CN1326997A - Method for preparing high molecular weight poly lactic acid by direct polycondensation - Google Patents
Method for preparing high molecular weight poly lactic acid by direct polycondensation Download PDFInfo
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- CN1326997A CN1326997A CN 01113146 CN01113146A CN1326997A CN 1326997 A CN1326997 A CN 1326997A CN 01113146 CN01113146 CN 01113146 CN 01113146 A CN01113146 A CN 01113146A CN 1326997 A CN1326997 A CN 1326997A
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- lactic acid
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- dewatering agent
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Abstract
One polycondensation process of preparing high molecular weight polylactic acid is disclosed. During the process, one kine of dewatering agent is used to dewater selectively in a closed environment. Owing to the continuous dewatering and no loss of lactide, polylactic acid with very high molecular weight may be prepared. Without organic solvent used, the process can obtain very clean polylactic acid at lower operation cost.
Description
The present invention relates to the manufacture method of poly(lactic acid), relate to the method that a kind of direct method prepares poly-lactic acid in high molecular weight specifically.
Poly(lactic acid) is a kind of synthetic macromolecular compound with good physiologically acceptable performance, energy complete biodegradable.Because material acid can utilize the agricultural-food fermentation to produce, thereby is considered to Sustainable development, eco-friendly product.Its synthetic method can be divided into two big classes: (1) direct method: directly prepared by condensation by lactic acid: (2) indirect method: prepare rac-Lactide by lactic acid through cyclisation, become poly(lactic acid) by the rac-Lactide ring-opening polymerization again.Directly condensation generally can only make the low molecular weight that molecular weight is little, use value is limited because polycondensation and depolymerization reaction can not independently be controlled.Indirect method can prepare the very big poly-lactic acid in high molecular weight of molecular weight, but in the process of preparation intermediate product rac-Lactide, because the side reactions such as polycondensation that are difficult to avoid, a large amount of lactic acid oligomers and other rings except that rac-Lactide have been generated, these by products not only make the separation of rac-Lactide and purification become very difficult, and the recycling of by product also makes technical process become very complicated.The preparation of rac-Lactide is not only consumed energy, and facility investment is big---and this is a poly(lactic acid) production cost major reason for higher.
The lactic acid condensation reaction is:
Depolymerization reaction is:
Above-mentioned reaction all is a reversible.For improving the polylactic acid molecule amount, need when promoting condensation reaction, suppress depolymerization reaction.But though small molecules commonly used remove measure as vacuumize, effective elimination water molecules such as intensification and inert gas purge and promote condensation reaction, accelerated depolymerization reaction because of having removed rac-Lactide simultaneously inevitably.This is that the direct condensation yield is low and be difficult to obtain the basic reason of poly-lactic acid in high molecular weight.Experiment showed, that different catalyzer can influence the relative rate of condensation and depolymerization reaction, and change of molecular weight in the decision polymerization process.But on the principle, if do not consider other side reactions, the final molecular weight of poly(lactic acid) is not decided by catalyzer when reaction system reaches balance, and is decided by the concentration of micromolecular water and rac-Lactide in the system.
In order to obtain poly-lactic acid in high molecular weight, the concentration of water molecules must be enough low in the reaction system, and the concentration of rac-Lactide must be enough high.Document (Masanobu Ajioka, Katashi Enomoto, Kazuhiko Suzuki, andAkihiro Yamaguchi, Bull.Chem.Soc, Jpn., 68,2125-2131 (1995)) has been described a kind of method of direct condensation synthetic macromolecule amount poly(lactic acid).This method is to utilize high boiling organic solvent such as phenyl ether optionally to remove water by azeotropic distillation under high vacuum condition.But,, increased the complicacy and the running cost of operation owing to used organic solvent and high vacuum rectification.And owing to the solvent in the finished product poly(lactic acid) also is difficult to remove fully, thereby the performance of product also is affected.
