Boards and method for producing boards

Abstract

A plate-shaped board 1 comprising lignocellulosic material, for example lignocellulosic particles, and comprising glue and scavengers, wherein said lignocellulosic material is pressed and bound together with said glue, wherein the board 1 comprises, from top to bottom, at least three layers, wherein at least one of said layers comprises scavengers and with the amount of scavengers being different for at least two of said layers and method for manufacturing said boards 1.

Description

[0001] Boards and method for producing boards

[0002] The present invention relates to plate-shaped boards comprising lignocellulosic material, glue and scavengers and also methods for producing board material and said boards.

[0003] This invention relates to boards, such as particle boards, oriented strand boards (OSB) and fiber boards, for example wood fiber boards such as MDF (medium-density fiberboard) or HDF (high-density fiberboard) or plant fiber boards such as flax boards or hemp boards. This invention can also relate to panels comprising a substrate, such as a particle board substrate, which is derived from a said board, and at least one decorative layer, wherein said panels can be floor panels, furniture panels or wall panels. This decorative layer can comprise one or several paper layers impregnated with a resin and / or a timber layer and / or thermoplastic layers and / or other layers. Preferably this invention relates to particle boards. Another term for particle boards is chip boards. Particle boards comprise wood chips which are bonded to each to each other by glue, such as a ureaformaldehyde based glue.

[0004] Said boards are manufactured by pressing, for example in a continuous press or in a discontinuous press. The pressing conditions, such as time, pressure and temperature have a major influence upon the quality of the boards. Of course the choice of raw material to form said boards also has a major influence. The internal bond, the bending strength, the density, are important characteristics. The aim is to obtain boards with the desired characteristics, thus good quality boards, and this by pressing as short as possible. Preferably the speed of production is as high as possible. During production of said boards, there is emission of harmful substances, such as formaldehyde. This emission is preferably as low as possible. Also when said boards are being used, for example are being used indoor, it is preferred that the emission of harmful substances is as low as possible. For several harmful substances there are emission norms. This is for example the case for formaldehyde. With regard to formaldehyde and particles boards, said particle boards are preferably El class and even more preferably E0.5 class. Formaldehyde-emission can be the result of the used glues. The commonest glue used in the production of said boards is an aminoplast polymer, produced by a polycondensation reaction from urea and formaldehyde to a urea formaldehyde resin (UF resin). Optionally melamine is added and a melamine urea formaldehyde resin (MUF resin) is obtained, or melamine and / or phenol are added (for example MUPF resins: melamine urea phenol formaldehyde). The great advantages of these glues are their low cost - on account of the use of generally available and cheap raw materials in their preparation and their high reactivity, such that high production speeds can be obtained. Glues of this kind may release formaldehyde during and after polymerization, under the effect of temperature, moisture, or pH change. Formaldehyde-free glues for producing the aforementioned boards have been found, but it is not possible or more difficult to obtain a sufficient speed of production and / or these formaldehyde-free glues can have safety issues.

[0005] Formaldehyde-emission can also be the result of the used lignocellulosic material. Said lignocellulosic material can comprise a certain amount of recycled material. Said recycled material can be derived from solid wood waste, particle board waste, wood fiber board waste, etc. For the production of particle boards, it is known to make use of wood chips derived from old particles boards and / or other wood waste. This recycled material often comprises a higher amount of formaldehyde and / or emits a higher amount of formaldehyde. This means that, even when formaldehyde-free glues are used, formaldehyde-emissions remains an issue.

[0006] To avoid harmful emissions, scavengers are used as raw material. Said scavengers remove / neutralize harmful substances, such as formaldehyde, during production and / or when using said board. However said scavengers negatively influence the speed of production. For example formaldehyde scavengers can become active before and / or during pressing of the board, such that the reactivity of the glue is reduced. When using scavengers the speed of production significantly decreases. It is therefore an object of the invention to obtain boards and methods for producing said boards which solves one or more of the above mentioned problems.

[0007] The invention, according to a first aspect, relates to a plate-shaped board comprising lignocellulosic material, for example lignocellulosic particles, and comprising glue and scavengers, wherein said lignocellulosic material is pressed and bound together with said glue, wherein the board comprises, from top to bottom, at least three layers, wherein at least one of said layers comprises scavengers and with the amount of scavengers being different for at least two of said layers. Said lignocellulosic material has been pressed and is bound together with said glue, and this for example with the aid of a continuous or a discontinuous press. For the plate-shaped board according to the first aspect of the invention, the scavengers are disproportionately distributed throughout the board and / or the scavengers are not homogeneously distributed throughout the board. The amount of scavengers can be expressed as the weight percentage of scavengers and / or a weight ratio. For example the weight percentage of scavengers upon the total weight of the layer, or the weight percentage of scavengers upon the total weight of the scavengers, the glue and the lignocellulose material, or the weight ratio of scavengers upon glue. The weight of the scavengers and / or the glue and / or the lignocellulosic material is preferably the dry matter weight. By having layers with different amounts of scavengers, said scavengers can be present at the desired locations and perform their activity, namely removing / neutralizing harmful substances, at the desired places and this with as little possible negatively influencing other properties such as board characteristics and / or production conditions of said board. For example said scavengers can be located in such a way that said boards can be produced at high speed and this while the boards have the desired technical characteristics, such as internal bond, density, strength, etc. It is possible that only one of said three layers comprises scavengers and / or at least one of said three layers does not comprise scavengers. If a said layer does not comprise scavengers, this indicates that there are no scavengers present which can negatively influence said layer. With scavengers are indicated chemical substances that remove and / or neutralize (deactivate) harmful substances. Preferably the scavengers are formaldehyde scavengers which neutralize formaldehyde.

[0008] The board comprises glue. Said glue is hardened / cured glue. In order to form this board, use is made of a glue which has not yet hardened / cured or is not yet completely hardened / cured. During manufacturing said board, this glue will (further) harden / cure so as to give a hardened / cured glue that bonds the lignocellulosic material together. The glue of the board, means a glue that has undergone hardening / curing during forming of the board, is sufficiently dry and bonds the lignocellulosic material together. This does not mean per se that the glue is completely hardened / cured. Here, a hardened / cured glue may or may not be a fully hardened / cured glue. By having layers with different amounts of scavengers, said scavengers can be present at the desired locations and not hinder the or less hinder the curing / hardening of the glue, such that the production speed of said boards can be sufficiently high.

[0009] The scavengers present in the board may or may not have already reacted with harmful substances, such as formaldehyde, and thus may or may not have removed / neutralised said harmful substances. During manufacturing of the board, scavengers are added. The board will comprise said scavengers, however it is possible that said scavengers are present in the board in another chemical form, then the form in which they were added when forming the board.

[0010] Percentages and amounts of the board of the different components of the board, e.g. the lignocellulosic material, the glue, the scavengers, are preferably expressed on the basis of the amounts of dry matter that were provided for manufacturing said board. This is because during formation of the board the different components will react with each other and there is also evaporation of for example (during production formed) water. The scavengers preferably comprise one or more of the list of: scavengers comprising sulphite, such as metabisulphite, bisulphite, e.g. sodium metabisulphite, sodium bisulphite, sodiumsulphite or potassium metabisulphite, potassium bisulphite or potassium sulphite, or scavengers comprising urea. Metabisulphite has been found to be a very suitable scavenger for formaldehyde. Other possible scavengers are tannines, ammonium salts, melamine, acetoacetamide, polyamine, compounds containing a bisulphite anion, compounds containing free or protected primary / secondary amines. The scavengers can also comprise or be hyperbranched polyamides. Preferably said hyperbranched polyamides are obtained by polymerisation of amino acids, preferably amino acids chosen from the list of: lysine, histidine, glutamine and asparagine. The scavengers can for example comprise hyperbranched polylysine. The scavengers can be combination of sodium metabisulphite and urea and hyperbranched polylysine, or a combination of sodium metabisulphite and urea or a combination of sodium metabisulphite and hyperbranched polylysine.

