JP2016053161A - Core-shell particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a core-shell particle in which a large amount of inclusions can be encapsulated, and which can achieve both inclusion encapsulation stability and sustained release ability.SOLUTION: Provided are: a nano-sized core-shell particle obtained by using a block polymer having a hydrophilic block and a hydrophobic block, and having a solid, liquid or gas therein, and in which a shell contains at least one kind of inorganic matter selected from among metal oxide, metal hydroxide, metal carbide, metal nitride, metal boride and boron nitride; and a core-shell particle in which the inorganic matter is preferably at least one kind selected from among silica (silicon dioxide), titania (titanium dioxide), alumina (aluminum oxide) and zirconia (zirconium oxide).SELECTED DRAWING: Figure 1

Description

The present invention relates to a core-shell particle that can encapsulate a large amount of inclusions, and can achieve both the encapsulation stability and sustained release properties of the inclusions.

There are known micelle-like particles encapsulating a functional liquid or gas inside an assembly of amphiphilic substances such as surfactants. For example, Patent Document 1 discloses a hydrophilic block and a hydrophobic block. Polymeric micelles comprising a block polymer having a polynucleotide are described.
However, since such polymer micelles are only self-assembled with molecules, unintentional leakage of inclusions occurs and the inclusion stability of the inclusions is low.

On the other hand, a microcapsule obtained by polymerizing a shell by a precipitation phase separation method by radical polymerization is disclosed.
However, the microcapsules obtained by such a method have a problem that transparency cannot be obtained due to their large size. Further, the obtained microcapsules have a problem of poor dispersibility and inferior permeability to small gaps. Furthermore, since the thickness of the shell becomes large, there have been problems that the inclusion rate of the functional liquid or the like is lowered, or the release of the functional liquid or the like is deteriorated.

On the other hand, there is known a method of obtaining a microcapsule by forming a film by curing an epoxy resin at an interface between oil droplets and water by interfacial polymerization.
In such a method, the size of the microcapsules is reduced, but since the role of holding and releasing the inclusions is only played by the epoxy resin, the encapsulation stability decreases when the shell is thin, and the amount of inclusions when the shell is thick There was a problem that there were fewer. Furthermore, the obtained microcapsules have a problem that they cannot be stabilized in a state of a high encapsulation rate.

Special table 2011-520901 gazette

The present invention provides a core-shell particle that can encapsulate a large amount of inclusions while being nano-sized, and can achieve both encapsulation stability and sustained-release properties of the inclusions in view of the above-mentioned present situation. For the purpose.

The present invention is a core-shell particle obtained by using a block polymer having a hydrophilic block and a hydrophobic block, and has a solid, liquid or gas inside, and the shell is a metal oxide, metal hydroxide, metal Core-shell particles containing at least one inorganic substance selected from the group consisting of carbide, metal nitride, metal boride and boron nitride.
Hereinafter, the present invention will be described in detail.

As a result of intensive studies, the present inventors have used a block polymer having a hydrophilic block and a hydrophobic block as a raw material for the core-shell particles, and by containing a predetermined inorganic substance in the shell, while being nano-sized, A core-shell particle capable of encapsulating a large amount of inclusions and capable of achieving both encapsulation stability and sustained-release properties of the inclusions; and core-shell particles excellent in transparency and dispersibility As a result, the present invention has been completed.

The core-shell particle of the present invention is obtained using a block polymer having a hydrophilic block and a hydrophobic block. That is, the core-shell particle of the present invention contains a block polymer having a hydrophilic block and a hydrophobic block. By using the block polymer, it is possible to maintain a nano size (size on the order of nanometers) in a solvent.
The block polymer may be nonionic, anionic, cationic or amphoteric, but is preferably nonionic.

