CN111793055A - Method for preparing high-gloss pure lactide by suspension crystallization method - Google Patents
Method for preparing high-gloss pure lactide by suspension crystallization method Download PDFInfo
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- CN111793055A CN111793055A CN202010814524.XA CN202010814524A CN111793055A CN 111793055 A CN111793055 A CN 111793055A CN 202010814524 A CN202010814524 A CN 202010814524A CN 111793055 A CN111793055 A CN 111793055A
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- lactide
- cooling
- suspension
- mother liquor
- molten
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- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 title claims abstract description 74
- 239000000725 suspension Substances 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000002425 crystallisation Methods 0.000 title claims abstract description 31
- 238000001816 cooling Methods 0.000 claims abstract description 58
- 239000013078 crystal Substances 0.000 claims abstract description 39
- 239000012452 mother liquor Substances 0.000 claims abstract description 31
- 238000005406 washing Methods 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims abstract description 15
- 239000012535 impurity Substances 0.000 claims abstract description 14
- 238000003756 stirring Methods 0.000 claims abstract description 11
- 238000004140 cleaning Methods 0.000 claims description 20
- 239000007788 liquid Substances 0.000 claims description 15
- 230000008025 crystallization Effects 0.000 claims description 13
- 238000002156 mixing Methods 0.000 claims description 10
- 238000007599 discharging Methods 0.000 claims description 5
- 238000005469 granulation Methods 0.000 claims description 5
- 230000003179 granulation Effects 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 230000003287 optical effect Effects 0.000 claims description 5
- 238000004806 packaging method and process Methods 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 5
- 238000000746 purification Methods 0.000 abstract description 7
- 230000006340 racemization Effects 0.000 abstract description 5
- 238000005265 energy consumption Methods 0.000 abstract description 4
- 238000002360 preparation method Methods 0.000 abstract description 3
- 230000008569 process Effects 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 229920000747 poly(lactic acid) Polymers 0.000 description 6
- 239000004626 polylactic acid Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000005292 vacuum distillation Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- JJTUDXZGHPGLLC-IMJSIDKUSA-N 4511-42-6 Chemical compound C[C@@H]1OC(=O)[C@H](C)OC1=O JJTUDXZGHPGLLC-IMJSIDKUSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000011846 petroleum-based material Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 238000007151 ring opening polymerisation reaction Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D319/00—Heterocyclic compounds containing six-membered rings having two oxygen atoms as the only ring hetero atoms
- C07D319/10—1,4-Dioxanes; Hydrogenated 1,4-dioxanes
- C07D319/12—1,4-Dioxanes; Hydrogenated 1,4-dioxanes not condensed with other rings
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
- C07B2200/00—Indexing scheme relating to specific properties of organic compounds
- C07B2200/07—Optical isomers
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a method for preparing high-gloss pure lactide by a suspension crystallization method, and relates to the technical field of lactide preparation. The process for preparing the high-gloss pure lactide by the suspension crystallization method comprises the following steps: s1, cooling the crude lactide in the molten state to 85-95 ℃, then cooling at a uniform speed under the stirring condition of 50-1000r/min, and stopping cooling when the temperature is reduced to 80-84 ℃ to obtain a suspension; s2, pre-separating the suspension obtained in the step 1, and removing most of mother liquor in the suspension. According to the invention, the purity of crystal grains in the system is ensured by adopting a temperature control method, impurities adhered to the surfaces of the crystal grains are removed by a crystal grain washing method, the temperature in the whole operation process is lower than 100 ℃, the energy consumption is low, and the problem of easy racemization of materials is well solved; meanwhile, continuous operation can be carried out, and the purification efficiency is effectively improved; in addition, the operation is normal pressure operation, the equipment requirement is low, and the equipment investment cost is low.
Description
Technical Field
The invention relates to the technical field of lactide preparation, in particular to a method for preparing high-gloss pure lactide by a suspension crystallization method.
Background
With the enhancement of environmental awareness of people, the green degradable material is paid attention to by people, the performance of polylactic acid is similar to that of the existing plastic polyethylene, polypropylene, polystyrene and other petroleum-based materials, and the polylactic acid can be completely degraded into carbon dioxide and water after being used without environmental pollution, so that the polylactic acid becomes one of the most studied green degradable materials at present. Lactide is an important intermediate for preparing polylactic acid by a two-step method, and the preparation cost, purity and the like of the lactide seriously influence the cost and quality of the polylactic acid. Crude lactide contains impurities such as water, free acid, and M-lactide, and needs to be purified before ring-opening polymerization to produce polylactic acid.
