Conductive soil-repellent core-sheath fiber of high chemical resistance, its preparation and use

Abstract

Conductive soil-repellent core-sheath fiber of high chemical resistance, its preparation and use Described is a melt-spun fiber having a core-sheath structure and a high tensile strength whose core contains a synthetic thermoplastic polymer which is not a fluoropolymer and whose sheath contains at least one melt-spinnable fluoropolymer and particles comprising electroconductive material. The fibers of the invention are useful especially in the form of monofilaments for producing textile fabrics for industrial applications

What is claimed is:  
     
         1 . A melt-spun fiber having a core-sheath structure and a tensile strength of at least 15 cN/tex whose core contains a synthetic thermoplastic polymer which is not a fluoropolymer and whose sheath contains at least one melt-spinnable fluoropolymer and particles comprising electroconductive material.  
     
     
         2 . The melt-spun fiber of  claim 1 , wherein the synthetic thermoplastic polymer of the core is a polyamide and especially a polyester.  
     
     
         3 . The melt-spun fiber of  claim 2 , wherein the polyester is a polyethylene terephthalate.  
     
     
         4 . The melt-spun fiber of  claim 2 , wherein the polyester is a liquid-crystalline polyester.  
     
     
         5 . The melt-spun fiber of  claim 1 , wherein the melt-spinnable fluoropolymer is a copolymer of tetrafluoroethylene with at least one alpha-olefin, preferably ethylene.  
     
     
         6 . The melt-spun fiber of  claim 1 , wherein the melt-spinnable fluoropolymer is a polyvinylidene fluoride.  
     
     
         7 . The melt-spun fiber of  claim 1 , wherein the sheath contains up to 50% by weight and preferably 2 to 15% by weight of electroconductive particles.  
     
     
         8 . The melt-spun fiber of  claim 6 , wherein the sheath contains between 2% by weight and 15% by weight and especially between 4% by weight and 9% by weight of electroconductive particles.  
     
     
         9 . The melt-spun fiber of  claim 1 , wherein the particles comprising electroconductive material consist of carbon, metals or metal alloys and are especially carbon black or graphite.  
     
     
         10 . The melt-spun fiber of  claim 1  which is a filament, especially a monofilament.  
     
     
         11 . A process for preparing the melt-spun core-sheath fiber of  claim 1 , comprising the measures of: 
 i) selecting a first polymer which is a synthetic thermoplastic polymer and not a fluoropolymer and which has a first melting point,    ii) selecting a second polymer which contains particles comprising electroconductive material and which is a melt-spinnable fluoropolymer which has a second melting point at least 20° C. below the first melting point,    iii) coextruding the first polymer and the second polymer through a heterofilament spinneret at a spinning temperature above the first melting point to form a bicomponent fiber having a core comprising the first polymer and a sheath comprising the second polymer and    iv) drawing the produced core-sheath filament to increase the tensile strength.    
     
     
         12 . The use of melt-spun core-sheath fibers of  claim 1  for producing industrial wovens.  
     
     
         13 . The use of  claim 12 , wherein the industrial woven is a paper machine wire, a filter cloth, a screen printing cloth, a conveyor belt or a reinforcing ply.