Internal components and leaching column and removal system and method for removing small molecule substances from polyglycolic acid and resulting products and applications

Abstract

The application discloses an inner component, a leaching tower and a removal system, a method for removing small molecular substances in polyglycolic acid, a product and application. The inner component comprises a conical part and a trumpet part; at least part of the wide opening end of the conical part is arranged in the trumpet part, and there is an annular gap between the wide opening end of the conical part and the inner surface of the trumpet part on the same plane as the wide opening end of the conical part; in the generatrix of the conical part, the line connecting the wide opening end and the narrow opening end of the conical part is an arc; in the generatrix of the trumpet part, the line connecting the wide opening end and the narrow opening end of the trumpet part is an arc. The newly developed inner component can improve the liquid-solid two-phase speed in the leaching tower, improve the mass transfer coefficient, and at the same time, the curved surface design can increase the rotating speed of the particles to improve the surface renewal effect of the particles, thereby promoting the leaching effect of the small molecular substances. The method for removing small molecular substances in polyglycolic acid can effectively reduce the small molecular content in PGA.

Description

Technical Field

[0001] This invention relates to the field of polyglycolic acid purification technology, and more specifically, to internal components, leaching towers and removal systems, methods for removing small molecule substances from polyglycolic acid, the resulting products and applications. Background Technology

[0002] Polyglycolic acid (PGA) is an aliphatic polyester polymerized from glycolic acid or glycolide, exhibiting excellent biodegradability and biocompatibility. Currently, PGA's primary application is in the biomedical field, where it can be used to manufacture medical sutures, drug delivery systems, fracture fixation materials, tissue engineering scaffolds, and suture reinforcement materials.

[0003] The PGA system produced by the polymerization of glycolide still contains about 5% small molecules. The presence of these small molecules seriously affects the downstream applications of PGA, such as causing filament breakage during spinning. Therefore, the content of small molecules in PGA must be reduced to below 0.6%. The removal of small molecules from polymers is a common engineering problem in materials synthesis. Existing technologies for removing small molecules mainly include drum devolatilization, twin-screw melt devolatilization, and falling film devolatilization. Drum devolatilization is an intermittent process and is not suitable for large-scale production. While twin-screw and falling film devolatilization are both melt devolatilization technologies, polymers undergo thermal degradation at high temperatures, especially PGA, which degrades more rapidly than traditional polyesters, easily leading to depolymerization of polymer molecules at high temperatures.

[0004] Therefore, a new method needs to be developed that can simply and effectively reduce small molecules in polyglycolic acid. Summary of the Invention

[0005] To address the problems in existing technologies, this invention proposes an internal component, an leaching tower, a removal system, a method for removing small molecule substances from polyglycolic acid (PGA), the resulting products, and their applications. This invention develops a novel internal component. Adding this internal component to the leaching tower increases the liquid-solid two-phase rate and improves the mass transfer coefficient. Simultaneously, the curved surface design increases the particle rotation speed, thereby improving the particle surface renewal effect and promoting the leaching of small molecule substances. The method for removing small molecule substances from PGA of this invention can effectively reduce the content of small molecules in PGA to below 0.4%. When using a removal device or system containing this internal component, the method for removing small molecule substances from PGA of this invention can operate stably and continuously, improving production efficiency.

[0006] One objective of this invention is to provide an internal component comprising a tapered portion and a flared portion; at least a portion of the tapered portion including a wide end is disposed within the flared portion, and an annular gap exists between the wide end of the tapered portion and the inner surface of the flared portion, which lies on the same plane as the wide end of the tapered portion;

[0007] In the generatrix of the tapered portion, the line connecting the wide end and the cone-angle end of the tapered portion is an arc, denoted as A1; and / or,

[0008] In the busbar of the horn section, the line connecting the wide end and the narrow end of the horn section is an arc, denoted as A2.

[0009] Existing internal components are typically herringbone shaped, which easily creates dead angles at the edges. The internal components in this invention have special parts and structures with curved surface designs, which can increase the rotational speed of particles, thereby improving the surface renewal effect of particles, increasing the liquid-solid two-phase rate, and improving the mass transfer coefficient.

[0010] In this invention, the conical portion and the flared portion of the internal component may or may not be connected. Specifically, for example, when the internal component is installed inside the tower, if there is a central axis at the center of the entire tower, the conical portion of the internal component is fixed to the central axis, and the flared portion is fixed to the tower wall (e.g., by pressing the flared portion with a flange). The vertical distance of the internal component is adjusted by adjusting the vertical height of the central axis. In this case, the conical portion and the flared portion of the internal component do not need to be directly connected. Alternatively, if there is no central axis at the center of the entire tower, then a connection needs to be provided between the conical portion and the flared portion. The connection method adopts existing connection methods, such as direct welding connection through a connecting rod (the installation diagram is shown below). Figure 1 (As shown), then fix all the internal components to the tower wall. At this time, the height of the conical part and the trumpet part is fixed. If you want to change the height, you need to replace the internal components.

