Vertical Condensing Tube Reactor for High Viscosity Polyamide
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Solution Overview
Problem
Current methods for producing high-viscosity PA6 polymers either result in undesirable by-products during solid phase post-condensation or require excessive vacuum in polymerization reactors, leading to operational instabilities and contamination, which limits the achievable relative viscosity of the polymer.
Innovation Solution
A reactor system comprising an upper and lower reactor region connected via a line, with independent heating and cooling units, and a prepolymerization stage that allows for the production of high-viscosity polyamide melt without the need for solid phase post-condensation, utilizing a VK tube reactor that operates at moderate pressures to achieve relative viscosities of 2.4 to 4.5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional reactor stages are added to increase polymer viscosity, then the viscosity increases, but the system complexity and space requirements increase
Solution Approach 1:
The VK tube reactor is divided into multiple pressure zones (first pressure zone with higher pressure, second pressure zone with lower pressure) within a single continuous reactor structure. This segmentation allows different polymerization conditions in different zones, achieving progressive water removal and viscosity increase without requiring separate reactor stages, thus avoiding increased system complexity while maintaining high viscosity production
2Manufacturing precision
If excessive vacuum is applied in the polymerization reactor to achieve high viscosity, then the viscosity increases, but operational instabilities and contamination increase
Solution Approach 1:
The reactor operates with pressure gradients rather than excessive vacuum - the first pressure zone maintains higher pressure (reducing contamination risk) while the second pressure zone uses moderate vacuum. This parameter change from uniform high vacuum to graduated pressure zones achieves the required water removal and viscosity increase while maintaining operational stability and reducing contamination
3Manufacturing precision
If the reactor operates at negative pressure up to 400 mbar absolute to maximize viscosity, then the relative viscosity reaches RV=3.2, but contamination problems and operational instabilities increase
Solution Approach 1:
The reactor is segmented into pressure zones where the first zone operates at higher pressure and the second zone at lower pressure. This segmentation allows the system to achieve high viscosity in the second zone without the entire reactor operating at excessive vacuum, thereby reducing contamination risks while maintaining the desired RV=3.2 viscosity level
Solution Approach 2:
The first pressure zone performs preliminary polymerization and water removal at higher pressure before the melt enters the second pressure zone. This preliminary action reduces the water content and viscosity requirements for the second zone, allowing it to operate at moderate vacuum levels that minimize contamination while still achieving the target viscosity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of polyamide melts with exceptionally high relative viscosities without additional reactor stages, reducing system complexity and costs, while maintaining operational stability and quality by effectively managing heat and pressure within the reactor system.
Implementation Method 1
The upper reactor area has an inlet area for adding the prepolymer melt, a heating unit, a first flow tube part, a heated discharge cone and wall heating over the entire height of the upper reactor area
Implementation Method 2
The lower reactor area has an inlet area for adding the melt from the upper reactor area, a degassing option for separating process steam, a static cooling unit
Implementation Method 3
a degassing option for separating process steam
Data Source
Figure 1
Figure 2
AI summary
Reactor in the form of simplified continuous tube, comprises an upper reactor region and a lower reactor region. The upper reactor region comprises an inlet region for the addition of prepolymer melt, a heating unit (12), a first flow tube, a heated discharge cone, and a wall heater. The lower reactor region comprises an inlet region for the addition of the melt from the upper reactor region and for the separation of process steam, a static refrigeration unit (13), a second flow tube, a heated discharge cone, and a wall heater. Reactor in the form of simplified continuous tube, comprises an upper reactor region and a lower reactor region. The upper reactor region comprises an inlet region for the addition of prepolymer melt, a heating unit (12), a first flow tube, a heated discharge cone, and a wall heater that is arranged over the entire height of the upper reactor region. The lower reactor region comprises an inlet region for the addition of the melt from the upper reactor region and for the separation of process steam, a static refrigeration unit (13), a second flow tube, a heated discharge cone having a discharge conduit, and a wall heater that is arranged over the entire height of the lower reactor region. The upper and lower regions are connected by a line. Independent claims are included for: (1) the polymerization of polyamides in the reactor, comprising (a) providing the prepolymer in the inlet region of the upper reactor region, (b) heating the prepolymer melt in the heating unit at a temperature of 240-280[deg] C, preferably 250-265[deg] C, (c) passing the heated prepolymer melt through a cooling unit and then passing through the first flow pipe, which is coupled with a separate heating unit, in which the polymer melt temperature is 225-260[deg] C, preferably 230-240[deg] C, and (d) passing the prepolymer melt through the second flow pipe which is coupled with a separate heating unit to avoid a heat loss and then transporting through an outlet pipe; and (2) the polyamide obtained by the above method, having a relative viscosity of 2.4-4.5, preferably 3-3.6, measured in a solution of 1 g of polyamide in 96% sulfuric acid.