Method for producing coated photochromic fine particles and apparatus for producing coated photochromic fine particles using the same

Abstract

To provide a manufacturing method of covered photochromic fine particles capable efficiently manufacturing desired photochromic fine particles, irrespective of kind of a photochromic compound used and a manufacturing unit of the covered photochromic fine particles using the same.SOLUTION: A method of manufacturing covered photochromic fine particles of the present invention comprises a step of preparing an O / W emulsion by directly irradiating a preliminary mixture of a photochromic core particle, a polymer, a polar solvent and a low polar organic solvent with a direct ultrasonic wave, and a step of mixing the O / W emulsion with a supercritical fluid in an occluded container, and a step of opening an inside the closed container.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a method for producing coated photochromic fine particles and an apparatus for producing coated photochromic fine particles using the same.

Background Art

[0002] A photochromic compound (also referred to as a photochromic dye) has the property of being colored or changing its color tone by light irradiation and returning to its original state by heat or light of a different wavelength, and is widely used in, for example, dimming lenses.

[0003] On the other hand, although it has been proposed to use such a photochromic compound for a photosensitive nanodevice, it is in a difficult situation to be realized. This is because it is possible to produce capsules having a diameter of about several millimeters using a photochromic compound, but it is difficult to produce fine capsules or composites having a diameter of about several hundred nanometers.

[0004] As a technique for micronizing a photochromic compound, for example, Patent Documents 1 to 4 are known.

[0005] Patent Document 1 discloses a method in which an O / W emulsion containing a photochromic dye is formed and then the photochromic dye in the emulsion is polymerized to be micronized. However, the fine particles obtained by the method of Patent Document 1 have a drawback that the surface is not coated with a polymer, and thus the stability is lost depending on the type of the photochromic dye. Patent Document 2 discloses a method for producing a photochromic composite material through the sol-gel method. However, since the method of Patent Document 2 involves multiple steps such as hydrolysis, condensation, and drying, it lacks industrial productivity in that it takes a long time to obtain the desired fine particles. Regarding Patent Document 3, it discloses a method of inserting one or more organic photochromic coloring agent molecules into a transparent polymer-like plastic material having nano-sized pores to form a photochromic nanocomposite material. However, in the method of Patent Document 3, the types of photochromic coloring agent molecules that can be used are limited to organic photochromic compounds, and there is a drawback in that the selectivity is poor. Regarding Patent Document 4, it describes a method of preparing a nanoemulsion containing a photochromic dye and then coating the surface with a polymer such as silicate by a chemical reaction. However, the method of Patent Document 4 lacks industrial productivity in that it takes about two days to dry the organic solvent used.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention aims to solve the above problems, and its object is to provide a method for producing coated photochromic fine particles and a production apparatus for coated photochromic fine particles that can efficiently produce desired photochromic fine particles regardless of the type of photochromic compound used.

Means for Solving the Problem

[0008] The present invention relates to a method for producing coated photochromic fine particles, comprising: a step of directly irradiating ultrasonic waves to a preliminary mixture of photochromic core material particles, a polymer, a polar solvent, and a low-polarity organic solvent to prepare an O / W emulsion; a step of mixing the O / W emulsion with a supercritical fluid in a closed container; and a step of opening the inside of the closed container. It is a method including these steps.

[0009] In one embodiment, the supercritical fluid is supercritical carbon dioxide.

[0010] In one embodiment, the low-polarity organic solvent is at least one solvent selected from the group consisting of toluene and hexane.

[0011] In one embodiment, the polymer is a thermoplastic resin.

[0012] In a further embodiment, the thermoplastic resin is polystyrene.

[0013] In one embodiment, the mixing step is performed at a temperature of 35°C to 55°C.

[0014] In one embodiment, the ultrasonic irradiation is performed by a horn-type ultrasonic vibrator.

[0015] In a further embodiment, the ultrasonic waves are irradiated in a uniaxial direction with respect to the preliminary mixture.

[0016] The present invention also relates to a production apparatus for coated photochromic fine particles, comprising: ultrasonic irradiation means for directly irradiating ultrasonic waves to a preliminary mixture of photochromic core material particles, a polymer, a polar solvent, and a low-polarity organic solvent to prepare an O / W emulsion; and A closable container in which the O / W emulsion and the supercritical fluid are mixed; is a device comprising.

Advantages of the Invention

[0017] According to the present invention, nano-order fine particles can be efficiently processed from a photochromic compound. Thereby, the industrial low productivity of the photochromic fine particles can be enhanced.

