EP2939807B1 - Method and apparatus for manufacturing a wood fibreboard - Google Patents

Description

The invention relates to a method and a plant for producing a wood fiber board.

1. 1. Aufbereitung des Rohmaterials (Rundholz, Holzhackschnitzel),
2. 2. Erzeugung des Faserstoffs,
3. 3. Beleimung und Hydrophobierung,
4. 4. eventuell Trocknung,
5. 5. Formung eines Faserkuchens (Faservlies),
6. 6. Verpressung des Faserkuchens zu einer Platte gewünschter Dicke.

Fiberboard is mainly produced by the following steps:

1. 1. Preparation of the raw material (roundwood, wood chips),
2. 2. generation of the pulp,
3. 3. gluing and waterproofing,
4. 4. possibly drying,
5. 5. forming a fiber cake (non-woven fabric),
6. 6. pressing the fiber cake to a plate of desired thickness.

The different production methods differ mainly in the type of cake formation and pressing. Depending on whether fiber transport and cake formation take place in water or air, it is called wet or dry process. In the semi-dry process, air is used to form the fiber mat, but the hot pressing of the wet pulp is similar to the wet process. Above all, softwoods are being processed, and increasingly also hardwoods. As far as the wood is not already present in small pieces, it is shredded into chips. The wood chips are then sorted, freed of iron parts by means of magnets, washed and finally stored in storage bunkers. A moisture content of chips / shavings of 50% to 60% has proved favorable for further processing.

Before defibration, the chips are boiled or steamed in a cooker in order to soften the cell structure, in particular the lignin, and thus allow a gentle separation of the fiber fabric into individual elements. The pre-bake temperature is about 180 ° C and the treatment time is about three minutes. Due to the thermal effect, low molecular weight carbohydrates and lignins go to a small extent in solution. From the acetyl groups of the wood are formed acetic acids and small amounts of acetic anhydride. After damping, the chips are fed to a refiner (disc refiner). In the refiner then the defibration takes place. Due to the high pressure of up to 8 bar and more in the refiner this is left by the fibers at high speed. The fibers pass into the gluing device in a stream of superheated steam, a blow line, in which the gluing of the fibers takes place. In the blowing line, the glueing of the wet fibers takes place. After gluing, the fiber stream is fed into a dryer and the glued fibers are dried there. After drying, the glued fibers are spotted and then scattered by means of a spreader to the fiber cake. This scattered fiber cake is then pressed in a hot press (Konti press) to a fiberboard of desired thickness.

As adhesives mainly urea-formaldehyde resins (UF) are used. Alternatively, these resins can be made reinforced melamine and / or phenol (MUF, MUPF). For wood-based panels for special applications also Methylendiphynyldiisozianate (MDI) are provided as an adhesive.

The method of wet gluing is also called "blowline" gluing method. In this process, the adhesive is sprayed into the production tube or blow tube, where the fiber transport from the refiner to the dryer takes place. In " Deppe / Ernst, MDF medium density fiberboard ", DRW-Verlag, ISBN 3-87181-329-X, the wet gluing on pages 81-84 described in detail. The principle is that the adhesive (glue) is sprayed into a fiber stream that moves at a speed of 150 m / s to 500 m / s. In order to increase the mechanical strengths of wood-based panels, it is known to scatter tissue fibers into the cover layers. Such a wood-based panel is for example in the EP 1 754 583 A1 disclosed.

From the US 3,231,458 A It is known to first mix wood particles and foreign fibers, to glue them and then to press. Since not all fibers are equally miscible, this method is not well suited.

The EP 1 623 807 B1 describes a method for producing a wooden material body, in which wood material is cut into wood chips and in which filamentary fiber material is first comminuted into individual fibers. These fibers are then interspersed in the wood chips and then at least on the wood chips, a binder (glue) is applied. The fibers can also be collected first and then mixed with the wood chips. With this method, it may be possible to introduce fibers specifically for influencing the mechanical properties, but complete distribution and good mixing of fibers and wood chips in a continuous production process is only possible with unacceptably high outlay. The fiber cutting and Beleimvorrichtungen proposed for this purpose are structurally very complex, therefore expensive and complicated to handle.

From the magazine " European Journal of Wood and Wood Products 2011, 69: pages 199 to 206 "It is known to lay in the fiber cake nets that were previously embedded themselves in adhesive, but these networks are provided only in a horizontal plane of the MDF board, so that only certain mechanical properties can be influenced.

