JP4858482B2 - Method for producing microcapsules - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of simply and conveniently manufacturing a microcapsule having a narrow particle size distribution and a uniform particle size. <P>SOLUTION: The method of manufacturing the microcapsule comprises: using an apparatus provided with a stator having a cylinder formed with a plurality of through holes along the circumferential direction and a rotor having a cylinder formed with a plurality of through holes along the circumferential direction so as to dispose coaxially and with a definite distance necessary for generating shearing action between the cylinder of the stator and the cylinder of the rotor; fixing the rotor; rotating the rotor coaxially with respect to the stator; supplying a liquid to be treated composed of a hydrophobic liquid and a hydrophilic liquid from the central direction of the cylinder of the rotor; making the hydrophobic liquid emulsify and disperse into the hydrophilic liquid to be a liquid emulsion by passing through the through holes of the cylinder of the stator and the through holes of the cylinder of the rotor and expelling outside the cylinders; and successively forming a capsule wall film containing the hydrophobic liquid emulsified and dispersed. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a microcapsule containing a hydrophobic substance, and particularly relates to a method for producing a microcapsule having a uniform particle size with a narrow particle size distribution.

  Microcapsules are suitable for stably holding chemically reactive substances, unstable substances, liquid substances, etc., and are used for various applications such as pressure-sensitive copying paper, pharmaceuticals, adhesives, and dye capsules. It has been.

  In general, in microcapsules, the uniformity of the capsule particle size is an important factor in quality. For example, in pressure-sensitive copying paper, a microcapsule that normally contains a colorless color-developing agent that develops color when contacted with a developer is present on the back side of the copying paper. In the case where a capsule having a large particle size is present, the capsule is easily broken due to friction during storage or handling, which causes coloring stains. On the other hand, when capsules extremely smaller than the average particle diameter are present, the capsules are difficult to be destroyed, and there is a problem that the color developability at the time of recording deteriorates.

  Usually, microcapsules are manufactured by a method in which a hydrophobic liquid is mixed and emulsified in a hydrophilic liquid to form an emulsion, and then a wall film is formed. It is important to obtain an emulsion of uniform particle size. In the production of microcapsules, as a method for obtaining an emulsion having a uniform particle size, a method for improving the uniformity of the emulsion by adding a water-soluble solvent (Japanese Patent Laid-Open No. 56-147627), specific There are known methods for improving the uniformity of an emulsion using an emulsifier of JP-A No. 58-40142, JP-A No. 58-202034, and the like.

  In any of these methods, an emulsifying disperser called a homomixer is used as an emulsifying device. This emulsification disperser will be described based on a schematic diagram of an example of a homomixer shown in FIG. This apparatus basically includes a rotor 17 having four to five blades rotating at high speed, a stator 19 having a substantially conical depression that matches the rotor 17 and having several discharge holes 18 facing the blades. And the rectifying plate 20, the rotor 17 is rotated at a high speed via the shaft 21, and the dispersion liquid is sucked from the lower part of the stator 19 using the suction action generated by this rotation, and the blades of the rotor 17 A shearing force is generated in the gap portion 22 between the stator 19 and emulsified and dispersed, and an emulsion is discharged upward from the discharge hole 18 of the stator, and this rising flow is changed by the upper rectifying plate 20. It is poured down along the side of the tank and returned to the bottom of the container. There are two types of emulsification methods using such a homomixer. One is a batch method, in which a rotor and a stator are set in a tank, and the mixed liquid in the tank is fixed by the rotor and the stator. In this method, emulsification is performed by time dispersion. In order to promote the circulation of the liquid, the same angle and twist as the blades in the spiral pump are added to the stator to perform circulation dispersion. On the other hand, the continuous type is a method in which the rotor and the stator are not put in the liquid in the tank, but are put in another cylindrical container, and the mixed liquid is introduced into the emulsifying disperser through a pipe and emulsified and dispersed. is there. In this case, in order to increase the dispersion efficiency, it is generally performed that a set of several stages of rotors and stators is placed in a cylinder and a circulation line is provided to increase the number of shears. Furthermore, a spiral pump blade-like twist is added to increase the number of shears as in the batch type.

