EP2062709A1 - Method for manufacturing boards using small parts applied with bonding agent and boards produced by this means - Google Patents

Abstract

The board has a molded density profile on a wood fiberboard with a center molded density of approximately 60 kilograms/meter cube. The profile is sectioned into two cover layers and has a center layer lying between the cover layers. Small parts e.g. fibers containing lignocellulose, in the board are glued with a bonding agent to form a preform (6). The molded density of the board is increased from the center layer to one cover layer. One molded density of the board in an area of the center layer is larger than another molded density of the board in an area of another cover layer.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a process for the production of boards based on particles glued with a binder, in particular wood fibers glued on the basis of binder having an NCO group, having the features of the preamble of independent claim 1. Furthermore, the invention relates to a board on the basis of particles glued with a binder, in particular on the basis of binder having an NCO-group-containing wood fibers, having the features of the preamble of independent claim 8.

In principle, the particles from which plates are formed in the present invention, any particles containing lignocellulose, so in addition to wood fibers, other fibers of plant origin, or other wood particles, such as wood chips or grinding dust, or particles of wood substitutes, including plastic and textile fibers , his. The particles may also be a mixture of different ones of said particles. However, of particular interest to the present invention are boards based on wood fibers, ie wood fiber boards, which at most have a small addition of other particles. This is because wood fiber boards can be produced industrially with low bulk density and are therefore well suited for insulation and insulation purposes. Particularly interesting fields of application of all plates produced by the method of the present invention and of all plates according to the present invention are in the field of insulation. It is mainly about the isolation of buildings primarily in thermal, but also in acoustic terms.

Also suitable as binders for the particles are various substances, but NCO-containing binders, in particular in the form of so-called PMDI binders, are preferred. The binder is particularly preferably a PUR binder which, in addition to the PMDI component with the NCO groups, has a polyol component. In addition, various additives may be added to the binder.

STATE OF THE ART

A method for producing a wood fiber board, which differs from the preamble of independent claim 1 in that the binder is heated not by a hot gas, but by contact of the preform with hot closed press plates or bands, the press plates or bands indeed Apply pressure on the preform, but are controlled with respect to their distance from each other, and a wood fiber board with the features of the preamble of independent claim 8 are from the EP 1 110 687 A1 known. Here, a PUR binder, ie, an intumescent binder, is formed from a PMDI component and a polyol component that reacts to fill cavities between the wood fibers to be bonded by a PUR foam. Thus, dimensionally stable wood fiber boards are produced whose average density is in the range of 60 to 250 kg / m ³ . The dimensional stability of fiberboard just at the lower edge of this range of density depends on the fact that the density profile of the wood fiber boards still has a marginal increase in density compared to the average density of at least 20%. The well-known wood fiber board can be used as an insulating plate in the wall, ceiling and roof area.

A method having the features of the preamble of claim 1 has compared to one of EP 1 110 687 A1 known method has the advantage that the curing of the binder with the aid of hot gas in the volume of the preform within a short time periods, while this according to the EP 1 110 687 A1 if no additional measures are taken to introduce thermal energy into the preform, relatively long pressing times are required. In this case, in a method having the features of the preamble of independent claim 1, the hot gas usually passes through perforated press plates or bands, with which the pressure is also applied to the preform. The hot gas Water vapor may be added to increase its heat capacity; The hot gas can only be steam.

In principle, known lignocellulosic particle-based particle boards made by a process having the features of the preamble of independent claim 1 exhibit an edge overshoot of their bulk density relative to their average bulk density, which is due to the application of pressure to the preform during curing of the greenware Binder goes back. It is known in the art that he can increase this edge overshoot by spraying water on the preform.

