TWI425979B - A method for producing sub-micrometric particles of several materials - Google Patents

Description

Method for preparing submicron particles

The invention relates to a method for preparing submicron-sized particles, in particular to a method for preparing submicron-sized particles of submicron-sized organic and inorganic particles, which has the property of precipitating ultrafine particles and high yield, and the organic solution and The advantages of both aqueous solutions are available.

Conventional methods for preparing microparticles include gas phase coagulation, mechanical milling, precipitation, spray drying, sol-gel, plasma spray, liquid anti-solvent Method, reverse micelles method, supercritical fluid technology, and the like. Among them, gas phase condensation method and spray drying method are not suitable for heat sensitive substances; mechanical grinding method requires long program time and cleaning and filtering grinding medium; sol gel method requires expensive precursor and regrind procedure; liquid phase resistance The solvent rule is difficult to obtain fine particles due to lower supersaturation; the inverse microcell method requires selection of a suitable surfactant and its particle size is not easily controlled.

Because the fluid has many physical properties superior to liquid or gaseous state in the supercritical state, for example, high diffusion coefficient, low viscosity, low surface tension, and easy control of the density. If carbon dioxide is used as the supercritical fluid medium, the system can be operated near room temperature, plus the fluid is non-toxic and non-flammable. Therefore, carbon dioxide is one of the most commonly used media in supercritical fluid applications, and is classified according to the different role functions of supercritical fluids, including: Rapid Expansion of Supercritical Solution. , RESS); Supercritical Anti-Solvent (SAS) as an anti-solvent function; "Particle from Gas-Saturated Solutions" (PGSS) Supercritical Assisted-Atomization (SAA), which functions as an atomizing medium. Among them, the RESS method is not applicable to substances with low solubility in supercritical fluids. Wu et al. (Please refer to Wu, HT; Lin, HM; Lee, MJ, "Ultra-fine particles Formation of Pigment Green 36 in Different Phase Regions Via a Supercritical Anti-Solvent Process" Dyes & Pigments, page 75, 328, 2007). The nano-red Red 177 pigment particles are prepared by the SAS method. In order to overcome the shortcomings of the pigment being insoluble in the supercritical fluid, the supercritical fluid of the program (SAS) is an anti-solvent function, and the organic solvent in the pigment solution is dissolved, and the pigment is precipitated due to high supersaturation. The particles and particles are precipitated in a high-pressure vessel, so the yield is limited by the volume of the high-pressure vessel, and since the water is not easily soluble in carbon dioxide, it is not suitable for use in an aqueous solution system. Reverchon et al. (please refer to Revechon, E.; Antonacci, A., "Polymer Microparticles Productions by Supercritical Assisted Atomization" J. Supercritical Fluids, page 39, 444, 2007) for the simultaneous preparation of Red 66 pigment particles using SAS and SAA methods. It shows that the SAS method can prepare nano-sized particles, but the yield is low, while the SAA method can prepare sub-micron particles with high yield. On the other hand, because carbon dioxide plays an atomizing medium, it can be applied to the solubility of water. Aqueous system.

SUMMARY OF THE INVENTION One object of the present invention is to provide a method for preparing submicron-sized particles having the advantages of being able to precipitate ultrafine particles and having a high yield, and both an organic solution and an aqueous solution system can be used.

For the purpose of the above, a method for preparing a submicron-sized particle of the present invention comprises the steps of: (a) pumping a solute solution of a particle to be formed and a supercritical fluid into a high-pressure saturation tank for mixing to form a carbon dioxide saturated solution; (b) passing the carbon dioxide saturated solution through one of the atomizing nozzles at the bottom of the high pressure saturated tank, spraying into one of the atmospheric pressure precipitation tanks to form an atomized droplet; and (c) the atomized droplet The nitrogen gas preheated in the precipitation tank is contacted to release carbon dioxide and evaporate the solvent, and the solute is supersaturated to precipitate submicron-sized particles.

The detailed description of the drawings and the preferred embodiments are set forth in the accompanying drawings.

1 and FIG. 2, FIG. 1 is a schematic flow chart showing a method for preparing submicron-sized particles according to a preferred embodiment of the present invention; and FIG. 2 is a schematic view showing an apparatus for preparing submicron-sized particles of the present invention. .