Brief Description of the Drawings

[0018]

Figure 1

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Figure 4

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Figure 8

Mode for Carrying Out the Invention

[0019] (Method for Producing Coated Photochromic Fine Particles) In the method for producing the coated photochromic fine particles of the present invention, first, an O / W emulsion is prepared from a preliminary mixture.

[0020] The preliminary mixture contains photochromic core material particles, a polymer, a polar solvent, and a low-polarity organic solvent.

[0021] The photochromic core material particles in the present invention are materials (core materials or core substances) that can constitute the core of the coated photochromic fine particles, and are solids containing a photochromic compound.

[0022] Photochromic compounds are roughly classified into P-type compounds that return to their original structure by irradiation with light of another wavelength after the molecular structure changes by light irradiation, and T-type compounds that return to their original structure by a thermal reaction. The photochromic core material particles in the present invention may contain either P-type or T-type photochromic compounds. Examples of the photochromic compound include, but are not necessarily limited to, azobenzene-based compounds, spiropyran-based compounds (e.g., naphthopyran), fulgide-based compounds, fulgimide-based compounds, and diarylethene-based compounds. Such photochromic core material particles can be obtained, for example, by pulverizing a cured product of a commercially available photochromic material (monomer) containing various photochromic compounds.

[0023] The size (average particle diameter) of the photochromic core material particles is not necessarily limited, but may be larger than the size (average particle diameter) of the coated photochromic fine particles that can ultimately be produced. For example, it has an average particle diameter of 1 μm to 500 μm, preferably 10 μm to 100 μm. When the average particle diameter of the photochromic core material particles is less than 1 μm, it is difficult to produce because the particles themselves are nanoparticles. When the average particle diameter of the photochromic core material particles exceeds 500 μm, the photochromic core material particles may not be sufficiently dissolved in the oil phase, and the average particle diameter of the resulting coated photochromic fine particles may vary. The shape of the photochromic core material particles is also not necessarily limited. For example, it may be any of spherical, ellipsoidal, disc-shaped, scaly, columnar, polyhedral, irregular three-dimensional shapes, and other arbitrary three-dimensional shapes.

[0024] The amount (concentration) of the photochromic core material particles contained in the closed container described later varies depending on the type of the photochromic core material particles and the like, and is not necessarily limited. For example, it is 0.01 (w / v)% to 1 (w / v)%. By containing the photochromic core material particles in such a range in the closed container, the coated photochromic fine particles can be efficiently produced in the closed container.

[0025] The polymer contained in the preliminary mixture is a resin that has an affinity for the supercritical fluid described later and can form an interface with the supercritical fluid. Such a polymer is a material that can coat a part or all of the surface of the photochromic core material particles, and is preferably a thermoplastic resin. Examples of the thermoplastic resin that can be used include polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polyurethane, ABS (acrylonitrile-butadiene-styrene) resin, and combinations thereof. Polystyrene is preferred because it has a high affinity for supercritical carbon dioxide that can be used as the supercritical fluid described later, and the average particle diameter of the resulting coated photochromic fine particles is stable.

[0026] The content of the polymer contained in the preliminary mixture is not necessarily limited, but is preferably 10 parts by mass to 100 parts by mass, more preferably 40 parts by mass to 60 parts by mass, based on 100 parts by mass of the above photochromic core material particles. When the content of the polymer contained in the preliminary mixture is less than 10 parts by mass, a sufficient coating cannot be formed on the photochromic core material particles, and depending on the type of the photochromic dye constituting the core material particles, stability may be lost due to leakage of the components from between the coatings. When the content of the polymer contained in the preliminary mixture exceeds 100 parts by mass, the polymer becomes excessive with respect to the photochromic core material particles, which may reduce industrial productivity.

[0027] The polar solvent is water, and the water can function as an aqueous phase for preparing an O / W emulsion. Specific examples of the water include ultrapure water, pure water, ion-exchanged water, distilled water, and the like. Considering performing emulsion extraction with a supercritical fluid using the SFEE (Supercritical Fluid Extractions of Emulsion) method, it is preferable to use ultrapure water.

[0028] The content of the polar solvent contained in the preliminary mixture is not necessarily limited, but is preferably 5000 parts by mass to 30000 parts by mass, more preferably 15000 parts by mass to 20000 parts by mass, based on 100 parts by mass of the above photochromic core material particles. When the content of the polar solvent contained in the preliminary mixture is less than 5000 parts by mass, it becomes difficult to form an O / W emulsion over all the added materials, which may reduce industrial productivity. When the content of the polar solvent contained in the preliminary mixture exceeds 30000 parts by mass, the concentration of the prepared O / W emulsion becomes low, and it may not be possible to obtain coated photochromic fine particles in a sufficient yield.

