High-permeability and high-toughness polylactic acid and preparation method thereof
阅读说明：本技术 一种高透高韧的聚乳酸及其制备方法 (High-permeability and high-toughness polylactic acid and preparation method thereof ) 是由 陈光泽 戴春发 王仕杰 吴立丰 于 2021-05-14 设计创作，主要内容包括：本发明公开了一种高透高韧的聚乳酸,包括乳酸低聚物、PLA-PEG共聚物和交联剂聚合反应制成。本发明还公开了高透高韧聚乳酸的制备方法,包括将L-乳酸(纯度≥95％)进行缩聚和解聚得到L-丙交酯,L-丙交酯与聚乙醇酸进行共聚得到PLA-PEG共聚物,聚乳酸低聚物、交联剂和PLA-PEG共聚物进一步聚合得到高透高韧的聚乳酸。该高透高韧聚乳酸相比于普通PLLA,分子链呈现更复杂的立体网络结构,降低了聚乳酸分子链的结晶度而且通过交联使得分子链间相互作用加强,在保证高透明性的同时大大提高了韧性。(The invention discloses a high-transparency high-toughness polylactic acid which is prepared by polymerization reaction of a lactic acid oligomer, a PLA-PEG copolymer and a cross-linking agent. The invention also discloses a preparation method of the high-transparency high-toughness polylactic acid, which comprises the steps of carrying out polycondensation and depolymerization on L-lactic acid (the purity is more than or equal to 95%) to obtain L-lactide, carrying out copolymerization on the L-lactide and polyglycolic acid to obtain a PLA-PEG copolymer, and further polymerizing the polylactic acid oligomer, the cross-linking agent and the PLA-PEG copolymer to obtain the high-transparency high-toughness polylactic acid. Compared with the common PLLA, the molecular chain of the high-transparency high-toughness polylactic acid has a more complex three-dimensional network structure, the crystallinity of the molecular chain of the polylactic acid is reduced, the interaction between the molecular chains is enhanced through crosslinking, and the toughness is greatly improved while the high transparency is ensured.)
1. The polylactic acid with high permeability and high toughness is characterized by being prepared by polymerization reaction of lactic acid oligomer, PLA-PEG copolymer and cross-linking agent.
2. The polylactic acid with high transparency and high toughness as claimed in claim 1, wherein the amount of the lactic acid oligomer is 10-40 wt%, the amount of the PLA-PEG copolymer is 60-90 wt%, and the amount of the cross-linking agent is 0.5-5.0 wt%.
3. The polylactic acid with high transparency and high toughness as claimed in claim 1, wherein the lactic acid oligomer is obtained by dehydration polycondensation of L-lactic acid, the purity of the L-lactic acid is not less than 95%, and the molecular weight of the lactic acid oligomer is 0.5-1 ten thousand.
4. The polylactic acid with high transparency and high toughness as claimed in claim 1, wherein the PLA-PEG copolymer is obtained by copolymerizing L-lactide and PEG, wherein the L-lactide is obtained by cracking lactic acid oligomer, and the molecular weight of the PEG is 0.3-0.8 ten thousand.
5. The polylactic acid with high transmittance and high toughness as claimed in claim 1, wherein the crosslinking agent comprises one or more of isocyanate compounds, anhydride compounds, amide compounds and epoxy compounds.
6. The preparation method of the polylactic acid with high transmittance and high toughness as claimed in claim 1, characterized by comprising the following steps:
(1) mixing L-lactic acid with a catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
(2) heating the lactic acid oligomer obtained in the step (1) to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
(3) mixing the refined L-lactide with PEG and an initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
(4) and (3) mixing the lactic acid oligomer obtained in the step (1), the PLA-PEG copolymer obtained in the step (3) and a cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a final product.
7. The method for preparing polylactic acid with high permeability and high toughness according to claim 6, wherein in the step (1), the catalyst comprises one or more of tin salt, aluminum salt, zinc salt and zirconium salt, and the amount of the catalyst is 0.5-1.5 wt%.
