Melt polycondensation reaction method for preparing high-viscosity molten mass, and special reactor and falling film element used for same

Abstract

The invention discloses a melt polycondensation reaction method for preparing a high-viscosity molten mass, which comprises steps as follows: a molten monomer blend or prepolymer slides down along the outer wall of a tubular falling film element to carry out polycondensation reaction; molten masses on all falling film elements are mixed at the bottom 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, falling film elements, a heat-transfer system, a film distributor, a helical ribbon stirrer and the like. The upper section of each falling film element is a wave node tube or corrugated tube, and the lower section is a circular tube, thereby adapting to the variation of molten mass viscosity increase in the reaction process. 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 for preparing high-viscosity melt, melting polycondensation reaction equipment and falling film components. 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 satis...

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Problems solved by technology

However, it has been found through research that the melt of this type of reactor slides faster and faster from top to bottom due to the action of gravity on the heat exchange tube, the residence time is shorter, and the surface area produced by the melt per unit volume flow rate is small. The film forming efficiency is low; as the melt continues to slide, it can cause the instability of the liquid film flow process, and the liquid film fluctuates and propagates downstream, where the liquid film at the peak is thicker, and its velocity is greater than that of the laminar flow film , which is not conducive to the effective devolatilization of the polycondensation process; the speed of the melt along the inner and outer layers of the heat exchange tube is different, resulting in axial back-mixing, insufficient homogenization and mixing of the melt, insufficient uniform residence time, and wide molecular weight distribution; this type of reactor As the polycondensation reaction proceeds, the physical properties of the material change continuously, but its internal structure does not change. The process adjustment method is single, and the internal components of a single structure do not always match and optimize the fluid dynamics and mass transfer characteristics of the changing material.

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