As shown in the figure, a method for preparing submicron-sized particles according to a preferred embodiment of the present invention includes the following steps: (a) saturating a solute solution of a particle to be fabricated and a supercritical fluid by pumping 2, 3, and a high pressure. The tank 8 is mixed to form a carbon dioxide saturated solution; (b) the carbon dioxide saturated solution is passed through one of the atomizing nozzles 9 at the bottom of the high pressure saturated tank 8, and sprayed into one of the atmospheric pressure precipitation tanks 10 to form atomized droplets; And (c) contacting the atomized droplets with nitrogen preheated in the precipitation tank 10 to release carbon dioxide and evaporate the solvent, and the solute is supersaturated to precipitate submicron-sized particles.

In the step (a), the solute solution of the particles to be formed and the supercritical fluid are pumped into the high pressure saturation tank 8 through the pumps 2 and 3 to be mixed to form a carbon dioxide saturated solution; wherein the supercritical fluid is, for example but not limited to, It is selected from the group consisting of carbon dioxide, nitrogen monoxide, chlorofluorocarbons and mixtures thereof. In the present embodiment, carbon dioxide is taken as an example, but not limited thereto; the solute in the solute solution of the particles to be formed is, for example, The material is not limited to being selected from the group consisting of a polymer, a medicine, a pigment, a photocopying toner, and a metal oxide. In the present embodiment, a polymethyl methacrylate (PMMA) polymer material is taken as an example, but The solvent is, for example but not limited to, selected from the group consisting of dimethyl hydrazine, dichloromethane, acetone, methanol, ethanol, pure water, aqueous ethanol, and aqueous acetic acid. In the present embodiment, acetone is taken as an example for illustration. , but not limited to this.

In addition, in the step (a), the concentration of the polymer solution can be further adjusted to change the concentration of the polymer solution in a range of 1 kg/m ³ to 50 kg/m ³ to facilitate particle size refinement and concentration thereof. It is preferably from 1 kg/m ³ to 10 kg/m ³ .

In addition, in the step (a), the volumetric flow rate ratio (F _CO2 /F1) of the carbon dioxide to the polymer solution can be further adjusted, so that the volumetric flow rate ratio of the carbon dioxide to the polymer solution is varied from 0.8 to 2.8, so as to facilitate The particle diameter is fine, and the solution volume flow rate thereof is preferably from 1.2 to 2.4.

In the step (b), the carbon dioxide saturated solution is passed through an atomizing nozzle 9 at the bottom of the high-pressure saturated tank 8, and is sprayed into one of the atmospheric pressure precipitating tanks 10 to form atomized droplets.

In addition, in the step (b), the angle of the nozzle 9 can be further adjusted, so that the angle of the nozzle 9 can be varied within a range of 5 to 90 degrees to facilitate the finening of the particle diameter, and the angle of the nozzle 9 is preferably 50. Degree angle.

In addition, in the step (b), the temperature of the saturation tank 8 can be further adjusted so that the temperature range of the saturation tank 8 can be varied from 313 K to 363 K to facilitate the grain size miniaturization and the saturation tank temperature thereof. The range is preferably 333 K to 353 K.

In the step (c), the atomized droplets are contacted with the preheated nitrogen gas in the precipitation tank 10 to release the carbon dioxide and evaporate the solvent, and the solute is supersaturated to precipitate the submicron-sized particles, that is, the preparation work is completed.

The preparation process of the present invention is as follows with reference to the flow chart of FIG. 1 as follows: the nitrogen flow rate is fixed by the mass flow controller 6, and the constant temperature tank 5 and the nitrogen heat exchanger 7 are set at a predetermined temperature; The high-pressure liquid pump 2 is preheated by the constant temperature tank at a fixed flow rate and then input into the saturation tank 8, and the carbon dioxide is sprayed into the sedimentation tank 10 through the nozzle 9, and the heated nitrogen gas passes through the bottom filter screen 11 of the sedimentation tank 10, and passes through the wet flow meter 15 After observing that the two streams are stable for 10 minutes, the pump 3 is turned on, the polymer solution is preheated through the constant temperature tank 5, and then pumped into the saturation tank 8, and the flow rate is fixed at 5 ml/min. This setting can provide several minutes of saturation. The tank 8 is retained for a time to facilitate the dissolution of carbon dioxide into the polymer solution. The saturated solution is sprayed into the precipitation tank 10 through the nozzle 9 for two-stage atomization, and at the same time, it is contacted with the heated flowing nitrogen gas, and the solvent in the atomized droplet is evaporated, and the polymer particles are precipitated to precipitate the bottom of the tank. 11 interception is collected, the pump solution is turned off after the input of the polymer solution is completed, and the collected sample is placed in a drying chamber for sample analysis.

