Method for producing vattable organic pigments
View Patent ↗The invention relates to a method for producing vattable organic pigments. The invention is characterized in that an agueous or an aqueous-organic suspension of a coarse crystalline raw mineral is vatted and re-oxidised, and the pigment suspension is ground to a diameter equal to or less than 0.9 mm during vatting and/or during oxidation by means of an agitator ball mill, which is operated at a power density of more than 1.0 KW per litre per grinding chamber and at an agitator peripheral speed of more than 12 m/s, using grinding bodies.
1. A method of producing a vattable organic pigment comprising the steps of vatting an aqueous or aqueous-organic suspension of a coarsely crystalline crude pigment and oxidizing the aqueous or aqueous-organic suspension of a coarsely crystalline crude pigment, wherein at least one of the steps of vatting and oxidizing further comprises milling the aqueous or aqueous-organic suspension of a coarsely crystalline crude pigment with a stirred ball mill operated with a power density of more than 1.0 kW per liter of milling space and with a peripheral stirrer speed of more than 12 m/s, under the action of grinding media with a diameter of less than or equal to 0.9 mm.
2. The method as claimed in claim 1 , wherein the coarsely crystalline pigment is selected from the group consisting of indanthrone, anthanthrone, thioindigo, perinone and perylene pigments.
3. The method as claimed in claim 1 , wherein the coarsely crystalline pigment is C.I. Pigment Blue 60, 66, C.I. Pigment Red 88, 168, 123, 149, 178, 179, 181, 189, 194, C.I. Vat Red 14, 41, C.I. Pigment Orange 43, C.I. Pigment Violet 29, C.I. Pigment Black 31 or 32, a mixture thereof or a mixed crystal thereof.
4. The method as claimed in claim 1 , wherein the vatting step occurs with sodium dithionite or potassium dithionite.
5. The method as claimed in claim 1 , wherein the pigment concentration in the suspension is from 2.5% to 40% by weight, based on the total weight of the suspension.
6. The method as claimed in claim 1 , wherein the milling duration is between 3 and 60 minutes.
7. The method as claimed in claim 1 , wherein vatting, oxidation and milling are conducted at a temperature between 0 and 100° C.
8. The method as claimed in claim 1 , wherein the suspension comprises water or a mixture of C 1 –C 6 alcohols, N-methylpyrrolidone, toluene and/or nitrobenzene with water.
9. The method as claimed in at claim 1 , wherein at least one of the vatting and oxidizing steps further comprises adding at least one auxiliary selected from the group consisting of surfactants, pigmentary and nonpigmentary dispersants, fillers, standardizers, resins, waxes, defoamers, antidust agents, extenders, shading colorants, preservatives, drying retardants, rheology control additives, wetting agents, antioxidants, UV absorbers, light stabilizers and a combination thereof.
10. The method as claimed in claim 1 , wherein milling occurs during at least the vatting step and wherein the compound formed during the vatting step is milled in the form of its salt or in the form of its acid.
11. A method of producing a vattable organic pigment comprising the steps of vatting an aqueous or aqueous-organic suspension of a coarsely crystalline crude pigment and oxidizing the aqueous or aqueous-organic suspension of a coarsely crystalline crude pigment, wherein the steps of vatting and oxidizing further comprises milling the aqueous or aqueous-organic suspension of a coarsely crystalline crude pigment with a stirred ball mill operated with a power density of more than 1.0 kW per liter of milling space and with a peripheral stirrer speed of more than 12 m/s, under the action of grinding media with a diameter of less than or equal to 0.9 mm.