PROCESS FOR THE PRODUCTION OF PARTICLE BOARD OR WOOD FIBER BOARD

Abstract

A process for the production of particle board, MDF board or HDF board includes the step of recycling particle board material, MDF and/or HDF board material in which recycled chips and/or recycled wood fibers are produced. The process includes the step in which the particle board material, the MDF and/or HDF board material is wetted, heated and pressurized, such that this material is kept under pressure and at an elevated temperature for a certain time. The process involves the step of supplying the recycled chips and/or the recycled wood fibers as base material in a production process of particle board, MDF board or HDF board.

Claims

1. A process for production of particle board, MDF board or HDF board, wherein the process comprises recycling board material in which recycled chips and/or recycled wood fibers are produced, said board material comprising particle board material and/or MDF board material and/or HDF board material; and wherein the process comprises a step in which the board material is wetted, heated and pressurized; wherein the process comprises a step of steam explosion of the wetted, heated and pressurized board material, in which recycled chips and/or recycled wood fibers are produced during the steam explosion; wherein the recycled chips and/or recycled wood fibers are coated with adhesive; wherein the coated recycled chips and/or the coated recycled wood fibers are supplied for producing particle board, MDF board or HDF board.

2. The process as in claim 1, wherein said adhesive is a urea-formaldehyde adhesive, a melamine urea-formaldehyde adhesive, a phenol adhesive, or a MDI or pMDI adhesive, or a bio-adhesive.

3. The process as in claim 1, wherein new chips and/or new wood fibers are provided and coated with adhesive, wherein the coated new chips and/or the coated new wood fibers are also supplied for producing said particle board, MDF board or HDF board.

4. The process as in claim 3, wherein the recycled chips and/or recycled wood fibers are coated with adhesive together with the new chips and/or new wood fibers.

5. The process as in claim 3, wherein the new chips and/or new wood fibers are coated with adhesive in a step which is separate from said coating the recycled chips and/or recycled wood fibers with adhesive.

6. The process as in claim 1, wherein the recycled chips and/or recycled wood fibers are coated with adhesive by introducing the recycled chips and/or recycled wood fibers into a pneumatic flow and injecting adhesive into this flow.

7. The process as in claim 6, wherein into said pneumatic flow also hardeners and/or additives are injected.

8. The process as in claim 6, wherein into said pneumatic flow also wax is injected.

9. The process as in claim 1, wherein the coated recycled chips and/or coated recycled wood fibers are conveyed in a turbulent air stream.

10. The process as in claim 3, wherein the coated recycled chips and/or coated recycled wood fibers and the coated new chips and/or coated new wood fibers, are conveyed in a turbulent air stream.

11. The process as in claim 9, wherein conveying in the turbulent air stream is followed by one or more separation units, for separating off water vapor and/or hot gasses and/or for heavy constituents.

12. The process as in claim 5, wherein the coated recycled chips and/or coated recycled wood fibers are mixed with the coated new chips and/or coated new wood fibers before, in or after a blowline which pneumatically conveys the coated new chips and/or coated new wood fibers to a dry production process of the particle board, MDF board or HDF board.

13. The process as in claim 1, wherein the production process is via a dry production process.

14. The process as in claim 3, wherein the proportion recycled chips and/or recycled wood fibers to the sum of the recycled chips and/or recycled wood fibers and the new chips and/or new wood fibers is less than 50 percent by weight, for example less than 20 percent by weight.

15. The process as in claim 1, wherein the step of wetting, heating and pressurizing the board material, comprises the step of wetting the board material using steam.

16. The process as in claim 1, wherein during the step of wetting, heating and pressurizing, the board material, the board material is heated to a temperature of less than 240 C.

17. The process as in claim 1, wherein during the step of wetting, heating and pressurizing, the board material, the board material is subjected to a pressure of between 3 and 30 bar for a time of at least 15 seconds.

18. A process for production of particle board, MDF board or HDF board, wherein the process comprises a step of recycling board material in which recycled chips and/or recycled wood fibers are produced, said board material comprising particle board material and/or MDF board material and/or HDF board material; and wherein the process comprises a step in which the board material is wetted, heated and pressurized; wherein the board material is kept under pressure and at an elevated temperate for a certain time; wherein the process comprises a step of steam explosion of the wetted, heated and pressurized board material, in which recycled chips and/or recycled wood fibers are produced during the steam explosion; wherein the recycled chips and/or recycled wood fibers are coated with a first adhesive; wherein new chips and/or new wood fibers are provided and coated with a second adhesive; wherein said first adhesive and second adhesive are a urea-formaldehyde adhesive, a melamine urea-formaldehyde adhesive, a phenol adhesive, or a MDI or pMDI adhesive, or a bio-adhesive; wherein the coated recycled chips and/or the coated recycled wood fibers and the coated new chips and the coated new wood fibers are supplied to a dry production process of the particle board, MDF board or HDF board.

19. The process as in claim 18, wherein said new chips and/or new wood fibers are coated with said second adhesive in a step which is separate from said coating the recycled chips and/or recycled wood fibers with said first adhesive.

20. The process as in claim 19, wherein the coated recycled chips and/or coated recycled wood fibers are mixed with the coated new chips and/or coated new wood fibers before, in or after a blowline which pneumatically conveys the coated new chips and/or coated new wood fibers to the dry production process of the particle board, MDF board or HDF board.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0073] In order to show the features of the invention in more detail, some preferred embodiments are described below by way of example and without being limited thereto, with reference to the accompanying drawings, in which:

[0074] FIG. 1 diagrammatically illustrates an example or a process according to the invention for the production of MDF or HDF boards; and

[0075] FIG. 2 illustrates an example of an MDF board produced by means of a process according to the invention.

