EP1110687B1 - Process for producing a light weight fibre board with a closed surface, and board so produced - Google Patents

Abstract

Moldings from lignocellulose particles, bound with polyurethane by applying binder component (I) containing isocyanate (NCO) groups and binder component(s) (II) containing polyol(s) to the particles separately, preforming, calibration and heating to initiate the polyurethane reaction of the binder. The particles are first divided into >= 2 batches, (I) is applied to one batch and (II) to the other and the batches are mixed before molding to the preform.

Description

The invention relates to a process for the preparation a lightweight fiberboard according to the preamble of the claim 1 and on a lightweight fiberboard according to the preamble of patent claim 15.

In other words, the invention relates a lot to fiberboard low density, in particular as insulating material, but also as Design elements can be used, and on their Production. A typical representative of known fiberboard the aforementioned field of application are so-called wood soft fiber boards.

For the production of soft wood fiber boards is a wet process known. By grinding, grinding or squeezing force fibers made of wood are turned into an aqueous Suspension, which is typically only 2 to 3% by weight Contains fibers. This suspension with the maximum swollen Fibers are applied to a screen belt through which a Drainage first by gravity and then over various suction and Vorpreßeinrichtungen done. The case achievable degree of drainage is due to the water storage capacity the swollen fibers and the face of the aimed at low density of later fiberboard only limited permissible compression forces downwards. By the pre-dewatering of the suspension obtained fiber mat moist fibers are dried without pressure after their calibration. During drying, the individual wood fibers shrink fixed, if no binder is used. If a binder is used, so that it is in the known method to such after the preamble of claim 1 Care must be taken to ensure that the binder to the Fibers are fixed, otherwise it is with the water of the Suction suspension is sucked or pressed. The after the Although known wet process obtained fiberboard can indeed have desired low density. But they have a loose open surface, which is unsuitable for many applications is on. For example, after the wet process manufactured fiberboard used as insulation panels in interior design used, not readily papered or otherwise be coated with thin materials. This expresses itself too easy the on the structure of in their preparation used sieve bands returning surface structure Fiberboard through, and used binders are too large Shares sucked into the volume of fiberboard and stand so as not for the attachment of wallpaper or other thin Materials available on the surface of the fiberboard.

In addition to the wet process, a so-called dry process for the production of fiberboards from lignocellulosic fibers and binders is known. The fibers are obtained in the same way as for the wet process. Subsequently, however, they are not transferred into a suspension, but dried in current dryers, ie in flight, to a level that later allows easier removal of the residual moisture. The residual moisture content of the fibers after drying is less than 20%, typically less than 10%. Before or after drying, a binder is added to the fibers, which, after the subsequent shaping of the fibers into a fiber mat during hot pressing of the fiber mat between pressure-controlled heating surfaces to a fiberboard, glues the individual fibers together. Dry-laid fibreboards are subdivided into high-density fibreboard (HDF), medium-density fibreboard (MDF), light and ultra-light fibreboard (ULF) within a density range of 900 to 450 kg per m ³ . Characteristic of fiberboard according to the known dry process is that even with so-called ultra-light fibreboard (ULF) due to the still relatively high density no good insulation effects are achieved and when using the fiberboard as construction elements, the relatively high weight of the fiberboard is taken into account. However, these known fiberboard on smooth closed surfaces that are directly coated even with thin materials.

Furthermore, a so-called semi-dry process is known in which the first dried as in the dry process fibers after the formation of a fiber mat moistened again and then pressed hot. In this way, with relatively light fiberboard in the range above 450 kg / m ^3, a particularly firm, smoothly closed surface is achieved.

From DE 196 74 240 A1 a process for the production of fiberboard is known which is also to be arranged between a real wet process and a dry process. With this known method, fibreboards with a low density of up to well below 150 kg / m ³ , allegedly down to 60 kg / m ³ can be produced. For this purpose, fibers made of wood, the moisture content of which remains unchanged after a refiner process which concludes a defibration process, are mixed with a binder and applied to a forming station with a spreader to form a fiber mat. The fiber mat is precalibrated in width and basis weight and shaped and cured after activation of the binder by a heat treatment to form the fiberboard. The activation of the binder should be done for example by steam. To harden the fiber mat, this is to be flowed through with a drying medium, for example with hot air. If a thickness formation takes place in a press, the pressing surfaces should be designed like a sieve. In this way, as in a wet process fiberboard with open and structured by the screen surfaces used surface are produced, which thus also have all the disadvantages of known produced in the wet process fiberboard.

