JP2016097324A - Method for manufacturing hollow particle and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a large amount of hollow particles having an arbitrary hollow rate, circularity, and particles size in a short time without removing a core material.SOLUTION: In a process of preparing a microcapsule enclosing a liquid or solid by an interfacial polymerization method, the enclosed liquid is pressurized by gas to dissolve the gas therein more excessively than in an atmospheric pressure environment, and foaming of the enclosed liquid is promoted at the time of film formation in an atmospheric pressure environment, whereby film formation occurs in a state still including a gas phase inside to produce a hollow particle. A hollow particle having an arbitrary hollow rate, circularity, and particles size can be produced by changing a pressurizing pressure, solubility of gas into a droplet, and a distance from droplet formation means to a liquid to be reacted.SELECTED DRAWING: Figure 2

Description

The present invention relates to an apparatus for producing particles having a hollow structure with a diameter of 1 mm or less (hereinafter referred to as hollow particles) produced by utilizing a foaming phenomenon when a gas is pressurized and decompressed from a state in which the gas is excessively dissolved in a liquid. The present invention relates to a method for controlling the particle size and shape of hollow particles.

Hollow particles with a gas structure inside and a solid outside structure are low in density and can suppress the transmission of sound and heat, so they are used for lightening materials, soundproofing materials, and heat insulating materials that adjust the specific gravity of materials. It has been.

As a conventional method for producing hollow particles, solid particles containing a substance that becomes a liquid or solid core (core substance) are generated, and the core substance is extracted from the solid particles by an operation such as heating or decompression to make it hollow. (See Patent Documents 1 and 2), or a technique for vaporizing a core material to give a hollow structure (see Patent Document 3).

Moreover, as a method of directly creating hollow particles using bubbles, a method of polymerizing substances in a liquid phase around the bubbles on the surface of the bubbles to produce a solid film to form hollow particles (see Patent Document 4), liquid A method in which polymerization of substances in a phase is promoted by a catalyst contained in a gas phase to form hollow particles (see Patent Document 5), and droplets are formed while bubbles are stably present in droplets in which a membrane material is dissolved. A method of forming a hollow particle with a hollow structure by drying and precipitating a film material (see Patent Document 6), a gas containing a reactive gas that reacts with a liquid and causes film formation as fine bubbles in the liquid There is a method of supplying hollow particles (see Patent Document 7).

In addition, prior to the present invention, the present inventors have promoted foaming inside droplets during the formation of particles by spraying a liquid that has been pre-pressurized and saturated with gas (patented). (Ref. 8).

JP 2002-105104 A Japanese National Patent Publication No. 9-508067 Japanese Patent Publication No. 3-79060 JP 2007-21315 A JP 2007-196223 A Japanese Patent Laid-Open No. 2007-75660 Japanese Patent Application Laid-Open No. 2011-245452 Japanese Patent Application No. 2013-158353

In the above background art, the method of hollowing out the core material contained in the solid particles by extraction or vaporization is difficult to control the pressure and heat of the hollowing process, and the deformation of the particles and the damage of the surface during the hollowing. It is a problem that is likely to occur.

In addition, in the method using bubbles in the background art described above, a hollowing step is not required, so that hollow particles can be easily produced, but the amount of hollow particles to be generated is small with respect to the amount of bubbles generated, and the yield is low. In addition, in the case of drying in liquid, it takes a long time to prepare.

The method disclosed by the inventors in Patent Document 8 shows a method for easily producing hollow particles by promoting foaming inside droplets during particle formation. For control of particle diameter, hollow ratio, and external shape, It was not specified and the parameters controlling the above items for hollow particles were not shown.

An object of the present invention is to solve the above-mentioned problems relating to the conventional method for producing hollow particles, and to provide a method for controlling the size of the hollow particles and the external / internal structure.