[0029] Low-polarity organic solvents, also known as non-polar organic solvents, include organic solvents with lower polarity than water, which is a polar solvent. Low-polarity organic solvents can function as the oil phase for preparing O / W emulsions. Specific examples include toluene, hexane, dioxane, tetrahydrofuran, and combinations thereof. Toluene, hexane, and combinations thereof are preferred because of their high affinity with supercritical fluids and high extraction yields of low-polarity organic solvents in the SFEE (Superctitical Fluid Extractions of Emulsion) method.

[0030] The content of the low-polarity organic solvent contained in the preliminary mixture is not necessarily limited, but is preferably (500 parts by mass to 3000 parts by mass, more preferably 1500 parts by mass to 2000 parts by mass) with respect to 100 parts by mass of the above photochromic core material particles. When the content of the low-polarity organic solvent contained in the preliminary mixture is less than 500 parts by mass, an O / W emulsion may not be formed, and it may be difficult to obtain the desired coated photochromic fine particles. When the content of the low-polarity organic solvent contained in the preliminary mixture exceeds 3000 parts by mass, the amount of the low-polarity organic solvent contained in the obtained O / W emulsion becomes excessive, the extraction time of the low-polarity organic solvent in the SFEE method becomes long, and the industrial production efficiency may be deteriorated.

[0031] It should be noted that it is preferable that a small amount of surfactant is contained in the preliminary mixture. The content of the surfactant contained in the preliminary mixture is not particularly limited, and an appropriate amount can be appropriately selected by those skilled in the art.

[0032] The photochromic core material particles, polymer, polar solvent, low-polarity organic solvent, and surfactant added as required may be combined in any order, and then stirring or the like may or may not be performed as required.

[0033] The preparation of the O / W emulsion is carried out by directly irradiating the above preliminary mixture with ultrasonic waves.

[0034] In the present invention, an O / W emulsion can be prepared, for example, by adding a preliminary mixture into a predetermined container and directly irradiating the preliminary mixture with ultrasonic waves to promote stirring of the preliminary mixture, thereby promoting the formation of micelles at the interface between the oil phase and the water phase, and wrapping the oil phase with the micelles. That is, an oil-in-water emulsion is prepared.

[0035] The ultrasonic waves are directly irradiated onto the preliminary mixture through the vibrating part of an ultrasonic vibrator introduced so as to be in contact with the preliminary mixture. Here, the term “direct irradiation (of ultrasonic waves)” used in the present specification refers to directly irradiating an object (preliminary mixture) with ultrasonic waves emitted from an ultrasonic vibrator without passing through other members. In the present invention, by directly irradiating the preliminary mixture with ultrasonic waves, the particle size of the particles constituting the O / W emulsion can be reduced to, for example, the order of 1 percent, as compared with the case of irradiating ultrasonic waves through other members.

[0036] In the present invention, it is preferable that the ultrasonic waves are irradiated onto the preliminary mixture in a uniaxial direction. When the ultrasonic waves are irradiated in a uniaxial direction, convection (eddy current) is promoted in the preliminary mixture along with the irradiation, and as a result, the entire preliminary mixture can be efficiently stirred. For the reason that such convection of the preliminary mixture can be easily formed, it is preferable to use a horn-type ultrasonic vibrator as the ultrasonic vibrator.

[0037] In a horn-type ultrasonic vibrator, electrical energy amplified to, for example, 20 kHz by a solid-state power supply (power source) can be converted into mechanical vibrations in a uniaxial direction (longitudinal direction) by a converter, and the converted mechanical vibrations can be transmitted to the horn as ultrasonic vibrations. The ultrasonic vibrations become pressure waves and can perform continuous formation and attenuation (cavitation) of innumerable extremely small bubbles due to local pressure drops in the solution (fluid) in a uniaxial direction. Such a horn-type ultrasonic vibrator is preferably arranged along the vertical direction in a closed container in order to more easily generate convection of the preliminary mixture (that is, eddy current of the preliminary mixture based on the gravitational direction).

[0038] The frequency of the ultrasonic wave is preferably 15 kHz to 25 kHz, more preferably 19 kHz to 21 kHz. By being within the above range, the formation efficiency of the O / W emulsion can be further improved. The ultrasonic irradiation may be performed once, or may be performed in multiple times with appropriate intervals.

