PLAIN PLATES AND METHODS FOR THEIR MANUFACTURE

Description

Technical area

[0001] The present invention relates to a method for producing panels for forming a large-area floor, which consist of one or more layers and preferably have a decorated surface. Background of the invention

[0002] Panels used to form floors (floor coverings / floor tiles), walls, or ceilings are often made of thermoplastic materials such as polyvinyl chloride (PVC) or polyolefins (polypropylene (PP) or polyethylene (PE)). However, panels made of homogeneous materials have numerous disadvantages. For example, such panels exhibit low thermal and dimensional stability, causing them to shrink or expand with temperature changes, resulting in warping of the resulting floors. If these panels are manufactured using injection molding, they tend to cup, i.e., bend, which leads to installation problems and can also result in uneven floors. Furthermore, panels made almost exclusively of thermoplastic materials, and especially those made of only one specific material type, are often not very durable and must be relatively thick to withstand significant loads.

[0003] Some of these disadvantages are addressed by using multilayer panels, for example by incorporating layers of materials with higher thermal stability, dimensional stability, and / or stiffness (see, for example, EP 3 556 819 A1). Another aspect is the desire to decorate the surface of the panels, for example, to give the finished floor a specific appearance. This can be achieved, for example, by applying a decorative layer, such as paper (with protective additives, e.g., impregnated with resin), near the surface of the flooring, or by printing or pressing a decorative design onto these layers. EP 3 121 004 A1 describes polypropylene-based, multilayer floor panels containing glass fibers in a carrier layer and methods for their production based on extrusion and calendering.

[0004] The individual layers of such panels are often glued or pressed together. Numerous such processes, with their disadvantages, are described in international patent application WO 2013 / 017543 A1, which describes a method for improving, in particular, the water resistance of decorated multilayer panels, requiring the impregnation of the panel's top layer. US 2014 / 0150842 A1 describes a method for manufacturing panels from glass fiber-reinforced polymer composites, wherein the heated mixture of glass fibers and polymer component is injected into a mold and cools therein.

[0005] To increase thermal stability, dimensional stability, and compressive strength, some manufacturers, such as Gerflor, use fiberglass mats as one of the sheet layers. The other layers of the sheet, made of thermoplastic material, are bonded or pressed to the fiberglass mat and to each other, for example, by calendering. These processes are relatively complex because all layers must first be manufactured separately and precisely positioned, and the sheets must be cut or die-cut from the large blank after the layers are bonded. Furthermore, the aforementioned fiberglass mat is only present in one layer in such sheets, or in more complex cases, in several layers, meaning that the strengthening properties are not conferred to the entire sheet.While the plate as a whole has increased load-bearing capacity, the surface of the plate produced in this way may still be relatively weak in terms of load-bearing capacity.

[0006] If injection molding is used as an alternative to calendering to produce such plates, a further problem arises: the plates formed in this way are often not straight, as they often warp (cup) when cooling, especially if the plates produced in this way consist of several layers where the individual layers contract to different degrees when cooling.

[0007] Therefore, there is a need for new methods for manufacturing plates using injection molding that prevent or at least reduce the cupping of the plates. The term "cupping", which has already been mentioned above, is derived from the image of a bowl, which usually has curved edges, while the desired plates should be as flat as possible. Brief description of the invention

[0008] The present invention relates to the embodiments characterized in the claims.

[0009] Generally speaking, the invention relates to processes for producing panels. Both the panels and processes for their production are described herein. Except as a direct product of the process, the panels themselves do not form part of the invention. The following descriptions of the panels themselves therefore serve only to illustrate the process according to the invention and are to be understood as referring to the products directly produced by the process according to the invention. The term "panel(s) according to the invention" is therefore used herein exclusively to refer to panel(s) directly produced by the process according to the invention.

[0010] In particular, the present invention relates to the following aspects and embodiments.

[0011] The present invention relates to a method for producing plates comprising a carrier layer and optionally a cover layer comprising the following steps in the following order: a) Optionally, the top layer is placed in a first mold; b) A mixture comprising a thermoplastic polymer and pulverized fibers is produced; c) The mixture from b) is heated while mixing until the thermoplastic polymer melts; d) The heated mixture is injected into the mold (onto the back of the top layer); e) The sheet is cooled in the mold to a temperature at which it is stable enough to be removed from the mold; f) The sheet is removed from the mold and placed into a second mold that has a bend in the opposite direction to the expected cupping of the sheet; g) The sheet is cooled in the mold to approximately 30°C; h) The sheet is transferred to a third mold, the third mold having a flat bottom, and the sheet is placed on this flat surface; and i) The sheet is cooled in the third mold to 15-20°C below room temperature.

[0012] The process according to the invention is preferably characterized in that the thermoplastic material is selected from a polyolefin and polyvinyl chloride. Furthermore, the comminuted fibers are preferably ground glass fibers. If a cover layer is provided in the mold, this preferably consists of polyvinyl chloride (PVC) according to the process of the invention.

[0013] If, in addition to fibers and thermoplastic polymer, other materials are mixed and used in the process in step b), the mixture in step b) additionally comprises wood fibers, lime flour, stone flour and / or additives according to the invention.

[0014] According to the present invention, the process of the invention as described herein is carried out such that the mixture: In step d) the product has a temperature of approximately 150°C-210°C when injected into the mold; in step e) it is cooled down to approximately 80-110°C in the first mold (injection molding chamber); and in step f) it is placed into the second mold at approximately 80-110°C.

[0015] Preferably, according to the present invention, in step d) when using PVC as a thermoplastic material, a temperature of about 170-180°C is selected, for PE a temperature of preferably 180-200°C and for PP a temperature of 180-210°C.

[0016] Preferably, the first mold (injection molding chamber) used in the inventive method has one side with a three-dimensional structure, characterized in that the produced plate has the imprint of the three-dimensional structure on its upper surface, or, if the top layer was placed in the mold, on the upper surface of the top layer, after completion of the method. Based on the inventors' experiments, the inventive method was configured such that the produced plates are preferably characterized in that they have a maximum curvature of 0.5%, but not more than 2 mm, relative to the side length.

