AT526772B1 - Wood fibreboard and method for producing a wood fibreboard - Google Patents

Abstract

The invention relates to a resource-saving wood fiber board with coffee grounds, in which the wood fibers and the coffee grounds are bonded with a urea-formaldehyde resin. The coffee grounds are waste products that accrue during the production of coffee using a portafilter or during the production of instant coffee. If a solids content of coffee grounds between 20% and 45% is used, the technical properties of the board according to the invention are in the range of MDF standards when manufactured industrially.

Description

Description

[0001] The invention relates to a wood fiber board with a solid content of wood fibers and coffee grounds, which are bonded with a urea-formaldehyde resin, and a process for the production thereof.

[0002] The resource "wood" has become valuable worldwide and especially in Europe due to climate change, as many trees are under massive threat due to heat and drought. Pests are also spreading extremely quickly, so that forests have to be cleared, but subsequent reforestation takes decades. Wood should also be used as sparingly as possible in terms of the CO2 balance.

[0003] On the other hand, there is an extremely wide range of applications for wood fibre boards with very different requirements in terms of technical properties, in particular mechanical strength. Examples include the use of wood fibre boards in the construction and furniture industries, the funeral industry and the automotive industry.

[0004] In order to save resources, Poo Chow suggested in his 1976 publication "The Use of Crop Residues for Boardmaking", Environmental Conservation, Vol. 3, No.1, Spring 1976, pages 59-62, that typical waste products from US agriculture, such as peanut shells, be mixed with another waste product, including coffee grounds, glued together with a urea resin (UF glue) and pressed into a board. In a series of tests, maple shavings from a furniture factory were also added and a chipboard was produced, which, however, is unsuitable for use as a load-bearing element in the construction industry due to its low bending elasticity.

[0005] WO-A2-2018/078391 discloses a process in which agricultural waste products, namely straw fibers, are pressed into panels. Another waste product, namely coffee grounds, is used as an additive. In addition, the teaching according to WO-A2-2018/078391 is based on the task of dispensing with formaldehyde-containing adhesive resins and instead using pMDI (polymeric diphenylmethane diisocyanate) to bond the starting materials. However, pDMDI is very 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. In addition, pMDI must under no circumstances come into contact with the skin, let alone be inhaled. The safety precautions during processing are also correspondingly more complex. Therefore, not every company can process pMDI. The use of pMDI is therefore disadvantageous.

[0006] WO 2022/073078 A1 discloses plastic composites in the production of which recycled products such as coffee grounds are used. Other recycled materials are jute fibers and sawdust.

[0007] From the publication by Yang, In ET AL: "Manufacture and Performance Evaluation of Medium-density Fiberboard Made with Coffee Bean Residue-Wood Fiber", Journal of the Korean Wood Science and Technology, Vol. 41, No. 4, July 25, 2013 (2013-07-25), pages 293-301 and KR-A-2015/0028029, wood fiberboards in MDF quality are known in which the wood fibers are bonded with a urea-formaldehyde resin during production. Since formaldehyde is harmful to health, it is proposed that any formaldehyde released be adsorbed on an additive. This additive is specifically coffee grounds. It was found that a proportion of coffee grounds of no more than 9% is sufficient to adsorb released formaldehyde. Furthermore, the data contained in these previous publications indicate an increasing deterioration in the strength values of the panels produced in this way with increasing proportion of coffee grounds.

[0008] The object of the present invention is to provide a wood fiber board which requires less of the natural resource wood in favor of coffee grounds and yet has satisfactory product properties, some of which even correspond to relevant standards, and can be manufactured in conventional production facilities.

[0009] This object is achieved with a wood fiber board having the features of claim 1.

[0010] This object is further achieved by a method having the features of claim 15.

[0011] Preferred embodiments of the invention are the subject of the subclaims.

[0012] The invention essentially consists in the fact that the wood fibre board contains not only wood fibres as a solid component but also coffee grounds as a solid component.

[0013] According to the invention, the proportion of coffee grounds is between 20% by weight and 45% by weight, because in this case strength values are achieved which correspond to the standards of a pure wood fibre board.

