JP2001137690A - Method for producing powdery microcapsules and powdery microcapsules obtained thereby - Google Patents

Abstract

(57) [Problem] To provide a method for producing a powdery microcapsule without mechanically breaking a microcapsule wall film and a powdery microcapsule obtained by the method. SOLUTION: A microcapsule aggregate formed by agglomeration of a microcapsule composed of a core material and a polyurea-based wall film covering the core material is made to collide with each other in a supersonic flow to dissolve the aggregation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powdery microcapsule enclosing a curing agent for an epoxy resin and the like, and a powdery microcapsule obtained by the method.

[0002]

2. Description of the Related Art Microcapsules formed by forming a core material (core) and a wall film (shell) covering the core material have been conventionally manufactured by devising a core material and a wall film forming material. For example, they are used in various fields such as various recording materials, pharmaceuticals, fragrances, agricultural chemicals, adhesives, and display materials. Above all, those in which the wall film is made of a polyurea-based material have an excellent isolation function, and the particle size and the thickness of the wall film can be adjusted relatively easily. It is suitably used as a microcapsule for a pressure-sensitive recording sheet. Such a microcapsule whose wall film is made of polyurea can be produced, for example, as follows. That is, in the hydrophobic solution which is the core material component,
O / W type (oil phase / water phase type) emulsion by dissolving polyvalent isocyanate as a wall film material to form an oil phase, and emulsifying this oil phase in an aqueous phase containing a dispersion stabilizer. Then, a polyvalent amine is added to and dissolved in the aqueous phase of this emulsion to allow interfacial polymerization with the polyvalent isocyanate in the oil phase to carry out the polyaddition reaction, or The emulsion is heated, the polyvalent isocyanate in the oil phase reacts with water at the interface with the aqueous phase to form an amine, and subsequently a self-polyaddition reaction is caused to form a polyurea-based wall film. Microencapsulation results in a suspension in which the resulting microcapsules are suspended. This suspension is a state in which the microcapsules are dispersed in an aqueous solution. As described above, when the microcapsules are used for a pressure-sensitive recording sheet, a binder component or the like is added to the suspension. By blending the agent, it can be coated on paper as it is. However, when dispersing the microcapsules in a hydrophobic resin or the like, it is necessary to remove the microcapsules from the suspension. As this method, for example, a method of removing the dispersion stabilizer or the like in the aqueous phase from the above suspension by centrifugation or filter filtration, and then removing water by freeze-drying or spray-drying, and taking out the microcapsules. Has been done.

[0003]

However, when water is removed from the aqueous suspension and the microcapsules are taken out, there is a problem that the microcapsules aggregate and form microcapsule aggregates. One of the factors is
Water-soluble polymers such as polyvinyl alcohol and hydroxymethyl cellulose blended as the dispersion stabilizer are mentioned. The above water-soluble polymers react with polyisocyanate, which is a constituent material of the microcapsule wall film, and chemically and physically adsorb to the microcapsule wall film, so that they are sufficiently removed by washing by centrifugation or filtration. I ca n’t,
As a result, it is considered that the remaining ones act as a binder when drying the microcapsules, and strongly aggregate the microcapsules. For example, JP-A-8-337
If such agglomeration occurs in the microcapsule-type epoxy resin curing agent disclosed in JP-A-633, the dispersibility of the curing agent becomes poor, so that the curing agent cannot exhibit stable curability. Have difficulty. Therefore, in order to dissolve such agglomeration, for example, a method of crushing by applying a hammer mill, a turbo mill, a roll mill, or the like is conceivable, but the microcapsule wall film is mechanically broken by the impact force or the shearing force. As a result, the curing agent contained in the wall film may be released.

The present invention has been made in view of such circumstances, and provides a method for producing a powdery microcapsule without mechanically destroying the microcapsule wall film, and a powdery microcapsule obtained by the method. For that purpose.

