Device for applying liquid coating, method for coating surface of substrate and method for producing sandwich panel

Abstract

The invention relates to a device for applying a liquid coating on a surface (49) of a substrate (51), comprising a tube (33) for feeding the liquid coating and a pad (43) made of a porous material, in which the tube (33) comprises at least one opening (35) extending parallel to the main axis of the tube (33), and / or in which the tube (33) comprises a plurality of openings arranged in rows parallel to the main axis of the tube (33), the invention relates to a device for feeding liquid coating into a mat (43) through which liquid coating can be fed, comprising a metering device for feeding liquid coating into a tube (33) at a predetermined pressure, where the mat is arranged in a tank (37), the tube (33) is arranged below the tank (37), and at least one opening (35) or openings in the tube (33) are in fluid contact with openings in the bottom of the tank, the liquid paint can flow into the groove from the pipe, and the pad (43) can be uniformly soaked by the liquid paint. The invention also relates to a method for coating a surface by using an application device (17) and to a method for producing a sandwich panel, wherein a primer is applied to the surface of a sheet by means of the method for coating the surface.

Description

[0001] The present invention relates to a method for producing a sandwich panel comprising a first sheet and a second sheet and a foam layer applied between the first sheet and the second sheet, the method comprising: applying a primer to an inner surface of the first sheet; applying a liquid reaction mixture comprising a foaming agent and a reactant for producing a polymer to the primer on the inner surface of the first sheet, wherein after application, the reaction mixture begins to react and expand, thereby forming a foam layer; applying a primer to an inner surface of the second sheet; and feeding the second sheet such that the primer on the inner surface of the second sheet rests on the foam layer, thereby forming a sandwich panel.

[0002] Sandwich panels produced using this method are used, for example, as facade elements for buildings, particularly in commercial settings such as warehouses or industrial buildings, including workshops, stadiums, department stores, or assembly plants. In addition to their use as facade elements, sandwich panels can also be used as insulation panels in cold storage facilities, climate chambers, or truck-built-up spaces. Sandwich panels are often also referred to as composite elements or sandwich elements.

[0003] Sandwich panels are typically produced using a continuous process, in which first and second sheets are fed into an application apparatus where a primer is applied to the inner surface of the first layer to improve adhesion of the foam layer to the inner surface of the first sheet. Methods for applying a primer to the first sheet are described, for example, in WO-A 2006 / 120234, EP-A 2 412 526, WO-A20010 / 060864, ​​or EP-A 1 593 438. In these methods, the primer is applied only to the sheet forming the exterior of the building. These exterior sheets are typically exposed to greater stress than the interior sheets due to wind loads or heating and thermal expansion caused by solar radiation.

[0004] However, the main reason for applying the primer only to the first sheet is that it is difficult to apply the primer evenly to the inner surface of the second sheet, which is exposed downwards during the production process.

[0005] To apply the primer to the inner surface of the second layer, which is arranged opposite to the inner surface of the first layer, WO-A 2015 / 155138 uses a rotating roller or rotating brush to transfer the primer from the inner surface of the first layer to the inner surface of the second layer. After the primer is applied to the inner surfaces of the first and second sheets, a reaction mixture is applied, and the composite comprising the first and second sheets with the primer coated on their inner surfaces and the reaction mixture applied thereon is fed into a dual belt, in which the reaction mixture reacts and expands to form a foam layer.

[0006] In addition to applying primer to the second sheet using a rotating roller or rotating brush, it is also known to apply primer by using a tube with an opening, a small hose connected to the opening, and the primer being applied to the inner surface of the second sheet through the hose in contact with the inner surface of the second sheet.

[0007] However, a disadvantage of all methods of applying primer to the second sheet is that, since the inner surface of the second sheet faces downwards, the primer may be applied unevenly or drip, resulting in contamination of the inner surface of the first sheet. Furthermore, it is particularly impossible to apply a uniform layer of primer when using a tube (with a flexible hose connected to it).

[0008] Therefore, the object of the present invention is to provide an apparatus for coating a surface of a substrate, by which a uniform coating can be applied to the surface even if the surface is not horizontally extended or the bottom surface of the substrate; to provide a method for coating the surface and a method for continuous production of sandwich panels, wherein a primer is applied to the inner surface of a second sheet to form a uniform coating without dripping.

[0009] This objective is achieved by an apparatus for applying liquid coating to the surface of a substrate, the apparatus comprising a tube for feeding the liquid coating and a pad made of a porous material, wherein the tube includes at least one opening extending parallel to the main axis of the tube, and / or wherein the tube includes a plurality of openings arranged in a row parallel to the main axis of the tube, through which the liquid coating can be fed into the pad, the apparatus including a metering device for feeding the liquid coating into the tube at a predetermined pressure, wherein the pad is disposed in a tank, the tube is disposed below the tank, and at least one or more openings in the tube are in fluid contact with openings in the bottom of the tank, such that the liquid coating can flow from the tube into the tank, and the pad can be uniformly soaked in the liquid coating.

