JP2017029876A - Hollow particle made from bubbles and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably generate a large number of hollow particles without the removal of core materials.SOLUTION: The present invention provides a hollow particle generation method for forming a solid membrane at the gas-liquid boundaries of bubbles generated by blowing a gas including monomers into a liquid, wherein, an ozone gas is contained in the gas including monomers to stably produce a large number of fine hollow particles.SELECTED DRAWING: Figure 5

Description

The present invention relates to a hollow particle manufactured using an interface of bubbles and a manufacturing method thereof.

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 adjusting the specific gravity of materials, soundproofing materials, heat insulating materials, etc. It is also used for tracers that visualize the flow on the surface of liquid by utilizing the characteristics of floating in the liquid. In recent years, advanced medical research using hollow particles as a medical material such as a contrast agent for ultrasonic diagnosis and a drug transport carrier for drug delivery has been performed using the frequency response of the hollow particles to ultrasonic waves.

As a conventional method for producing hollow particles, particles containing liquid or solid are generated, and the liquid or solid inside is extracted and hollowed (see Patent Documents 1 and 2), or particles containing liquid or solid are used. There is a technique (refer to Patent Document 3) in which heat expansion is vaporized to make it hollow.

In addition, as a method of directly creating hollow particles using bubbles, a method of polymerizing substances in the liquid phase on the surface of the bubbles to produce a solid film to form hollow particles (see Patent Document 4), A method in which polymerization of a substance is promoted by a gas phase catalyst to form hollow particles (see Patent Document 5), and a film is deposited by drying the liquid droplets while keeping the bubbles stably dissolved in the film raw material. For example, there is a method of forming hollow particles while having a hollow structure (see Patent Document 6).

Japanese National Patent Publication No. 9-508067 JP 2002-105104 A 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 Laying-Open No. 2015-85251 JP 2011-50832 A

Journal of Fluid Mechanicals, 548 (2006), pp. 113-131. Materials Letters, 63 (2009), pp. 703-705. Ultrasonics, 53 (2013), pp. 196-202.

In the above-mentioned background art, the method of removing the inclusion substance from the particles containing the liquid or solid and making it hollow is difficult to control the pressure and heat in the hollowing process using evaporation and expansion of the inclusion substance, The problem is that particle deformation and surface damage are likely to occur.

In addition, in the method using bubbles in the background art described above, the hollowing process is not required, so that hollow particles can be easily produced. However, the raw material to be a solid film is dissolved and dispersed in the liquid phase. Therefore, it is a problem that the portion other than the vicinity of the bubble interface is not effectively used as a solid film of hollow particles.

In order to solve such problems, the present inventor previously described "a method for producing hollow particles by forming a solid film at a gas-liquid interface of bubbles generated by blowing a gas containing a monomer into a liquid". (Patent Document 7, Patent Document 8)

According to the method of the inventors, a large amount of hollow structure particles having a diameter of about 1 μm to 200 μm can be generated in a short time. However, in the process of blowing the monomer gas into the liquid, the monomer gas is easily clogged by polymerization in the vicinity of the gas outlet of the fine bubble generating means. For example, in the method described in Patent Document 7, it takes about 15 to 20 minutes. The gas supply tube was clogged and the generation of bubbles was stopped, and continuous hollow structure particles could not be generated.

In the method of producing hollow particles by directly blowing bubbles containing monomer gas into a liquid to produce hollow particles, the present invention suppresses polymerization before microbubble formation by mixing ozone gas with monomer gas, The problem is to solve the problems of the prior art.

As a result of intensive studies to achieve the above object, the inventors of the present invention have already proposed ozone gas to a gas containing a monomer gas in the method described in Japanese Patent Application Laid-Open No. 2011-245452 (Patent Document 7). It was found that by mixing, clogging due to polymer formation in the gas flow path that feeds the fine bubble generating means that turns into fine bubbles in the liquid is suppressed, and minute hollow particles can be generated continuously and in large quantities. .

With the particles having a hollow structure according to the present invention, the following effects can be obtained. In the present invention, a hollow particle produced using an interface between bubbles and a method for producing a hollow particle described in JP-A-2011-244542 (Patent Document 7) by mixing ozone gas into a gas containing monomer gas in the production method. On the other hand, it is possible to prevent clogging of the flow path for supplying the air-fuel mixture and to improve the yield by 8 times or more in volume concentration.