[0014] According to the invention, coffee grounds are preferably used, which are a waste product or residue from coffee preparation or coffee production.

[0015] Coffee grounds resulting from the production of instant coffee typically have an average particle size of 125 µm to 2000 µm.

[0016] Coffee grounds resulting from the production of coffee beverages using a portafilter have an average particle size of 125 µm to 2000 µm.

[0017] Both coffee grounds variants can be used equally in the invention and have the advantage that they are available worldwide in very large quantities and have essentially equally good product properties for the present invention.

[0018] The use of urea-formaldehyde resin as a binder should of course be carried out in the smallest possible amounts, whereby 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.

[0019] This means that, for example, with a non-inventive proportion of 80% by weight of coffee grounds and 20% by weight of wood fibers, these proportions together make up 100% of the solids content. If, for example, 10% by weight of urea-formaldehyde resin is added, this means that the 100% by weight of the finished board is made up of 90% by weight of solids content (coffee grounds and wood fibers) and 10% by weight of urea-formaldehyde resin.

[0020] With such a proportion of binder, a very uniform 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 the tests on a laboratory scale have shown that a proportion of 10% by weight to 12% by weight of urea-formaldehyde resin leads to very uniform 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 production of the board according to the invention on an industrial scale.

[0021] The density of the wood fiber board according to the invention is in the range from 500 kg/m*® to 1,000 kg/m®, preferably in the range from 550 kg/m? to 950 kg/m®. Boards with a density in these ranges are boards used in many areas of application, in which the board according to the invention can also achieve the good technical properties explained in detail below.

[0022] 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. It shows:

[0023] Fig. 1 is an exemplary process diagram,

[0024] Fig. 2 is a diagram showing the bulk density of all fibreboards produced and examined,

[0025] Fig. 3 is a diagram showing the bending strength of all the fibreboards produced and tested,

[0026] Fig. 4 is a diagram showing the elastic modulus of all the fibreboards produced and tested,

[0027] Fig. 5 is a diagram showing the transverse tensile strength of all the fibreboards produced and tested, and

[0028] Fig. 6 is a diagram showing the increase in length, thickness and mass after 24 hours of water storage of all manufactured and examined fiberboards.

[0029] In the following, the invention is explained in more detail using an exemplary and non-limiting working instruction for producing a wood fiber board according to the invention.

[0030] Whenever percentages are given below, they are always by weight.

[0031] The wood fiber boards developed within the scope of the present invention were produced using different types of coffee grounds.

[0032] As already mentioned, coffee grounds include waste products or residual materials that accrue during the production of coffee beverages using a portafilter. This type of coffee grounds is abbreviated to ST in the following.

[0033] Another waste product used in the invention in the form of coffee grounds arises during the production of instant powder for soluble coffee. This type of coffee grounds is abbreviated to INSTA below. The average particle size is usually between 125 µm and 2000 µm.

[0034] The proportions of portafilter coffee and instant coffee used for both coffee variants were - in 5% increments - from 20% to 45% and additionally - as non-inventive embodiments for illustration purposes - 55%, 65% and 75% for the portafilter variant.

[0035] As is usual in the industrial production of fiberboards, a common urea-formaldehyde resin with different binder contents (10% and 12%) was used.

[0036] A urea-formaldehyde resin (UF) was deliberately chosen because it is very reactive and therefore binds well and quickly. Furthermore, the resin can be worked onto the wood fibers in conventional systems without the need for additional technical equipment.

[0037] The wood fibers used were MDF quality, as is also standard in industry. The fibers were preferably softwood fibers, for example spruce fibers or a mixture of spruce and pine.

[0038] However, it is also possible to use recycled fibers from wood fiber materials. In the event that recycling results in damage to the fibers, such as shortening of the fiber length, which is unacceptable for the particular application, the recycled fibers can also be combined with fresh wood fibers in order to achieve the desired mechanical properties.

[0039] The wood fiber boards with coffee grounds according to the invention were produced with a target density of 550 kg/m*® and 650 kg/m® and with a coffee grounds content of between 20% and 45% (in 5% increments). The binder contents were 10% and 12%, respectively.