[0017] Furthermore, the method according to the invention is preferably characterized in that the first form is designed such that connecting means are created on each side of the carrier layer in the manufactured plates in order to be able to connect the plates with at least one adjacent plate, wherein the connecting means are opposing extensions and recesses on each side of the carrier layer, wherein the extensions are intended for positive engagement in the recesses.

[0018] Preferably, in the inventive method described herein, the cover layer, if used, is presented in such a way that it extends completely over the connecting means of the respective plate on at least one side of the plate and that, if the plate is laterally connected to adjacent plates via the connecting means, the connecting means on the connected sides are covered by the cover layer. Description of the characters

[0019] Fig. 1: (A) Top view of the reverse side of an exemplary plate (10) according to the invention with a protruding surface of the carrier layer or, if present, the cover layer. As connecting means (14), rows of teeth with alternating projections / teeth (20) and corresponding recesses (22) are arranged on the outer edges (12) of the plate. Two outer edges (top and right) have open teeth and two (left and bottom) have concealed teeth, the teeth being covered by a protruding part of the plate surface (30) or the cover layer. (B)Cross-section through a section of the outer edge of plate (A) in the area of ​​plate (10) marked by arrows AA, in conjunction with a corresponding section of the outer edge of another plate (10'). The connecting elements (14, 14') are located in these sections. The sealing lip (16) of plate (10) lies in the groove (17). A displacement channel (18) is located below the connected plate (10'). The groove, if present, can be designed such that it itself, or parts thereof, also function as a displacement channel (19). The plate section above the sealing lip is referred to as the top surface, or, if more than one layer is present, as the cover layer (110), and can be made of a different material than the underlying support layer (120). The cover layer (110) can also consist of several layers. Fig. 2:Formation of a composite / floor covering from the panels 10, 10' and 10". Panels 10 and 10' are already connected to each other by means of the connecting elements (14, 14'). The interlocking rows of teeth are visible here. Panel 10" will be connected to panel 10, whereby the projections (20) will engage in the recesses (22), as indicated by the superimposed, alternately oriented arrows. Fig. 3: Schematic cross-section through the connecting element (14) of the plate (10) made of Fig. 1A and B without the additional plate 10'. In particular, it should be noted here that the optional sealing lip (16) preferably runs at an angle (28) towards the underside (26) of the plate. Fig. 4: (A1) Top view of the back of an exemplary square plate according to the invention (200). Connecting means are provided on the outer edges (12) of the plate as shown in Fig. 1Rows of teeth are arranged with alternating projections / teeth (20) and matching recesses (22). Two outer edges (top and left) exhibit open teeth, and two (right and bottom) exhibit concealed teeth, with the teeth being concealed by a protruding portion of the panel surface or by a cover layer (30). The four corner areas of the floor element (e1-e4) are designed differently here as an example, but are symmetrical about the axis 46. (A2) Cross-section parallel to the vertical axis of the plate (A1). (A3)Cross-section parallel to the horizontal axis of the plate (A1). The design of the plate edges is shown enlarged over the cross-sections from A2 and A3. The top layer (120) and the carrier layer (110) are indicated (B). Top view of the front side of an exemplary plate according to the invention in an elongated form (100) with the entire visible top surface of the top layer. The projections (20) are still clearly visible here, without the connection of another plate, on the two sides that are not overlaid by the top layer (open interlocking). Fig. 5 Example of a floor covering / composite made of elongated (100) and square (200) tiles. Detailed description of the invention

[0020] The present invention relates to the embodiments characterized in the claims.

[0021] Unless the context clearly indicates otherwise, the use of singular and plural forms always includes both the singular and the plural. The article "ein, eine, eines" refers not only to one instance of the object denoted by the following noun, but also to several of them. Thus, the term "eine / die Platte" (a record / the record), as used here, stands in for one or more such records. Therefore, in the following, the terms "ein / eine / eines," "ein / eine / eines or several," and "zumindest / mindestens ein / eine / eines" are essentially used interchangeably.

[0022] The term "approximately / essentially" defines a possible deviation from the value(s) mentioned below. This deviation is in the range of 1-30%, in particular 1-20%, in particular 1-10%, in particular 1-5% and in particular 1-2% of the nominal value of the stated amount / value as it would be defined without this amount.

[0023] The terms floor element, floor panel, and panel are used interchangeably below to refer to a planar, preferably rectangular, device that can be used to manufacture floors. These terms refer to preferred embodiments of the devices according to the invention from the total set of connectable elements, whereby their use for manufacturing floors is only meant to serve as an example of these preferred devices, and identical or similar elements or connectable elements are also suitable for installation on surfaces other than floors, for example, on walls or ceilings. It is therefore understood that the term floor element and the corresponding description of its features are not largely limited to elements for manufacturing floors, but can and should also accordingly characterize the features of other elements, such as wall and ceiling coverings.The designation "same or similar" refers in particular to the features of the connection between the joinable means according to the invention, as described in more detail below.

[0024] This document describes a plate comprising a thermoplastic polymer and ground fibers. The plate according to the invention can consist of only one layer, which is hereinafter also referred to as the carrier layer, comprising or alternatively consisting of a thermoplastic polymer and ground fibers. Preferably, the plate according to the invention comprises more than one layer, wherein at least one of the layers comprises or consists of the mixture of polymer and ground fibers specified in more detail below. Particularly preferably, the plate according to the invention comprises at least two layers: a carrier layer and a cover layer. Preferably, at least the carrier layer comprises the ground fibers in addition to the thermoplastic polymer or consists of these two materials. The carrier layer and the cover layer can also both consist of the same mixture of thermoplastic polymer and ground fibers.In this case, the two layers may be indistinguishable from each other, or the top layer may only be recognizable by a decoration. According to the present invention, a decoration can be selected from the group consisting of a different color of the top layer compared to the substrate layer, a print on the top layer, or, if the top layer itself consists of several layers, on one of these layers, or a three-dimensional pattern embossed in the top layer.