In addition to wood fiber boards with a marginal increase in the gross density on both sides, which results in a desired dimensional stability, wood fiber insulation boards are also known, which do not have this edge overshoot their bulk density or not to a significant extent. These wood fiber insulation boards are not dimensionally stable at a low average density. Conversely, they can be adapted by pressing on uneven surfaces, with their cover layers forming on these uneven surfaces without air gaps remaining. This possibility does not exist with a dimensionally stable fiberboard. For a Holzfaserdämmplatte without marginal exaggeration of their bulk density in their outer layers, for example, not be provided directly with a plaster or papered. Rather, this is an additional stable dimensionally stable plate to arrange in front of the wood fiber insulation board.

For the production of Holzfaserdämmplatten without marginal exaggeration of their bulk density, it is known to flow through a calibrated in thickness preform of glued wood fibers from one side with hot gas to activate the binder and cure the preform.

OBJECT OF THE INVENTION

The invention has for its object to provide a method having the features of the preamble of independent claim 1 and a plate having the features of the preamble of independent claim 8, which allow the production of new products or new applications.

SOLUTION

The object of the invention is achieved by a method having the features of independent claim 1 and by a plate having the features of independent claim 8. The independent claim 12 relates to another new plate, as it can be produced by the new method. The dependent claims describe preferred embodiments of the new method and plates.

DESCRIPTION OF THE INVENTION

In the new method for producing sheets based on particles glued with a binder, the entry of moisture and hot gas into the preform formed from the glued particles and the effect of pressure on the preform are timed to be a part the preform having a first bulk density is cured at an earlier time than another part of the preform which is adjusted to a different bulk density after curing of the one part. In the new method, the curing of the preform thus takes place in several stages, not only different parts of the preform are cured in the individual stages, but between the individual stages, a setting of a different density in the uncured part of the preform. Thus, the new process is not concerned with, for example, the outer layers hardening earlier than the middle layer of the preform because the outer layers are closer to a heating source. Rather, it is about taking advantage of the already existing curing of part of the mold to adjust the density in another part of the preform to a certain value others, without having to take account of the already cured part, because in this the bulk density by the Curing is already fixed. In particular, the parts of the preform cured at different times according to the new process may be their two outer layers.

Specifically, the entry of moisture and hot gas into the preform and the effect of pressure on the preform may be timed so that a portion of the preform, which is compressed under pressure to a lower bulk density, is cured at an earlier time as another part of the preform, which is softened after curing of the one part softened by the moisture under pressure to a higher bulk density. The pressure can be increased after curing of one part to effect compression to the higher bulk density. But it can also be set exclusively on the softening by the moisture, which allows even at constant pressure, a greater compression of the other part of the preform, because the lignocellulosic particles lose their stiffness in the softened state and therefore, where they are softened, more compressive than where they are not softened or already a curing of the preform has occurred.

Conversely, it is also possible that the entry of moisture and hot gas into the preform and the effect of pressure on the preform be timed so coordinated that a part of the preform softened by the moisture under pressure to a higher bulk density is cured at an earlier time than another part of the preform, which is relaxed after curing of one part under reduced pressure to a lower density. A not yet cured part of the preform, in which the lignocellulose-containing particles are not softened, is at least partially elastically compressed by the applied pressure. Accordingly, this part of the preform expands again when the pressure is reduced. This can be used specifically to set a lower bulk density in certain parts of the preform before these parts of the preform are cured.

In the method according to the invention, moisture can be introduced via water vapor, which at the same time can form the hot gas, and / or by spraying water onto the preform. In the case of spraying water onto the preform, a release agent or other additive may also be added to the water. For example, it is possible to use a curing accelerator for the binder in order to cure it particularly quickly in the areas of the preform with softened fibers. Basically, the sprayed water with its heat capacity delays the heat activation of the binder. This delay can be used, for example, for high densification of areas of the preform with softened fibers prior to curing of the binder there, or even enhanced by a curing retarder added to the binder. Even in the case of the entry of moisture by spraying water, the hot gas may consist entirely or partially of water vapor. In the case of introducing moisture via water vapor as the hot gas or as a component of the hot gas, it is preferable that the pressure of the water vapor or the proportion of the water vapor to the hot gas is variable during the curing of the preform.