As the hydrophilic block constituting the block polymer, for example, a polymer comprising a monomer of a linear, branched, or cyclic aliphatic or aromatic hydrocarbon compound containing at least one unsaturated bond and having a hydrophilic group Thing etc. are mentioned.
Examples of the hydrophilic group include an amino group, a hydroxyl group, a carboxyl group, an isocyanate group, an amide group, a sulfonic acid group, an ethyleneoxy group, a phosphoric acid group, a urea group, a thiol group, and a sulfuric acid group. Of these, an amino group, a hydroxyl group, a carboxyl group, an isocyanate group, and an amide group are preferable.

Specific examples of the hydrophilic block include (meth) acrylic acid, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, (meth) acrylamide, N-isopropyl ( (Meth) acrylamide, N-cyclopropyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2- (N, N-diethylamino) Polymers such as ethyl (meth) acrylate are exemplified. Of these, a polymer of dimethylaminoethyl methacrylate (PDMAEMA) is preferable. These may be used alone or in combination of two or more.

Examples of the hydrophobic block constituting the block polymer include a polymer of a monomer of a linear, branched, or cyclic aliphatic or aromatic hydrocarbon compound containing at least one unsaturated bond.
Examples of the polymer include aromatic vinyl resins, aliphatic vinyl resins, and acrylic ester resins. Specifically, for example, styrene, α-methylstyrene, vinyl acetate, (meth) acrylonitrile, butadiene, isoprene, male vinyl ether, vinyl chloride, vinylidene chloride, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) Polymers such as acrylate and butyl (meth) acrylate are exemplified. Among these, a polymer of styrene is preferable. These may be used alone or in combination of two or more.

The weight ratio of the hydrophilic block to the hydrophobic block in the block polymer is preferably 10:90 to 90:10. By setting the weight ratio within the above-mentioned range, it is possible to obtain a high inclusion rate and retention with a smaller particle size. The weight ratio is more preferably 20:80 to 80:20.

The number average molecular weight of the block polymer is not particularly limited, but is preferably 2,000 to 100,000. By being within the above range, the size of the core-shell particles can be reduced, the encapsulation rate can be increased, and good dispersibility can be obtained. A more preferred number average molecular weight is 4,000 to 40,000.
The molecular weight distribution (weight average molecular weight / number average molecular weight) of the block polymer is preferably 1.00 to 2.00. By being within the above range, the uniformity of size and inclusion rate can be improved.

The core-shell particles of the present invention preferably have a form in which the block polymer is in the form of an aggregate (micelle). In particular, the core-shell particles are arranged radially with a hydrophobic block on the inside and a hydrophilic block on the outside. It is preferable. Thereby, the outstanding dispersibility is realizable.

The shell constituting the core-shell particle of the present invention contains at least one inorganic substance selected from the group consisting of the metal oxide, metal hydroxide, metal carbide, metal nitride, metal boride and boron nitride.
By containing at least one inorganic substance selected from the group consisting of metal oxide, metal hydroxide, metal carbide, metal nitride, metal boride and boron nitride in the shell, the strength of the shell is increased, The shape can be maintained even when the encapsulation rate is high.

Examples of the metal in the at least one inorganic material selected from the group consisting of the metal oxide, metal hydroxide, metal carbide, metal nitride, metal boride and boron nitride include aluminum, silicon, zirconium, zinc, Examples include titanium, tin, antimony, cerium, magnesium, iron, barium, calcium, strontium, copper, and the like.

Specific compounds used as the inorganic substance include silica (silicon dioxide), titania (titanium dioxide), alumina (aluminum oxide), zirconia (zirconium oxide), ceria (cerium oxide), magnesia (magnesium oxide), ferrite (Iron oxide), silicon carbide, silicon nitride, aluminum nitride, boron nitride, barium titanate, lead zirconate titanate, titanium boride, zirconium boride, vanadium boride, tungsten boride and the like. Among these, silica (silicon dioxide), titania (titanium dioxide), alumina (aluminum oxide), and zirconia (zirconium oxide) are preferable. In particular, silica, titania or alumina is more preferable. These may be used alone or in combination of two or more.

