Method and apparatus for the production of a spreading mat for pressing into a mineral slab, as well as mineral slab

Abstract

Method and apparatus for producing a spreading mat (1) using particles (2, 3, 4), in particular fibers, made of mineral materials, for example rock or glass wool, on a moving forming belt (23), comprising the following steps: a) Providing a bunker (20) with mixed fine and coarse particles (2, 3) and shot (4), b) Dividing the particles (2, 3) and shot (4) exiting the bunker (5) via at least a first size-separating device (8) into at least a first subset (5) with fine and coarse particles and at least a second subset (6) with predominantly shot (4), c) furthermore, forwarding the first subset into a second size-dividing device (9) in a first feed area (14) and fractionating the first subset (5) again according to particle size and d) Scattering of the particles (2, 3) of the subset (5) as a layer of increasing or decreasing size onto the forming belt (23) to form the spreading mat (1) with a desired thickness. In order to obtain a particularly smooth surface, it is provided that the second subset (6), containing the shot (4), is also fed to the second size-dividing device (9) in a second feed area (15) different from the first, but is spread onto the moving forming belt (23) at such a time offset to the first subset that at least the shot (4) is arranged above a layer of fine particles (2) in the thickness of the spreading mat (1).

Description

[0001] The invention relates to a method for producing a spreading mat using particles, in particular fibers made of mineral materials, for example rock or glass wool, on a moving forming belt, comprising the following steps: a) Providing a bunker containing mixed fine and coarse particles and shot, b) Dividing the particles exiting the bunker by means of at least a first size-separating device into at least a first subset with fine and coarse particles and at least a second subset with predominantly shot, c) furthermore, forwarding the first subset into a second size-dividing device in a first feed area and fractionating the first subset again according to particle size and, d) Scattering of the particles of the first subset as a layer of increasing or decreasing size onto the forming belt to form the spreading mat with a desired thickness.

[0002] The invention further relates to a device for producing a grit mat in the course of manufacturing mineral slabs according to one of the method claims with • at least one bunker containing fine and coarse particles of mineral materials, for example rock or glass wool, and shot, • at least one first size-separating device for dividing the spreading material exiting the bunker into at least a first subset with fine and coarse particles and a second subset with predominantly shot, • at least a second size-dividing device for fractionating the first subset fed into a first feed area, and • a form strip onto which the first subset can be scattered.

[0003] Finally, the invention comprises a mineral material plate which was produced, for example, using the method and / or the device.

[0004] Mineral fiber boards are typically manufactured, at least predominantly, from mineral materials of varying shapes and sizes. They serve as thermal insulation for energy conservation, and potentially also for fire protection and sound insulation. The invention described here defines a mineral fiber board as a board with a density of 15 to 1400 kg / m³. 3 Therefore, the following count • Sound and heat insulation panels with a density of 15 to 160 kg / m³ 3 , as well as • Facade panels or wall claddings with a density of 400 to 1400 kg / m³ 3 in addition.

[0005] According to the manufacturers' specifications for the most commonly used fabrics, a) Rock wool is used. This is produced by fusing stone, limestone, and recycled molded bricks with other raw materials at 1,500 °C. The molten rock is then spun into fibers in a further step. Binders and impregnating oil are added to give the products stability and water-repellent properties. The rock wool is then heated again to approximately 200 °C to harden the binders and stabilize the material for final processing. Environmentally friendly equipment—filters, air preheaters, afterburners with heat recovery systems, and other cleaning and collection systems—ensures that the process is as environmentally sound as possible. b) Glass wool is used. It is manufactured in a very similar way. The required quantities of raw material are weighed, mixed, and fed into a melting furnace. The raw materials used include primarily recycled glass, sand, limestone, and soda ash, as well as production offcuts that are reintroduced into the manufacturing process. The starting material is melted in a furnace at very high temperatures of approximately 1400°C. After passing through the melting furnace, the glassy molten glass is fiberized by directing a thin jet of glass onto rapidly rotating discs, where it is ejected through thousands of tiny holes in the outer wall of the disc. The resulting fibers are then further processed into fine wool fibers using gas burners. The fibers are sprayed with small amounts of a water-soluble binder. The binder is then cured in a continuously running hardening oven at approximately 200°C.The structure and density of the product can be adapted to the exact application requirements.

