Patent ID: 7662474

Claim:
A flame-retarded composite yarn comprising a core and a plastic sheath comprising a halogen-free fire retarded composition, consisting of at least one acrylic resin and an intumescent agent that are dispersed in a plasticizing medium, obtained by the process wherein: a) a die suitable for passage of the core of said yarn is used; b) the plastic sheath comprising a halogen-free fire retarded composition is used in an ungelled plastisol state; c) the core of the yarn is passed through said die, with a peripheral distribution of the plastisol around said core; d) rheological properties of the plastisol at a shear rate of the die, at least equal to 20,000 s −1 , are adapted by formulating said ungelled plastisol comprising a plasticizing medium comprising predominantly an organic phosphate and a phthalate, so that at low shear rate, at most equal to 400 s −1 , it exhibits a Newtownian behaviour, with a viscosity of less than or equal to 6,000 mPa·s, measured with a Brookfield RVT viscometer at 20 rpm, and at high shear rate, at least equal to 10,000 s −1 , it exhibits a pseudoplastic behaviour; and e) the gelling of the fire-retarded composition is carried out, wherein the plastic sheath is halogen free.