JP2006326457A - Hollow microcapsule and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a hollow microcapsule having a protection film with a high strength and causing no crushing or deformation, and the hollow microcapsule produced according to the method. <P>SOLUTION: The method for producing a hollow microcapsule comprises the steps of: reacting 100 parts by mass of a volatile solvent as a core material with an emulsifying liquid containing 60 to 100 parts by mass of an aromatic isocyanate as a material for forming the protection film to form a microcapsule containing the volatile solvent in the protection film; and vaporizing the volatile solvent to form a hollow microcapsule containing a gas in the protection film during or after forming the microcapsule. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hollow microcapsule and a method for producing the same.

  The microcapsule is a functional polymer fine particle containing a core substance having various functions. In recent years, the needs for microcapsules in the medical, food, and industrial fields have increased, and various attempts have been made to further enhance the functions of microcapsules. Active development of various functional polymer fine particles has been actively conducted. It has been broken. As an example of a method for producing such a microcapsule, an interfacial polymerization method using isocyanate as a starting material for a film constituting the microcapsule is known.

  Microcapsules containing a gas inside are called hollow microcapsules, and those conventionally disclosed in Patent Documents 1 to 3 are known. Since conventional hollow microcapsules are produced from a monomer having a vinyl group, there are problems such that the production method is complicated and troublesome, and the polymerization time is also long.

Microcapsules using the urethane-urea resin-based protective film material produced by the above-mentioned interfacial polymerization method are widely used for pressure-sensitive and thermal paper containing dyes in the core substance. There is no example applied to hollow microcapsules contained in a substance. When trying to produce hollow microcapsules with urethane-urea protective film material by the interfacial polymerization method, there is a problem that the strength of the protective film is low depending on the type of isocyanate used, causing deformation such as collapse and particle dents. In addition, there is a problem that microcapsules containing no gas are generated.
JP-A-6-2448012 JP-A-8-20604 JP 2002-80503 A

  The present invention has been made under such circumstances, and an object of the present invention is to provide a method for producing a hollow microcapsule having a high protective film strength and being less crushed and deformed, and a hollow microcapsule produced thereby.

  In order to solve the above-mentioned problem, the first aspect of the present invention protects by reacting an emulsion containing 100 parts by mass of a volatile solvent as a core substance and 60-100 parts by mass of an aromatic isocyanate as a protective film forming substance. Forming a microcapsule containing a volatile solvent in the film, and evaporating the volatile solvent during or after the formation of the microcapsule to form a hollow microcapsule containing a gas in the protective film A method for producing hollow microcapsules is provided.

  In such a method for producing hollow microcapsules, the emulsion can be formed by mixing a dispersed phase containing a volatile solvent and an aromatic isocyanate and an aqueous continuous phase.

  In the second aspect of the present invention, 100 parts by mass of a volatile solvent as a core substance, 50 to 100 parts by mass of an aromatic isocyanate as a protective film forming substance, and an emulsion containing hydrophobic silica are reacted to form a protective film. Forming a microcapsule containing a volatile solvent on the surface, and forming a hollow microcapsule containing a gas in the protective film by vaporizing the volatile solvent during or after the formation of the microcapsule. A method for producing hollow microcapsules is provided.

  In such a method for producing hollow microcapsules, an emulsion can be formed by mixing a dispersed phase containing a volatile solvent, aromatic isocyanate and hydrophobic silica and an aqueous continuous phase.

  Moreover, in the manufacturing method of the hollow microcapsule which concerns on the above 1st and 2nd aspect of this invention, it is desirable that the compounding quantity of hydrophobic silica is 1-30 mass parts with respect to 100 mass parts of aromatic isocyanate. .

  As the aromatic isocyanate, one selected from the group consisting of tolylene diisocyanate, xylene diisocyanate, and diphenylmethane diisocyanate can be used. Moreover, toluene or xylene can be used as a volatile solvent.

Further, the dispersed phase may contain a dye. Furthermore, the protective film can be made of a polyurea resin or a polyurethane resin.
The third aspect of the present invention provides a hollow microcapsule produced by the above method.

