CN118541251A - Method for producing fiber board - Google Patents

Abstract

The present invention relates to a method for producing a water-repellent fiberboard comprising lignocellulose fibers and a binder. In order to provide a cost-effective waterproof fiberboard, the following steps are provided, -providing lignocellulose fibers, -providing a binder, -providing an elastic additive, -applying the binder and the elastic additive, -forming a fiber cake from the fibers provided with the binder and the elastic agent, -pressing the fiber cake in a press while curing the binder to produce the fiberboard, wherein 15 to 35 wt.% of melamine resin, phenolic resin, mixtures and mixed condensates thereof and/or guanamine resin, and 5 to 20 wt.% of urea resin, and 0.1 to 7 wt.% of elastic additive are used as binders, respectively, based on the total weight of the (absolute dry) fiberboard. The invention also relates to a fiberboard.

Description

Method for producing fiberboard

Technical Field

The invention relates to a method for producing a fiberboard. The invention also relates to a fiberboard.

Background Art

Fiberboards, in particular waterproof fiberboards, are known, for example, from WO 2020/211988 A1. However, due to the high binder content, these fiberboards have proven to be very expensive.

Summary of the invention

The object of the present invention is to provide a waterproof fiberboard which is more cost-effective to produce.

This object is achieved by a method according to claim 1 and a fiberboard according to claim 10 .

The method for producing a waterproof fiberboard comprising fibers and a binder according to the present invention is carried out in the following steps:

- Provides fiber,

- provide adhesive,

- Provide elastic additives,

- application of adhesive and elastic additives,

- forming a fiber cake from the fibers provided with a binder and an elastomer,

- Pressing the fiber cake in a press while curing the binder to produce a fiberboard, wherein

As binders, 15 to 35 wt. % of melamine resin, phenolic resin, mixtures and mixed condensates thereof and/or guanamine resin, and 5 to 20 wt. % of urea resin, and 0.1 to 7 wt. % of elastic additives are used, each based on the total weight of the (absolutely dry) fiberboard.

Urea resins are cheaper than melamine resins. It has surprisingly been found that binders for waterproof fiberboards can be supplemented with urea resins. Urea resins are hydrolyzable, in particular by hot water, and therefore appear to be unsuitable for the production of waterproof fiberboards. In this respect, the suitability of urea resins for the production of waterproof fiberboards was unexpected to a person skilled in the art. The use of urea resins makes fiberboards cheaper.

In order to produce the waterproof fiberboard according to the present invention, first provide fibers. Organic or inorganic fibers can be used. Natural fibers, such as lignocellulosic fibers, cotton or linen fibers or synthetic fibers, such as fibers made of thermoplastic materials such as polyethylene or polypropylene, and polycarbonate, polyacrylate, polymethacrylate or polyurethane can be used to produce the fiberboard according to the present invention. Inorganic fibers such as carbon fibers or fibers made of mineral or ceramic raw materials or glass fibers are particularly suitable for producing waterproof fiberboards when mixed with other fibers. In particular, a mixture of fibers, in particular a mixture of the aforementioned fibers, can be used to produce the material according to the present invention. The mixture of fibers can adjust the properties of the material according to the present invention, such as elasticity or bending properties, shape stability, strength, and also manufacturing properties or processing properties. If the fiber is made of renewable raw materials, in particular lignocellulosic fibers, for example, fibers from wood, bamboo or annual plants are used, cheap and easy-to-process fibers can be obtained. Natural fibers are preferably used untreated, that is, the fiber components are cellulose and lignin and possible hemicellulose, and their properties are not changed by chemical processes. The use of hygroscopic fibers is not excluded, especially if these hygroscopic fibers are at least partially dried before producing or pressing the material according to the present invention.

The above-mentioned lignocellulosic fibers particularly include all fibers obtained from plants by chemical or physical methods. Typical examples of physically obtained fibers are softwood fibers, hardwood fibers or bamboo fibers, or fibers from other organic raw materials obtained by mechanical fiber separation. Examples of chemically obtained fibers are pulp fibers from wood, annual plants or other raw materials, especially renewable raw materials. Wood fibers produced by mechanical fiber separation are particularly commonly used, with the aim of minimizing the loss of lignin and hemicellulose. A mixture of fibers can also be used, particularly in order to adjust the properties (strength properties, weight) of the material, and raw material fibers can also be used in a cost-optimized manner. Fibers in the sense of the present invention are also fiber bundles; smaller fragments are also included, as long as their fibers can still be coated with adhesive to a large extent. According to the present invention, it is preferred that the fiber content of the fiberboard exceeds 50% by weight of the total weight of the fiberboard. It is further preferred that the proportion of lignocellulosic fibers is greater than 50% by weight of the total fiber content.

As far as the information given for the use of the substances related to the present invention is concerned, it is usually an adhesive, elastic agent or hydrophobic agent, curing agent, colorant or other additive, especially information in weight %, which refers to 100% solids of the corresponding substance. The actual dosage of the substance can be a solution, a mixture or other forms with a solid content of less than 100% by weight. In this case, it is advantageous to also indicate or to indicate the solid content of the solution or mixture provided. Examples of common solid contents are given below, but these examples are not considered binding: for adhesives and for elastic agents or for emulsions, the solid content can be assumed to be, for example, 50% to 60% by weight, for curing agents, a solid content of, for example, 15% by weight is common, and colorants can have, for example, a solid content of 24% by weight. In particular, for fibers or fiber-containing products such as fiberboards, the term "absolutely dry (atro)" is used in conjunction with the present invention, which refers to absolutely dry fibers or fiber-containing products. If the fibers or fiber-containing products or water-containing products are dried to constant weight at 105°C, they are called "absolutely dry".