It is the figure which showed the apparatus structure of this invention. It is a photograph showing the generation state of fine bubbles by ultrasonic waves. 2 is an electron microscope image of hollow particles obtained in Example 1. FIG. 2 is a particle size distribution of hollow particles produced in Example 1. 3 is an electron microscope image of hollow particles obtained in Example 2. FIG. 2 is a particle size distribution of hollow particles produced in Example 2. It is an electron microscope image of the hollow particles obtained in the comparative example. It is a particle size distribution of the hollow particle produced | generated by the comparative example. It is a photograph of the gas inlet and outlet of a hollow ultrasonic horn after producing hollow particles in Examples 1 and 2 and a comparative example.

In the hollow particle produced using the bubble interface in the present invention and the production method thereof, a gas containing monomer gas and ozone gas is supplied as a bubble into the liquid using a known fine bubble generation method, and the monomer gas on the bubble surface And a liquid come into contact with each other, a film formation reaction occurs, and hollow particles in which a gas is covered with a solid film are generated. 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, a mixed gas 4 of a supply gas 1 containing ozone gas and a monomer gas obtained by vaporizing the monomer 3 in the vaporization vessel 2 is used as a bubble generating means 6 using an air supply means 5. The bubbles 9 containing the gas obtained by vaporizing the monomer 3 by the bubble generating means 6 are generated in the liquid 8 maintained at a suitable temperature by the temperature adjusting means 7. In the bubbles 9 generated in the liquid 8, the monomer gas in the bubbles and the liquid 8 contact and solidify at the interface, whereby a solid film is formed on the surface of the bubbles, and the hollow particles 10 are generated and floated.

The vaporization vessel 2 is particularly limited as long as it has a function capable of holding the monomer 3 in the vessel and holding it, and vaporizing it by heating the monomer 3 above the boiling point or reducing the vapor pressure below the vapor pressure by a known heating or decompression means. Rather, a method of heating or depressurizing a glass or metal container with an alcohol lamp, a gas burner, a hot plate, an oil bath or the like with a vacuum pump or the like is exemplified. The vaporization container 2 is not essential when the monomer 3 is a gas at normal temperature.

The monomer 3 only needs to be reactive with the liquid 8 or a component dissolved in the liquid 8, and as a combination of the monomer 3 and the liquid 8, a cyanoacrylate composition, water, a silicone composition, Examples include water, a moisture-curable urethane composition and water, a lower aliphatic hydrocarbon containing an olefinic hydrocarbon and a catalyst, and the like. In addition, the time required for film formation in the combination is preferably longer than the time required for generating bubbles and shorter than the time required for bubbles to disappear due to dissolution or floating from the viewpoint of preventing clogging and disappearance of the reaction interface. More specifically, the range of the film formation time is 50 microseconds or more, which is a standard time for bubble generation by 20 kHz ultrasonic waves (see Non-Patent Document 1), and 4 hours or less in which bubbles can stably exist in a liquid (non- (See Patent Document 2). However, the time required for the generation of bubbles is limited to the above range because the bubble generation device, the time for the bubbles to disappear by dissolution or floating is greatly affected by the environment surrounding the bubbles, such as the solubility of the bubble inclusion component in the liquid and the viscosity of the liquid. Is not to be done.

The concentration of the monomer gas in the mixed gas 4 is not particularly limited as long as it contains the monomer gas.

The gas supply means 5 is not particularly limited as long as it can supply the bubble generating means 6 with a mixed gas 4 of a gas obtained by vaporizing the supply gas 1 containing ozone gas and the monomer 3, and a diaphragm pump, a gear pump, a rotary pump, a tubing pump, etc. Is exemplified. Further, when the supply gas 1 is pressurized and supplied, the air supply means 5 is not essential.

The fine bubble generating means 6 is not particularly limited as long as it is a method capable of supplying the mixed gas 4 as bubbles into the liquid 8, and a method of jetting gas into the liquid through a tube having a micropore or a porous body. Examples include a method in which a gas phase is engulfed in a liquid phase using a shear force generated in a jet flow or a swirling flow, and a method in which a gas-liquid interface is vibrated using ultrasonic waves to generate fine bubbles. As a particularly preferred example, a method of generating fine bubbles using a hollow ultrasonic horn that is unlikely to be clogged due to a film formation reaction because fine bubbles are instantaneously generated in an ultrasonic cycle (Patent Document 9). Non-patent document 3).