[0011] By having formaldehyde scavengers, the glue can be a ureaformaldehyde based glue, such as an urea formaldehyde glue (UF glue), a melamine urea formaldehyde resin (MUF glue), or a melamine urea phenol formaldehyde glue (MUPF glue). The glue can also be a phenol formaldehyde glue. These are reactive glues which allow such board to be produced in a fast manner. Of course other glues can be used such as polyvinyl acetate glues; polyurethane glues, poly acrylate glues, (polymeric) methylene difenyl diisocyanate glues, polyvinyl butyral (PVB) glues, polyurethane (PUR) hotmelts, polyester glues, bio-based glues based on for example sugars, lignin, hyper branched polyamides, etc. It is not excluded that the glue contains an additional hardener to improve the bonding, such hardener can be based on for example isocyanates, carbodiimides, aziridine, epoxy, etc. The glue can also be a mixture of two or more types of glue and / or different layers can comprise different glues.

[0012] By having formaldehyde scavengers, use can be made of recycled material comprising formaldehyde and / or emitting formaldehyde. For example if the board is a particle board, one can make use of old particles boards and other wood waste sources to manufacture particle boards. Preferably said lignocellulosic material comprises or is lignocellulosic particles. Said lignocellulosic particles can be chosen from the list of: wood chips, wood fibers, wood shavings, non-wood lignocellulosic fibers such as hemp fibers or flax fibers. The lignocellulosic material can comprise different types of lignocellulosic particles. The lignocellulosic material can comprise or be wood veneers. For example the board can be a plywood board comprising two or more wood veneers that are attached to each other with glue layers, with for example at least one of said glue layers comprising glue and scavengers and said wood veneers being layers of the board.

[0013] The lignocellulosic material can comprise two or more types of material, for example can comprise wood chips and wood fibers or can comprise wood chips and wood veneer.

[0014] One of said layers can comprise only scavengers or at least 90 weight percentage of scavengers. One of said layers can comprise no scavengers or at most 5 weight percentage of scavengers, preferably at most 1 weight percentage, most preferably at most 0,1 weight percentage. For example the board can comprise three layers with two outer layers and one central layer between said two outer layers. The central layer can comprise no scavengers or at most 3 weight percentage of scavengers, preferably at most 1 weight percentage, more preferably at most 0,1 weight percentage, and this while the outer layers comprise scavengers, preferably have an amount of scavengers which is at least higher than the amount of scavengers in the middle layer, preferably have at least 0,5 weigh percentage of scavengers, more preferably at least 1 weight percentage. Another option is that the board can comprises at least two outer layers, one middle layer located between said two outer layers, and at least one scavenger layer sandwiched between said middle layer and a said outer layer, with said scavenger layer for example comprising at least 80 weight percentage of scavengers.

[0015] Alternatively, instead of having at least three layers, the board can only comprise one or two layers, wherein said scavengers are not homogeneously distributed throughout the board and / or are disproportionately distributed throughout the board. This embodiment relates to a first variant of the invention. Preferred / specific embodiments of the first aspect of the invention apply mutatis mutandis to this first variant. For example the board can be a one-layered board, such as a one-layered wood fiberboard, comprising hyperbranched polylysine scavengers, wherein said scavengers are not homogeneously distributed throughout the board and / or are disproportionately distributed throughout the board.

[0016] In a preferred embodiment said lignocellulosic material comprises lignocellulosic particles, such as wood chips and / or wood fibers, and the board comprises at least three layers, being at least two lignocellulosic layers comprising at least lignocellulosic particles and glue, and a scavenger layer comprising at least scavengers, with said scavenger layer being located between said two lignocellulosic layers, preferably being sandwiched between said two lignocellulosic layers. Said lignocellulosic layers preferably comprise no scavengers or the weight ratio of scavengers upon dry weight of glue is lower than 5 percentage, preferably lower than 3 percentage, more preferably lower than 1 percentage, most preferably lower than 0,5 percentage. Here the scavenger action is largely or entirely performed by the scavenger layer. The lignocellulosic layers do not comprise scavengers or can comprise scavengers in a lower amount. This means that no scavengers or a lower amount of scavengers need to be added when forming a said lignocellulosic layer and also that there is less contact between scavengers and the glue of the lignocellulosic layers, such that scavengers will not or will less hinder the bonding together of said lignocellulosic particles by the glue in said lignocellulosic layers. Such boards can therefore be made in a fast manner and this while still having low emissions of harmful substances, such as formaldehyde. To make said lignocellulosic layers, preferably glue and lignocellulosic particles are mixed together in mixing equipment, since these lignocellulosic layers comprise no scavengers or comprise scavengers in a low amount, there is less risk of damage by scavengers to the mixing equipment. The thickness of a said scavenger layer can be small or even negligible in comparison to the thickness of the lignocellulosic layers. Said scavenger layer can or cannot be a complete contiguous layer. Preferably the scavenger layer is embedded between two lignocellulosic layers. If this is the case, there can or there can be no direct contact between said lignocellulosic layers. If the scavenger layer is not completely contiguous, there can be direct contact between said lignocellulosic layers, such that the scavenger layer does not negatively influence or has little influence upon the internal bond of the board.

[0017] Further preferably a said scavenger layer takes up at most 1% of the total thickness of the board, preferably at most 0,5%, most preferably at most 0,1%. This scavenger layer is very thin, such that the internal bond of the board, e.g. the bonding strength between the different layers is not negatively influenced and the risk of delamination at the height of the scavenger layer can be low.

[0018] Also further preferably, a said scavenger layer takes up between 0,1 and 2 weight percentage of the total weight of the particle board, preferably between 0,2 and 1 weight percentage, for example 0,3 or 0,5 or 0,7 or 1,5 weight percentage. This indicates that a said scavenger layer is a thin layer and that the amount of scavengers needed is low. A said scavenger layer can have a weight of between 10 and 60 gram / m2plate shaped board, for example 20 or 30 or 35 gram / m2plate shaped board, wherein a said scavenger layer then preferably only comprises scavengers.

[0019] Also further preferably, the at least two lignocellulosic layers comprise at least two types of lignocellulosic layers, being a core lignocellulosic layer and an outer lignocellulosic layer which forms an outer main surface of the board, wherein said core lignocellulosic layer and said outer lignocellulosic differ in one or more of the following:

[0020] -the amount of lignocellulosic particles, for example the weight percentage of lignocellulosic particles in said lignocellulosic layer;

[0021] -the amount of glue, for example the weight percentage of the glue;

[0022] -the type of glue;

[0023] -the type of lignocellulosic particles, for example the lignocellulosic particles of the core lignocellulosic layer can be more coarse than the lignocellulosic particles of the outer lignocellulosic layer and / or the lignocellulosic particles of the core lignocellulosic layer can comprise more recycled lignocellulosic particles than the lignocellulosic particles of the outer lignocellulosic layer;

[0024] -the amount and / or type of scavengers, for example the weight percentage of scavengers in said lignocellulosic layer; -the thickness.

[0025] Said differences are the result of the required characteristics of the board and the way the board is produced. For example, it can be desired that the density of the core lignocellulosic layer is lower than the density of the outer lignocellulosic layer and this for example by making use of more coarse lignocellulosic particles, and this to have a lighter panel with less material, but still with a sufficient strength. The lignocellulosic particles of the outer lignocellulosic layer can be finer than the lignocellulosic particles of the core lignocellulosic layer, such that the outer main surface of the board is more fit for applying a (decorative) top layer, such as one or more resin impregnated papers, to the board. A said outer lignocellulosic layer can comprise scavengers, while the core lignocellulosic layer can comprise no scavengers.