[0011] In the internal components described in this invention, the angles of A1 and A2 only need to meet the immersion requirements. Preferably, the angle corresponding to A1 is 20-90°, more preferably 30-90°; for example, the angles corresponding to A1 are 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, and 90°; and / or,

[0012] The angle corresponding to A2 is 20-90°, preferably 30-90°; for example, the angle corresponding to A2 is 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, or 90°; at this time, the immersion efficiency of the internal components is relatively high.

[0013] In the internal components described in this invention, preferably:

[0014] The centerline of the tapered portion and the centerline of the flared portion are on the same straight line; and / or,

[0015] The wide end of the tapered portion is located within the outwardly opening of the flared portion; and / or,

[0016] The height of the horn-shaped portion is denoted as H1, the height of the conical portion is denoted as H2, and the distance between the wide end of the conical portion and the narrow end of the horn-shaped portion is denoted as H3. The sum of H2 and H3 is greater than H1. Preferably, the values ​​of H1 and H2 are equal. More preferably, H3 is 0.2 to 2 times the value of H1, for example, it can be 0.2 times, 0.4 times, 0.6 times, 0.8 times, 1 time, 1.2 times, 1.4 times, 1.6 times, 1.8 times, or 2 times.

[0017] A second objective of this invention is to provide a leaching tower equipped with the internal components described in one objective of this invention.

[0018] In the leaching tower of the present invention, preferably:

[0019] The length-to-diameter ratio of the leaching tower is 5:1 to 30:1, preferably 5:1 to 20:1; and / or,

[0020] The internal components H1 and H2 are each independently 1 / 4 to 1 / 32 of the diameter of the leaching tower body, preferably H1 and H2 are equal in value and are 1 / 4 to 1 / 32 of the diameter of the leaching tower body.

[0021] In the leaching tower of the present invention, preferably:

[0022] When installing the internal components of the leaching tower

[0023] The vertical distance between two adjacent internal components within the leaching tower is 1 to 10 times the diameter of the leaching tower body, preferably 1 to 4 times; and / or,

[0024] Inside the leaching tower, 1 to 8 internal components are installed at the same height. Preferably, the flared ends of the internal components are horizontally connected.

[0025] Furthermore, the leaching tower includes a solid feed inlet, a liquid feed inlet, and a discharge outlet. The discharge outlet preferably includes a liquid discharge outlet and a solid discharge outlet; more preferably, the liquid discharge outlet is located in the upper part of the leaching tower, most preferably at the top; and the solid discharge outlet is located in the lower part of the leaching tower, most preferably at the bottom.

[0026] In this invention, the connection method between the conical and flared portions of the internal components can adopt the connection method of the internal components inside the tower described above. If multiple internal components need to be installed at the same height in the leaching tower, and if a central shaft is provided at the center of the entire leaching tower, the conical portions of multiple internal components at the same height can be fixed to the central shaft, the flared portions at both ends can be fixed to the tower wall (e.g., by pressing the flared portions with flanges), and the flared portions in the middle can be horizontally connected by welding or other connection methods. If there is no central shaft at the center of the entire leaching tower, the conical and flared portions are directly welded together by connecting rods, and the internal components at both ends are fixed to the tower wall. The flared portions of the internal components in the middle are horizontally connected by welding or other connection methods (the installation diagram is shown below). Figure 3 (As shown).

[0027] A third objective of this invention is to provide a removal system comprising the leaching tower described in the second objective of this invention.

[0028] In the removal system described in this invention, preferably:

[0029] It also includes a particle feeding system, a liquid feeding system, a particle conveying system, and a liquid-solid separation system;

[0030] The discharge port of the particle feeding system is connected to the solid feed port of the leaching tower;

[0031] The outlet of the liquid phase feeding system is connected to the liquid inlet of the leaching tower;

[0032] The feed inlet of the particle conveying system is connected to the discharge outlet of the leaching tower;

[0033] The discharge port of the particle conveying system is connected to the inlet of the liquid-solid separation system.

[0034] Preferably,

[0035] The particle conveying system also includes a pressure regulating pipe and a fluid tank. One end of the pressure regulating pipe is connected to the fluid tank, and the other end is connected to the particle conveying system. The fluid tank is a sealed tank containing liquid and gas. The inlet of the particle conveying system is divided into a solid inlet and a liquid inlet. The outlet of the leaching tower is divided into a solid outlet and a liquid outlet. The liquid inlet of the particle conveying system is connected to the outlet of the liquid phase feed system. The solid inlet of the particle conveying system is connected to the solid outlet of the leaching tower. The liquid level in the liquid-solid separation system is the same as the liquid level in the leaching tower.

[0036] Viewed from the direction of solid particle flow in the particle conveying system, the liquid inlet of the particle conveying system is preferably located after the position where the pressure regulating pipe is connected to the particle conveying system.

[0037] In this invention, the particle feeding system feeds solid particles from the top of the leaching tower, which then fall to the solid outlet at the bottom of the tower. The liquid feeding system enters the leaching tower from the bottom and flows upward, thus forming a countercurrent contact with the falling solid particles. Combined with the action of the internal components of the leaching tower, this ensures even contact and improves leaching efficiency. After leaching, the liquid in the leaching tower does not exit with the solid particles; only the solid particles are discharged. The leached liquid exits from the liquid outlet at the top of the leaching tower.