[0025] Preferably, the proportion of ground fibers in the plates according to the invention, or in at least one layer of the plates, preferably the carrier layer, is between 1% and 35%, more preferably 10% to 35%, 10% to 30%, 10% to 25%, 15% to 25%, or 15% to 20%. If glass fibers are used, their proportion in at least one layer of the plates according to the present invention is preferably 1% to 35%, 10% to 35%, 10% to 30%, 10% to 25%, more preferably 15% to 25%, and particularly preferably 15% to 20% glass fibers, since these ranges have been found to be optimal for imparting the desired stabilizing effects to the plates without these effects becoming weaker (below about 10% to 15%) or the plates beginning to become brittle (above 35%).Furthermore, the increase in stability is greatest when using up to 25% glass fibers, while above this value the stability increases only slightly, while the costs of the panels produced in this way continue to rise sharply.

[0026] According to the invention, the fibers are preferably distributed substantially or largely uniformly in the respective layer. The term "substantially / largely uniformly" is used here to describe that the fibers are distributed in substantially equal quantities over the entire thickness, width, and length of the plate and are not, for example, only found at the bottom of the layer.

[0027] The percentages used in this description regarding the proportion of certain materials in a component, e.g., in the core layer or top layer, refer to the total weight of the respective component. For panels consisting of a single layer, e.g., only the core layer, the percentage refers to the total weight of the panel.

[0028] Different fibers can be used in the plates according to the invention or in the carrier layer of the plates according to the invention.

[0029] Preferably, the fibers in the plates disclosed herein are selected from the group consisting of: glass fibers, natural fibers, and polyester fibers. The term "natural fibers" includes plant fibers, animal fibers, and mineral natural fibers. Plant fibers are preferably selected from the group consisting of cotton, bamboo fibers, hemp fibers, jute fibers, kenaf fibers, linen fibers, nettle fibers, and coconut fibers. Animal fibers or fibers of animal origin are preferably selected from wool, cattle hair, horsehair, goat hair, pig bristles, and silk. Mineral natural fibers are preferably selected from the group consisting of attapulgite (or palygorskite), sepiolite, and wollastonite.

[0030] If the panel consists of more than one layer, the top layer, as described above, can be made of the same material as the substrate, or of a homogeneous material, or it can itself be multilayered, for example, a laminate. Preferably, the top layer consists of a homogeneous material. Polyvinyl chloride (PVC) is particularly preferred.

[0031] The term "thermoplastic polymers," as used herein, refers to plastics that can be deformed (thermoplastically) within a specific temperature range. This process is reversible, meaning it can be repeated any number of times by cooling and reheating back to the molten state, as long as overheating does not cause the so-called thermal decomposition of the plastic.

[0032] In principle, the plates according to the invention can comprise various thermoplastic materials (according to the proportions or mixing ratios with fibers mentioned above). Preferably, however, the present invention provides a plate as described above, wherein the thermoplastic material is selected from the group consisting of polyolefins and polyvinyl chloride (PVC). From the group of polyolefins, polyethylene (PE) or polypropylene (PP) are preferably used according to the present invention. Thus, the plate according to the invention preferably comprises PVC, PE, or PP as a thermoplastic material in the carrier layer. With regard to the PVC, according to the present invention, both with respect to the plates and to the process described below, a PVC with a density of approximately 1.3 to 1.45 g / cm³ and a Shore A value of approximately 85-95 is preferably used.Preferably, a PVC with a K-value of 50 or 70 is used in the plates and in the method according to the present invention.

[0033] The first tests of the properties of plates containing an admixture of glass fibers according to the invention, carried out by the inventors, showed that by adding fibers in the specified proportions to the plate backing layer, numerous properties of the plates were improved compared to plates whose backing layer consisted only of thermoplastic materials or in which no ground fibers were present. For example, plates without fiber admixture showed an expansion of 1.2–1.6% when heated to 95–100°C, while the plates according to the invention exhibited an expansion of only 0.12–0.16%, i.e., a thermal stability that was ten times lower. Likewise, the shrinkage (dimensional change) of the plate dimensions at 25–35°C was only 0.01–0.02% for plates according to the invention with fiber admixture, whereas it was 1.2–1.6% for plates made solely of thermoplastic material.Furthermore, the point load that the panels according to the invention could bear was significantly higher at 65-70 kg / cm² than that of panels without glass fiber reinforcement at 30-35 kg / cm² at room temperature (22-25°C) (see Example 3). It was also shown that the panels according to the invention can be manufactured much thinner than panels made of thermoplastic material, since while the conventional panel had to be 10 mm thick to bear the aforementioned pressure load of 30-35 kg / cm², the panels according to the invention achieved the same pressure load of 65-70 kg / cm² at a thickness of only 6.5 mm. Another advantageous property of the panels according to the invention is that they have been classified as flame-retardant floor coverings with regard to their fire behavior, as described in more detail in Example 2.

[0034] The substrate layer or panel can comprise other materials besides the thermoplastic polymer and fibers in the aforementioned proportions. Preferably, one or more of these additional materials are selected from the group consisting of wood, preferably wood flour, lime flour, stone flour, and additives. Instead of wood flour, other plant fibers can also be used. Preferably, these alternative plant fibers are selected from the group consisting of kenaf, jute, or flax. Preferably, the use of these additional materials does not change the aforementioned proportion of fibers in the substrate layer or panel, but rather reduces the proportion of the thermoplastic polymer accordingly.If one or more of the additional materials selected from the group consisting of wood, preferably wood flour, lime flour and stone flour, are used, then according to the invention their proportion in the thermoplastic polymer of the carrier layer is between about 10 and about 90%, preferably between about 20-90%, 20-80%, 20-70%, 20-60%, 20-50%, 30-50%, 35-50%, 40-50%, 50-60% or at about 50%.

