Claims
- 1. A process for the purification of an azo pigment which comprises stirring a suspension of the crude pigment in water adjusted to a pH-valve of 9 to 12 at a temperature of 20.degree. to 80.degree. C., isolating the pigment and washing it neutral.
- 2. A process as defined in claim 1, wherein the pH is adjusted with an alkali metal hydroxide.
- 3. A process as defined in claim 1, wherein the suspension obtained after coupling is adjusted to said pH-value.
- 4. A process as defined in claim 1, wherein the crude pigment is isolated from the coupling suspension, is washed free of salt and is stirred into the aqueous solution of a base.
- 5. A process as defined in claim 1, wherein the pigment concentration in said suspension allows intensive stirring.
- 6. A process as claimed in claim 1, wherein the pH-value of the aqueous suspension is from 11 to 12.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2302517 |
Jan 1973 |
DEX |
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Parent Case Info
This is a continuation of application Ser. No. 434,003, filed Jan. 17, 1974. now abondoned.
US Referenced Citations (6)
Continuations (1)
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Number |
Date |
Country |
Parent |
434003 |
Jan 1974 |
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