[0006] These two materials have also been experimentally mixed with organic substances, such as wood chips or fibers, or synthetic substances, such as plastics like EPS, XPS, PUR and PIR.

[0007] The production of mineral composite panels ultimately takes place either in cycles or continuously. Since significant pressures are generally applied in the compaction units, or the combined joining and compaction units, during mineral composite panel production, these units are usually referred to by those skilled in the art as the press section when referring to the entire system. In the production of mineral composite panels as described in this document, the operating pressures here, depending on the material and size of the mineral composite panel to be produced, are usually in the range of approximately 50 N / cm². 2 and approximately 500 N / cm 2 and advantageously between 100 N / cm 2 and 400 N / cm 2The operating principle of the joining and / or compaction unit determines whether the overall process is described as a cycle-based or continuous process. In cycle-based production, the mineral material sheets are pressed as flat objects with finite dimensions in all three spatial directions, whereas mineral material sheets produced in a continuous process represent lengths of a continuously pressed web.

[0008] To produce all of these mineral slabs, aggregate must first be spread onto a forming belt. This aggregate, continuously spread to the desired thickness, forms the basis for the production of the mineral slab.

[0009] Fibers of mineral materials, typically between 1.5 and 10 mm long, are used as spreading material. Often, in addition to fibers, shot is also found in a bunker. This shot can consist of very small, unmelted lumps or particles of stone, glass, or glue. Colloquially, these particles are also called "shots." The majority of shot has a grain size of 50 µm to 250 µm in diameter, but can sometimes reach up to one millimeter. Nowadays, shot is scattered stochastically along with mineral materials, which has negative consequences. Because the shot is also distributed across the cross-section of the resulting mineral slab, the surfaces are too rough to be properly finished.If the small lumps are sorted out beforehand by separation, as is known, for example, from the production of wood-based panels, then a great deal of additional design effort is required.

[0010] In the wood-based materials industry, for example, it is often desirable for spreading machines to separate particles according to size or shape in order to positively influence the product properties of the subsequently manufactured panels. For instance, with particleboard, the smallest geometrically defined particles are scattered towards the surface of the spreading mat, while with OSB, the largest particles are scattered towards the respective surface.

[0011] For fractionation and the size separation device mentioned here, sieves, so-called roller spreaders, or sometimes air classifiers are frequently used. Both methods can be seen in DE 10 2016 113 014 B4. After air classification of the spreading material, roller spreaders are used to distribute the material – possibly classified by size – by, for example, transferring the material from roller to roller, allowing increasingly larger particles to fall through the gaps between the spreading rollers. Finally, large clumps are sorted out and removed via a screw conveyor.

[0012] It should also be noted that the rollers of the roller spreading heads can have different designs, allowing, for example, longer chips or fibers to be oriented as they are spread onto the forming belt, for instance, perpendicular or parallel to the direction of travel of the forming belt. This enables layers with different fiber orientations to be created in the spreading mat. A descriptive prior art patent, DE 10 2007 049 947 A1, should also be mentioned here. The rollers can also consist of discs with a defined spacing to allow the passage of spreading material of specific sizes, and may optionally be star-shaped to improve material transport with their teeth.

[0013] In this invention, a roller spreading head as a possible size division device is understood to mean all roller spreading heads consisting of at least three adjacent rotatable rollers which are capable of allowing particles of a defined size or weight to fall between the rollers, transporting particles resting on them in one direction or distributing particles evenly.

[0014] The object of the invention is to ensure that the grit is present only to a small extent or not at all on at least one surface of the mineral board, so that the overall tactile impression of the board is smoother than with conventional mineral boards. This also results in, for example, a smoother finish for paint or coating.

