This invention relates to board material, to methods for manufacturing board material and to panels which contain such board material.

More particularly, the invention relates to board material of the type which substantially is composed of bound flax shives, also called flax splinters or flax chips (English: flax shives). Such board material is widely known as such. Flax shives are recovered from flax as a waste product in the flax fiber production and relate to pieces from the stem of the flax plant which are broken up into chips. However, the invention also relates to board material of other types, for example, to board material of the type which is substantially composed of bound lignocellulose particles.

Flax boards are known as light-weight, inexpensive boards, which can be used, for example, as a filling material for a door panel, as the basis for a furniture or wall panel or as an environmentally friendly insulating board. Flax chipboard also has good acoustic properties and has a larger fire-retardant capacity than wood chipboard.

From DE 20 2007 017 713 U1 , it is already known for wood chipboards to reduce the weight by applying foamed polystyrene globules in the middlemost layer of such wood chipboard. Polystyrol or polystyrene as such is known as a not fireproof material. Therefore, it is also suggested in the above-mentioned document to apply separate fire-retarding additives in such board.

The present invention aims at still further optimizing boards of the above- mentioned type. Herein, it is striven for the possibility to offer thick boards, which still have a restricted weight, such that these boards are more ergonomic in use and more ecologic in transport. To this aim, the invention, according to its first independent aspect, relates to a board-shaped material of the type which substantially is composed of bound flax shives, with the characteristic that said board material comprises particulate filling material, preferably foamed particles, which is situated at least among said flax shives. As the flax shives as such have a fire-retarding capacity, particulate filling materials can be applied which have less fire-retarding capacity, with only a limited decrease of the global fire-retarding capacity of such board. Preferably, a synthetic filling material is used. It is possible to work without adding separate fire-retarding additives or with less of such additives and still achieve a similar result in respect to fire safety than it is the case with the wood chipboards of the above-mentioned state of the art.

According to a preferred embodiment, a particulate filling material is used which has a lower density than flax shives. Preferably, this density is at least 10% and at least 20% lower than the density of flax shives. Such density difference can be achieved with filling material having the form of foamed particles. In this matter, a more light-weight flax chipboard can be obtained, which further shows all positive features of the flax chipboards from the state of the art. For example, as particulate filling material a material can be used which comprises at least polystyrene, such as foamed particles which comprise polystyrol or polystyrene or consist thereof. It is also possible to apply polyurethane particles as particulate filling material.

According to another possibility, also natural particulate material can be used, for example, particulate filling material, which comprises cork granulate. According to an important possibility, cork with a low density can be applied, which, during the manufacture of cork products, is considered waste. Preferably, the cork granulate has a density of 10 to 80 kg/m ³ , or still better of 20 to 40 kg/m ³ . In this manner, still another example of the herein above-mentioned preferred embodiment is obtained. Moreover, cork as such has a fire-retarding property, which makes it ideally suited for being combined with flax shives. Moreover, in this manner a very ecologically sound board material is obtained. Preferably, the cork granulate which is applied has an average particle size situated between 0.3 and 5 millimeters, and still better between 0.5 and 3 millimeters. Such granulate, namely, is excellently suited for being applied as a filling material in flax shives, or even, according to a different variant, among wood chips. It is possible to select the cork granulate such that said average particle size is met. In this manner, a pre-treatment of the particles becomes unnecessary or almost unnecessary.

According to still another possibility, use can also be made of cork powder. Herein, this then relates to mechanically fractured cork granules, for example, ground cork granulate. The application of such small cork particles may also relate to the application of cork particles, which can be incorporated in a surface layer of a board material. In this manner, for example, sound-dampening effects can be achieved without reducing the properties of the surface layers possibly consisting of fine chips. The dimensions of cork powder -are^extremely suited for^being applied as a filling material in fiberboards, such as MDF or HDF.

