Apparatus for producing polylactic acid microspheres

Abstract

Apparatus for the production of polylactic acid microspheres, characterized in that it comprises: a reactor body, a reactor lid arranged on the reactor body to cover an opening of the reactor body, and a solvent recovery device by distillation connected to the reactor lid; the reactor body comprises an inner cylinder, an outer cylinder, an intermediate space formed between the inner cylinder and the outer cylinder, an intermediate space inlet and outlet provided on the outer surface of the intermediate space, a tank bottom valve located under the reactor body, and a high-temperature circulation device connected to the intermediate space inlet and outlet; The reactor lid comprises an inlet opening and a distillation opening provided in the surface of the reactor lid, as well as a stirring device and an emulsifying device, wherein the stirring device comprises a stirring motor and an associated stirring blade, the stirring motor being located centrally above the reactor lid and the stirring blade projecting into the inner cylinder of the reactor body to stir a reaction liquid; and the emulsifying device comprising an emulsifying motor located above the reactor lid and an associated emulsifying head, the emulsifying head projecting into the inner cylinder of the reactor body to generate polylactic acid microsphere droplets by shear force; The solvent recovery device by distillation comprises a condensation tube, a circulation inlet and outlet provided on the surface of the condensation tube, a low-temperature circulation device connected to the condensation circulation inlet and outlet, a reflux head located at the bottom of the condensation tube, and a collection bottle located below and connected to the reflux head.

Description

Technical field

[0001] The present invention relates to a medical beauty product and in particular to a device for the production of polylactic acid microspheres. State of the art

[0002] Biodegradable polymer microspheres—represented by polylactic acid microspheres—are frequently used in the medical and cosmetic fields due to their excellent biocompatibility and biodegradability. The intermediate product in the degradation of polylactic acid is lactic acid, which ultimately breaks down into carbon dioxide and water, both of which are harmless to the human body and the environment. During the degradation of polylactic acid, lactic acid is gradually released, increasing the activity of fibroblast-transforming growth factor (TGF-β), proline hydroxylase, and matrix metalloproteinase inhibitor. This stimulates fibroblast proliferation, differentiation, and metabolism, and promotes collagen secretion until the polylactic acid is completely degraded. Therefore, collagen-stimulating fillers made with polylactic acid microspheres as the primary material can provide a longer-lasting plumping effect.

[0003] The most common methods for producing polylactic acid microspheres include spray drying, phase separation, and emulsion solvent evaporation. In spray drying, a suspension or emulsion is sprayed into hot air. This causes the solvent to evaporate within seconds, transforming into solid particles. This requires precise control of the hot air temperature. In phase separation, a non-solvent liquid is added to the polymer solution, causing the polymer to precipitate and form by exploiting its physicochemical properties. However, this method consumes an extremely large amount of organic solvent. Emulsion solvent evaporation offers the advantages of ease of operation, a simple process, and easy production scaling, making it suitable for a wide range of applications.In emulsion solvent evaporation, particle size control is often achieved by adjusting the emulsification speed, solvent type, emulsification temperature and time, etc. However, if the process conditions are not well controlled, irregular morphology of the polylactic acid microspheres occurs, along with agglomeration and adhesion between the microspheres and a wide size distribution of the microspheres, which seriously impairs the application of the microspheres.

[0004] In CN116139790A, polylactic acid microspheres with a uniform particle size are produced using the principle of solvent evaporation via a microfluidic device. The microfluidic device places high demands on precision, and the yield in microsphere production is low, which complicates its application in large-scale industrial production. In CN115531607A, CN114931554A, and CN108653817A, microspheres are all produced using solvent evaporation, but the removal methods for the organic solvents used to dissolve polyester materials are all natural evaporation or evaporation by heating, which poses a significant hazard to the environment and production personnel.The microsphere production device of the present invention utilizes a solvent recovery system by distillation to achieve complete recycling of organic solvents. This significantly reduces the risk to the environment and production personnel, representing a major innovation. Content of the invention

[0005] In light of existing problems in the prior art, the present invention offers improvements and provides a device for the production of polylactic acid microspheres. The present invention is implemented by the following technical solutions: The present invention discloses a device for the production of polylactic acid microspheres, comprising: a reactor body, a reactor lid arranged on the reactor body to cover an opening of the reactor body, and a solvent recovery device by distillation connected to the reactor lid.

