Polylactic acid preparation device and preparation method

Abstract

The invention discloses a polylactic acid preparation device and a polylactic acid preparation method, and relates to the technical field of polylactic acid preparation, the polylactic acid preparation device comprises a micro-fluidic chip and a screw extruder, the micro-fluidic chip is provided with a first catalyst conveying channel, a second catalyst conveying channel, a mixture output channel and a mixing channel with a microscale effect, the first catalyst conveying channel and the second catalyst conveying channel are both communicated with one end of the mixing channel, the other end of the mixing channel is communicated with the mixture output channel, and the mixture output channel and the reaction raw material supply channel are both communicated with the screw extruder. A first heater for providing a reaction temperature is arranged on the periphery of a barrel of the screw extruder; the first catalyst solution and the second catalyst solution are rapidly mixed by the micro-fluidic chip, the mixing effect of the first catalyst solution and the second catalyst solution is improved, and then the mixture of the catalysts is conveyed into the screw extruder to react with the reaction raw materials, so that the production efficiency, the molecular weight of the product and the purity of the product can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polylactic acid preparation, and in particular to a polylactic acid preparation device and a preparation method. Background Art

[0002] Polylactic acid is an important biodegradable polymer material. Taking L-polylactic acid as an example, it has great application potential in many fields such as biomedicine, packaging, and textiles due to its good biocompatibility, mechanical properties and degradability.

[0003] At present, the main methods for preparing L-polylactic acid are direct polycondensation and ring-opening polymerization. In the direct polycondensation, the water generated during the reaction is difficult to completely remove, resulting in a low molecular weight product, usually only up to 10 4 -10 5 g / mol, which is difficult to meet the application scenarios with high requirements for material performance; although the general ring-opening polymerization method has a high product molecular weight, it requires the intervention of relatively expensive catalysts, and requires precise control of high temperature and high pressure environments. The reaction time is also as long as several hours, and there will be catalyst residue problems, which seriously affect the biocompatibility of the product and pose a safety hazard when used in biomedicine and other fields.

[0004] Therefore, people are in urgent need of a polylactic acid preparation device with high product molecular weight, high production efficiency and good product quality. Summary of the Invention

[0005] The purpose of the present invention is to provide a polylactic acid preparation device and preparation method to solve the problems existing in the above-mentioned prior art, combining microfluidic mixing technology and screw extrusion technology to improve product molecular weight, production efficiency and product purity.

[0006] To achieve the above-mentioned purpose, the present invention provides the following solution: The present invention provides a polylactic acid preparation device, comprising a microfluidic chip and a screw extruder, wherein the microfluidic chip is provided with a first catalyst delivery channel, a second catalyst delivery channel, a mixture output channel and a mixing channel with a microscale effect, the first catalyst delivery channel and the second catalyst delivery channel are both connected to one end of the mixing channel, the other end of the mixing channel is connected to the mixture output channel, the mixture output channel and the reaction raw material supply channel are both connected to the screw extruder, and the outer periphery of the barrel of the screw extruder is provided with a first heater for providing reaction temperature.

[0007] Preferably, a plurality of fins are provided in the mixing channel.

[0008] Preferably, the fins are inclined to the axis of the mixing channel.

[0009] Preferably, the mixing channel is arranged in a serpentine shape.

[0010] Preferably, a plurality of fins are provided in the first catalyst delivery channel.

[0011] Preferably, the inner wall of the first catalyst delivery channel, the inner wall of the second catalyst delivery channel, the inner wall of the mixture output channel and the inner wall of the mixing channel are subjected to hydrophilic treatment.

[0012] Preferably, the microfluidic chip is located within the heating range of the second heater.

[0013] Preferably, a plurality of first heaters with successively increasing heating temperatures are provided along the conveying direction of the screw extruder.

[0014] Preferably, the polylactic acid preparation device further comprises a granulator, and the output port of the screw extruder is connected to the feed port of the granulator.

