Polymerization reaction device, polylactic acid polymerization method, and polymerization reaction device cleaning method

Abstract

The present invention discloses a polymerization reaction device for preparing polylactic acid by utilizing lactic acid, a polylactic acid polymerization method, and a polymerization reaction device cleaning method, and relates to the technical field of polylactic acid synthesis. The polymerization reaction device comprises a cavity, a fixing part, a heating unit, a driving unit, an exhaust unit, and also a cleaning unit for cleaning the cavity. By cooperating with the above components, the polymerization of polylactic acid is completed, and the cleaning of the cavity in the polymerization reaction device is achieved. The present invention utilizes the driving unit to drive the rotation of the first cavity and the second cavity to achieve the effect of stirring the liquid in the cavity, which can improve the uniformity of heating and mixing of the liquid in the cavity; at the same time, the continuous tumbling of the liquid is also conducive to the discharge of water vapor generated during the polymerization process, and promotes the progress of the polymerization reaction. At the same time, the combined design of the bidirectional thread structure of the second telescopic rod and the bidirectional screw rod is utilized, and the cleaning of the two cavities is achieved by using one driving unit, which reduces the equipment cost and simplifies the device.

Description

Technical Field

[0001] The present invention relates to the technical field of polylactic acid synthesis, and more particularly to a polymerization reaction device for preparing polylactic acid by utilizing lactic acid, a polylactic acid polymerization method, and a polymerization reaction device cleaning method. Background Art

[0002] As air pollution and greenhouse effects caused by the petrochemical industry become increasingly severe, bio-based materials, especially biodegradable polylactic acid, are receiving more and more attention.

[0003] Polylactic acid is synthesized using lactic acid produced by fermentation of starch or sugar as raw material. The synthesis of polylactic acid from lactic acid can be carried out in a one-step or two-step process. The core technology of the two-step process lies in the synthesis and purification of lactide. The main problem is that the crude lactide contains impurities such as water, lactic acid, and lactic acid oligomers. The purity and yield of lactide will directly affect the quality and production cost of polylactic acid. At the same time, the entire process needs to be carried out under high temperature and negative pressure catalysis conditions. The process is complex and the cost is high. The key to the one-step method is that the water molecules formed during the synthesis process must be discharged from the reaction system in a timely manner to facilitate the reaction towards the synthesis of polylactic acid.

[0004] During the one-step synthesis of polylactic acid, the viscosity of the solution gradually increases as the reaction proceeds. Most prior arts employ a stirring mechanism to stir the solution in order to quickly expel water molecules from the reaction system.

[0005] Patent CN113896867B discloses a method for synthesizing polylactic acid from lactic acid in one step. The method involves adding the product of the dehydration and polycondensation reactions of lactic acid in a primary reactor to a secondary reactor while uniformly coating the product on the inner wall of the secondary reactor. Stirring is also performed to maintain a total residence time of the product in the secondary reactor of 30 to 60 minutes, thereby producing the polylactic acid. The primary reactor is stirred and vacuumed to completely remove free water from the lactic acid. The product exhibits a linear molecular structure, and the secondary reactor is a ribbon reactor with a scraper, a screw reactor with a scraper, or an anchor reactor with a scraper. This patented device is simple and facilitates the removal of water molecules during the synthesis process. However, the use of a stirring device with a scraper to uniformly coat the polymer melt from the primary reactor onto the walls of the secondary reactor limits the coating area, limiting the amount of polymer that can be polymerized per reaction and resulting in low polymerization efficiency. Furthermore, the presence of a stirring mechanism makes cleaning the cavities of the primary and secondary reactors difficult after polymerization, making automated cleaning difficult.

[0006] In order to solve the problems existing in the one-step polymerization process of polylactic acid, it is necessary to provide a polymerization reaction device and method that can quickly discharge water molecules in the reaction process and realize automatic cleaning of the cavity. Summary of the Invention

[0007] The purpose of the present invention is to provide a polymerization reaction device for preparing polylactic acid using lactic acid, a polylactic acid polymerization method, and a polymerization reaction device cleaning method, so as to solve the problems raised in the above background technology.

[0008] To achieve the above objectives, the present invention is implemented through the following technical means:

[0009] A polymerization reaction device for preparing polylactic acid using lactic acid, comprising a cavity, a fixing part, a heating unit, a driving unit, and a steam exhaust unit; wherein

[0010] The cavity includes a first cavity for dehydration prepolymerization of lactic acid and a second cavity connected to or closed with the first cavity through a connecting pipe;

[0011] The heating unit includes a first heating unit and a second heating unit for heating the object to be processed and is respectively arranged on the outer circumference of the first cavity and the second cavity;

[0012] The fixing member includes a first fixing member, a second fixing member, and a third fixing member for supporting the cavity and movably cooperating with the cavity. The first fixing member, the second fixing member, and the third fixing member are sequentially arranged at the front end, the middle part, and the rear end part of the cavity;

[0013] The driving unit includes a first driving unit for rotating the first cavity and a second driving unit for rotating the second cavity;

[0014] The steam exhaust unit includes a first steam exhaust unit for exhausting water vapor from the first cavity and a second steam exhaust unit for exhausting water vapor from the second cavity.

[0015] A polylactic acid polymerization method, using the polymerization device of the present invention to achieve polylactic acid polymerization, comprises the following steps:

[0016] Step 1: Check the device to ensure that the first cleaning part and the second cleaning part are in the initial position;

[0017] Step 2: Start the first drive motor and the second drive motor of the device to rotate the first cavity and the second cavity to ensure normal operation of the device;

[0018] Step 3: Heat sources, such as heating oil, are fed into the first heat source inlet and the second heat source inlet respectively until heat flows out of the first heat source outlet and the second heat source outlet, indicating that the heat source space of the heating unit is full of heat sources;

[0019] Step 4: Control the peristaltic pump in the connecting pipeline to shut down;

[0020] Step 5: Add lactic acid raw material from the first feeding pipe to ensure continuous supply of lactic acid raw material;

[0021] Step 6: The lactic acid continuously supplied to the first cavity rotates in the first cavity, and the liquid continuously tumbles in the first cavity, so that the lactic acid is evenly heated. During this process, the lactic acid is dehydrated and prepolymerized, and the generated water vapor is discharged through the exhaust unit above the first cavity;

[0022] Step 6: Control the liquid level in the first cavity to reach near the horizontal center line of the first cavity, start the peristaltic pump in the connecting pipeline, and intermittently discharge liquid into the second cavity;

[0023] Step 7: Close the valve at the discharge port near the third fixing member below the second cavity;

[0024] Step 8: When liquid enters the second cavity from the first cavity, a catalyst is added into the second cavity through the second feeding pipe. At this time, the pre-polymerized lactic acid and the catalyst undergo a polymerization reaction in the second cavity to produce polylactic acid;

[0025] Step 9: When the liquid level in the second cavity reaches the vicinity of the horizontal center line of the second cavity, the valve of the discharge port is opened, and the polylactic acid produced by the polymerization is discharged from the discharge port;

[0026] Step 10: Under the continuous rotation of the first cavity and the second cavity, the raw material input port and the liquid discharge port and the material discharge port of the first cavity are kept open, so that the raw material is continuously and intermittently input, the first cavity continuously and intermittently supplies liquid to the second cavity, and the second cavity continuously and intermittently discharges the polymerized product;

[0027] By controlling the rotation speed of the first cavity and the second cavity, the speed of the entire polymerization reaction can be controlled;

[0028] Step 11: Complete the polymerization reaction of polylactic acid.