  According to the present invention, a spherical hollow microcapsule having high strength of a protective film and less crushing or deformation by using aromatic isocyanate as a protective film forming substance and limiting the amount of aromatic isocyanate to a predetermined range. It is possible to obtain

The best mode for carrying out the invention will be described below.
In the method for producing hollow microcapsules according to the first aspect of the present invention, a volatile solvent as a core substance and an emulsion containing an aromatic isocyanate as a protective film forming substance are reacted to form a volatile solvent in the protective film. A microcapsule containing is formed, and a volatile solvent is vaporized to form a hollow microcapsule containing a gas in the protective film.

  In such a method for producing a hollow microcapsule, it is necessary to use an aromatic isocyanate as a film-forming substance. By using such an aromatic isocyanate, the strength of the protective film is high, and the film is not crushed. A spherical hollow microcapsule with less deformation is obtained. When an isocyanate other than aromatic isocyanate, such as hexamethylene diisocyanate, is used, it is difficult to obtain spherical hollow microcapsules, and dents in the membrane and crushing of the capsules are also observed.

  Examples of the aromatic isocyanate include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, naphthylene 1,5-diisocyanate, and tetramethylxylene diisocyanate. In particular, good results are obtained when tolylene diisocyanate / trimethylolpropane adduct is used.

  The compounding quantity of a volatile solvent and aromatic isocyanate is 60-100 mass parts of aromatic isocyanate with respect to 100 mass parts of volatile solvents. If the aromatic isocyanate is less than 60 parts by mass, the strength of the formed protective film is weak, so that the microcapsules are crushed when the volatile solvent is vaporized and expanded. On the other hand, when the amount of aromatic isocyanate exceeds 100 parts by mass, the thickness of the protective film becomes too thick, and it takes a long time to vaporize the volatile solvent, which is not practical. In addition, a ball-like sphere that is not porous or hollow may be formed.

  As the core material, it is desirable to use a volatile solvent having a low boiling point to a medium boiling point. During or after the production of the microcapsules, a hollow microcapsule containing a gas in the protective film is obtained by vaporizing a volatile solvent as a core material by drying. The solvent having a low boiling point to a medium boiling point refers to an organic solvent having a boiling point of about 100 ° C. to 200 ° C. or less as a guide. As such an organic solvent, aromatics such as toluene and xylene. Aliphatic organic solvents such as heptane, octane, nonane, decane. Ethylbenzene. Alcohols such as isobutyl alcohol, butanol and pentanol. Examples thereof include esters such as butyl acetate. Among organic solvents, a solvent that is not mixed with water but mixed with isocyanate and that does not dissolve the capsule film after the reaction can be selected. For example, since toluene and xylene have good compatibility with isocyanate, they can be used favorably for the production of hollow microcapsules.

  Specifically, an emulsified liquid containing a volatile solvent as a core material and an aromatic isocyanate as a protective film forming material is a high-speed dispersion by gradually adding a dispersed phase containing a volatile solvent and an aromatic isocyanate to a continuous phase. Is obtained. As the continuous phase, water can be used, and water added with polyvinyl alcohol, polyethylene glycol, or the like can be used.

  Such an emulsified liquid is then reacted at a predetermined temperature, for example, 40 to 80 ° C. with stirring for a predetermined time, for example, 1 to 12 hours, to obtain a microcapsule slurry containing a volatile solvent in the protective film. It is done.

  Next, the microcapsule slurry is washed to separate the microcapsule and water, and then dried to vaporize the volatile solvent in the protective film. The drying conditions for vaporizing the volatile solvent are not particularly limited, but it is desirable to heat and dry at an appropriate temperature and time in consideration of the temperature characteristics of the protective film and the volatility of the volatile solvent. Such temperature and time are, for example, 100 to 200 ° C. and 3 to 72 hours. Since the vaporized volatile solvent is replaced with air, hollow microcapsules containing air in the protective film are obtained.

  The particle size of the hollow microcapsules produced as described above is not particularly limited, but according to the above production method, hollow microcapsules having a particle size of 0.5 to 50 μm can be easily obtained.

