CN209957681U - Polylactic acid devolatilization device - Google Patents
Polylactic acid devolatilization device Download PDFInfo
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- CN209957681U CN209957681U CN201920228439.8U CN201920228439U CN209957681U CN 209957681 U CN209957681 U CN 209957681U CN 201920228439 U CN201920228439 U CN 201920228439U CN 209957681 U CN209957681 U CN 209957681U
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Abstract
The utility model relates to the technical field of polylactic acid synthesis, and discloses a polylactic acid devolatilization device, which comprises a film evaporator, wherein the film evaporator comprises a tank body, a motor arranged at the top end outside the tank body, a rotating shaft arranged inside the tank body and extending along the axial direction of the tank body and connected with the motor, a steam outlet and a feed inlet which are arranged at the upper part of the outer wall of the tank body, and a discharge outlet which is arranged at the bottom end of the tank body; the motor drives the rotating shaft to rotate in the tank body, a plurality of rows of scraping plates are axially arranged on the outer wall of the rotating shaft, and two adjacent rows of scraping plates are arranged in a staggered mode. The device is simple in structure, and can greatly reduce the content of low-molecular volatile matters, especially monomer content, in the polylactic acid slices on the premise of not influencing the property of polylactic acid.
Description
Technical Field
The utility model relates to a polylactic acid synthesis field, concretely relates to polylactic acid devolatilizes device.
Background
At present, two problems of environmental pollution and resource shortage constitute a great threat to human society, and the development of renewable resources and renewable degradation polymer materials for replacing petroleum plastic products is in the trend. Among them, the synthesis and application of polylactic acid (PLA) are being actively studied.
The polylactic acid belongs to a chemically synthesized completely biodegradable green high polymer material, and the development and the utilization of the polylactic acid can solve the problem of environmental pollution and open up inexhaustible raw material resources for the plastic industry mainly based on petroleum resources. Therefore, the development of polylactic acid materials is of great importance both from the viewpoint of environmental protection and from the viewpoint of resource development.
Among the many methods for synthesizing polylactic acid, the lactide ring-opening polymerization method is an effective method for obtaining high molecular weight and high strength polylactic acid, and has a wide application prospect. The lactide ring-opening polymerization process and the subsequent devolatilization process become important research contents in the field of polylactic acid synthesis. On one hand, the research focuses on the improvement of the polymerization process so as to further improve the molecular weight of the polymer and meet the requirements of various polylactic acid materials; on the other hand, the improvement of the devolatilization process at the later stage of the reaction is aimed at removing low-molecular volatiles from the polymerization product with high viscosity characteristic as completely as possible and improving the purity of the polymer so as to improve the moldability and the thermal stability of the polylactic acid material.
In the continuous polymerization method for producing polylactic acid by taking lactide as a raw material, a devolatilization method and equipment are a key link, and because the system viscosity is higher and the boiling point of a lactide monomer is higher, devolatilization is always a difficult problem in the production process and technical development of polylactic acid. The devolatilization process utilizes the reduction of the volatilization equilibrium concentration of the gas-liquid interface, so that the volatile components in the liquid phase are rapidly transferred to the gas phase, while the volatile components in the deep part of the liquid phase need to be separated from the liquid phase and transferred to the gas phase through diffusion, and therefore, the transfer rate of the volatile components is a control step for controlling the devolatilization speed. Under constant temperature, three ways are available for improving the transfer rate of the volatile component, namely, the liquid film is thinned, and the diffusion distance is shortened; secondly, the turbulence intensity of the liquid is increased, so that the gas-liquid interface is continuously updated; thirdly, the volatile components are promoted to be vaporized and are easy to be separated from the liquid phase.
At present, the devolatilization method by adopting a screw extruder is high in energy consumption, a polymer is subjected to high shear load in the screw extruder, polylactic acid is a heat-sensitive polymer, and the molecular weight of the polylactic acid is easily reduced due to the high shear load. CN116777A provides a method and a device for removing residual volatile components in a polymer system, which comprises a heater which is gradually enlarged, a devolatilization tank with a built-in heating distributor, a stirring paddle and a distribution plate, wherein the polymer enters the devolatilization tank after passing through a multi-stage heater which is gradually expanded, and then the residual volatile components are removed by a separator. However, the devolatilization method is not suitable for a polylactic acid system having a high system viscosity because gas-liquid separation is achieved by the stirring action of the stirring paddle.
