METHOD OF MANUFACTURING A WOOD-BASED PANEL

Abstract

The present invention concerns a method for the manufacture of a wood-based panel comprising providing wood fibers which are impregnated with a phenolic resin, the ratio of resin (based on the solids content) to wood fibers being 10 to 50% by weight. The impreganted fibers are pre-compacted in a press at press temperatures below 110° C. to a chemically reactive fiber board and then pressed to compact panels at temperatures between 130 and 180° C.

Claims

1. A method for manufacturing a wood-based panel comprising the following steps in the indicated order: Provision of wood chips; Breaking down the wood chips into wood fibers in a refiner for 3 to 20 minutes at a pressure of 4 to 16 bar; Gluing the wood fibers with a phenolic resin, the ratio by weight based on the solids content of resin to wood fibers being 10 to 50%; Pre-compacting the fibers in a press at pressing temperatures below 110° C. to form chemically reactive fiber boards; and Pressing the pre-compacted fiber boards into panels at temperatures between 130 and 180° C.

2. The method according to claim 1, wherein an amount of power of 25 to 70 kW/t is applied when the wood chips are broken down.

3. The method according to claim 1, wherein the ratio by weight based on the solids content of resin to wood fibers is 10 to 40%, more preferably 15 to 30% and most preferably 15 to 25%.

4. The method according to claim 1, wherein the pre-compaction of the fibers is carried out in such a way that the phenolic resin does not undergo any chemical reaction.

5. The method according to claim 1, wherein the pre-compacted chemically reactive fiber boards have a density of 300 to 900 kg/m.sup.3, more preferably from 500 to 800 kg/m.sup.3 and even more preferably from 650 to 750 kg/m.sup.3.

6. The method according to claim 1, wherein the pressing of the pre-compacted chemically reactive fiber boards to panels takes place at temperatures between 140 and 170° C., more preferably between 140 and 160° C.

7. The method according to claim 1, wherein the pressing of the pre-compacted chemically reactive fiber boards to panels takes place at a pressing pressure of 4 to 10 MPa, preferably 7 to 9 MPa.

8. The method according to claim 1, wherein mineral fillers are added to the binder.

9. The method according to claim 8, wherein the mineral fillers are added in an amount of 5 to 150% by weight based on the mass of the binder, preferably 10 to 100% by weight and most preferably 35-90% by weight, based on the solids content of the binder.

10. The method according to claim 8, wherein the mineral fillers comprise flame retardants, such as in particular aluminum hydroxide or borates.

11. The method according to claim 1, wherein mineral fillers are added to the binder in a type and quantity so that the finished wood fiber panel achieves a fire behavior quality of B1 according to DIN 4102-1 or better.

12. The method according to claim 1, wherein inorganic phosphorus compounds are added to the binder, particularly preferably in combination with nitrogen-containing compounds such as amines, and the mineral fillers are added to the binder and the mineral fillers are particles with an average particle size of 10 nm to 150 μm, preferably 500 nm to 50 μm and most preferably 800-900 nm.

13. (canceled)

14. The method according to claim 1, wherein the step of breaking down the wood chips into wood fibers is carried out at a pressure of 5 to 16 bar, preferably 6 to 15 bar and most preferably at 8 to 15 bar, and the step of breaking down the wood chips into wood fibers takes place in the refiner for a duration of 3 to 18 minutes, preferably 3 to 15 minutes and most preferably for a duration of 3 to 10 minutes.

15. (canceled)

16. The method according to claim 1, wherein the gluing of the wood fibers with binder is carried out in a blow line.

17. The method according to claim 1, wherein the wood fibers are glued with binder by means of mechanical gluing, and the ratio by weight based on the solids content of binder to wood fibers is 10 to 50%, more preferably 15 to 40% and most preferably 15 to 25%.

18. (canceled)

19. The method according to claim 1, wherein the pre-compacting to chemically reactive fiber boards is carried out in a continuous press in such a way that the fiber boards are pressed to a density of 300 to 900 kg/m.sup.3 and preferably to 650 to 750 kg/m.sup.3 and the temperature of the glued wood fibers during pre-compaction is between 30 and 110° C., more preferably between 50 and 105° C., more preferably between 60 and 100° C., and most preferably between 70 and 100° C.