Starting from this problem, a method for producing a fiberboard is to be specified, with which it is possible to improve the mechanical properties of the wood-based panel in a simple manner and / or targeted to influence. Furthermore, a suitable for carrying out the process plant should be specified.

1. a) Zerfasern von Holzschnitzeln in einem Refiner,
2. b) Transportieren der im Refiner erzeugten Holzfasern in eine Beleimvorrichtung,
3. c) Mischen von Fremdfasern mit einem Klebstoff zu einer Fremdfaser-Klebstoff-Emulsion in einem Mischer,
4. d) Transportieren der Fremdfaser-Klebstoff-Emulsion in die Beleimvorrichtung,
5. e) Mischen der Fremdfaser-Klebstoff-Emulsion mit den Holzfasern zu einem Fasergemisch in der Beleimvorrichtung,
6. f) Transportieren des Fasergemisches aus der Beleimvorrichtung in einen Trockner,
7. g) Trocknen des Fasergemisches im Tockner,
8. h) Transportieren des getrockneten Fasergemisches aus dem Trockner in eine Streuvorrichtung,
9. i) Streuen des Fasergemisches zu einem Faserkuchen,
10. j) Verpressen des Faserkuchens zu einer Holzfaserplatte gewünschter Dicke in einer Heißpresse.

To solve the problem, a method for producing a wood-based panel characterized by the following steps:

1. a) defibration of wood chips in a refiner,
2. b) transporting the wood fibers produced in the refiner into a gluing device,
3. c) mixing foreign fibers with an adhesive into a foreign-fiber adhesive emulsion in a mixer,
4. d) transporting the foreign-fiber adhesive emulsion into the gluing device,
5. e) mixing the foreign-fiber adhesive emulsion with the wood fibers to form a fiber mixture in the gluing device,
6. f) transporting the fiber mixture from the gluing device into a dryer,
7. g) drying the fiber mixture in Tockner,
8. h) transporting the dried fiber mixture from the dryer into a spreading device,
9. i) spreading the fiber mixture into a fiber cake,
10. j) pressing the fiber cake into a fibreboard of desired thickness in a hot press.

From a conventional method for producing an MDF board, the method according to the invention differs in that foreign fibers are glued and these glued foreign fibers are introduced into the production process. These foreign fibers glued with a glue surplus are referred to below as a foreign-fiber adhesive emulsion. This emulsion serves to glue the conventionally prepared wood fibers in the gluing device. The gluing of the fibers is thus not carried out as in the known MDF production process with an adhesive, but with the foreign-fiber adhesive mixture, the foreign fiber adhesive emulsion.

For this purpose, the foreign-fiber adhesive emulsion in the gluing device is preferably sprayed onto the wood fibers in motion. In this case, the spraying of the foreign-fiber adhesive emulsion on the wood fibers with a pressure between 4 bar and 20 bar, preferably 12 bar, take place.

It is preferably provided that the foreign-fiber adhesive emulsion and the wood fibers in the gluing device are mixed to form a homogeneous fiber mixture. The fiber mixture can consist of 10% to 70% wood fibers. The extraneous-fiber adhesive emulsion preferably consists of 10% to 70%, particularly preferably 50%, of adhesive.

As foreign fibers, natural or artificial fibers can be used. In particular, plant fibers, in particular cotton fibers or fabric fibers, or glass fibers, mineral fibers or synthetic fibers or a mixture of various fibers are suitable.

The wood fibers are transported from the refiner, preferably by means of superheated steam, into the gluing device and conveyed in the gluing device as a wood fiber-steam stream.

• einen Refiner zum Aufschließen von Holzhackschnitzeln zu Holzfasern,
• einem Mischer zum Mischen von Fremdfasern mit einem Klebstoff zu einer Fremdfaser-Klebstoff-Emulsion,
• einer Beleimvorrichtung zum Vermischen der Holzfasern mit der Fremdfaser-Klebstoff-Emulsion zu einem Fasergemisch,
• einem Trockner zum Trocknen des Fasergemisches,
• einer Streuvorrichtung zum Streuen des Fasergemisches zu einem Faserkuchen,
• eine Heißpresse zum Verpressen des Faserkuchens zu einer Holzfaserplatte.

