Method for determining the amount of at least one sealant applied to a side edge of a composite wood board

Abstract

The present invention relates to a method for determining the amount of at least one sealant applied to at least one side edge of a composite wood board, comprising the following steps: recording at least one NIR spectrum of a plurality of reference samples of at least one sealant applied to a side edge of a composite wood board, wherein the at least one sealant has been applied in a known amount to the one side edge of a composite wood board, using at least one NIR probe in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm; assigning the amount applied of the at least one sealant of the reference samples to the recorded NIR spectra of the reference samples; and creating a calibration model for the correlation between the spectral data of the NIR spectra and the amounts applied of the impregnating agent of the reference samples by means of multivariate data analysis; recording at least one NIR spectrum of at least one sealant applied to a side edge, using the at least one NIR probe in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm; and determining the amount applied of the at least one sealant by comparing the NIR spectrum recorded for the sealant with the created calibration model.

Description

[0001] Method for determining the application quantity of at least one sealing agent to a side edge of a wood-based panel

[0002] The present invention relates to a method for determining the application quantity and, if applicable, penetration of at least one sealing agent on or into a side edge of a wood-based panel.

[0003] Description

[0004] Laminate flooring has been manufactured and sold worldwide for over twenty years. This flooring has a greater or lesser market share in almost every market worldwide. Today, laminate flooring is almost exclusively a product with a fiberboard core, which is coated with resin-impregnated paper using the so-called direct coating process. The large-format coated boards are then milled into floorboards.

[0005] Compared to many other floor coverings, laminate flooring benefits from its reputation as a wood product. However, like many other wood products, laminate flooring is sensitive to moisture or water exposure.

[0006] This has proven even more critical as more and more manufacturers have switched to so-called "glueless profiles." These floor panels are provided with tongue-and-groove profiles on the side edges for installation in panel assemblies, such as laminate flooring. These tongue-and-groove profiles enable easy installation of floor panels to floor coverings. Such tongue-and-groove profiles have a tongue (or tongue) on a first side edge with a (first) joining surface provided above the tongue, and a groove with a lip and a (second) joining surface on a second side edge. When the panels are installed, the tongue and groove are pushed into each other so that contact is made between the first and second joining surfaces.However, this approach creates a gap on the upper side of the joined panels, particularly at the contact points of the joining surfaces of the two opposite side edges of two joined floor panels, through which moisture and dirt can penetrate between the floor panels. To reduce water penetration at the contact points of the tongue-and-groove profiles, modern click profiles also feature a rebate in the area of ​​the joining edge. A rebate is defined as a ledge, edge, or fold.

[0007] Laminate flooring with so-called V-joints has also proven very popular. These V-joints are created when installing floorboards with bevels. The bevels are angled milled grooves on the side edges of the floorboards, which are then painted with colored varnishes and give the laminate flooring a visual impression similar to parquet.

[0008] However, all of these panel connection variants still offer inadequate protection against water penetration at the connection or contact point. This is due to the fact that with these products, water is sucked into the profile area through the fine joints or gaps between the floor panels via capillary action (e.g., during cleaning), causing swelling there. To investigate this problem, the so-called NALFA test was developed. In this test, a defined amount of water is applied to the connection area of ​​three installed planks. After a defined test time (24 hours), the test is analyzed to determine whether water is still present on the surface and whether any clearly visible swelling of the planks is detectable.

[0009] To improve the watertightness of the profiles, sealants applied to the profiles have been tested to remedy this deficiency. These sealants can be those that simply form a film, thus preventing or at least impeding water penetration. They can also be sealants that react with the fiberboard. This is described, for example, in WO 216 / 182896 A1, Unilin North America, LLC. There, the use of isocyanates reduces swelling and water absorption in the profile area.

[0010] However, applying the sealing materials is difficult at the production speeds typically achieved on flooring lines. These speeds on modern flooring lines exceed 200 m / min. The same applies to controlling the applied quantities. Coloring the substances could at least enable simple visual inspection, but has the problem that overspray could soil the decorative surface. Even colorless sealing materials can be problematic with regard to overspray, as they can lead to widespread soiling and / or sticking when the planks are stacked on top of each other. Furthermore, this control provides little insight into the exact application quantity. Depending on the agent used, this can also be absorbed by the highly absorbent fiberboard. This can be particularly problematic with paraffins, as these are particularly well absorbed by wood fibers (blotting paper effect).This problem can occur to a greater or lesser extent depending on the density of the fiberboard. The type of wood fiber can also play a role.

[0011] Boards could, of course, be removed from the milling lines and examined at regular intervals. However, considerable quantities may have been produced between the last and the current removal. Furthermore, a purely visual inspection would not be conclusive due to the absorbency of the fiberboard.

[0012] The resulting disadvantages include difficulty in controlling the sealant application rate, high machine speeds, and a strong influence of the fiberboard. Furthermore, continuous analysis is not possible.

[0013] The invention is therefore based on the technical problem of continuously and non-destructively checking the application quantities of the sealing material on the side edges, in particular on profile surfaces, joining surfaces and / or bevels of side edges, of wood-based panels and its distribution. This should, if possible, be possible for a variety of sealants without the need to use different measuring systems. Furthermore, a measurement should be able to detect not only the sealing material directly on the surface but also material that has penetrated the fiberboard. The measurement should be spatially undemanding and not be subject to any restrictions due to on-site conditions (dust). Changing from one sealing material to another should be possible quickly with regard to the measurements.