As mentioned, the application of cork granulate and/or cork powder is interesting for other board types, too. This is why the invention, according to a deviating aspect, also relates to a board material having the characteristics of the first aspect, or the preferred embodiments thereof, wherein instead of flax shives, wood chips or wood fibers are applied and wherein the particulate filling material either comprises a fraction of cork granulate and/or cork powder, or substantially or completely consists thereof. Herein, thus, a modified chipboard, OSB board, wood fiber board, MDF or HDF board is obtained. It is also possible to apply cork granulate and/or cork powder as a filling material in a board material, which substantially is composed of a bound mixture of wood and flax particles, such as a bound mixture of wood chips and flax shives. This embodiment is of interest in view of the fact that the availability of flax shives can fluctuate strongly according to the season. With less availability of such flax shives, these then can be supplemented with wood chips. Herein, the share of the wood chips in the mixture of wood chips/flax shives may amount to between 10 and 50 weight percent. Preferably, this share amounts to between 25 and 40%.

It is noted that the geometry of pressed flax shives is well suited for offering space to filling materials, and in particular to globular or particulate filling materials. As flax shives typically are rougher than wood chips, they will earlier form intermediate spaces for such filling material; moreover, filling material can be distributed more easily in a relatively homogenous manner among the flax shives.

Preferably, the flax shives mentioned in the first aspect are bound by means of polycondensation glue. Preferably, said polycondensation glue comprises at least urea formaldehyde. Whether or not in combination with urea formaldehyde, such polycondensation glue can also comprise at least lignosulphonate and/or can comprise materials which are chosen from the list of melamine glue, melamine formaldehyde glue, methane diphenyl diisocyanate glue, phenol formaldehyde glue, resorcinol formaldehyde glue and resorcinol phenol formaldehyde glue. Preferably, said polycondensation glue substantially consists of thermo-hardening polycondensation glue. Preferably, a weight ratio of binding agent, for example, polycondensation glue, to flax shives situated between 2:98 and 12:88 is applied. Preferably, when manufacturing the board-mateτiat-of theHnventiorrand in the case of applying urea formaldehyde as a binding agent for flax shives, use is made of an added amount of urea, such that possible free formaldehyde still can be bound. It is clear that the ratios mentioned here also are valid when wood chips or wood fibers or mixtures of wood particles and flax particles are applied instead of flax shives, wherein then the weight ratio of binding agent to lignocellulose particles is taken into consideration.

The also herein above-mentioned lignosulphonate can be obtained, for example, as a waste product from paper production, and a board material containing at least a fraction of lignosulphonate as a binding agent thus can be considered very ecological. An ideal combination is created when such lignosulphonate is applied with particulate filling material consisting substantially or entirely of cork granulate.

According to a preferred embodiment of the first aspect, the bound flax shives form a layer which is situated centrally in the thickness of the board material, whereas one or both surfaces of the board material are formed by a layer which comprises bound wood chips or wood fibers. By means of this preferred embodiment, various effects are achieved. As one or both of the surfaces show the composition of wood fiberboard, a layer with a relatively high density is obtained at these surfaces, which can contribute to the strength of the board material in a significant manner, and in particular to the bending strength and/or resistance against impact loads and/or the hardness of the board or the board material. Moreover, by means of such layer a surface can be obtained which is easy to finish and which, probably after grinding, is excellently suited for being finished with a laminate layer, a veneer layer, a lacquer layer or another, preferably decorative, layer, whether or not showing a pattern. Preferably, the thickness of the layer formed by the flax shives is at least 70% of the thickness of the board material. As the major part of the board material consists of flax shives, the positive features of flax shives, such as the low density thereof, largely are kept. Preferably, the average dimensions of the wood chips or wood fibers situated at one or both surfaces are smaller than the average dimensions of the flax shives situated centrally. Hereby, it is obtained that the texture of the surfaces, possibly after grinding, can be made smooth. As the determining dimension preferably the longest dimension of the respective chips or shives is used.

It is clear that the board material irrthe-case of the-alsσabove=mentiσned deviating aspect also may show different layers, wherein the filling material then preferably is situated at least in a central layer of wood chips or wood fibers, whereas at one or more surfaces a layer is formed with wood chips or wood fibers of smaller average dimensions, wherein these layers preferably are free from the aforementioned filling material.

Preferably, the board material of the invention has an overall thickness situated between 18 and 60 millimeters, and still better situated between 25 and 50 millimeters. In this range, a significant weight reduction can be achieved.

