US 12,187,623 B2
Process for producing haematite pigments
Larissa Schaufler, Essen (DE); Anna Weber-Czaplik, Duesseldorf (DE); Carsten Rosenhahn, Kempen (DE); and Christine Kathrein, Duesseldorf (DE)
Assigned to LANXESS Deutschland GmbH, Cologne (DE)
Appl. No. 17/419,587
Filed by LANXESS Deutschland GmbH, Cologne (DE)
PCT Filed Jan. 15, 2020, PCT No. PCT/EP2020/050844
§ 371(c)(1), (2) Date Jun. 29, 2021,
PCT Pub. No. WO2020/148302, PCT Pub. Date Jul. 23, 2020.
Claims priority of application No. 19152213 (EP), filed on Jan. 17, 2019.
Prior Publication US 2022/0073366 A1, Mar. 10, 2022
Int. Cl. C01G 49/06 (2006.01)
CPC C01G 49/06 (2013.01) [C01P 2004/64 (2013.01); C01P 2006/12 (2013.01); C01P 2006/63 (2013.01); C01P 2006/80 (2013.01)] 13 Claims
 
1. A process for producing a haematite pigment having an a* value greater than 20 CIELAB units measured as a full shade in alkyd resin to DIN EN ISO 787-25:2007, comprising the steps of
(1) providing water comprising
i) at least one pigment seed selected from the group consisting of FeOOH and Fe2O3 and
ii) iron sulfate to form an initial charge (a) and
(2) adding at least one alkaline earth metal carbonate (b) and oxygen-containing gas (c) to the initial charge,
wherein at least 95% by weight of the total amount of iron sulfate used in the process is present in the initial charge (a) prior to addition of components (b) and (c).