  However, in the emulsification method using these homomixers, even though the action of the uniform shearing force is limited to a very limited range near the rotor and the stator, the circulation number of the dispersion liquid in this part is dispersed. The liquid as a whole is not uniform, and there are coarse particles in the part where the number of shears in the dispersion is small, and on the contrary, particles with a very small particle size are generated in the part where the number of shears is large. Only an emulsion having a particle size distribution in a wide range of several percent to several hundred percent with respect to the target particle size can be obtained. As a result, the obtained microcapsules also have a wide particle size distribution, which is not satisfactory in terms of particle size uniformity.

  The main object of the present invention is to provide a method for easily and stably producing uniform microcapsules having a narrow particle size distribution.

  According to the method of the present invention, a liquid to be treated comprising a hydrophobic liquid and a hydrophilic liquid can be easily made into an emulsion having a uniform particle size with a narrow particle size distribution in a short time. Further, by changing the rotational speed of the rotor, the particle size can be easily controlled, and adjustment to the target particle size is simple. Then, by forming a capsule wall film containing the emulsified and dispersed hydrophobic liquid, the resulting microcapsules have a uniform particle size with a narrow particle size distribution.

  The microcapsules thus obtained can be used effectively in various fields where microcapsules are conventionally used, such as pressure-sensitive copying paper, pharmaceuticals, adhesives, and dye capsules. For example, pressure-sensitive copying paper using microcapsules containing an electron-donating organic color former has good microcapsule particle size uniformity, so that some microcapsules are destroyed during storage and handling. Therefore, it is possible to reduce the amount of microcapsules used because color stains are less likely to occur.

  As a result of intensive studies in view of the problems of the prior art as described above, the present inventor provided a plurality of through holes along the circumferential direction in the emulsion production stage of the microcapsule production process. A rotor having a cylindrical portion and a rotor having a cylindrical portion provided with a plurality of through holes in the circumferential direction are positioned concentrically with an interval necessary for the cylindrical portions to generate a shearing action. According to the method for producing an emulsion by rotating a rotor at a high speed and emulsifying and dispersing a liquid to be treated consisting of a hydrophobic liquid and a hydrophilic liquid using an apparatus installed so as to Due to the action of sound waves, the liquid to be treated is continuously subjected to actions such as shearing, crushing, and mixing, and a uniform emulsified dispersion with a narrow particle size distribution can be obtained in a short time. Form capsule wall film in liquid By, it found that microcapsules having a uniform particle size can be obtained in a short time by a simple method, thereby completing the present invention herein.

  That is, the present invention provides a stator having a cylindrical portion provided with a plurality of through holes along the circumferential direction and a rotor having a cylindrical portion provided with a plurality of through holes along the circumferential direction. Using a device installed so that the cylindrical portion and the cylindrical portion of the rotor have a certain interval necessary to generate a shearing action and are positioned concentrically, the stator is fixed, and the rotor is concentric with the stator The liquid to be treated consisting of a hydrophobic liquid and a hydrophilic liquid is supplied from the central direction of the cylindrical portion of the rotor, and passes through the through hole of the cylindrical portion of the stator and the through hole of the cylindrical portion of the rotor. A method for producing a microcapsule characterized by forming a capsule wall film containing a hydrophobic liquid emulsified and dispersed in a hydrophilic liquid by discharging to the outside, and then encapsulating the emulsified and dispersed hydrophobic liquid Concerning.

  In the present invention, as a method of emulsifying and dispersing a liquid to be processed comprising a hydrophobic liquid and a hydrophilic liquid, a stator having a cylindrical portion provided with a plurality of through holes along the circumferential direction, and along the circumferential direction. Using a rotor having a cylindrical portion provided with a plurality of through-holes so that the cylindrical portion of the stator and the cylindrical portion of the rotor are concentrically positioned with a spacing necessary for generating a shearing action. The stator is fixed, the rotor is rotated concentrically with respect to the stator, the liquid to be treated is supplied from the central direction of the cylindrical portion of the rotor, and the through hole of the cylindrical portion of the stator and the through hole of the cylindrical portion of the rotor It is necessary to adopt a method of making an emulsion in which a hydrophobic liquid is emulsified and dispersed in a hydrophilic liquid by passing it through and discharging it to the outside of the cylindrical portion.

