CN113150375B - Method for recycling polylactic acid material under catalysis of zinc catalyst - Google Patents
Method for recycling polylactic acid material under catalysis of zinc catalyst Download PDFInfo
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Abstract
The invention discloses a method for recycling a polylactic acid material under catalysis of a zinc catalyst, and belongs to the technical field of polylactic acid recycling. The invention solves the problem that the existing method for post-treating the polylactic acid waste is to degrade and utilize the polylactic acid waste or convert the polylactic acid waste into other products and is lack of a real recycling method of polylactic acid materials. The invention adopts a degradation and polymerization strategy, utilizes the same catalyst to firstly carry out transesterification reaction to degrade polylactic acid waste into short-chain polymers, then adds monomers to carry out polymerization reaction, and finally obtains new polymer materials, thereby realizing the real cyclic utilization of the polylactic acid materials.
Description
Technical Field
The invention belongs to the technical field of polylactic acid recovery; in particular to a method for recycling a polylactic acid material under the catalysis of a zinc catalyst.
Background
White pollution from waste plastics is a huge harm to the ecological environment and human health. In recent years, with the increasing of people's awareness of environmental protection and the upgrading of the policy of ' plastic restriction ' the degradable plastics are receiving increasingly extensive attention and are greatly developed. Among them, polylactic acid can be used as a substitute for conventional petroleum-based non-degradable plastics due to its good biocompatibility and physical and mechanical properties, and is widely used in various fields of social life. However, as the amount of polylactic acid used increases, the post-treatment problem of the polylactic acid waste generated in large quantities has also attracted attention.
Polylactic acid is a novel degradable material, and common waste post-treatment methods comprise biodegradation, physical recovery, chemical degradation and the like. The degradation of polylactic acid can be achieved under specific conditions by biodegradation such as bio-composting, but usually takes a long time, and the final degradation products are carbon dioxide and water, which cannot be directly and rapidly recycled, and are essentially huge wastes without better utilization of resources. The recovery of polylactic acid materials by physical methods such as melting remolding or granulating remolding is also a waste recycling way, but the physically recovered polylactic acid materials can only be made into low value-added products such as fiber products, and the method is a degraded utilization process. The recycling of polylactic acid is realized by a chemical recycling method, and an effective solution for post-treatment of waste polylactic acid is provided, but most of the existing chemical recycling methods convert polylactic acid into organic small-molecule chemicals, for example, enthaler et al report that polylactic acid can be degraded into methyl lactate by DMAP catalysis (chemistry select 2019,4, 6845-6848).
Therefore, although some methods for post-treating polylactic acid waste exist at present, the methods degrade and utilize or convert the polylactic acid waste into other products. So far, no method can realize the real recycling of polylactic acid materials, and the polylactic acid waste is recovered in a high-quality polylactic acid mode. Therefore, there is a need for the development of a novel method for recovering and reusing polylactic acid in the true sense, which is important for environmental protection and sustainable development.
Disclosure of Invention
The invention provides a method for catalyzing polylactic acid materials to be recycled by using a zinc catalyst, aiming at the problems that the existing polylactic acid waste post-treatment method is to degrade and utilize or convert the polylactic acid waste into other products and is lack of a real recycling method of the polylactic acid materials.
The technical scheme of the invention is as follows:
the method for recycling the polylactic acid material catalyzed by the zinc catalyst is realized by the following steps:
degrading the polylactic acid material into a short-chain polymer, and then carrying out polymerization reaction with a lactone monomer to realize recycling; or dissolving the polylactic acid material in an organic solvent, degrading the polylactic acid material into a short-chain polymer, and then carrying out polymerization reaction with a lactone monomer to realize recycling;
wherein, the degradation is carried out under the conditions of normal pressure, inert gas protection, certain temperature, zinc catalyst catalysis and participation of a certain amount of alcohol compounds.
Further, the catalyst employed is selected from any one of the following structures:
wherein R is 1 Represents alkyl, R 2 Represents an alkyl group, a carboxylic acid group or a halogen atom.
Further, R 1 Represents methyl, R 2 Represents ethyl, acetate or Cl.
Further, the alcohol compound is an alcohol having a carbon number of 1 to 50.
Furthermore, the alcohol compound is one or a mixture of several of methanol, ethanol, isopropanol, butanol, tert-butanol, benzyl alcohol and phenylpropanol in any proportion.