[0014] This object is achieved by a method having the features of claim 1.

[0015] Accordingly, a method is provided for determining the application quantity of at least one sealing agent or impregnating agent to at least one side edge, in particular to profile surfaces, joining surfaces and / or chamfers of side edges, of a wood-based panel, preferably a floor panel.The present method comprises the following steps: - recording at least one NIR spectrum of a plurality of reference samples of at least one sealant applied to a side edge of a wood-based panel, wherein the at least one sealant was applied to one side edge of a wood-based panel in a known amount, using at least one NIR measuring head in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm, or also preferably between 1150 and 1250 nm and / or between 1350 nm and 1650 nm;.

[0016] - Assignment of the application quantity of at least one sealant of the reference samples to the recorded NIR spectra of the reference samples; and

[0017] - Creation of a calibration model for the relationship between the spectral data of the NIR spectra and the application quantities of the impregnating agent of the reference samples using a multivariate data analysis;

[0018] - Recording at least one NIR spectrum of at least one sealing agent applied to a side edge using the at least one NIR measuring head in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm, or also preferably between 1150 and 1250 nm and / or between 1350 nm and 1650 nm; and

[0019] - Determining the application quantity of at least one sealant by comparing the NIR spectrum recorded for the sealant with the created calibration model.

[0020] According to the present method, the application quantity of the sealant is determined by an NIR measurement in the areas of the profile exposed to the sealing materials (particularly the profile areas close to the surface), the joining surfaces, and / or bevels of the side edges of wood-based panels. A wide variety of sealing materials can be detected and quantitatively evaluated. As described in more detail later, the sealants used are film-forming compositions, preferably consisting of non-crosslinked materials or components. In particular, no curable formaldehyde-containing resins are used as sealants for the side edges.

[0021] In addition, NIR spectroscopy also offers the possibility of detecting sealant that has penetrated the fiberboard at the side edges. This can occur not only with paraffin but also with materials with low viscosity. Detection of sealant in the surface of the board is not possible with IR spectroscopy or other spectroscopic methods.

[0022] In addition to determining the application quantity (and distribution) of at least one sealing agent on a side edge of a wood-based panel, the present method also enables the determination of the penetration of the

[0023] Sealant (e.g. the penetration depth of the sealant) into the side edge of at least one wood-based panel. The determination of the penetration of the

[0024] Sealant into the wood-based panel is particularly advantageous for low-viscosity sealants or sealants with a high water content.

[0025] In one embodiment of the present method, the recorded NIR spectrum, in combination with a test of the percentage of sealant penetration into the side edge, enables a correlation to the penetration depth. Surprisingly, it has been shown that, depending on how far the sealant penetrates into the side edge, a signal increase for the main peak of the respective sealant can be observed.

[0026] From the prior art (e.g., WO 2020 / 016176 A1), it is known to measure a melamine-formaldehyde resin coating applied to the planar surface of wood-based panels using NIR spectroscopy, but not to the side edges of the panels. However, coating a narrow surface / profile / bevel of a wood-based panel and measuring a sealing layer applied to a narrow surface / profile / bevel presents a greater technical challenge and a greater susceptibility to errors than coating a surface.

[0027] Furthermore, the planar surface and side edges of wood-based panels differ in that the surface of the wood-based panels has a pressed skin due to the pressing process, which at least makes liquid penetration difficult, whereas such a skin is absent at the side edges, so liquid can be more easily absorbed at the side edges of the wood-based panels. Rather, the side edges of wood-based panels are open-pored, which allows the sealant applied to the side edges to penetrate and penetrate.

[0028] Due to the pressing process, wood-based panels also have a lower bulk density in the center of the panel than on the planar surface, which has a much higher bulk density. Accordingly, a liquid, such as a sealant, can penetrate the panel much better at the side edges in the center of the panel than at the surface. This problem is not mentioned in WO 2020 / 016176 A1, since it only measures a layer applied to the planar surface of a wood-based panel.

[0029] This measurement method also takes into account the high production speeds, which place significantly higher demands on the analysis than a slow-running system. For example, the speed of a production system, in particular a system for applying a sealant to a side edge, is between 100 and 250 m / min, preferably between 120 and 200 m / min, and particularly preferably between 150 and 180 m / min. The measurement along the side edge of a wood-based panel, in particular in the form of a plank, is carried out at at least one, preferably at 3-4 different measuring points. Since NIR spectroscopy involves multiple scans per second, this means that with a milling line speed of, for example, 200 m / min (3.3 m / sec) and a measuring frequency of 8 NIR measurements / sec, it is ensured that each passing plank is measured multiple times.

[0030] The advantages resulting from the present method include the possibility of online measurement, analysis of different sealing materials, rapid correction, determination of the total application, no coloring of the sealing material necessary.

[0031] According to this method, an NIR spectrum of the side edge of the wood-based panel coated with the sealant is recorded. NIR radiation is generated and directed onto the sample to be analyzed, where it interacts with the sample components and is reflected or scattered. An NIR detector captures the reflected or scattered NIR radiation and generates an NIR spectrum containing the desired chemical information of the sample. During this measurement, a large number of individual NIR measurements are performed within one second, thus ensuring statistical validation of the measured values. NIR spectroscopy, together with the multivariate data analysis (described below), offers a way to establish a direct relationship between the spectral information (NIR spectra) and the parameters of the applied sealant to be determined.

