Double acrylate dispersion coating for roof tiles

Abstract

Coated roof tile, available through a process that includes the following steps: • Providing the roof tile (10) from a mixture which contains or is formed from water, sand and cement; • Applying less than 158 g per square meter of a first acrylate dispersion to at least one surface (14) of the roof tile (10), wherein the application takes place at a time when the roof tile (10) is still moist; • at least partial drying of the first acrylate dispersion to obtain at least a partially dried first coating layer (11); • Applying less than 115 g per square meter of a second acrylate dispersion to the at least partially dried first coating layer (11), wherein the application takes place at a time when the roof tile (10) has already partially dried; wherein • the first acrylate dispersion and the second acrylate dispersion have a viscosity of 17 DINsec to 24 DINsec, in particular 18 DINsec to 22 DINsec, a glass transition temperature (Tg) of 35 degrees Celsius to 40 degrees Celsius, preferably 36 to 38 degrees Celsius, and a minimum film-forming temperature (MFFT) of 5 degrees Celsius to 10 degrees Celsius.

Description

TECHNICAL AREA

[0001] The invention relates to a roof tile coated with two layers of an acrylate-containing dispersion.

[0002] Roof tiles are made from concrete or concrete mixtures. To enhance their appearance and protect them from environmental influences, roof tiles are coated.

[0003] DE3901073A1 relates to a concrete roof tile coated on at least one of its surfaces with a film of a copolymer, optionally filled with aggregates and / or pigments, characterized in that the copolymer contains the following polymerized monomer units: (a) DEG 0.03 to 2 wt.% tin in the form of units of at least one organotin compound with one or more polymerizable C=C bonds, (b) 0.5 to 5 wt.% units of acrylic acid, methacrylic acid, acrylamide, methacrylamide and / or vinylsulfonic acid, (c) 0.1 to 5 wt.% units of carbonyl group-bearing monomers cross-linked with dihydrazides of aliphatic dicarboxylic acid containing 2 to 10 carbon atoms, and (d) the difference to 100 wt.-% of units of at least two monomers from the group of acrylic and methacrylic acid esters of C1 to C8 alkanols and styrene in such selection and in such proportions that the copolymer has a glass transition temperature of -15 to +10 °C before crosslinking. For the production of the coating mass, DE3901073A1 discloses the use of an aqueous dispersion of the copolymer having a viscosity at 23 °C of 0.5 to 2.5 Pa·s and preferably a pH of about 8.

[0004] EP0915071A2 relates to an aqueous composition containing a copolymer formed from ethylene unsaturated monomers as a film-forming component. This composition is used for coating mineral molded parts. The copolymer has a glass transition temperature of 25-80°C, and the monomer contains 0.2-5.0 wt% itaconic acid. Further aspects relate to the production of coated mineral molded parts by application to at least one surface of the part and subsequent drying, resulting in the coated molded part.

[0005] GB2030890A relates to a method for producing a concrete construction product, comprising applying an intermediate layer of cement slurry to a substrate of concrete mix and subsequently applying a coating of a polymer emulsion. GB2030890A further relates to a method in which the slurry layer is applied to an uncured substrate, wherein the substrate and slurry layer are subsequently cured before the polymer coating is applied.

[0006] WO2021209543A1 relates to a process for the production of aqueous polymer dispersions. These aqueous polymer dispersions are suitable as binders in water-based coating formulations, particularly as binders in water-based coating formulations for molded mineral objects. SUMMARY OF THE INVENTION

[0007] The present invention is based on the objective of providing a coated roof tile that overcomes the disadvantages of the prior art, in particular a coated roof tile with a filler-free coating, wherein the coating provides scratch-resistant hardness and application reliability. The use of fillers should be avoided as far as possible. The coating should be high-gloss and prevent efflorescence.

[0008] The problem is solved by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims, which can be combined with one another in any technologically meaningful way. The description, particularly in conjunction with the figures, further characterizes and specifies the invention.

