ES2623824T3 - Procedure and installation to manufacture a wood fiber panel - Google Patents

Abstract

Procedure for manufacturing a wood composite panel with the following stages: a) defibration of wood chips (HS) in a refiner (4), to form wood fibers (HF), b) transport of wood fibers (HF ) generated in the refiner (4) to a sizing equipment (8), c) mixing of foreign fibers (FF) with an adhesive (KL) to form an emulsion of foreign-adhesive fibers in a mixer (7), d) transporting the emulsion of non-adhesive fibers to the sizing equipment (8), e) mixing the emulsion of non-adhesive fibers with the wood fibers (HF) to form a mixture of fibers (FG) in the sizing equipment (8), f) transport of the fiber mixture (FG) from the sizing equipment (8) to a dryer (9), g) drying of the fiber mixture (FG) in the dryer (9), h) transport of the dried fiber mixture (FG) from the dryer (9) to a spreading device (13), i) spreading the fiber mixture (FG) to form a fiber cake, j) pressing the cake a of fibers to form a panel of wood fibers of the desired thickness in a hot press (15).

Description

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PROCEDURE AND INSTALLATION TO MANUFACTURE A WOOD FIBER PANEL

DESCRIPTION

The invention relates to a process and an installation for manufacturing a panel of wood fibers.

Fiber panels are essentially manufactured by the following work steps:

1. Preparation of the raw material (wood roll, chopped wood),

2. generation of the fibrous substance,

3. gluing and hydrophobicization,

4. possibly dried,

5. formation of a fiber cake (fiber veil),

6. Pressing the fiber cake to form a panel of the desired thickness.

The various manufacturing processes differ mainly in the way in which the cake is formed and in the pressing. Depending on whether the transport of the fibers and the formation of the cake are carried out in water or air, we speak of a wet process or dry procedure. In the semi-dry process, air is used to form the fiber mat, but hot pressing of the wet fibrous substance is carried out similarly to that in the wet process. They are mainly treated with wood of comifers and in increasing proportion, also wood of frond trees. When the wood is no longer available in the form of small pieces, it is crushed to form chopped wood. The resulting pieces are then classified, released by magnets of iron parts, washed and finally stored temporarily in storage hoppers. A moisture content of wood chips / chips of between 50% and 60% has been found to be favorable for subsequent processing.

Before defibration, the pieces of wood are cooked and / or steamed in a baking oven, to soften the structure of the cells, in particular the lignin and thus allow a careful breakdown of the fiber fabric in the different elements . The previous vaporization temperature is about 180 ° C and the treatment time is about three minutes. Due to the influence of heat, low molecular carbohydrates and lignin dissolve in small proportions. From the acetyl groups of the wood, acetic acid is formed, as well as in small amounts acetic antidire. After softening, the pieces of wood are led to a refiner (disc refiner). In the refiner then defibration is performed. Due to the high pressure of up to 8 bar and even more in the refiner, they leave the fibers at high speed. The fibers arrive in a hot steam flow to the gluing equipment, a blow pipe in which the fibers are bonded. In the blow pipe the gluing of the wet fibers is carried out. After gluing, the flow of fibers is conducted to a dryer and the glued fibers are dried there. After drying, the glued fibers are screened and then spread using a spreading device to form the fiber cake. This scattered fiber cake is then pressed into a hot press (Konti press or continuous press), to form a panel of wood fibers of the desired thickness.

Urea-formaldehyde (UF) resins are used as adhesives. Alternatively, these resins may also be reinforced with melamine and / or phenol (MUF, MUPF). For wood composite panels for special applications, methylene diphenyl diisocyanates (MDI) are also provided as an adhesive.

The wet gluing procedure is also called the "blowline" gluing procedure. In this procedure, the adhesive is sprayed on the transport tube or blow tube, in which the fibers are transported from the refiner to the dryer. In "Deppe / Ernst, MDF-medium density fibreboard", DRW editorial, ISBN 3-87181-329-X, wet gluing is widely described on pages 81 to 84. The principle is that the adhesive ( glue) is injected into a flow of fibers that moves with a speed of 150 m / s to 500 m / s To increase the mechanical strength of wood composite panels, it is known to spread tissue fibers by intermingling them in the layers A wooden composite panel is disclosed, for example, in EP 1 754 583 A1.

