JP2011240214A - Water-dispersible fine particle, aqueous dispersion of the fine particle, and water-dispersed gel containing the fine particle, and method for producing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent stability and enable long-term stable dispersion in fine particles coated with crystalline amphiphile and having excellent water dispersibility, an aqueous dispersion of the fine particles coated with crystalline amphiphile and having excellent dispersion stability, and a method for producing the aqueous dispersion.SOLUTION: The easily dispersible fine particle is coated with a crystalline material consisting of an amphiphile having a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water, and an auxiliary dispersant consisting of at least one selected from a fatty acid, an aliphatic alcohol, and an aliphatic amine. The aqueous dispersion of the fine particles is produced by mixing the crystalline amphiphile, the auxiliary dispersant and water with the fine particles, and then agitating and mixing them at the phase transition temperature or higher to form a film consisting of stable crystalline amphiphile on the fine particle surfaces.

Description

  The present invention relates to water-dispersible microparticles, a stable dispersion composed of water-dispersible microparticles, a stable water-dispersed gel containing water-dispersible microparticles, and methods for producing them.

  A method for uniformly dispersing fine particles is a technique demanded by various industries. In particular, nano-sized fine particles such as carbon, metal, metal oxide, and metal sulfide are known to exhibit special functions such as size-specific fluorescence based on their fine internal structure. In addition, a dispersion in which particles having a particle size smaller than the wavelength of light are dispersed becomes transparent. In addition, organic substances (organic dye compounds, amino acids, contrast agents, etc.) are also expected to have characteristics such as improved chemical activity, changes in electronic state, and improved dispersion stability due to the increase in specific surface area resulting from micronization. . The aqueous dispersion of fine particles having such characteristics is expected to be applied in a wide range of fields including ink, cosmetics, food, and medical fields.

As a method for preparing an aqueous dispersion of fine particles, a method of generating fine particles by a chemical reaction from a raw material solution in the presence of a stabilizer and a dispersant is well known. There is also a method in which fine particles prepared in advance are dispersed in water by some method.
In particular, in order to prepare an aqueous dispersion of fine particles by the latter method, fine particles that are usually highly agglomerated and formed into secondary particles can be obtained using a device such as a bead mill, an ultrasonic homogenizer, or an optimizer. Two technical elements are necessary: crushing and then modifying the surface of the microparticles to improve the affinity for water.

There are several methods for modifying the surface of the fine particles depending on the chemical composition of the particles.
For example, for hydrophobic fine particles such as silicon-based and carbon-based, there is a method in which a carboxyl group or the like, which is a hydrophilic functional group, is directly expressed on the surface by a chemical reaction (Patent Document 1). Moreover, it is also possible to disperse the particles having a hydrophilic surface by adsorbing the surfactant onto the surface of the particles (Patent Document 2).
On the other hand, in the case of inorganic particles containing a metal such as iron or titanium oxide or a metal oxide in the composition, a method using a dispersant having both a functional group capable of binding to a metal and hydrophilicity (Patent Document 3), There is a method in which the surface is subjected to a hydrophobic treatment and then coated with a polymeric nonionic surfactant (Patent Document 4).

JP 2003-95624 A JP 2008-230935 A JP 2007-25445 A JP-A-7-247119 Japanese Patent Application No. 2009-184487