From DE 196 04 575 A1 a process for the production of polyurethane-bonded fiberboard is known, which is classified as a special dry process. The known method makes use of a binder having a first, NCO-containing binder component and a second, at least one polyol-containing binder component. Here, the at least two binder components are applied separately or at least without significant pre-reaction in the mixture on fibers, so that the polyurethane bond takes place as late as possible in the manufacturing process and thus substantially during a hot pressing as a heat treatment. For separate application of the two binder components, for example, first the second binder component comprising the polyol is applied to the fibers, while the first NCO-containing binder component is applied to the same fibers only thereafter and as late as possible before the fibers are formed into the fiber mat. By separately applying the binder components for the polyurethane bond or suppressing a pre-reaction of the binder components, the entire reactivity of the binder for the bonding of the fibers during hot pressing of the fiber mat to the fiberboard should be maintained. Namely, it is known that the polyurethane reaction between the binder component containing the NCO groups and the binder component containing the polyol spontaneously starts when these two binder components come together unless it is chemically blocked. As a result, the pot life of mixtures of the two binder components is limited. Conversely, in the case of a chemical blockade of the polyurethane reaction, very high reaction temperatures must be achieved by the heat treatment for triggering the polyurethane reaction of the binder in the fiber mat. The process known from DE 196 04 575 A1 has the disadvantage that immediately after both binder components have been applied to the fibers, the polyurethane reaction is used. That is, the period between the application of the two binder components to the fibers and the heat treatment for curing the binder content of the desired fiberboard must be kept as short as possible. Interruptions in the manufacturing process in the area of forming the fibers to the fiber mat, calibrating the fiber mat, and the heat treatment cause the polyurethane reaction on the fibers to progress so far that they must be discarded. A temporary storage is not possible. In addition, there is a risk that fibers in the suspended material flow stick together so far that production equipment clog and must be cleaned consuming. The bulk densities of the polyurethane-bonded fiberboards produced by the known process are in the usual range well above 450 kg / m ³ .

The invention has for its object to provide a method for Production of light fiberboard according to the preamble of Claim 1 show that simple and economical is feasible and yet improved to fiberboard with Surface properties leads. Furthermore, a slight Fiberboard according to the preamble of claim 15 be shown, the improved surface properties having.

According to the invention, this object is achieved by the method according to Claim 1 and the fiberboard according to claim 15 solved.

Advantageous embodiments of the method are in the Subclaims 2 to 15 and advantageous embodiments of Fiber board described in the subclaims 16 to 20.

Despite the low average bulk density of less than 400 kg / m ³ achieved, the new process is a dry process because the fiber moisture content of the fibers is less than 20% when calibrating the fiber mat and during the heat treatment to cure the binder. It can be in the range below 10% as with conventional dry processes. As with a traditional dry process, the heat treatment of the fiber mat via smooth closed heating surfaces, via which the heat is transferred to the curing of the binder on the fiber mat. It is important that the heating surfaces are distance-controlled and not pressure-controlled, as is the case when carrying out conventional drying processes. The very low bulk density of the fiber boards produced by the new process does not allow controlled pressure control of the heating surfaces. Due to the distance control of the heating surfaces, however, a density profile is impressed on the fiberboards produced which has an edge increase of the bulk density compared with the average bulk density of the fiberboards of at least 20%. The edge regions of the fiberboard are thus compressed compared to their average density. In conjunction with the smooth heating surfaces that cause this compaction results in a smooth closed surface of the fiberboard produced. This smoothly closed surface is an absolute novelty for fiberboard in the density range below 400 kg / m ³ . Thus, highly effective thermal insulation panels for interior work can be produced, which can be directly over-wallpapered. The smooth closed surface of the new fiberboard is also very beneficial in other applications.

In the new process is not to be overlooked that the low Density, which is already present in the fiber mat, a heat transfer to the middle of the fiber mat during the heat treatment not exactly relieved. That's why it's new Method preferred, the fiber mat before heat treatment with To spray water or an aqueous solution. In this way can be steamed by water evaporating on the heating surfaces be directed into the interior of the fiber mat, there the Curing of the binder promotes. In addition, the water gives way to the Fibers on the surface of the fiber mat, so that through the Influence of smooth heating surfaces particularly good smooth surfaces can be achieved in the finished fiberboard.