  The method for producing hollow microcapsules according to the second aspect of the present invention comprises a protective film obtained by reacting a volatile solvent as a core substance, an aromatic isocyanate as a protective film-forming substance, and an emulsion containing hydrophobic silica. A microcapsule containing a volatile solvent is formed therein, and a low-boiling solvent is vaporized to form a hollow microcapsule containing a gas in the protective film.

  The method for producing such hollow microcapsules is the same as the method for producing hollow microcapsules according to the first embodiment of the present invention, except that hydrophobic silica is added to the dispersed phase. Thus, by adding hydrophobic silica to the dispersed phase, hollow microcapsules can be obtained in high yield. In this case, the compounding quantity of a volatile solvent and aromatic isocyanate is 50-100 mass parts of aromatic isocyanate with respect to 100 mass parts of volatile solvents, and the hollow microcapsule which concerns on the 1st form of this invention mentioned above. The lower limit of the compounding amount of the aromatic isocyanate can be lowered than in the production method. Moreover, the effect that the thickness of a protective film can be made thin by addition of hydrophobic silica is also acquired.

The amount of hydrophobic silica added is suitably about 1 to 30 parts by mass with respect to 100 parts by mass of the isocyanate which is a protective film forming substance.
The kind of hydrophobic silica is not particularly limited as long as it can be mixed with an aromatic isocyanate. Hydrophobic silica has an OH end group treated with a hydrophobic group, but the formation of microcapsules is not affected by the type of hydrophobic group.

  In order to disperse the hydrophobic silica in the dispersed phase, a dispersing device such as a ball mill can be used. Depending on the performance of the hydrophobic silica, such as the surface area, the viscosity of the dispersed phase may increase. At that time, a low-boiling solvent such as ethyl acetate that volatilizes during the reaction is mixed to lower the viscosity of the entire dispersed phase. I can do it. If hydrophilic silica is used, it is difficult to mix with the aromatic isocyanate, and it shifts to the aqueous phase during the reaction, so that the effect of addition cannot be obtained.

Examples of the present invention and comparative examples will be shown below to describe the effects of the present invention more specifically.
Example 1
15 parts by mass of toluene as a core material serving as a gas component, and 14 parts by mass of Takenate D-103 (tolylene diisocyanate / trimethylolpropane adduct; 75% ethyl acetate: manufactured by Mitsui Takeda Chemical Co., Ltd.) as a protective film forming material Was dissolved to form a dispersed phase. Next, 1.5 g of PVA-205 (polyvinyl alcohol, degree of saponification of about 88%, degree of polymerization of 500, manufactured by Kuraray Co., Ltd.) was dissolved in 150 g of water to form a continuous phase.

  The dispersed phase was gradually mixed with the continuous phase thus obtained and dispersed at a high speed with an Ultra Turrax T25 basic (IKA homogenizer) to obtain an emulsion. 300 ml of this emulsified liquid was transferred to a three-necked round bottom flask, and a reflux tube, a thermometer and a stirrer were attached thereto, and the temperature was kept constant at 70 ° C. with a water bath and reacted for 3 hours.

  The particle size of the microcapsules obtained by the reaction was measured with a particle size distribution analyzer LA-920 (Laser diffraction / scattering type particle size distribution meter: manufactured by Horiba, Ltd.) and found to be 13 μm. When this microcapsule was observed with an optical microscope, it was found that it was spherical and the core substance was a liquid.

  The washing process of separating the obtained microcapsule slurry into water and microcapsules by centrifugation and discarding the water was repeated several times. After the washing step, drying was performed at normal pressure of 70 ° C. to volatilize toluene contained in the core material of the microcapsule and replace the toluene content with air. When observed with this microcapsule optical microscope, it was confirmed to be a hollow microcapsule.

  In order to obtain hollow microcapsules, the denseness of the protective film may be adjusted by further mixing a polyol such as polyethylene glycol with the continuous phase. Any polyol may be used, and the polyol is not limited to being continuous, and may be added to the dispersed phase.