[0010] This objective is also achieved by a method for coating the bottom surface of a substrate using such a device for applying liquid coating to a rectangular surface of a substrate, the method comprising: (i) Feeding liquid paint from a pipe through at least one opening into a tank to soak a pad with the liquid paint; and (ii) The surface of the substrate is passed along the surface of the pad under a predetermined pressure, so that the liquid coating is applied to the surface of the substrate.

[0011] By using a device for applying liquid coating, uniform coating can be achieved across the entire surface of the substrate. Liquid coating is applied to the substrate surface as long as pressure is applied to the surface of the pad in contact with the substrate. Delivery of the liquid coating stops once pressure is no longer applied to the pad.

[0012] Placing the pad in the groove has the additional advantage that no liquid drips through the location of the pad and contaminates the inner surface of the first sheet or the application device.

[0013] To ensure uniform immersion of the pad with liquid coating, at least one opening is preferably arranged such that the liquid coating can flow into the pad along its entire length. For this purpose, the at least one opening may be in the form of a slot extending along the main axis of the tube. Alternatively, multiple openings may be provided. In this case, the multiple openings are arranged in a row parallel to the main axis of the tube. Furthermore, it is preferred that the distance between the openings is constant. If multiple openings are arranged in a row, the openings can have any cross-sectional shape, such as circular, elliptical, rectangular, square, or polygonal with any number of vertices. However, in this case, for manufacturing reasons, it is particularly preferred that the openings be circular or slot-shaped.

[0014] Liquid coating can be metered using a pad made of porous material, such that the liquid coating is dispensed only from the porous material as long as the substrate surface is in contact with the pad. Dispensing of the liquid coating ceases once there is no contact between the substrate surface and the porous material of the pad. This can be achieved, for example, by using a compressible porous material that can be compressed under pressure and returns to its initial shape once the pressure acting on the porous material is interrupted. In this case, the porous material used to impregnate the substrate surface is pressed against the porous material. To achieve this, the compressible porous material is embedded in a groove that holds the liquid therein and prevents fluid dripping. To allow the substrate surface to be pressed against the compressible porous material, the sidewalls of the groove need to be lower than the height of the compressible porous material when it is not compressed. By compressing the porous material, the liquid coating to be applied to the substrate surface is released. For the liquid coating to leave the porous material, it is preferable that the porous material is saturated with liquid coating at least in the area where the substrate surface is pressed against. When the substrate surface is pressed against the porous material, the volume decreases due to the associated compression, and the liquid coating leaves the porous material in a uniform manner to be applied to the substrate surface and form a uniform coating. Once the pressure is no longer applied to the porous material, the porous material returns to its original shape, and since the liquid coating remains within the tank, no more liquid coating leaves.

[0015] Alternatively, the liquid coating can also be transferred from the porous material to the surface of the substrate by capillary force through contact with the surface of the substrate to be coated, and replenished by the distribution of the liquid coating by capillary force within the porous material. Again, in this case, the liquid coating is only distributed from the porous material when it comes into contact with the surface of the substrate to be coated.

[0016] To enable the delivery of liquid coating to the surface of the pad in contact with the surface of the substrate to be coated, it is preferable that the porous material allows for the delivery of liquid along its length by capillary force. In this case, the cross-sectional shape of the porous material perpendicular to the feed direction of the substrate can have any arbitrary shape. Preferably, the cross-sectional area of ​​the pad perpendicular to the feed direction of the second sheet is circular, rectangular, or square.

[0017] If a liquid coating is applied to the surface of a substrate by pressing the surface of the substrate against a porous material, then an apparatus is needed to press the surface of the substrate against the porous material. Such an apparatus could be, for example, a roller acting on the substrate, thereby pressing the surface of the substrate to be coated against the porous material.

[0018] Porous materials can be any kind that allows liquid coatings to transfer to a substrate surface, such as felt, woven fabric, nonwoven fabric, perforated elastic material, or open-cell foam. Particularly preferred are open-cell foams having pore sizes with an average diameter in the range of 70µm to 1500µm, more preferably in the range of 70µm to 800µm, even more preferably in the range of 70µm to 500µm, and particularly in the range of 70µm to 250µm. Porous materials are particularly preferably foams consisting essentially only of a mesh. In the context of this invention, "consisting essentially only of a mesh" means that more than 90% of the foam, preferably more than 95% of the foam, and particularly more than 98% of the foam, has only a mesh without pore walls.

[0019] Suitable materials for preparing porous materials include all materials that do not react with liquid coatings. If the porous material is an open-cell foam, the material used to make the porous material can be any material that does not react with liquid coatings and can form an open-cell foam, preferably a polymer. Suitable polymers that can be used to make porous materials are, for example, polyolefins, particularly polyethylene or polypropylene, polyurethane or melamine resins. As porous materials, open-cell polymer foams made of polyurethane or melamine resins are particularly preferred.