Preferably, said particulate material, for example, said foamed particles or said cork granulate, as also mentioned above, are spread homogenously or almost homogenously in the entire layer formed by flax shives. In this manner, the invention is very efficient. A homogenous or approximately homogenous distribution of the filling material minimizes the risk of the occurrence of defects, such as porous areas, in a laminate top layer provided on the board material. Namely, inhomogeneities may lead to pressure differences in the press device, which in their turn lead to defects in the solidification of melamine or other resin situated in the laminate top layer.

Preferably, said particulate material, for example, said foamed particles or said cork granulate, are situated substantially only in the layer formed by the flax shives. Still better, such particles are absent in possible other layers, which are free or at least almost free from flax shives.

Preferably, the layer formed by the flax shives is free or almost free from wood chips and/or other chip-like material.

Preferably, the board material of the invention has a density of less than

500 kilograms per cubic meter, and still better of less than 300 kilograms per cubic meter. Boards of interest have, for example, a density situated between 350 and

450 kilograms per cubic meter. Within this range, the boards of the invention can show the combination of a limited weight and acceptable mechanical properties as well. Of course, it is not excluded that good mechanical properties can also be obtained with lower densities, depending on the intended use.

According to a second independent aspect, the invention also relates to a board material of the above-mentioned type, characterized in that said flax shives are at least partially bound by means of a foamed binding agent. It is evident that by means of such board material similar effects can be obtained as with the above- mentioned board materials in respect to weight reduction. Moreover, it is possible to obtain a more pronounced weight reduction. Said foamed binding agent may comprise, for example, melamine foam, urea foam and/or polyurethane foam. It may also concern a foamed binding agent on the basis of polyethylene, polystyrene, polyurethane, polyvinyl chloride or the like. Preferably, here also a board is concerned which, at one or both surfaces thereof, has a layer formed by bound wood chips or wood fibers.

Preferably, the foaming of the binding agent is performed at least partially in a press device. For example, for manufacturing the board material of the second aspect, use can be made of a method starting from a material mass comprising flax shives and binding agent, wherein this material mass is brought into a press device or is fed there through, and wherein foaming or expanding the binding agent occurs at least partially in the press device. The press device as such then can be used as a calender for adjusting the final thickness of the board material concerned.

A method in which a component of a board material is foamed or expanded in the press device, as such is of interest, independently from the fact whether this respective component now is applied as a binding agent, filling material or independent layer. Thus, such method forms a third independent aspect of the present invention. For example, the particulate filling material of the first aspect can be foamed or expanded in this manner, or by means of such method, a board material can be obtained internally comprising a layer of foamed or expanded synthetic material. It is clear that for the material of such component, the foamable or expandable materials mentioned in connection with the first aspect can be applied. Preferably, synthetic materials comprising polyurethane or polystyrene are applied. Preferably, the board material obtained according to the third aspect comprises one or more layers, for example, surface layers, which comprise bound flax shives and/or wood chips and/or wood fibers. In this manner then again a lightweight, ecological board is obtained, which nevertheless has sufficient strength and/or allows good finishing of the flat sides thereof.

It is clear that the invention according to the aforementioned third independent aspect can be defined as a method for manufacturing board material, with the characteristic that it starts from a material mass which comprises at least flax shives or other lignocellulose particles, and an expandable or foamable component, wherein this material mass in brought into a press device or fed therethrough, and wherein foaming or expanding said expandable or foamable component is at least partially performed in the press device. Preferably, herein the press device as such is applied for adjusting the final thickness of the board material. Preferably, herein a press device of the continuous type is applied. However, it is not excluded to work with so-called cycle presses. Preferably, said material mass is subjected to at least two press cycles, whether or in direct succession, wherein in the second press cycle a lower pressure and/or temperature is applied than in the first press cycle, and wherein the expansion of said component will take place substantially during this second press cycle. In the first press cycle, the higher pressure and/or temperature present there can be applied at least for binding the material mass which shall be present in the surface layers of the board material.

According to a deviating variant of the above-mentioned aspects of the invention, instead of flax shives chips can be applied which are obtained from dried grass species, such as straw, hay, hemp, elephant grass, bamboo and the like.