Alternatively or additionally, the entry of moisture or the entry of hot gas into the preform may be asymmetric with respect to its middle layer. This means that when spraying water onto the preform, this only occurs from one side. Preferably, the spraying of the water takes place from below onto the preform, since then the weight of the preform has a compressing effect only where this is desired. The one-sided spraying of water may be combined with the introduction of hot gas from the other side of the preform. It is also possible to introduce hot gas from both sides of the preform into it, but at different times and / or in different quantities and / or with different additions of water vapor.

The glued particles of the preform have a comparatively very low moisture content in the process according to the invention, which may be in the range of less than 5% of dry particles. The particles can thus absorb part of the registered moisture. Excess moisture can be removed after curing of the binder by suction of water vapor and / or flowing through the plates with air. This is sufficient to stabilize the plates even if the hot gas used to activate the binder is pure water vapor for maximum heat capacity and resulting minimum cure time.

The new plate based on lignocellulose-containing particles whose density increases from a middle layer to a cover layer of the plate, according to the invention is characterized in that the bulk density of the plate from the middle layer to the other cover layer of the plate does not increase. The bulk density of the plate may even drop from the middle layer to the other top layer of the plate, whereby the decrease in the bulk density of the plate may be continuous from one or the other top layer of the plate. However, such a continuous drop is not a prerequisite for a special property of this new plate: it has a cover layer that is stiff due to the edge increase of its bulk density and a cover layer that is deformable due to the lack of marginal elevation of its bulk density. Thus, the new plate can be formed, for example, in the old building renovation on an uneven wall, in order to provide before this both an insulation and a front lying rigid plane, for example, for the application of a plaster. The deformability of the new plate may also be limited to a very thin cover layer, based on the total thickness of the plate, in order to provide a substantially pressure-resistant plate despite its formability on an uneven surface.

Preferably, the bulk density of the new plate in the region of its one cover layer is at least 5%, more preferably at least 10%, even more preferably at least 15%, and most preferably at least 20% above its bulk density in the region of its middle layer, thus concretely Gross density in the region of its geometric center is meant. Conversely, the apparent density of the new plate does not exceed its other top layer, more preferably at least 5% lower, even more preferably at least 10% lower and most preferably at least 15% below its bulk density in the region of its middle layer. The preferred gross density ranges of the two outer layers are independent of each other.

As already mentioned in the introduction, the new plate can be used particularly in the insulation sector. For this purpose, if the lignocellulose-containing particles of the plate are fibers, in particular wood fibers, they have a mean apparent density of regularly not more than 280 kg / m ³ . Preferably, their average apparent density is not more than 240 kg / m ³ , more preferably not more than 200 kg / m ³ , even more preferably not more than 120 kg / m ³ and in special cases not more than 60 kg / m ³ . With decreasing density of the plate increases their thermal insulation ability, but at the same time the substance goes back to fibers, which are needed as a basis for the dimensional stability of the plate, so that the lighter plates can be kept dimensionally stable only by locally increasing their bulk density, if desired ,

In a concrete embodiment in which the lignocellulose-containing particles of the plate are fibers, in particular wood fibers, the bulk density of the plate falls from one to its other cover layer from over 100 kg / m ³ to less than 80 kg / m ³ , in particular from above 130 kg / m ³ to less than 50 kg / m ³ . With these values, three functionalities of the new plate are achieved: it is well with its back on an uneven surface formable; it has a low thermal conductivity; and its front is sufficiently dimensionally stable to arrange directly on her a plaster or other decorative or functional further level. In addition, the stiffness is so great that here local fasteners for the plate, such as fastened with dowels holding plate, without the risk of tearing of the plate, for example, as a result of wind suction can support.