An adhesive is provided for the production of waterproof fiberboard. Melamine resins, phenolic resins, mixtures and mixed condensates thereof are used, or guanamine resins are used on the one hand and urea resins are used on the other hand. The adhesive used according to the invention preferably comprises a melamine resin. The melamine resin, typically a melamine-formaldehyde resin, is used in the form of an aqueous solution, wherein the solid content of the melamine resin is preferably at least 45% by weight based on the aqueous solution, and the solid content is advantageously more than 50% by weight. The upper limit of the solid content is determined by the solubility of the melamine resin and the processing properties under necessary circumstances, for example in a nozzle. Alternatively, the melamine resin can also be used in solid form, in particular in powder or granular form. Melamine resin is preferably used as an adhesive because it does not swell, does not absorb moisture and is resistant to hydrolysis. Phenolic resins can be used as a substitute for melamine resins or a mixture with melamine resins. Although phenolic resins are waterproof, they are darker in color and have a slight hygroscopicity due to their alkali content, which may be disadvantageous when used for waterproof fiberboards. Suitable resins are, for example, guanamine resins, melamine-formaldehyde resins, melamine-urea-formaldehyde resins (MUF resins) and melamine-urea-phenol-formaldehyde resins (MUPF). The various resins mentioned above, in particular melamine resins, urea resins and phenol-formaldehyde resins, can be used either as a mixture or as a mixed condensate. Suitable guanamine resins, for example with methyl-hydroxymethyl groups, are disclosed, for example, in EP 0011049A1.

According to the invention, melamine resin and/or phenolic resin or guanamine resin are used in combination with urea resin. In the context of the present invention, combination means that a mixture of two or more adhesives is applied to the fibers simultaneously or at intervals from each other, for example, as a MF resin (melamine formaldehyde resin) mixed with a urea resin. Alternatively, mixed condensates such as MUF resin or MUPF resin can be used. Combinations of adhesives are used successively, for example because they cannot be mixed or because the individual application of different adhesives has a favorable effect. Preferably, the adhesive mainly comprises melamine resin.

According to the invention, the proportion of melamine resin in the binder is 15% to 35% by weight, in particular 20% to 30% by weight, advantageously 20% to 25% by weight, particularly preferably 15% to 25% by weight, based on the total weight of the (absolutely dry) fiberboard. The melamine resin can be replaced in whole or in part by a phenolic resin. According to the invention, the proportion of urea resin is 5% to 20% by weight, advantageously 5% to 18% by weight, preferably 10% to 18% by weight, particularly preferably 10% to 15% by weight, based on the total weight of the (absolutely dry) fiberboard, respectively. A high proportion of urea resin in the waterproof fiberboard is very advantageous. Since urea resin is an inexpensive binder, the use of urea resin contributes to a significant reduction in the costs of the fiberboard according to the invention.

The total amount of binder used for producing the waterproof fiberboard is preferably at most 48% by weight, particularly preferably at most 45% by weight, advantageously at most 43% by weight, particularly advantageously 20% to 40% by weight, based on the total weight of the (absolutely dry) fiberboard, respectively. The total amount of binder used for producing the waterproof fiberboard can preferably be, for example, at most 40% by weight, advantageously at most 35% by weight, particularly advantageously at most 30% by weight, based on the total weight of the (absolutely dry) fiberboard, while the minimum amount used is advantageously 25% by weight. The overall reduction in the amount of binder used also contributes to reducing the production costs of the waterproof fiberboard compared to known waterproof fiberboards. It seems unusual to reduce the use of binders in the production of waterproof fiberboards. It is even more surprising that waterproof fiberboards that do not swell or swell little can be produced by reducing the use of binders. If the total amount of binder used is related to the amount of melamine resin and/or phenolic resin used on the one hand and the amount of urea resin used on the other hand, it can be clearly seen that the amount of melamine resin or phenolic resin on the one hand and the amount of urea resin on the other hand can vary within a wide range. This provides flexibility in the production of the fiberboards according to the invention and enables extensive cost savings, in particular by using inexpensive urea resins.

Advantageously, the ratio of melamine resin or phenolic resin on the one hand and urea resin on the other hand is 3.5:1 to 1:1, preferably 3:1 to 1:1, particularly advantageously 2.5:1, preferably 2.5-1.5:1. Within the above limits, the ratio between melamine resin or phenolic resin on the one hand and urea resin on the other hand can be adjusted continuously. Mixtures of melamine or phenolic resin on the one hand and urea resin on the other hand outside this mixing range can also produce waterproof fiberboards, but can only use the advantages of the invention to a lesser extent.

The use of thermoplastic binders is advantageously avoided or excluded, in particular more than 7% by weight of thermoplastic binders. The fiberboard according to the invention is preferably free of halogens (eg fluorine, chlorine) and free of terephthalates.

According to an advantageous embodiment, the sheet-like material can be manufactured by adding an elastomer or a thermoplastic, which serves as an elastic additive, for example, its elastic properties can be modified, in particular improved, by adding polyvinyl acetate (PVAc) or ethyl vinyl acetate and a modified isocyanate compound. Acrylates or styrene acrylates are preferably used to elasticize the waterproof fiberboard according to the present invention, in particular in the form of a liquid additive, such as a dispersion or an emulsion, because they are waterproof. It is preferred to use acrylates and styrene acrylates with a glass transition temperature TG of less than 0°C. Also diols, such as monoethylene glycol or diethylene glycol, are suitable for elasticizing the waterproof fiberboard, as are caprolactam, long-chain diols or triols such as glycerol, and polyols, sugars, sugar alcohols or guanamine compounds are suitable as elastic additives. The above-mentioned elasticizing additives can be used individually, but can also be used in the form of a mixture of two or more of the above-mentioned components. The addition of elastomers or thermoplastics reduces the brittleness of the waterproof fiberboard and improves its elastic properties, such as the elastic modulus. In addition, the addition of elastic additives makes the waterproof fiberboard according to the present invention flatter. The proportion of the elastic additive, calculated as 100% by weight solids, based on the total amount of the (absolutely dry) waterproof fiberboard, is 0.1% to 7% by weight, preferably 1% to 5% by weight, advantageously 2% to 4% by weight.