[0005]

In order to achieve the above object, the present invention provides a microcapsule aggregate formed by agglomerating microcapsules comprising a core material and a polyurea-based wall film covering the core material. A first aspect of the present invention is a method for producing a powdery microcapsule in which the above-mentioned aggregates collide with each other in a sonic flow to disperse the aggregates, and the method comprises a step of classifying the microcapsules thus crushed by a high-speed swirling vortex flow. A second aspect of the present invention relates to a method for producing a microcapsule, which is a powdery microcapsule obtained by the method, wherein the powdery microcapsule whose average particle diameter is set in a range of 0.5 to 20 μm is referred to as a third The summary of the

[0006] That is, the present inventors have repeated a series of studies to dissolve the aggregation of microcapsule aggregates without mechanically breaking the microcapsules. As a result, in order to deagglomerate, for example, a hammer mill, a turbo mill,
Rather than using a device such as a roll mill that may mechanically break the microcapsules due to the impact force or shear force, supply the aggregate in a supersonic flow,
The present inventors have found that, by vigorously colliding aggregates in a supersonic flow, the aggregates are broken without causing mechanical destruction of the microcapsule wall film, whereby powdery microcapsules can be obtained. Here, the term “agglomeration” includes not only the fact that the whole is made into primary particles, but also the case where particles of the aggregate become smaller remain. Therefore, the powdery state in the powdery microcapsules includes not only the microcapsules of the primary particles but also the state in which the microcapsules and the aggregate of a plurality of microcapsules coexist. The reason that the microcapsules are not destroyed by the collision between the aggregates in the supersonic flow is that the microcapsule wall is a polyurea-based wall and is relatively flexible. Even if it does, it is considered that no damage that directly destroys the wall film of the microcapsules (primary particles) is given.

[0007] The powder microcapsules thus obtained are made of polyurea such as polyurea and polyurethane / polyurea, and the storage stability during storage and the encapsulation when heated are used. The substance (core material) is excellent in releasability, and the powdery microcapsules are excellent in dispersibility since the agglomeration is broken.

Further, as described above, when the agglomerates of the microcapsules are pulverized by deagglomerating the agglomerates, and then the obtained powdery microcapsules are fed into a high-speed swirling vortex, The powdery microcapsules are classified, and as a result, primary particle-like microcapsules can be efficiently obtained.

[0009]

Next, embodiments of the present invention will be described in detail.

As shown in FIG. 1, a powdery microcapsule (primary particle) according to the present invention comprises a core material 1 and a polyurea-based wall film 2 covering the core material.

The core material 1 is not particularly limited, but is preferably liquid at room temperature and hydrophobic in view of workability in preparing microcapsules and characteristics of the microcapsules. The term “liquid at room temperature” includes not only the case where the property of the core material 1 is liquid at room temperature, but also the case where the core material 1 is solid at room temperature and is dissolved or finely dispersed in an arbitrary organic solvent or the like to be liquid.

The material for forming the core 1 is not particularly limited, and examples thereof include agrochemicals, pharmaceuticals, pheromones,
Liquid crystals, adhesives, dyes and the like can be mentioned. Particularly, a resin curing agent such as a rubber vulcanizing agent (crosslinking agent), a curing agent for an acrylic resin monomer, a curing agent for an epoxy resin (curing accelerator), a crosslinking agent, a catalyst, and an accelerator are preferable. Among them, the epoxy resin curing agent and the curing accelerator are in the form of powdered microcapsules, and the epoxy resin composition in which the epoxy resin composition is dispersed can be used to obtain cured material properties such as curability, heat resistance, water resistance, and insulation. , And the storage stability during storage is also increased, so that good results can be obtained.

Examples of the epoxy resin curing agent include acid anhydrides such as methylhymic acid anhydride, phthalic anhydride and benzophenonetetracarboxylic acid anhydride, phenols such as bisphenol A and phenol resin, and tributylamine. Aliphatic tertiary amines such as benzyldimethylamine, 2- (dimethylamino) phenol, and 2.
Aromatic tertiary amines and alicyclics such as 4.6-tris (diaminomethyl) phenol or modified amines thereof, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-dodecylimidazole, 2-
Imidazoles such as undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, and these imidazoles Carboxylic acid salts with acetic acid, lactic acid, salicylic acid, benzoic acid, adipic acid, phthalic acid, citric acid, tartaric acid, maleic acid, trimellitic acid, and Lewis acids such as boron trifluoride and phosphorus pentafluoride Etc. can be used. Among these, it is preferable to use a catalytic curing agent such as a tertiary amine or imidazole from the viewpoint of curing reactivity during heating.

