TECHNICAL FIELD

Present disclosure relates in general to a field of micro-particle synthesis and drug encapsulation processes. Particularly, but not exclusively the present disclosure relates to a spinning disc atomization process for producing micro-particles. Further embodiments of the disclosure disclose, a method for producing micro-particles.

BACKGROUND OF THE DISCLOSURE

Atomization is a process of breaking a liquid solution into small droplets and this process is used to produce micro-particles such as metal powders or alloys. Different types of atomization process are carried out based on the type of fluid being used such as centrifugal atomization, soluble gas atomization, ultrasonic or vibrating electrode atomization. In centrifugal atomization, a liquid solution is introduced onto a rotating disc. When the liquid contacts the disc spinning at a high speed, the liquid spreads out over the surface of the disc due to the centrifugal force to which it is subjected. Then, when the liquid reaches the edge of the disc, the surface tension is insufficient to maintain the bulk liquid mass and accordingly turns into a spray of small droplets. These droplets further need to be solidified to form micro-particles. Spray drying and fluidized bed drying processes are the other common methods used for producing microparticles. Spray drying includes the steps of atomization of fluid solution and exposing the fluid to a hot gas to evaporate the solvent. This rapidly dries the droplets into solid particles. These particles are then separated from the gas and are sent to the next phase of the manufacturing process.

Fluidized bed drying is a process by which particles, typically greater than 100 microns, are fluidized and dried. For the material to become fluidized, the particulates are placed under conditions that cause it to behave like a fluid. In a fluid bed drying system, air is passed through a perforated distributor plate which provides significant air flow to support the weight of the particles. All these conventional processes are suitable for mass production. Further, the micro-particles produced using these techniques have a broad size distribution and require extreme operating conditions. This variation in micro-particle size may not be suitable for the synthesis of microparticles for drug encapsulation where the micro-particles need to be of uniform size and have narrow distribution. Although, recent methods employing microfluidics have enabled the production of micro-particles with a uniform size distribution. However, these methods are limited to low and moderate production rates and can handle only fluids with a limited range of properties.

Therefore, a need exists for an apparatus for producing the micro-particles to mitigate one or more of the above disadvantages.

SUMMARY OF THE DISCLOSURE

The one or more shortcomings of the prior art are overcome by a spinning disc atomization apparatus as claimed and additional advantages are provided through the provisions as claimed in the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein.

Present disclosure provides spinning disc atomization apparatus comprising a first enclosure defining a platform. The first enclosure is configured to receive and dispense a feed solution. A rotating disc is coupled to a motor unit positioned within the first enclosure, such that the feed solution is configured to contact the rotating disc and form micro-droplets to dispense into the first enclosure. A second enclosure is concentrically coupled to the first enclosure, wherein the second enclosure defines a collection area. A base is provided for supporting the first enclosure and the second enclosure. Further, at least one slit is defined on each of the first enclosure and the second enclosure to dispense a predefined volume of the micro-droplets in to a precipitation chamber. The micro-droplets comes into contact with an anti-solvent mixture in the precipitation chamber to form solid micro-particles of a predefined size.

In an embodiment, the first enclosure, the second enclosure and the precipitation chamber are in fluid communication with each other and form a single unit for micro-particle production.

In an embodiment, the apparatus comprises a feed vessel configured to supply the feed solution at a predefined volumetric flow rate into the first enclosure. In another embodiment, the apparatus comprises at least one non-contact seal positioned between the motor unit and the first enclosure, the non-contact seal is defined with two cylindrical compartments arranged one above the other.

In an embodiment, each of the two cylindrical compartments comprise at least one channel for fluid circulation between a rotating shaft connecting the rotating disc to the motor unit and the first enclosure.

In an embodiment, the apparatus comprises a top cover defined with a provision to receive the feed solution at a predefined volumetric flow rate.

In an embodiment, the at least one slit defined on the first enclosure and the second enclosure are in line with each other.

In an embodiment, the micro-droplets are generated upon contact of the feed solution with the rotating disc, and the micro-droplets are directed from a centre of the rotating disc through the at least one slit into the precipitation chamber.

In an embodiment, the non-contact seal, the precipitation chamber and the first and second enclosures are supplied with nitrogen gas through connecting channels from at least one cylinder.