  FIG. 1 shows a longitudinal sectional view of an example of an emulsifying disperser used in this emulsifying dispersion method, and FIG. 2 shows a front view of the rotor.

  In this emulsifying disperser, 1 is a casing, and a stator 3 is fixed by a suction cover 2. The suction cover 2 is provided with a suction port 4, and the casing 1 is provided with a discharge port 5. A main shaft 7 is rotatably provided through a shaft sealing device 6 provided in the casing 1, and a rotor 8 is fixed to the tip of the main shaft 7 by a nut 9.

The rotor 8 is provided with a cylindrical portion 10 supported by a shroud 11, and the cylindrical portion 10 is provided with a plurality of through holes 14 along the circumferential direction. The stator 3 is provided with two cylindrical portions 12 and 13 so as to sandwich the cylindrical portion 10 of the rotor concentrically from both sides with a distance of S ₁ and S ₂ therebetween in the radial direction. Also, a plurality of through holes (not shown) are provided along the circumferential direction. An interval S ₁ between the rotor cylindrical portion 10 and the stator cylindrical portion 12 and an interval S ₂ between the rotor cylindrical portion 10 and the stator cylindrical portion 13 are the gap portions between the rotor cylindrical portion 10 and the stator cylindrical portion 12 due to the rotation of the rotor 8. And it sets suitably in the range which a shearing action produces in a to-be-processed liquid in each of the clearance gap part of the rotor cylindrical part 10 and the stator cylindrical part 13. FIG.

  The shape of the through holes of the rotor and the stator is not particularly limited, and may be any shape such as a slit shape, a circle shape, an ellipse shape, a star shape, a diamond shape, and the like. In the rotor and the stator, the shape and number of the through holes may be the same or different. The through holes may be equally spaced or unequal. By appropriately selecting the number and interval of the through holes, the shearing action does not occur at one time, and vibration and noise can be prevented. The emulsifying and dispersing apparatus shown in FIG. 1 is provided with slit-shaped through holes in the rotor cylindrical portion 10 and the stator cylindrical portions 12 and 13, and the rotor cylindrical portion 10 and the stator cylindrical portions 12 and 13 are both combs. Tooth-shaped ring shape.

  When the slit-like through hole 14 is provided in the cylindrical portion 10 of the rotor 8, the through hole 14 is selected to have an appropriate length. The through holes 14 are not limited to being parallel, and one or both may be inclined with respect to the radial direction. The ends 15 and 16 are preferably sharp.

  In such an emulsifying disperser, when the rotor 8 is rotated by driving the main shaft 7, the liquid to be processed is sucked from the suction port 4 by the pumping action of the rotor 8, and the through hole of the stator cylindrical portion 12 and the through hole of the rotor cylindrical portion 10. 14, flows out through the through hole of the stator cylindrical portion 13 and is discharged from the discharge port 5.

  According to such a method, in the respective gaps between the cylindrical portions 12 and 13 of the stator 3 and the cylindrical portion 10 of the rotor 8, the liquid to be processed generates a swirling flow and a uniform high-speed shearing force acts, Further, a centrifugal flow is generated in the radial direction in the through holes of the rotor and the stator, and this radial flow continuously repeats the collision with the swirling flow. Furthermore, when the rotor 8 provided with the through holes rotates at a high speed, a high frequency is generated, and effects such as crushing and dispersion can be obtained. Due to these actions, the liquid to be treated is continuously subjected to actions such as shearing, crushing, and mixing, and a uniform emulsified dispersion having a narrow particle size distribution can be obtained in a short time.

  In the emulsifying disperser shown in FIG. 1, the stator 3 is provided with two cylindrical portions 12 and 13 so as to concentrically sandwich the cylindrical portion 10 of the rotor 8 from both sides. May be only one place. In this case, either the cylindrical portion of the stator 3 or the cylindrical portion of the rotor 8 may be outside. Furthermore, the rotor 8 can be provided with two or more cylindrical portions, and the stator 3 can be provided with three or more cylindrical portions.