[0040] In addition, boards with instant coffee grounds contents of 20%, 35% and 45%, a binder content of 10% and a bulk density of 950 kg/m3 were produced.

[0041] In a further series of tests - as non-inventive embodiments for illustration purposes - portafilter coffee grounds proportions of 55%, 65% and 75% were used for portafilter coffee plates with 650 kg/m®.

[0042] Finally, for comparison, corresponding reference plates without the addition of coffee (each with the designation REFLAB and further information) were prepared.

[0043] 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 to size using a circular saw and examined for their flexural strength, their flexural elastic modulus (EN 310), and their transverse tensile strength (EN 319) and thickness swelling after 24 hours of water storage (EN 317), and the data were evaluated and interpreted.

[0044] The manufacturing steps for carrying out the general working procedure are described below, whereby - for the sake of illustration only - reference is made to the process diagram according to Fig. 1.

[0045] In Fig. 1, a wood fiber board 1 with coffee grounds, the wood fibers 2, the coffee grounds 3, measuring devices 4 for measuring the moisture content by means of 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 are shown.

[0046] The parameters described in the manufacturing process were independent of the desired bulk density and were identical for ultra-light MDF, light MDF and MDF boards with higher bulk densities. The production of the boards differed essentially only in the total board mass, which was weighed per defined volume.

[0047] 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 drying method. A few grams of samples were taken from the respective materials, weighed and then the samples were stored at a drying temperature of 103 °C until the weight was constant. The moisture content was then determined based on the difference between the moist and the dried sample. All ratios in the board composition were related to the dried mass or the dry solids content.

[0048] Based on the dried 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 production process on a laboratory scale due to the gluing process, a 10% safety margin (additional weight) was used for the gluing for all components.

[0049] The mixing of wood fibers and coffee grounds, as well as their gluing, took place 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 into the drum without being mixed. The gluing process began immediately after the set rotation speed was reached. The mixing and gluing took place in the same work step and took between 5 and 10 minutes until the gluing container was empty, which depended on the amount of glue.

[0050] 2% ammonium sulfate was added to the UF glue as a hardener. The glue was then applied using a pneumatic glue gun that was inserted centrally into the gluing drum. The feed pressure and the feed volume were selected so that a fine adhesive mist was formed in the gluing drum without the formation of large droplets, in order to achieve the most homogeneous possible glue distribution on the fibers. The glued fiber/coffee grounds mixture was then removed from the drum and the final mass (without a safety margin) was weighed.

[0051] The weighed glued fiber/coffee grounds material was spread by hand as homogeneously as possible into a 250 x 250 mm plate 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-compacting step in the frame is important because the fiber cake spreads out within the plate plane if pre-compacting is insufficient during hot pressing.

stretched so that the target density cannot be achieved.

[0052] 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 was carried out. Hot pressing was carried out 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 up to the spacers with a maximum pressure of 3 MPa.

[0053] After completion of the pressing process, the plates were placed vertically to allow even cooling and stored for at least 7 days in a standard climate at 20 °C and 65% relative humidity before further testing for conditioning.

[0054] The following Table 1 lists all manufactured and tested plate variants.