[0029] A method for cleaning a polylactic acid polymerization device is applied to the polylactic acid polymerization device, comprising the following steps:

[0030] Step 1: After the polymerization is completed, the residual liquid in the first cavity and the second cavity is drained. Clean water or cleaning liquid is introduced into the first cavity and the second cavity to maintain the continuous rotation of the cavity;

[0031] Step 2: After preliminary cleaning with clean water or cleaning fluid, the third drive motor is started, and the first telescopic rod is extended to push the first cleaning element to remove the attachments on the inner wall of the first cavity;

[0032] Step 3: After the first cleaning component finishes cleaning the first cavity, the third drive motor is kept rotating in the same direction to continue extending the second telescopic rod, thereby pushing the second cleaning component to remove the attachments on the inner wall of the second cavity;

[0033] Step 4: After the second cleaning element finishes cleaning the inner wall of the second cavity, the third drive motor continues to rotate in the same direction, driving the second telescopic rod to shorten and retract, and retracting the second cleaning element to its initial position;

[0034] Step 5: After the second cleaning element returns to its initial position, the third drive motor is rotated in the opposite direction. At this time, the first telescopic rod is shortened and retracted, driving the first cleaning element to return to its initial position.

[0035] The cleaning of the device cavity is now completed.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention utilizes a driving unit to drive the rotation of the first cavity and the second cavity to achieve the effect of stirring the liquid in the cavity. In the absence of a stirring structure, the uniformity of heating and mixing of the liquid in the cavity can still be improved. At the same time, the continuous tumbling of the liquid is also conducive to the discharge of water vapor generated during the polymerization process, promoting the progress of the polymerization reaction. The present invention does not have a stirring structure in the cavity, which is conducive to the cleaning of the cavity. At the same time, the combined design of the bidirectional thread structure of the second telescopic rod and the bidirectional screw is utilized, and the cleaning of the two cavities is achieved by using a single driving unit, which reduces the equipment cost and simplifies the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Overall front view of the device;

[0039] Figure 2 Schematic diagram of the overall device;

[0040] Figure 3 A schematic structural diagram of a first fixing member;

[0041] Figure 4 Schematic diagram of the first cavity structure;

[0042] Figure 5 Schematic diagram of the state of the first cavity during feeding;

[0043] Figure 6 Schematic diagram of the state of the first cavity when no material is fed;

[0044] Figure 7 Schematic diagram of the implementation method of the first cavity rotation;

[0045] Figure 8 Schematic diagram of the heat exchange unit of the first cavity;

[0046] Figure 9 Schematic diagram of the cross section of the heat exchange unit;

[0047] Figure 10 Schematic diagram of the exhaust unit structure;

[0048] Figure 11 Schematic diagram of exhaust unit exhaust realization method;

[0049] Figure 12 Schematic diagram of the communication mode between the first cavity and the second cavity;

[0050] Figure 13 Schematic diagram of the telescopic rod between the first cavity and the second cavity;

[0051] Figure 14 A schematic diagram of the end face of the second telescopic rod facing the first cavity;

[0052] Figure 15 A schematic diagram of the end face of the first cleaning component facing the second cavity;

[0053] Figure 16 Schematic diagram of one-way screw and two-way screw thread;

[0054] Figure 17 Schematic diagram of the second cavity rotation implementation method. DETAILED DESCRIPTION

[0055] The following detailed description of the embodiments of the technical solution of this application is provided in conjunction with the accompanying drawings. The following embodiments and drawings are intended only to more clearly illustrate the technical solution of this application and are therefore provided as examples only and are not intended to limit the scope of protection of this application. The accompanying drawings schematically illustrate only the parts relevant to the technical solution of this application and do not represent the actual structure of the product.

[0056] In this embodiment, a polymerization reaction device for preparing polylactic acid using lactic acid includes a cavity, a fixing member, a heating unit, a driving unit, and a steam exhaust unit; wherein

[0057] The cavity includes a first cavity 111 for dehydration prepolymerization of lactic acid and a second cavity 112 connected to or sealed with the first cavity 111 through a connecting pipe 102;

[0058] The heating unit includes a first heating unit 121 and a second heating unit 122 for heating the object to be processed and are respectively arranged on the outer circumference of the first cavity 111 and the second cavity 112;

[0059] The fixing member includes a first fixing member 161, a second fixing member 162, and a third fixing member 163 for supporting the cavity and cooperating with the cavity. The first fixing member 161, the second fixing member 162, and the third fixing member 163 are sequentially arranged at the front end, the middle part, and the rear end of the cavity;

[0060] The driving unit includes a first driving unit for rotating the first cavity 111 and a second driving unit for rotating the second cavity 112;

[0061] The exhaust unit includes a first exhaust unit 63 for exhausting water vapor from the first cavity 111 and a second exhaust unit 64 for exhausting water vapor from the second cavity.

[0062] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the embodiments of the present application. The following examples illustrate the above-mentioned components of the present invention in accordance with the drawings disclosed in the present invention, and the ends of each component are referred to as the front end and the rear end from left to right.

[0063] In some embodiments of the present invention, the first cavity 111 is used for dehydration prepolymerization of lactic acid, and is arranged horizontally and transversely. A first front end outer groove 44 for cooperating and connecting with the first fixing member 161 is provided on the outside of the front end thereof, and a first rear end outer groove 45 for cooperating and connecting with the second fixing member 162 is provided on the outside of the rear end thereof. In a possible embodiment of the present invention, the first front end outer groove 44 is movably connected to the first fixing member 161, and the first rear end outer groove 45 is movably connected to the second fixing member 162. The first cavity 111 can be rotated relative to the first fixing member 161 and the second fixing member 162 under the action of the first driving unit through the first front end outer groove 44 and the first fixing member 161 being movably connected, and the first rear end outer groove 45 and the second fixing member 162 being movably connected. Specifically, the first front end outer groove 44 and the first rear end outer groove 45 can be respectively embedded in the structures corresponding to the first fixing member 161 and the second fixing member 162.

