microcapsules having a protein film using the complex coacervation method. And a water-soluble polymer compound selected from the group consisting of:

  Furthermore, in another method for producing a microcapsule according to the present invention, the protein film curing agent is transglutaminase in the above method.

  In the microcapsule according to the present invention, the film comprises a protein and a water-soluble polymer compound having an electrical conductivity of 0.005 to 1.2 S / m when a 10% by weight aqueous solution is obtained. It is characterized by.

  In another microcapsule according to the present invention, the film comprises a protein, a water-soluble polymer compound selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and derivatives thereof, and mixtures thereof. It is characterized by comprising.

  Furthermore, a magnetic display medium according to the present invention comprises the above-described microcapsule.

  According to the present invention, a microcapsule with less shape expansion and distortion can be produced as a VOC and without using highly harmful aldehydes that can cause sick house syndrome. By using the microcapsules obtained by this method, it is possible to form a display medium or recording material that does not contain harmful substances and has excellent resolution.

Microcapsule production method The microcapsule production method according to the present invention uses a complex coacervation method, in which a water-soluble polymer compound coexists when a protein film is cured (crosslinked and / or modified). It is characterized by. The method of the present invention will be described as follows according to the order of manufacturing steps.

  First, a core substance (oil-based substance) is dispersed in an aqueous solution containing a film substance to form 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. It is also possible to use a display medium element or the like, for example, an oily substance containing fine magnetic particles of a magnetic display medium as a dispersion, or a heat-sensitive recording material that changes color by heating. 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 film substance, a hydrophilic colloid having an isoelectric point as a polycation and capable of being gelled 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 coating 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 microcapsule size, specifically the diameter in terms of sphere, is generally 0.1 to 3000 μm, preferably 0.1 to 2000 μm, more preferably 0.1 to 1000 μm. To disperse.

  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. Among them, gum arabic has a tendency to be slightly inferior in the ability to form a coacervate film with respect to an emulsion having a relatively large particle size of 100 μm or more. Is particularly preferable because a sufficient coacervate film can be easily formed.

  After mixing the polyanions, the pH of the emulsion is adjusted to acidic, for example, pH 3-5, preferably 4-4.5. As the acid used at this time, it is preferable to select an acid that does not impair the properties of the core substance and the coating material. 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. Examples of the curing agent include conventionally known curing agents such as transglutaminase, formaldehyde, glutaraldehyde, alum, gallic acid, and tannic acid. Of these, aldehydes such as formaldehyde and glutaraldehyde are not preferably used from the viewpoints of toxicity and environmental considerations. Formaldehyde and glutaraldehyde are both designated as PRTR Class 1 Designated Chemical Substances. In particular, formaldehyde has been suspected of being a causative substance of sick house syndrome in recent years, and is further regarded as an emission-regulated substance as VOC. Yes.

  In general, it is preferable to use a curing agent that is less toxic and less harmful to the environment as the curing agent. Specifically, it is preferable to use transglutaminase, alum, gallic acid, tannic acid, and the like. Curing agents such as alum, gallic acid and tannic acid are not problematic in terms of toxicity and environmental load, but transglutaminase is particularly preferably used from the viewpoint of insufficient curability and odor. Since transglutaminase is neutral, specifically, an enzyme that exhibits high activity in the range of pH 5-9, the curing reaction using transglutaminase is generally performed in the range of pH 5-9, preferably 6-8. Is. In addition, even when aldehydes are used as a curing agent, the pH needs to be alkaline, specifically, pH 9 or higher in order to allow a rapid reaction to proceed.

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

  The method for producing microcapsules according to the present invention is characterized in that a water-soluble polymer compound is allowed to coexist in the complex coacervation method described above. In particular, when the film is cured after the coacervate film is formed, the water-soluble polymer compound may be introduced into the system before the pH is changed to any reaction conditions. preferable.