[0055] Table 1: Overview of fiberboards produced on a laboratory scale

KaTceSalz Holziaser- Coffee grounds type | Bulk density Pindemilter Description 0% 100 % X 550 kg/m? 10% REFLAB-550-UF10 20 % 80 % portafilter 550 kg/m) 10% ST20-550-UF10 25% 75% portafilter 550 kg/m? 10% ST25-550-UF10 30 % 70 % portafilter 550 kg/m? 10% ST30-550-UF10 35% 65 % portafilter 550 kg/m? 10% ST35-550-UF10 40 % 60 % portafilter 550 kg/m) 10% ST40-550-UF10 45 % 55 % portafilter 550 kg/m) 10% ST45-550-UF10 0% 100 % X 650 kg/m? 10% REFLAB-650-UF10 20 % 80 % portafilter 650 kg/m? 10% ST20-650-UF10 25% 75% portafilter 650 kg/m? 10% ST25-650-UF10 30 % 70 % portafilter 650 kg/m) 10% ST30-650-UF10 35 % 65 % portafilter 650 kg/m) 10% ST35-650-UF10 40 % 60 % portafilter 650 kg/m? 10% ST40-650-UF10 45 % 55 % portafilter 650 kg/m? 10% ST45-650-UF10 0% 100 % X 650 kg/m? 10% REFLAB2-650-UF-10 55 % 45 % portafilter 650 kg/m) 10% ST55-650-UF-10 65 % 35% portafilter 650 kg/m? 10% ST65-650-UF-10 75% 25% Portafilter 650 kg/m? 10% ST75-650-UF-10 0% 100 % X 950 kg/m? 10% REFLAB-950-UF-10 20 % 80 % Instant 950 kg/m? 10% INSTA20-950-UF-10 35% 65 % Instant 950 kg/m) 10% INSTA35-950-UF-10 45 % 55 % Instant 950 kg/m? 10% INSTA45-950-UF-10 0% 100 % X 550 kg/m? 12% REFLAB-550-UF12 20 % 80 % Portafilter 550 kg/m? 12% ST20-550-UF12 25 % 75% portafilter 550 kg/m) 12% ST25-550-UF12 30 % 70 % portafilter 550 kg/m) 12% ST30-550-UF12 35% 65 % portafilter 550 kg/m? 12% ST35-550-UF12 40 % 60 % portafilter 550 kg/m? 12% ST40-550-UF12 45 % 55 % portafilter 550 kg/m? 12% ST45-550-UF12 0% 100 % X 650 kg/m) 12% REFLAB-650-UF12 20 % 80 % portafilter 650 kg/m? 12% ST20-650-UF12 25 % 75 % Portafilter 650 kg/m) 12% ST25-650-UF12 30 % 70 % Portafilter 650 kg/m) 12% ST30-650-UF12 35 % 65 % Portafilter 650 kg/m? 12% ST35-650-UF12 40 % 60 % Portafilter 650 kg/m? 12% ST40-650-UF12 45 % 55 % Portafilter 650 kg/m? 12% ST45-650-UF12 20 % 80 % Instant 650 kg/m) 12% INSTA20-650-UF12

25 % 75% Instant 650 kg/m? 12% INSTA25-650-UF12 30 % 70 % Instant 650 kg/m? 12% INSTA30-650-UF12 35 % 65 % Instant 650 kg/m? 12% INSTA35-650-UF12 40 % 60 % Instant 650 kg/m? 12% INSTA40-650-UF12 45 % 55% Instant 650 kg/m? 12% INSTA45-650-UF12 Total panels produced 126

[0056] To determine the transverse tensile strength and the water storage, samples measuring 50 x 50 mm were prepared using a circular saw, 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.

GROSS DENSITY

[0057] The density determination was carried out after conditioning in standard climate (20 °C and 65 % relative humidity) on three 50 x 50 mm samples per plate.

[0058] The diagram in Fig. 2 shows the bulk density of all fiberboards examined.

[0059] As can be seen from Fig. 2, all desired 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. Thus, no significant connection can be determined between density and coffee grounds content or binder content. This means that the density of the board does not change significantly, even if the proportion of coffee grounds or binder content 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 drying method for both the wood fibers and the types of coffee grounds (portafilter coffee grounds and instant coffee), and that the desired ratios between wood fibers and coffee grounds as well as the respective glue content are calculated based on the drying mass and then related to the actual moist mass (determined moisture content).

[0060] Of course, the homogeneous production of the fibre cake and its pre-compaction also have an influence on the bulk density.

BEND STRENGTH AND BEND MODULE OF ELASTICITY

[0061] The bending strength and the bending elastic modulus provide information about the influence of the wood fiber content used, since fibers generally have a positive effect on the bending properties of materials due to their geometry. Three bending tests were carried out on the panels in accordance with EN 310, and the bending strength and the bending elastic modulus were determined using the crossbar (Zwick and Roell Z20 universal testing machine). A statistical mean value comparison was then carried out (PostHoc Scheffe, p=0.05).

