ROOF COATING SYSTEM

Abstract

The invention relates to a roof coating comprising a bitumen layer with embedded particles.

Claims

1. A roof coating comprising a bitumen layer with embedded particles, wherein said embedded particles comprise particles that are fired mix-tures of from 40 to 70% by weight clay minerals; from 0 to 32% by weight crystalline silicas; from 28 to 45% by weight feldspar; from 0 to 15% by weight other aggregates.

2. The roof coating according to claim 1, wherein said fired mixtures have an open porosity of 0 to 14% by volume as measured according to DIN 993-1.

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

4. The roof coating according to claim 1, wherein said particles are present in an amount of 0.5 to 5 kg per square meter of roof coat-ing.

5. The roof coating according to claim 1, wherein said particles have a particle coating.

6. The roof coating according to claim 5, wherein said particle coating is selected from the group consisting of the group consisting of silicon-containing compounds, fluorine-containing compounds, silicon-fluorine-containing compounds and mixtures thereof.

7. The roof coating according to claim 5, wherein said particle coating comprises a fluorine-containing polymer.

8. The roof coating according to claim 7, wherein said fluorine-containing polymer is present in an amount of 0.1 to 2.0% by weight, based on the particles.

9. The roof coating according to claim 7, wherein said fluorine-containing polymer is a thermoplastic fluoropolymer.

10. The roof coating according to any of claim 7, wherein said fluorine-containing polymer is a fluorinated (meth)acrylate or a fluorinated sili-cone.

11. The roof coating according to any of claim 1, wherein said roof coating has a solar reflectance of at least 80% as measured according to ASTM Standard C1549.

12. The roof coating according to claim 1, wherein said mixtures comprise from 45 to 65% by weight clay minerals; from 5 to 18% by weight crystalline silicas; from 28 to 40% by weight feldspar; from 0 to 10% by weight other aggregates.

13. A process for preparing particles, comprising: a) firing a mixture of from 40 to 70% by weight clay minerals; from 0 to 32% by weight crystalline silicas; from 28 to 45% by weight feldspar; from 0 to 15% by weight other aggregates; b) crushing the mixture into particles.

14. A method of using particles being fired mixtures of from 40 to 70% by weight clay minerals; from 0 to 32% by weight crystalline silicas; from 28 to 45% by weight feldspar; from 0 to 15% by weight other aggregates; comprising the steps of embedding said particles in bitumen.

15. The method of claim 14, wherein said particles are used for roof coverings.

Description

[0061] FIGS. 1 and 2 show embodiments after a soiling test.

[0062] The invention is further illustrated by the following Examples:

EXAMPLE 1: PREPARATION

[0063] The following particles were prepared:

TABLE-US-00001 Sample 1 Sample 2 Sample 3 China clay 59.88% by weight 49% by weight 46.6% by weight Quartz flour 8.97% by weight 16% by weight 15.1% by weight Feldspar 31.15% by weight 35% by weight 33.3% by weight Aluminum oxide 5.0% by weight

[0064] All three samples were fired at 1150 C. under oxidizing conditions, and subsequently crushed to a grain size d50 of 1 mm.

EXAMPLE 2: WATER ABSORPTION

[0065] The samples were weighed exactly in beakers and then soaked with a large excess of water. After 60 min at 25 C., the particles were filtered off, carefully dabbed and weighed again.

[0066] The samples showed the following water absorption:

TABLE-US-00002 Sample 1 Sample 2 Sample 3 10.2% by weight 8.4% by weight 9.4% by weight

EXAMPLE 3: SOLAR REFLECTANCE

[0067] The total solar reflection is measured for an incident angle of 20 to the vertical by means of a reflectometer SSR-ER of the company Devices and Services Co. of Dallas, Tex. Thus, a representative and sufficiently large partial quantity of the sample to be measured is removed. A sample dish with a diameter of 55 mm is filled with the sample to a level of 10 mm, and the surface is leveled with a spatula. The solar reflectance is stated as a mean of five measurements. The particles had the following solar reflectance:

TABLE-US-00003 Sample 1 Sample 2 Sample 3 83.8% 84.1% 85.1%

[0068] The fired china clay as used in the prior art has a solar reflectance of about 81-83%.