The second novel plate based on lignocellulose-containing particles is characterized in that its bulk density from its middle layer to at least one of its outer layers falls off. When the bulk density of the plate thereby increases to its other cover layer, this corresponds to a specific embodiment of the first novel plate described above. In the second new plate, the bulk density of the plate may drop from its middle layer but also towards both cover layers. The dimensional stability of the plate is then based on its middle layer, and both cover layers are more easily deformable compared to the middle layer.

This results in advantages when using the second new plate as an interface between two uneven surfaces.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the introduction to the description are merely exemplary and can come into effect alternatively or cumulatively, without the advantages having to be achieved by embodiments according to the invention. Further features are the drawings - in particular the illustrated geometries and the relative dimensions of several components to each other and their relative arrangement and operative connection - refer. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1

zeigt das Rohdichteprofil einer erfindungsgemäßen Holzfaserplatte.

Fig. 2

zeigt das Rohdichteprofil einer anderen erfindungsgemäßen Holzfaserplatte.

Fig.3

zeigt das Rohdichteprofil noch einer anderen erfindungsgemäßen Holzfaserplatte.

Fig. 4

skizziert eine erste Ausführungsform des neuen Verfahrens.

Fig. 5

skizziert eine zweite Ausführungsform des erfindungsgemäßen Verfahrens.

Fig. 6

skizziert eine dritte Ausführungsform des erfindungsgemäßen Verfahrens.

Fig. 7

skizziert eine vierte Ausführungsform des erfindungsgemäßen Verfahrens.

Fig. 8

skizziert eine fünfte Ausführungsform des erfindungsgemäßen Verfahrens.

Fig. 9

zeigt das Rohdichteprofil noch einer weiteren neuen Platte.

Fig. 10

skizziert eine Anwendung der Platte mit dem Rohdichteprofil gemäß Fig. 9.

The invention is explained in more detail below with reference to concrete embodiments with reference to the accompanying figures and described.

Fig. 1

shows the density profile of a wood fiber board according to the invention.

Fig. 2

shows the density profile of another wood fiber board according to the invention.

Figure 3

shows the density profile of yet another wood fiber board according to the invention.

Fig. 4

outlined a first embodiment of the new method.

Fig. 5

outlined a second embodiment of the method according to the invention.

Fig. 6

outlined a third embodiment of the method according to the invention.

Fig. 7

outlined a fourth embodiment of the method according to the invention.

Fig. 8

outlined a fifth embodiment of the method according to the invention.

Fig. 9

shows the density profile of yet another new plate.

Fig. 10

outlined an application of the plate with the density profile according to Fig. 9 ,

DESCRIPTION OF THE FIGURES

In the Fig. 1 to 3 and 9 Raw density profiles of wood fiberboards according to the invention are shown, wherein the x-axis indicates the thickness direction of the plate and the y-axis represents the bulk density in working units. It is about the representation of the course of the bulk density and not about the reproduction of absolute values, as far as in the following figure description such absolute values are not specified. In particular, can be from the Fig. 1 to 3 and 9 do not read off individual bulk densities for specific areas of the respective plate.

The density profile 1 according to Fig. 1 refers to a wood fiber board with an average apparent density R _M of about 60 kg / m ³ . The raw density profile 1 can be regarded as being divided into two cover layers 2 and 3 and an intermediate middle layer 4 therebetween. However, clear boundaries between layers 2 to 4 do not exist. Therefore, if the density of the plate in the middle layer is mentioned below, this means, unless stated otherwise, its density in the region of its center plane 5. The bulk density of the cover layer 2 or the cover layer 3, however, denotes the average density of the respective Cover layer 2 or 3 in the region of a local maximum of the bulk density within the cover layer, if such a local maximum is present. This is in Fig. 1 in the cover layer 3 of the case. One speaks here also of a marginal exaggeration of the bulk density. The cover layer 2 does not show such an edge overshoot of the bulk density. Their density R ₂ is the value of the bulk density before the edge drop of the bulk density. In the density profile 1 according to Fig. 1 the bulk density R _{2 of} the cover layer 2 is just below the bulk density R _{4 of} the middle layer 4, while the bulk density R _{3 of} the cover layer 3 is significantly higher. The average density R _{M of} the fiberboard is slightly above the density R ₄ in the middle plane 5. This corresponds to a marginal increase in bulk density (from here more than 20%) only in the region of the top layer 3 and no increase in bulk density of the middle layer. 4 towards the cover layer 2.

