CZ307829B6 - Method of producing nanostructured or microstructured materials and the equipment for doing this - Google Patents

Abstract

According to the method, a solution, emulsion or liquid suspension of one substance or mixture of substances or microorganisms optionally saturated with gas, liquefied gas or supercritical fluid is fed into the disc’s inner space by a hollow shaft and a combination of centrifugal force and liquid pressure the liquid outflows through the expansion gap to form microscopic droplets. The microscopic droplets are subsequently secondarily disintegrated in the drying chamber by expanding the gas present into smaller droplets to form an aerosol. The aerosol is subsequently dried by a gas drying stream to form solid particles. In special cananofibersses, microfibres or can be formed in certain polymers under certain conditions instead of particulate forms. The device for producing nanostructured or microstructured materials consists of a chamber (1) in which a hollow shaft (3) is mounted, which has at least one disc (2), with an expansion gap (4), and the hollow shaft (3) has openings that connect the inner space through the hollow shaft (3) to the expansion gap (4). In addition, the chamber (1) can have an independent spray nozzle (32).

Description

Technical field

The invention relates to a process for the production of nanostructured or microstructured materials and to a device for their production.

BACKGROUND OF THE INVENTION

At present, there are a number of methods for the production of nanostructured or microstructured materials, and this is also the basis for their production. One of these is that the solution for producing these materials is stored in a separate container and is conveyed by pump through a pipeline to a mixing chamber in which it is mixed with pressurized carbon dioxide, which is also separately conveyed by a pump to a mixing chamber . From the mixing chamber, the saturated solution is conveyed directly to the nozzle. In some cases, the mixing chamber is even omitted and the mixing of the material and gas solution takes place in the nozzle itself.

Said production methods are characterized by frequent clogging of the nozzles, which results in production interruption and reduced labor productivity.

SUMMARY OF THE INVENTION

The disadvantages of the process for producing nanostructured or microstructured materials and the apparatus for carrying out the process can be largely overcome by the solution according to the invention, which consists in the solution, emulsion or liquid suspension of one substance or mixture of substances or microorganisms optionally saturated with gas, liquefied gas or supercritical fluid, is introduced into the inner space of the disc through a hollow shaft and a combination of centrifugal force and fluid pressure exits the fluid through an expansion gap to form microscopic droplets. The microscopic droplets are subsequently disintegrated in the drying chamber by expansion of the gas present therein into smaller droplets to form an aerosol. The aerosol is then dried with a drying gas stream to form solid particles. In special cases, microfibers or nanofibers can be formed instead of particulate forms when drying some polymers under certain conditions.

A solution, emulsion or liquid suspension of a single substance or mixture of substances or microorganisms optionally saturated with gas, liquefied gas or supercritical fluid is pumped into the interior of the disk under a pressure of 10 to 400 bar and exits through the expansion gap into the drying chamber. atmospheric or the pressure is lower than the saturated solution. A drying gas of defined properties is blown into the chamber. The drying gas may be air or nitrogen at a temperature of 20 to 200 ° C with a defined humidity.

The formed nanostructures or microstructures are separated in solid form from the drying gas stream and the gas saturating gas using a filter, a cyclone or an electrically charged header.

In the case of a two-piece rotating disk, the amount of expansion gap is formed by deforming at least one portion of the disk as a function of the pressure of the liquid medium in the interior of the disk and the pressure generated by the pressure member.

- 1 GB 307829 B6

The gas, liquefied gas, or supercritical fluid may preferably be carbon dioxide.

The essence of the device for producing nanostructured or microstructured materials according to the invention is that it consists of a chamber in which a hollow shaft is mounted, on which at least one disk having an expansion gap is mounted, the hollow shaft being provided with openings connecting the inner space of the hollow shaft with expansion gap. The chamber may additionally be provided with an independent spray nozzle.