The objective of the invention is to disclose the method that a kind of direct condensation that adopts dewatering agent optionally to remove water prepares poly-lactic acid in high molecular weight, be difficult to remove fully to overcome solvent in complicated operation that prior art exists, running cost height, the finished product poly(lactic acid), the not good defective of performance of product.
Technical conceive of the present invention is such:
Do not lose rac-Lactide in order to remove the water in the reaction system, can use a kind of dewatering agent in airtight environment, optionally to remove water.Water is constantly removed in the condensation course, but therefore rac-Lactide can make the very high poly(lactic acid) of molecular weight without any loss.Adsorption dewatering can carry out under negative pressure, but does not require high vacuum.This is that the direct condensation legal system poly(lactic acid) of characteristics is exactly a core of the present invention optionally to dewater by dewatering agent in airtight environment.Owing to not with an organic solvent, thereby can obtain very clean poly(lactic acid) with lower running cost.
Technical scheme of the present invention:
Method of the present invention comprises the steps:
With lactic acid or low molecular weight and dewatering agent place together can be airtight polymeric kettle, with vacuumizing or the mode of inert gas purge is got rid of oxygen in the polymeric kettle, closed reactor carries out polyreaction then at a certain temperature afterwards.
Vacuum state can be in the reactor, also a certain amount of rare gas element can be contained.Reacted under 60～300 ℃ temperature 0.1～100 hour, cooling can obtain molecular-weight average and be 10,000～500,000 poly(lactic acid).
Said dewatering agent is dewatering agent or the physical adsorption dewatering agent that utilizes chemical reaction.
Utilize the dewatering agent of chemical reaction dehydration owing to do not adsorb rac-Lactide thereby better effects if.This class dewatering agent comprises Na, K, metal oxide, nonmetal oxide, acid, alkali, can form a kind of and composition thereof in the inorganic salt of crystalline hydrate with water;
Preferred metal oxide is CaO, BaO, MgO, Al
2O
3, Na
2O or K
2O;
Preferred nonmetal oxide is P
2O
5
Preferred acid is phosphoric acid, tetra-sodium or polyphosphoric acid;
Preferred alkali is NaOH or KOH;
Preferred inorganic salt are CaCl
2, K
2CO
3, CaSO
4, MgCl
2, MgSO
4, MnSO
4, MnCl
2, CuSO
4, NiSO
4Or ZnSO
4
Utilize the dewatering agent of physisorption, comprise silica gel and various dehydration property resin, as acrylic resin.In principle, under the temperature of polyreaction, can reduce the equilibrium partial pressure of water, again can not (or few) absorption rac-Lactide or make rac-Lactide and the dewatering agent of poly(lactic acid) dehydration or oxidation all can use.Dewatering agent can disposablely use, and also can continue to use after regenerating.
The theoretical consumption of dewatering agent can calculate according to the kind and the required moisture that removes of lactic acid condensation reaction of dewatering agent, and in order to reach dehydrating effect preferably, actual amount can be 1.1～1.5 times of theoretical consumption.
In the preferred scheme of the present invention, for consumption and the regeneration cost that reduces dewatering agent, lactic acid can adopt conventional method to carry out precondensation to remove portion water.After arriving certain polymerization degree requirement, under airtight condition, carry out fusion or solid phase polycondensation again.
In order to improve the speed that removes of polymkeric substance internal water, can under higher temperature, react on the one hand, when solid phase polycondensation, adopt less granularity on the other hand, or when melt phase polycondensation, show renewal.Therefore, preferably performed polymer being crushed to mean particle size is 0.01mm～5mm, and then carries out polycondensation;
According to the present invention, when utilizing dewatering agent to carry out fusion or solid phase polycondensation, but reactor forvacuum, closed reactor afterwards, and carry out polymerization at a certain temperature.Different with polymerization time according to polymerization temperature, the pressure in the reactor may be negative pressure or malleation.Reactor also can be full of rare gas element, as N
2, He, CO
2, so that polycondensation is carried out under bigger pressure condition.
According to the present invention, the gas in the polymerization reactor can remain static, and water molecules diffuses to polymkeric substance and melts body or solid surface from polymkeric substance, diffuse to the dewatering agent surface again, catches for final dehydrated dose.