At present, the lactide purification commonly used methods are four methods, namely a vacuum rectification method, a solvent purification method, a layer type melt crystallization method, and a vacuum rectification and layer type melt crystallization coupling purification method. The vacuum distillation method has the problems of high energy consumption, high equipment investment and the like, and meanwhile, the difference between the normal pressure boiling point of the M-lactide and the target lactide (D-lactide or L-lactide) is about 10 ℃, the difference under the vacuum condition is smaller, the separation difficulty is large, the height of a tower is high, the temperature of a tower kettle is high, side reactions such as polymerization, racemization and the like are serious, the separation is not thorough, and finally, the extraction yield of the lactide is low and the cost is high; the solvent method has the problems of solvent residue, environmental pollution, low yield and the like; the layered melt crystallization method has the problems of intermittent operation, long time consumption, low treatment efficiency, low product yield with low treatment purity and the like; the coupling method of vacuum distillation and melt crystallization integrates the advantages of the distillation method and the layered melt crystallization method, properly reduces the height of the distillation tower, but has the defects of high tower kettle temperature, easy racemization and layered crystallization intermittent operation, and still has unsatisfactory overall purification effect.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a method for preparing high-gloss pure lactide by a suspension crystallization method, which solves the defects and shortcomings in the prior art.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme: a method for preparing high-gloss pure lactide by a suspension crystallization method comprises the following steps:
s1, cooling the crude lactide in the molten state to 85-95 ℃, then cooling at a uniform speed under the stirring condition of 50-1000r/min, and stopping cooling when the temperature is reduced to 80-84 ℃ to obtain a suspension;
s2, pre-separating the suspension obtained in the step 1, removing most of mother liquor in the suspension, and controlling the amount of the residual mother liquor to be below 10%;
s3, transferring the crystals containing a small amount of mother liquor obtained in the step 2 into a cleaning tower filled with molten pure lactide, feeding materials into the cleaning tower from the top end of the tower, heating and cooling the cleaning tower, continuously cleaning and removing surface impurities along with falling of the crystals, feeding the surface impurities into molten lactide washing liquid, purifying the crystals, discharging redundant polluted molten lactide washing liquid along with falling of the crystals, and mixing the redundant polluted molten lactide washing liquid with crude lactide;
s4, granulating, cooling and packaging the lactide purified in the step 3 to obtain a lactide product;
s5, continuously cooling the mother liquor obtained in the step 2 under the stirring condition of 50-1000r/min for suspension crystallization, uniformly cooling to 70-78 ℃, and stopping cooling;
and S6, completely separating the crystal and the mother liquor of the suspension obtained in the step 5, mixing the crystal and the crude lactide, continuing to perform melt crystallization, and treating or discarding the mother liquor.
Preferably, the uniform cooling speed in the step 1 is 0.1-0.5 ℃/10 min.
Preferably, the material obtained by lactide granulation in the step 4 is a flaky solid, the cooling temperature is 10-20 ℃, and the optical purity is more than 99.5%.
Preferably, the uniform cooling speed in the step 5 is 0.5-1.5 ℃/10 min.
(III) advantageous effects
The invention provides a method for preparing high-gloss pure lactide by a suspension crystallization method. The method has the following beneficial effects:
according to the invention, the purity of crystal grains in the system is ensured by adopting a temperature control method, impurities adhered to the surfaces of the crystal grains are removed by a crystal grain washing method, the temperature in the whole operation process is lower than 100 ℃, the energy consumption is low, and the problem of easy racemization of materials is well solved; meanwhile, continuous operation can be carried out, and the purification efficiency is effectively improved; in addition, the operation is normal pressure operation, the equipment requirement is low, and the equipment investment cost is low.
Detailed Description
The following will clearly and completely describe the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
the embodiment of the invention provides a method for preparing high-gloss pure lactide by a suspension crystallization method, which comprises the following steps:
s1, cooling the crude lactide in the molten state to 85 ℃, then cooling at a uniform speed under the stirring condition of 100r/min, wherein the uniform cooling speed is 0.1 ℃/10min, and stopping cooling when the temperature is reduced to 80 ℃ to obtain a suspension;
s2, pre-separating the suspension obtained in the step 1, removing most of mother liquor in the suspension, and controlling the amount of the residual mother liquor to be below 10%;
s3, transferring the crystals containing a small amount of mother liquor obtained in the step 2 into a cleaning tower filled with molten pure lactide, feeding materials into the cleaning tower from the top end of the tower, heating and cooling the cleaning tower, continuously cleaning and removing surface impurities along with falling of the crystals, feeding the surface impurities into molten lactide washing liquid, purifying the crystals, discharging redundant polluted molten lactide washing liquid along with falling of the crystals, and mixing the redundant polluted molten lactide washing liquid with crude lactide;
s4, granulating, cooling and packaging the lactide purified in the step 3 to obtain a lactide product, wherein the material obtained by lactide granulation is a flaky solid, the cooling temperature is 10 ℃, and the optical purity is more than 99.5%;
s5, continuously cooling the mother liquor obtained in the step 2 under the stirring condition of 100r/min for suspension crystallization, uniformly cooling to 70 ℃, and stopping cooling, wherein the uniform cooling speed is 0.5 ℃/10 min;
and S6, completely separating the crystal and the mother liquor of the suspension obtained in the step 5, mixing the crystal and the crude lactide, continuing to perform melt crystallization, and treating or discarding the mother liquor.