In an embodiment, the micro-particles are produced in a narrow distribution size distribution with an average size ranging about 50 micron and above.

In an embodiment, the micro-droplets generated about 10 % of the total volume are passed through the at least one slit and the remaining volume of the micro-droplets are collected in the collection area.

In a non-limiting embodiment of the present disclosure, a method for producing micro-particles by the spinning disc atomization apparatus is disclosed. The method comprises introducing a feed solution onto a centre position of the rotating disc disposed within a first enclosure through a feed vessel. Generating micro-droplets at a periphery of the rotating disc. Then Directing the generated micro-droplets from the first enclosure to a precipitation chamber through at least one slit. Retaining the micro-droplets within a second enclosure and directing the retained micro-particles to the feed vessel. Collecting the micro-droplets in the precipitation chamber containing anti- solvent and lastly drying the mixture collected in the precipitation chamber to produce solid microparticles.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The novel features and characteristics of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Fig. 1 illustrates a schematic layout of a spinning disc atomization apparatus, in accordance with an embodiment of the present disclosure;

Fig. 2a illustrates a perspective view of the spinning disc atomization apparatus in accordance with an embodiment of the present disclosure;

Fig. 2b illustrates a top view and side view of a precipitation chamber of fig. 1.

Fig. 3 illustrates a recycle drum assembly formed with a first and second enclosures, in accordance with an embodiment of the present disclosure;

Fig. 4 illustrates a perspective view of a motor unit connecting a rotating disc, in accordance with an embodiment of the present disclosure; Figs 5a and 5b illustrates a non-contact seal positioned between the motor unit and the recycle drum assembly in accordance with an embodiment of the present disclosure; and

Fig. 6 illustrates a front view of a feed vessel to supply a feed solution into the spinning disc atomization apparatus, in accordance with an embodiment of the present disclosure.

Fig. 7a-7d illustrates the images of the microparticles produced using the spinning disc atomization apparatus in one hour under scanned electron microscopy (SEM).

Fig. 8 is a graph showing the variation of average particle size with distance from the centre of the rotating disc (4).

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the apparatus and methods illustrated herein may be employed without departing from the principles of the disclosure described herein

DETAILED DESCRIPTION

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a nonexclusive inclusion, such that an apparatus or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or process. In other words, one or more elements in a system or apparatus proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.

Embodiments of the present disclosure discloses a spinning disc atomization apparatus for producing micro-particles with a uniform size distribution. Conventionally, the micro-particles are produced using a spray drying and fluidized bed drying process. These conventional processes are suitable for mass production. Further, the micro-particles produced using these techniques have a broad distribution i.e. variations in size of the micro-particles and further require extreme operating conditions. This variation in micro-particle size may not be suitable for the synthesis of microparticles for drug encapsulation where the micro-particles need to be of uniform size and have narrow size distribution. Although, recent methods employing microfluidics have enabled the production of micro-particles with a uniform size distribution. However, these methods are limited to low and moderate production rates and can handle only fluids with a limited range of properties.

In view of the above, embodiments of the present disclosure disclose a spinning disc atomization apparatus. The apparatus comprises a first enclosure defining a platform and is configured to receive and dispense a feed solution. A rotating disc is coupled to a motor unit positioned within the first enclosure, such that the feed solution is configured to contact the rotating disc and form micro-droplets to dispense into the first enclosure. A second enclosure is concentrically coupled to the first enclosure, wherein the second enclosure defines a collection area. A base is provided for supporting the first enclosure and the second enclosure. Further, at least one slit is defined on each of the first enclosure and the second enclosure to dispense the micro-droplets that are passed through the at least one slit. The micro-droplets comes in contact with an anti-solvent mixture in the precipitation chamber to form solid micro-particles of a predefined size.

Further, the present disclosure also discloses a method for producing micro-particles by the spinning disc atomization apparatus. The method comprises introducing a feed solution onto a centre position of the rotating disc disposed within a first enclosure through a feed vessel. Then, the micro-particles are generated at a periphery of the rotating disc. Eater, the generated microparticles are directed from the first enclosure to a precipitation chamber through at least one slit. Followed by retaining the micro-particles within a second enclosure and directing the retained micro-particles to the feed vessel. The method further includes collecting the micro-particles in the precipitation chamber containing anti-solvent and lastly drying the mixture collected in the precipitation chamber to produce solid micro-particles.

