Wood fiber board and method for producing a wood fiber board

Abstract

The invention relates to a wood fiber board which saves resources, said wood fiber board comprising coffee grounds, wherein the wood fibers and the coffee grounds are adhered using a urea-formaldehyde resin. Waste products which are accumulated during the production of coffee using portafilters or during the production of instant coffee are used as the coffee grounds. A solids content of coffee grounds between 20% and 45% is used, and the technical properties of the board according to the invention lie in the range of MDF standards for industrial production.

Description

[0001]WOOD FIBERBOARD AND METHOD FOR PRODUCING A WOOD FIBERBOARD The invention relates to a wood fiberboard with coffee grounds and a method for its production. Due to climate change, wood has become a precious resource worldwide, and particularly in Europe, as many trees are severely threatened by heat and drought. At the same time, pests are spreading extremely rapidly, necessitating deforestation, but subsequent reforestation takes decades. Wood should also be used as sparingly as possible with regard to its carbon footprint. On the other hand, wood fiberboards have an extremely broad range of applications, with very different requirements regarding their technical properties, particularly their mechanical strength. Examples include the use of wood fiberboards in the construction and furniture industries, the funeral industry, and the automotive industry.In order to save resources, Poo Chow proposed as early as 1976 in his publication "The Use of Crop Residues for Board-making", Environmental Conservation, Vol. 3, No. 1, Spring 1976, pages 59-62, mixing typical waste products from US agriculture, such as peanut shells, with another waste product, including coffee grounds, gluing them together with a urea resin (UF glue), and pressing the resulting board. In a series of experiments, maple shavings from a furniture factory were also added, producing a particle board which, however, is unsuitable for use as a load-bearing element in the construction industry due to its low flexural elasticity. WO-A2-2018 / 078391 describes a process in which agricultural waste products, namely straw fibers, are pressed into boards. Another waste product, namely coffee grounds, is used as an additive.Furthermore, the teaching of WO-A2-2018 / 078391 is based on the task of avoiding formaldehyde-containing adhesive resins and instead using pMDI (polymeric diphenylmethane diisocyanate) to bond the starting materials. However, pMDI is highly reactive and requires the use of a special, closed production facility because the isocyanate contained in pMDI adheres to all metallic materials and subsequently causes wear. Furthermore, pMDI must not come into contact with the skin under any circumstances, let alone be inhaled. Accordingly, the safety precautions during processing are more complex. Therefore, not every company can process pMDI. The use of pMDI is therefore disadvantageous.The object of the present invention is to provide a wood fiber board which requires less of the natural resource wood and yet has satisfactory product properties, some of which even correspond to relevant standards, and which can be manufactured in conventional production plants. This object is achieved by a wood fiber board having the features of claim 1. This object is further achieved by a method having the features of claim 16 and claim 19. The invention further relates to the use of a wood fiber board produced according to claim 19 for the construction and furniture industry. Preferred embodiments of the invention are the subject of the subclaims. The invention essentially consists in the fact that the wood fiber board, in addition to wood fibers as a solid component, also contains coffee grounds as a solid component. Tests (see further below) have shown that a proportion of coffee grounds of up to 80 wt.-% yields acceptable strength values. The solids content of the board according to the invention can accordingly comprise up to 80 wt.% and correspondingly 20 wt.% or more of wood fibers. In particular, a coffee grounds content of between 20 wt.% and 45 wt.% is preferred in the invention, because in this case strength values ​​are achieved that correspond to the standards of a pure wood fiber board. According to the invention, coffee grounds are preferably used which are a waste product or residue from coffee preparation or coffee production. The coffee grounds which accrue during the production of instant coffee, also called soluble coffee, are generally incinerated. However, these coffee grounds, hereinafter referred to as "INSTANT" or "INSTA", can also be recycled, as proposed in the application.The coffee grounds that accumulate in the portafilter of the espresso machine or coffee machine during coffee preparation using a portafilter (hereinafter abbreviated to "ST") accumulate in the portafilter after coffee preparation and are usually disposed of. However, this coffee ground can also be recycled, as proposed in the application. Coffee grounds that accrue during the production of instant coffee usually have an average particle size of 125 µm to 2000 µm. Coffee grounds that accrue during the production of coffee beverages using a portafilter have an average particle size of 125 µm to 2000 µm. Both coffee ground variants can be used equally well in the invention and have the advantage that they are available in very large quantities worldwide and have essentially equally good product properties for the present invention.The use of urea-formaldehyde resin as a binder should, of course, be in the smallest possible quantities. According to the invention, the amount of urea-formaldehyde resin is at least 8 wt.%, preferably in a range of 10 wt.% to 12 wt.%, based on 100 wt.% of the sum of wood fibers and coffee grounds. This means that, for example, with a proportion of 80 wt.% coffee grounds and 20 wt.% wood fibers, these proportions together make up 100% of the solids content. If, for example, 10 wt.% urea-formaldehyde resin is added, this means that the 100 wt.% of the finished board is composed of 90 wt.% solids (coffee grounds and wood fibers) and 10 wt.% urea-formaldehyde resin. With such a proportion of binder, a very even distribution of the binder and good homogeneity of the glue distribution in the board, and thus a very uniform strength structure, can be achieved.Since laboratory-scale tests have shown that a proportion of 10% to 12% by weight of urea-formaldehyde resin leads to very consistent results, it is realistic to assume that a minimum proportion of 8% by weight of urea-formaldehyde resin will also lead to satisfactory results in the industrial-scale production of the board according to the invention. The density of the wood fiber board according to the invention is in the range from 500 kg / m³ to 1,000 kg / m³, preferably in the range from 550 kg / m³ to 950 kg / m³. Boards with a density in these ranges are used in many applications, and in which the board according to the invention can also achieve the good technical properties explained in detail below.Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, which do not limit the scope of protection, with reference to the attached drawings. These show: Fig. 1 is an exemplary process diagram, Fig. 2 is a diagram showing the bulk density of all fiberboards produced and tested, Fig. 3 is a diagram showing the flexural strength of all fiberboards produced and tested, Fig. 4 is a diagram showing the modulus of elasticity of all fiberboards produced and tested, Fig. 5 is a diagram showing the transverse tensile strength of all fiberboards produced and tested, Fig. 6 is a diagram showing the increase in length, thickness and mass after 24 hours of water storage of all fiberboards produced and tested, and Fig. 7 is a possible process scheme for implementation on an industrial scale.The invention is explained in more detail below using an exemplary working procedure for producing a wood fiber board according to the invention, which does not limit the scope of protection. When percentages are given below, they are always % by weight. The wood fiber boards developed within the scope of the present invention were produced using different types of coffee grounds. As already mentioned, the coffee grounds included, among other things, waste products or residual materials that arise from the production of coffee beverages using a portafilter. This type of coffee grounds is abbreviated below as ST. Another waste product used in the invention in the form of coffee grounds arises from the production of instant powder for soluble coffee. This type of coffee grounds is abbreviated below as INSTA. The average particle size is usually between 125 µm and 2000 µm.The proportions of portafilter coffee and instant coffee used ranged from 20% to 45% for both coffee varieties – in 5% increments – and additionally 55%, 65%, and 75% for the portafilter version. As is common in the industrial production of fiberboard, a standard urea-formaldehyde resin with different binder proportions (10% and 12%) was used. Urea-formaldehyde resin (UF) was deliberately chosen because it is highly reactive and therefore binds well and quickly. Furthermore, the resin can be applied to the wood fibers in conventional equipment without the need for additional technical equipment. The wood fibers used were MDF-quality, as is standard in industry. The fibers were preferably softwood fibers, for example, spruce fibers or a blend of spruce and pine. However, recycled fibers from wood fiber materials can also be used.In the event that recycling results in fiber damage, such as a shortening of the fiber length, which is unacceptable for the respective application, the recycled fibers can also be combined with fresh wood fibers to achieve the desired mechanical properties. The wood fiber boards with coffee grounds according to the invention were produced with a target density of 550 kg / m³ and 650 kg / m³ and with a coffee grounds content between 20% and 45% (in 5% increments). The binder contents were 10% and 12%, respectively. In addition, boards were produced with instant coffee grounds contents of 20%, 35%, and 45%, a binder content of 10%, and a bulk density of 950 kg / m³. In another series of tests, portafilter coffee grounds contents of 55%, 65%, and 75% were used for portafilter coffee boards with a weight of 650 kg / m³.Finally, corresponding reference panels were produced for comparison without the addition of coffee (each with the designation REFLAB and further information). After production, the pressed panels were conditioned for at least 7 days in a standard climate at 20 °C and 65% relative humidity. The panels were then cut using a circular saw and tested for their flexural strength, flexural elastic modulus (EN 310), transverse tensile strength (EN 319), and thickness swelling after 24 hours of water storage (EN 317). The data were then evaluated and interpreted. The manufacturing steps for implementing the general working procedure are described below; reference is made to the process diagram in Fig. 1 for illustrative purposes only. In Fig.1 shows a wood fiber board 1 with coffee grounds, the wood fibers 2, the coffee grounds 3, measuring devices 4 for measuring the moisture content using the drying method, measuring devices 5 for weighing the glued wood fiber-coffee grounds mixture, storage container 6 for the dried wood fibers, storage container 7 for the dried coffee grounds, storage container 8 for the resin-hardener mixture (binder), a gluing drum 9, a pneumatic glue gun 10, a storage container 11 for the glued wood fiber-coffee grounds mixture, a board cake frame 12, a hydraulic cold press 13, a press plate 14 and a hydraulic hot press 15. The parameters described in the manufacturing process were independent of the desired bulk density and were identical for ultra-light MDF, lightweight MDF, and MDF boards with higher bulk densities. The manufacturing of the boards differed essentially only in the total board mass, which was weighed per defined volume.In a first step, the moisture content of both the wood fibers and the coffee grounds types (portafilter coffee grounds and instant coffee grounds) was determined using the kiln-dried method. A few grams of samples were taken from each material, weighed, and then stored at a kiln-dried temperature of 103°C until constant weight was reached. Constant weight means that the materials are dried until the weight of each sample remains constant. The moisture content was then determined based on the difference between the moist and kiln-dried sample. All ratios in the board composition were related to the kiln mass or the dry solids content. Based on the kiln mass, the desired ratios between wood fibers and coffee grounds as well as the respective resin content were calculated and then related to the actual moist mass (determined moisture content).Since material can be "lost" during the gluing process on a laboratory scale, a 10% safety margin (overweight) was added to all components for the gluing. The wood fibers and coffee grounds were mixed and glued together in a gluing drum with a diameter of 100 cm, a depth of 45 cm, and a rotation speed of 80 rpm. For this purpose, the two solids were tipped unmixed into the drum. The gluing process began immediately after the set rotation speed was reached. Mixing and gluing took place in the same step and took between 5 and 10 minutes, depending on the amount of glue, until the gluing container was empty. 