CN1621433A - Process for preparing high-molecular lactic acid copolymer - Google Patents
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Abstract
The present invention relates to the preparation of high molecular weight polylactic acid (PLA) through copolymerization and chain expansion. Lactic acid is dewatered and polycondensated into lactic acid oligomer of molecular weight 1,000-60,000; and through the further copolymerization and chain expansion with fatty polymer B with molecular weight 400-10,000 and active functional radicals on two ends and chain expanding agent E, PLA copolymer of molecular weight up to 100,000-300,000 may be prepared. The said preparation process is simple, controllable and low in cost. The kind and consumption of the polymer B and chain expanding agent E and the conditions of the copolymerization and chain expansion may be controlled properly to control the constitution and structure and thus the performance of the copolymer. The present invention has the features of molecular design.
Description
The technical field is as follows:
the present invention relates to a method for preparing a high molecular weight polymer, particularly to a method for preparing a lactic acid copolymer, and more particularly to a method for preparing a high molecular weight lactic acid copolymer.
Background art:
the main production raw materials of the lactic acid polymer (also called Polylactic acid, PLA for short) are from plant resources such as corn, potato and the like. The polymer and the post-processed products thereof have good biodegradability and renewability, and accord with the strategy of human environmental protection and sustainable development, so the polymer has very good application prospect. The research on PLA in countries around the world is continuously advancing, and among the research results obtained so far, there are the following major routes for PLA:
(1) direct polycondensation process
The direct polycondensation method includes a solution polycondensation method and a melt polycondensation method. The solution polycondensation method can prepare a polymer having a high molecular weight, but since a large amount of a solvent used needs to be recovered, the production cost increases, and the product application is limited. The melt polycondensation method is a relatively economic method, but the polylactic acid synthesized by the method at present has low molecular weight, and the industrial scale production is not available.
(2) Ring opening polymerization process
The method firstly prepares lactic acid into lactide, and then carries out ring-opening polymerization. This is currently the predominant method of preparing high molecular weight lactic acid polymers, with which Cargill-Dow corporation, usa, filed numerous patents and established a 14 million ton/year industrial production line. From the technical and economic aspects, the method needs to prepare lactide with polymer grade purity, and has complex process and relatively high cost.
(3) Chain extension method
To obtain polylactic acid with a sufficiently high molecular weight, a chain extension method may be used. In "petrochemical industry" at volume 30, volume 2 of 2001, the subject of "influence of polymerization method and chain extender on relative molecular mass of lactic acid polymer" of end capping river and time vibration discusses the influence of aliphatic isocyanate and aromatic isocyanate as chain extenders on lactic acid polymerization, that is, adding the two types of chain extenders to low molecular weight lactic acid polymer for chain extension to improve the relative molecular weight of the polymer, and considers that: the chain extension effect of the aliphatic isocyanate chain extender is better than that of the aromatic isocyanate. From the molecular structure investigation, one end of the polylactic acid molecule is hydroxyl, and the other end is carboxyl, most of the chain extenders can not react with the carboxyl end group and the hydroxyl end group of the PLA at the same time, so that a more ideal high molecular weight polymer can not be prepared.
(4) Copolymerization process
In order to increase the molecular weight of polylactic acid and improve the properties such as impact resistance and degradation resistance, many researchers have conducted research on copolymerization methods. US 561344, US5916998, US5952913 and other patents describe the addition of comonomers during the ring opening polymerization to produce high molecular weight copolymers. However, these methods all use lactide as raw material, and have high cost and are difficult to popularize and apply. US5922832 et al use high molecular weight PLA blended with other polymers to improve impact resistance, and its use is still premised on the preparation of high molecular weight PLA.