In the case of modifying the surface by a chemical reaction, a large number of complicated steps such as pretreatment for generating a functional machine and purification after the reaction are required. Even when a polymer nonionic surfactant is used as a water-dispersed coating agent, a step such as a hydrophobic treatment in an organic solvent using low molecules on the surface of fine particles is required as a pretreatment.
On the other hand, a dispersion of fine particles produced using a low molecular weight surfactant has a limit in the concentration of dispersed particles, and the dispersion stability decreases when the concentration of the particles exceeds about 5 wt%. In the industry using a dispersion liquid, since the concentration of particles dispersed in the dispersion liquid is low, excess dispersion medium (for example, water) becomes a problem when the concentration of particles necessary for an actual product is satisfied (for example, water). In many cases, the amount of water in the product is 100 ml, but the amount of water becomes 130 ml by adding the dispersion. The advantages of using a dispersion liquid are that the worker does not touch the powder so that the health of the worker can be protected, a clean work environment is maintained, and the work is easy. However, it is difficult to apply to products that require high concentrations. Met. Furthermore, since the cost of the dispersion process is included, the price of the dispersion increases. Therefore, the dispersion liquid has been limited to the case where the particle size needs to be uniform even at high cost, or when the quality can be greatly improved with a small addition amount. As a method for preventing such drawbacks, there are cases where an operator disperses and uses silane coupling or particles whose surface is modified with a polymer. However, in most cases, other dispersants are required and it is difficult to obtain a dispersion having a uniform particle size distribution.
Since the particles obtained by drying the dispersion containing the dispersant are dried while the dispersant is adsorbed on the surface of the particles, it can be assumed that the dispersion can be obtained more easily than the dispersion method described above. However, when the dispersion is dried, the fine particles are aggregated and welded. Aggregated and welded fine particles are often difficult to redisperse in water or are in a state different from the initial dispersed state. Considering transportation and storage of fine particles, dry solids are more advantageous in terms of weight and volume. However, from the above background, fine particles produced using a water-dispersed coating agent are not dried, but in a dispersion state. It was necessary to handle.
In addition, existing water-dispersed coating agents are individually designed with respect to the particle surface, and the coating method differs depending on the core particles, and there is a problem that versatility is not high.

In view of such circumstances, the present inventors have obtained fine particles having good water dispersibility, and can be redispersed in water without causing aggregation or welding even when dried from the dispersion. The inventors have intensively studied and previously proposed the use of a specific dispersion coating agent (Patent Document 5).
That is, when the dispersion of fine particles is dried, the particles are often agglomerated and welded. This low molecular weight aqueous dispersion coating agent is often in a liquid crystal or dissolved state near room temperature. For example, sodium dodecyl sulfate or poly It is considered that oxyethylene sorbitan monooleate is in a state of being dissolved in water at room temperature, and therefore, fusion of the dispersants easily occurs during drying.
The low molecular weight amphiphile used as the water-dispersible coating agent is a compound having both a hydrophilic group A and a hydrophobic group B in the molecule and represented by the general formula AB.
As a result of studying a method for solving problems such as aggregation caused by drying, the present inventors have found that, in order to suppress aggregation and welding caused by drying, the amphiphilic substance does not dissolve in a coating state, and gel-liquid crystal Using a crystalline amphiphile having a phase transition temperature higher than room temperature and lower than the boiling point of water, adding the amphiphile and water to the agglomerated fine particles, and then crushing while heating above the phase transition temperature -It was found that a film made of a stable crystalline amphiphile can be formed on the surface of fine particles by mixing.

However, in the previous proposal, since the fine particles are coated using only the crystalline amphiphile, the particle size of the water-dispersible fine particles is larger than the primary particle size, and the dispersion liquid is used for a long time (one month). Above) It was not stable.
The present invention improves the above-mentioned drawbacks of the invention according to the previous proposal, has a good water dispersion stability for a long time of one month or more, and does not cause aggregation or welding even when dried from the dispersion liquid. An object of the present invention is to provide easily-divided acid particles that can be redispersed in water and a method for producing the same.

The crystalline amphiphile used in Patent Document 5 is insufficient in the effect of maintaining water dispersion for a long time because its hydrophilic portion is glucose where ionic repulsion and steric hindrance important for water dispersion stability are not expected. Therefore, the dispersion stability of the fine particles coated only with the crystalline molecules is not practically sufficient, and it is difficult to disperse the particles up to the primary particle size.
As a result of studies to solve this problem, by adding an auxiliary dispersant, the fine particles coated with the crystalline amphiphile can be dispersed to the primary particle size, and the dispersion stability of the dispersion is also remarkably high. I found that it can be improved.

