CN1295264C - Method for preparing high molecular weight poly-L-lactic acid by melt polycondensation-solid phase polymerization - Google Patents
Method for preparing high molecular weight poly-L-lactic acid by melt polycondensation-solid phase polymerization Download PDFInfo
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- CN1295264C CN1295264C CNB2004100414268A CN200410041426A CN1295264C CN 1295264 C CN1295264 C CN 1295264C CN B2004100414268 A CNB2004100414268 A CN B2004100414268A CN 200410041426 A CN200410041426 A CN 200410041426A CN 1295264 C CN1295264 C CN 1295264C
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- lactic acid
- state polymerization
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- molecular sieve
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- 238000000034 method Methods 0.000 title claims abstract description 31
- 238000006116 polymerization reaction Methods 0.000 title claims abstract description 27
- 229920001432 poly(L-lactide) Polymers 0.000 title claims abstract description 18
- 239000007790 solid phase Substances 0.000 title abstract description 5
- JVTAAEKCZFNVCJ-REOHCLBHSA-N L-lactic acid Chemical compound C[C@H](O)C(O)=O JVTAAEKCZFNVCJ-REOHCLBHSA-N 0.000 claims abstract description 48
- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 19
- 239000002808 molecular sieve Substances 0.000 claims abstract description 16
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910001220 stainless steel Inorganic materials 0.000 claims abstract description 9
- 239000010935 stainless steel Substances 0.000 claims abstract description 9
- 239000002994 raw material Substances 0.000 claims abstract description 8
- 239000007787 solid Substances 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 239000013078 crystal Substances 0.000 claims description 7
- 239000003054 catalyst Substances 0.000 claims description 5
- 239000003795 chemical substances by application Substances 0.000 claims description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 4
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 4
- ADCOVFLJGNWWNZ-UHFFFAOYSA-N antimony trioxide Chemical compound O=[Sb]O[Sb]=O ADCOVFLJGNWWNZ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052718 tin Inorganic materials 0.000 claims description 4
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 3
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 3
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 claims description 3
- 229910052791 calcium Inorganic materials 0.000 claims description 3
- 239000011575 calcium Substances 0.000 claims description 3
- 230000018044 dehydration Effects 0.000 claims description 3
- 238000006297 dehydration reaction Methods 0.000 claims description 3
- 229910052700 potassium Inorganic materials 0.000 claims description 3
- 239000011591 potassium Substances 0.000 claims description 3
- 229910052708 sodium Inorganic materials 0.000 claims description 3
- 239000011734 sodium Substances 0.000 claims description 3
- 229910052712 strontium Inorganic materials 0.000 claims description 3
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 3
- KSBAEPSJVUENNK-UHFFFAOYSA-L tin(ii) 2-ethylhexanoate Chemical compound [Sn+2].CCCCC(CC)C([O-])=O.CCCCC(CC)C([O-])=O KSBAEPSJVUENNK-UHFFFAOYSA-L 0.000 claims description 3
- 229910021626 Tin(II) chloride Inorganic materials 0.000 claims description 2
- 229910021627 Tin(IV) chloride Inorganic materials 0.000 claims description 2
- 229910052788 barium Inorganic materials 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims description 2
- 235000011150 stannous chloride Nutrition 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- AXZWODMDQAVCJE-UHFFFAOYSA-L tin(II) chloride (anhydrous) Chemical compound [Cl-].[Cl-].[Sn+2] AXZWODMDQAVCJE-UHFFFAOYSA-L 0.000 claims description 2
- HPGGPRDJHPYFRM-UHFFFAOYSA-J tin(iv) chloride Chemical compound Cl[Sn](Cl)(Cl)Cl HPGGPRDJHPYFRM-UHFFFAOYSA-J 0.000 claims description 2
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 claims description 2
- 239000011787 zinc oxide Substances 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims 1
- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 abstract description 11
- 239000002904 solvent Substances 0.000 abstract description 6