[0020] If the porous material is a felt, woven fabric, or nonwoven fabric, any material that forms a soft surface that does not abrade the material from the substrate can be used to make fibers, felt, woven fabrics, or nonwoven fabrics. In this case, suitable fibers can be polymer fibers or natural fibers. Suitable polymers for fibers are, for example, polyolefins, polyurethanes, or polyamides. Suitable natural fibers are, for example, wool, cotton, flax, or hemp.

[0021] If the porous material is a perforated elastic material, the elastic material can be, for example, synthetic or natural rubber, silicone, or leather.

[0022] In addition to the materials mentioned above, porous materials made of metal, glass, or ceramic can also be used, such as felts or nonwoven fabrics made of metal or glass fibers, or sintered bodies made of metal or ceramic. However, in this case, to avoid damaging the surface of the substrate, it is preferable to attach a soft material, such as a soft felt, nonwoven fabric, knitted fabric, or woven fabric, to the surface of the porous material, or alternatively, a small layer of open-cell polymer foam through which the liquid coating is applied to the surface of the substrate.

[0023] In particular, when liquid coatings leave the porous material due to pressure on the surface of the substrate and no longer release liquid coatings once the pressure is lifted, it is advantageous to use elastic open-cell polymer foams that recover their original shape after the pressure is lifted.

[0024] To enable continuous coating of very long sheets, a sufficient supply of liquid paint is necessary. However, for the liquid paint to leave the porous material only upon contact with the substrate surface, the porous material must not be oversaturated. Saturation is achieved when the porous material can no longer receive any further liquid paint without any liquid paint being dispensed at any point on the surface. This requires that the liquid paint be re-metered into the porous material during the coating of the substrate surface. For this purpose, the porous material is preferably connected to a storage container in which the liquid paint is located. The liquid paint can then be fed into the porous material using a suitable metering device, such as a metering pump. Alternatively, the liquid paint can be allowed to simply continue flowing, for example, under the influence of gravity. For this purpose, a buffer container filled with liquid paint up to a predetermined fill level can be used above the porous material, for example. Thus, the hydrostatic pressure of the liquid paint delivered into the porous material remains largely constant. Furthermore, it is also possible that the connection from the storage container storing the liquid paint to the porous material is filled with another porous material, such that the liquid paint is guided by capillary force through the connecting line into the porous material.

[0025] Placing a pad made of porous material in a suitable tank has the advantage of preventing dripping from the porous material when coating the substrate. The tank can be made of any material inert to the liquid coating, such as metal, polymer, glass, or ceramic. To feed the liquid coating into the porous material, a tube is arranged below the tank, with an opening on its upper side that is in fluid contact with an opening in the bottom of the tank. The liquid then flows from the tube into the tank through the tube and the opening in the tank. For this purpose, a channel connecting the tube and the opening in the tank can be provided, or the tube can be directly attached to the tank such that the tube and the opening in the tank are in the same position. In this case, the tube can be fixed to the tank by welding, brazing, or gluing, thereby achieving a fluid-tight connection, and no liquid coating can escape between the tube and the tank.

[0026] To allow pressure to be applied to the porous material, the sidewalls of the groove have a lower height than the uncompressed pad. In this document, the pad height corresponds to an extension perpendicular to the surface of the substrate to be coated, the length corresponds to an extension transverse to the extension direction of the substrate, and the width corresponds to an extension in the extension direction of the substrate. Conversely, the length of the substrate or the surface of the substrate corresponds to an extension in the extension direction of the substrate, and the width of the substrate or the surface of the substrate corresponds to an extension transverse to the extension direction of the substrate.

[0027] In particular, if the aim is to coat the surface of the substrate in a continuous process, it is further preferred that the edges of the substrate to be coated, extending transversely to the coating direction, are parallel.

[0028] The surface of the pad that contacts the substrate surface during liquid coating application can be flat or curved. Additionally, the surface may include protrusions along the width of the pad that contact the substrate surface during liquid coating application. These protrusions may have, for example, circular, curved, or triangular cross-sections perpendicular to the substrate surface. For uniform application of the primer in a thin coating, it is crucial that the width of the pad's contact with the substrate surface remains constant along the entire width of the substrate surface to be coated. Ideally, the pad should have a uniform thickness along the entire width of the substrate surface to be coated.

[0029] If the surface of the substrate to be coated has a structure that extends parallel to the extension direction of the substrate during coating, such as if the substrate has a wavy or serrated surface structure or any other surface structure (which has protrusions and recesses extending parallel to the extension direction of the substrate during the coating process), it is preferable that the pad includes a structured surface having a structure corresponding to the structure on the surface of the substrate, such that during the application of the primer, the entire structured surface of the pad is in contact with the surface of the substrate to be coated.