According to a fourth independent aspect, the invention aims at an alternative board material, which, according to various preferred embodiments, can have particular decorative and/or technical features and/or allows that a decorative and/or technically superior board can be manufactured in a relatively simple manner. To this aim, the invention relates to a board material which is substantially composed of bound lignocellulose particles, for example, in the form of flakes, chips, powder and/or fibers, with the characteristic that at least one flat side of the board material substantially is formed by bound cork granulate. Preferably, the binding among the separate cork granules as well as the binding among the granulate and the underlying lignocellulose particles has been realized by means of polycondensation glue, preferably by means of the same polycondensation glue. To this aim, the polycondensation glues mentioned in connection with other aspects can be applied. As the conVgranuSaterthe=ateove=rrfentionecHow-density cork can be applied and/or cork with the particle size mentioned there. Preferably, the board material of the fourth aspect has an internal transition zone between the bound lignocellulose particles and the bound cork granulate, wherein this transition zone comprises a bound mixture of cork granules and lignocellulose particles.

Said lignocellulose particles preferably are chosen from the series of wood particles, grass particles and flax particles. This may relate, for example, to wood chips, wood fibers or flax shives. For the binding among the lignocellulose particles, the also above-mentioned polycondensation glues, whether or not in the above-mentioned ratios, can be applied, too.

The overall thickness of the board material of the fourth aspect preferably is situated between 5 and 25 millimeters, and still better between 10 and 20 millimeters. Such thickness is suitable, for example, when the board material of the second aspect serves as a starting material for manufacturing floor panels or other decorative interior panels. For example, the respective flat side can be finished with one or more layers of lacquer, varnish or melamine, wherein then the appearance of the decor side of the panels concerned preferably is determined by said cork granulate. According to another example, another decor-forming material can be applied on the respective flat side, such as a printed decor or a veneer, wherein the cork granulate then, at least partially, fulfills the function of damping sounds which occur when the panels are in use.

According to a particular embodiment of said fourth aspect, a print is performed on the cork granulate, whether or not directly thereon. Preferably, to this aim one or more primer layers are provided on the cork granulate, such as primer layers comprising levelling material, and/or such imparting an approximately uniform or uniform basic color to the board material or panel. The print then can be performed directly on these primer layers by means of a technique such as roto-offset printing or rotation gravure printing, or by means of a digital technique, such as inkjet printing. Such print then can be finished further by means of one or more transparent layers of lacquer, varnish or melamine, wherein such, layers can comprise hard particles, such as aluminum oxide, in order to increase the wear- resistant features of such board material or panel. According to this particular embodiment, a decorative panel is obtained having very good sound-proofing or sound-dampening properties.

Preferably, the board material of the fourth aspect is manufactured by means of a method wherein the binding among the cork granules, as well as the binding between the cork granulate and the, whether or not already bound, lignocellulose particles, is obtained simultaneously or at least almost simultaneously, for example, in the same press device. For example, it can be started from a, whether or not pre-densified and/or whether or not already consolidated, material mass comprising at least a layer of lignocellulose particles provided with glue, wherein preferably un-bound or not completely bound cork granules are provided on this material mass, wherein the whole of material mass and cork granules is provided in a heated press device or is fed therethrough, wherein the mutual binding among the cork granules, as well as the binding among the cork granulate and the underlying material mass are obtained in said press device. Preferably, by means of the same press treatment also the final binding among the lignocellulose particles is obtained. To this aim, for example, the continuous press devices can be applied, which are usual in the production of flax chipboard or wood chipboard. For composing said material mass, one or more strewing treatments can be applied. Also for applying the loose cork granules, one or more strewing treatments can be applied. Possibly, the whole of material mass and cork granules, or only a portion thereof, can be pre-densified or deaerated before being brought into the actual press device. It is even possible that the material mass of lignocellulose particles is already completely bound and densified before the loose cork granules are provided thereon.