[0032] First, reference samples of a wood-based panel are provided, the side edge of which is coated with the respective sealant. It is essential that the reference sample is similar to the sample to be measured; in particular, the sealant and the wood-based panel with the side edge of the reference sample to be coated have the same composition as the sample to be measured. The similarity of the sample to be measured and the reference sample is essential, especially when using sealants with solvents and possibly other additives.

[0033] At least one NIR spectrum of these reference samples is recorded in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm, or also preferably between 1150 nm and 1250 nm and / or between 1350 nm and 1650 nm.

[0034] The respective application quantity of at least one sealant of the reference samples is then assigned to the recorded NIR spectra of these reference samples, and a calibration model for the relationship between the spectral data of the NIR spectra of the reference samples and the associated parameter values ​​(application quantity) is created using multivariate data analysis; i.e., each parameter value of the reference sample corresponds to an NIR spectrum of the reference sample. The calibration models created for the various parameters are stored in a suitable data storage.

[0035] Subsequently, at least one sealant is applied to one side edge of a wood-based panel, and at least one NIR spectrum of the applied sealant is recorded. The desired parameter of the sealant (here, the application quantity and, if applicable, the penetration depth into the side edge) can then be determined by comparing the NIR spectrum recorded for the sample with the created calibration model. It is thus possible to simultaneously determine several parameters of interest of the applied sealant from a single NIR spectrum determined for the sample to be measured through an automated comparison or alignment with the calibration models created for the respective parameters.

[0036] A comparison and interpretation of the NIR spectra is best performed across the entire recorded spectral range. This is best done using a well-known multivariate data analysis (MDA). Multivariate analysis methods typically examine several statistical variables simultaneously in a well-known manner. To achieve this, these methods typically reduce the number of variables contained in a data set without simultaneously diminishing the information contained therein.

[0037] In this case, the multivariate data analysis is performed using partial least squares regression (PLS), which allows for the creation of a suitable calibration model. The obtained data is preferably evaluated using suitable analysis software, such as SIMCA-P from Umetrics AB or The Unscrambler from CAMO.

[0038] In a further embodiment, spectral data from the NIR spectral range between 1150 and 1250 nm and / or between 1350 and 1650 nm are used to create the calibration model, which data are pretreated using suitable mathematical methods and then fed to the multivariate data analysis.

[0039] The significance of a wavelength for predicting parameters of the applied sealant, such as application quantity and penetration, from the NIR spectrum is illustrated using the regression coefficients. Regions with large coefficient values ​​have a strong influence on the regression model. The representation of the regression coefficients in a PLS regression model for determining the sealant shows that the wavelength range between 1150 and 1250 nm and / or between 1400 nm and 1600 nm, with a maximum at 1490 nm, is the most important for calculating the model, as this is where the regression coefficient values ​​are greatest. Although the other ranges in the spectrum have less information content with regard to the NIR measurement, they nevertheless contribute to considering or minimizing other information and interfering influences. To eliminate interfering influences (such asDue to the partially rough nature of the surface of the side edges of the wood-based panel, it is necessary to process the spectral data using mathematical pretreatment methods (e.g., derivative data pretreatment, standardization according to SNVT (Standard Normal Variate Transformation), multiplicative signal correction (EMSC, Extended Multiplicative Signal Correction, etc.). This removes the baseline effects, which are mainly caused by the different colors of the samples, from the spectra, separates overlapping bands, and takes into account the dependence of light scattering at the substrate surface. Thus, data pretreatment is preferably carried out to reduce light scattering at the rough surface of the substrate. During the measurement, the focus of calibration and data pretreatment is on removing the baseline shift.

[0040] Using multivariate data analysis, a calibration model is developed from the pretreated data that includes all aspects used in the calibration.

[0041] Accordingly, the comparison and interpretation of NIR spectra are preferably carried out in the spectral range between 1150 and 1250 nm and / or between 150 and 1650 nm using multivariate data analysis (MDA). Multivariate analysis methods typically examine several statistical variables simultaneously in a conventional manner. This involves reducing the number of variables contained in a data set without simultaneously diminishing the information contained therein.

[0042] This method enables the provision of measured values ​​in a short time (online, preferably without disruptive time delays) compared to conventional (known) measurement methods. The measured data can be used for quality assurance, research and development, process monitoring, control, etc. The measurement process does not reduce production speed, etc. Fundamentally, it improves production monitoring. Furthermore, downtimes due to quality control and system adjustments are reduced.

[0043] The advantages of the present method are manifold: non-contact multi-parameter determination ("real-time" measurement) with significantly reduced time delay in the evaluation of the measured parameter values; improved plant control and regulation, reduction of waste, improvement in the quality of the products manufactured on the plant, and improvement in plant availability. In one embodiment of the present method, the at least one wood-based panel is a medium-density fiberboard (MDF), high-density fiberboard (HDF), oriented strand board (OSB), plywood, or wood-plastic board (WPC).

[0044] The width of the side edge to be coated with the sealant is between 2.5 and 3.5 mm, preferably 3 mm.

[0045] In one embodiment, the at least one sealant has a solids content of between 30 and 100 wt%, preferably between 50 and 100 wt%, in particular between 70 and 100 wt%. The sealant is preferably present as a suspension, in particular as an aqueous suspension. In a preferred embodiment, aqueous suspensions with a solids content of 50-70 wt% and a water content of 30-50 wt% are used.