[0039] In this way, an O / W emulsion is prepared from the above-mentioned preliminary mixture.

[0040] Next, in the present invention, the O / W emulsion and the supercritical fluid are mixed in a closed container.

[0041] The closed container in the present invention is a container that can contain the O / W emulsion and the supercritical fluid in a closed state, and is a container capable of repeating closing and opening (i.e., an openable and closable container), and examples thereof include a high-pressure cell, a pressure-resistant cell, and an autoclave of a supercritical device. The capacity that the closed container can accommodate is not particularly limited, and a container having an appropriate capacity can be arbitrarily selected by those skilled in the art.

[0042] The supercritical fluid refers to a fluid composed of a certain substance in a supercritical state, which has both the diffusibility of a gas and the solubility of a liquid.

[0043] Here, the term "supercritical state" used in this specification refers to a state in which a certain substance is placed in a temperature and pressure region above the critical point. In contrast, the subcritical state refers to a state in which a certain substance is placed in a region near the critical point and slightly lower. The liquid state refers to a state in which a certain substance is placed at a temperature lower than the supercritical or subcritical state. These states can be changed by controlling the pressure or temperature. High pressure means a pressure higher than atmospheric pressure (i.e., exceeding 0.1 MPa), and is a high pressure at which a substance can be in a supercritical state, a subcritical state, or a liquid state. The high pressure can vary depending on the type of substance used as the fluid.

[0044] A supercritical fluid is a fluid with a high density exceeding the critical point and critical pressure, preferably having a density of 200 kg / m 3 ~900 kg / m 3 and preferably having a viscosity of 10 -5 Pa·s to 10 -4 Pa·s, and preferably having a diffusion coefficient of 10 -8 m 2 / s to 10- 7 m 2 / s, and / or preferably having a thermal conductivity of 10 -3 W / m 2 ·K to 10 -1 W / m 2 ·K.

[0045] A subcritical fluid is a fluid in a liquid state at a pressure higher than the vapor pressure curve in a temperature range lower than the critical temperature, preferably having a density of 500 kg / m 3 ~1100 kg / m 3 and preferably having a viscosity of 10 -4 Pa·s to 10 -3 Pa·s, and preferably having a diffusion coefficient of 10 -10 m 2 / s to 10- 9 m 2 / s, and / or preferably having a thermal conductivity of 0.08 W / m·K to 0.10 W / m·K.

[0046] The supercritical state, subcritical state, or liquid state can be changed by controlling the temperature and pressure. Therefore, in the process of the manufacturing method of the present invention, the fluid in a closed container can be in a supercritical state, subcritical state, or liquid state. Thus, for example, even when "supercritical carbon dioxide is used" in this specification, the use of subcritical state or (especially under high pressure) liquid state carbon dioxide is not necessarily excluded.

[0047] The supercritical fluid may be a single substance or a mixture of two or more substances. Examples of substances constituting the supercritical fluid include carbon dioxide, water, methane, propane, nitrogen, and ammonia, as well as combinations thereof. In the present invention, the supercritical fluid is preferably supercritical carbon dioxide because it is chemically inert and non-toxic, its density and the like can be easily controlled, and post-treatment such as removal is easy because it is released as a gas under normal temperature and pressure. Supercritical carbon dioxide refers to carbon dioxide at a pressure equal to or higher than the critical temperature (Tc: 31.1 °C) and equal to or higher than the critical pressure (Pc: 7.38 MPa). Supercritical carbon dioxide can be handled at a relatively low temperature. Therefore, supercritical carbon dioxide has the advantage of being effective for heat-unstable raw materials such as the above-mentioned heat-labile core material particles.

[0048] Since the supercritical fluid exceeds the critical temperature, the thermal motion of the molecules is intense, and moreover, it is possible to continuously change the density from a dilute state close to an ideal gas to a high-density state corresponding to a liquid. Therefore, the physical properties of the supercritical fluid that depend on density (solubility, diffusion coefficient, thermal conductivity, dielectric constant, ion product, etc.) can be controlled by minute changes in temperature and pressure. It can be seen that the density of the supercritical fluid is approximated to that of a liquid, and the viscosity and diffusion coefficient are approximated to those of a gas. Since the greater the density of the solvent, the greater the solubility in the target substance, the supercritical fluid is considered to have a solubility comparable to that of a liquid. On the other hand, the viscosity and diffusion coefficient have a high fluidity comparable to that of a gas. From these physical properties, it can be said that the supercritical fluid is a functional solvent having the characteristics of both a liquid and a gas.