  Although the emulsification disperser of FIG. 1 has one set of the combination part of a stator and a rotor, in this invention, the emulsification disperser which has a combination part of two or more sets of a stator and a rotor can also be used.

  FIG. 3 shows a longitudinal sectional view of an example of an emulsifying disperser having three sets of stator and rotor combination portions.

  In the disperser of FIG. 3, when the rotor 8 rotates, the liquid to be treated is sucked from the suction port 4, and the through hole of the cylindrical portion 12 of the first stage stator 3, the through hole of the cylindrical portion 10 of the rotor 8, and the cylinder of the stator 3. Then, the liquid to be treated flows out through the through hole of the portion 13, and then, the rotation of the second stage rotor 8 ′ causes the through hole of the cylindrical portion 12 ′ of the second stage stator 3 ′, the rotor 8. Through the through hole of the 'cylindrical portion 10' and the through hole of the stator cylindrical portion 13 ', the liquid to be treated flows outward, and the third stage stator is rotated by the rotation of the third stage rotor 8 ". It flows out through the through hole of the cylindrical portion 12 ″ of 3 ″, the through hole of the cylindrical portion 10 ″ of the rotor 8 ″, and the through hole of the cylindrical portion 13 ″ of the stator 3 ″, and is discharged from the discharge port 5. .

  In the case of using an emulsifier / disperser having a combination of two or more stators and rotors, since the shearing action works in each stator / rotor combination, uniform emulsification with a narrow particle size distribution in a shorter time. A dispersion can be obtained.

  Regarding the operating conditions of the emulsifying disperser when emulsifying and dispersing into an emulsion, the diameter of the cylindrical portion of the rotor and stator, the number of rotors and the stator, the shape and number of the through holes in the emulsifying disperser, Although it is not uniform because it can vary depending on the type and the like, the flow rate of the liquid to be treated, the rotational speed of the rotor, etc. may be appropriately set so that a uniform emulsified dispersion can be obtained in a short time. If necessary, the emulsion discharged from the emulsifier / disperser can be supplied again to the emulsifier / disperser and repeatedly emulsified and dispersed. The particle diameter of the dispersed particles in the emulsion can be easily controlled by changing the number of rotations of the rotor.

  In the present invention, the mixed liquid of the hydrophobic liquid and the hydrophilic liquid used as the liquid to be treated is emulsified in a state where the hydrophobic liquid and the hydrophilic liquid are mixed in advance and the hydrophobic liquid is pre-emulsified and dispersed in the hydrophilic liquid. It can be fed to the disperser or the hydrophobic and hydrophilic liquids can be added separately to the emulsifier disperser.

  In the present invention, the hydrophobic liquid serves as a core material of the microcapsule, and various components included depending on the purpose of use of the microcapsule, and components necessary for forming the capsule wall film as necessary. Additions can be used.

  For example, when used as a microcapsule for pressure-sensitive copying paper, the hydrophobic liquid used as the core material of the microcapsule is obtained by dissolving an electron-donating organic color former in oil and further adopting a microcapsule What added a required wall film component according to the method can be used. As the oil, natural or synthetic oil can be used alone or in combination. Examples thereof include cottonseed oil, kerosene, paraffin, naphthenic oil, alkylated biphenyl, alkylated terphenyl, chlorinated paraffin, alkylated naphthalene, And dibasic acid esters such as diarylalkanes and phthalic acid esters. As the electron donating organic color former, a known material corresponding to a desired color tone can be used. Specific examples thereof include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3. Triallylmethane compounds such as bis (p-dimethylaminophenyl) phthalide and 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide; 4,4′-bis -Diphenylmethane compounds such as dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucooramine, N-2,4,5-trichlorophenylleucooramine; 7-dimethylamino-3-chlorofluorane, 7-dimethyl Amino-3-chloro-2-methylfluorane, 2-phenylamino-3-methyl-6- (N-ethyl-Np-tri Fluorane compounds such as aminofluorane; thiazine compounds such as benzoyl leucomethylene blue and p-nitrobenzyl leucomethylene blue; Examples include spiro compounds such as -propyl-spiro-dibenzopyran.