[0006] The reactor body comprises an inner cylinder, an outer cylinder, an intermediate space formed between the inner cylinder and the outer cylinder, an intermediate space inlet and outlet provided on the outer surface of the intermediate space, a tank bottom valve located under the reactor body, and a high-temperature circulation device connected to the intermediate space inlet and outlet.

[0007] The reactor lid comprises an inlet opening and a distillation opening provided in the surface of the reactor lid, as well as a stirring device and an emulsifying device, wherein the stirring device comprises a stirring motor and an associated stirring blade, the stirring motor being located centrally above the reactor lid and the stirring blade projecting into the inner cylinder of the reactor body to stir a reaction liquid; and the emulsifying device comprising an emulsifying motor located above the reactor lid and an associated emulsifying head, the emulsifying head projecting into the inner cylinder of the reactor body to generate polylactic acid microsphere droplets by shear force.

[0008] The solvent recovery device by distillation comprises a condensation tube, a circulation inlet and outlet provided on the surface of the condensation tube, a low-temperature circulation device connected to the condensation circulation inlet and outlet, a reflux head arranged at the bottom of the condensation tube, and a collection bottle arranged below and connected to the reflux head.

[0009] In a further development of the present invention, the high-temperature circulation device allows a circulation fluid of the high-temperature circulation device to circulate through the interspace inlet and outlet to supply heat to the reactor body in real time, causing a solvent in the polylactic acid microsphere droplets to evaporate and solidify into polylactic acid microspheres; and the tank bottom valve is used to drain the reaction fluid from the inner cylinder.

[0010] In a further development of the present invention, the reflux head is provided with three open ends, one end of which is connected to the distillation opening, one end to the bottom of the condensation tube, and the last end to the collection bottle in order to divert the evaporated solvent from the inner cylinder to the condensation tube and to collect the condensed solvent. The collection bottle collects the condensed solvent, and the condensation tube has a double-layer structure and is connected to the low-temperature circulation device to enable the condensation of the evaporated solvent.

[0011] In a further development of the present invention, the reactor body is connected to the reactor lid via a sealing ring, a screw or a clamp, and the reactor body, the reactor lid and the solvent recovery device by distillation are made of corrosion-resistant materials, preferably stainless steel 316.

[0012] To further illustrate the invention, an unclaimed method for producing polylactic acid microspheres is disclosed, wherein the production is carried out using a device for producing polylactic acid microspheres. The method comprises the following steps: 1) Preparation of a polyvinyl alcohol continuous phase solution and a polylactic acid dispersed phase solution; 2) First, the polyvinyl alcohol solution of the continuous phase is introduced into an inner cylinder of a reactor, and then the polylactic acid solution of the dispersed phase is added slowly to the polyvinyl alcohol solution of the continuous phase to obtain a reaction liquid, wherein a stirring motor drives a stirring blade to allow the reaction liquid to flow, and an emulsifying motor drives an emulsifying head to generate and exert a continuous shear force on the reaction liquid, thereby forming the polylactic acid microsphere droplets; 3) Switching off the emulsifying motor and keeping the stirring motor running, whereby the reaction liquid is heated in real time by a high-temperature circulation device, causing a solvent in the polylactic acid microsphere droplets to evaporate and solidify into polylactic acid microspheres, and the evaporated solvent is cooled in real time by a low-temperature circulation device, causing it to condense and be collected in a collection bottle via a reflux head; 4) Washing and drying of a polylactic acid microsphere crude product contained in the reaction liquid obtained by distillation of the solvent to obtain finished polylactic acid microspheres.