From US 3,231,458 A it is known the preliminary mixture of wood particles and foreign fibers, gluing them and then pressing. Since not all fibers can be mixed with the same ease, this procedure is not very suitable.

EP 1 623 807 B1 discloses a process for manufacturing a wood composite body in which wood material is deflected to form chips and in which preliminary filiform fibrous material is crushed to form individual fibers. These fibers are then spread by intermingling them with wood chips and then at least one binder (glue) is applied to the wood chips. In this regard, the fibers can also be assembled first and then mixed with the wood chips. With this procedure fibers can be introduced selectively to influence the mechanical properties, but a complete distribution and a good mixture of fibers and wood chips is only possible in a continuous manufacturing process with an unreasonably high cost. The fiber cutting and gluing equipment proposed for this purpose have a very complex and therefore expensive design and its handling is complicated.

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From the magazine "European Journal of Wood and Wood Products 2011, 69 (European magazine of wood and wood products), pages 199 to 206" the insertion of lattices in the fiber cake is known, which have previously even been stuffed in adhesive. However, these grids are only provided in a horizontal plane of the MDF panel, which can only influence certain mechanical characteristics.

Starting from this problem, a procedure for manufacturing a wood fiber panel with which it is possible to selectively improve and / or influence in a simple way the mechanical characteristics of the wood composite panel should be indicated. In addition, an appropriate installation must be indicated to carry out the procedure.

To solve the problem, a procedure for manufacturing a wooden composite panel is characterized by the following stages:

a) defibration of pieces of wood in a refiner,

b) transport of the wood fibers generated in the refiner to a gluing equipment,

c) mixing of foreign fibers with an adhesive to form an emulsion of foreign-adhesive fibers in a mixer,

d) transport of the emulsion of non-adhesive fibers to the gluing equipment,

e) mixing the emulsion of foreign-adhesive fibers with the wood fibers to form a mixture of fibers in the gluing equipment,

f) transport of the fiber mixture from the gluing equipment to a dryer,

g) drying the fiber mixture in the dryer,

h) transport of the dried fiber mixture from the dryer to a spreader device,

i) spreading the fiber mixture to form a fiber cake,

j) pressing the fiber cake to form a panel of wood fibers of the desired thickness in a hot press.

The process according to the invention differs from a traditional method for manufacturing an MDF panel in which foreign fibers are glued and these non-bonded fibers are included in the manufacturing process. These foreign fibers glued with an excess of glue are referred to below as the emulsion of foreign-adhesive fibers. This emulsion serves to glue the wood fibers traditionally prepared in the gluing equipment. The gluing of the fibers is therefore not carried out, as in the process of manufacturing known mDf, with only one adhesive, but with the mixture of foreign-adhesive fibers, the emulsion of foreign-adhesive fibers.

For this, the emulsion of foreign-adhesive fibers is sprayed in the gluing equipment, preferably on the wood fibers that are in motion. In this regard, the emulsion of foreign adhesive fibers can be sprayed onto the wood fibers with a pressure between 4 bar and 20 bar, preferably 12 bar.

It is preferably provided that the emulsion of non-adhesive fibers and wood fibers be mixed in a sizing equipment to form a mixture of homogeneous fibers. The fiber blend may be composed of between 10% and 70% wood fibers. The emulsion of foreign-adhesive fibers is preferably composed of between 10% and 70%, in particular preferably with 50% adhesive.

As foreign fibers, natural or artificial fibers can be used. In particular, vegetable fibers are suitable, in particular cotton fibers or textile fibers, or glass fibers, mineral fibers or plastic fibers or a mixture of various fibers.

The wood fibers are transported from the refiner preferably by hot steam to the gluing equipment and in the gluing equipment they are transported as a flow of wood-steam fibers.

An installation for manufacturing a wood fiber panel according to the process according to the invention is characterized by the following features:

- a refiner for breaking up pieces of wood forming wood fibers,

- a mixer for mixing foreign fibers with an adhesive to form an emulsion of foreign-adhesive fibers,

- a gluing equipment for mixing the wood fibers with the emulsion of non-adhesive fibers to form

a mixture of fibers,

- a dryer to dry the fiber mixture,

- a spreader device for spreading the fiber mixture to form a fiber cake,

- a hot press to press the fiber cake to form a panel of wood fibers.