SUMMERY OF THE UTILITY MODEL
The utility model aims at overcoming prior art and taking off and wave the device and can not effectively get rid of the low molecule volatile substance among the polylactic acid to and take off and wave the problem that the device structure is complicated, provide a polylactic acid and take off and wave the device, the device is simple structure not only, can be in addition the content of the low molecule volatile substance among the greatly reduced polylactic acid under the prerequisite that does not influence polylactic acid nature, especially monomeric content.
In order to achieve the above object, the present invention provides a polylactic acid devolatilization device, which comprises a film evaporator, wherein the film evaporator comprises a tank body, a motor arranged at the top end of the outside of the tank body, a rotating shaft arranged inside the tank body and extending along the axial direction of the tank body and connected with the motor, a steam outlet and a feed inlet arranged at the upper part of the outer wall of the tank body, and a discharge outlet arranged at the bottom end of the tank body; the motor drives the rotating shaft to rotate in the tank body, a plurality of rows of scraping plates are axially arranged on the outer wall of the rotating shaft, and two adjacent rows of scraping plates are arranged in a staggered mode.
According to the technical scheme, the combined process of high-torque high-speed shearing film forming, quick and continuous updating of the film surface and flash evaporation is adopted at the tail section of polylactic acid synthesis, so that most of residual lactide monomers in the polylactic acid can be recycled, the content of the monomers in the polylactic acid can be reduced to be below 0.3%, the internal quality of the polylactic acid slices is improved, and the production cost is reduced.
Drawings
FIG. 1 is a schematic structural view of a polylactic acid devolatilization device of the present invention;
FIG. 2 is a perspective view of the thin film evaporator of FIG. 1 with the scraper blades arranged on the rotating shaft;
FIG. 3 is a plan view of the arrangement of the blades of the thin film evaporator of FIG. 1 on the rotating shaft;
FIG. 4 is a schematic view of the liquid guiding groove on the surface of the scraper of the present invention;
FIG. 5a is a front view of a prior art thin film evaporator with wipers positioned on the rotating shaft;
figure 5b is a top view of the manner in which the flights of a prior art thin film evaporator are arranged on a rotating shaft.
Description of the reference numerals
1-film evaporator 2-desublimation device 3-vacuum device 4-tank body
11-distributing device 12-rotating shaft 13-scraper 14-feed inlet
15-steam outlet 16-discharge outlet 17-motor 21-steam inlet
22-condensate outlet 23-vacuum air outlet 24-liquid guide groove
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The utility model provides a polylactic acid devolatilization device, as shown in figure 1, the device comprises a film evaporator 1, the film evaporator comprises a tank body 4, a motor 17 arranged at the top end outside the tank body, a rotating shaft 12 arranged inside the tank body and extending along the axial direction of the tank body and connected with the motor, a steam outlet 15 and a feed inlet 14 arranged at the upper part of the outer wall of the tank body, and a discharge outlet 16 arranged at the bottom end of the tank body; the motor 17 drives the rotating shaft 12 to rotate in the tank body, a plurality of rows of scraping plates 13 are axially arranged on the outer wall of the rotating shaft, and two adjacent rows of scraping plates are arranged in a staggered mode.
In the present invention, the tank 4 is generally referred to as a closed tank, unless otherwise specified; the bottom of the tank body can be of any structure capable of realizing smooth outflow of liquid materials, preferably, the bottom of the tank body is in an inverted cone shape, and the material outlet is in an inverted cone angle.
In the present invention, the scraping plate generally refers to a "sheet-like" structure; the utility model discloses it is right the geometry of scraper blade does not have the restriction, can be the rectangle, and is trapezoidal, oval, toper or fan-shaped, preferably the rectangle.
In the present invention, as shown in fig. 2, the "each row of scrapers" refers to a row of scrapers that is disposed on the outer wall of the rotating shaft and is parallel to the central axis of the rotating shaft. Preferably, the flights in each row are equally spaced.
