Non-magnetizable effect pigments

Abstract

The present invention relates to a coloured effect pigment, comprising a substrate made of aluminium or an aluminium alloy which is optionally coated with one or more passivation layers, and an aluminium-doped iron oxide layer.

Claims

1. A colored effect pigment, comprising a substrate comprising aluminum or an aluminum alloy which is optionally coated with one or more passivation layers, and an aluminum-doped iron oxide layer, wherein no separate Al.sub.2O.sub.3, Al(OH).sub.3 and/or AlO(OH) phase is present in the aluminum-doped iron oxide layer, and wherein the optional one or more passivation layers are made of at least one selected from the group consisting of a metal phosphate, a Ti oxide, a V oxide, a Cr oxide, a Mn oxide, a Co oxide, a Ni oxide, a Cu oxide, a Zn oxide, an Al oxide, a Zr oxide, a Nb oxide, a Mo oxide, a Ta oxide, a W oxide, a Ge oxide, a Si oxide, a Sn oxide, and a Bi oxide.

2. The colored effect pigment according to claim 1, wherein the aluminum-doped iron oxide layer comprises up to 10 wt % Al, based on a total amount of Fe and Al atoms in the aluminum-doped iron oxide layer.

3. The colored effect pigment according to claim 1, wherein the Al concentration in a substrate-near part of the aluminum-doped iron oxide layer is higher than the Al concentration in a substrate-remote part of the aluminum-doped iron oxide layer.

4. The colored effect pigment according to claim 1, further comprising an additional coating layer on the aluminum-doped iron oxide layer.

5. A composition, comprising the colored effect pigment according to claim 1.

6. A process for preparing a colored effect pigment, comprising coating a substrate comprising aluminum or an aluminum alloy which is optionally coated with one or more passivation layers, in a liquid coating medium with an aluminum-doped iron oxide layer to obtain the colored effect pigment according to claim 1, wherein the liquid coating medium comprises an iron oxide precursor compound and an aluminum compound.

7. The process according to claim 6, wherein the aluminum compound is one or more members selected from the group consisting of an aluminum salt, a hydrolyzable aluminum compound, and a complex compound of aluminum; and/or the iron oxide precursor compound is at least one member selected from the group consisting of an iron salt, a hydrolyzable iron compound, and a complex compound of iron.

8. The process according to claim 6, wherein the aluminum compound is at least partly dissolved in the liquid coating medium, followed by adjusting a pH and/or a temperature of the liquid coating medium to an iron oxide forming condition and then adding the iron oxide precursor compound: or a pH and/or a temperature of the liquid coating medium is/are adjusted to an iron oxide forming condition, followed by adding the aluminum compound and the iron oxide precursor compound, either simultaneously or the aluminum compound first and subsequently the iron oxide precursor compound.

9. The process according to claim 6, wherein the aluminum-doped iron oxide layer is applied on the substrate at a pH of 5 or less.

10. The process according to claim 6, wherein the aluminum-doped iron oxide layer applied on the substrate is a hydroxyl-containing aluminum-doped iron oxide layer of a first colored effect pigment CEP1; and wherein the process further comprises heating a liquid post-treatment medium comprising the first colored effect pigment CEP1 and an organic liquid having a boiling point of at least 90 C. to a temperature of at least 90 C. so as to convert the first colored effect pigment CEP1 to a second colored effect pigment CEP2.

11. The process according to claim 10, wherein the first colored effect pigment CEP1 is provided in the liquid post-treatment medium by partially removing the liquid coating medium, thereby obtaining the first colored effect pigment CEP1 as a wet material, and suspending the wet CEP1 in the liquid post-treatment medium.

12. The process according to claim 10, wherein the first colored effect pigment CEP1 is provided in the liquid post-treatment medium by using a liquid coating medium which already comprises an organic liquid having a boiling point of at least 90 C., or adding one or more organic liquids each having a boiling point of at least 90 C. to the liquid coating composition during or after the formation of the first colored effect pigment CEP1, and subsequently increasing a relative amount of the organic liquid by a thermal treatment.

13. The process according to claim 6, wherein the aluminum or aluminum alloy of the substrate is not subjected to a wet-chemical oxidation treatment.

14. The colored effect pigment according to claim 4, wherein the additional coating layer is at least one elected from the group consisting of an inorganic oxide layer, an organosilane layer, and a polymer layer.

15. The colored effect pigment according to claim 1, wherein the iron oxide is at least one selected from the group consisting of: Fe.sub.2O.sub.3, FeO(OH), Fe.sub.2O.sub.3.H.sub.2O, Fe.sub.2O.sub.3.nH.sub.2O with n2, Fe(OH).sub.3, and Fe(OH).sub.2, and the iron oxide optionally comprises a hydroxyl group and/or water derived from an incomplete condensation during a formation of the iron oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A shows the surface of the solidified paint film (see Example 2; 1% A1OOH). As the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remains smooth.

