Continuous processes for making composite fibers

Abstract

The present invention relates to continuous processes for making composite fibers from aramid polymers. The processes produce fibers that are useful in a variety of applications, including reinforcing elastomeric materials.

1 . A process for making a composite fiber, comprising continuously combining an anisotropic solution of an aramid polymer and an isotropic solution of a flexible chain polymer to form a combined polymer solution; mixing the combined polymer solution by passing the combined polymer solution through at least one static mixer to form a mixed combined polymer solution; and forming a composite fiber from the mixed combined polymer solution.  
   
   
       2 . The process of  claim 1 , wherein the anisotropic solution of an aramid polymer comprises para-aramid.  
   
   
       3 . The process of  claim 2 , wherein the anisotropic solution of an aramid polymer comprises greater than 18 weight percent para-aramid, based on the total weight of the anisotropic solution.  
   
   
       4 . The process of  claim 3  wherein the anisotropic solution of an aramid polymer comprises, as a solvent, sulfuric acid.  
   
   
       5 . The process of  claim 1  wherein the anisotropic solution of an aramid polymer comprises, as a solvent, sulfuric acid.  
   
   
       6 . The process of  claim 1  wherein the isotropic solution of a flexible chain polymer comprises a polymer selected from: PVP, PVP/VA, PEKK, nylon 6, nylon 6,6, nylon 6,12, MPD-I, MPD-I/T, and polyaniline.  
   
   
       7 . The process of  claim 6  wherein the isotropic solution of a flexible chain polymer comprises PVP.  
   
   
       8 . The process of  claim 6  wherein the isotropic solution of a flexible chain polymer comprises 5 to 25 weight percent of polymer based on the total weight of the isotropic polymer solution.  
   
   
       9 . The process of  claim 6  wherein the solution comprises, as a solvent, an acid selected from H 2 SO 4 , CISO 3 H, and FSO 3 H.  
   
   
       10 . The process of  claim 7  wherein the solution comprises, as a solvent, sulfuric acid.  
   
   
       11 . The process of  claim 10  wherein the solution is mixed to a degree sufficient to produce an average droplet size of 1.5 to 12 percent of the diameter of the composite fiber.  
   
   
       12 . The process of  claim 1  wherein the composite fiber comprises 80 to 99 weight percent aramid and 1 to 20 weight percent polymer from the isotropic solution of a flexible chain polymer based on the total weight of the composite fiber.  
   
   
       13 . An article comprising a composite fiber produced by the method of  claim 1  or  12 .