[0046] In a further embodiment, the at least one sealing agent is applied to the side edge in an amount between 0.1 g / lfm and 1.5 g fl / lfm, preferably between 0.2 and 1.5 g fl / lfm, particularly preferably between 0.25 and 0.75 g fl / lfm, e.g. preferably 0.5 g fl / lfm.

[0047] As a sealing agent, a composition comprising at least one compound of the general formula (I) SiX 1 4 where X 1Alkoxy-, aryloxy-, acyloxy-, at least one compound of the general formula (II) R 2 bSiX 2 <4-b), where X 2 H or alkoxy, aryloxy, acyloxy, R 2 a non-hydrolyzable organic residue R 2 is selected from the group comprising alkyl and aryl, and b = 1, 2, 3, or 4, and at least one aqueous polymer dispersion. Such a composition is described in WO2020 / 016176 A1,

[0048] This silane-containing sealant fills the pores in the wood fiberboard and envelops the wood fibers, thereby "sealing" them. On the other hand, the use of hydrophobic modifications creates a "hydrophobic treatment" of the remaining pores and the still uncoated wood fibers. To achieve the highest possible flexibility of the coating, the silane compounds are mixed with a suitable aqueous polymer dispersion. The polymers used have functional groups that are compatible with the inorganic silane matrix. Therefore, a coating with a high degree of crosslinking can be produced even at low temperatures. The remainder X 1 is advantageously selected from a group containing C 1-6 alkoxy, in particular methoxy, ethoxy, n-propoxy and butoxy, C 1-w aryloxy, in particular phenoxy, C 2-7 acyloxy, in particular acetoxy or propionoxy, and the radical X 2is advantageously selected from a group containing H, C1-6-alkoxy, in particular methoxy, ethoxy, n-propoxy and butoxy, C1-w aryloxy, in particular phenoxy, C2-7-acyloxy, in particular acetoxy or propionoxy,

[0049] In a particularly preferred variant of the silane-containing sealant, the compound of general formula (I) corresponds to the formula SiX 1 4, where the remainder X 1 Alkoxy, especially methoxy, ethoxy, n-propoxy, or i-propoxy. Tetramethoxysilane and tetraethoxysilane are particularly preferred crosslinkers.

[0050] In a further embodiment of the silane-containing sealant, the non-hydrolyzable organic radical R 2the compound according to formula (II) is selected from a group comprising C1-C18-alkyl, in particular C1-C10-alkyl, and C1-C10-aryl. These may be unsubstituted or substituted with another hydrophobic group. It is preferred if the non-hydrolyzable organic radical R 2 is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, cyclohexyl, phenyl, and naphthyl. Methyl, ethyl, propyl, octyl, or phenyl radicals are particularly preferred.

[0051] The compound of formula (II) may in particular comprise one of the following formulas:

[0052] - R 2 4Si with R 2 as a C1-C5 alkyl group, preferably methyl or ethyl such as tetramethylsilane;

[0053] - R 2 sSiX 2 with R 2 as a C1 -C5 alkyl group, preferably methyl or ethyl and with X 2 as H, such as trimethylsilane,

[0054] - R 2 Six 2 3 with R 2 as a C1-C10 alkyl group, preferably methyl, ethyl, propyl, pentyl, hexyl, heptyl, octyl, or as a C6-C10 aryl group, preferably phenyl and with X 2 as alkoxy, in particular methoxy, ethoxy, n-propoxy or i-propoxy, such as octyltriethoxysilane, phenyltriethoxysilane.

[0055] In one variant of the silane-containing sealant, one compound of general formula (I) and one compound of general formula (II) are used as additives. In another variant of the silane-containing sealant, however, the additive may also contain at least one compound of general formula (I) and at least two, preferably at least three, compounds of general formula (II). Any combination is conceivable here.

[0056] In a further embodiment of the silane-containing sealant, the at least one polymer is selected from the group consisting of polyurethanes, epoxy resins, and polyacrylates. In the present case, the use of a polyurethane polymer is preferred, with the polyurethane polymer being based on aromatic polyisocyanates, in particular polydiphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI), and / or diphenylmethane diisocyanate (MDI), with PMDI being particularly preferred. The polymer is incorporated into the network formed from the silane compounds and imparts flexible properties to the composition, facilitating application.

[0057] A silane with hydrophobic residues, such as trimethylsilane, phenyltriethoxysilane, and octyltriethoxysilane, is preferably used, preferably in a mixture with another (hydrophilic) silane, such as tetraethoxysilane (WO 2020 / 016176 A1). Alcohols, especially ethanol, or water are used as solvents. The solids content of the sealant used in this case is 50 wt%.

[0058] In a further embodiment of the silane-containing sealant, at least one chamfer color is added to the mixture of silanes and polymer dispersion. Such a sealant is used in particular for coating chamfers.

[0059] In another embodiment, the at least one bevel color used in the present composition comprises color pigments and an aqueous solvent or suspending agent. Carbon black, iron oxides, titanium dioxide, and / or organic pigments are used as color pigments. Suitable solvents or suspending agents are melamine resin-formaldehyde resins or acrylates. In one embodiment, the bevel color comprises color pigment, acrylate, and water.

