Process method for preparing glycolide from glycolate

Abstract

The invention discloses a process method for preparing glycolide from glycolate, and belongs to the technical field of chemical products. The method comprises the following steps: carrying out primaryreaction on reaction raw materials glycollate and a catalyst in a pre-polymerization kettle; transferring the obtained mixture into a final polymerization kettle connected with a pre-polymerization kettle; oligomers formed by the reaction in the final polymerization kettle flow into a depolymerization kettle to be subjected to a depolymerization reaction; enabling a part of the crude product glycolide obtained in the depolymerization kettle directly to directly flow into a crude product storage tank; and feeding the rest of depolymerized materials into the wiped film evaporator by a circulating pump; separating out a crude product glycolide and other materials in the wiped film evaporator, collecting the crude product glycolide in a crude product storage tank, enabling the other materialsto flow into the depolymerization kettle again for further depolymerization reaction; and purifying the crude product glycolide collected in the crude product storage tank through a melting crystallizer to obtain a pure product glycolide. The polymerization process designed by the invention is divided into two steps, so that the production energy consumption is effectively reduced; meanwhile,, bymeans of the thin-film evaporator, side reactions such as further polymerization and coking caused by the fact that the oligomer stays in the depolymerization kettle for a long time are avoided.

Description

technical field [0001] The invention relates to the technical production of glycolide, which belongs to the technical field of chemical products, in particular to a process for preparing glycolide from glycolate. Background technique [0002] Polyglycolide is a synthetic polymer material with good biodegradability and biocompatibility. Its application is mainly in two aspects of biomedicine and ecology. Glycolide is a ring dimer of glycolic acid. The ring-opening polymerization of glycolide is a relatively mature method for preparing polyglycolic acid. This method can obtain polyglycolic acid products with higher relative molecular weight. Glycolide’s Purity is directly related to the performance of polyglycolic acid. [0003] At present, there are two main synthetic routes of glycolide: the first is to prepare glycolide with chloroacetic acid as raw material; the second is to prepare glycolide with glycolic acid (ester) as raw material. The disadvantage of the first metho...

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Problems solved by technology

However, these patents report the addition of high-boiling point polar solvents and solubilizers, heating to form a liquid phase of glycolic acid oligomers, resulting in many depolymerization solvents prone to thermal deterioration, difficult separation and purification of glycolide, and complicated procedures

[0007] Chinese invention patent application (application publication number: CN105622567A, application publication date: 2016-6-1) discloses a high-yield preparation method of glycolide, which mainly solves the low yield of glycolide existing in the prior art The problem, by adopting the following steps: heating under normal pressure to melt glycolic acid, and then raising the temperature of the system to 180-200°C within 1-3 hours to carry out normal-pressure reaction, and distilling off the formed water, and then under the reaction pressure of 1-200°C Carry out a decompression reaction at 10kPa, dehydration and polycondensation of reactants to generate glycolic acid oligomers, and completely melt the glycolic acid oligomers. At a reaction temperature of 240-290°C and a reaction pressure of 10Pa-1kPa, a depolymerization catalyst exists The glycolic acid oligomer depolymerization reaction is carried out under reduced pressure, and the glycolide crude product is obtained through the cooling collection system, and the obtained glycolide crude product is recrystallized to obtain the technical scheme of the pure glycolide product, preferably Solve this problem effectively, can be used in the industrialized production of glycolide

However, the method reported in this patent causes problems such as internal coking and pipeline blockage in the reactor.

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