It is preferred that the at least one disk is rotating and is formed by two adjacent parts, wherein an expansion gap is formed circumferentially between the upper part and the lower part. Preferably, the expansion gap is formed over the entire circumference of the at least one disk.

At least one of the parts of the rotating disc is provided with a thrust element. Preferably, the pressing element is a pressing nut. At least one portion of the disc or the rotating disc may be frustoconical.

The hollow shaft is connected to a rotary unit that connects the stationary part of the device to the hollow shaft and allows fluid to enter from the stationary part of the device.

The solution according to the invention is based on the use of a disk which is provided with outlet nozzles or an internal space with an expansion gap, into which liquid is supplied by a hollow rotating shaft. If the disc is two-piece, the expansion gap opens by expanding at least one disc part by deforming the material to a width of 1 to 500 microns at an overpressure in the range of 10 to 400 bar, which is controlled by a thrust element, such as a nut.

A pressure rotating disk combines spraying of liquid through nozzles or expansion gap due to centrifugal force and liquid overpressure in the interior of the disk with secondary atomization caused by subsequent rapid expansion of carbon dioxide from the formed microdroplets in the drying chamber to form a very fine aerosol.

Compared to devices using static nozzles, the present invention provides a significant increase in solution flow, drying rate and hence productivity in the entire production. The device is particularly suitable for quick gentle drying of thermolabile molecules or microorganisms while maintaining their activity or vitality.

Clarification of drawings

An exemplary embodiment of a device for producing nanostructured or microstructured materials is shown in the accompanying drawings, wherein Fig. 1 shows the overall engagement of the entire device, Fig. 2 shows the hollow shaft with the disc in axonometric view and partial longitudinal section; .

DETAILED DESCRIPTION OF THE INVENTION

Example 1. Drying of NaCl

Sodium chloride was chosen as a model inorganic salt. 5 L of a 10% (w / w) NaCl solution was prepared. The solution was pumped from the liquid reservoir 11 by a high pressure pump 12 at a flow rate of 80 ml / min. via a relief valve 13 and a first check valve 14 to the mixing chamber 15. At the same time, a carbon dioxide pump 17 equipped with a condenser 13 was pumped from the pressure vessel 16 through the second check valve 12 to the mixing chamber 15 with carbon dioxide. Sodium chloride solution which was saturated with oxide in the mixing chamber 15

It proceeded through the heater 20 and the liquid inlet 21 to the rotary unit 10, from which it proceeded to the interior of the hollow shaft 3, housed in the tube 22 in the base frame 23 of the drying chamber 1. From the interior of the hollow shaft 3 saturated with carbon dioxide holes in the hollow shaft into the interior of the disc 2 between its upper part 7 and the lower part 8. A conical shaped disc 2 with a diameter of 120 mm was used, with a thrust element 9 in the form of a nut as shown in FIG. the nut was gradually changed to open the expansion gap 4 at an overpressure in the range of 10 to 400 bar. The rotating hollow shaft disk 2 was spun through the intermediate gear 24 by the drive motor 25 at a speed of 0 to 10,000 rpm. Through the base frame 23, it was blown into the drying chamber at a rate of 0.8 m ³ / min. the drying air preheated to a temperature of 35 ° C from a drying gas source 26 consisting of a compressor and a heater. By combining the centrifugal force and the overpressure of the liquid in the inner space of the disk 2, primary expansion of the liquid into microscopic droplets occurred in the expansion gap 4. The microscopic droplets were subsequently disintegrated in the drying chamber 1 by expanding the carbon dioxide escaping from the saturated liquid into smaller droplets to form a very fine aerosol. This aerosol was dried in the drying chamber 1 in a preheated air stream. The resulting sodium chloride microcrystals were separated from the drying air and carbon dioxide stream in a particle separation cyclone 21. The upper part of the cyclone under the drying gas outlet 29 was equipped with a breathable nanofiber layer filtration membrane 28 and the dried sodium chloride microcrystals were collected in a collection vessel 30 for the dried material. The separation efficiency of the sodium chloride particles was higher when the collecting vessel 30 was equipped with an electrically charged header 31.

