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Process for preparing lactide using microwave radiation pressure reducing catalystic method

A technology of microwave radiation and lactide, applied in the direction of organic chemistry, can solve the problems of long preparation time, long reaction time, and low yield, and achieve the effects of reducing energy consumption, shortening reaction time, and reducing production costs

Inactive Publication Date: 2006-08-23
HARBIN INST OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although the normal pressure air flow method is relatively safe and reliable, its disadvantages are long preparation time and low efficiency, and the air flow will take away part of the product resulting in low yield
Although the dehydration and polymerization time of the decompression method is short and the efficiency is high, the system is viscous in the late stage of depolymerization, carbonization is serious, lactide is not easy to distill, and some unclear by-products are often produced
In general, the preparation of lactide under traditional heating conditions is faced with the defects of long reaction time, high energy consumption, and low yield, which makes the preparation cost of lactide very high.

Method used

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Experimental program
Comparison scheme
Effect test

specific Embodiment approach 1

[0009] Specific embodiment 1: This embodiment prepares lactide according to the following steps: lactic acid is used as a raw material, a composite system of catalyst stannous salt and p-toluenesulfonic acid is added to the lactic acid, and the amount of stannous salt is controlled to be 0.1 to the quality of lactic acid. 1%, the ratio of the amount of stannous salt to p-toluenesulfonic acid is 1:0.1~5, polymerize for 20~50min under the pressure of 1~20kPa and microwave power of 50~400W, and obtain the viscosity average molecular weight of 1000-8000 oligomeric lactic acid; then cracked under the conditions of pressure 0.1-10kPa and microwave power 100-600W for 20-70min to obtain crude lactide; the crude product is purified to obtain pure lactide.

[0010] In this embodiment, the stannous salt is SnCl 2 ·2H 2 O, Sn(Oct) 2 Or SnSO 4 . The method for purifying the crude lactide product is as follows: the crude lactide product is washed with water and filtered, recrystallized with abs...

specific Embodiment approach 2

[0011] Specific embodiment 2: This embodiment uses D,L-lactic acid as raw material: 270g D,L-lactic acid is placed in a 500mL flask, and SnCl accounting for 0.4% of the mass fraction of lactic acid is added 2 ·2H 2 O, then join with SnCl 2 ·2H 2 TSA with a ratio of the amount of O substance of 1:2 is used as a catalyst. Under the conditions of system pressure of 5kPa and microwave power of 170W for 30 minutes, the intermediate product of oligomeric lactic acid was obtained; then, under the conditions of pressure of 1kPa and microwave power of 200W, the oligomeric lactic acid was cracked to prepare and collect crude lactide. The time is 60 minutes; the collected crude lactide product is slightly cooled and then washed with distilled water, filtered and dried, recrystallized with absolute ethanol, and filtered and dried to obtain colorless flaky lactide crystals with a yield of 35.7%. The filtrate was reused, and the final total yield of lactide was 52%.

specific Embodiment approach 3

[0012] Specific embodiment three: This embodiment prepares lactide according to the following steps: take the aqueous lactic acid solution as a raw material, and dehydrate it under the conditions of 10-60 kPa and a microwave power of 100-1000 W to obtain lactic acid; add the catalyst stannous to the lactic acid The compound system of salt and p-toluenesulfonic acid, the amount of stannous salt is controlled to be 0.1-1% of the mass of lactic acid, the ratio of the amount of stannous salt to p-toluenesulfonic acid is 1:0.1-5, and the pressure is 1 Under the conditions of ~20kPa and microwave power of 50~400W, polymerize for 20~50min to obtain oligomeric lactic acid with a viscosity average molecular weight of 1000~8000; then crack 20~ under the conditions of pressure of 0.1~10kPa and microwave power of 100~600W. 70min, the crude lactide product is obtained; the crude product is purified to obtain pure lactide.

[0013] In this embodiment, the stannous salt is SnCl 2 ·2H 2 O, Sn(Oct...

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Abstract

The present invention relates to lactide preparing process, and is especially microwave radiation and pressure reducing catalysis process of preparing lactide. The process includes the following steps: decompression dewatering water solution of lactic acid material or using lactic acid material directly; adding catalyst and decompressing microwave polymerizing to obtain lactic acid oligomer; decompressing microwave cracking to obtain crude product; and purification to obtain pure lactide. The preparation process has short period within 2 hr, no need of nitrogen protection, high lactide yield, low power consumption, and low production cost.

Description

Technical field [0001] The invention relates to a method for preparing lactide, in particular to a method for preparing lactide by using a microwave radiation decompression catalytic method. Background technique [0002] Polylactic acid is a new type of polymer material with good biocompatibility, biodegradability and environmentally friendly properties. It has broad application development prospects in environmental protection, medicine and other fields. At present, polylactic acid with high molecular weight and high purity is mostly synthesized by the lactide ring-opening polymerization method (referred to as the ring-opening method). Since the ring-opening method firstly uses lactic acid as a raw material to prepare the intermediate lactide, the synthesis route is lengthy and the yield is low, resulting in a higher cost of preparing lactide. Therefore, the preparation of lactide with high efficiency, high yield and low cost has become an important technical key to the industri...

Claims

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Application Information

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IPC IPC(8): C07D319/12
Inventor 王鹏韩宁张英民
Owner HARBIN INST OF TECH
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