Comparative Example 1
In 15 parts by mass of toluene as a core material serving as a gas component, 14 parts by mass of Sumijoule N75 (HDI burette; 75% ethyl acetate: manufactured by Sumika Bayer Urethane Co., Ltd.) as a protective film forming material is dissolved to obtain a dispersed phase. Formed. Dibutyltin dilaurate was added to this dispersed phase as a catalyst. Next, 1.5 g of PVA-217 (polyvinyl alcohol, degree of saponification of about 88%, degree of polymerization of 1700, manufactured by Kuraray Co., Ltd.) was dissolved in 150 g of water to form a continuous phase.

  The dispersed phase was gradually mixed with the continuous phase thus obtained and dispersed at a high speed with an Ultra Turrax T25 basic (IKA homogenizer) to obtain an emulsion. 300 ml of this emulsified liquid was transferred to a three-necked round bottom flask, and a reflux tube, a thermometer and a stirrer were attached thereto, and the temperature was kept constant at 70 ° C. with a water bath and reacted for 10 hours.

  The particle size of the microcapsules obtained by the reaction was measured with a particle size distribution analyzer LA-920 (Laser diffraction / scattering type particle size distribution meter: manufactured by Horiba, Ltd.) and found to be 15 μm. When this microcapsule was observed with an optical microscope, it was found that it was spherical and the core substance was a liquid.

  The obtained microcapsule slurry was washed and dried in the same manner as described above, and then observed with an optical microscope. As a result, it was confirmed that the fine particles were deformed and almost all of them were crushed and contained gas. could not.

  From the comparison between Example 1 and Comparative Example 1 described above, when microcapsules were formed using aromatic isocyanate (tolylene diisocyanate) as the protective film forming substance (Example 1), fine hollow microcapsules were obtained. In contrast, when microcapsules are formed using isocyanate (hexamethylene diisocyanate) that is not an aromatic isocyanate as a protective film forming substance (Comparative Example 1), hollow microcapsules may not be obtained. Recognize.

  Thus, by using aromatic isocyanate as the protective film forming substance, even if toluene, which is a low-boiling to medium-boiling solvent, volatilizes and expands, the capsule does not deform, and the core substance does not deform. Hollow microcapsules containing can be produced.

  In addition, as shown in Example 1, the manufacturing method of the hollow microcapsule according to the present invention is not complicated, and the hollow microcapsule containing gas as a core substance is made in the same manner as a general microcapsule manufacturing process. Obtainable.

  In Example 1, a polyurea resin or a polyurethane resin was formed by the reaction of isocyanate and water. However, the present invention is not limited to this, and a substance (for example, amines or polyols) that reacts with isocyanate is used as a dispersed phase or a continuous phase. It may be added to form a polyurea resin or a polyurethane resin. Further, a catalyst such as amines or dibutyltin dilaurate may be added to assist the protective film formation reaction.

  In Example 1, polyvinyl alcohol was used as an emulsifier. However, the polymerization degree and molecular weight of polyvinyl alcohol in this case are not limited, and other water-soluble polymers used as a general emulsifier (for example, Gelatin, polyvinylpyrrolidone, carboxymethylol cellulose, etc.) and surfactants can be used. Of these, water-soluble polymers that are not highly reactive with isocyanates are particularly desirable.

When there is intense foaming during emulsification or during the reaction, an industrial product (for example, silicone oil) generally used as an antifoaming agent may be added.
In Example 1, hollow core fine particles of 100% gas were used as the core material, but it may be designed so that a part of the liquid remains by mixing the core material with a high boiling point solvent (boiling point 200 ° C. or higher). good. At that time, a hollow microcapsule containing a gas can be similarly produced even if a coloring material such as pigment or dye is dispersed and dissolved in a high boiling point solvent.

Example 2
As a blue leuco dye, 0.2 part by mass of crystal violet lactone was added to 10 parts by mass of diphenylnaphthalene and dissolved at 80 ° C. with stirring. 10 parts by mass of toluene as a core material to be a gas component, 4 parts by mass of Millionate MR-200 (Polymetric MDI: manufactured by Nippon Polyurethane Industry Co., Ltd.) and Takenate D110N (xylene diisocyanate adduct; 75% ethyl acetate: 7 parts by mass of Mitsui Takeda Chemical Co., Ltd.) was dissolved to form a dispersed phase.