[0013] In a further development of the present invention, the continuous phase polyvinyl alcohol solution is prepared by adding polyvinyl alcohol to water for injection and dissolving it under stirring, wherein the concentration range is between 0.05-0.1 g / ml; the dispersed phase polylactic acid solution is prepared by adding polylactic acid to dichloromethane or chloroform or a mixture of both and dissolving it under stirring under closed conditions, wherein the concentration range is between 0.1-0.2 g / ml.

[0014] In a further development of the present invention, the volume ratio of the continuous phase to the dispersed phase is 5:1-50:1, the mass ratio of the polyvinyl alcohol to the polylactic acid is 1:0.1-1:2, the stirring speed is 30-150 rpm and the emulsifying speed is 100-3000 rpm.

[0015] In a further development of the present invention, the volume ratio of the continuous phase to the dispersed phase is 8:1-20:1, the mass ratio of the polyvinyl alcohol to the polylactic acid is 1:0.3-1:0.7, the stirring speed is 60-90 rpm and the emulsifying speed is 500-1500 rpm.

[0016] In a further development of the present invention, in step 3) the solvent in the polylactic acid microsphere droplets is removed by heating, wherein the temperature of the heating is 30-50 °C, preferably 40-50 °C.

[0017] To further illustrate the invention, an unclaimed use of polylactic acid microspheres produced by a polylactic acid microsphere production process is described. In this process, the polylactic acid microspheres are used as a component of a filler, suspended in an aqueous solution of sodium carboxymethylcellulose and mannitol, and freeze-dried to obtain a polylactic acid filler for medical cosmetic injections.

[0018] The advantageous effects of the present invention are as follows: 1. In the device according to the invention for the production of polylactic acid microspheres, the polylactic acid solution of dispersed phase can be efficiently and uniformly divided into polylactic acid droplets by the simultaneous use of a stirring device and an emulsifying device for the production of microspheres, in order to produce the polylactic acid microspheres with a concentrated particle size distribution in large quantities and quickly. 2. Furthermore, in the device according to the invention for the production of polylactic acid microspheres, the space formed between the inner cylinder and the outer cylinder allows the circulation fluid heated by the high-temperature circulation device to circulate, which achieves water bath heating of the reaction fluid and thus avoids temperature fluctuations caused by direct heating of the reaction fluid; at the same time, for the production of microspheres, where the heating temperature range is from 30 to 50 °C, it is made possible that the temperature of the polylactic acid in the reaction solution always remains below its glass transition temperature, thereby preventing changes in the physicochemical properties of the polylactic acid microspheres. 3. Furthermore, in the apparatus according to the invention for the production of polylactic acid microspheres, the evaporated dichloromethane or chloroform gas, when the polylactic acid droplets are heated and solidified into polylactic acid microspheres, can be directed to the condensation tube via the reflux head in order to continuously condense the evaporated solvent; the condensed solvent is then collected in the collection bottle via the reflux head, thereby achieving complete recovery and reuse of the organic solvent to avoid toxic exposure of personnel, prevent environmental damage and simultaneously ensure solvent recovery. 4 Brief description of the drawings Fig. Figure 1 is a schematic representation of an embodiment of a device for the production of polylactic acid microspheres; Fig.Figure 2 is a diagram showing the particle size distribution of polylactic acid microspheres produced using a microsphere manufacturing process; Fig. Figure 3 is a photograph of polylactic acid microspheres with a particle size range of 10-50 µm, produced using a microsphere manufacturing process; Fig. Figure 4 is a histological section diagram of the collagen formation stimulated by the polylactic acid microspheres produced according to the invention after 3 months of subcutaneous implantation in rabbits; Fig. Figure 5 is a histological section diagram of the collagen formation stimulated by the polylactic acid microspheres produced according to the invention after 6 months of subcutaneous implantation in rabbits;