[0038] To prevent the liquid in the leaching tower from exiting without accompanying the solid particles, i.e., to allow only the solid particles to exit, this invention incorporates a pressure regulating pipe and a fluid tank to achieve this operation. The pressure regulating pipe is connected to a fluid tank at its top, which contains a certain liquid level and gas (generally air). This fluid tank is a sealed system, while the leaching tower and the liquid-solid separation system connected to the particle conveying system are not sealed. This creates a communicating vessel-like structure between the pressure regulating pipe, the liquid-solid separation system connected to the particle conveying system, and the leaching tower, thereby achieving pressure balance. Simultaneously, because the fluid tank at the top of the pressure regulating pipe is sealed and contains gas above it, this gas is compressed during the formation of the communicating vessel. The pressure of this gas causes the pressure in the pressure regulating pipe to be slightly higher than that in the leaching tower, preventing the liquid in the leaching tower from flowing out. However, this slight pressure difference is relatively small, and the resistance generated by this pressure difference is less than the kinetic energy of the solid particles falling under gravity in the leaching tower. Therefore, the design of the pressure regulating pipe and the sealed fluid tank ensures that the liquid does not flow out of the leaching tower outlet, but the solid particles can flow out smoothly. After the solid material flows out of the leaching tower, the leaching solvent exits from the liquid outlet inside the leaching tower for subsequent solvent reuse or material recovery units. This allows for continuous operation of the leaching process within the leaching tower, which is more efficient than batch reactors. The outlet of the leaching tower only discharges solid material; however, this method is not limited to the one described above, and other existing process devices capable of achieving this function can also be used.

[0039] In the removal system described in this invention, preferably:

[0040] The particle feeding system can use existing conventional solid feeding devices, preferably screw-type metering solid feed pumps; and / or,

[0041] The liquid phase feeding system can be any existing conventional liquid feeding device, preferably a combination of a general pump and a flow meter or at least one of a metering pump; and / or,

[0042] The particle conveying system can be any existing conventional liquid-solid mixing conveying device, preferably a combination of a common pump and a flow meter or at least one of a metering pump; and / or,

[0043] The liquid-solid separation system can be any existing conventional liquid-solid separation device, preferably at least one of a solid-liquid centrifuge or a hydrocyclone. The solvent obtained from the liquid-solid separation is returned to the solvent storage tank, and the solid enters the subsequent drying section.

[0044] The fourth objective of this invention is to provide the application of the leaching tower described in the second objective of this invention or the removal system described in the third objective of this invention in the leaching of substances, preferably the application of leaching small molecules from macromolecular substances, and more preferably the application of leaching small molecules from polymers.

[0045] The fifth objective of this invention is to provide a method for removing small molecule substances from polyglycolic acid, including the step of leaching polyglycolic acid with a leaching solvent; preferably, the leaching is performed using a leaching tower as described in the second objective of this invention or a removal system as described in the third objective of this invention, or by using a batch reactor.

[0046] In this invention, a leaching solvent is used to leach polyglycolic acid, thereby dissolving small molecules in the polyglycolic acid and removing them.

[0047] In the method for removing small molecules from polyglycolic acid according to the present invention, preferably:

[0048] Polyglycolic acid particles are leached with an leaching solvent, preferably polyglycolic acid particles with a particle size range of 0.2-2 mm; and / or,

[0049] The small molecule substance is a substance with a degree of polymerization of Pn < 10, preferably a substance with a degree of polymerization of Pn < 5.

[0050] In the method for removing small molecules from polyglycolic acid according to the present invention, preferably:

[0051] The leaching solvent is selected from one or more of alkyl alcohols or alkyl esters with fewer than C10;

[0052] Preferably, it is selected from one or more alkyl alcohols or alkyl esters with fewer than 5 carbon atoms;

[0053] More preferably, it is selected from one or more of methanol, ethanol, isopropanol, methyl acetate or ethyl acetate.

[0054] In the method for removing small molecules from polyglycolic acid according to the present invention, preferably:

[0055] During leaching, the mass ratio of the leaching solvent to polyglycolic acid is 1–20:1, preferably 2–10:1; for example, it can be 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 20:1; and / or,

[0056] The soaking time is 1 to 30 hours, preferably 3 to 25 hours, for example, 1 hour, 3 hours, 10 hours, 15 hours, 20 hours, 25 hours, or 30 hours; and / or,

[0057] The immersion temperature is 20-150℃, preferably 20-60℃, such as 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, or 150℃.

[0058] In the method for removing small molecules from polyglycolic acid according to the present invention, preferably:

[0059] In the removal of small molecules from polyglycolic acid, the fluid used in the particle conveying system for transporting polyglycolic acid particles is selected from at least one of the leaching solvents, preferably the same type of fluid as the leaching solvent used in the leaching process.