The invention content is as follows:
the invention aims to provide a preparation method of a lactic acid copolymer (also called as PLA copolymer) with low production cost and simple and easy-to-control process, and the lactic acid copolymer prepared by the method has the advantages of high molecular weight, good biodegradability, excellent post-processing performance, wide application range and the like.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a high molecular weight lactic acid copolymer comprises the steps of carrying out copolymerization reaction on a lactic acid oligomer A with a viscosity average molecular weight (which is not particularly specified below) of 1,000-60,000 and one or more other aliphatic polymers B with viscosity average molecular weights of 400-10,000 and active functional groups at two ends according to the use amount of the B accounting for 20-60% of the sum of the weights of the A and the B at the temperature of 150-220 ℃ under the absolute pressure of 5-3000 Pa, carrying out vacuum unloading and positive pressure protection by using inert gas after reacting for 0.5-3 hours, then adding a chain extender E with bifunctional groups, wherein the molar ratio of the added chain extender E to the aliphatic polymer B is 1: 5-5: 1, continuously heating to 180-200 ℃, and reacting for 0.1-1 hour to obtain the high molecular weight lactic acid copolymer.
The purpose of the invention can be further realized by the following technical scheme:
in the preparation method of the high molecular weight lactic acid copolymer, the lactic acid oligomer a is prepared by a dehydration method, that is: stirring and heating an L-shaped lactic acid raw material with the weight content of more than or equal to 97% to 100-140 ℃, and dehydrating for 2-4 hours under the negative pressure of 50-500 Pa; then, maintaining the reaction temperature at 100-140 ℃, reducing the pressure to 30-300 Pa, adding one of stannous octoate, stannous chloride, stannic chloride and antimony trioxide as a catalyst, wherein the weight ratio of the added catalyst to the lactic acid raw material is 0.1-5%, and continuing to react for 3-5 hours; and finally, raising the temperature to 150-200 ℃, reducing the pressure to 20-160 Pa, and continuously reacting for 4-6 hours to obtain the lactic acid oligomer A.
In the preparation method of the high molecular weight lactic acid copolymer, in the preparation process of the lactic acid oligomer A, the weight ratio of the catalyst to the lactic acid raw material is preferably 0.1-1.0%; in the last step of reaction, the temperature is preferably 160-180 ℃.
In the preparation method of the high molecular weight lactic acid copolymer, the polymer B is one or more of polyester diol, polyether diol, hydroxyl-terminated nitrile rubber, carboxyl-terminated nitrile rubber, polyethylene terephthalate prepolymer, polybutylene terephthalate prepolymer, polycarbonate prepolymer and polyurethane prepolymer.
In the preparation method of the high molecular weight lactic acid copolymer, the polymer B is preferably polyester diol and/or polyether diol.
In the preparation method of the high molecular weight lactic acid copolymer, the chain extender E is one or more of an active diester, an active heterocyclic compound, diisocyanate, bicyclo-carboxylic anhydride, bicyclo-imino ester and lactam.
In the above-mentioned method for preparing a high molecular weight lactic acid copolymer, the chain extender E is preferably diisocyanate.
In the above-mentioned method for producing a high molecular weight lactic acid copolymer, the inert gas is preferably nitrogen.
The invention provides a preparation method of a high molecular weight lactic acid copolymer, which adopts the technical means of copolymerization and chain extension at the same time, does not need to directly prepare high molecular weight PLA and pure lactide, only needs to dehydrate and condense lactic acid to prepare a lactic acid oligomer, and then prepares the high molecular weight lactic acid copolymer with the highest molecular weight of 10-30 ten thousand through the combined action of copolymerization and chain extension. The preparation method is simple and convenient in process, easy to control and low in production cost. In specific implementation, reaction raw materials, dosage and operation conditions can be reasonably selected, and the composition and structure of the copolymer can be conveniently controlled, so that the mechanical property, the mechanical property and the biodegradation property of the copolymer can be controlled, and the copolymer has the characteristics of molecular design. Therefore, the lactic acid copolymer prepared by the method has excellent post-processing performance and wide application range.