[0030] The apparatus for coating a substrate surface can be used, for example, in the production of sandwich panels or for applying adhesives to a surface. If the apparatus is used in the production process of sandwich panels, the liquid coating is typically a primer used to improve the adhesion of the foam layer to the outer sheet.

[0031] A method for producing a sandwich panel, the sandwich panel comprising a first sheet and a second sheet and a foam layer applied between the first sheet and the second sheet, the method comprising: (a) Apply a primer to the inner surface of the first sheet; (b) A liquid reaction mixture comprising a foaming agent and reactants for producing a polymer is applied to a primer on the inner surface of a first sheet, wherein, after application, the reaction mixture begins to react and expand, thereby forming a foam layer; (c) Applying a primer to the inner surface of the second sheet using a method for coating surfaces; and (d) Feed the second sheet so that the primer on the inner surface of the second sheet is placed on the foam layer, thereby forming a sandwich panel.

[0032] In the context of this invention, the terms "inner surface of the first sheet" and "inner surface of the second sheet" each refer to the surface that appears to enter the sandwich panel and is in contact with the foam layer. During production, the first and second sheets are typically fed horizontally into a double-belt assembly. In this document, the first sheet is the lower sheet, and the second sheet is the upper sheet, such that the inner surface of the first sheet is the upper surface, and the inner surface of the second sheet is the bottom surface.

[0033] If the sandwich panel is used as a facade element of a building, it is preferable that at least one of the first and second sheets is made of metal, wherein if only one sheet is made of metal, the sheet made of metal is preferably the one that points outward after assembly. In a preferred embodiment, the first and second sheets are made of metal.

[0034] The metals used for the first and second sheets, if made of metal, are typically aluminum, steel, stainless steel, or copper. Steel or stainless steel is particularly preferred. The metals of the first and / or second sheets may be coated or uncoated on the outer surface (the outward-facing surface of the sandwich panel). Furthermore, the metals of the first and / or second layers may be pretreated, for example, by corona treatment, plasma treatment, flame impact, or other standard methods. In this case, the first and second sheets can use different materials. However, preferably, the first and second sheets use the same material.

[0035] Depending on the intended use of the sandwich panel, in addition to metal sheets, metal films, polymer films, or organic sheets (such as multilayer composite films) can also be used as the first and second sheets of the sandwich panel. Additionally, bitumen nonwoven fabrics can also be used as the sheet material.

[0036] If the material is metal and used as a facade element of a building, the first and second sheets typically have a thickness ranging from 0.25 mm to 1.5 mm. If steel is used as the material for the first and / or second sheets, its thickness is preferably in the range of 0.25 mm to 0.88 mm, particularly preferably in the range of 0.4 mm to 0.75 mm. The thickness of stainless steel sheets is preferably in the range of 0.3 mm to 0.9 mm, particularly preferably in the range of 0.4 mm to 0.6 mm. The thickness of aluminum sheets is preferably in the range of 0.3 mm to 1.5 mm, particularly preferably in the range of 0.5 mm to 0.8 mm, and the thickness of copper sheets is preferably in the range of 0.3 mm to 1 mm, particularly preferably in the range of 0.4 mm to 0.7 mm. The surfaces of the first and second sheets can have any structure, but preferably the surface is planar or has only a light structure, i.e., so-called microprofilation. This means that the protrusions or depressions in the surface due to the structure are preferably no deeper than 2 mm, preferably no deeper than 1 mm. The structure may exist only on the outer surface of the first and / or second sheet, or it may exist on both the outer and inner surfaces.

[0037] Mezzanine panels used for building facades can have any length and width typically used for such panels. Typically, mezzanine panels have a length of 2.5m to 30m, preferably in the range of 3m to 24m, and particularly in the range of 5m to 20m. The width of the mezzanine panels is preferably in the range of 0.5m to 1.25m, and particularly in the range of 0.9m to 1.2m.

[0038] To ensure uniform application of the primer to the inner surface of the second sheet, the pad preferably has a length at least equal to the width of the inner surface of the second sheet. However, preferably, the length of the pad is greater than the width of the inner surface, such that the pad extends beyond the width of the second sheet during primer application.

[0039] The foam layer of the sandwich structure is typically made of isocyanate-based rigid foam, such as polyurethane (PUR) foam, polyisocyanurate (PIR) foam, or poly(urethane-isocyanurate) foam (PU / PIR). For this purpose, the reaction mixture applied to the primer on the inner surface of the first sheet contains reactants for generating polyurethane foam, polyisocyanurate foam, or poly(urethane-isocyanurate) foam. Such reaction mixtures are well known to those skilled in the art and are described, for example, in WO-A 2010 / 060864.

[0040] The primer applied to the inner surfaces of the first and second sheets is typically an adhesive or binder, and is well known to those skilled in the art. Suitable primers are described, for example, in WO-A 2006 / 120234, EP-A 2 412526, WO-A 20010 / 060864, ​​or WO-A 2015 / 155138. Particularly preferred is the primer as a one-component binder, which is an isocyanate prepolymer having free isocyanate groups.