Furthermore, as a molecular structure of the water-dispersed coating agent having such characteristics, the present inventors have examined that the hydrophilic part of A is a monosaccharide or a disaccharide, preferably a monosaccharide, more preferably glucose. In addition, the hydrophobic part of B may contain saturated or unsaturated alkyl or aromatic or other elements, but it has been found that the carbon is preferably unsaturated aliphatic having 10 to 24 carbon chains.
And as for the fatty acid, aliphatic alcohol, or aliphatic amine used as an auxiliary dispersant, it has been found that unsaturated aliphatic groups having 10 to 24 carbon chains are effective as in the hydrophobic part B of the amphiphile. .

The present invention has been completed based on these findings, and according to the present invention, the following inventions are provided.
[1] Coating with a crystalline amphiphile having a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water, and an auxiliary dispersant comprising at least one selected from fatty acids, aliphatic alcohols and aliphatic amines Easily dispersible fine particles, characterized in that
[2] The crystalline amphiphile is represented by the following general formula (1)
G-NHCO-R ₁ (1)
(In the formula, G represents a sugar residue excluding the hemiacetal hydroxyl group bonded to the anomeric carbon atom of the sugar, and R ₁ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The easily dispersible fine particles according to [1] above, which are N-glycoside type glycolipids represented by the formula:
[3] The auxiliary dispersant is represented by the following general formulas (2), (3), (4)
HOOC-R ₂ (2)
HOOC-R ₂ (3)
_{H 2 N-R 2 (4} )
(In the formula, R ₂ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The easily dispersible fine particles according to [1] above, which are a fatty acid, an aliphatic alcohol or an aliphatic amine represented by any of the above:
[4] A fine particle aqueous dispersion in which the easily dispersible fine particles according to any one of [1] to [3] are dispersed in water.
[5] Fine-particle water-dispersed gel, wherein the easily dispersible fine particles according to any one of [1] to [3] are dispersed in water containing organic nanotubes formed of the amphiphilic substance. .
[6] Dispersant for dispersing fine particles in water, a crystalline substance composed of an amphiphilic substance having a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water, and fatty acid and aliphatic alcohol And an auxiliary dispersant comprising at least one selected from aliphatic amines as an active ingredient.
[7] The amphiphilic substance is represented by the following general formula (1)
G-NHCO-R ₁ (1)
(In the formula, G represents a sugar residue excluding the hemiacetal hydroxyl group bonded to the anomeric carbon atom of the sugar, and R ₁ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The mixed dispersant for fine particles according to [6] above, which is an N-glycoside glycolipid represented by the formula:
[8] The auxiliary dispersant is represented by the following general formulas (2), (3), (4)
HOOC-R ₂ (2)
HO-R ₂ (3)
_{H 2 N-R 2 (4} )
(In the formula, R ₂ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The mixed dispersant for fine particles according to [6] above, which is a fatty acid, an aliphatic alcohol or an aliphatic amine represented by any of the above:
[9] Fine particles, characterized by adding to the fine particles the mixed dispersant for fine particles according to any one of the above [6] to [8] and water, and then crushing and mixing while heating to the phase transition temperature or higher. A method for producing a dispersion.
[10] A fine particle aqueous dispersion, wherein the fine particle mixed dispersant of any one of the above [6] to [8] and water are added to the fine particles, followed by stirring and mixing while heating above the phase transition temperature. A method for producing a gel.

The easily dispersible fine particles of the present invention include gold (Au), silver (Ag), iron (Fe) as metals, zinc oxide (ZnO) as metal oxides, magnetite (Fe ₃ O ₄ ), titanium dioxide, and organic substances. Is low in solubility in water and has a wide range and high versatility such as carbon materials, amino acids, enzymes, organic dyes and organic pigments having —OH or —COOH functional groups. Magnetite can be dispersed at an extremely high concentration of 50 g / L. In the dynamic light scattering measurement, in any fine particle, the particle size decreased before and after the operation of the present invention, and the secondary particles were crushed, the water dispersibility was improved by coating, and the dispersion medium Improvement of dispersion stability by gelation is achieved in a single step and in a short time. In the past, the preparation of the fine particle aqueous dispersion by coating often required a multi-step operation including the use of an organic solvent, whereas according to the present invention, the medium used in one step was used. Is only water, which is advantageous in terms of cost. Moreover, since the easily dispersible fine particles prepared according to the present invention can be dried and redispersed, it is possible to save space and light weight during storage and transportation, and a great advantage can be expected.