[0064] Referring to the above content, similarly, the front end and the rear end of the second cavity 112 are respectively provided with a second front end outer groove and a second rear end outer groove (not marked in the figure), which are respectively movably connected with the second fixing member 162 and the third fixing member 163. The cooperation method is the same as the cooperation method between the first cavity 111 and the first fixing member 161 and the second fixing member 16. In this way, the second cavity 112 can rotate relative to the second fixing member 162 and the third fixing member 163 under the drive of the second driving unit.

[0065] In some embodiments of the present invention, the second cavity 112 is arranged horizontally, and the center line of the first cavity 111 and the center line of the second cavity 112 are on the same horizontal line. Of course, the center line of the first cavity 111 and the center line of the second cavity 112 are on the same horizontal line only in the ideal state of the device of the present invention. In actual production installation, the center line of the first cavity 111 and the center line of the second cavity 112 of the present invention are allowed to be installed within the range of industrial production control error; of course, in addition to the above content, the inner diameter of the first cavity 111 is smaller than the inner diameter of the second cavity 112. This arrangement facilitates the processing material to enter the connecting pipe 102 from the discharge port 101 set at the edge of the rear end face of the first cavity 111, thereby effectively entering the second cavity 112 through the connecting pipe 102.

[0066] In some embodiments of the present invention, the first cavity 111 and the second cavity 112 are both provided with a feed port for feeding materials. Of course, according to actual production needs, the types of materials fed into the first cavity 111 and the second cavity 112 are different, wherein the first cavity 111 supplies lactic acid to the interior of the first cavity 111 through the feed port, and the second cavity 112 supplies catalyst through the feed port; In combination with the above content, in some possible embodiments of the present invention, the first cavity 111 is surrounded by a first feeding member 41 near the outer wall of the first fixing member 161, and the first feeding member 41 is in a sealed state at the junction with the first cavity 111, and the first feeding member 41 can rotate relative to the first cavity 111, and the first feeding member 41 is annular. Structure, and is fixed to the frame (not shown in the figure) by a connecting rod. Specifically, the connection structure between the first cavity 111 and the first feeding member 41 is a commonly used technical means in the field. The first feeding member 41 surrounds the periphery of the first cavity 111 and is tightly fitted with the outer wall of the first cavity 111. The connection structure between the first cavity 111 and the first feeding member 41, such as various sealing members, sealing rings, etc., is no longer disclosed in the present invention. In addition, in order to realize feeding, the first feeding member 41 is equipped with a first feeding pipe 42 that is tangent to the outer wall of the first cavity 111. The outer wall of the first cavity 111 is located at a corresponding position of the first feeding member 41. There is at least one first feeding port 43 that cooperates with the first feeding pipe 42 and communicates with the interior of the first cavity 111.

[0067] In this way, it can be known from the above content that under the rotation of the first cavity 111, the first feeding port 43 opened on the first cavity 111 rotates along with the first cavity 111, and the position of the first fixing member 41 is fixed. When the first feeding port 43 is rotated to cooperate with the first feeding pipe 42 and the first feeding pipe 42 is connected to the first cavity 111, the lactic acid material supplied through the first feeding port 43 can enter the first cavity 111 through the first feeding port 43, and the feeding speed can be adjusted according to the rotation angle; in addition, after the first cavity 111 rotates a certain angle, the first feeding port 43 and the first feeding pipe 42 are completely staggered, and the material cannot enter the interior of the first cavity 111; in this way, the feeding speed to the first cavity 111 can be adjusted, and the speed of feeding to the interior of the first cavity 111 can be adjusted according to the number of the first feeding ports 43 opened and the rotation speed of the first cavity 111, and the material mixing can be fully completed to improve the processing efficiency;

[0068] In combination with the above content, the feed port structure for opening the second cavity 112 and supplying the catalyst to the interior of the second cavity 112 through the feed port is the same as the above-disclosed feed structure and method, and will not be described in the present invention. After the above content is disclosed, those skilled in the art can realize the supply of catalyst to the interior of the second cavity 112 according to the above-disclosed technical solution.

[0069] As can be seen from the above content, the driving unit includes a first driving unit for rotating the first cavity 111 and a second driving unit for rotating the second cavity 112. In some possible embodiments of the present invention, the first driving unit includes a first gear 131 provided on the outer circumference of the middle position of the first cavity 111, and the first gear 131 is connected to a first driving motor 151 connected to a first driving wheel 51 and provided below the first cavity 111. The first driving motor 151 is mounted on a frame (not shown in the figure). In this way, the first driving wheel 51 is engaged with the first gear 131, and the first driving motor 151 drives the first cavity 111 to rotate; as for the structure of the second driving unit driving the second cavity 112, the structure is the same as that of the first driving unit. For example, the second driving unit includes a second driving motor 152 for transmission, and the output end of the second driving motor 152 is equipped with a second driving wheel 52. The second driving wheel 52 is engaged with the second gear 132 provided on the outer circumference of the middle position of the second cavity 112.

[0070] In this way, by setting the first driving unit and the second driving unit to control the first cavity 111 and the second cavity 112 respectively, the rotational speeds of the first cavity 111 and the second cavity 112 can be controlled respectively, and the feed amount from the first cavity 111 to the second cavity 112 can be adjusted according to processing needs and in conjunction with the structure of the first cavity 111.

[0071] Of course, in some other embodiments of the present invention, the driving components in the first driving unit and the second driving unit are driven by the same driving structure, and the driving structure drives the first cavity 111 and the second cavity 112 with the same transmission ratio. In this way, the rotation of the first cavity 111 and the second cavity 112 can be controlled by one driving unit, which can effectively reduce the equipment cost.

[0072] In the present invention, the fixing member includes a first fixing member 161, a second fixing member 162, and a third fixing member 163 for supporting the cavity and movably cooperating with the cavity. The first fixing member 161, the second fixing member 162, and the third fixing member 163 are sequentially arranged at the front end, the middle part, and the rear end part of the cavity. In some possible embodiments of the present invention, the first fixing member 161 has a cylindrical structure and is mounted on the first leg 171. The first fixing member 161 has an end surface relative to the first cavity 111 and is provided with a first inner groove 31 that is movably connected and engaged with the first front outer groove 44 provided in the first cavity 111.