According to the invention, the purity of crystal grains in the system is ensured by adopting a temperature control method, impurities adhered to the surfaces of the crystal grains are removed by a crystal grain washing method, the temperature in the whole operation process is lower than 100 ℃, the energy consumption is low, and the problem of easy racemization of materials is well solved; meanwhile, continuous operation can be carried out, and the purification efficiency is effectively improved; in addition, the operation is normal pressure operation, the equipment requirement is low, and the equipment investment cost is low.
Example two:
the embodiment of the invention provides a method for preparing high-gloss pure lactide by a suspension crystallization method, which comprises the following steps:
s1, cooling the crude lactide in the molten state to 90 ℃, then cooling at an even speed under the stirring condition of 300r/min, wherein the even cooling speed is 0.3 ℃/10min, and stopping cooling when the temperature is reduced to 82 ℃ to obtain a suspension;
s2, pre-separating the suspension obtained in the step 1, removing most of mother liquor in the suspension, and controlling the amount of the residual mother liquor to be below 10%;
s3, transferring the crystals containing a small amount of mother liquor obtained in the step 2 into a cleaning tower filled with molten pure lactide, feeding materials into the cleaning tower from the top end of the tower, heating and cooling the cleaning tower, continuously cleaning and removing surface impurities along with falling of the crystals, feeding the surface impurities into molten lactide washing liquid, purifying the crystals, discharging redundant polluted molten lactide washing liquid along with falling of the crystals, and mixing the redundant polluted molten lactide washing liquid with crude lactide;
s4, granulating, cooling and packaging the lactide purified in the step 3 to obtain a lactide product, wherein the material obtained by lactide granulation is a flaky solid, the cooling temperature is 15 ℃, and the optical purity is more than 99.5%;
s5, continuously cooling the mother liquor obtained in the step 2 under the stirring condition of 300r/min for suspension crystallization, uniformly cooling to 74 ℃, and stopping cooling, wherein the uniform cooling speed is 1 ℃/10 min;
and S6, completely separating the crystal and the mother liquor of the suspension obtained in the step 5, mixing the crystal and the crude lactide, continuing to perform melt crystallization, and treating or discarding the mother liquor.
Example three:
the embodiment of the invention provides a method for preparing high-gloss pure lactide by a suspension crystallization method, which comprises the following steps:
s1, cooling the crude lactide in the molten state to 95 ℃, then cooling at an even speed under the stirring condition of 800r/min, wherein the even cooling speed is 0.5 ℃/10min, and stopping cooling when the temperature is reduced to 84 ℃ to obtain a suspension;
s2, pre-separating the suspension obtained in the step 1, removing most of mother liquor in the suspension, and controlling the amount of the residual mother liquor to be below 10%;
s3, transferring the crystals containing a small amount of mother liquor obtained in the step 2 into a cleaning tower filled with molten pure lactide, feeding materials into the cleaning tower from the top end of the tower, heating and cooling the cleaning tower, continuously cleaning and removing surface impurities along with falling of the crystals, feeding the surface impurities into molten lactide washing liquid, purifying the crystals, discharging redundant polluted molten lactide washing liquid along with falling of the crystals, and mixing the redundant polluted molten lactide washing liquid with crude lactide;
s4, granulating, cooling and packaging the lactide purified in the step 3 to obtain a lactide product, wherein the material obtained by lactide granulation is a flaky solid, the cooling temperature is 20 ℃, and the optical purity is more than 99.5%;
s5, continuously cooling the mother liquor obtained in the step 2 under the stirring condition of 800r/min for suspension crystallization, uniformly cooling to 78 ℃, and stopping cooling, wherein the uniform cooling speed is 1.5 ℃/10 min;
and S6, completely separating the crystal and the mother liquor of the suspension obtained in the step 5, mixing the crystal and the crude lactide, continuing to perform melt crystallization, and treating or discarding the mother liquor.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (4)
1. A method for preparing high-gloss pure lactide by a suspension crystallization method is characterized by comprising the following steps: the method comprises the following steps:
s1, cooling the crude lactide in the molten state to 85-95 ℃, then cooling at a uniform speed under the stirring condition of 50-1000r/min, and stopping cooling when the temperature is reduced to 80-84 ℃ to obtain a suspension;
s2, pre-separating the suspension obtained in the step 1, removing most of mother liquor in the suspension, and controlling the amount of the residual mother liquor to be below 10%;
s3, transferring the crystals containing a small amount of mother liquor obtained in the step 2 into a cleaning tower filled with molten pure lactide, feeding materials into the cleaning tower from the top end of the tower, heating and cooling the cleaning tower, continuously cleaning and removing surface impurities along with falling of the crystals, feeding the surface impurities into molten lactide washing liquid, purifying the crystals, discharging redundant polluted molten lactide washing liquid along with falling of the crystals, and mixing the redundant polluted molten lactide washing liquid with crude lactide;
s4, granulating, cooling and packaging the lactide purified in the step 3 to obtain a lactide product;
s5, continuously cooling the mother liquor obtained in the step 2 under the stirring condition of 50-1000r/min for suspension crystallization, uniformly cooling to 70-78 ℃, and stopping cooling;
and S6, completely separating the crystal and the mother liquor of the suspension obtained in the step 5, mixing the crystal and the crude lactide, continuing to perform melt crystallization, and treating or discarding the mother liquor.
