JP2002361064A - Method of producing coated particle and coated particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing coated particles by which the coating ability of a film to amorphous particles is improved and a uniform, thin and stable film can be formed, and to provide coated particles obtained by the same. SOLUTION: The method of producing coated particles comprises bringing the amorphous particles into contact with supersaturated vapor of a compound being solid at ordinary temperature and vapor when it is heated, and condensing and depositing the compound on the surface of each amorphous particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing coated particles and coated particles, and more particularly to a method for producing coated particles and a method for coating amorphous particles with a specific compound in a uniform and thin film form.

[0002]

2. Description of the Related Art Conventionally, in order to protect fine particles or change their surface characteristics, a method of coating the surfaces of fine particles with lipids or the like has been used.

[0003] As a method of coating the surface of the fine particles with lipids or the like, a method of suspending the particles in a dissolved hardened oil, wax, or the like, followed by spray cooling using a sprayer or a rotating disk, or floating the particles by wind power. In addition, various methods such as a method of spraying hardened oil, wax, and the like from above are used.

However, these methods have insufficient coating performance, and it is difficult to form a uniform coating. In particular, when the particles have an irregular shape, unevenness of the coating becomes remarkable. Further, since a large amount of lipids and the like are required, it is impossible to reduce the thickness of the film, and the time for forming the film is increased, which leads to an increase in manufacturing cost. Furthermore, since the above-mentioned method performs drying or the like in an atmosphere of a relatively high temperature, depending on the material such as particles and lipids, the quality of the material is changed, and stress of the particles or the coating due to a temperature difference or the like is caused.

As another method, there is a method in which powdery lipids or the like are brought into contact with and collided with particles to coat the surface of the fine particles with lipids or the like.

However, in this method, the uniformity of the coating is affected by the shape of the particles, and there is a problem that a uniform, thin, and stable coating cannot always be obtained.

[0007] Further, a method of applying a double coating of lipid to the surface of a core substance by combining the above two methods is disclosed in Japanese Patent Application Laid-Open No.
-87950. However, even in such a method, since a large amount of lipids and the like are required,
It is not possible to reduce the thickness of the film, so that the time for forming the film is increased and the production cost is increased.

The present invention has been made in view of the above problems, and a method for producing coated particles capable of forming a uniform, thin, and stable coating by improving the coating performance of the coating on irregular-shaped particles, and a method for producing the same. To provide coated particles obtained by the method described above.

[0009]

According to the present invention, an amorphous particle is brought into contact with a supersaturated vapor of a compound which becomes a solid at normal temperature or becomes a gas by heating or depressurizing, whereby the compound is brought into contact with the surface of the irregular particle. A method for producing coated particles to be coagulated and precipitated is provided. Further, according to the present invention, there is provided a coated particle formed by the above method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides
This is a method of forming a film with a specific compound. From another viewpoint, this method can be regarded as a method of modifying the surface of the irregular-shaped particles using a specific compound.

The particles that can be used in the present invention are irregular shaped particles. The irregular particles mean particles satisfying B / S ≧ 1.2. Here, B is the BET surface area (m ²
/ G: method of measuring surface area by nitrogen adsorption amount), S is 6 /
ρ · dp (ρ is the true specific gravity of the particles, dp is the average particle size (μm) in number% of the particle size distribution). When the shape of the particles can be measured, separately from the above equation, the particle size degree φ ≦
Those satisfying the condition of 0.8 may be used as the irregular shaped particles.
Where φ is (the diameter of the largest circle inscribed in the projection of the particle) /
(The diameter of the smallest circle circumscribing the projection of the particle).

The irregular particles include titanium oxide, zinc oxide, silica, talc, kaolin, mica powder, pearl pigment,
Inorganic particles such as mica, BN, sericite, salt, and metal;
Examples include starch, resin powder, pharmaceutical ingredients, foods, organic particles such as proteins, vitamins, and fungi. These particles are particles that can be used for cosmetics, pharmaceuticals, foods, feeds, quasi-drugs, and the like. Is particularly effective. The size of the particles is not particularly limited, and examples thereof include particles having a diameter (length) of several nm to several μm. In some cases, granules or tablets having a diameter of about several mm may be used as particles.

The compound which is solid at ordinary temperature and which becomes a gas when heated or reduced in pressure is not particularly limited, but when used for cosmetics, pharmaceuticals, foods, etc., it is not harmful to the human body. Compounds that do not adversely affect the skin or the like are preferred. Specifically, natural animal and vegetable oils (hardened tallow oil, hardened fish oil, hardened soybean oil, hydrogenated jojoba oil, etc.), higher alcohols (palmityl alcohol, stearyl alcohol, etc.), waxes (carnauba wax, rice wax, beeswax) Etc.), sugars, fatty acids (stearic acid, palmitic acid, caprylic acid, etc.), fatty acid ethylene glycol (ethylene glycol distearate, etc.), fatty acid glycerin (hydrogenated tallow fatty acid triglyceride, hydrogenated palm oil fatty acid triglyceride,
One or a combination of two or more of glyceryl monostearate, tetraglyceryl tristearate, etc., fatty acid sorbitan (sorbitan monostearate, etc.), phosphorus or nitrogen-containing phospholipids (tripalmityl phosphate, etc.), sterol, cocoa butter, etc. Is mentioned. In the present invention, raw materials for forming the surface modified film can be appropriately selected according to the type of the particles.