[0015] The present invention also provides a method for preparing polylactic acid using the polylactic acid preparation device, comprising the following steps:

[0016] S1: Precisely controlling the first catalyst solution and the second catalyst solution to be injected into the first catalyst delivery channel and the second catalyst delivery channel at a certain flow rate, respectively. The first catalyst solution and the second catalyst solution enter the mixing channel for mixing, and the mixed mixture enters the screw extruder through the mixture output channel;

[0017] S2: injecting the reaction raw materials into the screw extruder from the injection port of the screw extruder;

[0018] S3: The catalyst reacts with the reaction raw materials in the screw extruder, and the desired product is generated and discharged from the screw extruder.

[0019] Compared with the prior art, the present invention mainly achieves the following technical effects:

[0020] First, the first catalyst solution and the second catalyst solution are quickly mixed using a microfluidic chip to improve the mixing effect of the two, and then the catalyst mixture is transported to a screw extruder to react with the reaction raw materials. This can shorten the reaction time to improve production efficiency, and can also improve the reaction effect, increase the product molecular weight and product purity. Moreover, thanks to the precise control and mixing of the catalyst by the microfluidic chip, it can achieve lower catalyst residues and further improve the purity of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A schematic diagram of the structure of a microfluidic chip in an embodiment of the present invention;

[0023] Figure 2 This is a schematic structural diagram from a first perspective of a polylactic acid preparation device according to an embodiment of the present invention;

[0024] Figure 3 This is a schematic structural diagram from a second perspective of the polylactic acid preparation device in an embodiment of the present invention;

[0025] Figure 4 A top view of a polylactic acid production device according to an embodiment of the present invention;

[0026] Figure 5 for Figure 4 Cross-sectional view at AA in the middle;

[0027] Among them, 1. microfluidic chip; 2. screw extruder; 3. first catalyst delivery channel; 4. second catalyst delivery channel; 5. mixture output channel; 6. mixing channel; 7. injection module; 8. injection port; 9. fin; 10. first heater; 11. insulation layer; 12. granulator; 13. slide; 14. collection container; 15. baffle plate. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] The purpose of the present invention is to provide a polylactic acid preparation device and preparation method to solve the problems existing in the prior art, combine microfluidic mixing technology and screw extrusion technology to improve product molecular weight, production efficiency and product purity.

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Please refer to Figures 1 to 5As shown, a polylactic acid preparation device is provided, including a microfluidic chip 1 and a screw extruder 2, the microfluidic chip 1 is provided with a first catalyst delivery channel 3, a second catalyst delivery channel 4, a mixture output channel 5 and a mixing channel 6 with a microscale effect, the first catalyst delivery channel 3 and the second catalyst delivery channel 4 are both connected to one end of the mixing channel 6, and the other end of the mixing channel 6 is connected to the mixture output channel 5, the mixture output channel 5 and the reaction raw material supply channel are both connected to the screw extruder 2, and the outer periphery of the barrel of the screw extruder 2 is provided with a first heater 10 for providing a reaction temperature. The mixing channel 6 in the microfluidic chip 1 forms a microscale effect with a small diameter, so that the catalysts can be mixed quickly and the mixing effect is improved, and there is no need to mix the two catalysts. By carrying out a separate synthesis treatment, the mass transfer and heat transfer efficiency are significantly improved, the reaction time is greatly shortened, and the production efficiency is effectively improved. Moreover, by precisely controlling the flow rate, pressure and other data of the first catalyst solution and the second catalyst solution in the microfluidic chip 1 and the temperature, speed and other parameters during the screw extrusion process, the occurrence of side reactions can be effectively suppressed. The prepared polylactic acid has a high molecular weight and a narrow molecular weight distribution, the product performance is more stable and uniform, and the product purity is improved. In addition, since it is necessary to control the flow rate of the first catalyst solution and the second catalyst solution, it is beneficial to avoid waste of catalyst solutions and reduce costs. Thanks to the precise control and mixing of the catalyst by the microfluidic chip, it can achieve lower catalyst residues and further improve the purity of the product.

[0032] The microfluidic chip 1 is made of silicon carbide.

