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Method for preparing refined level lactide from recovered polylactic acid

A technology for polylactic acid and lactide, which is applied in the field of recovering polylactic acid to prepare refined-grade lactide, can solve problems such as waste of resources, and achieve the effects of improving quality, stabilizing product quality, and increasing unit output.

Active Publication Date: 2012-10-24
XIAOGAN ESUN NEW MATERIAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This approach wastes a lot of resources

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] A. Raw material pretreatment: The secondary brand of polylactic acid is crushed into 3cm particles by a crusher, then washed with water, filtered to remove impurities, and then dried to remove moisture; the moisture content is controlled below 0.1% by weight.

[0025] B. Melting: The pretreated polylactic acid secondary brand material is transported to the silo of the twin-screw extruder, melted and extruded through the twin-screw extruder, and the melt enters the pre-depolymerization kettle for chain breaking treatment to obtain poly Lactic acid melt;

[0026] C. Chain breaking: Put the polylactic acid melt at 200°C, use zinc lactate and zinc powder as the catalyst (the weight ratio of the two is 1:1), and the weight ratio of the catalyst added is 1 / 1 of the weight of the polylactic acid melt. 10000. Under the condition of stirring, the chain scission reaction is carried out to break the molecular chain of the melt. After 3 hours of reaction, the number average molecu...

Embodiment 2

[0030] A. Raw material pretreatment: crush waste polylactic acid sheets, waste polylactic acid film materials and waste polylactic acid products through a crusher into 4cm particles, then wash with water, filter to remove impurities, and then dry to remove moisture; moisture is controlled at a weight percentage less than 0.1%.

[0031] B. Melting: transport the pretreated waste polylactic acid sheets, waste polylactic acid film materials and waste polylactic acid products to the silo of the twin-screw extruder, melt and extrude through the twin-screw extruder, and the melt enters the pre-processed Depolymerization kettle, carry out chain scission treatment, obtain polylactic acid melt;

[0032] C. Chain breaking: Put polylactic acid melt at 180°C, use stannous octoate, stannous lactate, and tin lactate as catalysts (the weight ratio of the three is 2:1:1), and the weight ratio of the catalyst added is poly 50 / 10000 of the weight of lactic acid melt. The chain scission reacti...

Embodiment 3

[0036]A. Raw material pretreatment: crush polylactic acid waste products and leftovers during the processing of polylactic acid products into 4cm particles through a crusher, then wash and filter to remove impurities, and then dry to remove moisture; moisture is controlled at a weight percentage less than 0.1%.

[0037] B. Melting: transport the waste polylactic acid products after pretreatment and the leftover materials in the processing of polylactic acid products to the silo of the twin-screw extruder, and melt and extrude through the twin-screw extruder, and the melt enters the pre-processed Depolymerization kettle, carry out chain scission treatment, obtain polylactic acid melt;

[0038] C. Chain breaking: Put the polylactic acid melt under the condition of 250 ℃, and use the composite catalyst of zinc lactate, stannous lactate, and butyl titanate in a weight ratio of 1:1:1, and the weight ratio of the catalyst added is the polylactic acid melt 100 / 10000 of body weight. ...

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Abstract

The invention relates to a method for preparing refined level lactide from recovered polylactic acid. The method includes the following steps of: A. crushing a recovered polylactic acid material by a crusher; B. conducting melting: subjecting the crushed recovered polylactic acid material to melt extrusion in a double-screw extruder, putting the obtained melt into a predepolymerization kettle, thus obtaining a polylactic acid melt; C. at a temperature of 180-250DEG C and in the presence of a catalyst, subjecting the polylactic acid melt to a chain breakage reaction to cause breakage of a melt molecular chain and decline of the number average molecular weight of the melt to less than 5000; D. bringing the chain broken polylactic acid melt to a depolymerization reaction under the conditions of a temperature of 150-250DEG C and a vacuum degree ranging from -0.1 to -0.09MPa to generate a lactide crude product; and E. subjecting the lactide crude product to melt crystallization for separation so as to obtain refined lactide. Detected by a conventional method, the refined level lactide produced by the invention has content up to more than 99.5% and optical purity up to over 99.9%.

Description

technical field [0001] The invention belongs to the technical field of organic chemical industry, and in particular relates to a method for recovering polylactic acid to prepare refined-grade lactide. Background technique [0002] Lactide is a white powdery crystal. It is a natural and renewable compound that can be completely biodegraded. It is a green chemical raw material and is mainly used for ring-opening polymerization to produce polylactic acid. With the advancement of lactide production technology and the progress of applied research, the application field of lactide has begun to expand. It can be used as acidifying slow-release agent, expansion agent, pH regulator, preservative, etc. in the food industry. It can also be used in the industrial field. As a chemical reactant produced by anhydrous molecules, it participates in transesterification reactions, amination reactions, polymerization reactions, etc. The production method of polylactic acid in the prior art oft...

Claims

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Application Information

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IPC IPC(8): C07D319/12
Inventor 杨义浒徐杰
Owner XIAOGAN ESUN NEW MATERIAL
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