The elastic additive is added to, for example, a binder such as a melamine resin before application to the fibers and applied to the fibers together with the binder. Alternatively, the elastic agent is advantageously applied to the fibers before or more preferably after the binder, for example at the end of a drying tube blowing line.

According to a particularly advantageous embodiment of the present invention, the elastic additive is added during the production process of the adhesive and condensed into the adhesive. This process ensures the high efficiency of the elastic additive.

According to an advantageous embodiment of the invention, a curing agent is added to the adhesive, which causes curing of the adhesive, usually a chemical reaction, such as accelerating a condensation reaction or an addition reaction. A typical example of a curing agent is ammonium sulfate. By adding a curing agent, the curing of the adhesive in the press can be optimized. The curing agent does not become part of the adhesive here, because as a catalyst, it only triggers a chemical reaction and does not become part of the resulting polymer. The curing agent is used in an amount of 0.1% to 2% by weight, preferably up to 1% by weight, based on the total weight of the (absolutely dry) waterproof fiberboard, more preferably applied after applying the adhesive, advantageously for example at the end of the drying pipe blowing line.

The use of a hydrophobing agent for producing the waterproof fiberboard according to the invention has proven to be further advantageous. For example, paraffin or wax can be used, usually as an emulsion, usually in an amount of up to 4% by weight, usually in an amount of up to 2% by weight, usually in an amount of 0.1% to 1.5% by weight, based on the weight of the board material, respectively, based on the total amount of the (absolutely dry) waterproof fiberboard. The hydrophobing agent is usually used in liquid form, for example as an emulsion or dispersion. Alternatively, hot paraffin can be used. It can be used before or after the adhesive, or together with the adhesive. The use of a hydrophobing agent also helps to reduce the tendency of the board material to swell.

In order to ensure that the waterproof fiberboard according to the invention can be correctly identified when the waterproof fiberboard is used, it can prove to be advantageous to color the fiberboard according to the invention with pigments. For this purpose, for example, 0.01% to 2% by weight, advantageously 0.05% to 1.5% by weight, in particular 0.1% to 1% by weight of colorant, based on the total amount of the (absolutely dry) waterproof fiberboard, can be used.

The waterproof fiberboard optionally contains additives. As a possible additive, fillers can help optimize the weight of the board material, usually to reduce weight, but in some cases it can also be to increase weight, or they can help further improve the matrix structure made of binder and fiber. Additives or combinations of additives can be used alternatively or additionally to optimize certain properties of the board, such as electrical or thermal conductivity, insulation properties or strength properties. Additives usually replace the fibers in the fiberboard according to the present invention. Since the waterproof fiberboard should have minimal swelling in the presence of water, especially minimized thickness swelling, it is preferred to select additives or fillers that are not hygroscopic or non-swelling and additives or fillers that are resistant to hydrolysis. Such additives or fillers can be mineral particles, or ceramics, synthetic materials, or particles made of glass or metal. For example, calcium carbonate (CaCO3) and/or barite (BaSO4) can be used as fillers, metal particles can be used to improve thermal conductivity and/or electrical conductivity, or expanded plastic particles can be used to reduce weight. The size of the particles is preferably not greater than one millimeter, preferably between 10μm and 800μm. The particles can have any shape, such as granular or powdery, and also filamentous. Mixtures of different particles can also be used, for example mixtures of different materials, shapes or sizes. Based on the total weight of the (absolutely dry) waterproof fiberboard, up to 30% by weight, particularly preferably up to 20% by weight, advantageously up to 15% by weight of additives are used. The lower limit of the amount of additives or fillers used depends on their detectability. The additives or fillers can be applied to the fibers before or after the application of the adhesive, preferably by spraying or spreading on the fibers.

The pressing conditions for the waterproof fiberboard, in particular the pressure and temperature, are essentially the same as those for the known wood materials. The pressures and temperatures for producing the fiberboard according to the invention are, for example, in the range of ordinary HDF boards (high-density fiberboards). However, the pressing time can be significantly shorter than the pressing time for known non-waterproof HDF boards. The material according to the invention can be produced very well in presses such as those used for the production of wood materials. In particular, continuous or discontinuous hot presses, such as continuous double-belt presses with rotating heated metal belts or intermittently working presses with press plates. In this way, board forms other than WPC can be produced without being limited to the production of narrow wooden board forms with a width of no more than 100 cm. On the contrary, conventional board forms can be provided, as is common for wood boards. The waterproof fiberboard is preferably not extruded.

As with wood materials, fiber cakes are usually produced by spreading. The preferably dry fibers, which are advantageously provided with the entire amount of binder, are spread onto a carrier, usually on a conveyor belt, usually in the form of a uniform layer, but also in the form of multiple layers, wherein the layers may have different compositions with regard to fibers, binder or additives. If necessary, the dispersed fiber cake first passes through a pre-press on a carrier and is then pressed in a press.