This in Fig. 2 Outlined raw density profile 1 not only has the monotonous decrease in the bulk density of the cover layer 3 to the cover layer 2 towards, the Fig. 1 outlined. Here, this drop in bulk density is even constant, so that the average bulk density R _M coincides with the bulk density R _{4 of} the middle layer or at the location of the center plane 5.

In the density profile 1 according to Fig. 3 the gross density is the bulk density R _{4 of} the middle layer 4 in the region of the center plane 5. The bulk density drops from the center plane 5 to both cover layers 2 and 3 to the same values R ₂ = R ₃ .

In the Fig. 4 to 7 various embodiments of the new process for the production of plates based on lignocellulose-containing particles are sketched, which are suitable for forming an asymmetric density profile, as shown in the Fig. 1 and 2 is shown. In contrast, this is in Fig. 8 sketched method suitable to the density profile according to Fig. 3 adjust. Of the process for the preparation of plates based on lignocellulose-containing particles, only the steps which are particularly relevant to the invention are shown. In the figures, there are relative indications of the respectively applied pressure p _A , p _B and p _C ; but that does not mean that a distance control could not be used, but it also leads to different pressures.

Fig. 4A shows the one-sided spraying a preform 6 of glued wood fibers with water 9 from below. According to Fig. 4B the preform 6 is subjected to a pressure p _B between perforated pressing plates 7 and 8. At the same time through the upper pressure plate 7 through hot Gas 10 introduced into the preform 6. This hot gas 10, which consists essentially of water vapor 11, may be added to the air, first activates the binder in the upper region of the preform, which is adjacent to the pressing plate 7, so that the preform 6 first in this, one of the later outer layers corresponding Area is cured. In the next step according to Fig. 4C the distance of the press plates 7 and 8 is reduced and thus the pressure exerted on the preform 6 increases (p _C > p _B ). As a result, the wood fibers at the bottom of the preform 6, which have been softened by the water 7, are compressed. This is equivalent to the fact that the apparent density increases in this region of the preform 6 corresponding to the other of the later cover layers. In the upper part of the preform 6, this increase in bulk density does not occur for two reasons. First, the wood fibers have not been exposed to the water 9 here and have not been softened accordingly. On the other hand, the preform is different here than in its lower region, in which the water 9 has prevented a rapid increase in temperature, already in the step according to FIG Fig. 4B cured. Then, when the preform 6 is cured by the hot gas 10 also in its compressed lower region, a density profile results over the thickness of the resulting plate, as in Fig. 1 outlined.

At the in Fig. 5 sketched procedure will be different than the one in Fig. 4 sketched method before placing the preform 6 between the press plates 7 and 8 is still no moisture used to set an asymmetric density profile. In the step according to Fig. 5A some water vapor 11 is introduced through the lower pressure plate 8 in the preform 6, which condenses in the lower portion of the preform 6, without there curing the binder, which may be added for this purpose a Aushärtungsverzögerer. Then, in a step according to Fig. 5B hot gas 10 is introduced through the upper die 7 into the preform which cures the preform 6 adjacent to the die 7. Subsequently, in a step according to Fig. 5C the preform 6 is selectively compressed in its lower portion and cured in this state by hot gas 10 which passes through the lower pressure plate 8 or can continue to flow through the upper pressure plate 7. Again arises in this way a plate with the density profile according to Fig. 1 ,

The method according to Fig. 6 begins again with the spraying of water 9 on the preform 6 from below ( Fig. 6A ). Then, the preform 6 is pressed together between the press plates 7 and 8 ( Fig. 6B ), which in particular in the lower part of the preform 6 in a compression of the same effect, because the fibers are softened there by the water 9.