[0060] The method for removing small molecules from polyglycolic acid according to the present invention preferably includes the following steps:

[0061] (1) The initial material of polyglycolic acid and the leaching solvent enter the leaching tower or the batch reactor; preferably, the initial material of polyglycolic acid enters the leaching tower or the batch reactor through a particle feeding system, and the leaching solvent enters the leaching tower or the batch reactor through a liquid phase feeding system; more preferably, the initial material of polyglycolic acid enters from the top of the leaching tower or the top of the batch reactor.

[0062] (2) In the leaching tower or batch vessel, the initial material of polyglycolic acid comes into contact with the leaching solvent to achieve leaching; preferably, when leaching is carried out in the leaching tower, the leaching tower is filled with leaching solvent, the initial material of polyglycolic acid first passes through the conical part of the internal component in the leaching tower, then flows into the trumpet part through the annular gap between the wide end of the conical part and the inner surface of the trumpet part, and finally flows out from the narrow end of the trumpet part to achieve leaching;

[0063] (3) After leaching, the polyglycolic acid particles are discharged from the leaching tower or batch reactor and then processed to obtain polyglycolic acid after the removal of small molecules; preferably, the post-processing includes a solid-liquid separation step; more preferably, the post-processing includes the polyglycolic acid particles being discharged from the leaching tower or batch reactor and then entering the particle conveying system, and being sent to the liquid-solid separation system for solid-liquid separation; more preferably, when the polyglycolic acid particles are discharged from the leaching tower, only solid particles are discharged, and then they enter the particle conveying system, while liquid is introduced into the particle conveying system; then they are sent to the liquid-solid separation system for solid-liquid separation.

[0064] In this invention, small molecules dissolve in the leaching solvent during mixing with polyglycolic acid (PGA), thereby removing these small molecules from the PGA. Specifically, the specially designed internal components, a key objective of this invention, significantly increase the turbulence between the solid and liquid phases within the leaching tower, improving the liquid-solid phase velocity and mass transfer coefficient. Furthermore, the curved surface design increases the particle rotation speed, further accelerating particle surface renewal and enhancing the leaching effect of small molecules. After the small molecules are removed, the PGA particles exiting the leaching tower undergo liquid-solid separation to separate the particles from the solvent. Drying then yields even purer PGA particles.

[0065] The sixth objective of this invention is to provide polyglycolic acid obtained by the method for removing small molecule substances from polyglycolic acid as described in the fifth objective of this invention.

[0066] The seventh objective of this invention is to provide the application of polyglycolic acid as described in the sixth objective of this invention in the biomedical field, preferably in at least one of the fields of manufacturing medical sutures, drug-controlled release carriers, fracture fixation materials, tissue engineering scaffolds, or suture reinforcement materials.

[0067] Compared with the prior art, the present invention has at least the following advantages:

[0068] This invention develops a novel internal component. Adding this internal component to the leaching tower significantly increases the disturbance between the solid and liquid phases, improves the liquid-solid phase rate, and enhances the mass transfer coefficient. Simultaneously, the curved surface design increases the rotational speed of the particles, further accelerating particle surface renewal and thus improving the surface renewal effect, thereby promoting the leaching effect of small molecule substances.

[0069] The leaching and removal method described in this invention can remove small molecules from polyglycolic acid at low temperatures, effectively reducing the thermal degradation of the system compared to melt deashing and solid-phase vacuum devouring processes.

[0070] The method for removing small molecules from polyglycolic acid using the present invention can effectively reduce the content of small molecules in PGA to below 0.45 wt%.

[0071] When the method for removing small molecules from polyglycolic acid of the present invention uses an extraction tower or removal system containing the internal component, continuous devolatilization of polyglycolic acid can be achieved, ensuring stable and continuous operation and improving production efficiency. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the internal components of the present invention;

[0073] Figure 2This is a front view of the internal components of the present invention;

[0074] Figure 3 This is a schematic diagram of the internal components of the present invention installed inside the leaching tower;

[0075] Figure 4 This is a schematic diagram of the removal system of the present invention.

[0076] Explanation of reference numerals in the attached figures:

[0077] 1-Conical section, 11-Wide end of conical section, 12-Conical angle of conical section, 2-Flat section, 21-Wide end of flat section, 22-Narrow end of flat section, 3-Annular gap, 4-Leaching tower, 5-Particle feeding system, 6-Liquid phase feeding system, 7-Metering pump, 8-Particle conveying system, 9-Liquid-solid separation system, 10-Pressure regulating pipe, 11-Fluid tank, 12-Connecting rod. Detailed Implementation

[0078] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0079] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0080] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0081] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0082] Methods for determining the content of small molecules in polyglycolic acid:

[0083] 1 g of polyglycolic acid solid was placed in 50 g of dimethyl sulfoxide solution and dissolved at 150 °C. After cooling to room temperature, the solution was analyzed by gas chromatography, and quantification was performed using the external standard method to determine the content of small molecule substances in polyglycolic acid. The small molecule substance Pn was ≤ 5 during the test.

[0084] Example 1

[0085] An internal component such as Figure 1 and Figure 2 As shown, it includes a conical part 1 and a horn part 2; at least the wide end 11 of the conical part 1 is disposed in the horn part 2, and the wide end 11 of the conical part and the inner surface of the horn part on the same plane as the wide end 11 of the conical part are welded together by a connecting rod 10 and have an annular gap 3.