The specific implementation mode is as follows:
the preparation method comprises the steps of firstly preparing a lactic acid oligomer with the molecular weight of 1,000-60,000 by a melt polycondensation method, then carrying out copolymerization reaction on the lactic acid oligomer and other aliphatic polymers with the molecular weight of 400-10,000 and active functional groups at two ends, and then adding a chain extender containing bifunctional groups for chain extension to form a block copolymer, thereby obtaining the lactic acid copolymer with high molecular weight. The reaction mechanism is as follows:
1. formation of lactic acid oligomers. Dehydrating a lactic acid raw material at a certain temperature under a vacuum condition, carrying out a polymerization reaction to a certain extent at a higher temperature under a lower pressure under the action of a catalyst, pouring out a reaction product under the protection of inert gas, and cooling at room temperature to obtain a lactic acid oligomer with a molecular weight of about 1,000-60,000. Catalysts used include, but are not limited to: stannous octoate, stannous chloride, stannic chloride, antimony trioxide, and the like.
2. And (3) preparing a lactic acid copolymer. Lactic acid oligomer and other polymer with active functional group in both ends are copolymerized in molten state and under vacuum condition, and after reaction to some extent, inert gas is used to unload vacuum and protect positive pressure, and then chain extender containing bifunctional group is added, and proper temperature rise is carried out to continue reaction. The reaction formula is as follows:
(1) copolymerization reaction
(2) Chain extension reaction
(3) Integrated reaction
Wherein HOOC-PLA-OH represents: a lactic acid oligomer A;
X-Polymer B-X represents: an aliphatic polymer B having reactive functional groups at both ends;
Y-Extender-Y represents: a chain extender E;
x and Y are reactive functional groups.
The molecular weight of the polymer B is preferably 400-10,000, and the polymer B comprises but is not limited to: polyether diols, polyester diols, hydroxyl terminated nitrile rubbers, carboxyl terminated nitrile rubbers, PET prepolymers, PBT prepolymers, PC prepolymers, polyurethane prepolymers, and the like. The reactive functional group X may be a hydroxyl group, a carboxyl group, an acid anhydride, an epoxy group, an isocyanate group (-NCO), an ester group or the like.
Chain extenders E include, but are not limited to: active diesters, active heterocyclic compounds, diisocyanates, bicyclic carboxylic anhydrides, bicyclic imidates, lactams, and the like.
The technical solution of the present invention will be specifically described below by way of examples and comparative examples.
Preparation of PLA/PEA lactic acid copolymer
1.1 preparation of lactic acid oligomer
300 g of lactic acid (L-form content: 97% or more, the same applies below) was added to a 500ml three-necked flask, and the mixture was heated to 130 ℃ with stirring and dehydrated in vacuum for 3 hours. Then adding 1.5g stannous octoate as catalyst, stirring uniformly, keeping at 130 ℃, and continuing to react for 3 hr. Finally, the temperature is increased to 160 ℃ again, and the reaction is carried out for 6 hr. The whole process is carried out in a negative pressure environment, and the pressure in the bottle (absolute pressure, the same applies below) is as follows: 133.3Pa in the early stage of the reaction, 133.3Pa in the middle stage of the reaction and 66.7Pa in the later stage of the reaction.
After the reaction is finished, the product is poured out under the protection of nitrogen and cooled at room temperatureBut, lactic acid oligomer is obtained. The polylactic acid was confirmed by infrared spectroscopy and nuclear magnetic resonance analysis. Viscosity average molecular weight M of the product is measured by a viscosity methodη22719, a weight average molecular weight Mw of 14136 and a number average molecular weight Mn of 6926 as determined by gel chromatography (GPC method); a glass transition temperature (Tg) of 50.90 ℃ and a melting point (Tm) of 156.86 ℃ as determined by differential scanning calorimetry (DSC method); the thermogravimetric analysis (TGA) showed that the temperature of the thermogravimetric analysis was 278.37 ℃.