Any press capable of applying sufficient pressure and temperature is suitable, not only a discontinuous plate press in which the fiberboard is pressed between two sheets, but also a continuous press in which the waterproof fiberboard is pressed between two rotating metal belts. Preferably, a hot press is used, whose pressing plate or rotating metal belt is heated to a predetermined temperature. Suitable pressing temperatures can be selected from 110° C. to 250° C., preferably 110° C. to 180° C., advantageously 140° C. to 160° C. (temperature of the pressing sheet or pressing belt). The thinner the sheet, the lower the pressing temperature can be selected. Alternatively, the pressing speed can be increased, i.e. the pressing time can be shortened. Suitable pressing pressures are, for example, in the range of 0.3 N/mm ² to 5.5 N/mm ² , in particular 1 N/mm ² to 3 N/mm ^2. The pressing time is advantageously 6 seconds/mm of board thickness (hereinafter: s/mm) to 60 s/mm, typically 10 s/mm to 30 s/mm, preferably 20 s/mm to 25 s/mm. In order to minimize the pressing time, the temperature can be increased within the above range. In the case of continuous pressing, the feed speed of the rotating metal belt for producing the waterproof fiberboard by pressing is generally between 250 mm/sec and 400 mm/sec, preferably between 300 mm/sec and 350 mm/sec, depending on the length of the press.

The actual pressing process may be preceded by a pre-pressing to compact the fiber cake. Optionally, the press may be followed by a device for cooling the fiberboard, in particular for cooling at a predetermined pressing pressure, which may be lower than the pressing pressure during pressing of the material. Cooling star turners are often used to cool the board. Cooling prevents deformation of the board.

The invention also relates to a waterproof fiberboard, comprising fibers and a binder, wherein the fiberboard contains 15 to 35% by weight of melamine resin, phenolic resin, mixtures and mixed condensates thereof or guanamine resin, and 5 to 20% by weight of urea resin, each based on the total weight of the fiberboard (absolutely dry). The advantages of the composition of such a waterproof fiberboard have already been explained above in conjunction with the method according to the invention. All components of the waterproof fiberboard explained above in conjunction with the method can be components of the waterproof fiberboard according to the invention, in particular in the proportions mentioned therein. The individual features of the method or the fiberboard described in the present application can be freely combined with one another and are technically as independent of one another as possible.

The waterproof fiberboard according to the invention is characterized in that it does not show any significant thickness expansion under the influence of moisture (i.e. water). A thickness expansion of less than 3%, preferably less than 2%, based on the original board thickness is considered to be insignificant within the meaning of the invention. Fiberboards that are optimized according to the invention for minimum thickness expansion and are considered to be waterproof have a thickness expansion according to DIN EN 317 or, as coated fiberboards, an edge expansion of only 0.5% to 1% according to DIN 13329. It should be pointed out here that the fiberboards according to the invention are uncoated, so that the data given in this application are based on tests according to DIN EN 317.

The waterproof fiberboard according to the invention is thus low-expansion or, when reaching a maximum thickness expansion of up to 1% based on the original board thickness, non-expansion and dimensionally stable. This allows, for example, the production of an inexpensive, board-shaped, substantially non-swelling, dimensionally stable material with respect to water or humidity on known equipment for producing wood-based panels, which is not limited to narrow specifications and preferably maximizes the use of renewable raw materials.

The waterproof fiberboard according to the invention has good strength properties, in particular a high transverse tensile strength, which is at least 2.5 N/mm2, preferably at most 3 N/mm2, in particular at most 4 N/mm2. The fiberboard according to the invention has a high compressive strength. The good strength properties mean that according to the invention, fewer fastening devices, such as screws, need to be used when fastening the waterproof fiberboard, because the individual fastening devices are better fixed in the board. The high transverse tensile strength also allows for more intensive processing of the fiberboard according to the invention, such as milling complex contours on narrow surfaces. For example, complex contours can be incorporated into the narrow surface of a board with a thickness of only 4.3 mm, so that two interlocking boards can be aligned or connected to each other in the vertical and horizontal direction. The high compressive strength enables the waterproof fiberboard to achieve high point loads, so that it can be suitable, for example, for vehicle loading floors or as floors for storage areas. The high bending stiffness of the waterproof fiberboard makes it possible to use it as a building element, for example for wall reinforcement.

The density of the waterproof fiberboard according to the invention is preferably between 1000 kg/m ³ and 1800 kg/m ³ , in particular between 1000 kg/m ³ and 1600 kg/m ³ , advantageously between 1000 kg/m ³ and 1300 kg/m ³ , particularly advantageously between 1000 kg/m ³ and 1200 kg/m ^3. Due to the higher amount of binder, the fiberboard according to the invention has a higher weight compared to, for example, wood materials with a lower binder content, such as HDF boards.

The fiberboard according to the invention generally has two main surfaces, which are also referred to below as the top and the bottom. The narrow surface or edge of the fiberboard is arranged between the top and the bottom. The thickness of the finished fiberboard can be from 0.8 mm to 50 mm, typically between 1 mm and 25 mm, usually between 3 mm and 20 mm. Typical applications may require a waterproof fiberboard thickness of 4 mm to 10 mm, in particular between 4 mm and 7 mm. The fiberboard according to the invention can have flat main surfaces; the top and/or the bottom can also be embossed or milled or processed in some other way so that the surface fiberboard based on the material has a variable thickness, for example on a furniture front with an embossment. The waterproof fiberboard preferably has a composition that is substantially uniform throughout its thickness.

