SHEET MATERIAL

Abstract: The invention relates to a sheet material comprising a substrate coated with at least one layer of a preferably thermoplastic plastic, said substrate and/or the substrate side of said layer being provided with fibers that are anchored to the plastic layer and/or the substrate and partly project therefrom, and said plastic layer being bonded to the substrate by means of a bonding agent.

Description: Title: Sheet material The present invention relates to a sheet material based on a substrate coated with at least one layer of a thermoplastic plastic. Such material can be flat, but can also have a round or other bent form. Generally, the manufacture of sheet materials based on more than one layer involves the problem that a proper bond should be provided between the various layers. This problem for instance occurs when sandwich sheets are manufactured, but also when protective and/or decorative surfaces are provided on composite or non-composite sheet materials. Particularly in the case of sheet materials having a non-flat form, this may be a greater problem. US Patent 5,037,690 describes a sandwich material built up of a core layer having its two surfaces provided with a layer of fiber material impregnated with a polyurethane resin. Especially in the case where the core material has a honeycomb structure, a proper bond can thus be obtained between the fiber layer and the honeycomb structure, because the honeycomb material i_ --.lightly pressed into the fiber layer where the polyurethane resin provides a bond between fiber and core. The polyurethane resin also has the function of binding agent for the surface layer. Although a simple structure for a sandwich material is provided in this manner, there is nevertheless a need for a more universal method for obtaining a bond of inter alia surface layers to substrates . This need exists both for providing decorative layers and/or protective layers on substantially single materials, and for sandwich structures. In respect of single materials, one may for instance think of providing protective and/or decorative layers on sheets used for drainboards, tabletops and the like. For finishing such materials, a layer of plastic is often provided on the surface. For this purpose, acrylate polymers or olefin polymers are preferably used, because they are chemically particularly inert and typically have a mechanically strong surface (scratch-resistant) . On the other hand, this inertness has the problem that the bond of the plastic to the base material, the substrate, is difficult. Many types of glue have already been tested, but hitherto no satisfactory solution has been found for obtaining a proper bond. Another group of materials for which a proper bond is of great importance is formed by the sandwich materials . These materials consist of a typically light-weight core material, for instance a honeycomb material, comprising two top layers. In many cases, it is desired to build up the top layers of a number of layers, which often involves the problem of bonding. If it is desired that one or more materials be processed that are difficult to bond, the consequence could be that the strength of the entire sheet is too slight. This may for instance occur if it is desired to incorporate a polyolefin or poly ethacrylate into the sheet. The invention provides a solution to the problem of obtaining a sufficient bond between various materials. Hence, the invention relates to a sheet material comprising a substrate coated with at least one layer of a prefi --- ij thermoplastic plastic, which substrate and/or substrate side of this layer is provided with fibers that are anchored to the plastic layer and/or the substrate and partly project therefrom, while this plastic layer is bonded to the substrate by means of a bonding agent. In practice, this means that the layer of plastic material to be applied is treated so that a fiber layer is anchored to its surface. This may for instance be effected by means of a (direct or indirect) heating of the surface layer, whereupon a fiber layer is partly pressed into the surface. Examples of heating methods are heat radiation, open-flame heating, induction heating, electromagnetic radiation and radiation utilizing a hot plate or a hot liquid. It is also possible to soften the surface with a suitable solvent or to use a combination of the two methods. The thus produced thermoplastic plastic whose surface has been provided with fibers is subsequently provided on the surface of the substrate by means of a bonding agent. Yet another possibility is formed by bonding a fiber layer to a base by means of an adhesive, such as an acrylate adhesive or a thermosetting plastic, such as an epoxy or unsaturated polyester resin. In accordance with the invention, a single or a composite material is generally employed as substrate. This material can be selected from the group consisting of sheet material of thermoplastic plastic, wood, plywood, chipboard, sheet material from fillers (popcorn, polystyrene granules, microspheres, glass globules or glass fibers, earth, clay, foamed rock, and the like) , bound with organic and/or inorganic binders (thermosetting plastics, biological binders, cement, water glass, gypsum and the like), multilayer systems on the basis of core material and/or film material and optionally filled honeycomb material. If a honeycomb material is employed, this material will have two top layers on which the plastic provided with f be s is provided. It is also possible to use various combinations of this type of materials. An interesting variant is fαrs-ed by ^ater-resistant gypsum board, with which, according to the invention, an excellent non-inflammable sheet material can be produced, without it having the somewhat unattractive appearance of conventional gypsum boards . The above-mentioned products are divisible into two groups, i.e. the single materials, suitable for the manufacture of worktops and other sheet-shaped objects, and the composite materials or sandwich materials, consisting of a light core and two surface layers. However, both groups of materials concern relatively high-grade materials, as opposed to the materials described in European patent application 179.451. This application particularly relates to