[0060] In another embodiment, the at least one bevel paint used comprises color pigments and an aqueous solvent or suspending agent. Carbon black, iron oxides, titanium dioxide, and / or organic pigments are used as color pigments. Suitable solvents or suspending agents are melamine resin-formaldehyde resins or acrylates. In one embodiment, the bevel paint comprises color pigment, acrylate, and water.

[0061] The silane-containing sealant, in particular the composition of silanes, polymer dispersion and chamfer paint, has a viscosity (measured according to EN ISO 2431:2011, Paints and varnishes - Determination of flow time using flow cups, 21 °C) with a flow time between 20 and 100 see, preferably between 30 and 80 see, particularly preferably between 35 and 60 see over a period of at least 30 minutes, preferably at least 60 minutes, particularly preferably at least 120 minutes.

[0062] In another embodiment, at least one isocyanate is used as a sealant. Preferred isocyanates are polydiphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI), and / or diphenylmethane diisocyanate (MDI). Diphenylmethane diisocyanate (MDI) is particularly preferred. MDI is preferably applied with a solids content of 100%.

[0063] The isocyanate can be used alone or in combination with other sealants. For example, a mixture of MDI and an epoxy resin with acetic anhydride can be used. Acetic anhydride acetylates the wood fibers, making them less susceptible to moisture.

[0064] It is also possible for the at least one isocyanate as a sealant to comprise at least one solvent. Suitable solvents are water, a glycol ether such as dipropylene glycol dimethyl ether, ethyl acetate, propyl acetate, butyl acetate, acetone, butyldiphenylmethane, tetramethoxy ether, and benzoic acid esters. The use of hydrophobic solvents such as propyl acetate, diphenylmethane, and diphenylethane has proven particularly advantageous. The solvent content is 10-40% by weight, preferably 15-30% by weight.

[0065] In another embodiment, a UV varnish, especially a monomer-free UV varnish, can be used as the sealant. A suitable UV varnish would be a water-based copolymer of ethylene-acrylic acid. Such products form a stable hydrophobic layer.

[0066] In yet another embodiment, a hot melt adhesive can be used as a sealant. Suitable hot melt adhesives are polypropylene (PP), polysulfones, polyurethanes (PUR), polyetherimides, and / or polyolefins. These hot melt adhesives are applied at temperatures between 150 and 200°C.

[0067] It is also possible to use paraffin as a sealant. Paraffin is a mixture of acyclic alkanes (saturated hydrocarbons) with the general formula CnHsn+s, where n is between 18 and 32, and can be used as a liquid or solid. The paraffin is preferably applied to the side edges as an emulsion with a solids content of 50% by weight.

[0068] As already indicated above, the sealants applied to the side edges of wood-based panels are compositions that preferably form a film on the side edge. These compositions preferably consist of at least two or three or more components that are in uncrosslinked form prior to application. The precursors contained in the composition are measured accordingly. This applies in particular to the silane-containing sealants described above.

[0069] When mixtures of different components are used, aqueous suspensions are often used, e.g., with a water content of 50 wt%. However, measuring suspensions with a high water content using NIR spectroscopy is not trivial, since the water signal (at approximately 1450 nm) in the NIR spectrum partially overlaps the NIR signals of the excess components essential for film formation of the sealant, complicating meaningful evaluation. Accordingly, the present method requires a careful analysis of the determined NIR spectrum.

[0070] As already mentioned, formaldehyde resins, such as melamine-formaldehyde resin or urea-formaldehyde resin, which are typically used to coat the planar surface of wood-based panels and impregnate paper layers, are not used as sealants for side edges. Therefore, no resins that harden or cure, particularly through condensation or polycondensation reactions, are used as sealants.

[0071] The sealant can be applied to the edges of the wood-based panels, for example, by spraying with a spray system, rolling, transfer printing, or using a vacuum coater and transfer wheel. Suitable vacuum coaters for overspray-free, profile-independent vacuum coating or partial coating of profile elements are available from Schiele (Vacumat®). Transfer wheels allow for the coating of bevels (Schiele's TransferDisc).

[0072] As already indicated, the sealant is applied in particular to the side edges of floorboards. The floorboards used here preferably have the following formats: length between 1200 and 2000 mm, preferably between 1300 and 1500 mm, particularly preferably between 1350 and 1400 mm, such as 1375 mm, 1380 mm, or 1875 mm; width between 100 and 300 mm, preferably between 150 mm and 250 mm, particularly preferably between 180 and 200 mm, such as 157 mm, 188 mm, 193 mm, or 244 mm. Typical formats are 1380 x 193 mm; 1380 x 244 mm; 1380 x 157 mm; 1375 x 188 mm; and 1875 x 244 mm.

[0073] The format size of the planks, combined with the system speed (200 m / min), plays a major role in developing a measurement method suitable for side edges. The NIR measurements are performed eight times per year. This means that a measurement is taken approximately every 40 cm on a plank (3-4 measurements per side edge per plank). This ensures that variations in the application (plank infeed / outfeed) can be detected. Any other, slower analysis method than the NIR spectroscopy used here would not be able to handle this task.

[0074] The layer thickness of the sealant on the side edge can be in a range between 10 and 50 μm, preferably between 20 and 40 μm. However, it is also possible for the layer thickness of the sealant on the side edge to be less than 10 μm, since the sealant has largely penetrated into the wood-based panel.