[0035] Additives are substances that, for example, protect the plastics used from thermo-oxidative decomposition, acid scavengers (such as hydrotalcite or DHT-4A), antioxidants, colorants / pigments, flame retardants, biocides, and plasticizers. The total proportion of additives in the carrier layer is preferably about 0.1–5%, more preferably about 0.1–2%, and particularly preferably about 0.5–1.0%. According to the present invention, bis(2-ethylhexyl) terephthalate (DOTP, especially DOTP 40) or diisononyl phthalate (DINP) are preferably used as plasticizers.

[0036] The additional materials are preferably either mixed with the thermoplastic polymer and the fibers in the carrier layer or, if applicable, in the plate, or they are present in layers, wherein the carrier layer then consists of one or more layers containing only the thermoplastic polymer and the fibers in the aforementioned proportions and of one or more layers comprising thermoplastic polymer and one or more of the additional materials or of one or more layers comprising thermoplastic polymer, one or more of the additional materials and ground fibers in the aforementioned proportions.

[0037] Alternatively or additionally, the thermoplastic polymer in the carrier layer is present in a composite material. According to the invention, the composite material is preferably selected from the group consisting of laminates, wood-plastic composites (WPCs), and stone-plastic composites (SPCs). WPCs comprise a thermoplastic polymer, as defined herein, and wood or wood flour or plant fiber flour in the aforementioned proportions, while SPCs, according to the invention, comprise a thermoplastic polymer and stone or lime flour in the aforementioned proportions. The terms WPC or SPC, as used herein, preferably refer only to the layer comprising a polymer / wood (fiber), polymer / lime flour, or polymer / stone flour composite.

[0038] The plates according to the invention, or one or more layers of the plates, contain milled fibers according to the invention. Preferably, the milled fibers have a length of 0.1-6 mm, more preferably 1-6 mm, 1.5-5.5 mm, 2-5 mm, 2-4.5 mm, 2-4 mm, 2-3.5 mm, and particularly preferably 2-3 mm.

[0039] Preferably, the panels according to the invention are designed such that they can be connected to one another to form a large-area covering, e.g., a floor covering, if the area to be covered is larger than the dimensions of the individual panel. Accordingly, panels are provided herewith, wherein the individual panel preferably has connecting means on each side of the panel or the carrier layer in order to be able to connect the panel to at least one adjacent, preferably identical, panel.

[0040] The connecting means used on the panels according to the invention can be of a wide variety of types. Suitable connecting means include, for example, mechanical, chemical, and physical means. Mechanical connecting means that can be configured or attached to at least one outer edge of the panels according to the invention are understood, in particular, to be outer edge configurations that are suitable for forming a positive connection with corresponding, complementary configurations on an outer edge of another panel. Toothed systems are preferably used as such connecting means.According to the present invention, gear systems are generally understood to consist of areas comprising protrusions and indentations, i.e., projecting areas, which are also referred to herein as bulges or teeth, these terms being used interchangeably; and recessed areas (indentations or recesses, respectively, both terms being used interchangeably), wherein the protrusions and indentations are each designed such that the protrusions can engage the indentations in a form-fitting manner to a large extent and fill them completely. Preferably, the protrusions and indentations are arranged alternately along the outer edge. The protrusions are preferably designed such that, at the end of their stem-like projecting area, areas with a larger lateral extent, i.e., areas extending substantially parallel to the outer edge, are connected.With this design, the protrusions preferably cannot penetrate into or be removed from the recesses when both are in the same plane. Rather, they must be inserted into or removed from one another perpendicular to the plane of the connection, since the interlocking of the protrusions of one plate into the recesses of the other plate horizontally locks both plates in place. Such connections preferred according to the present invention are generally also known as puzzle, buttonhole, or dovetail joints.

[0041] Therefore, the plate or base element according to the invention is preferably provided such that, as a connecting means, serrations for a positive-locking connection with another, in particular similar, base element or plate are provided on at least one edge or outer edge of the plate. As explained above, the plates according to the invention are preferably designed such that the serrations are formed from projections and recesses, wherein the projections are intended for positive engagement in the recesses on another (opposite) plate.

[0042] The toothings provided by the panel according to the invention can be openly visible in the connecting area between the panels after they have been joined, i.e. presented openly, or can be invisible, i.e. presented concealed. A mixture of visible and concealed toothings can also be selected. For this purpose, the panel according to the invention is preferably provided such that the toothings, in particular the extensions and recesses, protrude openly from at least one outer edge of the panel and / or are concealed. If the toothings are to be concealed at least on one outer edge, the panel according to the invention is designed such that the panel surface or the cover layer, if present, lies over the toothing and covers it at least on this outer side. The same embodiment is selected on the corresponding side of another panel according to the invention.This ensures that, after the two plates are joined together, the plate surfaces abut each other, thus concealing the underlying, interconnected interlocking of both plates.

[0043] To better connect the panels and, in particular, to make a composite of several panels according to the invention as liquid-tight as possible, it is often necessary to bond the panels together with an adhesive in addition to the interlocking system. Excess adhesive often occurs between the panels in this process, and it is preferably prevented from migrating from the interface between the panels onto the surface of the panels, as this can significantly increase installation efficiency.

[0044] Particularly suitable means for this purpose have proven to be the combination of a sealing lip and one or, if necessary, several displacement channels, which, individually or preferably in combination, are suitable for either preventing excess adhesive from escaping from the joint area between the panels (sealing lip groove) and / or providing alternative locations (displacement channel) to which the adhesive can be displaced by the pressure of the adjacent panels. This prevents or at least reduces the hydropneumatic effect that frequently occurs during the installation of floor coverings, which causes the installed panels to lift at specific points, thus making the installed floor uneven and potentially leaking with respect to liquids. Preferably, therefore, the panels according to the invention include combinations of sealing lips and displacement channels on the sides with the interlocking elements.The sealing lips and displacement channels are particularly preferably designed as described and shown in the international patent application WO 2017 / 202486 A1 of the same applicant on pages 14, line 26 to page 16, line 25. Figures 1 and 3 (there and here).

[0045] The toothing and corner areas of the plates according to the invention are preferably also designed as described in WO 2017 / 202486 A1, in particular according to the arrangement of the toothing as described there on page 17, line 18 to page 19, line 9, and preferably the corner areas as described there on page 19, line 11 to page 20, line 8, page 21, line 18 to page 23, line 3 and as shown there in Fig. 7.

