URETHANE RESIST LJN possesses excellent effect to prevent contamination on spandex by disperse dyes when polyester/ spandex knit fabrics are dyed with disperse dyes. Spandex is a fibre with superb elasticity and is widely used for swim wear, foundation, socks and sports wear etc in combination with polyamide or polyester fibres. Less yellowing phenomena by C1, Nox gas etc, compared with polyamide/ spandex fabrics dyed with acid dyes, is a characteristic of polyester/spandex fabrics dyed with disperse dyes. On the contrary, contamination on spandex by disperse dyes is terrible and poor colour fastness caused by contamination sometimes comes up. URETHANE RESIST LJN shows excellent effect to prevent contamination on spandex by disperse dyes in dyeing process. In order to get high colour fastness of polyester/spandex knit fabrics, it is effective to apply special soaping agent, ITOCOL SPN2, in reduction cleaning process after dyeing with URETHANE RESIST LJN.