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Method for synthesizing polylactic acid

A polylactic acid and lactic acid technology, applied in the field of polymer synthesis, can solve the problems of tin compound cytotoxicity, difficult removal of residual solvents, low molecular weight of polylactic acid, etc. The effect of shortening the reaction time

Inactive Publication Date: 2018-10-02
SHANGHAI CHANGFA NEW MATERIAL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although this method can prepare high-molecular-weight polylactic acid, there are problems of solvent recovery and residual solvent in the product that are difficult to remove; and, in the direct melt polycondensation method of lactic acid, the water generated in the later stage of the reaction is difficult to discharge from the system, resulting in the molecular weight of polylactic acid. However, the product of melt polycondensation of lactic acid can increase the molecular weight through solid-state polymerization. At this time, how to effectively reduce the vapor pressure of the system and suppress the side reaction of lactide formation is very critical.
[0004] Tin-based compounds and zinc-based compounds have good catalytic effects on many organic reactions, but tin-based compounds have certain cytotoxicity, which hinders the application of PLA in the field of medical polymer materials

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] Weigh 400g of 85% lactic acid solution into a 1000ml reaction vessel, and dehydrate under nitrogen protection at 105°C and 1kpa pressure for 3 hours until the water content is 0.8wt%. Maintain nitrogen protection, add 2g of zinc acetate, raise the temperature to 130°C, reduce the vacuum to 100pa, and react for 10 hours. After the reaction is completed, the lactic acid prepolymer is prepared and poured into a stainless steel pan.

[0030] The above-mentioned lactic acid prepolymer was placed in a drying oven, heated to 120° C., crystallized isothermally for 10 hours, and then pulverized. Take the pulverized lactic acid prepolymer and place it in a stainless steel tray, add 1g of pentaerythritol and 1g of p-phenylmethanesulfonic acid, stir evenly, and take 400g of 5A molecular sieves in another stainless steel tray, put both in an oven at 120°C, Vacuumize and polymerize for 3 hours at a pressure of 4kpa; then raise the temperature to 160°C and polymerize for 3 hours at a ...

Embodiment 2

[0032]Weigh 450g of 80% lactic acid solution in a 1000ml reaction vessel, and dehydrate under nitrogen protection at 105°C and 1kpa pressure for 3.5 hours until the water content is 0.9wt%. Maintain nitrogen protection, add 2g of zinc acetate, raise the temperature to 130°C, reduce the vacuum to 100pa, and react for 10 hours. After the reaction is completed, the lactic acid prepolymer is prepared and poured into a stainless steel pan.

[0033] The above-mentioned lactic acid prepolymer was placed in a drying oven, heated to 120° C., crystallized isothermally for 10 hours, and then pulverized. Take the pulverized lactic acid prepolymer and place it in a stainless steel tray, add 1g of pentaerythritol and 1g of p-phenylmethanesulfonic acid, stir evenly, and take 400g of 5A molecular sieves in another stainless steel tray, put both in an oven at 120°C, Vacuumize and polymerize for 3 hours at a pressure of 4kpa; then raise the temperature to 160°C and polymerize for 3 hours at a p...

Embodiment 3

[0035] Weigh 400g of 90% lactic acid solution into a 1000ml reaction vessel, and dehydrate under nitrogen protection at 105°C and 1kpa pressure for 3 hours until the water content is 0.5wt%. Maintain nitrogen protection, add 2g of zinc acetate, raise the temperature to 130°C, reduce the vacuum to 100pa, and react for 10 hours. After the reaction is completed, the lactic acid prepolymer is prepared and poured into a stainless steel pan.

[0036] The above-mentioned lactic acid prepolymer was placed in a drying oven, heated to 120° C., crystallized isothermally for 10 hours, and then pulverized. Take the pulverized lactic acid prepolymer and place it in a stainless steel tray, add 1g of pentaerythritol and 1g of p-phenylmethanesulfonic acid, stir evenly, and take 400g of 5A molecular sieves in another stainless steel tray, put both in an oven at 120°C, Vacuumize and polymerize for 3 hours at a pressure of 4kpa; then raise the temperature to 160°C and polymerize for 3 hours at a ...

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Abstract

The invention provides a method for synthesizing polylactic acid. The method comprises the following steps: taking and putting 75-95 percent by mass of lactic acid solution in a reaction container andde-watering at a temperature of 90-120 DEG C and a pressure intensity of 1-2 kpa till the moisture content is 0.1-1 percent by weight; adding a zinc catalyst in the reaction container, increasing thetemperature to 120-150 DEG C and reacting for 5-15 hours at a pressure intensity of 0.001-2 kpa to prepare a lactic acid prepolymer; performing isothermal crystallization on the lactic acid prepolymer at a temperature of 90-140 DEG C, crushing, adding pentaerythritol and p-toluene sulfonic acid and reacting for 2-6 hours at a pressure intensity of 5 kpa and a temperature of 90-150 DEG C in a molecular sieve environment; and then reducing the pressure intensity to 0.001-2 kpa and reacting for 3-6 hours at a temperature of 130-170 DEG C to prepare a polylactic acid product. The method for synthesizing the polylactic acid can obtain the polylactic acid with more dealer molecular weight and solve the problems of tedious solvent recovery steps and solvent residue in the product, thereby improving the reaction rate, shortening the reaction time and facilitating large-scale industrial production.

Description

technical field [0001] The invention relates to the technical field of polymer synthesis, in particular to a method for synthesizing polylactic acid. Background technique [0002] In recent years, the research interest in biodegradable polymer materials has become increasingly strong at home and abroad, and biodegradable polymer materials involve various fields such as industrial and agricultural production and medical fields. Polylactic acid (PLA) has excellent biocompatibility and biodegradability, and the final product of its degradation is CO 2 and H 2 O. The research and development of polylactic acid has received more and more attention, especially in the field of medicine. As early as the 1930s, Carothers, a famous American polymer chemist, reported on PLA, but in the following forty years, due to the low molecular weight and poor mechanical properties of the polymer, he did nothing. By the 1970s, people began to synthesize high-molecular-weight optically active D...

Claims

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Application Information

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IPC IPC(8): C08G63/08C08G63/80C08G63/83
CPCC08G63/08C08G63/80C08G63/823
Inventor 施晓旦李赛赵吉郑璐
Owner SHANGHAI CHANGFA NEW MATERIAL CO LTD
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