2. The method for preparing high-gloss pure lactide by using the suspension crystallization method according to claim 1, wherein the method comprises the following steps: the uniform cooling speed in the step 1 is 0.1-0.5 ℃/10 min.
3. The method for preparing high-gloss pure lactide by using the suspension crystallization method according to claim 1, wherein the method comprises the following steps: and 4, the material obtained by lactide granulation in the step 4 is a flaky solid, the cooling temperature is 10-20 ℃, and the optical purity is more than 99.5%.
4. The method for preparing high-gloss pure lactide by using the suspension crystallization method according to claim 1, wherein the method comprises the following steps: the uniform cooling speed in the step 5 is 0.5-1.5 ℃/10 min.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010814524.XA CN111793055A (en) | 2020-08-13 | 2020-08-13 | Method for preparing high-gloss pure lactide by suspension crystallization method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010814524.XA CN111793055A (en) | 2020-08-13 | 2020-08-13 | Method for preparing high-gloss pure lactide by suspension crystallization method |
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| CN111793055A true CN111793055A (en) | 2020-10-20 |
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| CN202010814524.XA Pending CN111793055A (en) | 2020-08-13 | 2020-08-13 | Method for preparing high-gloss pure lactide by suspension crystallization method |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114133374A (en) * | 2021-12-15 | 2022-03-04 | 浙江海正生物材料股份有限公司 | Method for purifying lactide |
| CN115536629A (en) * | 2022-10-18 | 2022-12-30 | 山东寿光巨能金玉米开发有限公司 | Preparation method of high-purity glycolide |
| CN115677649A (en) * | 2022-11-16 | 2023-02-03 | 寿光金远东变性淀粉有限公司 | Method for efficiently preparing and purifying lactide |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007148975A2 (en) * | 2007-03-14 | 2007-12-27 | Niro Process Technology B.V. | Purification of lactide rich streams |
| EP2080545A1 (en) * | 2008-01-18 | 2009-07-22 | NIRO Process Technology B.V. | Method for solid liquid separation |
| CN109776482A (en) * | 2019-03-19 | 2019-05-21 | 上海新宁生物材料有限公司 | The method of the continuous preparation high-purity lactide of industrialization |
-
2020
- 2020-08-13 CN CN202010814524.XA patent/CN111793055A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007148975A2 (en) * | 2007-03-14 | 2007-12-27 | Niro Process Technology B.V. | Purification of lactide rich streams |
| EP2080545A1 (en) * | 2008-01-18 | 2009-07-22 | NIRO Process Technology B.V. | Method for solid liquid separation |
| CN109776482A (en) * | 2019-03-19 | 2019-05-21 | 上海新宁生物材料有限公司 | The method of the continuous preparation high-purity lactide of industrialization |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114133374A (en) * | 2021-12-15 | 2022-03-04 | 浙江海正生物材料股份有限公司 | Method for purifying lactide |
| CN115536629A (en) * | 2022-10-18 | 2022-12-30 | 山东寿光巨能金玉米开发有限公司 | Preparation method of high-purity glycolide |
| CN115536629B (en) * | 2022-10-18 | 2024-03-22 | 山东寿光巨能金玉米开发有限公司 | Preparation method of glycolide |
| CN115677649A (en) * | 2022-11-16 | 2023-02-03 | 寿光金远东变性淀粉有限公司 | Method for efficiently preparing and purifying lactide |
| CN115677649B (en) * | 2022-11-16 | 2024-02-13 | 寿光金远东变性淀粉有限公司 | Method for efficiently preparing and purifying lactide |
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