GRANULES FOR ROOF COATINGS

Abstract

Granules for a roof coating, wherein said granules comprise particles that have a coating, wherein said coating comprises at least one layer of an inorganic powder in a binder, wherein said inorganic powder has a d50 grain size of from 0.5 to 25 μm, and wherein a hydrophobizing and/or oleophobizing agent is present on said coating.

Claims

1. Granules for a roof coating, wherein said granules comprise particles that have a coating, wherein said coating comprises at least one layer of an inorganic powder in a binder, wherein said inorganic powder has a d50 grain size of from 0.5 to 25 μm, and wherein a hydrophobizing and/or oleophobizing agent is present on said coating.

2. The granules for a roof coating according to claim 1, wherein said particles are selected from the group consisting of calcined kaolin, calcined mixtures of clay minerals, feldspar and quartz, calcined mixtures of clay minerals, silicates and oxides, and mixtures thereof, preferably wherein the particles have a solar reflection of at least 80% before being coated.

3. The granules for a roof coating according to claim 1, wherein said particles have a d50 grain size of from 0.1 to 3 mm.

4. The granules for a roof coating according to claim 1, wherein said inorganic powder is selected from the group consisting of calcined mineral powders, metal oxides, metal hydroxides, sulfates, silicate hydrates, glasses, carbonates, mica, and mixtures thereof.

5. The granules for a roof coating according to claim 1, wherein said inorganic powder has a d50 grain size of from 0.5 to 10 μm.

6. The granules for a roof coating according to claim 1, wherein said binder is an inorganic binder.

7. The granules for a roof coating according to claim 6, wherein said inorganic binder is a siliceous binder.

8. The granules for a roof coating according to claim 1, wherein said coating is applied repeatedly.

9. The granules for a roof coating according to claim 1, wherein the amount of inorganic powder is from 1 to 10% by weight, based on the weight of the granules.

10. The granules for a roof coating according to claim 9, wherein said hydrophobizing and/or oleophobizing agent is selected from the group consisting of siliceous compounds, fluorine-containing compounds, siliceous fluorine-containing compounds, and mixtures thereof.

11. A roof coating comprising a bitumen layer having granules embedded therein according to claim 1.

12. The roof coating according to claim 11, wherein the granules are present in an amount of from 0.5 to 5 kg per square meter of the roof coating.

13. A process for producing granules for a roof coating according to claim 1, comprising the steps of: a) providing particles, b) mixing the particles with a coating agent comprising an inorganic powder, c) drying the coating, d) optionally repeating steps b) and c), and/or e) applying a hydrophobizing and/or oleophobizing agent.

14. The granules for a roof coating according to claim 2, wherein the particles have a solar reflection of at least 80% before being coated.

Description

DESCRIPTION OF THE FIGURES

[0032] FIG. 1A shows the material before the coating.

[0033] FIG. 1B shows the material according to Example 1.

[0034] FIG. 1C shows the material according to Example 2.

[0035] FIG. 2 shows an example of a cohesive failure in bitumen.

[0036] FIG. 3 shows an example of an adhesive failure in bitumen.

[0037] The invention is further illustrated by the following Examples.

EXAMPLES

[0038] In the following Examples, granules are treated with the coatings according to the invention, whose compositions have been described in the patent EP 3 164 554 B1. They consist of a deliberately constituted composition of kaolin, feldspar, and crystalline silica in the form of quartz in ratios of 64:28:8% by weight.

Example 1

[0039] A dispersion containing 30% by weight of calcined kaolin with an average grain diameter d50 of 7 μm (as measured using a Sedigraph 5120, applying the method described in the Zellcheming protocol V/27.3/90) was used as the anchoring layer. The product employed is sold by Amberger Kaolinwerke Eduard Kick GmbH & Co. KG, Hirschau (Germany), under the designation of AS 45/10.000. Sodium water glass (37° BE=degrees Baumé) in an aqueous dilution of 1:5 served as the inorganic binder. For each coating run, 1.8% by weight thereof was applied (dry matter of calcined kaolin, based on granules), i.e., 6% by weight of the dispersion, based on the granules.

Composition of the Dispersion:

[0040] 30% by weight of AS 45/10.000 [0041] 11.7% by weight of Na water glass (37° BE) [0042] 58.3% by weight of water.

[0043] Three coatings were applied, with drying in between.

TABLE-US-00001 uncoated 1 X coated 2 X coated 3 X coated Reflection 81.7% 82.0% 82.8% 82.9%

[0044] The reflection is determined according to ASTM Standard C 1549, “standard test method for determination of solar reflection near ambient temperature using a portable solar reflectometer”.