[0019] Reference numeral list: 11. Inner cylinder, 12. Outer cylinder, 13. Intermediate inlet and outlet, 14. Tank bottom valve, 15. High-temperature circulation device; 21. Inlet port, 22. Distillation port, 23. Emulsifying motor, 24. Emulsifying head, 25. Stirring motor, 26. Stirring blade; 31. Condensation tube, 32. Condensation circulation inlet and outlet, 33. Low-temperature circulation device, 34. Reflux head, 35. Collection bottle. Detailed description of embodiments

[0020] The present invention is explained in more detail below with reference to specific embodiments and drawings. Further details are explained in the following description to enable a comprehensive understanding of the invention. Of course, the present invention can also be implemented in other ways that differ from the description. Those skilled in the art can draw similar generalizations and conclusions based on actual application situations without infringing the purpose of the present invention. The scope of protection of the present invention is therefore not limited by the specific embodiment.

[0021] It should be noted that these and other subsequent drawings are merely examples and are not to scale and should not be used to limit the actual scope of protection of the present invention.

[0022] As in Fig.As shown in Figure 1, the apparatus for the production of polylactic acid microspheres comprises a reactor body 10, a reactor lid 20 arranged on the reactor body to cover an opening of the reactor body, and a recovery device 30 of solvents by distillation connected to the reactor lid.

[0023] As in Fig. As shown in Figure 1, the reactor body 10 comprises an inner cylinder 11, an outer cylinder 12, an intermediate space 13 formed between the inner cylinder and the outer cylinder, an intermediate space inlet and outlet 14 provided on the outer surface of the intermediate space, a tank bottom valve 15 located under the reactor body, and a high-temperature circulation device 16 connected to the intermediate space inlet and outlet.

[0024] As in Fig.As shown in Figure 1, the reactor lid 20 comprises an inlet opening 21 and a distillation opening 22, which are provided in the surface of the reactor lid, as well as a stirring device and an emulsifying device, wherein the stirring device comprises a stirring motor 23 and an associated stirring blade 24, the stirring motor 23 being located centrally above the reactor lid and the stirring blade 24 projecting into the inner cylinder 11 of the reactor body 10 to stir a reaction liquid; and the emulsifying device comprising an emulsifying motor 25 located above the reactor lid and an associated emulsifying head 26, the emulsifying head 26 projecting into the inner cylinder of the reactor body 10 to generate polylactic acid microsphere droplets by shear force.

[0025] As in Fig.As shown in Figure 1, the solvent recovery device 30 by distillation comprises a condensation tube 31, a circulation inlet and outlet 32 ​​provided on the surface of the condensation tube, a low-temperature circulation device 33 connected to the condensation circulation inlet and outlet, a reflux head 34 arranged at the bottom of the condensation tube, and a collection bottle 35 arranged below and connected to the reflux head.

[0026] In one or more embodiments, the high-temperature circulation device 15 allows a circulation fluid of the high-temperature circulation device to circulate through the interspace inlet and outlet 13 to supply heat to the reactor body 10 in real time, causing a solvent in the polylactic acid microsphere droplets to evaporate and solidify into polylactic acid microspheres; and the tank bottom valve 14 is used to drain the reaction fluid from the inner cylinder 11.

[0027] In one or more embodiments, the reflux head 34 is provided with three open ends, one end of which is connected to the distillation opening 22, one end to the bottom of the condensation tube 31, and the last end to the collection bottle 35 to achieve the diversion of the evaporated solvent from the inner cylinder 11 to the condensation tube 31 and the accumulation of the condensed solvent. The collection bottle 35 collects the condensed solvent, and the condensation tube 31 has a double-layer structure and is connected to the low-temperature circulation device 33 to enable the condensation of the evaporated solvent.

