Claims
- 1. A process for increasing the opacity of 1,4-diketopyrrolo[3,4-c]-pyrrole pigments of the formula ##STR3## wherein one of R.sub.1 and R.sub.2 is hydrogen, halogen or C.sub.1 -C.sub.4 -alkyl and the other is hydrogen, which process consists essentially of milling the pigment in an alcohol which is present in an amount ranging from 5 to 25 times the weight of the diketopyrrolopyrrole and in the presence of a base which is present in an amount ranging from 2 to 50% by weight of the diketopyrrolopyrrole at a temperature below 50.degree. C.
- 2. The process of claim 1, wherein said alcohol is selected from the group consisting of alkanols and glycols.
- 3. The process of claim 1, wherein said alcohol is selected from the group consisting of methanol, ethanol, butanol, pentanol and ethylene glycol.
- 4. The process of claim 1, wherein said alcohol is methanol or ethanol.
- 5. The process of claim 1, wherein said base is an alkali metal hydroxide.
- 6. The process of claim 1, wherein said base is sodium or potassium hydroxide.
- 7. The process of claim 1, wherein said base is a quaternary ammonium hydroxide.
- 8. The process of claim 1, wherein said alcohol is methanol and said base is sodium hydroxide.
- 9. The process of claim 1, wherein the milling occurs between 10.degree. and 40.degree. C.
- 10. The process of claim 1, wherein in formula I R.sub.1 is hydrogen, chlorine, methyl or tert.-butyl and R.sub.2 is hydrogen.
- 11. The process of claim 1, wherein in formula I R.sub.1 and R.sub.2 are hydrogen.
Parent Case Info
This application is a continuation of application Ser. No. 181,864, filed 4/15/88 now abandoned.
US Referenced Citations (6)
Continuations (1)
|
Number |
Date |
Country |
Parent |
181864 |
Apr 1988 |
|