[0009] Accordingly, a coated roof tile is planned, obtainable through a process that includes the following steps: • Providing the roof tile from a mixture containing or formed from water, sand and cement; • Applying less than 158 g per square meter of a first acrylate dispersion to at least one surface of the roof tile, the application taking place at a time when the roof tile is still wet when it is made available; • at least partial drying of the first acrylate dispersion to obtain at least a partially dried first coating layer; • Applying less than 115 g per square meter of a second acrylate dispersion to the at least partially dried first coating layer, the application taking place at a time when the roof tile has already begun to dry; wherein • the first acrylate dispersion and the second acrylate dispersion have a viscosity of 17 DINsec to 24 DINsec, in particular 18 DINsec to 22 DINsec, a glass transition temperature of 35 degrees Celsius to 40 degrees Celsius, preferably 36 to 38 degrees Celsius, and a minimum film formation temperature of 5 degrees Celsius to 10 degrees Celsius.

[0010] The resulting roof tile has a high gloss level and is scratch-resistant. A closed, crack-free film forms during the drying of the coating layers. The gloss level can be quantified and measured using optical inspection methods.

[0011] The acrylate dispersions form homogeneous, uniformly thick layers at the specified application rates. This can be achieved with the stated physical properties and an amount of less than 3 g (grams) per roof tile. The mass of 3 g per square meter refers to the moist, wet dispersion. In the dried state, this mass is reduced according to the solids content.

[0012] The first and second coating layers of the acrylate dispersion are sprayed onto the roof tile. Due to its precisely defined viscosity, the acrylate dispersion, as prepared and applied, does not flow into the deeper areas of the tile. Therefore, the acrylate dispersion is distributed evenly and with a uniform thickness across the surface. Tested roof tiles weighed between 3.6 and 3.9 kg when wet and between 3.55 and 3.85 kg when dry. Thus, between 0.05 kg and 0.35 kg of liquid escapes from the roof tiles during drying.

[0013] The viscosity was determined using a viscosity cup. In this method, the acrylate dispersion is poured into a cup immediately before application to the roof tiles. The cup has a circular opening with a defined diameter of 4 mm. Based on the cup volume, the nozzle diameter, and the measured time it took for the liquid to flow out, its viscosity can be determined. The measurement was taken at approximately room temperature, i.e., around 21 degrees Celsius.

[0014] Here, the flow time (with reference to the standard and nozzle size) is specified as a measure of viscosity, based on DIN EN ISO 2431:2019. Viscosity is measured as flow time in "DIN seconds". Therefore, a viscosity range is also specified within which sufficient wetting of the roof tile can be achieved with the acrylate dispersion.

[0015] The glass transition temperature (Tg) is the temperature at which the acrylate dispersion transitions from a rigid, glassy state to a soft, rubbery state. Using an acrylate dispersion with a glass transition temperature (Tg) within the specified temperature range of 35°C to 40°C, particularly 36°C to 38°C, allows for a compromise even with various drying processes, such as those encountered in differently configured curing chambers. This compromise lies in the fact that cracking and flaking can be avoided at the specified glass transition temperature. Cracks and flaking occur when the dispersion is already dry near the surface and floats on a still-moist coating layer of the dispersion.

[0016] The minimum film formation temperature, or minimum film temperature, represents the lowest temperature at which the acrylate dispersion forms a tightly cohesive film.

[0017] In other words, a certain minimum film formation temperature is required for the formation of a solid, continuous surface from the acrylate dispersion. According to DIN 53 787, the minimum film formation temperature is defined as the lowest temperature at which a thin coating layer of a polymer dispersion still dries to form a continuous film. If the minimum film formation temperature is not reached, a cracked film will form. An acrylate dispersion must be selected that exhibits both the aforementioned glass transition temperature and the minimum film formation temperature.

[0018] The aforementioned properties can be adjusted in a process preceding the coating process by modifying the acrylate dispersion. Additives can be used to adjust the viscosity. Defoamers can be used to prevent foaming beforehand. The same acrylate dispersion is used for both the first and second coating layers.

[0019] In other words, the aforementioned physical properties such as viscosity, glass transition temperature, and minimum film-forming temperature refer to the acrylate dispersion after the addition of pigments and other additives (defoamers, viscosity modifiers, and the like). After the addition, the acrylate dispersion is mechanically stirred in tanks.

[0020] For further clarification, the physical properties refer to the acrylate dispersion in the form in which it is applied to the roof tiles, particularly by spraying. The properties are checked again in a tank by taking samples. The tank is located downstream of a pump that pressurizes the acrylate dispersion. The pressurized acrylate dispersion is then sprayed as evenly as possible onto the roof tiles through nozzles. The pressure can reach up to 8 bar. The nozzles are adjusted to ensure that a layer of uniform thickness is formed on the roof tile, distributed across its surface.