The shape of the inorganic material is not particularly limited, but it is preferably a film or an aggregated laminated state of fine particles.
When the inorganic substance is in a state of aggregation and lamination of fine particles, the average particle diameter of the fine particles is preferably 1 to 10 nm.
In the core-shell particles of the present invention, the presence state of the inorganic substance is not particularly limited, and may be distributed inside the particles, may be localized in the vicinity of the particle surface, or may be localized in the vicinity of the particle surface. It may be localized in the form of a film. Among these, it is preferable that the film is localized in the vicinity of the particle surface.

The inorganic material is preferably three-dimensionally cross-linked from the viewpoint of further improving the strength and improving the solvent resistance.

The core-shell particles of the present invention preferably have an inorganic content of 1 to 50% by weight. By making content of the said inorganic substance into the said range, higher enclosure stability can be obtained with much inclusion amount. More preferably, it is 5 to 30% by weight.

The core-shell particles of the present invention have a solid, liquid or gas (hereinafter also referred to as an internal substance) inside.
The solid, liquid, or gas does not include liquid crystal that is in an intermediate state between the solid and the liquid.
The internal substance is different from the block polymer.

Examples of the solid include polymer fine particles, amines such as wax and imidazole, salts, inorganic powders such as silica, metal nanoparticles such as gold nanoparticles, metal complexes, and the like.
Examples of the polymer fine particles include fine particles composed of acrylic, polystyrene, polyester, polyurethane, epoxy, polyamide, olefin and the like.
Examples of the wax include normal paraffins having 20 or more carbon atoms, such as animal waxes such as beeswax and whale wax, plant waxes such as wood wax and rice bran wax, mineral waxes such as montan wax and ozokerite, paraffin wax, Examples include petroleum waxes such as microcrystalline wax, synthetic waxes such as Fischer-Tropsch wax and polyethylene wax.
Examples of the amines include hydrazide compounds, aliphatic polyamine compounds, primary amine compounds, tertiary amine compounds, and imidazole compounds. More specifically, malonic acid dihydrazide, dicyandiamide, 2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, and adducts thereof Can be mentioned.
Examples of the salts include hydrochloride, sulfate, malonate, tartrate, maleate, phosphate, citrate, acetate, and the like.
Examples of the inorganic powder include silica (silicon dioxide), titania (titanium dioxide), alumina (aluminum oxide), zirconia (zirconium oxide), ceria (cerium oxide), magnesia (magnesium oxide), and ferrite (iron oxide). , Silicon carbide, silicon nitride, aluminum nitride, boron nitride, barium titanate, lead zirconate titanate and the like.
Examples of the metal nanoparticles include gold, silver, copper, nickel, iron, platinum, tungsten, and cobalt.
Examples of the metal complex include a diammine silver complex, a tetraammine copper complex, a hexacyanoiron complex, and a tetrachloride iron complex.

Examples of the liquid include aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, aqueous solutions of salts, amines such as imidazole, and the like.
Examples of the aromatic hydrocarbon include toluene, xylene, benzene and the like.
Examples of the aliphatic hydrocarbon include aliphatic hydrocarbons and isomers having 5 to 19 carbon atoms, such as pentane, hexane, heptane, octane, and decane.
Examples of the alicyclic hydrocarbon include cyclohexane, cyclohexene, cycloheptane, and the like.
Examples of the aqueous salt solution include sodium chloride, and examples of the amines include hydrazide compounds, aliphatic polyamine compounds, primary amine compounds, tertiary amine compounds, and imidazole compounds. More specifically, 1-benzyl-2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1 -Cyanoethyl-2-ethyl-4-methylimidazole, adducts thereof and the like. Examples of the aqueous salt solution include an aqueous salt solution exemplified in the above solid.

Examples of the gas include air, nitrogen, low boiling point hydrocarbon gas, and the like.
Examples of the low boiling point hydrocarbon gas include butane and propane, and aliphatic hydrocarbons having 4 or less carbon atoms.