[0028] In one or more embodiments, the reactor body 10 is connected to the reactor lid 20 via a sealing ring, a screw or a clamp, and the reactor body 10, the reactor lid 20 and the recovery device 30 of solvents by distillation are made of corrosion-resistant materials, preferably stainless steel 316.

[0029] In one or more embodiments, a dispersed phase is continuously added to the mobile phase through the inlet opening 21 at a uniformly low rate to improve the uniformity of the produced polylactic acid microspheres.

[0030] In one or more embodiments, the continuous phase is an aqueous system containing a polyvinyl alcohol surfactant; the dispersed phase is an organic solvent system containing polylactic acid, and the organic solvent is preferably dichloromethane or chloroform, or a mixture of both. Due to the general corrosiveness, flammability, and explosiveness of organic solvents, the reactor is preferably an explosion-proof system, and the material is preferably stainless steel 316.

[0031] In combination with the above introduction to the apparatus for producing polylactic acid microspheres, an unclaimed method for producing polylactic acid microspheres with a concentrated particle size distribution can also be understood. The unclaimed method essentially comprises the following steps: Preparation of a polyvinyl alcohol continuous phase solution and a polylactic acid dispersed phase solution; introduction of the polyvinyl alcohol continuous phase solution first into an inner cylinder 11 of a reactor and then slowly adding the polylactic acid dispersed phase solution to the polyvinyl alcohol continuous phase solution to obtain a reaction liquid, wherein a stirring motor 25 drives a stirring blade 26 to allow the reaction liquid to flow, and an emulsifying motor 23 drives an emulsifying head 24 to generate and exert a continuous shear force on the reaction liquid, thereby forming the polylactic acid microsphere droplets;Switching off the emulsifying motor 23 and keeping the stirring motor 25 running, the reaction liquid being heated in real time by a high-temperature circulation device 15, causing a solvent in the polylactic acid microsphere droplets to evaporate and solidify into polylactic acid microspheres, and the evaporated solvent being cooled in real time by a low-temperature circulation device 33, causing it to condense and be collected via a reflux head 34 in a collection bottle 35; washing and drying of a polylactic acid microsphere crude product contained in the reaction solution obtained by distillation of the solvent to obtain finished polylactic acid microspheres.

[0032] In one or more embodiments, the continuous-phase polyvinyl alcohol solution is prepared by adding polyvinyl alcohol to water for injection and dissolving it under stirring, wherein the concentration range is between 0.05-0.1 g / ml; the dispersed-phase polylactic acid solution is prepared by adding polylactic acid to dichloromethane or chloroform or a mixture of both and dissolving it under stirring under closed conditions, wherein the concentration range is between 0.1-0.2 g / ml.

[0033] In one or more embodiments, the volume ratio of the continuous phase to the dispersed phase is 5:1-50:1, the mass ratio of the polyvinyl alcohol to the polylactic acid is 1:0.1-1:2, the stirring speed is 30-150 rpm and the emulsifying speed is 100-3000 rpm.

[0034] In one or more embodiments, the volume ratio of the continuous phase to the dispersed phase is 8:1-20:1, the mass ratio of the polyvinyl alcohol to the polylactic acid is 1:0.3-1:0.7, the stirring speed is 60-90 rpm and the emulsifying speed is 500-1500 rpm.

[0035] In one or more embodiments of the unclaimed method for producing polylactic acid microspheres, the solvent in the polylactic acid microsphere droplets is removed by heating, wherein the heating temperature is 30-50 °C, preferably 40-50 °C.

