Patent ID: 8003027

Claim:
Process for the preparation of polymer yarns from ultra high molecular weight homopolymers or copolymers, wherein the process comprises the following steps: (a1) preparing a suspension of a homopolymer or copolymer and a spinning or gelling solvent, of a non polar nature and having a long carbon atoms chain, in a vessel, followed by its transfer to the mixer, under continuous stirring and room temperature, under regular atmospheric or inert conditions, and at a weight of homopolymer or copolymer to solvent ratio from 2/98 to 30/70; wherein said homopolymer or copolymer has a monomodal, bimodal or multimodal molecular weight distribution, and is obtained from C 2+n monomers, wherein n varies from 0 to 2; (b1) feeding said homopolymer or copolymer suspension, under regular atmospheric or inert conditions, to an extruder; (c1) extruding the suspension with the formation of a gel, at a temperature in excess of 150° C., under regular atmospheric or inert conditions; (d1) spinning the gel, as obtained from the extrusion, in a spin block, so as to obtain non-stretched filaments with diameters of at least 1 mm, at a temperature in excess of 150° C., maintaining regular atmospheric or inert conditions; (e1) cooling the non-stretched filaments or yarns coming from the spin block, by immersion in a tank with a circulation system, wherein the renovation of cold water enters said tank at a spot directly opposite and aligned with the center of the filament bundle, guaranteeing a perfect homogeneity of the cooling system; (f1) taking up the non stretched filaments or yarns, prior to the gelling or spinning solvent extraction, on a perforated take-up spool, at a velocity in excess of 10 m/min; (g1) feeding the perforated spools, loaded with the non stretched filaments or yarns, in an extractor operating in batches, together with the feed of an organic extraction solvent, with a boiling point below 80° C.; (h1) extracting said non polar long chain solvent impregnated in the yarns loaded on the spools, in at least one stage, by means of the turbulent circulation of said organic solvent, in an ascending and transversal flow, the system operating with a residence time sufficient to achieve equilibrium concentration, at a temperature of at least 30° C. and a pressure of at least 196 kPa (2 kgf/cm 2 ); (i1) removing the spent organic solvent from the extractor, and later recovering the solvents in a solvent separation process; (j1) drying the non stretched filament bundles or yarns, loaded on the spools, inside the extractor, by means of a gaseous nitrogen stream, which is fed into the extractor in the same manner as the organic solvent, wherein the dry yarn has at most 4%, by weight, and preferably 0%, by weight, of the non polar long chain solvent; and (k1) stretching said dry yarns by means of a stretching system, said yarn having up to 4%, by weight, of the non polar solvent, in at least one stretching step, at a temperature in excess of 80° C.