EP1435281B1 - Method and press for continuous manufacturing of fiberboards from wood - Google Patents

Abstract

The continuous belt press, for the production of wood boards, has upper and lower frame sections (7,8) and continuous steel belts (9,10) to draw the wood material mat (4) through the press (3). The steel belts are supported by roller rods (16) at the heated plates (12,14). The length of the press zone is at most11 m, the entry zone has a length of 1.3-1.7 m, and there is a joint at the upper frame section. The upper heated plate (14) is expanded after being in contact with the wood mat for 1.8-2.4 m, to give an abrupt pressure release (11) at the press gap (23) for a heated plate thickness of 90-100 mm, with flexible rolling plates (15) at the roller rods.

Description

The invention relates to a method for the continuous production of wood-based panels according to the preamble of claim 1 and a continuously operating press according to claim 10.

A process for the continuous production of wood-based panels, in particular plates in the thickness range 1-9 mm, in the dry process is known. In the DE 101 63 090 For example, such a method is described, and in particular, plates with low adhesive contents can be produced by this method. In the DE 101 09 316 a method for the continuous production of a wood-based panel is described with very low pressing times. For this purpose, a very reactive adhesive system is used. These short pressing times result in a feed rate of almost 1000 mm / sec. Higher feed rates are currently not technically possible due to limitations on the forming belt. With the DE 195 18 879 a method has become known with which according to Pre-compaction the chip fiber mat in the inlet gap in the following main press lines by means of flexible press racks and / or press segments a low-pressure zone decompressing and compressing with a steep slope or falling angle tangent β and β ₁ of about 0.05 for a vertical stroke from 0 to approx. 10 mm increasing extremely short at maximum production speed during production (online) can be controlled.
However, it has been found that the existing methods and equipment have some disadvantages in the production of thin plates. This essentially relates to the achieved average density and the surface density of the plate. Thin plates of wet thickness, 2 - 4 mm thick, are partly replaced by fibreboards of the same thickness from the dry process and chipboard of a thickness of about 15 mm. The 15 mm chipboard absorbs about the same force as the fiberboard. But by using the thick chipboard furniture is heavier, so that only a limited use is possible.
The thin panels are mainly used as furniture backs and drawer bottoms. With this use, they can also be coated on one side or painted. Lately, the direct painting of the plate surface is becoming increasingly prevalent. The previously necessary grinding process is eliminated. However, for economical direct painting, the panels must meet certain requirements. The surface density must be above 1000 kg / m ³ and the density maximum must be directly at the Be surface. At a lower density of the paint is absorbed by the plate, resulting in the increased use of paint at a higher cost.

For drum presses DE 41 03 342 C1 and DE 42 43 917 C1 could be improved with the introduction of transverse correction rolls (so-called Nipco rolls) with regard to the formation of a higher cover layer density and a more uniform cover layer density distribution across the plate width. These very expensive rolls are installed immediately after entry to a length of up to 30% of the press length and about half of the press length. Through these rollers, the specific pressure within certain limits, which are dictated by the storage of the large press drum, can be increased. However, the density profile is not uniformly high across the plate width: in the middle and on the outermost edge is usually a density drop, which is caused by the drum bending and the worse heat input at the outermost edge.

In the known drum presses and the known double belt presses, it is very difficult, despite a Mattenbesprühung and or cover layer steam preheating to achieve very high density differences between the top and middle layer, since the heat and pressure curve during the hot pressing can not be optimally controlled.

Out US 2002 036046 A For example, a method for optimizing production capacity and flexibility of product characteristics in the production of chip, fiber and similar plates has become known. Various parameters are proposed in a continuous process, in particular a steam treatment of the pressed material mat to influence the density profile, wherein the density profile is measured during operation at the outlet of the hot press and this is used to change the temperature and moisture content of the pressed material before the press to optimize the desired product quality. A different density profile adjustment across the thickness of the plate is sought by the proposed method.