  As the hydrophilic liquid, an aqueous solution in which a surfactant, a protective colloid, components necessary for forming a capsule wall film and the like are dissolved in water as necessary is usually used.

  The mixing ratio of the hydrophobic liquid and the hydrophilic liquid is not particularly limited, and may be used at a ratio at which a stable oil-in-water emulsion can be obtained according to the type of components used. Usually, the weight ratio of the hydrophobic liquid to the hydrophilic liquid is used in the range of the former: the latter = 10: 90 to 60:40.

  After producing an emulsion having a uniform particle diameter by the above-described method, a microcapsule can be obtained by forming a capsule wall film at the interface between the emulsified and dispersed hydrophobic liquid and the hydrophilic liquid.

  As a method for forming the capsule wall film, various conventionally known methods such as a coacervation method, an in situ method, and an interfacial polymerization method can be applied. The formation conditions of the capsule wall film itself may follow a known method. In these cases, necessary components may be previously present in the hydrophobic liquid and / or the hydrophilic liquid according to the encapsulation method employed.

  For example, in the coacervation method, an emulsion is typically formed using an aqueous solution containing gelatin, which is then added to gum arabic, sodium alginate, styrene maleic anhydride copolymer, vinyl methyl ether maleic anhydride. A capsule wall membrane can be formed by adding an anionic substance such as a copolymer, starch phthalate ester, or polyacrylic acid, and adjusting the concentration, pH, and the like.

  In the in situ method, a monomer, a low polymer or a condensate that forms a wall film is supplied from only one of the inside and outside of the core material dispersed in the dispersion medium together with the polymerization catalyst, and a polymerization or condensation reaction is performed on the surface of the core material. This is an encapsulation method, and typical wall membranes include melamine-formalin resin. For melamine-formalin resin capsules, after obtaining an emulsified dispersion, a partially condensed melamine-formalin prepolymer aqueous solution is added, the pH is adjusted, and the temperature is raised to precipitate and cure the resin around the hydrophobic liquid. It can be obtained by forming a capsule wall membrane. As a method of forming a melamine-formalin resin capsule from a hydrophobic liquid by an in situ method, after dissolving the melamine-formalin prepolymer in the hydrophobic liquid and emulsifying and dispersing it in the hydrophilic liquid, There is a method of forming a capsule wall film by depositing and curing a resin around the periphery.

  The interfacial polymerization method is a method of forming a wall film such as polyamide, epoxy resin, polyurethane, or polyurea at the interface between the hydrophobic liquid and the hydrophilic liquid, and a hydrophilic monomer such as polyamine, glycol, or polyhydric phenol, A capsule wall membrane can be formed by dissolving a hydrophobic monomer such as polybasic acid halide, bishaloformer, polyisocyanate, etc. in a hydrophilic liquid and a hydrophobic liquid, respectively, and causing a polymerization reaction at the interface. In the present invention, this method is preferable, and it is particularly preferable to use an aromatic polyisocyanate and an aliphatic polyisocyanate in combination as the hydrophobic monomer. The mixing ratio of the two in this case is preferably about aromatic polyisocyanate: aliphatic polyisocyanate (weight ratio) = 1: 0.01 to 100, more preferably about 1: 0.1 to 10, In this way, by using an aromatic polyisocyanate and an aliphatic polyisocyanate together, it is possible to obtain a microcapsule having a uniform particle size distribution and excellent color development, friction resistance, pressure resistance, etc. .