Various drying conditions for sodium chloride were tested. In one case, the drying was carried out without rotation of the disc 2. The primary atomization of the sodium chloride solution was limited to spraying in a narrow expansion gap 4 due to overpressure in the inner space of the disc 2 without centrifugal force, analogous to that of spraying on a nozzle. disintegrating the resulting microdroplets by expanding the carbon dioxide to form even smaller droplets. The effect of disk 2 rotation rate at a constant flow rate of sodium chloride and carbon dioxide through the system on the size of the sodium chloride microcrystals formed was also tested. Further, it was tested how the size of the formed microcrystals is influenced by the pressure changes in the interior of the disc 2. The pressure in the interior of the disc 2 was controlled by tightening or loosening the pressure element 9. Drying of sodium chloride was also performed at zero carbon dioxide flow only by primary centrifugal force In this case, there was no secondary atomization due to the expansion of carbon dioxide from the formed microdroplets. Finally, the possibility of placing two rotating disks 2 one above the other on the same hollow shaft 3 or on two independent hollow shafts 3 was tested.

In the case of drying without rotation of the disc 2, the microcrystalline size distribution, expressed as the cubic microcrystalline wall length, ranged from 2 to 8 microns, depending on the pressure in the internal environment of the disc 2 which was controlled between 10 and 400 bar. The size of the resulting microcrystals decreased with increasing pressure in the internal space of the disk 2. At zero carbon dioxide flow, the microcrystal size distribution ranged from 30 to 150 microns depending on the rotation speed ranging from 100 to 10,000 rpm. As the speed of rotation of the disk 2 increased, the size of the microcrystals formed decreased. At a constant flow of sodium chloride and carbon dioxide solution through the system, the microcrystal size distribution ranged from 0.5 to 3 microns depending on the rotation speed of disk 2 and the pressure in the interior of disk 2. The size of the resulting microcrystals decreased again with increasing pressure in the inner space of the disc 2 and with increasing speed of the disc 2.

Sodium chloride yields ranged from 80 to 95% in all experiments. The losses were caused by the adherence of sodium chloride to the walls and to the duct of the drying chamber 7. It has been shown that two-stage atomization realized by a combination of primary atomization by centrifugal force resulting from the rotation of disk 2 and the overpressure of the liquid in the inner space of disk 2 and secondary atomization by expansion

The carbon dioxide from the formed microdroplets allows to reduce the size of the sodium chloride microcrystals formed. Thus, the effects of primary atomization and secondary atomization add up and allow the production of smaller dry particles than if these primary and secondary atomization methods were used alone. By placing multiple disks 2 on the same hollow shaft 3, or independent hollow shafts 3, in the same drying chamber 1, it allows to increase the drying rate.

Example 2. Drying of polyvinyl alcohol

Polyvinyl alcohol was chosen as a model spinnable polymer. A commercial solution of polyvinyl alcohol Sloviol R 16, 16% (w / w) dry matter (Fichema) was used for the experiments. The experimental design, conditions and apparatus were the same as in Example 1. The flow rate of the polyvinyl alcohol solution was 70 ml / min. In the expansion gap 4 of the rotating disk 2, nanofibers and microfibers were formed by centrifugal force. The fiber formation rate gradually increased over the rotational speed range of the disc 2. The pressure in the internal space of the disc 2 did not significantly affect the fiber formation rate. The yields of polyvinyl alcohol in the fibers were in the range of 75 to 90% depending on the conditions. Losses were due to the adhesion of the polyvinyl alcohol to the walls and in the duct of the drying chamber. The diameter of the fibers decreased with increasing pressure in the inner space of the disc 2 and with increasing speed of the disc 2 in the range of 500 to 3000 rpm. Further increase in the speed of rotation of the disc 2 resulted in the predominant formation of microdroplets and irregularly shaped particles.

