Patent ID: 7566496

Claim:
A 3-D crimp polyethylene terephthalate multifilament prepared by spinning a polyethylene terephthalate polymer which contains 90 mol % or more of ethylene terephthalate as a repeating unit, the 3-D crimp polyethylene terephthalate multifilament having an intrinsic viscosity of 0.4 to 1.0 and containing 0.05 to 5 wt % of a phosphorus-based flame retardant based on a phosphorus atom which is a compound represented by the following Formula (1) or Formula (2) Formula (1): wherein R 1 and R 2 are hydrogen atoms, or the same or different radicals containing a ω-hydroxyl group having 2 to 4 carbon atoms, and n is an integer ranging from 1 to 5, Formula (2): wherein the 3-D crimp polyethylene terephthalate multifilament has a stress-strain curve that (a) it elongates less than 5.0% when subjected to an initial stress of 1.0 g/d, (b) it has an initial modulus of 20 to 60 g/d, (c) it elongates at least 20% when subjected to a stress region of 1.0 to 2.5 g/d and (d) it elongates from a tensile strength of at least 3.0 g/d to the tensile strength at break.