Dyed sheath/core fibers and methods of making same

Abstract

Dyeable and dyed filaments have a core and a sheath which entirely surrounds the core. The core is formed of a core polymer which is susceptible to dyeing by a dye bath chemical, while the sheath is formed of a sheath polymer which is resistant to dyeing by the dye bath chemical. When the filament is brought into contact with a dye bath containing the dye chemical, the dye chemical in the dye bath will physically diffuse or migrate through the sheath polymer to cause the core polymer to be dyed a color of the dye bath chemical, while the sheath polymer is substantially undyed thereby.

What is claimed is:  
     
         1 . A method of making a dyed sheath/core filament having an essentially undyed sheath and a dyed core which is surrounded entirely by said sheath, said method comprising the steps of: 
 (a) forming a sheath/core filament from a sheath polymer that is resistant to dyeing by dyes in a dye bath, and a core polymer that is susceptible to dyeing by the dyes in the dye bath    (b) bringing the sheath/core filament into contact with a dye bath; and    (c) allowing the dyes in the dye bath to physically diffuse or penetrate through the sheath to dye the core while the sheath remains substantially undyed.    
     
     
         2 . The method of  claim 1 , wherein step (a) is practiced to form a trilobal filament  
     
     
         3 . The method of  claim 1 , wherein the filament contains less than about 10 wt. % of the sheath polymer.  
     
     
         4 . The method of  claim 3 , wherein the filament contains between about 90 wt. % to about 97 wt. % of the core polymer, and between about 3 wt. % to about 10 wt. % of the sheath polymer.  
     
     
         5 . The method of  claim 4 , wherein the core polymer is a nylon having an amine end group content (AEG) of between about 10 meq/kg to about 100 meq/kg, and wherein the sheath polymer is a nylon having an AEG of less than about 10 meq/kg.  
     
     
         6 . The method of  claim 5 , wherein the nylon sheath polymer has an AEG content of less than about 5 meq/kg.  
     
     
         7 . The method of  claim 6 , wherein the nylon sheath polymer is a nylon-6, 12 homopolymer.  
     
     
         8 . The method of  claim 1 , wherein the core is a nylon polymer which is at least one selected from the group consisting of nylon-6, nylon-12, nylon-11, nylon-6/6, nylon-6/10 and copolymers and blends thereof.  
     
     
         9 . The method of  claim 8 , wherein the core nylon polymer has an amino end group (AEG) content of between about 10 meq/kg and about 100 meq/kg.  
     
     
         10 . A dyeable sheath/core filament comprising a sheath polymer which is resistant to, and thereby essentially undyed by, dyes in a dye bath, and a core polymer entirely surrounded by the sheath which is susceptible to dyeing by the dyes in the dye bath.  
     
     
         11 . The filament of  claim 10 , which is a trilobal filament  
     
     
         12 . The filament of  claim 10 , having less than about 10 wt. % of the sheath polymer.  
     
     
         13 . The filament of  claim 12 , which has between about 90 wt. % to about 97 wt. % of the core polymer, and between about 3 wt. % to about 10 wt. % of the sheath polymer.  
     
     
         14 . The filament of  claim 13 , wherein the core polymer is a nylon having an amine end group content (AEG) of between about 10 meq/kg to about 100 meq/kg, and wherein the sheath polymer is a nylon having an AEG of less than about 10 meq/kg.  
     
     
         15 . The filament of  claim 14 , wherein the nylon sheath polymer has an AEG content of less than about 5 meq/kg.  
     
     
         16 . The filament of  claim 15 , wherein the nylon sheath polymer is a nylon-6, 12 homopolymer.  
     
     
         17 . The filament of  claim 10 , wherein the core is a nylon polymer which is at least one selected from the group consisting of nylon-6, nylon-12, nylon-11, nylon-6/6, nylon-6/10 and copolymers and blends thereof.  
     
     
         18 . The filament of  claim 17 , wherein the core nylon polymer has an amino end group (AEG) content of between about 10 meq/kg and about 100 meq/kg.  
     
     
         19 . A dyed filament made by the method of any one of claims  1 - 9 .  
     
     
         20 . A dyed filament having a core and a sheath which surrounds entirely said core, wherein said core is formed of a core polymer which is susceptible to dyeing by a dye bath chemical, and said sheath is formed of a sheath polymer which is resistant to dyeing by said dye bath chemical, and wherein said filament is dyed such that said dye bath chemical physically diffuses or migrates through said sheath polymer to cause the core polymer to be dyed a color of the dye bath chemical, while the sheath polymer is substantially undyed thereby.