2% ammonium sulfate was added to the UF glue as a hardener. The glue was then applied using a pneumatic glue gun inserted centrally into the gluing drum.The feed pressure and feed volume were selected so that a fine adhesive mist formed in the gluing drum without the formation of large droplets, thus achieving the most homogeneous glue distribution over the fibers. The glued fiber / coffee grounds mixture was then removed from the drum and the final mass (without a safety margin) was weighed in. The weighed-in glued fiber / coffee grounds material was scattered by hand as evenly as possible into a 250 x 250 mm board cake frame and pre-compacted in the frame using a hydraulic cold press from a fiber cake height of several centimeters to a fiber cake height of approximately 5 cm. This pre-compaction step in the frame by cold pressing, i.e. applying pressure but without increasing the temperature, is important because if pre-compaction is insufficient during hot pressing, the fiber cake expands within the board plane, meaning the target density cannot be achieved.After pre-compaction, the frame was removed and 9 mm steel spacers were positioned next to the fiber cake on the press plate, after which hot pressing began. Hot pressing took place at a pressing surface temperature of 200 °C with a pressing factor of 10 sec / mm (90 seconds pressing time), whereby the press had to be closed to the spacers with a maximum pressure of 3 MPa. After pressing, the boards were placed upright to allow even cooling and stored for at least 7 days in a standard atmosphere at 20 °C and 65 % relative humidity before further testing. The following Table 1 lists all manufactured and tested board variants. Table 1: Overview of fiberboards produced on a laboratory scale, coffee grounds, wood fiber, binder content. anteil Coffee grounds type density anteilDescription 0% 100% x 550 kg / m³ 10% REFLAB-550-UF10 20% 80% Portafilter 550 kg / m³ 10% ST20-550-UF10 25% 75% Portafilter 550 kg / m³ 10% ST25-550-UF10 30% 70% Portafilter 550 kg / m³ 10% ST30-550-UF10 35% 65% Portafilter 550 kg / m³ 10% ST35-550-UF10 40% 60% Portafilter 550 kg / m³ 10% ST40-550-UF10 45% 55% Portafilter 550 kg / m³ 10% ST45-550-UF10 0% 100% x 650 kg / m³ 10% REFLAB-650-UF10 20% 80% Portafilter 650 kg / m³ 10% ST20-650-UF10 25% 75% Portafilter 650 kg / m³ 10% ST25-650-UF10 30% 70% Portafilter 650 kg / m³ 10% ST30-650-UF10 35% 65% Portafilter 650 kg / m³ 10% ST35-650-UF10 40% 60% Portafilter 650 kg / m³ 10% ST40-650-UF10 45% 55% Portafilter 650 kg / m³ 10% ST45-650-UF10 0% 100% x 650 kg / m³ 10% REFLAB2-650-UF-10 55% 45% Portafilter 650 kg / m³ 10% ST55-650-UF-10 65% 35% Portafilter 650 kg / m³ 10% ST65-650-UF-10 75% 25% Portafilter 650 kg / m³ 10% ST75-650-UF-10 0% 100% x 950 kg / m³ 10% REFLAB-950-UF-10 20% 80% Instant 950 kg / m³ 10% INSTA20-950-UF-10 35% 65%Instant 950 kg / m³ 10% INSTA35-950-UF-10 45% 55% Instant 950 kg / m³ 10% INSTA45-950-UF-10 0% 100% x 550 kg / m³ 12% REFLAB-550-UF12 20% 80% Portafilter 550 kg / m³ 12% ST20-550-UF12 25% 75% Portafilter 550 kg / m³ 12% ST25-550-UF12 30% 70% Portafilter 550 kg / m³ 12% ST30-550-UF12 35% 65% Portafilter 550 kg / m³ 12% ST35-550-UF12 40% 60% Portafilter 550 kg / m³ 12% ST40-550-UF12 45% 55% Portafilter 550 kg / m³ 12% ST45-550-UF12 0% 100% x 650 kg / m³ 12% REFLAB-650-UF12 20% 80% Portafilter 650 kg / m³ 12% ST20-650-UF12 25% 75% Portafilter 650 kg / m³ 12% ST25-650-UF12 30% 70% Portafilter 650 kg / m³ 12% ST30-650-UF12 35% 65% Portafilter 650 kg / m³ 12% ST35-650-UF12 40% 60% Portafilter 650 kg / m³ 12% ST40-650-UF12 45% 55% Portafilter 650 kg / m³ 12% ST45-650-UF12 20% 80% Instant 650 kg / m³ 12% INSTA20-650-UF12 25% 75% Instant 650 kg / m³ 12% INSTA25-650-UF12 30% 70% Instant 650 kg / m³ 12% INSTA30-650-UF12 35% 65% Instant 650 kg / m³ 12% INSTA35-650-UF12 40% 60% Instant 650kg / m³ 12% INSTA40-650-UF12 45% 55% Instant 650 kg / m³ 12% INSTA45-650-UF12 Total produced boards 126 To determine the transverse tensile strength and water storage, samples measuring 50 x 50 mm, and for the bending tests, samples measuring 230 x 50 mm were prepared using a circular saw. Before the tests, the bulk densities of the individual samples were determined. Bulk density The bulk density was determined after conditioning in a standard climate (20 °C and 65% relative humidity) on three 50 x 50 mm samples per board. The diagram in Fig. 2 shows the bulk density of all fiberboards tested. As can be seen from Fig. 2, all desired bulk density ranges were easily achieved. Very small density fluctuations can be observed in all three density groups, which indicates a homogeneous scattering and distribution of the fibers and particles. Therefore, no significant correlation can be found between density and coffee grounds or binder content. This means thatThe bulk density of the board does not change significantly, even if the proportion of coffee grounds or binder is varied. This effect is due, among other things, to the fact that in the first process step, the moisture content is determined using the kiln drying method, both from the wood fibers and from the coffee ground types (portafilter coffee grounds and instant coffee). Based on the kiln drying mass, the desired ratios between wood fibers and coffee grounds, as well as the respective glue content, are calculated and then related to the actual moist mass (determined moisture content). Of course, the homogeneous production of the fiber cake and its pre-compaction also have an influence on the bulk density. Bending strength and flexural modulus of elasticity Bending strength and flexural modulus of elasticity provide information about the influence of the wood fiber content used, since fibers generally have a positive effect on the flexural properties of materials due to their geometry.Three bending tests were carried out on the panels according to EN 310, and the flexural strength and flexural modulus of elasticity were determined using a crosshead (Zwick and Roell Z20 universal testing machine). Subsequently, a statistical comparison of the mean values ​​(PostHoc Scheffé, p=0.05) was carried out. For this purpose, the specimens were positioned in a 3-point bending test setup, with the support spacing corresponding to 20 times the panel thickness (approx. 180 mm support spacing). The loading rate was set so that the breaking force was reached within 60 ± 30 seconds. Fig. 3 shows a diagram with the flexural strength according to EN 310 of all produced fiberboards. As can be seen from Fig. 3, the influence of the bulk density is evident in the flexural strength, and the coffee grounds content in the panels also becomes apparent in the strength values ​​above a certain amount. Not surprisingly, the panels in the 550 kg / m³ group show lower strength compared to the 650 kg / m³ groupor 950 kg / m³. No statistically significant differences can be observed between the boards with coffee content and the reference boards without coffee (each with the designation REFLAB and further information). For the boards with 650 kg / m³ and 10% binder content, differences can be seen between individual variants, but not between the two pure MDF reference fiberboards, which is why a comparison between the portafilter boards with 55% or more portafilter coffee grounds content and those with 45% or less portafilter coffee grounds content is permissible. When considering the group with 20% to 45% portafilter coffee grounds content, no difference can be assumed between the individual board types within the group. Only when the values ​​from 55% onwards are taken into account can a certain trend with decreasing flexural strength with increasing coffee grounds content be assumed. In this case, the boards only show a recognizable difference from 55% onwards and abovedifference to the reference plates. It can therefore be stated that the flexural strength at a raw density of 