The core-shell particles of the present invention preferably have a content of the internal substance of 5 to 90% by weight. By setting the content of the internal substance within the above range, the internal substance can be diffused at a high concentration and uniformly to the surroundings during use. More preferably, it is 10 to 80% by weight.

In the core-shell particle of the present invention, the content of the internal substance is preferably 5 to 90% by volume. By setting the content of the internal substance within the above range, the internal substance can be diffused at a high concentration and uniformly to the surroundings during use. More preferably, it is 10-80 volume%.

The core-shell particle of the present invention may have a shape having a solid, liquid, or gas inside the block polymer aggregate, and is a hollow particle obtained by removing a portion corresponding to a hydrophobic block from the block polymer aggregate. A shape having a solid, liquid, or gas inside may be used.

The core shell particles of the present invention have a preferred lower limit of the average particle diameter of 10 nm and a preferred upper limit of 100 nm. Within the above range, good transparency and dispersibility can be obtained. A more preferable lower limit of the average particle diameter is 20 nm, and a more preferable upper limit is 70 nm.

The average upper limit of the CV value of the average particle diameter of the core-shell particles of the present invention is 50%. When the CV value is in the above range, good transparency and dispersibility can be obtained. A more preferable upper limit of the CV value is 40%. The CV value is a numerical value indicated by a percentage (%) of a value obtained by dividing the standard deviation by the average particle diameter.

In the core-shell particles of the present invention, the preferred lower limit of the shell thickness is 1 nm, and the preferred upper limit is 30 nm. When the thickness is in the above range, higher encapsulation stability can be obtained with a large amount of inclusion. The more preferable lower limit of the thickness is 2 nm, and the more preferable upper limit is 20 nm. A more preferred lower limit is 3 nm, and a more preferred upper limit is 10 nm.

The core-shell particles of the present invention include drug delivery carrier, diagnostic agent carrier, bacteria or cell separation carrier, nucleic acid or protein separation / purification carrier, enzyme reaction carrier, cell culture carrier, X-ray contrast agent, adhesive curing control agent, rubber It can be suitably used as a vulcanization control agent, a catalyst reaction control agent, and the like.

Examples of the method for producing the core-shell particles of the present invention include a step of producing a block polymer having a hydrophilic block and a hydrophobic block, and an oil phase containing an internal substance is added to the aqueous phase containing the block polymer. And a step of forming a block polymer aggregate (emulsion), a step of adding and reacting the raw material to be the inorganic substance, and laminating the inorganic substance as a shell.
FIG. 1 is a diagram schematically showing a process for producing core-shell particles of the present invention. As shown in FIG. 1, by using the above production method, the core-shell particles of the present invention can be easily produced in a series of steps.

As a process for producing the block polymer having the hydrophilic block and the hydrophobic block, for example, living radical polymerization, living cation polymerization, living anion polymerization, and the like, which are iniferter polymerization and living polymerization, are possible. In particular, it is preferable to use living radical polymerization, and atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer (RAFT) polymerization, polymerization using nitroxide (Nitroxide) -Mediated Polymerization: NMP), etc., may be prepared by polymerizing the monomer that forms the hydrophilic block and the monomer that forms the hydrophobic block.

By performing the step of adding the oil phase containing the internal substance to the aqueous phase containing the block polymer, an aggregate (emulsion) of the block polymer containing the internal substance can be formed (emulsified).
Specifically, it is preferable to use a phase inversion emulsification method, a D phase emulsification method, a gel emulsification method, a liquid crystal emulsification method, a solubilization method (aggregation method), a phase inversion emulsification method, or the like. In the phase inversion emulsification method, in particular, an oil phase containing an internal substance is added to an aqueous phase containing a block polymer, and the temperature is kept below the phase inversion temperature of the block polymer, and then heated to above the phase inversion temperature with stirring. The phase inversion temperature emulsification method by rapidly cooling to the phase inversion temperature or lower is preferable as a method for easily obtaining fine and uniform size particles.