(2) FIG. 1B shows the surface of the solidified paint film (see Example 3; 0.5% A1OOH). As the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remains smooth. There is no deformation pattern.

(3) FIG. 1C shows the surface of the solidified paint film (see Example 4; 0.25% A1OOH). As the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remains smooth. There is no deformation pattern.

(4) FIG. 1D shows the surface of the solidified paint film (see Example 1; 0% A1OOH). As the effect pigment prepared in Example 1 was magnetic, the surface of the paint film shows a deformation pattern.

(5) FIG. 2 shows a TEM picture including an elemental analysis (EDXS) from different areas of the Al-doped iron oxide layer. Elemental analysis confirmed that the iron oxide layer was doped with Al in an amount of less than 10 mol%. The Al concentration in the substrate near part (weight ratio Fe/Al=96/4, i.e. 4 wt% Al based on amount of (Fe+Al)) was higher than in the substrate remote part (weight ratio Fe/Al=98/2, i.e. 2 wt% Al based on amount of (Fe+Al)). Key: 1=lacquer; 2=Fe+(Al); 3=Si; 4=Al; 5=Fe:Al (96:4); 6=Fe:Al (98:2).

(6) FIG. 3 shows a TEM picture including an elemental analysis (EDXS) from different area of the Al-doped iron oxide layer. Elemental analysis confirmed that the iron oxide layer was doped with Al in an amount of less than 10 mol%. The Al concentration in the substrate near part (weight ratio Fe/Al=98:2, i.e. 2 wt% Al based on amount of (Fe+Al)) was higher than in the substrate remote part (weight ratio Fe/Al=99:1, i.e. 1 wt% Al based on (Fe+Al)). The right side of the image is the substrate side. Key: 1=lacquer; 6=Fe:Al (98:2). 7=Fe:Al (99:1).

(7) The present invention will now be described in further detail by the following Examples.

EXAMPLES

Example 1

Liquid Coating Medium to which no Al Compound is Added

(8) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(9) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3 and dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water. Subsequently, the product was treated in air at 300 C. for 20 minutes.

(10) A paint film containing the effect pigment of Example 1 (i.e. no Al compound being present in the liquid coating medium) was prepared and a magnet was positioned parallel to the surface of the paint film while solidifying the paint film.

(11) FIG. 1d shows the surface of the solidified paint film. As the effect pigment prepared in Example 1 was magnetic, the surface of the paint film shows a deformation pattern.

Example 2

Liquid Coating Medium to which an Al Compound is Added (1 wt % AlOOH Based on Al/SiO.SUB.2.)

(12) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(13) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3, followed by adding 4.95 g Al.sub.2(SO.sub.4).sub.3*12 H.sub.2O. Subsequently, dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water. Subsequently, the product was treated in air at 300 C. for 20 minutes.

(14) A paint film containing the effect pigment of Example 2 (i.e. Al compound being present in the liquid coating medium) was prepared and a magnet was positioned parallel to the surface of the paint film while solidifying the paint film.

(15) FIG. 1a shows the surface of the solidified paint film. As the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remains smooth. There is no deformation pattern.

(16) Elemental analysis (TEM/EDXS) of the effect pigment prepared in Example 2 confirmed that the iron oxide layer was doped with Al in an amount of less than 10 wt %. The Al concentration in the substrate near part (weight ratio Fe/Al=97/3, i.e. 3 wt % Al based on amount of (Fe+Al)) was higher than in the substrate remote part (weight ratio Fe/Al=98/2, i.e. 2 wt % Al based on amount of (Fe+Al)).

Example 3

Liquid Coating Medium to which an Al Compound is Added (0.5 wt % AlOOH Based on Al/SiO.SUB.2.)

(17) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(18) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3, followed by adding 2.48 g Al.sub.2(SO.sub.4).sub.3*12 H.sub.2O. Subsequently, dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water. Subsequently, the product was treated in air at 300 C. for 20 minutes.

(19) FIG. 1b shows the surface of the solidified paint film. As the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remains smooth. There is no deformation pattern.

(20) FIG. 2 shows a TEM picture including an elemental analysis (EDXS) from different areas of the Al-doped iron oxide layer. Elemental analysis confirmed that the iron oxide layer was doped with Al in an amount of less than 10 mol %. The Al concentration in the substrate near part (weight ratio Fe/Al=96/4, i.e. 4 wt % Al based on amount of (Fe+Al)) was higher than in the substrate remote part (weight ratio Fe/Al=98/2, i.e. 2 wt % Al based on amount of (Fe+Al)).