[0021] In one embodiment, the first acrylate dispersion and / or the second acrylate dispersion are each a so-called pure acrylate dispersion. Pigments for coloring may be present, as well as additives for adjusting the desired properties, minor residues, and minor impurities, the latter in each case without significant effects on the basic properties.

[0022] An acrylate dispersion is an aqueous polymer dispersion whose polymer component consists predominantly of acrylic and / or methacrylic acid esters; other monomers may be present in relevant proportions. A so-called pure acrylate dispersion, on the other hand, is a polymer dispersion whose polymer component consists exclusively or to a very high extent of acrylic and methacrylic acid esters.

[0023] Short-chain alkyl acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate and isobutyl acrylate, long-chain or branched alkyl acrylates such as 2-ethylhexyl acrylate, n-hexyl acrylate, n-octyl acrylate, lauryl acrylate, isotridecyl acrylate, stearyl acrylate, cyclohexyl acrylate, norbornyl acrylate, isobornyl acrylate or tert-butyl acrylate, functional monomers such as hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, glycidyl methacrylate as well as benzyl acrylate, methoxyethyl acrylate and methoxypropyl acrylate, the corresponding methacrylates and other commonly used (meth)acrylates can be used as monomers.

[0024] The pure acrylate dispersion contains no or only negligible amounts (at most 5%) of monomers that are not acrylic or methacrylic acid esters, such as styrene, vinyl acetate, acrylonitrile or butadiene.

[0025] The main monomers can be, in particular, methyl methacrylate (MMA), n-butyl acrylate (n-BA), ethyl acrylate (EA) and 2-ethylhexyl acrylate (2-EHA).

[0026] Furthermore, a coated roof tile is provided, wherein the first acrylate dispersion and / or the second acrylate dispersion each has a solids content of 45 to 52 wt.%, preferably 48 to 50 wt.%, based on the total weight of the respective acrylate dispersion.

[0027] The solids content is a portion of the acrylate dispersion that can be described as non-volatile. The volatile components are primarily solvents and / or water. The non-volatile fraction can consist of high-molecular-weight organic compounds. Besides practical determination by weighing, before and after drying the acrylate dispersion, the solids content can also be calculated if the composition is known.

[0028] In one embodiment, a roof tile is provided in which the first acrylate dispersion and / or the second acrylate dispersion each has a pigment content of 2 to 12 wt.%, preferably 4 to 6 wt.%, based on the total weight of the respective acrylate dispersion.

[0029] In one embodiment, the first acrylate dispersion and / or the second acrylate dispersion each have a pH value in the range of 7.0 to 9.0.

[0030] Concrete has a pH value of 12.5 to 13. The pH value of the acrylate dispersion should be lower to ensure the formation of a closed, crack-free film.

[0031] In one embodiment, a roof tile is provided in which the first acrylate dispersion and / or the second acrylate dispersion is / are each free of fillers and / or film preservatives.

[0032] It can also be stipulated that no film preservatives or biocides are included. Furthermore, the acrylic dispersion should not contain microplastics. Defoamers can be added if excessive foaming occurs. An acrylic dispersion with high colorfastness and weather resistance should be selected.

[0033] Another aspect concerns a roof tile, where the same acrylate dispersion was used for both the first coating layer applied in a wet state and the second coating layer applied in a partially dried state.

[0034] In this way, both coating processes can be carried out with the same dispersion. The costs for procuring, storing, and preparing a separate second dispersion are eliminated.

[0035] Another aspect concerns a method for manufacturing a roof tile, wherein the method includes a further process step between the provision of the roof tile and the application of the first acrylate dispersion, wherein the further process step comprises the application of a fine mortar layer, preferably a smoothing fine mortar layer, to at least one surface of the roof tile.

[0036] The fine mortar smooths the otherwise rough surface of the roof tile. Surprisingly, this leads to a less favorable behavior of the coating.