The following paragraphs describe the present disclosure with reference to Figs, la to 6. In the figures, the same element or elements which have similar functions are indicated by the same reference signs.

Fig. 1 illustrates a schematic layout of a spinning disc atomization apparatus (100) [hereinafter referred to as “the apparatus (100) for producing micro-particles. The apparatus (100) among other components includes a liquid collection drum assembly (200), a spinning motor assembly (300), a precipitation chamber (14), feed vessel (16) and various connecting channels (40) for flow of a feed solution and a gas. In accordance with embodiments of the present disclosure, the recycle drum assembly (200), the spinning motor assembly (300) and the precipitation chamber (14) are combined together to produce micro-particles with narrow size distribution.

The apparatus (100) comprises a liquid collection drum assembly configured to receive a feed solution. The liquid collection drum assembly comprises a first enclosure (1) defined with a platform. A second enclosure (2) is concentrically disposed around the first enclosure (1) and is coupled to the first enclosure (1) with a fastening means. In an embodiment, the first enclosure (1) is substantially cylindrical in shape and such construction cannot be considered as a limitation and the first enclosure (1) may be configured in any of a rectangular, square or a polygonal shape based on requirement. A second enclosure (2) is concentrically disposed around the first enclosure (1) such that a diameter of the second enclosure (2) is larger than the first enclosure (1). The second enclosure (2) is also configured to be in a cylindrical shape and is defined with a side wall (20). A collection area (12) is defined between the first enclosure (1) and the second enclosure (2) to receive and retain the micro-droplets after an atomization process. At least one slit (8) is defined on a portion of the first enclosure (1) and on the side wall (20) of the second enclosure (2). Each of the at least one slit (8) of the first and second enclosures (1, 2) are in line with each other. The first and second enclosures (1, 2) are fastened to a base (5) to support the liquid collection drum assembly. In an embodiment, the first and second enclosures (1, 2) are bolted to the base (5). Further, the spinning motor assembly (300) is disposed within the first enclosure (1) and is fixed on the platform using suitable fastening means. The spinning motor assembly comprises a motor unit (6) mounted on a support plate (30). In an embodiment, a cylindrical metal skirt (not shown) is also attached to a bottom portion of the first enclosure (1) to enclose the motor unit (6). In an embodiment, vent gas provisions may be given on the cylindrical metal skirt to supply nitrogen and keep the motor unit (6) free from oxygen and to minimize the risk associated with any hydrocarbon vapor reaching near the motor unit (6). In an embodiment, the cylindrical metal skirt has a diameter of 340 mm which is sufficient to cover a base portion of the motor unit (6). The motor unit (6) is supported on a support ring (9) defined with a plurality of holes to receive support rods (11). The support plate (30) is positioned above a base plate (32) and is adjustable over the base plate (32) along a length of the support rods (11). A rotating disc (4) is coupled to the motor unit (6) by a rotating shaft (7) which is rotated at high speeds by the motor unit (6). In an embodiment, the height of the rotating disc (4) is adjustable within the first enclosure (1) by changing the position of the support plate (30) about the support rods (11) with respect to the base plate (32). In an embodiment, the rotating disc (4) may be configured as a flat disc or a cup shaped disc. The support plate (30) and the base plate (32) are fixed in position about the support rods (11) through fasteners. In an embodiment, the support rods (11) may be bolts that are fastened by nuts. A non-contact seal (22) is positioned within the liquid collection drum assembly between the rotating shaft (7) and the first enclosure (1). The non-contact seal is defined with two cylindrical compartments (38) of varying diameters placed one above the other. Each of the cylindrical compartments are defined with at least one passage (36) therewith-in for a flow of nitrogen between the rotating shaft (7) and the first enclosure (1) such that the flow of hydrocarbons generated during the atomization process is restricted from entering the motor unit (6).