1.2 preparation of PLA/PEA copolymer
The lactic acid oligomer prepared in 1.1 was melted, and polyethylene glycol adipate diol (PEA) having a molecular weight of about 1530 was added in various proportions (see Table 1), stirred, and reacted at 160 ℃ under an absolute pressure of 40Pa for 1 hr. Then, vacuum relief and positive pressure protection are carried out by using nitrogen, chain extender HDI (hexamethylene diisocyanate) is added, the molar ratio of HDI to PEA is 2: 1, the temperature is raised to 180 ℃, and the reaction is carried out for 12min, thus obtaining the PLA/PEA copolymer.
Table 1 shows the molecular weight comparison of copolymers prepared using different ratios of the raw materials, where MηThe viscosity average molecular weight, Mn, number average molecular weight, Mw, weight average molecular weight, and Mw/Mn are molecular weight distributions. Table 2shows the comparison of the thermal properties of PLA/PEA copolymers prepared from different raw material ratios, and the DSC method is adopted for testing, wherein Tg is the glass transition temperature, Tc is the cold crystallization temperature, Delta Hc is the hot enthalpy of the cold crystallization peak, Tm is the melting point, and Delta Hm is the hot enthalpy of the melting peak.
The reference numerals in the present example are the same when appearing hereinafter, and the method of testing the thermal properties is the same in the following examples, and will not be described repeatedly.
Table 1: molecular weight comparison of PLA/PEA copolymers prepared under different raw material ratios
| Raw materialsWeight ratio of | Mη | Mn | Mw | Mw/Mn | |
| Lactic acid oligomer | PEA | ||||
| 80 | 20 | 50995 | 14700 | 18649 | 1.93 |
| 70 | 30 | 116345 | 28109 | 50708 | 1.80 |
| 64 | 36 | 86984 | 19600 | 47359 | 2.41 |
| 53 | 47 | 87156 | 21048 | 49234 | 2.33 |
| 40 | 60 | 86730 | 20482 | 49500 | 2.10 |
Table 2: thermal property comparison of PLA/PEA copolymer prepared under different raw material proportions
| Raw material weight ratio | Tg (℃) | Tc (℃) | ΔHc (J/g) | Tm (℃) | ΔHm (J/g) | |
| Lactic acid oligomer | PEA | |||||
| 80 | 20 | 48.03 | 81.98 | 16.06 | 145.01 | 22.56 |
| 70 | 30 | 48.50 | 83.64 | 18.58 | 145.14 | 20.97 |
| 64 | 36 | 48.65 | 84.47 | 16.21 | 145.69 | 26.80 |
| 53 | 47 | 47.32 | 91.64 | 15.79 | 141.90 | 17.12 |
| 40 | 60 | 46.25 | 80.25 | 16.16 | 140.96 | 16.98 |
Preparation of PLA/PCL lactic acid copolymer
2.1 preparation of lactic acid oligomer
300 g of lactic acid was added to a 500ml three-necked flask, and the mixture was heated to 100 ℃ with stirring and dehydrated in vacuo for 4 hr. Then 8g of antimony trioxide as a catalyst was added, stirred uniformly, kept at 100 ℃ and reacted for 4 hr. Finally, the temperature is raised to 150 ℃ again, and the reaction is carried out for 7 hr. The whole process is carried out in a reduced pressure environment, and the pressure in the bottle is as follows: 123.0Pa in the early stage of the reaction, 78.8Pa in the middle stage of the reaction and 40.6Pa in the later stage of the reaction. After the reaction is finished, the product is poured out under the protection of nitrogen, and the lactic acid oligomer is obtained after cooling at room temperature. The polylactic acid is confirmed by infrared spectroscopy and nuclear magnetic resonance analysis; measurement of M by viscometryη26047, Mw was 16623 and Mn was 9526 by GPC; tg by DSC was 52.7 ℃ and Tm was 166.7 ℃; the thermogravimetric temperature was 298.73 ℃ as measured by TGA.
