PHOSPHATE-CONTAINING ANTI-CORROSIVE PIGMENT

Abstract

The present invention relates to a method for producing a phosphate-containing anti-corrosive pigment, to the phosphate-containing anti-corrosive pigment obtainable by this method, and to the use of the phosphate-containing anti-corrosive pigment for passive protection against corrosion.

Claims

1: A method for producing a phosphate-containing anti-corrosion pigment, comprising the following steps: a) providing hydroxyapatite or calcium-magnesium-phosphate particles or mixtures of the aforementioned as start particles in an aqueous solvent or dispersant, b) adding lime milk, a magnesium compound, and phosphoric acid to the aqueous solvent or dispersant in order to produce a reaction mixture, c) reacting the reaction mixture to form the phosphate-containing anti-corrosion pigment: at a temperature in the range of 20 C. to 105 C. and at a pH value in the range of 6.0 to 13.0, d) separating at least a part of the phosphate-containing anti-corrosion pigment from the aqueous solvent or dispersant, and e) Optionally: drying the phosphate-containing anti-corrosion pigment.

2: The method according to the claim 1, wherein the method steps a) to d) are repeated at least once so that a method cycle is created, and wherein in method step a), instead of the hydroxyapatite particles, either: 1) the part of the phosphate-containing anti-corrosion pigment that is separated from the aqueous solvent or dispersant in method step d), or 2) the part of the phosphate-containing anti-corrosion pigment that remains in the aqueous solvent or dispersant in method step d) is used as the starting particle.

3: The method according to claim 1, wherein the magnesium compound is selected from the group consisting of magnesium oxide, hydroxide, carbonate, and phosphate.

4: The method according to claim 1, wherein prior to step b), the magnesium compound is dissolved or dispersed in the phosphoric acid.

5: The method according to claim 1, wherein the reaction in step c) takes place at a temperature in the range of 90 C.

6: The method according to claim 1, wherein the added chlorine and/or sulphate content of hydroxyapatite start particles, lime milk, magnesium compound, and phosphoric acid is 500 ppm.

7: The method according to claim 1, wherein the method is carried out either: f.sup.1) in semi-continuous operation, wherein that proportion of the phosphate-containing anti-corrosion pigment separated in method step d) that in the dried state has a median of the primary particles of >0.10 m is always removed from the process, while the remaining proportion is again suspended in the aqueous solvent or dispersant in method step a), or f.sup.2) in fully continuous operation, wherein in method step d), that proportion of phosphate-containing anti-corrosion pigment that in the dried state has a median of the primary particles of >0.10 m is continuously separated and removed from the method cycle, while the remaining proportion continues to remain in the method cycle.

8: The method according to claim 1, wherein the lime milk, the magnesium compound, and the phosphoric acid in step c) are added at least partially simultaneously.

9: The method according to claim 1, wherein the phosphoric acid is dilute aqueous phosphoric acid having a concentration of 5-25 vol. %.

10: The method according to claim 1, wherein the oxide-based lime milk (CaO) has a concentration of 2-20 wt % based on the total weight of the lime milk.

11: A phosphate-containing anti-corrosion pigment obtainable by the method according to claim 1, wherein the phosphate-containing anti-corrosion pigment comprises 1 atom % of metals having a density >5 g/cm.sup.3 and in that the oil absorption value determined according to DIN EN ISO 787-5 is 40 g/100 g.

12: The phosphate-containing anti-corrosion pigment according to claim 11, wherein the oxide-based magnesium proportion of the dried phosphate-containing anti-corrosion pigment (MgO) is 2-15 wt %, wherein dried is understood to mean a residual water content of 1 wt %.

13: The phosphate-containing anti-corrosion pigment according to claim 1, wherein the specific surface area is 50 m.sup.2/g.

14. (canceled)

15: A method comprising using a phosphate-containing anti-corrosion pigment comprising calcium-magnesium phosphate particles having a specific surface area 50 m.sup.2/g and an aspect ratio of the primary particles <5 as phosphate-containing anti-corrosion pigment.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0189] FIG. 1a: Electron microscopy image of sample 1 (acceleration voltage of 1 kV).

[0190] FIG. 1b: Electron microscopy image of sample 1 (acceleration voltage of 10 kV).

[0191] FIG. 2: Mapping of the electron microscopy image of FIG. 1b for the element calcium (element distribution determined by energy-dispersive x-ray spectroscopy).

[0192] FIG. 3: Mapping of the electron microscopy image of FIG. 1b for the element magnesium (element distribution determined by energy-dispersive x-ray spectroscopy).

[0193] FIG. 4: Electron microscopy image of the comparison sample VM1.

[0194] FIG. 5: Mapping of the electron microscopy image of FIG. 4 for the element calcium (element distribution determined by energy-dispersive x-ray spectroscopy).

[0195] FIG. 6: Mapping of the electron microscopy image of FIG. 4 for the element magnesium (element distribution determined by energy-dispersive x-ray spectroscopy).

DETAILED DESCRIPTION OF THE FIGURES

[0196] FIG. 1a: Shows an electron microscopy image of the inventive sample 1. As can be seen from the illustration, the particles have a spherical shape, wherein the diameter is in the range of 6-10 m. All subsequent images (FIG. 1b-FIG. 6) were recorded with the same magnification (6,000) and thus have the same scale as this image.

[0197] FIG. 1b: Shows an electron microscopy image of the inventive sample 1. Same image detail as FIG. 1a but at an acceleration voltage of 10 kV. This acceleration voltage is also used for all subsequent electron microscopy images.

[0198] FIG. 2: The mapping of the electron microscopy image of FIG. 1b for the element calcium shows an even distribution of calcium over the entire particle.

[0199] FIG. 3: The mapping of the electron microscopy image of FIG. 1b for the element magnesium shows an even distribution of magnesium over the entire particle.

[0200] FIG. 4: Shows an electron microscopy image of the comparison sample VM1. As can be seen from the illustration, the particles have a fine crystalline, leaf-like structure.

[0201] FIG. 5: The mapping of the electron microscopy image of FIG. 4 for the element calcium shows an even distribution of calcium over the entire particle.

[0202] FIG. 6: The mapping of the electron microscopy image of FIG. 4 for the element magnesium shows local clusters of the magnesium concentration (particularly brightly pronounced area of the mapping).

[0203] The particles obtained from the above production examples and shown in the figures may also be used as a plastic additive, i.e., as exemplary embodiments for the invention according to aspects 1-20.