The conceptual diagram of this invention. It is a transmission electron microscope image of the sample which freeze-dried the magnetite nanoparticle aqueous dispersion, (a) is a magnetite without a coating, (b) is the nanoparticle obtained in Example 2, (c) is a comparative example. Nanoparticles obtained in 1 and (d) are nanoparticles obtained in Comparative Example 2. The scanning electron microscope image of the sample which freeze-dried the aqueous dispersion of the leucine nanoparticle obtained in Example 6. FIG. The scanning electron microscope image of the sample which freeze-dried the aqueous dispersion of the 2,4,6- triiodophenol nanoparticle obtained in Example 7. FIG. The transmission electron microscope image of the magnetite water dispersion gel obtained in Example 8. FIG.

FIG. 1 is a conceptual diagram for explaining the present invention.
As shown in the figure, the fine particles of the present invention have a crystalline substance (hereinafter referred to as “crystalline amphiphilic substance”) composed of an amphiphilic substance having a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water. And at least one auxiliary dispersant selected from fatty acids, fatty alcohols and aliphatic amines, and is water dispersible.
The fine particles in the dispersion of the present invention are further stabilized by nanofibers formed of a crystalline amphiphile and the auxiliary dispersant to form an aqueous dispersion gel.

In the present invention, the crystalline amphiphile used as a water-dispersed coating agent is a compound having both a hydrophilic group A and a hydrophobic group B in the molecule and represented by the general formula AB. The microparticles dried from the dispersion cause aggregation and welding because the amphiphilic substance used for dispersion is in a liquid crystal or dissolved state at room temperature in the dispersion medium. In the present invention, by using a crystalline amphiphile, aggregation and welding due to drying are suppressed. As the crystalline amphiphile, a substance that does not dissolve in a coating state and has a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water is used.
Further, in the present invention, as the auxiliary dispersant that plays an important role in enhancing the water dispersibility of fine particles and the formation of nanofibers, fatty acids such as the hydrophobic group B of the crystalline amphiphile, aliphatic alcohols And at least one selected from aliphatic amines, and performing molecular packing with the crystalline amphiphile.

The hydrophilic group A of the crystalline amphiphile is a monosaccharide or a disaccharide, preferably a monosaccharide, more preferably glucose.
The hydrophobic group B may contain saturated or unsaturated alkyl or aromatic or other elements, but is preferably saturated or unsaturated aliphatic having 10 to 24 carbon chains. In addition to the straight chain type, it may be branched, but in general, the alkyl chain has a large number of carbon atoms and tends to have a high phase transition point in the straight chain type.

In particular, a functional group that causes an intermolecular interaction such as an amide in the molecular structure, and this forms a stable crystalline molecular film with an adjacent amphiphile through a hydrogen bond, etc. In Japanese Patent Application Laid-Open No. 2008-30185, etc., the following general formula (1) is used as a raw material for organic nanotubes.
G-NHCO-R ₁ (1)
An N-glycoside glycolipid represented by the formula is preferably used.
G in the general formula (1) is a sugar residue excluding the hemiacetal hydroxyl group bonded to the anomeric carbon atom of the sugar. Examples of the sugar include glucose, galactose, maltose, lactose, cellobiose, and chitobiose. Preferably, it is glucopyranose. The sugar is a monosaccharide or oligosaccharide, preferably a monosaccharide. The sugar residue may be D, L, or racemic, but naturally derived is usually D. Furthermore, in the aldopyranosyl group, since the anomeric carbon atom is an asymmetric carbon atom, there are α-anomers and β-anomers, but any of α-anomers, β-anomers and mixtures thereof may be used. In particular, those in which G is a D-glucopyranosyl group, a D-galactopyranosyl group, particularly a D-glucopyranosyl group are preferred because they are easy to produce and easy to produce.
R ₁ in the general formula (1) is an unsaturated hydrocarbon group, preferably a straight chain, and more preferably 3 or less double bonds as an unsaturated bond. The number of carbon atoms in _{R 1} is 10-24, preferably 11-19, more preferably 17. Such hydrocarbon groups include decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl And those containing a monoene, diene or triene moiety as an unsaturated bond in a tetracosyl group or the like.