  In the method for producing microcapsules according to the present invention, a method of allowing a water-soluble polymer compound to coexist is arbitrary, but it is general to add a water-soluble polymer compound or an aqueous solution thereof to the system. The addition timing of the water-soluble polymer compound is not particularly limited. That is, it can be added in advance to an aqueous solution containing a water-soluble protein before dispersing the core substance, or can be added at any time before and after the addition of the polyanion. Furthermore, even if the water-soluble polymer compound is added to the microcapsule dispersion having a swollen film after the addition of the curing agent, the film has a shrinking effect. However, the water-soluble polymer compound is added after the formation of the coacervate film from the viewpoint of increasing the viscosity of the aqueous solution by adding the water-soluble polymer compound, increasing the viscosity of the dispersion due to film swelling, and changing the coacervate conditions. It is preferable. In particular, when the pH is adjusted after the coacervate film is gelled, it is preferable to add a water-soluble polymer compound before that. This is because if the increase in viscosity due to gel swelling exceeds the desired range, it is necessary to apply a larger shearing force to maintain the stirring condition, and if the shearing force is too strong, the capsule film is broken, which is not preferable.

  In addition, the coacervate film has a strong tendency to swell as the pH rises, but the water-soluble polymer compound in the present invention suppresses or reduces the swelling of the film, so when adjusting the pH to adjust the curing conditions, It is particularly preferable to add a water-soluble polymer compound before adjustment. Therefore, the most preferable is after the polyanion is added, after the formation and gelation of the coacervate film in the system, and before the pH adjusting agent and / or the curing agent is added to cure the film. By adding the water-soluble polymer compound at such a time, the water-soluble polymer compound does not affect the formation of the coacervate film, and the surface of the coacervate film is effectively treated with the polymer compound.

  When transglutaminase is used as a curing agent, it is essential to adjust the pH to 5-9, preferably 6-8 as described above as the curing condition. Swelling of the film is suppressed or reduced.

  Note that if the water-soluble polymer compound is not added or the pH is adjusted to a neutral range with insufficient addition, the film tends to swell, but even after the film swells, the water-soluble polymer compound The swelling of the film is reduced by the addition of. In order to apply the production method of the present invention to an existing production process, it is easy and preferable to employ such an addition time.

  The water-soluble polymer compound used in the method for producing the first microcapsule according to the present invention has an electric conductivity of 0.005 to 1.2 S / m, preferably 0.005 when a 10% by weight aqueous solution is used. -0.3 S / m.

  Examples of the water-soluble polymer compound used in the method for producing the second microcapsule according to the present invention include polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and mixtures thereof. These all suppress or reduce the swelling of the film as described above. In the present invention, the terms polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene oxide include derivatives thereof.

  The water-soluble polymer compound may be a compound in which part or all of the water-soluble polymer compound is modified. In particular, when it is appropriately denatured by a chemical species containing an ionic group, the water-soluble polymer compound itself can be configured to have an appropriate ionicity, and the interaction with the protein film is generated, making it more effective. This is preferable (details will be described later).

  Examples of such an ionic group include a sulfone group, a carboxyl group, and a phosphoric acid group. In the method for producing microcapsules according to the present invention, one or more selected from sulfonic acid and / or carboxylic acid-modified polyvinyl alcohol is particularly preferable as the water-soluble polymer compound.

  Further, a copolymer containing the water-soluble polymer compound as a polymerization unit, such as a copolymer having polyvinyl pyrrolidone as a polymerization unit, can also be used. Polyvinyl pyrrolidone and derivatives thereof may act more favorably than other water-soluble polymers when using alkali-processed gelatin as a protein, and are more preferred in combination.

  Although the molecular weight of these water-soluble polymer compounds is not particularly limited, those having a weight average molecular weight of 2000 to 200000, preferably 2000 to 20000 are generally used. In general, a water-soluble polymer compound having a large molecular weight has a large viscosity when it is used as an aqueous solution, and therefore, care must be taken because a load is applied to the stirring power during stirring and excessive shearing occurs on the microcapsules. Polyvinyl alcohol is not particularly limited to a completely saponified type or a partially saponified type, but a partially saponified type is preferred from the viewpoint of solubility in water.

