Sulfur dye range and processes, and yarns and fabrics produced therefrom

Abstract

The present invention generally relates to sulfur dyeing of fabrics. In particular, a process is provided which provides a sulfur dyed yarn having reduced dye penetration and a white core. The process involves modification of existing sulfur dye ranges in order to more efficiently and in an environmentally improved method produce dyed fabrics. The process involves modifying the immersion time, temperature, pH, and/or dye oxidation of existing sulfur dye ranges. The resulting yarns may then be woven into fabrics used to produce garments.

What is claimed is: 
     
         1 . A method for dyeing a yarn with a sulfur dye, comprising the steps of
 a. providing a dye range comprising a scouring stage, a scour rinsing stage, at least a first sulfur dyeing stage, and a dye rinsing stage; and   b. modifying the operation of the dye range by at least one of the following steps to provide a modified dye range:
 i. performing the scouring stage in a single scour vat, 
 ii. reducing immersion time in the scouring stage to between 4 seconds and 18 seconds, 
 iii. reducing a wetting agent in the scouring stage to about 0.7 g/L to about 4 g/L, and 
 iv. adjusting immersion time of the yarn in a sulfur dyeing stage to about 3 seconds to 14 seconds. 
   
     
     
         2 . The method of  claim 1 , wherein step iv is about 3 seconds to 12 seconds on a rope style dye range. 
     
     
         3 . The method of  claim 1 , wherein step iv is about 6 seconds to 14 seconds on a slasher style dye range. 
     
     
         4 . The method of  claim 1 , wherein the sulfur dying stage occurs in a sulfur dye vat containing the sulfur dye maintained at a pH between about 11.7 and 13.1. 
     
     
         5 . The method of  claim 1 , wherein the scouring stage contains no caustic. 
     
     
         6 . The method of  claim 1 , wherein the scouring stage involves the use of a wetting agent at between about 0.5 g/L and 2.0 g/L. 
     
     
         7 . The method of  claim 1 , wherein minimal exposure to air is maintained when the yarn traverses from the dyeing stage to the dye rinsing stage. 
     
     
         8 . The method of  claim 1 , wherein step ii is accomplished by rethreading the yarn through the range. 
     
     
         9 . A method for dyeing a yarn with a sulfur dye, comprising steps of
 a. providing a dye range comprising a scouring stage, a scour rinsing stage, an air oxidation stage, at least a first sulfur dyeing stage, and a dye rinsing stage; and   b. modifying the dye range by at least one of the following steps to provide a modified dye range:
 i. adding sulfur dye to the scouring stage, 
 ii. reducing immersion time in the scour stage having the sulfur dye therein to about 3 to 14 seconds, 
 iii. exposing the yarn to no more than 25 seconds to air in the air oxidation stage, and 
 iv. immersing the yarns in a water vat after the dyeing stage so that the water oxidizes the sulfur dye and washes away loose dye. 
   
     
     
         10 . The method of  claim 9 , wherein step ii is about 3 seconds to 12 seconds on a rope style dye range. 
     
     
         11 . The method of  claim 9 , wherein step ii is about 6 seconds to 14 seconds on a slasher style dye range 
     
     
         12 . The method of  claim 9 , wherein the scour rinsing stage occurs in two scour rinse vats. 
     
     
         13 . The method of  claim 9 , wherein the yarn is rethreaded throughout the range. 
     
     
         14 . The method of  claim 9 , wherein the air oxidation stage lasts no more than 25 seconds. 
     
     
         15 . The method of  claim 9 , wherein the dye rinsing stage occurs in two dye rinse vats containing water. 
     
     
         16 . A method for dyeing a yarn with a sulfur dye, comprising steps of
 a. providing a dye range, said dye range includes a scouring stage, a scour rinsing stage, a dyeing stage, an oxidation stage, and a dye rinsing stage; and   b. modifying the dye range by at least one of the following steps to provide a modified dye range:
 i. adding sulfur dye to the scouring stage, 
 ii. reducing the air oxidation stage to no more than 25 seconds, and 
 iii. immersing the yarns in a water vat after the dyeing stage so that the water oxidizes the sulfur dye and washes away loose dye. 
   
     
     
         17 . The method of  claim 16 , wherein the modifying step further comprises reducing the dyeing stage to about 6 seconds to 14 seconds, when the range is a slasher style dye range. 
     
     
         18 . The method of  claim 16 , wherein the modifying step further comprises reducing the dyeing stage to about of 3 seconds to 12 seconds when the range is a rope style dye range. 
     
     
         19 . The method of  claim 16 , wherein the dye rinsing stage occurs in two dye rinse vats containing water. 
     
     
         20 . The method of  claim 19 , wherein the pH of the dye rinse vats is controlled with freshwater flow rates so that the pH does not exceed 11.5. 
     
     
         21 . The method of  claim 19 , wherein the modifying step further comprises reducing a wetting agent in the scouring stage to about 0.5 g/L to 2 g/L. 
     
     
         22 . A yarn dyed by the method of  claim 16 . 
     
     
         23 . A fabric, comprising: a plurality of the yarns of  claim 22  woven together in the warp and weft directions. 
     
     
         24 . A garment comprising: the fabric of  claim 23  sewn together with one or more other fabrics into a garment.