Abstract A polyamide fiber excellent in strength, which is characterized by being made of a polyamide having a relative viscosity of not less than 3.5 (measured on a 96% by weight sulfuric acid solution having a polyamide concentration of 10 mg/ml at 20° C.), showing an index of birefringence (Δn) of not less than 50×10 -3 and having the following relationship between the break strength and the break elongation: Break strength (g/d)×(Break elongation (%)) 1/2 ≧46.0, the index of birefringence in the section of fiber satisfying the following relationship: Δn.sub.A -Δn.sub.B ≧0.5×10.sup.-3 (wherein Δn A is the index of birefringence of fiber at the position of r/R=0.9, Δn B is the index of birefringence of fiber at the position of r/R=0.0, R is the radius of the section of fiber and r is the distance from the central axis of the section of fiber).
A polyamide fiber excellent in strength, comprising a polyamide having a relative viscoisty of not less than 3.5 measured on a 96% by weight sulfuric acid solution having a polyamide concentration of 10 mg/ml at 20° C. and an index of birefringence (Δn) of not less than 50×10 -3 , wherein: the fiber long-period spacing value at length by small angle X-ray diffraction is not less than 100 Å; the break strength is not less than 11.0 g/d; the break strength (g/d)×(break elongation (%)) 1/2 ≧46.0; and the index of birefringence in the section of the fiber satisfies the following relation: Δn.sub.A -Δn.sub.B ≧0.5×10.sup.-3, where: Δn A =the index of birefringence of fiber at the position of r/R=0.9; Δn B =the index of birefringence of fiber at the position of r/R=0.0; R=the radius of the section of fiber; and r=the distance from the central axis of the section of fiber
Claim 2
Dependent Claim
150 words
A polyamide fiber excellent in strength, comprising a polyamide having a relative viscoisty of not less than 3.5 measured on a 96% by weight sulfuric acid solution having a polyamide concentration of 10 mg/ml at 20° C. and an index of birefringence (Δn) of not less than 50×10 -3 , wherein: the fiber long-period spacing value at length by small angle X-ray diffraction is not less than 100 Å; the break strength is not less than 11.0 g/d; the break strength (g/d)×(break elongation (%)) 1/2 ≧46.0; and the index of birefringence in the section of the fiber satisfies the following relation: Δn.sub.A -Δn.sub.B ≧0.5×10.sup.-3, where: Δn A =the index of birefringence of fiber at the position of r/R=0.9; Δn B =the index of birefringence of fiber at the position of r/R=0.0; R=the radius of the section of fiber; and r=the distance from the central axis of the section of fiber
Claim 3
Dependent Claim
27 words
The polyamide fiber according to claim 1 which comprises polycapramide in an amount of not less than 75% by weight on the basis of the polyamide fiber.
Claim 4
Dependent Claim
19 words
The polyamide fiber according to claim 1, wherein the relative viscosity of the polyamide is not less than 4.0.
Claim 5
Dependent Claim
18 words
The polyamide fiber according to claim 1, of which the knot strength is not less than 8.0 g/d.
Claim 6
Dependent Claim
17 words
The polyamide fiber according to claim 1, of which the break elongation is not less than 15%.