[0033] The outer periphery of the first heater 10 needs to be wrapped with a thermal insulation layer 11 to prevent heat from dissipating and save heat energy.

[0034] An injection module 7 is provided on one side of the screw extruder 2 to connect the mixture output channel 5 with the inner cavity of the screw extruder 2. A flow control valve and a pressure monitoring device can be provided on the channel between the mixture output channel 5 and the injection module 7. The injection port 8 of the screw extruder 2 is used to input the reaction raw materials.

[0035] In this embodiment, the diameter of the mixing channel 6 is 50 μm. In other embodiments, the diameter can be designed according to actual needs.

[0036] In some embodiments, the first catalyst delivery channel 3 , the second catalyst delivery channel 4 , and the output channel are all channels with microscale effects, and their diameters are the same as that of the mixing channel 6 .

[0037] In some embodiments, a plurality of fins 9 are provided in the mixing channel 6 to change the flow channel through the fins 9, thereby increasing the turbulence of the flow channel and further improving the mixing effect of the catalyst.

[0038] The fins 9 are inclined relative to the axis of the mixing channel 6, further improving the mixing effect of the catalyst.

[0039] The mixing channel 6 can be configured to be serpentine in order to extend the mixing path and thereby improve the mixing effect of the catalyst.

[0040] On the basis that the mixing channel 6 is serpentine, wherein the first catalyst delivery channel 3 is far away from the inlet of the mixing channel 6 , a plurality of fins 9 can be arranged in the first catalyst delivery channel 3 , and the fins 9 in the first catalyst delivery channel 3 can be arranged according to the fins 9 in the mixing channel 6 .

[0041] The inner wall of the first catalyst delivery channel 3, the inner wall of the second catalyst delivery channel 4, the inner wall of the mixture output channel 5 and the inner wall of the mixing channel 6 may be hydrophilic treated to improve the fluidity of the catalyst solution in each channel.

[0042] Since the first catalyst solution and the second catalyst solution need to enter the screw extruder 2 to react with the reaction raw materials after mixing, the reaction requires the first heater 10 to provide a certain temperature. Therefore, the time for the first catalyst solution and the second catalyst solution to mix can be used to set a second heater, and the microfluidic chip 1 can be located within the heating range of the second heater. At this time, the second heater can be used to preheat the first catalyst solution and the second catalyst solution, which is beneficial to improve the subsequent reaction efficiency. At the same time, the addition of heat is also beneficial to improve the mixing effect of the first catalyst solution and the second catalyst solution.

[0043] On the basis of providing the fins 9, the fins 9 can further improve the preheating effect of the catalyst solution.

[0044] In some embodiments, multiple first heaters 10 with successively increasing heating temperatures are provided along the conveying direction of the screw extruder 2. Specifically, three first heaters 10 may be provided. Along the conveying direction of the screw extruder 2, the heating intervals of the three first heaters 10 may be set to 140-160°C, 160-180°C, and 180-205°C. The three first heaters 10 correspond to the feed section, melting section, and extrusion section of the screw extruder 2, respectively.

[0045] In some embodiments, the polylactic acid preparation device further includes a granulator 12 , and the output port of the screw extruder 2 is connected to the feed port of the granulator 12 , and the product generated by the reaction in the screw extruder 2 is directly manufactured into a granular product through the granulator 12 .

[0046] A slide 13 can be set at the outlet of the granulator 12, and the surface of the slide 13 is set at an angle. A collection container 14 is set at the lower end of the slide 13, so that the products manufactured by the granulator 12 fall on the slide 13 and slide on the surface of the slide 13 to be collected in the collection container 14.

[0047] Baffles can be provided on both sides of the surface of the slide 13 to prevent the product from slipping out from the side.

[0048] A baffle plate 15 is provided at the outlet of the granulator 12 to ensure that the granular product enters the surface of the slide 13 .

