EP2388117A1 - Method and assembly for manufacturing a wooden work surface - Google Patents

Abstract

The method involves scattering the wood fibers or chipped woods on an endlessly revolving conveyor belt (7) into a mud cake (6). The wood fibers or chipped woods are wetted with a adhesive. An impregnating medium is applied from the top of the mud cake made of wood fibers or chipped woods on the conveyor belt before the hot press (2). The impregnating medium is cross-linked during pressing. An independent claim is also included for a system for manufacturing a wood plate, particularly a wood fiber plate.

Description

The invention relates to a method and plant for producing a wood-based panel, in particular a wood fiber board, are sprinkled with an adhesive wetted wood fibers or wood chips on an endlessly circulating conveyor belt to a cake, the cake of wood fibers or wood chips in a transport direction T to various processing stations promoted, compressed in a pre-press and then pressed under pressure and temperature influence in a hot press to a plate of desired thickness.

Such a method is for example from the DE 10 2005 033 687 A1 known. In order to produce an MDF or HDF board according to this method, long fibers must first be produced in a defibration step, which can be done in an upstream process or immediately before the plant for producing the wood fiber boards. The coarse, long wood fibers are then applied with additives, such as flame retardants and water repellents. Subsequently, binder (urea-formaldehyde glue) is added via a blowline and the fibers are then dried with appropriate additives and the fiber sizing via a power tube dryer. Subsequently, the fiber mixture is sprinkled on a spreading device to an endless cake on the endless circulating conveyor belt. The loosely sprinkled mixed fiber cake is then fed from the conveyor belt to a cold pre-press and cold pre-compaction of the fiber web is achieved. Subsequently, the nonwoven fabric is fed back via the conveyor belt of a continuous hot press, in which it to a Plate of desired thickness is hot pressed. The press belts are advantageously coated with a release agent to prevent adhesion of the plates formed. In a next process step, the endlessly produced plates are then formatted and separated into individual plates and then assembled.

When manufacturing MDF (Medium Density Fiberboard) or HDF (High Density Fiberboard), it is often desired that the final product have certain properties that are relevant to further production steps and / or use. Such property may be, for example, the conductivity that is involved or desired for a fiberboard either in powder coating the panel itself or when the panel is to be used as a laminate flooring panel support and the flooring must have antistatic properties. The conductivity can be achieved by adding salts in the manufacturing process, for example in the refining process. Another desired property may be a fire retardant design. Unfortunately, as the wood fibers in the blowline dry relatively high temperatures on the mixture of pretreated wood fibers, interactions of the added salts with other components often occur.

Another disadvantage is that all wood fibers are treated, no matter if necessary or not. To compensate for this disadvantage, is in the DE 199 63 203 A1 proposed, for the production of laminate flooring panels, first to produce a support plate made of lignocellulose-containing wood material, which is at least partially impregnated with an impregnating agent, wherein the impregnating agent penetrates into the support plate or impregnates this. Subsequently, the carrier plate is cut in the impregnated areas and provided for further processing at the edges in each case with an edge profile. By impregnating the edge areas, laminate flooring panels are to be provided which are more resistant to moisture and moisture.

The preparation of such carrier plates is very time-consuming, since the drawing of the impregnation medium in the plate takes a certain amount of time. In addition, to ensure a uniform impregnation, the top of the carrier plate must be evenly wetted with the impregnating medium. Density fluctuations within the support plate lead to an uneven distribution of the impregnation, which is not recognizable from the outside, so that there is a risk that later produced panels from the support plate, especially in the edge area, can penetrate into the moisture in the laid floor, not sufficiently impregnated are.

The EP 1 710 061 A1 discloses a method for continuously preheating a mat or mat. This steam is introduced into a mat of scattered wood chips or chips. This distributes itself within the mat and heats it up.

The DE 20 50 530 A1 discloses a method of impregnating preformed sounding material with a binder. The Beschalungsmaterial consists of porous plates, on one surface of the binder is applied. The opposite surface is then subjected to a negative pressure, whereby the binder is pulled into the openings of the porous plate.

The non-prepublished European patent application 09005468.5 , to which reference is made in its entirety, describes a generic method in which the cake of wood chips or wood fibers on the conveyor belt behind the pre-press and before the hot press is exposed to a vacuum, and at the same time an impregnating medium is applied to the cake due to of the vacuum distributed in the cake, and that the impregnating medium is crosslinked during pressing. By this configuration, the impregnation takes place at a time within the manufacturing process, too still a high porosity of the surface is present, which means that the impregnation medium can easily evenly distributed.

The plates produced by the methods described above are subsequently further refined, for example by providing them with a decorative layer and a protective layer covering the decoration. These panels can then be further processed for example to furniture panels or wall, ceiling or floor panels. The decorative layer and the protective layer are laid on the previously prepared core, and then the core and the laid-up layers are pressed together (laminated) in a hot press. In particular, when HDF boards are used, their press skin, which is also referred to as press-patina or rotting layer, must be sanded before the decorative layer and the protective layer are applied, because in this area the heat input during hot pressing is so high that the adhesive Cures too quickly, which glue bridges at least partially break and make the layer vulnerable.

