Method for producing fine monofilaments consisting of polypropylene, fine monofilaments consisting of polypropylene and the use thereof

Abstract

In a process for producing fine monofilaments having improved abrasion resistance from a polypropylene having a melt flow index (MFI)<SUB>230° C./2.16 kg </SUB>of 2-16 g/10 min at a linear density of 5-20 dtex (0.027 mm-0.053 mm), a compound consisting of 80 to 99.9% by weight of chips and 20 to 0.1% by weight of an additive is added to the extruder, the melt is spun at a speed of at least 1200 m/min, the fibre is cooled in an air bath at room temperature, supplementarily stretched at a temperature of 110-150° C. to a linear density of 5-20 dtex and wound up. The monofilaments comprising a polypropylene having a melt flow index (MFI)<SUB>230° C./2.16 kg </SUB>of 2-16 g/10 min, having improved abrasion resistance, and a linear density of 5-20 dtex (0.027 mm-0.053 mm) and an abrasion resistance score <=2. The monofilaments have a tenacity of at least 48 cN/tex and an elongation at break of less than 45% for a mechanical constant (constante méchanique) of at least 295 cN/tex and a specific work to break value of more than 61.5 cN.cm/dtex. The fine monofilaments according to the invention are useful for producing woven screen fabrics for filtration and screen printing without abrasion deposits.

1 . Process for producing fine monofilaments having improved abrasion resistance from a polypropylene having a melt flow index (MFI)  230° C./2.16  kg of 2-16 g/10 min, comprising adding a compound comprising 80-99.9% by weight of chips and 20 to 0.1% by weight of an additive to the extruder, the melt is spun at a speed of at least 1200 m/min, the fibre is cooled in an air bath at room temperature, supplementarily stretched at a temperature of 110 to 150° C. to a linear density of 5-20 dtex (0.027 mm-0.053 mm) and wound up.  
     
     
         2 . Process according to  claim 1 , wherein the additive used is selected from the group consisting of modified polyolefins and aliphatic diesters.  
     
     
         3 . Process according to  claim 1 , wherein the additive used is 4.5 to 15% by weight of a polyolefin from polypropylene/polyethylene having a melting point >140° C.  
     
     
         4 . Process according to  claim 1 , wherein the additive used is 3-10% by weight of an impact modifier.  
     
     
         5 . Process according to  claim 1 , wherein the additive used is 0.1-0.2% by weight of a plasticizer.  
     
     
         6 . Process according to  claim 1 , wherein the additive used is 0.05 to 1.0% by weight of a lubricant.  
     
     
         7 . Process according to  claim 1 , wherein the additive used is 0.01-1.0% by weight of fillers.  
     
     
         8 . Process according to  claim 1 , wherein the additive used is a compounded combination of impact modifier, plasticizer, fillers, lubricants and heat stabilizers.