[0015] The problem is solved with regard to the method by the features of claim 1 and in particular by the fact that the second subset, containing the shot, is also fed to the second size-dividing device in a second feed area different from the first, but is spread onto the moving forming belt in such a time offset to the first subset that at least the shot is arranged above a layer of fine particles in the thickness of the spreading mat.

[0016] The problem is solved with regard to the device by the features of claim 13 and in particular by the fact that the second size division device has at least a second feed area for the second subset, away from the first feed area and in the direction of travel of the forming belt behind the first feed area, and that the second subset can also be scattered onto the forming belt.

[0017] The inventors recognized that it is best to separate the shot from the fine and coarse spreading material beforehand. The fine and coarse spreading material, i.e., the fine and coarse particles, can then be separated and spread in such a way that the fine particles are near the surface and the coarser particles, or increasingly coarser particles, are spread further down the slope. Only then, according to the invention, is the shot, which is also fed into the second size-separation device, spread after the fine and coarse spreading material. This ensures that the surface of the mat and the subsequently pressed plate, which rests on the forming belt during the process, remains shot-free and particularly smooth. With the preferred third spreading layer, consisting, for example, of fine particles, the upper surface can then also be finished so that it remains smooth and free of shot particles on the outer surface.

[0018] The rationale is to continue using the shot without scattering it in near-surface areas, as it remains beneficial for certain plate properties, such as increased strength. Furthermore, this eliminates the need for an alternative, more complex method of shot removal to achieve smooth surfaces.

[0019] To distribute the necessary third fraction, which is preferable for achieving a smooth, even surface on both sides of the finished mat or sheet, and which ensures the second fraction of the shot is evenly distributed across the thickness of the mat or sheet, the spreading head can be designed so that this third fraction also comes from the same hopper from which the first and second fractions were generated. However, it is also advantageous to install the existing spreading head, along with a possible second hopper, as a mirror image, behind the first spreading head in the direction of travel of the forming belt. In this case, the shot last distributed in the first spreading head is first applied to the already partially formed mat, followed by the coarse and fine particles, which then create a smooth surface after the entire mat has been compressed, for example, in a continuous double-belt press.

[0020] To avoid confusion in terminology, it should be noted that a spreading head refers to an entire spreading device, including a hopper. A spreading head can contain several size-division devices, such as roller spreading heads, preferably arranged one above the other.

[0021] It is advantageous if at least a subset is fed to the second size-dividing device with the assistance of gravity.

[0022] This eliminates the need for guiding devices for the fine and coarse particles or the shot, which significantly simplifies the process.

[0023] It is also preferred that, during fractionation of the first subset in the second size-dividing device, the coarse particles of the first subset are fed to the second subset.

[0024] This supports the desired internal structure of the mineral board, in which the fine particles are arranged on the outermost surface and then increasingly larger particles and fibers are scattered until finally the shot is embedded.

[0025] This also has the advantage that both the first sub-quantity and the second sub-quantity from the second size-dividing device are spread onto the forming belt.

[0026] It is particularly advantageous to use roller spreading heads with at least three adjacent rollers as size division devices.

[0027] These rollers form at least two, preferably stacked, roller beds, which are generally arranged horizontally, but can also be found in inclined arrangements in the prior art. The rollers are positioned so close together that the gaps between them only allow particles of a certain maximum size to pass through. Otherwise, the spreading material is transported further on the rotating rollers. The distance between the rollers can increase from roller to roller, so that progressively larger particles are then ejected. Depending on the design of the rollers, the spreading material also behaves differently. In one example, the adjacent rollers have interlocking teeth. In a second example, the rollers consist of spaced-apart discs, with the discs of the following roller engaging precisely in the spaces between them. These discs can also have teeth on their circumference with a geometry adapted to the spreading material.

[0028] The two size-division devices can thus be formed by just a first and a second roller spreading head, which does not preclude the possibility of further roller spreading heads being arranged above or below. In a simple manner, the spreading material can fall onto the second spreading head below after being divided on a first roller spreading head. For example, the lowest roller spreading head, which has two feed areas for the first and second portions, can be the second spreading head from which both portions are spread onto the forming belt.