[0036] The unclaimed method for producing microspheres is explained in more detail below using specific embodiments. Example 1: (1) Poly-L-lactic acid was dissolved in dichloromethane to prepare a dispersed phase solution at a concentration of 0.5 g / ml, dissolved under closed conditions by stirring to prevent evaporation of the dichloromethane and to obtain the dispersed phase. Polyvinyl alcohol was added to purified water to prepare a continuous phase solution at a concentration of 0.06 g / ml. (2) The continuous phase was first added to the inner cylinder to cover the stirring blade and the emulsifying head. Then the stirring motor was started at 50 rpm, and the emulsifying motor was started at 750 rpm. The dispersed phase was added continuously at a low speed to the continuous phase, so that the final ratio of the continuous phase to the dispersed phase was 10:1, and the emulsification time was 30 minutes. (3) After emulsification, the emulsifying motor was switched off, and the high-temperature circulation device was switched on to heat the reaction liquid. The temperature was set to 40 °C, causing the solvent in the polylactic acid microsphere droplets to evaporate and solidify into polylactic acid microspheres. The evaporated solvent was continuously condensed and recovered by distillation through the solvent recovery device. (4) The solidified microspheres were collected, washed and dried to obtain finished polylactic acid microspheres. Determination of microsphere properties:

[0037] As in Fig.As shown in Figure 3, the microspheres obtained in this embodiment are observed as regular circles using an optical microscope; the microspheres obtained in this embodiment are measured using a Mastersize 3000 laser particle size analyzer in a dry process, and as shown in Figure 3. Fig. As shown in Figure 2, the volume distribution range of the microsphere particle size is 10-50 µm, of which the microspheres with a particle size range of 15-45 µm make up more than 90%; the residual amount of dichloromethane is less than 0.01% and the residual amount of polyvinyl alcohol is less than 0.5%. Example 2:

[0038] In comparison to embodiment 1, the concentration of the dispersed phase solution was 0.2 g / ml. Determination of microsphere properties:

[0039] The microspheres obtained in this embodiment are observed as regular circles using an optical microscope; the microspheres obtained in this embodiment are measured using a Mastersize 3000 laser particle size analyzer in a dry process, and as in Fig. As shown in Figure 2, the volume distribution range of the microsphere particle size is 25-110 µm, of which the microspheres with a particle size range of 40-80 µm make up more than 90%; the residual amount of dichloromethane is less than 0.01% and the residual amount of polyvinyl alcohol is less than 0.5%. Example 3:

[0040] In comparison to embodiment 1, the rotational speed of the emulsifying motor was 1000 rpm. Determination of the microsphere properties: The microspheres obtained in this embodiment are observed as regular circles using an optical microscope; the microspheres obtained in this embodiment are measured using a Mastersize 3000 laser particle size analyzer in a dry process, and as in Fig. As shown in Figure 2, the volume distribution range of the microsphere particle size is 10-40 µm, of which the microspheres with a particle size range of 15-30 µm make up more than 90%; the residual amount of dichloromethane is less than 0.01% and the residual amount of polyvinyl alcohol is less than 0.5%.

[0041] The unclaimed method for producing polylactic acid microspheres and the embodiments shown can yield a polylactic acid microsphere with a concentrated particle size distribution, smooth surface and low residue. Comparative example 1:

[0042] In comparison to embodiment 1, different volume ratios of the continuous phase to the dispersed phase were set; the test results are shown in the following Table 1: Table 1 Continuous phase : Dispersed phase Average particle size (µm) Yield (%) 5:1 68,3 87 8:1 28,5 85 10:1 24,3 82 20:1 26,8 60 30:1 28,9 43

[0043] Table 1 shows that as the volume ratio of the continuous phase to the dispersed phase increases, the average particle size initially decreases and then increases, and the yield decreases further; therefore, it is more appropriate to select a volume ratio of the continuous phase to the dispersed phase in the range of 8:1–20:1. Comparative example 2:

[0044] In comparison to embodiment 1, different solvent distillation temperatures were set, and the test results are listed in Table 2 below: Table 2 Solvent distillation temperature (°C) Distillation time (h) Percentage of distilled solvent (%) 30 14 42 35 13,5 55 40 8 68 45 6,5 70 50 5 76

[0045] Table 2 shows that as the solvent distillation temperature increases, the distillation time becomes shorter and the proportion of distilled solvent increases. Considering the glass transition temperature of polylactic acid (approximately 60 °C), the distillation time, and the proportion of distilled solvent, a heating temperature of 40–50 °C is more suitable for solvent removal. Example 4:

[0046] The polylactic acid microspheres produced by embodiment 3 were suspended in an aqueous solution of sodium carboxymethylcellulose and mannitol and subsequently injected subcutaneously into several rabbits. The rabbits were euthanized three and six months later, and tissue samples from the injection sites were taken and embedded in paraffin to obtain tissue sections. Collagen regeneration was observed using Masson staining.