[0049] In some embodiments, the polylactic acid preparation device also includes a product post-processing device, including a precipitation container, a centrifuge and a vacuum drying oven. Taking the left-handed polylactic acid product as an example, after the product is cooled, the product is placed in a precipitation container containing an excess of anhydrous ethanol for precipitation, and then centrifuged by a centrifuge (the speed is set to 5000-10000 rpm, and the time is 5-15 min) to separate the precipitate from the supernatant. The precipitate is then washed with anhydrous ethanol for multiple times to completely remove the residual catalyst and the lactide (reaction raw material) that has not undergone ring-opening polymerization. Finally, the washed precipitate is placed in a vacuum drying oven and dried to constant weight at a temperature of 40-60°C to obtain a pure left-handed polylactic acid product.

[0050] The present invention also provides a method for preparing polylactic acid using the polylactic acid preparation device, comprising the following steps:

[0051] S1: Using a high-pressure nitrogen tank and a precisely controlled air valve as a pneumatic control system or a pump as a delivery control system, the first catalyst solution and the second catalyst solution are precisely controlled to be injected into the first catalyst delivery channel 3 and the second catalyst delivery channel 4 at a certain flow rate by air pressure delivery or pump delivery. The first catalyst solution and the second catalyst solution enter the mixing channel 6 for mixing, and the mixed mixture enters the screw extruder 2 through the mixture output channel 5;

[0052] S2: injecting the reaction raw materials into the screw extruder 2 from the injection port 8 of the screw extruder 2;

[0053] S3: The catalyst and the reaction materials react in the screw extruder 2 under the shearing action of the screw and the temperature field to achieve ring-opening polymerization. After the reaction generates the desired product, it is discharged from the screw extruder 2 and processed by the granulator 12 or the post-processing device.

[0054] The following provides the experimental results of the actual preparation of L-polylactic acid:

[0055] 1. Preparation of L-polylactic acid under conventional conditions

[0056] Parameters of the microfluidic chip 1: silicon carbide material, mixing channel 6 diameter 50 μm, serpentine mixing channel 6 length 10000 μm (inner wall hydrophilic treatment + 45° fin 9 design).

[0057] Raw materials and flow:

[0058] First catalyst delivery channel 3: Sn(Oct)2 solution (0.16 mol / L, toluene solvent), flow rate 1 mL / min. Second catalyst delivery channel 4: CH3(CH2)11OH solution (0.16 mol / L, toluene solvent), flow rate 2 mL / min.

[0059] The injection pressure of the first catalyst solution and the second catalyst solution is 1 MPa, and the mixing time of the two in the microfluidic chip 1 is about 1500 ms.

[0060] Screw extruder 2 parameters: screw length-diameter ratio 20:1, speed 60r / min.

[0061] The temperature of the first heaters 10 is divided into sections: 150°C for the feeding section, 170°C for the melting section, and 190°C for the extrusion section.

[0062] Post-processing:

[0063] Precipitation: Precipitation with anhydrous ethanol, centrifugation at 8000 rpm for 10 min, washing 3 times. Drying: Dry in a vacuum at 50°C to constant weight, the product molecular weight is about 1.5×10 6 g / mol.

[0064] 2. Preparation of L-polylactic acid under optimized conditions (microfluidic chip 1 remains unchanged)

[0065] Raw materials and flow:

[0066] First catalyst delivery channel 3: Sn(Oct)2 solution (0.16 mol / L, toluene solvent), flow rate 1.2 mL / min. Second catalyst delivery channel 4: CH3(CH2)11OH solution (0.16 mol / L, toluene solvent), flow rate 2.4 mL / min.

[0067] The injection pressure of the first catalyst solution and the second catalyst solution is 1.2 MPa, and the mixing time of the two in the microfluidic chip 1 is about 20 seconds.

[0068] Screw extruder 2 parameters: screw length-to-diameter ratio 20:1, speed increased to 80r / min to enhance shearing effect.

[0069] The temperature of the first heaters 10 is divided into sections: 160°C in the feeding section, 180°C in the melting section, and 200°C in the extrusion section.

[0070] Post-processing:

[0071] Precipitation: Precipitation with anhydrous ethanol, centrifugation at 10,000 rpm for 15 min, washing 3 times. Drying: Dry under vacuum at 60°C to constant weight (8 hours), the product molecular weight is about 1.8×10 6 g / mol.