In the method disclosed in Patent Document 8, the present inventors have carried out a step of pressurizing a liquid as a dispersoid with a gas and dissolving the gas in excess over that in a normal pressure environment, whereby an interfacial polymerization method in a normal pressure environment. (Emulsion containing different components in the dispersoid and disperse medium in which different components contained in each phase react with each other at the contact interface to form a film) Bubbles are generated inside the dispersoid during film formation, and film formation Later, it was found that hollow particles having a gas phase inside can be prepared. Regarding the generation of bubbles inside the dispersoid, the amount of gas dissolved in the liquid is proportional to the pressure (Henry's law). Under high pressure, a larger amount of gas dissolves in the liquid than under atmospheric pressure. It utilizes the principle that when a saturated and dissolved liquid is depressurized to atmospheric pressure, a supersaturated dissolved gas is generated as bubbles. In the present invention, as a result of intensive research to solve the problems described in the preceding paragraph, by changing the solubility of the gas, the pressurized pressure, the distance from the liquid discharge port to the liquid in which the reactant is dissolved, respectively, It was found that the hollowness, average particle diameter, and circularity of the hollow particles can be controlled by changing the internal foaming amount, the droplet formation state, and the shape stability depending on the surface tension.

The hollow particle production apparatus and the method for controlling the particle size and shape of the hollow particles according to the present invention can provide the following effects. (1) The core substance removing step is not necessary. (2) The minimum required apparatus is a simple configuration including only a pressure vessel, a droplet forming means, and a reaction tank, and hollow particles can be prepared easily and inexpensively. (3) It is possible to prepare hollow particles having an optimum particle diameter, hollow ratio, and circularity according to the application.

It is the figure which showed the apparatus structure of this invention. 2 is an optical microscope image of hollow particles prepared in Example 1. FIG. It is a figure which shows the relationship between the solubility of gas in this invention, and an average hollow rate. It is a figure which shows the relationship between the pressurization pressure in this invention, and the average particle diameter of a hollow particle. 2 is an optical microscope image of hollow particles prepared in Example 7. FIG.

The present invention is described in Patent Document 8 invented by the inventors of the present invention. (1) The liquid held in the container is pressurized to atmospheric pressure or higher by a gas so that the liquid is excessively contained in the liquid than in the atmospheric pressure environment. Dissolve the gas. (2) Discharge the pressurized liquid into the liquid held in the reaction vessel as droplets by the droplet forming means, disperse the droplets in the dispersoid and the liquid held in the reaction vessel. (3) The liquid and liquid droplets held in the reaction tank react with each other at the liquid droplet interface to form a film and form particles, and atmospheric pressure is generated inside the liquid droplets. By depressurizing under the environment, the gas is dissolved in excess as compared to the saturated state under the atmospheric pressure environment by the pressurization operation, so that a hollow structure is imparted to the particles. Capable of easily producing capsules containing cavities In this technology, the hollow ratio, average particle diameter, and circularity of the hollow particles are changed by changing the solubility of the gas, the pressure of the gas, and the distance from the nozzle that generates the droplet to the liquid that contains the target substance for film formation. It is a method to control. Hereinafter, the best mode for carrying out the present invention will be described with reference to FIG.

In the best mode for carrying out the present invention, hollow particles are generated through the following pressurizing step, droplet forming step, and film forming step.
A liquid 3 in which the particulate material 2 is dissolved or dispersed is put into the pressure vessel 1 and pressurized by the gas 4 (pressurizing step).
The liquid 3 which is pressurized by the gas 4 and in which the gas 4 is excessively dissolved in the atmospheric pressure environment is discharged as droplets 6 by the droplet forming means 5 and collected in the reaction tank 7 (droplet forming step).
The liquid droplet 6 is a liquid 9 in which the particle material 8 filled in the reaction vessel 7 is dissolved or dispersed. The material 8 comes into contact with the film to form fine particles 10 (film forming process).
From the formation of the droplet 6 until the generation of the fine particles 10 is completed, a part of the gas 4 excessively dissolved by the pressurizing operation is generated as single or plural bubbles 11 inside the droplet 6 under the atmospheric pressure environment. By doing so, a hollow structure can be provided inside the fine particles 10.
The present invention, in the hollow particle formation step,
(1) By changing the solubility of the gas by changing the gas or liquid in the pressurization step, the hollow ratio (total volume of cavities inside the particle / external volume of the particle) is controlled in the range of 0% to 55%. .
(2) The pressure in the pressurizing step is changed to control the average particle diameter in the range of 15 μm to 80 μm.
(3) The position where the droplet is formed by the droplet forming means 6 and the distance between the liquid 9 are changed and the circularity is controlled in the range of 0.5 to 1.
The above three points are possible.

