Process for melt-spinning synthetic fibers

Claim 1

In a process for melt spinning synthetic fibers from a high-molecular weight thermoplastic polymer selected from the group consisting of linear polyester and polyamide polymers, comprising the steps of supplying a melt of said polymer at a temperature below the spinning temperature, heating the melt to spinning temperature immediately prior to filament formation, extruding the molten synthetic polymer downwardly through a spinneret having a plurality of extrusion orifices into a gaseous medium and cooling the polymer to form filaments and drawing the filaments at draw ratios of at least 4, the improvement comprising: extruding the molten synthetic polymer at a rate of at least 50 pounds per hour downwardly through a spinneret having a plurality of extrusion orifices; advancing the extruded filaments downwardly through a substantially stationary column of air having a height of 0.5 to 2 feet and a temperature of 100° to 330° C. immediately below the spinneret, the average distance between adjacent filaments immediately below the spinneret being at least 0.24 inch; continuously advancing the filaments downwardly through a top zone of a quenching chamber wherein the filaments are cooled with cooling air laterally introduced into the path of the filaments at a temperature not above 35° C., said top zone of said quenching chamber having 2 to 5 horizontal sections, intended to provide guided travel of the cooling air transverse to the downward movement of said filaments; then continuously advancing the filaments downwardly through a middle zone of said quenching chamber wherein the filaments are cooled with cooling air laterally introduced into the path of the filaments not above 35° C., said cooling air passing upwardly to a vent opening, thereby contacting said filaments countercurrent to the downward movement of said filaments; and then continuously advancing the filaments downwardly through a bottom zone of said quenching chamber wherein the filaments are cooled with cooling air laterally introduced into the path of the filaments at a temperature not above 35° C., said cooling air passing downwardly to a vent opening, thereby contacting said filaments cocurrent to the downward movement of said filaments; said quenching chamber having a height of at least 60 inches and said filaments being contacted with air at a volumetric rate of 200 to 700 cubic feet of air per pound of filaments entering the quenching chamber, the temperature of the filaments being reduced to not over 55° C., whereby a yarn having improved uniformity is produced at a production rate of at least 50 pounds per hour through the spinneret.