  As described in the above-mentioned patent publications, the present inventors can manufacture anhydrous organic nanotubes easily and in large quantities by self-assembling the N-glycoside type glycolipid in an organic solvent. As a result of subsequent studies, these N-glycoside type glycolipids are amphiphiles and have a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water. Therefore, it has been proved useful as a water dispersion agent for nanoparticles.

The crystalline amphiphile exhibits excellent effects even with a single crystalline compound having the above-described characteristics. However, in the present invention, X-R ₂ (wherein R ₂ represents the number of carbon atoms) is used as an auxiliary dispersant. Represents an unsaturated hydrocarbon group of 10 to 24, and X represents a hydrophilic group such as —COOH, —OH, —NH ₂ , or —PEG.) Is mixed to form a molecular film. As a result, it is possible to obtain more stable and easily dispersible particles and a stable dispersion composed of the fine particles.
In particular, the auxiliary dispersant bet is represented by the following general formulas (2), (3), (4)
HOOC-R ₂ (2)
HO-R ₂ (3)
_{H 2 N-R 2 (4} )
Preferably, at least one selected from fatty acids, aliphatic alcohols and aliphatic amines represented by any of the above is used.
In the general formulas (2) to (4), R ₂ is an unsaturated hydrocarbon group, preferably linear, and more preferably 3 or less double bonds as an unsaturated bond, as in R _1. Including. R ₂ has 10 to 24 carbon atoms, preferably 11 to 19 carbon atoms, and more preferably 17 carbon atoms. Such hydrocarbon groups include decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl And those containing a monoene, diene or triene moiety as an unsaturated bond in a tetracosyl group or the like.

  On the other hand, in the present invention, the core particles may be any particles that do not melt or decompose under the conditions of the boiling point of water and the phase transition temperature of the amphiphile to be coated. Preferably, metal oxides such as magnetite, zinc oxide, titanium oxide, calcium oxide and silica, metal chalcogenides such as cadmium sulfide, salts such as barium sulfate, organic substances such as molecules having an —OH or —COOH group in the molecular structure and amino acids Etc.

As shown in FIG. 1, the core microparticles are often aggregated to form secondary particles. However, the method for producing the microparticles of the present invention involves crushing the aggregated secondary particles and amphiphilic properties. It is characterized in that heating is performed at the same time or more than the phase point transfer of the substance.
Specifically, by adding the crystalline amphiphile, auxiliary dispersant, and water to the fine particles, pulverizing and mixing while heating above the phase transition temperature of the crystalline amphiphile. can get.
That is, the heating causes the amphiphilic substance, which has become a molecular state having surface activity, to become higher than its phase transition temperature, adsorbs the crushed fine particles as a core, and then becomes thermodynamically stable. The alkyl group of the fatty acid molecule is adsorbed on the particle. Thereafter, by cooling, a stable crystalline film in which hydrophilic groups such as fatty acid —COOH, aliphatic alcohol —OH, and aliphatic amine —NH ₂ are oriented on the outer surface side is used as an auxiliary dispersant. Water dispersible fine particles can be formed.
When the crystalline amphiphile and the auxiliary dispersant are present in excess, the extra crystalline amphiphile and the auxiliary dispersant, fatty acid, aliphatic alcohol or aliphatic amine, It becomes a long fiber structure in water and forms a network structure in the dispersion. Thereby, the dispersion stability of the aqueous dispersion is further increased, and an aqueous dispersion gel can be formed. The diagram on the right side of FIG. 1 schematically shows the situation.