  According to the method of the present invention, when a hydrophobic liquid to which a wall film forming component is added by an interfacial polymerization method or an in situ method is used, in the emulsification method using a conventional homomixer, the capsule particle size is particularly uneven. A microcapsule having a uniform particle size and an appropriate strength can be easily formed, although the strength of the formed microcapsule tends to be low. The reason for this is not clear, but in the emulsification method using a homomixer, heat is generated during emulsification and a part of the monomer component in the hydrophobic liquid reacts, forming a thin film on the surface and making it difficult to obtain a uniform particle size. Moreover, since this thin film may be destroyed during emulsification, the strength of the wall film may be reduced when the capsule wall film is formed. It is presumed that because the average particle size is obtained, the emulsification time is short, and it is difficult to form a thin film due to the reaction of the monomer component in the hydrophobic liquid.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

Example 1
Diisopropyl naphthalene (KMC-113, Kureha Chemical Co., Ltd.), crystal violet lactone 5% as an electron-donating organic color former, and polymethylene polyphenyl isocyanate (millionate MR300, an aromatic polyvalent isocyanate) as a microcapsule wall membrane material 5% of a polyurethane manufactured by Nippon Polyurethane Industry Co., Ltd. and 5% of a trimer of hexamethylene diisocyanate having an isocyanurate ring which is an aliphatic polyisocyanate (Coronate EH, manufactured by Nippon Polyurethane Industry Co., Ltd.) were dissolved.

  This hydrophobic liquid was added to a 4% aqueous solution of polyvinyl alcohol (PVA-117, manufactured by Kuraray Co., Ltd.) and preliminarily stirred with a propeller mixer. The weight ratio of the hydrophobic liquid and the aqueous polyvinyl alcohol solution was 100: 100.

  Next, using the continuous emulsion disperser (Ebara Milder, manufactured by Ebara Seisakusho Co., Ltd.) having the combination of the three rotors and the stator shown in FIG. 3, the mixed liquid is put into a hopper and the flow rate is 250 g / min. The solution was fed and stirred at a rotational speed of the rotor of 6,000 rpm / min to obtain an emulsion from the outlet.

  When the particle size distribution of the obtained emulsion was measured with a commercially available particle size measuring device (Coulter Multisizer, manufactured by Coulter, Inc.), the average particle size was 7.0 μm, and the particle size difference was within 20%. Was 70% and was excellent in uniformity.

  After adding 1 part of diethylenetriamine, which is a polyvalent amine, to 100 parts (nonvolatile content) of this emulsion, the mixture was heated to 80 ° C. while stirring with a mixer, and reacted for 3 hours by interfacial polymerization. To form microcapsules.

  The obtained microcapsules had the same average particle size and particle size distribution as the above emulsion, and had good uniformity.

Comparative Example 1
The average particle size of the premixed liquid similar to that in Example 1 was 7 using a continuous emulsion disperser (TK pipeline homomixer, manufactured by Tokushu Kika Kogyo Co., Ltd.) having a rotor and a stator shown in FIG. Continuous emulsification in the circulatory system until reaching 0.0 μm. The obtained emulsion was inferior in uniformity with a particle size difference of 43% within a range of ± 20% of 7.0 μm.

  Using this emulsion, microcapsules were prepared in the same manner as in Example 1. However, the average particle size and particle size distribution of the obtained microcapsules were almost the same as those of the used emulsion, and the uniformity was poor. It was a thing.

Example 2
An emulsion was obtained in the same manner as in Example 1 except that the same emulsification disperser as in Example 1 was used, except that the flow rate was 400 g / min and the rotation speed was 8,000 rpm / min.

  When the particle size distribution of the obtained emulsion was measured with a Coulter Multisizer (manufactured by Coulter Co., Ltd.), the average particle size was 6.7 μm, and the proportion within which the particle size difference was within ± 20% was 71%. Was good.

  Using this emulsion, a capsule wall membrane was formed in the same manner as in Example 1 to obtain microcapsules. The obtained microcapsules had an average particle size and particle size distribution almost the same as the emulsion used, and had good uniformity.

Comparative Example 2
The average particle size of the premixed liquid similar to that in Example 1 was 6 using a continuous emulsion disperser (TK pipeline homomixer, manufactured by Tokushu Kika Kogyo Co., Ltd.) having a rotor and a stator shown in FIG. Continuous emulsification in the circulatory system until reaching 7 μm. The obtained emulsion was inferior in uniformity with a particle size difference of 42% within a range of ± 20% of 6.7 μm.

  Using this emulsion, microcapsules were prepared in the same manner as in Example 1. However, the average particle size and particle size distribution of the obtained microcapsules were almost the same as those of the used emulsion, and the uniformity was poor. It was a thing.