550 kg / m³ or 650 kg / m³ and a binder content of 10% or 12% does not change significantly when coffee grounds are added up to 45%, and surprisingly good values ​​are obtained. Depending on the intended use and the required flexural strength, and taking into account the object of the invention to reduce the use of wood in the production of wood fiber boards and to enable effective further use of coffee grounds, a coffee ground content of up to 80% can certainly be considered. In the case of the instant coffee boards with a raw density of 950 kg / m³, the boards already differ noticeably from the reference boards from a coffee ground content of 20%. However, higher flexural strength values ​​can be achieved here than with the boards with a lower raw density, and boards with a raw density of 950 kg / m³ are therefore also preferred within the scope of the invention.It was shown that the binder content had no significant influence on the flexural strength within the variants investigated (10% and 12%). Fig. 4 shows a diagram with the modulus of elasticity according to EN 310 for all produced fiberboards. A similar picture to that for the flexural strength is shown in Fig. 4 for the modulus of elasticity. Here, too, a clear difference can be seen between the two bulk density groups, although differences between the coffee content can only be seen in the 650 kg / m³ boards. Here, although a trend towards a decrease in the modulus of elasticity with increasing coffee grounds content is not statistically significant, both coffee variants show a trend. Here, too, the conditions for the flexural strength for the boards with a bulk density of 950 kg / m³ are almost identical to those for the flexural strength. The only notable exception here are the values ​​for instant coffee, which show lower values ​​for a coffee grounds content of 35% and above.than the reference laboratory board. It can therefore be stated that the modulus of elasticity does not change significantly with the addition of coffee grounds up to 45% at a raw density of 550 kg / m³ or 650 kg / m³ and a binder content of 10% or 12%, and the values ​​obtained are surprisingly good. Transverse tensile strength The transverse tensile strength of board materials provides insight into the homogeneity of the glue distribution within the board and the fiber distribution (scattering) before pressing. Since the test is carried out in parallel with the fiber orientation of the board, factors that are inherently positive for the mechanics of a board, such as fiber length, are of less importance here. For the investigations, three samples per board were tested according to EN 319 and then a statistical comparison of the mean values ​​(PostHoc Scheffé, p=0.05) was carried out. For the investigation, the 50 x 50 mm samples were bonded to aluminum transverse tensile yokes using hotmelt adhesive (Henkel Technomelt Supra 325 HT).The offset between the two yokes was 90° to minimize the occurrence of torque during the tensile test and thus avoid cracking. Fig. 5 shows a diagram with the transverse tensile strength according to EN 319 of all produced fiberboards. Fig. 5 shows the absolute values ​​of the measured transverse tensile strength, whereby differences between the two bulk density ranges can be seen here, with the higher bulk density having the highest transverse tensile strengths. In general, the values ​​for portafilter coffee show a very high scatter, although it should be noted that no statistical difference can be detected between the two reference board variants with 650 kg / m³ and 10% binder. Even if individual board variants show statistically significant differences to their boards with a similar coffee content, overall there is no significant difference to the reference boards. As an example, the portafilter boards with 10%Binder is called the binder, where the plate with 45% coffee differs from the version with 35%, but not from the versions with 40%, 30%, or 20% coffee content. The situation is similar for the portafilter plates with 12% binder content. It is interesting to note that the scatter of the portafilter plates decreases with increasing coffee grounds content, and that the plates with 55%, 65%, and 75% portafilter content differ from the values ​​with 40% and 45% coffee content, but not from the plates with 35% and 25%, and thus not from the entire group as a whole. For the instant coffee plates, a tendency towards a decrease in strength with increasing coffee content can be seen, but due to the scatter, one cannot speak of a statistically significant difference between the plates. Based on the results obtained, no difference between 10% and 12% binder content can be seen for the portafilter plates. Since all plates were treated with the same agentswere produced, the variation of the portafilter plates at 650 kg / m³ bulk density can probably be attributed to the portafilter material. In comparison to instant coffee grounds, a higher degree of agglomeration was subjectively observed in the portafilter grounds during processing during gluing in the gluing drum. This could have led to partially more varied coffee grounds contents in the plates and thus also explain the variation. Even if values ​​for individual variants appear higher here, they are still within the variation range in relation to the reference and, based on the available values, no significant difference can be assumed. The determined values ​​can therefore be interpreted in such a way that at 650 kg / m³ for instant coffee, there was a reduction in transverse tensile strength at higher coffee contents of over 35% and there was no noticeable reduction in the transverse tensile strength for (the smaller sample of) portafilter plates. In general, it should be noted thatWith varying board mixing ratios, the total volume of coffee grounds and wood fibers to be glued also varies greatly between the individual board types. A board with, for example, 20% coffee grounds content has a significantly higher volume during gluing than a mixture with 45% coffee grounds or higher. This means that the gluing drum is filled much more heavily with low coffee grounds contents than with mixtures with high coffee grounds contents. This can significantly influence the distribution of the glue across the fibers and coffee grounds, which is why it cannot be ruled out that a better or more homogeneous gluing could be achieved with higher coffee grounds contents during the gluing process used. Overall, it can be stated that wood fiber boards with a coffee grounds content of up to 80%, especially between 20% and 45%, exhibit surprisingly good results in terms of flexural strength and flexural elastic modulus, as well as transverse tensile strength.Values ​​when they are bonded with a urea-formaldehyde resin, and this in a bulk density range of 550 kg / m³ to 950 kg / m³. This applies to both instant coffee grounds and portafilter coffee grounds. Thickness swelling after 24 hours of storage in water For the water storage test, three samples per plate were placed in a water bath (water temperature approx. 