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Process for direct preparation of poly-lactic acid from lactic acid by melt/solid phase polycondensation

A technology of solid-state polycondensation and lactic acid ester, which is applied in the field of synthesis of polylactic acid by melting/solid-state polycondensation, which can solve the problems of lactic acid corrosion to equipment, uselessness, and failure to obtain high-molecular-weight polylactic acid.

Inactive Publication Date: 2006-03-29
HARBIN INST OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

But, because the preparation of lactic acid and the preparation of polylactic acid are carried out respectively in different manufacturers, there are many useless procedures in the synthetic process from the preparation of lactic acid to polylactic acid, have increased process cost; And, when using lactic acid as raw material In the process of synthesizing polylactic acid, there is also the problem of corrosion of equipment by lactic acid
Chinese patent CN1298892A discloses a method of directly condensing lactic acid into polylactic acid. This method needs to consume a large amount of azeotropic solvent, and there is also the problem of removing the azeotropic solvent remaining in the lactic acid polymer.
Chinese patent CN1326997A also discloses a method for preparing high-molecular-weight polylactic acid by direct polycondensation of lactic acid. This method needs to consume a large amount of dehydrating agent during the preparation process, which increases the process cost.
Chinese patent CN1068011C discloses a method for preparing polylactic acid by lactide melting / solid-state polycondensation method. This method adopts the ring-opening polymerization method of lactide, but the raw material lactide needs to be recrystallized several times. Re-polymerization, otherwise high-molecular-weight polylactic acid cannot be obtained, and the cost is high

Method used

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Experimental program
Comparison scheme
Effect test

specific Embodiment approach 1

[0004] Specific Embodiment 1: This embodiment is prepared according to the following steps: a. Use lactic acid ester as raw material or a mixture of lactic acid and lactic acid ester as raw material, feed inert gas, control the reaction temperature at 100-160°C, and the pressure Pre-polymerize under the condition of 30-760mmHg for 8-12 hours to obtain a lactic acid oligomer with a weight-average molecular weight of 700-1100; b. Add a catalyst to the above-mentioned lactic acid oligomer, control the reaction temperature at 120-190°C and pressure Melt polymerization under the condition of 1~20mmHg for 4~8 hours, then reduce the reaction temperature, control the reaction temperature to cool down for 1~2 hours under the condition of 100~110°C, to obtain polylactic acid with a weight average molecular weight of 12000~15000; c, Finally, control the reaction temperature at 100-175°C and the pressure at 0.5-10mmHg for solid-state polymerization for 10-25 hours to obtain a high-molecula...

specific Embodiment approach 2

[0005] Specific embodiment 2: This embodiment is prepared according to the following steps: a. Use lactic acid ester as raw material or a mixture of lactic acid and lactic acid ester as raw material to feed inert gas, control the reaction temperature at 140-160°C, and the pressure at Under the condition of 30-760mmHg, pre-polymerize for 8-12 hours to obtain lactic acid oligomers with a weight average molecular weight of 700-1100; b. Add catalyst to the above-mentioned lactic acid oligomers, control the reaction temperature at 180°C and the pressure at 1- Melt polymerization under the condition of 20mmHg for 4 to 8 hours, then reduce the reaction temperature, control the reaction temperature and cool it under the condition of 105°C for 1 to 2 hours to obtain polylactic acid with a weight average molecular weight of 12000 to 15000; c. Finally, control the reaction temperature Solid phase polymerization under the conditions of 150°C and pressure of 5mmHg to obtain high molecular w...

specific Embodiment approach 3

[0006] Specific embodiment three: this embodiment is prepared according to the following steps: a, 145.0g butyl lactate is put into the 500ml four-necked bottle that has stirring device and nitrogen inlet tube, feeds nitrogen after 1 hour, puts into 160 ℃ in an oil bath, and under nitrogen flow, reduce the pressure from 760mmHg to 200mmHg in stages over 10 hours to obtain a lactic acid oligomer with a weight average molecular weight of 1000; In the flask, add 1% of the total weight of polymer monomer SnCl 2 2H 2 A binary composite catalyst of O and p-toluenesulfonic acid, in which SnCl 2 2H 2 The weight ratio of O to p-toluenesulfonic acid is 1:1. After the beaker is sealed and connected to a decompression system, it is immersed in an oil bath at 180°C. It is stirred and polymerized under a pressure of 15mmHg for 6 hours, and then put into an oil bath at 105°C. After cooling and crystallizing in the bath for 1.5 hours, make it into granular shape to obtain polylactic acid w...

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Abstract

The present invention provides one kind of melting / solid condensation process of preparing polylactate directly with lactate. The preparation process includes the following steps: pre-polymerization to obtain lactic acid oligomer with lactate or its mixture with lactic acid via introducing inert gas and controlling the conditions of 100-160 deg.c temperature and 30-760 mmHg pressure; further melting polymerization via adding catalyst and controlling the conditions of 120-190 deg.c temperature and 1-20 mmHg pressure and then cooling to 100-110 deg.c to obtain polylactic acid; and finally solid polymerization via controlling the conditions of 100-175 deg.c temperature and 0.5-10 mmHg pressure to obtain high molecular weight polylactic acid solid. The present invention has the advantages of simple technological process, low cost and less corrosion.

Description

technical field [0001] The invention relates to a preparation method of polylactic acid, in particular to a synthesis process for preparing polylactic acid through a melting / solid-state polycondensation method. Background technique [0002] Polylactic acid is a synthetic aliphatic polyester polymer material that can be completely degraded. It is a polymer obtained by polymerizing lactic acid as the main monomer. The polymer includes not only homopolymers of lactic acid, but also lactic acid and Copolymers of other monomers. Generally, there are three methods for preparing polylactic acid, namely the direct polycondensation method of lactic acid, the dealcoholization condensation method of lactate and the ring-opening polymerization method of lactide. But, because the preparation of lactic acid and the preparation of polylactic acid are carried out respectively in different manufacturers, there are many useless procedures in the synthetic process from the preparation of lact...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08G63/02C08G63/80C08G63/85
Inventor 汪群慧孙晓红马睿
Owner HARBIN INST OF TECH