What is dry spinning?
In the dry spinning process, the melted polymer is fed into the spinneret at a constant rate, and the filaments which come out of the spinneret are dried by the help of heated airflow. The solvent which is used to dissolve the polymer must have the ability to evaporate. Heat transfer, mass transfer and stress on the filament are three of the key variables in dry spinning method.
In this method, the raw materials are dissolved in a volatile solvent to form a salutation. Using a filter, the solution is purified after which the solution is extruded through a spinneret. After which the filament directly enters warm chambers, where the filaments are solidified by evaporating the solvent in a stream of air or inert gas. After which the filaments yarns are wounded onto bobbins or treated further to achieve desired characteristics.
The evaporation of the solvent starts from the surface and proceeds towards the fiber core, this results in trapping the air in the skin core structure. As this residual solvent diffuses, it leads to collapsing of the cylindrical structure of fiber and forming the ‘dogbone’ cross-sectional structure. Most of the fibers produced through dry spinning have this ‘dogbone’ structure. This shape improves the comfort and cover of the fabric made from these filament yarns. This process is used for manufacturing filament yarns of acetate, triacetate, acrylic, modacrylic, spandex, polybenzimidazole (PBI) and polyvinyl chloride (PVC).