[0037] Fine mortar can be formed from a mixture consisting of 60 wt% sand with a particle size of 0 to 2 mm, 36 wt% cement, 3.4 wt% pigments, and 0.6 wt% residues or additives, with a water-cement ratio of 0.3 to 0.35. In tests on roof tiles coated with fine mortar, cracking and defects in the coating layers were more likely to occur when the viscosity of the acrylate dispersion was too low or the application rate was too high. The application rate is the mass or weight of the acrylate dispersion applied to a roof tile in its wet state, i.e., immediately after spraying or application.The claimed properties, wherein the first acrylate dispersion and the second acrylate dispersion have a viscosity of 17 DINsec to 24 DINsec, in particular 18 DINsec to 22 DINsec, a glass transition temperature (Tg) of 35°C to 40°C, preferably 36°C to 38°C, and a minimum film-forming temperature (MFFT) of 5°C to 10°C, result in uniform, closed coating layers on surfaces with a fine mortar layer. The fine mortar layer is applied in liquid form to the still-damp roof tile immediately after its shaping by extrusion and cutting.

[0038] Tests have shown that less than 130 g per square meter of the first coating layer of acrylate dispersion needs to be applied if the corresponding fine mortar layer has been applied beforehand.

[0039] This prevents the formation of an inhomogeneous, unevenly distributed first coating layer. On a rough surface without fine mortar, the acrylate dispersion does not flow as well, allowing a larger quantity of acrylate dispersion to be sprayed on.

[0040] As mentioned, the quantity or mass specification refers to the wet acrylate dispersion. In the finished roof tile, a liquid portion evaporates, leaving a solids content of 45 to 52 wt.%, preferably 48 to 50 wt.%, based on the total weight of the acrylate dispersion.

[0041] In a further embodiment, a roof tile is provided in which less than 72 g per square meter of the second acrylate dispersion is applied to the dried first coating layer of acrylate dispersion, if the second coating layer is dried within less than 10 seconds after application at temperatures of 50 degrees Celsius to 100 degrees Celsius.

[0042] In tests, drying at relatively high temperatures (> 70 degrees Celsius) following the application of the second coating layer led to cracking in the second coating layer. Reducing the amount of coating applied allows for the formation of a closed, crack-free, and uniform film.

[0043] In a further embodiment, a roof tile is provided in which less than 115 g per square meter of the second acrylate dispersion is applied to the dried first coating layer of acrylate dispersion, if the second coating layer can dry at ambient temperature without the application of heat.

[0044] If dried at ambient temperature, which is generally less than 30 degrees Celsius, the acrylate dispersion hardens sufficiently slowly. Even with larger application quantities, cracking does not occur. SHORT FIGURE DESCRIPTION

[0045] Further details and advantages of the disclosure are described below with reference to the accompanying drawings. These show: Fig. 1: Schematic diagram of a plant for the production and packaging of concrete roof tiles; Fig. 2: schematically a cross-section through a roof tile which has been coated with two layers of an acrylate dispersion; Fig. 3: schematically a cross-section through a roof tile which was coated with a coating layer of a smoothing, low-viscosity concrete mixture before two layers of an acrylate dispersion were applied; Fig. 4a: schematically, an upper side of a roof tile on which a film has formed as a result of a drying process, floating on still moist acrylate dispersion; and Fig. 4b: schematically, an upper side of a roof tile on which cracks and flakes or slabs have formed due to improper processing. DETAILED FIGURE DESCRIPTION

[0046] The figures serve to illustrate one or more exemplary embodiments. In the figures, roof tiles and the layers or coatings applied to them are not shown to scale. Terms such as "right," "left," "above," "below," "above," and "below" are used to explain the elements depicted in the figures and should not be interpreted as indicating that the illustration represents the only possible embodiment. "Downstream" and "upstream" refer to a transport direction of roof tiles on a transport device, for example, in Fig. 1, where "upstream" denotes a movement or arrangement opposite to a transport direction and "downstream" denotes a movement or arrangement in the transport direction. Identical or equivalently acting elements each have the same reference numerals, in particular roof tiles, regardless of their processing state.

[0047] Fig. Figure 1 schematically shows a plant 101 for the production and packaging of concrete roof tiles 10. Such a plant was used in numerous test series for the production of roof tiles to find a suitable acrylate dispersion. Concrete for roof tiles of this type 10 is essentially made from sand, cement, and water.

[0048] Sand and cement are temporarily stored in storage silos 102. Pipe systems 103 connect the storage silos 103 to so-called premixers 104. A circulating conveyor belt 106 is used to transport the roof tiles 10 to the respective plant components.