[0086] Preferably, the center line of the tapered portion 1 and the center line of the flared portion 2 are on the same straight line; and / or,

[0087] The wide end 11 of the tapered portion is located within the outwardly opening of the flared portion, and the outer diameter of the wide end 11 of the tapered portion is smaller than the inner diameter of the inner surface of the flared portion, which is on the same plane as the wide end of the tapered portion; and / or,

[0088] The height of the horn-shaped portion is denoted as H1, the height of the conical portion is denoted as H2, and the distance between the wide end 11 of the conical portion and the narrow end 22 of the horn-shaped portion is denoted as H3. The sum of H2 and H3 is greater than H1. Preferably, the values ​​of H1 and H2 are equal. More preferably, H3 is 0.2 to 2 times the value of H1.

[0089] Preferably, in the generatrix of the tapered portion, the arc connecting the wide end of the tapered portion and the cone angle is denoted as A1, and the angle corresponding to A1 is 20-90°, preferably 30-90°; and / or,

[0090] In the busbar of the horn section, the arc connecting the wide end and the narrow end of the horn section is denoted as A2, and the angle corresponding to A2 is 20-90°, preferably 30-90°.

[0091] In this embodiment, H1 and H2 have the same value, and H3 is 1 times the value of H1; the angles corresponding to A1 and A2 are both 90°.

[0092] In this invention, the connection between the conical part and the flared part of the internal component adopts an existing connection method. For example, when the internal component is installed inside the tower, if there is a central shaft at the center of the entire tower, the conical part of the internal component is fixed to the central shaft, and the flared part is fixed to the tower wall (e.g., by pressing the flared part with a flange). The vertical distance of the internal component is adjusted by adjusting the vertical height of the central shaft. If there is no central shaft at the center of the entire tower, the conical part and the flared part are directly welded together by the connecting rod 12 (the installation diagram is shown below). Figure 1 (As shown), then fix all the internal components to the tower wall. At this time, the height of the conical part and the trumpet part is fixed. If you want to change the height, you need to replace the internal components.

[0093] Example 2

[0094] A leaching tower, equipped with the internal components shown in Example 1, specifically:

[0095] The length-to-diameter ratio of the leaching tower is 5:1 to 30:1, preferably 5:1 to 20:1; and / or,

[0096] The internal components H1 and H2 are each independently 1 / 4 to 1 / 32 of the diameter of the leaching tower body, preferably H1 and H2 are equal in value and are 1 / 4 to 1 / 32 of the diameter of the leaching tower body.

[0097] Preferably, when installing the internal components of the leaching tower,

[0098] The vertical distance between two adjacent internal components within the leaching tower is 1 to 10 times the diameter of the leaching tower body, preferably 1 to 4 times; and / or,

[0099] Inside the leaching tower, 1-8 internal components are installed at the same height. Preferably, the flared sections of the internal components are horizontally connected. In this invention, the connection method between the conical and flared sections of the internal components can adopt the connection method of the internal components in the tower described in Example 1. If multiple internal components need to be installed at the same height in the leaching tower, if the entire leaching tower has a central shaft, the conical sections of multiple internal components at the same height can be fixed to the central shaft, the flared sections at both ends can be fixed to the tower wall (e.g., by pressing the flared sections with flanges), and the flared sections in the middle can be horizontally connected by welding or other connection methods. If the entire leaching tower does not have a central shaft, the conical and flared sections are directly welded together by connecting rods, and the internal components at both ends are fixed to the tower wall. The flared sections of the internal components in the middle are horizontally connected by welding or other connection methods (the installation diagram is shown below). Figure 3 (As shown).

[0100] In this embodiment, the length-to-diameter ratio of the leaching tower is 10:1; H1 and H2 are equal in value and are 1 / 4 of the diameter of the leaching tower; when the internal components are installed in the leaching tower, the vertical distance between two vertically adjacent internal components in the leaching tower is twice the diameter of the leaching tower, and the number of internal components at the same tower height is 1.

[0101] Example 3

[0102] A removal system, such as Figure 4 As shown, the removal system of the present invention also includes a particle feeding system 5, a liquid phase feeding system 6, a particle conveying system 8, and a liquid-solid separation system 9.

[0103] The discharge port of the particle feeding system 5 is connected to the solid feed port of the leaching tower 4;

[0104] The outlet of the liquid phase feeding system 6 is connected to the liquid inlet of the leaching tower 4;

[0105] The feed inlet of the particle conveying system 8 is connected to the discharge outlet of the leaching tower 4;

[0106] The discharge port of the particle conveying system 8 is connected to the inlet of the liquid-solid separation system 9;

[0107] Preferably,

[0108] The particle conveying system 8 also includes a pressure regulating pipe 10 and a fluid tank 11. One end of the pressure regulating pipe 10 is connected to the fluid tank 11, and the other end is connected to the particle conveying system 8. The feed inlet of the particle conveying system 8 is divided into a solid feed inlet and a liquid feed inlet. The discharge outlet of the leaching tower 4 is divided into a solid discharge outlet and a liquid discharge outlet. The liquid feed inlet of the particle conveying system 8 is connected to the discharge outlet of the liquid phase feed system 6. The solid feed inlet of the particle conveying system 8 is connected to the solid discharge outlet of the leaching tower 4.