It is clear that the herein above-described method as such forms a particular independent aspect of the present invention, which can be defined as a method for manufacturing board material, starting from a material mass which comprises at least a layer of lignocellulose particles provided with glue, with the characteristic that cork granules or other particulate filling material is provided on this material mass, wherein the whole of material mass and cork granules, or other filling material, is provided in a heated press device, wherein the mutual binding among the cork granules or the filling material as well as the -binding among the cork granulate, or the filling material, and the underlying material mass is obtained in said press device. For another particulate filling material, the filling materials mentioned elsewhere can be applied, such as, for example, said expanded or expanding filling materials.

It is clear that also board material which is obtained or can be obtained by means of a method with the characteristics of the above-mentioned particular aspect, forms a subject of the present invention. Such board material can be defined in an independent manner as a board material which comprises at least a first layer and a second layer of particles bound by means of polycondensation glue, with the characteristic that said first layer substantially is composed of bound lignocellulose particles, whereas said second layer substantially is composed of bound cork granules or filling particles. Preferably, the binding between the first and the second layer also is obtained by means of polycondensation glue, still better by means of the same polycondensation glue which is applied in the first and/or the second layer. Preferably, the cork granules or the filling particles have a lower density than the applied lignocellulose particles. Preferably, this density is 10% and still better 20% lower than the density of the lignocellulose particles. It is clear that as a filling material or cork granules those can be applied which are mentioned in connection with other aspects and that similar advantages can be achieved herewith, for example, in respect to ecological and/or economical features of the board material. Further, it is clear that as lignocellulose particles, for example, wood chips, wood fibers, flax shives or mixtures thereof can be applied. It is noted that said second layer, according to a first possibility, can be situated at the surface of the board material, whereby in fact an embodiment of the aforementioned fourth aspect can be obtained. According to a second possibility, said second layer can be realized as an internal layer, wherein said first layer then preferably is situated at a surface of the board material. In this latter case, the overall thickness of the board material preferably is situated between 18 and 60 millimeters, and still better between 25 and 50 millimeters. Preferably, the board material of said second possibility is applied as filling material, for example, of a door or other comparable wall or furniture panel. It is not excluded that both aforementioned possibilities are combined and that, for example, a board material is realized having an internal layer as well as a surface layer which is substantially composed of particulate filling material, for example, of cork granules. Preferably, the board material of the second possibility mentioned in the particular aspect has a density of less than 500 kilograms per cubic meter, and still better of less than 300 kilogram per cubic meter. Boards of interest have, for example, a density situated betweert'βSO and— 4§§ ^~ kttegFams- peF^eabicr-meterr WithtnHihis range, the boards of the invention can show the combination of a limited weight and acceptable mechanical properties as well. Of course, it is not excluded that good mechanical properties can also be obtained with lower densities, depending on the intended use. For using the board material as a filling material in a door or other panel, a density situated between 200 and 300 kilograms per cubic meter may suffice.

According to the invention in general, an internal layer, whether formed by filling material or cellulose particles or both, preferably forms at least 50% of the overall thickness of the board material, and still better at least 70% of this thickness.

It is noted that according to the fourth aspect or the herein above-mentioned particular aspect, also other components may be provided in the bound cork granulate. For example, metal particles or color pigments may be mixed therewith, wherein then a very attractive decorative effect can be achieved.

It is also noted that according to a deviating variant of said fourth aspect or said particular aspect and the preferred embodiments thereof, a preferably compressible other granulate can be applied instead of cork granulate, such as, for example, a synthetic material granulate, such as a granulate on the basis of polystyrene. By "compressible", it is meant here more compressible than the lignocellulose particles which are applied in the same board material. Also, it is possible that the granulate comprises a mixture of different granulates, whether or not on the basis of cork. The difference between the granulates may manifest itself, for example, in a difference in grain size, color and/or material or the like. According to this deviating variant, particularly interesting effects can be achieved. Possibly, even motifs can be realized, which are or are not repeatable and/or can be pre-set beforehand.

The invention also relates to panels manufactured on the basis of the board materials of the invention. To this aim, the invention relates to a panel for furniture, doors or walls, characterized in that-this panel substantially consists of the above- mentioned board material, wherein one or both surfaces of this panel are provided with a finishing layer on the basis of paper and/or synthetic material and/or a layer of wood, such as veneer. This may relate, for example, to a lacquer layer, a melamine layer, a laminate layer or to a layer of wood which is thicker than veneer. Preferably, herein the board material of the invention is used as a filling material.