bituminous roofing materials that are constructed by means of a fiber layer as bonding layer. Providing the coating of a thermoplastic plastic on the substrate can be effected in a number of manners . It can for instance be effected by means of hot melts or a thermosetting plastic (resin with hardener) . Examples of thermosetting plastics are epoxy resins, polyurethane resins and unsaturated polyester resins. However, if a plastic material is used as substrate, it is also possible to anchor the fibers to the substrate in the same manner as to the coating, for instance by providing the fibers of the coating in a softened surface of the substrate. This softening can be realized by heating the surface of the substrate, or by softening by means of a solvent. Of course, in the case where an adhesive is used that is dissolved in a solvent for the plastic, a combination of the two effects occurs . It is also possible to apply the coating directly after the production of the substrate, when it is still in a soft condition. Obviously, in such systems the method can also be reversed, i.e. the fiber layer is provided in the surface of the substrate, after which the coating is bonded to the surface of the fibers by the use of techniques suitable for that purpose, such as the use of adhesive, or by means of softening. Accordiii tc th invention, various materials can be used as fibers, which may each in itself be incorporated in various structures into the thermoplastic plastic. As materials for the fibers, synthetic and/or natural fibers and/or metal fibers can be used. Preferably, fibers are used selected from the group consisting of hemp, flax, elephant grass, jute, bagasse, glass fibers, carbon fibers and synthetic fibers such as polyester fibers, acrylic fibers, polyethylene fibers, polypropylene fibers and polyamide fibers. These fibers can be provided in the thermoplastic plastic material as separate fibers, or as non-woven, knit fabric, felt, a woven material or a scrim. When metal fibers are used, it is also possible to use a net of metal. As mentioned before, the sheet materials according to the invention may consist of single materials provided with a coating or of composite materials. With respect to the synthesis and structure of these material there are hardly any limitations. The form can be adjusted to the eventual application, which means that it can be flat, but it is also possible to create round or other forms. An important use of the invention lies in the manufacture of worktops, such as drainboard tops or tabletops, which worktops should have a plastic finishing layer. It is not easy to apply such a layer, because the materials that can most suitably be used as finishing layer, such as acrylate polymers and more particularly polymethylmethacrylate, exhibit a poor bond to the conventional substrate materials. However, the invention provides a simple system for these worktops which also permits realization of a good bond of acrylates to the conventional base materials, such as wood, plywood, chipboard, MDF and the like. It is observed that two problems play a part in the production of such worktops. In the first place, the top layer should be properly bonded to the substrate. Sometimes, this can conveniently be realized during the manufacture of the top. A second aspect forms the finishing strip that is to be provided on the lateral side of the material afterwards. This strip should bond properly and uiu-cct to the material so as to be water-resistant. Particularly in respect of the use of PMMA in this application, no good solution has hitherto been found. According to the invention, it is now possible to properly apply PMMA utilizing an anchored fiber layer with a thermosetting plastic or a hot melt adhesive. Another important field of application of the invention lies in the composite materials or sandwich constructions. Due to the nature of the invention, it is now possible to provide various types of sandwich materials having various suitable properties. As material for the core of the sandwich material, various types of honeycomb materials can be used, for instance produced from paper, metal, or plastic. It is also possible to use plastic foams such as polyurethane foam, polyether foam, polyolefin foam or styrene polymer foam. Optionally, the core can also be built up of a number of layers of a different nature. Because it is now possible to provide relatively inert materials as coating on other materials, light-weight construction materials can be provided according to the invention in a relatively cheap manner and for various applications. Examples thereof are, inter alia, sheet materials for grease traps, sewer components and (insulating) sandwich boards, for instance for wall or roof panels, by incorporating blister padding that can optionally be provided with an aluminum layer, in combination with honeycomb materials in the core, on which a finishing layer has been provided. On the outer side, such wall and roof panels can be provided with a brickwork structure or a rooftile structure. It is also possible to provide heating elements in the material, for instance in the form of heating strips of conductive plastic (having a fiber layer), or to use decorative materials in or under the top layer. Within the scope cf the invention, it is also possible to use structures based on paper impregnated with plastic or provided with a layer of plastic, with anchoring to the synthetic fibers. Other applications of the sandwich panels according to the invention are silos for solids or liquids, housings for air-ventilation/airconditioning systems, gas washers and cooling towers and the like. Generally, it applies that these materials can be used where a supporting power should be combined with a low weight and possibly a chemical resistance. In this connection, it is observed that when such composite materials are produced, it is also possible to employ plastic layers having fibers on both sides, enabling as it were "building on" . Both the worktops and the sandwich materials according to the invention can be provided with a decorative layer. A possible embodiment of such decorative layers is formed by synthetic resin bound solids with a decorative effect. Examples thereof are natural stone, waste materials with