[0026] In a further preferred embodiment, the board comprises at least five layers, being two said scavenger layers and three said lignocellulosic layers, of which one said core lignocellulosic layer and two said outer lignocellulosic layers, wherein the board comprises from top to bottom, a first said outer lignocellulosic layer, a first said scavenger layer, the core lignocellulosic layer, a second said scavenger layer and a second said outer lignocellulosic layer. In this embodiment the core lignocellulosic layer preferably does not comprise scavengers or comprises at most 0,5 weight percentage of scavengers, preferably at most 0,1 weight percentage. Said board is made with the aid of pressing. During pressing, the lignocellulosic particles get bonded to each other by hardening / curing of the glue. Since said core lignocellulosic layer is embedded between other layers, it undergoes the pressure conditions, e.g. pressure and temperature, delayed and / or in a lesser amount, e.g. such that maximum temperature or pressure is less and / or the maximum temperature or pressure is present during a smaller time interval. The total amount of time needed to manufacture a board with the required characteristics, is thus determined by the time it takes for the glue of the core lignocellulosic layer to sufficiently harden / cure. Since in this embodiment no or almost no scavengers are present in said core lignocellulosic layer, bonding together of said lignocellulosic particles can take place in a good manner and this despite of said delayed and / or less strong pressure conditions (e.g. lower pressure and / or lower temperature), and this because there are no or little scavengers present which can hinder the curing / hardening of the glue. Said outer lignocellulosic layer can or cannot comprise scavengers. Since said outer lignocellulosic layers are located on the outside during pressing, there is a rapid build up of pressure conditions, e.g. pressure and temperature, such that the presence of scavengers will have less negative impact upon the bonding of the lignocellulosic particles of the outer lignocellulosic layer during pressing. Preferably the amount of scavengers in the outer lignocellulosic layer is at most 0,1%. Further preferably said scavenger layers comprise at least 80 weight percentage of scavengers, preferably at least 99 weight percentage of scavengers or only scavengers. Said scavenger layer can comprise glue, for example at least 1 weight percentage of glue and / or at most 20 weight percentage of glue, and this to improve the bonding strength between the different layers. Said scavenger layer can also comprise lignocellulosic particles, for example at most 20 weight percentage of lignocellulosic particles, preferably at most 5 weight percentage of lignocellulosic particles. Said scavenger layer can also comprise glue, for example at most 20 weight percentage of glue, preferably at most 5 weight percentage of glue. A said core lignocellulosic layers can be one-layered, but can also comprise two or more sublayers, wherein each sublayer can or cannot have approximately the same composition. There can also be two core lignocellulosic layers present with a said scavenger layers located between said two core lignocellulosic layers. There can also be reinforcement scrims or nets, such as glass fiber scrims present, for example between two of said abovementioned layers.

[0027] Further in a specific embodiment, the board can have two core lignocellulosic layers and three scavengers layers, with two said scavenger layers located between a said outer lignocellulosic layer and a said core lignocellulosic layer and with one said scavenger layer located between said two core lignocellulosic layers.

[0028] Also further preferably, in the abovementioned embodiment with at least 5 layers, a said outer lignocellulosic layer takes up between 4 and 20 percentage of the total thickness of the board. Preferably the core lignocellulosic layer takes up between 60 and 90 percentage of the total thickness of the board. Preferably, the thickness of a said scavenger layer is negligible, e.g. less than 0,1% of the total thickness of the board. In this manner the scavenger layer cannot negatively influence the internal bond of the said board.

[0029] Also further preferably, the total thickness of a said outer lignocellulosic layer is located between 0,3 mm and 3 mm. In this manner the scavenger layer is located inside the board, not to close to the outer surface, but also not to close to the center. The scavenger layer can perform its scavenger action in a good manner and this while the negative influence of the scavengers during manufacturing of said board is neglectable or small.

[0030] Also further preferably, the weight ratio of scavengers upon the glue of the core lignocellulosic layer is situated between 2% and 17%, preferably between 3% and 9%. Preferably at least 90 weight percentage of the scavengers is present in the scavenger layers, more preferably at least 95 weight percentage, most preferably at least 99 weight percentage. Therefore the weight ratio of scavengers present in the scavenger layers upon the glue of the core lignocellulosic layer is preferably situated between 2% and 17%, preferably between 3% and 9%. The amount of scavengers needed will be determined by the thickness of the board. The thicker the board, the more glue is needed and the more lignocellulosic particles are needed. This means, if the glue is a ureaformaldehyde based glue, that the ticker the board, the more formaldehyde will be present and therefore the more scavengers are needed. Surprisingly it has been found that even for thicker boards, for example boards having a core lignocellulosic layer with a thickness of more than 1cm, more than 2cm or more than 3cm, there is no need for scavengers in the core lignocellulosic layer, when it is embedded between two scavenger layers. The emission of harmful substances of said thicker boards can be sufficiently low.

[0031] In a preferred embodiment a said scavenger layer comprises at least 10 weight percentage of scavengers, preferably at least 30 weight percentage, more preferably at least 50 weight percentage, most preferably at least 80 weight percentage, and the most preferable at least 99 weight percentage, for example only scavengers. Scavengers can be provided in powder form. Therefore a said scavenger layer can be formed by strewing / scattering scavengers in powder form, if a said scavenger layer comprises high amounts of scavengers, and this ensuring easy production of a said board. If said scavengers are provided in powder form, use can be made of a roller scatterer or a shaking spreader. With the aid of a roller scatterer, scavengers can be very uniformly strewn / scattered. If said scavengers are provided in powder form to form said board, than preferably said powder is not to fine, but also not to coarse. A too fine powder could result in a poor internal bound of the board, a too coarse powder could result in less scavenger activity per gram of scavengers. Preferably the particles size of the scavengers is as such that at most 30 percentage of the scavengers by weight, preferably at most 20 percentage by weight, pass through a sieve with sieve diameters of 160 pm and / or at least 45 percentage of scavengers by weight, preferably at least 55 percentage by weight, does not pass through a sieve with diameters of 300 pm. Preferably at least 20 percentage of scavengers by weight, more preferably at least 35 percentage by weight, pass through a sieve with diameters of 300 pm, but do not pass through a sieve with sieve diameters of 160 pm. Preferably the average particle size D90 values are preferably smaller than 1000 pm, or even smaller than 700 pm or smaller than 500 pm, the average particle size D90 values may be between 100 pm and 500 pm. The average particle size may be measured by various techniques known in the art. Particularly for larger granules, the particle size may possibly be determined by sieving techniques, for example as described in EN 933- 2:2020. The particle size of smaller particles may be determined by laser granulometry, in particular, the median particle size D90 may be determined using laser granulometry, which may be performed in accordance with ISO 13320:2020.

[0032] In a preferred embodiment a said lignocellulosic layer comprises at most 1 weight percentage of scavengers, preferably at most 0, 1 weight percentage of scavengers and more preferably no scavengers. Here the scavenger action is substantially or only performed by said scavenger layers, such that the board can be made in a fast manner and / or comprises good properties, e.g. strength, etc.

[0033] In a preferred embodiment a said lignocellulosic layer comprises at least 97 percentage by weight of lignocellulosic particles and glue. A said lignocellulosic material here comprises substantially lignocellulosic particles and glue. Of course other materials, such as colorants, pigments, wax, flame-retardant additives, hardeners, moisture resistant components, antifungal additives, antimicrobial additives, etc. can also be present. The scavengers used in said board can be water-activatable scavengers, can for example be hydrolysable scavengers.