With the intention of better showing the characteristics of the invention, hereafter, as an example without any limitative character, a preferred embodiment is described, with reference to the sole accompanying drawing, wherein:

Figure 1 , in a cross-section across the thickness, represents the composition of a board material having the characteristics of, amongst others, the first aspect of the invention;

Figure 2, in a same view, represents the composition of a board material having the characteristics of, amongst others, the fourth aspect of the invention;

Figure 3 represents some steps in a possible method for manufacturing a board material having the characteristics of the fourth aspect;

Figure 4, in a view similar to that of figures 1 and 2, represents the composition of a board material which is obtained by means of a method having the characteristics of the third aspect; and

Figure 5 represents another board material in a view similar to that of figure

4.

As represented in figure 1, the present invention, according to its first aspect, relates to a board material 1 of the type which substantially is composed of bound flax shives 2. The bound flax shives 2 form a layer 3, which is situated at least centrally in the thickness T of the board material 1. Herein, the thickness T1 of the respective layer 3 is at least 70%, and in this case even more than 90%, of the overall thickness T of the board material 1.

The particularity of the first aspect of the present invention consists in that the board material 1 comprises filling material, in this case, foamed polystyrene particles 4, which are situated at least among said flax shives 2. In this case, the foamed particles 4 are situated exclusively in said layer 3 formed by bound flax shives 2. While the overall thickness T of the board material 1 of the example is approximately 30 millimeters, the central layer 3, which comprises flax shives 2, makes up a thickness T1 thereof of approximately 28 millimeters, and the outermost layers 5 of the board material 1 respectively are formed by a separate layer 5 having a thickness of approximately 1 millimeter. Figure 1 shows this very clearly. In this case, both surfaces 6 of the board material 1 are formed by a separate layer 5 which comprises finer material, for example, bound wood chips or wood fibers. For example, the board material 1 may show the typical composition of a wood chipboard or a wood fiberboard at its surface, wherein said wood particles preferably are bound with a similar or the same binding agent as the flax shives 2 of the central layer 3, this is to say, also by means of a polycondensation glue chosen from the above-mentioned possibilities therefor.

Figure 1 also shows that the outermost zones 7 of the central layer 3 are densified more than the internal zone 8 of this central layer 3. The filling material 4 situated in the outermost zones 7 then also is substantially less expanded or foamed than the filling material 4 situated in the internal zone 8, or are compressed more than the filling material 4 situated in the internal zone 8. The more densified zones 7 together make up approximately a third of the thickness T1 of the central layer 3 which contains flax shives 2.

Figure 1 also illustrates that the foamed particles 2 are almost homogenously distributed in the entire layer 3 formed by the flax shives.

In dashed line 9, it is also represented that by means of such board material 1 a panel can be manufactured which, at least at one of said surfaces 6, however, preferably at both surfaces 6, is provided with one or more finishing layers (10-11- 12). As, in the example, finishing is provided on both surfaces 6, the risk of warping of the panel is minimized. Possibly, on one of these surfaces 6 a so-called balancing layer 10 can be used, having the main purpose of counteracting such warping as much as possible. At the other surface 6 then, as in the example, a laminate layer can be used, which comprises, for example, a decor layer 11 and a transparent or translucent protective layer 12 or overlay, both preferably on the basis of paper and synthetic material. Said decor layer may be provided, for example, with a print of a motif, however, this is not represented here. It is clear that on the basis of the example of Figure 1 also an example of the deviating aspect mentioned in the introduction can be formed, when said flax shives are replaced by wood chips and when in the respective layer^particulate filling material, which comprises cork granulate, is used.