[0073] In order to realize the communication between the first cavity 111 and the second cavity 112, the second fixing member 162 is annular in structure, the second fixing member 162 is fixed on the second leg 172, and the inner wall of the second fixing member 162 is respectively provided with a second front end inner groove and a second rear end inner groove (not shown in the figure) that are movably connected and engaged with the first rear end outer groove 45 of the first cavity and the second front end outer groove of the second cavity 112. Similarly, the third fixing member 163 is a cylindrical structure, the third fixing member 163 is mounted on the third leg 173, and the third fixing member 163 is provided with a second rear end inner groove of the second cavity 112 relative to the end surface of the second cavity 112. The outer groove is movably connected to the third front end inner groove (not shown in the figure), so that the first fixing member 161, the second fixing member 162, and the third fixing member 163 are movably connected and matched with the first cavity 111 and the second cavity 112 respectively, so that the first cavity 111 and the second cavity 112 can rotate relative to the first fixing member 161, the second fixing member 162, and the third fixing member 163 under the drive of external force, thereby achieving the effect of stirring the liquid in the cavity. At the same time, the continuous tumbling of the liquid is also beneficial to the water vapor generated during the polymerization process, and the water vapor is discharged from the cavity through the exhaust unit, thereby promoting the polymerization reaction.

[0074] During the polymerization process, the presence of moisture is the main factor hindering the polymerization reaction. In the present invention, an exhaust unit is provided to timely discharge the moisture generated during the polymerization process. In the above content, the exhaust unit includes a first exhaust unit 63 for discharging water vapor from the first cavity 111 and a second exhaust unit 64 for discharging water vapor from the second cavity. In some embodiments of the present invention, the first exhaust unit 63 includes two groups of exhaust vertical pipes 81 symmetrically arranged at the top of the first cavity 111 and connected to the first cavity 111. Exhaust valves 82 are provided on the inner wall pipes of the two exhaust vertical pipes 81. The exhaust valves 82 can discharge water vapor and prevent liquid from being discharged from the exhaust vertical pipes 81. The tops of the other two exhaust vertical pipes 81 are interconnected through a condensation member. The condensation member includes an upwardly convex arc-shaped top plate 83 and a downwardly concave arc-shaped bottom plate 84 that cooperates with the arc-shaped top plate 83. In this way, a connecting member is formed by the cooperation of the arc-shaped top plate 83 and the arc-shaped bottom plate 84, so that after the water vapor is discharged through the exhaust valve 82, it meets the inner wall frozen by the freezing device on the arc-shaped top plate 83, condenses into liquid water and falls onto the arc-shaped bottom plate 84, and is discharged through the drain pipe 85 connected to the opening at the bottommost end of the arc-shaped bottom plate. Through the above structure of the first exhaust unit 63, it is more conducive to the collection and discharge of the condensed liquid water, and avoids the condensed liquid water from entering the first cavity 111 again; In some possible embodiments of the present invention, the second exhaust unit 64 has the same structure as the first exhaust unit 63, and the second exhaust unit 64 will not be described again in the present invention.

[0075] To achieve better exhaust of water vapor in the cavity, the present invention also discloses other embodiments. The present invention takes the first cavity 111 and the first exhaust unit 63 as an example for illustration. An outer sleeve 91 is provided on the outer circumference of the first cavity 111. A plurality of hollow holes 92 are provided at the corresponding positions of the pipe wall of the first cavity 111 and the outer sleeve 91. Combining the attached drawings disclosed in the present invention, the cross-section of the outer sleeve 91 is in a "U" shape. An exhaust space 93 is formed between the inner wall of the outer sleeve 91 and the outer wall of the first cavity 111. The first exhaust unit 63 is fitted on the outer sleeve 91. In this way, the outer sleeve 91 is fixed on a frame (not shown in the figure). The outer sleeve 91 can ensure the sealing effect when the first cavity 111 rotates by cooperating with corresponding seals. Thus, when the first cavity 111 rotates, the liquid in the first cavity 111 tumbles inside the first cavity 111. During the polymerization process, as the liquid continuously tumbles, the generated steam enters the exhaust space 93 through the hollow holes 92 and is discharged from the exhaust vertical pipes 81 in the first exhaust unit 63 above the exhaust space 93;

[0076] By setting the hollow hole 92 and the exhaust space 93, the separation effect of the liquid and the generated water vapor can be better achieved when the first cavity 111 rotates; in actual production, the liquid after reaction processing is discharged from the inside of the first cavity 111, and a certain amount of liquid will remain at the bottom of the exhaust space 93, but because the distance between the inner wall of the outer sleeve 91 and the outer wall of the first cavity 111 is relatively close, the volume of the exhaust space 93 is limited. During cleaning, the inside of the first cavity 111 will be flushed with water, and the residual liquid will be taken away, which will not affect the processing quality of the liquid to be processed next.

[0077] In order to process polylactic acid, the present device needs to heat the material in the cavity. Therefore, in the above disclosure of the present invention, the heating unit includes a first heating unit 121 and a second heating unit 122 for heating the material to be processed and are respectively arranged on the outer circumference of the first cavity 111 and the second cavity 112. In some possible embodiments of the present invention, the first heating unit 121 and the second heating unit 122 can be heated by using one of the liquid heat sources such as electric heating, hot water or hot oil. In other embodiments of the present invention, the present invention discloses The heating method using a liquid heat source such as hot water or hot oil is disclosed. The first heating unit 121 and the second heating unit 122 have the same structure. Specifically, the present invention takes the first heating unit as an example. The first heating unit 121 includes a front heating unit 1211 and a rear heating unit 1212 surrounding the outside of the first cavity 111. The inner walls of the front heating unit 1211 and the rear heating unit 1212 are tangent to the outer wall of the first cavity 111. Of course, the above content is an ideal state of cooperation of the components in the device of the present invention. Specifically, in actual production and processing In the embodiment, the distance between the inner wall of the front section heating unit 1211 and the rear section heating unit 1212 and the outer wall of the first cavity 111 is allowed to be within the error range, so that the first cavity 111 can rotate relative to the first heating unit 121 and ensure the heat conduction efficiency; the front section heating unit 1211 and the rear section heating unit 1212 have cavities for storing hot water or hot oil inside, and the front section heating unit 1211 and the rear section heating unit 1212 are connected through the first connecting pipe 141. In the present invention, in order to avoid the influence on the driving unit, the first connecting pipe 141 is U-shaped The shape is arranged so that the first connecting pipe 141 can cross the first gear 131, thereby not contacting the first gear 131 and not affecting the rotation of the first gear 131. Accordingly, the top of the front heating unit 1211 is provided with a first heat source outlet 62, and the bottom of the rear heating unit 1212 is provided with a first heat source inlet 61. The accompanying drawings of the present invention disclose the matching mode of the front heating unit 1211 and the first heat source outlet 62, and the rear heating unit 1212 and the first heat source inlet 61. The first heat source outlet 62 and the first heat source inlet 61 are both provided at the ends of the corresponding mounting components.