20 °C) and fixed below the water surface using a metal sieve. The lengths, thicknesses and mass increase were determined on 50 x 50 mm samples after 24 hours of storage in water. For this purpose, the samples were simply lightly dabbed and measured after the water bath. Fig. 6 shows a representation of the length, thickness and mass increase after 24 hours of storage in water according to EN 317. Fig. 6 again shows a difference between the two bulk density ranges. The most obvious difference is in the mass increase, with the plates with the lower binder content tending to gain more mass and with higher coffee contents partlysignificantly higher mass increases compared to the reference. The 550 kg / m³ boards also show a significantly higher increase in thickness swelling than the 650 kg / m³ boards. The lowest values ​​were found for the boards with instant coffee and a bulk density of 950 kg / m³, whereby statistically significantly higher increases can be observed with increasing coffee grounds content. Thus, the boards with 35% and 45% coffee grounds content show statistically significantly higher values ​​for mass increase and with 45% coffee grounds content for thickness increase than the reference boards without coffee grounds. For the portafilter boards with a bulk density of 650 kg / m³ and a binder content of 10%, statistically significant differences to the reference boards can only be observed for the mass increase of the board variant with 75%. All other variants do not differ significantly from one another in terms of mass increase or thickness swelling, whereby for the boards withCoffee grounds contents of >45%, a trend with increasing values ​​can be observed with increasing coffee grounds content. Even for the boards with instant coffee and a density of 650 kg / m³, no statistically significant differences between the different coffee grounds contents can be determined. Interestingly, even during water storage, no difference can be found between the two binder contents of 10% and 12%. With regard to the different properties after water storage, however, it should be added that the generally poorer properties of some tested boards do not in any way indicate that their use is not advisable, because, as with the mechanical strength, whether a certain composition of a wood fiber board according to the invention is suitable or not depends on the respective intended use of the boards. Evaluation of the measurement results All measurements taken as part of the general working procedure for carrying out theThe findings of this invention relate to a laboratory-produced wood fiber board using coffee grounds. However, due to the good measurement results, upscaling to an industrial scale is realistic, especially if the board is used in dry areas. Table 2: Requirements for general-purpose boards for use in dry areas according to EN 622-5 Type MDF Nominal thickness ranges [mm] E igenschaft Prüf- v erfahren Einheit 1.8 >2.5 >4 >6 >9 >12 >19 >30 to to to to to to to to >45 2.5 4 6 9 12 19 30 45 Thickness swelling 2 4 h EN 317 % 45 35 30 17 15 12 10 8 6Transverse tension f estigkeit EN 319 N / mm² 0.65 0.65 0.65 0.65 0.60 0.55 0.55 0.50 0.50Bending f estigkeit EN 310 N / mm² 23 23 23 23 22 20 18 17 15Bending Elasticity EN 310 N / mm² - - 2700 2700 2500 2200 2100 1900 Modulus Type Light MDF Nominal thickness ranges [mm] E igenschaft Prüf- v erfahren Einheit>6 >9 >12 >19 >30 to to to to to >45 9 12 19 30 45 Thickness swelling 2 4 h EN 317 % 20 16 14 12 11 11Transverse tension f estigkeit EN 319 N / mm² 0.45 0.45 0.45 0.45 0.40 0.40Bending f estigkeit EN 310 N / mm² 20 20 18 15 14 14Bending Elasticity EN 310 N / mm² 1700 1700 1600 1500 1400 1200 modulus Ultralight MDF Nominal thickness ranges [mm] E igenschaft Prüf- v erfahren Einheit >9 >12 >30 >19 up to up to >45 up to 30 12 19 45 Thickness swelling EN 317 % 18 14 13 12 12 24 h Transverse tensile strength f estigkeit EN 319 N / mm² 0.15 0.15 0.15 0.13 0.13 Bending f estigkeitEN 310 N / mm² 7.7 6.9 6 5.1 5.1Bending modulus of elasticity EN 310 N / mm² 600 560 510 470 470 Table 2 lists the minimum requirements according to EN 622-5 for industrially manufactured MDF boards for the furniture sector. Experience has shown that fiberboards produced in the laboratory are 50% to 66% below the strength values ​​of comparable industrial fiberboards, which is why the reference board produced in the laboratory with a gross density of 550 kg / m³ and 650 kg / m³ without coffee content would currently not meet the requirements of EN 622-5. The boards with a gross density of 950 kg / m³ do achieve higher flexural strength and flexural moduli of elasticity than specified in EN 622-5, but their transverse tensile strength remains below the minimum requirements. In principle, it can be statedthat the production of laboratory fiberboards always results in compromises in board properties compared to industrially produced boards. This is due to the gluing,the manual scattering and the time between glue application and hot pressing. However, the low density scatter suggests a homogeneous distribution and, by laboratory standards, high-quality and well-glued boards. The influence of the density was significantly greater in relation to the glue content. Regarding strength and water storage, a consistently significant difference was observed essentially only in the density. The mean values ​​and standard deviations of all tested boards are summarized in Table 3. Table 3: Mean values ​​(MW) including standard deviation (STDEV) of all tested plate variants MW STDEV MW STDEV MW STDEV Transverse tensile Transverse tensile MW Bending STDEV Bending MW STDEV Thickness to Thickness labels Bulk density Bulk density strength strength E-modulus E-modulus Flexural strength Flexural strength [kg / m³] [kg / m³] [MPa] [MPa] [GPa] [GPa] strength [MPa] strength [MPa] [%] [%] RELAB-550-UF10 519.08 58.00 0.03 0.03 0.60 0.31 4.65 2.65 84% 64% ST20-550-UF10 554,28 30,26 0,05 0,02 0,64 0,12 4,79 0,86 33% 5% ST25-550-UF10 547,44 23,14 0,07 0,02 0,60 0,18 4,53 1,50 28% 3% ST30-550-UF10 545,30 40,15 0,08 0,02 0,59 0,14 4,71 1,32 37% 5% ST35-550-UF10 506,46 77,57 0,18 0,20 0,83 0,28 4,68 3,62 62% 55% ST40-550-UF10 570,93 58,79 0,13 0,09 0,87 0,28 6,16 3,58 37% 13% ST45-550-UF10 556,53 37,08 0,04 0,05 0,51 0,17 5,35 1,24 41% 7% REFLAB-650-UF10 635,98 18,68 0,19 0,08 1,96 0,35 18,52 4,57 26% 4% ST20-650-UF10 632,84 14,41 0,29 0,06 2,21 0,10 20,00 0,76 26% 1% ST25-650-UF10 648,35 42,28 0,08 0,03 1,47 0,19 9,44 2,74 41% 9% ST30-650-UF10 635,29 29,61 0,30 0,07 2,14 0,14 20,50 3,11 27% 4% ST35-650-UF10 642,16 15,23 0,09 0,06 1,67 0,39 11,68 5,84 41% 8% ST40-650-UF10 658,40 11,78 0,27 0,05 1,71 0,19 14,54 1,86 33% 1% ST45-650-UF10 645,15 15,63 0,31 0,06 1,55 0,18 13,89 2,34 29% 2% REFLAB2-650-UF-10 645,06 24,81 0,15 0,07 2,62 0,11 19,88 6,69 17% 8% ST55-650-UF-10 669,87 28,94 0,14 0,05 1,11 0,16 8,31 1,20 36% 9% ST65-650-UF-10 678,07 27,52 0,13 0,06 0,78 0,27 5,67 2,23 39% 14% ST75-650-UF-10 648,93 35,83 0,09 0,02 0,51 0,16 4,01 1,27 35% 6% REFLAB-950-UF-10 922,22 23,59 0,32 0,09 4,38 0,31 41,54 3,40 12% 3% INSTA20-950-UF-10 909,39 16,39 0,34 0,10 3,83 0,24 33,27 1,44 13% 1% INSTA35-950-UF-10 928,58 33,87 0,36 0,14 3,65 0,19 30,59 