The pressure vessel 1 is not particularly limited as long as the inside is maintained at atmospheric pressure or higher and can be sealed. However, the pressure glass bottle, the pressure glass tube, the stainless bottle, the stainless tube, the stainless tank, the fluororesin bottle, the pet Examples include bottles and aluminum bottles. The pressure to be pressurized is not particularly limited as long as it is atmospheric pressure or higher, but is preferably in the range of 0.1 MPa to 12 MPa that can be implemented with a gas cylinder or the like, and from atmospheric pressure to 0.1 MPa that can be implemented with a compressor or the like. A range of 1.5 MPa is particularly preferred. In addition, the holding time in the pressurized state is not particularly limited as long as the gas 4 is in the liquid 3 and the gas 4 is in excess of the saturated dissolved amount in the atmospheric pressure environment.

The combination of the particulate material 2 and the particulate material 8 is particularly limited as long as it is a combination of particulate materials that form a film by reaction such as polymerization, condensation, dehydration, cooling and solidification, water absorption, hydration, and hydrolysis when they come into contact with each other. Not, but sodium alginate and calcium chloride, 1,8-octanedicarbonyl chloride and 1,6-hexanediamine, L-lysine and terephthaloyl dichloride, acid chloride (adipic acid chloride, sebacoyl chloride, terephthalic acid chloride, etc. ) And polyamines (1,6 hexamethylenediamine, piperazine, rheridine, etc.), acid chlorides and polyphenols (2,2-bis (4-hydroxyphenyl) propane, etc.), isocyanates (hexamethylene diisocyanate, metaphenylene diisocyanate, Ruylene isocyanate, 2,4-tolylene diisocyanate, 3,3-dimethyl-diphenyl-4,4-diisocyanate, diphenylmethane-4,4 diisocyanate, triphenylmethane-triisocyanate, naphthalene-1,5-diisocyanate, etc.) or Examples include combinations of isothiocyanates (ethyl isothiocyanate, methyl isothiocyanate, benzyl isothiocyanate, allyl isothiocyanate, pyridine-3-isothiocyanate, etc.) and water or polyol or polyamine, polyisocyanate and polyamine, and the like. The liquid 3 in which the particulate material 2 is dissolved or dispersed and the liquid 9 in which the particulate material 8 is dissolved or dispersed are not particularly limited as long as they are liquid at normal temperature and normal pressure. Water, known oils (castor oil, salad oil) , Corn oil, soybean oil, sesame oil, rapeseed oil, safflower oil, coconut oil, palm oil, olive oil, liquid paraffin, silicone oil, etc., known organic solvents (hexane, benzene, toluene, diethyl ether, chloroform, ethyl acetate, Methylene chloride, tetrahydrofuran, acetone, acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, acetic acid, 1-butanol, 2-propanol, 1-propanol, ethanol, methanol, formic acid, etc.) or any gas solubility in liquid Two types of liquids with different gas solubilities Upper combined mixed solution (such as a lower alcohol solution or aqueous polyhydric alcohol solution) is exemplified. Particularly preferred forms are known in at least one of the liquid 3 in which the particle material 2 is dissolved or dispersed or the liquid 9 in which the particle material 8 is dissolved or dispersed in order to improve the stability of coalescence and dispersion stability of the discharged droplets. It is preferable to dissolve the surfactant. Non-ionic, anionic, cationic and zwitterionic types may be used as the surfactant, polyvinyl alcohol, TWEEN 20, TWEEN 80, Triton X-100, sodium dodecyl sulfate, sodium cholate, Examples include sodium deoxycholate, hexadecyltrimethylammonium, bromide cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide and the like. Further, when the particulate material 2 or the particulate material 8 is liquid at normal temperature and normal pressure, the particulate material in a liquid state may be used as it is. Moreover, one particle material of the combination mentioned above should just be enclosed with the pressure vessel 1, and the other material should just be hold | maintained at the reaction tank 7, and whichever may be enclosed with the pressure vessel 1. FIG.

The gas 4 used for pressurization of the pressure vessel 1 is not particularly limited as long as it is a gas at normal temperature and normal pressure, but is not limited to carbon fluoride (0.0043: hereinafter, solubility in water at 25 ° C. ml / ml]), sulfur hexafluoride (0.0054), helium (0.0087), neon (0.010), nitrogen (0.0150), hydrogen (0.018), air (0.0017) , Oxygen (0.029), argon (0.031), hydrocarbon (0.031 to 0.042), nitrogen dioxide (0.074), ozone (0.29), chlorine (0.64), dioxide Carbon (1.1), halogenated hydrocarbon (2.3), sulfur dioxide (31), hydrogen chloride (430), ammonia (610), and multiple gases to arbitrarily change the solubility of the gas in the liquid A mixed gas mixture is illustrated The gas diaphragm pump, gear pump, rotary pump, the interior of the pressure vessel 1 is pressurized by air from the pressure vessel, such as air or gas cylinder according to the tube pump.