[0109] In the removal system described in this invention, preferably:

[0110] The particle feeding system can use existing conventional solid feeding devices, preferably screw-type metering solid feed pumps; and / or,

[0111] The liquid phase feeding system can be any existing conventional liquid feeding device, preferably a combination of a general pump and a flow meter or at least one of a metering pump; and / or,

[0112] The particle conveying system can be any existing conventional liquid-solid mixing conveying device, preferably a combination of a common pump and a flow meter or at least one of a metering pump; and / or,

[0113] The liquid-solid separation system can be any existing conventional liquid-solid separation device, preferably at least one of solid-liquid centrifuge or hydrocyclone. The solvent obtained from the liquid-solid separation is returned to the solvent storage tank, and the solid enters the subsequent drying section.

[0114] In this embodiment, the particle feeding system 5 uses a screw metering solid feed pump, and the liquid phase feeding system 6 uses a metering pump 7. The leaching tower 4 described in Embodiment 2 of the present invention uses the pressure regulating pipe and the fluid tank in the particle conveying system to ensure that only solid material flows out of the outlet of the leaching tower 4. The particle conveying system 8 uses a metering pump to introduce fluid from the liquid phase feeding system 6. The fluid and the solid material are mixed and flow into the liquid-solid separation system 9. The liquid-solid separation system 9 uses a hydrocyclone to separate the solid material and the fluid.

[0115] Example 4

[0116] A method for removing small molecule substances from polyglycolic acid, using the removal system of Example 3, includes the following steps:

[0117] (1) The initial material of polyglycolic acid and the leaching solvent enter the leaching tower; wherein the initial material of polyglycolic acid enters from the top of the leaching tower through the particle feeding system; the leaching solvent enters the leaching tower through the liquid phase feeding system.

[0118] (2) In the leaching tower, the initial material of polyglycolic acid comes into contact with the leaching solvent to achieve leaching; wherein the leaching tower is filled with leaching solvent, the initial material of polyglycolic acid first passes through the conical part of the internal component in the leaching tower, then flows into the trumpet part through the annular gap between the wide end of the conical part and the inner surface of the trumpet part, and finally flows out from the narrow end of the trumpet part to achieve leaching.

[0119] (3) When the leached polyglycolic acid particles are discharged from the leaching tower, only solid particles are discharged. Then they enter the particle conveying system. At the same time, the leaching solvent in the liquid phase feed system is introduced into the particle conveying system as a fluid. Then, the particles are sent to the liquid-solid separation system for solid-liquid separation.

[0120] The initial material of polyglycolic acid (PGA) leached with leaching solvent contained 5.3 wt% PGA particles (Pn≤5), with a particle size range of 0.2-2 mm. The leaching solvent was isopropanol, with a mass ratio of isopropanol to PGA particles of 3:1. The leaching tower temperature was 50℃, and the residence time was 10 h.

[0121] The small molecule content in the PGA particles obtained by the above method is 0.58 wt%.

[0122] Examples 5-11

[0123] Examples 5-11 are based on Example 4, with different solvents, leaching temperatures, residence times, and liquid-to-solid ratios. The results show the content of small molecules in the system after drying of the leached particles. The results are shown in Table 1 below.

[0124] Table 1

[0125] Solvent types Leaching temperature (°C) Duration of stay (h) Liquid-to-solid ratio Small molecule content Example 5 methanol 20 25 10:1 0.63wt% Example 6 methanol 40 20 5:1 0.60wt% Example 7 ethanol 50 10 2:1 0.65wt% Example 8 ethanol 45 15 6:1 0.53wt% Example 9 Methyl acetate 30 20 5:1 0.49wt% Example 10 Ethyl acetate 30 10 8:1 0.44wt% Example 11 Ethyl acetate 60 15 2:1 0.53wt%

[0126] Examples 12-16

[0127] Examples 12-16 are based on Example 4, only changing the A1 and A2 angles and the H3 distance of the internal components of Example 1. The content of small molecules in the system of the obtained polyglycolic acid particles after leaching and drying is shown in Table 2 below.

[0128] Table 2

[0129]

[0130]

[0131] Example 17

[0132] The content of small molecule substances (Pn<5) in the polymerized PGA particles was 5.3 wt%. The solvent was isopropanol, and the mass ratio of isopropanol to PGA particles (liquid-solid ratio) was 3:1. Leaching was carried out in a batch reactor at a temperature of 50°C for 10 hours. After drying and analysis, the content of small molecule substances in the leached particles was 1.07%. Fresh isopropanol was added to the leached particles and leaching was continued for another 8 hours under the same conditions. After drying and analysis, the content of small molecule substances in the particles was 0.75%.

[0133] In Example 17, intermittent leaching was performed using a batch vessel, which required multiple intermittent leachings to obtain a relatively low content of small molecules.