[0078] When heating the liquid in the first cavity 111, the heat source used for heating can be a liquid heat source such as hot water or hot oil. When the heat source enters the heat source space 71 of the rear heating unit 1212 from the first heat source inlet 61, the heat source liquid level in the rear heating unit 1212 gradually rises. When the liquid level reaches the interface of the first connecting pipe 141, the heat source enters the heat source space 71 of the front heating unit 1211 from the first connecting pipe 141. At this time, the liquid level in the heat source space of the front section gradually rises. When the liquid level rises to the interface of the first connecting pipe 141 of the front heating unit, the liquid levels of the heat source spaces of the front and rear heating units rise synchronously. Finally, the heat source fills the heat source space in the entire first heating unit 121, and is then discharged from the first heat source outlet 62, thereby effectively heating the liquid in the first cavity 111 and effectively constructing a heating heat source cycle to ensure the heating temperature.

[0079] As can be seen from the above content, the cavity includes a first cavity 111 for dehydration prepolymerization of lactic acid and a second cavity 112 connected or closed to the first cavity 111 through a connecting pipe 102. The liquid processed in the first cavity 111 enters the interior of the second cavity 112 through the connecting pipe 102. In some embodiments of the present invention, the connecting pipe 102 is sequentially provided with a liquid storage area 1021, a pump area 1022, and a liquid discharge area 1023 along the material conveying direction. The liquid storage area 1021 is a cylindrical cavity structure, and a liquid storage area 1021 is provided between the pump area 1022 and the liquid storage area 1021. The baffle with an opening, the drainage area 1023 is a conical truncated cone structure with upper and lower openings. A peristaltic pump 103 is provided in the cavity of the pump area 1022. The peristaltic pump 103 is connected to the opening on the baffle and the opening of the drainage area 1023 near the pump area 1022 by providing an infusion hose 1031. In this way, when the liquid in the first cavity 111 enters the above-mentioned liquid storage area 1021, the peristaltic pump 103 sucks the liquid out of the liquid storage area 1021 through the infusion hose 1031 and transports it to the downstream drainage area 1023. The liquid then enters the second cavity 112 from the drainage area 1023;

[0080] Of course, in order to achieve the above purpose, the end of the first cavity 111 is provided with a liquid discharge port 101, and the second cavity 112 is provided with a corresponding liquid inlet. By rotating the first cavity 111 and the second cavity 112, and cooperating with the above-mentioned connecting pipe 102, the liquid is transported from the first cavity 111 to the second cavity 112.

[0081] Based on the above description, those skilled in the art will be able to understand and implement the technical solution disclosed in the present invention, which achieves the purpose of tumbling the liquid in the cavity without providing a stirring mechanism. This facilitates uniform heating and mixing of the liquid in the cavity, and the water vapor generated during the reaction can be promptly discharged from the cavity through the exhaust unit during the continuous tumbling of the liquid, thereby improving the efficiency of the polymerization reaction.

[0082] In some embodiments of the present invention, the polymerization reaction device further comprises a cleaning unit for cleaning the cavity;

[0083] Specifically, the cleaning unit includes a first cleaning unit for cleaning the first cavity 111 and a second cleaning unit for cleaning the second cavity 112, wherein the first cleaning unit includes a first cleaning member 33 provided on the front end surface of the first cavity 111. The function of the first cleaning member 33 is to clean the attachments on the inner wall of the first cavity 111 after the polymerization reaction is completed. The outer diameter of the first cleaning member 33 is tightly fitted with the inner diameter of the first cavity 111. On the one hand, it is ensured that the liquid in the first cavity 111 does not reversely seep out from between the first cleaning member 33 and the inner wall of the first cavity 111, and on the other hand, it is ensured that the attachments on the inner wall of the first cavity 111 can be effectively removed by the first cleaning member 33.

[0084] The center of the first cleaning member 33 is connected to the first telescopic rod 32. One end of the first telescopic rod 32 is connected to the first cleaning member 33. The other end of the first telescopic rod 32 extends through the end surface of the first cavity 111 facing the first fixing member 161 and is connected to the one-way screw 19. The one-way screw 19 is coupled to the third drive motor 18, which is fixedly mounted on the frame (not shown). The first telescopic rod 32 is composed of a multi-stage screw assembly. Thus, under the drive of the third drive motor 18, the one-way screw 19 is driven to rotate, thereby extending or shortening the multi-stage screws of the first telescopic rod 32. That is, when the third drive motor 18 rotates in the forward direction, the one-way screw 19 rotates in the forward direction, causing the multi-stage screws to extend step by step. When the multi-stage spiral rod is extended, the first telescopic rod 32 is extended, pushing the first cleaning component forward to scrape off the attachments on the inner wall of the first cavity 111; in order to improve the stability of the first cleaning component 33, a stopper 34 is provided around the first telescopic rod 32 at the connection between the side of the first cleaning component 33 facing the first fixing component 161 and the first telescopic rod 32, to ensure that when the first telescopic rod 32 pushes the first cleaning component 33 for cleaning, the relative position of the first cleaning component 33 relative to the first telescopic rod 32 remains unchanged.

[0085] The second cleaning unit includes a second telescopic rod 107 arranged between the first cavity 111 and the second cavity 112, and the second telescopic rod 107 is connected to the second cleaning member 106 arranged in the second cavity 112 through a bidirectional screw rod 201. The front end of the second telescopic rod 107 is provided with a locking recess 108, and the locking recess 108 is matched with the locking protrusion 109 provided at the top of the first telescopic rod 32 facing the second cavity 112. In the drawings of the present invention, the shapes of the locking recess 108 and the locking protrusion 109 are disclosed, wherein the locking recess 108 and the locking protrusion 109 are matched. The concave part 108 is an inward concave type, and its shape is a groove in four directions. Each groove has two sides, one of which is a straight side and the other is an arcuate side. The locking protrusion 109 matches the shape and size of the above-mentioned locking concave part 107. In specific applications, the locking protrusion 109 and the first telescopic rod 32 can rotate synchronously and are not fixedly connected to the first cleaning part 33. The locking protrusion 109 can also play a role in limiting the first cleaning part 33; of course, in order to achieve the cooperation between the locking concave part 108 and the locking protrusion 109, the rear end surface of the first cavity 111 A circular hole is opened at the center to ensure that the locking protrusion 109 can cooperate with the locking concave part 108. In order to prevent the liquid inside the first cavity 111 from splashing out from the above-mentioned circular hole, the present invention accordingly, in conjunction with the drawings of the present invention, an outer cover 105 is installed between the first cavity 111 and the second cavity 112 on the outside of the second telescopic rod 107. The outer cover 105 is fixed on the end face of the first cavity 111, and its central axis coincides with the first cavity 111 and the second cavity 112. The second telescopic rod 107 is installed inside. The outer wall of the outermost rod sleeve of the telescopic rod 107 is tangent to the inner wall of the outer cover 105, which can prevent water vapor and liquid from being discharged from the above-mentioned through hole, and the outermost rod sleeve of the second telescopic rod 107 is fixed relative to the outer cover 105, so only the bidirectional screw rod 201 inside the second telescopic rod 107 needs to cooperate and rotate, where the mark 202 on the bidirectional screw rod 201 is a forward thread, and 203 is a reverse thread. Through the above design, while completing the cleaning of the first cavity 111 and the second cavity 112, the corresponding sealing performance of the first cavity 111 can be guaranteed.