glittering effect (anthracite grit and the like), natural substances such as maize, peas, rice and other seeds. If so desired, such a decorative layer, based on a transparent synthetic resin, may comprise glass particles, preferably provided in the top layer of the resin, resulting in a strong, scratch-resistant and decorative top. Preferably, the resin and the glass particles are chosen so that the refractive indices are identical, which is advantageous from a decorative point of view. It is observed that such a decorative layer can also be applied without the used of the bonding layer on the basis of fibers. A suitable material that according to the invention can be used as core material for a sandwich sheet comprises an optionally filled honeycomb material and two upper layers built up of a layer of a plastic, bonded to a fibrous web containing expanded microglobules, the upper layers being bonded to the honeycomb material via the fibrous web utilizing a thermosetting plastic. On such core material, a finishing layer may be provided again, with this core material functioning as substrate for the finishing layer. Other embodiments and applications of the invention are described with reference te the Figures and further elaborated in the Examples. In this respect, it is observed that the invention is not limited to what is shown in these Figures and Examples . Fig. 1 shows a conventional sandwich panel built up of a core material (honeycomb) combined with two layers of thermosetting material. Fig. 2 shows a thermoplastic sheet to which a fiber mat is anchored. Fig. 3 shows a comparable sheet to which a glass fabric is anchored. Fig. 4 shows a sheet as in Fig. 2, having a fiber mat on both sides. Fig. 5 shows a sandwich material based on a conventional sandwich material, having two sheets according to Fig. 2 provided thereon by means of a thermosetting resin. Fig. 6 shows a -multi-layer construction built up of a sheet according to Fig. 4 and two sheets according to Fig. 2, bonded together with layers of thermosetting resin. Fig. 7 shows an insulating sandwich construction built up of a honeycomb core material and two layers of plastic blister padding, provided with the blisters facing the honeycomb and having a layer of aluminum on the outer side. Provided on the layer of aluminum by means of the invention is a coating of a thermoplastic plastic, such as polyolefin or polyester. Fig. 8 shows the principle of providing a finishing strip on the lateral side of a worktop.

Claims: 1. A sheet material comprising a substrate coated with at least one layer of a preferably thermoplastic plastic, said substrate and/or the substrate side of said layer being provided with fibers that are anchored to the plastic layer and/or the substrate and partly project therefrom, and said plastic layer being bonded to the substrate by means of a bonding agent. 2. A sheet material according to claim 1, wherein the substrate used is a single material or a composite material (core material). 3. A sheet material according to claim 1 or 2, wherein the substrate is selected from the group consisting of sheet material of thermoplastic plastic, wood, plywood, chipboard, MDF, sheet material from fillers bound with organic and/or inorganic binders, multilayer systems on the basis of core material and/or film material and optionally filled honeycomb material having two top layers . 4. A sheet material according to ciairαs ±- r> , comprising two layers of a thermoplastic plastic which may or may not be produced from the same material, said layers comprising fibers that are anchored to the plastic layer and partly project therefrom and bonded to a core material by means of a bonding agent. 5. A sheet material according to claims 1-4, wherein the bonding agent used is a thermosetting plastic or a hot melt. 6. A sheet material according to claims 1-5, wherein said fibers are used in the form of a non-woven, a knit fabric, a woven material or a scrim. 7. A sheet material according to any one of claims 1-6 in the form of a sandwich material, consisting of at least one core material and at least two top layers bonded to the core material and said fibers being anchored to the core material and/or the top layers . 8. A sheet material according to claims 1-7, wherein said fibers are selected from the group consisting of natural or synthetic fibers such as hemp, flax, jute, elephant grass, glass fibers, carbon fibers and synthetic fibers such as polyester fibers, acrylic fibers, polyethylene fibers, polypropylene fibers and polyamide fibers. 9. A method for producing a sandwich material comprising a core layer and one or more top layers of thermoplastic plastic, said top layer and/or core layer being provided, at one surface thereof, with a fiber layer that is partly anchored to the layer and partly projects therefrom, said layers being bonded together by means of a bonding agent. 10. A method according to claim 9, characterized in that said fiber layer is impregnated with a thermosetting plastic and optionally a hardener therefor, whereupon said layer provided with the impregnated fiber layer and the other layer are joined together and the thermosetting plastic is cured. 11. A sheet material suitable for use as core material in the production of the sandwich material according to claim 9 or 10, comprising i.τ. eptieeeily filled honeycomb material and two upper layers that are built up of a layer of a plastic bonded to a fibrous web containing expanded microglobules, the upper layers being bonded to the honeycomb material via the fibrous web utilizing a thermosetting plastic. 12. A worktop comprising a sheet-like base material, provided with a finish on the basis of an acrylic plastic, preferably poly ethylmethacrylate, the finish being applied by providing the plastic with fibers anchored to the surface of the plastic that is to be bonded to the base material, while a part of said fibers project from the surface and said plastic being bonded to the base material by means of a bonding agent.

Inventors: VAN DER WIJNGAART ADRIAAN HUBE, VAN DER WIJNGAART, ADRIAAN, HUBERTUS, JOHANNES
Applicants: WIJNGAART ADRIAAN HUBERTUS JOH, VAN DER WIJNGAART, ADRIAAN, HUBERTUS, JOHANNES
Application year: 1995
Main classification: C08J5
IPC codes: B29C37, B32B7, C08J5