[0041] The same primer can be used on the inner surfaces of the first sheet and the second sheet, or different primers can be used on the inner surfaces of the first sheet and the second sheet. However, it is preferable to use the same primer on the first sheet and the second sheet.

[0042] The primer used is preferably a single-component system to allow application with a single pad. If the aim is to apply a primer containing two components or two different primers to the inner surface of the second sheet, this is achieved by applying the first component or first primer with a first pad and the second component or second primer with a second pad, thus applying the second component or second primer onto the first component or first primer. In this case, the mixing of two different primers or two components is performed directly on the inner surface of the second sheet by applying the second primer or second component onto the first primer or first component before the first primer or first component begins to cure. Furthermore, a thicker primer coating can be achieved on the inner surface of the second sheet by applying the same primer with at least two pads arranged in series. However, it is generally preferred to apply a primer as thin as possible so that there is very little foreign material in the sandwich panel, but thick enough that the primer remains liquid when in contact with the expanding reaction mixture forming the foam layer.

[0043] The thickness of the primer coating on the inner surface of the second sheet, and if a pad made of porous material is also used to apply the primer coating to the inner layer of the first sheet, the thickness of the primer coating on the inner surface of the first sheet can also be set by the following: the pressure of the porous material against the inner surface of the second sheet and / or the first sheet, the application width of the porous material, the type of material used for the porous material, the back pressure set by the pressure reducing valve if the primer is fed into the porous material in the pump circuit, the pressure height if the primer is fed into the porous material under gravity, and / or the speed at which the inner surfaces of the first sheet and / or the second sheet pass through the porous material.

[0044] Sandwich panels can be produced using a continuous or discontinuous process.

[0045] For continuous production of sandwich panels, the first sheet is preferably fed from the roll to a device for applying a primer to the inner surface of the first sheet. The device for applying the primer to the inner surface of the first sheet can be any device known to those skilled in the art, such as a rotary disc, as described, for example, in WO-A 2006 / 120234, EP-A 2 412 526, WO-A20010 / 060864, ​​or WO-A 2015 / 155138. However, any other suitable device for applying the primer to the inner surface of the first sheet may be used besides such a rotary disc. In addition to known devices, a pad as described above may also be used to apply the primer to the inner surface of the second sheet. In particular, if the first sheet is an irregularly shaped sheet, especially if the first sheet has a wavy or serrated cross-sectional shape or a cross-sectional shape with recesses and protrusions of any shape, a pad having an irregularly shaped surface corresponding to the contour of the inner surface of the first sheet, as described above, is preferably used to apply the primer to the inner surface of the first sheet to achieve a uniform coating over the entire inner surface.

[0046] After the primer is applied to the inner surface of the first sheet, a reaction mixture for producing the foam layer is applied to the primer on the inner surface of the first sheet. Any suitable apparatus known to those skilled in the art may be used to apply the reaction mixture.

[0047] Typically, the first sheet is fed horizontally into the apparatus for applying the primer and the reaction mixture. Thus, the primer and reaction mixture are applied from above to the inner surface of the first sheet on the upper side of its formation.

[0048] The second sheet is placed on top of the first sheet and is preferably also fed horizontally from the roll. As described above, a primer is applied with a pad to the inner surface of the second sheet that points downward and is opposite to the inner surface of the first sheet.

[0049] After being applied to the inner surface of the first sheet, the reaction mixture begins to react and expands due to the foaming agent contained in the reaction mixture, forming foam. After the primer is applied to the inner surface of the second sheet, the second sheet is conveyed along the direction of the first sheet until the distance between the inner surfaces of the first and second sheets corresponds to the desired thickness of the foam layer. Due to the expansion of the reaction mixture, the foam extends upwards into the direction of the inner surface of the second sheet and comes into contact with the primer, thereby achieving a stable bond between the foam layer and the inner surface of the second sheet.

[0050] To avoid wrinkles and deviations in the thickness of the foam layer that could lead to uneven thickness in the sandwich panel, the first and second sheets are fed into a dual belt after the reaction mixture is applied, where the reaction mixture reacts and expands. Furthermore, the dual belt is used to transport the first and second sheets and, after the reaction mixture has reacted and expanded, to deliver the produced sandwich panel.

[0051] Typically, each belt of a dual-belt system comprises a chain conveyor guided around rollers. For moving the belts, at least one roller on each belt is a driven roller. The chain conveyors are arranged in parallel, with the distance corresponding to the thickness of the sandwich panel to be produced. During the expansion of the reaction mixture and the formation of foam, a first sheet is pressed against the bottom belt, and a second sheet is pressed against the upper belt of the dual-belt system. Due to the pressure on the belts, a constant thickness of the sandwich panel is achieved. To prevent the sandwich panel from expanding after leaving the dual-belt system, the dual-belt system preferably has such a length that the reaction mixture completes and a rigid foam forms when the sandwich panel leaves the dual-belt system.