Next, a step of laminating the inorganic material as a shell is performed.
In order to laminate, there are a method of adding and reacting an inorganic raw material to laminate the inorganic material as a shell, a method of adding and reacting inorganic powder to laminate the inorganic material as a shell, and the like.
Examples of the raw material to be inorganic include metal alkoxide, a compound having both a metal alkoxide and an organic functional group in the molecule, specifically, tetraethoxysilane (tetraethyl orthosilicate), tetramethoxysilane, Examples include titanium isopropoxide, titanium normal butoxide, methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and tetrabutyl orthotitanate.
Examples of the inorganic powder include silica (silicon dioxide), titania (titanium dioxide), alumina (aluminum oxide), zirconia (zirconium oxide), ceria (cerium oxide), magnesia (magnesium oxide), ferrite (iron oxide), and silicon carbide. , Silicon nitride, aluminum nitride, boron nitride, barium titanate, lead zirconate titanate, titanium boride, zirconium boride, vanadium boride, tungsten boride and the like. These inorganic powders are preferably laminated as a shell by reacting with a silane coupling agent or the like.
By performing such a process, the hydrophilic block of the block polymer has a structure in which an inorganic substance is present. Therefore, it is possible to obtain core-shell particles having an inorganic substance in the shell portion.

According to the present invention, it is possible to obtain core-shell particles that can encapsulate a large amount of inclusions and can achieve both the encapsulation stability and sustained release properties of the inclusions. The core-shell particles of the present invention can have a small particle size and excellent transparency and dispersibility.

It is the figure which showed typically the process of manufacturing the core-shell particle of this invention.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
(1) Synthesis of block polymer DMAEMA (7.9 g), N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine (0.17 g) and methanol (2.0 mL) were added. Further, 2.0 mL of methanol and 2-hydroxyethyl-2-bromoisobutyrate were added to another container, and freeze deaeration of these two solutions was performed. To the solution to which DMAEMA was added, 0.050 g of copper (I) chloride was added under a nitrogen atmosphere, and then a 2-hydroxyethyl-2-bromoisobutyrate solution was added and reacted in a constant temperature water bath at 25 ° C. for 3 hours to give PDMAEMA. Was synthesized. After completion of the reaction, purification was performed by reprecipitation using n-hexane as a poor solvent through an alumina column.
Next, 0.34 g of synthesized PDMAEMA, 0.47 g of styrene, 0.010 g of N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine were added, and freeze deaeration was performed. Subsequently, 0.0030 g of copper (I) chloride was added under a nitrogen atmosphere, and the reaction was performed in a 110 ° C. oil bath for 2 hours. After completion of the reaction, purification was performed by reprecipitation using n-hexane through an alumina column.
The number average molecular weight and molecular weight distribution of the obtained block polymer were measured using gel permeation chromatography.

(2) Synthesis of emulsion 0.030 g of the synthesized block polymer was dissolved in 0.030 g of toluene, and 6.0 g of ultrapure water was added. After stirring at 45 ° C. for 10 minutes, the mixture was quickly transferred to an ice bath and stirred for 10 minutes.

(3) Preparation of core-shell particles 10 μL of tetraethyl orthosilicate was added to 2.0 mL of the synthesized emulsion solution, reacted at room temperature for 24 hours, and then centrifuged to contain toluene inside and silica in the shell. Core-shell particles were prepared.

(Example 2)
Core-shell particles having toluene inside and containing silica in the shell were prepared in the same manner as in Example 1 except that “(2) Synthesis of emulsion” in Example 1 was changed to the following method.

(2) Synthesis of emulsion 0.030 g of the block polymer synthesized in Example 1 was dissolved in 0.060 g of toluene, and 6.0 g of ultrapure water was added. After stirring at 45 ° C. for 10 minutes, the mixture was quickly transferred to an ice bath and stirred for 10 minutes.