The top and bottom surfaces as well as the narrow surfaces can be processed using standard tools. They can, for example, be sawn, cut or milled. The maximum length and width of the fiberboard according to the invention are limited only by the available presses for producing the material. By disassembling or splitting the finished waterproof fiberboard, smaller sizes can be made. The typical dimensions of the fiberboard can be 5600mm (length) x 2070mm (width) or 5600mm x 2800mm after production in the press, and 1380mm x 195mm or 3048mm x 2800mm after being split into floors, walls or ceilings. The latter form is particularly suitable for use as a structural board in construction, because the width of the board is the height of the floor.

The waterproof fiberboards according to the invention can be used in various ways, in particular for structural purposes in interior and exterior construction or in outdoor applications. They can be used, for example, as floor, ceiling and/or wall coverings, for the production of interior fittings or furniture, in particular for interior fittings in vehicles, such as cabins or floors, but also outdoors as facades or claddings, for example as curtain wall facades, as balcony claddings, as exterior window sills or roof coverings, also for outdoor furniture or for making signs. The waterproof fiberboards according to the invention are suitable as wall, ceiling and/or floor coverings in wet rooms, but also for equipping them with partitions, benches or furniture.

The waterproof fiberboard according to the invention can be coated, colored, painted or decorated in another way. In particular, surface coatings, such as are known from the field of wood materials, can be applied to the surface of the material according to the invention. Furthermore, the sheet-like material according to the invention can be used as a component of a sandwich panel, i.e. a component of a sandwich panel connecting the material according to the invention to the same or other membranes or sheet-like materials, in particular wood panels, but also plastic panels or films, to form a sandwich panel. The coating can further improve the expansion and contraction properties of the waterproof fiberboard.

Each of the above-mentioned features of the present invention can be freely combined with each other.

DETAILED DESCRIPTION

Exemplary embodiments are used to explain the details of the present invention.

Example 1

In order to produce a fiberboard with a thickness of 8 mm or a thickness between 0.8 mm and 50 mm, lignocellulose fibers produced by mechanical or chemical mechanical methods or synthetic fibers, such as chemical fibers made of plastics, inorganic fibers or lignocellulose materials, can be provided. Mixtures of different fibers can also be used. In the present exemplary embodiment, 50% by weight of fibers are provided.

A binder is also provided, in this case as indicated in Table 1. For this exemplary embodiment, 29% by weight of melamine resin and 16% by weight of urea resin, respectively, based on the total weight of the waterproof fiberboard, are used. According to the invention, these amounts are in the range of 15% by weight to 35% by weight of melamine or phenolic resin and 5% by weight to 20% by weight of urea resin. A total of 45% by weight of binder is used, based on the total weight of the (absolutely dry) fiberboard. In proportion, the melamine resin and urea resin, which can be replaced entirely or partially by phenolic resin, are used in a ratio of 1.9:1, based on the weight of the respective components used, wherein the ratio can be set in a preferred range of 3.5:1 to 1:1. In this exemplary embodiment, the melamine resin is applied in the form of a solution with a solid content of 50% by weight; the urea resin is also applied in the form of a solution, but with a solid content of 60% by weight. The two components of the binder are sprayed onto the fibers simultaneously; alternatively, they can be applied sequentially.

The elasticizer (here styrene acrylate) is sprayed onto the fibers as a solution in a proportion of 2.5% by weight based on 100% by weight solids. The amount of elasticizer used can be 0.1% by weight to 7% by weight, based on the total weight of the (absolutely dry) fiberboard. It makes the waterproof fiberboard less brittle. This means that the waterproof fiberboard remains flat and avoids brittle fracture behavior.

The amount of binder used in the fiberboard according to this exemplary embodiment is reduced to 45% by weight, and even taking into account the elastic agent, the proportion of binder is less than 50% by weight, specifically 47.5% by weight. In principle, the binder proportion can preferably be a maximum of 48% by weight to a minimum of 25% by weight based on an absolutely dry fiberboard.

In addition, optional components may be added, such as those listed in Table 1, which are explained below. Typically, a curing agent for the binder is sprayed onto the fibers, here ammonium sulfate, in a proportion of 0.9% by weight based on the amount of binder used. In an exemplary embodiment, the non-swelling properties of the waterproof fiberboard are supported by adding 1.5% by weight of wax or oil, which is used here as an emulsion. Finally, the waterproof fiberboard according to the exemplary embodiment is visually identifiable by using 0.1% by weight of a colorant so that it will not be confused with other non-waterproof fiberboards when used.

In this exemplary embodiment, the above components can be applied to the fibers simultaneously or sequentially, preferably sequentially, since the dosage of the components can be better controlled. According to an exemplary embodiment, after the application of the components, the fibers are then dried to a moisture content of about 8%. Alternatively, the components, in particular the optional components, can also be applied to the already dried fibers. According to another option, for example, curing agents, colorants and hydrophobic agents can also be applied to the already dried fibers and provided with a binder and an elastic agent after drying but before spreading to form a fiber cake.

The fibers containing all the components are spread into a fiber cake. The fiber cake is pressed into a waterproof fiberboard in a known continuously operating double belt press at 180°C and a pressure of 2.5 N/ ^mm2 with a pressing time factor of 15 s/mm. These conditions are selected from the range of pressing temperature of 110°C to 250°C and pressing pressure of 0.3 N/ ^mm2 to 5.5 N/ ^mm2 . The pressing time factor can be selected in the range of 6 s/mm to 60 s/mm. The waterproof fiberboard produced in this way has a thickness of 8 mm and a density of 1113 kg/ ^m3 (absolute dry), see Table 1. The moisture content of the finished waterproof fiberboard is usually around 6%, so the weight of the fiberboard when ready for use is about 1180 kg/ ^m3 .