[0029] This allows the first size-division device, for example, a first roller spreader, to feed the fine and coarse spreading material, which is often interwoven as fibers of mineral insulation material, along the roller bed towards the first spreading area of ​​the second size-division device. Meanwhile, the roller bed of the first spreader directly discharges the small shot pellets and carries them to the second feed area of ​​the second roller spreader. This departs from the conventional principle of spreading even the smallest particles, in this case the shot, immediately with a roller spreader. Instead, the shot is spread by being transferred or added to the second feed area of ​​the second roller spreader, after the fine and coarse particles have been spread.

[0030] This advantageously ensures that the first subset (fine and coarse spreading material) is dropped from the first roller spreading head onto the first feed area of ​​a second roller spreading head, and the second subset (shot) is dropped from the first roller spreading head onto the second feed area of ​​the second roller spreading head.

[0031] By using a suitable roller geometry and a tested roller spacing, it is preferred that fine particles are scattered onto the forming belt at one end of a roller spreading head, while coarser particles are transported via the roller spreading head in the direction of the supplied second subset in the second feed area.

[0032] This ensures that the fine particles are the first material to be spread onto the forming belt. Increasingly larger particles follow, until finally the shot is also spread onto a specific area of ​​the forming belt.

[0033] To better adapt to potentially varying spreading materials or to counteract possible clumping, it is advantageous if the rollers of a roller spreader head are driven at alternating speeds and / or directions of rotation within a row of rollers. This allows the spreading material to be distributed more effectively, and particles above a certain size to be guided more efficiently over the roller spreader head.

[0034] To improve the quality of the mineral slab to be produced, it is possible to add additives to the spreading material, for example onto a roller spreading head or deeper in the direction of fall of the spreading material.

[0035] This creates a mineral board with additional positive properties.

[0036] A roller spreading head arranged above, in accordance with the invention, for shot, but also for other solid or powdered additives, such as binders, fire retardants or insecticides, can be designed in such a way that it doses these in a targeted manner in different proportions as a gradient to the building layer of spreading material.

[0037] Furthermore, it is useful if the dispersion of the first subset is supported by a suction device for fine particles.

[0038] A suction device prevents the release of fine particles into the ambient air. Furthermore, these particles, which can significantly affect the surface quality and smoothness, are precisely directed to form the surface on the forming belt.

[0039] With regard to the device for producing a grit mat during the production of mineral slabs according to any one of claims 1 to 12, the claims are adapted accordingly to the process description. The advantages of the device are also analogous to those in the process description.

[0040] Only the different geometry of the rollers of the second roller spreader in the at least two feed areas requires further explanation. The advantage here is that the rollers below the first feed area are suitable for transporting at least coarser material, while the rollers in the second feed area deposit the grit precisely onto the lower top layer already on the forming belt, i.e., onto fine and coarse particles.

[0041] The inventors have also recognized that the workability of a mineral mat, particularly with regard to surface treatment, depends to a very high degree on the design of the outermost layers of the grit mat. Producing the surfaces from the finest fibers enables good post-processing. For this reason, it is particularly preferred to spread the top layers of the grit mat from the first batch after the size-division device and to shape the mineral mat, containing fine and coarse fibers of mineral materials and grit, optionally using the described device or method, such that the grit is located only in the interior of the mineral mat and not in its surface area.

[0042] Furthermore, it is also preferably provided that the mineral board also contains organic particles.

[0043] Understandably, if desired, mats with coarse particles near the surface and core layers with fine particles could also be produced using the device and method according to the invention.

[0044] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. These show: Fig. 1: a schematically represented first spreading device according to the invention, Fig. 2: a schematically illustrated second spreading device according to the invention, which the Fig. 1 is essentially double and mirrored. Fig. 3: Schematic section through a grit mat or a finished mineral slab

[0045] The figures are intended to illustrate, by way of example, the inventive method for producing a grit mat and a suitable system for its production. Furthermore, they show Fig. 3 a spreading mat and the structure of the produced mineral plate.

