(A) study on solvent and monomer system in acrylic fiber manufacturing process

Abstract

Process for the production of aqueous zinc chloride solution, one of the most suitable and economical solvent to spinning and polymerization of acrylic fiber, process for the stripping and recycling of the solvent, and process for the recovery of the residual acrylonitrile monomer from the polymerization system were developed. The local commercial grade zinc chloride containing impure metals such as Fe, Mn, Al, Ca, Pb, Cu is dissolved in water. The aqueous zinc chloride solution is reacted with water soluble persulfate, thereby Fe, Mn, Al, Ca were precipitated. After removal of precipitates through the filtration the remaining Pb, Cu ions in the solution are removed in packed bed of metal zinc. The purified solution is adjusted the specific pH 3.5, the concentration 60\%, and cupric ion content to control the molecular weight of polymer, thereby solvent is produced. The diluted solvent, 30-35 wt \% concentration, from the spinning system is stripped almost completely loss free to 60 wt \% concentration in the evaporating system. The steam consumption in the evaporating system would be about $\frac{1}{4}$ of other process using nitric acid or thiocyanate. The stripped solvent is recycled to the polymerization system. For the recovery of acrylonitrile monomer, the vapor from the debubbling unit is condensed in the condenser working with refrigerant. The monomer is separated from the warermonomer mixture and recycled to the polymerization system.