Although high pressure can be applied very quickly to the aforementioned drum presses, it is not possible to relieve pressure after forming the cover layer after mat contact because of the ever-present steel strip tension, which would be particularly important in the case of preheated plates. Since it can not be relieved accordingly, the cover layer thickness is too wide and the middle layer density is too high.

Even with the existing double belt presses a quick relief after the formation of the cover layer is not possible, whereby also the width of the cover layer density is formed unnecessarily large. The relief is not possible due to the limited flexibility of the heating plates, so the possible deformation per meter of press length. The use of longer presses where the flexibility per meter press length could be less, is uneconomical at low press times.

The invention has for its object to provide a method with which at very short pressing times thin fiberboard with optimum density profile, in particular a high density in the outer layers with density difference between the top and middle layer can be produced and to provide a continuously operating press for carrying out the process.

• bei der Herstellung von in ihren Deckschichten über 1000 kg/m³ und einer mittleren Dichte unter 750 kg/m³ aufweisenden Faserplatten oder bei der Herstellung von in ihrer Deckschicht über 1000 kg/m³ und einer mittleren Dichte unter 730 kg/m³ aufweisenden und einseitig höher verdichteten Faserplatte wird
• die Preßgutmatte mit Dampf vorgewärmt und/oder mit Wasser besprüht, nach Kontaktnahme mit den auf 140° Celsius und mehr aufgeheizten Stahlbändern wird nach 2 Sekunden ein spezifischer Pressdruck von größer 2 N/mm² aufgebracht, der über die Breite im Einlaufbereich nahezu gleichmäßig gehalten wird, nach 3 Sekunden der Kontaktnahme erfolgt eine Druckentlastung auf unter 1 N/mm², wobei vorab die Preßgutmatte auf etwa Fertigplattendicke verdichtet ist und anschließend wird die Druckentlastung auf 0,5 N/mm² weiter abgebaut.

The solution of this problem for the production of both sides higher density fiberboard is derived from the characterizing part of claim 1 as follows out:

• in the production of in their outer layers over 1000 kg / m ³ and an average density of less than 750 kg / m ³ having fiberboard or in the production of their top layer over 1000 kg / m ³ and an average density below 730 kg / m ³ having and one-sided higher density fiberboard
• the Preßgutmatte preheated with steam and / or sprayed with water, after contacting with the heated to 140 ° C and more steel strips is applied after 2 seconds, a specific pressure of greater 2 N / mm ² , which is held almost uniform across the width in the inlet region , After 3 seconds of contacting a pressure relief to less than 1 N / mm ² , wherein in advance the Preßgutmatte is compressed to about finished plate thickness and then the pressure relief to 0.5 N / mm ² further reduced.

For these one-side compacted fiberboard, especially for very thin plates, it is sufficient if the heat is a sole heat input into the Preßgutmatte from above.

The plant for carrying out the method comprises a scattering station for forming a two or more layers Preßgutmatte on a continuously moving forming belt, a pretreatment device for the Preßgutmatte for adjusting the heat and / or moisture and a continuously operating press for pressing and curing the pressed material under pressure and Warmth.
For a continuous press, the solution is that the press length of the continuous press is less than 11 m, the inlet section has a length of 1.3 m to 1.7 m and is articulated in the upper part, and that the upper heating plate is formed after 1.8 to 2.4 m matte contact for a relief shock widening the press nip, for which the Heizplattendicke is between 90-100 mm and is provided opposite the rolling rods with flexible Abrollplatten ..

With the method, and the continuous press according to the invention, thin fiberboards can be produced at shortest pressing times with high density differences between the cover layers and the middle layer, with a density of over 1000 kg / m ³ in the cover layers and less than 600 kg in the middle layer / m ³ , at an average density of the plate less than 750 kg / m ³ , are achievable.

For the production of high densities in the outer layers is advantageous if the structure of the particles on the surface of the material to be pressed are very fine and no Dust is present. Very suitable for this purpose are so-called microfibers, in which the fiber structure with respect to the length is still preserved, but the cell walls are partially decomposed, so that the lumen of the cell is exposed. The spreading of the cover layers with microfibers takes place through a separate fine material spreading machine or through a separating spreading machine. In addition to the closed surface, these microfibers also transmit bending forces, which results in higher bending strengths. Coarse fiber bundles or glue lumps are expediently dissolved before depositing and / or detected with a special device prior to scattering.