This compressed state of the preform 6 at its upper side is fixed by hot gas 10 flowing into the preform 6 through the pressure plate 8 by hardening the hot gas 10 in its lower portion. In a subsequent step according to Fig. 6C the pressure (p _C <p _B ) exerted on the preform 6 via the press plates 7 and 8 is withdrawn so that the preform 6 can relax. However, this relaxation no longer covers the lower region of the preform 6, because it has already hardened there. Thus, only in the upper region of the preform 6 results in a lower bulk density, which is then fixed by hot gas 10, which enters through the upper pressure plate 7 in the preform 6.

The method according to Fig. 7 corresponds to the result of that according to Fig. 6 , wherein here in a step according to Fig. 7A with simultaneous application of high pressure p _A between the pressure plates 7 and 8 water vapor 11 is introduced as hot gas 10 through the lower pressure plate 8 in the lower region of the preform 6. This leads to a softening of the wood fibers in the lower region of the preform 6, a compression of the preform 6 in the area of softened wood fibers and an immediately subsequent fixation of this compressed state of the preform 6 in its lower region by curing. Subsequently, in a step according to Fig. 7B the pressure between the press plates 7 and 8 reduced (p _B <p _A ). This can be as in the step of Fig. 6C but only the upper part of the preform 6 to relax, because the lower compressed portion of the preform 6 is already cured. The methods according to the Fig. 6 and 7 lead to a density profile, as in Fig. 1 outlined. All methods according to Fig. 4 to 7 but can be easily modified so that a density profile according to Fig. 2 can be achieved by making the transitions between the individual steps outlined here fluently.

At the in Fig. 8 sketched method, the preform 6 between the press plates 7 and 8 in a first step according to Fig. 8A only put under low pressure. By hot gas 10, which enters the preform 6 through both press plates 7 and 8, but reaches only the outer regions there, these outer regions of the preform 6 are cured. Subsequently, in a step according to Fig. 8B Water vapor 11 is introduced into the preform through both press plates 7 and 8, which precipitate in particular in the still comparatively cold middle layer of the preform 6 where it softens the wood fibers. During the subsequent compression of the press plates 7 and 8 in step C, the preform 6 is primarily compressed in the region of its middle layer, because there are different than adjacent to the press plates 7 and 8, the wood fibers softened and the preform 6 is not cured. This compressed Condition of the preform 6 in the region of its middle layer is then fixed by hot gas 10 entering through both pressing plates 7 and 8 into the middle layer of the preform 6. In this way, a density profile according to Fig. 3 receive.

Fig. 9 shows a raw density profile 1, which in the region of both outer layers 2 and 3, a marginal increase of the bulk density, ie a local maximum density has. Such edge elevations may be unavoidable under certain circumstances of manufacture solely by contacting the preform with the press plates. However, the apparent density R _{2 of} the cover layer 2 is clearly below the bulk density R _{3 of} the cover layer 3, and it is also below the density R _{4 of} the middle layer 4 in the region of the median plane 5. Accordingly, the bulk density R _{4 of} the middle layer 4 is in the region of the median plane 5 below the average gross density R _{M of} the gross density profile 1. Despite the slight increase in the density in the region of the cover layer 2, the cover layer 2 is a wood fiber board with the density profile according to Fig. 9 easily deformable, while the cover layer 3 is substantially dimensionally stable.