8. The method for preparing polylactic acid with high permeability and high toughness according to claim 6, wherein the purity of purified L-lactide in step (2) is not less than 99.5%.
9. The method for preparing polylactic acid with high permeability and high toughness according to claim 6, wherein in the step (3), the initiator is one or more of tin salt, aluminum salt, titanium salt, zinc salt and zirconium salt.
10. The method for preparing polylactic acid with high transparency and high toughness according to claim 6, wherein in the step (3), the amount of PEG is 1-20 wt%, and the amount of the initiator is 0.03-0.5 wt%.
Technical Field
The invention relates to polylactic acid, in particular to high-transparency high-toughness polylactic acid and a preparation method thereof.
Background
Polylactic acid (PLA) is a widely used green polymer material, and is one of the best choices for solving the problem of "white pollution". It has good mechanical strength, transparency, chemical stability, biocompatibility, biodegradability and bioabsorbability; meanwhile, it is non-toxic and pollution-free, and its degradation product can participate in metabolism of human body, and can be extensively used in the fields of medical industry, agriculture, food packaging and daily necessities.
However, polylactic acid has a disadvantage of high brittleness under conventional processing conditions. In general, polylactic acid is considered as a brittle polymer, the impact strength of PLLA is only 26Jm-1, and the elongation at break of polylactic acid is very low, which is also an indication of its brittleness. The brittleness of polylactic acid limits its mechanical applications. In order to make polylactic acid material have wider application, it is necessary to toughen polylactic acid. The toughness of polylactic acid is improved by blending the polylactic acid with other tough materials, but the transparency of the polylactic acid is greatly influenced by the method, so that the research on the polylactic acid with high transparency and high toughness and the preparation method thereof have important significance.
Disclosure of Invention
The purpose of the invention is as follows: the first purpose of the present invention is to provide a polylactic acid having high transparency and high toughness, and the second purpose of the present invention is to provide a method for producing such a polylactic acid.
The technical scheme is as follows: the polylactic acid with high permeability and high toughness is prepared by the polymerization reaction of lactic acid oligomer, PLA-PEG copolymer and cross-linking agent.
Further, the dosage of the lactic acid oligomer is 10-40 wt%, the dosage of the PLA-PEG copolymer is 60-90 wt%, and the dosage of the cross-linking agent is 0.5-5.0 wt%.
Further, the lactic acid oligomer is obtained by dehydration and polycondensation of L-lactic acid, wherein the purity of the L-lactic acid is more than or equal to 95%, and the molecular weight of the lactic acid oligomer is 0.5-1 ten thousand.
Further, the PLA-PEG copolymer is obtained by copolymerizing L-lactide and PEG, wherein the L-lactide is obtained by cracking lactic acid oligomer, and the molecular weight of the PEG is 0.3-0.8 ten thousand.
Further, the cross-linking agent comprises one or more of isocyanate compounds, anhydride compounds, amide compounds and epoxy compounds.
The invention relates to a preparation method of polylactic acid with high transparency and high toughness, which comprises the following steps:
(1) mixing L-lactic acid with a catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
(2) heating the lactic acid oligomer obtained in the step (1) to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
(3) mixing the refined L-lactide with PEG and an initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
(4) and (3) mixing the lactic acid oligomer obtained in the step (1), the PLA-PEG copolymer obtained in the step (3) and a cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a final product.
Further, in the step (1), the catalyst comprises one or more of tin salt, aluminum salt, zinc salt and zirconium salt, and the amount of the catalyst is 0.5-1.5 wt%.
Further, in the step (2), the purity of the purified L-lactide is more than or equal to 99.5%.
Further, in the step (3), the initiator is one or more of tin salt, aluminum salt, titanium salt, zinc salt and zirconium salt.