The paint consumption when directly painting an entire paint line depends on the location on a disk surface which has the lowest density. Targeted overpainting Low surface density areas are not possible. To achieve a low paint consumption, therefore, the plates must have a consistently high density both across the width and over the length in the plate surface. This is achieved if over the width in the inlet region of the specific pressure is applied almost uniformly.

The claimed in claim 12 continuously operating press a very flexible system is created, with which it is possible to produce fiberboard in the thickness range of 1-9 mm with optimum density profiles. For a correspondingly accurate distribution and flexibility on the way the Press length necessary. The mat is first compressed in the inlet to the finished plate thickness or slightly below finished plate thickness. At this time, the maximum compressive stress is applied to the mat and the height of the top layer density is formed. The height of the cover layer density is influenced by the compressive stress as well as the humidity and the temperature of the respective mat layers. Only with an optimum combination of 9% humidity and a high temperature, a high density can be achieved. Immediately after the maximum tension is reached, the path must be maintained or slightly relieved to prevent further mat layers being further compacted by moisture and temperature increase. After forming the cover layer maxima in the desired width, the mat must be relieved as quickly as possible so that only a compressive stress of less than 0.5 N / mm ^{2 is} applied in order to prevent further surface-near mat layers from being compacted. This is possible with the inventive method and the system by means of the relief shock and the soft heating plates with a thickness between 90 and 100 mm, which is arranged according to the invention 1.8 to 2.4 m after mat contact. The relief shock can be constructively designed so that a relief of up to 2.5 mm is possible, with the bending with these soft heating plates and abutting rolling plates after DE 40 10 308 and by means of an ankle joint between two hot plates on a very short distance is reached.

Accordingly, the heating plates are designed very flexible after the inlet to the discharge shock. It can therefore be relieved immediately after the enema more than other double belt presses or the distance can still be maintained until the discharge shock to achieve an even higher and wide top layer peak. The high flexibility of the heating plates in this area thus make it possible to design the profile density profile in the outer layers in a wider range than before.

Since, according to the invention, the press is provided with a relief shock of this size, a very large distance can be relieved faster at the right time than in other double belt presses. Thus, a U-shaped density profile, ie a very rapid drop in the cover layer density to the middle layer density can be achieved.

The compaction to the final size of the plate (secondary compaction) is carried out after heating the center of the mat to about 100 ° C. Depending on the press speed and plate thickness, this time or the distance from the beginning of the press will be different. Since the press is very short, the second compression must also be carried out over a short distance. In order to get the necessary flexibility in this area, the heating plate must be made under 100 mm thickness and the frame distance reduced to about 1000 mm. As an alternative or as a supplement, the heating plate also be subdivided and the shocks are executed from about 5 m as impact shocks. The load impacts are preferably arranged after 5 and 7 m. When reaching a temperature of 100 ° C in the middle of the mat and a secondary compaction of about 3 N / mm ² , the distance in the press nip is not changed and a flexibility of the heating plates is no longer required, therefore, the distance can be made larger in the last two racks become.

Significant next to the flexibility of the heating plates is the temperature of the steel strips in contact with the mat. The temperature must be above 140 ° C, preferably 155 ° C, so that at the time of maximum pressure sufficient heating of the mat surfaces has taken place. If the mat was sprayed, the water with high enthalpy of vaporization must be evaporated in a very short distance. Therefore, the press must be equipped against the environment, but especially with good insulation of steel strip and rolling rods in the return. An inlet drum heating and a roll bar preheating is also beneficial. These measures are necessary in one-sided paintable plates only in the upper press body. By a deliberately higher setting of the steel strip temperature on the Gutseite of the plate (usually upper side), can also on the Gutseite produce a higher cover layer density than on the lower side of the plate. Thus, the average density of the plate can be lowered further. For this case, the steel strip temperature should preferably can only be set higher in the inlet, otherwise the pressing time increases with a lower heating plate temperature of the underside.