Further, the number average molecular weight of the polylactic acid material is 10 2 ～10 7 g/mol。
Furthermore, the addition amount of the catalyst accounts for 0.1-10 wt% of the polylactic acid, and the addition amount of the alcohol compound accounts for 0.1-10 wt% of the polylactic acid.
Further, the reaction temperature is 20 ℃ to 200 ℃.
Further, the organic solvent is one or a mixture of several of benzene, toluene, xylene, chlorobenzene, dichloromethane, chloroform and tetrahydrofuran in any proportion.
Further, the inert gas is argon or nitrogen.
Further, the lactone monomer structure is:
The invention has the following beneficial effects:
(1) The method adopts a strategy of degradation and repolymerization to realize conversion of the polylactic acid waste into a new polylactic acid material, and realizes the real chemical recycling of the polylactic acid material.
(2) The same catalyst is used in the degradation and repolymerization processes, so that the polylactic acid recovery process is simpler and more efficient.
(3) According to the invention, the recycled new polylactic acid material has different molecular weights and different microstructures by regulating the amount of the supplementary monomer, the chirality of the supplementary monomer and the type of the supplementary monomer, so that the polylactic acid material with various structures and functions is obtained, thereby providing a foundation for the study on the properties of the polylactic acid material and the relationship between the structure and the properties of the material.
Drawings
FIG. 1 is a schematic of a degradation repolymerization strategy;
FIG. 2 shows the results of the recovery and reuse of polylactic acid in example 1 1 H NMR comparison chart.
Detailed Description
The present invention is further illustrated by the following examples. The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional and commercially available to those skilled in the art.
Example 1: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk flask, evacuate and replace with argon, then place in a glove box, add 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, 30. Mu. Mol of methanol was added, 144mg of L-configuration polylactic acid PLLA (molecular weight: 24.6kg/mol, molecular weight distribution: 1.18) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature for 6 hours to complete the degradation.
And step two, adding 432mg of L-lactide monomer dissolved in 1mL of dichloromethane solvent into the reaction system for polymerization, wherein after 10 minutes of polymerization reaction, the nuclear magnetism monitoring monomer conversion rate is 93%, and reacting to obtain the polylactic acid polymer, thereby realizing reutilization.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain a new polylactic acid material which is marked as a polymer A.
The molecular weight and molecular weight distribution of the obtained polymer A were measured by Gel Permeation Chromatography (GPC), and the weight of the polymer A was 535mg, the molecular weight was 23.1kg/mol, and the molecular weight distribution was 1.14.
In this example, the L-configuration polylactic acid PLLA and the Polymer A 1 FIG. 2 shows the H NMR chart showing the isotacticity P of L-configuration polylactic acid PLLA m Value of 0.99, isotacticity P of recovered polylactic acid m The value was 0.99. The isotacticity and molecular weight of the recovered polymer were unchanged.
Example 2: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, taking a 5mL Schlenk bottle, vacuumizing and replacing argon,then placed in a glove box and 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) was added 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, 30. Mu. Mol of methanol was added, 144mg of random polylactic acid PLA (molecular weight 17.8kg/mol, molecular weight distribution 1.13) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature for 6 hours to complete degradation.
And step two, adding 432mg of racemic lactide monomer dissolved in 1mL of dichloromethane solvent into the reaction system for polymerization, after 10 minutes of polymerization reaction, monitoring the monomer conversion rate by nuclear magnetism to be 97%, and reacting to obtain the polylactic acid polymer, thereby realizing reutilization.
And step three, removing the reaction solvent in vacuum, washing with n-hexane to separate out the polymer, and drying in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the new polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 545mg, the molecular weight is 17.5kg/mol, and the molecular weight distribution is 1.18.
Example 3: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk flask, evacuate and replace the argon, then put in a glove box, add 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, 30. Mu. Mol of methanol was added, 144mg of random polylactic acid PLA (molecular weight 17.8kg/mol, molecular weight distribution 1.13) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature. The degradation was completed after 6 hours of reaction with methanol.
And step two, adding 144mg of racemic lactide monomer into the reaction system for polymerization, wherein after the polymerization reaction is carried out for 10 minutes, the nuclear magnetism monitoring monomer conversion rate is 96%, and the polylactic acid polymer is obtained through reaction, so that the reutilization is realized.
And step three, removing the reaction solvent in vacuum, washing and separating the polymer by using normal hexane, and drying the polymer in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 275mg, the molecular weight is 8.8kg/mol, and the molecular weight distribution is 1.38.