[0134] Comparative Example 1

[0135] Comparative Example 1 used essentially the same preparation conditions and removal system as Example 3, with the only difference being that in the internal components of Comparative Example 1, the line connecting the wide end and the cone corner end of the conical section in the generatrix of the conical part was a straight line, and the line connecting the wide end and the narrow end of the flared section in the generatrix of the flared part was a straight line, i.e., A1 and A2 were both straight lines. The remaining operating conditions were the same as in Example 4. After drying, the particles were analyzed, and the content of small molecule substances was 1.15%.

[0136] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A leaching tower, characterized in that: The leaching tower is equipped with internal components, which include a conical part and a trumpet part; the wide end of the trumpet part and the cone apex of the conical part are in the same direction; at least the portion of the conical part including the wide end is disposed inside the trumpet part, and there is an annular gap between the outer edge of the wide end of the conical part and the inner surface of the trumpet part, which are on the same plane as the wide end of the conical part; In the generatrix of the tapered section, the line connecting the wide end and the cone corner end of the tapered section is an arc, denoted as A1; the angle corresponding to A1 is 20-90°; In the busbar of the horn section, the line connecting the wide end and the narrow end of the horn section is an arc, denoted as A2; the angle corresponding to A2 is 20-90°; the height of the horn section is denoted as H1, the height of the conical section is denoted as H2, the distance between the wide end of the conical section and the narrow end of the horn section is denoted as H3, and the sum of H2 and H3 is greater than H1.

2. The leaching tower according to claim 1, characterized in that: The angle corresponding to A1 is 30-90°; and / or, The angle corresponding to A2 is 30-90°.

3. The leaching tower according to claim 1, characterized in that: The centerline of the tapered portion and the centerline of the flared portion are on the same straight line; and / or, The wide end of the tapered portion is located inside the outwardly opening of the flared portion, and the outer diameter of the wide end of the tapered portion is smaller than the inner diameter of the inner surface of the flared portion, which is on the same plane as the wide end of the tapered portion.

4. The leaching tower according to claim 3, characterized in that: The values ​​of H1 and H2 are equal.

5. The leaching tower according to claim 4, characterized in that: H3 is 0.2 to 2 times the value of H1.

6. The leaching tower according to claim 1, characterized in that: The length-to-diameter ratio of the leaching tower is 5:1 to 30:1; and / or, The internal components H1 and H2 are each independently 1 / 4 to 1 / 32 of the diameter of the leaching tower body.

7. The leaching tower according to claim 6, characterized in that: The length-to-diameter ratio of the leaching tower is 5:1 to 20:

1.

8. The leaching tower according to claim 7, characterized in that: When installing the internal components of the leaching tower The vertical distance between two adjacent vertical internal components within the leaching tower is equal to the diameter of the leaching tower body; and / or, Inside the leaching tower, 1 to 8 internal components are installed at the same height.

9. The leaching tower according to claim 8, characterized in that: The vertical distance between two adjacent internal components within the leaching tower is 1 to 4 times the diameter of the leaching tower body; and / or, The flared sections of the internal components are horizontally connected.

10. A removal system comprising an leaching tower as described in any one of claims 1 to 9.

11. The removal system according to claim 10, characterized in that: It also includes a particle feeding system, a liquid feeding system, a particle conveying system, and a liquid-solid separation system; The discharge port of the particle feeding system is connected to the solid feed port of the leaching tower; The outlet of the liquid phase feeding system is connected to the liquid inlet of the leaching tower; The feed inlet of the particle conveying system is connected to the discharge outlet of the leaching tower; The discharge port of the particle conveying system is connected to the inlet of the liquid-solid separation system.

12. The removal system according to claim 11, characterized in that: The particle conveying system also includes a pressure regulating pipe and a fluid tank. One end of the pressure regulating pipe is connected to the fluid tank, and the other end is connected to the particle conveying system. The fluid tank is a sealed tank containing liquid and gas. The inlet of the particle conveying system is divided into a solid inlet and a liquid inlet. The outlet of the leaching tower is divided into a solid outlet and a liquid outlet. The liquid inlet of the particle conveying system is connected to the outlet of the liquid phase feed system. The solid inlet of the particle conveying system is connected to the solid outlet of the leaching tower. The liquid level in the liquid-solid separation system is the same as the liquid level in the leaching tower.

13. The removal system according to claim 11, characterized in that: The particle feeding system is selected from a screw metering solids feed pump; and / or The liquid phase feed system is selected from at least one of a combination of a conventional pump and a flow meter, or a metering pump; and / or, The particle conveying system is selected from at least one of a combination of a conventional pump and a flow meter, or a metering pump; and / or, The liquid-solid separation system is selected from at least one of centrifuges or hydrocyclones.

14. The application of the leaching tower according to any one of claims 1 to 9 or the removal system according to any one of claims 10 to 13 in the leaching of substances.

15. The application according to claim 14, characterized in that: The aforementioned removal system is used to extract small molecules from macromolecules.

16. The application according to claim 15, characterized in that: The aforementioned removal system is used for leaching small molecules from polymers.