Example 3. Drying of ovalbumin as a model protein.

Ovalbumin from egg white (Sigma-Aldrich) was selected as a model protein. The experimental set-up, conditions and apparatus were the same as in Example 1. A solution containing 5% (w / w) ovalbumin and 5% (w / w) trehalose (Fluka) was prepared in distilled water. Trehalose was used as a stabilizing agent. The flow rate of the ovalbumin solution was 90 ml / min. Spherical particles with a diameter in the range of 0.4 to 2 microns were obtained, depending on the conditions of the experiment. The particle diameter decreased with increasing pressure in the interior of disk 2 and with increasing speed of disk 2. In an alternative embodiment, a 120 mm disk with ten outlet nozzles circumferentially was used for primary atomization of the ovalbumin solution instead of the expansion gap disk 2. The diameter of the individual outlet nozzles was 100 microns. In this case, under the same conditions, the spherical particle size was in the range of 1 to 3 microns.

Example 4. Drying of the heterocysts isolated from cyanobacteria and the enzyme nitrogenase.

The drying of the heterocysts was chosen as a model case for gentle drying of living cells while maintaining their vitality. Drying of the enzyme nitrogenase isolated from the heterocysts illustrates the possibility of gentle drying of the enzymes while maintaining their biological activity and the possibility of drying under anaerobic conditions. Heterocysts are specialized cells of some filamentous cyanobacteria with a thin cell wall, light yellow color. Their function is to fix nitrogen from the air in case of deficiency of other forms of this element. Heterocysts use the enzyme nitrogenase, which is inactivated by oxygen, to fix air oxygen. Heterocysts must create a microanaerobic environment. Heterocysts were isolated from Cyanobacterium Anabaena SP cyanobacteria fibers. strain CA (ATCC 33047) following the procedure of Smith R.L. et al. (RL Smith, D. Kumar, Z. Xiankong, FR Tabita, and C. Van Baalen. 1985. H2, N2, and 02 metabolism by isolated heterocysts from Anabaena SP. Strain CA. J. Bacteriol. 162: 565-570) . Metabolic activity of isolated heterocysts was measured by reducing acetylene under anaerobic conditions using the methodology described by Kumar A. et al. (A. Kumar, F. R. Tabita, and C. Van Baalen. 1983. High endogenous nitrogenase activity in isolated heterocysts of Anabeana SP. Strain CA after nitrogen starvation. J. Bacteriol. 155 (2): 565-570). A portion of the obtained heterocysts was used to isolate the nitrogenase enzyme (ECI. 7.99.2) as described by Song S.-D. Et al. (Song S.-D., A. Hartmann, and R. H. Burris. 1985. Purification and Properties of the Nitrogenase

-4GB 307829 B6 of Azospirillum amazonense. J. Bacteriol. 164 (3): 1271-1277. Isolated nitrogenase activity was measured again by reducing acetylene under anaerobic conditions according to the procedure described by Shah v.K. et al. (V.K. Shah, L.c. Davis, and W.J. Brill. 1975. Nitrogenase. VI. Acetylene reduction assay: Dependence of nitrogen fixation estimates on component ratio and acetylene concentration. Biochim Biophys Acta 384 (2): 353-359).

Isolated heterocysts and nitrogenase were stored without air under nitrogen atmosphere. Heterocysts were suspended in saline to dryness of 6% (w / w). The suspension was kept in the liquid reservoir 11 under a nitrogen atmosphere. The experimental set-up and equipment were the same as in Example 1. The cell suspension flow rate was 80 ml / min. The pressure in the interior of the disc 2 was set to 60 bar with the pressure nut. The drying gas in this case was nitrogen. The nitrogen source 26 was a high-capacity pressure vessel. The nitrogen flow through the drying chamber 1 was 0.8 m ³ / min, the temperature of the nitrogen entering the drying chamber 1 was 40 ° C. The dried cell culture was separated from the stream of nitrogen and carbon dioxide in cyclone 21 and collected in a collection vessel 30. The product was in the form of a fine powder. The yield of the heterocysts in dry form was more than 90%. The decrease in cell culture vitality was only 4.7%. The decrease in metabolic activity measured as acetylene reduction under anaerobic conditions was not statistically significant.