3,08 14% 5% INSTA45-950-UF-10 924,69 18,79 0,27 0,08 3,14 0,18 24,76 2,34 22% 2% RELAB-550-UF12 589,00 58,62 0,03 0,02 0,75 0,12 5,71 1,00 40% 4% ST20-550-UF12 558,47 31,17 0,07 0,03 0,92 0,21 5,92 1,62 25% 5% ST25-550-UF12 537,29 49,25 0,03 0,02 0,36 0,17 3,21 1,01 36% 5% ST30-550-UF12 546,18 33,72 0,07 0,03 0,66 0,15 4,68 1,12 30% 2% ST35-550-UF12 575,68 17,17 0,10 0,04 0,74 0,17 5,89 1,21 29% 3% ST40-550-UF12 541,30 30,25 0,06 0,02 0,37 0,17 3,32 0,94 39% 5% ST45-550-UF12 577,72 37,94 0,10 0,02 0,47 0,09 3,83 0,95 32% 3% REFLAB-650-UF12 659,65 24,52 0,27 0,11 2,24 0,31 20,25 4,32 22% 7% ST20-650-UF12 625,54 40,73 0,14 0,07 1,86 0,42 12,94 4,57 32% 6% ST25-650-UF12 660.57 22.12 0.13 0.03 1.91 0.23 13.73 2.09 34% 2% ST30-650-UF12 635.17 24.20 0.28 0.08 2.05 0.13 20.16 1.15 28% 3% ST35-650-UF12 663.87 16.84 0.13 0.03 1.80 0.20 14.20 2.22 29% 2% ST40-650-UF12 655.71 58.06 0.07 0.02 1.33 0.31 7.99 0.97 37% 4% ST45-650-UF12 637.69 24.94 0.32 0.10 1.67 0.14 15.63 1.80 25% 3% INSTA20-650-UF12 632.09 19.02 0.23 0.08 1.86 0.25 14.95 2.71 24% 6% INSTA25-650-UF12 635.56 24.34 0.20 0.04 1.88 0.23 15.78 2.42 24% 3% INSTA30-650-UF12 616.85 25.90 0.19 0.06 1.88 0.22 16.75 2.33 23% 2% INSTA35-650-UF12 635.36 28.01 0.19 0.05 1.56 0.21 13.07 2.49 23% 2% INSTA40-650-UF12 634.21 24.25 0.15 0.05 1.48 0.11 11.96 0.46 24% 3% INSTA45-650-UF12 637.27 19.09 0.24 0.03 1.41 0.19 11.96 2.18 21% 2% Based on the results of the tests carried out, it can be stated that although not all panels have fulfilled the minimum requirements of EN 622-5,However, at least in most cases, for the portafilter variant with a bulk density of 650 kg / m³ and a binder content of 10% up to a coffee grounds content of 45%, no statistically significant differences following a trend compared to the reference plates produced in the laboratory without coffee content can be detected. Assuming that, in the course of industrial production, plates with coffee grounds content can be produced with higher mechanical parameters and exhibit similar relationships as in the present patent application, a greater decrease in the mechanical parameters or a greater increase in mass and thickness after 24 hours of water storage would only be expected with an addition of >45% coffee grounds. Comparing the two coffee grounds variants, the somewhat lower scatter of the instant coffee plates is striking. Summary: In summary, it can be said that the properties of the plate according to the invention,in particular their MDF quality, is influenced by the following material and process parameters: - Particle size of coffee grounds: Smaller particles are better embedded between the fibers than larger particles. - Fiber length: Longer wood fibers are more flexible than shorter ones. This must be taken into account when using shorter wood fibers, such as those obtained from recycling waste products from the forestry, building materials, or furniture industries. - Drying method: The starting materials, wood fibers and coffee grounds, are dried to constant weight. This creates a free-flowing bulk material that can be easily stored and further processed. Furthermore, the proportions of wood fibers and coffee grounds, as well as the resin content, can be precisely calculated for the subsequent process. - Resin application: A homogeneous resin application is achieved whenwhen the resin is continuously applied to the preferably uniformly moving starting products. This also makes it possible to reduce the resin content to as little as 8%. In industrial production of the board according to the invention, the resin can be applied using a blowline process. - Pre-compaction: The homogeneous distribution of coffee grounds and wood fibers is significantly influenced after resin application if a type of board blank is produced that has been pre-compacted by cold pressing. - Target density: The target density of the boards is achieved using a pressing diagram with the parameters pressure and temperature. Taking these material and process parameters into account, it is routine for a person skilled in the art of wood fiber board production to carry out up-scaling to an industrial scale. Thus, the inventive,Resource-saving fiberboard made with coffee grounds can also be produced sustainably and successfully on an industrial scale. This means that not only large-scale technical parameters but also requirements for environmental compatibility and climate neutrality are met. Since MDF boards are primarily made from spruce wood, this raw material can be saved, especially since spruce is particularly vulnerable to climate change ("spruce dieback"). Furthermore, it must be considered that the ever-increasing global consumption of coffee makes waste disposal a problem. This is because vast quantities of coffee grounds would have to be burned, for example, which, of course, has a negative impact on the carbon footprint. The resource-saving fiberboard according to the invention can be provided in MDF and HDF qualities.Thus, areas of application include the construction and furniture industries (including the provision of coffins) and the automotive industry. Process for producing the resource-saving wood fiber board according to the invention on an industrial scale: A possible process for producing the resource-saving wood fiber board according to the invention on an industrial scale is described below using Fig. 7 as an example. First, wood fibers are produced from wood chips. The starting material for the wood chips is, for example, round wood 16 from the sawmill industry. The choice of wood species with regard to availability and quality can vary regionally. The most commonly used wood species are spruce, pine, and beech. The round wood 16 is first mechanically debarked. For this purpose, the round wood 16 is pressed against rotating knives 17,to remove the bark. The debarked logs 18 are then cut into a standard size using saws 19. In the next step, the debarked and cut logs 20 are cut into chips 22 by a disc chipper 21, each of which has a length of approximately 25-30 mm, a width of approximately 20-25 mm, and a thickness of approximately 4-6 mm. The oversized pieces resulting from this step are then screened out for further shredding. To remove soil and sand from the chips, they are washed in a device 23. In this step, the chips are also softened.to wash out the resins contained or to thaw frozen water residues. The softened wood chips are conveyed via a dewatering screw 24 to the pre-steam tank 25 and heated to approximately 100°C by supplying steam for 3-6 minutes. The wood chips then pass via a conveyor belt into the cooker 26, where they are heated to approximately 170°C with saturated steam. The heated wood chips are then mixed with the coffee grounds, and the mixture 31 is conveyed by means of a screw conveyor 27 to a thermomechanical pulping refiner, namely a defibrator 28, which consists of a stationary disc 30 and an axially adjustable, rotating disc 29 (both with a diameter of approximately 600 mm) at a rotation speed of approximately 1500 rpm.Centrifugal force pushes the wood chips and coffee grounds outward from the center of the discs, gradually shredding