Except for the determination of the area-related mass occupancy the fiber mat through the spaced controlled heating surfaces also be calibrated.

The given distance of the heating surfaces, the thickness of the is typically 20 up to 300 mm. It's just in the area of bigger thicknesses in This area amazing that the fiberboard still after can be produced by a dry process.

It is particularly preferred in the new method, if the Density profile of the fiberboard is adjusted so that an edge exaggeration of the density compared to the middle Density of the fiberboard of at least 60% results. A Stronger marginal increase in density is the basis for the Forming a particularly strong closed surface of finished fiberboard, for example, a considerable Pressure stability compared to the average density of the Can have fiberboard.

If the average bulk density of the fiberboards is set to 150 to 350 kg / m ³ in the new method, a common synthetic resin of the wood-based material industry can be used as the binder. The usual synthetic resins of the wood-based materials industry include urea-formaldehyde, melamine-urea-formaldehyde, melamine-urea-phenol-formaldehyde, phenol-urea-formaldehyde, phenol-formaldehyde and PMDI resins.

When the average apparent density of the fiberboards is set at 60 to 250 kg / m ³ in the new method, a foaming polyurethane binder may be used as the binder. In the overlying range of bulk density, the advantage of filling the voids in the fiberboard between the individual fibers by the polyurethane foam is no longer noticeable in an economically utilizable way. The particularly light fiberboard in the range below 150 kg / m ³ but can not be produced in usable quality without the use of a foam-forming binder.

As foam-forming polyurethane binder may be a so-called One-component system are used, which for example was developed by the company Bayer and basically is available. Preferably, however, an easier manageable Used two-component system, wherein the foam-forming Polyurethane binders a first, having NCO groups Binder component and a second at least one polyol comprising binder component.

It is in a particularly preferred embodiment of the new process, the fibers before applying the Binder divided into at least two batches and on a first of these games only the first, having the NCO groups Binder component and on a second of these parts only the second, the polyol-containing binder component to apply and the parts of the fibers only just before molding to mix the fiber mat together. Until mixing the Lots of fibers are the two binder components so completely separated from each other. Also during mixing The parts of the fibers are not yet worth mentioning Contact of the two binder components. Only when molding the Fiber mat turns this contact at the contact points of the Fibers. But this contact is still not enough to alone trigger a significant amount of polyurethane reaction. Only over very long periods of time or through the Heat treatment becomes the relevant main part of the polyurethane reaction which then causes the desired binding of the fibers in the fiberboard leads. It is surprising that the Polyurethane reaction ultimately, despite the microscopic view inhomogeneous distribution of binder components in the Heat treatment is complete. That means it is not noticeable loss of reaction as a result of both Binder components are not present on all fibers. There at the same time the reactivity of the binder fully on the Polyurethane reaction is concentrated within the fiber mat, the binder can be obtained in relatively small proportions the fibers and the desired strength of the fiberboard be used.

In the new process, the first batch can basically be 10 up to 90% and the second batch corresponding to 90 to 10% of the contain entire fibers. But it makes sense if the first and second parts of the fibers are about the same size are, d. H. For example, each 40 to 60% of the total Contain fibers.

But that does not stand in the way that even a third game subjecting the fibers to another treatment prior to blending becomes. In particular, a third batch of fibers be left without binder component until with the other parts is mixed. This procedure is particular interesting in the range of very low binder proportions.

The new process can be both discontinuous as well be carried out continuously, which is preferred. at continuous process control are the heating surfaces typically at rear heated metal endless belts intended.

If the new process using a polyurethane binder carried out continuously with two binder components After the application of the fibers, the batches of fibers can Binder components and before mixing them separately be stored by each other. The reactivity of the Binder components increases in separate storage of the Part of the fibers does not decrease even for longer periods of time.

In the new method, the heat treatment can be made be that in the middle of the molding a temperature of only 50 to 100 ° C is reached. That means that compared to known methods very low temperatures in the middle of the Shaped body are sufficient. These result inversely in a high efficiency of the used in the heat treatment Energy and short periods of time for the heat treatment needed. The low temperature is at the new Process at least then for the curing of the binder content in the middle of the molding sufficient if highly reactive polyurethane binders are used, whose Reaction is not chemically hindered to a pre-reaction suppress.

Preferably, the fibers used in the new process be processed, wood fibers in the form of conventional Defibratorfaserstoff.