[0034] In a preferred embodiment, for the board, the weight ratio scavengers upon glue is situated between 0,5% and 10%, preferably between 1% and 4%. This indicates that with low amounts of scavengers, low emissions of harmful substances can be obtained.

[0035] The invention, according to a second aspect, relates to a plate-shaped board comprising lignocellulosic material, glue and scavengers, wherein said lignocellulosic material is pressed and bound together with said glue, and wherein the scavengers that are used in this board are heat and / or pressure activatable scavengers. Said lignocellulosic material has been pressed and is bound together with said glue. The plate-shaped board according to the second aspect of the invention can or cannot be according to the first aspect of the invention. This means that said heat and / or pressure activatable scavengers can be homogeneously distributed throughout the board, meaning that every layer, if the board is multilayered, comprises the same amount of scavengers, e.g. the same weight percentage of scavengers, such that the plate-shaped board is not according to the first aspect. If the board is also according to the first aspect, said heat and / or pressure activatable scavengers are not homogeneously distributed throughout the board. The advantage of heat and / or pressure activatable scavengers is that during production of a said board, said scavengers will only become active when needed, e.g. when sufficient heat and / or pressing is present, thus when curing / hardening of the glue happens or is done, such that they do not or less negatively influence the production speed.

[0036] Said heat and / or pressure activatable scavengers can be encapsulated scavengers, meaning that said scavengers are encapsulated with a shell or similar, which shell then disintegrates under the influence of heat and / or pressure. Said encapsulated scavengers can comprise a shell which encapsulates one or more of the list of: sulphites, such as metabisulphite, bisulphite, e.g. sodium metabisulphite, sodium bisulphite, sodiumsulphite or potassium metabisulphite, potassium bisulphite or potassium sulphite, or urea, tannines, ammonium salts, melamine, acetoacetamide, polyamine, compounds containing a bisulphite anion, compounds containing free or protected primary / secondary amines, or hyperbranched polyamides, such as hyperbranched polylysine.

[0037] The lignocellulosic material of the plate-shaped board preferably comprises wood chips and more preferably only comprises wood chips, such that the board is a particle board. Said wood chips can comprise virgin wood chips and / or recycled wood chips. Particle boards can be made by scattering different lignocellulosic base layers comprising glue and wood chips, such that the formation of a said scavenger layer can be easily implanted in the production process of particle boards and this by providing a unit that can scatter / apply scavengers upon a said lignocellulosic base layer. Of course, in another embodiment said lignocellulosic material can comprise wood fibers since also wood fiber boards can comprise different layers comprising wood fibers and glue. Of course, in another embodiment, said lignocellulosic material can comprise wood shaving since also OSB boards can comprise different layers comprising wood shavings and glue. The board can also be hybrid boards comprising at least two lignocellulosic layers having different lignocellulosic material choses from the list of: wood chips, wood fibers, wood shavings, veneers.

[0038] The invention, according to a third aspect, relates to a method for producing board material, wherein raw material is provided and production steps are performed to obtain said board material from this raw material, said raw material comprising at least lignocellulosic material, such as lignocellulosic particles (for example wood chips and / or wood fibers), glue and scavengers wherein the productions steps comprise at least the following production steps:

[0039] -a basic step wherein said raw material is brought together and transported to a shaping unit;

[0040] -a shaping step, wherein said brought together raw material is pressed into plate shaped material by said shaping unit to form said board material; wherein, in said basic step to bring said raw material together, at least three base layers are formed above each other, wherein at least one of said base layers comprises scavengers and with the amount of scavengers being different for at least two of said base layers.

[0041] The shaping unit preferably is or is part of a continuous press such as a continuous double belt press. Of course the pressing unit can also be or be part of a discontinuous press. Such a continuous press then preferably comprises one or more strewers / scatterers to strew / scatter one or more or all of said base layers. Preferably said base layers are subsequently formed above each other, for example subsequently strewn / scattered above each other. Further said continuous press preferably comprises a bottom belt upon which the base layers are formed above each other and an upper belt, wherein said base layers are pressed together between said lower and upper belt.

[0042] Preferably a sawing unit is present to saw said manufactured board material into base boards. Said base boards preferably being boards according to the first and / or second aspect of the invention or being submitted to further processing steps to form boards according to the first and / or second aspect of the invention. Said layers of the boards are thus respectively derived from said base layers.

[0043] Said board material as such can form a board. Preferably further process steps are performed upon said board material, such as sawing and / or sanding, to form said boards. The method for manufacturing board material is therefore also a method for manufacturing boards. Said boards are preferably boards according to the first and / or second aspect of the invention. The advantages and embodiments of the board of the first and / or aspect of the invention, therefore also are applicable to this method and vice versa.

[0044] In a preferred embodiment, said lignocellulosic material comprises lignocellulosic particles, and preferably only comprises lignocellulosic particles, such as wood chips or plant fibers, wherein said at least three base layers comprise at least two lignocellulosic base layers comprising at least lignocellulosic particles and glue, and a scavenger base layer comprising at least scavengers, with said scavenger base layer being located between said two lignocellulosic base layers. Preferably first a said lignocellulosic base layer is formed, for example scattered, then, upon this lignocellulosic base layer said scavenger base layer is applied, preferably scattered, and subsequently another said lignocellulosic base layer is applied upon the scavenger base layer, preferably scattered. The scavengers can be in particle form / powder form and can have particles sizes such that at most 30 percentage of the scavengers by weight pass through a sieve with sieve diameters of 160 pm and / or at least 55 percentage of scavengers by weight do not pass through a sieve with diameters of 300 pm. The average particle size D90 values are preferably smaller than 1000 pm, or even smaller than 700 pm, the average particle size D90 values may be between 100 pm and 500 pm. The average particle size may be measured by various techniques known in the art. Particularly for larger granules, the particle size may possibly be determined by sieving techniques, for example as described in EN 933-2:2020. The particle size of smaller particles may be determined by laser granulometry, in particular, the median particle size D90 may be determined using laser granulometry, which may be performed in accordance with ISO 13320:2020.

[0045] Further preferably the at least two lignocellulosic base layers comprise at least two types of lignocellulosic base layers, being a core lignocellulosic base layer and an outer lignocellulosic base layer, an outer lignocellulosic layer of the board material being derived from a said outer lignocellulosic base layer, wherein said core lignocellulosic base layer and said outer lignocellulosic base differ in one or more of the following: -the amount of lignocellulosic particles;

[0046] -the amount of glue;

[0047] -the type of glue;

[0048] -the type of lignocellulosic particles, for example the lignocellulosic material of the core lignocellulosic material can be more coarse than the lignocellulosic material of the outer lignocellulosic layer and / or the lignocellulosic material of the core lignocellulosic material can comprise more recycled lignocellulosic material than the lignocellulosic material of the outer lignocellulosic layer;

[0049] -the amount and / or type of scavengers;

[0050] -the thickness.

[0051] Typically the thickness of a said outer lignocellulosic base layer is smaller than the thickness of the core lignocellulosic base layer. Also typically, the weight percentage of glue of a said outer lignocellulosic base layer is higher than the weight percentage of glue of the core lignocellulosic base layer. Also typically, if the board is a particle board comprising wood chips as lignocellulosic particles, the wood chips of a said outer lignocellulosic base layer are finer (less coarse) than the wood chips of the core lignocellulosic base layer. For example the weight ratio glue to lignocellulosic particles of a said outer lignocellulosic layer can be between 6% and 15% and the weight ratio glue to lignocellulosic particles of the core lignocellulosic layer can be between 3% and 10%.

