Roof coating material

Abstract

A method for producing coated particles for a roof coating, comprising the steps of: a) providing cristobalite particles, wherein the cristobalite particles have a D50vol of 0.1 to 5 mm, b) providing a silanizing agent, and c) mixing the cristobalite particles and the silanizing agent in order to obtain coated particles.

Description

[0001] 251058WO - August 15, 2025

[0002] Roof coating material

[0003] The present invention relates to a method for producing coated particles for a roof coating, the coated particles, a method for producing a roof coating, and the roof coating thus obtained.

[0004] It is known to incorporate granules into bitumen roof coatings, which are common in many countries – for example, the USA and Canada – to improve the roof's solar reflection. Such materials are known, for example, from WO 2016 / 001303 Al.

[0005] It is also known to coat such particles with coatings based on silicon compounds or fluorine compounds for hydrophobization.

[0006] WO 2024 / 044527 describes reflective particles in which silicon dioxide in a size of 0.5 to 50 pm is granulated with a binder and sintered at 1300 to <1550 °C to obtain a particularly white product.

[0007] EP 4 086 403 Al describes a granulate in which a particle is coated with an inorganic powder and this is coated with a hydrophobizing or oleophobizing agent.

[0008] Numerous other variations are known.

[0009] The granules must meet numerous requirements:

[0010] • a high reflectivity,

[0011] • good adhesion to the bitumen,

[0012] • a low tendency to become dirty (would reduce reflection),

[0013] • high mechanical and chemical stability,

[0014] • inexpensive and environmentally friendly production.

[0015] The usual manufacturing processes for such particles (see EP 4 086 403 Al or WO 2016 / 001303 Al) apply suitable coating materials 251058WO - 15 August 2025 from aqueous emulsions. This is necessary to achieve full-surface coating of the particles. Suitable coating materials are typically supplied by the manufacturers as aqueous emulsions. They are then further diluted (aqueous) to achieve wetting of the particles with minimal chemical input.

[0016] Although a wide variety of particles and roof coating systems are known, there remains a need for roof coating particles that meet the above requirements.

[0017] The purpose of the invention was to provide alternative roof coating materials.

[0018] The problem is solved by a process for producing coated particles for a roof coating comprising the steps: a) providing cristobalite particles b) providing a silanizing agent c) mixing the cristobalite particles and the silanizing agent to obtain coated particles.

[0019] Surprisingly, it was found that cristobalit particles can be coated with significantly lower water contents in the silanizing agents than other particles, so that the drying process can be carried out more cheaply and in a more environmentally friendly way using less energy.

[0020] According to the invention, cristobalite particles are provided in the first step.

[0021] Cristobalite is a naturally occurring material, but is predominantly produced synthetically from pure quartz sand. Its chemical formula is SiO₂.

[0022] For the process according to the invention, the use of cristobalite particles with a d50voi grain size of 0.1 to 5 mm is particularly suitable. 251058WO - August 15, 2025

[0023] Preferably, crushed cristobalite is used, i.e., cristobalite produced by crushing. Due to the grain shape, better coverage of the bitumen membrane is possible than with round cristobalite, and at the same time the crushed particles are better anchored in the bitumen.

[0024] The d50voi particle size describes the diameter at which 50 voi-% of the particles are smaller than this value and 50 voi-% of the particles are larger than this value. Such particle size distributions are usually determined by sieve analysis, see DIN 66165-2:2016-08.

[0025] In some embodiments, at least one first particle size fraction and one second particle size fraction are used. In a preferred embodiment, the d50voi particle size of the first particle size fraction can be 1.1 to 3 mm and the d50voi particle size of the second particle size fraction 0.1 to 1 mm. Smaller particles offer a larger specific surface area and thus more reflectivity per unit weight. Larger particles exhibit better mechanical stability. Different particle size distributions can also achieve better coverage as a roof coating.

[0026] In principle, three or more particle size fractions can also be used.

[0027] Such particle size fractions are commercially available.

[0028] In a second step, a silanizing agent is provided. The silanizing agent is preferably selected from silanes, siloxanes, fluorosilanes, fluorosilanes, and mixtures thereof.

[0029] Silanes and siloxanes are able to form stable bonds with the cristobalite surface. Fluorosilanes and fluorosilanes exhibit hydrophobic and, above all, oleophobic properties, which, among other things, increase the water repellency of the particles.

[0030] The silanizing agent preferably comprises a mixture of silanes and siloxanes. 251058WO - August 15, 2025

[0031] In a further preferred embodiment, the silanizing agent is combined with a fluorine compound. The fluorine compound can be a fluorosilane or fluorosilanxane, but it can also be, for example, a fluoropolymer (without silicon).

[0032] In another preferred embodiment, the reaction includes an acid. The acid can be added to the silanizing agent or, preferably, to the cristobalite particles. The exact mechanism of action of the acid is not fully understood.

[0033] In a preferred embodiment, amounts of 0.1 to 4 wt% of silanizing agent, based on the weight of the uncoated cristobalite particles, are used to achieve a good coating. Generally, the smaller the particle size of the cristobalite particles, the more silanizing agent must be used.

[0034] Preferably, the water content in the reaction mixture is less than 5 wt%, preferably less than 4 wt%. The less water that can be used, the more energy-efficient the production process.

[0035] The invention also relates to coated particles obtainable by the inventive method and their use for the production of a roofing membrane or a roof coating.