[0086] In light of the above, the bidirectional screw 201 can extend or retract the multi-stage screw rods when rotating in the same direction. Specifically, when the bidirectional screw 201 rotates in the forward direction, the first telescopic rod 32 extends. When the telescopic rod reaches its end point, the bidirectional screw 201 reaches its top, and the screw rods at each stage also extend to their tops. After the bidirectional screw 201 reaches its top, the third drive motor 18 maintains its same-direction rotation. At this point, based on the forward and reverse helical structure of the bidirectional screw 201 and the forward and reverse thread structures on the screw rods at each stage, the telescopic rods are gradually retracted and shortened.

[0087] When the third driving motor 18 drives the first telescopic rod 32 to extend, the first telescopic rod 32 pushes the first cleaning member 33 to scrape off the attachments on the inner wall of the first cavity 111 .

[0088] When the first cleaning member 33 moves to the end surface of the first cavity 111 located at the second fixing member 162, the first telescopic rod 32 no longer extends. At this time, the locking protrusion 109 at the top of the first telescopic rod 32 and the locking concave part 108 on the second telescopic rod 107 are interlocked.

[0089] At this time, the rotation direction of the third drive motor 18 remains unchanged, so the first telescopic rod 32 remains in the extended state and continues to rotate. The rotation of the first telescopic rod 32 drives the rotation of the second telescopic rod 107 under the action of the mutual engagement of the locking protrusion 109 and the locking concave 108.

[0090] The premise for the first telescopic rod 32 to drive the rotation of the second telescopic rod 107 is that the rotation direction of the first telescopic rod 32 is consistent with the straight edge of the locking protrusion 109 or the locking concave part 108, otherwise it cannot drive the rotation.

[0091] When the first telescopic rod 32 continues to rotate, it continuously drives the second telescopic rod 107 to continuously extend, thereby pushing the second cleaning member 106 to move along the inner wall of the second cavity 112 to remove the attachments on the inner wall.

[0092] When the second telescopic rod 107 is extended to its maximum, the second cleaning element 106 moves to the side end of the second cavity 112. Utilizing the bidirectional spiral structure of the second telescopic rod 107, the third drive motor 18 maintains rotation in the same direction. When the second telescopic rod 107 reaches its maximum position, it begins to shrink in the reverse spiral direction, driving the second cleaning element 106 to move back to its initial position.

[0093] When the second telescopic rod 107 is retracted to the shortest initial position, the second telescopic rod 107 stops moving. At this time, the third drive motor 18 rotates in the opposite direction, the first telescopic rod 32 begins to shorten, and the locking protrusion 109 moves out of the locking recess 108.

[0094] As the first telescopic rod 32 shortens, the first cleaning member 33 moves to the initial position.

[0095] At this point, the first cleaning unit 33 has completed cleaning the first cavity 111 , and the second cleaning unit 106 has completed cleaning the inner wall of the second cavity 112 .

[0096] The viscous attachments cleaned by the first cleaning member 33 enter the second cavity 112 through the connecting pipe 102 , and are then carried to the discharge port at the rear end of the second cavity 112 and discharged during the movement and cleaning process of the second cleaning member 106 .

[0097] In order to achieve the above-mentioned purpose, the second cleaning member 106 of the present invention is provided with a through hole, and a one-way baffle 104 is provided at the through hole. When the discharge port 101 of the first cavity 111 is rotated to a position aligned with the connecting pipe 102, the liquid in the first cavity 111 enters the connecting pipe 102 through the discharge port 101, and enters the second cavity 112 through the through hole of the second cleaning member 106 from the connecting pipe 102.

[0098] The parts involved in relative rotation in the present invention are all treated with sealing materials with low friction coefficient and good sealing effect (such as nitrile rubber, chloroprene rubber or polytetrafluoroethylene, etc.) to ensure smooth rotation and no leakage.

[0099] A polylactic acid polymerization method, using the polymerization device of the present invention to achieve polylactic acid polymerization, comprises the following steps:

[0100] Step 1: Check the device to ensure that the first cleaning member 33 and the second cleaning member 106 are in their initial positions;

[0101] Step 2: Start the first drive motor 151 and the second drive motor 152 of the device to rotate the first cavity 111 and the second cavity 112 to ensure normal operation of the device;

[0102] Step 3: Heat sources, such as heating oil, are introduced into the first heat source inlet 61 and the second heat source inlet respectively until heat flows out of the first heat source outlet 62 and the second heat source outlet, indicating that the heat source space of the heating unit is full of heat source;

[0103] Step 4: Control the peristaltic pump 103 in the communication pipe 102 to be turned off;

[0104] Step 5: Add lactic acid raw material through the first feeding pipe 42 to ensure continuous supply of lactic acid raw material;

[0105] Step 6: The lactic acid continuously supplied into the first cavity 111 rotates in the first cavity 111, and the liquid continuously tumbles in the first cavity 111, thereby achieving uniform heating of the lactic acid. During this process, the lactic acid is dehydrated and prepolymerized, and the generated water vapor is discharged through the exhaust unit above the first cavity 111;

[0106] Step 6: Control the liquid level in the first cavity 111 to reach near the horizontal center line of the first cavity 111, start the peristaltic pump 103 in the connecting pipe 102, and intermittently discharge liquid into the second cavity 112;

[0107] Step 7: Close the valve at the discharge port near the third fixing member 163 below the second cavity 112;

[0108] Step 8: When liquid enters the second cavity 112 from the first cavity 111, a catalyst is added into the second cavity 112 through the second feeding pipe. At this time, the pre-polymerized lactic acid and the catalyst undergo a polymerization reaction in the second cavity 112 to produce polylactic acid;

[0109] Step 9: When the liquid level in the second cavity 112 reaches the vicinity of the horizontal center line of the second cavity 112, the valve of the discharge port is opened, and the polylactic acid produced by the polymerization is discharged from the discharge port;

[0110] Step 10: Under the continuous rotation of the first cavity 111 and the second cavity 112, the raw material input port and the liquid discharge port 101 and the material discharge port of the first cavity 111 are kept open, so that the raw materials are continuously and intermittently input, the first cavity 111 continuously and intermittently supplies liquid to the second cavity 112, and the second cavity 112 continuously and intermittently discharges the polymerized product;

[0111] By controlling the rotation speed of the first cavity 111 and the second cavity 112, the speed of the entire polymerization reaction can be controlled.

