Iodine Separation in Polyarylene Sulfide Production
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Solution Overview
Problem
Current methods for separating iodine and diiodinated aromatic compounds from polycondensation processes are inefficient, particularly due to the corrosive nature of iodine and the high costs associated with equipment and material losses, with existing separation techniques like rectification and pervaporation being ineffective below the triple point of iodine, and requiring expensive materials and high vacuum tightness.
Innovation Solution
A method involving the separation of iodine and diiodinated aromatic compounds at two different pressure points, one above and one below the triple point of iodine, allowing for efficient recovery and recycling of these substances, using a device with staged polycondensation and separation units including distillation and desublimation stages to manage iodine and p-DIB streams effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If rectification or pervaporation is used to separate iodine below the triple point, then separation can be performed, but equipment cost increases and vacuum tightness requirements become extremely high
Solution Approach 1:
The patent changes the pressure parameter from below-triple-point vacuum conditions to above-triple-point pressure conditions, enabling the use of condensation and desublimation techniques instead of complex rectification or pervaporation systems. This parameter change eliminates the need for extreme vacuum tightness while achieving effective iodine separation.
Solution Approach 2:
The patent utilizes phase transitions (condensation and desublimation) of iodine at pressures above the triple point to achieve separation. By operating at pressures where iodine can condense or desublime directly from vapor to solid, the process avoids the need for complex membrane-based pervaporation or high-vacuum rectification systems.
2Reliability
If iodine is removed using hot inert gas or vacuum, then iodine can be separated from the solidified end product, but material loss increases and recycling efficiency decreases
Solution Approach 1:
The patent extracts iodine from the reaction system at the optimal point during polycondensation, separating it before it contaminates the final product. By removing iodine continuously during the reaction rather than from the solidified product, the method achieves both high product purity and minimal iodine loss through controlled condensation and desublimation.
Solution Approach 2:
The patent implements a feedback loop where separated iodine is recycled back into the polycondensation process. The condensation and desublimation units recover iodine vapor, which is then fed back to the reactor, minimizing material loss and improving overall process efficiency while maintaining product purity.
3Reliability
If terminator additives are used to capture iodine, then iodine content in end product decreases, but additional substances are introduced and separation complexity increases
Solution Approach 1:
The patent uses condensation and desublimation units as intermediary devices to capture and separate iodine from the reaction system. These units act as mediators that remove iodine vapor without introducing additional chemical substances into the polymer product, avoiding the complications associated with terminator additives while maintaining high product purity.
4Loss of substance
If p-DIB is not efficiently separated and recycled, then material loss increases and production cost rises, but efficient separation requires advanced processing units
Solution Approach 1:
The patent merges the separation functions for both iodine and p-DIB into a single integrated condensation-desublimation system. This combined approach efficiently recovers both substances without requiring separate complex processing units, minimizing material loss while avoiding the need for multiple advanced separation technologies.
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 nearly complete separation of iodine and diiodinated aromatic compounds from polyarylene sulfide production, achieving high recovery rates and minimizing material losses, thus producing highly pure polymers while optimizing economic and operational efficiency.
Implementation Method 1
a first separation unit which serves to remove volatile substances from the polymer melt
Implementation Method 2
achieve an iodine content of less than 1000 ppm in the end product
Implementation Method 3
using a device with staged polycondensation and separation units including distillation and desublimation stages
Implementation Method 4
separation of iodine and diiodinated aromatic compounds at two different pressure points, one above and one below the triple point of iodine
Data Source
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AI summary
Separating iodine, at least one diiodinated aromatic compound (I) and/or substance mixtures containing iodine and/or (I), comprises (a) separating a first part of iodine and/or (I) at a pressure >= the pressure prevailing at the triple point of iodine, and (b) separating a second part of iodine and/or (I) at a pressure >= the pressure prevailing at the triple point of iodine. The substance mixture in both the steps exhibit temperatures at which at least iodine is present in gaseous form. Separating iodine, at least one diiodinated aromatic compound of formula (I-A-I) (I) and/or substance mixtures containing iodine and/or (I), comprises (a) separating a first part of iodine and/or (I) at a pressure >= the pressure prevailing at the triple point of iodine, and (b) separating a second part of iodine and/or (I) at a pressure >= the pressure prevailing at the triple point of iodine. The substance mixture in both the steps exhibit temperatures at which at least iodine is present in gaseous form. A : divalent aromatic radical. An independent claim is also included for a device for producing polyarylene sulfide containing (II) by polycondensation of (I) with a sulfiding agent comprising (aii) pre-condensation stage comprising a stirred reactor or a stirred reactor cascade made of many successively connected stirred reactors. The stirred reactor or a first stirred reactor of the stirred reactor cascade comprises a first inlet for the starting materials and a first outlet for the prepolymers, which are connected downstream to the stirred reactor or the stirred reactor cascade, (bii) a polycondensation stage comprising at least one polycondensation reactor stage or a cascade of many sequentially connected polycondensation reactors. The polycondensation reactor or the first polycondensation reactor of the polycondensation reactor cascade exhibits a second inlet for the prepolymer obtained from the first stage and a second outlet for the polycondensate. The pre-condensation stage is connected with the polycondensation stage via a product pipe. The stirred reactor or at least one stirred reactor of stirred reactor cascade comprises first outlet for gaseous byproducts and/or unreacted starting materials, preferably iodine and/or (I).The polycondensation reactor or at least one polycondensation reactor of the cascade comprises second outlet for gaseous byproducts and/or unreacted starting materials, preferably iodine and/or (II).