Described are dyes of formula (I) where R1 is hydrogen, alkyl, alkoxy, trifluoromethyl or halogen, M is hydrogen, an alkali metal cation or an optionally substituted ammonium cation, R2 and R3 are each independently hydrogen, alkyl or alkoxy, R4 is alkyl or alkoxy, R5 and R6 are each independently moieties of the formula —(CmH2m)—O—CnH2n+1, m is an integer from 3 to 6, and n is an integer from 0 to 8. These dyes are useful for dyeing and printing materials having polar groups.