Thermostabilization and Drying of Composite Chemical Filaments in the Process of Pneumatic Texturing

Abstract

A method of calculation of the output of a thermostabilization chamber in the process of drying of composite chemical filaments in pneumatic texturing is given.The process of production of pneumotextured composite chemical filaments in pneumotexturing devices (PTDs) with the use of air heat fluxes occurs simultaneously with drying and thermostabilization [1]. The process of thermostabilization of filaments ensures a high quality of treatment: shrink resistance, stability to deformations, higherthan-average sorption capacity, wrinkle resistance, and strength. The duration of the process of heat treatment of filaments depends on the type of heat-transfer agent used and its temperature; the character of the fiber influences the duration of heat treatment only slightly.In a PTD (Fig. 1), the prewetted filament interacts with a heated compressed air with a temperature t a = 120-150 o C and a pressure p = 0.35-0.55 MPa. The process of drying and thermostabilization represents a complex process of heat and mass exchange accompanied by the physicomechanical changes in the properties of the filament. Under these conditions, pneumatic texturing of wetted filaments may be considered as a process of high-rate drying of fine capillary-porous materials. As has been shown by the practice of drying of fine woven products and filaments, the process of dehydration occurs in the period of a constant rate of drying up to the equilibrium moisture content.The heat-flux density for the period of a constant rate of drying (heat treatment) is determined by the following relation [2]:(1)The drying rate in the first period is found from the initial U __ 0 and final U __ fin or equilibrium U __ eq moisture content of the filament over the period of heat treatment in the pneumotexturing chamber:The ratio of the volume of the filament to its surface iswhere M fl = V fl ρ 0 is the mass of the filament. Equation (1) with account for expressions (2) and (3) has the following form:The ratio M fl ⁄ τ 1 represents the output of the PTD as far as the pneumotextured filament is concerned. We denote it by G fl ; then Eq. (4) will take the form