Patent ID: 7314273

Claim:
In a process for preparing a mixture of copper phthalocyanine dyes of Formula (1): CuPc(SO 3 M) x (SO 2 NH 2 ) y Formula (1) wherein: CuPc is copper phthalocyanine; M is a cation; x and y each independently have a value of from 0.5 to 3.5; and (x+y)=2 to 5; which process comprises: (i) chlorosulphonating a copper phthalocyanine compound using a chlorosulphonating agent; and (ii) condensing the product of step (i) with ammonia to give a mixture of copper phthalocyanine dyes of Formula (1); (iii) optionally exchanging the cation M in the mixture of copper phthalocyanine dyes of Formula (1) resulting from step (ii) for an alternative cation M; the improvement wherein the chlorosulphonating agent used in (i) comprises a mixture of chlorosulphonic acid and phosphorous oxychloride the molar ratio of chlorosulphonic acid to copper phthalocyanine compound in (i) being in the range 10 to 75:1 and the molar ratio of phosphorous oxychloride to copper phthalocyanine compound being in the range 10 to 0.5:1.