Polyamide fibers for airbag and method for producing same

Polyamide fibers for an airbag, wherein

• the size of the fibers is 200 dtex to 800 dtex, and
• the stress retention is 3.0% or greater, as determined by the following steps 1) to 6):
• 1) the fibers are immersed for 5 seconds in water at 20° C. and removed out, and subsequently anchored in a thermal shrinkage stress measuring device under an initial load of 0.4 mN/dtex;
• 2) a heating furnace is set to 130° C. and the fibers are placed in the heating furnace for 5 minutes and heated;
• 3) the fibers are removed out of the heating furnace and the temperature of the heating furnace is increased to 190° C., without releasing the anchoring that holds the fibers during that time, to maintain fixed lengths,
• 4) after the furnace has reached 190° C., the fibers are placed in the heating furnace for 3 minutes and heated, and the shrinkage stress at 3 minutes after heating is measured;
• 5) the fibers are removed from the heating furnace, and the shrinkage stress is measured at 3 minutes after removal;
• and
• 6) the stress retention is calculated by the following formula:
• Stress retention (%)={[Residual stress from step 5)]/[shrinkage stress from step 4)]}×100,
• where [shrinkage stress from step 4)] is the value of the shrinkage stress determined in step 4) minus the value of the initial load applied in step 1), and [residual stress from step 5)] is the value of the shrinkage stress determined in step 5) minus the value of the initial load applied in step 1).