In the utility model, the included angle formed by the staggered arrangement of the adjacent scraper plates in columns is used for realizing the purpose that the material flowing down from any scraper plate edge can flow to the 'sheet-shaped' plane of the scraper plate below the scraper plate, and the 'scraper plate below the scraper plate' mainly refers to the scraper plate which is in two adjacent columns with the scraper plate and has the closest spatial distance along the extension direction of the rotating shaft; preferably, as shown in fig. 3, the included angle of the scrapers in two adjacent rows in the cross-sectional direction of the rotating shaft is 0-60 degrees.
In the present invention, preferably, the rotating shaft extends to the bottom of the tank body along the axial direction of the tank body inside the tank body; preferably, the rotating speed of the rotating shaft is 9-25 rpm.
The utility model discloses in, the scraper blade is in the angle that sets up on the rotation axis outer wall is in order to realize that the scraper blade holds the material as the purpose, according to this implementation with neotype a preferred embodiment, the "slice" plane of scraper blade is parallel with the horizontal plane and with the rotation axis is perpendicular.
In the present invention, as a preferred embodiment of the present invention, the surface of the scraper is provided with a plurality of liquid guiding grooves 24 along the extension direction of the scraper, the depth of the liquid guiding grooves can be smaller than any depth of the thickness of the scraper, and the plurality of liquid guiding grooves are preferably linear and arranged in parallel with each other (as shown in fig. 4).
In the present invention, the thickness of the scraper is preferably 0.10-0.80mm, and more preferably 0.40-0.60mm, and as a preferred embodiment of the present invention, the thickness of the scraper is 0.50 mm.
According to the present invention, the distance between adjacent scrapers along the axial direction of the rotating shaft is preferably 0.10-0.20mm, and more preferably 0.12-0.16mm, and as a preferred embodiment of the present invention, the distance between adjacent scrapers along the axial direction of the rotating shaft is 0.15 mm.
According to the present invention, the distance between the scraper and the inner wall of the tank body in the horizontal direction (the direction perpendicular to the rotating shaft) is preferably 1.0-8.0mm, and more preferably 4.0-6.0mm, and as a preferred embodiment of the present invention, the distance between the scraper and the inner wall of the tank body in the horizontal direction is 5.0 mm.
The utility model discloses in, film evaporator is still including setting up the distributing device 11 at jar internal portion, distributing device 11 passes the rotation axis sets up the top at all scraper blades 13, distributing device 11 follows the rotation of rotation axis 12 is rotatory, makes the liquid material that gets into from feed inlet 14 can distribute evenly in all directions.
The utility model discloses in, jar external portion still is provided with the heating jacket, be provided with heating steam entry and condensate outlet on the heating jacket. Heating steam can enter the heating jacket through the heating steam inlet to heat the tank body, so that light components in the tank body material can be fully evaporated, the light components are fully separated, and preferably, the heating jacket heats the tank body to enable the temperature in the tank body to be 180-210 ℃.
In the utility model, the device also comprises a desublimation device 2 and a vacuum device 3, wherein the top end of the desublimation device 2 is provided with a steam inlet 21 and a vacuum gas outlet 23, and the bottom end is provided with a condensate outlet 22; and a steam inlet 21 of the desublimation device 2 is connected with a steam outlet 15 of the thin film evaporator 1, and light components in the tank material are evaporated, come out from the steam outlet 15, enter the desublimation device from the steam inlet 21 of the desublimation device 2, are collected and are discharged from a condensate outlet 22. The vacuum air outlet 23 of the desublimation device 2 is connected with the vacuum device 3, the vacuum device is used for adjusting the air pressure in the devolatilization device, preferably, the vacuum device adjusts the air pressure in the devolatilization device and enables the pressure in the thin film evaporator tank to be 2-5 KPa.
The utility model discloses take off and wave device's work flow as follows:
polylactic acid materials generated after lactide polymerization enter the tank body 4 from the feed inlet 14 of the film evaporator 1, are uniformly distributed on the distributor 11 and flow onto the scrapers 13, each scraper 13 is driven by the motor 17 to rotate, heavy components in the materials flow downwards onto the next layer of scraper at the moment, and are thrown onto the inner wall of the tank body under the action of high-speed high-shear force to form a material film; with the continuous downward flow of the materials on the scraper 13 and the continuous rotation of the scraper, the materials on the scraper are continuously thrown onto the inner wall of the tank body, so that a material film formed on the inner wall of the tank body is continuously scraped and continuously updated, the film-formed materials continuously flow downward on the inner wall of the tank body and finally flow out of the discharge port 16, and light components in the materials are evaporated to form steam to ascend and flow out of the steam outlet 15 to reach the desublimation device 2.