[0052] In a continuous process, after leaving the twin belts, the produced sandwich panels are cut into components of predetermined lengths.

[0053] If the sandwich panel is produced using a discontinuous process, the primer and reaction mixture are applied by moving the application device. That is, a pad for applying the primer, made of a porous material, and a device for applying the reaction mixture move along the first sheet, and the application device for the primer moves along the second sheet to apply the primer to the entire inner surface of the first and second sheets, and to apply the reaction mixture onto the primer applied to the inner surface of the first sheet. The second sheet is then placed in its position to obtain the sandwich panel.

[0054] In addition to being used as facade elements, particularly in commercial settings such as warehouses or industrial buildings, such as workshops, stadiums, department stores, or assembly workshops, the sandwich elements produced by the method of this invention can be used as insulation panels, as walls or doors for cold storage or climate chambers, or as walls or doors for truck beds.

[0055] Embodiments of the present invention are shown in the accompanying drawings and explained in more detail in the following description.

[0056] In the attached diagram: Figure 1 A schematic diagram of an apparatus for producing sandwich components is shown; Figure 2 A pump circuit is shown for feeding liquid coating into an application device having a pad made of porous material; Figure 3 A three-dimensional view of the feeding section of the application device is shown; Figure 4A cross-sectional view of the applying device is shown; Figure 5 A pad made of a porous material with a structured surface is shown; Figure 6 An application device for applying a primer to the top surface of a sheet is shown; Figure 7 An application device for applying primer to the bottom surface of a sheet is shown.

[0057] Figure 1 A schematic diagram of an apparatus for the continuous production of sandwich elements is shown.

[0058] The apparatus 1 for producing sandwich panels includes a first application device 3 for applying a primer to the inner surface 5 of a first sheet 7. In a continuous process, the first sheet 7 is typically unwound from a roll and fed into the apparatus 1 for producing sandwich elements. If the process is not performed continuously, a first sheet 7 having the dimensions of the sandwich panel to be produced can be fed into the apparatus 1 for producing sandwich panels. The primer is applied in a uniform coating by feeding the first sheet 7 under the first application device 3 at a constant speed.

[0059] The second application device 9 for applying the reaction mixture is located downstream of the first application device 3. The reaction mixture contains a foaming agent and reactants for forming a polymer, such that a foam layer 11 is formed during the reaction. To achieve a stable bond of the foam on the inner surface 5 of the first sheet 7, the reaction mixture is applied to the inner surface 5 of the first sheet 7 before the primer cures.

[0060] Above the first sheet 7, the second sheet 13 is fed into the apparatus 1 for producing sandwich panels. Since the first sheet 7 and the second sheet 13 are connected by the foam layer 11, the feeding speed of the second sheet 13 is the same as that of the first sheet 7.

[0061] To achieve a stable bond between the foam layer 11 and the inner surface 15 of the second sheet 13, a primer is applied using an application device 17 for liquid coating. Due to the expansion of the reaction mixture, the foam obtained from the reaction mixture comes into contact with the primer on the inner surface 15 of the second sheet 13. For the first sheet, a stable bond between the foam layer 11 and the second sheet 13 is achieved if the foam layer 11 contacts the primer before the primer cures.

[0062] In order to transport the first sheet 7 and the second sheet 13 and produce a sandwich panel with a uniform thickness, a double belt 19 is arranged downstream of the first application device 3, the second application device 9, and the application device 17 for liquid coating.

[0063] The dual-belt 19 includes a first conveyor belt 21 below the first sheet 7 and a second conveyor belt 23 above the second sheet 13. During the production of the sandwich panel, the first sheet 7 is pressed against the first conveyor belt 21 and the second sheet 13 is pressed against the second conveyor belt 23 by expanding foam. Due to the conveyor belts, the foam cannot lift the second sheet 13 above the distance between the first conveyor belt 21 and the second conveyor belt 23, thereby achieving a constant thickness of the sandwich element. For this purpose, the lengths of the conveyor belts 21 and 23 are selected such that the first sheet 7 and the second sheet 13 are in contact with the conveyor belts until the reaction mixture solidifies and produces stable foam.

[0064] In order to apply a uniform primer coating to the inner surface of the second sheet 13, the liquid coating application device 17 includes a pad made of porous material that presses against the inner surface 15 of the second sheet 13.

[0065] In a continuous process, the primer needs to be continuously fed into the application device 17 for liquid coating. Figure 2 The diagram shows a pump circuit for feeding primer into the application device 17 for liquid coating.

[0066] Pump circuit 25 for feeding liquid paint into application device 17 includes a storage container 27 in which the liquid paint is stored. A pump 29 pumps the liquid paint from the storage container 27 into application device 17. Downstream of application device 17, the circuit includes a valve 31. Valve 31 sets the back pressure of the liquid paint in the circuit, and thus sets the amount of liquid paint in the porous material of application device 17 and the amount of liquid paint applied to the surface of the substrate.