[0045] A suitable measuring device is available from the company Devices and Services, 2835 Virgo Ln., Dallas, Tex. 75229, under the designation of Solar Spectrum Reflectometer Model SSR.

Example 2

[0046] A dispersion containing 30% by weight of alumina with an average grain diameter d50 of 4 μm (as measured using a Sedigraph 5120) was used as the anchoring layer. Alumina is available under the designation of “Nabalox TC 115” from Nabaltec GmbH, Schwandorf (Germany). Sodium water glass (37° BE) in an aqueous dilution of 1:5 serves as the inorganic binder. Three coatings were applied in the Example, with drying in between, wherein 1.8% by weight alumina was used in each case, based on the granules.

Composition of the Solution:

[0047] 30% by weight of Nabalox TC 115 [0048] 11.7% by weight of Na water glass (37° BE) [0049] 58.3% by weight of water.

TABLE-US-00002 uncoated 1 X coated 2 X coated 3 X coated Reflection 81.7% 82.1% 82.8% 82.8%

Example 3

[0050] A dispersion containing 20% by weight of calcined kaolin with an average grain diameter d50 of 0.9 μm (as measured using a Sedigraph 5120) was used as the anchoring layer. This calcined kaolin is available from BASF OY, Helsinki, under the designation of “Ansilex 93”. Sodium water glass (37° BE) in an aqueous dilution of 1:5 serves as the inorganic binder. In this Example, three coatings were applied, with drying in between. For each coating run, 1.2% of Ansilex 93 was used, based on the granules.

Composition of the Solution:

[0051] 20% by weight of Ansilex 93 [0052] 13.3% by weight of Na water glass (37° BE) [0053] 66.7% by weight of water.

TABLE-US-00003 uncoated 1 X coated 2 X coated 3 X coated Reflection 81.7% 81.8% 82.6% 82.7%

[0054] These results show that the coating is able to increase reflection again.

[0055] Thus, the first part of the task is accomplished; the reflection is not deteriorated, but improved, by the coating.

Analyses

[0056] Of Example 1 and Example 2, scanning electron micrographs were made that show the change of the surface topography by the coating. From these, it is clearly seen that the coating causes a change in structure; the fractured surfaces, which are relatively smooth, become significantly rougher from the deposit of the particles in the coating, see FIGS. 1A to 1C.

Example 4

[0057] The systems obtained in Examples 1-3 then received a further layer having a hydrophobizing and oleophobizing effect as the (n+1)th layer. The latter consists of an aqueous dilution [1:5 with water] of equal proportions of a silane (Silres BS 1001 from Wacker, Burghausen, Germany) and a fluorine-containing compound (Unidyne TG 8111, Daikin). For each coating run, 50 mg of dispersion per g of granules was applied.

Example 5

[0058] For verifying the fixation, the thus coated products of Example 4 were embedded into a bitumen matrix. For this purpose, the latter is heated at 200° C. for a short time. The embedded granules remained in storage at 80° C. for a curing time of 24 hours. After having coiled down to room temperature, the granules were torn out of the matrix using a pair of tweezers. It was evaluated whether the fracture was a (desirable) cohesive failure within the bitumen layer, or an adhesive failure, which would indicate weaker binding. In a cohesive failure, the bitumen layer breaks before the particle is detached from the bitumen layer. Such a fracture represents a course of fracture in the region of the bitumen that is not affected by the phase boundary. Such a fracture is a very good indication of high-quality adhesive bonding, see FIG. 2.

[0059] In an adhesive failure, the bitumen layer remains essentially intact. An adhesive failure is a fracture that runs along the phase boundary between the particle and bitumen. In this type of failure, a complete separation of the particle from the bitumen layer occurs. Since this idealized form of failure virtually never occurs in practice, cases with very thin adhering layers of bitumen are also referred to as “adhesive failure”, even though, strictly speaking, it would have to be referred to as an “almost 100% adhesive failure” in this case, see FIG. 3.

[0060] Hereinafter, particles that break when removed from the bitumen layer (cohesive failure in the adherend) are considered to be “sufficiently well fixed”. Together with the cohesive failures, this group forms the numerical value for the desired good fixation.

[0061] Granules that merely received the hydrophobizing and oleophobizing coatings serve as a reference.

TABLE-US-00004 Cohesive failure Adhesive within the within the failure particle bitumen Reference + 86%  7%  7% hydro-/oleophobically coated Example 1 20% 13% 67% Calcined kaolin d50 = 7 μm + hydro-/oleophobically coated Example 2 13% 20% 67% Alumina + hydro-/oleophobically coated Example 3 13% 60% 27% Calcined kaolin d50 = 0.9 μm + hydro-/oleophobically coated Reference, completely uncoated  0% 53% 47%

[0062] The data obtained show that the fixation is significantly improved by the coating.