Falling film melt polycondensation reaction method and reactor between rows of tubes

Abstract

The invention relates to a method for melting and polycondensation reaction of falling film between rows of tubes. The melted prepolymer flows downward from the pores between the film cloth plate and the tubes, and forms a waterfall falling film flow between the rows of U-shaped tubes for melting. In the polycondensation reaction, the melt slides from the tubes, gathers at the bottom of the reactor, is stirred and homogenized by the agitator, and then discharged. The reactor for implementing the method is an integral vertical structure, including a shell, a heat medium box at the upper end and a material box connected thereto, a U-shaped pipe, a bottom shell at the lower end, a stirrer, and the like. The U-shaped tubes are hung vertically, arranged in rows, and evenly pass through the pores of the membrane cloth, and the ports of the U-shaped tubes are connected with the heat medium box for the flow of the heat medium. This reactor has the advantages of small flow resistance, no dead zone, large film forming area, fast surface renewal, uniform and controllable residence time, and meets flexible production. It is suitable for the production of polymers such as polyethylene terephthalate .

Description

technical field [0001] The invention relates to a falling film type melt polycondensation reaction method and melt polycondensation reaction equipment in polymer production. Background technique [0002] Polycondensation reaction is a reversible polymerization reaction that continuously produces small molecular compounds, including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate ( Polymers such as PBT), polyethylene naphthalate (PEN), polyamide (PA) and polycarbonate (PC) are all prepared by polycondensation. The similar feature of this kind of polymer is that in the process of polycondensation reaction, the devolatilization process of eliminating small molecular compounds must be continuously carried out to promote the continuous positive reaction, so the viscosity of the material is extremely high, especially in the late stage of polycondensation, the material The dynamic viscosity will change by an order of magnitude. Th...

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Problems solved by technology

Especially when preparing high-viscosity materials, the falling film reactor outside the tube can make the material flow outside the tube by gravity alone, providing a suitable residence time so that the material can fully react, but the complete wall-attached falling film flow will Due to the speed difference between the inner and outer layers of the melt film, the flow rate of the outer layer of the liquid film is fast, while the inner layer of the film is slower, causing some materials to be attached to the internal components of the reactor for a long time and degrade and turn yellow, affecting the quality of the final product. However, the free falling film of the falling strip will make the flow rate of the melt film free fall too fast and the residence time too short, and the film surface shrinks significantly during the process of the melt film falling, and the film forming efficiency is very low.

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