Process for spinning uhmwpe, uhmwpe multifilament yarns produced thereof and their use

Abstract

Gel-spinning processes for producing a high tensile strength ultra high molecular weight polyethylene (UHMWPE) multifilament yarn comprising ultra-low dtex filaments, include applying a draw ratio DR fluid to fluid filaments obtained by spinning a solution of UHMWPE through a spinneret and into an air gap, is at least 450, wherein DR fluid =DR sp ×DR ag , the DR sp and DR ag being the draw ratios in the spinholes and in the air gap, respectively; and provided that DR ag is at least 30. The UHMWPE multifilament yarns produced thereof were characterized by a tensile strength of at least 3.5 GPa and contained filaments having a dtex of at most 0.5. The invention further relates to products comprising said yarns, e.g. fabrics, medical devices and composite and ballistic articles.

1 . An ultra high molecular weight polyethylene (UHMWPE) multifilament yarn, wherein the UHMWPE has an intrinsic viscosity as measured on solution in decalin at 135° C. of at least 3 dl/g and at most 40 dl/g, and the yarn has a tensile strength of 3.5-5.5 GPa and comprises filaments of 0.06-0.5 dtex. 
     
     
         2 . The yarn according to  claim 1 , wherein the yarn has a tensile strength of 4.0-5.5 GPa. 
     
     
         3 . The yarn according to  claim 1 , wherein the yarn has a tensile modulus of at least 100 GPa. 
     
     
         4 . The yarn according to  claim 1 , wherein the yarn has a tensile modulus of at least 130 GPa. 
     
     
         5 . The yarn according to  claim 1 , wherein the yarn comprises filaments of 0.09 -0.45 dtex. 
     
     
         6 . The yarn according to  claim 1 , wherein the yarn comprises filaments of 0.09-0.3 dtex. 
     
     
         7 . The yarn according to  claim 1 , wherein the UHMWPE has an intrinsic viscosity of at least 5 dl/g. 
     
     
         8 . The yarn according to  claim 1 , wherein the UHMWPE is a linear polyethylene containing up to 5 mol-% of one or more comonomers, such as alkenes like propylene, butene, pentene, 4-methylpentene or octene, and less than 3 wt-% of customary additives, such as anti-oxidants, thermal stabilizers, colorants, flow promoters, etc. 
     
     
         9 . The yarn according to  claim 1 , wherein the the UHMWPE contains 0.2-20 per 1000 carbon atoms of C1-C4 alkyl groups as side chains. 
     
     
         10 . The yarn according to  claim 1 , wherein the yarn comprises residual spinning solvent in an amount of below 800 ppm. 
     
     
         11 . The yarn according to  claim 1 , wherein the yarn comprises residual spinning solvent in an amount of below 300 ppm. 
     
     
         12 . The yarn according to  claim 1 , wherein the yarn comprises residual spinning solvent in an amount of below 100 ppm. 
     
     
         13 . A semi-finished or end-use article containing the yarn according to  claim 1 . 
     
     
         14 . The semi-finished or end-use article according to  claim 13 , selected from the group consisting of ropes, fishing lines, fishing nets, ground nets, cargo nets, cargo curtains, kite lines, dental floss, tennis racquet strings, canvas, webbings, battery separators, capacitors, pressure vessels, hoses, automotive equipment, power transmission belts, building construction materials, cut and stab resistant articles, incision resistant and abrasion resistant articles, protective gloves, skis, helmets, kayaks, canoes, bicycles, boat hulls and spars, speaker cones, high performance electrical insulation, and radomes. 
     
     
         15 . A medical device containing the yarn according to  claim 1 . 
     
     
         16 . The medical device according to  claim 15 , selected from the group consisting of a surgical repair product, a suture, a medical cable, a vascular graft, a mesh, and an implantable valve. 
     
     
         17 . A composite article containing at least one monolayer that comprises the UHMWPE yarn according to  claim 1 . 
     
     
         18 . A multifilament ultrahigh molecular weight polyethylene (UHMWPE) yarn having a tensile strength of 3.5-5.5 GPa and comprising filaments of 0.06-0.5 dtex which is obtained by a gel-spinning process comprising the steps of:
 a) preparing a solution of an UHMWPE in a solvent;   b) spinning through a spinneret and into an air gap the solution of step a) to form fluid filaments, the spinneret containing multiple spinholes and wherein each spinhole comprises at least one zone with a gradual decrease in diameter and wherein the downstream diameter of the spinhole from which the solution is issued in the air gap is between 0.1 and 1.5 mm;   c) drawing the fluid filaments with a fluid draw ratio DR fluid =DR sp ×DR ag , wherein DR sp  and DR ag  are the draw ratios in the spinholes and in the air gap, respectively, wherein the fluid filaments are drawn with a fluid draw ratio DR fluid  of 450-1200, provided that DR ag  is at least 50, and with an overall draw ratio DR overall  of 12000-50000, wherein DR overall =DR fluid ×DR gel ×DR solid  where DR fluid  is the fluid draw ratio of the fluid filaments, DR gel  is a draw ratio of the gel filaments and DR solid  is a draw ratio of the solid filaments;   d) cooling the fluid filaments to form solvent-containing gel filaments; and   e) removing at least partly the remaining solvent from the gel filaments to form solid filaments, before, during or after drawing the solid filaments with a draw ratio DR solid  of at least 4 and thereby obtain a UHMWPE yarn having a tensile strength of 3.5-5.5 GPa comprised of UHMWPE filaments of 0.06-0.5 dtex.   
     
     
         19 . The yarn according to  claim 18 , wherein the yarn has a tensile strength of 4.0-5.5 GPa. 
     
     
         20 . The yarn according to  claim 18 , wherein the yarn has a tensile modulus of at least 100 GPa. 
     
     
         21 . The yarn according to  claim 18 , wherein the yarn comprises filaments of 0.09-0.45 dtex. 
     
     
         22 . The yarn according to  claim 21 , wherein the filaments are 0.09-0.3 dtex.