The droplet forming means 5 is not particularly limited as long as the liquid 3 can be discharged into the atmosphere as an independent droplet 6 having a volume sphere equivalent diameter of 1 mm or less. It is appropriately selected from known droplet forming means such as spray nozzles and ink jet generating nozzles.

The reaction tank 7 that holds the liquid 9 in which the particulate material 8 is dissolved or dispersed is not particularly limited as long as the liquid can be held. Bottles, beakers, flasks using solid materials such as glass, metal, earthenware, and resin A water tank etc. are illustrated. Although not essential, temperature control means exemplified by hot plates, cool stirrers, heat exchangers, oil baths, etc., magnetic stirrers, vortex mixers, and homogenizers are used to control the temperature of the film formation reaction environment. It is desirable to provide the reaction tank 7 with means such as these.

The distance between the position where the droplet forming unit 5 forms the droplet and the liquid 9 is not particularly limited as long as the shape of the droplet 6 changes due to the surface tension of the liquid 3. A range of 1 cm to 500 cm, which is easy to form and collect, is desirable, and a range of 10 cm to 100 cm is particularly desirable.

EXAMPLES Hereinafter, although this invention is further demonstrated based on an Example, this invention is not limited to this.

Place 10 mL of 1% sodium alginate aqueous solution in a 300 mL stainless steel pressure vessel, pressurize to 5 atm with oxygen (water solubility at 25 ° C .: 0.029 mL / mL), pressurize for 30 minutes, dissolve oxygen in 1% sodium alginate aqueous solution Let Pressurized 1% sodium alginate aqueous solution is formed into droplets using a K-12 type circular full surface spray nozzle (Katori Gumi Seisakusho) with an inner diameter of 2.0 mm and separated from the discharge port to the 1% calcium chloride aqueous solution surface by 100 cm into a 5000 mL beaker. Release into 400 mL of retained 1% aqueous calcium chloride solution. The 1% sodium alginate aqueous solution and the 1% calcium chloride aqueous solution form a gel-like insoluble film at the contact interface with each other, and many calcium alginate gel particles are generated in a 5000 mL beaker. In addition, the 1% sodium alginate aqueous solution pressurized with oxygen inside the pressurized container is foamed under reduced pressure when forming droplets or gelling under an atmospheric pressure environment to form a gas phase region in the calcium alginate gel particles. .

As shown in FIG. 2, the calcium alginate gel particles prepared through the above series of steps have a hollow ratio of 17.5% having a single or plural cavities having an outer diameter of 15 μm to 200 μm and an inner diameter of 5 μm to 150 μm. As a result, particles having a circularity of 0.85 were confirmed.

The gas to be pressurized was changed to argon (solubility at 25 ° C. in water: 0.031 mL / mL) and prepared in the same manner as in Example 1. As a result, the outer diameter was 15 μm to 200 μm and the inner diameter was 5 μm to 150 μm. A calcium alginate gel particle having a hollow ratio of 13.4% having a plurality of cavities was confirmed.

The gas to be pressurized was changed to nitrogen (solubility at 25 ° C. in water: 0.015 mL / mL) and prepared in the same manner as in Example 1. As a result, the outer diameter was 15 μm to 200 μm, and the inner diameter was 5 μm to 150 μm. Calcium alginate gel particles having a plurality of cavities and a hollowness of 24.6% were confirmed.

The gas to be pressurized was changed to sulfur hexafluoride (water solubility at 25 ° C .: 0.0055 mL / mL) and prepared in the same manner as in Example 1. As a result, the outer diameter was 15 μm to 200 μm and the inner diameter was 5 μm to 150 μm. A calcium alginate gel particle having a hollow ratio of 47.5% having single or plural cavities was confirmed.

FIG. 3 shows a graph in which the horizontal axis represents the solubility in Examples 1 to 4 and the vertical axis represents the average hollowness of the generated calcium alginate gel particles. As shown in FIG. 3, as the solubility increases, the void ratio decreases, and a single composition gas or a plurality of gases having different solubility as appropriate using the following equation (1) and the approximate curve shown in FIG. It is possible to control the hollow ratio of the hollow particles in the range of 0 to 55% by using an air-fuel mixture in which. In the formula (1), y means the hollow ratio [%] of the hollow particles, and x means the solubility [mL / mL].