17. A method for removing small molecule substances from polyglycolic acid, comprising the step of leaching polyglycolic acid with a leaching solvent; leaching is performed using a leaching tower comprising any one of claims 1 to 9 or a removal system comprising any one of claims 10 to 13 or a batch reactor.

18. The method for removing small molecule substances from polyglycolic acid according to claim 17, characterized in that: The leaching solvent is an organic solvent; and / or The polyglycolic acid is in the form of polyglycolic acid particles.

19. The method for removing small molecule substances from polyglycolic acid according to claim 18, characterized in that: The polyglycolic acid is polyglycolic acid particles with a particle size range of 0.2-2 mm.

20. The method for removing small molecule substances from polyglycolic acid according to claim 19, characterized in that: The leaching solvent is selected from one or more alkyl alcohols or alkyl esters with a C10 or less.

21. The method for removing small molecule substances from polyglycolic acid according to claim 20, characterized in that: The leaching solvent is selected from one or more alkyl alcohols or alkyl esters with a C5 or less.

22. The method for removing small molecule substances from polyglycolic acid according to claim 21, characterized in that: The leaching solvent is selected from one or more of methanol, ethanol, isopropanol, methyl acetate, or ethyl acetate.

23. The method for removing small molecule substances from polyglycolic acid according to claim 18, characterized in that: During leaching, the mass ratio of the leaching solvent to polyglycolic acid is 1~20:1; and / or, The immersion time is 1 to 30 hours; and / or, The immersion temperature is 20 ~ 150℃.

24. The method for removing small molecule substances from polyglycolic acid according to claim 23, characterized in that: During leaching, the mass ratio of the leaching solvent to polyglycolic acid is 2~10:1; and / or, The soaking time is 3 to 25 hours; and / or, The immersion temperature is 20 ~ 60℃.

25. The method for removing small molecule substances from polyglycolic acid according to claim 18, characterized in that: In the removal of small molecules from polyglycolic acid, the fluid used in the particle conveying system for transporting the polyglycolic acid particles is selected from at least one of the leaching solvents.

26. The method for removing small molecule substances from polyglycolic acid according to claim 25, characterized in that: The fluid is the same type as the solvent used during leaching.

27. The method for removing small molecule substances from polyglycolic acid according to any one of claims 18 to 26, characterized in that, Includes the following steps: (1) The initial material and leaching solvent of polyglycolic acid enter the leaching tower or batch reactor; (2) In the leaching tower or batch vessel, the initial material of polyglycolic acid comes into contact with the leaching solvent to achieve leaching; when the leaching tower is used, the leaching tower is filled with leaching solvent, the initial material of polyglycolic acid first passes through the conical part of the internal component in the leaching tower, then flows into the trumpet part through the annular gap between the wide end of the conical part and the inner surface of the trumpet part, and finally flows out from the narrow end of the trumpet part to achieve leaching; (3) After leaching, the polyglycolic acid particles are processed by leaching tower or batch reactor to obtain polyglycolic acid after small molecules are removed.

28. The method for removing small molecule substances from polyglycolic acid according to claim 27, characterized in that, Includes the following steps: (1) The initial material of polyglycolic acid enters the leaching tower or batch reactor through the particle feeding system, and the leaching solvent enters the leaching tower or batch reactor through the liquid phase feeding system; (2) In the leaching tower or batch vessel, the initial material of polyglycolic acid comes into contact with the leaching solvent to achieve leaching; when the leaching tower is used, the leaching tower is filled with leaching solvent, the initial material of polyglycolic acid first passes through the conical part of the internal component in the leaching tower, then flows into the trumpet part through the annular gap between the wide end of the conical part and the inner surface of the trumpet part, and finally flows out from the narrow end of the trumpet part to achieve leaching; (3) After leaching, the polyglycolic acid particles are discharged from the leaching tower or batch reactor and then processed to obtain polyglycolic acid after the removal of small molecules; the processing includes a solid-liquid separation step.

29. The method for removing small molecule substances from polyglycolic acid according to claim 28, characterized in that, Includes the following steps: Step (1): The initial material of polyglycolic acid enters from the top of the leaching tower or the top of the batch reactor; Step (3) The process includes the polyglycolic acid particles being discharged from the leaching tower or batch reactor and then entering the particle conveying system, which then sends them to the liquid-solid separation system for solid-liquid separation.

30. The method for removing small molecule substances from polyglycolic acid according to claim 29, characterized in that, Includes the following steps: In step (3), when the polyglycolic acid particles are discharged from the leaching tower, only solid particles are discharged, and then they enter the particle conveying system. At the same time, liquid is introduced into the particle conveying system; then the particles are sent to the liquid-solid separation system for solid-liquid separation.

31. Polyglycolic acid obtained by the method for removing small molecules from polyglycolic acid according to any one of claims 17-30.

32. The application of polyglycolic acid according to claim 31 in the biomedical field.

33. The application of polyglycolic acid in the biomedical field according to claim 32, characterized in that, Applications in at least one of the following areas: manufacturing medical sutures, drug-controlled release carriers, fracture fixation materials, tissue engineering scaffolds, or suture reinforcement materials.

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