Examples of the means for dispersing and coating include an optimizer, an ultrasonic homogenizer, and a ball mill, but an optimizer and an ultrasonic homogenizer are more preferable.
In the case of the Optimizer, the treatment liquid temperature becomes higher than the phase transition temperature of the water-dispersed coating agent due to the heat generated by passing through the orifice, and the water-dispersed coating agent in the liquid crystal state is coated with finely divided fine particles as the core. To do.
Also in the case of an ultrasonic homogenizer, the water-dispersed coating agent, which is higher than the phase transition point of the water-dispersed coating agent due to the heat generated by ultrasonic irradiation, is coated with fine particles obtained by pulverizing the ultrasonically-dispersed water-dispersed coating agent. .
In the present invention, the weight ratio of the core particles to the crystalline amphiphile is 1: 0.05 to 1:10, and the crystalline amphiphile and the auxiliary dispersant, fatty acid and aliphatic alcohol. Alternatively, the weight ratio of the aliphatic amine is 1: 0.001 to 1:10.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this Example.
<Dispersant used>
In this example, as a crystalline amphiphilic substance, a compound represented by the following formula in which 1-aminoglucopyranoside and oleic acid are linked by an amide bond (referred to as amphiphilic compound 1).
And the fatty acid is oleic acid which is a hydrophobic group of the amphiphilic compound 1
Also, oleylamine as an aliphatic amine
Was used.
The amphiphilic compound 1 has a gel-liquid crystal phase transition temperature in water of 68 ° C. and is in a stable crystalline state at room temperature.
As comparative examples, commercially available polyoxyethylene sorbitan monooleate (Tween 80, nonionic surfactant) and sodium dodecyl sulfate (SDS, anionic surfactant) were used.

(Example 1: Production of nanoparticles having magnetite as a core using an optimizer)
1000 mg of magnetite (manufactured by Aldrich, particle size of about 20 nm as primary particles), 4000 mg of the amphiphilic compound 1 and 2 ml of oleic acid were weighed, and 500 mL of distilled water was added. The mixture was stirred with a homogenizer for 30 minutes, and then charged into an optimizer (Sugino Machine HJP25005) and subjected to 20 passes at a pressure of 245 MPa to obtain an aqueous dispersion of nanoparticles coated with a crystalline amphiphile.
In dynamic light scattering, a decrease in particle size was observed with an increase in the number of passes, and the primary particle size was reached in 20 passes (20 to 40 nm). This nanoparticle aqueous dispersion did not precipitate for more than 6 months, and maintained a stable dispersion state.
Furthermore, when the nanoparticles were lyophilized and then redispersed in water, a slightly increased particle size (80 to 120 nm) and a good dispersion of nanoparticles were obtained.

(Example 2: Production of nanoparticles having magnetite as a core using an ultrasonic homogenizer)
40 mg of magnetite, 400 mg of the amphiphilic compound 1 and 0.2 ml of oleic acid were weighed out and 40 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation using a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with a crystalline amphiphile.
In dynamic light scattering, the primary particle size was 10 to 40 nm, and no subsequent change in particle size was observed. This nanoparticle aqueous dispersion did not precipitate for more than 6 months, and maintained a stable dispersion state.
Furthermore, when these nanoparticles were lyophilized and then redispersed in water, a dispersion having a substantially unchanged particle size (15 to 50 nm) and a good dispersion of nanoparticles was obtained. (Fig. 2 (b))

(Comparative Example 1: Production of nanoparticles having magnetite as a core coated only with amphiphilic compound 1)
10 mg of magnetite and 10 mg of amphiphilic compound 1 were weighed and 10 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation with a probe ultrasonic generator (50 W, 3 minutes) to obtain an aqueous dispersion of nanoparticles coated only with the amphiphilic compound 1.
Dynamic light scattering resulted in large aggregates (350-450 nm). The nanoparticle aqueous dispersion had a precipitate after one month.