A plant for producing a wood fiber board according to the method of the invention is characterized by the following features:

• a refiner for breaking woodchips into wood fibers,
• a mixer for mixing foreign fibers with an adhesive into a foreign-fiber adhesive emulsion,
• a gluing device for mixing the wood fibers with the foreign-fiber adhesive emulsion into a fiber mixture,
• a dryer for drying the fiber mixture,
• a spreader for spreading the fiber mixture into a fiber cake,
• a hot press for pressing the fiber cake to a fiberboard.

The mixer may be a static mixer or a stator-rotor mixer.

Preferably, the gluing device has a plurality of nozzles arranged one behind the other. Such Beleimvorrichtung is per se, for example, from EP 2 431 144 A1 known.

For conveying the foreign-fiber adhesive emulsion to the nozzles, at least one pump, in particular a high-pressure pump, is preferably provided.

With the aid of a drawing, an embodiment of the invention will be explained in more detail below.

Figur 1 -

ein Prozessschema zur Herstellung einer Holzfaserplatte,

Figur 2 -

den mit "R" in Figur 1 bezeichneten Rohrabschnitt, der die Beleimvorrichtung bildet.

Show it:

FIG. 1 -

a process scheme for making a fiberboard,

FIG. 2 -

the one with "R" in FIG. 1 designated pipe section which forms the Beleimvorrichtung.

Based on FIG. 1 If the manufacturing method according to the invention is to be explained. Provided roundwood 1 is first crushed in a chipper 2 to Holzhackschnitzeln HS and washed in an adjoining cooker 3 and cooked. The thus prepared chips HS are then transferred to the refiner 4, where they are digested to wood fibers HF. In a bunker 5 foreign fibers FF are provided, which are mixed in a mixer 7 with a supplied from a container 6 adhesive KL to a foreign-fiber adhesive emulsion. In a superheated steam stream, the wood fibers HF are conveyed from the refiner 4 into the pipe section R. This tube section R forms the gluing device 8, which is a blow line (blowline).

In the Blowline ( FIG. 2 ) is a plurality of gluing nozzles D ₁ , D ₂ , ..., D _i , ... D _L arranged in a ring around the tube R. At the beginning A of the gluing zone BZ, the pipe cross-section d - seen in the flow direction - expands before the first gluing nozzle D ₁ by up to 30%. The speed of the wood fiber stream is thereby reduced and the residence time in the gluing zone BZ is increased. At the end E of the gluing zone BZ, the expanded tube cross-section is again reduced behind the last gluing nozzle D _{L, as} viewed in the flow direction S. About the nozzles D ₁ , D ₂ , ..., D _L promoted from the mixer 7 foreign fiber adhesive emulsion is sprayed onto the wood fibers HF, so that a homogeneous mixing of wood fibers and Foreign fiber adhesive emulsion to a fiber mixture FG sets. This fiber mixture is then transferred from the glueing device 8 into the dryer 9, in which the water vapor in which the fiber mixture was conveyed and the wood moisture is removed from the pre-dryer 10 and an after-dryer 11 and the adhesive KL is dried. After the dryer 9, the fiber mixture FG is transported for classification in the classifier 12, from which it then enters the scattering device 13. About the scattering device 13, the fiber mixture FG is sprinkled on a not shown here in detail revolving conveyor belt to a fiber cake. This fiber cake is passed over the conveyor belt through a pre-press 14 and then fed to the hot press 15, in which it is pressed under high pressure and high temperature to a wood fiber plate of desired thickness. In this case, the adhesive melts on KL and combines wood fibers HF and foreign fibers FF together.

As foreign fibers FF is any kind of fibers in question, which can be glued with a suitable adhesive KL. Synthetic fibers such as glass fibers, plastic fibers, or thin wires drawn into fibers may also be used, such as vegetable fibers, especially bum wool fibers, or cloth fibers. The selection of suitable foreign fibers FF determines the mechanical properties of the finished fiberboard. If the plate weight is to be reduced compared to a conventional MDF plate, it is advisable to use here foreign fibers FF of a material of lower density than the wood fibers HF used. If the bending strength is to be increased compared with a conventionally produced MDF board, it is suitable, for example, to use glass fibers as foreign fibers. The adhesives KL used are the adhesives customary in MDF board production, such as urea-formaldehyde resins (UF), which may also be melamine-reinforced and / or phenol-reinforced (MUF, MUPF) or also methylenediphenyl diisocianates (MDI).

The glueing device 8 can also be designed with a constant line cross-section. However, it must be ensured that a sputtering energy is present, which allows a homogeneous distribution of the foreign-fiber adhesive emulsion on the wood fibers, so that a homogeneous fiber mixture FG can form.