[0049] The mixing of the above O / W emulsion and the supercritical fluid can be carried out, for example, by adding the supercritical fluid to the O / W emulsion previously contained in a closed container. When mixing with the supercritical fluid, the photochromic core material particles and the polymer contained in the O / W emulsion may be, for example, in a molten state (molten liquid) or in a state dissolved in a solvent (solution), respectively.

[0050] The mixing of the O / W emulsion and the supercritical fluid in a closed container is preferably carried out at a temperature of 35°C to 55°C, preferably 38°C to 42°C. When the temperature set during the mixing is lower than 35°C, uniform dissolution of the O / W emulsion and the supercritical fluid does not occur, and the production efficiency of the resulting coated photochromic fine particles may decrease. When the temperature set during the mixing exceeds 55°C, the specific properties of the encapsulated photochromic core material particles and the polymer for coating may change depending on the temperature.

[0051] In the present invention, the mixing in the closed container is preferably carried out over a predetermined period of time. The mixing time varies depending on the volume of the closed container, the type and amount of the photochromic core material particles and / or polymer contained in the O / W emulsion, and is not necessarily limited, but is, for example, 0.5 hours to 5 hours.

[0052] In the present invention, thereafter, the closed container is opened.

[0053] By this opening, the inside of the container is depressurized, and the supercritical fluid is discharged outside the container, for example, through a nozzle. At this time, the mixture of the photochromic core material particles and the polymer in the container rapidly expands to near atmospheric pressure, promoting the precipitation of the photochromic core material particles in a molten or dissolved state and the polymer. Then, when the photochromic core material particles and the polymer precipitate, the polymer is coated as a film on the surface of the photochromic core material particles in a state where the average particle diameter of the photochromic core material particles is reduced.

[0054] In this way, the desired coated photochromic fine particles can be obtained.

[0055] (Manufacturing apparatus for coated photochromic fine particles) An example of an apparatus that can be used in the method for producing coated photochromic fine particles of the present invention will be described.

[0056] FIG. 1 shows a manufacturing apparatus 100 for coated photochromic fine particles when supercritical carbon dioxide is used as a supercritical fluid. In this apparatus 100, a pressure boosting section A1 for providing supercritical carbon dioxide obtained by pressurizing carbon dioxide, a preparation section A2 for preparing an O / W emulsion from a preliminary mixture, and a mixing section A3 for mixing the O / W emulsion and supercritical carbon dioxide in a state where a closable container is closed are configured. The pressure boosting section A1 and the mixing section A2 are separated with a stop valve 202 as a boundary. The preparation section A2 and the mixing section A3 are separated with a stop valve 206 as a boundary.

[0057] In the pressure boosting section A1, the pressure of carbon dioxide can be boosted by a pressure boosting pump 105 for liquid carbon dioxide. A cylinder 101 for supplying carbon dioxide to the pressure boosting pump 105 is provided. As a supply source of liquid carbon dioxide, a cylinder with a siphon filled with liquid carbon dioxide can be used.

[0058] A drying tube 102 filled with a desiccant is provided between the cylinder 101 and the pressure boosting pump 105. By the liquid carbon dioxide from the cylinder 101 passing through this drying tube 102, moisture in the liquid carbon dioxide is removed.

[0059] A cooling unit 103 is provided downstream of the drying tube 102. For example, ethylene glycol is filled in the cooling unit 103, and this ethylene glycol is cooled to about 260K. The liquid carbon dioxide from which moisture has been removed by the desiccant during passage through the drying tube 102 above is cooled by the ethylene glycol of the cooling unit 103 and supplied to the pressure boosting pump 105.

[0060] Also, a filter 104 is provided between the cooling unit 103 and the pressure boosting pump 105. By the filter 104, impurities such as dust can be removed, and it can be prevented that impurities mix into the pressure boosting pump 105.

[0061] The carbon dioxide that has passed through the filter 104 is supplied to the booster pump 105. A cooler may be attached to the head portion of the booster pump 105 to prevent the vaporization of liquid carbon dioxide (not shown).

[0062] A pressure regulating valve 201 is provided in the boosting section A1. The pressure regulating valve 201 can set the pressure inside the system of the boosting section A1 to an arbitrary pressure. Also, a pressure gauge 106 may be provided in the boosting section A1. The pressure inside the system of the boosting section A1 can be measured by the pressure gauge 106. The pressure gauge 106 is provided with an upper limit contact output terminal and can be set to cut off the power supply of the booster pump 105 at a specified pressure.

