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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Abstract
The present invention relates to a method for preparing poly-L-lactic acid with high molecular weight via melt polycondensation and solid phase polymerization. The present invention is characterized in that the method comprises the following procedures: a. melt polycondensation, an L-lactic acid raw material is dewatered and is used for preparing an L-lactic acid prepolymer through melt polycondensation under the action of a catalyst; b. solid phase polymerization, the L-lactic acid prepolymer is ground after isothermal crystallization and are processed through solid phase polymerization when a water absorbent which is used as a molecular sieve exists, and poly-L-lactic acid with high molecular weight is prepared. The method uses L-lactic acid with low price as a raw material, and the poly-L-lactic acid with high molecular weight is prepared by the method through direct melt polycondensation and solid phase polymerization. The method of the present invention can avoid the problems of solvent recovery in the process of the solution polycondensation of L-lactic acid and solvent residue in product, and can also avoid the problems of lactide synthesis, purification, etc. in the process of preparing poly-L-lactic acid via lactide ring-opening polymerization.
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 | The preparation technology of poly lactic acid in use 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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