In the method for producing the microcapsules of the present invention, after using the water-soluble polymer compound having a relatively low electrical conductivity in this way, the coacervate film is gelled and then, for example, the pH is set to a neutral region. However, the film is less likely to swell. Such swelling of the film can be evaluated by the degree of swelling. In the present invention, the degree of swelling is calculated using the following method.
1) A constant weight was collected from the stirred microcapsule dispersion (pH = 4.3) after stirring, and a prescribed centrifuge tube (inner diameter 14 mm, height 105 mm: with IWAKI GLASS rim, 16.5 × 105 m) / M) using a centrifuge (Centrifuge H-18 manufactured by Kokusan Co., Ltd.) at 2000 rpm for 1 min to separate into a microcapsule layer and an aqueous solution layer.
2) The length of the separated microcapsule layer is measured, and the volume of the microcapsule layer is determined from the product of the areas calculated from the inner diameter of the centrifuge tube.
3) The volume of the core substance in the dispersion is calculated from the collected microcapsule dispersion weight and the mixing ratio, and the volume of the microcapsule film before pH adjustment is calculated from the difference in volume of the microcapsule layer.
4) Samples are taken from the microcapsule dispersion after the addition of the water-soluble polymer compound, the pH adjustment, the addition of the curing agent, and the curing are completed according to the desired addition timing, and the microcapsules after the pH adjustment by the same method Calculate the volume of the film.
5) Based on the film volume before pH change, the amount of increase in volume is calculated from the film volume after pH adjustment according to the following formula, and the degree of swelling is expressed as a percentage.
Swelling degree (%) = {(film volume after pH adjustment−film volume before pH adjustment) / film volume before pH adjustment} × 100

  When the water-soluble polymer compound specified in the present invention is used, the degree of swelling measured by the above-described method is generally 0% to 60%, preferably 0% to 20%, more preferably 0% to 10%. is there.

  The protein film swells in the neutral region because the dissociation of the carboxyl group of the protein constituting the film is promoted by the increase in pH, so that the anionic amount of the carboxyl group in the protein molecule increases, It is considered that the carboxyl groups having the same sign electric charges repel each other electrically. The complex coacervation method is driven by an electric ion complex of polycation and polyanion. Since the temperature in the system is below the gel point of the protein film, protein dissolution does not occur, but anionically charged protein molecules are thought to cause phenomena such as swelling or swelling of the protein film due to electrical repulsion. It is done. In the method for producing microcapsules according to the present invention, the reason why the swelling of such a protein film is suppressed by the coexistence of a specific water-soluble polymer compound is not clear, but the protein to be swollen by electrical repulsion It is presumed that the swelling is suppressed or reduced by coordinating the water-soluble polymer compound with the film in molecular association. At this time, if a water-soluble polymer compound having high electrical conductivity is used, the ion balance is considered to be destroyed due to the strong ionicity of the coordinated water-soluble polymer compound. End up. This is considered to influence the density of the ionic group which the water-soluble polymer compound to coordinate has in the molecular structure. In contrast, when a water-soluble polymer compound having a low electrical conductivity, particularly a water-soluble polymer compound having a moderately ionic group and having a relatively low electrical conductivity, is present in the protein film, Is coordinated effectively and at the same time does not destroy the ion balance.

Microcapsule A first microcapsule according to the present invention comprises a protein as a film and a water-soluble polymer having an electric conductivity of 0.005 to 1.2 S / m when a 10% by weight aqueous solution is used. It is. In the second microcapsule according to the present invention, the film comprises a protein, a water-soluble polymer compound selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and derivatives thereof, and mixtures thereof. It contains. These microcapsules contain a specific water-soluble polymer compound in the film, so that the swelling of the film is suppressed or reduced, and the shape distortion due to pH change is small.

  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 the toxicity, it is preferable not to use toxic aldehydes such as formaldehyde and glutaraldehyde as the microcapsule material. 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 7). However, aldehydes are often used to harden protein films in the manufacturing method of microcapsules used therefor. The use of such aldehydes is not preferable due to considerations of toxicity and the environment, but using only the above-mentioned transglutaminase as a curing agent to replace aldehydes, for example, distortion in the shape of the coacervate film and volume expansion of the film occur. . For this reason, the final microcapsule has a larger volume of the film than the core substance. In order to use microcapsules as a display medium or a recording material, the microcapsules are usually arranged on a support. However, when the microcapsule film is expanded, the film is swelled between the core materials even if it is arranged at a high density. A gap corresponding to the thickness tends to occur, which causes a decrease in resolution and contrast. However, since the microcapsules according to the present invention have a small coating volume compared to the volume of the core material, it is possible to arrange the core material at a high density on the support, so that the resolution and contrast are excellent and harmful. It is possible to provide a magnetic display medium and a heat-sensitive recording material that are substantially free of aldehydes.