Table 1 Composition of waterproof fiberboard (representing 100% solids or absolute dryness, respectively, based on absolute dry waterproof fiberboard)

Components Absolute weight (kg/m ³ ) Ratio (weight %) Waterproof fiberboard 1113 100 fiber 556 50 Melamine resin 325 29 Phenolic resin 175 16 Ammonium sulfate 10 0.9 Styrene Acrylate 28 2.5 Lotion 17 1.5 Colorants 2 0.1

The waterproof fiberboards produced in this way were subjected to the expansion test for uncoated fiberboards according to DIN EN 317 and to the edge expansion test according to DIN 13329. The thickness expansion was determined in the middle of the specimen as the change in mm based on an absolute initial thickness of 8 mm and also as a relative change. The edge expansion was determined at the edge of the coated material as the change in mm based on an absolute initial thickness of 8 mm and as a relative change (%).

The thickness expansion rate of the waterproof fiberboard produced according to the above embodiment is less than 2% of the fiberboard thickness. Therefore, compared with the thickness expansion of non-waterproof fiberboard (more than 20%), its thickness expansion is reduced by more than 90%. The edge expansion of the waterproof fiberboard according to the exemplary embodiment is less than 1.5%, while the edge expansion of the known non-waterproof fiberboard is greater than about 15%. Here, the edge expansion is also reduced by about 90%. This result is even more surprising because the waterproof fiberboard according to the present invention contains urea resin. In the case of the waterproof fiberboard according to the exemplary embodiment, it is 16% by weight or about one-third of the total amount of adhesive used. Despite the high proportion of urea resin (easy to hydrolyze), the edge expansion and thickness expansion are reduced by about 90% or more, thereby providing a waterproof fiberboard that can be produced more cost-effectively than the known waterproof fiberboard by using cheaper adhesives. Since the adhesive content has been reduced to 45%, there is also a significant cost advantage. Another significant cost advantage comes from the use of urea resin, although urea resin is hydrolyzable, but is used in the production of waterproof fiberboards here. Even taking into account the elastic agent, the amount of adhesive used is less than 50% by weight, here 47.5% by weight.

Despite this change in composition, the waterproof fiberboard still has comparable strength properties compared to the waterproof fiberboard known from WO 2020/211988 A1. Therefore, the inexpensive and waterproof fiberboard according to the invention can be used in the same way as the known waterproof fiberboard.

The fiberboard according to the invention can be easily coated, wherein the coating generally further reduces the thickness expansion and possibly also the edge expansion.

Example 2

In this exemplary embodiment, about 99% by weight of adhesive is used based on the proportion of wood fibers. About 45% by weight of adhesive is used based on the total weight of the waterproof fiberboard. The amount of adhesive is divided into 33.8% by weight of melamine resin and 11.22% by weight of urea resin based on the total weight of the fiberboard. The amount ratio of melamine resin and urea resin is about 3:1. In addition, 0.9% by weight of curing agent, here ammonium sulfate, is used. 2.5% by weight of styrene acrylate is used to reinforce the fiberboard. In addition, the amount of wax emulsion is 1.5% by weight and the amount of colorant is 0.05% by weight, respectively based on the total weight of the fiberboard.

Table 2 Alternative ingredients for waterproof fiberboard including about 99% by weight of binder based on fiber content (representing 100% solids or absolute dry, respectively, based on absolute dry waterproof fiberboard)

Components Absolute weight (kg/m ³ ) Ratio (weight %) Waterproof fiberboard 1113.00 100.00 fiber 556.91 50.03 Melamine resin 376.27 33.80 Phenolic resin 124.95 11.22 Ammonium sulfate 10.02 0.90 Styrene Acrylate 27.85 2.50 Lotion 16.71 1.50 Colorants 0.50 0.05

The table shows the composition of the fiberboard in % by weight based on the total weight of the fiberboard. The pressing conditions, the addition or mixing of the individual components and the solids content of the components are the same as in exemplary embodiment 1. The weights also correspond to the board in exemplary embodiment 1.

Fiberboard produced using the mixture shown in Table 2 is cheaper due to the urea resin, but is still waterproof.

Example 3

In this exemplary embodiment, the proportion of binder is reduced to 70 wt % based on the proportion of fibers. The ratio of melamine resin to urea resin is 3:1, which is set in the same way as in Example 1; however, due to the reduced binder content, only 29.28 wt % of melamine resin and 9.72 wt % of urea resin are used. Therefore, the amount of curing agent used is reduced to 0.68 wt %. On the other hand, the amount of styrene acrylate used is slightly increased to 2.7 wt %, and the amount of waterproofing agent (here wax emulsion) used is also slightly increased to 1.62 wt %. The use of colorant is limited to 0.4 wt %. Unless otherwise stated, all weight information above refers to the total weight of the fiberboard.

Table 3 Alternative ingredients for waterproof fiberboard including 70 wt. % binder based on fiber content (representing 100 % solids or absolute dry, respectively, based on absolute dry waterproof fiberboard)

Components Absolute weight (kg/m ³ ) Ratio (weight %) Waterproof fiberboard 1113.00 100.00 fiber 620.28 55.72 Melamine resin 325.95 29.28 Phenolic resin 108.24 9.72 Ammonium sulfate 7.82 0.68 Styrene Acrylate 31.03 2.70 Lotion 18.62 1.62 Colorants 0.43 0.04

The table shows the composition of the fiberboard in % by weight based on the total weight of the fiberboard. The pressing conditions, the addition or mixing of the individual components and the solids content of the components are the same as in exemplary embodiment 1. The weights also correspond to the board in exemplary embodiment 1.