The temperature adjusting means 7 is not particularly limited as long as the temperature of the liquid 8 can be prevented from flowing through the mixed gas or the bubble generating means, and examples thereof include a cool stirrer, a heat exchanger, and a cooling block. Further, the temperature of the liquid 8 is preferably lowered from room temperature in order to promote condensation of the monomer, and is preferably 15 ° C. or less.

The liquid 8 is not particularly limited in configuration as long as it contains a component or catalyst that reacts with the monomer 3, a liquid composed of only the reaction component or catalyst, a solution in which the reaction component or catalyst is dissolved in the solvent, a solvent Any state such as an emulsion in which a reaction component or a catalyst is emulsified and dispersed may be used. The liquid 8 preferably contains a surfactant in order to refine and stabilize the bubbles. 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, deoxycholic acid, hexadecyltrimethylammonium, bromidecetyltrimethylammonium bromide, dodecyltrimethylammonium bromide and the like. Moreover, about the pH environment of the said liquid 8, it is preferable to add a pH adjuster to the said liquid 8, and to make it pH 7 or less, More preferably, it is desirable to make it pH 4 or less. Examples of the pH adjusting agent include citric acid, acetic acid, hydrochloric acid, hypochlorous acid, sulfuric acid, nitric acid, fluorosulfonic acid, phosphoric acid, boric acid, benzenesulfonic acid, formic acid, lactic acid, oxalic acid, tartaric acid, ascorbic acid, etc. Is done.

The gas phase components inside the hollow particles 10 that are finally generated can be changed depending on the components of the supply gas 1 containing the ozone gas. The supply gas 1 containing the ozone gas is not particularly limited as long as ozone gas is contained in the gas phase gas at normal temperature and pressure, and air, hydrogen, nitrogen, oxygen, chlorine, fluorine, rare Examples include gas, carbon dioxide, ammonia, sulfur dioxide, hydrogen chloride, nitrogen dioxide, sulfur fluoride, hydrocarbons, halogenated hydrocarbons, and a gas in which ozone gas is mixed with a mixture of a plurality of the gases. The concentration in the supply gas 1 containing the ozone gas is not particularly limited as long as ozone is contained, but a preferable ozone concentration is 0.1 ppm or more, particularly preferably 1 ppm or more. The supply means of the supply gas 1 containing ozone gas is not particularly limited, and examples thereof include air supply using a high-pressure cylinder, a diaphragm pump, a gear pump, a rotary pump, and a tubing pump.

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

4 g of ethyl cyanoacrylate is sealed in a 50 mL Erlenmeyer flask provided with a gas inlet and a mixed gas outlet, and heated and stirred by a hot stirrer at 250 ° C. to generate ethyl cyanoacrylate vapor. The generated ethyl cyanoacrylate vapor is sent to the microbubble generator together with dry air containing 50 ppm of ozone taken in from the gas inlet, and maintained at 12 ° C. by the cooling water circulating device in a 500 mL beaker capable of circulating cooling water. Fine bubbles are generated by discharging from a hollow ultrasonic horn into 400 mL of 0.02% sodium deoxycholate aqueous solution. The hollow ultrasonic horn is equipped with a spray nozzle with a nozzle inner diameter of 6 mm. It vibrates at a frequency of 15 kHz and an amplitude of 40 μm (Peak to Peak). It becomes. When ethyl cyanoacrylate comes into contact with water at the bubble interface in a 0.02% sodium deoxycholate aqueous solution, a polymerization reaction starts to form a solid film, and fine hollow particles are generated. In addition, due to the formation and dispersion of hollow particles, the transparent aqueous phase becomes cloudy with time. FIG. 3 shows an electron microscope image of the spherical particles in the aqueous phase that has become cloudy by the operation shown in Example 1. Since hollow particles having a size of 10 μm or less can be confirmed as shown in FIG. 3, it was confirmed that hollow particles having a size of 10 μm or less containing air taken in from the air suction port were confirmed. In Example 1, preparation for 20 minutes or more is possible without clogging, and the particle volume concentration in the hollow particle dispersion at 20 minutes is 0.10 vol%, as shown in the distribution shown in FIG. Particles having a hollow structure in the range of 0.8 to 100 μm were produced, and the average diameter in number was 1.69 μm.

