초록 ▼

A process for the manufacture of a red pigment from perylene-3,4,9,10-tetracarboxylic acid N,N′-bis-methylimide which has been obtained by methylating the corresponding diimide or by fusing naphthalic acid N-methylimide with an alkali metal hydroxide which comprises vatting a suspension of N,N′-bis-

A process for the manufacture of a red pigment from perylene-3,4,9,10-tetracarboxylic acid N,N′-bis-methylimide which has been obtained by methylating the corresponding diimide or by fusing naphthalic acid N-methylimide with an alkali metal hydroxide which comprises vatting a suspension of N,N′-bis-methylimide dye with 0.5-1.5 times by weight of an alkali metal dithionite in the presence of up to 4 times by weight of an alkali metal hydroxide relative to the quantity of the dithionite, at a temperature of from room temperature to 100°C., to obtain the corresponding leuco compound, cooling the resulting solution to 20°-40°C., isolating and washing the leuco compound with fresh vatting solution until the solution is virtually colorless and clean and then oxidizing the leuco compound.

대표청구항 ▼

A process for the manufacture of a red pigment from perylene-3,4,9,10-tetracarboxylic acid N,N′-bis-methylimide which has been obtained by methylating the corresponding diimide or by fusing naphthalic acid N-methylimide with an alkali metal hydroxide, which comprises vatting a suspension of said N,N

A process for the manufacture of a red pigment from perylene-3,4,9,10-tetracarboxylic acid N,N′-bis-methylimide which has been obtained by methylating the corresponding diimide or by fusing naphthalic acid N-methylimide with an alkali metal hydroxide, which comprises vatting a suspension of said N,N′-bis-methylimide with 0.5-1.5 times by weight of an alkali metal dithionite in the presence of up to 4 times by weight of an alkali metal hydroxide relative to the quantity of said ditionite, at a temperature of from room temperature to 100°C., to obtain the corresponding leuco compound, cooling the resulting solution to 20°-40°C., isolating and subsequently washing said leuco compound with fresh vatting solution until the solution is virtually colorless and clear and then, oxidizing said leuco compound.