2.2 preparation of PLA/PCL copolymer
2.2.1 different raw material ratios
Melting the lactic acid oligomer obtained in 2.1, adding polycaprolactone diol (PCL) with number average molecular weight of about 1000 according to different proportions (shown in Table 3), stirring, and reacting at 170 deg.C under absolute pressure of 400Pa for 3 hr. Then, vacuum relief and positive pressure protection are carried out by nitrogen, chain extender TDI (methyl diisocyanate) is added, the molar ratio of TDI to PCL is 1: 2, the temperature is raised to 190 ℃, and the reaction is carried out for 20min, thus obtaining the PLA/PCL copolymer. The molecular weight and thermal property contrast of the PLA/PCL copolymer prepared by different raw material ratios are respectively shown in the table 3 and the table 4.
Table 3: molecular weight comparison of PLA/PCL copolymer prepared under different raw material ratios
| Raw material weight ratio | Mη | |
| Lactic acid oligomer | PCL | |
| 80 | 20 | 52840 |
| 70 | 30 | 116345 |
| 60 | 40 | 186825 |
| 50 | 50 | 115267 |
| 40 | 60 | 103671 |
Table 4: thermal performance contrast of PLA/PCL copolymer prepared under different raw material proportions
| Raw material weight ratio | Tg (℃) | Tc (℃) | ΔHc (J/g) | Tm (℃) | ΔHm (J/g) | |
| Lactic acid oligomer | PEA | |||||
| 80 | 20 | 21.27 | 84.33 | 14.25 | 150.19 | 32.07 |
| 70 | 30 | 26.92 | 89.66 | 24.09 | 145.85 | 23.74 |
| 60 | 40 | 44.03 | 99.30 | 19.17 | 158.11 | 21.44 |
| 50 | 50 | 19.11 | 97.13 | 14.08 | 132.92 | 24.98 |
| 40 | 60 | 25.38 | 90.47 | 16.35 | 138.47 | 23.86 |
2.2.2 different reaction times
160 g of lactic acid oligomer prepared by the method described in 2.1 was melted, 40 g of PCL with a number average molecular weight of 1000 was added, stirred, and reacted at 180 ℃ under an absolute pressure of 600Pa for 2.5 hr. Then, vacuum relief and positive pressure protection are carried out by using nitrogen, chain extender HDI is added, the molar ratio of HDI to PCL is 4: 1, the temperature is raised to 200 ℃, different chain extension reaction times are adopted, and PLA/PCL copolymers with different molecular weights are prepared, and the results are compared and shown in Table 5.
Table 5: reaction time vs. copolymer molecular weight
| Chain extension reaction time (min) | 6 | 9 | 12 | 15 | 30 | 45 |
| Mη | 49470 | 52647 | 50995 | 45485 | 51721 | 43015 |
Preparation of PLA/PEG lactic acid copolymer
3.1 preparation of lactic acid oligomer
300 g of lactic acid was added to a 500ml three-necked flask, and the mixture was heated to 120 ℃ with stirring and dehydrated in vacuo for 4 hr. Then 2.5g stannous chloride is added as catalyst, stirred evenly, kept at 120 ℃ and continuously reacted for 4 hours. Finally, the temperature is increased to 180 ℃ again, and the reaction is carried out for 7 hr. The whole process is carried out in a reduced pressure environment, and the pressure in the bottle is as follows: the early stage of the reaction is 103.0Pa, the middle stage of the reaction is 78.8Pa, and the later stage of the reaction is 40.6 Pa. After the reaction is finished, the product is poured out under the protection of nitrogen, and is cooled at room temperature to obtain a colorless transparent solid. The polylactic acid is confirmed by infrared spectroscopy and nuclear magnetic resonance analysis; measurement of M by viscometryη26047, Mw was 16623 and Mn was 9526 by GPC; tg by DSC was 52.7 ℃ and Tm was 166.7 ℃; the thermogravimetric temperature was 298.73 ℃ as measured by TGA.