(Comparative Example 2: Production of nanoparticles having magnetite core coated with SDS)
40 mg of magnetite, 261 mg of SDS as an amphiphile, and 0.2 ml of oleic acid were weighed out and 40 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation with a probe type ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with SDS.
In dynamic light scattering, the primary particle size was 20 to 50 nm. This nanoparticle aqueous dispersion did not precipitate for more than one week thereafter, and maintained a stable dispersion state.
Furthermore, when the nanoparticles were dried and redispersed in water, no welding due to concentration was observed, and a slightly increased particle size (30 to 60 nm), a good dispersion of nanoparticles was obtained. (Fig. 2 (c))

(Comparative Example 3: Production of nanoparticles having magnetite core coated with Tween 80)
40 mg of magnetite, 1184 mg of Tween 80 as an amphiphilic substance, and 0.2 ml of oleic acid were weighed and 40 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation with a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with Tween 80.
In dynamic light scattering, the primary particle size was 10 to 40 nm. This nanoparticle aqueous dispersion did not precipitate for more than one week thereafter, and maintained a stable dispersion state.
Further, when the nanoparticles were dried and redispersed in water, no welding due to concentration was observed, and a slightly increased particle size (40 to 80 nm), a good dispersion of nanoparticles was obtained. (Fig. 2 (d))

  As is clear from the particle size results of Comparative Examples 2 and 3 above, when the amphiphilic substance 1 of the present invention is used, the nanoparticles are dispersed close to the primary particle size by redispersion even when dried. On the other hand, the dried sample using Tween 80 or SDS was found to be a slightly larger aggregate than the sample using the amphiphilic substance 1 of the present invention.

(Example 3: Production of nanoparticles having magnetite as a core using an ultrasonic homogenizer)
100 mg of magnetite, 100 mg of the amphiphilic compound 1 and 0.05 ml of oleylamine were weighed out and 10 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation using a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with a crystalline amphiphile.
In dynamic light scattering, the particle size was larger than the primary particle size (60 to 120 nm), but no subsequent particle size change was observed. The nanoparticle aqueous dispersion did not precipitate for more than one month thereafter, and maintained a stable dispersion state.

(Example 4: Production of nanoparticles having titanium oxide as a core using an ultrasonic homogenizer)
200 mg of titanium oxide (Ishihara Sangyo, ST-21, primary particle size of about 20 nm), 400 mg of the amphiphilic compound 1 and 0.2 ml of oleic acid were weighed, and 40 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation using a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with a crystalline amphiphile.
In dynamic light scattering, the primary particle size became 10 to 30 nm, and no subsequent change in particle size was observed. This nanoparticle aqueous dispersion did not precipitate for more than 6 months, and maintained a stable dispersion state.

(Example 5: Production of nanoparticles having zinc oxide as a core using an ultrasonic homogenizer)
200 mg of zinc oxide (primary particle size of about 50 nm), 400 mg of the amphiphilic compound 1 and 0.2 ml of oleic acid were weighed and 40 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation using a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with a crystalline amphiphile.
In dynamic light scattering, the primary particle size (50 to 90 nm) was obtained, and no subsequent change in particle size was observed. This nanoparticle aqueous dispersion did not precipitate for more than 6 months, and maintained a stable dispersion state.

(Example 6: Production of fine particles having amino acid leucine as a core)
100 mg of leucine (manufactured by Aldrich, crystal particle size of about 500 nm), 400 mg of the amphiphilic compound 1 and 0.2 ml of oleic acid were weighed and 40 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation with a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of fine particles coated with a crystalline amphiphile.
In dynamic light scattering, particles (70 to 120 nm) smaller in size than the original crystals were observed, and when observed with a scanning electron microscope, spherical particles were observed and it was confirmed that leucine was coated (Fig. 3).

(Example 7: Production of nanoparticles having 2,4,6-triiodophenol as a core)
100 mg of 2,4,6-triiodophenol (manufactured by TCI), 400 mg of the amphiphilic compound 1 and 0.05 ml of oleic acid were weighed, and 40 mL of distilled water was added. This mixture was subjected to ultrasonic irradiation using a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with a crystalline amphiphile.
In dynamic light scattering, fine particles of 50 to 230 nm were obtained, and observation with a scanning electron microscope revealed that spherical particles were observed and that 2,4,6-triiodophenol was coated (see FIG. 4).