(Example 3)
Core-shell particles having toluene inside and containing silica in the shell were prepared in the same manner as in Example 1 except that “(1) Synthesis of block polymer” in Example 1 was changed to the following method.

(1) Synthesis of block polymer 15.7 g of DMAEMA, 0.47 g of 2,2′-bipyridine, and 4.0 mL of methanol were added. Further, 4.0 mL of methanol and 0.21 g of 2-hydroxyethyl-2-bromoisobutyrate were added to another container, and these two solutions were freeze-degassed. To the solution to which DMAEMA was added, 0.099 g of copper (I) chloride was added under a nitrogen atmosphere, and then a 2-hydroxyethyl-2-bromoisobutyrate solution was added, and the reaction was performed in a 25 ° C. constant temperature water bath for 6 hours. After completion of the reaction, purification was performed by reprecipitation using n-hexane through an alumina column.
Next, 1.4 g of synthesized PDMAEMA, 1.0 g of styrene, 0.092 g of tris [2- (dimethylamino) ethyl] amine, and 1.0 mL of N, N-dimethylformamide were added, and freeze deaeration was performed. Subsequently, 0.020 g of copper (I) chloride was added under a nitrogen atmosphere, and the reaction was performed in a 110 ° C. oil bath for 26 hours. After completion of the reaction, the mixture was passed through an alumina column, reprecipitated with n-hexane, and then purified by dialysis with toluene / methanol = 1/1 (v / v).
The number average molecular weight and molecular weight distribution of the obtained block polymer were measured using gel permeation chromatography.

Example 4
Core-shell particles having toluene inside and containing silica in the shell were prepared in the same manner as in Example 3 except that “(2) Synthesis of emulsion” in Example 3 was changed to the following method.

(2) Synthesis of emulsion 0.030 g of the block polymer synthesized in Example 3 was dissolved in 0.060 g of toluene, and 6.0 g of ultrapure water was added. After stirring at 45 ° C. for 10 minutes, the mixture was quickly transferred to an ice bath and stirred for 10 minutes.

(Example 5)
The core-shell particles obtained in Example 1 were put in a ceramic crucible and heated at 800 ° C. for 3 hours in a muffle furnace to obtain sintered core-shell particles.

(Example 6)
The core-shell particles obtained in Example 3 were placed in a ceramic crucible and heated at 800 ° C. for 3 hours in a muffle furnace to obtain sintered core-shell particles.

(Example 7)
Core-shell particles having toluene inside and containing titania in the shell were produced in the same manner as in Example 3 except that “(3) Production of core-shell particles” in Example 3 was changed to the following method.

(3) Production of core-shell particles To 2.0 mL of the synthesized emulsion solution, 10 μL of tetrabutyl orthotitanate was added, reacted at room temperature for 24 hours, and then centrifuged to have toluene inside and titania to the shell. The contained core-shell particles were obtained.

(Example 8)
The core-shell particles obtained in Example 7 were put in a ceramic crucible and heated at 800 ° C. for 3 hours in a muffle furnace to obtain sintered core-shell particles.

(Comparative Example 1)
To a solution of 1.0 g of sodium dodecyl sulfate (sulfate group as hydrophilic part, dodecyl group as hydrophobic part, molecular weight 288) dissolved in 200 g of water, 1 g of toluene is added and emulsified and dispersed with an ultrasonic homogenizer. Core / corona particles in which the dodecyl group was in contact with the core and the sulfate group spread on the aqueous phase side were obtained.

(Comparative Example 2)
1 g of toluene is added to a solution obtained by dissolving polyethylene glycol (PEG, hydroxyl group as a hydrophilic group) as a hydrophilic block and 1 g of polylactic acid (PLGA) as a hydrophobic block in 200 g of water, and emulsified and dispersed with an ultrasonic homogenizer. Core / corona particles in which toluene was the core and the PLGA block was in contact with the core and PEG spread on the water phase side were obtained.

