Process for the production of PBT carpet yarn

A process for the production of polybutyleneterephthalate carpet yarn having a bulk level of at least 15% with thread development at 120.degree. C., and a bulkiness defined as the difference of the degree of bulk with thread development at 120.degree. C. to that at room temperature, of at least 9% absolute, by means of an integrated spinning-draw texturing process comprising:

• (a) melt spinning polybutyleneterephthalate having an intrinsic viscosity of 0.9 to 1.2, and a water content of not more than 50 ppm by weight
• said spinning being carried out at a temperature of 245.degree. to 270.degree. C., and a spinning draw down of 1:20 to 1:100;
• (b) cooling the filaments in a quenching shaft by means of turbulence-free air flowing perpendicularly to the direction of the filaments at a speed of 0.4 to 0.8 m/sec.;
• (c) coating the cooled filaments with an oil layer in the amount of at least 0.5% relative to the filament weight by means of an oil in water emulsion;
• (d) drawing the filaments between two heated roller systems, the temperature of the first system lying in the range of 30.degree. C. above or below the glass transition temperature, and that of the second system being at least 100.degree. C. higher, the stretching ratio being high enough that the break elongation of the finished filaments is not in excess of 45%;
• (e) feeding the drawn filaments from the second roller system at a speed of at least 1800 m/min. to a texturing unit, in which the filaments are blown and deformed in three dimensions with air having a temperature at least as high as that of said second roller system;
• (f) discharging the filaments from the texturing unit to a cooling unit for a residence time sufficient to cool the filaments below the glass transition temperature;
• (g) removing the filaments from said cooling unit by means of an unheated, third roller system, operating at a speed of at least 10% lower than that of said second roller system;
• (h) controlling the process conditions of stage (a) to (g) in such a manner that the intrinsic viscosity in stage (j) is at maximum 5% lower than that in stage (a);
• (i) intermingling the filaments by means of an air-blowing nozzle at an air pressure sufficient to attain an entangling node number of at least 12 per meter;
• and
• (j) winding up the filaments.