These properties are used in the Fig. 10 sketched application of a plate 12 with the density profile according to Fig. 1, 2 or 9 exploited. The plate 12 is fastened with fastening elements, not shown here, for example in the form of holding plates and dowels, on a wall 13 having an uneven surface 14. At this uneven surface 14, the plate 12, which is a wood fiber plate 15, pressed with its cover layer 2, so that the cover layer 2 forms a negative impression 16 of the surface 14. In other words, the cover layer 2 abuts the surface 14 everywhere without an air gap. By this adaptation to the surface 14, the cover layer 2 is indeed compressed locally to a higher density. The plate 12 retains its middle layer 4 low density but a very good insulation effect. In addition, with its dimensionally stable cover layer 3, it provides a flat surface 17 which, for example, can be directly plastered or over-wallpapered.

LIST OF REFERENCE NUMBERS

1

ply construction

2

topcoat

3

topcoat

4

middle class

5

midplane

6

preform

7

press plate

8th

press plate

9

water

10

Hot gas

11

Steam

12

plate

13

wall

14

surface

15

Fiberboard

16

negative impression

17

flat surface

Claims (13)

A method of making particles based on binder-sized particles, wherein the particles coated with the binder are formed into a preform, and wherein the preform is cured by introducing moisture and hot gas into the preform and under pressure from the preform is characterized in that the entry of moisture and hot gas (10) in the preform (6) and the action of pressure on the preform (6) are coordinated so timed that a part of the preform (6) with a cured first density than any other part of the preform (6), which is set after curing of one part to a different density. A method according to claim 1, characterized in that the entry of moisture and hot gas (10) into the preform (6) and the action of pressure on the preform (6) are timed controlled so that a part of the preform (6 ), which is compressed under pressure to a lower bulk density, is cured at an earlier time than another part of the preform (6) which, after curing of the one part softened by the moisture under pressure, is compressed to a higher bulk density. A method according to claim 2, characterized in that the pressure after curing of the one part is increased. A method according to claim 1, characterized in that the entry of moisture and hot gas (10) into the preform (6) and the action of pressure on the preform (6) are timed controlled so that a part of the preform (6 ) softened by the moisture compressed under pressure to a higher bulk density, is cured at an earlier time than another part of the preform (6), which is relaxed to a lower bulk density after curing of the one part under reduced pressure. Method according to one of claims 1 to 4, characterized in that the entry of moisture at least partially via water vapor (11), in particular as a component of the hot gas (10). Method according to one of claims 1 to 5, characterized in that the entry of moisture at least partially by spraying water (9) on the preform (6). Method according to one of claims 1 to 6 , characterized in that at least the entry of moisture and / or the entry of hot gas (10) takes place asymmetrically with respect to a middle layer of the preform (6). Plate based on particles glued with a binder, the particles in the plate being bonded to the binder and the density of the plate rising from a middle layer to a cover layer of the plate, characterized in that the bulk density of the plate (12) from the middle layer (4) to the other cover layer (2) of the plate (12) does not rise. Plate according to claim 8, characterized in that the bulk density of the plate (12) drops from the middle layer (4) to the other covering layer (2) of the plate (12). Plate according to claim 8 or 9, characterized in that the bulk density of the plate (12) from the one cover layer (3) to the other cover layer (2) of the plate (12) towards steadily decreases. Plate according to one of claims 8 to 10, characterized in that the bulk density (R ₃ ) of the plate (12) in the region of its one cover layer (3) by at least 5%, preferably by at least 10%, more preferably by at least 15% and most preferably at least 20% above their bulk density (R ₄ ) in the region of their middle layer (4) and the bulk density (R ₂ ) of the plate (12) in the region of their other cover layer (2) not above, preferably at least 5% below , more preferably at least 10% below and most preferably at least 15% below its bulk density (R ₄ ) in the region of its middle layer (4). Plate based on particles glued with a binder, wherein the particles in the plate are bonded to a binder and wherein the bulk density of the plate changes from a middle layer to a cover layer of the plate, characterized in that the bulk density of the plate (12 ) drops from the middle layer (4) to the one cover layer (2) of the plate (12). Plate according to claim 12, characterized in that the bulk density of the plate (12) from the middle layer (4) to the other cover layer (3) of the plate (12) also decreases.

Images