Cost effective strategy for the synthesis of azo dyes by using cashew nut shell liquid (CNSL)

The synthesis and dyeing properties of two types of azo dyes are reported in this paper. The two types of dyes were obtained from coupling of amino cardanol with unsaturated anacardic acid [ACUSA (Aminocardanol unsaturated anacardic acid)] and saturated anacardic acid [ACSA (Aminocardanol saturated anacardic acid)] separately. Both, anacardic acid and aminocardanol were obtained from CNSL as their source material. ACSA dyes were solid and dark brown while ACUSA were gelatinous and dark red. The performance of both ACUSA and ACSA dyes was moderate on textile fabrics with varying cotton content. The dyeing efficiency of the ACUSA was better than that of ACSA. ACUSA dyes had 33% total extent of fixation on the 100% cotton fabrics and 27% for 35% cotton and 65% polyester content fabrics. Likewise, 13% total extent of fixation was observed for ACSA on 100% cotton fabrics and 12% on 35% cotton and 65% polyester fabrics. While ACUSA had a fair fastness to washing on 100% cotton fabrics, the rest had poor fastness. Successful synthesis of azo dyes starting from CNSL as the only carbon source demonstrates further the versatility of this renewable resource as an industrial raw material.