[0052] Further preferably, at least five base layers are formed on top of each other, being two said scavenger base layers and three said lignocellulosic base layers, of which one said core lignocellulosic base layer and two said outer lignocellulosic base layers, with from top to bottom, a first said outer lignocellulosic base layer, a first said scavenger base layer, the core lignocellulosic base layer, a second said scavenger base layer and a second said outer lignocellulosic base layer. Said core lignocellulosic base layer can be one-layered or can comprise two or more sublayers. For example, if the core lignocellulosic base layer is being scattered, use can be made of two scatterers to obtain a thicker core lignocellulosic base layer, of course use can also be made of a scatterer which can scatter thick layers.

[0053] In a very preferred embodiment said base layers are subsequently formed, preferably strewn or scattered, above each other and wherein the scavenger base layer is deposited, preferably strewn or scattered, in an amount between 5 and 100 g / m2of scavengers, preferably between 6 and 70 g / m2, more preferably between 10 and 30 g / m2, for example 14, 15, 16 or 17 g / m2or between 30 and 40 g / m2, e.g. 35 g / m2. Preferably said scavenger base layer substantially comprises scavengers, said scavengers being preferably in powder form, such that they can be easily strewn or scattered. The scavengers can also be in liquid form, for example dissolved in a liquid, and are then preferably poured or sprayed.

[0054] With such small amounts of scavengers, bonding between the different lignocellulosic base layers with a said scavenger layer in-between can be performed very well by pressing such that the obtained board material and therefore the obtained board will have a good internal bond. Preferably a said scavenger base layer takes up at most 1% of the total thickness of the said base layers formed above each other before pressing, preferably at most 0,5%, more preferably at most 0,1%. Also preferably a said scavenger base layer takes up between 0,1 and 1 weight percentage of the total weight of the said base layers.

[0055] Preferably a said outer lignocellulosic base layer takes up between 4 and 20 percentage of the total thickness of the base layers formed above each other. Also preferably the core lignocellulosic base layer takes up between 60 and 90 percentage the total thickness of the base layers formed above each other.

[0056] In a preferred embodiment a said scavenger base layer comprises at least 10 weight percentage of scavengers, preferably at least 30 weight percentage, more preferably at least 50 weight percentage, most preferably at least 80 weight percentage. Said scavenger base layer can for example only comprise scavengers. Said scavenger layer can also comprise glue and / or lignocellulosic particles, for example small amounts of glue, e.g. less than 20 weight percentages, preferably less than 5 weight percentage, to ensure good bonding between the different base layers.

[0057] In a very preferred embodiment a said lignocellulosic base layer comprises at most 1 weight percentage of scavengers, preferably at most 0,5 weight percentage of scavengers and more preferably no scavengers. For example the core lignocellulosic base layer comprises at most 0,1% of scavengers or no scavengers. During pressing, the pressure and temperature will gradually increase, however this will be slower for the core lignocellulosic base layer then for a said outer lignocellulosic base layer. To ensure good curing / hardening of the glue, no presence of scavengers and / or little presence of scavengers are beneficial. The outer lignocellulosic base layers can comprise higher amounts of scavengers, however the presence of said scavenger base layers omits the need for scavengers in said outer lignocellulosic base layers.

[0058] Preferably a said lignocellulosic base layer comprises at least 97 weight percentages of lignocellulosic material and glue. In a very preferred embodiment, the scavengers are water-activatable, for example are hydrolysable. During pressing, water / steam can be used / added. This water will then come in contact with said scavengers during pressing, such that the risk that the scavengers become active before their activity is needed, thus before the formation of formaldehyde as a result of curing / hardening of the glue, is low. The result is that the scavengers will not or will in a lesser amount negatively influence the hardening / curing of the glue, and good production speeds can be obtained.

[0059] Preferably said brought together raw material forms a cake, wherein said cake is pressed into plate shaped material by said shaping unit, and wherein before pressing by said shaping unit, steam is applied trough said cake, for example by steam injection and / or vacuum, said steam preferably comprising at least 95 wt% of water. With the aid of steam, heat and / or water is added to said cake. Said steam is therefore beneficial for heat- activatable and / or water-activatable scavengers. For example, adding said steam is very beneficial when said scavengers comprise or are sodium metabisulphite. By adding steam before pressing by said shaping unit, said scavengers are active from the moment pressing starts.

[0060] The invention, according to a fourth aspect, relates to a method for producing board material, wherein raw material is provided and production steps are performed to obtain said board material from this raw material, said raw material comprising at least lignocellulosic material, for example lignocellulosic particles such as wood chips and / or wood fibers, glue and scavengers wherein the productions steps comprise at least the following production steps:

[0061] -a basic step wherein said raw material is brought together and transported to a shaping unit;

[0062] -a shaping step, wherein said brought together raw material is pressed into plate shaped material by said shaping unit to form said board material; and wherein the scavengers are heat and / or pressure activatable scavengers. This method according to the fourth aspect of the invention can or cannot be according to the third aspect of the invention. This means that said heat and / or pressure activatable scavengers can be homogeneously distributed throughout said brought together raw material, meaning that every base layer, if the board is multilayered, comprises the same amount of scavengers, e.g. the same weight percentage of scavengers, such that the method is not according to the third aspect.

[0063] The advantage of heat and / or pressure activatable scavengers is that during production of a said board material, said scavengers will only become active when needed, such that they do not or less negatively influence the production speed. Said heat and / or pressure activatable scavengers can be encapsulated scavengers, meaning that said scavengers are encapsulated with a shell or similar, which shell then disintegrates under the influence of heat and / or pressure.

[0064] In a very preferred embodiment of the abovementioned aspects or of the first variant, the scavengers comprise one or more of the list of: scavengers comprising sulphite, such as metabisulphite, bisulphite, e.g. sodium metabisulphite, sodium bisulphite, sodium sulphite or potassium metabisulphite, potassium bisulphite or potassium sulphite, or scavengers comprising urea or scavengers comprising hyperbranched polyamides, e.g. hyperbranched polylysine. Said scavengers are formaldehyde scavengers.

[0065] Also preferably the lignocellulosic material comprises wood chips and the board is a particle board.

[0066] The invention, according to a fifth aspect, also relates to a decorative panel, preferably a floor panel or wall panel or furniture panel, comprising a substrate having one or more substrate layers and an applied thereon decorative top layer, wherein at least one of said substrate layers is obtained from a board according to the first and / or the second aspect of the invention and / or from a board material manufactured by the third and / or fourth aspect of the invention. Since these boards / board material have low emissions of harmful substances and can have good technical properties, these boards / board material are very suitable to form decorative panels. Said decorative top layers can comprise one or more resin impregnated papers, wherein the resin is for example a thermosetting resin such as a melamine resin. Said resin impregnated papers for example comprise a (digitally) printed resin impregnated paper and a translucent / transparent resin impregnated paper (e.g. a wear layer) optionally comprising hard particles such corundum to provide for additional wear resistance. Said decorative top layer can also be a HPL (high pressure laminate) comprising, in addition to a said printed resin impregnated paper and wear layer, one or more resin impregnated kraft papers. The resin of the resin impregnated kraft paper can be a phenol resin.

[0067] In a preferred embodiment a said decorative panel is rectangular and comprises two pairs of opposite edges, wherein said at least one substrate layer comprises an exposed portion at least at one of said edges.

[0068] Further preferably a said exposed portion is profiled and at least partially forms a first coupling part at the respective edge that allows said edge to be coupled to a second coupling part at the opposite edge of a similar decorative panel, wherein in the coupled condition a locking is obtained between the respective edges in a direction perpendicular to the plane of coupled panels and / or in the plane of coupled panels and perpendicular to the respective edges. It has been found that said scavenger layers have no negative influence upon the technical properties of the board / board material, such that coupling parts can be made in said board / board material.