Example 4: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk flask, evacuate and replace the argon, then put in a glove box, add 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, 30. Mu. Mol of methanol was added, 144mg of random polylactic acid PLA (molecular weight 17.8kg/mol, molecular weight distribution 1.13) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature for 6 hours to complete degradation.
And step two, adding 720mg of racemic lactide monomer dissolved in 2mL of dichloromethane solvent into the reaction system for polymerization, wherein after 10 minutes of polymerization reaction, the nuclear magnetism monitoring monomer conversion rate is 97%, and reacting to obtain the polylactic acid polymer, thereby realizing reutilization.
And step three, removing the reaction solvent in vacuum, washing and separating the polymer by using normal hexane, and drying the polymer in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 830mg, the molecular weight is 26.1kg/mol, and the molecular weight distribution is 1.15.
Examples 2 to 4, initial molecular weights of polylactic acids were the same, and by adjusting the amount of lactide monomer added during the repolymerization, it was possible to recover and obtain new polylactic acid materials having a molecular weight equal to the initial molecular weight, a molecular weight half of the initial molecular weight, and a molecular weight 1.5 times the initial molecular weight.
Example 5: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, taking 5mL of SchlenkThe flask was evacuated and replaced with argon, then placed in a glove box and 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, then 90. Mu. Mol of methanol was added, 144mg of random polylactic acid PLA (molecular weight 20.0kg/mol, molecular weight distribution 1.12) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature. The degradation was completed after 8 hours of reaction with methanol.
And step two, adding 576mg of racemic lactide monomer dissolved in 2mL of dichloromethane solvent into the reaction system for polymerization, wherein after 30 minutes of polymerization reaction, the nuclear magnetic monitoring monomer conversion rate is 94%, and reacting to obtain the polylactic acid polymer, so that reutilization is realized.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 670mg, the molecular weight is 12.3kg/mol, and the molecular weight distribution is 1.17.
Example 6: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk flask, evacuate and replace with argon, then place in a glove box, add 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, followed by addition of 28. Mu. Mol of methanol, and 144mg of random polylactic acid PLA (molecular weight: 40.0kg/mol, molecular weight distribution: 1.16) dissolved in 1mL of methylene chloride solvent, and the reaction was stirred at room temperature. The degradation was completed after 6 hours of reaction with methanol.
Step two, 1008mg of racemic lactide monomer dissolved in 3mL of dichloromethane solvent is added into the reaction system for polymerization, after 30 minutes of polymerization reaction, the nuclear magnetism monitoring monomer conversion rate is 92%, and polylactic acid polymer is obtained through reaction, so that reutilization is realized.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the new polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 1050mg, the molecular weight is 40.4kg/mol, and the molecular weight distribution is 1.20.
Example 7: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk flask, evacuate and replace with argon, then place in a glove box, add 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of toluene solvent, 30. Mu. Mol of methanol was added, 144mg of random polylactic acid PLA (molecular weight 17.8kg/mol, molecular weight distribution 1.13) dissolved in 1mL of toluene solvent was added, and the reaction was stirred at room temperature for 6 hours to complete degradation.
And step two, adding 342mg of caprolactone monomer into the reaction system, polymerizing at 70 ℃, monitoring the monomer conversion rate to be 99% through nuclear magnetism after 3 hours of polymerization reaction, and reacting to obtain a copolymer, so that recycling is realized.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The copolymer of the random polylactic acid PLA recovery product and the caprolactone monomer after the third step of treatment has the weight of 475mg, the molecular weight of 13.7kg/mol and the molecular weight distribution of 1.77.
In this embodiment, a caprolactone monomer is added during the repolymerization process, so that the copolymerization of polycaprolactone and polylactide can be realized, and a copolymer with a new microstructure can be obtained.
Example 8: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take 5mL Schlenk's bottle, after evacuating and replacing argon, then put into glove box, add 7.8mg (20. Mu. Ofmol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, 30. Mu. Mol of methanol was added, 144mg of polylactic acid beverage cup waste (molecular weight: 57.7kg/mol, molecular weight distribution: 1.88) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature. The degradation was completed after 6 hours of reaction with methanol.
