Method of applying atomized liquid plasticizer to a running tow of filamentary filter material

A method of applying droplets of liquid plasticizer to successive increments of a foraminous tow of filamentary filter material, comprising the steps of transporting the tow lengthwise along a predetermined path;

• establishing and maintaining a source of liquid plasticizer;
• conveying liquid plasticizer from said source solely to one side of said path;
• propelling droplets of the conveyed liquid plasticizer against successive increments of the running tow at said one side of said path whereby certain droplets adhere to the filamentary material and the remaining droplets penetrate through the foraminous tow to the other side of said path;
• intercepting the remaining droplets at the other side of said path;
• propelling, exclusively, at least some of the intercepted remaining droplets against successive increments of the running tow at said other side of said path so that all droplets which are propelled against the running tow at said other side of said path consist only of plasticizer which has penetrated through the running tow from said one side of said path;
• and atomizing, in the course of said last named propelling step, the droplets which are propelled against the running tow at said other side of said path.