  1.5 g of PVA-205 (polyvinyl alcohol, degree of saponification of about 88%, degree of polymerization of 500, manufactured by Kuraray Co., Ltd.) was dissolved in 150 g of water to form a continuous phase. To this continuous phase, 1 g of PEG-400 (polyethylene glycol: manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred well.

  The dispersed phase was gradually mixed with the continuous phase thus obtained and dispersed at a high speed with an Ultra Turrax T25 basic (IKA homogenizer) to obtain an emulsion. 300 ml of this emulsified liquid was transferred to a three-necked round bottom flask, and a reflux tube, a thermometer and a stirrer were attached thereto, and the temperature was kept constant at 70 ° C. with a water bath and reacted for 5 hours.

  In the same manner as in Example 1, after washing and drying to obtain a microcapsule, the microcapsule was observed with an optical microscope and confirmed to be a hollow microcapsule containing a gas and a liquid as a core substance. did it.

Examples 3-8, Comparative Example 2
Seven types of dispersed phases having the composition shown in Table 1 below were formed. Next, 1.5 g of PVA-205 (polyvinyl alcohol, degree of saponification of about 88%, degree of polymerization of 500, manufactured by Kuraray Co., Ltd.) was dissolved in 150 g of water to form a continuous layer.

  The dispersed phase was gradually mixed with this continuous phase and dispersed at a high speed with an Ultra Tarax T25 Basic (IKA homogenizer) to obtain an emulsion. 300 ml of this emulsified liquid was transferred to a three-necked round bottom flask, and a reflux tube, a thermometer and a stirrer were attached thereto, and the temperature was kept constant at 70 ° C. with a water bath and reacted for 3 hours.

After washing and drying to obtain microcapsules in the same manner as in Example 1, the microcapsules were observed with an optical microscope, and the results shown in Table 1 below were obtained.

  In Table 1 above, coronate L is tolylene diisocyanate / trimethylolpropane adduct (75% ethyl acetate: manufactured by Nippon Polyurethane Industry Co., Ltd.), and its solid content is 75%. RX-50 and RY-50 are hydrophobic silica manufactured by Nippon Aerosil Co., Ltd., and TG-810G is hydrophobic silica manufactured by Cabot Specialty Chemicals Inc.

  The hollow microcapsules were evaluated according to the following criteria.

○: It is a hollow microcapsule △: Core material is gas and liquid (liquid remains inside)
X: Microcapsule whose core substance contains only liquid or crushed microcapsule From Table 1 above, in Comparative Example 2 where the amount of coronate L (solid content) is 10 g (50% by mass with respect to toluene) Example 3 and 15 g (75% by mass with respect to toluene) in which the amount of coronate L (solid content) is 12 g (60% by mass with respect to toluene), whereas the substance is only a gas and liquid microcapsule. It can be seen that good hollow microcapsules are obtained in Example 4 as described above. In Comparative Example 2, the drying time is as long as 14 days, and it cannot be used practically.

  In addition, when the dispersed phase contains hydrophobic silica (Examples 5 to 8), even if the amount of coronate L (solid content) is 10 g (50% by mass with respect to toluene), both are good hollow micros. It can be seen that capsules are obtained.

Example 9
0.7 part by mass of RY-50 (manufactured by Nippon Aerosil Co., Ltd.), which is hydrophobic silica, was mixed with 15 parts by mass of toluene as a core substance. Next, 0.2 part of crystal violet lactone as a blue leuco dye was added to 10 parts of diphenylnaphthalene, dissolved with stirring at a temperature of 80 ° C., and then mixed with the toluene solution. Further, 8 parts by mass of coronate L (tolylene diisocyanate / trimethylolpropane adduct; 75% ethyl acetate: manufactured by Nippon Polyurethane Industry Co., Ltd.) was dissolved in this mixed solution as a protective film forming substance to form a dispersed phase. .