The mixer can be a static mixer or also a stator-rotor mixer.

Preferably, the gluing equipment has a plurality of nozzles arranged one after the other. Such gluing equipment is known for example from EP 2 431 144 A1.

For transporting the emulsion of non-adhesive fibers to the nozzles, at least one pump, in particular a high pressure pump, is preferably provided.

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An example of embodiment of the invention will be described in more detail below with the help of a drawing.

It is shown in:

Figure 1 - a scheme of the process for manufacturing a wood fiber panel,

Figure 2 - the tubular segment marked "R" in Figure 1, which constitutes the gluing equipment.

Based on Figure 1, the manufacturing process according to the invention will be described. The prepared roundwood 1 is first crushed in a deflector 2 to form pieces of HS wood and washed and cooked in a baking oven 3 which follows. The pieces of HS wood thus prepared are then transferred to refiner 4, in which they disintegrate to form HF wood fibers. Outside FF fibers are provided in a hopper 5, which are mixed in a mixer 7 with an adhesive KL provided from a container 6, to form an emulsion of foreign-adhesive fibers. In a hot steam flow, the wood fibers HF are transported from the refiner 4 to the tubular segment R. This tubular segment R constitutes the gluing equipment 8, which is a blow pipe.

In the bowline (figure 2) a plurality of gluing nozzles D1, D2, ..., Di, ... Dl are arranged annularly around the tube R. At the beginning A of the gluing area BZ the section is widened of the tube d - seen in the flow direction - even before the first gluing nozzle D1 by up to 30%. The speed of the flow of wood fibers is thus reduced and the residence time in the gluing zone BZ increases. At the end E of the gluing zone - seen in the direction of the flow S - behind the last gluing nozzle Dl the section of the widened tube is reduced again. By means of the nozzles D1, D2, ..., Dl, the emulsion mixture of foreign-adhesive fibers transported from the mixer 7 is sprayed on the HF wood fibers, resulting in a homogeneous mixture of wood fibers and emulsion of foreign fibers -adhesive to form a mixture of FG fibers. This fiber mixture is then transferred from the gluing equipment 8 to the dryer 9, in which in a preliminary dryer 10 and a final dryer 11 the water vapor with which the fiber mixture was transported is extracted, as well as moisture from the wood and the KL adhesive dries. After the dryer 9, the fiber mixture FG is transported, for classification, to the screen 12, from which the spreader device 13 then arrives. By means of the spreader device 13 the fiber FG mixture is spread on a conveyor belt that circulates and that is not represented here in more detail, to form a fiber cake. This fiber cake is conducted on the conveyor belt through a preliminary press 14 and then taken to the hot press 15, in which it is pressed under a high pressure and a high temperature to form a fiber panel of wood of the desired thickness. Then the KL adhesive melts and joins together the HF wood fibers and the FF foreign fibers.

As foreign fibers FF, any kind of fibers that can be glued with a suitable KL adhesive is suitable. Artificial fibers, such as glass fibers, plastic fibers or stretched thin threads can also be used to form fibers, such as vegetable fibers, in particular cotton fibers or textile fibers. The choice of suitable foreign FF fibers determines the mechanical properties of the finished wood fiber panel. When the weight of the panel must be reduced compared to that of a traditional MDF panel, it is appropriate to use FF foreign fibers of a material with a density lower than that of the HF wood fibers used. If the flexural strength is to be increased compared to that of a traditionally manufactured MDF panel, it is appropriate, for example, to use glass fibers as FF outside fibers. As a KL adhesive, customary adhesives are used in the manufacture of MDF panels, such as urea-formaldehyde (UF) resins, which can also be made reinforced with melamine and / or phenol (MUF, MUPF) or methylene diphenyl diisocyanates can also be used. (MDI).

The gluing equipment 8 can also be made with a constant pipe section. But it must be ensured that there is a spray energy that allows a homogeneous distribution of the emulsion of foreign-adhesive fibers on the wood fibers, such that a mixture of homogeneous FG fibers can be configured.