[0075] The wood-based panels used here can contain various binder systems, which are mixed and pressed with the wood fibers or wood particles as binders. Preferred binder systems are: formaldehyde resins, such as urea-formaldehyde resins, melamine-formaldehyde resins, or melamine-urea-formaldehyde resins; polyurethanes, preferably based on polydiphenylmethane diisocyanate (PMDI), epoxy resins, or polyester resins.

[0076] The present wood-based panels can also have a coating on the top surface with films, e.g., films made of thermoplastic materials such as PVC or PP, or paper layers, such as decorative paper layers or overlay papers. Particularly preferred wood-based panels, especially in the form of floorboards, are:

[0077] - HDF board with urea-formaldehyde glue

[0078] - HDF board with urea-formaldehyde glue and a film, such as PVC film, glued to at least one of the board's upper sides;

[0079] - HDF board with melamine-urea-formaldehyde glue;

[0080] - HDF board with PMDI glue, and

[0081] - WPC board with glued film, such as polypropylene (PP) film.

[0082] In a further embodiment, it is provided that the side edge of the wood-based panel to be provided with the sealing agent and a side edge opposite this comprise mechanical coupling means which enable a coupling or connection of the wood-based panel with similar wood-based panels to form a composite (panel composite).

[0083] Preferably, the mechanical coupling means are provided in the form of a groove and a tongue. For example, EP 1026341 B1 discloses a floor panel for implementing a floor covering, wherein coupling parts in the form of a groove and a tongue are provided on the edges of two opposite sides of the panels. The tongue and groove are designed such that, when two or more floor panels are joined together, a tensioning force is exerted on them, forcing the floor panels together. The tensioning force is created by an elastically bendable lip in the groove, which is at least partially bent when joined together and thus provides the aforementioned tensioning force.

[0084] In another variant, the NIR measurement can be carried out both online and offline.

[0085] The present method is carried out in a production line comprising at least one NIR multi-measuring head, preferably at least two NIR multi-measuring heads, particularly preferably at least four measuring heads (two measuring heads for the longitudinal edges and two measuring heads for the transverse edges), and at least one control system. Such a production line can be a production line for manufacturing material panels. The present method for determining the application quantity of the sealant to the side edges is preferably carried out continuously and online.

[0086] The production line's control system comprises at least one computer-based evaluation unit (or processor unit) and a database. The evaluation unit compares or compares the NIR spectrum measured for the product (i.e., the side edges coated with the sealant) with the calibration models created for each individual parameter. The parameter data thus determined is stored in the database.

[0087] The data determined using this spectroscopic method can be used to control the production line. The non-contact measured parameter values ​​of the NIR multi-sensor head ("actual values") can, as previously described, be used directly and in real time for the control or regulation of the relevant system. For example, by storing the measured actual values ​​in a database, e.g., a relational database, and comparing them with the target values ​​of these parameters available there. The resulting differences are then used to control or regulate the production line.

[0088] For the calibration and control of the production line, a computer-implemented method and a computer program comprising instructions that, when executed by a computer, cause the computer to execute the computer-implemented method are provided. The computer program is stored in a memory unit of the production line's control system.

[0089] The invention will be explained in more detail below with reference to an exemplary embodiment of the invention and the accompanying drawings. It shows:

[0090] Figure 1 NIR spectra of different sealants applied to a side edge or a bevel of a wood-based panel;

[0091] Figure 2 NIR spectra of paraffin as a sealant applied to a side edge of a wood-based panel;

[0092] Figure 3 NIR spectra of paraffin in different amounts as a sealant applied to a side edge of a wood-based panel before heating;

[0093] Figure 4 NIR spectra of paraffin in different amounts as a sealant applied to a side edge of a wood-based panel after heating, and Figure 5 NIR spectra of a mixture of silane, polymer dispersion and chamfer paint as sealants applied to a side edge of a wood-based panel.

[0094] Example 1:

[0095] Sealing materials were applied to a glueless flooring profile in a continuous flow pattern on the tongue side, in the area below the decor, in a width of approximately 3 mm and across the entire length of the plank. The sealing materials were paraffin, aromatic isocyanates (MDI), and silanes with aliphatic chains (trimethylsilane, phenyltriethoxysilane, and octyltriethoxysilane in a mixture with tetraethoxysilane). The same sealing material was applied to the groove side, also in a width of 3 mm, across the entire length of the plank below the decor. This was done on both the long and short sides.

[0096] The application rate was approximately 0.5 g of sealant per cubic meter. Except for the isocyanate-containing sealant, which had a solids content of 100%, the other sealants had a solids content of approximately 50%. The planks were subjected to intermediate drying with hot air.

[0097] A NIR measurement head was then used to create a spectrum of the sealed area. This was repeated on additional planks using different sealing materials. A blank sample without sealing material was also measured.

[0098] As can be seen from the diagram in Figure 1, even chemically very different compounds are detected. This is surprising, given that the sealing materials are chemically very different compounds.

[0099] The NIR spectra of the sealing materials show particularly in the range of approx. 1500 nm (wavelength: 6666 cm~ 1} distinct bands (methyl-Zmethylene groups), which allow an evaluation with regard to the applied amounts. But also other areas of the spectrum, such as the range around 1200 - 1220 nm (8333 - 8200 cm -1 ) are eligible for evaluation.