Examples of the epoxy resin curing accelerator include amine-based, imidazole-based, phosphorus-based, boron-based, and the like.
A curing accelerator such as a phosphorus-boron type is exemplified. Specifically, alkyl-substituted guanidines such as ethyl guanidine, trimethyl guanidine, phenyl guanidine, diphenyl guanidine and the like, 3- (3.4-dichlorophenyl)-
3-substituted phenyl-1.1-dimethylureas such as 1.1-dimethylurea, 3-phenyl-1.1-dimethylurea, 3- (4-chlorophenyl) -1.1-dimethylurea, 2-methyl Imidazolines such as imidazoline, 2-phenylimidazoline, 2-undecylimidazoline and 2-heptadecylimidazoline; monoaminopyridines such as 2-aminopyridine; N-dimethyl-N- (2
-Hydroxy-3-allyloxypropyl) amine-N '
Amine imides such as lactoimide, ethyl phosphine, propyl phosphine, butyl phosphine, phenyl phosphine, trimethyl phosphine, triethyl phosphine, tributyl phosphine, trioctyl phosphine, triphenyl phosphine, tricyclohexyl phosphine, triphenyl phosphine / triphenyl borane complex, Organophosphorus compounds such as tetraphenylphosphonium tetraphenylborate, diazabicycloundecene such as 1.8-diazabicyclo [5.4.0] undecene-7,1.4-diazabicyclo [2.2.2] octane And the like. These can be used alone or 2
Used in combination of more than one species. Above all, the imidazole-based compound and the organic phosphorus-based compound are preferably used from the viewpoint of easy production and handling of the microcapsules. In addition, the compounds exemplified as the curing agent can also be used as the curing accelerator.

Polyurea-based wall film 2 covering core material 1
Is preferably a polymer having a structural unit represented by the following general formula (1). As a result, the storage stability of the microcapsules during storage and the ease of breakage of the wall film during heating use can be obtained.

[0016]

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As described above, in equation (1), R ₁ ,
R ₂ is a hydrogen atom or a monovalent organic group. Among them, it is preferable that both R ₁ and R ₂ are hydrogen atoms.

The polymer having the structural unit represented by the above formula (1) can be obtained, for example, by a polyaddition reaction between a polyvalent isocyanate and a polyvalent amine. Can also be obtained by reacting.

The polyvalent isocyanate may be any compound having two or more isocyanate groups in the molecule. Specific examples thereof include m-phenylene diisocyanate, p-phenylene diisocyanate, and 2.4-tolylene diisocyanate. , 2.6-tolylene diisocyanate, naphthalene-1.4-diisocyanate, diphenylmethane-4.4'-diisocyanate, 3.3'-dimethoxy-4.4'-biphenyl diisocyanate,
3.3'-dimethyldiphenylmethane-4.4'-diisocyanate, xylylene-1.4-diisocyanate, 4.4'-diphenylpropane diisocyanate,
Trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1.2-diisocyanate,
Butylene-1.2-diisocyanate, cyclohexylene-1.2-diisocyanate, cyclohexylene-
Diisocyanates such as 1.4-diisocyanate, p
-Phenylenediisothiocyanate, xylylene-1.
Diisothiocyanates such as 4-diisothiocyanate and ethylidene diisothiocyanate, 4.4'-dimethyldiphenylmethane-2.2 '. 5.5'-tetraisothiocyanate and other tetraisocyanates, adducts of hexamethylene diisocyanate and hexanetriol, adducts of 2.4-tolylenediisocyanate and prenzcatechol, addition of tolylenediisocyanate and hexanetriol Products, adducts of tolylene diisocyanate and trimethylolpropane, adducts of xylylene diisocyanate and trimethylolpropane, adducts of hexamethylene diisocyanate and trimethylolpropane, triphenyldimethylenetriisocyanate, tetraphenyltrimethylenetetraisocyanate, pentane Such as trimers of aliphatic polyvalent isocyanates such as phenyltetramethylenepentaisocyanate, lysine isocyanate, and hexamethylene diisocyanate Socia Prepolymer the like. These may be used alone or in combination of two or more.

Among the above polyvalent isocyanates, adducts of tolylene diisocyanate and trimethylolpropane and adducts of xylylene diisocyanate and trimethylolpropane are preferable from the viewpoint of film forming property and mechanical strength when preparing microcapsules. It is preferable to use an isocyanate prepolymer represented by polymethylene polyphenyl isocyanate such as triphenyl dimethylene triisocyanate.