EXAMPLE 4: COATING

[0069] The particles according to the invention were then mixed with a fluorine-containing polymer (commercially available as Unidyne TG-8111 of the company Daikin Chemicals Ltd.) in amounts of 0.4% by weight, based on the particles, or 0.6% by weight, based on the particles, wherein the fluoropolymer was previously diluted with water at a ratio of 1:5 to ensure a better contact of the particle surface with the polymer.

[0070] The following solar reflectance was obtained:

TABLE-US-00004 Sample 1 - 0.4% Sample 2 - 0.4% Sample 3 - 0.4% 81.8% 83.9% 84.7% Sample 1 - 0.6% Sample 2 - 0.6% Sample 3 - 0.6% not determined 83.6% 84.8%

[0071] It is found that the fluorine coating does not significantly deteriorate the solar reflectance.

[0072] China clay fired at 1380 C. may also be provided with such a coating. The following values of solar reflectance were obtained:

TABLE-US-00005 Sample - untreated Sample 2 - 0.4% Sample 3 - 0.6% 81.9% 82.5% 82.8%

EXAMPLE 5: DISCOLORATION TEST

[0073] The hydrophobicity of the surface is evaluated by a discoloration test. Thus, 5 g of the granules to be evaluated is intimately mixed with 1.2 g of methyl red reagent (prepared from 7 mg of methyl red, CAS No. 845-10-3 in 200 ml of a 0.02 M sulfuric acid) and 5 ml of distilled water, collected by suction filtration and re-washed with water. Where no hydrophobicity could form, the granules show a reddish color. This is evaluated as failed. The granules remain white only where hydrophobicity could form, which is evaluated as passed.

TABLE-US-00006 Fired china clay - untreated Fired china clay - 0.6% F P Sample 1 - 0.4% Sample 2 - 0.4% Sample 3 - 0.4% P F P Sample 1 - 0.6% Sample 2 - 0.6% Sample 3 - 0.6% not determined P P F = failed P = passed

EXAMPLE 6: FIXATION

[0074] Subsequently, it was examined whether the particles are embedded firmly enough in the bitumen coating. Thus, an amount of about 2 g of bitumen was heated at 200 C. at first in an aluminum dish to produce a smooth surface. The granules are then scattered thinly onto this surface, and all is stored in a heat cabinet at 80 C. for four days. The individual granules are removed using tweezers after cooling down to room temperature. It is evaluated whether there has been a cohesive failure within the bitumen layer or an adhesive failure.

TABLE-US-00007 Fired china clay - untreated Fired china clay - 0.6% C A Sample 1 - 0.4% Sample 2 - 0.4% Sample 3 - 0.4% A C C Sample 1 - 0.6% Sample 2 - 0.6% Sample 3 - 0.6% A A C/A C = cohesive failure A = adhesive failure

[0075] It is found that the particles are embedded in the bitumen matrix relatively firmly. In a cohesive failure, the bitumen layer breaks before the particle is detached from the bitumen layer, while in an adhesive failure, the bitumen layer remains undamaged.

EXAMPLE 7: SOILING TEST

[0076] FIGS. 1 and 2 show a photograph according to Example 6 before the removal of the particles. After cooling, photographs were taken.

[0077] FIG. 1 shows fired china clay, untreated (bottom) and with 0.6% by weight fluorine coating (top).

[0078] FIG. 2 shows samples 1, 2 and 3 with 0.4% by weight fluorine coating in the upper row, and samples 1, 2 and 3 with 0.6% by weight fluorine coating in the lower row.

[0079] In the sample according to the prior art (pure fired china clay, untreated), a clear adhesion of bitumen is shown. In the coated fired china clay and in all six samples of FIG. 2, it is shown that the bitumen does not wet the surface, or only slightly so, so that the particles can cause solar reflection.

[0080] All cited documents are fully included in the disclosure herein, unless such disclosure would be in contradiction to the teaching of the invention.