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CN-121975290-A - Polylactic acid material with stereocomplex crystallization capability and preparation method thereof

CN121975290ACN 121975290 ACN121975290 ACN 121975290ACN-121975290-A

Abstract

The invention belongs to the field of polylactic acid materials and preparation thereof, and particularly relates to a polylactic acid material with a stereocomplex crystallization capability and a preparation method thereof. The invention provides a preparation method of a polylactic acid material with a stereocomplex crystallization capability, which comprises the steps of respectively initiating levorotatory lactide and dextrorotatory lactide by a functional initiator to carry out ring-opening polymerization to obtain levorotatory polylactic acid (PLLA) and dextrorotatory polylactic acid (PDLA) with main chains containing amide groups, preparing the polylactic acid material by adopting a solution blending method to obtain the PLLA and the PDLA, and adopting the structural formula of the functional initiator N is an integer of 0 to 10, and m is an integer of 2 to 12. According to the invention, the amide groups are introduced into the PLLA and PDLA main chains, and the interaction between chiral polylactic acid molecular chains is enhanced by utilizing the hydrogen bond action formed between the amide groups, so that the stereocomplex crystallization of the high molecular weight polylactic acid material is effectively promoted.

Inventors

  • BAI HONGWEI
  • ZHA CHENYING
  • FU QIANG

Assignees

  • 四川大学

Dates

Publication Date
20260505
Application Date
20260408

Claims (10)

  1. 1. The preparation method of the polylactic acid material with the stereocomplex crystallization capability is characterized by comprising the following steps: the method comprises the steps of initiating the ring-opening polymerization of the levorotatory lactide by using a functional initiator to prepare the levorotatory polylactic acid with the main chain containing the amide group, and initiating the ring-opening polymerization of the dextrorotatory lactide by using the functional initiator to prepare the dextrorotatory polylactic acid with the main chain containing the amide group; Then the obtained levorotatory polylactic acid and the levorotatory polylactic acid are subjected to a solution blending method to prepare the polylactic acid material with the stereocomplex crystallization capability; Wherein the structural formula of the functional initiator is N is an integer of 0 to 10, and m is an integer of 2 to 12.
  2. 2. The method for preparing a polylactic acid material with stereocomplex crystallization ability according to claim 1, wherein the functional initiator is prepared by reacting diethyl dicarboxylic acid with amino-terminated alkanol, wherein the diethyl dicarboxylic acid has the structural formula of N is an integer of 0-10, and the structural formula of the amino-terminated alkanol is M is an integer of 2 to 12.
  3. 3. The method for producing a polylactic acid material having stereocomplex crystallization ability according to claim 2, wherein the diethyl dicarboxylic acid is at least one selected from the group consisting of diethyl oxalate, diethyl malonate, diethyl succinate, diethyl glutarate, diethyl adipate, diethyl pimelate, diethyl suberate, diethyl azelate, diethyl sebacate, diethyl undecanedioate and diethyl dodecanedioate; The amino-terminated alkanol is at least one selected from ethanolamine, 3-amino-1-propanol, 4-amino-1-butanol, 5-amino-1-pentanol, 6-amino-1-hexanol, 7-amino-1-heptanol, 8-amino-1-octanol, 9-amino-1-nonanol, 10-amino-1-decanol, 11-amino-1-undecanol or 12-amino-1-dodecanol.
  4. 4. The preparation method of the polylactic acid material with the stereocomplex crystallization capability according to claim 2 is characterized in that the functional initiator is prepared by uniformly mixing diethyl dicarboxylate and a solvent to obtain a solution, then dropwise adding the obtained solution into a solution prepared by amino-terminated alkanol and the solvent, reacting for 12-96 hours at 10-50 ℃, filtering to obtain white precipitate, finally washing with an alcohol substance, and drying to obtain the functional initiator, wherein the molar ratio of diethyl dicarboxylate to amino-terminated alkanol is 1:2-1:6, the solvent is ethanol, methanol or tetrahydrofuran, and the alcohol substance is ethanol or methanol.
  5. 5. The method for producing a polylactic acid material having a stereocomplex crystallization ability according to any one of claims 1 to 4, wherein, In the method for preparing the levorotatory polylactic acid with the main chain containing amide groups by initiating the ring-opening polymerization reaction of the levorotatory lactide by using the functional initiator, the molar ratio of the levorotatory lactide to the functional initiator is 100:1-1000:1; In the method for preparing the dextrorotatory polylactic acid with the main chain containing amide groups by initiating the ring-opening polymerization reaction of the dextrorotatory lactide by using the functional initiator, the molar ratio of the dextrorotatory lactide to the functional initiator is 100:1-1000:1.
  6. 6. The method for preparing a polylactic acid material with stereocomplex crystallization ability according to any one of claims 1 to 4, wherein the ring-opening polymerization reaction temperature is 110 to 150 ℃ and the reaction time is 2 to 10 hours.
  7. 7. The method for producing a polylactic acid material having a stereocomplex crystallization ability according to any one of claims 1 to 4, wherein, In the method for preparing the levorotatory polylactic acid with the main chain containing amide groups by initiating the ring-opening polymerization reaction of the levorotatory lactide by using a functional initiator, a catalyst is added to promote the polymerization, the catalyst is a tin compound, and the addition mass of the catalyst is 0.01-0.1% of the mass of the levorotatory lactide; in the method for preparing the dextrorotatory polylactic acid with the main chain containing amide groups by initiating ring-opening polymerization reaction of dextrorotatory lactide by using a functional initiator, a catalyst is added to promote polymerization, the catalyst is a tin compound, and the addition mass of the catalyst is 0.01-0.1% of the mass of the dextrorotatory lactide; the catalyst is stannous octoate or stannous chloride.
  8. 8. The method for preparing the polylactic acid material with the stereocomplex crystallization capability according to any one of claims 1 to 4, wherein the solution blending method is characterized in that a solution with the concentration of 20-40 g/L is prepared by respectively preparing a solvent for the levorotatory polylactic acid and the dextrorotatory polylactic acid, stirring and mixing at least 1 h at room temperature, and then pouring into a poor solvent for precipitation to obtain the polylactic acid material with the stereocomplex crystallization capability, wherein the solvent is dichloromethane or trichloromethane, and the poor solvent is ethanol or methanol.
  9. 9. The method for preparing the polylactic acid material with the stereocomplex crystallization ability according to any one of claims 1 to 4, wherein the method for preparing the polylactic acid material with the stereocomplex crystallization ability by blending the obtained levorotatory polylactic acid and dextrorotatory polylactic acid with a solution is characterized in that the ratio of the levorotatory polylactic acid to the dextrorotatory polylactic acid is 40 to 60 parts by weight, and the ratio of the dextrorotatory polylactic acid is 40 to 60 parts by weight.
  10. 10. A polylactic acid material having a stereocomplex crystallization ability, characterized in that the polylactic acid material having a stereocomplex crystallization ability is produced by the production method according to any one of claims 1 to 9.