- 238000007151 ring opening polymerisation reaction Methods 0.000 abstract description 5
- 229920000642 polymer Polymers 0.000 abstract description 2
- 238000007670 refining Methods 0.000 abstract description 2
- 239000006096 absorbing agent Substances 0.000 abstract 1
- 230000015572 biosynthetic process Effects 0.000 abstract 1
- 238000002425 crystallisation Methods 0.000 abstract 1
- 230000008025 crystallization Effects 0.000 abstract 1
- 238000011084 recovery Methods 0.000 abstract 1
- 238000003786 synthesis reaction Methods 0.000 abstract 1
- -1 Poly(lactic acid) Polymers 0.000 description 20
- 229920000747 poly(lactic acid) Polymers 0.000 description 13
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 11
- 239000012071 phase Substances 0.000 description 9
- 229920003023 plastic Polymers 0.000 description 9
- 239000004033 plastic Substances 0.000 description 9
- 235000014655 lactic acid Nutrition 0.000 description 6
- 239000004310 lactic acid Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 3
- 239000004626 polylactic acid Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 239000003208 petroleum Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000000071 blow moulding Methods 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 244000309464 bull Species 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 125000004122 cyclic group Chemical class 0.000 description 1
- 238000012691 depolymerization reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- USIUVYZYUHIAEV-UHFFFAOYSA-N diphenyl ether Chemical compound C=1C=CC=CC=1OC1=CC=CC=C1 USIUVYZYUHIAEV-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000003348 petrochemical agent Substances 0.000 description 1
- 238000012643 polycondensation polymerization Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
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- Polyesters Or Polycarbonates (AREA)
Abstract
一种熔融缩聚—固相聚合制备高分子量聚L-乳酸的方法，其特征是按如下步骤进行a.熔融缩聚：将原料L-乳酸脱水后，在催化剂作用下，熔融缩聚获得L-乳酸预聚物；b.固相聚合：将L-乳酸预聚物等温结晶后粉碎，并置于不锈钢盘中，另取分子筛置于另一不锈钢盘中，在作为吸水剂的分子筛存在下固相聚合，制得高分子量的聚L-乳酸。本发明选择售价较低的L-乳酸为原料，通过直接熔融缩聚—固相聚合的方法，制备高分子量的聚L-乳酸。可以避免L-乳酸溶液缩聚过程中溶剂回收以及产品中溶剂残留的问题。也可以避开丙交酯开环聚合制备聚L-乳酸过程中丙交酯的合成与精制等问题。A method for preparing high-molecular-weight poly-L-lactic acid by melt polycondensation-solid phase polymerization, which is characterized in that: Polymer; b. Solid-state polymerization: After isothermal crystallization of L-lactic acid prepolymer, it is pulverized and placed in a stainless steel plate, and another molecular sieve is placed in another stainless steel plate, and solid-state polymerization is carried out in the presence of molecular sieve as a water-absorbing agent , to produce high molecular weight poly-L-lactic acid. The present invention selects L-lactic acid with relatively low price as a raw material, and prepares high-molecular-weight poly-L-lactic acid through a direct melt polycondensation-solid phase polymerization method. The problems of solvent recovery and solvent residue in the product during polycondensation of L-lactic acid solution can be avoided. It can also avoid problems such as synthesis and refining of lactide in the process of preparing poly-L-lactic acid by ring-opening polymerization of lactide.
Description
Technical field
The present invention relates to a kind of method for preparing the high molecular poly (l-lactic acid) of fully biodegradable by L-lactic acid.
Background technology
Plastics have been widely used in the every field of national economy and people's daily life.At present, about 1.5 hundred million tons of global plastics gross annual output amount, and with the speed increase more than 5%.But the development of plastics is faced with the difficult problem of twice sternness: the one, and raw material is limited, more and more shortage; The 2nd, serious environment pollution.The used resin raw material overwhelming majority of plastics derives from petrochemical complex, and people have found also that when opening up petrochemicals energetically petroleum resources are limited.Plastic material is because that be subjected to itself and effect and the influence external world, will wear out gradually and become waste, becomes social huge source of pollution.