[0063] The supply of carbon dioxide from the boosting section A1 to the mixing section A3 can be adjusted by a stop valve 202 disposed between the boosting section A1 and the mixing section A3. Further, a safety valve 107 may be provided between the boosting section A1 and the mixing section A3 to ensure safety.

[0064] The preparation section A2 is composed of a preliminary container 182 that houses a preliminary mixture 180, an ultrasonic vibrator 190 disposed inside the preliminary container 182, and a pipe 206 that feeds the O / W emulsion obtained from the preliminary mixture 180 to the mixing section A3.

[0065] The preliminary container 182 houses, as the preliminary mixture 180, photochromic core material particles, a polymer, a polar solvent, a low-polarity organic solvent, and, if necessary, a surfactant supplied from respective storage tanks (not shown). In FIG. 1, the upper part of the preliminary container 182 is open, but the present invention is not particularly limited thereto. The preliminary container 182 may be a closed container.

[0066] The ultrasonic vibrator 190 is electrically connected to a predetermined power source 184 such as a solid-state power supply, and is disposed in the preliminary container 182 so that the vibrating portion 192 contacts the preliminary mixture 180. In FIG. 1, the vibrating portion 192 of the ultrasonic vibrator 190 is disposed with respect to the preliminary mixture 180 such that the vibrating portion 192 faces downward. In such an arrangement, the ultrasonic waves emitted from the vibrating portion 192 of the ultrasonic vibrator 190 can be irradiated onto the preliminary mixture 180 in a uniaxial downward direction. When the ultrasonic waves are irradiated in the uniaxial direction, convection occurs in the vertical direction in the preliminary mixture 180 in the preliminary container 182, and an O / W emulsion having a smaller micelle diameter can be prepared as compared with the case of stirring in the horizontal direction, for example.

[0067] The prepared O / W emulsion is supplied from the preliminary container 180 to the mixing section A3 by a liquid feed pump (not shown) through the pipe 206 by opening the stop valve 208.

[0068] The mixing section A3 is installed in the constant temperature water bath 112. The temperature inside the constant temperature water bath 112 can be controlled to, for example, ±0.1 °C by a temperature controller (not shown), and the temperature inside the closable container 110 can be set to an arbitrary temperature preferably in the range of 35 °C to 55 °C. The constant temperature water bath 112 is provided with a temperature measuring section 116 as needed.

[0069] The closable container 110 is, for example, a high-pressure cell having heat resistance and pressure resistance. The O / W emulsion obtained from the preparation section A2 and the supercritical carbon dioxide (supercritical fluid) obtained from the pressure increasing section A1 are accommodated in the closable container 110, and these are mixed in a state where the container 110 is closed. The closable container 110 may be provided with a stirrer 111 for promoting such mixing.

[0070] The supply of supercritical carbon dioxide to the closable container 110 shown in FIG. 1 is performed, for example, as follows. The liquid carbon dioxide supplied from the stop valve 202 is prepared into a supercritical fluid (supercritical carbon dioxide) in the constant temperature water bath 112 before being supplied to the container 110. Specifically, the liquid carbon dioxide supplied from the stop valve 202 is prepared into supercritical carbon dioxide through a preliminary pipe (preheater) 108, a check valve 109, and a stop valve 203 installed in the constant temperature water bath 112, and is introduced into the closable container 110. The pressure inside the closable container 110 is appropriately monitored by a pressure gauge 113.

[0071] In the mixing section A3, the closable container 110 containing the above O / W emulsion and supercritical carbon dioxide (supercritical fluid) is closed, and then mixing is performed over a predetermined period of time. After that, the container 110 is opened again by the stop valve 204. As a result, the carbon dioxide fluid is discharged from the pipe 205, and the internal pressure of the container 110 can be reduced to atmospheric pressure. In order to avoid condensation of the liquid material inside the container 110 and generation of dry ice by the carbon dioxide fluid due to this pressure reduction, the stop valve 204 may be provided with a heater (not shown).

[0072] By opening the stop valve 204, the carbon dioxide fluid contained in the closable container 110 is discharged to the outside from the pipe 205 in a state where it has returned from the supercritical state to normal pressure. At this time, the polymer surrounds the photochromic core material particles in a state where the average particle diameter of the photochromic core material particles is reduced inside the closable container 110 to form a film, and coated photochromic fine particles are produced. The coated photochromic fine particles obtained by the present invention have an average particle diameter (for example, 0.05 μm to 0.5 μm) smaller than that of the photochromic core material particles used in the preparation of the above O / W emulsion. Thereby, so-called nano-order photochromic fine particles can be obtained.