[0062] For this purpose, the samples were positioned in a 3-point bending test setup, with the support distance corresponding to 20 times the plate thickness (approx. 180 mm support distance).

[0063] The loading rate was adjusted so that the breaking force was reached within 60 + 30 sec.

[0064] Fig. 3 shows a diagram with the bending strength according to EN 310 of all produced fibreboards.

[0065] 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 group with 550 kg/m*® show a lower strength compared to the group with 650 kg/m® or 950 kg/m®. No statistically significant differences can be found between the panels with coffee content and the reference panels without coffee (each with the designation REFLAB and further information).

[0066] In the case of the boards with 650 kg/m* 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. If one looks at 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 one assume a certain trend with decreasing bending strength as the coffee grounds content increases. The boards only show a noticeable difference to the reference boards from 55% onwards and above.

[0067] It can therefore be stated that the flexural strength at a bulk density of 550 kg/m? or 650 kg/m® and a binder content of 10% or 12% does not change significantly by adding coffee grounds up to 45% and results in surprisingly good values.

[0068] In the case of the instant coffee plates with a bulk density of 950 kg/m2, the plates differ noticeably from the reference plates even at a coffee grounds content of 20%. However, higher bending strength values can be achieved here than with the plates with a lower bulk density, and plates with a bulk density of 950 kg/m2 are therefore also preferred within the scope of the invention.

[0069] It has been shown that the binder content in the variants investigated (10% and 12%) has no significant influence on the flexural strength.

[0070] Fig. 4 shows a diagram with the modulus of elasticity according to EN 310 of all produced fibreboards.

[0071] A similar picture to that of 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 proportions can only be seen in the 650 kg/m? plates. Here, both coffee variants show a tendency, but not a statistically significant decrease, in the modulus of elasticity with increasing coffee grounds proportion. Here, too, the conditions for the plates with 950 kg/m* bulk density are almost identical to those for the flexural strength. The only notable exception here are the values for instant coffee, which have lower values than the reference laboratory plate for a coffee grounds proportion of 35% and above.

[0072] It can also be stated that the modulus of elasticity does not change significantly at a bulk density of 550 kg/m® or 650 kg/m*®* and a binder content of 10% or 12% by adding coffee grounds up to 45% and results in surprisingly good values.

TRANSVERSE TENSILE STRENGTH

[0073] 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 positive for the mechanics of a board, such as the fiber length, are of lesser importance here.

[0074] For the investigations, three samples per plate were tested according to EN 319 and then a statistical mean comparison (PostHoc Scheffe, p=0.05) was carried out. For the investigation, the 50 x 50 mm samples were glued to aluminum transverse tensile yokes using hot melt adhesive (Henkel Technomelt Supra 325 HT). The offset between the two yokes was 90° in order to avoid any torque during the tensile test and thus prevent cracking.

[0075] Fig. 5 shows a diagram with the transverse tensile strength according to EN 319 of all produced fibreboards.

[0076] Fig. 5 shows the absolute values of the measured transverse tensile strength, whereby differences between the two density ranges can be seen here too, and the higher density has the highest transverse tensile strength. In general, there is a very high scatter of values for portafilter coffee, whereby it should be noted that for the two reference plate variants

ants with 650 kg/m* and 10% binder, no statistical difference can be determined. Even if individual plate variants show statistically significant differences to their plates with a similar coffee content, overall there is no significant difference to the reference plates. An example of this is the portafilter plates with 10% binder, where the plate with 45% coffee differs from the variant with 35%, but not from the variants with 40%, 30% or 20% coffee. The situation is similar for the portafilter plates with 12% binder. It is interesting to note that the scatter of the portafilter plates decreases with increasing coffee grounds content and that the plates which were manufactured as non-inventive embodiments for illustration purposes 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 also not in total from the entire group.

[0077] In the instant coffee plates, a tendency towards a decrease in strength can be seen with increasing coffee content, but here too, due to the scatter, one cannot speak of a statistically significant difference between the plates. Based on the results obtained, no difference can be seen between 10% and 12% binding agent content in the portafilter plates.