Description

Polylactic acid material with stereocomplex crystallization capability and preparation method thereof Technical Field The invention belongs to the field of polylactic acid materials and preparation thereof, and particularly relates to a polylactic acid material with a stereocomplex crystallization capability and a preparation method thereof. Background The petroleum-based non-biodegradable polymer material brings great convenience to human production and living, and also causes the problems of serious environmental pollution, high carbon emission and the like. Therefore, bio-based biodegradable polymer materials have received much attention. Polylactic acid (PLA) is a bio-based degradable high polymer material with excellent biocompatibility, good processing performance and high mechanical strength, the synthetic raw material of the polylactic acid can be completely derived from biomass resources such as starch, the carbon emission is low, and the polylactic acid can be degraded into substances such as non-toxic and harmless water and carbon dioxide in natural environment after being abandoned, so that the polylactic acid is widely applied to the fields of packaging, spinning, 3D printing and the like. However, PLA has obvious performance defects that on one hand, the heat resistance of the product is poor, the heat distortion temperature is limited by the lower melting temperature (T m about 160-175 ℃), and on the other hand, the product is easy to be hydrolyzed and degraded in the use process and has poor durability. This severely restricts the application of PLA as engineering plastic in fields with high requirements for heat resistance and durability. The Stereocomplex (SC) between the molecular chains of the L-polylactic acid (PLLA) and the D-polylactic acid (PDLA) provides an important approach for realizing the high performance and application expansion of PLA. Studies show that PLLA and PDLA molecular chains can be alternately stacked through hydrogen bond interaction to form special SC crystals. Compared with a Homogeneous (HC) crystal formed by single crystallization of PLLA or PDLA, the SC crystal has stronger inter-chain interaction and denser chain stacking structure, and has more excellent heat resistance (the melting point can reach 220-240 ℃ and is higher than that of the HC crystal by about 60 ℃) and hydrolytic degradation resistance. In addition, the SC crystal can endow PLA with more excellent mechanical property and solvent resistance, so that the stereocomplex polylactic acid (SC-PLA) becomes a bio-based degradable engineering plastic with huge application potential. However, during the shaping process of PLLA/PDLA blends, there is often competition between SC and HC crystals, and the competition behaviour has a significant molecular weight dependence. When the molecular weight of the blend is low (e.g., below 2X 10 4 g/mol), the SC crystals predominate, and as the molecular weight increases, the HC crystals become more dominant. In particular, for high molecular weight (> 8×10 4 g/mol) PLLA/PDLA blends with commercial application value (only high molecular weight gives PLA better molding processability and physical properties), a large amount of HC and SC crystals are easily formed in the product at the same time, and the content of HC crystals is above 50%, which seriously deteriorates the comprehensive properties of the product, making it unusable as engineering plastic. The existing work mainly adopts a method of adding additives such as a compatibilizer, a plasticizer, a nucleating agent and the like to promote SC crystallization, however, the introduction of the added additives can bring a plurality of defects. For example, compatibilizers can promote the paired crystallization of enantiomer chains by improving the compatibility of PLLA and PDLA, but common compatibilizers such as polymethyl methacrylate, polyvinyl phenol and the like are not bio-based and biodegradable, and the addition amount is large (> 20 wt%), so that the full bio-based and full biodegradation properties of PLA are seriously damaged, and the mechanical property and the thermal stability of PLA are deteriorated due to the large addition of plasticizers such as polyethylene glycol, and the risk of migration and precipitation exists in the use process. Chinese patent CN105368023B discloses a method for modifying PLA by 2-ureido-4 [1h ] -pyrimidinone (UPy) functionalization, utilizing multiple hydrogen bond interactions of UPy groups to promote SC crystallization. However, the hydrogen bonding of UPy groups in this method is too strong, not only to form a phase separation structure by self-assembly, but also to severely limit molecular chain movement, resulting in difficulty in rapid formation of a large number of SC crystals during crystallization of the high molecular weight PLLA/PDLA blend. Therefore, there is an urgent need to develop a new material of all-bio-based degradable PLA that can achieve excellent S