[0100] Sealing materials were applied to a glueless flooring profile in a continuous process on the tongue side of the bevel, approximately 3 mm wide, and along the entire length of the plank. The sealing materials were paraffin, aromatic isocyanates (MDI), and silanes with aliphatic chains (trimethylsilane, phenyltriethoxysilane, and octyltriethoxysilane in a mixture with tetraethoxysilane). The same sealing material was applied to the groove side of the bevel, also in a 3 mm width, along the entire length of the plank. This was done on both the long and short sides.

[0101] The application rate was approximately 0.5 g of sealant per cubic meter. Except for the isocyanate-containing sealant, which had a solids content of 100%, the other sealants had a solids content of approximately 50%. The planks were subjected to intermediate drying with hot air.

[0102] A NIR measurement head was then used to create a spectrum of the sealed area. This was repeated on additional planks using different sealing materials. A blank sample without sealing material was also measured.

[0103] As can be seen from the diagram in Figure 1, even chemically very different compounds are detected. This is surprising, given that the sealing materials are chemically very different compounds.

[0104] The NIR spectra of the sealing materials show particularly in the range of approx. 1500 nm (wavelength: 6666 cm~ 1} distinct bands (methyl-Zmethylene groups), which allow an evaluation with regard to the applied amounts. But also other areas of the spectrum, such as the range around 1200 - 1220 nm (8333 - 8200 cm -1 ) are eligible for evaluation.

[0105] Example 3:

[0106] A paraffin emulsion was applied as a sealing material to a glueless flooring profile in a continuous run on the tongue side, in the area below the decor, in a width of approximately 3 mm and across the entire length of the plank. The emulsion had a solids content of approximately 50%. The paraffin was also applied to the groove side, in a width of 3 mm, across the entire length of the plank below the decor. This was repeated on another plank with the same application rate. It was found that a paraffin film could be felt and seen on the surface of both planks.

[0107] Both planks were subjected to intermediate drying with hot air. One of the two planks was treated with a hot air gun until the paraffin on the surface was no longer noticeable. This was done on both the long and short sides. A NIR measuring head was then used to create a spectrum of the area covered with sealing material during the run. A blank sample without sealing material was also measured.

[0108] As can be seen from the diagram in Figure 2, the paraffin, which had essentially migrated into the fiberboard as a result of treatment, was still detected.

[0109] Example 4:

[0110] Paraffin emulsion was applied as a sealing material to a glueless flooring profile in a continuous run on the tongue side, in the area below the decor, in a width of approximately 3 mm and over the entire length of the plank. The emulsion had a solids content of approximately 50%. The paraffin was also applied to the groove side, in a width of 3 mm, and over the entire length of the plank below the decor. This was carried out on several planks using different application quantities. The application quantities were approximately 0.25, 0.5, and 1 g of paraffin emulsion per 1 m³. It was observed that with the last two application quantities, a paraffin film could be felt on the surface of the plank.

[0111] All planks were subjected to intermediate drying with hot air. A set of samples with the same application quantities was heated with a hot air gun after application until the paraffin had penetrated the fiberboard. This was done on both the long and short sides. A spectrum of the area coated with sealing material was then created using an NIR measuring head. A blank sample without sealing material was also measured in each case.

[0112] As can be seen from the diagrams in Figures 3 and 4, the quantity gradations were recorded. This shows that even very small order quantities can be reliably recorded.

[0113] Preparation of a first silane-containing sealing composition:

[0114] 12.3 g of octyltriethoxysilane, 2.4 g of trimethylsilane, 6.1 g of phenyltriethoxysilane, 20.8 g of tetraethoxysilane, and 28.8 g of an aqueous SiO dispersion (50 wt.%) from Obermaier are initially charged, heated to 80 °C, and stirred. 3.6 g of para-toluic acid in water (30 wt.%) are then added while stirring and the mixture is stirred for 120 minutes. After a further 24 hours, the pH is raised to 7 by adding a 25% ammonia solution (6.2 g in the above example) while stirring.

[0115] After a further stirring time of 2 hours, 80 g of water is added, stirred again for 30 minutes and then the suspension is stored for 4 hours without stirring.

[0116] After this waiting period, the aqueous phase containing the binder separates from the ethanolic phase. The aqueous phase is then separated using a separating funnel, thus yielding the inorganic aqueous coating system.

[0117] 50 g of this coating system (solids: 52%) is now mixed with 20 g of an aqueous polyurethane solution (Alberdingk U 3251, solids: 35%).

[0118] The coating system can now be applied to an edge using a foam roller or a pipette.

[0119] A NIR measurement head was then used to create a spectrum of the area covered with sealing material during the run. A blank sample without sealing material was also measured.

[0120] Preparation of a second silane-containing sealing composition:

[0121] Preparation of dispersion A)

[0122] 28.8 g of an aqueous SiO2 dispersion (Köstrosol 3550) and 20 g of an aqueous polyurethane solution Alberdingk U 3215 are added. Preparation of solution B)

[0123] In parallel, 12.3 g of octyltriethoxysilane, 2.4 g of trimethylsilane, 6.1 g of phenyltriethoxysilane, 20.8 g of tetraethoxysilane, and 28.8 g of water are heated to 50 °C and stirred. 2.8 g of sulfuric acid are then added while stirring for 120 minutes. This solution is then stirred into the above suspension while still warm and stirred at room temperature for a further 60 minutes. A 0.1 molar NaOH solution is added until a pH of 7.5 is reached.

