Method for preparing lactide through high-gravity technology

A technology of lactide and supergravity, applied in the direction of organic chemistry, can solve the problem of low dehydration efficiency, achieve the effect of shortening the reaction time, shortening the reaction time and increasing the yield

Inactive Publication Date: 2017-05-31
NANJING UNIV OF TECH +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] Aiming at the defect of low dehydration efficiency in the process of preparing lactide from lactic acid, the object of the present invention is to provide a method for enhancing the dehydration efficiency through a high-gravity reactor, thereby improving the lactide preparation efficiency

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0031] Spray 80% lactic acid solution (with a water content of 18.3 wt%) into the horizontal supergravity reactor from the liquid feed port, where the flow rate of lactic acid liquid is 3mL / s; the rotor speed is 1500rpm, and the reactor jacket temperature is 80°C; The dehydrated lactic acid is released from the liquid outlet and sprayed into the reactor in a circular manner. The carrier gas helium is introduced from the inlet, the gas flow rate is 110mL / s, and the gas-liquid ratio is 1:37; after the gas flows out from the gas outlet, the water is separated by the condenser, and the gas is compressed and then circulated into the inlet again . Samples were taken during the dehydration cycle to determine the water content, and the results are shown in Table 1. Stop when the water content is below 1%.

[0032] time (h) 0 0.5 1.0 1.5 2.0 2.5 Water content (%) 18.3 12.8 3.4 1.4 0.7 0.6

Embodiment 2

[0037] Spray 80% lactic acid solution (water content 19.5%) into the vertical supergravity reactor from the liquid feed port, where the lactic acid liquid flow rate is 10mL / s; the rotor speed is 1600rpm, and the reactor jacket temperature is 80°C; from the liquid After dehydration is pumped out of the material outlet, the lactic acid is sprayed into the reactor in a circular manner. Vacuum is connected to the gas outlet, and the vacuum degree is 1kPa. After the water vapor flows out from the gas outlet, the water is separated by the condenser. Samples were taken during the dehydration cycle to determine the water content, and the results are shown in Table 3.

[0038] time (min) 0 20 40 60 80 100 Water content (%) 19.5 2.8 0.6 0.1 0.05 0.006

Embodiment 3

[0044] Add 1% (mass percentage) of the polymerization catalyst stannous octoate to the anhydrous lactic acid solution (water content 1.5%) from which free water has been removed, and stir evenly. Spray into a vertical supergravity reactor from the liquid feed port, where the liquid flow rate is 20mL / s; the rotor speed is 2000rpm, and the reactor jacket temperature is 120°C; the oligomeric lactic acid that has been polymerized and removed from the reaction water is released from the liquid discharge port The solution is circulated and sprayed into the reactor. The carrier gas nitrogen is introduced from the inlet, the gas flow rate is 430mL / s, and the gas-liquid ratio is 1:21.5; after the gas flows out from the gas outlet, the water is separated by the condenser, and the gas is compressed and then circulated into the inlet again. Samples were taken during the dehydration cycle to measure the water content, and the results are shown in Table 5. It can be seen from the table tha...

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Abstract

The invention discloses a method for preparing lactide through a high-gravity technology. The method comprises the following steps: injecting lactic acid aqueous solution into a high-gravity reactor, and removing free water under carrier gas desorption or a vacuum condition; adding catalyst into anhydrous lactic acid of which the free water is removed, generating polymerization reaction at a certain temperature after even mixing, then, injecting into the high-gravity reactor, further removing reaction water under the carrier gas desorption or the vacuum condition to obtain oligolactic acid; raising the temperature of the reaction liquid to a depolymerization temperature, injecting the reaction liquid into the high-gravity reactor, steaming the lactide from the reaction liquid under the vacuum condition, and cooling to obtain lactide crystal. In the process, a free water removal temperature is 60-100 DEG C, a reaction water removal temperature is 100-140 DEG C, and lactide steaming temperature is 160-220 DEG C. Compared with a traditional vacuum reaction process, the method disclosed by the invention has the advantages of high water removal efficiency, simple production process, high lactide yield and easiness in industrialization.

Description

technical field [0001] The invention belongs to the field of chemical synthesis, and in particular relates to a method for preparing lactide through a high-gravity reaction technology. Background technique [0002] Polylactic acid (PLA) is a green polymer material with a wide range of uses, and it is also one of the best choices to solve "white pollution". It has good mechanical strength, chemical stability, biocompatibility, biodegradability and bioabsorbability; at the same time, it is non-toxic and non-polluting, and its degradation products can participate in the metabolism of the human body, and can be widely used in the medical industry, Agriculture, food packaging, daily necessities and other fields. At present, the synthesis methods of PLA mainly include one-step method and two-step method: one-step method uses lactic acid, lactate and its derivatives as raw materials to directly synthesize PLA, but the synthesized PLA has low molecular weight and poor strength, and...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07D319/12
CPCC07D319/12
Inventor 曹飞初广文张丽丽罗勇陈建峰欧阳平凯
Owner NANJING UNIV OF TECH
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