In order to improve the rate of diffusion of water molecules from polymer surfaces to the dewatering agent surface, but the gas in the pump circulation reactor.If carry out solid phase polycondensation and adopt pump circulation, can utilize gas-solid reaction equipment such as packed bed, moving-bed and fluidized-bed to carry out polyreaction.(existing in principle melt polymerization and solid state polymerization reactor all can be used).
By above-mentioned disclosed technical scheme as seen, the present invention is simple to operate, and water is constantly removed in the condensation course, but therefore rac-Lactide can make the very high poly(lactic acid) of molecular weight without any loss.Owing to not with an organic solvent, thereby can obtain very clean poly(lactic acid) with lower running cost.
Following example will have been done further description to the present invention, but purpose does not lie in the restriction scope of the invention.Raw material used in the example is purchased the company in PURAC for L-lactic acid, and wherein lactic acid content is 87.5～88.5%.The molecular weight of poly(lactic acid) determines that with sticking equal method solvent is a tetrahydrofuran (THF), and temperature is 37 ℃.Molecular weight calculates and adopts following formula:
[η]=1.07 * 10
-4M
η 0.75Wherein [η] is the feature viscosity number, M
ηBe viscosity-average molecular weight.
Embodiment 1
In the 500ml there-necked flask, add the L-lactic acid of 300g88%, and place 110 ℃ oil bath vacuum hydro-extraction 6 hours.The heavy 245g of dehydration back lactic acid.Press SnCl
22H
2O/ lactic acid=0.2% (w/w), TSA/SnCl
22H
2O=1: the proportioning of 1 (mol/mol) adds catalyst S nCl
2And TSA (p-methyl benzenesulfonic acid.Vacuum (＜reaction 5 hours 10mmHg) and under 130 ℃ of temperature in the cooling rapidly after 5 hours of reaction under 150 ℃ of temperature, is smashed performed polymer with domestic mixer again, the lactic acid performed polymer of molecular weight 1.2 ten thousand.
Get 50g lactic acid performed polymer and 20gCaO and be tiled in the culture dish, layering placement afterwards and diameter are in the stainless steel vessel of 15mm.With vacuumizing at least three times so repeatedly behind the high purity nitrogen displacement air wherein.After vacuumizing for the last time, close all container terminal valves, and transferred in 130 ℃ the thermostat container reaction 10 hours, molecular weight is 2.3 ten thousand poly(lactic acid).
Embodiment 2
Get in the example 1 the 25g lactic acid performed polymer and the 10gCaO that obtain, in the stainless steel vessel that layering is tiled in, replace air wherein with high purity nitrogen repeatedly and vacuumize.Last encloses container, and be transferred in 135 ℃ the thermostat container reaction 20 hours.Molecular weight is 7.8 ten thousand white poly(lactic acid).
Embodiment 3
Get in the example 2 the poly(lactic acid) 2g and the CaO5g that obtain, in the stainless steel vessel that layering is tiled in, repeatedly with high purity nitrogen displacement wherein air and vacuumize, last encloses container and being transferred in 170 ℃ the thermostat container reacted 20 hours.Get the poly(lactic acid) of molecular weight 14.6 ten thousand.
Embodiment 4～5
Get the poly(lactic acid) 2g and the 5gCaO layering that obtain in the example 2 and be tiled in the stainless steel vessel, repeatedly with the displacement of high purity nitrogen wherein air and vacuumize, last airtight and container is transferred in the thermostat container of 144 ℃ or 160 ℃ and reacted 20h.Obtain 12.4 ten thousand and 13.1 ten thousand poly(lactic acid) respectively.
