Process for removing propylene oxide in PPC (polypropylene carbonate) production process

Abstract

The invention provides a process for removing propylene oxide in a PPC (polypropylene carbonate) production process, which comprises the following steps: customizing an SCP unit consisting of an SCP horizontal self-cleaning reactor, arranging a blanking bin at a discharge end at the lower part of the SCP unit, and connecting the blanking bin with a feed port of a double-screw extruder, so that the SCP unit and the double-screw extruder are integrated to form a double-screw PO removal unit; materials enter an SCP unit at a constant blanking amount, about 90% of light component epoxypropane is extracted through operations such as steam temperature rise heating, vacuum extraction, main shaft rotation stirring and material cutting by a hook claw, the materials are changed into small spherical solid material blocks from viscous liquid in the process, then the materials enter a double-screw extruder through an SCP blanking bin, and the materials are extruded by a twin-screw extruder. And further heating and vacuum extraction are carried out to extract all volatile components including epoxypropane and propylene carbonate so as to achieve the set PPC product quality index.

Description

technical field [0001] The invention relates to the technical field of fine chemicals, in particular to a process for removing propylene oxide in a PPC production process. Background technique [0002] PPC degradable plastic is a high-molecular polymer with high viscosity. In the traditional production process, the proportion of PPC increases with the progress of the reaction, and the viscosity of the material increases. Terminate the reaction, the propylene oxide that does not participate in the reaction exists in the form of a liquid, and the PPC is dissolved therein to ensure that the fluidity of the material meets the process requirements. In the prior art CN112358607A patent proposes to add a third organic solvent in the reaction process to ensure that all propylene oxide participates in the reaction, but after the reaction is completed, PPC is still dissolved in the organic solvent. In the above two cases, solvent removal is required, and the PPC product can be produc...

AI Technical Summary

Problems solved by technology

[0004] Existing solvent extraction technology is to utilize organic solvents such as ethanol to extract PPC, concrete operation is as follows, after reaction finishes, add ethanol or other organic solvents to the PPC slurry of synthesis, PPC material is extracted in ethanol or other organic solvent phases, separate ring Propylene oxide, and then add hydrochloric acid and other extracts to the organic solvent phase to precipitate PPC, so as to achieve the purpose of separation and purification of PPC. This process has the following disadvantages: although the purity of the produced PPC is high, the separation and purification process is cumbersome. Propylene oxide recovery The difficulty of reuse increases, and the energy consumption of production is relatively high. At the same time, a large amount of process wastewater is generated in this process, which is difficult to treat and causes environmental pollution.

[0005] The existing twin-screw devolatilization technology utilizes the physical characteristic of low boiling point of propylene oxide or other organic solvents involved in PPC synthesis. When the material passes through the twin-screw unit, it adopts the method of heating and vacuum extraction at the same time to separate the volatile matter in the material. , to achieve the purpose of purifying PPC. Although this process is simple in operation and low in energy consumption, due to the small internal cavity of the twin-screw and the low average residence time of the material, the processing capacity of the equipment is limited, and it is impossible to carry out 10,000-ton PPC equipment. production requirements, and at the same time there is a quality problem of incomplete removal of light components

[0006] The present invention is mainly based on the problems of high energy consumption, large waste water output, environmental pollution, and small processing capacity in the above-mentioned PPC post-treatment technology, and invents a new generation of SCP devolatilization post-treatment technology to achieve the goal of simplifying the PPC post-treatment process. increase production capacity

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