[0072] 3. Preparation of L-polylactic acid under the high-flow rate capacity improvement solution (microfluidic chip 1 remains unchanged)

[0073] Raw materials and flow:

[0074] First catalyst delivery channel 3: Sn(Oct)2 solution (0.16 mol / L, toluene solvent), flow rate 1.5 mL / min. Second catalyst delivery channel 4: CH3(CH2)11OH solution (0.16 mol / L, toluene solvent), flow rate 3.0 mL / min.

[0075] Injection pressure of the first catalyst solution and the second catalyst solution: 1.5 MPa.

[0076] Screw extruder 2 parameters: screw length-to-diameter ratio 20:1, speed increased to 100r / min, matching high flow rate.

[0077] The temperature of the first heaters 10 is divided into the following sections: 160° C. in the feeding section, 185° C. in the melting section, and 205° C. in the extrusion section (for enhanced polymerization depth).

[0078] Post-processing:

[0079] Precipitation: Precipitation with anhydrous ethanol, centrifugation at 8000 rpm for 10 min, washing 3 times. Drying: Vacuum drying at 50°C to constant weight (6 hours), increasing production capacity by 50%.

[0080] The following table provides a comparison of key parameters (A is the parameter of the first catalyst solution, B is the parameter of the second catalyst solution)

[0081]

[0082] Adaptive changes based on actual needs are all within the scope of protection of the present invention.

[0083] It should be noted that it will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims, not the foregoing description, and it is intended that all variations within the meaning and range of equivalents of the claims be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0084] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A polylactic acid production device, characterized in that: It includes a microfluidic chip and a screw extruder. The microfluidic chip is provided with a first catalyst delivery channel, a second catalyst delivery channel, a mixture output channel and a mixing channel with a microscale effect. The first catalyst delivery channel and the second catalyst delivery channel are both connected to one end of the mixing channel, and the other end of the mixing channel is connected to the mixture output channel. The mixture output channel and the reaction raw material supply channel are both connected to the screw extruder. A first heater for providing reaction temperature is provided on the outer periphery of the barrel of the screw extruder.

2. The polylactic acid production device according to claim 1, characterized in that: A plurality of fins are arranged in the mixing channel.

3. The polylactic acid production device according to claim 2, characterized in that: The fins are inclined with respect to the axis of the mixing channel.

4. The polylactic acid production device according to claim 2, characterized in that: The mixing channel is arranged in a serpentine shape.

5. The polylactic acid production device according to claim 4, characterized in that: A plurality of fins are provided in the first catalyst delivery channel.

6. The polylactic acid production device according to claim 1, characterized in that: The inner wall of the first catalyst delivery channel, the inner wall of the second catalyst delivery channel, the inner wall of the mixture output channel, and the inner wall of the mixing channel are subjected to hydrophilic treatment.

7. The polylactic acid production device according to claim 1, characterized in that: The microfluidic chip is located within the heating range of the second heater.

8. The polylactic acid production device according to claim 1, characterized in that: A plurality of first heaters with successively increasing heating temperatures are arranged along the conveying direction of the screw extruder.

9. The polylactic acid production device according to claim 1, characterized in that: The polylactic acid preparation device also includes a granulator, and the output port of the screw extruder is connected to the feed port of the granulator.

10. A method for preparing polylactic acid, characterized in that: The polylactic acid production device according to any one of claims 1 to 9 comprises the following steps: S1: Precisely controlling the first catalyst solution and the second catalyst solution to be injected into the first catalyst delivery channel and the second catalyst delivery channel at a certain flow rate, respectively. The first catalyst solution and the second catalyst solution enter the mixing channel for mixing, and the mixed mixture enters the screw extruder through the mixture output channel; S2: injecting the reaction raw materials into the screw extruder from the injection port of the screw extruder; S3: The catalyst reacts with the reaction raw materials in the screw extruder, and the desired product is generated and discharged from the screw extruder.

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