Poly(lactic acid) is stable performance at normal temperatures, can adopt the working method of general-purpose plastics, as extrude, injection moulding, slush molding etc., can be made into film, sheet material, porous plastics, injection-molded item, hollow blow molding bottle etc.Under oxygen enrichment and high humidity, can be degraded to CO fully by microorganism
2And H
2O is one of effective way that solves the waste plastic problem of environmental pollution.The material acid of poly(lactic acid) can belong to the environment renewable resources by fermentative preparation such as starch, can avoid the problem of petroleum resources exhaustion.Poly(lactic acid) and human body have good consistency, obtain than widespread use in medical field.
The research and development of poly(lactic acid) can be traced back to the thirties in last century, mainly contains two approach by the lactic acid synthesizing polylactic acid: direct polycondensation method and ring-opening polymerization method.The ring-opening polymerization method is the cyclic dimer-rac-Lactide of preparation lactic acid earlier, and rac-Lactide ring-opening polymerization again obtains poly(lactic acid).Require highly purified rac-Lactide in this method, route is long, and complex process causes the price height of poly(lactic acid), is difficult to compete with general-purpose plastics.Direct polycondensation method is by dehydrating condensation polymerization between lactic acid or its oligomer molecules, solution polycondensation (Bull Chem Soc Jpn is arranged usually, 1995, NO.8, P2125), melt-polycondensation (Macromolecules, 1997, NO.3, P373), melt phase polycondensation-solid phase polymerization method (Polymer, 2001, NO.11, P5059) etc.The gordian technique of direct polycondensation method is effectively to get rid of the water that generates in the reaction, and suppresses the reaction that the poly(lactic acid) depolymerization is a by product such as rac-Lactide.The lactic acid solution direct polycondensation method, the water that adopts high boiling phenyl ether equal solvent and reaction to generate forms azeotrope, take the water that reaction generates out of reaction system, to react simultaneously in the rac-Lactide Returning reacting system that generates, can prepare high molecular weight polylactic acid, but have the problem that residual solvent is difficult to remove in solvent recuperation and the product.In the lactic acid direct melt polycondensation, react deuterogenic shipwreck, cause the molecular weight of poly(lactic acid) lower with the discharge system.The product of lactic acid melt phase polycondensation can improve its molecular weight through solid state polymerization, and the side reaction that the vapour pressure of water and inhibition rac-Lactide generate in the how reduction system is very important at this moment.
Summary of the invention
The present invention is for avoiding above-mentioned existing in prior technology weak point, a kind of method that is prepared the high molecular poly (l-lactic acid) by L-lactic acid by melt phase polycondensation-solid state polymerization being provided.
The characteristics of the inventive method are to have following steps:
A, melt phase polycondensation: behind raw material L-acid by dehydrating lactic, at catalyst action, melt phase polycondensation obtains the L-lactic acid prepolymer;
B, solid state polymerization: will pulverize behind the above-mentioned L-lactic acid prepolymer isothermal crystal, and place Stainless Steel Disc, other gets molecular sieve and places another Stainless Steel Disc, and solid state polymerization in the presence of as the molecular sieve of water-retaining agent makes the high-molecular weight poly (l-lactic acid).
By the gordian technique of L-lactic acid direct condensation synthesizing polylactic acid is effectively to get rid of the water that generates in the reaction, and suppresses the reaction that the poly(lactic acid) depolymerization is a by product such as rac-Lactide.By the synthetic low-molecular-weight L-lactic acid prepolymer of L-lactic acid melt phase polycondensation, prepolymer can keep it not melt under the solid phase polymerization conditions of comparatively high temps behind isothermal crystal earlier in the present invention, and the depolymerization reaction of poly(lactic acid) greatly suppresses when solid state polymerization.Be added in this moment and still have strong water sorption under high temperature and the vacuum condition, and the molecular sieve less to the rac-Lactide adsorption, reduce the vapour pressure of water in the solid state polymerization environment, driving a reaction carries out to the direction of high molecular poly (l-lactic acid).