On the other hand, the polyvalent amines to be reacted with the above polyvalent isocyanates may be any compounds having two or more amino groups in the molecule, and specifically, diethylenetriamine, triethylenetetramine, tetraethylenepentamine. Min, 1,6-hexamethylenediamine, 1,8
-Octamethylenediamine, 1,12-dodecamethylenediamine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, menthanediamine, bis (4-amino-3-methylcyclohexyl) methane, isophoronediamine, 1,3
-Diaminocyclohexane, spiroacetal diamine and the like. These may be used alone or in combination of two or more.

In the present invention, a polyhydric alcohol may be used together with a polyvalent isocyanate in the oil phase, and a polyurethane / polyurea having a urethane bond may be used as the wall film. The polyhydric alcohol used above may be any of aliphatic, aromatic and alicyclic. For example, catechol, resorcinol, 1.2-dihydroxy-4-methylbenzene, 1.3-dihydroxy- 5-methylbenzene, 3.4-dihydroxy-1-
Methylbenzene, 3.5-dihydroxy-1-methylbenzene, 2.4-dihydroxyethylbenzene, 1.3
-Naphthalene diol, 1.5-naphthalene diol,
2.7-naphthalene diol, 2.3-naphthalene diol, o. o'-biphenol, p. p'-biphenol, bisphenol A, bis- (2-hydroxyphenyl) methane, xylylene diol, ethylene glycol, 1.3-propylene glycol, 1.4-butylene glycol, 1.5-pentanediol, 1.6- Hexanediol, 1.7-heptanediol, 1.8-octanediol, 1.1.1-trimethylolpropane, hexanetriol, pentaerythritol, glycerin, sorbitol and the like can be mentioned. These may be used alone or in combination of two or more.

The powdery microcapsules according to the present invention are:
For example, it can be manufactured as follows. That is, a polyvalent isocyanate serving as a wall film material is dissolved in a hydrophobic solution as a core material component to form an oil phase. This oil phase is emulsified in an aqueous phase containing a dispersion stabilizer and
A W-type (oil / water phase) emulsion is prepared. Next, a polyvalent amine is added to and dissolved in the aqueous phase of this emulsion, whereby the polyaddition reaction is carried out by interfacial polymerization with the polyvalent isocyanate in the oil phase. Alternatively, by heating the emulsion, the polyisocyanate in the oil phase is reacted with water at the interface with the aqueous phase to form an amine, followed by a self-polyaddition reaction. In this way, a suspension (aqueous suspension) of polyurea-based microcapsules having a polymer having the structural unit represented by the above formula (1) as a wall film is obtained. Next, the dispersion stabilizer and the like in the aqueous phase are removed from the suspension by centrifugation or filtration, and then the remaining water is removed by freeze-drying or spray-drying to obtain microcapsule aggregates. At this time, if necessary, the organic solvent in the microcapsules can be removed by using a means such as drying under reduced pressure. Then, by supplying this aggregate in a supersonic flow, the aggregation is broken without causing breakage of the microcapsules, and as a result, powdery microcapsules are obtained. The pressure of the supersonic flow at this time is 49 × 10 ⁴ Pa It is preferable to set the degree to the extent that the microcapsules are not broken and the aggregation is released. Further, by supplying the powdery microcapsules into a high-speed swirling vortex flow, the powdery microcapsules are classified to obtain primary particulate, powdery microcapsules. The device that generates the airflow under the conditions of the supersonic flow and the high-speed swirling vortex flow is not particularly limited. For example, a supersonic jet crusher (TYPE PJM, manufactured by Nippon Pneumatic Industries, Ltd.) is a supersonic crusher. Suitable for generating flow. Some of the devices have a mechanism for classifying by the high-speed swirling vortex flow. In this case, the object treated by the supersonic flow can be continuously supplied to the high-speed swirling vortex flow for classification. Therefore, it is more preferable.

Examples of the dispersion stabilizer usable in the present invention include water-soluble polymers such as polyvinyl alcohol and hydroxymethyl cellulose, anionic surfactants, nonionic surfactants, and cationic surfactants. Surfactants and the like. In addition, hydrophilic inorganic colloids such as colloidal silica and viscous minerals can also be used. Among these, water-soluble polymers such as polyvinyl alcohol and hydroxymethyl cellulose are particularly preferable from the viewpoint of stability of the emulsion during interfacial polymerization.