[0049] In a roof tile machine 105, concrete is pressed into a strand 109 by a roller (not shown), which rests on the aluminum forms 107. The term "aluminum form" is a combination of the abbreviation for aluminum and the word "form." The aluminum forms 107 are accordingly made of an aluminum material or an aluminum alloy. The aluminum forms 107 support the still-soft concrete roof tiles 10 and serve to transport them to the respective processing stations without damage. The aluminum forms lie flat on the conveyor belt 106. In a cutting device 108, the strand 109 is cut to the length required for the roof tiles 10.

[0050] After the roof tiles 10 are cut in the cutting device 108, the roof tiles 10 are optionally coated with a first coating layer 11 of acrylate dispersion. This takes place in a first coating device 110.

[0051] The first coating device 110 comprises a tank 111 and a pump 112. The pump delivers liquid, in particular acrylate dispersion, at a preset pressure to one or more nozzles 113. The acrylate dispersion is checked in the tank 111 for its chemical and physical properties. In particular, its viscosity is measured. Pigments can also be added. Furthermore, an antifoaming agent can be added if the acrylate dispersion is found to be prone to foaming. The acceptable degree of foaming can be determined empirically. The viscosity can be adjusted by means of further additives.

[0052] The acrylate dispersion is sprayed evenly onto the moving roof tiles 10 via nozzles 113. During the tests, the system 101 and the nozzles 113 were set so that less than 22 grams of the acrylate dispersion were applied to each roof tile. This corresponded to a quantity of 158 grams per square meter, as the roof tile is 330 mm wide and 420 mm long. A first coating layer 11 is formed on the roof tile 10 (see Fig. 2).

[0053] The applied quantity of moist acrylate dispersion can be measured by placing a clean, weighed reference element (not shown) the size of a roof tile 10 onto the conveyor belt 106. The reference element can then be weighed again as quickly as possible. The difference between the clean reference element and the coated reference element allows the application quantity sprayed onto each roof tile 10 through the nozzles 113 to be determined. While a roof tile 10 could also be weighed, the resulting inaccuracy would be too high since these tiles adhere to the aluminum plates 107, each has a different weight, and they dry on their own. Easily handled objects such as sheets of metal are suitable as reference elements.

[0054] Immediately after the first coating layer 11 is applied to the coating device 110, the roof tiles 10 are dried in a hardening chamber 114.

[0055] The hardening chambers 114 are not universally identical in their construction at every plant 101. The transport of the roof tiles 10 into and out of the hardening chamber 114 also varies slightly at each roof tile factory. In some hardening chambers, the roof tiles are moved into the chamber 114 using forklifts. In other plants, the roof tiles 10 are conveyed into the hardening chamber 114 via conveyor belts. In some plants where trials are being conducted, the roof tiles 10 are dried at room temperature, i.e., approximately 21 degrees Celsius.

[0056] The required application quantity or mass of a coating layer 11, 12 and composition could be applied and dried in all plants, resulting in a homogeneous and closed coating layer. Good results are achieved when no cracks appear according to the specifications. Fig. 4b form on the layers and a scratch-resistant, closed coating layer 11, 12 is formed, which protects the concrete of the roof tile 10 for as long as possible from environmental influences such as ultraviolet light, chemical influences such as acid rain and particles as well as plant growth.

[0057] The roof tiles 10, still lying on the aluminum trays 107, are returned to the conveyor belt 106, either mechanically or manually. This can take place the day after the first coating layer 11 has been applied.

[0058] After the roof tiles 10 have been returned to the circulating conveyor belt, they are removed from the aluminum supports 107 in a stripping machine 115.

[0059] A second coating layer 12 is applied to a further (second) coating device 116 (see Fig. 2 and Fig. 3) The second coating layer 116 is the same acrylate dispersion that was already applied to the still dry roof tiles 10 in the first coating unit 110. By using only one acrylate dispersion for the first coating layer 11 and the second coating layer 12, costs for storage and handling of the acrylate dispersion can be saved.

[0060] In a surface dryer 117, the roof tiles 10 are dried downstream of the coating unit 116. In some plants where trials were conducted, the roof tiles 10 are dried in the surface dryer 117 under the influence of hot air or a hot gas stream at temperatures between 80°C and 200°C. In other plants, the roof tiles 10, or the second coating layer 12, are dried for approximately 30 minutes at ambient temperature. In the latter surface dryer, the roof tiles 10 remain for 30 minutes at approximately 20°C before they are sufficiently dry to be processed further.

[0061] In a quality control station 118, the finished roof tiles 10 are inspected and any defects are sent to a breakage box 119. If the roof tiles 10 pass quality control station 118, they are packed into packages (not shown) in a packaging unit 120. Further steps can be carried out after coating. Within the packages, the roof tiles 10 touch each other at contact points (not shown). At these contact points, the roof tiles 10 may have undesirable stains and damage. Therefore, the areas on the underside of the roof tiles 10 that come into contact with the upper sides are coated with a layer of hot melt adhesive.

[0062] In plant 101 with different curing chambers 114 and different surface dryers 117 such as the one described herein, nine test series with different colors were carried out. In addition to the already mentioned objective of using only one acrylate dispersion for both layers 10 and 11, the different concrete compositions, curing chambers 114 and surface dryers 117 also had to be taken into account.

[0063] After applying two coats to approximately 1000 roof tiles (10), they were tested for suitability. The roof tiles (10) are then wrapped in plastic film in packaging equipment and stacked on pallets.

[0064] This is followed by tests such as freeze-thaw cycle tests, chemical tests and irrigation tests.

[0065] Fig. Figure 2 shows a correspondingly produced concrete roof tile 10, wherein the concrete is formed from water, sand and cement, and wherein the roof tile is 300 mm to 350 mm wide and 400 mm to 450 mm long (not shown), wherein the roof tile 10 is coated with two coating layers 11, 12 of an acrylate dispersion on a surface 14 as intended, which is exposed to environmental influences such as light, water and dirt.

[0066] The first coating layer 11 was applied to still-damp roof tiles 10 in a coating device 110 as described above. The second coating layer 12 was applied to roof tiles 10 after they had been dried in a curing chamber 114.

[0067] Fig. Figure 3 shows a roof tile 10, which was produced by means of a further process step, wherein the further process step comprises the application of a fine mortar layer 16. The fine mortar can be formed by a mixture consisting of 60 wt% sand with a particle size of 0 to 2 mm, 36 wt% cement, 3.4 wt% pigments and 0.6 wt% residues or additives, with a water-cement ratio of 0.3 to 0.35.

[0068] Fig. Figure 4a schematically shows a cross-section of a roof tile 10 on which a film 42 has formed as a result of a drying process, floating on a portion 41 of still moist acrylate dispersion. During drying, the portion 41 itself becomes film 42 until the acrylate dispersion is no longer moist. The film 42 should not crack during drying.

[0069] Fig. Figure 4b schematically shows a cross-section of a roof tile 10 where the acrylic dispersion dried too quickly. The film 42 (see also Fig. 4a) breaks open, consequently forming platelets 43, which are located on the portion 41 (see also Fig. 4a) float on liquid acrylate dispersion and cause cracking 43.

[0070] If the drying process is slower, i.e., at lower temperatures, over a longer period, or at room temperature, cracking does not occur as described in [reference]. Fig.Figure 4b illustrates this. Therefore, cracking is more likely to occur with surface dryers operating at high temperatures between 50 and 100 degrees Celsius, or even 200 degrees Celsius. This can be prevented by reducing the amount of acrylate dispersion applied to less than 72 g per square meter. In a corresponding test, roof tiles 10 were dried at 80 degrees Celsius within 5 seconds of applying the second coating layer of acrylate dispersion.

[0071] A larger quantity, namely a maximum of 115 g per square meter, of the second acrylate dispersion can be applied to the dried first coating layer 11 if the second coating layer 12 is allowed to dry at ambient temperature without heat treatment. In a corresponding test, the roof tiles 10 were dried at room temperature, i.e., approximately 21 degrees Celsius, for 30 minutes before further processing. Under these conditions, a continuous film 42 can form and dry evenly, creating a closed surface.

