Process for the manufacture of a fiber comprising meta-aramid

Abstract

A process for manufacturing a fiber including meta-aramid having a breaking tenacity of at least 300 mN/tex including the steps of preparing a spin dope including meta-aramid and sulfuric acid having a concentration of at least 80 wt % and passing the spin dope through a spinneret into a coagulation bath, wherein the spin dope has a meta-aramid concentration of at least 10 wt %. The invention also pertains to a meta-aramid fiber, a multifilament yarn, a textile sheet and protective clothing.

1 . A process for manufacturing a fiber comprising meta-aramid having a breaking tenacity of at least 300 mN/tex comprising the steps of preparing a spin dope comprising meta-aramid and sulfuric acid having a concentration of at least 80 wt % and passing the spin dope through a spinneret into a coagulation bath, wherein the spin dope has a meta-aramid concentration of at least 10 wt %. 
     
     
         2 . The process according to  claim 1 , wherein the fiber comprising meta-aramid has a breaking tenacity of at least 350 mN/tex. 
     
     
         3 . The process according to  claim 1 , wherein the spin dope has a meta-aramid concentration in the range of 10-30 wt %. 
     
     
         4 . The process according to  claim 1 , wherein the meta-aramid is co-poly(m-phenylene isophthalamide) comprising at most 5 molar % of aromatic moieties other than m-phenylene. 
     
     
         5 . The process according to  claim 1 , wherein the spin dope is prepared by mixing meta-aramid and sulfuric acid. 
     
     
         6 . The process according to  claim 1 , wherein the spin dope is prepared at a temperature in the range of 30 to 90° C. 
     
     
         7 . The process according to  claim 1 , wherein the spin dope is passed through a gaseous medium after exiting the spinneret and before entering the coagulation bath. 
     
     
         8 . The process according to  claim 7 , wherein the spin dope passes through a gaseous medium of a length in the range of 2 to 20 mm. 
     
     
         9 . The process according to  claim 1 , wherein the sulfuric acid has a concentration of at least 85 wt %. 
     
     
         10 . The process according to  claim 1 , wherein the fibers are heated in at least one heating step to a temperature in the range of 250 to 400° C., optionally followed by a further heating step at a temperature in the range of 250 to 400° C. 
     
     
         11 . A meta-aramid fiber having a breaking tenacity of at least 300 mN/tex, obtainable by the process according to  claim 1 . 
     
     
         12 . The meta-aramid fiber having breaking tenacity of at least 300 mN/tex and a sulfonic acid group content of at least 0.001 wt %. 
     
     
         13 . The meta-aramid fiber according to  claim 11 , having a breaking tenacity of at least 350 mN/tex. 
     
     
         14 . The meta-aramid fiber according to  claim 11  having an organic solvent content below 250 ppm. 
     
     
         15 . The meta-aramid multifilament yarn comprising the meta-aramid fiber of  claim 11 . 
     
     
         16 . The meta-aramid multifilament yarn according to  claim 15  wherein at least 50% of individual filaments have a round cross section such that the average ratio of [diameter of the minimum circumscribed circle] to [diameter of the maximum inscribed circle] is at most 1.3. 
     
     
         17 . A textile sheet comprising the meta-aramid fiber of  claim 11  and/or the meta-aramid multifilament yarn. 
     
     
         18 . A protective clothing comprising the textile sheet of  claim 17 .