The binder content can be far in the new process Borders are selected by the necessary strength of the Fiberboard on the one hand and the economy of the Process face high binder costs on the other hand are set. The following information refers to the Use of a polyurethane binder.

In one embodiment of the new process, the average density of the shaped body is adjusted to 60 to 250 kg per m ³ , wherein the binder content of the molding is adjusted to a total of 2.5 to 5% by weight based on atro wood fibers.

This results in moldings, some of them as pure Heat insulation body and to greater densities also as Wall elements with high rigidity and high insulation potential are usable.

In a further embodiment of the novel process, the average density of the molding is adjusted to 250 to 400 kg / m ³ , wherein the binder content of the molding is adjusted to a total of 7 to 15% by weight based on atro wood fibers. This results, for example, extremely strong but still very light fiberboard with high sound insulation potential. Due to their strength and the resistance to moisture of their bonding, the fibreboards can also be used as building materials, with their relatively low weight still being particularly advantageous.

The new method can also be carried out so that the Forming the preform from the fibers using a layer construction different compositions and / or proportions of Binder is set in each layer. So For example, the binder levels in the topcoats a fiberboard be larger than in the middle layer, to a particularly high stability of the outer layers too to reach. But there are also other layer structures for Adaptation to specific requirement profiles with the new procedure realizable. It is understood that lots of Fibers used for different layers of the layer structure are provided, not with each other before forming the fiber mat but only those fibers that are mixed for each provided a layer of uniform composition are.

In the new process in the embodiments with the PUR binder of two binder components may in particular by variation of composition and relative proportion of the Polyol-containing binder component known wide Spectrum of the properties of polyurethane bonds exploited become. It is also a use of as an accelerator or retarder additives to one or both of the Binder components possible. Likewise, fungicidal and / or herbicidal additives used for the shaped body to be produced become.

Figur

ein Flußdiagramm zum prinzipiellen Ablauf einer speziellen Ausführungsform des neuen Verfahrens.

The invention is explained in more detail below with reference to exemplary embodiments and described. It shows the

figure

a flowchart for the basic procedure of a specific embodiment of the new method.

Before referring to the figure on specific embodiments of the new Process is to be received, in which a PUR binder made of various binder components used comes, should the basic embodiments of the new Be explained method based on different density ranges.

In the density range of 60 to 150 kg / m ³ , mechanically stable fiberboards result using a foam-forming binder, ie a polyurethane binder which has at least two binder components PMDI and polyol or which is a one-component system. Such fiber boards may also be considered fiber stabilized polyurethane foam. The binder content of atro fibers is at least 5%, so in absolute terms it is still relatively small.

From an average density of about 150 kg / m ³ less voids between the fibers are present, so that the binder content can be reduced when using a foam-forming polyurethane binder below 5% atro fibers. If the stabilities are not paramount, binder levels down to within 1% may be sufficient. All percentages are, as usual, weight percentages.

From average densities of about 150 to 200 kg / m ³ , it is also possible to use non-foam-forming binders, ie customary synthetic resins from the wood-based panel industry. With lower densities in this range, however, the binder content should also be selected for lower strengths above 5%, and for higher strengths 7 to 15% binder content should be used. Preference is given to mixing systems with additions of melamine and phenols instead of the relatively brittle hardening urea-formaldehyde resins. The usual considerations between the price of the binder, possible formaldehyde elimination and possible harmful residual phenols must be taken.

Also in the range average gross densities up to 350 kg / m ³ and above, a foam-forming binder can be used, in which case high-strength fiberboard can be produced even with relatively low binder levels.