[0112] Step 11: Complete the polymerization reaction of polylactic acid.

[0113] A method for cleaning a polymerization reaction device for preparing polylactic acid is applied to the polylactic acid polymerization device, comprising the following steps:

[0114] Step 1: After the polymerization is completed, the residual liquid in the first cavity 111 and the second cavity 112 is discharged. Clean water or cleaning liquid is introduced into the first cavity 111 and the second cavity 112 to maintain the continuous rotation of the cavity;

[0115] Step 2: After preliminary cleaning with clean water or cleaning liquid, start the third drive motor 18, and the first telescopic rod 32 extends to push the first cleaning member 33 to clean the attachments on the inner wall of the first cavity 111;

[0116] Step 3: After the first cleaning element 33 finishes cleaning the first cavity 111 , the third drive motor 18 is kept rotating in the same direction to continue extending the second telescopic rod 107 , thereby pushing the second cleaning element 106 to remove the attachments on the inner wall of the second cavity 112 ;

[0117] Step 4: After the second cleaning element 106 has finished cleaning the inner wall of the second cavity 112, the third drive motor 18 continues to rotate in the same direction, driving the second telescopic rod 107 to shorten and retract, and retracting the second cleaning element 106 to its initial position;

[0118] Step 5: After the second cleaning element 106 returns to its initial position, the third drive motor 18 is rotated in the opposite direction. At this time, the first telescopic rod 32 is shortened and retracted, driving the first cleaning element 33 to return to its initial position.

[0119] The cleaning of the device cavity is now completed.

[0120] Since there is no stirring unit in the cavity, after the polymerization reaction is completed, there is no interference mechanism in the entire cavity, which is conducive to cavity cleaning. By setting a one-way screw in the first cavity 111, the first cleaning member is moved by the action of the first telescopic rod to automatically remove the attachments on the inner wall of the first cavity.

Claims

1. A polymerization reaction device, characterized in that: It includes a cavity, a fixing part, a heating unit, a driving unit, and a steam exhaust unit; The cavity comprises a first cavity (111) for dehydration prepolymerization of lactic acid and a second cavity (112) connected to or sealed with the first cavity (111) via a connecting pipe (102); The heating unit comprises a first heating unit (121) and a second heating unit (122) for heating the object to be processed and respectively arranged on the outer circumference of the first cavity (111) and the second cavity (112); The fixing member includes a first fixing member (161), a second fixing member (162), and a third fixing member (163) for supporting the cavity and movably cooperating with the cavity. The first fixing member (161), the second fixing member (162), and the third fixing member (163) are sequentially arranged at the front end, the middle, and the rear end of the cavity. The driving unit comprises a first driving unit for rotating the first cavity (111) and a second driving unit for rotating the second cavity (112); The steam exhaust unit comprises a first steam exhaust unit (63) for exhausting water vapor from the first cavity (111) and a second steam exhaust unit (64) for exhausting water vapor from the second cavity; The first cavity (111) is used for dehydration prepolymerization of lactic acid and is arranged horizontally and transversely. A first front outer groove (44) for cooperating with a first fixing member (161) is arranged on the outside of the front end thereof, and a first rear outer groove (45) for cooperating with a second fixing member (162) is arranged on the outside of the rear end thereof. The second cavity (112) is arranged horizontally and transversely. The center line of the first cavity (111) and the center line of the second cavity (112) are on the same horizontal straight line. The front end and the rear end of the second cavity (112) are respectively provided with a second front outer groove and a second rear outer groove. The second front outer groove and the second rear outer groove are respectively connected to the second fixing member (162) and the third fixing member (162). (163) corresponding to the movable fitting connection; the first feeding member (41) is arranged around the outer wall of the first cavity (111) near the first fixing member (161), the first feeding member (41) and the first cavity (111) are in a sealed state at the junction, and the first feeding member (41) can rotate relative to the first cavity (111), the first feeding member (41) is annular, the first feeding member (41) is equipped with a first feeding pipe (42) tangent to the outer wall of the first cavity (111), and the outer wall of the first cavity (111) is provided with at least one first feeding port (43) that cooperates with the first feeding pipe (42) and communicates with the interior of the first cavity (111) at a corresponding position of the first feeding member (41).

2. A polymerization reaction device according to claim 1, characterized in that: The first driving unit includes a first gear (131) arranged on the outer circumference of the middle position of the first cavity (111), the first gear (131) is connected to a first driving motor (151) connected to the first driving wheel (51) and arranged below the first cavity (111), and the first driving motor (151) is installed on the frame; the first fixing member (161) is a cylindrical structure, and the first fixing member (161) is installed on the first leg (171), wherein the first fixing member (161) is provided with a first inner groove (330) on the end surface relative to the first cavity (111) and is movably connected and engaged with the first front outer groove (44) provided on the first cavity (111). 1), the second fixing member (162) is an annular structure, the second fixing member (162) is fixed on the second leg (172), and the inner wall of the second fixing member (162) is respectively provided with a second front end inner groove and a second rear end inner groove that are movably connected and engaged with the first rear end outer groove (45) of the first cavity and the second front end outer groove of the second cavity (112). Similarly, the third fixing member (163) is a cylindrical structure, the third fixing member (163) is installed on the third leg (173), and the end surface of the third fixing member (163) relative to the second cavity (112) is provided with a third front end inner groove that is movably connected and engaged with the second rear end outer groove of the second cavity (112).

3. A polymerization reaction device according to claim 1, characterized in that: The first steam exhaust unit (63) includes two groups of steam exhaust vertical pipes (81) symmetrically arranged on the top of the first cavity (111) and connected to the first cavity (111), and the inner wall pipes of the two steam exhaust vertical pipes (81) are each provided with a steam exhaust valve (82), and the steam exhaust valve (82) can discharge water vapor and prevent liquid from being discharged from the steam exhaust vertical pipe (81). The tops of the other two steam exhaust vertical pipes (81) are connected to each other through a condensation component, and the condensation component includes an upwardly protruding arc-shaped top plate (83) and a downwardly concave arc-shaped bottom plate (84) that cooperates with the arc-shaped top plate (83). The arc-shaped top plate (83) and the arc-shaped bottom plate (84) cooperate to form a connecting piece, and the bottom opening of the arc-shaped bottom plate (84) is connected to a drain pipe (85).