Embodiment 6～9
Respectively get the different-grain diameter that 2g obtains by example 1 (be 20～40 orders, 40～60 orders, 60～80 orders, 80～100 orders) performed polymer, and be tiled in the stainless steel sealed vessel with the 20gCaO layering, repeatedly with high purity nitrogen displacement air wherein, vacuumize again, airtight at last.Container is transferred to constant temperature polymerization 9 hours in 130 ℃ thermostat container, afterwards 145 ℃ of following polymerizations 6 hours, again 166 ℃ of reactions 6 hours.Gained polylactic acid molecule amount size sees Table 1.
| Particle diameter | Molecular weight (* 10-4) | |
| Embodiment 6 | ?20-40 | ?17 |
| Embodiment 7 | ?40-60 | ?19.2 |
| Embodiment 8 | ?60-80 | ?16.7 |
| Embodiment 9 | ?80-100 | ?17 |
Table 1
Embodiment 10
Adopt the method identical with embodiment 3, dewatering agent is the 50g strong phosphoric acid, poly(lactic acid) that must molecular weight 8.9 ten thousand.
Embodiment 11
Adopt the method identical with embodiment 3, dewatering agent is 50gNaOH, poly(lactic acid) that must molecular weight 6.4 ten thousand.
Embodiment 12
Adopt the method identical with embodiment 3, dewatering agent is 50gK
2CO
3, the poly(lactic acid) of molecular weight 5.4 ten thousand.
Embodiment 13
Adopt the method identical with embodiment 3, dewatering agent is 80gMnSO
4, the poly(lactic acid) of molecular weight 5.7 ten thousand.
Embodiment 14
Adopt the method identical with embodiment 3, dewatering agent is a 60g silica gel, poly(lactic acid) that must molecular weight 6.8 ten thousand.
Embodiment 15
Extracting lactic acid 5g and 0.1gSnCl
2Mix, place culture dish, get CaO10g and be tiled in the culture dish.Two culture dish layerings are positioned in the stainless steel vessel, repeatedly with the displacement of high purity nitrogen wherein air and vacuumize.Last encloses container, and be transferred in 160 ℃ the thermostat container reaction 8 hours continues reaction 12 hours afterwards under 140 ℃ of temperature, molecular weight is 5.1 ten thousand poly(lactic acid).
Embodiment 16
Adopt the method identical with embodiment 3, polymerization reaction kettle outfit whipping appts, mixing speed is 1200rpm.The result gets 16.2 ten thousand poly(lactic acid).
Comparative Examples 1
Get in the example 2 in the stainless steel vessel that the poly(lactic acid) 2g that obtains is tiled in, repeatedly with high purity nitrogen displacement wherein air and vacuumize, last encloses container and being transferred in 170 ℃ the thermostat container reacted 20 hours.Get the poly(lactic acid) of molecular weight 3.9 ten thousand.
Claims (10)
1. direct condensation prepares the method for poly-lactic acid in high molecular weight, it is characterized in that, this method comprises the steps:
Lactic acid or low molecular weight and dewatering agent are placed airtight polymeric kettle together, get rid of the oxygen in the polymeric kettle, under 60～300 ℃ temperature, reacted 0.1～100 hour, can obtain molecular-weight average and be 10,000～500,000 poly(lactic acid).
2. the method for claim 1 is characterized in that, said dewatering agent is Na, K, metal oxide, nonmetal oxide, acid, alkali, can forms a kind of and composition thereof in the inorganic salt of crystalline hydrate with water, or is silica gel or dehydration property resin.
3. method as claimed in claim 2 is characterized in that, said dewatering agent is CaO, BaO, MgO, Al
2O
3, Na
2O, K
2O, P
2O
5, phosphoric acid, tetra-sodium, polyphosphoric acid, NaOH, KOH, CaCl
2, K
2CO
3, CaSO
4, MgCl
2, MgSO
4, MnSO
4, MnCl
2, CuSO
4, NiSO
4Or ZnSO
4In a kind of, or be acrylic resin.
4. as claim 1,2 or 3 described methods, it is characterized in that the actual amount of dewatering agent is 1.1～1.5 times of theoretical consumption.
5. as claim 1,2 or 3 described methods, it is characterized in that, in the reactor for vacuum state or contain rare gas element.