Since the necessary temperature for the inlet drum heating is not very high, if necessary, a steam drum heating can be performed. The heating plates need to be equipped with only one heating circuit, as with the thin plates and the short press a large temperature difference along the heating plate is not necessary.

By the method and the inventive design of the press now fiberboard can be produced with an average density below 740 kg / m ³ and a top layer density of 1040 kg / m ³ , which was previously possible on no other press. Due to the high steel strip temperature in the inlet, even very short pressing times can be achieved.

Directly painted panels require a very smooth surface. Foreign matter, glue lumps or local scattering often increase the specific pressure locally to a few centimeters in the press. These pressure peaks lead to dents in the steel strip in the area of the maximum pressing pressure. The indentations considerably reduce the value of directly paintable panels. In order to avoid Stahlbandeindellungen, on the one hand, the steel strip can be made as thick as possible. At present, steel strips with a thickness of 3 mm can be delivered without any problems. The thick However, steel strip only has to be used at the top if the board is to be painted on one side only. As a further measure, the heating plate can be made softer in the region of maximum pressure. For this purpose, small cylinders are arranged over the entire Heizplattenbreite, yielding to the pressure at a small distance.

With regard to the transverse deformation, the press must have approximately the same press nip thickness in the inlet region across the width, as a result of which the specific pressure across the width is also almost constant. Due to the constant sp. Pressure across the width of the cover layer is formed evenly across the width. Since the plate thickness differences are not very large, production is easily possible at the beginning of the press with a setting of the press nip across the width. This setting can be made, for example, by inserting the hot plates. At the press outlet, however, a possibility of the transverse deformation of the heating plate must be provided for the exact thickness adjustment across the width. This can be done for example by means of multipots.

Further advantageous measures and embodiments of the subject matter of the invention will become apparent from the dependent claims and the following description with the drawing.

Figur 1

Eine Anlage in Seitenansicht,

Figur 2

die Entlastungsstoßvorrichtung in größerem Maßstab nach einem Ausschnitt A aus Figur 1 und

Figur 3

die Entlastungsstoßvorrichtung in größerem Maßstab in einem Schnitt a-a aus Figur 1.

Show it:

FIG. 1

An attachment in side view,

FIG. 2

the discharge shock device on a larger scale after a cutout A from FIG. 1 and

FIG. 3

the discharge shock device on a larger scale in a section aa FIG. 1 ,

In the drawing, the attachment is in FIG. 1 shown in side view. In the structure there is a scattering station, a pretreatment device and the continuously operating press 3. The scattering station is either a three- or a Zweischichtpressgutmatte sprinkled on the gas-permeable mold belt 6, then introduced with the forming belt 6 via the inlet gap 19 in the continuously operating press 3 and pressed there to a fiberboard 5. In the pretreatment device, the pressed material mat 4 is preheated with steam and / or sprayed with water.

After the FIGS. 1 to 3 The continuous press 3 consists in its main parts of the upper frame part 7, the lower frame part 8 and these connecting racks 20. To adjust the press nip 23 arranged in the frame part 8 heating plates 13 and 14 by means of hydraulic cylinder piston units (not shown) against the lower Heating plate 12 up and down and locked in the selected position.
For drawing and pressing the Preßgutmatte 4 by the continuously operating press 3 is a steel strip 9 to the lower frame part 8 and in Steel band 10 around the upper frame part 7 circumferentially arranged and guided. The steel belts 9 and 10 are thereby pulled by drive drums 21 and 22 through the press nip 23 and initially deflected by inlet drums 17 and 18. To reduce friction between the attached to the lower frame part 8 and the upper frame part 7 heating plates 12, 13 and 14, the steel strips 9 and 10 are also circumferentially provided each one of rolling rods 16 forming roll bar carpet. To protect the heating plates 12, 13 and 14 hardened Abrollplatten 15 low density are attached to them. The application of the rolling plates 15 to the heating plates 12, 13 and 14 goes in detail from the DE 40 10 308 C2 out.