[0036] The subject matter is a process for manufacturing a roof coating, comprising the steps:

[0037] • Providing a layer of bitumen on a roof, and

[0038] • Application of the coated cristobalite particles of the invention.

[0039] The invention also relates to a method for manufacturing a roofing membrane comprising the steps

[0040] Providing a carrier layer with a bitumen layer; applying the coated particles according to claim 10. 251058WO - August 15, 2025

[0041] This is typically done directly during the manufacturing of the roofing membrane.

[0042] The invention also relates to the roofing membrane obtained thereby.

[0043] The invention further relates to a method for producing a roof coating in which the roofing membrane already coated with the particles according to the invention is attached to a roof.

[0044] The invention further relates to the roof coating obtainable by these methods.

[0045] The invention is further explained by the following examples:

[0046] Examples

[0047] materials

[0048] To ensure comparability of the experiments, a mixture of 53 wt% Unidyne TG 8111 and 47 wt% Silres BS 3003 was prepared.

[0049] Unidyne TG 8111 is a fluoropolymer available as an anionic solution with a solids content of approximately 20 wt% from Daikin, Japan.

[0050] Silres BS 3003 is a mixture of silanes and siloxanes available from Wacker, Germany. It is an aqueous solution with a solids content of approximately 60% by weight.

[0051] The composition of mixture A was

[0052] The mixture contains 61.2% water by weight. 251058WO - August 15, 2025

[0053] The cristobalit grain size was mixed from two products with a grain size range of 1 to 3 mm (d50voi 1.7 mm) and a grain size range of 0.5 to 1 mm (d50voi 0.75 mm) in a weight ratio of 4:1 ("Cristobalit").

[0054] The calcined mineral mixture analogous to WO 2016 / 001303 ("calcined mineral mixture") served as a comparison example. The particle size distribution approximately corresponded to the cristobalite mixture.

[0055] The following acids were used:

[0056] HCl concentration = 1 wt.%

[0057] Concentration H2SO4 = 1 wt% Discoloration test:

[0058] A small piece of tar paper is preheated in an oven at 80 °C, the surface is further heated with a gas burner, the particles are homogeneously sprinkled on, pressed down, and then treated in the oven at 80 °C for 4 days. Discoloration of the particles is considered negative. The evaluation, based on a school grading system, was done visually.

[0059] 251058WO - August 15, 2025

[0060] Results

[0061] Influence of acid addition on cristobalite

[0062] V1-V4 - Comparative tests

[0063] With Cristobalit, products can be obtained with lower water contents that have comparably good properties to the state of the art.

[0064] Adding acid improves the product properties of cristobalite, but not of products based on the mineral mixture.

[0065] 251058WO - August 15, 2025

[0066] Influence of acid addition to the silanizing agent

[0067] VI, V2, V5, V6 - Comparative trials

[0068] With Cristobalit, products can be obtained with lower water contents that have comparably good properties to the state of the art.

[0069] Adding acid improves the product properties of cristobalite, but not of products based on the mineral mixture.

[0070] Adding the acid to the cristobalite is more effective than adding the acid to the silanizing agent.

[0071] 251058WO - August 15, 2025

[0072] It has been shown that a lower water content in cristobalite leads to better products. The addition of acid significantly improves the products, especially when it is added to the grain.

Claims

251058WO - August 15, 2025 Patent claims 1. A method for producing coated particles for a roof coating comprising the steps of: a) providing cristobalite particles, wherein the cristobalite particles have a dSOvoi particle size of 0.1 to 5 mm; b) providing a silanizing agent; c) mixing the cristobalite particles and the silanizing agent to obtain coated particles.

2. The method of claim 1, wherein the silanizing agent is selected from silanes, siloxanes, fluorosilanes, fluorosilanes and mixtures thereof.

3. The method of claim 2, wherein the silanizing agent comprises a mixture of silanes and siloxanes.

4. Method according to any one of claims 1 to 3, wherein the silanizing agent additionally contains a fluorine compound, in particular a fluoropolymer.

5. Method according to any one of claims 1 to 4, wherein the cristobalite particles are broken cristobalite particles.

6. Method according to any one of claims 1 to 5, wherein the cristobalite particles comprise at least a first particle size fraction and a second particle size fraction.

7. Method according to claim 6, wherein - the d50voi grain size of the first grain size fraction 1.1 to 3 mm and - the d50voi particle size of the second particle size fraction is 0.1 to 1 mm. 251058WO - August 15, 2025 8. Method according to any one of claims 1 to 7, wherein an acid is added to the silanizing agent or the cristobalite particles.

9. Method according to any one of claims 1 to 8, wherein the cristobalite particles are mixed with 0.1 - 4 wt% of the silanizing agent.

10. Coated particles obtainable by a method according to any one of claims 1 to 9.

11. Use of the coated particles according to claim 10 for the manufacture of a roofing membrane or a roof coating.

12. Method for manufacturing a roofing membrane, comprising the steps - Providing a carrier layer with a bitumen layer - Application of the coated particles according to claim 10.

13. Roofing membrane obtainable by the method according to claim 12.

14. Method for producing a roof coating, comprising the steps: - Providing a layer of bitumen on a roof - Application of the coated particles according to claim 10.

15. Method for producing a roof coating, comprising the steps: - Attaching the roofing membrane according to claim 13 to a roof.

16. Roof coating obtainable by the method according to claim 14 or 15.

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