[0046] This document describes a plate in which at least one connecting element for connecting the plate to another, in particular similar, plate is provided on at least one outer edge, characterized in that the connecting element (i) has a sealing lip which fits into a negative shape (groove) of the connecting element which is present on at least one outer edge of the further, in particular similar, plate; and (ii) preferably a displacement channel which, in the case of the positive connection of the two plates, is suitable to receive any excess jointing material.

[0047] As mentioned above, in the plates according to the invention, the connecting means can be exposed, i.e., visible on all sides in the case of a single plate, or they can be concealed on one or more sides (or edges) of the plate according to the invention by the plate's surface. Preferably, the plates provided herein are designed such that the surface, or, if present, the cover layer of the plate, extends completely over the connecting means of the respective plate on at least one side of the plate, and if the plate is laterally connected to an adjacent plate via the connecting means, the connecting means are covered on the connected sides. Preferably, this covering is achieved by the cover layer, if one is present. If the plate is single-layered, the upper area of ​​the plate is designed such that it projects beyond the connecting means.

[0048] The panel provided by the present invention and described here is preferably characterized in that the carrier layer is applied to a cover layer present in a mold using an injection molding process. This is described in more detail below. Briefly, this preferred design is achieved in that the cover layer is first manufactured separately or, optionally, is purchased already manufactured and this cover layer is then placed in a mold in which the panel can be finished using an injection molding process by spraying a heated mixture of a thermoplastic and ground fibers, as described herein, onto the cover layer. Particular preference is given to using prefabricated layers as the cover layer, which impart the desired decoration to the ultimately produced panel. PVC panels or laminates with a decoration can preferably be used for this purpose.The decoration can also be embossed during the injection molding process. For example, the side of the mold facing the top layer (or an inserted partition) can have bulges and indentations (embossed). When the heated mixture of thermoplastic polymer and ground fibers is injected under pressure into the mold behind the top layer, these bulges and indentations heat the top layer and press it against the embossing on the mold, thereby transferring the embossing as a three-dimensional pattern onto the top layer or pressing it into it. Preferably, the mold can have a tree bark pattern embossed on it.

[0049] In the experiments that contributed to the selection of materials for manufacturing the panels according to the invention, the inventors found that when using only thermoplastic materials, the panels produced by injection molding are often curved, exhibiting a curvature of more than 0.5% and even more than 2 mm relative to the side length. Large-area composites made of such panels are uneven, which is not only aesthetically unappealing but also poses a tripping hazard and makes joining multiple panels difficult and weakens the connection. In particular, by adding fibers in the quantities described herein and by designing the panel as described herein, the dimensional stability of the panels according to the invention could be increased and the curvature reduced below the aforementioned values.Therefore, the plates produced according to the present invention and described here are characterized in that the plate(s) is / are flat and has a maximum curvature of 0.5% but not more than 2 mm with respect to its side length (according to standard EN 14411).

[0050] The underside of the plates according to the invention can be smooth, but it can also have three-dimensional structures. Preferably, the underside of the plates according to the invention is characterized by having bumps and / or channels. Due to this design, the plates according to the invention do not lie completely flat on the underlying surface, e.g., on a floor. This has the advantage that liquids that get under the plates do not accumulate underneath and thus lead to soiling or odor formation, e.g., through the growth of bacteria and / or mold, but rather that the liquids can at least partially drain away, thereby reducing or even completely avoiding the aforementioned negative effects.

[0051] The panels according to the invention can be used for numerous purposes and applications. Preferably, according to the present invention, a panel as described herein is provided, wherein the panel is a floor panel, a wall panel, or a ceiling panel.

[0052] The present invention relates to a method for producing plates comprising a carrier layer, the method comprising the following steps in the following order: b) Producing a mixture comprising or consisting of a thermoplastic polymer and pulverized fibers; c) Heating the mixture from b) while mixing until the thermoplastic polymer melts; d) Injecting the heated mixture into the mold; e) Cooling the sheet in the mold to a temperature at which the sheet is stable enough to be removed from the mold; f) Removing the sheet from the mold into a second mold having a bend in the opposite direction to the expected cupping of the sheet; g) Cooling the sheet in the mold to about 30°C; h) Transferring the sheet into a third mold, the third mold having a flat bottom, and placing the sheet onto this flat; and i) Cooling the sheet in the third mold to 15-20°C below room temperature.

[0053] Preferably, the method according to the invention relates to the production of plates comprising at least two layers, wherein the produced plates comprise a carrier layer and a cover layer. For this purpose, according to the invention, a further step (step a)) is carried out before step b), in which a cover layer is placed in the first mold before the mixture comprising or consisting of thermoplastic material with comminuted fibers is produced (in step b)), heated until the thermoplastic material melts (step c)), and injected into the mold (step d). The cover layer is preferably placed in the mold with its future top side facing the wall opposite the opening through which the heated mixture is injected into the mold as defined above, so that the heated mixture is injected onto the back side of the cover layer.

[0054] In this preferred embodiment, the inventive method for producing plates is thus provided comprising a carrier layer and a cover layer, wherein the method comprises the following steps in the following order: a) Placing the top layer in a first mold; b) Creating a mixture comprising or consisting of a thermoplastic polymer and pulverized fibers; c) Heating the mixture from b) while mixing until the thermoplastic polymer melts; d) Injecting the heated mixture into the mold onto the back of the top layer; e) Cooling the sheet in the mold to a temperature at which the sheet is stable enough to be removed from the mold; f) Removing the sheet from the mold into a second mold, which has a bend in the opposite direction to the expected cupping of the sheet; g) Cooling the sheet in the mold to about 30°C; h) Transferring the sheet to a third mold, the third mold having a flat bottom, and placing the sheet onto this flat; and i) Cooling the sheet in the third mold to 15-20°C below room temperature.