Referring to Fig. 2b, the precipitation chamber (14) is coupled to the liquid collection drum assembly about the side wall (20) through a suitable fastening means. In an embodiment, the precipitation chamber (14) is removably coupled by fasteners such as nuts and bolts etc. In an embodiment, the precipitation chamber (14) may be riveted or welded to the liquid collection drum assembly. The precipitation chamber (14) is defined as a rectangular container with two side walls and a rear wall. The precipitation chamber (14) comprises at least one supporting rod (10) attached to the side walls to accommodate a plurality of precipitation trays (21). The plurality of precipitation trays (21) is configured to store a predefined volume of anti-solvent for precipitation process. The liquid collection drum assembly and the precipitation chamber (14) are enclosed with a top cover (26). In an embodiment, the top cover (26) is made of polycarbonate material or any thermoplastic material depending on the requirement. The top cover (26) is defined with at least one first provision at the vicinity of the liquid collection drum assembly for receiving a feed solution from a feed vessel (16). At least one second provision (24) is defined on the top cover near the precipitation chamber (14) to receive an anti-solvent for the precipitation process. The feed solution is introduced or poured from the at least one first provision into the first enclosure (1). In an embodiment, the feed solution may be poured directly from the feed vessel (16) and may be introduced through a connecting channel. The feed solution is poured at the center of the rotating disc (4) which rotates at high speed upon actuation of the motor unit (6). Upon contact, the feed solution is thrown outward from the center of the rotating disc (4) in all directions due to centrifugal force. Due to this, micro-droplets are formed at the periphery of the rotating disc (4) and the same are accumulated in the first enclosure (1). The micro-droplets are dispensed from the first enclosure (1) to the precipitation chamber (14) through the at least one slit (8) defined in line with the first and second enclosures. A fraction of micro-droplets is dispensed through the at least one slit (8) to achieve narrow size distribution of the micro-droplets. In other words, the size of the micro-droplets will be in the same range of 20-50 microns. The dispensed micro-droplets are collected within the plurality of precipitation trays (21) which are positioned at a distance from the liquid collection drum assembly. The micro-droplets collected within the precipitation trays (21) come in contact with the anti-solvent to form solid micro particles by precipitation process. The micro-particles are collected in the precipitation trays (21) based on their size which depends on the distance travelled by the micro-droplets from the center of the disc in a horizontal plane to a centroid of the precipitation tray. The solid micro-particles are then transferred from the precipitation trays (21) and the atomization process is continued. The first enclosure (1) is further defined with an aperture at its bottom surface to dispense the micro-droplets into the collection area (12). The micro-droplets are further transferred into the feed vessel (16) through the connecting line for recycling or atomization process.

Fig. 6 illustrates the feed vessel (16) to introduce the feed solution into the first enclosure (1) of the liquid collection drum assembly. The feed vessel (16) comprises a cylindrical feed drum (42) defined with a conical cross section towards a bottom end of the cylindrical feed drum (42). The feed solution is supplied within the feed drum through a feed dip pipe (43). The feed drum (42) is connected to a flow line (44) having a flow meter (45) to calibrate the flow rate of the feed solution within the flow line (44). A filter (46) is positioned upstream of the flow meter (45) to remove any solid impurities present within the feed solution flowing through the flow line (44). In an embodiment, a plurality of vent lines (not shown) is provided at the outlet of the flow meter (45) which removes the trapped air and ensures that no air bubble is attached to the float of the flowmeter (45) which can affect the indicated flow. In an embodiment, the flow meter (45) is a variable area flow meter (rotameter) that measures the flow in the range of 0-20 L/h. In an embodiment, an isolation valve and a manual control valve are provided on the flow line to (44) restrict and control the fluid flow as per the requirement. A feed nozzle (48) is provided at an end of the flow line (44) to introduce the feed solution. The feed nozzle (48) is connected to the top cover through the at least one first provision (24) to introduce the feed solution onto the rotating disc (4) to produce micro-droplets. Further, nitrogen gas is supplied from at least one cylinder (28) to various components of the apparatus (100) such as the liquid collection drum assembly, precipitation chamber (14) and the non-contact seal (22) to prevent fire hazards while producing the micro-particles using volatile organic solvents. In an embodiment, a pressure regulator and gauge assembly (50) is connected to the cylinder (28) and is provided to control the supply nitrogen gas at required pressure. The nitrogen gas is supplied through the plurality of connecting channels to various points such as non-contact seal (22), middle and bottom of the precipitation chamber (14) and at the bottom portion of the recycle liquid collection drum assembly. In an embodiment, the plurality of connecting channels (40) may be flexible tubes. The vent gas from the vessel is removed by flexible tubes from the connection points given at the end of the precipitation chamber (14) and from the bottom skirt of the recycle liquid collection drum assembly. A portable oxygen and hydrocarbon analyzer (3) is in communication with the plurality of connecting channels (40) to monitor oxygen levels at the vent gas outlets at regular intervals during the initial preparation activities of the equipment and during the production process using a portable oxygen measurement device. The oxygen levels are ensured to be less than 1% during any activity involving organic solvents in the apparatus (100).