3.2 preparation of PLA/PEG copolymer
Melting the lactic acid oligomer obtained in 3.1, adding polyethylene glycol (PEG) with number average molecular weight of 1500 according to different proportions (shown in Table 6), stirring, and reacting at 160 deg.C under absolute pressure of 40Pa for 1 hr. Then, vacuum relief and positive pressure protection are carried out by nitrogen, chain extender TDI (methyl diisocyanate) is added, the molar ratio of TDI to PEG is 1: 1.5, the temperature is raised to 185 ℃, and the reaction is carried out for 9min, thus obtaining the PLA/PEG copolymer. The molecular weight comparisons of the copolymers are shown in Table 6.
Table 6: molecular weight comparison of PLA/PEG copolymers prepared under different raw material ratios
| Raw material weight ratio | Mη | |
| Lactic acid oligomer | PEG | |
| 80 | 20 | 47840 |
| 70 | 30 | 76345 |
| 60 | 40 | 132829 |
| 50 | 50 | 95621 |
| 40 | 60 | 76458 |
Preparation of PLA/hydroxy-terminated nitrile rubber/PCL copolymer
4.1 preparation of lactic acid oligomers
300 g of lactic acid was added to a 500ml three-necked flask, and the mixture was heated to 140 ℃ with stirring and dehydrated in vacuum for 3 hours. Then 3g of tin tetrachloride was added as a catalyst, and the mixture was stirred uniformly and kept at 140 ℃ for further reaction for 3 hours. Finally, the temperature is raised to 200 ℃ again, and the reaction lasts 8 hours. The whole process is carried out in a reduced pressure environment, and the pressure in the bottle is as follows: 123.0Pa in the early stage of the reaction, 78.8Pa in the middle stage of the reaction and 40.65Pa in the later stage of the reaction. After the reaction is finished, the product is poured out under the protection of nitrogen, and the lactic acidoligomer is obtained after cooling at room temperature. The polylactic acid is confirmed by infrared spectroscopy and nuclear magnetic resonance analysis; measurement of M by viscometryη31247, Mw by GPC was 19823, Mn was 11415; tg of 52.7 ℃ and Tm of 166.70 ℃ as measured by DSC; the thermogravimetric temperature was 298.73 ℃ as measured by TGA.
4.2 preparation of PLA/hydroxy-terminated nitrile rubber/PCL copolymer
Melting the lactic acid oligomer prepared in 4.1, adding hydroxyl-terminated butadiene-acrylonitrile rubber with Mn of about 3500 and polycaprolactone diol (PCL) with Mn of about 2000, wherein the weight ratio of the three substances is as follows: lactic acid oligomer, hydroxyl-terminated nitrile rubber and polycaprolactone dihydric alcohol in the weight ratio of 50 to 30 to 20; stirring, and reacting at 160 deg.C under 40Pa for 1 hr. Then, vacuum relief and positive pressure protection are carried out by nitrogen, chain extender TDI (methyl diisocyanate) is added, the molar ratio of TDI to PCL is 2: 1, the temperature is raised to 190 ℃, and the reaction is carried out for 9min, thus obtaining the PLA/hydroxyl-terminated nitrile rubber/PCL copolymer. The weight average molecular weight of the copolymer was 284500 by GPC.
It can be seen from the above specific examples that the invention does not need to directly prepare high molecular weight PLA or pure lactide, but only needs to prepare low molecular weight lactic acid oligomer, and then can prepare the high molecular weight lactic acid copolymer through the combined action of copolymerization and chain extension. According to the reasonable selection of factors such as the species of the copolymerization raw materials, the raw material proportion, the operation conditions and the like, the prepared PLA copolymer has the molecular weight of 16-30 ten thousand at most. The method is simple and easy to control in process, low in production cost and easy to popularize commercially. The preparation method can be used for molecular design and controlling the composition and the structure of the copolymer, thereby conveniently controlling the mechanical property, the mechanical property and the biodegradation property of the copolymer. The prepared PLA copolymer with high molecular weight has good thermal stability in a molten state, is easy to process and form, and can be applied to the fields of spinning, film drawing and the like.