To carry out the method according to the invention, the continuous press 3 is provided after the inlet region of 1.8 m to 2.4 m with a discharge shock device 11 in or between two heating plates 13 and 14 or 14 and 14 or 12 and 12, the Pressing nip 23 forms expanding and what the Heizplattendicke between 90 mm and 100 mm and is provided with respect to the rolling rods 16 with flexible Abrollplatten 15. For a relief shock and / or a load impact on the Preßgutmatte 4, one or more recesses 28 are provided in or between two heating plates 12, 13 and 14, in which a plurality of printing units are arranged embedded, via the pressure cylinder 27, plunger 26, push rod 25 and Pressure elements 24 a partially very high or partially very low pressure is einsteuerbar.

List of Reference Numerals: DP 1288 EP

Third

Continuously working press

4th

press material mat

5th

fibreboard

6th

forming belt

7th

Upper frame part

8th.

Lower frame part

9th

Lower steel band

10th

Upper steel band

11th

Relief pusher

12th

Lower heating plate

13th

heating plate

14th

Upper heating plate

15th

rolling plate

16th

roll bars

17th

Lower inlet drum

18th

Upper inlet drum

19th

inlet gap

20th

frame

21st

Lower drive drum

22nd

Upper drive drum

23rd

press nip

24th

print elements

25th

pressure plunger

26th

pressure piston

27th

cylinder

28th

recess

Claims (24)

1. A method for the continuous production of wood-based boards with a thickness of 1 to 9 mm, especially fiberboards made of wood and other lignocellulose-containing materials, according to the drying method, in which a compressed-material mat which is laced with a reactive binding agent is formed which is hardened into a strand of boards or an endless wood-based board after the insertion between the steel bands of a continuously working press under application of pressure and heat, which steel bands are guided in a revolving manner about an upper and bottom frame part, characterized by the following method steps in the production of fiberboards having over 1000 kg/m³ in their cover layers and a mean density beneath 750 kg/m³ or in the production of fiberboards compressed higher on one side and having over 1000 kg/m³ in their cover layers and a mean density beneath 730 kg/m³:

   1.1 the compressed-material mat is preheated with steam and/or sprayed with water;

   1.2 after making contact with the steel bands heated up to 140° Celsius or more a specific pressing pressure of higher than 2N/mm² is applied after 2 seconds which is held virtually evenly over the width in the entry area;

   1.3 after three seconds of making contact there is a pressure relief to under 1 N/mm², with the compressed-material mat being compressed to approximately the thickness of the finished board, and