The pressure applied was changed to 2 atm, and the same preparation as in Example 1 was performed. As a result, the outer diameter was 15 μm to 200 μm and the inner diameter was 53.8 μm to 150 μm and the average diameter was 73.8 μm. Calcium alginate gel particles were confirmed.

The pressure to be applied was changed to 10 atm. As a result of the same preparation as in Example 1, the outer diameter was 15 to 200 μm, and the inner diameter was 55.6 to 150 μm with an average diameter of 45.6 μm. Calcium alginate gel particles were confirmed.

FIG. 4 shows a graph in which the pressurization pressure in Example 1, Example 5 and Example 6 is the horizontal axis and the average particle diameter of the generated calcium alginate gel particles is the vertical axis. As shown in FIG. 4, the average particle diameter decreases as the pressurizing pressure increases. By adjusting the pressure appropriately using the following equation (2) and the approximate curve shown in FIG. 4 as an index, 15 μm to 80 μm It is possible to control the average particle diameter of the hollow particles in the range of. In the formula (2), y means the average particle diameter [μm] of the hollow particles, and x means the pressurized pressure [atmospheric pressure].

The distance from the spray nozzle outlet to the 1% calcium chloride aqueous solution surface was changed to 10 cm, and the same preparation as in Example 1 was carried out. As a result, as shown in FIG. Calcium alginate gel particles were confirmed.

From the results of Example 1 and Example 7, since the circularity of the spherical particles is higher as the distance from the discharge port to the surface of the 1% calcium chloride aqueous solution is increased, the sprayed droplets can be sufficiently collected. By changing the distance from the outlet of the spray nozzle to the surface of the 1% calcium chloride aqueous solution within the range, it is possible to control the circularity of the generated hollow particles in the range of 0.5 to 1.

Since the hollow particles obtained in the present invention can easily give a hollow structure to the inside of the particles, the application to industrial materials that absorb changes in thermophysical properties, sound and impact, and the texture of the hollow structure. It can be used for various purposes such as application to food that can be changed, application to cosmetics that can change the touch and texture, application to pharmaceuticals such as contrast media using signals by acoustic characteristics In addition, since the internal hollowness, particle diameter, and shape can be appropriately changed, it is possible to provide optimum particles.

Claims (8)

In two different liquids having the characteristic of forming a film at the contact interface, when one liquid is supplied into the other liquid as a droplet and the film is formed at the droplet interface to form particles, the gas is formed before the droplet is formed. A hollow particle characterized in that a hollow structure is imparted by dissolving a gas in a liquid that becomes a droplet by being pressurized to atmospheric pressure or higher and foaming under reduced pressure inside the droplet when the droplet is formed In two different liquids having the characteristic of forming a film at the contact interface, a pressure vessel capable of holding one liquid and a gas and holding it at atmospheric pressure or higher, a reaction vessel holding the other liquid, and the pressure vessel The apparatus for producing hollow particles according to claim 1, further comprising droplet forming means for supplying the liquid in the form of fine droplets into the reaction vessel. 3. The hollow particle production apparatus according to claim 1 and the hollow particle production apparatus according to claim 2, wherein the droplet forming means is a discharge of liquid from pores having an equivalent diameter of 5 mm or less of an opening cross-sectional area. The hollow particle according to claim 1 and the production of the hollow particle according to claim 2, wherein a surfactant is contained in at least one liquid of two different liquids having the characteristic of forming a film at the contact interface. apparatus The hollow ratio of the hollow particles according to any one of claims 1 to 4 (total volume of cavities inside the particles), wherein the solubility of the gas pressurized in the pressure vessel in the liquid to be the droplets is changed / External volume of particles). The means for changing the solubility of the gas in the liquid is any one of a change of the gas type, a mixture of two or more types of gas, a change of the liquid type, and a mixture of two or more types of liquid. The method for controlling the hollow ratio of the hollow particles according to claim 5. The method for controlling the degree of circularity of hollow particles according to any one of claims 1 to 4, wherein a distance between the droplet forming means and a liquid level held in the reaction vessel is changed. The method for controlling the particle size of the hollow particles according to any one of claims 1 to 4, wherein the pressure applied by the pressure vessel is changed.