  The microcapsules according to the present invention that can be used for such applications can be produced, for example, by the method for producing microcapsules described above. 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., stirring 90 parts by weight of 10% by weight acid-treated gelatin aqueous solution (AP200 manufactured by Nippi Co., Ltd.), 120 parts by weight of 40 ° C. warm water (ion exchange water), isoparaffin (manufactured by Esso Chemical Co., Ltd.) Isopar M) 120 parts by weight were sequentially added and emulsified and dispersed to form an O / W emulsion. Furthermore, 90 parts by weight of a 1.25% by weight aqueous sodium carboxymethylcellulose solution (Serogen F-7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a polyanion was mixed and made uniform. Acetic acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust pH to 4.3 to form a coacervate film. The emulsion was gradually cooled to 5 ° C. with stirring to gel the film, and kept at 30 ° C. for 30 minutes for stabilization. The temperature of the system was raised again to 15 ° C., and 30 parts by weight of a 10% by weight aqueous solution of sulfonic acid-modified polyvinyl alcohol (Goseiran L3266 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added. A 50 wt% aqueous sodium hydroxide solution was added to adjust the pH to 7.2, and 0.18 parts by weight of transglutaminase (Activa TG-S manufactured by Ajinomoto Co., Inc.) was added. Stirring was continued for 16 hours while maintaining the temperature of the system at 15 ° C. to obtain a microcapsule dispersion having a cured film. The obtained microcapsules were mononuclear microcapsules having no heat swell and heat resistance.

  The final concentrations of acid-treated gelatin, sodium carboxymethylcellulose, and sulfonic acid-modified polyvinyl alcohol in the aqueous solution of the system were 2.73 wt%, 0.34 wt%, and 0.91 wt%, respectively.

Comparative Example 1
A microcapsule was produced in the same manner as in Example 1 except that the water-soluble polymer compound was not added.

Examples 2-9, Comparative Examples 2-4
Further, microcapsules were produced in the same manner as in Example 1 except that the water-soluble polymer compound and the pH adjustment value were changed to those shown in Table 1.

  The water-soluble polymer compound, final concentration, electrical conductivity, swelling degree, pH adjustment value, and film thickness at completion (pH 6-8) in each example are as shown in Table 1.

ここで、
電気伝導度は電気伝導度０．０００４Ｓ／ｍのイオン交換水を用いて水溶性高分子化合物を１０重量％水溶液としたときの電気伝導度値（東亜ディーケーケー株式会社製 電気伝導率計ＣＭ−３０Ｖ 測定温度２５℃）である。 Table 1

here,
The electric conductivity is an electric conductivity value when a water-soluble polymer compound is made into a 10% by weight aqueous solution using ion-exchanged water having an electric conductivity of 0.0004 S / m (electric conductivity meter CM-30V manufactured by Toa DK Corporation). Measurement temperature 25 ° C.).

The degree of swelling was calculated using the following method.
1) A constant weight was collected from the stirred microcapsule dispersion (pH = 4.3) after stirring, and a prescribed centrifuge tube (inner diameter 14 mm, height 105 mm: with IWAKI GLASS rim, 16.5 × 105 m) / M) using a centrifuge (Centrifuge H-18 manufactured by Kokusan Co., Ltd.) at 2000 rpm for 1 min to separate into a microcapsule layer and an aqueous solution layer. The temperature condition was appropriately determined depending on the type of the curing agent to be used, and the temperature condition immediately before the curing agent was used was used. (When transglutaminase is used as a curing agent, it is 15 ° C., and when formaldehyde is used, it is 5 ° C.)
2) The length of the separated microcapsule layer is measured, and the volume of the microcapsule layer is determined from the product of the areas calculated from the inner diameter of the centrifuge tube.
3) The volume of the core substance in the dispersion is calculated from the collected microcapsule dispersion weight and the mixing ratio, and the volume of the microcapsule film before pH adjustment is calculated from the difference in volume of the microcapsule layer.
4) Samples are taken from the microcapsule dispersion after the addition of the water-soluble polymer compound, the pH adjustment, the addition of the curing agent, and the curing are completed according to the desired addition timing, and the microcapsules after the pH adjustment by the same method Calculate the volume of the film. The temperature conditions were 15 ° C. when transglutaminase was used as the curing agent, and 20 ° C. when formaldehyde was used.
5) Based on the film volume before pH change, the amount of increase in volume is calculated from the film volume after pH adjustment according to the following formula, and the degree of swelling is expressed as a percentage.
Swelling degree (%) = {(film volume after pH adjustment−film volume before pH adjustment) / film volume before pH adjustment} × 100

  The film thickness is a value obtained by actually measuring a microcapsule having a core material particle diameter of about 500 μm with a microscope.