[0078] Since all plates were manufactured using the same means, the variation of the portafilter plates at 650 kg/m* bulk density can probably be attributed to the portafilter material. In comparison to instant coffee grounds, a higher degree of agglomeration was subjectively found in the portafilter set during processing during gluing in the gluing drum. This could have led to partially more varied coffee grounds proportions in the plates and thus also explain the variation. Even if values for individual variants appear higher here, they are still within the range of variation in relation to the reference and no significant difference can be assumed based on the available values. The values determined can therefore be interpreted in such a way that at 650 kg/m? there was a reduction in the transverse tensile strength for instant coffee with higher coffee proportions 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 that with varying mixing ratios of the boards, 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 content has a much higher volume when glued than a mixture with 45% coffee grounds or more. This means that the gluing drum is filled much more with low coffee grounds content than with mixtures with high coffee grounds content. This can significantly influence the distribution of the glue on 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 content in the gluing process used.

[0079] Overall, it can be stated that wood fibre boards with a coffee grounds content of 20% to 45% have surprisingly good values for both the bending strength and the bending elastic modulus, as well as the transverse tensile strength, when they are bonded with a urea-formaldehyde resin, and this in a density range of 550 kg/m® to 950 kg/m®,

[0080] This applies to both instant coffee grounds and portafilter coffee grounds.

THICKNESS SWELLING AFTER 24 H WATER STORAGE

[0081] For water storage, three samples per plate were placed in a water bath (water temperature approx. 20 °C) and fixed under the water surface using a metal sieve.

[0082] The lengths, thicknesses and mass increase of 50 x 50 mm samples were determined after 24 hours of water storage. For this purpose, the samples were simply dabbed lightly after the water bath and measured.

[0083] Fig. 6 shows a representation of the increase in length, thickness and mass after 24 hours of water storage according to EN 317

[0084] In Fig. 6, a difference between the two density ranges is again shown.

The most obvious difference is in the values for mass increase, with the boards with the lower binder content tending to gain more mass, and with higher coffee contents, sometimes significantly higher mass increases can be seen compared to the reference. The 550 kg/m*® boards also show a significantly higher increase in thickness swelling than the 650 kg/m® boards. The boards with instant coffee and a bulk density of 950 kg/m? showed the lowest values, with statistically significantly higher increases being seen with increasing coffee grounds content. 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 content.

[0085] In the case of the portafilter plates with a bulk density of 650 kg/m*® and a binder content of 10%, statistically significant differences to the reference plates can only be determined in the mass increase of the plate variant that was produced as non-inventive embodiments for illustration purposes with 75% coffee grounds. All other variants do not differ significantly from one another in terms of either the mass increase or the thickness swelling, whereby in the case of the plates that were produced as non-inventive embodiments for illustration purposes with coffee grounds contents of >45%, a trend with increasing values as the coffee grounds content increases can be determined. Even in the case of the plates with instant coffee and a density of 650 kg/m®, no statistically significant differences between the different coffee grounds contents can be determined.

[0086] Interestingly, even during water storage, no difference can be observed between the two binder contents of 10% and 12%.

[0087] With regard to the different properties after water storage, however, it should be added that the fact that some of the tested boards tend to have poorer properties does not in any way indicate that their use is not advisable, because, as with the mechanical strength, it depends on the respective intended use of the boards whether a particular composition of a wood fibre board according to the invention is suitable or not.

EVALUATION OF MEASUREMENT RESULTS

[0088] All findings obtained in the course of the general working procedure for carrying out the invention relate to a wood fibre board with coffee grounds produced in the laboratory.

[0089] However, due to the good measurement results, up-scaling to an industrial scale is realistic, especially if the plate is used in dry areas.