20. (canceled)

21. The method according to claim 1, wherein the pre-compaction to chemically reactive fiber boards is carried out in a continuous press at a temperature of the press belts of 15 to 150° C., preferably of 30 to 140° C., further preferably of 60 to 140° C. and most preferably of 70 to 110° C., such that the core temperature of the chemically reactive fiber boards to be produced does not exceed 110° C., and the pre-compacted chemically reactive fiber boards are compacted to panels having a density of 1,200 to 1,900 kg/m.sup.3, preferably 1,400 to 1,650 kg/m.sup.3 and even more preferably 1,450 to 1,550 kg/m.sup.3.

22. The method according to claim 1, wherein the wood fibers are fed to the gluing step with a moisture content of 2 to 8%, preferably 3 to 5%.

23. (canceled)

24. The method according to claim 1, wherein the pre-compacted chemically reactive fiber boards are provided with decorative melamine resin-impregnated papers before being pressed into panels.

25. The method according to claim 1, wherein the pre-compacted chemically reactive fiber boards are provided with phenolic resin-impregnated kraft papers on both sides or one side before the step of pressing into panels.

Description

4. DESCRIPTION OF PREFERRED EMBODIMENTS

[0043] In the following, the invention is explained in more detail with reference to the attached figures.

[0044] FIG. 1 is a schematic block diagram of a sequence of an inventive process; and

[0045] FIG. 2 shows schematically a production line for an inventive wood-based panel.

[0046] FIG. 1 shows a schematic flow chart for an inventive process for the production of a wood-based panel. In step S1, wood chips are provided. In step S2, the wood chips are processed into wood fibers by pulping them in a refiner for a few minutes at a pressure of 4 to 16 bar. In step S3, the wood fibers are glued with a phenolic resin, for example using a blow line or a mechanical gluing system known from MDF production. In step S4, the glued wood fibers are pre-compacted into a chemically reactive fiber board in a moulding press at pressing temperatures below 110° C. and in step S5 the pre-compacted fiber boards are pressed into the desired panels at temperatures between 130 and 180° C. It is clear to the skilled person that further process steps are possible between, before and after the mentioned processing steps, such as in particular drying of the wood chips and/or the wood fibers or the application of melamine resin-soaked kraft papers, cleaning of the wood chips and/or the produced wood fibers, etc.

[0047] FIG. 2 schematically shows a line for the production of an inventive wood-based panel. Wood chips are fed to a refiner 10 by means of a transport device 14. In Refiner 10, the wood chips are broken down into wood fibers and these are then fed to a dryer 12, where they are dried. From dryer 12 the wood fibers are fed to a gluing plant 16, where they are applied with a liquid phenolic resin. The glued fibers 40 are deposited on a transport device and fed to a double belt press 20 for pre-compaction. In belt press 20, the press belt temperatures are increased but kept well below 110° C. to avoid a chemical reaction of the resin in the glued fibers 40. At the exit of the double belt press 20 a chemically reactive pre-compacted fiber board 42 is provided, which has a density of about 650 to 750 kg/m.sup.3. This pre-compacted fiber board 42 is then fed to a high-pressure multi-level press 30 for final compaction. In this press 30, the fiber board 42 is further compacted using heat and pressure and in particular the binder is chemically crosslinked. The second press 30 operates at considerably higher temperatures than the first continuously operating press 20 for pre-compaction. In particular, the temperatures of the second press 30 are around 130 to 180° C. In addition, a considerably higher specific pressing pressure of up to 10 MPa is applied in the second press. After the pressing process at press 30, a panel 44 with a density of approx. 1,600 kg/m.sup.3 is present. The panel 44 can be subjected to further processing steps and in particular can be cut to the desired sizes.

REFERENCE CHARACTER LIST

[0048] 10 Refiner

[0049] 12 Dryer

[0050] 14 Wood chips

[0051] 16 Glueing plant

[0052] 20 Double belt press for pre-compacting

[0053] 30 Double belt press for final compaction

[0054] 40 Glued fibers

[0055] 42 Pre-compacted fiber board

[0056] 44 Finished wood-based panel