Claims (8)
1. A method for preparing a high molecular weight lactic acid copolymer, characterized in that: carrying out copolymerization reaction on a lactic acid oligomer A with the viscosity average molecular weight of 1,000-60,000 and one or more other aliphatic polymers B with the viscosity average molecular weight of 400-10,000 and active functional groups at two ends according to the use amount of the B accounting for 20-60% of the total weight of the A and the B at the temperature of 150-220 ℃ and under the absolute pressure of 5-3000 Pa, carrying out vacuum relief and positive pressure protection by using inert gas after reacting for 0.5-3 hours, then adding a bifunctional chain extender E, wherein the molar ratio of the added chain extender E to the aliphatic polymer B is 1: 5-5: 1, continuously heating to 180-200 ℃, and reacting for 0.1-1 hour to obtain the high-molecular-weight lactic acid copolymer.
2. The process for preparing a high molecular weight lactic acid copolymer according to claim 1, wherein: the lactic acid oligomer A is prepared by adopting a dehydration method, namely: stirring and heating an L-shaped lactic acid raw material with the weight content of more than or equal to 97% to 100-140 ℃, and dehydrating for 2-4 hours under the negative pressure of 50-500 Pa; then, maintaining the reaction temperature at 100-140 ℃, reducing the pressure to 30-300 Pa, adding one of stannous octoate, stannous chloride, stannic chloride and antimony trioxide as a catalyst, wherein the weight ratio of the added catalyst to the lactic acid raw material is 0.1-5%, and continuing to react for 3-5 hours; and finally, raising the temperature to 150-200 ℃, reducing the pressure to 10-160 Pa, and continuing to react for 4-10 hours to obtain the lactic acid oligomer A.
3. The process for preparing a high molecular weight lactic acid copolymer according to claim 2, wherein: in the preparation process of the lactic acid oligomer A, the weight ratio of the catalyst to the lactic acid raw material is preferably 0.1-1.0%; in the last step of reaction, the temperature is preferably 160-180 ℃.
4. The process for preparing a high molecular weight lactic acid copolymer according to claim 1, wherein: the polymer B is one or more of polyester diol, polyether diol, hydroxyl-terminated nitrile rubber, carboxyl-terminated nitrile rubber, polyethylene terephthalate prepolymer, polybutylene terephthalate prepolymer, polycarbonate prepolymer and polyurethane prepolymer.
5. The process for preparing a high molecular weight lactic acid copolymer according to claim 4, wherein: the polymer B is preferably polyester diol and/or polyether diol.
6. The process for preparing a high molecular weight lactic acid copolymer according to claim 1, wherein: the chain extender E is one or more of active diester, active heterocyclic compound, diisocyanate, bicyclic carboxylic anhydride, bicyclic imidate and lactam.
7. The process for preparing a high molecular weight lactic acid copolymer according to claim 6, wherein: the chain extender E is preferably diisocyanate.
8. The process for preparing a high molecular weight lactic acid copolymer according to claim 1, wherein: the inert gas is preferably nitrogen.
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| CN103328547A (en) * | 2011-01-25 | 2013-09-25 | Sk化学株式会社 | Polylactic acid resin film |
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| CN103328547B (en) * | 2011-01-25 | 2016-03-09 | Sk化学株式会社 | Polylactic acid resin film |
| WO2018112870A1 (en) * | 2016-12-23 | 2018-06-28 | 王璐 | Preparation method for degradable controlled-release coating material and slow-release fertilizer thereof |
| CN110903452A (en) * | 2019-11-22 | 2020-03-24 | 广州睿特新材料科技有限公司 | Preparation method of lactic acid copolymer with high relative molecular mass |
| CN114957941A (en) * | 2022-04-25 | 2022-08-30 | 青岛科技大学 | Functional material for toughening polylactic acid by modified carboxyl nitrile rubber and preparation method thereof |
| CN114957941B (en) * | 2022-04-25 | 2024-03-15 | 青岛科技大学 | Functional material of modified carboxyl nitrile rubber toughened polylactic acid and preparation method thereof |
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