[0055] According to the present invention, in step d) of the method provided herein, the heated mixture is preferably injected into the injection mold under a pressure of about 4000-10,000 bar, more preferably under a pressure of about 4000-7000 bar, and particularly preferably under a pressure of about 5000-6000 bar.

[0056] Preferably, in one, several, or all steps e) to i) of the process according to the invention, pressure is also exerted on the plate being manufactured in the respective shape. Preferably, this pressure in these steps of the process according to the invention is approximately 5-500 bar.

[0057] The thermoplastic polymer, fibers and optionally other materials to be used in the process according to the invention are selected and used in the same proportions as already described above for the plates according to the invention.

[0058] Thus, the proportion of ground fibers in the mixture in step b) of the process according to the invention is preferably between 1% and 35%, more preferably 10% to 35%, 10% to 30%, 10% to 25%, 15% to 25%, or 15% to 20%. If glass fibers are used, their proportion in the mixture in step b) of the process according to the present invention is preferably 1% to 35%, 10% to 35%, 10% to 30%, 10% to 25%, more preferably 15% to 25%, and particularly preferably 15% to 20% glass fibers, since these ranges have been found to be optimal for imparting the desired stabilizing effects to the plates without this effect becoming weaker (below about 10% to 15%) or the plates beginning to become brittle (above 35%). The remainder of the mixture is formed by the thermoplastic polymer, preferably selected from polyolefins and PVC, wherein PE or PP is preferably used among the polyolefins and optionallyfrom other materials, as also described in detail above with regard to possible other materials and their proportions in relation to the plates according to the invention and also below for the method.

[0059] According to the present invention, in step b) the production of the mixture, both the thermoplastic polymer and the fibers are present in small particles, the fibers preferably ground, wherein the comminuted or ground fibers have a length of 0.1-6 mm, more preferably 1-6 mm, 1.5-5.5 mm, 2-5 mm, 2-4.5 mm, 2-4 mm, 2-3.5 mm, and particularly preferably 2-3 mm, and the thermoplastic polymer is preferably present as granules. According to the process according to the invention, the fibers are selected from the same materials as already described above for the sheets according to the invention, i.e., the fibers are preferably selected from the group consisting of: glass fibers, natural fibers, and polyester fibers. The term natural fibers as used herein refers to plant fibers, animal fibers, and mineral natural fibers.According to the present invention, plant fibers are preferably selected from the group consisting of cotton, bamboo fibers, hemp fibers, jute fibers, kenaf fibers, linen fibers, nettle fibers, and coconut fibers. Animal fibers or fibers of animal origin are preferably selected from wool, cattle hair, horsehair, goat hair, pig bristles, and silk. Natural mineral fibers are preferably selected from the group consisting of attapulgite (or palygorskite), sepiolite, and wollastonite. Ground glass fibers are particularly preferred in the process according to the invention.

[0060] As already mentioned, according to the present invention, in addition to the thermoplastic polymer and fibers, other materials may also be present in the mixture in step b). These other materials are preferably selected from the group consisting of wood, preferably wood flour, lime flour, stone flour, and additives. Instead of wood flour, other plant fibers may also be used. Preferably, these alternative plant fibers are selected from the group consisting of kenaf, jute, or flax. Preferably, the use of these additional materials does not change the aforementioned proportion of fibers in the mixture, but rather the proportion of the thermoplastic polymer is reduced accordingly.If one or more of the additional materials selected from the group consisting of wood, preferably wood flour, lime flour and stone flour, are used, then according to the invention their proportion, based on the proportion of the thermoplastic polymer in the mixture produced in step b) of the process according to the invention, is between about 10 and about 90%, preferably between about 20-90%, 20-80%, 20-70%, 20-60%, 20-50%, 30-50%, 35-50%, 40-50%, 50-60% or about 50%.

[0061] In this context, additives are understood to be substances that, for example, protect the plastics used from thermo-oxidative decomposition, acid scavengers (such as hydrotalcite or DHT-4A), antioxidants, colorants / pigments, flame retardants, or biocides. The total proportion of additives in the mixture from step b) of the process according to the invention is preferably about 0.1–5%, more preferably about 0.1–2%, and particularly preferably about 0.5–1.0%.

[0062] Preferably, wood flour, lime flour, stone flour and / or additives are added to the mixture in step b) as additional materials according to the process according to the invention.

[0063] In step d) of the process according to the invention, the heated and thus liquid mixture is injected under pressure into the mold or injection mold onto the back of the cover layer. The pressure is preferably between 4,000 and 10,000 bar.

[0064] To counteract cupping and avoid it as far as possible, the inventive method includes, among other things, step f), in which the plate is removed from the mold in which it was produced and placed in a second mold that has a bend in the opposite direction to the expected cupping of the plate. The plate's own weight alone reduces cupping simply by resting on this bend. Preferably, to further reduce cupping, additional pressure is applied to the plate in this step, causing it to flatten again via the counter-bend. This step, in combination with the subsequent steps g), h), and i) of the inventive method, ultimately results in the plates produced by the method being largely flat, i.e.,have a curvature of no more than 0.5% but not more than 2 mm based on their side length, while panels in which one or more of these steps are omitted have a higher curvature after production.

[0065] According to the process according to the invention, the thermoplastic material is preferably selected from polyolefins and polyvinyl chloride. The cover layer consists of one of: polyvinyl chloride (PVC).

[0066] In step b) of the process according to the invention, if, in addition to the plastic and the fibers, or preferably the ground glass fibers, further materials are added to the mixture, these further materials are preferably selected from the group consisting of wood flour, lime flour, stone flour and / or additives. Preferably, the process according to the invention is provided wherein the mixture in step b) additionally comprises wood flour, lime flour, stone flour and / or additives.

[0067] The temperatures used in the inventive process for melting the mixture comprising the thermoplastic polymer and also later for cooling the plates produced by the process depend essentially on the polymer used. Preferably, the inventive process is carried out as described herein such that the mixture: in step d) when injected into the mold, it has a temperature of approximately 150°C-210°C, preferably 160°C-180°C or 170°C-180°C; in step e) it is cooled to approximately 80-110°C in the first mold; and in step f) it is placed into the second mold at approximately 80-110°C.

