Patent ID: 7597722

Claim:
A single-dyeing-step process for manufacturing a fabric having distinctive and sharp differentially colored patterns or designs, which process comprises the steps of: i) producing a first polyamide having an increased amount of amino end-groups for enhanced anionic dyeing, said first polyamide having a concentration of amine groups in the range of 70-150 meq/kg; ii) producing a second polyamide, said second polyamide having a concentration of carboxyl end-groups in the range of 60-120 meq/kg, and a concentration of sulfonate groups in the range of 100-150 meq/kg; iii) reacting said second polyamide with a blocking agent selected from caprolactones and butyrolactones, to reduce the content of amino end-groups of said second polyamide and replace them with hydroxylated groups, and thus simultaneously reduce anionic dyeing and improve cationic dyeing of said second polyamide; iv) producing a first yarn from said first polyamide and a second yarn from said second polyamide, said second yarn having a concentration of amine groups in the range of 5-18 meq/kg; v) making a fabric having first surface areas defined by said first yarn and second surface areas defined by said second yarn; and vi) chemically dyeing said fabric in a dyeing bath comprising at least one anionic (acid) dyestuff and at least one cationic (basic) dyestuff, whereby said first yarn and therefore said first surface areas are dyed predominantly by said anionic dyestuff, and said second yarn and therefore said second surface areas are dyed predominantly by said cationic dyestuff; thereby minimizing cross-staining of said two yarns and achieving said sharp colored patterns or designs.