[0073] The coated photochromic fine particles obtained by the present invention are useful as constituent materials for, for example, photosensitive nanodevices (specific examples include nano quantum dots, nanosensors, nanotubes, biosensors, etc.).

Examples

[0074] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0075] (Reference Example 1: Preparation of Photochromic Core Material Particles) 10 g of a liquid photochromic material (a commercially available light control lens material containing naphthopyran) was placed in a beaker, and 0.1 g each of polymerization initiators Irgacure 184 (98.0%, manufactured by Tokyo Chemical Industry Co., Ltd.) and Irgacure 819 (96.0%, manufactured by Tokyo Chemical Industry Co., Ltd.) were added thereto, and UV irradiation (wavelength 302 nm) was performed at room temperature for 24 hours to cure. The cured product of the obtained photochromic material was subjected to cryogenic pulverization to obtain solid powder-like photochromic core material particles (R1).

[0076] (Example 1: Preparation of Coated Photochromic Fine Particles) As the aqueous phase, 9.5 g of ultrapure water and 0.08 g of a surfactant (Tween 80 manufactured by SIGMA-ALDRICH) were charged into a beaker. As the oil phase, 1.5 g of toluene (99.5%, manufactured by Fuji Film Wako Pure Chemical Corporation), 0.025 g of polystyrene (manufactured by Aldrich Chemical Company, Inc. / weight average molecular weight (Mw) 200,000), and 0.05 g of the photochromic core material particles (R1) obtained in Reference Example 1 were charged into another beaker. Then, after adding the oil phase to the aqueous phase, ultrasonic irradiation was performed for 5 minutes to prepare an O / W emulsion.

[0077] Thereafter, using the manufacturing apparatus 100 shown in FIG. 1, coated photochromic fine particles were prepared as follows.

[0078] A closable container 110 (50 cc) made of stainless steel, the O / W emulsion obtained above was put into the container 110 through the stop valve 208, the container 110 was closed, and it was placed in a thermostatic bath 112 pre-controlled at the reaction temperature (40 °C). It was left standing until the inside of the closed container 110 reached the reaction temperature (40 °C). Next, the stop valves 201, 202, and 203 were opened, and supercritical carbon dioxide was fed into the container 110 to make the inside of the container 110 in a high-pressure state (10 MPa). In this state, the inside of the container 110 was stirred for 1 hour by a magnetic stirrer 111. Then, the stop valve 204 was opened to perform a depressurization operation on the container 110, and carbon dioxide gas was discharged from the inside of the container 110 through the stop valve 204 and the pipe 205. Then, the upper lid of the container 110 was opened, and the product inside the container 100 was recovered together with the reaction solution of the reaction residue, and solid powder-coated photochromic fine particles (E1) were obtained by centrifugation and freeze-drying.

[0079] (Photochromism of photochromic core material particles (R1)) An appropriate amount of the liquid photochromic material used in Reference Example 1 was placed on a petri dish. The state of the petri dish at that time is shown in Fig. 2. Also, an appropriate amount of the photochromic core material particles (R1) obtained in Reference Example 1 was placed on another petri dish under artificial light (indoor fluorescent lamp). The state of the petri dish at that time is shown in Fig. 3. Furthermore, the photochromic core material particles (R1) placed on this petri dish were irradiated with UV light (wavelength 302 nm) under an indoor fluorescent lamp. The state of the petri dish at that time is shown in Fig. 4.

[0080] As shown in Figs. 2 to 4, the liquid photochromic material (Fig. 2) clearly became a solid powder through the above operations (Figs. 3 and 4). Furthermore, the photochromic core material particles (R1) obtained in Reference Example 1 exhibited different colors under natural light (Fig. 3) and UV light (Fig. 4), and it can be seen that the photochromic properties are appropriately maintained even in the form of solid powder.

[0081] (Electron micrographs of photochromic core material particles (R1) and coated photochromic fine particles (E1)) The surface states of the photochromic core material particles (R1) obtained in Reference Example 1 and the coated photochromic fine particles (E1) obtained in Example 1 were observed and measured using a scanning electron microscope (JSM6060 manufactured by JEOL Ltd.). The results obtained are shown in FIGS. 5 and 6.

[0082] As shown in FIG. 5, the photochromic core material particles (R1) obtained in Reference Example 1 had the form of solid particles with large surface irregularities. In contrast, the photochromic core material particles (E1) obtained in Example 1 had the form of particles with a smooth surface.