Figure 2 represents a board material 1 which is substantially composed of bound lignocellulose particles, in this case, wood chips and/or flax shives 2. In the example, one flat side or surface 6 of the board material 1 is formed by bound granulate 13, in this case, bound cork granulate. The binding among the separate cork granules 14 as well as between the cork granulate and the underlying wood chips and/or flax shives 2 is obtained by means of polycondensation glue. Also the underlying wood chips and/or flax shives 2 themselves are bound by polycondensation glue. In this case, the represented board material 1 also shows a transition zone 15 between the granulate 13 and the bound lignocellulose particles, wherein this transition zone 15 comprises a bound mixture of cork granules 14 and lignocellulose, namely, wood particles and/or flax shives 2. In this zone 15, the granules 14 rather are present as a particulate filling material .4. This mixture, too, is bound by means of polycondensation glue. It is clear that according to a variant of the embodiment represented in figure 2, wood fibers, too, can be applied instead of wood chips and/or flax shives 2.

Figure 3 represents how such variant can be formed by consolidating a composed material mass 16 consisting substantially or entirely of particles.

To this aim, figure 3 schematically represents some steps S0-S1-S2 in a method with the characteristics of the particular independent aspect of the invention mentioned in the introduction. In the example, this relates to a method which is performed by means of a production line 17, which substantially corresponds to a typical MDF or HDF production line. Herein, it is started from a material mass 18, which, in a preceding step SO, is composed at least by means of two components. In this case, both components together are supplied to a strewing machine 19, in the form of wood particles previously provided with binding agent, namely, with polycondensation glue, more particularly wood fibers 20 provided with polycondensation glue. The strewing machine 19 of such production line 17 can be constructed in any manner. In the example, a strewing machine 19 is applied such as it is known as such from WO 03/053642. The strewing machine 19 of the example is provided with a plurality of agitating elements 21 , which set the glue-provided wood fibers 20 into motion in the strewing chamber 22. By means of the wood fibers 20 exiting the strewing chamber 22 at the bottom side, the material mass 18 is composed on the transport device or transport conveyor 23 situated there underneath. For further description of such strewing machine 19, reference is made to the aforementioned international patent application. Of course, other types of strewing machines are also suitable, such as, for example, the strewing machines described in the international patent applications WO 99/36623 and WO 2005/044529. It is clear that when wood chips and /or flax shives 2 are used instead of wood fibers 20, preferably at least the strewing machine 19 is adapted thereto.

Seen in transport direction, downstream from the strewing machine 19, there is a so-called scalpel roller 24, which removes possible excess wood fibers 20 from the material mass 18, after which then a material mass 18 with a flat or quasi-flat upper surface is obtained. It is noted that it is not mandatory to work with such scalpel roller 24.

Seen in transport direction, downstream from the strewing machine 19, there is a device 25 for providing unbound, however, provided with polycondensation glue, cork granules 14 on the material mass 18. In this case, the device 25 performs a strewing treatment. To this aim, for example, a strewing device can be applied such as known as such from GB 1 ,003,597 or GB 1,035,256. As depicted in figure 3, such strewing device may comprise a recipient 26, which is in connection with a dosing roller 27, which removes the granules 14 from the recipient 26. Such dosing roller 27 preferably is made with a structure, wherein the granules 14 then substantially are carried along by the lower-situated structural portions of the dosing roller 27. Further, such strewing device preferably also comprises a device 28, which removes the granules 14 from said dosing roller 27. In this case, a brushing device is applied for that purpose. By means of such strewing device, a sufficiently homogenous strewing pattern can be obtained.

The thus obtained composed material mass 16 can have a thickness D which is up to 50 times or more larger than the thickness T of the board material 9 finally to be obtained, as it is pressed, in one or more densifying steps S1-S2, until this required thickness T of the board 1 or the panel is achieved. During these densifying steps S1-S2, the com posechnaterøMrnass-16- preferably experiences at least a doubling of its density. These further densifying steps S1-S2 are also schematically represented here.

In transport direction downstream from said scalpel roller 24, there is a densifying device or pre-press 29, in which the composed material mass 16, prior to the actual hot pressing in step 2, gradually is densified to a condition in which it can be transported in a simpler manner in comparison to the un-densified composed material mass 16. To this aim, the composed material mass 16, during step S1 , preferably, as represented here, is transported between pressing belts 30, wherein these pressing belts 30 have an intermediate distance which decreases in transport direction. During this pre-densification in the pre-press 29, preferably no heat is supplied and/or preferably the binding agent which is present is not yet or only partially activated. Rather, the pre-densification preferably relates to at least partially removing the gasses, such as air, present in the composed material mass 16.