[0046] In Fig. Figure 1 shows a spreading device 10 according to the invention, which is mounted in a stand structure. A hopper 20 is located at the top, containing both coarse particles 3 and fine particles 2 to be spread, as well as the shot 4. In this embodiment, the particles are primarily fibers made of mineral materials. Ultimately, a spreading mat 1 is to be formed on a forming belt 23 circulating around deflection rollers 24, which, after subsequent compaction, has a particularly smooth surface. For this purpose, a method and a device are provided that keep the rough shot particles away from the surface. The fiber material to be spread, with its fine and coarse particles 2, 3, can be further separated so that particularly fine particles 2 form at least one surface of the mat.

[0047] This is achieved by feeding the spreading material 2, 3, 4, which is at least partially coated with a binder, in the hopper 20 via a circulating hopper belt 22 towards R1 to a hopper discharge metering unit 21. The hopper discharge metering unit 21 continuously delivers approximately the same quantity of spreading material per unit of time from the hopper 20, consisting of fine particles 2, coarse particles 3, and shot 4. The terms coarse and fine are understandably relative, but the mineral fibers, which are primarily considered here, are generally longer (1.5 to 10 mm) than the shot (50 to 250 µm). From the hopper, the material falls towards R2 to a first size-division device, which in this embodiment is formed by a preferred first roller spreading head 12. This transports via its rollers a first subset 5, consisting of fine and coarse particles 2, 3 further onto a conveyor belt 11 running in the direction of R4.The granular shot particles, on the other hand, fall as a second subset 6, sorted through the adjustable gaps between the rollers of the first roller spreading head 12, and land in the second feed area 15 on a second size-separating device 9, which in this embodiment is also a second roller spreading head 13. From this roller spreading head 13, all particles 2, 3 and shot 4 are fed onto the moving forming belt 23. Thus, the spreading material 2, 3, 4 from the hopper is separated into two subsets 5, 6 and subsequently heterogeneously recombined.

[0048] Therefore, the fine particles 2 and coarse particles 3 in the feed area 14 also fall onto the second roller spreading head 13, but in the direction of travel R3 of the forming belt 23, significantly ahead of the shot in the feed area 15. The roller spreading head is thus relatively long and covers at least partial areas of all spreading areas 25, 26, 27 for fine and coarse spreading material as well as shot.

[0049] In Fig. In Figure 1, the shot particles 4 are depicted as small, but nevertheless oversized, black dots. The fine particles 2, on the other hand, are shown as light dots. For the sake of clarity, the additional coarse particles 3 are not shown. In this embodiment, the coarse particles 3 migrate from the first feed area 14, across the roller spreading head 13, towards the second feed area 15 and are gradually dropped onto the forming belt 23 through the gaps between the rollers as the distance between them increases, i.e., from left to right in the drawing, with increasing size.

[0050] The fine particles 2 fall directly from the first feed area 14 onto the forming belt. To ensure that particularly fine particles, which later provide the smooth surface of the mineral sheet, are the very first to land on the forming belt 23, these are drawn into the foremost area of ​​the spreading area 25 by a suction device 17 using air drawn in towards R5. The suction device is dimensioned so that hardly any particles are extracted, but rather they are only drawn in, so that they ultimately fall onto the forming belt 23 by the force of gravity.

[0051] It should also be noted that the rollers of the roller spreading head 13, in which the material placed on the rollers is transported via the rotation D of the rollers and separated or fractionated by certain distances, have a different geometry, here for example roller type 1 with the designation 18, in contrast to rollers that meter the material placed on the rollers directly, here for example roller type 19.

[0052] At various points throughout the entire spreading device 10, solid or powdered additives, such as binders, fire retardants, or insecticides, or even organic fibers, for example from wood, can be added to the spreading material 2, 3, 4. An optional particle feed 28 is shown with a dashed line to indicate an example location.

[0053] Profile errors can be automatically corrected using a measuring head 31 extending across the width of the spreading mat 1, which can measure the thickness or density of the spreading mat 1. For this purpose, sectionally inserted adjustable guide plates, roller spacing, feed positions, and many other actuators can be used and adjusted by motor.