Therefore, the utility model discloses a scraper blade is in rotatory epaxial mode that sets up can further improve the renewal speed of material film on the internal wall of jar, guarantees that the light component in the material fully evaporates under the condition of heating.
The utility model discloses in, preferably, for preventing lactide from causing the corruption to film evaporator, film evaporator adopts titanium metal material preparation to form.
The technical effects of the devolatilization apparatus of the present invention will be described below with reference to the embodiments.
In the following examples:
in the film evaporator shown in FIG. 1, the included angle between adjacent rows of the scrapers is 30 degrees, the thickness of the scrapers is 0.50mm, the linear distance of the adjacent scrapers along the axial direction of the rotating shaft is 0.15mm, and the distance between the scrapers and the inner wall of the tank body is 5.0 mm.
Example 1
A polylactic acid/lactide mass with a 95% conversion of lactide obtained by melt polymerization was passed through a devolatilization apparatus comprising as shown in fig. 1 at a flow rate of 5kg/h for residual monomer removal.
Wherein the rotating speed of the rotating shaft is 9 r/min, the temperature in the tank body is 190 ℃, the pressure is 2KPa, and the content of the monomer in the polylactic acid slice at the discharge port of the film evaporator is measured to be 0.26 wt%.
Example 2
A polylactic acid/lactide material having a conversion of 96% obtained by a melt polymerization method of lactide was passed through a devolatilization apparatus as shown in FIG. 1 at a flow rate of 4kg/h to remove residual monomers.
Wherein the rotating speed of the rotating shaft is 17 r/min, the temperature in the tank body is 200 ℃, the pressure is 3KPa, and the content of the monomer in the polylactic acid slice at the discharge port of the film evaporator is measured to be 0.18 wt%.
Example 3
A polylactic acid/lactide material having a conversion of 93.5% obtained by a melt polymerization process of lactide was passed through a devolatilization apparatus as shown in FIG. 1 at a flow rate of 3kg/h to remove residual monomers.
Wherein the rotating speed of the rotating shaft is 25 r/min, the temperature in the tank body is 210 ℃, the pressure is 5KPa, and the content of the monomer in the polylactic acid slice at the discharge port of the film evaporator is measured to be 0.13 wt%.
Comparative example 1
The polylactic acid/lactide material with a conversion of 93.5% obtained by melt polymerization of lactide was passed at a flow rate of 3kg/h through a devolatilization apparatus comprising a thin film evaporator (rotating shaft and scraper) as shown in fig. 5a and 5b for residual monomer removal.
Wherein the rotating speed of the rotating shaft is 25 r/min, the temperature in the tank body is 210 ℃, the pressure is 5KPa, and the content of the monomer in the polylactic acid slice at the discharge port of the film evaporator is measured to be 0.39 wt%.
As can be seen from the comparison between examples 1-3 and comparative example 1, the use of the devolatilization apparatus of the present invention to devolatilize polylactic acid/lactide can reduce the monomer content in the polylactic acid to less than 0.3%.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. In the technical idea scope of the present invention, it can be right to the technical solution of the present invention perform multiple simple modifications, including each technical feature combined in any other suitable manner, these simple modifications and combinations should be regarded as the disclosed content of the present invention, and all belong to the protection scope of the present invention.
Claims (16)
1. A polylactic acid devolatilization device is characterized by comprising a film evaporator, wherein the film evaporator comprises a tank body, a motor arranged at the top end outside the tank body, a rotating shaft arranged inside the tank body, a steam outlet and a feed inlet which are arranged at the upper part of the outer wall of the tank body, and a discharge outlet arranged at the bottom end of the tank body, wherein the rotating shaft extends along the axial direction of the tank body and is connected with the motor; the motor drives the rotating shaft to rotate in the tank body, a plurality of rows of scraping plates are axially arranged on the outer wall of the rotating shaft, and two adjacent rows of scraping plates are arranged in a staggered mode.
2. The device of claim 1, wherein the included angle between two adjacent rows of squeegees is greater than 0 degrees and equal to or less than 60 degrees in a row unit.
