Dye range and processes, and yarns and fabrics produced therefrom

Abstract

The invention generally relates to fabric dyeing, such as fabric dyeing using indigo or sulphur dyes. A process is provided which provides a dyed yarn having reduced dye penetration and a white core. The process involves modification of existing sulfur dye ranges to more efficiently and in an environmentally improved method produce dyed fabrics. The modification involves one or more of i) using of a barrier compound to subsequent dye applications; ii) performing a scouring stage without a caustic agent; iii) bypassing scouring and/or scour rising; iv) using sodium bicarbonate to control the pH of dye tanks; v) reducing the dye concentration and increasing the number of dye vats; and vi) adding a sizing stage to the dye range. The invention also is directed to yarns dyed on dye ranges through use of the process, and fabrics formed from the dyed yarns.

What is claimed is: 
     
         1 . A method for dyeing a yarn, comprising the steps of
 a. providing a dye range comprising a scouring stage, a scour rinsing stage, a dyeing stage(s), and a dye rinsing stage; and   b. modifying the dye range by one or more of the following steps to provide a modified dye range:
 i. in the dyeing stage, immersing the yarn in a barrier compound before dyeing the yarn with a dye, wherein the barrier compound has a larger or the same mean particle size than the dye, 
 ii. performing the scouring stage with a wetting agent and without a caustic agent, 
 iii. eliminating the scouring stage and/or the scour rinsing stage, 
 iv. in the dyeing stage, adding sodium bicarbonate to dye vats of the dyeing stage, 
 v. when the dye is a sulphur dye, reducing a dye concentration in the dyeing stage and increasing a number of vats in the dyeing stage, 
 vi. adding a sizing stage to the dye range. 
   
     
     
         2 . The method of  claim 1 , wherein step i, the barrier compound is sulphur dye, sulphur compound, dimethylol dihydroxyethyleneurea (DMDHEU), high density polyethylene (HDPE), or combinations thereof. 
     
     
         3 . The method of  claim 2 , wherein the sulphur compound is colorless. 
     
     
         4 . The method of  claim 3 , wherein a concentration of the sulphur compound is 200-350 g/L. 
     
     
         5 . The method of  claim 2 , wherein the sulphur dye is at a concentration of 0.5-5 g/L. 
     
     
         6 . The method of  claim 1 , wherein step i includes reducing the temperature of a solution containing the barrier compound to 50-80° C. 
     
     
         7 . The method of  claim 1 , wherein step i includes reducing the pH of a solution containing the barrier compound to 11.0-12.5. 
     
     
         8 . The method of  claim 7 , wherein further comprising adding sodium bicarbonate to lower the pH. 
     
     
         9 . The method of  claim 1 , wherein step ii wherein the wetting agent concentration is 0.5 g/L-4.5 g/L. 
     
     
         10 . The method of  claim 1 , wherein step iii includes adding a wetting agent to dye vats in the dyeing stage or scour vats in the scouring stage. 
     
     
         11 . The method of  claim 10 , wherein the concentration of the wetting agent is 0.25-3.0 g/L. 
     
     
         12 . The method of  claim 1 , wherein step iii includes eliminating the scouring stage, but not the scour rinsing stage. 
     
     
         13 . The method of  claim 1 , wherein step iv includes adding sufficient sodium bicarbonate to reduce the pH of a solution in the dye vats to a pH of 12.3-13. 
     
     
         14 . The method of  claim 1 , wherein step v includes reducing the dye concentration to 150 g/L or less. 
     
     
         15 . The method of  claim 1 , wherein step v includes increasing the number of vats to three or more. 
     
     
         16 . The method of  claim 1 , wherein step vi includes adding one or more vats containing a sizing agent. 
     
     
         17 . The method of  claim 16 , wherein the sizing agent comprises a starch, carboxy methyl cellulose (CMC), polyvinyl alcohol (PVA), combinations thereof. 
     
     
         18 . The method of  claim 17 , wherein the starch is potato starch, corn starch, rice starch, tapioca starch, or combinations thereof. 
     
     
         19 . The method of  claim 1 , wherein a percent add-on of the sizing is 5-12%. 
     
     
         20 . A method for dyeing a yarn, comprising the steps of
 a. immersing the yarn in solution containing a barrier compound; and   b. dyeing the yarn, wherein the barrier compound has a larger or the same mean particle size than the dye.