[0069] In a second variant of the first and / or the second and / or the third and / or the fourth and / or the fifth aspect of the invention or of the first variant of the invention, instead of scavengers or in addition to said scavengers, additives are present which enhance specific properties of the board. For example instead of scavengers or in addition to said scavengers, fire resistant additives are present. Examples of fire resistant additives can be chosen from the list of: phosphates, such as ammonium phosphates or magnesium phosphates or aluminum phosphates, sulphates, sulfamates, aluminum trihydrate, huntite, magnesite and antimony oxide. The fire-resistant additives can or cannot be a combination of the above mentioned examples. A said scavenger (base) layer is in this second variant, an additive (base) layer, with said additive (base) layer at least comprising additives, such as fire resistant additives, which enhance a specific property of the board and optionally scavengers. A said additive (base) layer can for example have a weight ratio scavengers upon additives of between 10: 100 and 100: 10. In the prior art, to obtain fire-resistant boards, such as fire-resistant particles boards or fire-resistant fiber boards, fire resistant additives are mixed with the lignocellulosic material. By having a said additive (base) layer, as in our variant of the invention, we surprisingly found that we can obtain the same fire-resistant properties with less fire resistant additives. All the preferred embodiments of the first and / or second and / or third and / or fourth and / or fifth aspect of the invention also apply to this second variant. Some preferred embodiments of this second variant are further listed below.

[0070] Preferably the board is a particle board.

[0071] In a preferred embodiment the lignocellulosic material comprises lignocellulosic particles, such as wood chips, and the board comprises at least three layers, being at least two lignocellulosic layers comprising at least lignocellulosic particles and glue, and an additive layer comprising at least fire resistant additives and being located between said two lignocellulosic layers. Preferably said additive layer only comprises fire-resistant additives or only comprises fire-resistant additives and scavengers.

[0072] A said additive layer can take up at most 1% of the total thickness of the board, preferably at most 0,5%, most preferably at most 0,1%.

[0073] A said additive layer can take up between 0,1 and 1 weight percentage of the total weight of the particle board. Preferably the board comprises at five layers, being two said additive layers and three said lignocellulosic layers, of which one said core lignocellulosic layer and two said outer lignocellulosic layers, wherein the board comprises from top to bottom, a first said outer lignocellulosic layer, a first said additive layer, the core lignocellulosic layer, a second said additive layer and a second said outer lignocellulosic layer. A said outer lignocellulosic layer can take up between 4 and 20 percentage of the total thickness of the board and wherein preferably the core lignocellulosic layer takes up between 60 and 90 percentage of the total thickness of the board. The total thickness of a said outer lignocellulosic layer can be located between 0,3 mm and 3 mm.

[0074] The fire-resistant additives are at most 20 weight percentage of the board, preferably at most 15 weight percentage and / or preferably at least 10 weight percentage.

[0075] A said additive layer comprises at least 10 weight percentage of fire resistant additives, preferably at least 30 weight percentage, more preferably at least 50 weight percentage, most preferably at least 80 weight percentage.

[0076] A said core lignocellulosic layer comprises at most 1 weight percentage of fire resistant additives, preferably at most 0,1 weight percentage, and more preferably no fire resistant additives.

[0077] A said outer lignocellulosic layer preferably comprises fire-resistant additives, such that already a fire-resistant barrier is present above said additive layer. For example the outer lignocellulosic layer comprises between 10 weight percentage and 20 weight percentage of fire-resistant additives.

[0078] A said core lignocellulosic layer preferably comprises at least 97 weight percentages of lignocellulosic material and glue. Said fire resistant additives can be scattered / strewn to form a said additive base layer.

[0079] With the intention of better showing the characteristics of the invention, herein below, as an example without any limitative character, embodiments of the invention are described, with reference to the following schematic figures:

[0080] -figure 7 is a perspective view of a board according to the invention;

[0081] -figure 2 is a possible cross section of the board shown in figure 1;

[0082] -figure 3 is a cross section of a decorative panel comprising a substrate derived from a board according to the invention;

[0083] -figure 4 shows a possible method to manufacture particles board as shown in figures 1 and 2.

[0084] Figure 1 shows a plate-shaped board 1 comprising lignocellulosic particles, glue and scavengers. Said lignocellulosic particles can comprise wood chips, wood fibers or other plant fibers or wood shaving or a combination of two or more types of lignocellulosic particles. Preferably the lignocellulosic particles are wood chips and even more preferably at least part of said wood chips are recycled wood chips derived from for example end-of-life wood based panels / boards. Whit end-of-life panels / boards are indicated panels / boards of the non-exhaustive list: panels / boards that have been used by an end consumer and / or waste from production and / or waste from installation, shipping, marketing and / or unsold stock.

[0085] Said lignocellulosic material is pressed and bound together with said glue, and the board 1 preferably comprises, from top to bottom, at least three layers, wherein at least one of said layers comprises scavengers and with the amount of scavengers being different for at least two of said layers.

[0086] Figure 2 shows one possible embodiment of a board 1 according to the first aspect of the invention and optionally according to the second aspect of the invention. Preferably the lignocellulosic particles are wood chips, but the lignocellulosic particles can also be wood fibers or other plant fibers or wood shavings. As can be seen in figure 2, the board 1 comprises, from top to bottom, a first outer lignocellulosic layer 2, a first scavenger layer 4, a core lignocellulosic layer 7, a second scavenger layer 4 and a second outer lignocellulosic layer 3.

[0087] The core lignocellulosic layer 7 comprises lignocellulosic particles, glue and no scavengers. The outer lignocellulosic layers 2-3 each have the same composition and comprise lignocellulosic particles, glue and no scavengers or scavengers in an amount of less than 5 weight percentage, preferably less than 3 weight percentage, more preferably less than 1 weight percentage. The glue of the outer lignocellulosic layers 2-3 is the same as the glue of the core lignocellulosic layer 7 and is preferably a ureaformaldehyde glue. Other possibilities are a melamine ureaformaldehyde glue, a phenol formaldehyde glue, a pMDI glue, a bio-based glue. When the lignocellulosic particles are wood chips, then the wood chips of the core lignocellulosic layer 7 are more coarse then the wood chips of the outer lignocellulosic layers 2-3. The density of the outer lignocellulosic layers 2- 3 is higher than the density of the core lignocellulosic layer 7 and the average density is preferably situated between 500 and 1000 kg / m3, for example between 650 and 750 kg / m3. The scavenger layers 4 comprise scavengers and optionally glue, but then preferably in an amount of less than 5 weight percentage. The weight ratio glue upon lignocellulosic particles for the core lignocellulosic layer 7 is between 5 % and 8 %. The weight ratio glue upon lignocellulosic particles for the core lignocellulosic layer 7 is between 9 % and 12 %.

[0088] The scavengers are sulphite based scavengers and preferably are metabisulphite. Metabisulphite is very suitable to neutralize formaldehyde, such that the board 1 has low formaldehyde-emission. Metabisulphite is water-activatable, namely hydrolysable.

[0089] Said scavenger layers 4 are preferably substantially identical, meaning that they have the same composition and / or thickness. Each scavenger layer 4 preferably takes up at most 0,5% of the total thickness of the board 1, preferably at most 0,1%. A said scavenger layer 4 preferably takes up between 0, 1 and 2 weight percentage of the total weight of the board 1, preferably between 0,2 and 1 weight percentage. A said outer lignocellulosic layer 2-3 preferably takes up between 4 and 20 percentage of the total thickness of the board 1 and preferably the core lignocellulosic layer 7 takes up between 60 and 90 percentage of the total thickness of the board 1. For example the board 1 can have a thickness of 12 mm, with a core lignocellulosic layer 7 of 9 mm, outer lignocellulosic layers 2-3 of 1,5 mm and with scavenger layers 4 of which the thickness is neglectable in comparison to the said lignocellulosic layers 2, 3, 7. In figure 2 the scavengers layers 4 are indicated with a thick line to show were the scavengers layers 4 are present. In reality said scavenger layers 4 will be less thick.

