Because the macromolecular structure, melting point and properties of PBT fiber have many similarities with PA6, the spinning process conditions are very similar to PA6. (1) The chip drying and pre-crystallization temperature and time are shorter than those of PET. The pre-crystallization temperature is generally 100-120°C, about 10 minutes. However, the drying time is longer. If filling drying is used, it will take 12 to 20 hours. The drying temperature of the slices should not be higher than 145°C. (2) Spinning temperature, spinning pressure, cooling and blowing conditions are almost similar to those of PA6. The spinning temperature is 250～290℃ (depending on the high and low intrinsic viscosity). Spinning pressure is 10-20MPa. Cooling blowing wind speed is 0.2～0.5m/s, wind temperature is 22～28℃, relative humidity is 65%. (3) The winding speed is above 1100m/min. Other spinning process conditions are the same as spinning PA6.
PBT fiber has good elasticity and normal pressure boiling dyeability of disperse dyes, while maintaining the washability, crispness and dimensional stability of polyester, and its elasticity is between spandex and nylon. PBT filament modified by blending, copolymerization, compounding and other means can further improve its performance and reduce cost. It can be used to process silk fabrics, yarn-dyed fabrics, warp knitted fabrics and decorative fabrics; high-elastic yarns are used to make sportswear, elastic bandages, hosiery and elastic labor cloth.