the wood chips into fiber bundles and individual fibers (fiber length between 1.0 mm and 5.0 mm, fiber diameter between 10 µm and 500 µm), while simultaneously allowing the coffee grounds to adhere to the fibers. The resulting wood fiber-coffee grounds mixture 31' is transported further via an air flow line 32 with a diameter of approximately 120 mm and fed to a blow line 33. There, the wood fiber-coffee grounds mixture 31' is accelerated by steam expansion, so that the resulting turbulence enables uniform gluing. For this purpose, a solution of urea-formaldehyde resin (UF glue) 35 is applied via water-cooled gluing nozzles 34 with an average droplet size of 25-80 µm, a droplet velocity of approximately 10-35 m / s, a volume flow density of approximately 0.1-0.4 cm, 3 / cm 2 / s and a throughput of approximately 3 t / h into the blow line 33. The glued wood fiber coffee grounds mixture 36 is then fed to a flash tube dryer 37. The flash tube dryer 37 consists of a pipeline that dries the wet material to the desired residual moisture content within a few seconds. Drying takes place indirectly using a steam heat exchanger. Following the gluing process, there is a forming strand 38 with a length of approximately 10 - 15 m. The glued fiber coffee grounds cake 39 is evenly spread onto this. This is followed by continuous pre-pressing 40 of the fiber coffee grounds cake 39 and subsequent trimming, followed by cutting 42 to the production size of approximately 750 x 260 cm. The main pressing takes place in a multi-stage press 41 with a pressing pressure of approximately 7 MPa, a pressing temperature of approximately 170°C, and a pressing time of approximately 6 minutes. After the pressing process, panel 1 has a material thickness of approximately19 mm and is cut to the target dimensions of 366 x 244 cm at 43 ° C. The boards are then stored for 7 days in a standard climate. Both the pressing time and the pressing pressure influence the density of the wood fiber board with coffee grounds according to the invention and the associated intended use and area of ​​application. Table 4 summarizes the boards produced according to the process diagram shown in Figure 7. Table 4: Overview of wood fiber boards with coffee grounds produced on an industrial scale. Coffee grounds. Wood fiber. Coffee grounds. R. ohdichte Boards Binder -proportion -proportion -typ -strength -anteilDescription 45% 55% portafilter 1105 8.02 14% UF fiber - kg / m³ mm GC8920_45_5 PORTAFILTER 45% 55% portafilter 1089 8.10 14% UF fiber - kg / m³ mm GC8920_45_6 PORTAFILTER 45% 55% portafilter 1156 7.62 12% UF fiber - kg / m³ mm GC8920_45_7 PORTAFILTER 45% 55% portafilter 1063 8.09 10% UF fiber - kg / m³ mm GC8920_45_8 PORTAFILTER 45% 55% Instant 983 7.89 12% UF fiber - kg / m mm GC8920_45_9 INSTANT 45% 55% Instant 787 18.87 12% UF Fiber - kg / m mm GC19720_45_6 INSTANT Total of manufactured boards 6 Explanation of terms: Fiber = pine wood fibers GC = ground coffee / coffee grounds 8920 = 8 mm, 920 kg / m3 19720 = 19 mm, 720 kg / m3 45 = coffee grounds content in % 1 to 6 = consecutive numbering of the boards PORTAFILTER = coffee grounds from portafilter coffee machines INSTANT = coffee grounds from instant coffee production UF = urea-formaldehyde resin The wood fiber boards with coffee grounds listed in Table 4 were measured in accordance with the standards applicable to medium-density fiberboards (MDF boards).The requirements for these MDF boards are summarized in Table 5. Table 5: Requirements for general-purpose boards for use in dry areas according to EN 622-5. Type MDF Nominal thickness ranges [mm] E. igenschaft Prüf- v erfahren Einheit 1.8 >2.5 >4 >6 >9 >12 >19 >30 to to to to to to to to >45 2.5 4 6 9 12 19 30 45 Thickness swelling 2 4 h EN 317 % 45 35 30 17 15 12 10 8 6Transverse tension f estigkeit EN 319 N / mm² 0.65 0.65 0.65 0.65 0.60 0.55 0.55 0.50 0.50Bending f estigkeit EN 310 N / mm² 23 23 23 23 22 20 18 17 15Bending Elasticity EN 310 N / mm² - - 2700 2700 2500 2200 2100 1900 Modulus Type Light MDF Nominal thickness ranges [mm] E igenschaft Prüf- v erfahren Einheit >6 >9 >12 >19 >30 to to to to to >45 9 12 19 30 45 Thickness swelling 2 4 h EN 317 % 20 16 14 12 11 11Transverse tension f estigkeit EN 319 N / mm² 0.45 0.45 0.45 0.45 0.40 0.40Bending f estigkeitEN 310 N / mm² 20 20 18 15 14 14 Flexural modulus of elasticity EN 310 N / mm² 1700 1700 1600 1500 1400 1200 Table 5 shows that the properties of the boards are divided into nominal thickness ranges. To enable a comparison between the boards according to the invention and the standardized MDF boards,The properties of the plates according to the invention with a nominal thickness between 6 and 9 mm are listed in Table 6a. Table 6a: Measurement results of industrially produced wood fiber boards with coffee grounds with a nominal thickness between 6 mm and 9 mm Requirements Fiber Fiber Fiber Fiber Fiber Fiber Fiber Parameters acc. to GC8920_45_ GC8920_45_ GC8920_45_ GC8920_45_ GC8920_45_ EN 622- 5 6 7 8 9 5 PORTAFILTER PORTAFILTER PORTAFILTER INSTANT Type of Pine Pine Pine Pine Pine Wood fibers Binder content 14% UF 14% UF 12% UF 10% UF 12% UF Pressing time 4 min 45 s 4 min 40 s 5 min 30 s 5 min 50 s 5 min 15 s Pressing temperature 165°C 165°C 165°C 165°C 165°C Moisture content before pressing 7.15% 7.80% 6.45% 5.27% 6.30% Elastic modulus >2700 3191 3003 2599 2477 2980 (N / mm) N / mm Flexural strength >23 39 36 38 22 31 (N / mm) N / mm Thickness ±0.2 8.02 8.10 7.62 8.09 7.89 (mm) mm Density >830 1105 1089 1156 1063 983 (kg / m) kg / m Transverse tensile strength >0.65 1.22 1.71 0.97 0.56 0.83 (N / mm) N / mm Thickness swelling <17 15.68 11.05 9.35 8.34 10.92 (%) % Moisture 4 – 11 5.98 5.61 5.74 5.21 6.76 content (%) % To enable a further comparison between the boards according to the invention and the standardized MDF boards, the properties of a board according to the invention with a nominal thickness between 12 mm and 19 mm are shown in Table 6b. Table 6b: Measurement results of an industrially produced wood fiber board with coffee grounds with a nominal thickness between 12 mm and 19 mm Fiber requirements GC19720_45_6 according to EN 622-5 INSTANT Type of wood fibers Pinewood Binder content 12% UF Pressing time 5 min 45 s Pressing temperature 165°C Moisture content 6.97% before pressing Elastic modulus >2200 2387 (N / mm) N / mm Bending strength >20 26 (N / mm) N / mm Thickness ±0.2 18.87 (mm) mm Density >760 787 (kg / m) kg / m Transverse tensile strength >0.55 0.52 (N / mm) N / mm Thickness swelling <12 8.12 (%) % moisture content 4 – 11 6.95 (%) % The measurement results presented in Tables 6a and 6b show that even industrially produced wood fiberboards made with coffee grounds meet the requirements of the applicable standard EN 622-5. This is surprising because wood fibers and coffee grounds are different materials and – see Table 4 – are present in almost equal proportions, namely 45% coffee grounds and 55% wood fibers. The measurement results thus demonstrate that the production of wood fiberboards with coffee grounds is not only technically feasible, but also suitable for the full use and application range of conventional wood fiberboards.