[0054] Would this in Fig. If the spreading device 10 described in Figure 1 is used, only one surface of the resulting mineral plate would be particularly smooth, namely the one lying at the bottom on the forming belt 23. The rough shot 4 would even collect on the other surface. This may suffice for many purposes, but if one wants both mineral plate surfaces to be as smooth as possible, it is particularly easy to place the "same" spreading device 10' again, mirrored, behind the first spreading device 10. This is shown schematically in Figure 1. Fig. Figure 2 shows that this results in the shot 4' being first dropped onto the forming belt 23, i.e., into the future midpoint of the spreading mat 1 or the later pressed dam plate. Predominantly coarse particles 3' then follow on top, and finally the fine particles 2'. Thus, at least a new third subset 7 is obtained, which covers the central area of ​​the spreading mat 1 with shot 4'.

[0055] Bunker 20, which is shown here for both spreading devices 10, 10', can of course also be divided. This is indicated in Fig. 2 also a press roller 29 to pre-compact the spreading mat 1, which may consist of bulk-forming rock or glass wool, before a final, preferably continuous press not shown.

[0056] With the combined spreading device 10, 10' from Fig. 2. The only very schematic representation is then... Fig.The three indicated spreading mats 1 and the similarly structured, but compacted, finished mineral material panels are also represented. Fine particles 2, 2' are located in the layers closest to the surface 30. Further inwards are the coarser particles 3, 3' and embedded within them is the grit 4, 4'. The surface 30 is characterized by an excellent smoothness that is easy to coat. The grit, which is not laboriously separated beforehand, also has a strength-enhancing effect. Reference symbol list 1 grit mat 2.2' Fine particles 3.3' Coarse particles 4.4 shot 5 First subset 6 Second subset 7 Third subset 8 First size division device 9 Second size division device 10, 10' Spreading device 11 Conveyor belt 12, 12' First roller spreader head 13, 13' Second roller spreader head 14 First feed area 15 Second feed area 16 Stand construction 17 Suction device for fine spreading material 18 Roll Type 1 19 Roll Type 2 20 bunkers 21 Bunker outlet dosing 22 Bunker Band 23 Form band 24 Deflection roller 25 Spreading area fine spreading material 26 Spreading area coarse spreading material 27 Shot dispersion range 28 Optional particle input (additives, organic substances) 29 Press roller 30 surface 31 Measuring head R1 Flow direction of grit in the bunker R2 outflow from bunker R3 Direction of travel of the forming belt R4 Transport direction first subset R4 air intake direction Direction of rotation 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 10 2016 113 014 B4

[0011] DE 10 2007 049 947 A1

[0012]