Present disclosure also provides a method of producing micro-particles using the spinning disc atomization apparatus (100). Initially, the feed solution is continuously introduced into the liquid collection drum assembly through the feed vessel (16). The feed solution is poured onto a rotating disc (4) positioned within the first enclosure (1) of the liquid collection drum assembly. The rotating disc (4) produces micro-droplets at the periphery of the rotating disc (4). The produced micro-droplets are then dispensed through the at least one slit (8) into the precipitation chamber (14). The un-dispensed micro-droplets are accumulated in the collection area (12) defined within the liquid collection drum assembly. Lastly, the micro-droplets cone in contact with the antisolvent stored in the plurality of precipitation trays (21) and produce the solid micro-particles of predefined size.

In an embodiment, the diameter of the rotating disc (4) is in range of 50 mm - 100 mm and thickness may be in a range of 2 mm -5 mm. In an embodiment the rotating disc (4) and the rotating shaft (7) are manufactured by stainless steel.

In and embodiment, the vibrations in the apparatus (100) are reduced as there is no direct contact of the rotating shaft (7) with the stationary first enclosure (1) and by use of non-contact seal (22).

In an embodiment, the at least two cylindrical compartments (38) of the non-contact seal minimize the vapor leaks towards the motor unit (6).

In an embodiment, the volume of the micro-particles generated by the apparatus (100) depends on a width of the at least one slit (8).

In an embodiment, the liquid collection drum assembly and the precipitation chamber (14) is covered using a polycarbonate sheet for transparency and sufficient strength to support the feed system which is directly connected to the inlet points on the sheet.

In an embodiment, silicone rubber gaskets are used to seal a gap between the liquid collection drum assembly and the polycarbonate sheet. However, this cannot be considered as a limitation and the gasket material is selected based on the compatibility of various types of rubber with the solvents used in the atomization process.

In an embodiment, the micro-droplets generated about 10 % of the total volume are passed through the at least one slit (8) and the remaining volume of the micro-particles are collected in the collection area (12) of the liquid collection drum assembly. However, this cannot be considered as a limitation and the volume of micro-droplets dispensed may be based upon the dimensions of the at least one slit (8). It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

In the detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

EXPERIMENTAL RESULTS

EXPERIMENT 1- GENERATION OF MICROPARTICLES AND PERFORMANCE EVALUATION OF THE EQUIPMENT

The micro-particles are produced using the spinning disc atomization apparatus (100) for a duration of one hour and the results are analysed. The efficiency of the liquid collection drum assembly is evaluated by measuring the quantity of the micro-droplets collected in the first enclosure and by analysing the solid content of the material by drying a known sample volume of the micro-droplets. It is observed that for a total feed of 5100 mL, approximately 4675 mL of recycled liquid is collected. Thus, the recycle efficiency, which is defined as the ratio of the volume of the liquid collected from the first enclosure (1) of the liquid collection drum assembly to the volume of the total feed material used, is calculated to be 0.917. It is observed that, the material losses are mainly due to the discrepancies in the size between the provision on the first enclosure (1) and the at least one slit (8) which causes material to be collected in the collection area (12) of the liquid collection drum assembly. Additional losses are accounted for by the material that gets distributed on the walls and other parts of the precipitation chamber (14). The high volatility of the solvent is another factor that causes problems with the recovery of the material due to the high rate of drying leading to solid accumulation in the equipment.