[0090] The weight ratio scavengers upon the glue of the core lignocellulosic layer 7 is preferably situated between 1,5 % and 17 %, preferably between 3 % and 9 %.

[0091] Said scavengers can be encapsulated scavengers, e.g. comprise a shell which breaks under pressure and / or temperature, wherein for example metabisulphite is located inside said shell.

[0092] Figure 3 shows a decorative furniture panel 9 comprising a substrate derived from a board 1 according to the first aspect of the invention and optionally the second aspect of the invention. Here the panel 9 comprises, from top to bottom, a first decorative layer 8, a substrate and a second decorative layer 8. The substrate comprises, from top to bottom, a first outer lignocellulosic layer 2, a scavenger layer 4, a first core lignocellulosic layer 7, a scavenger layer 4, a second core lignocellulosic layer 7, a scavenger layer 4 and a second outer lignocellulosic layer 3. Said decorative layers 8 comprise one or more resin impregnated papers, wherein the resin is for example a melamine resin. Said resin impregnated papers for example comprise a (digitally) printed resin impregnated paper and a translucent / transparent resin impregnated paper (e.g. a wear layer) optionally comprising hard particles such corundum to provide for additional wear resistance. Said decorative layer 8 can also be a HPL (high pressure laminate) comprising, in addition to a said printed resin impregnated paper and wear layer, one or more resin impregnated kraft papers. The resin of the resin impregnated kraft paper can be a phenol resin. The said three scavenger layers 4 can be identical layers (e.g. thickness and composition) and can be the same as described for the embodiment shown in figure 2. It is also possible that the scavenger layer 4 located between the said core lignocellulosic layers 7 differs from the other scavenger layers 4. For example the scavenger layer 4 located between the said core lignocellulosic layers 7 can comprise encapsulated scavengers.

[0093] Figure 4 shows a possible way to manufacture said board 1 shown in figure 2. Said board 1 is made by scattering layers subsequently above each other, prepressing said layers and pressing said layers into board material 10. Said board material 10 is then sawn, and optionally sanded to form said board 1. In figure 4, as can be seen from the left to the right of figure 4, firstly an outer lignocellulosic base layer 30 is scattered upon a lower belt, subsequently a first scavenger base layer 40 is scattered upon said outer lignocellulosic base layer 20, then a core lignocellulosic base layer 70 is scattered upon said first scavenger base layer 40, subsequently a second scavenger base layer 40 is scattered upon said core lignocellulosic base layer 70 and finally another outer lignocellulosic base layer 20 is scattered upon said second scavenger base layer 40. When all the base layers 20, 30, 40, 70 are scattered above each other, said base layers undergo prepressing with the aid of a first press 5. During prepressing there is no rise in temperature or hardly any rise in temperature. If encapsulated scavengers are present, they will not be active during prepressing. After prepressing is the actual pressing with a heated double belt press 6. During pressing the temperature and pressure rises and the scavengers, if they are heat and / or pressure and / or water activatable, become active, such that formaldehyde formed during pressing is neutralized and the amount of formaldehyde emission during manufacturing said board material 10 is low. The amount of scavengers is as such that also during use of boards 1 derived from this board material 10, formaldehyde emission is low. The composition of said base layers 20, 30, 40, 70 corresponds to the composition of the respective layers 2, 3 ,4 ,7 of the corresponding board 1 as described above.

[0094] A said board 1 preferably has the following characteristics:

[0095] Transverse tensile strength (in accordance with EN 319): between 0,4 and 1,0 N / mm2Bending strength (in accordance with EN 310): between 12 and 18,0 N / mm2Young's Modulus (in accordance with EN 310): between 2500 and 3500 N / mm2 A said particle board 1 can be a El class (low formaldehyde) and even E0.5 class (very low formaldehyde).

[0096] The composition of said base layers 20, 30, 40, 70 is the same as for the corresponding layer 2, 3, 4, 7 of the board 1 of figure 2.

[0097] The present invention is in no way limited to the herein above-described embodiment; on the contrary, such method can be realized according to various variants, without leaving the scope of the present invention, as defined by the appended claims.

Claims

Claims.

1. A plate-shaped board comprising lignocellulosic material, for example lignocellulosic particles, and comprising glue and scavengers, wherein said lignocellulosic material is pressed and bound together with said glue, wherein the board (1) comprises, from top to bottom, at least three layers, wherein at least one of said layers comprises scavengers and with the amount of scavengers being different for at least two of said layers.

2. The plate-shaped board of claim 1, wherein said lignocellulosic material comprises lignocellulosic particles, such as wood chips and / or wood fibers, and wherein the board (1) comprises at least three layers, being at least two lignocellulosic layers comprising at least lignocellulosic particles and glue, and a scavenger layer (4) comprising at least scavengers, with said scavenger layer (4) being located between said two lignocellulosic layers.

3. The plate-shaped board of claim 2, wherein a said scavenger layer (4) takes up at most 1% of the total thickness of the board (1), preferably at most 0,5%, most preferably at most 0,1%.

4. The plate-shaped board of claim 2 or 3, wherein a said scavenger layer (4) takes up between 0,1 and 2 weight percentage of the total weight of the board (1), preferably between 0,2 and 1 weight percentage.

5. The plate-shaped board according to any of the claims 2 to 4, wherein the at least two lignocellulosic layers comprise at least two types of lignocellulosic layers, being a core lignocellulosic layer (7) and an outer lignocellulosic layer (2-3) which forms an outer main surface of the board (1), wherein said core lignocellulosic layer (7) and said outer lignocellulosic layer (2-3) differ in one or more of the following:-the amount of lignocellulosic particles;-the amount of glue;-the type of lignocellulosic particles, for example the lignocellulosic particles of the core lignocellulosic layer (7) can be more coarse than the lignocellulosic particles of the outer lignocellulosic layer (2-3) and / or the lignocellulosic particles of the core lignocellulosic layer (7) can comprise more recycled lignocellulosic particles than the lignocellulosic particles of the outer lignocellulosic layer (2-3);-the type of glue;-the amount and / or type of scavengers;-the thickness.

6. The plate-shaped board of claim 5, wherein the board (1) comprises at least five layers, being two said scavenger layers (4) and three said lignocellulosic layers, of which one said core lignocellulosic layer (7) and two said outer lignocellulosic layers (2-3), wherein the board (1) comprises from top to bottom, a first said outer lignocellulosic layer (2), a first said scavenger layer (4), the core lignocellulosic layer (7), a second said scavenger layer (4) and a second said outer lignocellulosic layer (3).

7. The plate-shaped board of claim 6, wherein a said outer lignocellulosic layer (2- 3) takes up between 4 and 20 percentage of the total thickness of the board (1) and wherein preferably the core lignocellulosic layer (7) takes up between 60 and 90 percentage of the total thickness of the board (1).

8. The plate-shaped board of claim 6 or 7, wherein the total thickness of a said outer lignocellulosic layer (2-3) is located between 0,3 mm and 3 mm.

9. The plate-shaped board according to any of the claims 5 to 8, wherein the weight ratio of scavengers upon the glue of the core lignocellulosic layer (7) is situated between 1,5 % and 17 %, preferably between 3 % and 9 %.