In order to convert the above compound into a supersaturated vapor,
First, in a closed container, the compound is optionally heated without or under pressure to vaporize the compound to a saturated state, and then the pressure of the saturated vapor is rapidly reduced or decreased. In this case, the degree of pressure to be applied and the heating temperature can be appropriately set depending on the type of the compound to be used and the like, but it is necessary to set the pressure and / or the temperature so that the compound to be used does not decompose. . Further, the pressure reduction or the temperature decrease for converting the saturated vapor into the supersaturated vapor can be appropriately set depending on the degree of supersaturation and the type of the compound used. Also in this case, it is necessary to set a pressure and / or a temperature at which the compound used does not decompose.

The degree of supersaturation and contact time when the particles are brought into contact with supersaturated vapor are appropriately adjusted depending on the size, surface area, characteristics of the surface-modified particles to be obtained, degree of supersaturation, and the like. Can be. For example, the weight ratio between the particles and the solid compound is about 1: 0.01 to 10 ⁶ ,
Preferably, about 1: 0.1 to 10 ⁴ can be mentioned. The contact time is about 1 to 60 seconds, preferably 1 to 60 seconds.
About 30 seconds.

The above-described series of steps can be easily performed using, for example, an apparatus described in Japanese Patent Application Laid-Open No. 9-296128.

According to such a method, even in the case of irregular-shaped particles, a compound can be formed on the surface of the compound by coagulation and precipitation to form a very thin uniform coating film of the compound on the particle surface. Further, from another viewpoint, the surface of the particle surface can be modified. The film formed on the particle surface usually has a thickness of about 5 nm to 100 nm, but a thicker coating film can be formed by repeating the above operation.

Hereinafter, the method for producing coated particles and the coated particles of the present invention will be described in detail based on examples.

In order to produce the coated particles of the present invention, for example, a particle surface modifying apparatus described in JP-A-9-296128 can be used. As shown in FIG. 1, the particle surface reforming apparatus 1 has a condensing box 2 provided with a particle inlet 4, a particle outlet 5, and a pressure reducing port 6. The coagulation box 2 is composed of an outer wall 2a and an inner wall 2b made of a porous material such as ceramic, and has a vertically extending cylindrical shape having a processable space 3 that can be sealed therein. Is established. An introduction pipe 7 for introducing particles into the space is connected to the particle introduction port 4, and a discharge pipe 8 for discharging particles from the space is connected to the particle outlet 5. The pressurizing and depressurizing port 6 is connected to a pressurizing and depressurizing pipe 9 for pressurizing and depressurizing the processing space 3.
The particle surface reforming apparatus 1 has an inner wall 2 of the coagulation box 2.
A heater 10 is provided as a heating unit for heating b and the processing space 3.

Using such a device, first, the condensation box 2
460 K of a stearic acid, which is a coating material for coating the particles, is introduced into the inner wall 2b of the substrate.

Next, in the processing space 3 in the coagulation box 2,
NaCl particles having an average particle size of about 100 nm (B / S is about 1.2) obtained by spraying a solution of sodium chloride at a temperature of 420 K at a temperature of 420 K are supplied at a rate of 10 ¹¹ particles / m ³ ,
Through the particle inlet 4 as an aerosol.

Subsequently, in order to generate a saturated vapor of stearic acid in the processing space 3, the inside of the coagulation box 2 is set to 120 kP.
Pressurize to about a and heat to 460K. The pressurization is performed by opening the pressurizing / depressurizing port 6 and sending clean air into the processing space 3 through the pressurizing / depressurizing pipe 9. Then, until a saturated vapor of stearic acid is obtained,
The pressure and temperature in the coagulation box 2 are appropriately maintained for a few minutes.

Next, the temperature of the inside of the processing space 3 is lowered to 300 k, and the pressure is reduced to normal pressure, so that the saturated vapor of stearic acid is brought into a supersaturated state. At this time, the pressurizing / depressurizing port 6 is opened to open the processing space 3 to the atmosphere, and a saturated vapor of stearic acid in the processing space 3 is adiabatically expanded. Thereby, the processing space 3
Within, the saturated vapor of stearic acid becomes supersaturated, a condensation reaction of stearic acid occurs on the surface of NaCl particles, and the surface of NaCl particles is coated with stearic acid. Can be formed.

Thereafter, the coated particles in the processing space 3 are taken out from the particle outlet 5 through the discharge pipe 8, and the processing is completed. At this time, the process is performed by opening the particle inlet 4 and the particle outlet 5, introducing cleaning air from the introduction pipe 8 into the processing space 3, and replacing the aerosol containing the coated particles in the processing space 3 with clean air.

