Coating system based on a combination of monoaluminum phosphate with magnesium oxide

Abstract

A coating system for coating inorganic substrates with a wide range of functional materials without having to use the usually necessary high temperatures includes an aqueous solution as component K1, which aqueous solution contains at least Al(H.sub.2PO.sub.4).sub.3 and Al(NaHPO.sub.4).sub.3 in the following fractions on an oxide basis and in mass percent with respect to the total mass of the solution: P.sub.2O.sub.5=25.0 to 37.0, Al.sub.2O.sub.3=5.8 to 9.0, Na.sub.2O=0.1 to 2.0, and H.sub.2O=54.0 to 66.0, and which includes an additional component K2 having the constituents magnesium oxide, silicate, and borate, which are contained in K2 in the following fractions on an oxide basis and in mass percent with respect to the total mass of component K2: MgO=70.0 to 95.0, SiO.sub.2=1.0 to 19.0, and B.sub.2O.sub.3=1.0 to 3.0, wherein there is a reactivity of the magnesium oxide of 40 to 400 seconds in the citric acid test and the loss on ignition of component K2 is 0 to 3.0.

Claims

1. A coating system comprising: at least one liquid component K1 and at least one solid component K2, wherein the component K1 is an aqueous solution which contains at least the constituents: Al(H.sub.2PO.sub.4).sub.3 and Al(NaHPO.sub.4).sub.3, wherein said constituents of the component K1 are contained on an oxide basis and specified in mass percent with respect to the total mass of the solution with the following proportions in the component K1: P.sub.2O.sub.5 between 25.0 and 37.0 Al.sub.2O.sub.3 between 5.8 and 9.0 Na.sub.2O between 0.1 and 2.0 H.sub.2O between 54.0 and 66.0, wherein the component K2 includes at least the constituents: magnesium oxide, silicate and borate, wherein said constituents of the component K2 are contained on an oxide basis and specified in mass percent with respect to the total mass of the component K2 with the following proportions in the component K2: TABLE-US-00017 MgO between 70.0 and 95.0 SiO.sub.2 between 1.0 and 19.0 B.sub.2O.sub.3 between 1.0 and 3.0, wherein the reactivity of the magnesium oxide determined in accordance with the citric acid test is in the range of between 40 and 400 seconds, the citric acid test corresponding to a time to neutralize a predetermined amount of citric acid by a predetermined amount of magnesium oxide, and wherein the ignition loss of the component K2 after tempering for 2 hours at 800 C. is in the range of between 0 wt. % and 3.0 wt. %.

2. The coating system as set forth in claim 1, wherein the component K1 additionally contains dissolved borates which are contained on an oxide basis and specified in mass percent with respect to the total mass of the solution with up to 1.5 mass percent of B.sub.2O.sub.3 in the component K1.

3. The coating system as set forth in claim 1, wherein the component K1 additionally contains dissolved silicates which are contained on an oxide basis and specified in mass percent with respect to the total mass of the solution with up to 1.0 mass percent of SiO.sub.2 in the component K1.

4. The coating system as set forth in claim 1, wherein the component K1 additionally contains dissolved fluorides which are contained on an oxide basis and specified in mass percent with respect to the total mass of the solution with up to 1.0 mass percent of F.sup. in the component K1.

5. The coating system as set forth in claim 1, wherein the component K2 contains borates of calcium, aluminum and/or zinc or mixtures thereof which are contained on an oxide basis and specified in mass percent with respect to the total mass of the component K2 with the following proportions in the component K2: up to 5.0 mass percent of CaO, between 7.5 and 15.0 mass percent of Al.sub.2O.sub.3, and up to 4.5 mass percent of ZnO.

6. The coating system as set forth in claim 1, wherein the silicate is present in the component K2 in mineral form, selected from talcum, mica, kaolin, metakaolin, bentonite, wollastonite, silicate glass and combinations thereof.

7. The coating system as set forth in claim 1, wherein the mixture ratio of component K1 to component K2 is in the range of between 5:1 and 10:1.

8. The coating system as set forth in claim 1, wherein as a constituent of component K1, as a constituent of component K2 and/or as a constituent of an additional component K3, the coating system includes a substance selected from the group consisting of functional pigments, catalytically active pigments, bio- or fungicidal substances, and fluorescent substances or substances which alter the surface structure, the electrical resistance, the thermal resistance or the reflection properties of a surface.

9. The coating system as set forth in claim 1, wherein the component K1 specified in mass percent with respect to the total mass of the component K1 includes at least the following constituents: between 40 and 50% of Al(H.sub.2PO.sub.4).sub.3 up to 7% of Mg(H.sub.2PO.sub.4).sub.2 between 0.5 and 2% of Al(NaHPO.sub.4).sub.3 between 42.5 and 52.5% of H.sub.2O.