Fiberboards produced according to the mixtures shown in Table 3 are waterproof despite the reduced proportion of binder and the relatively high proportion of urea resin and can of course be produced particularly cost-effectively.

Example 4

In exemplary embodiment 4, the proportion of binder is further reduced to only 60% by weight, based on the fiber content. At the same time, the proportion of urea resin is increased to 1:1. The proportion of binder is about 36% by weight, based on the total weight of the waterproof fiberboard. The proportion of curing agent (ammonium sulfate here as well) is set at 0.71% by weight. The proportion of styrene acrylate for elasticizing the fiberboard is increased to 2.95% by weight, and the proportion of waterproofing agent, also in the form of a wax emulsion, is also increased to 1.77% by weight. The amount of colorant added is 0.04% by weight. Unless otherwise stated, all weight information above refers to the total weight of the fiberboard.

Table 4 Alternative ingredients for waterproof fiberboard including 60 wt. % binder based on fiber content (representing 100 % solids or absolute dry, respectively, based on absolute dry waterproof fiberboard)

Components Absolute weight (kg/m ³ ) Ratio (weight %) Waterproof fiberboard 1113.00 100.00 fiber 657.69 59.08 Melamine resin 197.01 17.70 Phenolic resin 197.61 17.75 Ammonium sulfate 7.89 0.71 Styrene Acrylate 32.88 2.95 Lotion 19.73 1.77 Colorants 0.39 0.04

The table shows the composition of the fiberboard in % by weight based on the total weight of the fiberboard. The pressing conditions, the addition or mixing of the individual components and the solids content of the components are the same as in exemplary embodiment 1. The weights also correspond to the board in exemplary embodiment 1.

Fiberboards produced according to the mixtures shown in Table 4 are waterproof despite the reduced proportion of binder and the high proportion of urea resin and can of course be produced particularly cost-effectively.

Claims (as amended under Article 19)

1. A method for producing a waterproof fiberboard comprising lignocellulosic fibers and a binder, the method comprising the following steps:

- Provides fiber,

-Provide adhesive,

-Provide elastic additives,

- Application of adhesive and elastic additives,

-forming a fiber cake from fibers provided with a binder and an elastomer,

-The fiber cake is pressed in a press while the binder is cured to produce fiberboard, where

Based on the total weight of the absolutely dry fiberboard, 15 to 35 wt% of melamine resin, phenolic resin, their mixtures and mixed condensates and/or guanamine resin, and 5 to 20 wt% of urea resin, and 0.1 to 7 wt% of elastic additives are used as binders.

2. The method according to claim 1, characterized in that 15% to 30% by weight, in particular 20% to 25% by weight, of melamine resin or phenolic resin is used, based on the total weight of the absolutely dry fiberboard.

3. The method according to claim 1 or 2, characterized in that 5% to 18% by weight of urea resin, preferably 10% to 18% by weight, advantageously 10% to 15% by weight of urea resin, are used, based on the total weight of the absolutely dry fiberboard.

4. The method according to any of the preceding claims, characterized in that the amount of binder used is at least 20% by weight and at most 48% by weight, preferably at most 45% by weight, advantageously at most 40% by weight, particularly preferably at most 35% by weight, particularly advantageously at most 30% by weight, based on the total weight of the absolutely dry fiberboard.

5. The method according to any one of the preceding claims is characterized in that the ratio of melamine resin or phenolic resin to urea resin used in the adhesive is 3.5:1 to 1:1, preferably 3:1 to 1.5:1, particularly advantageously 2.5:1, preferably 1.5:1 to 2.5:1.

6. Method according to any of the preceding claims, characterized in that 1% to 5% by weight, advantageously 2% to 4% by weight, of elastic additives are used, based on the total weight of the absolutely dry fiberboard.

7. Method according to any of the preceding claims, characterized in that 0.1% to 4% by weight of hydrophobic agent, advantageously up to 1% by weight of hydrophobic agent, based on the total weight of the absolutely dry fiberboard, is used.

8. The method according to any of the preceding claims, characterized in that 0.1% by weight to a maximum of 2% by weight of curing agent, in particular 0.5% by weight to a maximum of 1.5% by weight of curing agent, is used for the adhesive, based on the total weight of the absolutely dry fiberboard.

9. Method according to any of the preceding claims, characterized in that 0.01% to 2% by weight of colorant, advantageously 0.05% to 1.5% by weight of colorant, are used, based on the total weight of the absolutely dry fiberboard.

10. A waterproof fiberboard comprising fibers and an adhesive, wherein the fiberboard contains 15 to 35 weight percent of melamine resin, phenolic resin, mixtures and mixed condensates thereof or guanamine resin, and 5 to 20 weight percent of urea resin, based on the total weight of the absolutely dry fiberboard.

11. Fiberboard according to claim 10, characterized in that it contains at least 20% by weight, at most 48% by weight, preferably at most 45% by weight, advantageously at most 40% by weight, preferably at most 30% by weight of binder, based on the total weight of the fiberboard (absolutely dry).

12. The fiberboard according to claim 10 or 11 is characterized in that the ratio of melamine resin or phenolic resin to urea resin included in the adhesive is 3.5:1 to 1.5:1, preferably 3:1 to 2:1, particularly advantageously 2.5:1, preferably 1.5:1 to 2.5:1, preferably 2:1.

13. The fiberboard according to any one of claims 10 to 12, characterized in that the fiberboard contains 0.1% to 7% by weight of an elastic additive, wherein the elastic additive is selected from the group consisting of elastomers, in particular polyvinyl acetate (PVAc), ethyl vinyl acetate, acrylates, styrene acrylates or polyurethanes (PU), thermoplastics, but also diols, in particular monoethylene glycol or diethylene glycol, and caprolactam, long-chain diols or triols, in particular glycerol, and polyols, sugars, sugar alcohols or guanamine compounds.