[0047] As in Fig. As shown in Figure 4, accumulations of round, granular polylactic acid microspheres were visible beneath the dermis, with a few damaged polylactic acid microspheres occasionally observed. At the implantation site deep in the dermis, the collagen fibers were disordered, and the reticular structure was absent. A small amount of fine, new collagen forms, enveloping the polylactic acid microspheres and dividing them into several platelets. As shown in Fig. Figure 5 shows accumulations of round, granular polylactic acid microspheres visible beneath the dermis, with slight increase in filler damage. At the implantation site deep in the dermis, the collagen fibers were disordered, and the reticular structure had disappeared. The production of fine, new collagen increases; some of the collagen thickens and encapsulates the polylactic acid microspheres. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 116139790A

[0004] CN 115531607A

[0004] CN 114931554A

[0004] CN 108653817A

[0004]

Claims

[1] Device for the production of polylactic acid microspheres, characterized by , that it comprises: a reactor body, a reactor lid arranged on the reactor body to cover an opening of the reactor body, and a solvent recovery device by distillation connected to the reactor lid; the reactor body comprises an inner cylinder, an outer cylinder, an intermediate space formed between the inner cylinder and the outer cylinder, an intermediate space inlet and outlet provided on the outer surface of the intermediate space, a tank bottom valve located under the reactor body, and a high-temperature circulation device connected to the intermediate space inlet and outlet; The reactor lid comprises an inlet opening and a distillation opening provided in the surface of the reactor lid, as well as a stirring device and an emulsifying device, wherein the stirring device comprises a stirring motor and an associated stirring blade, the stirring motor being located centrally above the reactor lid and the stirring blade projecting into the inner cylinder of the reactor body to stir a reaction liquid; and the emulsifying device comprising an emulsifying motor located above the reactor lid and an associated emulsifying head, the emulsifying head projecting into the inner cylinder of the reactor body to generate polylactic acid microsphere droplets by shear force; The solvent recovery device by distillation comprises a condensation tube, a circulation inlet and outlet provided on the surface of the condensation tube, a low-temperature circulation device connected to the condensation circulation inlet and outlet, a reflux head located at the bottom of the condensation tube, and a collection bottle located below and connected to the reflux head. [2] Apparatus for the production of polylactic acid microspheres according to claim 1, characterized by, that the high-temperature circulation device allows a circulation fluid of the high-temperature circulation device to circulate through the interspace inlet and outlet to supply heat to the reactor body in real time, causing a solvent in the polylactic acid microsphere droplets to evaporate and solidify into polylactic acid microspheres; and the tank bottom valve is used to drain the reaction fluid from the inner cylinder. [3] Apparatus for the production of polylactic acid microspheres according to claim 2, characterized by, that the reflux head is provided with three open ends, one end of which is connected to the distillation opening, one end to the bottom of the condensation tube and the last end to the collection bottle in order to divert the evaporated solvent from the inner cylinder to the condensation tube and to collect the condensed solvent, the collection bottle collects the condensed solvent, and the condensation tube has a double-layer structure and is connected to the low-temperature circulation device to enable the condensation of the evaporated solvent. [4] Apparatus for the production of polylactic acid microspheres according to claim 1, characterized bythat the reactor body is connected to the reactor lid via a sealing ring, screw or clamp, and that the reactor body, reactor lid and solvent recovery device by distillation are made of corrosion-resistant materials.

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