The nitrogenase was suspended in distilled water to a concentration of 5% (w / w) with the addition of 5% (w / w) sucrose, which served as a stabilizing agent. The nitrogenase was dried under the same conditions as the heterocysts. Spherical particles having a diameter of about 1 micrometer were obtained. The nitrogenase yield in dry form was approximately 80%. Again, the decrease in enzyme activity was not statistically significant.

Example 5. Encapsulation of probiotic bacteria in aqueous suspensions of cellulose derivatives.

This example was chosen as an illustration of the possibility of using the device according to the invention for encapsulating compounds or microorganisms. Probiotic microorganisms must meet some basic requirements in order to benefit their host. These essential requirements include that they must be sufficiently resistant to the acidic environment of the stomach and the action of bile acids in the small intestine. However, not all commercially available strains of probiotic micro-organisms fully meet these requirements. One of the frequently used ways to increase their resistance to these effects is to encapsulate them with various materials.

In the first part of the experiment, a suspension was prepared containing 0.5 L of commercial enteric ethylcellulose preparation in nanoparticulate form of FMCs Aquacoat ECD and 2 L of similar preparation containing cellulose acetate phthalate FMCs Aquacoat CPD, 2 kg of microbial preparation BA (1.10 ⁹ KTJ / g) (Milcom) containing probiotic strains of the genera Lactobacillus acidophillus and Bifidobacterium bifidum lyophilized with milk powder, 200 g of the prebiotic inulin Frutafit HP preparation and 5 l of distilled water. The experimental set-up and the apparatus were the same as in Example 1. The drying gas was air preheated to 35 ° C, which was blown into the drying chamber 1 at a rate of 0.8 m ³ / min. from a source 26 formed by a compressor and a heater. The flow rate of the dried suspension was 75 ml / min. The dried cell culture was separated from the drying air and carbon dioxide stream in cyclone 21 and collected in a collection vessel 30. The product was in the form of a fine powder. The bacteria were encapsulated within the cellulose derivative particles. The particles were irregular in shape. The particle size distribution was in the range of 4 to 7 microns. The dry yield of the suspension was approximately 80%. It was found by standard methods of microbiological analysis that there was no statistically significant decrease in the original vitality of bacterial culture. Microbiological tests confirmed a significant protective effect of the encapsulation against the simulated acid environment of the stomach and against the action of bile acids.

In the second part of the experiment, a suspension was prepared containing 0.5 L of a commercial enteric preparation of ethylcellulose in nanoparticulate form FMCs Aquacoat ECD and 2 L of a similar preparation containing cellulose acetate phthalate FMCs Aquacoat CPD in 3.8 L of distilled water. Addition

A bacterial suspension containing 2 kg of microbial preparation BA (1.10 ⁹ cfu / g) (Milcom) and 200 g of the prebiotic inulin Frutafit H preparation was prepared. Both suspensions were simultaneously sprayed into the drying chamber 1 with two rotating discs 2 on independent hollows. The drying gas was again preheated to 35 ° C, which was blown into the drying chamber 1 at a rate of 0.8 m ³ / min. from a source 26 formed by a compressor and a heater. The suspension flow through each rotating disc or nozzle was equal to 35 ml / min. The dried cell culture was separated from the drying air and carbon dioxide stream in cyclone 27 and collected in a collection vessel 30. The product was in the form of a fine powder. The bacteria were encapsulated within the cellulose derivative particles. The particles were irregular in shape. The particle size distribution was in the range of 3 to 6 microns. The dry yield of the suspension was approximately 85%. Again, there was no statistically significant decrease in the original vitality of the bacterial culture. Microbiological tests again confirmed a significant protective effect of the encapsulation against the simulated acid environment of the stomach and against the action of bile acids.

