Iron oxide pigments containing Al

Patent metadata

Field	Value
Publication number	US-11634342-B2
Application number	US-202217700428-A
Country	US
Kind code	B2
Filing date	Mar 21, 2022
Priority date	Mar 31, 2017
Publication date	Apr 25, 2023
Grant date	Apr 25, 2023

Abstract

Aluminium-containing iron oxide pigments of the formula Fe 2-x Al x O 3 with x values from 0.01 to 0.25, characterized in that they possess an a* value of 30.5 to 32.5 CIELAB units and a b* value of 25.5 to 30.5 CIELAB units, measured in each case as full shade in the alkyd resin according to DIN EN ISO 787-25:2007.

First claim

What is claimed is:

1. A process for producing aluminium-containing haematite pigments of formula
Fe 2-x Al x O 3 with x values from 0.01 to 0.25, wherein the pigments possess an a* value of 30.5 to 32.5 CIELAB units and a b* value of 25.5 to 30.5 CIELAB units, and Al-containing iron oxides have a saturation Cab* of 39.8 to 44.6 CIELAB units, measured in each case as full shade in the alkyd resin according to DIN EN ISO 787-25:2007, comprising at least the steps of a) precipitation, b) oxidation and c) calcination, wherein:
a1) an aqueous solution comprising ions of iron, of sulfate and of aluminium, a molar ratio of iron ions to Al ions being 199:1 to 7:1, is reacted with sodium hydroxide NaOH, as an alkaline compound, with the aqueous solution comprising ions of iron, of sulfate and of aluminium being metered into an initial charge of the alkaline compound, or
a2) an aqueous solution comprising ions of iron and of sulfate is reacted with sodium hydroxide NaOH, as an alkaline compound, and with at least one alkali metal aluminate aluminium compound, with the molar ratio of iron in the solution to aluminium in the aluminium compound being 199:1 to 7:1 and with the alkaline compound being introduced as an initial charge with the at least one alkali metal aluminate aluminium compound, and the aqueous solution comprising ions of iron and of sulfate being metered in,
b) an aqueous suspension obtained after step a1) or a2) is oxidized in the presence of an oxidizing agent, and
c) an oxidation product obtained after b) is calcined at a temperature of 500 to 1100° C. in an oxidizing atmosphere.

2. The process according to claim 1 , wherein the aqueous solution comprising ions of iron, of sulfate and of aluminium in step a1) has an Fe(III) fraction of 5 to 30 mol %, based on a total amount of iron in the solution.

3. The process according to claim 1 comprising at least the steps of a) precipitation, b) oxidation and c) calcination, wherein:
a1) an aqueous solution comprising ions of iron, of sulfate and of aluminium, the molar ratio of iron ions to Al ions being 199:1 to 7:1, is reacted with sodium hydroxide NaOH, as an alkaline compound, with the aqueous solution comprising ions of iron, of sulfate and of aluminium being metered into the initial charge of the alkaline compound in the form of its aqueous solution, or
a2) an aqueous solution comprising ions of iron and of sulfate is reacted with sodium hydroxide NaOH, as an alkaline compound, and with an aluminium compound sodium aluminate, with the molar ratio of iron in the solution to aluminium in the aluminium compound being 199:1 to 7:1 and with the alkaline compound being introduced as an initial charge with an aluminium compound sodium aluminate solution, and the aqueous solution comprising ions of iron and of sulfate being metered in,
b) an aqueous suspension obtained after step a1) or a2) is oxidized in the presence of an oxidizing agent, and
c) an oxidation product obtained after b) is calcined at a temperature of 500 to 1100° C. in an oxidizing atmosphere.

4. A process for colouring of pastes, paints, plastics, paper and building materials, wherein the pigments of formula Fe 2-x Al x O 3 with x values from 0.01 to 0.25 made by a process according to claim 1 are utilized.

Assignees

• Lanxess Deutschland Gmbh

Inventors

• Buetje Kai
• Kathrein Christine
• Rosenhahn Carsten
• Kischkewitz Juergen
• Meisen Ulrich
• Koehler Peter

Classifications

• C08K2201/006

  Additives being defined by their surface area · CPC title

• C09D7/61

  inorganic · CPC title

• C08K3/013

  Fillers, pigments or reinforcing additives · CPC title

• C01G49/06

  Ferric oxide [Fe2O3] · CPC title

• C09C1/24 Primary

  Oxides of iron · CPC title