Reference List

1 round wood

2 deflector

3 baking oven

4 refiner

5 hopper

6 bowl

7 mixer

8 gluing / blowline equipment

9 dryer

10 preliminary dryer

11 final dryer

12 sieve

13 spreader device

14 preliminary press

15 hot press

At the beginning

BZ gluing area

Say nozzle

 D diameter

 Final E

 FF foreign fibers

 FG fiber blend

 5

 HF wood fibers

 HS wood chips

 P pump

 R tubular segment

 10

 S flow direction

Claims (14)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1. Procedure for manufacturing a wood composite panel with the following stages: a) defibration of wood chips (HS) in a refiner (4), to form wood fibers (HF), b) transport of the wood fibers (HF) generated in the refiner (4) to a gluing equipment (8), c) mixing of foreign fibers (FF) with an adhesive (KL) to form an emulsion of foreign-adhesive fibers in a mixer (7), d) transport of the emulsion of non-adhesive fibers to the gluing equipment (8), e) mixing the emulsion of foreign-adhesive fibers with wood fibers (HF) to form a mixture of fibers (FG) in the gluing equipment (8), f) transport of the fiber mixture (FG) from the gluing equipment (8) to a dryer (9), g) drying the fiber mixture (FG) in the dryer (9), h) transport of the dried fiber mixture (FG) from the dryer (9) to a spreader device (13), i) spreading the fiber blend (FG) to form a fiber cake, j) pressing the fiber cake to form a panel of wood fibers of the desired thickness in a press hot (15). 2. Procedure according to claim 1, characterized in that the emulsion of foreign-adhesive fibers is sprayed in the gluing equipment (8) on the wood fibers (HF) that are in motion. 3. Procedure according to claim 2, characterized in that the spraying of the emulsion of foreign-adhesive fibers on wood fibers (HF) is carried out with a pressure between 4 bar and 20 bar, preferably 12 bar. 4. Method according to one of the preceding claims, characterized in that the emulsion of non-adhesive fibers and wood fibers (HF) are mixed in the gluing equipment (8) to form a mixture of homogeneous fibers (FG). 5. Method according to one of the preceding claims, characterized in that the fiber blend (FG) is composed of between 10% and 70% wood fibers (HF). 6. Method according to one of the preceding claims, characterized in that the emulsion of non-adhesive fibers is composed of between 10% and 70%, preferably 50% adhesive (KL). Method according to one of the preceding claims, characterized in that the foreign fibers (FF) are natural or artificial fibers. 8. Procedure according to claim 7, characterized in that the foreign fibers are plant fibers, in particular cotton fibers or textile fibers or glass fibers, mineral fibers, plastic fibers or a mixture of these fibers. 9. Method according to one of the preceding claims, characterized in that the wood fibers (HF) are transported from the refiner (4) by hot steam to the gluing equipment (8). 10. Procedure according to claim 9, characterized in that the wood fibers (HF) are transported through the gluing equipment (8) as a flow of wood-steam fibers. 11. Installation for manufacturing the wood fiber panel according to the method according to at least one of the preceding claims with: - a refiner (4) for breaking up pieces of wood (HS) to form wood fibers (HF), - a mixer (7) for mixing foreign fibers (FF) with an adhesive (KL) to form an emulsion of foreign-adhesive fibers, - a gluing equipment (8) for mixing the wood fibers (HF) with the emulsion of non-adhesive fibers to form a fiber mixture (FG), - a dryer (9) to dry the fiber mixture (FG), - a spreader device (13) for spreading the fiber mixture (FG) to form a fiber cake, - a hot press (15) for pressing the fiber cake to form a panel of wood fibers of the desired thickness. 12. Installation according to claim 11, characterized in that the gluing equipment (8) has a plurality of nozzles (D1, D2, ..., Di, ... Dl) arranged one after the other. 13. Installation according to claim 12, characterized by at least one pump (P) for transporting the emulsion of non-adhesive fibers to the nozzles (Di, D2, ..., Di, ... Dl). 14. Installation according to one of claims 11 to 13, 5 characterized in that the mixer (7) is a static mixer or a stator-rotor mixer.