During this one -hour experiment, 1.2 g of final dried micro-particles were produced. The low production rate of the final product is due to the small size of the slit that allows only 9% of the total droplets generated by the rotating disc (4) to pass through the slit. This was necessary to minimize the quantity of precipitation solvent to be handled in a laboratory setup. Out of all the droplets passed through the slit, 3% is collected in the precipitation tray to form the desired product. In case of continuous operation, the remaining 97% liquid can also be recycled by providing another precipitation tray (21) inside the precipitation chamber (14). Further, the amount of product can be increased by increasing the slit size and by increasing the size and number of precipitation chambers (14) around the rotating disc (4). By providing a concentric precipitation tray (21) around the rotating disc (4) and by supplying a sufficient amount of precipitation solvent, the efficiency can be considerably improved. But this requires a large space for the equipment and arrangements to handle large volumes of precipitation solvent during feeding, final slurry collection and separation operations.

Since, the process is carried out at ambient temperature and pressure and no gas flow is required, the operations are easier and safer when compared with a spray drying process. On a larger scale this can help to reduce the maintenance, operation and safety requirements.

In this current setup, the smallest average size of the particle that can be achieved at a given distance is limited by the maximum possible speed of the spinning disk motor; which is 4000 rpm. By employing a motor that can go to higher speeds, smaller particles can be produced and a higher throughput also can be achieved by increasing the disc (4) speed while maintaining the desired particle size. Since a non-contact seal is used, operating at higher disc (4) speeds will not result in excessive vibration of the equipment and no associated equipment modifications are required. A corresponding increase in the volume of the precipitation solvent is also necessary to solidify the higher amount of droplets emerging from the disc (4) when operated at an increased feed rate. This suggests that the process can be scaled up with minimum changes in the key equipment configurations to meet the large-scale production requirements.

Fig. 7a-7d illustrates the images of the micro-particles produced using the spinning disc atomization apparatus (100) in one hour under scanned electron microscopy (SEM). 7a depicts an overview of the micro-particles produced using the apparatus (100) in a narrow size distribution and 7b is an enlarged view of the same showing the shape and surface morphology. Further, 7c depicts a surface morphology of a single particle. Lastly. 7d is a graph showing the size distribution of the micro-particles with respect to number of micro-particles produced.

EXPERIMENT 2 - VARIATION OF PARTICLE SIZE WITH DISTANCE FROM THE SPINNING DISC (4)

By observing the size of the solidified particles in samples collected at different distances from the centre of the rotating disc (4) (4) using SEM, it can be concluded that the average particle size increases with the average distance from the rotating disc (4). The average particle size in a sample is approximately estimated by finding the number-average value of the size of the particles measured using SEM images of a given sample. The average distance travelled by a sample of particles is defined as the horizontal distance from the centre of the rotating disc (4) to the centroid of the top view area of the precipitation chamber (14).

Referring to Fig. 8, the graph is plotted with average particle size of a sample against the average distance travelled at various rotating disc (4) speeds. The graph clearly demonstrates the increasing trend of average micro-particle size with the increase in average distance from the rotating disc (4) at a given rotating disc (4) speed. The size of the solid particles is measured. The final solid microparticle size varies directly with the size of the solution droplets, since the particle is formed only by the removal of the solvent from the solution droplets of a given concentration. Assuming that the particle is spherical in shape, the size of the droplet emerging from the rotating disc (4) can be approximately estimated from the size of the dried particle by knowing the values of the concentration of solids in the solution, the average density of the solids and the density of the solvent. If the process involves a highly volatile solvent such as DCM, the droplet size considerably varies along the travel path between the rotating disc (4) edge and the precipitation liquid due to evaporation of the solvent and therefore a measurement of the droplet size will only give the size of the droplet at a particular location on this path. Therefore, it is concluded that a direct measurement of the final dried particle helps to correlate the size of the droplet or particle with the average distance travelled.

This graph shown in fig. 8 can serve as a guideline for estimating the average distance of the precipitation tray from the centre of the rotating disc (4) to produce particles within a required size range at a given speed. Similar correlations can be found for liquid flow rate and particle size. By combining these observations, the precipitation tray position can be varied according to the variation in flow rate

The present disclosure provides a spinning disc apparatus (100) to produce solid micro-particles in a uniform distribution.

Equivalents:

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals: