Method for producing mineral chips with coating for roofing buildings

Abstract

FIELD: construction materials.SUBSTANCE: present invention relates to a method for producing coated mineral chips for the manufacture of roofing elements with a bitumen base or a base comprising a vinyl or acrylic adhesive material for roofing buildings. The method includes the following steps: preparing a certain quantity of unprocessed mineral chips; after preparing a certain quantity of unprocessed mineral chips, introducing said unprocessed mineral chips into a mixing device together with a first processing mixture comprising water, pigments, sodium silicate and / or potassium silicate, kaolin; after introducing the unprocessed mineral chips into the mixing device, mixing the unprocessed mineral chips and the first processing mixture to obtain coated mineral chips. After mixing the unprocessed mineral chips and the first processing mixture, the coated mineral chips are heated to a firing temperature (Tc) of 300 °C to 480 °C, and after heating the coated mineral chips, the coated mineral chips are cooled to the intermediate cooling temperature (Tri), which is 280 °C to 390 °C. The first processing mixture comprises one or more organosiloxanes and / or silanes, which are thus applied to the untreated mineral chips using an aqueous solution.EFFECT: obtaining coated chips at relatively low production costs and operating time, as well as to chips with a specific colour, high surface hydrophobicity and high adhesion to bitumen-type bases or to bases comprising acrylic or vinyl adhesive materials.13 cl, 5 tbl, 6 dwg

Description

[0001] The present invention relates to a method for producing coated mineral chips suitable for the manufacture of roofing products having a bitumen-type base or a base containing a vinyl or acrylic-type adhesive material for roofing buildings (e.g. roofs), such as, for example, flexible shingles (Canadian tiles), bitumen sheathing, etc.

[0002] Currently, it is known to cover the roofs of buildings with roofing products such as flexible shingles or bitumen sheathing, containing a bitumen-type base or a base containing a vinyl or acrylic-type adhesive material coated with mineral chips.

[0003] The main purpose of these roofing products is to protect the roof covering of buildings from the effects of weather conditions.

[0004] Raw mineral chips are usually colored with inorganic pigments to obtain roofing products of the desired color.

[0005] It should be noted that in this text the term "raw mineral chips" means chips consisting of a group of small fragments of a particular mineral (or group of minerals) as they occur in their natural state, i.e. not previously subjected to processing by applying a coating of other substances and / or surface treatment that changes the chemical and / or physical properties.

[0006] It is known that in order to impart antifouling properties to untreated mineral chips and thus prevent the formation of algae, mold, lichen, etc. on roofing products coated with them, additives such as metal oxides (e.g. copper oxides and / or zinc oxide and / or silver oxide) or metal particles (e.g. copper and / or zinc) in the form of fine powders are added to them; such additives are usually added to the chips during the painting process.

[0007] These processes produce a chip that is referred to in this document as "coated mineral chip." It is also known to treat mineral chip by applying a coating of hydrocarbon oil or a mixture of hydrocarbon oils containing hydrophobic molecules (i.e., molecules capable of imparting hydrophobicity to the coated surface of the mineral chip) and molecules that promote adhesion to the substrate. Examples of molecules used as hydrophobic and adhesion-promoting agents include organosiloxanes, silanes, and silicones with alkyl chains ranging in length from 1 to 25 carbon atoms (C1-C25).

[0008] These molecules, carried by the hydrocarbon oil (or mixture of oils), are fixed on the surface of the crumb, forming chemical bonds with the atoms of this surface.

[0009] The alkyl groups of these molecules, chemically bonded to the surface of the chips, have a low chemical affinity for water molecules; the location of these alkyl groups between possibly present water molecules and the surface of the coated mineral chips makes this surface hydrophobic.

[0010] Alkyl groups, on the other hand, have a high chemical affinity for organic molecules, such as those of the bitumen used as a base in roofing products; this affinity results in the ability of these molecules to improve the adhesion between the mineral chips and the bitumen base.

[0011] However, this well-known method of producing coated mineral chips has some disadvantages.

[0012] In fact, the high chemical affinity between the hydrocarbon oil (or mixture of hydrocarbon oils) used to carry the hydrophobic and adhesion promoting molecules and the alkyl groups of these molecules prevents the formation of strong chemical bonds between these molecules and the surface of the coated mineral chips.

[0013] Therefore, the hydrophobic and adhesion promoting molecules tend to remain dispersed in the hydrocarbon oil (or hydrocarbon oil mixture) so that when roofing products with such known type of chips are installed, these molecules are quickly washed away in the weather along with the oil or oil mixture.

[0014] As a result, such mineral chips with a known type of coating lose their hydrophobicity over time.

[0015] The main object of the present invention is to solve the problems listed above and, therefore, to obtain a coated mineral chips for roofing products for building roofs, which is hydrophobic, antifouling, has high adhesion to bitumen bases and to bases containing vinyl or acrylic type adhesive material, in particular for outdoor use, and which maintains these characteristics unchanged for a relatively long time, even when exposed to atmospheric conditions or significant mechanical loads.

[0016] Within the framework of this problem, one of the objectives of the invention is to obtain a coated mineral chip for covering roofing products of buildings at relatively low production costs.

[0017] The applicant realized that it is possible to apply a coating containing organosiloxanes and / or silanes to untreated mineral chips using water instead of hydrocarbon oil (or oils) as a carrier, thereby eliminating the above-mentioned leaching problem found in the prior art and obtaining a coated mineral chip with high and durable hydrophobic and antifouling properties, which has high adhesion to bitumen bases or bases containing vinyl or acrylic adhesive material, and which maintains these characteristics unchanged for a relatively long time even when exposed to atmospheric conditions or significant mechanical loads.

[0018] In particular, the objective and purpose of the present invention are achieved by a method for producing coated mineral chips for the manufacture of roofing elements with a bitumen base or a base containing a vinyl or acrylic type adhesive material for roofing buildings, comprising the following steps:

[0019] - preparation of unprocessed mineral chips;

[0020] - after preparing the raw mineral chips, introducing said raw mineral chips into a mixing means together with a first processing mixture containing water, pigments, sodium silicate and / or potassium silicate, kaolin and, preferably, but not necessarily, one or more additives with antifouling properties, such as, for example, copper oxides and / or zinc oxide and / or silver oxide and / or metallic copper and / or metallic zinc;

[0021] - after introducing this raw mineral chips into the mixing means, mixing the raw mineral chips and the first processing mixture to obtain coated mineral chips;

[0022] After mixing the raw mineral chips and the first processing mixture, heating the coated mineral chips to a predetermined firing temperature;

[0023] - after heating the coated mineral chips, cooling the coated mineral chips to a predetermined intermediate cooling temperature.

[0024] In the method according to the invention, the first treatment mixture comprises one or more organosiloxanes and / or silanes, which are thus applied to the untreated mineral chips using an aqueous solution.

[0025] Preferably, in the case where the method according to the invention includes applying one or more organosiloxanes and / or silanes to mineral chips on a coated mineral chip, this method includes, after or simultaneously with cooling the coated mineral chip, an additional step of bringing the coated mineral chip into contact with a second processing mixture containing water and one or more organosiloxanes and / or silanes.

[0026] Preferably, the first treatment mixture contains one or more additives with antifouling properties.

[0027] Preferably, one or more additives with antifouling properties include copper oxides and / or zinc oxide and / or silver oxide and / or metallic copper and / or metallic zinc.

[0028] The firing temperature is preferably less than 480°C.

[0029] The firing temperature is more preferably between 300°C and 350°C.

[0030] The heating stage of the coated mineral chips to the specified firing temperature preferably lasts from 10 to 25 minutes.

[0031] This firing time is reduced compared to the firing time of known solutions, which is approximately 30-40 minutes; this reduction in firing time is advantageous because it reduces the risk of decomposition of organosiloxanes and / or silanes as a result of the firing itself.

[0032] The intercooling temperature is preferably between 280 and 390°C.

[0033] Preferably, the method according to the invention includes, after or simultaneously with cooling the coated mineral chips to an intermediate cooling temperature, a step of bringing the coated mineral chips into contact with a third processing mixture containing a hydrocarbon solvent based on polyalkylbenzenes, in which phosphorus and / or silane esters of ethoxylated fatty acids are dispersed.

[0034] Preferably, the method according to the invention includes, after preparing a certain amount of unprocessed mineral chips and before introducing the unprocessed mineral chips into the mixing means, a preheating step in which the unprocessed mineral chips are heated to a predetermined preheating temperature.

[0035] The preheating temperature set preferably is between 60 and 70°C.

[0036] Preferably, during the preheating step, the raw mineral chips are heated to a preheating temperature for a predetermined time, preferably within 5 to 10 minutes.

[0037] Preferably, the method according to the invention includes, simultaneously with or after the preheating step and before introducing the raw mineral chips into the mixing means, a step of mechanically mixing the raw mineral chips.

[0038] Preferably, in the method according to the invention, between the preheating stage and the stage of introducing the unprocessed mineral chips into the mixing means, the unprocessed mineral chips are contained in a heating furnace, wherein the method preferably includes simultaneously or after the preheating stage and before introducing the unprocessed mineral chips into the mixing means, a stage of removing air present in the zone of the preheating furnace containing the unprocessed mineral chips.

[0039] Preferably, the unprocessed mineral chips have a grain size of 100 to 10 mesh.

[0040] Preferably, the crumbs may consist of grains of different sizes; for example, the crumbs may preferably consist of less than 10% of granules with a size of 10 mesh (average diameter of about 2 mm), from 55 to 75% of granules with a size of 14 mesh (average diameter of 1.41 mm), from 15 to 30% of granules with a size of 20 mesh (average diameter of 0.84 mm), from 5 to 15% of granules with a size of 30 mesh (average diameter of 0.59 mm), less than 10% of granules with a size of 35 mesh (average diameter of 0.5 mm).

[0041] Preferably, the unprocessed mineral chips include basaltic and / or shale and / or cristobalite and / or olivine chips, or, more generally, one or more rocks and / or minerals of the type commonly used for the manufacture of building products.

[0042] The features and advantages of the present invention will become more apparent from the following description, which is to be understood as illustrative and not limiting, with reference to the accompanying schematic drawings, where:

[0043] - Fig. 1 is a schematic representation of a preferred embodiment of an installation for implementing the method according to the invention;

[0044] - Fig. 2 shows a schematic sectional view of an example of a possible grain of coated mineral chips at a stage of the method according to the invention;

[0045] - Fig. 3 shows a schematic cross-sectional view of the grain shown in Fig. 2 after it has been subjected to another preferred step of the method according to the invention;

[0046] - Fig. 3a shows an enlarged fragment of Fig. 3;

[0047] - Fig. 4 shows a sectional view of the grain shown in Fig. 3 at another preferred stage of the method according to the invention;

[0048] - Fig. 4a shows an enlarged fragment of Fig. 4.

[0049] The method for producing coated mineral chips according to the invention includes an initial stage in which untreated mineral chips are placed preferably in a first storage means 1, such as, for example, one or more bins.

[0050] Preferably, the unprocessed mineral chips may comprise basaltic and / or shale and / or cristobalite and / or olivine chips, or, more generally, one or more rocks and / or minerals of the type commonly used for the manufacture of building products.

[0051] Preferably, the grain size distribution of the raw mineral chips is substantially uniform and is preferably from 100 to 10 mesh.

[0052] Alternatively, unprocessed mineral chips may contain a variety of grains with different sizes.

[0053] It should be noted that "mesh" is a unit of measurement used in the gravel industry, indicating the number of openings per linear inch (1 inch = 25.40 mm) of the "sieve" formed when particles are placed side by side on a flat surface. Conventional sieves are classified based on the "number of openings contained in a linear inch (of mesh)," and the particle sizes of powders or crushed aggregates can be classified in the same way. In practice, the spaces between particles along a linear inch are taken into account.

[0054] After the step in which the raw mineral chips are prepared, the method according to the invention includes the step in which the raw mineral chips are introduced into the mixing means 2 (for example, into a concrete mixer or other rotary mixer of a known type) together with a mixture, which is hereinafter referred to as the "first processing mixture", including water, pigments, sodium silicate and / or potassium silicate, kaolin and, preferably, but not necessarily, additives with antifouling properties.

[0055] The antifouling additives may preferably include copper oxides (Cu2O and CuO) and / or zinc oxide (ZnO) and / or silver oxide (Ag2O) and / or metallic copper (Cu(M)), and / or metallic zinc (Zn(M)), preferably in the form of powders.

[0056] Preferably, the embodiment of the method according to the invention includes, after the stage in which a certain amount of unprocessed mineral chips is prepared and before the stage in which the unprocessed mineral chips are introduced into the mixing means 2, a preheating stage in which the mineral chips are heated to the required preheating temperature Tpr for a given time tpr, preferably from 5 to 10 minutes.

[0057] The preheating temperature Tpr is preferably 60 to 70°C.

[0058] The preheating is preferably carried out inside a preheating furnace 3, more preferably a rotating furnace, preferably comprising a rotating drum (not shown) inside which the raw mineral chips are mixed to ensure their uniform heating.

[0059] Preferably, the preheating furnace 3 comprises first temperature detection means, not shown in the drawings, such as thermocouples, arranged therein so as to be able to detect the temperature of the unprocessed mineral chips; for example, in a preferred case, the thermocouples can be arranged so that they are in contact with the unprocessed mineral chips when they are inside the preheating furnace 3.

[0060] Heating and simultaneously stirring the raw mineral chips, preferably inside the preheating furnace 3, typically results in the formation of a powder that remains suspended in the air surrounding the raw mineral chips inside the preheating furnace 3.

[0061] In a preferred embodiment, simultaneously with or after the step in which the raw mineral chips are heated to a predetermined preheating temperature Tpr, the method according to the invention preferably provides for the removal of air present in the zone of the preheating furnace 3 containing the raw mineral chips (for example, from a rotating drum, if provided); the removal of this air allows for the simultaneous removal of suspended powder, preventing it from settling on the chips with the risk of disrupting their optimal subsequent coating.

[0062] The following are preferred concentrations of various elements included in the first processing mixture, expressed as a percentage by weight relative to the total weight, which may be the weight of the unprocessed mineral chips, designated m g , or the mass of a hydrocarbon solvent based on polyalkylbenzenes, designated m s .

[0063] Preferably, the mass percentage concentration of the pigments in the first processing mixture is from 0.3 to 1.8% m / m g (i.e. the mass of pigments in the first processing mixture is from 0.3% to 1.8% of the total mass of unprocessed mineral chips onto which the first processing mixture is to be applied).

[0064] Preferably, the mass percentage concentration of water in the first treatment mixture is from 0.6 to 1.1% m / m g .

[0065] Preferably, the mass percentage concentration of kaolin in the first processing mixture is from 0.7 to 1.2% m / m g .

[0066] Preferably, the mass percentage concentration of sodium silicate and / or potassium silicate in the first treatment mixture is from 3.2 to 4.0% m / m g .

[0067] In a preferred embodiment of the method according to the invention, additives with antifouling properties include copper oxides (CuO, Cu2O), and / or zinc oxide (ZnO), and / or silver oxide (Ag2O).

[0068] Preferably, the mass percentage concentration of copper oxides (CuO, Cu2O) in the first processing mixture is from 0.4 to 0.6% m / m g .

[0069] Preferably, the mass percentage concentration of zinc oxide (ZnO) in the first treatment mixture is from 0.4 to 0.6% m / m g .

[0070] Preferably, the mass percentage concentration of silver oxide (Ag2O) in the first treatment mixture is from 0.4 to 0.6% m / m g .

[0071] In another preferred embodiment of the method according to the invention, the additives with antifouling properties include metallic copper (Cu(M)) and / or metallic zinc (Zn(M)) added to the first treatment mixture in the form of fine particles having a size preferably less than 50 mesh.

[0072] Preferably, the mass percentage concentration of metallic copper (Cu(M)) in the first processing mixture is from 0.4 to 0.6% m / m g .

[0073] Preferably, the mass percentage concentration of metallic zinc (Zn(M)) in the first treatment mixture is from 0.4 to 0.6% m / m g .

[0074] After the step of introducing the untreated mineral chips into the mixing means 2, the method according to the invention includes, in the mixing means 2, a step in which the untreated mineral chips and the first processing mixture are mixed to obtain chips, which are referred to in the present text as "coated mineral chips", which include (or consist of) untreated mineral chips, the grains of which are coated with the first processing mixture, preferably substantially uniformly, during the mixing step.

[0075] The coated mineral chips comprise grains 8, for example of the type shown schematically in Fig. 2, including a core 9, preferably of basalt, slate or cristobalite, and / or olivine, or, more generally, of one or more rocks and / or minerals of types commonly used for the manufacture of building products, coated with a first layer 10 having the composition of the first processing mixture.

[0076] The first processing mixture further comprises one or more organosiloxanes and / or silanes.

[0077] Preferably, the mass percentage concentration of organosiloxanes that are added to the raw mineral chips through the first processing mixture is from 0.010 to 0.030% m / m g .

[0078] Preferably, the functional groups of organosiloxanes are alkyl chains having a number of carbon atoms from 1 to 5 (C1-C5).

[0079] The addition of organosiloxanes and / or silanes to the first processing mixture results in them remaining included in the first layer 10, thereby increasing its hydrophobicity, resulting in a mineral chip coated with hydrophobic molecules.

[0080] The high hydrophobicity imparted by organosiloxanes and / or silanes reduces the stability of water on the surface of the coated mineral chips, thereby preventing the growth of algae, mold, fungi, etc. on this surface, as well as preventing the settling of any solid residues (limestone, fine powder, etc.) present in the water on this surface.

[0081] The method according to the invention provides, after the stage in which the untreated mineral chips and the first processing mixture are mixed, a stage of heating the coated mineral chips to a predetermined firing temperature Tc.

[0082] Heating is preferably carried out inside a calcining furnace 4, preferably a rotating furnace, comprising a rotating drum (not shown), inside which the coated mineral chips are preferably mixed to ensure uniform heating.

[0083] Preferably, the calcining furnace 4 comprises second temperature measuring means, not shown, such as thermocouples, arranged therein so as to be able to determine the temperature of the coated mineral chips; for example, in a preferred case, the thermocouples can be arranged in such a way that they are in contact with the coated mineral chips when they are inside the calcining furnace 4.

[0084] Preferably, the firing temperature Tc is less than 450°C, preferably from 450°C to 480°C or from 300°C to 380°C; preferably, such firing includes at least partial (preferably complete) vitrification of the first processing mixture on the outer surface of the untreated mineral chips.

[0085] It was found that heating coated mineral chips to temperatures below 480°C does not result in the destruction of silanes or organosiloxanes present in the coating of these mineral chips, while higher temperatures may destroy these components.

[0086] The heating stage of the coated mineral chips to the predetermined firing temperature preferably lasts from 10 to 25 minutes.

[0087] This firing time is reduced compared to the firing time of known solutions, which is approximately 30-40 minutes; this reduction in firing time is advantageous because it reduces (along with the reduction in firing temperature) the risk of decomposition of organosiloxanes and / or silanes as a result of the firing itself.

[0088] The method according to the invention provides that after the stage in which the coated mineral chips are heated, the coated mineral chips are cooled to a predetermined intermediate cooling temperature Tri, preferably inside the first cooling device 5.

[0089] The preferred Tri intercooling temperature is 290°C to 380°C.

[0090] Preferably, the first cooling device 5 may be a rotary type cooling device, for example, in which a rotating drum (not shown) rotates, stirring and mixing the coated mineral chips exiting the calcining kiln 4. The continuous movement of the coated mineral chips inside the first cooling device 5 causes it to cool by simple contact with the air inside the first cooling device 5.

[0091] Preferably, the first cooling device 5 comprises third temperature detection means, not shown, for example, thermocouples, arranged therein in such a way as to be able to determine the temperature of the coated mineral chips; for example, in a preferred case, the thermocouples can be arranged in such a way that they are in contact with the coated mineral chips when they are inside the first cooling device 5.

[0092] A preferred embodiment of the method according to the invention includes, after or simultaneously with cooling the coated mineral chips, a step in which the coated mineral chips are brought into contact with a second processing mixture containing water and organosiloxanes and / or silanes; this step is preferably carried out inside the first cooling device 5, and it facilitates cooling of the coated mineral chips.

[0093] It should be noted that the step in which the coated mineral chips are brought into contact with the second treatment mixture containing water and organosiloxanes and / or silanes is optional.

[0094] Preferably, the second processing mixture can be dosed through a special first dispenser, schematically shown in Fig. 1 and designated by the number 20.

[0095] Preferably, the mass percentage concentration of organosiloxanes and / or silanes with which the coated mineral chips are contacted through the second processing mixture is from 0.010 to 0.030% m / m g .

[0096] Preferably, the functional groups of organosiloxanes are alkyl chains having a number of carbon atoms from 1 to 5 (C1-C5).

[0097] Preferably, as for example in the preferred embodiment shown in Fig. 1, in the case where in the first cooling device 5 a second processing mixture is applied to the coated mineral chips, at the outlet from said first cooling device 5 a coated mineral chips is obtained having hydrophobic molecules on its outer surface, the grains 8 of which have a second layer 111, such as the grain 8 shown schematically and in section in Fig. 3 and 3a, where the hydrophobic molecules are represented by solid lines protruding from the first layer 10.

[0098] Preferably, in the case where the first processing mixture contains one or more organosiloxanes and / or silanes, the outer surface of the grains of the coated mineral chips already contains hydrophobic molecules of organosiloxanes and / or silanes, even without processing said coated mineral chips at the stage in which the coated mineral chips are brought into contact with the second processing mixture, which thus becomes optional.

[0099] In a preferred embodiment of the method according to the invention, after or simultaneously with cooling the coated mineral chips to the intermediate cooling temperature Tri, the coated mineral chips are brought into contact with a third processing mixture containing a hydrocarbon solvent based on polyalkylbenzenes, in which phosphorus and / or silane esters of ethoxylated fatty acids are dispersed.

[0100] Phosphorus and / or silane esters of ethoxylated fatty acids are organic molecules consisting of a polar part and a non-polar part, the latter consisting of alkyl chains of varying lengths.

[0101] Through the polar part, these molecules bind to the surface of the coated mineral chips and thus to the first layer 10, and through the non-polar alkyl chains they interact with the bitumen or vinyl / acrylic base of the roofing products.

[0102] Such molecules improve the adhesion of coated mineral chips to bitumen-type bases or to bases containing vinyl or acrylic adhesive material.

[0103] Preferably, the weight percentage concentration of phosphorus and / or silane esters of ethoxylated fatty acids in the second processing mixture is from 0.2 to 0.4% m / m s(i.e., the mass of phosphorus and / or silane esters of ethoxylated fatty acids in the second processing mixture is from 0.2% to 0.4% of the total mass of the polyalkylbenzene-based hydrocarbon solvent present in the mixture).

[0104] In a preferred embodiment of the method according to the invention, as shown in Fig. 1, the coated mineral chips treated with hydrophobic molecules (organosiloxanes and / or silanes) using a second processing mixture, exiting the first cooling device 5, are brought into contact with a third processing mixture in a second cooling device 6; in this advantageous case, at the exit from the second cooling device 6, coated mineral chips are obtained, treated with hydrophobic molecules (organosiloxanes and / or silanes) and adhesion promoting molecules, the grains 8 of which have a second layer 111, having both hydrophobic molecules, shown in Fig. 4a by solid lines, and adhesion promoting molecules, shown in Fig. 4a by dashed-dotted lines, in both cases protruding from the first layer 10.

[0105] Advantageously, in another preferred embodiment, the step in which, after leaving the first cooling device 5, the coated mineral chips are brought into contact with the third processing mixture inside the second cooling device 6, can also be carried out without pre-treating the coated mineral chips with the second processing mixture; in this advantageous case, the hydrophobic molecules are included in the first layer 10, and the adhesion-promoting molecules protrude outward from it.

[0106] Preferably, the third processing mixture can be dosed using a special second doser, schematically shown in Fig. 1 and designated by the number 30.

[0107] Preferably, the second cooling device 6 may be a rotary type cooling device in which a rotating drum, not shown in the drawing, rotates to stir and mix the mineral chips coated at the outlet of the first cooling device 5.

[0108] The continuous movement of the coated mineral chips inside the second cooling device 6 causes it to be further cooled by simple contact with the air inside the second cooling device 6.

[0109] Preferably, the second cooling device 6 comprises fourth temperature measuring means, not shown in the drawings, for example, thermocouples, arranged therein in such a way as to be able to determine the temperature of the coated mineral chips; for example, in a preferred case, the thermocouples can be arranged in such a way that they are in contact with the coated mineral chips when it is placed inside the second cooling device 6.

[0110] It should be noted that for the purposes of the present invention, possible local deviations in the temperature of the crumbs at various stages of the method in relation to the specified temperature ranges are not significant.

[0111] In a preferred embodiment of the method according to the invention, shown in Fig. 1, the coated mineral chips are ultimately stored in a second storage means 7, such as, for example, one or more bins.

[0112] Preferably, the method according to the invention provides for processing raw mineral chips in accordance with a continuous flow process, so that there is no need for intermediate storage of chips between different stages.

[0113] Continuous flow processing of mineral chips makes the process simpler, faster, as it is continuous, and cheaper.

[0114] It was then discovered that the method according to the invention solves the above-mentioned problem and objective, since by using water to transfer molecules of one or more organosiloxanes and / or silanes into the mineral chips, the formation of a greater number of chemical bonds between these molecules and the chips can be achieved, which makes it difficult for them to be washed out due to weather conditions, ensuring a long-lasting effect of surface hydrophobicity.

[0115] Furthermore, the method according to the invention makes it possible to obtain coated crumbs at relatively low production costs and operating time.

[0116] Furthermore, the method according to the invention makes it possible to process untreated mineral chips in such a way as to impart thereto a certain coloration, high surface hydrophobicity and high adhesion to bitumen-type bases or to bases containing acrylic or vinyl adhesive materials, using one continuous process, therefore without intermediate breaks and without the need to store the chips between one and another stage of this process.

[0117] It should be noted that the high hydrophobicity of the surface gives the crumbs obtained by the method according to the invention a significant effect of preventing the fouling / formation of algae / fungus, which consists in the fact that by preventing the deposition of water on the crumbs and, consequently, on the roofing product covered with it, an environment is created on its outer surface that is unfavorable for the proliferation of plants, algae, and fungi.

[0118] In addition, by using different functional groups of silane / siloxane molecules (in the non-polar part that remains outside the chips), the range of substrates on which the chips can be applied can be expanded; for example, if the organosilanes contain an epoxy functional group, it will react with acrylic / polyurethane resins / adhesives, and thus can form strong and durable bonds with the substrate on which the treated chips are applied if it is based on acrylic / polyurethane resins / adhesives.

[0119] Furthermore, the use of adhesion promoting additives, i.e. phosphorus and / or silane esters of ethoxylated fatty acids, can significantly improve the adhesion of the chips to bitumen bases or to bases containing acrylic or vinyl adhesive material, reducing the amount of additives used in general and, as a result, reducing the final cost of roofing products.

[0120] Finally, the results of some comparative tests carried out by the applicant on some examples of bituminous tiles coated with crumbs obtained by the method according to the invention and on the same type of bituminous tiles coated with known crumbs always produced by the applicant are presented below.

[0121] In particular, the type of flexible shingles used was known under the trade name "Premium Rectangular", sold by a flexible shingle supplier.

[0122] The known type of chips used in the tests are basalt chips colored by applying an inorganic coating, obtained by the following procedure: the mineral material is placed in a mixer together with the coating (with a composition in mass percentage according to the following table 1 relative to the mass m guntreated mineral chips); then the chips are "vitrified" in a rotary kiln at a temperature of 450-480°C and then cooled using two continuously rotating cylinders. Inside the first cylinder, the mineral material is cooled with water to reach a temperature of 130-150°C through a spray system. Next, in the second cylinder, the material is treated with a solution based on polyalkylbenzenes (hydrocarbon oil), containing adhesion promoters (with a mass percentage of the oil of 0.2-0.4% m / m oil ), organosiloxanes (with a mass percentage content of 2-3% m / m of oil oil ), catalysts and special solvents (with a mass percentage content of 1.5-2% m / m of oil oil ) and finally, the finished product is sent to storage bins.

[0123]

[0124] This known type crumb does not have a specific grain size, but a group of different grain sizes according to the percentage content shown in the following Table 2 (where the mesh value, the corresponding average grain diameter and the percentage of grains with a specific mesh size / average grain diameter are indicated.

[0125]

[0126] Tests were also carried out on a sample of the crumb obtained by the method according to the invention, and in particular on the crumb described in the following example, called New Grit 1.

[0127] New Grit 1: This is a grit obtained by the method according to the invention, wherein the raw mineral grit is of the basalt type, the first processing mixture consists of the components shown in the following Table 3; the organosiloxane is an organosiloxane with C1-alkyl side chains (polydimethylsiloxane), applied to the raw mineral grit in an aqueous solution as part of the first processing mixture. The grain size of the grit is not a single one, but the grit consists of a combination of different grain sizes shown in Table 1.

[0128]

[0129] It should be noted that the pigment used is the same for the two types of crumbs tested.

[0130] Premium Rectangular tiles coated with the above two types of chips were subjected to the following tests.

[0131] Biological growth test Accelerated biological aging test in bioreactors with a mixture of cyanobacteria and algae on flexible shingle samples covered with 50×50 mm chips in a plane.

[0132] Tile samples coated with known type of chips showed visible and abundant growth / proliferation of algae and cyanobacteria on their surfaces.

[0133] Tile samples coated with New Grit 1 grit showed zero / minimal algae and cyanobacteria growth on the surface when visually inspected (specifically, much less than tile samples coated with known grit type).

[0134] Adhesion Test to Bitumen Substrate (ASTM D4977 Brush Test) Rectangular specimens (with a plane dimension of 277 mm × 70 mm) obtained from flexible roofing tiles (with a plane dimension of 100 cm × 34 cm) coated with the two kinds of chips described above were subjected to a brush test of the so-called "ASTM D4977 brush test" type (in which the tiles are subjected to 50 cycles of brushing with stainless steel bristles, and at the beginning and end of the test, the specimens are weighed and the percentage of chips lost and chips still attached to the substrate is determined); as can be seen from the following Table 4, at the end of the test, the tiles using the chips produced by the method of the invention retained a percentage of chips much higher than those using the chips of the known type.

[0135]

[0136] Hydrophobicity test (volcano test) 40 grams of the test crumbs were placed in a round dish / container to form a kind of "volcano" with an outer diameter of 70-90 mm and an inner diameter of 20-40 mm; then 80-100 ml of non-distilled water at a temperature of 23-28 °C was poured between the edge of the container and the granules and the time T required for the water to overcome the surface tension of the granules and penetrate into the round top of the "volcano"; as can be seen from Table 5 below, in the case of the crumbs obtained by the method according to the invention, significantly more time is required for water to penetrate into the round top than for the crumbs of the known type.

[0137]

[0138] Contact Angle Measurement (Surface Wettability Measurement) It is a measurement of the angle between the surface of a crumb granule and the surface of a water droplet deposited on the granule.

[0139] The test showed that the known type of crumb had a contact angle of 80 to 120° (excluding the extremes), so it was classified as "hydrophobic", while the New Grit 1 crumb had a contact angle greater than 120°, so it was classified as "superhydrophobic" (i.e. not wetted by water).

[0140] It should be noted that the above tests were repeated for several samples of the same type of crumb, and the result values ​​given in the tables are the average values ​​of the results obtained for different samples.

[0141] Tests conducted by the applicant have shown that the crumb obtained by the method according to the invention has characteristics of hydrophobicity, antifouling / anti-algae / fungus properties, adhesion and durability over time of said crumb that are significantly higher than crumb of the known type.

Claims

1. A method for producing coated mineral chips for the manufacture of roofing elements with a bitumen base or a base containing vinyl or acrylic adhesive material for roofing buildings, comprising the following stages: - preparation of unprocessed mineral chips; - after preparing the unprocessed mineral chips, introducing said unprocessed mineral chips into the mixing means (2) together with the first processing mixture containing water, pigments, sodium silicate and / or potassium silicate, kaolin; - after introducing said untreated mineral chips into the mixing means (2), mixing said untreated mineral chips and said first processing mixture to obtain coated mineral chips; - after mixing said untreated mineral chips and said first processing mixture, heating said coated mineral chips to a firing temperature (Tc) of from 300°C to 480°C; - after heating the said coated mineral chips, cooling the said coated mineral chips to an intermediate cooling temperature (Tri) of 280°C to 390°C; wherein said method is characterized in that said first processing mixture contains one or more organosiloxanes and / or silanes, which are thus applied to said untreated mineral chips using an aqueous solution.

2. The method according to claim 1, comprising, after or simultaneously with cooling said coated mineral chips, an additional step of bringing said coated mineral chips into contact with a second processing mixture containing water and one or more organosiloxanes and / or silanes.

3. The method according to any of the preceding claims, wherein said first treatment mixture comprises one or more additives with antifouling properties.

4. The method according to claim 3, wherein said one or more additives with antifouling properties include copper oxides and / or zinc oxide and / or silver oxide and / or metallic copper and / or metallic zinc.

5. The method according to any of the preceding claims, wherein said firing temperature (Tc) is less than 480°C.

6. The method according to claim 5, wherein said firing temperature (Tc) is from 300°C to 450°C.

7. The method according to claim 5, wherein said firing temperature (Tc) is from 450°C to 480°C.

8. The method according to claim 7, wherein said intermediate cooling temperature (Tri) is from 280° to 390°C.

9. A method according to any one of the preceding claims, comprising, after or simultaneously with cooling said coated mineral chips to an intermediate cooling temperature (Tri), a step of bringing said coated mineral chips into contact with a third processing mixture containing a hydrocarbon solvent based on polyalkylbenzenes in which phosphorus and / or silane esters of ethoxylated fatty acids are dispersed.

10. A method according to any of the preceding claims, comprising, after preparing the untreated mineral chips and before introducing said untreated mineral chips into the mixing means (2), a preheating step in which said untreated mineral chips are heated to a preheating temperature (Tpr) of between 60°C and 70°C.

11. The method according to claim 10, comprising simultaneously with or after said preheating stage and before introducing said untreated mineral chips into said mixing means (2), a stage of mechanically mixing said untreated mineral chips.

12. The method according to claim 10 or 11, in which between said preheating stage and said stage of introducing said untreated mineral chips into the mixing means (2), said untreated mineral chips are contained in a heating furnace (4), wherein said method includes simultaneously or after said preheating stage and before introducing said untreated mineral chips into the mixing means (2), a stage of removing air present in the area of ​​said preheating furnace (4) containing said untreated mineral chips.

13. The method according to any of the preceding claims, wherein said unprocessed mineral chips comprise basalt and / or shale and / or cristobalite and / or olivine chips.

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