[0124] After 24 hours of standing, the alcoholic phase is separated using a separating funnel.

[0125] The additive (Inosil AS) can now be added up to 50 wt.% to a commercially available bevel paint, which remains stable for several weeks. After application, curing occurs thermally (e.g., 100 °C, 5 minutes).

[0126] The mixture of bevel paint and silane additive (Inosil AS) was applied to a glueless flooring profile as a sealing material on the tongue side in the area below the decor, in a width of approximately 3 mm and over the entire length of the plank. The mixture of bevel paint and silane additive was also applied to the groove side, in a width of 3 mm, and over the entire length of the plank, below the decor.

[0127] This was carried out on several planks using different application quantities (see Table 1 ).

[0128] A NIR measurement head was then used to create a spectrum of the area covered with sealing material during the run. A blank sample without sealing material was also measured.

[0129] As can be seen from the diagram in Figure 5, the quantity gradations were recorded. This demonstrates that even very small application quantities can be reliably recorded. The differences in the application quantities can be evaluated in the spectrum at at least two points in the NIR spectrum (1150 to 1250 nm and 1350 to 1650 nm). A malfunction (zero sample) is also clearly recognizable.

Claims

Claims 1. Method for determining the application quantity of at least one sealant to at least one side edge of a wood-based panel, in particular a floor panel, comprising the steps - Recording of at least one NIR spectrum of several reference samples of at least one sealant applied to a side edge of a wood-based panel, wherein the at least one sealant was applied to the side edge of a wood-based panel in a known quantity, using at least one NIR measuring head in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm, - Assignment of the quantity of at least one sealing agent applied to the reference samples to the recorded NIR spectra of the reference samples; and - Creation of a calibration model for the relationship between the spectral data of the NIR spectra and the application quantities of the impregnating agent of the reference samples using a multivariate data analysis; - Recording at least one NIR spectrum of at least one sealing agent applied to a side edge using the at least one NIR measuring head in a wavelength range between 700 nm and 2000 nm, preferably between 900 nm and 1700 nm, particularly preferably between 1100 nm and 1700 nm, even more preferably between 1200 nm and 1700 nm, - Determining the application quantity of at least one sealant by comparing the NIR spectrum recorded for the sealant with the created calibration model, - wherein no thermosetting formaldehyde resins are used as a sealant. Method according to claim 1, characterized in that the side edges have profiled surfaces, joining surfaces and / or chamfers onto which the sealant is applied. Method according to any of the preceding claims, characterized in that the penetration of the sealant into the side edge of the at least one wood-based panel is determined. Method according to any of the preceding claims, characterized in that the at least one wood-based panel is a medium-density fiberboard (MDF), high-density fiberboard (HDF), oriented strand board (OSB), plywood, or wood-plastic composite (WPC) panel.A method according to any one of the preceding claims, characterized in that the at least one sealing agent is an isocyanate, in particular methylenediphenyl diisocyanate (MDI), toluene diisocyanate (TDI), a fluoro copolymer, in particular perfluoroalkyl methacrylate copolymer, an epoxy resin, acetic acid anhydrous, or paraffin. A method according to any one of claims 1-4, characterized in that the at least one sealing agent is a mixture of at least one compound of the general formula (I) SiX. 1 4 where X 1 alkoxy-, aryloxy-, acyloxy- is, at least one compound of the general formula (II) R 2 bSiX 2 <4-b), where X 2 H or alkoxy, aryloxy, acyloxy, R 2 a non-hydrolyzable organic residue R 2is selected from the group comprising alkyl and aryl, and b = 1, 2, 3, or 4, is at least one aqueous polymer dispersion, and optionally is at least one bevel color. A process according to any of the preceding claims, characterized in that the at least one sealing agent comprises at least one solvent. A process according to claim 7, characterized in that the at least one solvent is water, a glycol ether such as dipropylene glycol dimethyl ether, ethyl acetate, acetone, butyldiphenylmethane, or tetramethoxy ether.

9. Method according to one of the preceding claims, characterized in that the at least one sealing agent has a solids content between 30 and 100 wt%, preferably 50 and 100 wt%.

10. Method according to one of the preceding claims, characterized in that the at least one sealing agent is applied to the side edge in an amount between 0.2 and 1.5 g fl / lfm, preferably between 0.25 and 1 g fl / lfm, particularly preferably 0.5 g fl / lfm.

11. Method according to one of the preceding claims, characterized in that spectral data from the entire recorded spectral range are used for the creation of the calibration model.

12. Method according to one of the preceding claims, characterized in that spectral data from the NIR spectral range between 1150 and 1250 nm and / or between 1350 nm and 1550 nm are used for the creation of the calibration model, which are pretreated by means of suitable mathematical methods and subsequently subjected to multivariate data analysis.

13. Method according to one of the preceding claims, characterized in that the determination of the application quantity and / or penetration of the sealing agent into the side edge of the wood-based panel is carried out continuously and online.

14. Method according to one of the preceding claims, characterized in that the side edge of the wood-based panel to be provided with the sealing agent and a side edge opposite it comprise mechanical coupling means which enable coupling or connection of the wood-based panel with similar wood-based panels to form a composite (panel composite).

15. Method according to claim 14, characterized in that the mechanical coupling means are provided in the form of a groove and a spring.

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