Compared with the prior art, the beneficial effect of the inventive method is embodied in:
It is raw material that the present invention selects the lower L-lactic acid of price, by the method for direct melt polycondensation-solid state polymerization, and preparation high-molecular weight poly (l-lactic acid).Can avoid in the L-lactic acid solution polycondensation process problem of solvent residue in solvent recuperation and the product.Also can avoid the problem such as synthetic and refining that the rac-Lactide ring-opening polymerization prepares rac-Lactide in the poly (l-lactic acid) process.
Embodiment:
Be prepared according to the following steps:
1, melt phase polycondensation: raw material L-lactic acid under 100～150 ℃, 1000～2000Pa condition, was dewatered 2～4 hours, was 1～2wt% until its water ratio, added catalyzer, and 140～200 ℃ of reaction 5～30h obtain the L-lactic acid prepolymer;
In concrete the enforcement, the catalyzer of melt phase polycondensation comprises: stannous octoate, tin protochloride, tin tetrachloride, tin protoxide, tin, antimonous oxide, zinc oxide, tetra-n-butyl titanate and titanium isopropylate etc.; Catalyst levels is 0.01～1.0wt% of dehydration back L-lactic acid consumption.
2, solid state polymerization: with above-mentioned L-lactic acid prepolymer isothermal crystal 2～20h under 90～140 ℃ of conditions, pulverize, solid state polymerization under the condition that 130～170 ℃, 0.1～2000Pa, molecular sieve water-retaining agent exist again, solid state polymerization 5～30h makes the high-molecular weight poly (l-lactic acid).
In concrete the enforcement, the water-retaining agent that uses in the solid state polymerization is for still to have the molecular sieve of water sorption under high temperature and vacuum condition, and its chemical general formula is: [M (I), M (II)] OAl
2O
3NSiO
2MH
2O, M in the formula (I) and M (II) are respectively monovalence and divalent metal, are generally sodium, potassium, calcium, strontium, barium etc., n=2-10, m=0-9.The water-retaining agent molecular sieve is specifically as follows the mixture that elements such as the oxide compound of oxide compound, aluminium of silicon and sodium, potassium, calcium, strontium, barium form.
Embodiment 1:
Take by weighing 400g, 85wt%L-lactic acid in the 1000mL single necked round bottom flask, flask is placed on the rotatory evaporator, the rotating speed of rotatory evaporator is 100rpm/min, 100 ℃ oil bath heating, under the 1000Pa condition, dewatering 2～4 hours, is 1～2wt% until its water ratio.Add the stannous octoate catalyst of dehydration back L-lactic acid weight 0.5wt%, oil bath temperature rises to 180 ℃, and the rotating speed of rotatory evaporator still is 100rpm/min, progressively is decompressed to 100Pa, reaction 10h, and reaction is poured in the Stainless Steel Disc after finishing.
Above-mentioned prepolymer is placed loft drier, be warming up to 110 ℃, allow and pulverize behind the prepolymer isothermal crystal 10h.The prepolymer 200g that gets after isothermal crystal is also pulverized places Stainless Steel Disc, and other gets 5A molecular sieve 500g and places another Stainless Steel Disc, and both are all put into 150 ℃ vacuum drying oven, is evacuated to 300Pa, solid state polymerization 15 hours.Testing thus with GPC, the weight-average molecular weight Mw of the poly (l-lactic acid) of preparation is 14.7 ten thousand.
Embodiment 2:
The preparation of L-lactic acid prepolymer, the condition that reaches solid state polymerization are with embodiment 1, and with the 5A molecular sieve among the 3A molecular sieve replacement embodiment 1, the Mw that the GPC method records poly (l-lactic acid) is 12.6 ten thousand.