LIST OF REFERENCE NUMBERS

1

spar

2

chipper

3

Stove

4

refiner

5

bunker

6

container

7

mixer

8th

Gluing device / Blowline

9

dryer

10

pre-dryer

11

after-dryer

12

sifter

13

spreader

14

pre-press

15

hot press

A

Beginning

BZ

Beleimzone

D _i

jet

d

diameter

e

The End

FF

foreign fiber

FG

fiber mixture

HF

wood fiber

HS

wood chips

P

pump

R

pipe section

S

flow direction

Claims (14)

1. Method for manufacturing a wood fibreboard, the method comprising the following steps:

   a) defibrating wood chips (HS) in a refiner (4), so as to form wood fibres (HF);

   b) conveying the wood fibres (HF) produced in the refiner (4) to a gluing device (8);

   c) mixing foreign fibres (FF) with an adhesive (KL) in a mixer (7), so as to form a foreign-fibre/adhesive emulsion;

   d) conveying the foreign-fibre/adhesive emulsion to the gluing device (8);

   e) mixing the foreign-fibre/adhesive emulsion with the wood fibres (HF) in the gluing device (8), so as to form a fibre mixture (FG);

   f) conveying the fibre mixture (FG) from the gluing device (8) to a dryer (9);

   g) drying the fibre mixture (FG) in the dryer (9);

   h) conveying the dried fibre mixture (FG) from the dryer (9) to a scattering device (13);

   i) scattering the fibre mixture (FG), so as to form a fibrous cake;

   j) pressing the fibrous cake in a hot press (15) so as to form a wood fibreboard of a desired thickness.
2. Method according to Claim 1, characterized in that the foreign-fibre/adhesive emulsion in the gluing device (8) is sprayed onto the moving wood fibres (HF).
3. Method according to Claim 2, characterized in that the spraying of the foreign-fibre/adhesive emulsion onto the wood fibres (HF) is performed at a pressure between 4 bar and 20 bar, preferably at 12 bar.
4. Method according to one of the preceding claims, characterized in that the foreign-fibre/adhesive emulsion and the wood fibres (HF) are mixed in the gluing device (8), so as to form a homogeneous fibre mixture (FG).
5. Method according to one of the preceding claims, characterized in that the fibre mixture (FG) is composed of 10% to 70% wood fibres (HF).
6. Method according to one of the preceding claims, characterized in that the foreign-fibre/adhesive emulsion is composed of 10% to 70%, preferably 50%, adhesive (KL).
7. Method according to one of the preceding claims, characterized in that the foreign fibres (FF) are natural or artificial fibres.
8. Method according to Claim 7, characterized in that the foreign fibres are vegetable fibres, in particular cotton fibres, or material fibres or glass fibres, mineral fibres, plastics fibres, or a mixture of these fibres.
9. Method according to one of the preceding claims, characterized in that the wood fibres (HF) are conveyed from the refiner (4) to the gluing device (8) by means of hot steam.
10. Method according to Claim 9, characterized in that the wood fibres (HF) are conveyed through the gluing device (8) as a wood-fibre/steam flow.
11. Plant for manufacturing the derived-timber board as per the method according to at least one of the preceding claims, the plant having:

    - a refiner (4) for decomposing wood chips (HS) to form wood fibres (HF);

    - a mixer (7) for mixing foreign fibres (FF) with an adhesive (KL), so as to form a foreign-fibre/adhesive emulsion;

    - a gluing device (8) for mixing the wood fibres (HF) with the foreign-fibre/adhesive emulsion, so as to form a fibre mixture (FG);

    - a dryer (9) for drying the fibre mixture (FG);

    - a scattering device (13) for scattering the fibre mixture (FG), so as to form a fibrous cake;

    - a hot press (15) for pressing the fibrous cake, so as to form a derived-timber board of a desired thickness.
12. Plant according to Claim 11, characterized in that the gluing device (8) has a plurality of sequentially disposed nozzles (D₁, D₂, ..., D_i, ... D_L).
13. Plant according to Claim 12, characterized by at least one pump (P) for pumping the foreign-fibre/adhesive emulsion to the nozzles (D₁, D₂, ..., D_i, ..., D_L).
14. Plant according to one of Claims 11 to 13, characterized in that the mixer (7) is a static mixer or a static/rotary mixer.

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