10. The plate-shaped board according to any of the preceding claims 2 to 9, wherein a said scavenger layer (4) comprises at least 10 weight percentage of scavengers, preferably at least 30 weight percentage, more preferably at least 50 weight percentage, most preferably at least 80 weight percentage.

11. The plate-shaped board according to any of the preceding claims 2 to 10, wherein a said lignocellulosic layer comprises at most 0,5 weight percentage of scavengers, preferably at most 0,1 weight percentage of scavengers and more preferably no scavengers.

12. The plate-shaped board according to any of the preceding claims 2 to 11, wherein a said lignocellulosic layer comprises at least 97 weight percentage of lignocellulosic material and glue.

13. The plate-shaped board according to any of the preceding claims, wherein the scavengers used in said board (1) are water-activatable, for example are hydrolysable.

14. The plate-shaped board according to any of the preceding claims, wherein the weight ratio scavengers upon glue is situated between 0,5% and 10%, preferably between 1% and 4%.

15. A plate-shaped board, optionally according to any of the preceding claims, comprising lignocellulosic material, glue and scavengers, wherein said lignocellulosic material is pressed and bound together with said glue, and wherein the scavengers used in said board (1) comprise heat and / or pressure activatable scavengers.

16. The plate-shaped board according to any of the preceding claims wherein the scavengers comprise one or more of the list of: scavengers comprising sulphite, such as metabisulphite, bisulphite, e.g. sodium metabisulphite, sodium bisulphite, sodium sulphite or potassium metabisulphite, potassium bisulphite or potassiumsulphite, scavengers comprising urea, scavengers comprising hyperbranched polyamides.

17. The plate-shaped board according to any of the preceding claims, wherein the lignocellulosic material comprises wood chips and wherein the board (1) is a particle board.

18. A method for producing board material, wherein raw material is provided and production steps are performed to obtain said board material (10) from this raw material, said raw material comprising at least lignocellulosic material, for example lignocellulosic particles such as wood chips and / or wood fibers, glue and scavengers, wherein the productions steps comprise at least the following production steps:-a basic step wherein said raw material is brought together and transported to a shaping unit;-a shaping step, wherein said brought together raw material is pressed into plate shaped material by said shaping unit to form said board material (10); characterized in that, in said basic step, to bring said raw material together, at least three base layers are formed above each other, wherein at least one of said base layers comprises scavengers and with the amount of scavengers being different for at least two of said base layers.

19. The method according to claim 18, wherein said lignocellulosic material comprises lignocellulosic particles and wherein said at least three base layers comprise at least two lignocellulosic base layers comprising at least lignocellulosic particles and glue, and a scavenger base layer (40) comprising at least scavengers, with said scavenger base layer (40) being located between said two lignocellulosic base layers.

20. The method according to claim 19, wherein the at least two lignocellulosic base layers comprise at least two types of lignocellulosic base layers, being a core lignocellulosic base layer (70) and an outer lignocellulosic base layer (20-30), anouter lignocellulosic layer of the board material (10) being derived from a said outer lignocellulosic base layer (20-30), wherein said core lignocellulosic base layer (70) and said outer lignocellulosic base layer (20-30) differ in one or more of the following ways:-the amount of lignocellulosic material;-the amount of glue;-the type of lignocellulosic particles, for example the lignocellulosic particles of the core lignocellulosic base layer (70) can be more coarse than the lignocellulosic particles of the outer lignocellulosic base layer (20-30) and / or the lignocellulosic particles of the core lignocellulosic base layer (70) can comprise more recycled lignocellulosic particles than the lignocellulosic particles of the outer lignocellulosic base layer (20-30);-the type of glue;-the amount and / or type of scavengers;-the thickness.

21. The method according to claim 20, wherein at least five base layers are formed on top of each other, being two said scavenger base layers (40) and three said lignocellulosic base layers, of which one said core lignocellulosic base layer (70) and two said outer lignocellulosic base layers (20-30), with from top to bottom, a first said outer lignocellulosic base layer (20), a first said scavenger base layer (40), the core lignocellulosic base layer (70), a second said scavenger base layer (40) and a second said outer lignocellulosic base layer (30).

22. The method according to any of the claims 18 to 21, wherein said base layers are formed, preferably strewn, above each other, and wherein a said scavenger base layer (40) is deposited, preferably strewn, in an amount between 5 and 100 g / m2of scavengers, preferably between 6 and 70 g / m2, more preferably between 10 and 30 g / m2.

23. The method according to any of the preceding claims 18 to 22, wherein a said scavenger base layer (40) comprises at least 10 weight percentage of scavengers,preferably at least 30 weight percentage, more preferably at least 50 weight percentage, most preferably at least 80 weight percentage.

24. The method according to any of the preceding claims 18 to 23, wherein a said lignocellulosic base layer comprises at most 1 weight percentage of scavengers, preferably at most 0, 1 weight percentage of scavengers and more preferably no scavengers.

25. The method according to any of the preceding claims 18 to 24, wherein a said lignocellulosic base layer comprises at least 97 weight percentage of lignocellulosic material and glue.

26. The method according to any of the preceding claims 18 to 25, wherein the scavengers are water-activatable, for example are hydrolysable.

27. The method according to any of the preceding claims 18 to 26, wherein said brought together raw material forms a cake, wherein said cake is pressed into plate shaped material by said shaping unit, and wherein before pressing by said shaping unit, steam is applied trough said cake, for example by steam injection and / or vacuum, said steam preferably comprising at least 95 wt% of water.

28. A method for producing board material, optionally according to any of the preceding claims 18 to 27, wherein raw material is provided and production steps are performed to obtain said board material (10) from this raw material, said raw material comprising at least lignocellulosic material, for example lignocellulosic particles such as wood chips and / or wood fibers, glue and scavengers, wherein the productions steps comprise at least the following production steps:-a basic step wherein said raw material is brought together and transported to a shaping unit;-a shaping step, wherein said brought together raw material is pressed into plate shaped material by said shaping unit to form said board material (10); and wherein the scavengers comprise heat and / or pressure activatable scavengers.

29. The method according to any of the preceding claims 18 to 28, wherein the scavengers comprise one or more of the list of: scavengers comprising sulphite, such as metabisulphite, bisulphite, e.g. sodium metabisulphite, sodium bisulphite, sodium sulphite or potassium metabisulphite, potassium bisulphite or potassium sulphite, scavengers comprising urea, or scavengers comprising hyperbranched polyamides.

30. The method according to any of the preceding claims 18 to 29, wherein the particle size of the scavengers is as such that at most 30 percentage of the scavengers by weight pass through a sieve with sieve diameters of 160 pm and / or at least 55 percentage of scavengers by weight do not pass through a sieve with diameters of 300 pm.

31. The method according to any of the preceding claims 18 to 30, wherein the lignocellulosic material comprises wood chips and wherein the board material (10) is particle board material.

32. A decorative panel, preferably a floor panel or wall panel or furniture panel, comprising a substrate having one or more substrate layers and an applied thereon decorative top layer (8), characterized in that at least one of said substrate layers is obtained from a board (1) in accordance with any of claims 1 to 17 or obtained from board material (10) manufactured in accordance with any of claims 18 to 31.

33. The decorative panel according to claim 32, wherein said decorative panel (9) is rectangular and comprises two pairs of opposite edges, wherein said at least one substrate layer comprises an exposed portion at least at one of said edges.

34. The decorative panel according to claim 33, wherein said exposed portion is profiled and at least partially forms a first coupling part at the respective edge that allows said edge to be coupled to a second coupling part at the opposite edge of a similar decorative panel, wherein in the coupled condition a locking is obtained between the respective edges in a direction perpendicular to the planeof coupled panels and / or in the plane of coupled panels and perpendicular to the respective edges.

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