(429a) An Efficient, Cost-Effective, Continuous Polymer Purification Method

Polymer precipitation is a crucial process in chemical engineering and is widely applicable to many industries including semiconductors, pharmaceuticals, and wastewater treatment. In many industries, batch polymer precipitation is a common technique for polymer purification. However, batch polymer precipitation is an arduous and inefficient process, which generates excess solvent waste. It is labor-intensive, time-consuming, and demanding. We have designed a more optimal method to purify polymers by removing residual monomers and impurities from polymer solutions using continuous polymer precipitation. Continuous polymer precipitation allows for ease in scale-up of polymer purification and would provide significant energy and cost savings. Furthermore, while batch polymer precipitation requires several additional steps to get back to the same original polymer solution, this novel continuous process eliminates several steps and significantly decreases processing time. Thus, our continuous system is efficient, significantly reduces impurities in polymer solutions, and provides a viable, cost-effective alternative to batch polymer precipitation.

Continuous static mixing processes have been explored in the pharmaceutical industry relating to precipitation of nanoparticles¹. However, this variation has not been explored in depth in the semiconductor industry. In the proposed process, after the polymer chains collapse, aggregate, and precipitate, the liquid waste is continuously isolated from the solid polymer and the solid polymer is completely dried. The purified polymer is then re-diluted to the same conditions of the original polymer solution. We have optimized this continuous process using a Design of Experiments (DOE) approach by varying factors such as the ratio of antisolvent to polymer solution, the flow rate of the polymer solution, and the retention rating of the phase-separation component. Additionally, computational fluid dynamics (CFD) were utilized to complete optimization of this process to improve the yield and efficiency.

The molecular weight (M_w) and high-performance liquid chromatography (HPLC) profiles show a significant reduction in residual monomer concentrations. This provides a significant advantage, as these impurities often have negative impacts on the properties and performance of the final product, including sublimation and defects. The antisolvent required for this continuous process has been reduced by 37% - 52% when compared to a batch process. The expected sublimation defects for the final product have been reduced by 53% when compared to the original polymer solution. Furthermore, the residual monomers have been significantly reduced through this continuous precipitation process, ranging from 67% - 86% reduction. For high-demand manufacturing materials, this continuous process would reduce polymer purification processing time by over 63% when compared to batch polymer precipitation. CFD has been used to optimize the location and number of mixers in addition to the ratio of antisolvent to polymer solution, which allowed us to maximize the yield of this process. The reduction in residual monomers and impurities, reduction in processing time, and system design optimization through CFD clearly demonstrate the advantages of this continuous precipitation process over the traditional batch precipitation process. This continuous polymer precipitation system has the potential to revolutionize the way polymer solutions are purified, making the process more efficient, cost-effective, and sustainable.

1. Dong, Yuancai. “A continuous and highly effective static mixing process for antisolvent precipitation of nanoparticles of poorly water-soluble drugs”. International Journal of Pharmaceutics 386 (2010) 256-261.