# US 10,479,893 B2 · Preparation of iron (III) oxide pigment > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,479,893 B2 - Document ID: US10479893B2 - Status: Granted - Kind: B2 - Application number: 15/507,808 - Filed: 2015-09-04 - Published: 2017-10-12 - Granted: 2019-11-19 - Earliest claimed: 2014-09-05 - Assignees: LANXESS Deutschland GmbH - Applicants: Lanxess Deutschland GmbH - Inventors: Waldemar Czaplik; Guido Ketteler; Jurgen Kischkewitz - Web page: https://patentgrep.com/patent/US10479893B2 ## CPC - C09C 1/24: Oxides of iron - C01G 49/06: Ferric oxide [Fe2O3] - C01P 2004/64: Nanometer sized, i.e. from 1-100 nanometer - C01P 2006/12: Surface area - C09C: TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES (treatment of materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone C04B14/00, C04B18/00, C04B20/00); PREPARATION OF CARBON BLACK {; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS} - C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20) - C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS ## Abstract The present invention relates to an improved process for producing iron oxide red pigments by the Penniman process using nitrate (also referred to as nitrate process or direct red process). ## Claims ### Claim 1 A process for producing haematite pigments, the process comprising: contacting iron, an aqueous haematite nucleus suspension containing haematite nuclei which have a particle size of 100 nm or less and a specific BET surface area of 40 m2/g to 150 m2/g (measured in accordance with DIN 66131), and an iron(II) nitrate solution, in the presence of at least one oxygen-containing gas at temperatures of 70 to 99° C. to produce a suspension comprising haematite pigment, wherein the aqueous solution of the iron, the haematite nucleus suspension, and the iron(II) nitrate solution is mixed by means of hydraulic mixing; wherein the hydraulic mixing is carried out by means of at least one pump which takes a liquid phase from a reactor at an outlet and feeds it back into the reactor at another place by an inlet, and wherein the at least one oxygen-containing gas is introduced into the aqueous solution with a gas introduction volume of 6 m3 of gas volume/m3 of batch volume/hour or less. ### Claim 2 (depends on 1) The process according to claim 1, wherein the reaction is carried out until the haematite pigment has a desired colour shade. ### Claim 3 (depends on 1) The process according to claim 1 further comprising separating haematite pigment from the reaction mixture by conventional methods. ### Claim 4 (depends on 1) The process according to claim 1, wherein the haematite pigment has the α-Fe2O3 modification. ### Claim 5 (depends on 1) The process according to claim 1, wherein the hydraulic mixing is carried out at a pumped circulation volume of from 0.1 to 20 batch volumes/hour. ### Claim 6 (depends on 1) The process according to claim 1, wherein the hydraulic mixing is carried out in a reactor having at least one inlet and at least one outlet for the reaction mixture in such a way that the flow velocity at the inlet of the reactor is at least 0.05 m/s. ### Claim 7 (depends on 1) The process according to claim 1, further comprising mixing the iron(II) nitrate solution with the iron before mixing of the haematite nucleus suspension with the iron in such a way that the concentration of iron(II) nitrate is from 0.1 to 25 g/l of liquid phase, calculated on the basis of anhydrous Fe(NO3)2. ### Claim 8 (depends on 1) The process according to claim 1, further comprising mixing the iron(II) nitrate solution with the iron simultaneously with mixing of the haematite nucleus suspension with the iron in such a way that the concentration of iron(II) nitrate is from 0.1 to 25 g/l of liquid phase, calculated on the basis of anhydrous Fe(NO3)2. ### Claim 9 (depends on 1) The process according to claim 1, further comprising mixing the iron(II) nitrate solution with the iron after mixing of the haematite nucleus suspension with the iron in such a way that the concentration of iron(II) nitrate is from 0.1 to 25 g/l of liquid phase, calculated on the basis of anhydrous Fe(NO3)2. ### Claim 10 (depends on 1) The process according to claim 1, further comprising introducing the at least one oxygen-containing gas into the aqueous solution with a gas introduction volume of 0.2 to 3 m3 of gas volume/m3 of batch volume/hour. ### Claim 11 (depends on 1) The process according to claim 1, wherein the hydraulic mixing is carried out in a reactor having at least one inlet and at least one outlet for the reaction mixture in such a way that the flow velocity at the inlet of the reactor is at least 0.06 m/s. ### Claim 12 (depends on 1) The process according to claim 1, further comprising mixing the iron(II) nitrate solution with the iron before mixing of the haematite nucleus suspension with the iron in such a way that the concentration of iron(II) nitrate is from 1 to 20 g/l of liquid phase, calculated on the basis of anhydrous Fe(NO3)2. ### Claim 13 (depends on 1) The process according to claim 1, further comprising mixing the iron(II) nitrate solution with the iron simultaneously with mixing of the haematite nucleus suspension with the iron in such a way that the concentration of iron(II) nitrate is from 1 to 20 g/l of liquid phase, calculated on the basis of anhydrous Fe(NO3)2. ### Claim 14 (depends on 1) The process according to claim 1, further comprising mixing the iron(II) nitrate solution with the iron after mixing of the haematite nucleus suspension with the iron in such a way that the concentration of iron(II) nitrate is from 1 to 20 g/l of liquid phase, calculated on the basis of anhydrous Fe(NO3)2.