(Comparative Example 3)
Methyl methacrylate 0.9 g, ethylene glycol dimethacrylate 0.1 g, toluene 1.0 g, and azobisisobutyronitrile 0.1 g were dissolved to obtain an oil phase. 0.1 g of sodium dodecyl sulfate (sulfate group as hydrophilic part, dodecyl group as hydrophobic part, molecular weight 288) was dissolved in 10 g of water to obtain an aqueous phase. Add the oil phase to the aqueous phase, emulsify and disperse with an ultrasonic homogenizer, and heat at 70 ° C. for 8 hours with stirring to perform the polymerization reaction. Toluene is the core and the methyl methacrylate cross-linked polymer is the shell As a result, core-shell particles having sodium dodecyl sulfate attached to the shell surface were obtained.

(Comparative Example 4)
1.0 g of bis A type epoxy resin (JER828) manufactured by Japan Epoxy Resin Co., Ltd. and 1.0 g of toluene were dissolved to obtain an oil phase. 0.1 g of sodium dodecyl sulfate (sulfate group as hydrophilic part, dodecyl group as hydrophobic part, molecular weight 288) was dissolved in 10 g of water to obtain an aqueous phase. Add the oil phase to the water phase, emulsify and disperse with an ultrasonic homogenizer, add 0.02 g of 25 wt% ammonia aqueous solution over about 30 minutes using a syringe pump while stirring. Then, a core-shell particle was obtained in which a cross-linked epoxy resin was coated as a shell and sodium dodecyl sulfate was adhered to the shell surface.

(Comparative Example 5)
In Example 1, except that 10 μL of tetraethyl orthosilicate was not added, the core / corona particles in which toluene was in contact with the core and the polystyrene block in contact with the core and PDMAEMA spread on the aqueous phase side were obtained in the same manner as in Example 1. It was.

(Comparative Example 6)
1.0 g of epoxy group-containing silane coupling agent (Z-6040) manufactured by Toray Dow Corning Co., Ltd. and 1.0 g of toluene were dissolved to obtain an oil phase. 0.1 g of sodium dodecyl sulfate (sulfate group as hydrophilic part, dodecyl group as hydrophobic part, molecular weight 288) was dissolved in 10 g of water to obtain an aqueous phase. Add the oil phase to the water phase, emulsify and disperse with an ultrasonic homogenizer, add 0.02 g of 25 wt% ammonia aqueous solution over about 30 minutes using a syringe pump while stirring. Then, core-shell particles were obtained in which silica combined with a crosslinked epoxy resin was coated as a shell, and sodium dodecyl sulfate was adhered to the shell surface.

(Comparative Example 7)
The core-shell particles obtained in Comparative Example 6 were put in a ceramic crucible and heated at 800 ° C. for 3 hours in a muffle furnace to obtain sintered core-shell particles.

<Evaluation>
The following evaluation was performed on the core-shell particles obtained in Examples and Comparative Examples. The results are shown in Table 1.

(1) Inclusion rate (hollow rate)
About 0.0003 g of core-shell particles were measured with a pyrolysis GC / MS (Q1000) manufactured by JEOL Ltd. at a pyrolysis temperature of 550 ° C. By comparing and analyzing the peak area of the internal substance (core) with a calibration curve prepared in advance with a compound corresponding to the internal substance (core), the amount of core contained in the core-shell particles was calculated and used as the inclusion rate.

(2) Average particle diameter Core-shell particles and water were adjusted in a 10 mL sample bottle so that they would be about 0.05 g and about 6.0 g, and shaken up and down for 30 seconds, then the dynamic light scattering device “LPA- 3100, manufactured by Otsuka Electronics Co., Ltd., and the volume average particle size obtained was defined as the average particle size.