   1.4 subsequently the pressure relief is further reduced to 0.5 N/mm².
2. A method according to claim 1, characterized in that the dispersion of the cover layers or the upper cover layer occurs alone for forming the compressed-material mat with very fine wood particles (microfibers).
3. A method according to claim 1 or claim 2, characterized in that the dispersion of the cover layers with microfibers occurs by a fine-material dispersing machine or a separating dispersing machine.
4. A method according to claim 1 and claims 2 and 3, characterized in that coarse fiber bundles or lumps of adhesive are dissolved prior to depositing and/or are detected with a special device before dispersion.
5. A method according to claim 1 and the claims 2 to 4, characterized in that the compressed material mat is introduced with a humidity of under 9% into the continuously working press.
6. A method according to one of the claims 1 to 5, characterized in that a second compression with approx. 3 N/mm² up to hardening occurs upon reaching a temperature of 100°C in the middle of the compressed-material mat.
7. A method according to claim 1 and claims 2 to 6, characterized in that a loading jolt occurs on the compressed-material mat within the length of the continuously working press between 5 m and 7 m.
8. A method according to claim 1 and claims 2 to 7, characterized in that several loading jolts occur on the compressed-material mat within the length of the continuously working press between 5 m and 7 m.
9. A method according to claim 1 and claims 2 to 8, characterized in that the hardening of the compressed-material mat for a fiberboard with unilaterally increased cover layer density occurs only with heat introduction from above.
10. A continuously working press for performing the method according to the claims 1 to 9, consisting of a bottom and upper frame part (7, 8), two steel bands (9, 10) which are guided in a revolving manner about the frame parts and draw the compressed-material mat (4) through the press (3), with the steel bands being supported via co-revolving roller bars (16) on heating plates (12, 13, 14) of the frame parts (7, 8), characterized in that the pressing length of the continuously working press (3) is less than 11 m, the entry region has a length of 1.3 m to 1.7 m and is provided in the upper part with a joint, and the upper heating plate (14) is arranged to expand the press nip after 1.8 to 2.4 m of mat contact for a relief joint (11), for which purpose the thickness of the heating plate is between 90 and 100 mm and is provided in relation to the roller bars (16) with flexible rolling plates (15).
11. A continuously working press according to claim 10, characterized in that the relief joint (11) is arranged between two heating plates (entry heating plate 13 and heating plate 14) and is adjustable to expand the press nip (23) by means of hydraulic pressing cylinders (26, 27) to an offset of the heating plates (13 and 14) by up to 2.5 mm.
12. A continuously working press according to the claims 10 and 11, characterized in that an ankle joint with spring-elastic coupling is arranged for the relief between the two heating plates (13, 14).
13. A continuously working press according to the claims 10 and 12, characterized in that the steel bands (9, 10) and the roller bars (16) are guided through a heating device in return travel.
14. A continuously working press according to the claims 10 to 13, characterized in that the steel bands (9, 10) and the roller bars (10) are insulated against the ambient environment in return travel.
15. A continuously working press according to the claims 10 to 14, characterized in that the steel bands (9, 10) are jointly guided into the entry region with the roller bars (16) over a heated entry drum (18).
16. A continuously working press according to the claims 10 to 16, characterized in that a loading jolt can be activated after approx. 5 m from contact with the mat.
17. A continuously working press according to the claims 10 to 16, characterized in that several loading jolts can be activated between 5 m and 7 m from contact with the mat.
18. A continuously working press according to the claims 10 to 17, characterized in that the steel bands (9, 10) have a thickness of 3 mm and more.
19. A continuously working press according to the claims 10 to 18, characterized in that for producing a two-layer fiberboard with cover layer compression the continuously working press has the following features:

    19.1 the bottom heating plates (12) are arranged continually without ankle joint and apparatus for a relief joint (11);

    19.2 the bottom heating plates (12) are heated only very little or not at all;

    19.3 the bottom steel band (9) with associated roller bars (16) is not heated;

    19.4 the bottom entry drum (17) is arranged in a non-heated way, and

    19.5 the bottom steel band (9) has a lower thickness than the upper steel band (10).
20. A continuously working press according to the claims 10 to 19, characterized in that for the purpose of calibrating the fiberboard (5) in the outlet region the action of multiple potentiometers on the heating plates can be triggered.
21. A continuously working press according to the claims 10 to 20, characterized in that only one heating circuit, is provided.
22. A continuously working press according to claim 10, characterized in that for generating partly very high pressures of 4 to 8 N/mm² on the compressed-material mat (4) one or several recesses (28) are provided which reach across the width (b) of the heating plates (12, 14) and in which several pressure units (24, 25, 26, 27) are Incorporated, wherein a partial pressure which is increased in relation to the mean heating plate pressure can be applied via a pressure cylinder (27), pressure piston (26), pressure ram (25) and pressure element (24) on the pressing material/compressed-material mat (4).
23. A continuously working press according to claim 10, characterized in that for generating partly very low pressures on the compressed-material mat (4) one or several recesses (28) are provided which reach across the width (b) of the heating plates (12, 14) and in which several pressure units (21, 25, 26, 27) are incorporated, wherein a partial pressure which is reduced in relation to the mean heating plate pressure can be applied via a pressure cylinder (27), pressure piston (26), pressure ram (25) and pressure element (24) on the pressing material/compressed-material mat (4).
24. A continuously working press according to claims 10, 22 and 23, characterized in that the recesses (28) for the pressure units (24, 25, 26, 27) are provided only in the front part of the continuously working press (3).

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