In order to promote the removal of the solvent, the precipitation tank 10 and the preheated nitrogen temperature are both fixed at 333 K, which is higher than the boiling point of the solvent acetone 329 K, lower than the Tg point of the polymer material 372 K, and the nitrogen volume flow rate is fixed at 0.8 Nm. ³ /hr. In the following four examples, the effects of nozzle 9 angle, polymer solution concentration, saturation tank 8 temperature and carbon dioxide and polymer solution volume flow rate ratio are discussed. The effect of each effect on the prepared polymer microparticles FESEM photo particle morphology and particle size is discussed. Distribution impact.

As shown in Fig. 2, a partially enlarged schematic view of the nozzle 9 is seen. The inner diameter of the nozzle 9 is 130 μm. When the angle is smaller, the outlet fluid of the nozzle 9 will be approximately columnar, which is not conducive to the atomization efficiency.

Embodiment 1:

Please refer to FIG. 3, which illustrates the particle size distribution of the prepared polymer particles when the nozzle angle is adjusted by the method for preparing the submicron particles in the present case. As described above, in the step (b), the angle of the nozzle 9 can be further adjusted so that the angle of the nozzle 9 can be varied within a range of 5 to 90 degrees to facilitate the finening of the particle diameter, and the nozzle 9 has a better angle. It is a 50 degree angle. As shown in Fig. 3, the solid line in the figure is the particle size distribution of the polymer particles at a nozzle angle of 50°, and the dotted line is the particle size distribution of the polymer particles at a nozzle angle of 5°, showing a larger nozzle angle of 50°, which is more favorable for fog. Therefore, the prepared polymer particles are small and the particle size distribution is narrow.

Embodiment 2:

Referring to FIG. 4( a ) to FIG. 4( d ), respectively, the electron micrograph distribution map of the polymer microparticles prepared by different polymer solution concentrations in the preparation method of the submicron microparticles in the present invention is shown. As described above, in the step (a), the concentration of the polymer solution can be further adjusted to change the concentration of the polymer solution in a range of 1 kg/m ³ to 50 kg/m ³ to facilitate particle size miniaturization, and The concentration is preferably from 1 kg/m ³ to 10 kg/m ³ . As shown in FIG. 4(a) to FIG. 4(d), it is shown that the particle diameter of the prepared polymer particles becomes larger as the concentration increases, and the prepared polymer particles have a spherical shape, for example, the polymer solution of FIG. 4(a). The concentration of the polymer particles is also the smallest, and the polymer solution of Figure 4(d) has the highest concentration. Therefore, the prepared polymer particles have the largest particle size.

Please refer to FIG. 5( a ) to FIG. 5( b ) together, wherein FIG. 5( a ) illustrates the preparation method of the submicron particles in the present case, and the particle size of the prepared polymer particles is prepared at different polymer solution concentrations. FIG. 5(b) is a diagram showing the distribution of the number average particle diameter of the prepared polymer microparticles at different polymer solution concentrations in the preparation method of the submicron-sized microparticles in the present invention. As shown in the figure, the concentration of the polymer solution is increased from 1 kg/m ³ to 50 kg/m ³ , the average particle size increases as the concentration of the polymer solution increases, the particle size distribution also becomes wider, and the average particle size of the prepared polymer particles is average. Increasing from 82nm to 155nm, the viscosity and surface tension of the polymer solution increase with increasing concentration, which is not conducive to the miniaturization of atomized droplets, thus producing larger polymer particles and having a wide particle size distribution. The results show that the concentration of the low polymer solution is favorable for the miniaturization of the polymer particles and the narrowing of the particle size distribution.