Claims

[1] Method for producing a litter mat (1) using particles (2, 3, 4), in particular fibers, made of mineral materials, for example rock wool or glass wool, on a moving forming belt (23), comprising the following steps: a) Providing a bunker (20) with mixed fine and coarse particles (2, 3) and shot (4), b) Dividing the particles (2, 3) and shot (4) exiting the bunker (5) via at least a first size-separating device (8) into at least a first subset (5) with fine and coarse particles and at least a second subset (6) with predominantly shot (4), c) furthermore, forwarding the first subset into a second size-dividing device (9) in a first feed area (14) and fractionating the first subset (5) again according to particle size and d) Scattering of the particles (2, 3) of the first subset (5) as a layer of increasing or decreasing size onto the forming belt (23) to form the spreading mat (1) with a desired thickness, characterized by , that the second subset (6), containing the shot (4), is also fed to the second size division device (9) in a second feed area (15) different from the first, but is spread onto the moving forming belt (23) at such a time offset to the first subset that at least the shot (4) is arranged above a layer of fine particles (2) in the thickness of the spreading mat (1). [2] Method according to claim 1, characterized by , that a further layer of fine particles (2') of a third subset (7) is spread, so that the second subset (3) is arranged in the middle of the thickness of the spreading mat (1). [3] Method according to one of claims 1 or 2, characterized by, that at least a subset (5, 6, 7) is fed to the second size-dividing device (9) with the assistance of gravity. [4] Method according to any one of claims 1 to 3, characterized by , that when fractionating the first subset (5) in the second size division device, the coarse particles (3) of the second subset (6) are fed to the second subset (7). [5] Method according to any one of claims 1 to 4, characterized by , that both the first partial quantity (5) and the second partial quantity (6) from the second size division device (9) are scattered onto the forming belt (23). [6] Method according to any one of claims 1 to 5, characterized by , that roller spreading heads (12, 13) with at least three adjacent rollers (18, 19) are used as size division devices (8, 9). [7] Method according to claim 6, characterized by, that the first subset (5) is dropped from a first roller spreading head (12) into the first feed area (14) of a second roller spreading head (13) and the second subset (6) is dropped from a first roller spreading head (12) into the second feed area (15) of the second roller spreading head (13). [8] Method according to any one of claims 6 to 7, characterized by , that fine particles (2) are scattered at one end of a roller spreading head (12, 13) onto the forming belt (23), while coarser particles (3) are transported in the direction of the supplied second subset (6) in the second feed area (15) via the second roller spreading head (13). [9] Method according to any one of claims 6 to 8, characterized by , that the rollers (18, 19) of a roller spreading head (12, 13) are driven alternately in a row of rollers at different speeds and / or directions of rotation (D). [10] Method according to any one of claims 6 to 9, characterized by, that additives, for example fire retardants, are added to the spreading material (2, 3, 4). [11] Method according to any one of claims 1 to 10, characterized by , that the scattering of the first subset (5) is supported by a suction device (17) for fine particles (2). [12] Method according to any one of claims 1 to 11, characterized by , that particles of fibers (2, 3) and / or shot (4) of mineral materials are mixed with further particles, e.g. chips or fibers, and / or shot of organic materials. [13] Device for producing a grit mat in the course of producing mineral slabs according to one of claims 1 to 12, comprising at least one bunker (20) containing fine and coarse particles (2, 3) of mineral materials, for example rock or glass wool, and shot (4), at least one first size-division device (8, 12) for dividing the spreading material (2, 3, 4) exiting the bunker (20) into at least a first subset (5) with fine and coarse particles (2, 3) and a second subset (6) with predominantly shot (4), at least a second size-dividing device (9, 13) for fractionating the first subset (5) supplied in a first feed area (14), and a form strip (23) onto which the first subset (5) can be scattered, characterized by , that the second size division device (9, 13) has at least a second feed area (15) for the second subset (6), away from the first feed area (14) and in the direction of travel of the forming belt (R3) behind the first feed area (14), and that the second subset (6) can also be scattered onto the forming belt (6). [14] Device according to claim 13, characterized by, that a third subset (7) may be scattered from a second bunker, with fine particles (2') onto the first and second subsets (5, 6) as a top layer. [15] Device according to claim 13 or 14, characterized by , that the second feed area (15) lies below the first size division device (8, 12) on the second size division device (9, 13). [16] Device according to any one of claims 13 to 15, characterized by , that the first size division device (8, 12) and second size division device (9, 13) are designed as roller spreading heads (12, 13). [17] Device according to claim 16, characterized by , that at least the rollers (18, 19) of the second roller spreading head (13) have independent individual drives in their majority. [18] Device according to claim 16, characterized by , that the rollers (18, 19) of the second roller spreading head (13) are adjustable in their distances to each other. [19] Device according to claim 16, characterized by , that the rollers (18, 19) of the second roller spreading head (13) are formed from parallel disks on an axis, wherein the disks of one roller (18) in the first feed area (14) have a different shape to another roller (19) in the second feed area (15). [20] Mineral board comprising fine and coarse fibers (2, 2', 3, 3') of mineral materials and grit (4, 4') pressed together to form a mineral board, characterized by , that the shot (4, 4') is located only inside the mineral plate and not in its surface area (30). [21] Mineral board according to claim 20, characterized by that the mineral board also contains organic particles

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