In the step of producing particles having a hollow structure in Example 1, particles having a hollow structure were produced using the aqueous solution in which 0.2 g of tartaric acid was added to 400 mL of sodium deoxycholate and the pH was 3.5. Also in Example 2, the transparent aqueous phase becomes cloudy with time due to the generation and dispersion of particles having a hollow structure. FIG. 5 shows an electron microscope image of the spherical particles in the aqueous phase that has become cloudy by the operation shown in Example 2. As shown in FIG. 5, since particles having a hollow structure having a size of 1 μm or less can be confirmed, it was confirmed that hollow particles containing air taken in from the gas inlet were produced. Further, in Example 2, preparation for 20 minutes or more is possible without clogging, and the particle volume concentration in the hollow particle dispersion at the time of 20 minutes is 0.41 vol%, as shown in the distribution shown in FIG. Particles having a hollow structure in the range of 0.3 to 100 μm were produced, and the average diameter in number was 0.66 μm.

In the example (comparative example) created in the range described in Patent Document 7 by changing the gas taken in from the gas suction port in Example 1 to dry air not containing ozone, the image shown in FIG. 7 and FIG. 8 are shown. Although particles having a hollow structure of 1.34 μm on average were generated in the particle size range of 0.7 to 600 μm, clogging occurred in 18 minutes and the generation of bubbles stopped. At this time, in the ultrasonic horn, a cyanoacrylate resin adheres to the inside of the joint as shown in FIG. 9 or a lump is generated in the gas discharge port in the vicinity of the joint portion for introducing the gas and the gas discharge port for discharging the gas into the liquid. On the other hand, in Example 1 and Example 2 in which the gas containing ozone gas was supplied, the generation of bubbles was stable even after 20 minutes, and the inside of the joint of the cyanoacrylate resin as shown in FIG. Almost no adhesion was observed, and clogging due to solidification of the supplied monomer and plugging of the inside was possible. In addition, the particle volume concentration in the hollow particle dispersion which became cloudy in 18 minutes when clogging occurred was 0.013 vol%. Therefore, the yield improvement of Example 1 was confirmed to be 8 times that of the Comparative Example, and Example 2 was confirmed to be 31.5 times that of the Comparative Example.

The hollow particles obtained in the present invention do not dissolve the material in the liquid, but supply it as a gas inside the bubble, so that the material can be selectively supplied to the bubble surface as a reaction field. In addition, it is easy to adjust the film thickness and specific gravity by changing the concentration of monomer gas and supply gas contained in the bubbles, so heat insulation, soundproofing material, heat sensitive material, cushioning material, weight reduction material, shock absorber, optical It is effective for various applications such as materials, paints, cosmetics, and pharmaceuticals. For example, cyanoacrylate used in Examples 1 and 2 is a material that is also used for medical purposes, and can be expected to be used as an ultrasound contrast agent by utilizing the acoustic characteristics of the hollow structure.

DESCRIPTION OF SYMBOLS 1 Supply gas containing ozone gas 2 Vaporization container 3 Monomer 4 Mixed gas 5 Air supply means 6 Bubble generation means 7 Temperature adjustment means 8 Liquid 9 Bubble 10 Hollow particle

Claims (5)

A method for producing hollow particles, wherein a gas containing ozone gas and a monomer is blown into a liquid to generate bubbles, and a solid film is formed by contacting the monomer and the liquid at a gas-liquid interface of the bubbles. A device for producing hollow particles, comprising: a supply means for a gas containing ozone gas and a monomer; and a fine bubble generating means for making the gas into fine bubbles. The method for producing hollow particles according to claim 1 or the apparatus for producing hollow particles according to claim 2, wherein the pH of the liquid for generating bubbles is maintained on the acidic side of 7 or less. The method for producing hollow particles according to claim 1 or the apparatus for producing hollow particles according to claim 2, wherein a surfactant is contained in a liquid that generates bubbles. Hollow particles produced by the method or apparatus according to any one of claims 1 to 4.