Embodiment 3:

Please refer to FIG. 6 , which is a diagram showing the distribution of the average particle diameter of the prepared polymer particles at different saturation bath temperatures in the preparation method of the submicron particles in the present case. As shown in the figure, the higher the temperature of the saturated tank 8 is, the smaller the polymer particles can be prepared. For example, when the temperature of the saturated tank 8 is 353 K, the average particle diameter is 127 nm, and the average temperature of the saturated tank 8 is 313 K. It is 166nm, because the temperature of the saturated tank 8 is higher, the viscosity of the saturated solution formed is lower, which is more favorable for atomization, so it can effectively atomize to form tiny droplets, prepare smaller polymer particles and have narrow particle size distribution. Chemical. However, when the temperature of the saturated tank 8 is further increased to 363 K, the average particle diameter is 131 nm. The reason for the increase in particle size is that 363K is closer to the Tg point of 372K of PMMA, which tends to soften the particles and grow into larger particles, and the results show that it is advantageous for the particles. The saturation tank temperature at which the micronization and the particle size distribution are narrowed is 353K.

Embodiment 4:

Please refer to FIG. 7(a) to FIG. 7(c) together, wherein FIG. 7(a) shows the preparation method of the sub-micron-sized particles in the present case, and the optimum flow rate ratio R=1.2 at a saturated bath temperature of 353K. Figure 7 (b) shows the preparation method of the sub-micron particles in this case in the saturation tank The temperature is 333K, the optimum flow rate ratio is R=2.0; FIG. 7(c) shows the preparation method of the sub-micron particles in the present case, the optimum flow rate ratio R=2.4 under the saturation bath temperature of 313K. As shown in the figure, at the temperature of the fixed saturation tank 8, the increase of the flow rate ratio is advantageous for the micronization of the polymer particles, and exhibits an optimum flow rate ratio, for example, when the temperature of the saturation tank 8 is 353 K, the optimum flow rate ratio R = 1.2; When the temperature of the saturated tank 8 is 333 K, the optimum flow rate ratio is R=2.0; and when the temperature of the saturated tank 8 is 313 K, the optimum flow rate ratio is R=2.4. Assuming that the two feeds can form a homogeneous liquid phase, increasing the flow rate ratio can increase the carbon dioxide content of the saturated solution in the saturated tank 8, which will facilitate the atomization efficiency, thereby producing finer polymer particles, but with the flow The ratio of carbon dioxide can be dissolved in acetone, which is limited by the vapor-liquid phase boundary, that is, the carbon dioxide composition of the saturated compressed liquid phase (bubble point composition). If the flow rate ratio is too high, the carbon dioxide composition of the influent stream will exceed The bubble point composition enters the vapor-liquid coexistence zone to form a vapor-rich liquid phase and a carbon dioxide-rich vapor phase. Part of the acetone is dissolved in the carbon dioxide-rich vapor phase, so that the liquid phase polymer concentration increases, so the flow rate ratio is too high. It is not advantageous for the miniaturization of polymer particles. The optimum flow rate ratio increases as the temperature of the saturated tank 8 decreases, because the lower temperature can dissolve more carbon dioxide (ie, the low temperature has a higher bubble point composition).

Therefore, the preparation method of the submicron-sized fine particles of the present invention has the advantages that the ultrafine particles can be precipitated and the yield is high, and both the aqueous solution and the organic solution can be used. Therefore, the preparation method of the submicron-sized particles of the present invention is indeed more advanced than the prior art.

The disclosure of the present invention is a preferred embodiment. Any change or modification of the present invention originating from the technical idea of the present invention and being easily inferred by those skilled in the art will not deviate from the scope of patent rights of the present invention.

In summary, this case, regardless of its purpose, means and efficacy, is showing its technical characteristics that are different from the conventional ones, and its first invention is practical and practical, and it is also in compliance with the patent requirements of the invention. I will be granted a patent at an early date.

1‧‧‧Filter

2, 3‧‧ ‧ pump

5‧‧‧ thermostat

4‧‧‧ polymer solution

6‧‧‧Quality Flow Controller

7‧‧‧ nitrogen heat exchanger

8‧‧‧High pressure saturated tank

9‧‧‧ nozzle

10‧‧‧Sedimentation tank

11‧‧‧ Filter

12‧‧‧ thermometer

13‧‧‧ Pressure gauge

14. . . Vapor-liquid separation tank

15. . . Wet flow meter

Step (a): the solute solution of the particles to be formed and the supercritical fluid are pumped into the high pressure saturation tank 8 by pumping 2, 3, and mixed to form a carbon dioxide saturated solution;

Step (b): passing the carbon dioxide saturated solution through one of the atomizing nozzles 9 at the bottom of the high-pressure saturated tank 8, and spraying it into one of the atmospheric pressure precipitation tanks 10 to form atomized droplets;

Step (c): contacting the atomized droplets with the preheated nitrogen in the precipitation tank 10 to release the carbon dioxide and evaporate the solvent, and the solute is supersaturated to precipitate the submicron-sized particles.