The combination of two different disks 2 on the independent hollow shafts 3, or the combination of the disk 2 with the independent spray nozzle 32, allows simultaneously the atomization and drying of two different liquids - solutions, emulsions or suspensions simultaneously in the same drying chamber 1. these two different liquids in the drying chamber.

Industrial applicability

The invention relates to a process for the production of nanostructured or microstructured materials and to a device for their production. Compared to devices using static nozzles, the present invention provides a significant increase in solution flow, drying rate and hence productivity in the entire production. The device is particularly suitable for quick gentle drying of thermolabile molecules or microorganisms while maintaining their activity or vitality.

PATENT CLAIMS

Claims (12)

A process for the production of nanostructured or microstructured materials, wherein a solution, emulsion or liquid suspension of a single substance or mixture of substances or microorganisms saturated with a gas, a liquefied gas or a supercritical fluid is supplied to a space where liquid atomization occurs. an emulsion or a liquid suspension of a single substance or mixture of substances or microorganisms saturated with gas, liquefied gas or supercritical fluid is applied in the expansion space by centrifugal force and / or overpressure, atomizing the liquid into microscopic droplets which are dried and subsequently gas expansion, escaping from a saturated liquid, disintegrated into droplets to form an aerosol, which is then dried by a gas stream and the solid nanostructures or microstructures formed are separated from the gas mixture exiting the chamber by filtration, cyclone, or electrically charged collector. Method for producing nanostructured or microstructured materials according to claim 1, characterized in that a solution, emulsion or liquid suspension of one substance or mixture of substances or microorganisms saturated with gas, liquefied gas or supercritical fluid is injected into the expansion space under a pressure of 10 to 400 bar. wherein the drying pressure is equal to or less than atmospheric pressure. Method for producing nanostructured or microstructured materials according to claim 1 or 2, characterized in that the drying gas is air or nitrogen at a temperature of 20 to 200 ° C. -6GB 307829 B6 A method for producing nanostructured or microstructured materials according to any one of claims 1 to 3, characterized in that the gas, liquefied gas or supercritical fluid is carbon dioxide. An apparatus for producing nanostructured or microstructured materials according to any one of claims 1 to 4, comprising a chamber (1) in which a hollow shaft (3) is mounted, on which at least one disk (2) and a hollow shaft (3) are mounted. is provided with apertures (5) connecting the inner space of the hollow shaft (3) with the inner space of the disc (2), characterized in that it comprises an element for saturating the treated solution and at least one disc (2) is provided with an inner space with an expansion gap ( 4). Apparatus according to claim 5, characterized in that the at least one disc (2) is rotating and consists of two adjacent parts (7, 8), wherein the upper part (7) and the lower part (8) are circumferentially an expansion gap (4) is formed. Device according to claim 5 or 6, characterized in that at least one of the parts (7, 8) of the rotating disc (2) is provided with a thrust element (9). Device according to claim 7, characterized in that the pressure element (9) is a pressure nut. Device according to any one of claims 5 to 8, characterized in that the expansion gap (4) is formed over the entire circumference of the at least one disc (2). Device according to any one of claims 5 to 9, characterized in that the hollow shaft (3) is connected to a rotary unit (10) which connects the stationary part of the device with the hollow shaft (3) to allow liquid to enter from the stationary part of the device. Device according to any one of claims 5 to 10, characterized in that at least one disc portion (7, 8) or a rotating disc (2) is frustoconical. Device according to any one of claims 5 to 11, characterized in that the chamber (1) is provided with an independent spray nozzle (32).