14. The fiberboard according to any one of claims 10 to 13, characterized in that the fiberboard contains a maximum of 4% by weight of a water-repellent, a maximum of 2% by weight of a colorant and/or a maximum of 2% by weight of a curing agent, based on the total weight of the absolutely dry fiberboard.

15. The fiberboard according to any one of claims 10 to 14, characterized in that the fiberboard has a coating.

16. Use of a waterproof fiberboard according to claims 10 to 15, characterized in that the fiberboard is used for structural purposes in indoor and outdoor buildings, in particular for exterior wall panels, exterior window sills and roof coverings.

Claims (16)

1. A method for producing a waterproof fiberboard comprising lignocellulosic fibers and a binder, the method comprising the steps of:

-providing a fiber which is substantially free of fibers,

-Providing an adhesive agent, which is provided in the form of a gel,

-Providing an elastic additive to the substrate of the substrate,

-The application of an adhesive and an elastic additive,

Forming a fiber cake from fibers provided with a binder and an elastant,

Pressing the fiber cake in a press while curing the binder to produce a fiberboard, wherein

As binders, 15 to 35% by weight of melamine resin, phenolic resin, their mixtures and mixed condensates and/or guanamine resin, and 5 to 20% by weight of urea resin, and 0.1 to 7% by weight of elastic additives, respectively, are used, based on the total weight of the (absolute dry) fiberboard.

2. The method according to claim 1, characterized in that 15 to 30 wt.%, in particular 20 to 25 wt.%, of melamine resin or phenolic resin, respectively, is used, based on the total weight of the (absolute dry) fiberboard.

3. A method according to claim 1 or 2, characterized in that 5 to 18 wt.% urea resin, preferably 10 to 18 wt.%, advantageously 10 to 15 wt.%, urea resin, respectively, is used based on the total weight of the (absolute dry) fibreboard.

4. The method according to any of the preceding claims, characterized in that the amount of binder is at least 20 wt. -%, and at most 48 wt. -%, preferably at most 45 wt. -%, advantageously at most 40 wt. -%, particularly preferably at most 35 wt. -%, particularly advantageously at most 30 wt. -%, each based on the total weight of the (absolute dry) fiberboard.

5. A method according to any of the preceding claims, characterized in that the binder uses a ratio of melamine resin or phenolic resin to urea resin of 3.5:1 to 1:1. preferably 3:1 to 1.5: 1. particularly advantageously 2.5:1. preferably 1.5:1 to 2.5:1.

6. Method according to any of the preceding claims, characterized in that 1 to 5 wt. -%, advantageously 2 to 4 wt. -% of an elastic additive is used, based on the total weight of the (absolute dry) fiberboard, respectively.

7. A method according to any of the preceding claims, characterized in that 0.1 to 4 wt. -% of hydrophobizing agent, advantageously up to 1 wt. -% of hydrophobizing agent is used, based on the total weight of the (absolute dry) fiberboard.

8. Method according to any of the preceding claims, characterized in that 0.1 to at most 2 wt.% of a curing agent is used for the binder, in particular 0.5 to at most 1.5 wt.% of a curing agent, based in each case on the total weight of the (absolute dry) fiberboard.

9. A method according to any of the preceding claims, characterized in that 0.01 to 2 wt. -% of a colorant, advantageously 0.05 to 1.5 wt. -% of a colorant are used, respectively, based on the total weight of the (absolute dry) fiberboard.

10. A waterproof fiberboard comprising fibers and a binder, wherein the fiberboard contains 15 to 35% by weight of melamine resin, phenolic resin, their mixtures and mixed condensates or guanamine resins, and 5 to 20% by weight of urea resin, respectively, based on the total weight of the (absolute dry) fiberboard.

11. Fiberboard according to claim 10, characterized in that the fiberboard contains at least 20 wt. -%, at most 48 wt. -% binder, preferably at most 45 wt. -%, advantageously at most 40wt. -%, preferably at most 30 wt. -%, based on the total weight of the (absolute dry) fiberboard.

12. The fiberboard according to claim 10 or 11, characterized in that the binder comprises a ratio of melamine resin or phenolic resin to urea resin of 3.5:1 to 1.5: 1. preferably 3:1 to 2:1. particularly advantageously 2.5: 1. preferably 1.5:1 to 2.5: 1. preferably 2:1.

13. The fiberboard according to any one of claims 10 to 12, characterized in that the fiberboard contains 0.1 to 7 wt% of an elastic additive, wherein the elastic additive is selected from the group comprising: elastomers, in particular polyvinyl acetate (PVAc), ethyl vinyl acetate, acrylates, styrene acrylates or Polyurethanes (PU), thermoplastics, but also diols, in particular monoethylene glycol or diethylene glycol, and also caprolactam, long-chain diols or triols, in particular glycerol, and also polyols, sugars, sugar alcohols or guanamine compounds.

14. Fiberboard according to any one of claims 10 to 13, characterized in that the fiberboard contains at most 4 wt.% of water repellent, at most 2 wt.% of coloring agent and/or at most 2 wt.% of curing agent, respectively, based on the total weight of the (absolute dry) fiberboard.

15. The fiberboard according to any one of claims 10 to 14, characterized in that the fiberboard has a coating.

16. Use of a waterproof fiberboard according to claims 10 to 15, characterized in that the fiberboard is used for structural purposes in indoor and outdoor buildings, in particular for exterior wall panels, exterior window sill and roof coverings.