[0068] According to the method according to the invention, the cover layer can already have a decoration, e.g. a print, which gives the panels produced according to the method according to the invention a desired appearance (e.g. an appearance similar to a wood or stone surface). Alternatively or additionally, the method according to the invention is carried out in such a way that the first mold has a side with a three-dimensional structure, adjacent to which either the cover layer is placed into the mold with its upper side and on which the cover layer rests with its upper side when the mixture is injected in step d) or onto which side the mixture is injected directly in step d), characterized in that the cover layer or, if no cover layer was provided, the carrier layer has the imprint of the three-dimensional structure on its upper side after completion of the method.

[0069] If a top layer is placed in the mold in the process according to the invention, the increased temperature of the plastic-fiber mixture injected into the mold softens the top layer in the mold, and the applied pressure creates an imprint of the three-dimensional structure in the top of the top layer of the plate produced by the process. If no top layer is placed, the mold, as designed, creates the aforementioned imprint of the three-dimensional structure in the top of the carrier layer. According to the present invention, the three-dimensional pattern preferably consists of depressions and protrusions in the surface of the mold and their corresponding protrusions and depressions in the surface of the plate produced by the process. Examples of the pattern include bumps and a bark-like grain.The height of the raised areas and depressions can vary according to the present invention, preferably being 10, 9, 8, 7, 6, 5, 4, and 3 mm, and particularly preferably 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1 mm. Preferably, the height of the raised areas and depressions is from 0.1 mm to 2 mm, more preferably 0.4 to 0.7 mm, and particularly preferably 0.5 to 0.6 mm. In addition to its decorative effect, the three-dimensional pattern embossed according to the invention gives the panels produced by the present method increased slip resistance and reduced sensitivity to scratches, damage, and soiling on the surface, since these are less noticeable than on panels with a smooth surface and no three-dimensional pattern.

[0070] As already mentioned above, the inventive method has been designed to reduce or prevent bending (bowling) of the panels produced in this way, both through the materials used and through the process steps. Accordingly, the inventive method as disclosed here is characterized in that the panels produced by the method have a maximum curvature of 0.5%, but not more than 2 mm, based on the side length.

[0071] Furthermore, according to the method according to the invention, the first mold is preferably designed such that connecting means are created on each side of the carrier layer in the produced panels in order to be able to connect the panels to at least one adjacent panel, wherein the connecting means on each side of the carrier layer are opposite projections and recesses, wherein the projections are intended for positive engagement in the recesses.

[0072] In this context, the mold used in the method according to the invention is further designed such that, if a cover layer is provided, it either does not extend over the connecting means, so that these are each freely located on the sides of the panel and the connections are visible even after the panels have been laid to form a composite (and connected by means of the connecting means), or that the cover layer extends completely over the connecting means of the respective panel at least on one side of the panel and that, if the panel is laterally connected to adjacent panels via the connecting means, the connecting means on the connected sides are covered by the cover layer and are therefore no longer visible.

[0073] If no top layer is provided, the mold is designed according to the present invention such that the resulting top surface of the support layer extends only to the bases of the projections / teeth, so that these project visibly from above on each side of the plate, or the top surface of the support layer is designed such that it extends completely over the connecting means of the respective plate on at least one side of the plate, and that if the plate is laterally connected to adjacent plates via the connecting means, the connecting means on the connected sides are covered by the top surface of the support layer. An example of such a concealed design in the Fig. 1AThe figure shows an exemplary plate according to the present invention (or produced according to the inventive method) viewed from below. On the right and upper edges of the plate, the connecting elements project freely from the plate; on the left and lower edges, they are concealed by the top surface of the carrier layer or the cover layer, respectively. As can be seen in Fig. 5 In this preferred embodiment, the connecting means of the plates according to the invention are, when present in a composite, no longer visible from above in the areas of connection with other plates, but are concealed from the top of the carrier layer or from the cover layer.

[0074] Preferably, the mold used in the inventive method is characterized in that the wall of the mold, which is opposite the wall on the future top side of the plate, i.e., the mold wall on the future bottom side of the mold, is designed in such a way that it has a pattern of depressions and elevations which are designed in such a way that the underside of the plates produced by the method has the imprint of this pattern.Preferably, this pattern is selected from the group consisting of circular, regularly distributed depressions which create a nubbed pattern on the underside of the manufactured panels, or from linear, interlinked elevations which create a channel-like pattern on the underside of the manufactured panels, so that the panels lie more securely on their future substrate, for example a floor, and that liquids which, after the laying of the panels manufactured according to the invention as a continuous composite on a substrate, get under the composite or the panels can drain away more easily or do not accumulate under the panels.

[0075] A more complete understanding of the invention can be obtained from the following specific examples and figures, which are provided herein for illustrative purposes only and are not intended to limit the invention in any way. Examples Example 1

[0076] To produce the panels, a 2 mm thick PVC top layer, printed with a wood grain pattern, was placed in an injection mold. The top layer itself was multi-layered, comprising a base layer, a decorative layer with the print, and a transparent protective layer. The top layer, with the transparent protective layer attached, was positioned against the wall opposite the injection opening of the mold.

[0077] A mixture of 20 kg of ground, 2-3 mm long glass fibers and 80 kg of PVC granulate was fed into the flights of the rotating screw via a funnel, heated to 170°C there and injected as a melt through the nozzle into the mold onto the back of the cover layer under a pressure of 5000 bar.

[0078] The following PVC granules were used: S-PVC K-value 70 with 100 phr ("parts per hundred rubber," i.e., based on 100 (mass) parts of the base polymer), Paraloid K 125 with 1 phr as an acrylic processing aid (additive), DOTP with 40 phr (non-phthalate-based plasticizer), CaZn powder with 2 phr (Baerostab GS 8807-27), Baerolub FTA 0.15 phr (as an external lubricant), CaCOs with 60 phr.

