Poly(arylene thioether-ketone) fibers and production process thereof

Poly(arylene thioether-ketone) fibers obtained by melt-spinning a thermoplastic material which comprises:

• (A) 100 parts by weight of a melt-stable poly(arylene thioether-ketone) having predominant recurring units of the formula ##STR9## wherein the --CO-- and --S-- are in the para position to each other, and having the following physical properties (a)-(c):
• (a) melting point, Tm being 310.degree.-380.degree. C.;
• (b) residual melt crystallization enthalpy, .DELTA. Hmc (420.degree. C./10 min) being at least 10 J/g, and melt crystallization temperature, Tmc (420.degree. C./10 min) being at least 210.degree. C., wherein .DELTA.Hmc (420.degree. C./10 min) and Tmc (420.degree. C./10 min) are determined by a differential scanning calorimeter at a cooling rate of 10.degree. C./min, after the poly(arylene thioether-ketone) is held at 50.degree. C. for 5 minutes in an inert gas atmosphere, heated to 420.degree. C. at a rate of 75.degree. C./min and then held for 10 minutes at 420.degree. C.;
• and
• (c) reduced viscosity being 0.3-2 dl/g as determined by viscosity measurement at 25.degree. C. and a polymer concentration of 0.5 g/dl in 98 percent by weight sulfuric acid;
• and optionally,
• (B) up to 50 parts by weight of at least one of thermoplastic resins, wherein said fibers are stretched to a draw ratio of from 1.2:1 to 8:1 and have the following physical properties:
• (a) density of portions of said poly(arylene thioether-ketone) being at least 1.34 g/cm.sup.3 at 25.degree. C.;
• (b) tensile strength being at least 10 kg/mm.sup.2 at 23.degree. C. or at least 3 kg/mm.sup.2 at 250.degree. C.;
• (c) tensile modulus being at least 100 kg/mm.sup.2 at 23.degree. C. or at least 30 kg/mm.sup.2 at 250.degree. C.;
• (d) tensile elongation being at least 5% at 23.degree. C.;
• and
• (e) heat shrinkage (220.degree. C./30 min) being at most 20%.