To avoid this, the press skin is usually abraded by about 0.3 mm. In order to compensate for this grinding allowance, the plates are made stronger than they are needed, which not only adversely affects the cost.

There is therefore a very great need for abrasion-resistant and within the thickness tolerance directly printable wood-based panels that weitgehenst be used without grinding the surface.

The invention is therefore based on the problem described starting the task of specifying a resource-saving method for producing a direct-print wood-based panel.

To solve the problem, a generic method is characterized in that from the top of the cake from wood chips or wood fibers on the conveyor belt in front of the hot press vacuum impregnated an impregnating medium is applied, which is crosslinked during pressing.

This impregnation medium prevents the formation of a press skin, so that the top of the prefabricated plate no longer needs to be sanded before the decorative layer is placed or printed, which not only results in material savings on wood material, but the manufacturing costs are also reduced by eliminating handling time, which was previously necessary for the grinding process for grinding the press skin, and also eliminates the cost of the abrasive belts. The production plant is increased in its output (gross = net). By a correspondingly low penetration of the impregnation medium in the plate surface, this is shut off inline.

The impregnation medium influences the plate surface properties, such as strength, swelling behavior, and suction behavior before or during training, so that these measures no longer have to be taken during the subsequent finishing.

Preferably, the impregnation medium is applied to the chip or fiber cake behind the pre-press. Before the pre-press, the impregnating medium can be applied or sprinkled, for example by means of rollers, when it is firmly in particle form.

The impregnating medium is preferably made of melamine resins in a proportion of 4 - 30%, particularly preferably 20% melamine. However, it may also consist of urea-formaldehyde resins with a low molar ratio of urea to formaldehyde of 1: <1. Also, highly buffered condensation resins with urea or hexamine can be used for the impregnation medium.

The impregnation medium can be liquid or powdery.

If the impregnation medium is liquid, it can be sprayed onto the fiber cake by means of nozzles or rollers.

Characterized in that the fiber cake is transported during the impregnation by the conveyor belt, the device for applying the impregnation medium can be arranged stationary, which simplifies the construction of the production line and reduces its cost.

The impregnation is applied at least partially. In the case of part-surface application, areas are created with / without impregnation (tempering), the tempered areas having deviating properties in relation to non-tempered areas. The impregnation medium can for example also influence the water absorption capacity of the finished pressed wood-based panel.

• Mittel zur Erreichung eines Quellschutzes, Haftvermittler, Füllstoffe wie beispielsweise Zellulose, Additive, mit denen auf das Endprodukt abgestimmte und eigenschaftsändernde Zugaben gleich in der Platte "hinterlegt werden",
• beispielsweise antistatisch wirksame Zusätze, antibakteriell und/oder antialergen wirksame Zusätze, Zusätze zur Erhöhung der Fähigkeit tiefe Strukturen und/oder Fugen abzubilden, die Härte steigernde Bestandteile, wie beispielsweise Fasern, insbesondere Glasfasern und Zusätze mit pigmentierender Wirkung, beispielsweise zur Erzeugung einer Grundfärbung der Plattenoberfläche,
• die auf eine nachfolgende dekorierende Beschichtung abgestimmt ist, oder zur Erzielung einer zu einem später aufgebrachten Dekor passenden oder kontrastierenden Färbung einer Fuge durch freilegenden Abtrag der nachfolgend aufzutragenden Oberflächenbeschichtung.

To the impregnating agent can be further admitted:

• Means for achieving swelling protection, adhesion promoters, fillers such as cellulose, additives with which "endowments" matched to the final product and property-changing additions are immediately deposited in the board,
• For example, antistatic additives, antibacterial and / or anti-allergenic additives, additives to increase the ability to image deep structures and / or joints, the hardness-increasing ingredients such as fibers, especially glass fibers and additives with pigmenting effect, for example, to produce a basic color of the plate surface .
• which is adapted to a subsequent decorating coating, or to achieve a matching to a later applied decor or contrasting color of a joint by exposing removal of the subsequently applied surface coating.

With the help of a sketch, an embodiment of the invention will be described in more detail below.