10. A coating method using the coating system of claim 1, comprising bringing the liquid component K1 in into contact with the solid component K2 to form a coating.

11. A coating formed from the coating system of claim 1, comprising a combination of the liquid component K1 with the solid component K2.

12. An object comprising the coating of claim 11.

13. The method as set forth in claim 10, wherein the coating is effected on an inorganic material.

14. The method as set forth in claim 10, wherein the coating is a vitreous coating.

15. The method as set forth in claim 10, wherein the coating on an oxide basis and specified in mass percent of dry substance includes the specified constituents with the following proportions: TABLE-US-00018 P.sub.2O.sub.5 between 21.9 and 32.4 Al.sub.2O.sub.3 between 6.0 and 9.8 Na.sub.2O between 0.2 and 2.1 MgO between 8.1 and 11.1 SiO.sub.2 between 1.0 and 3.3 B.sub.2O.sub.3 between 0.2 and 1.7.

16. An object comprising a coating, wherein the coating is applied by the coating method of claim 10.

17. The coating as set forth in claim 11, wherein the coating is on an inorganic material.

18. The coating as set forth in claim 11, wherein the coating is a vitreous coating.

19. The coating as set forth in claim 11, wherein the coating on an oxide basis and specified in mass percent of dry substance includes the specified constituents with the following proportions: TABLE-US-00019 P.sub.2O.sub.5 between 21.9 and 32.4 Al.sub.2O.sub.3 between 6.0 and 9.8 Na.sub.2O between 0.2 and 2.1 MgO between 8.1 and 11.1 SiO.sub.2 between 1.0 and 3.3 B.sub.2O.sub.3 between 0.2 and 1.7.

Description

EMBODIMENTS BY WAY OF EXAMPLE

Example 1

(1) Bonding of black pigment (iron oxide black, Pigment Black 11 from Heucodur) on a quartz sand substrate particle size: 0.3-0.8 mm and with an SiO.sub.2 proportion >98%:

(2) K1: Solution

(3) TABLE-US-00009 Raw material Mass % Water 48.5 Monoaluminum phosphate 43.0 Monomagnesium phosphate 7.0 Sodium tetraborate 1.5
K2: Powder Mixture

(4) TABLE-US-00010 Raw material Mass % Magnesium oxide 70 Metakaolin 20 Calcium metaborate 10

Example 2

(5) Bonding of red pigment (iron oxide red, Pigment Red 101) on slate flakes (1.0-3.0 mm).

(6) K1: Solution

(7) TABLE-US-00011 Raw material Mass % Water 49.0 Monoaluminum phosphate 49.0 Sodium hydroxide 2.0
K2: Powder Mixture

(8) TABLE-US-00012 Raw material Mass % Magnesium oxide 70.6 Kaolin 13.4 Mica 5.0 Aluminum borate 11.0

Example 3

(9) Bonding of fluorescent glass beads (<100 m) on silicate glass.

(10) K1: Solution

(11) TABLE-US-00013 Raw material Mass % Water 49.0 Monoaluminum phosphate 49.0 Sodium hydroxide 1.0 Sodium tetraborate 1.0
K2: Powder Mixture

(12) TABLE-US-00014 Raw material Mass % Magnesium oxide 94.0 Metakaolin 1.0 Bentonite 1.0 Zinc borate 2.0 ZnO 2.0

Example 4

(13) Bonding of polystyrene balls (0.5-1.5 mm) on ceramic substrate.

(14) K1: Solution

(15) TABLE-US-00015 Raw material Mass % Water 49.0 Monoaluminum phosphate 49.0 Sodium hydroxide 1.0 Sodium tetraborate 1.0
K2: Powder Mixture

(16) TABLE-US-00016 Raw material Mass % Magnesium oxide 76.0 Metakaolin 15.0 Talcum 5.0 Zinc borate 2.0 ZnO 2.0
Results
Assessment of the Bonding Force and the Water Resistance of the Bond (Boiling Test)

(17) For determining the bonding force and the bonding strength of a coating produced with the coating system according to the invention a method is used, which is referred to hereinafter as the boiling test.

(18) A substrate coated with the coating system according to the invention is used for the boiling test, the coating produced in that way containing a pigment. After complete hardening of the coating the coated substrate is boiled in water for 30 minutes without further agitation at 100 C. Pigment which is released in that situation leads to clouding of the boiling water. That clouding is now measured. The lower the clouding value, the correspondingly better are the strength and water resistance of the coating bond.

(19) The determining procedure is not an absolute method but a relative method, that is to say it is not possible with that method to compare different coating agents in different substrate/pigment combinations with each other. It is only possible to compare together different coating agents within one substrate/pigment combination.

(20) For the standard test, the black pigment (Pigment Black 11 from Heucodur) in combination with a quartz sand, a slate flake or a silicate glass powder is used. The amount of pigment and the amount of coating agent depend on the substrate to be tested.