Example 8 Production of Nanoparticle Dispersion Gel with Magnetite as Core Using Ultrasonic Homogenizer
40 mg of magnetite, 400 mg of the amphiphilic compound 1 and 0.4 ml of oleic acid were weighed and 40 ml of distilled water was added. This mixture was subjected to ultrasonic irradiation using a probe ultrasonic generator (50 W, 10 minutes) to obtain an aqueous dispersion of nanoparticles coated with a crystalline amphiphile.
In dynamic light scattering, the primary particle size was 10 to 40 nm, and no subsequent change in particle size was observed. The aqueous nanoparticle dispersion gelled after 1 day and became a stable dispersion gel for 6 months or more. (Figure 5)

  Metal oxide and metal sulfide nanoparticles are promising as materials for quantum dots, DDS, magnetic medicine and biosensors, and they can be easily dispersed in water, making them widely applicable in the field of materials optics and medicine. Expect to expand the range. While organic substances such as amino acids are expected to be used as food additives and DDS materials, they are extremely poor in water dispersibility when used alone. According to the present invention, since it is well dispersed in water, can be dried and redispersed, and can be applied as a DDS material, application research in functional foods, pharmaceuticals, cosmetics, and the like may greatly advance.

Claims (10)

  Covered with a crystalline material comprising an amphiphile having a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water, and an auxiliary dispersant comprising at least one selected from fatty acids, aliphatic alcohols and aliphatic amines Easily dispersible fine particles, characterized in that The amphiphile is represented by the following general formula (1)
G-NHCO-R ₁ (1)
(In the formula, G represents a sugar residue excluding the hemiacetal hydroxyl group bonded to the anomeric carbon atom of the sugar, and R ₁ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The easily dispersible fine particles according to claim 1, wherein the easily dispersible fine particles are N-glycoside type glycolipids represented by the formula: The auxiliary dispersant is represented by the following general formulas (2), (3), (4)
HOOC-R ₂ (2)
HOOC-R ₂ (3)
_{H 2 N-R 2 (4} )
(In the formula, R ₂ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The easily dispersible fine particles according to claim 1, which are a fatty acid, an aliphatic alcohol or an aliphatic amine represented by any one of the following:   4. A fine particle aqueous dispersion in which the easily dispersible fine particles according to claim 1 are dispersed in water.   A fine-particle water-dispersed gel, wherein the easily dispersible fine particles according to any one of claims 1 to 3 are dispersed in water containing organic nanotubes formed of the amphiphilic substance.   A dispersing agent for dispersing fine particles in water, a crystalline substance comprising an amphiphilic substance having a gel-liquid crystal phase transition temperature higher than room temperature and lower than the boiling point of water, and fatty acids, aliphatic alcohols and aliphatics A mixed dispersant for fine particles, comprising an auxiliary dispersant comprising at least one selected from amines as an active ingredient. The amphiphile is represented by the following general formula (1)
G-NHCO-R ₁ (1)
(In the formula, G represents a sugar residue excluding the hemiacetal hydroxyl group bonded to the anomeric carbon atom of the sugar, and R ₁ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The mixed dispersant for fine particles according to claim 6, which is an N-glycoside type glycolipid represented by the formula: The auxiliary dispersant is represented by the following general formulas (2), (3), (4)
HOOC-R ₂ (2)
HO-R ₂ (3)
_{H 2 N-R 2 (4} )
(In the formula, R ₂ represents an unsaturated hydrocarbon group having 10 to 24 carbon atoms.)
The mixed dispersant for fine particles according to claim 6, which is a fatty acid, an aliphatic alcohol or an aliphatic amine represented by any one of:   A fine particle dispersion, wherein the fine particle mixed dispersant according to any one of claims 6 to 8 and water are added to the fine particles, and then pulverized and mixed while being heated to the phase transition temperature or higher. Manufacturing method.   A fine particle water-dispersed gel comprising: the fine particle mixed dispersant according to any one of claims 6 to 8 and water added to the fine particles, and then stirred and mixed while being heated to the phase transition temperature or higher. Production method.