The single figure shows the schematic arrangement of the individual components of the system. In the chipper 12, the wood fibers or shavings are first prepared and, before they are dried in the drier 10, wet-glued at the point marked 11. After drying, the fibers or chips are glued again at the point marked 9 and then fed to the scattering station 8. In the scattering station 8, the preferably glued with a urea-formaldehyde resin or melamine resin fibers or chips are sprinkled onto the endless in the direction of transport T driven conveyor belt 7 to a cake 6. In the pre-press 4, the cake 6 is compressed, so cold pre-compressed. Between the pre-press 4 and the hot press 2, in which the compressed cake 6 is pressed under high pressure and high temperature to a wood-based panel 1 of desired thickness, an impregnation station 3 is integrated, which consists of an over the conveyor belt 7 Auftragaggregat, such as nozzles, consists. The application unit is stationary and immovable. About the nozzles, an impregnating agent, which consists of a melamine resin in a proportion of 4 - 30% melamine, urea-formaldehyde resins with a low molar ratio of urea to formaldehyde = 1:> 1 or of highly buffered condensation resins with urea or hexamine, sprayed , In a corresponding embodiment of the system, it is conceivable that also on the underside of the cake 6 an impregnating agent between the pre-press 4 and the hot press 2 is applied.

If a particulate impregnating agent is used, it is also possible to sprinkle it on the upper side of the cake 6 in an impregnating station 5 arranged stationary in front of the pre-press 4. For this purpose, it would also be conceivable in principle to provide the underside of the cake 6 with an impregnating agent before the pre-compaction, the impregnating medium before the Sprinkle scattering station 8 on the conveyor belt 7 and then to scatter the fibers or chips. The impregnating agent can be applied fully or partially and also penetrate at different depths into the cake 6.

It is important that the impregnating agent consists of a thermally postcrosslinking substance and is applied to the cake 6 immediately before pressing. Parallel to the conveyor belt 7 laterally arranged - not shown here - sheets can be provided to ensure that the scattered cake 6 is maintained in its shape when it is transported. On the surface of the wood-based panel 1 can be directly gefillert / printed.

A plant for producing a wood-based panel with a transport belt 7 endlessly circulating in a transport direction T, a spreading device 8 for spreading a wood chips or wood fiber cake 6 onto the conveyor belt 7, a pre-press 4 arranged behind it in the transport direction T, in which the scattered cake 6 is compressed and a hot press 2 provided behind it, in which the compressed cake 6 is pressed under pressure and temperature influence to a plate 1 of desired thickness, characterized by an impregnating in the transport direction T before or behind the pre-press and before the hot press impregnating station 5, 3 ,

The impregnation station 3, 5 preferably consists of an applicator unit arranged above the conveyor belt 7 for an impregnating medium.

LIST OF REFERENCES

1

HPL plate / plate

2

hot press

3

impregnating

4

pre-press

5

impregnating

6

cake

7

conveyor belt

8th

spreader

9

Beleimstelle

10

dryer

11

Beleimstelle

12

chipper

T

transport direction

Claims (15)

Method for producing a wood-based panel, in particular a wood-fiber board, in which wood fibers or wood chips wetted with an adhesive are scattered on an endlessly circulating conveyor belt (7) to form a cake (6), the cake (6) being made of wood fibers or wood shavings in a transport direction T conveyed to various processing stations, compressed in a pre-press (4) and then pressed under pressure and temperature influence in a hot press (2) to a plate (1) of desired thickness, characterized in that from above on the cake (6) of wood chips or wood fibers on the conveyor belt (7) before the hot press (2) vacuum-applied an impregnating medium, which is crosslinked during pressing. A method according to claim 1, characterized in that the impregnating medium behind the pre-press (4) on the chip or fiber cake (6) is applied. A method according to claim 1, characterized in that the impregnating medium before the pre-press (4) on the chip or fiber cake (6) is applied. A method according to claim 1 or 2, characterized in that the impregnating medium is liquid. A method according to claim 4, characterized in that the impregnating medium is sprayed by means of nozzles on the chips or fiber cake (6). A method according to claim 3 or 4, characterized in that the impregnating medium by means of rollers on the chip or fiber cake (6) is applied. A method according to claim 1 or 3, characterized in that the impregnating medium is sprinkled in solid form. Method according to one or more of the preceding claims, characterized in that the impregnating medium consists of melamine resins in a proportion of 4 - 30%, preferably 20% melamine. Method according to one of the preceding claims, characterized in that the impregnating medium of urea-formaldehyde resins having a low molar ratio of urea to formaldehyde 1: <1. Method according to one of the preceding claims, characterized in that the impregnation medium consists of strongly puffed condensation resins with urea or hexamine. Wood material board produced according to one or more of the preceding claims. Plant for producing a wood-based panel with a transport belt (7) endlessly circulating in the transport direction T, a spreading device (8) for spreading a wood chips or wood fiber cake (6) onto the conveyor belt (7), a pre-press (4) arranged in the transport direction T, in which the scattered cake (6) is compressed and one behind provided hot press (2), in which the compressed cake (6) is pressed under pressure and temperature to a plate (1) of desired thickness, characterized by a in the transport direction T before the hot press (2) arranged impregnation (3, 5). Installation according to claim 12, characterized in that the impregnation station (5) is arranged in front of the pre-press (4). Installation according to claim 12 or 13, characterized in that the impregnation station (3, 5) is arranged stationary. Plant according to one of claims 12 to 14, characterized in that the impregnation station (3) has nozzles or rollers.

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