Polyester fibers, their production and their use

Abstract

Described are fibers comprising aliphatic-aromatic polyester and non-layered platelet-shaped particles selected from the group of inorganic oxides, hydroxides, carbonates, bicarbonates, nitrides and carbides, having a thickness in the range from 20 nm to not more than 100 nm and an aspect ratio of not more than 20:1. The polyester fibers possess excellent bending fatigue resistance, give distinctly reduced abrasion and are useful for producing screens or other industrial fabrics.

1 . A fiber comprising aliphatic-aromatic polyester and non-layered platelet-shaped particles selected from the group of inorganic oxides, hydroxides, carbonates, bicarbonates, nitrides and carbides, having a thickness in the range from 20 nm to not more than 100 nm and an aspect ratio of not more than 20:1.  
   
   
       2 . The fiber according to  claim 1  wherein the polyester comprises structural repeat units derived from an aromatic dicarboxylic acid and an aliphatic and/or cycloaliphatic diol, especially polyethylene terephthalate repeat units alone or combined with other structural repeat units derived from alkylene glycols and aliphatic dicarboxylic acids.  
   
   
       3 . The fiber according to  claim 1  wherein the aliphatic-aromatic polyester has a free carboxyl group content of not more than 3 meq/kg.  
   
   
       4 . The fiber according to  claim 3  comprising a hydrolysis stabilizer for blocking free carboxyl groups, preferably at least one carbodiimide and/or at least one epoxy compound.  
   
   
       5 . The fiber according to  claim 1  wherein the non-layered platelet-shaped particles are not more than 80 nm and in particular from 20 to 60 nm in thickness.  
   
   
       6 . The fiber according to  claim 1  wherein the non-layered platelet-shaped particles are oxides of magnesium, of calcium, of strontium, of aluminum, of gallium, of indium, of titanium, of zirconium, of hafnium, of scandium, of yttrium, of silicon, of germanium, of tin or mixed oxides of these metals or semimetals.  
   
   
       7 . The fiber according to  claim 1  wherein the non-layered platelet-shaped particles are carbonates of magnesium, of calcium or of strontium.  
   
   
       8 . The fiber according to  claim 1  wherein the non-layered platelet-shaped particles are carbides of aluminum, of gallium, of indium, of silicon, of germanium or of tin.  
   
   
       9 . The fiber according to  claim 1  wherein the non-layered platelet-shaped particles are nitrides of aluminum, of gallium, of indium, of silicon, of germanium or of tin.  
   
   
       10 . The fiber according to  claim 1  wherein the non-layered platelet-shaped particles are selected from the group consisting of aluminum oxide, aluminum nitride, silicon dioxide, zirconium dioxide, silicon carbide, silicon nitride, yttrium oxide or calcium carbonate.  
   
   
       11 . The fiber according to  claim 10  wherein the non-layered platelet-shaped particles are selected from the group consisting of aluminum oxide or calcium carbonate.  
   
   
       12 . The fiber according to  claim 1  whose content of non-layered platelet-shaped particles is in the range from 0.1% to 5% by weight and preferably in the range from 1% to 2% by weight, based on the mass of the fiber.  
   
   
       13 . The fiber according to  claim 1  which, as well as the aliphatic-aromatic polyester, comprises from 0.1% to 5% by weight and preferably from 0.5% to 2% by weight, based on the total mass of the polymers, of polycarbonate.  
   
   
       14 . The fiber according to  claim 1  which is transparent.  
   
   
       15 . The fiber according to  claim 1  which is a monofilament.  
   
   
       16 . The fiber according to  claim 1  incorporated into a screen or conveyor belt.  
   
   
       17 . The fiber according to  claim 1  incorporated into a wire screen intended for use in the dry end of papermaking machines.  
   
   
       18 . A process for producing the fibers according to  claim 1 , the process comprising the steps of: 
 i) mixing polyester pellet with non-layered platelet-shaped particles selected from the group of inorganic oxides, hydroxides, carbonates, bicarbonates, nitrides and carbides having a thickness in the range from 20 nm to not more than 100 nm and an aspect ratio of not more than 20:1,    ii) extruding the mixture comprising polyester and non-layered platelet-shaped particles through a spinneret die,    iii) withdrawing the resulting filament, and    iv) optionally drawing and/or relaxing the resulting filament.    
   
   
       19 . The process according to  claim 18  wherein the polyester fiber is subjected to single or multiple drawing.  
   
   
       20 . The process according to  claim 18  wherein the polyester fiber is produced using a polyester produced by solid state condensation.  
   
   
       21 . A process for producing the fibers according to  claim 1 , the process comprising the steps of: 
 i) feeding an extruder with polyester pellet mixed before or during the polycondensation with polyester pellet with non-layered platelet-shaped particles selected from the group of inorganic oxides, hydroxides, carbonates, bicarbonates, nitrides and carbides, having a thickness in the range from 20 nm to not more than 100 nm and an aspect ratio of not more than 20:1,    ii) extruding the mixture comprising polyester and non-layered platelet-shaped particles through a spinneret die,    iii) withdrawing the resulting filament, and    iv) optionally drawing and/or relaxing the resulting filament.    
   
   
       22 . In a process for making polyester monofilament, the improvement comprising providing high abrasion resistance by incorporating a non-layered platelet-shaped particles selected from the group of inorganic oxides, hydroxides, carbonates, bicarbonates, nitrides and carbides, having a thickness in the range from 20 nm to not more than 100 nm and an aspect ratio of not more than 20:1.