According to a variant of the method represented in figure 3, the granules 14 or a portion thereof are provided in the material mass 18 only after said pre- densification is performed in step S1.

Downstream from the densification device or pre-press 29, seen in transport direction, there is the actual press device 31 , in which the composed material mass 16, whether or not already pre-densified, is pressed under the influence of heat. The temperature applied may be, for example, between 100 ⁰ C and 150 ⁰ C, and the applied pressure may be, for example, on average between 4 and 10 bar, however, temporary peak pressures up to 40 bar are not excluded herein. Preferably, the activation of at least the binding agent present on the granules 14 substantially will take place in this press device 31. Preferably, here also the activation of the binding agent present on the wood fibers 20 will take place. In the case of polycondensation glue, water or rather steam may be formed in this press device 31. The press device 31 depicted here is of the continuous type, namely, of the type in which the composed material mass 16 is transported and/or gradually pressed between pressing belts 30. In transport direction of such press device 31 , a pressure and/or temperatαre-gradieBt-(3rrbe=set-By-means-oHhis-ρress"-devi ce 31 , the density of the already partially densified composed material mass 16 can at least be doubled. It is clear that the method of the invention can also be performed with other press devices, such as, for example, with a steam press, a multi- opening press or with a so-called short-cycle press. With these other press devices 31 , the applied pressure and/or temperature can be set in function of the time that the respective material mass 16 remains in the press device 31.

By means of the production line 17 represented here, also a method with the characteristics of the third aspect can be performed. For this purpose, an expandable or foamable agent must be taken up in the material mass 18, which agent then will expand or foam in the press device 31. To this aim, the temperature and/or pressure gradient in the press device 31 can be adjusted such that the material mass 18 undergoes at least two successive press cycles, wherein in the second press cycle a lower pressure and/or temperature is applied than in the first press cycle. Hereby, it can be achieved that the expansion or the foaming of the agent concerned substantially takes place in said second press cycle. Herein, the press device 31 then can be applied as a calender for adjusting the thickness T of the final board material 1. The first press cycle may lead substantially to binding the material mass 16 in the layers 5 to the surface 6 of the final board material 1. Such method is not illustrated here.

Figure 4, however, illustrates a board material 1 , which can have been obtained by means of such method. Herein, this relates to a board material 1, wherein the expanded or foamed agent forms an independent internal layer 32. This means, this layer 32 substantially is free from lignocellulose particles. At both surfaces 6, the board material 1 has a layer 5 which comprises bound wood chips and/or flax shives 2 or even substantially consists thereof.

Figure 5 represents another board material 1 which can be obtained by means of a method with the characteristics of the particular aspect of the invention mentioned in the introduction. The board material 1 concerned comprises an internal layer 32, which is substantially composed of bound cork granules 13. In this case, the board material is provided on both surfaces 6 with a layer 5, which substantially consists of bound lignocellulose particles, in this case, flax shives 2. The cork granules 13 as well as the lignocellulose particles 2 are bound by means of a polycondensation glue. Also the bonds between the internal layer 32 and the surface layers 5 are obtained by means of such polycondensation glue. It is clear that the board material 1 represented here forms an example of the second possibility of the second layer mentioned in connection with the particular aspect.

It is clear that the internal layer 32 of the board material of figure 5 also can be substantially composed of another filling material than the bound cork granules 13 or the cork granulate 14. For example, such internal layer 32 can also be composed substantially of expanded synthetic particles, such as polystyrene particles, which are bound by means of polycondensation glue.

The board material 1 of figure 5 may be applied, for example, as a substitute for a honeycomb board. In such board 1 , an internal layer is formed by a cardboard honeycomb structure. The board material 1 of figure 5 can offer higher fire- retarding properties than a board with a honeycomb core, as the cork granulate 14 as such has a fire-retarding capacity.

Generally, it is noted that the thickness of the different layers of the board material represented in the figures must be interpreted in a non-limitative manner.

The present invention is in no way limited to the embodiments described herein above, on the contrary, such board material, panels and methods may be realized according to various variants, without leaving the scope of the present invention.