Example 3
An emulsion was obtained in the same manner as in Example 1 except that the same emulsifying disperser as in Example 1 was used, except that the flow rate was 600 g / min and the rotation speed was 10,000 rpm / min.

  When the particle size distribution of the obtained emulsion was measured with a Coulter Multisizer (manufactured by Coulter Co., Ltd.), the average particle size was 6.4 μm, and the proportion that the particle size difference was within ± 20% was 68%. Was good.

  Using this emulsion, a capsule wall membrane was formed in the same manner as in Example 1 to obtain microcapsules. The obtained microcapsules had an average particle size and particle size distribution almost the same as the emulsion used, and had good uniformity.

Comparative Example 3
The average particle size of the premixed liquid similar to that in Example 1 was 6 using a continuous emulsion disperser (TK pipeline homomixer, manufactured by Tokushu Kika Kogyo Co., Ltd.) having a rotor and a stator shown in FIG. Continuous emulsification in the circulatory system until reaching 4 μm. The obtained emulsion was inferior in uniformity because the particle size difference was within 40% within ± 20% of 6.4 μm.

  Using this emulsion, microcapsules were prepared in the same manner as in Example 1. However, the average particle size and particle size distribution of the obtained microcapsules were almost the same as those of the used emulsion, and the uniformity was poor. It was a thing.

Example 4
An emulsion was obtained in the same manner as in Example 1 except that the same emulsifying disperser as in Example 1 was used, except that the flow rate was 100 g / min and the rotation speed was 4,000 rpm.

  When the particle size distribution of the obtained emulsion was measured with Coulter Multisizer (manufactured by Coulter Co., Ltd.), the average particle size was 7.4 μm, and the proportion within which the particle size difference was within ± 20% was 65%. Was good.

  Using this emulsion, a capsule wall membrane was formed in the same manner as in Example 1 to obtain microcapsules. The obtained microcapsules had an average particle size and particle size distribution almost the same as the emulsion used, and had good uniformity.

Comparative Example 4
The average particle size of the premixed liquid similar to that in Example 1 was 7 using a continuous emulsion disperser (TK pipeline homomixer, manufactured by Tokushu Kika Kogyo Co., Ltd.) having a rotor and a stator shown in FIG. Continuous emulsification in the circulatory system until reaching 4 μm. The obtained emulsion was inferior in uniformity, with the ratio of the particle size difference falling within ± 20% of 7.4 μm being 45%.

  Using this emulsion, microcapsules were prepared in the same manner as in Example 1. However, the average particle size and particle size distribution of the obtained microcapsules were almost the same as those of the used emulsion, and the uniformity was poor. It was a thing.

Test Example Using the microcapsules containing the color formers obtained in Examples and Comparative Examples, pressure-sensitive copying paper was prepared by the following method, and a performance test was performed.

  [Preparation of microcapsule coating solution] To 100 parts (solid content) of the microcapsule dispersion obtained in Examples or Comparative Examples, 70 parts of wheat starch granules and 15 parts of carboxy-modified styrene-butadiene copolymer latex (solid content) were added. In addition, the microcapsule coating solution was obtained by adjusting the solid concentration to 20%.

  [Preparation of developer coating solution] 65 parts of calcium carbonate, 20 parts of zinc oxide, 15 parts of 3,5-di (α-methylbenzyl) salicylic acid zinc salt, 3% polyvinyl alcohol (N-300, Nippon Synthetic Chemical Industry) 20 parts of carboxy-modified styrene butadiene copolymer latex (solid content) is added to a dispersion obtained by grinding 150 parts of aqueous solution and 100 parts of water with a ball mill for 24 hours so that the solid content concentration becomes 25%. To obtain a developer coating solution.

The above microcapsules coated liquid Production above paper], the coating amount after drying was applied and dried in an air knife coater so that 4g / m ² to the surface of quality paper having a basis weight of 40 g / m ^2, An upper paper for pressure-sensitive copying paper was prepared.