Claims

Claims:

1. A wood fiberboard with a solids content of wood fibers bonded with a urea-formaldehyde resin, characterized in that the wood fiberboard contains coffee grounds, and that the solids content of coffee grounds is at most 80 wt.%.

2. A wood fiberboard according to claim 1, characterized in that the solids content of coffee grounds is between 20 wt.% and 45 wt.%.

3. A wood fiberboard according to claim 1 or 2, characterized in that the coffee grounds are a waste product that arises during the production of coffee beverages using a portafilter.

4. A wood fiberboard according to claim 3, characterized in that the coffee grounds have an average particle size between 125 µm and 2000 µm.

5. A wood fiberboard according to claim 1 or 2, characterized in that the coffee grounds are a waste product that arises during the production of instant coffee.Wood fiberboard according to claim 5, characterized in that the average particle size is between 125 µm and 2000 µm.

7. Wood fiberboard according to one of claims 1 to 6, characterized in that the wood fibers are softwood fibers and / or wood fibers obtained by recycling.

8. Wood fiberboard according to one of claims 1 to 7, characterized in that the amount of urea-formaldehyde resin is at least 8 wt. %, preferably in a range from 10 wt. % to 12 wt. %, based on 100 wt. % of the sum of wood fibers and coffee grounds.

9. Wood fiberboard according to one of claims 1 to 8, characterized in that its density is in the range from 500 kg / m³ to 1000 kg / m³, preferably up to 950 kg / m³.

10. Wood fiberboard according to claim 3, characterized in that it has a solids content of 20 wt.% to 45 wt.% of portafilter coffee grounds and a content of 10 wt.% to 12 wt.%, based on 100 wt.% of the sum of wood fibers and coffee grounds, of urea-formaldehyde resin, and that the bulk density of the wood fiberboard has a value of 500 kg / m³ to 600 kg / m³, in particular of 550 kg / m³.

11. Wood fiberboard according to claim 5, characterized in that it has a solids content of 20 wt.% to 45 wt.% of instant coffee grounds and a proportion of 10 wt.% to 12 wt.%, based on 100 wt.% of the sum of wood fibers and coffee grounds, of urea-formaldehyde resin, and the raw density of the wood fiberboard has a value of 500 kg / m³ to 600 kg / m³, in particular of 550 kg / m³.

12. Wood fiberboard according to claim 3, characterized in that it has a solids content of 20 wt.% to 45 wt.% of portafilter coffee grounds and a proportion of 10 wt.-% to 12 wt.%, based on 100 wt.% of the sum of wood fibers and coffee grounds, of urea-formaldehyde resin, and that the raw density of the wood fiberboard has a value of 600 kg / m³ to 700 kg / m³, in particular of 650 kg / m³.

13. Wood fiberboard according to claim 5, characterized in that it has a solids content of 20 wt.% to 45 wt.% of instant coffee grounds and a content of 10 wt.% to 12 wt.%, based on 100 wt.% of the sum of wood fibers and coffee grounds, of urea-formaldehyde resin, and that the raw density of the wood fiberboard has a value of 600 kg / m³ to 700 kg / m³, in particular of 650 kg / m³.

14. Wood fibre board according to claim 3, characterized in that it has a solids content of 20 wt.% to 45 wt.% of portafilter coffee grounds and a content of 10 wt.% to 12 wt.%, based on 100 wt.-% of the sum of wood fibres and coffee grounds, of urea-formaldehyde resin, and that the raw density of the wood fibreboard has a value of 900 kg / m³ to 1,000 kg / m³, in particular 950 kg / m³.

15. Wood fiberboard according to claim 5, characterized in that it has a solids content of 20 wt.% to 45 wt.% of instant coffee grounds and a content of 10 wt.% to 12 wt.%, based on 100 wt.% of the sum of wood fibers and coffee grounds, of urea-formaldehyde resin, and the bulk density of the wood fiberboard has a value of 900 kg / m³ to 1,000 kg / m³, in particular 950 kg / m³. 16.A method for producing a board according to any one of claims 1 to 15, comprising the following steps: a) drying the starting products of wood fibers and coffee grounds to constant weight, b) calculating the desired ratios between wood fibers and coffee grounds and the proportion of urea-formaldehyde resin, c) continuously applying the urea-formaldehyde resin to the dried wood fiber-coffee grounds mixture, d) homogeneously scattering to produce a board blank, e) pre-compacting the board blank by cold pressing, and f) producing the wood fiber board with coffee grounds by pressing at elevated pressure and elevated temperature.

17. The method according to claim 16, characterized in that the drying of the starting products of wood fibers and coffee grounds is carried out by means of the kiln-dried method. 18.A method according to claim 16 or 17, characterized in that the urea-formaldehyde resin is continuously applied as a fine mist to the dried wood fiber-coffee grounds mixture.

19. A method for producing a board according to one of claims 1 to 15, comprising the following steps: a) Calculating the desired ratios between wood fibers and coffee grounds as well as the proportion of urea-formaldehyde resin, b) Producing wood chips from wood, c) Thermomechanically breaking down the wood chips to produce wood fibers and mixing them with the coffee grounds in a defibrator, d) Continuously gluing the wood fiber-coffee grounds mixture with a solution of urea-formaldehyde resin in a moving air stream (blow line), e) Homogeneously scattering the glued wood fiber-coffee grounds mixture to produce a wood fiber-coffee grounds cake, f) Producing a board blank by pre-pressing, and g) Producing the wood fiber board with coffee grounds by pressing at elevated pressure and elevated temperature.

20. Use of a board produced according to claim 19 for the construction and furniture industry.

21. Use according to claim 20, characterized in that the board used has a thickness of 1.8 mm to 65 mm. 22.Use according to claim 20, characterized in that the board used has a density of 500 kg / m³ to 2000 kg / m³.

23. Use according to claim 20, characterized in that the board used has a density of 110 to 270 kg / m³ and is used for insulation purposes.

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