Further, in the step (3), the amount of the PEG is 1-20 wt%, and the amount of the initiator is 0.03-0.5 wt%.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: according to the invention, through the structural design of a polylactic acid molecular chain, the problem of poor toughness of the existing polylactic acid is solved, and the transparency of the existing polylactic acid is not influenced, and the polylactic acid with high transparency and high toughness is obtained by polymerizing the polylactic acid oligomer, the cross-linking agent and the PLA-PEG copolymer.
Drawings
FIG. 1 is a graph showing a comparison of impact resistance of different samples in examples and comparative examples;
FIG. 2 is a graph showing a comparison of transparency properties of different samples in examples and comparative examples.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
Example 1
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 1g of cross-linking agent and PEG5 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 80g of refined lactide, 5g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 20g of lactic acid oligomer, 79g of PLA-PEG copolymer and 1g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
example 2
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 1g of cross-linking agent and PEG10 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 90g of refined lactide, 10g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 20g of lactic acid oligomer, 79g of PLA-PEG copolymer and 1g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
example 3
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 1g of cross-linking agent and PEG15 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 95g of refined lactide, 15g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 20g of lactic acid oligomer, 79g of PLA-PEG copolymer and 1g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
example 4
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 1g of cross-linking agent and PEG20 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 95g of refined lactide, 20g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 20g of lactic acid oligomer, 79g of PLA-PEG copolymer and 1g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
example 5
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 3g of cross-linking agent and PEG15 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 85g of refined lactide, 15g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 10g of lactic acid oligomer, 87g of PLA-PEG copolymer and 3g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
example 6
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 3g of cross-linking agent and PEG15 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 85g of refined lactide, 15g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 20g of lactic acid oligomer, 77g of PLA-PEG copolymer and 3g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
example 7
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 3g of cross-linking agent and PEG15 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 85g of refined lactide, 15g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 30g of lactic acid oligomer, 67g of PLA-PEG copolymer and 3g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
example 8
The high-permeability and high-toughness polylactic acid comprises the following raw materials: 500g of L-lactic acid (the purity is more than or equal to 95 percent), 5g of catalyst, 0.15g of initiator, 3g of cross-linking agent and PEG15 g.
The preparation process comprises the following steps:
s1: mixing 500g of L-lactic acid (the purity is more than or equal to 95%) and 5g of catalyst, heating to 120-175 ℃, and decompressing to 50-80 Kpa for polymerization reaction to obtain a lactic acid oligomer;
s2: heating 300g of lactic acid oligomer to 190-240 ℃, decompressing to 5-20 Kpa for depolymerization to obtain crude L-lactide, and purifying to obtain refined L-lactide;
s3: mixing 85g of refined lactide, 15g of PEG and 0.15g of initiator, and reacting at 120-170 ℃ under the protection of nitrogen to obtain a PLA-PEG copolymer;
s4: mixing 40g of lactic acid oligomer, 57g of PLA-PEG copolymer and 3g of cross-linking agent, and reacting at 120-170 ℃ under the protection of nitrogen to obtain high-transparency high-toughness polylactic acid;
comparative example 1
PLLA from polylactic acid, Fengyitai, Anhui, under the designation FY 801.
Comparative example 2
Commercially available PLLA from dow dalco benne, under the designation LX 175.
The impact resistance tests were conducted on examples 1 to 8 and comparative examples 1 to 2, and the test results are shown in FIG. 1.
From the impact resistance test results of FIG. 1, it can be seen that examples 1 to 8 all have improved toughness as compared with comparative examples 1 to 2, and particularly, the toughness is improved remarkably when the PEG content is increased or the lactic acid oligomer is increased.
The light transmittance of examples 1 to 8 and comparative examples 1 to 2 was measured, and the results are shown in FIG. 2. As is clear from FIG. 2, in examples 1 to 8, the transmittance was improved and the transparency of the material was better than in examples 1 to 2, and when the content of PEG or lactic acid oligomer was increased, the formation of a three-dimensional network structure in the material was better and the effect of breaking the crystals of polylactic acid was better.