When the above-mentioned powdery microcapsules have an average particle diameter in the range of 0.5 to 20 μm, for example, when the microcapsules coated with a curing agent or a curing accelerator of an epoxy resin are cured, It is preferable because it is suitable for uniformity. More preferably, it is in the range of 0.5 to 5 μm. The shape of the powdery microcapsule type curing agent according to the present invention is preferably spherical, but may be elliptical. If the microcapsules are not perfectly spherical and the particle diameter is not uniformly determined, such as elliptical or flat, the simple average value of the longest diameter and the shortest diameter is defined as the average particle diameter. The particle size can be measured by, for example, observation with an electron microscope or dry particle size distribution measurement.

The ratio of the thickness of the wall film to the average particle size of the powdery microcapsules is preferably set in the range of 5 to 25%. That is, if the above ratio is less than 5%, the mechanical strength is inferior, and the microcapsules may be broken in the process of colliding the microcapsule aggregates to dissolve the aggregation. This is because it is difficult to produce microcapsules by a method of forming microcapsules with a wall film (interfacial polymerization method).

Next, examples will be described together with comparative examples.

[0028]

Example 1 [Preparation of microcapsule-type curing accelerator]
11 parts by weight of an adduct of 3 mol of xylylene diisocyanate and 1 mol of trimethylolpropane (hereinafter abbreviated as "part") and 4.6 parts of an adduct of 3 mol of tolylene diisocyanate and 1 mol of trimethylolpropane are cured. 7 parts of triphenylphosphine as an accelerator and 3.9 of ethyl acetate
To obtain a liquid for an oil phase.

Further, a liquid for an aqueous phase composed of 100 parts of distilled water and 5 parts of polyvinyl alcohol is separately prepared, and the liquid for an oil phase prepared above is added thereto, and emulsified by a homomixer to form an emulsion. This was charged into a polymerization reactor equipped with a reflux tube, a stirrer, and a dropping funnel.

On the other hand, 10 parts of an aqueous solution containing 3 parts of triethylenetetramine was prepared, placed in the dropping funnel of the polymerization reactor, and dropped into the emulsion in the reactor at 70 ° C.
For 3 hours to obtain an aqueous suspension of a microcapsule-type curing accelerator. The average particle size of the microcapsules (primary particles) in the aqueous suspension was 1.
It was 8 μm. Subsequently, after removing polyvinyl alcohol and the like in the aqueous phase by centrifugation, agglomerates (particles) of free-flowing microcapsules are spray-dried.
I got The average particle size of the aggregate was about 50 μm. This aggregate is converted into a supersonic jet pulverizer (PJM-20).
0NC, manufactured by Nippon Pneumatic Industries Co., Ltd.) with a pulverizing pressure of 49 × 10 ⁴ Pa Under the same conditions as described above to obtain a powdery microcapsule-type curing accelerator. In addition, the state of pulverization of the aggregate by the supersonic jet pulverizer was confirmed by an electron microscope. FIG. 2 is an electron micrograph showing a final product (pulverized microcapsule-type hardening accelerator) obtained by the treatment with a supersonic jet particle grinder, and FIG. 3 is a treatment with a supersonic jet particle grinder. FIG. 4 is an electron micrograph showing the aggregate before (in both FIGS. 2 and 3, a magnification of 2000). From the electron micrographs, the microcapsule-type curing accelerator treated by the supersonic jet particle pulverizer is in the form of primary particles with almost no aggregation, and the wall film of the microcapsules is broken. It turns out there is no.

[Preparation of epoxy resin composition containing microcapsule-type curing accelerator] 12 parts of the powdery microcapsule-type curing accelerator obtained as described above is represented by the following general formula (2). Biphenyl type epoxy resin [in the formula (2), R _{1 to} R ₄ are a methyl group and an epoxy equivalent of 20.
0] 128 parts, phenol aralkyl resin represented by the following general formula (3) [in the formula (3), a mixture of n = 0 to 21, hydroxyl equivalent 175] 99 parts, spherical fused silica powder 1
280 parts, 550 parts of crushed crystalline silica powder, and 3 parts of a polyethylene-based wax were blended, and mixed on a mixing roll machine (10
(0 ° C.), cooled, and then pulverized to obtain a microcapsule-type curing accelerator-containing epoxy resin composition.

[0032]

Embedded image

[0033]

Embedded image

[0034]

Comparative Example 1 A microcapsule-type hardening accelerator (aggregate) was prepared in the same manner as in Example 1 except that the treatment was not carried out with a supersonic jet crusher. The microcapsule-type curing accelerator-containing epoxy resin composition was obtained in the same manner as in Example 1 except that the epoxy resin composition was used as is.