  The pH was measured with a glass electrode type hydrogen ion concentration meter (HM-30S manufactured by Toa DKK Corporation).

The water-soluble polymer compound used in each example is as follows.
Sulfonic acid-modified polyvinyl alcohol: Goseiran L-3266 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
Carboxylic acid-modified polyvinyl alcohol: GOHSENAL T-330 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
Polyvinyl alcohol (saponification degree: 86.5 to 89.5%): GOHSENOL GL-05 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
Polyvinylpyrrolidone: PVP K-15 manufactured by IS Japan Co., Ltd.
Vinyl acetate / vinyl pyrrolidone copolymer: PVP / VA S-630 manufactured by IPS Japan
Polyethylene oxide: Alcox R-150 manufactured by Meisei Chemical Industry Co., Ltd.
Gum arabic: Wako Pure Chemical Industries, Ltd. Reagent Carboxymethylcellulose Sodium: Daiichi Kogyo Seiyaku Serogen F-7A
Sodium polystyrene sulfonate: Wako Pure Chemical Industries, Ltd. Reagent isobutylene / maleic anhydride copolymer: Kuraray Co., Ltd. Isoban-104
Sulfonic acid-modified isoprene polymer: Dynaflow DK106 manufactured by JSR Corporation

Example 10
Maintaining the temperature of the system at 40 ° C., stirring 10 parts by weight of an alkali-treated gelatin aqueous solution (ST1 made by Nippi Co., Ltd., ST1), 120 parts by weight of 40 ° C. warm water (ion-exchanged water), isoparaffin (Esso Chemical Co., Ltd.) Isopar M) 120 parts by weight were sequentially added and emulsified and dispersed to form an O / W emulsion. Furthermore, 90 parts by weight of a 1.25% by weight aqueous sodium carboxymethylcellulose solution (Serogen F-7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a polyanion was mixed and made uniform. Acetic acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust pH to 4.0 to form a coacervate film. The emulsion was gradually cooled to 5 ° C. with stirring to gel the film, and kept at 30 ° C. for 30 minutes for stabilization. The temperature of the system was raised again to 15 ° C., and 30 parts by weight of a 10% by weight aqueous solution of polyvinylpyrrolidone (PVP K-15 manufactured by ASP Japan Co., Ltd.) was added. A 50 wt% aqueous sodium hydroxide solution was added to adjust the pH to 7.3, and 0.18 parts by weight of transglutaminase (Activa TG-S manufactured by Ajinomoto Co., Inc.) was added. Stirring was continued for 16 hours while maintaining the temperature of the system at 15 ° C. to obtain a microcapsule dispersion having a cured film. The obtained microcapsules were mononuclear microcapsules having little heat-swelling and heat resistance.

The final concentrations of alkali-treated gelatin, sodium carboxymethylcellulose, and polyvinylpyrrolidone in the aqueous solution of the system were 2.73 wt%, 0.34 wt%, and 0.91 wt%, respectively.
The obtained results were as shown in Table 2.

Example 11
Maintaining the temperature of the system at 40 ° C., stirring 90 parts by weight of 10% by weight acid-treated gelatin aqueous solution (AP200 manufactured by Nippi Co., Ltd.), 120 parts by weight of 40 ° C. warm water (ion exchange water), isoparaffin (manufactured by Esso Chemical Co., Ltd.) Isopar M) 120 parts by weight were sequentially added and emulsified and dispersed to form an O / W emulsion. Furthermore, 90 parts by weight of a 1.25% by weight aqueous sodium carboxymethylcellulose solution (Serogen F-7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a polyanion was mixed and made uniform. Acetic acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust pH to 4.3 to form a coacervate film. The emulsion was gradually cooled to 5 ° C. with stirring to gel the film, and kept at 30 ° C. for 30 minutes for stabilization. While maintaining the temperature of the system at 5 ° C., 12 parts by weight of sulfonic acid-modified polyvinyl alcohol (Nippon Synthetic Chemical Industry Co., Ltd. Goseiran L3266) was added and completely dissolved. After adding 3 parts by weight of a 37% by weight formaldehyde solution (reagent manufactured by Wako Pure Chemical Industries, Ltd.) and stirring for 30 minutes, a 50% by weight aqueous sodium hydroxide solution was added to adjust the pH to 10.0. The temperature of the system was gradually raised to 50 ° C., held for 30 minutes, and then cooled to 20 ° C. with stirring to obtain a microcapsule dispersion in which the film was cured. The obtained microcapsules were mononuclear microcapsules having little heat-swelling and heat resistance.