6. as claim 1,2 or 3 described methods, it is characterized in that the pressure in the reactor can be negative pressure or malleation.
7. as claim 1,2 or 3 described methods, it is characterized in that the gas in the reactor can remain static or the pump circulation state.
8. as claim 1,2 or 3 described methods, it is characterized in that it is 0.01mm～5mm that performed polymer is crushed to mean particle size, and then carries out polycondensation.
9. method as claimed in claim 6 is characterized in that, it is 0.01mm～5mm that performed polymer is crushed to mean particle size, and then carries out polycondensation.
10. method as claimed in claim 7 is characterized in that, it is 0.01mm～5mm that performed polymer is crushed to mean particle size, and then carries out polycondensation.
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| CN 01113146 CN1132868C (en) | 2001-06-28 | 2001-06-28 | Method for preparing high molecular weight poly lactic acid by direct polycondensation |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102040730B (en) * | 2009-10-13 | 2012-05-30 | 中国石油化工股份有限公司 | Melt/solid state polycondensation preparation method for polylactic acid |
| CN102757457A (en) * | 2012-07-30 | 2012-10-31 | 中国科学院长春应用化学研究所 | Schiff base aluminum compound and preparation method thereof, and preparation method of polylactic acid |
| CN103254409A (en) * | 2013-06-03 | 2013-08-21 | 北京理工大学 | Preparation method of high-molecular-weight polylactic acid based on metal alkoxide dehydrating agent |
| CN103254410A (en) * | 2013-06-03 | 2013-08-21 | 北京理工大学 | Preparation method of high-molecular-weight polylactic acid based on metal powder dehydrating agent |
| CN103300120A (en) * | 2013-06-25 | 2013-09-18 | 南京工业大学 | Green poultry and livestock depilating agent and preparation method thereof |
| CN104628563A (en) * | 2015-01-30 | 2015-05-20 | 湖北大学 | Synthetic process for preparing lactate from lactic acid |
| CN114213638A (en) * | 2021-11-16 | 2022-03-22 | 元嘉生物科技(浙江)有限公司 | Method for improving polylactic acid molecular weight based on in-situ drying dehydration |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115028615B (en) * | 2022-07-27 | 2024-01-09 | 万华化学(四川)有限公司 | L, L-lactide and preparation method and application thereof |
-
2001
- 2001-06-28 CN CN 01113146 patent/CN1132868C/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102040730B (en) * | 2009-10-13 | 2012-05-30 | 中国石油化工股份有限公司 | Melt/solid state polycondensation preparation method for polylactic acid |
| CN102757457A (en) * | 2012-07-30 | 2012-10-31 | 中国科学院长春应用化学研究所 | Schiff base aluminum compound and preparation method thereof, and preparation method of polylactic acid |
| CN102757457B (en) * | 2012-07-30 | 2015-05-20 | 中国科学院长春应用化学研究所 | Schiff base aluminum compound and preparation method thereof, and preparation method of polylactic acid |
| CN103254409A (en) * | 2013-06-03 | 2013-08-21 | 北京理工大学 | Preparation method of high-molecular-weight polylactic acid based on metal alkoxide dehydrating agent |
| CN103254410A (en) * | 2013-06-03 | 2013-08-21 | 北京理工大学 | Preparation method of high-molecular-weight polylactic acid based on metal powder dehydrating agent |
| CN103254409B (en) * | 2013-06-03 | 2015-07-01 | 北京理工大学 | Preparation method of high-molecular-weight polylactic acid based on metal alkoxide dehydrating agent |
| CN103300120A (en) * | 2013-06-25 | 2013-09-18 | 南京工业大学 | Green poultry and livestock depilating agent and preparation method thereof |
| CN104628563A (en) * | 2015-01-30 | 2015-05-20 | 湖北大学 | Synthetic process for preparing lactate from lactic acid |
| CN114213638A (en) * | 2021-11-16 | 2022-03-22 | 元嘉生物科技(浙江)有限公司 | Method for improving polylactic acid molecular weight based on in-situ drying dehydration |
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