[0067] Figure 3 The image shows a three-dimensional view of the feed section of an applicator for liquid coatings, and... Figure 4 The image shows a cross-sectional view of an apparatus for applying liquid coatings, including a feeding section.

[0068] The feed section for liquid coatings may include a pipe 33 through which the liquid coatings flow. If the liquid coatings are fed into the application device 17 via such a pump circuit, the pipe 33 may be, for example, as shown below. Figure 2 Part of the pump circuit shown.

[0069] On the upper side, pipe 33 has an opening 35 through which liquid paint flows into a channel 37, which is located above the pipe and connected to the opening 35 in the pipe via a suitable channel 39. In addition to the channel 39 shown here, the channel 37 can also be directly connected to pipe 33. If channel 39 is used to connect the channel 39 to pipe 33, the channel preferably has a cross-sectional shape corresponding to the cross-sectional shape of the opening 35 in pipe 33. To further allow liquid paint to flow into the channel 37, the channel 37 includes an opening 41 at its bottom. The cross-sectional shape of the opening 41 at the bottom of the channel 37 also corresponds to the cross-sectional shape of the channel 39. The channel 39 is installed in a fluid-tight manner on pipe 33 and at the bottom of channel 37, preventing leakage of liquid paint.

[0070] If channel 39 is not provided, groove 37 is directly mounted on pipe 33. In this case, it is preferable that openings 35 and 41 have the same cross-sectional shape and are mounted flush. Regardless of whether groove 37 is mounted on pipe 33 with or without channel 39, a fluid-tight connection can be achieved, for example, by welding, gluing, or brazing.

[0071] As an alternative to the slot-shaped openings 35, 41 shown herein, multiple openings may also be provided in the pipe 33 and / or in the bottom of the slot 37. If the slot 37 is installed to the pipe 33 in this case without the channel 39, it is preferable that one of these components includes slot-shaped openings, while the other includes a row of openings. In this case, after the slot is installed on the pipe, the row of openings must be completely within the cross-sectional area of ​​the slot, and welds, brazing, or adhesives must surround the slot-shaped openings to prevent leakage of liquid coating.

[0072] For coating the surface of a substrate with liquid paint, the groove 37 includes a pad 43. The pad 43 is made of a porous material, allowing liquid paint to flow from the pipe 33 through the channel 39 into the pad 43, and allowing the liquid paint to be released from the pad 43 onto the substrate surface once the surface of the substrate contacts the surface 45 of the pad 43. A suitable mounting device 47 is provided to secure the pad 43 in the groove 37. The mounting device 47 is, for example, a bracket or clamp that secures the pad 43 in the groove 37. However, any other mounting device besides a bracket or clamp may be used to secure the pad 43 in the groove 37. To allow for replacement of the pad 43, such as for cleaning or removing a used pad, it is preferable that the pad 43 is releasably mounted in the groove 37.

[0073] The advantage of using pad 43 for applying liquid coating to surface 49 of substrate 51 is that a uniform coating layer can also be applied to the structured surface 49. This is in Figure 5 The surface having protrusion 53 and recess 55 is shown as an example.

[0074] To ensure uniform application of the liquid coating, the pad has a surface 45 with a structure corresponding to that of surface 49. This means that where surface 49 of the substrate 51 has a recess 55, surface 45 of the pad 43 has a protrusion 57, and where surface 49 of the substrate 51 has a protrusion 53, surface 45 of the pad has a recess 59. If surface 49 has a different structure than that shown here, such as a wavy or serrated structure, then surface 45 of the pad 47 has a corresponding wavy or serrated structure.

[0075] Figure 6 An apparatus for applying liquid coating to the upper surface of a substrate is shown.

[0076] In order to apply liquid coating to the upper surface of the substrate, the surface 45 of the pad 43 faces downward and is in contact with the upper surface 49 during coating. The use of a porous material in the pad 43 has the advantage that the liquid coating stops flowing and does not drip from the pad 43 after the surface 49 is released from the surface 45 of the pad.

[0077] Liquid coatings can be applied through methods such as Figure 2 The pump circuit shown feeds into pad 43, or alternatively, as shown here, by using a storage container 61 for the liquid coating, which is located at a higher position than pipe 33 and pad 43. In this case, the liquid coating flows into pipe 33 due to gravity. Depending on the hydrostatic pressure of the liquid coating, the thickness and pore size of pad 43, pad 43 can be soaked with liquid coating, but over-soaking should be avoided, such that after pad 43 has been soaked with liquid coating, only liquid coating is fed into pad 43 when the liquid coating is removed by being applied to the surface 49 of the substrate 51 to be coated.

[0078] Figure 7 An apparatus for applying liquid coating to the bottom surface of a substrate is shown.

