Melt polycondensation reaction method, and reactor and falling film tube used for same

Abstract

The invention discloses a melt polycondensation reaction method which comprises steps as follows: a molten monomer blend or prepolymer slides down along the outer wall of a U tube to carry out polycondensation reaction, wherein a heat-transfer medium circularly flows in the U tube; molten masses in all U tubes are mixed at the lower part of a polycondensation reactor to be subjected to stirring reaction and mixing homogeneization; and the product is discharged after the reaction finishes. A polycondensation reactor for implementing the method comprises a vertical shell, an upper end socket, a lower end bottom shell, U tubes, a heat-transfer system, a film distributor, a helical ribbon stirrer and the like. The reactor has the advantages of simple structure, sufficient heat exchange, large film formation area, uniform reaction temperature, high polycondensation efficiency and the like, satisfies the plug flow in the process, and can be used for melt polycondensation reaction for producing polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyamide, polycarbonate and the like.

Description

technical field [0001] The invention relates to a melting polycondensation reaction method, melting polycondensation reaction equipment and a falling film element outside a tube. Background technique [0002] The implementation methods of polycondensation reaction include melt polycondensation, solution polycondensation, solid-state polycondensation and interfacial polycondensation, etc. Among them, melt polycondensation has obvious advantages in terms of product quality, economy, environmental protection and industrial implementation. Therefore, most polyesters Polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), poly Ethylene naphthalate (PEN), polyamide, polycarbonate, etc. The key to the implementation of the melt polycondensation process lies in the reactor. An ideal polycondensation reactor requires good material flow and mixing state, high heat and mass transfer efficiency, and the process satisfies plug flow, so a...

AI Technical Summary

Problems solved by technology

This type of reactor is limited by the bridge of the melt network, and the disc or mesh must be kept at a large distance, resulting in a limited surface area of ​​the melt per unit volume; limited by the structure of the reactor, the reaction temperature is not uniform enough; the melt in the molten pool stays The time is long and affected by the static pressure head, which is unfavorable to the polycondensation process; the inside of the reactor depends on the liquid level difference of the molten pool to flow, the flow condition at the kettle wall is not good, and there are many dead zones; and due to the adhesion of a large amount of melt, the stirring shaft produces Quite winding, there is not much room for further improvement of equipment for viscosity increase

Especially for the preparation of high-viscosity melts, its excessive dead zone, entrainment, limited film formation and surface renewal, and severe degradation caused by excessive residence time limit the application of this type of reactor.

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