Example 4

Liquid Coating Medium to which an Al Compound is Added (0.25 wt % AlOOH Based on Al/SiO.SUB.2.)

(21) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(22) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3, followed by adding 1.24 g Al.sub.2(SO.sub.4).sub.3*12 H.sub.2O. Subsequently, dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water. Subsequently, the product was treated in air at 300 C. for 20 minutes.

(23) FIG. 1c shows the surface of the solidified paint film. As the effect pigment prepared in Example 2 was non-magnetic, the surface of the paint film remains smooth. There is no deformation pattern.

(24) FIG. 3 shows a TEM picture including an elemental analysis (EDXS) from different area of the Al-doped iron oxide layer. Elemental analysis confirmed that the iron oxide layer was doped with Al in an amount of less than 10 mol %. The Al concentration in the substrate near part (weight ratio Fe/Al=98:2, i.e. 2 wt % Al based on amount of (Fe+Al)) was higher than in the substrate remote part (weight ratio Fe/Al=99:1, i.e. 1 wt % Al based on (Fe+Al)).

Example 5

Liquid Coating Medium Containing an Al Compound (0.25 wt % AlOOH Based on Al/SiO.SUB.2.) Followed by Heat Treatment in High Boiling Organic Solvent

(25) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(26) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3, followed by adding 1.24 g Al.sub.2(SO.sub.4).sub.3*12 H.sub.2O. Subsequently, dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water and subsequently with Isopropanol. 100 g of the wet filter cake were suspended in 900 ml of an isoparaffinic mixture (b.p.: 270 C.) as a high boiling solvent. The temperature was increased to about 235 C. and maintained there until desired color was achieved.

(27) The suspension was cooled down to RT.

(28) The final product showed high brilliant color travels without any magnetism. Further the humidity resistant properties were increased.

Example 6

Liquid Coating Medium Containing an Al Compound (0.25 wt % AlOOH Based on Al/SiO.SUB.2.) Followed by Heat Treatment in High Boiling Organic Solvent

(29) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(30) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3, followed by adding 1.24 g Al.sub.2(SO.sub.4).sub.3*12 H.sub.2O. Subsequently, dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water and subsequently with Isopropanol. 100 g of the wet filter cake were suspended in 900 ml methyl polyethylene glycol (molecular weight of about 350 g/mol) as an high boiling solvent. The temperature was increased to about 240 C. and maintained there until desired color was achieved.

(31) The suspension was cooled down to RT.

(32) The final product showed high brilliant color travels without any magnetism. Further the humidity resistant properties were increased.

Example 7

Liquid Coating Medium Containing an Al Compound (0.25 wt % AlOOH Based on Al/SiO.SUB.2.) Followed by Heat Treatment in High Boiling Organic Solvent

(33) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(34) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3, followed by adding 1.24 g Al.sub.2(SO.sub.4).sub.3*12 H.sub.2O. Subsequently, dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water and subsequently with Isopropanol. 100 g of the wet filter cake were suspended in mineral spirits as a high boiling solvent. The temperature was increased to about 235 C. and maintained there until desired color was achieved.

(35) The suspension was cooled down to RT.

(36) The final product showed high brilliant color travels without any magnetism. Further the humidity resistant properties were increased.

Example 8

Liquid Coating Medium Containing an Al Compound (0.25 wt % AlOOH Based on Al/SiO.SUB.2.) Followed by Heat Treatment in Organic Solvent

(37) Following the passivation method described in Example 1 (step a)) of EP 0 708 154, a SiO.sub.2 passivation layer was applied on an aluminium substrate.

(38) 100 g of the passivated aluminium (provided as a paste) with an Al to SiO.sub.2 weight ratio of about 66:33 was suspended in 800 ml water. The suspension was heated to 77 C. Then, pH was adjusted with HNO.sub.3 to about 3, followed by adding 1.24 g Al.sub.2(SO.sub.4).sub.3*12 H.sub.2O. Subsequently, dosing of a Fe(NO.sub.3).sub.3 solution (50 w/w) at 60 ml/h was started. Simultaneously, NaOH was added so as to keep pH at around 3. The dosing was stopped when the desired colour had been achieved. The resulting product was cooled down, filtered off and washed with water and subsequently with Isopropanol. 100 g of the wet filter cake were suspended in an aromatic liquid (b.p.: 242 C.) as a high boiling solvent. The temperature was increased to about 230 C. and maintained there until desired color was achieved.

(39) The suspension was cooled down to RT.

(40) The final product showed high brilliant color travels without any magnetism. Further the humidity resistant properties were increased.