[0079] The mold was cooled to 100°C, the mold (injection molding chamber) was opened, the resulting sheet was removed from the mold and placed into a second mold, which had an upwardly or downwardly curved base and a correspondingly shaped lid. The respective sheet was left in this mold, and a pressure of 300 bar was applied to the sheet to enhance the curved base effect and counteract warping until the sheet reached a temperature of approximately 30°C. To do this, the sheet was placed in the mold with the curvature opposite to the curvature of the base (and the same curvature of the mold lid), and then pressure was applied to the sheet during cooling.

[0080] The respective plate was then transferred into another mold, this time with a flat bottom, and there also cooled down to about 10°C under a pressure of 300 bar.

[0081] The process was carried out in injection molds of different sizes using the same material. In one case, square plates measuring 60 cm x 60 cm with a total thickness of 7.16 mm were obtained, and in the other case, rectangular plates measuring 33 cm x 63 cm with a total thickness of 8.1 mm. The manufactured plates were then examined for potential damage and bending. The plates mostly exhibited a curvature of 0.5% or less. Example 2

[0082] Six panels with a thickness of 7.16 mm and six panels with a thickness of 8.1 mm, as shown in Example 1, were subjected to a fire test for classification according to EN 13501-1:2010. The panels were multicolored; six had no pattern, and six had a colored, wood-like pattern. During the test, they were placed on a fiber cement board.

[0083] The ignitability under direct flame exposure was tested according to EN ISO 11925-2:2010 and the fire behavior under radiant heat was tested according to EN ISO 9239-1:2010.

[0084] None of the tested plates ignited. The fire behavior showed no melting / scorching during pre-irradiation, no warping / contraction in the ignition area, no burning through to the substrate, no flickering, no blistering, and no smoldering after the pilot light was extinguished.

[0085] All tiles were classified as B fl with regard to fire behavior and as s1 with regard to smoke development. Dripping was not classified, as it is negligible for floor coverings; however, no dripping was observed in the tests. Example 3

[0086] Plates produced in example 1 were subjected to strength tests according to EN ISO 23999 [EN 434].

[0087] The panels showed an expansion of only 0.12-0.16% when heated to 95-100°C. The shrinkage (dimensional change) of the panels at 25-35°C was only 0.01-0.02%. Finally, the point load that the panels produced using the inventive process could support was 65-70 kg / cm² at room temperature (22-25°C).

[0088] In contrast, boards without fiber admixture showed an expansion of 1.2-1.6% when heated to 95-100°C, a shrinkage of 1.2-1.6% at 25-35°C and a point load of 30-35 kg / cm2 at room temperature (22-25°C). List of reference symbols

[0089] Shown are only the simple reference symbols, without enumerations, which are used to describe several entities of the same genus, for example (10) for one plate and (10') for another plate that is connected to the first, for example. 10 Plate 12 Outer edge 14 Fastener 16 Sealing lip 17 Groove 18 Displacement channel 19 Displacement channel below and preferably adjoining the groove (17) 20 Extension of the toothing 22 Recess of the toothing 24 Plate surface / top of the plate or the cover layer 26 Plate bottom / bottom of the support layer 28 Inclination angle of the sealing lip (16) 30 Distance of the tip of the sealing lip (16) from the upper outer edge of the base element (10) 32 Thickness of the cover layer (110) or, in the case of single-layer plates, distance from the plate surface to the beginning of the upper edge of the sealing lip (16) 36 Penetration offset of the lower edge of the sealing lip into the outer edge of the plate 38 Depth of the displacement channel (18) 40 Width of the displacement channel (18) 42 Distance from the tip of the sealing lip (16) to the top edge of the interlocking area 44 Height of the base element 110 Top layer 120 Base layer

Claims

1. A method of manufacturing plates comprising a carrier layer and optionally a top layer comprising the following steps in the following order: a) optional pre-laying of the top layer in a first mold; b) production of a mixture comprising a thermoplastic plastic and chopped fibers; c) heating the mixture from b) while mixing until the thermoplastic plastic melts; d) injecting the heated mixture into the first mold (on the back of the top layer); e) cooling the plate in the first mold to a temperature at which the plate is stable enough to be removed from the first mold; f) removing the plate from the first mold and placing it in a second mold, which has a bend in the opposite direction to the expected cupping of the plate; g) cooling the plate in the second mold to about 30°C; h) transferring the plate to a third mold, the third mold having a plane as a bottom, and placing the plate on this plane; and i) cooling the plate in the third mold to 15-20°C below room temperature.

2. Method according to claim 1, wherein the thermoplastic plastic is selected from a polyolefin and polyvinyl chloride, wherein the chopped fibers are grinded glass fibers, wherein the top layer, if present, is polyvinyl chloride (PVC).

3. Method according to claim 1 or 2, wherein the mixture in step b) additionally comprises wood fibers, lime powder, stone powder and / or additives.

4. Method according to any one of claims 1 to 3, wherein the mixture: - in step d) has a temperature of about 150°C-210°C when injected into the mold; - in step e) is cooled down to about 80-1 10°C in the first mold; and - in step f) is placed in the second mold at about 80-110°C.

5. Method according to any one of claims 1 to 4, wherein the first mold has a side with a three-dimensional structure, characterized in that the produced plate has on its upper side, or if the top layer has been pre-laid into the mold, on the upper side of the top layer, the imprint of the three-dimensional structure after completion of the method.

6. Method according to any one of claims 1 to 5, wherein the plates produced are characterized in that they have a maximum curvature of 0.5% but not more than 2 mm relative to the side length.

7. Method according to one of claims 1 to 6, wherein the first mold is designed in such a way that connecting means are formed on each side of the carrier layer in the manufactured plates in order to be able to connect the plates to at least one adjacent plate, wherein the connecting means on each side of the carrier layer are projections and recesses located opposite each other, wherein the projections are intended for interlocking engagement in the recesses.

8. Method according to claim 7, wherein the top layer is pre-laid in such a way that it extends completely over the connecting means of the respective plate on at least one side of the plate and that when the plate is laterally connected to another plate via the connecting means, the connecting means on the connected sides are covered by the top layer.