[0035]

Comparative Example 2 [Preparation of a curing accelerator-containing epoxy resin composition] A biphenyl type epoxy resin represented by the above general formula (2) [In the formula (2), R _{1 to} R ₄ represent a methyl group and an epoxy equivalent of 200. 128 parts, 99 parts of a phenol aralkyl resin represented by the general formula (3) [a mixture of n = 0 to 21 in the formula (3), hydroxyl equivalent 175], 1280 parts of spherical fused silica powder, crushed crystalline silica 550 parts of powder, 3 parts of polyethylene wax, and 2.8 parts of triphenylphosphine are blended, kneaded and cooled with a mixing roll machine (100 ° C.), and then pulverized to obtain a curing accelerator-containing epoxy resin composition. Was.

[0036]

Example 2 [Preparation of microcapsule type curing agent] An adduct of 3 mol of xylylene diisocyanate and 1 mol of trimethylolpropane was added to 10 parts of 1-benzyl-2-phenylimidazole as a curing agent and 10 parts of toluene.
To obtain a liquid for an oil phase.

Further, a liquid for an aqueous phase composed of 100 parts of distilled water and 5 parts of polyvinyl alcohol is separately prepared, and the liquid for an oil phase prepared above is added thereto, and emulsified by a homomixer to form an emulsion. This was charged into a polymerization reactor equipped with a reflux tube, a stirrer, and a dropping funnel.

On the other hand, 10 parts of an aqueous solution containing 3 parts of triethylenetetramine was prepared, placed in the dropping funnel of the polymerization reactor, dropped into the emulsion in the reactor, and subjected to interfacial polymerization at 70 ° C. for 3 hours. An aqueous suspension of a microcapsule-type curing agent was obtained. The average particle size of the microcapsules (primary particles) in the aqueous suspension is 3.1 μm.
Met. Subsequently, after removing polyvinyl alcohol and the like in the aqueous phase by centrifugation, microcapsule aggregates (particles) having free flowability were obtained by spray drying.
The average particle size of the aggregate was about 45 μm. This aggregate is pulverized by the supersonic jet pulverizer at a pulverizing pressure of 4
9 × 10 ⁴ Pa , To obtain a powdery microcapsule type hardener with less aggregation.

[Preparation of Microcapsule-Type Hardener-Containing Epoxy Resin Composition] 10 parts of the powdery microcapsule-type hardener obtained as described above and a bisphenol A type epoxy resin (epoxy equivalent: about 190, weight Average molecular weight 380, viscosity at 25 ° C. 12.5 Pa · s) 100
Were kneaded in a mixing pot at room temperature for 1 hour to obtain an epoxy resin composition.

[0040]

Comparative Example 3 A microcapsule-type curing agent (aggregate) was prepared in the same manner as in Example 2 except that the treatment with a supersonic jet pulverizer was not performed. Except for using, a microcapsule-type curing agent-containing epoxy resin composition was obtained in the same manner as in Example 2.

[0041]

Comparative Example 4 1 part of 1-benzyl-2-phenylimidazole and bisphenol A type epoxy resin (epoxy equivalent: about 190, weight average molecular weight: 380, viscosity at 25 ° C. 1)
2.5 Pa · s) in a mixing pot at room temperature for 10 parts.
After kneading for 3 minutes, the mixture was further passed through a three-roll mill to obtain an epoxy resin composition.

Each property of each of the epoxy resin compositions thus obtained in Examples and Comparative Examples was measured and evaluated according to the following evaluation test methods. The results are shown in Table 1 below.

[Curability] The curability was evaluated by the gel time method and the hardness when heated.

[Gel time] 150 ° C. or 175 ° C.
Was measured according to a hot plate gel time measurement method. The measurement temperature of Example 1 and Comparative Examples 1 and 2 was 175 ° C., and that of Example 2 and Comparative Examples 3 and 4 was 150 ° C.

[Heat Hardness] The hardness (Shore D) of the cured product obtained by molding at 175 ° C. × 60 seconds was measured using a Shore D hardness meter.

[Storage Stability] Each of the obtained epoxy resin compositions was stored under the conditions of 30 ° C. × 1 month, and the viscosity change rate was calculated by the following equation. As for the measurement of the viscosity, in Example 2 and Comparative Examples 3 and 4, BH was used.
Example 1 The viscosity at 30 ° C. was measured using a viscometer.
For Comparative Examples 1 and 2, the viscosity at 175 ° C. was measured using a flow tester viscometer.