3. The device according to claim 1 or 2, characterized in that the scraper is arranged perpendicular to the rotation axis and that the scraper surface is provided with a number of liquid channels in the direction of extension of the scraper.
4. The device according to claim 1 or 2, wherein the thickness of the scraper is 0.10-0.80 mm.
5. The apparatus of claim 4, wherein the thickness of the blade is 0.40-0.60 mm.
6. The apparatus of claim 3, wherein the blade has a thickness of 0.10-0.80 mm.
7. The apparatus of claim 6, wherein the thickness of the blade is 0.40-0.60 mm.
8. The apparatus according to any one of claims 1, 2, 5-7, wherein the distance between adjacent scrapers in the axial direction of the rotating shaft is 0.12-0.20 mm; the distance between the scraper and the inner wall of the tank body in the horizontal direction is 1.0-8.0 mm.
9. The apparatus of claim 8, wherein the distance between adjacent squeegees in the axial direction of the rotary shaft is 0.14-0.16 mm; the distance between the scraper and the inner wall of the tank body in the horizontal direction is 4.0-6.0 mm.
10. The apparatus of claim 3, wherein the distance between adjacent squeegees in the axial direction of the rotary shaft is 0.12-0.20 mm; the distance between the scraper and the inner wall of the tank body in the horizontal direction is 1.0-8.0 mm.
11. The apparatus of claim 10, wherein the distance between adjacent squeegees in the axial direction of the rotary shaft is 0.14-0.16 mm; the distance between the scraper and the inner wall of the tank body in the horizontal direction is 4.0-6.0 mm.
12. The apparatus of claim 4, wherein the distance between adjacent squeegees in the axial direction of the rotary shaft is 0.12-0.20 mm; the distance between the scraper and the inner wall of the tank body in the horizontal direction is 1.0-8.0 mm.
13. The apparatus of claim 12, wherein the distance between adjacent squeegees in the axial direction of the rotary shaft is 0.14-0.16 mm; the distance between the scraper and the inner wall of the tank body in the horizontal direction is 4.0-6.0 mm.
14. The apparatus of claim 1, wherein the thin film evaporator further comprises a distributor disposed inside the tank body, the distributor being disposed above the scraper groups through the rotating shaft.
15. The apparatus of claim 1, wherein the thin film evaporator further comprises a heating jacket disposed outside the tank body, the heating jacket having a heating vapor inlet and a condensate outlet disposed thereon.
16. The apparatus according to claim 1, further comprising a desublimation device and a vacuum device, the desublimation device being connected to the steam outlet and the vacuum device, respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201920228439.8U CN209957681U (en) | 2019-02-20 | 2019-02-20 | Polylactic acid devolatilization device |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201920228439.8U CN209957681U (en) | 2019-02-20 | 2019-02-20 | Polylactic acid devolatilization device |
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| CN209957681U true CN209957681U (en) | 2020-01-17 |
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| CN201920228439.8U Active CN209957681U (en) | 2019-02-20 | 2019-02-20 | Polylactic acid devolatilization device |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111346394A (en) * | 2020-04-29 | 2020-06-30 | 吉林中粮生化有限公司 | Polylactic acid devolatilization evaporator |
| US11118006B1 (en) | 2020-06-28 | 2021-09-14 | Nutrition & Health Research Institute, COFCO Corporation | Method for producing polylactic acid |
| CN113896867A (en) * | 2021-11-16 | 2022-01-07 | 东华大学 | Method for synthesizing polylactic acid from lactic acid in one step and polylactic acid synthesized by method |
-
2019
- 2019-02-20 CN CN201920228439.8U patent/CN209957681U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111346394A (en) * | 2020-04-29 | 2020-06-30 | 吉林中粮生化有限公司 | Polylactic acid devolatilization evaporator |
| US11097248B1 (en) | 2020-04-29 | 2021-08-24 | Cofco (Jilin) Bio-Chemical Technology Co., Ltd | Polylactic acid devolatilization evaporator |
| US11118006B1 (en) | 2020-06-28 | 2021-09-14 | Nutrition & Health Research Institute, COFCO Corporation | Method for producing polylactic acid |
| CN113896867A (en) * | 2021-11-16 | 2022-01-07 | 东华大学 | Method for synthesizing polylactic acid from lactic acid in one step and polylactic acid synthesized by method |
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