(3) The sample was adjusted in a 10 mL sample bottle so that the transparent core-shell particles and water were about 0.05 g and about 6.0 g, shaken up and down for 30 seconds and allowed to stand for 5 minutes. For the appearance of the liquid after standing, transparency was judged according to the following criteria.
◎: Transparent and clear beyond the liquid ○: Slightly transparent and the other side of the liquid is blurred △: White and cloudy and almost the other side of the liquid cannot be seen ×: White and cloudy and the other side of the liquid cannot be seen at all

(4) The dispersible core-shell particles and water were adjusted in a 10 mL sample bottle so as to be about 0.05 g and about 6.0 g, shaken up and down for 30 seconds and allowed to stand for 5 minutes. About the external appearance of the liquid after standing, dispersibility was judged according to the following criteria.
◎: Transparent and there is no lump that can be visually discerned ○: Slightly cloudy, but there is no lump that can be visually discerned Δ: Slightly lump that can be visually discerned is visible in the liquid ×: In the liquid You can see many lumps that can be identified visually

(5) Encapsulation stability (retainability)
(5-1) Encapsulation Retention Core shell particles and water are adjusted in a 10 mL sample bottle so as to be about 0.05 g and about 6.0 g, shaken vigorously up and down for 30 seconds, and then 50 ° C. in a vacuum drying oven. The powder was dried for 1 day and night to obtain water / heat-treated core-shell particle powder. About 0.0003 g of the obtained powder was measured with a pyrolysis GC / MS (Q1000) manufactured by JEOL Ltd. at a pyrolysis temperature of 550 ° C. By comparing and analyzing the peak area of the internal substance (core) with a calibration curve prepared in advance with a compound corresponding to the internal substance (core), the amount of core contained in the water-heat treated core-shell particles was calculated. The inclusion retention was determined by the inclusion rate Y, Y / X after the water / heat treatment relative to the inclusion rate X before the water / heat treatment (the inclusion rate obtained by “(1) inclusion rate (hollow rate)”).
◎: 0.8 or more ○: 0.3 or more Δ: 0.1 or more ×: less than 0.1 (5-2) Shape-retaining core-shell particles are dispersed on a sheet mesh, and excess powder is blown off. Observation was performed with a transmission electron microscope TEM. The number of particles that looked like a circle and the number of particles that looked like fragments such as cracks and crushing were counted, and the number of particles that looked like a circle out of 30 particles was judged.
◎: 27 or more in a circular shape ○: 25 or more in a circular shape Δ: 20 or more in a circular shape ×: 19 or less in a circular shape

(6) Presence state of inorganic substance After the core-shell particles were dispersed on the sheet mesh and the excess powder was skipped, it was observed with a transmission electron microscope TEM attached with an energy dispersive X-ray analyzer (EDS). Real images and the distribution of elements other than carbon, oxygen, and nitrogen derived from inorganic substances (silicon or titanium in the examples) were analyzed. The existence state of silicon or titanium was compared with the real image.
◎: Silicon or titanium is not distributed inside the particle obtained in the real image, and silicon or titanium is localized in the form of a film only in the vicinity of the particle surface. ○: In the particle obtained in the real image When silicon or titanium is not distributed, and silicon or titanium is localized in a granular form only in the vicinity of the particle surface ×: When silicon or titanium is dispersed and distributed in all parts of the particles obtained in the real image

According to the present invention, it is possible to provide core-shell particles that can encapsulate a large amount of inclusions and can achieve both the encapsulation stability and sustained release properties of the inclusions.

Claims (2)

Core-shell particles obtained using a block polymer having a hydrophilic block and a hydrophobic block,
Has a solid, liquid or gas inside,
The core-shell particle, wherein the shell contains at least one inorganic substance selected from the group consisting of metal oxide, metal hydroxide, metal carbide, metal nitride, metal boride, and boron nitride. The core-shell particle according to claim 1, wherein the inorganic substance is at least one selected from the group consisting of silica (silicon dioxide), titania (titanium dioxide), alumina (aluminum oxide), and zirconia (zirconium oxide). .

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