[0083] (Particle size distribution of photochromic core material particles (R1) and coated photochromic fine particles (E1)) The particle size distributions of the photochromic core material particles (R1) obtained in Reference Example 1 and the coated photochromic fine particles (E1) obtained in Example 1 were measured by the dynamic light scattering (DLS) method using a laser diffraction particle size distribution measuring device (SALD-7500 manufactured by Shimadzu Corporation). The results obtained are shown in FIG. 7.

[0084] As shown in FIG. 7(a), the photochromic core material particles (R1) obtained in Reference Example 1 had a particle size distribution in the range of approximately 10 μm to 1000 μm, while the coated photochromic fine particles (E1) obtained in Example 1 had a particle size centered around 0.1 μm and hardly any particles reaching 1 μm were observed. The average particle diameter of the photochromic core material particles (R1) of Reference Example 1 obtained by these measurements was 71.295 μm, while the average particle diameter of the coated photochromic fine particles (E1) of Example 1 was 0.1532 μm. Thus, it can be seen that through the mixing of the O / W emulsion and the supercritical fluid, the average particle diameter of the obtained coated photochromic fine particles was clearly refined to the nano order as compared with that before mixing.

[0085] (Photochromism of coated photochromic fine particles (E1)) The upper lid of Example 1 was opened, and the reaction solution present in the container 110 (containing the coated photochromic fine particles (E1) of Example 1) was dispensed into a sample bottle, and UV light (wavelength: 302 nm) was irradiated from the side of the sample bottle. A photograph of the sample bottle before irradiation with the reaction solution is shown in Fig. 8(a), and a photograph of the sample bottle when irradiated with UV light is shown in Fig. 8(b).

[0086] As is clear from the comparison between Fig. 8(a) and Fig. 8(b), when UV light was irradiated from the non-irradiated state (Fig. 8(a)) to the reaction solution in the sample bottle, the reaction solution in the sample bottle was observed to change color to a blackish color (Fig. 8(b)). Thereafter, it was confirmed that when the irradiation with UV light was stopped, the blackish reaction solution returned to the original state (Fig. 8(a)). From this, it can be seen that the coated photochromic fine particles (E1) contained in the reaction solution obtained in Example 1 had the property of photochromism.

Industrial Applicability

[0087] The present invention is useful in various technical fields such as, for example, electronics, electrics, the automotive industry, fibers, cosmetics, printing, and the like.

Explanation of Signs

[0088] 100 Manufacturing apparatus for coated photochromic fine particles 101 Cylinder 102 Drying tube 103 Cooling unit 104 Filter 105 Booster pump 106 Pressure gauge 107 Safety valve 108 Preliminary piping (preheater) 109 Check valve 110 Closable container 111 Stirrer 112 Constant temperature water bath 113 Pressure gauge 116 Temperature measuring section 180 Preliminary mixture 182 Preliminary container 184 Power supply 190 Ultrasonic vibrator 192 Vibration part 201 Pressure regulating valve 202, 203, 204, 208 Stop valve 205, 206 Pipe

Claims

1. A method for producing coated photochromic fine particles, comprising: a step of directly irradiating a preliminary mixture of photochromic core material particles, a polymer, a polar solvent, and a low-polarity organic solvent with ultrasonic waves to prepare an O / W emulsion; a step of mixing the O / W emulsion with a supercritical fluid in a closed container; and a step of opening the closed container, The method comprising these steps.

2. The method according to claim 1, wherein the supercritical fluid is supercritical carbon dioxide.

3. The method according to claim 1 or 2, wherein the low-polarity organic solvent is at least one solvent selected from the group consisting of toluene and hexane.

4. The method according to any one of claims 1 to 3, wherein the polymer is a thermoplastic resin.

5. The method according to claim 4, wherein the thermoplastic resin is polystyrene.

6. The method according to any one of claims 1 to 5, wherein the mixing step is performed at a temperature of 35°C to 55°C.

7. The method according to any one of claims 1 to 6, wherein the ultrasonic irradiation is performed by a horn-type ultrasonic vibrator.

8. The method according to claim 7, wherein the ultrasonic waves are irradiated in a uniaxial direction with respect to the preliminary mixture.

9. An apparatus for producing coated photochromic fine particles, comprising: ultrasonic irradiation means for directly irradiating a preliminary mixture of photochromic core material particles, a polymer, a polar solvent, and a low-polarity organic solvent with ultrasonic waves to prepare an O / W emulsion; and a closable container in which the O / W emulsion and the supercritical fluid are mixed; The apparatus comprising these components.

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