Embodiment 3:
The preparation of L-lactic acid prepolymer, the condition that reaches solid state polymerization are with embodiment 1, and with the 5A molecular sieve among the mixture replacement embodiment 1 of 4A molecular sieve 200g and 5A molecular sieve 300g, the Mw that the GPC method records poly (l-lactic acid) is 15.2 ten thousand.
Claims (5)
1, a kind of melt phase polycondensation-solid state polymerization prepares the method for high molecular poly (l-lactic acid), it is characterized in that carrying out as follows:
A, melt phase polycondensation: behind raw material L-acid by dehydrating lactic, under catalyst action, melt phase polycondensation obtains the L-lactic acid prepolymer;
B, solid state polymerization: will pulverize behind the above-mentioned L-lactic acid prepolymer isothermal crystal, and place Stainless Steel Disc, other gets molecular sieve and places another Stainless Steel Disc, and solid state polymerization in the presence of as the molecular sieve of water-retaining agent makes the high-molecular weight poly (l-lactic acid).
2, method according to claim 1, it is characterized in that in step a, described raw material L-lactic acid is to dewater under 100～150 ℃, 1000～2000Pa condition, and to water ratio 1～2wt%, the processing condition of melt phase polycondensation are 140～200 ℃, 0.1～2000Pa, 5～30 hours reaction times.
3, method according to claim 1 is characterized in that in step b, and the processing condition of described isothermal crystal are 90～140 ℃ of temperature, 2～20 hours time; The processing condition of described solid state polymerization are: 130～170 ℃ of temperature, pressure 0.1～2000Pa, 5～30 hours time.
4, method according to claim 1, it is characterized in that in described step a, the catalyzer of melt phase polycondensation is: stannous octoate, tin protochloride, tin tetrachloride, tin protoxide, tin, antimonous oxide, zinc oxide, tetra-n-butyl titanate or titanium isopropylate; Catalyst levels is 0.01～1.0wt% of dehydration back L-lactic acid consumption.
5, method according to claim 1 is characterized in that in described step b, the chemical general formula of the molecular sieve that uses in the solid state polymerization is:
[M (I), M (II)] OAl
2O
3NSiO
2MH
2O, M in the formula (I) and M (II) are respectively monovalence and divalent metal, comprise sodium, potassium, calcium, strontium, barium, n=2-10, m=0-9.
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| CNB2004100414268A CN1295264C (en) | 2004-07-15 | 2004-07-15 | Method for preparing high molecular weight poly-L-lactic acid by melt polycondensation-solid phase polymerization |
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| CNB2004100414268A CN1295264C (en) | 2004-07-15 | 2004-07-15 | Method for preparing high molecular weight poly-L-lactic acid by melt polycondensation-solid phase polymerization |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100543060C (en) * | 2006-08-03 | 2009-09-23 | 西安工程大学 | Preparation Technology of Polylactic Acid for Spinning |
| CN101182369A (en) * | 2007-12-24 | 2008-05-21 | 安徽中人科技有限责任公司 | Method for preparing high-molecular-weight poly(L-lactic acid) |
| CN109180914B (en) * | 2018-04-05 | 2021-02-02 | 河南金丹乳酸科技股份有限公司 | Method for producing poly-L-lactic acid by using L-lactic acid through oligomerization, melt polycondensation and solid phase polycondensation |
| CN108610473A (en) * | 2018-05-09 | 2018-10-02 | 上海昶法新材料有限公司 | A kind of method of synthesizing polylactic 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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| CN1446836A (en) * | 2003-02-08 | 2003-10-08 | 同济大学 | Method for preparing poly-lactic acid with high molecular weight by polycondensing lactic acid directly |
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| CN1446836A (en) * | 2003-02-08 | 2003-10-08 | 同济大学 | Method for preparing poly-lactic acid with high molecular weight by polycondensing lactic acid directly |
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