Patent ID: 7654071

Claim:
A composite fiber comprising a polyester component and a polyamide component bound in a side-by-side or eccentric core-in-sheath structure, in which the polyester component is a modified polyester having an intrinsic viscosity (IV) of 0.30-0.43 and comprising 5-sodiumsulfoisophthalic acid copolymerized in an amount of 2.0-4.5 molar % based on the acid component, and which composite fiber exhibits a percentage of crimp DC of 1.3-15.0% after the composite fiber is treated in boiling water for 30 minutes under a load of 1.76×10 −3 cN/dtex, and then dry heat treated for 30 minutes at 100° C. under a load of 1.76×10 −3 cN/dtex for stabilization of the crimps and further dry heat treated for one minute at 160° C. under a load of 1.76×10 −3 cN/dtex, a percentage of crimp HC of 0.5-10% after the crimped composite fiber is immersed in water at 20-30° C. for 10 hours, and a difference ΔC between the percentages of crimp DC and HC of 0.5-7.0%, as defined represented by the following equation: Δ C (%)= DC (%)− HC (%).