[0072] In summary, the embodiments relate to a coated roof tile 10, obtainable by a method comprising the steps of: providing the roof tile 10 from a mixture comprising or formed from water, sand, and cement; applying less than 158 g per square meter, in particular less than 130 g per square meter, of a first acrylate dispersion to at least one surface 14 of the roof tile 10, wherein the application takes place at a time when the roof tile 10 is still moist; at least partially drying the first acrylate dispersion to obtain an at least partially dried first coating layer 11; applying less than 115 g per square meter of a second acrylate dispersion to the at least partially dried first coating layer 11, wherein the application takes place when the roof tile 10 has already partially dried;wherein the first acrylate dispersion and the second acrylate dispersion have a viscosity of 17 DINsec to 24 DINsec, in particular 18 DINsec to 22 DINsec, a glass transition temperature (Tg) of 35 degrees Celsius to 40 degrees Celsius, preferably 36 to 38 degrees Celsius, and a minimum film-forming temperature (MFFT) of 5 degrees Celsius to 10 degrees Celsius. REFERENCE MARK LIST 10 roof tiles 11 Coating layer 12 coating layers 14 Surface 16 Fine mortar layer 41 share 42 Film 43 tiles 44 Riss 101 Annex 102 storage silos 103 pipe system 104 premixers 105 Roof tile machine 106 Conveyor belt 107 Aluform 108 Cutting device 109 strand 110 Coating equipment 111 Tank 112 Pump 113 nozzles 114 Hardening chamber 115 Stripping machine 116 Coating equipment 117 Surface dryers 118 Quality control 119 Broken Box 120 packaging equipment QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 3901073A1

[0003] EP 0915071A2

[0004] GB 2030890A

[0005] WO 2021209543A1

[0006] Cited non-patent literature

[0000] DIN EN ISO 2431:2019

[0014]

Claims

[1] Coated roof tile, obtainable by a process comprising the steps: • Providing the roof tile (10) from a mixture which contains or is formed from water, sand and cement; • Applying less than 158 g per square meter of a first acrylate dispersion to at least one surface (14) of the roof tile (10), wherein the application takes place at a time when the roof tile (10) is still moist; • at least partial drying of the first acrylate dispersion to obtain at least a partially dried first coating layer (11); • Applying less than 115 g per square meter of a second acrylate dispersion to the at least partially dried first coating layer (11), wherein the application takes place at a time when the roof tile (10) has already partially dried; wherein • the first acrylate dispersion and the second acrylate dispersion have a viscosity of 17 DINsec to 24 DINsec, in particular 18 DINsec to 22 DINsec, a glass transition temperature (Tg) of 35 degrees Celsius to 40 degrees Celsius, preferably 36 to 38 degrees Celsius, and a minimum film-forming temperature (MFFT) of 5 degrees Celsius to 10 degrees Celsius. [2] Coated roof tile according to claim 1, wherein the first acrylate dispersion and / or the second acrylate dispersion each comprise a so-called pure acrylate dispersion. [3] Coated roof tile according to claim 1 or 2, wherein the first acrylate dispersion and / or the second acrylate dispersion each has a solids content of 45 to 52 wt.%, preferably 48 to 50 wt.%, based on the total weight of the respective acrylate dispersion. [4] Coated roof tile according to one of claims 1 to 3, wherein the first acrylate dispersion and / or the second acrylate dispersion each has a pigment content of 2 to 12 wt.%, preferably 4 to 6 wt.%, based on the total weight of the respective acrylate dispersion. [5] Coated roof tile according to any one of claims 1 to 4, wherein the first acrylate dispersion and / or the second acrylate dispersion each has a pH value in the range of 7.0 to 9.

0. [6] Coated roof tile according to any one of claims 1 to 5, wherein the first acrylate dispersion and / or the second acrylate dispersion is / are each free of fillers and / or film preservatives. [7] Coated roof tile according to any one of claims 1 to 6, wherein the first acrylate dispersion and the second acrylate dispersion are the same acrylate dispersion. [8] Coated roof tile according to one of claims 1 to 7, wherein the method comprises a further process step between the provision of the roof tile (10) and the application of the first acrylate dispersion, wherein the further process step comprises the application of a fine mortar layer (16), preferably a smoothing fine mortar layer (16), to at least one surface (14) of the roof tile (10). [9] Coated roof tile (10) of claim 8, wherein less than 130 g per square meter of the first coating layer (11) of acrylate dispersion is applied when the corresponding fine mortar layer (16) has been applied previously. [10] Coated roof tile (10) according to one of the preceding claims, wherein less than 72 g per square meter of the second acrylate dispersion is applied to the dried first coating layer (11) acrylate dispersion when the second coating layer (12) is dried within less than 10 seconds at temperatures of 50 degrees Celsius to 100 degrees Celsius following the application. [11] Coated roof tile according to one of the preceding claims, wherein less than 115 g per square meter of the second acrylate dispersion is applied to the dried first coating layer (11) acrylate dispersion, if the second coating layer can dry at ambient temperature without heat treatment following application.

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