The developer coated liquid Production of lower paper], the coating amount after drying on the surface of quality paper having a basis weight of 40 g / m ² is coated and dried in an air knife coater so that the 5 g / m ² A lower paper for pressure-sensitive copying paper was prepared.

  [Test Method] Using the above upper paper and lower paper, a performance test was conducted by the following method. The results are shown in Table 1 below.

(1) Color development The upper sheet and the lower sheet are overlapped so that the coated surfaces face each other, and are passed through a super calender to develop color, and after one hour, the color density on the developer coated surface is determined by Macbeth reflection densitometer RD914. Measured with a mold (Macbeth).

(2) Pressure resistance The upper paper and the lower paper are overlapped so that the coated surfaces face each other, and the paper is sandwiched from above and below by 50 sheets of high-quality paper, and a load of 20 kg / cm ² is applied to a 3 cm square area for 1 minute. Thereafter, the degree of coloring stains on the surface of the developer application surface was visually confirmed and evaluated according to the following criteria.
◎ Almost no coloring stains and very good.
○ Slight coloring stains occurred, but there is no practical problem.
× Colored stains are strong and impractical.

(3) Friction resistance The upper paper and the lower paper are overlapped so that the coated surfaces face each other, and are rubbed five times under a load of 4 kg / cm ^{2 to} reduce the degree of color stain on the developer coated surface. It confirmed visually and evaluated by the following reference | standard.
◎ Almost no coloring stains and very good.
○ Slight coloring stains occurred, but there is no practical problem.
× Colored stains are strong and impractical.

  As is clear from the above results, the microcapsules with good uniformity encapsulating the electron donating organic color former obtained by the method of the present invention have good color developability when used for pressure-sensitive copying paper, Moreover, color stains are less likely to occur during storage and handling.

The longitudinal cross-sectional view of an emulsification disperser. The front view of the rotor of the emulsification disperser of FIG. The longitudinal cross-sectional view of the continuous emulsification disperser provided with three sets of rotors and stators. Schematic of a homomixer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Casing 2 ... Suction cover 3, 3 ', 3 "... Stator 4 ... Suction port 5 ... Discharge port 6 ... Shaft seal device 7 ... Main shaft 8, 8' , 8 "... Rotor 9 ... Nuts 10, 10 ', 10" ... Rotor cylinder 11 ... Shroud 12, 12', 12 "... Stator cylinder 13, 13 ' 13 "... cylindrical portion 14 of the stator 14 ... through holes 15, 16 ... end 17 ... rotor 18 ... discharge hole 19 ... stator 20 ... current plate 21 ...・ Shaft 22 ... Gap

Claims (3)

  A stator having a cylindrical portion provided with a plurality of through holes along the circumferential direction, and a rotor having a cylindrical portion provided with a plurality of through holes along the circumferential direction, the cylindrical portion of the stator and the cylinder of the rotor Using a device installed so as to be concentrically positioned with a certain interval necessary for the part to generate a shearing action, fixing the stator, rotating the rotor concentrically with respect to the stator, A liquid to be treated consisting of a liquid and a hydrophilic liquid is supplied from the central direction of the cylindrical portion of the rotor, passes through the through hole of the cylindrical portion of the stator and the through hole of the cylindrical portion of the rotor, and is discharged to the outside of the cylindrical portion. A method for producing a microcapsule characterized in that a hydrophobic liquid is emulsified and dispersed in a hydrophilic liquid to form an emulsion, and then a capsule wall film that encapsulates the emulsified and dispersed hydrophobic liquid is formed. Dissolved in liquid The microcapsules are those in which the hydrophobic monomer is an aromatic polyisocyanate and an aliphatic polyisocyanate, and the formation method of the capsule wall film is an interfacial polymerization method in which a wall film is formed at the interface between the hydrophobic liquid and the hydrophilic liquid. Production method.   The mixing ratio of the aromatic polyisocyanate and the aliphatic polyisocyanate is aromatic polyisocyanate: aliphatic polyisocyanate (weight ratio) = 1: 0.1-10. The manufacturing method as described.   The manufacturing method according to claim 1, wherein the cylindrical portion of the stator and the cylindrical portion of the rotor are comb-shaped rings each having a slit-shaped through hole.

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