And step two, adding 1440mg of racemic lactide monomer dissolved in 3mL of dichloromethane solvent into the reaction system, carrying out polymerization reaction at room temperature, after 6 hours of polymerization reaction, carrying out nuclear magnetic monitoring to ensure that the monomer conversion rate is 96%, and reacting to obtain the polylactic acid polymer, thereby realizing reutilization.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the new polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 1500mg, the molecular weight is 47.6kg/mol, and the molecular weight distribution is 1.27.
In this embodiment, the waste polylactic acid beverage cup adopts a degradation and repolymerization strategy to realize the recycling of polylactic acid, the molecular weight distribution of the recovered new polylactic acid is reduced from 1.88 to 1.27, and the quality of the polylactic acid is improved.
Example 9: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk flask, evacuate and replace the argon, then put in a glove box, add 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) 3 ) 2 ] 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, then 30. Mu. Mol of methanol was added, 144mg of opaque polylactic acid coffee cup lid waste (molecular weight 29.8kg/mol, molecular weight distribution 2.70) dissolved in 1mL of methylene chloride solvent was added, and the degradation was completed after stirring reaction at room temperature for 6 hours.
And step two, adding 864mg of racemic lactide monomer dissolved in 2mL of dichloromethane solvent into the reaction system, carrying out polymerization reaction at room temperature, after the polymerization reaction is carried out for 18 hours, carrying out nuclear magnetic monitoring to ensure that the monomer conversion rate is 95%, and reacting to obtain the polylactic acid polymer, thereby realizing reutilization.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain a new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 950mg, the molecular weight is 40.2kg/mol, and the molecular weight distribution is 1.44.
Example 10: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk flask, evacuate and replace the argon, then add 7.8mg (20. Mu. Mol) of Zn [ N (SiMe) in a glove box 3 ) 2 ] 2 The catalyst is dissolved in 0.5mL of dichloromethane solvent, then 30 mu mol of methanol is added, 144mg of opaque polylactic acid coffee cup lid waste (molecular weight is 29.8kg/mol, molecular weight distribution is 2.70) dissolved in 1mL of dichloromethane solvent is added, and the degradation is completed after stirring reaction for 6 hours at room temperature.
Step two, adding 576mg of racemic lactide monomer dissolved in 1mL of dichloromethane solvent into the reaction system, carrying out polymerization reaction at room temperature, after 18 hours of polymerization reaction, wherein the nuclear magnetism monitoring monomer conversion rate is 94%, and reacting to obtain the polylactic acid polymer, thereby realizing reutilization.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain a new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the obtained new polylactic acid material is 670mg, the molecular weight is 31.2kg/mol, and the molecular weight distribution is 1.41.
Examples 9 and 10 degraded and re-polymerized the opaque polylactic acid coffee cup lid waste, and the degradation and re-polymerization proceeded smoothly even though the opaque impurities existed. The molecular weight of the recovered polylactic acid can be regulated and controlled by regulating the addition amount of the monomer, the molecular weight distribution of the recovered polylactic acid is narrow, and the quality of the recovered polylactic acid is superior to that of an initial polymer.
Example 11: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, a 5mL Schlenk bottle was evacuated and replaced with argon, and then placed in a glove box, and 20. Mu.L (20. Mu. Mol,1mol/L hexane solution) of ZnEt was added 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, 30. Mu. Mol of methanol was added, 144mg of random polylactic acid PLA (molecular weight: 17.8kg/mol, molecular weight distribution: 1.13) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature for 12 hours to complete degradation.
And step two, adding 432mg of racemic lactide monomer dissolved in 1mL of dichloromethane solvent into the reaction system for polymerization, wherein after 4 hours of polymerization reaction, the nuclear magnetism monitoring monomer conversion rate is 96%, and reacting to obtain the polylactic acid polymer, thereby realizing reutilization.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the new polylactic acid material obtained in the third step is 535mg, the molecular weight is 18.9kg/mol, and the molecular weight distribution is 1.21.
Example 12: the method for recycling the polylactic acid material catalyzed by the zinc catalyst in the embodiment is realized by the following steps:
step one, take a 5mL Schlenk bottle, evacuate and replace with argon, then place in a glove box and add 3.7mg (20. Mu. Mol) of Zn (OAc) 2 The catalyst was dissolved in 0.5mL of methylene chloride solvent, 30. Mu. Mol of methanol was added, 144mg of random polylactic acid PLA (molecular weight 17.8kg/mol, molecular weight distribution 1.13) dissolved in 1mL of methylene chloride solvent was added, and the reaction was stirred at room temperature for 24 hours to complete degradation.