Each of the obtained coated particles was a primary particle having a non-uniform shape, but a very thin film of stearic acid was uniformly formed around the particles.

[0026]

According to the present invention, a stable and extremely thin coating film can be reliably and simply formed even on the surface of irregular shaped particles. In addition, the stress of the particles due to the coating film, which has been a problem in the conventional coating film forming method, can be reduced, and the processing temperature and processing time can be significantly reduced. In particular, it is possible to easily form a coating film even on particles, such as proteins and vitamins, for which formation of a coating film was conventionally difficult, and it is also possible to increase the temperature during formation of the coating film. Even when it is necessary to avoid stress, the method of the present invention can minimize the temperature rise during the formation of a coating film, and can form a coating film having desired characteristics on any particles. It becomes possible.

In addition, in order to perform complete coating of amorphous particles, it has conventionally been necessary to form a laminated film or to form a thick coating film to prevent incomplete coating. However, in the present invention, the smaller the curvature, the faster the agglomeration and precipitation can be accelerated, and a stable and uniform coating film can be efficiently formed.

Further, since the compound coated on the surface of the particles is a compound which is solid at room temperature and becomes a gas by heating, it is possible to prevent aggregation of the particles after the treatment, and to improve the surface modification effect of the particles. It can be maintained for a long time. In addition, since the amorphous particles are stably and reliably coated with an extremely thin film, it is possible to prevent a change in the quality of the amorphous particles themselves and a reaction due to contact with other substances, so that the irregular particles are Long-term stability can be achieved.

Further, when a liquid is used as a coating agent, fine particles of the coating agent are combined with each other due to stress during long-term storage or kneading with a lipid, a polymer, or the like to complete cosmetics, and large liquid particles are formed. Grow into
Dispersion may be affected, but as in the present invention,
When a solid coating agent is used, the fine particles generated by the dropout do not grow into large particles, and even if aggregated, they can be dispersed again relatively easily. In addition, in the case of a liquid coating agent, the effect of surface modification may be deteriorated due to evaporation of the coating agent when left for a long period of time and stored for a long period of time. By coating a solid, such a phenomenon can be prevented. It becomes possible.

In the case of a liquid coating, it is necessary to consider the wettability of the surface that comes into contact with the particles. For example, when the material is stored in a container made of a material having good wettability, the adhesion to the container surface is reduced by a fan. The surface tension acts in addition to the Delwars force, making it very difficult to remove. However, such a problem can be avoided because a solid coat does not generate surface tension.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part showing a particle surface modifying apparatus used for producing coated particles of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Particle surface reforming apparatus 2 Aggregation box 2a Outer wall 2b Inner wall 3 Processing space 4 Particle inlet 5 Particle outlet 6 Pressurizing / reducing port 8 Discharge pipe 9 Pressurizing / reducing pipe 10 Heater 11 Base

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C09C 3/00 C09C 3/00 F term (Reference) 2B150 DJ01 DJ03 DJ28 4D075 BB18Z BB22Y BB56Y BB57Y BB69Y BB85Y CA40 CA42 CA47 DA11 DB11 DC30 EA01 EA37 EB07 EC07 EC30 4G004 BA00 4G075 AA27 AA30 BB10 BD14 CA02 CA05 CA57 DA02 DA11 DA18 EA06 EC25 EE02 FA14 FB04 4J037 AA04 AA08 AA11 AA17 AA18 AA22 AA26 CC04 CB CB CB CC FF21

Claims (5)

[Claims] 1. Coated particles wherein the amorphous particles are brought into contact with a supersaturated vapor of a compound which becomes a solid at ordinary temperature or becomes a gas when heated or depressurized, thereby coagulating and depositing the compound on the surface of the irregular particles. Manufacturing method. 2. An amorphous particle having a B / S ≧ 1.2 or a particle size φ ≦ 0.8 (where B is a BET surface area (m ² / g: a method of measuring a surface area by a nitrogen adsorption amount)). S is 6 / ρ · dp
(Ρ is the true specific gravity of the particle, dp is the average particle size (μm) in number% of the particle size distribution), φ is (the diameter of the largest circle inscribed in the projection of the particle) / (projection of the particle 2. The method according to claim 1, wherein the particles satisfy the following formula: 3. A compound which is solid at room temperature and becomes a gas when heated or decompressed is a natural animal or vegetable oil, higher alcohol, waxes, sugar, fatty acid, fatty acid ethylene glycol, fatty acid glyceride, fatty acid sorbitan, phosphorus or nitrogen-containing phospholipid. The method according to claim 1 or 2, wherein the method is selected from the group consisting of, sterols and cocoa butter. 4. The amorphous particles are introduced into a saturated vapor of a compound which becomes a solid at normal temperature and becomes a gas by heating or depressurizing, and then the saturated vapor of the compound is depressurized or cooled to supersaturated vapor, 3. The method of claim 1 or 2, comprising contacting the amorphous particles with a supersaturated vapor of the compound. 5. Coated particles obtained by the method according to claim 1.