[0090] Table 2: Requirements for general purpose boards for use in dry conditions according to EN 622-5

Type MDF

Nominal thickness ranges [mm]

. Test . . Property Unit | 1.8 |>2.5| >4 | >=6 | >9 | >12 | >19 | >30 procedure up to | up to | up to | up to | up to | up to | up to | >45 25| 4 | 6 | 9 | 12 | 19 | 30 | 45

Thickness swelling

24h EN 317% 45 | 35 | 30 | 17 | 15 | 12 | 10 8 6

Cross-tension

US EN 319 | N/mm? | 0.65 | 0.65 | 0.65 | 0.65 | 0.60 | 0.55 | 0.55 | 0.50 | 0.50 strength

Bending

2 strength EN 310 | N/mm 2323 |23 | 23 | 22 | 20 | 18 | 17 | 15

Bending elasticity EN 310 | N/mm? 2700 | 2700 | 2500 | 2200 | 2100 | 1900 modulus

Type Light MDF

Nominal thickness ranges [mm]

Property Fa Unit | >6 | >9 | >12 | >19 | >30 process up to | up to | up to | up to >45 9 | 12 | 19 | 30 | 45 Corner swelling EN 317 % 20 | 16 | 14 | 12 | 11 11 Transverse tensile EN 319 | N/mm? | 0.45 | 0.45 | 0.45 | 0.45 | 0.40 0.40 Bending strength EN 310 | N/mm? | 20 | 20 | 18 | 15 | 14 14 Bending strength Elasticity | EN310 | N/mm? |1700 | 1700 | 1600 | 1500 | 1400 1200 Modulus Ultralight MDF Nominal thickness ranges [mm] Property Fa Unit | >9 | >12 | >19 | >30 process up to up to up to >45 12 | 19 | 30 | 45 Corner swelling EN 317 % 18 | 14 | 13 | 12 12 Transverse tensile strength EN 319 | N/mm? | 0.15 | 0.15 | 0.15 | 0.13 0.13 Bending strength EN 310 | N/mm? | 7.7 | 69 | 6 | 51 5.1 Bending elasticity | EN 310 | N/mm? | 600 | 560 | 510 | 470 470 modulus

[0091] Table 2 shows 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 density of 550 kg/m® and 650 kg/m*®* without coffee content would currently not meet the requirements of EN 622-5. The boards with a density of 950 kg/m® achieve higher bending strength and bending elastic moduli than those provided for in EN 622-5, but remain below the minimum requirements in terms of transverse tensile strength.

[0092] In principle, it can be stated that the production of laboratory fiberboards always results in compromises in terms of board properties compared to industrially produced boards. This is due to the gluing, the manual spreading and the time between glue application and hot pressing. However, the low density scatter suggests a homogeneous distribution and, for laboratory conditions, high-quality and well-glued boards. The influence of the density was significantly greater in relation to the glue content. In terms of strength and water storage, a consistently significant difference could essentially only be observed in the density. The mean values and standard deviations of all tested boards are summarized in Table 3.

[0093] Table 3: Mean values (MW) including standard deviation (STDEV) of all plate variants examined

[0094] Based on the results of the tests carried out, it can be stated that although not all plates met the minimum requirements of EN 622-5, at least in most cases in the case of the portafilter variant with a bulk density of 650 kg/m® 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 components can be detected.

[0095] If one assumes that in the course of industrial production, plates with coffee grounds can be produced with higher mechanical parameters and have similar relationships as in the present patent application, a greater drop in the mechanical parameters or a greater increase in the mass and thickness after 24 hours of water storage would only be expected if >45% of coffee grounds were added. If one compares the two coffee grounds variants, the slightly lower scatter of the instant coffee plates is noticeable.

SUMMARY FINDINGS:

[0096] In summary, it can be said that the properties of the board according to the invention, in particular its MDF quality, are influenced by the following material or 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 wood fibers. This must be taken into account when using shorter wood fibers, such as those obtained through recycling.

- Drying method: The starting products wood fibers and coffee grounds are dried to a constant weight. This creates a free-flowing bulk material that can be easily stored and processed further. Furthermore, the proportions of wood fibers and coffee grounds as well as the resin content can be calculated precisely for the further process.

- Resin application: A homogeneous resin application is achieved when the resin is continuously applied to the starting products, which are preferably moved evenly. This also makes it possible to reduce the resin content to as little as 8%. In the industrial production of the plate according to the invention, resin application can be carried out using a blowline process.