And step two, adding 432mg of racemic lactide monomer dissolved in 1mL of dichloromethane solvent into the reaction system for polymerization, wherein after 24 hours of polymerization reaction, the nuclear magnetic monitoring monomer conversion rate is 85%.
And step three, removing the reaction solvent in vacuum, washing and separating by using normal hexane, and drying in vacuum at 40 ℃ to constant weight to obtain the new polylactic acid material.
And measuring the molecular weight and the molecular weight distribution of the novel polylactic acid material obtained in the third step by Gel Permeation Chromatography (GPC). The weight of the new polylactic acid material obtained in the third step is 460mg, the molecular weight is 13.9kg/mol, and the molecular weight distribution is 1.34.
Claims (5)
1. A method for recycling polylactic acid material catalyzed by a zinc catalyst is characterized by being realized by the following steps:
degrading the polylactic acid material into a short-chain polymer, and then adding a lactone monomer to perform a polymerization reaction to realize recycling; or dissolving the polylactic acid material in an organic solvent, degrading the polylactic acid material into a short-chain polymer, and then adding a lactone monomer to perform a polymerization reaction to realize recycling;
wherein, the degradation is carried out under the conditions of normal pressure, inert gas protection, certain temperature, zinc catalyst catalysis and participation of a certain amount of alcohol compounds, and the certain temperature is room temperature;
the same catalyst is used in the degradation and repolymerization processes;
the zinc catalyst is selected from any one of the following structures:
the number average molecular weight of the polylactic acid material is 10 2 ～10 7 g/mol；
The addition amount of the catalyst accounts for 0.1-20 wt% of the polylactic acid, and the addition amount of the alcohol compound accounts for 0.1-20 wt% of the polylactic acid;
the reaction temperature is 25 ℃;
the lactone monomer structure is as follows:
wherein R is 1 Represents hydrogen, alkyl, alkoxy, aryl or halogen atom, R 2 Represents hydrogen, alkyl, alkoxy, aryl or halogen atom, R 3 Represents hydrogen, alkyl, alkoxy, aryl or halogen atom, R 4 Represents hydrogen, an alkyl group, an alkoxy group, an aryl group or a halogen atom, and n is an integer of not less than 1.
2. The method for recycling polylactic acid material catalyzed by zinc catalyst according to claim 1, wherein R in the zinc catalyst is 1 Represents a methyl group.
3. The method for recycling the polylactic acid material catalyzed by the zinc catalyst as claimed in claim 1, wherein the alcohol compound is one or more of alcohols containing 1-50 carbon atoms in any proportion.
4. The method for recycling the polylactic acid material catalyzed by the zinc catalyst as claimed in claim 3, wherein the alcohol compound is one or more of methanol, ethanol, isopropanol, butanol, benzyl alcohol and phenylpropanol, and the mixture of the alcohol compound and the benzyl alcohol is mixed in any proportion.
5. The method for recycling the polylactic acid material catalyzed by the zinc catalyst as claimed in claim 1, wherein the organic solvent is one or more of benzene, toluene, xylene, chlorobenzene, dichloromethane, chloroform and tetrahydrofuran which are mixed in any proportion; the inert gas is argon or nitrogen.
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| CN113816938A (en) * | 2021-10-14 | 2021-12-21 | 中国科学院青岛生物能源与过程研究所 | Method for recovering lactide from polylactic acid waste |
| CN114591167A (en) * | 2022-03-11 | 2022-06-07 | 中国科学院青岛生物能源与过程研究所 | Method for recycling polylactic acid mixed plastic |
| CN115073418B (en) * | 2022-07-27 | 2024-01-26 | 中国科学院青岛生物能源与过程研究所 | Zinc complex catalyst and method for depolymerizing high-regularity polylactic acid and recycling racemic lactide |
| CN115160289B (en) * | 2022-07-27 | 2023-11-24 | 中国科学院青岛生物能源与过程研究所 | Magnesium catalyst and method for depolymerizing random polylactic acid and recycling lactide by using magnesium catalyst |
| CN115141364B (en) * | 2022-07-27 | 2023-11-03 | 中国科学院青岛生物能源与过程研究所 | Zinc catalyst and method for catalyzing recycling polylactic acid material by zinc catalyst |
| CN116060126B (en) * | 2023-01-17 | 2024-05-17 | 扬州大学广陵学院 | Method for preparing selenium catalyst by polylactic acid coking |
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