4. A polymerization reaction device according to claim 1, characterized in that: The first heating unit (121) includes a front section heating unit (1211) and a rear section heating unit (1212) surrounding the outside of the first cavity (111); the inner walls of the front section heating unit (1211) and the rear section heating unit (1212) are tangent to the outer wall of the first cavity (111); the front section heating unit (1211) and the rear section heating unit (1212) have cavities for storing hot water or hot oil; the front section heating unit (1211) and the rear section heating unit (1212) are connected via a first connecting pipe (141); the first connecting pipe (141) is arranged in a U shape; the top of the front section heating unit (1211) is provided with a first heat source outlet (62); the bottom of the rear section heating unit (1212) is provided with a first heat source inlet (61).

5. A polymerization reaction device according to claim 1, characterized in that: The connecting pipeline (102) is provided with a liquid storage area (1021), a pump area (1022), and a liquid discharge area (1023) in sequence along the material conveying direction. The liquid storage area (1021) is a cylindrical cavity structure. A baffle with an opening is provided between the liquid storage area (1021) and the pump area (1022). The liquid discharge area (1023) is a conical frustum structure with upper and lower openings. A peristaltic pump (103) is provided in the cavity of the pump area (1022). The peristaltic pump (103) is connected to the opening on the baffle and the opening of the liquid discharge area (1023) close to the pump area (1022) by providing an infusion hose (1031).

6. A polymerization reaction device according to claim 1, characterized in that: The polymerization reaction device further comprises a cleaning unit for cleaning the cavity.

7. A polymerization reaction device according to claim 6, characterized in that: The cleaning unit comprises a first cleaning unit for cleaning the first cavity (111) and a second cleaning unit for cleaning the second cavity (112), wherein the first cleaning unit comprises a first cleaning member (33) arranged on the front end surface inside the first cavity (111), the outer wall of the first cleaning member (33) is tightly fitted with the inner wall of the first cavity (111), the center position of the first cleaning member (33) is connected to the first telescopic rod (32), one end of the first telescopic rod (32) is connected to the first cleaning member (33), and the other end of the first telescopic rod (32) passes through the end surface of the first cavity (111) toward the first fixing member (161) and is connected to the one-way screw rod (19 ) is connected, the one-way screw (19) is connected with the third drive motor (18), the third drive motor (18) is fixedly mounted on the frame, the second cleaning unit includes a second telescopic rod (107) arranged between the first cavity (111) and the second cavity (112), the second telescopic rod (107) is connected with the second cleaning member (106) arranged in the second cavity (112) through the two-way screw (201), the front end of the second telescopic rod (107) is provided with a locking recess (108), and the locking recess (108) is matched with a locking protrusion (109) provided at the top end of the first telescopic rod (32) toward the second cavity (112).

8. The polylactic acid polymerization method according to claim 7, wherein: The steps include: Step 1: Check the device to ensure that the first cleaning member (33) and the second cleaning member (106) are in their initial positions; Step 2: Start the first drive motor (151) and the second drive motor (152) of the device to rotate the first cavity (111) and the second cavity (112) to ensure normal operation of the device; Step 3: Heat sources are fed into the first heat source inlet (61) and the second heat source inlet respectively until heat sources flow out of the first heat source outlet (62) and the second heat source outlet; Step 4: Control the peristaltic pump (103) in the connecting pipe (102) to be closed; Step 5: Add lactic acid raw material from the first feeding pipe (42) to ensure continuous supply of lactic acid raw material; Step 6: The lactic acid continuously supplied into the first cavity (111) rotates in the first cavity (111), and the liquid continuously tumbles in the first cavity (111), thereby achieving uniform heating of the lactic acid. During this process, the lactic acid is dehydrated and prepolymerized, and the generated water vapor is discharged through the exhaust unit above the first cavity (111); Step 6: Control the liquid level in the first cavity (111) to reach near the horizontal center line of the first cavity (111), start the peristaltic pump (103) in the connecting pipe (102), and intermittently discharge the liquid into the second cavity (112); Step 7: Close the valve at the discharge port near the third fixing member (163) below the second cavity (112); Step 8: When liquid enters the second cavity (112) from the first cavity (111), a catalyst is added into the second cavity (112) through the second feeding pipe, and the pre-polymerized lactic acid and the catalyst undergo a polymerization reaction in the second cavity (112) to generate polylactic acid; Step nine: When the liquid level in the second cavity (112) reaches the vicinity of the horizontal center line of the second cavity (112), the valve of the discharge port is opened, and the polylactic acid produced by the polymerization is discharged from the discharge port; Step 10: Under the continuous rotation of the first cavity (111) and the second cavity (112), the raw material input port and the liquid discharge port (101) and the material discharge port of the first cavity (111) are kept open, so that the raw material is continuously and intermittently input, the first cavity (111) continuously and intermittently supplies liquid to the second cavity (112), and the second cavity (112) continuously and intermittently discharges the polymerized product; By controlling the rotational speeds of the first cavity (111) and the second cavity (112), the speed of the entire polymerization reaction can be controlled to complete the polymerization reaction of polylactic acid.

9. A method for cleaning a polymerization reaction device for preparing polylactic acid, characterized in that: Applied to the above-mentioned polymerization reaction device, the method comprises the following steps: Step 1: After the polymerization is completed, the residual liquid in the first cavity (111) and the second cavity (112) is discharged, and clean water or cleaning liquid is introduced into the first cavity (111) and the second cavity (112) to maintain the continuous rotation of the cavity; Step 2: After preliminary cleaning with clean water or cleaning fluid, the third drive motor (18) is started, and the first telescopic rod (32) is extended to push the first cleaning member (33) to remove attachments on the inner wall of the first cavity (111); Step 3: After the first cleaning member (33) has finished cleaning the first cavity (111), the third drive motor (18) is kept rotating in the same direction, and the second telescopic rod (107) is continued to be extended, so as to push the second cleaning member (106) to remove the attachments on the inner wall of the second cavity (112); Step 4: After the second cleaning member (106) completes cleaning the inner wall of the second cavity (112), the third drive motor (18) continues to rotate in the same direction, driving the second telescopic rod (107) to shorten and retract, and retracting the second cleaning member (106) to the initial position; Step 5: After the second cleaning member (106) returns to the initial position, the third drive motor (18) is rotated in the opposite direction, and the first telescopic rod (32) is shortened and retracted, driving the first cleaning member (33) to return to the initial position; The cleaning of the device cavity is now completed.

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