1 is a schematic view showing a submicron particle of a preferred embodiment of the present invention Schematic diagram of the preparation method.

Figure 2 is a schematic diagram showing a schematic of an apparatus for preparing sub-micron particles of the present invention.

Fig. 3 is a schematic view showing the particle size distribution of the prepared polymer particles when the nozzle angle is adjusted by the method for preparing the submicron particles in the present case.

4(a) to 4(d) are schematic views respectively showing the electron micrograph distribution map of the polymer microparticles prepared by different polymer solution concentrations in the preparation method of the submicron-sized microparticles of the present invention.

Fig. 5(a) is a schematic view showing the distribution of the particle size of the prepared polymer particles at different polymer solution concentrations in the preparation method of the submicron-sized particles of the present invention.

Fig. 5(b) is a schematic view showing the distribution of the number average particle diameter of the prepared polymer microparticles at different polymer solution concentrations in the preparation method of the submicron-sized microparticles of the present invention.

Fig. 6 is a schematic view showing the distribution of the average particle diameter of the prepared polymer particles at different saturation bath temperatures in the preparation method of the submicron particles in the present case.

Fig. 7(a) is a schematic view showing the preparation method of the submicron-sized particles of the present invention at an optimum flow rate ratio of R = 1.2 at a saturation bath temperature of 353K.

Fig. 7(b) is a schematic view showing the preparation method of the submicron-sized particles of the present invention at an optimum flow rate ratio of R = 2.0 at a saturation bath temperature of 333 K.

Fig. 7(c) is a schematic view showing the preparation method of the submicron-sized particles of the present invention at an optimum flow rate ratio of R = 2.4 at a saturation bath temperature of 313 K.

Claims (8)

A method for preparing submicron-sized particles, comprising the steps of: (a) pumping a solute solution of a particle to be formed into a high-pressure saturation tank by pumping to form a saturated solution of carbon dioxide; (b) The carbon dioxide saturated solution passes through an atomizing nozzle at the bottom of the high pressure saturated tank, is sprayed into one of the atmospheric pressure precipitation tanks to form atomized droplets; and (c) contacts the atomized droplets with the preheated nitrogen gas in the precipitation tank The carbon dioxide is released and the solvent is evaporated, and the solute is supersaturated to precipitate submicron-sized particles. The method for preparing submicron-sized particles according to claim 1, wherein in the step (a), the supercritical flow system is selected from the group consisting of carbon dioxide, nitrogen monoxide, chlorofluorocarbons, and mixtures thereof. The method for preparing submicron-sized particles according to claim 2, wherein in the step (a), the solute in the solute solution of the particles to be formed is selected from the group consisting of a polymer, a medicine, a pigment, and a photocopying toner. a metal oxide material; the solvent is selected from the group consisting of dimethyl hydrazine, dichloromethane, acetone, methanol, ethanol, pure water, aqueous ethanol, and aqueous acetic acid. The method for preparing sub-micron particles according to claim 3, wherein the polymer material is a polymethyl methacrylate (PMMA) polymer material. The method for preparing submicron-sized microparticles according to claim 1, wherein in the step (a), the concentration of the polymer solution is further adjusted so that the concentration of the polymer solution is from 1 kg/m ³ to 50 kg/ The range of m ³ is varied to facilitate the miniaturization of the particle size. The method for preparing sub-micron-sized particles according to claim 3, wherein in the step (a), the volumetric flow rate ratio of the carbon dioxide to the polymer solution is further adjusted to make the volume flow of the carbon dioxide and the polymer solution The ratio is varied from 0.8 to 2.8 to facilitate particle size miniaturization. The method for preparing sub-micron-sized particles according to claim 1, wherein in the step (b), the nozzle angle is further adjusted so that the nozzle angle can be varied within a range of 5 to 90 degrees. In order to facilitate the finer particle size. The method for preparing sub-micron-sized particles according to claim 1, wherein in the step (b), the temperature of the saturation tank can be further adjusted so that the temperature range of the saturation tank can be varied from 313K to 363K. In order to facilitate the finer particle size.