The final concentrations of acid-treated gelatin, sodium carboxymethylcellulose, and sulfonic acid-modified polyvinyl alcohol in the aqueous solution of the system were 2.86 wt%, 0.36 wt%, and 3.8 wt%, respectively.
The obtained results were as shown in Table 2.

Comparative Examples 5-6
Microcapsules were produced in the same manner as in Examples 10 and 11 except that the water-soluble polymer compound was not added and the pH adjustment value was as described in Table 2.
The obtained results were as shown in Table 2.

Table 2

Application Example 1
While maintaining a system temperature of 40 ° C., 132% by weight of a 10% by weight acid solution is obtained by mixing 132 parts by weight of a plastic dispersion composed mainly of fine magnetic particles and isoparaffin (Isopar M manufactured by Esso Chemical Co., Ltd.). An S / O / W emulsion was formed by emulsifying and dispersing in an aqueous solution in which 90 parts by weight of a treated gelatin aqueous solution (AP200 manufactured by Nippi Corporation) and 120 parts by weight of warm water (ion exchange water) at 40 ° C. were uniformly mixed. Furthermore, 90 parts by weight of a 1.25% by weight aqueous sodium carboxymethylcellulose solution (Serogen F-7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a polyanion was mixed and made uniform. Acetic acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust pH to 4.3 to form a coacervate film. The emulsion was gradually cooled to 5 ° C. with stirring to gel the film, and kept at 30 ° C. for 30 minutes for stabilization. The temperature of the system was raised again to 15 ° C., and 30 parts by weight of a 10% by weight aqueous solution of sulfonic acid-modified polyvinyl alcohol (Goseiran L3266 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added. A 50 wt% aqueous sodium hydroxide solution was added to adjust the pH to 6.8, and 0.18 parts by weight of transglutaminase (Activa TG-S manufactured by Ajinomoto Co., Inc.) was added. Stirring was continued for 16 hours while maintaining the temperature of the system at 15 ° C. to obtain a microcapsule dispersion having a cured film.
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.

Claims (10)

  When producing a microcapsule having a protein film using the complex coacervation method, a water-soluble polymer compound having an electric conductivity of 0.005 to 1.2 S / m in a 10% by weight aqueous solution coexists. A method for producing a microcapsule, characterized by comprising:   When producing a microcapsule having a protein film using the complex coacervation method, a water-soluble polymer compound selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and mixtures thereof is allowed to coexist. A method for producing a microcapsule, which is characterized.   The method for producing a microcapsule according to claim 1 or 2, wherein the water-soluble polymer compound is one or more selected from sulfonic acid and / or carboxylic acid-modified polyvinyl alcohol.   The manufacturing method of the microcapsule of any one of Claims 1-3 whose hardening agent of a protein film is transglutaminase.   A microcapsule, wherein the film comprises a protein and a water-soluble polymer compound having an electric conductivity of 0.005 to 1.2 S / m when a 10% by weight aqueous solution is formed.   A microcapsule, wherein the film comprises protein and a water-soluble polymer compound selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, and derivatives thereof, and mixtures thereof.   The microcapsule according to claim 5 or 6, wherein the water-soluble polymer compound is sulfonic acid-modified polyvinyl alcohol or carboxylic acid-modified polyvinyl alcohol.   The microcapsule according to any one of claims 5 to 7, wherein the film is cured by transglutaminase.   The microcapsule according to any one of claims 5 to 8, wherein the film contains substantially no aldehydes.   A magnetic display medium comprising the microcapsule according to claim 5.