- Pre-compaction: The homogeneous distribution of coffee grounds and wood fibers is significantly influenced after the resin application when a type of board blank is produced that has been pre-compacted by cold pressing.

- Target density: The target density of the plates is achieved by a pressing diagram with the parameters pressure and temperature.

[0097] Taking these material or process parameters into account, it is the routine work of a person skilled in the field of wood fiber board production to carry out upscaling to industrial scale.

[0098] Thus, the resource-saving wood fiber board with coffee grounds according to the invention 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 starting product can be saved, especially since spruce is particularly at risk as a result of climate change ("spruce dieback"). It must also be taken into account that waste disposal is a problem due to the ever-increasing consumption of coffee worldwide. This is because huge amounts of coffee grounds would have to be burned, for example, which of course has a negative impact on the CO2 balance.

[0099] The resource-saving wood fiber board according to the invention can be provided in MDF and HDF quality, so that areas of application include the construction and furniture industries (including the provision of coffins) and the automotive industry.

Claims (17)

Patent claims 1. Wood fibreboard with a solid content of wood fibres and coffee grounds bonded with a urea-formaldehyde resin, characterized in that the solid content of coffee grounds is between 20 wt.% and 45 wt.%. 2. Wood fibreboard according to claim 1, characterized in that the coffee grounds are a waste product which arises during the production of coffee beverages using a portafilter. 3. Wood fiber board according to claim 2, characterized in that the coffee grounds have an average particle size between 125 µm and 2000 µm. 4. Wood fibre board according to claim 1, characterized in that the coffee grounds are a waste product resulting from the production of instant coffee. 5. Wood fiber board according to claim 4, characterized in that the average particle size is between 125 µm and 2000 µm. 6. Wood fiber board according to one of claims 1 to 5, characterized in that the wood fibers are softwood fibers and/or wood fibers obtained by recycling. 7. Wood fiber board according to one of claims 1 to 6, characterized in that 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. 8. Wood fibre board according to one of claims 1 to 7, characterized in that its density is in the range from 500 kg/m*® to 1,000 kg/m®, preferably up to 950 kg/m®. 9. Wood fiber board according to claim 2, 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 fiber board has a value of 500 kg/m® to 600 kg/m®, in particular of 550 kg/m®. 10. Wood fiber board according to claim 4, 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 fiber board has a value of 500 kg/m® to 600 kg/m®, in particular of 550 kg/m®. 11. Wood fiber board according to claim 2, 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 fiber board has a value of 600 kg/m® to 700 kg/m®, in particular of 650 kg/m®. 12. Wood fiber board according to claim 4, 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 bulk density of the wood fiber board has a value of 600 kg/m? to 700 kg/m®, in particular of 650 kg/m®. 13. Wood fiber board according to claim 2, 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 fiber board has a value of 900 kg/m® to 1,000 kg/m*®, in particular of 950 kg/m®. 14. Wood fibre board according to claim 4, characterized in that it contains 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 fibres and coffee grounds, of urea. substance-formaldehyde resin, and the gross density of the wood fibre board has a value of 900 kg/m® to 1,000 kg/m®, in particular 950 kg/m®. 15. A method for producing a plate according to one of claims 1 to 14 comprising the following ing steps: a) drying the raw materials from wood fibres and coffee grounds to constant weight, b) Calculating the desired ratios between wood fibres and coffee grounds as well as the proportion of urea-formaldehyde resin, c) Continuous application of the urea-formaldehyde resin to the dried wood fibre-coffee grounds mixture d) homogeneous spreading to produce a plate blank e) Pre-compaction of the plate blank by cold pressing and f) Manufacturing the wood fibre board with coffee grounds by pressing at increased pressure and temperature. 16. The method according to claim 15, characterized in that the drying of the starting products from wood fibers and coffee grounds is carried out by means of the kiln method. 17. The method according to claim 15 or 16, characterized in that the urea-formaldehyde resin is continuously applied as a fine mist to the dried wood fiber-coffee grounds mixture. 6 sheets of drawings