  On the other hand, 5 g of PVA-217 (polyvinyl alcohol, degree of saponification of about 88%, degree of polymerization of 1700, manufactured by Kuraray Co., Ltd.) was dissolved in 150 g of water to obtain a continuous phase. The dispersed phase was gradually mixed with this continuous phase and dispersed at a high speed with an Ultra Tarax T25 Basic (IKA homogenizer) to obtain an emulsion. 300 ml of this emulsified liquid was transferred to a three-necked round bottom flask, and a reflux tube, a thermometer and a stirrer were attached thereto, and the temperature was kept constant at 70 ° C. with a water bath and reacted for 3 hours.

  The particle size of the microcapsules obtained by the reaction was measured with a particle size distribution analyzer LA-920 (Laser diffraction / scattering particle size distribution meter: manufactured by Horiba, Ltd.), and was 5 μm. When the obtained microcapsule was observed with an optical microscope, it was a normal microcapsule containing a liquid as a core substance in the protective film.

  When the microcapsules were washed and dried in the same manner as in Example 1, toluene was vaporized, and hollow microcapsules containing liquid and gas as core materials were obtained.

  The hollow microcapsules were collected on a glass plate and applied with a solution in which an acidic substance was dissolved as a developer. However, no color was developed, and when the microcapsules were crushed, a blue color was confirmed.

  By the method according to Example 9 described above, hollow microcapsules having a particle diameter of 1 to 80 μm and containing pigment oil as a core substance and a gas-liquid phase of gas could be formed. Moreover, in Example 9, by adding hydrophobic silica to the dispersed phase, the amount of isocyanate used was reduced, and the film thickness of the hollow microcapsules could be reduced. Furthermore, by dispersing the hydrophobic silica in the dispersed phase, in the case of the same compounding composition, the yield of microcapsules containing bubbles was increased, and the advantage of being able to maintain a shape close to a spherical shape was obtained. .

  In Example 9 above, the substance added to the dispersed phase is hydrophobic silica. However, the material is not limited to hydrophobic silica, and may be fine particles that can be mixed and dispersed with the dispersed phase. Inorganic substances such as treated titanium oxide and aluminum oxide may be added.

  In addition, by adding an excessive amount of such fine particles, it is possible to reliably generate microcapsules (a powder exists in a hollow space) having a solid phase and a gas phase as a core substance in the microcapsules. I can do it.

Claims (10)

A step of reacting an emulsion containing 100 parts by mass of a volatile solvent as a core substance and 60-100 parts by mass of an aromatic isocyanate as a protective film forming substance to form microcapsules containing a volatile solvent in the protective film; A process for producing a hollow microcapsule comprising the step of vaporizing the volatile solvent during or after the formation of the microcapsule to form a hollow microcapsule containing a gas in the protective film.   The method for producing hollow microcapsules according to claim 1, wherein the emulsion is formed by mixing a dispersed phase containing the volatile solvent and aromatic isocyanate and an aqueous continuous phase. A microcapsule containing a volatile solvent in a protective film by reacting an emulsion containing 100 parts by mass of a volatile solvent as a core substance, 50 to 100 parts by mass of an aromatic isocyanate as a protective film forming substance, and hydrophobic silica. A hollow microcapsule comprising: a step of forming; and a step of vaporizing the volatile solvent during or after the formation of the microcapsule to form a hollow microcapsule containing a gas in the protective film. Manufacturing method.   The method for producing a hollow microcapsule according to claim 3, wherein the emulsion is formed by mixing a dispersed phase containing the volatile solvent, aromatic isocyanate and hydrophobic silica and an aqueous continuous phase. .   The method for producing a hollow microcapsule according to claim 3 or 4, wherein the amount of the hydrophobic silica is 1 to 30 parts by mass with respect to 100 parts by mass of the aromatic isocyanate.   The method for producing hollow microcapsules according to any one of claims 1 to 5, wherein the aromatic isocyanate is one selected from the group consisting of tolylene diisocyanate, xylene diisocyanate, and diphenylmethane diisocyanate.   The method for producing hollow microcapsules according to claim 1, wherein the volatile solvent is toluene or xylene.   The method for producing hollow microcapsules according to claim 1, wherein the dispersed phase contains a dye.   The method for producing hollow microcapsules according to claim 1, wherein the protective film is made of a polyurea resin or a polyurethane resin.   The hollow microcapsule manufactured by the method in any one of Claims 1-9.