DESCRIPTION OF EXAMPLES OF EMBODIMENTS

[0076] FIG. 1 diagrammatically illustrates an example of a process according to the invention for the production or MDF or HDF boards. This process comprises the step of recycling MDF and/or HDF board material in which recycled wood fibers are produced. The recycled wood fibers are fed into a dry production process for MDF board or HDF board as base material.

[0077] MDF and/or HDF board material (A) is introduced into the process and mechanically broken down in step S11, for example into pieces having an average size of less than 3 cubic centimeters. Preferably, dust is separated off in this step, or optionally after this step, for example by means of sieving or by means of another suitable technique.

[0078] In step S12, the broken material is wetted with steam S; optionally additives may be added in this case, but it may also be performed without additives.

[0079] In step S13, the material is then pressurized and heated; in this case, steam may be supplied, and then the steam explosion step is carried out, in which the material suddenly expands, with the pressure quickly, preferably in less than 0.5 seconds, dropping from, for example, 15 bar to 2.5 bar; or expands, preferably in 1 second or less, from 10 bar to 5 bar (with the material then, from a pressure of 5 bar being conveyed in a turbulent airflow in a blowline). This step S13 may, for example, be carried out partly or completely in a conveyor screw which conveys and compresses the material, in which case steamoptionally containing additives, but it may also not contain additivesis preferably injected into this screw. The steam explosion can then occur at the exit of the screw, where a specific opening or nozzle is provided for this purpose.

[0080] The recycled wood fibers produced in this way are then conveyed pneumatically in a turbulent flow (step S14) which may result in entangled recycled wood fibers being untangled. Optionally, the produced, recycled wood fibers may before or during this step be adhesive-coated by injecting adhesive in liquid form. To this end, the standard adhesives which are known for producing MDF or HDF boards may be used.

[0081] In parallel with the described production of recycled wood fibers, new wood fibers are produced from wood. Wood (B) is supplied. This wood (B) is supplied in the form of small pieces of wood and fed to the pre-heater and the boiler, which are denoted in FIG. 1 in combination by step S21. During pre-boiling, the small wooden pieces are heated to 80-95 C. by means of steam. In the boiler, the small wooden pieces are then brought to a temperature of, for example, 160 C. and a pressure of 8 bar by means of steam injection; the small wooden pieces remain at this temperature for three to five minutes, following which the small wooden pieces are added to the refiner. The refiner is a mechanical apparatus which consists of grinding discs with ridges into which the small wooden pieces are introduced. Due to the mechanical action of these grinding discs (step S22), the small pieces are refined to form wood fibers, so that wood fibers are obtained at the exit of the refiner which are conveyed further pneumatically in step S23. During this pneumatic conveying, the newly produced wood fibers may be coated with adhesive by injecting adhesive. It is also possible to coat the recycled wood fibers with adhesive together with the newly produced wood fibers.

[0082] In step S31, which is a pneumatic conveying step, the newly produced wood fibers are conveyed further, together with theoptionally adhesive-coatedrecycled wood fibers. In this case, the recycled wood fibers and the newly produced wood fibers become mixed. Preferably, the conveying step S31 comprises a hot, turbulent air stream which dries the conveyed material and also helps to untangle the entangled wood fibersboth the recycled wood fibers and newly produced wood fibers.

[0083] Preferablyalthough not shown in FIG. 1conveying in the turbulent air stream is followed by one or more separating units, for example for separating water vapor and hot gasesfor example by means of a cycloneand/or for separating off heavy constituentspreferably by means of the force of gravity.

[0084] In step S32, the actual production of the MDF or HDF board (C) takes place by means of fiber deposition and pressing the fiber mat at elevated temperature, during which the adhesive is cured.

[0085] The entire process as described proceeds in-line and continuous.

[0086] In the example described here, the composition will be uniform across the entire thickness of the produced MDF or HDF board with regard to the percentage of recycled fibers and the percentage of newly produced fibers. However, it is possible to use different supply channels, so that the board comprises layers which differ in composition regarding the combination of recycled wood fibers and newly produced wood fibers, or even comprises layers which do not comprise recycled wood fibers.

[0087] It should be noted that in the example illustrated in FIG. 1, no further mechanical refining of the recycled material occurs after the mechanical refining of the MDF or HDF board material in step S11 during the further process of producing and conveying the recycled wood fibers. However, this is possible, if desired, for example by passing the recycled material through a refiner after the steam explosion.

[0088] The example illustrated in FIG. 1 relates to a continuous process. However, it is also possible to carry out some or all of the steps in the production process discontinuouslyin batches. It is, for example, possible to carry out the step of the steam explosion in a discontinuous process, in which case the material is situated in a pressurized receptacle and the pressure is quickly released as a result of which the steam explosion takes place, the material being removed from the receptacle after the steam explosion.

[0089] FIG. 2 illustrates an example of an MDF board 100 produced using a process according to the invention. The resultant MDF board 100 is composed of three layers. More particularly, this MDF board is composed of a core layer 102. A surface layer 104, 106 is present on both sides of the core layer 102. The two surface layers 104, 106 do not comprises any recycled wood fibers, but only wood fibers produced from new and/or recycled wood. The core layer 102 comprises both wood fibers which have been produced from new and/or recycled wood and which have been coated with adhesive, as recycled wood fibers recovered from MDF and/or HDF board material. These recycled wood fibers may optionally have been coated with adhesive during the production process of the recycled fibers in the production process of the MDF board 100. It is possible for a decorative or functional layer to be applied to one or both surface layers, for example a printed paper layer soaked in melamine resin and pressed onto the MDF board.