[0047]

(Equation 1)

[Measurement of Wall Film Thickness, Particle Diameter and Ratio of Wall Film Thickness to Particle Size] The final microcapsules obtained in the above Examples were dispersed in a sample holder, and then placed in liquid nitrogen using a razor. And dried, and the cross section was measured with a scanning microscope. The ratio (d / R) of the wall film thickness to the particle size was calculated and obtained from the wall film thickness (d) and the particle size (R) at this time. The values of the wall thickness (d) and the particle size (R) were average values.

[0049]

[Table 1]

From the results in Table 1 above, all the products of the examples are
The rate of change in viscosity is smaller than that of Comparative Examples 2 and 4 in which microcapsulation is not performed, and it can be seen that the isolation effect by microencapsulation is exhibited. Further, with respect to the gel time and the heat hardness value, the product of Example 1 showed a value closer to that of Comparative Example 2 without microcapsulation than the product of Comparative Example 1 in which microcapsules were aggregated, and exhibited stable curability. You can see that it is. This can be said to be a comparison of the measured values of the product of Example 2 and the products of Comparative Examples 3 and 4. That is, it can be seen that all the products of Examples show good storage stability and curability.

[0051]

As described above, in the method for producing a powdery microcapsule of the present invention, a microcapsule aggregate obtained by agglomerating microcapsules having a polyurea-based wall film is supplied into a supersonic flow. Agglomerates collide with each other to break up the aggregates, thereby obtaining powdery microcapsules.
That is, the above-mentioned manufacturing method comprises the steps of:
Since there is no step or the like that may cause mechanical shearing or the like, in the process of deagglomeration of the agglomerate, no mechanical destruction occurs in the wall film, and as a result, the core material included in the wall film , And powder microcapsules can be obtained.

In the powdery microcapsules thus obtained, since the material constituting the wall film is a polyurea-based material such as polyurea and polyurethane / polyurea, the storage stability during storage and the encapsulation during heating are used. The substance (core material) is excellent in releasability, and the powdery microcapsules are excellent in dispersibility since the agglomeration is broken. Therefore, for example, when the curing agent is used as the core material of the powdery microcapsules, the cured product obtained therefrom can exhibit stable curability.

Further, as described above, when the microcapsule aggregate is pulverized and then the obtained powdery microcapsules are fed into a high-speed swirling vortex flow, the above-mentioned powdery microcapsules are classified. As a result, it is possible to efficiently obtain powdery microcapsules in the form of primary particles.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a powdery microcapsule (primary particle) according to the present invention.

FIG. 2 is an electron micrograph (2,000-fold magnification) showing a side surface of the powdery microcapsule-type curing accelerator prepared in Example 1.

FIG. 3 is an electron micrograph (2,000-fold magnification) showing a side surface of a microcapsule-type curing accelerator (aggregate) prepared in Example 1.

[Explanation of symbols]

 1 core material 2 polyurea-based wall film

Claims (7)

[Claims] A microcapsule aggregate formed by agglomerating microcapsules comprising a core material and a polyurea-based wall film covering the core material is made to collide with each other in a supersonic flow to dissolve the aggregates. A method for producing a powdery microcapsule characterized by the following. 2. The method for producing powdery microcapsules according to claim 1, wherein the microcapsule aggregate is obtained by drying an aqueous suspension of microcapsules. 3. A microcapsule aggregate formed by agglomeration of a microcapsule comprising a core material and a polyurea-based wall film covering the core material is formed by colliding the aggregates in a supersonic flow to dissolve the aggregates. A method for producing powdery microcapsules, comprising a step of pulverizing and a step of classifying the pulverized microcapsules by a high-speed swirling vortex flow. 4. The method for producing a powdery microcapsule according to claim 3, wherein the microcapsule aggregate is obtained by drying an aqueous suspension of the microcapsule. 5. A powdery microcapsule obtained by the method for producing a powdery microcapsule according to claim 3 or 4, wherein the average particle size is set in a range of 0.5 to 20 μm. Powdered microcapsules. 6. The ratio of the thickness of the wall film to the average particle size is as follows:
The powdery microcapsule according to claim 5, which is set in a range of 5 to 25%. 7. The core material according to claim 5, wherein the core material contains at least one of a curing agent and a curing accelerator.
The powdery microcapsules according to the above.