The method illustrated in the flow chart of the figure for the production of polyurethane-bound molded body goes from wood 1, which is comminuted in the usual way and then in a defibrator 2 in individual wood fibers 3 is digested. The stream of wood fibers 3 is then in a Dividing device 4 divided into two parts 5 and 6, wherein the games 5 and 6 are the same size. On the wood fibers 3 of the Lot 5 becomes in an applicator 7 an NCO groups containing binder component 8, a so-called PMDI, applied. The formulation of PMDI 8 corresponds to one such as those commonly used in the wood-based panel industry sole binder is used. On the wood fibers 3 of the Lot 6 is in an applicator 9 one at least one Polyol-containing binder component 10 applied. Here it is preferably a mixture of short chain with a long-chain polyol. For example, a mixture one part of diethylene glycol and one part of polyether alcohol the molecular weight 1000 can be used. Both application devices 7 and 9 work on the principle that the PMDI 8 and the polyol 10th is sprayed onto the wood fibers 3. Subsequently, the Lots 5 and 6 if necessary in separate buffers 11 and 12 intermediately stored. These may be conventional wood fiber bunkers act. An intermediate storage is basically optional and does not have to be mandatory. she allows it, however, the further process steps from here to here Decouple described method steps to ultimately to achieve optimum efficiency of the manufacturing process. In a mixing device 13, the wood fibers 3 of the Batches 5 and 6 mixed together. With a suitable combination the streams of lots 5 and 6 may be the required mixing also by rolling a scattering head a scattering device 14 done. From the wood fibers 3 both Batches 5 and 6 becomes a fiber mat in the spreader 14 15, which is a preform of fiberboard produced here 18 represents. The fiber mat 15 is in a calibration device 16 calibrated, which is a cold pre-compression Prepress is. Subsequently, in a Hot press 17 a heat treatment from which the desired Fiberboard 18 results. The hot press 17 is not so to understand that the fiber mat 15 under application compressed by pressure. Rather, the plates are the Hot press 17 distance-controlled, even without a constant back pressure the fiber mat 15 to fiber plates 18 with a defined thickness get. The new process can be done with both a belt press as a hot press 17 as well as with a discontinuous working Hot press to be performed. It can be beneficial instead of or alternatively to hot contact surfaces also a Hot air heating or high frequency heating of the calibrated Fiber mat 15 provide. When warming over hot contact surfaces, it is advantageous to the surfaces of Sprinkle fiber mat 15 with water, so that on the hot Contact surfaces evaporating water heat also into the interior of the Fiber mat 15 transfers. This is especially beneficial if the fiber mat 15 is very thick, d. H. more than 40 mm thick.

In the following, individual concrete embodiments will now be described for the production of fiberboard 18 after that in the figure outlined method described. The new procedure is but in principle also for the production of chipboard and other plates from other lignocellulosic or other applicable at least OH-containing particles. These do not really have to be made of wood. Especially You can also use other basic vegetable substances Find. Moreover, it is not possible, even substances of plant origin, provided they are in the polyurethane bond can be integrated with.

The following examples have in common that the PMDI used, d. H. the NCO group-containing binder component, a Had composition, as used in the wood-based panel industry is common. The second polyol component binder component was the already mentioned above mixture of one Part of diethylene glycol and one part of polyether alcohol of molecular weight 1000. As a mixing device 13 came a simple rotary drum for use. The mixing time of the two games 5 and 6 was 10 seconds. The temperature of the contact surfaces of Hot press 17 was set at 170 ° C. All% information is in weight%.

Example 1:

The PMDI 8 was used in a proportion of 2.5% and the polyol 10 in a proportion of 1% based on atro wood fibers 3. After 240 sec. Dwell time of the fiber mat 15 in the hot press 17, a 100 mm thick fiber plate 18 was removed. The average bulk density of this fiberboard 18 was 80 kg / m ³ . Despite the very low compression of the wood fibers in this fiber board, the fiber board for an insulating material was perfectly stable and manageable.

Example 2:

The binder proportions corresponded to Example 1. After 300 sec. Dwell time of the fiber mat 15 in the hot press 17, a 50 mm thick fiber plate 18 was removed. The average bulk density was 170 kg / m ³ . The flexural strength of the fiberboard 18 was 0.3 N / mm ² . The compressive stress at 10% compression was 0.18 N / m ² .

The above strength values clearly suggest that that the reactivity of both binder components 8 and 10 for the binding of the wood fibers in the fiberboard 18 fully exploitable is. At the same time it should be noted that despite the contribution the two binder components 8 and 10 via different Lots 5 and 6 of wood fibers 3 the polyurethane reaction in the increased temperature in the hot press 17 obviously not is hindered, which is considered quite surprising got to.