[0079] Figure 7 The application device 17 shown is Figure 6 The difference in the illustrated embodiment lies in the position of the surface 45 of the pad 43, through which the liquid coating is applied to the surface 49 of the substrate 51. Figure 7 In the illustrated embodiment, the surface 45 of the pad 43 faces upward, such that during the coating process, the surface 49 of the substrate to be coated rests on the surface 45 of the pad. In this case, the pressure at which the liquid paint is fed into the tube 33 must be high enough to completely saturate the pad 43. When the surface 49 to be coated comes into contact with the surface 45 of the pad, the liquid paint is applied to the surface 49 of the substrate 51 by a defined pressure (the substrate 51 is pressed against the surface 45 of the pad 43) or by capillary force. To achieve a sufficiently high pressure, a method such as... Figure 2The pump circuit shown, or alternatively, as shown here, can use a storage container 61 containing liquid coating, positioned such that the surface of the liquid coating is above the surface 45 of the pad to achieve a sufficiently high hydrostatic pressure.

Claims

1. An apparatus for applying a liquid coating to a surface (49) of a substrate (51), the apparatus comprising a tube (33) for feeding the liquid coating and a pad (43) made of a porous material, wherein the tube (33) includes at least one opening (35) extending parallel to a main axis of the tube (33), and / or wherein the tube (33) includes a plurality of openings arranged in a row parallel to the main axis of the tube (33), the liquid coating being feedable into the pad (43) through the plurality of openings, the apparatus comprising a metering device for feeding the liquid coating into the tube (33) at a predetermined pressure, wherein the pad is disposed in a groove (37), the tube (33) is disposed below the groove (37), and the at least one opening (35) or the plurality of openings in the tube (33) is in fluid contact with an opening in the bottom of the groove, such that the liquid coating is allowed to flow from the tube into the groove, and the pad (43) is allowed to be uniformly soaked by the liquid coating.

2. The apparatus of claim 1, wherein the porous material is an open-cell foam having a pore size with an average diameter in the range of 70µm to 1500µm.

3. The apparatus according to claim 1 or 2, wherein the pad (43) includes a structured surface (45) having a structure corresponding to the structure of the surface (49) of the substrate (51), such that during the application of the liquid coating, the entire structured surface (45) of the pad (43) contacts the surface (49) of the substrate (51) to be coated.

4. The device according to any one of claims 1 to 3, wherein the opening (35) is a slot parallel to the main axis of the tube (33), or wherein a plurality of openings are arranged in a row parallel to the main axis of the tube (33).

5. The device according to any one of claims 1 to 4, wherein the sidewall of the groove (37) has a height lower than that of the uncompressed pad (43).

6. A method for coating the bottom surface of a substrate using the apparatus according to any one of claims 1 to 5, the method comprising: (i) Feeding liquid paint from the pipe (33) through the at least one opening (35) into the tank (37) to soak the pad (43) with the liquid paint; and (ii) The surface (49) of the substrate (51) is passed along the surface (45) of the pad (43) under a predetermined pressure, so that the liquid coating is applied to the surface (49) of the substrate (51).

7. A method for producing a sandwich panel, the sandwich panel comprising a first sheet (7) and a second sheet (13) and a foam layer (11) applied between the first sheet (7) and the second sheet (13), the method comprising: (a) Apply a primer to the inner surface (5) of the first sheet (7); (b) A liquid reaction mixture containing a foaming agent and a reactant for producing a polymer is applied to the primer on the inner surface (5) of the first sheet (7), wherein after application, the reaction mixture begins to react and expand to form the foam layer (11). (c) Applying a primer to the inner surface (15) of the second sheet (13) by means of the method according to claim 6; and (d) Feeding the second sheet (13) such that the primer on the inner surface (15) of the second sheet (13) is placed on the foam layer (11) to form the sandwich panel.

8. The method according to claim 7, wherein in order to apply the primer to the inner surface (5) of the first sheet (7), the inner surface (5) of the first sheet (7) passes over a pad (43) made of a porous material and soaked in the primer, such that the inner surface (5) of the first sheet (7) is coated with the primer.

9. The method according to claim 7 or 8, wherein the first sheet and the second sheet (7, 13) are made of metal.

10. The method according to any one of claims 7 to 9, wherein the reaction mixture contains reactants for producing polyurethane foam, polyisocyanurate foam or poly(urethane-isocyanurate) foam.

11. The method according to any one of claims 7 to 10, wherein the primer is an adhesive or binder.

12. The method according to any one of claims 7 to 11, wherein a primer comprising two components or two different primers is applied to the inner surface (15) of the second sheet (13) by applying the first component or the first primer with the first pad (43) and applying the second component or the second primer with the second pad (43), such that the second component or the second primer is applied on the first component or the first primer.

13. The method according to any one of claims 7 to 12, wherein the method is performed continuously.

14. The method according to claim 13, wherein after the reaction mixture is applied, the first sheet and the second sheet (7, 13) are fed into a dual belt (19), wherein the reaction mixture and expansion occur in the dual belt (19).

Images