LIST OF REFERENCE NUMBERS

1 -

Wood

2 -

defibrator

3 -

fibers

4 -

A distributor

5 -

game

6 -

game

7 -

applicator

8th -

Binder component / PMDI

9 -

applicator

10 -

Binder component / polyol

11 -

cache

12 -

cache

13 -

mixing device

14 -

scattering device

15 -

fiber mat

16 -

calibration

17 -

hot press

18 -

fibreboard

Claims (20)

1. A method of producing light weight fibre boards having an average bulk density of less than 400 kg/m³ based on lingo cellulose containing fibres and binder, the binder being applied to the fibres and the fibres being then formed into a fibre mat which is calibrated and subjected to a heat treatment for curing the binder, characterized in that a moisture content of the fibres (3) is adjusted in such a way that it is below 20 % during calibrating the fibre mat (15) and during the heat treatment, and that the fibre mat (15) is contacted on both sides with smoothly closed heating surfaces for heat transfer during the heat treatment, the heating surfaces opposing each other being distance controlled to keep a predetermined distance, and the bulk density profile of the fibre boards (18) being adjusted in such a way that an increase of the bulk density at the boundary of the bulk density profile amounts to at least 20 % with regard to the average bulk density of the fibre boards (18).
2. The method of claim 1, characterized in that water or an aqueous solution is sprayed onto the fibre mat (15) prior to the heat treatment.
3. The method of claim 1 or 2, characterized in that the predetermined distance of the heating surfaces is between 20 and 300 mm.
4. The method according to any of the claims 1 to 3, characterized in that the bulk density profile of the fibre boards (18) is adjusted in such a way that an increase of the bulk density at the boundary of the bulk density profile amounts to at least 60 % with regard to the average bulk density of the fibre boards.
5. The method according to any of the claims 1 to 4, characterized in that the average bulk density of the fibre boards (18) is adjusted to 150 to 350 kg/m³, the binder (8, 10) being an usual artificial resin used in wood particle material industry and being selected from the group including UF, MUF, MUPF, PUF, PF and PMDI resins.
6. The method according to any of the claims 1 to 4, characterized in that the average bulk density of the fibre boards (18) is adjusted to 60 to 250 kg/m³, a foam forming PUR binder being used as the binder (8, 10).
7. The method of claim 6, characterized in that the foam forming PUR binder comprises a first binder component (8) having NCO groups and a second binder component (9) comprising at least one polyol.
8. The method of claim 7, characterized in that the fibres are divided up into at least two parts (5, 6) prior to applying the binder (8, 9), that only the first binder component (8) comprising the NCO groups is applied to the first (5) of these parts, and that only the second binder component (9) comprising the polyol is applied to the second (6) of these parts, and that the parts (5, 6) of the fibres (3) are mixed prior to forming the fibre mat (15).
9. The method of claim 8, characterized in that the first part (5) comprises 10 to 90 %, and the second part (6) comprises 90 to 10 % of the total fibres (3).
10. The method of claim 9, characterized in that the first part (5) comprises 40 to 60 %, and the second part (6) comprises 60 to 40 % of the total fibres (3).
11. The method according to any of the claims 8 to 10, characterized in that no binder component is applied to a third part of the fibres (3) prior to mixing.
12. The method according to any of the claims 1 to 11, characterized in that the method is carried out continuously.
13. The method according to any of the claims 1 to 12, characterized in that the heat treatment is carried out until a temperature of 50 to 100 °C is reached in the middle of the fibre mat (15).
14. The method of any of the claims 1 to 3, characterized in that, in forming the fibre mat (15) of the fibres (3), a layer arrangement with different compositions and/or concentrations of the binder within the single layers is formed.
15. A light weight fibre board having an average bulk density of less than 400 kg/m³ based on lingo cellulose containing fibres and binder, characterized in that the fibre board (18), on both sides, has smoothly closed surfaces and an increase of the bulk density at the boundary of its bulk density profile of at least 20 % with regard to its average bulk density.
16. Fibre board according to claim 15, characterized in that the fibre board (18) has a thickness between 20 and 300 mm.
17. Fibre board according to claim 15 of 16, characterized in that the increase of the bulk density at the boundary of the bulk density profile amounts to at least 60 % with regard to its average bulk density.
18. The fibre board according to any of the claims 15 to 17, characterized in that the average bulk density of the fibre board (18) is between 150 and 350 kg/m³, the binder being a usual artificial resin of wood particle material industry selected from a group including UF, MUF, LUPF, PUF, PF, and PMDI resins.
19. The fibre board according to any of the claims 15 to 17, characterized in that the average bulk density of the fibre board (18) is between 60 and 250 kg/m³, the binder being a foam forming PUR binder.
20. Fibre board according to any of the claims 15 to 19, characterized in that the fibre board (18) comprises a layer arrangement with different compositions and/or concentrations of the binder within the single layers.

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