EP-4549675-B1 - PROCESS FOR THE PRODUCTION OF PARTICLE BOARD OR WOOD FIBER BOARD

EP4549675B1EP 4549675 B1EP4549675 B1EP 4549675B1EP-4549675-B1

Inventors

ALLAERT, Laurens
COUDENYS, GEERT
HOFLACK, Veronique
GOEMINNE, Jan
NEL, Koen

Dates

Publication Date: 20260513
Application Date: 20210301

Claims (13)

Process for the production of particle board, MDF board or HDF board, wherein this process comprises the step of recycling particle board material, MDF and/or HDF board material in which recycled chips and/or recycled wood fibers are produced; and wherein the process comprises the step in which the particle board material, the MDF and/or HDF board material is wetted, heated - preferably using steam - and pressurized; wherein this material is kept under pressure and at an elevated temperature for a certain time; wherein the recycled chips and/or recycled wood fibers are coated with adhesive, preferably with urea-formaldehyde adhesive, with melamine urea-formaldehyde adhesive, phenol adhesive, or with MDI or pMDI adhesive, or with bioadhesive, or with adhesive compositions which comprise one or more of the adhesives mentioned; wherein this process comprises the step of supplying the adhesive-coated recycled chips and/or the adhesive-coated recycled wood fibers as base material in a production process - preferably in a dry production process - for particle board, MDF board or HDF board; wherein also new chips and/or new wood fibers are coated with adhesive in a step which is separate from the step of coating the recycled chips and/or recycled wood fibers with adhesive, to form new adhesive-coated chips and/or new adhesive-coated wood fibers which are used as base material in said production process; wherein the adhesive-coated recycled chips and/or the adhesive-coated recycled wood fibers are mixed with the new adhesive-coated chips and/or new adhesive-coated wood fibers.
Process as in claim 1, wherein the step of wetting, heating and pressurizing is preceded by the mechanical breaking down of the particle board material, the MDF and/or HDF board material, preferably into pieces having an average size according to numbers of less than 10 cubic centimeters, more preferably of less than 5 cubic centimeters, more preferably of less than 3 cubic centimeters, wherein preferably - dust is separated off after the mechanical breaking down, for example by means of sieving, by means of rinsing or by means of wind-sieving and/or - this mechanical breaking down takes place with the particle board material, the MDF and/or HDF board material in dry condition, wherein dry condition is understood to mean that no wetting step is carried out before this mechanical refining.
Process as in any of the preceding claims, wherein, during the wetting, heating and pressurizing step, the particle board material, the MDF and/or HDF board material is heated to a temperature of less than 240°C, preferably of less than 230°C; and preferably of more than 130°C, and more preferably of more than 150°C.
Process as in any of the preceding claims, wherein the particle board material, the MDF and/or HDF board material is subjected to a pressure of between 3 and 30 bar; preferably of more than 5 bar, more preferably of more than 7 bar, even more preferably of more than 15 bar; for a time of at least 15 seconds, preferably of at least one minute, preferably less than 5 minutes, more preferably less than 3 minutes and more preferably less than 1 minute, preferably at a temperature of less than 240°C, more preferably of less than 230°C; and preferably of more than 150°C.
Process as in any of the preceding claims, wherein the process comprises the step of steam explosion of the wetted, heated and pressurized particle board material, MDF and/or HDF board material, in which recycled chips and/or recycled wood fibers are produced during the steam explosion, wherein the steam explosion takes place in a continuous process or wherein the steam explosion takes place in a discontinuous process - for example by using a pressure vessel-.
Process as in claim 5, wherein the steam explosion step is performed in a discontinuous process, wherein the wetted, heated and pressurized particle board material, MDF and/or HDF board material is situated in a receptacle, and wherein a valve of the receptacle is opened, as a result of which the rapid pressure drop occurs which causes the steam explosion.
Process as in any of the preceding claims 5 - 6, wherein one or more of the following features are present: - the pressure drop during the steam explosion is at least 3 bar, and preferably is at least 4 bar, more preferably is at least 5 bar; and still more preferably is at least 7 bar, and preferably less than 12 bar and more preferably less than 10 bar, more preferably less than 8 bar, more preferably less than 7 bar; - during the steam explosion step, the pressure expands from a pressure of between 4 and 30 bar, preferably of more than 5 bar, more preferably of more than 10 bar, still more preferably of more than 15 bar; - during the steam explosion step, the pressure expands to under 3 bar; preferably wherein the pressure expands to under 2 bar, more preferably wherein the pressure expands to under 1.5 bar; - during the steam explosion step, the pressure expands in less than 3 seconds, preferably in less than 2 seconds, more preferably in less than 0.5 seconds; - during the steam explosion step, the ratio between the pressure drop during the steam explosion and the duration of the steam explosion is greater than 5 bar/second, preferably greater than 7 bar/second, more preferably greater than 10 bar/second, more preferably is greater than 15 bar/second, still more preferably is greater than 20 bar/second.
Process as in any of the preceding claims, wherein the material undergoes a mechanical dewatering process, for example by pressing - preferably between rollers - or by centrifuging; after the step in which the particle board material, the MDF and/or HDF board material has been wetted, heated - preferably using steam - and pressurized; wherein, if the process comprises the step of steam explosion of the wetted and pressurized particle board material, MDF and/or HDF board material, the mechanical dewatering process is performed after the steam explosion step.
Process as in any of the preceding claims 5 - 8, wherein the process comprises the step of mechanically refining recycled wood chips and/or the recycled wood fibers after the steam explosion, preferably by the recycled material being passed through a mechanically operating apparatus, more preferably in which the apparatus comprises grinding discs through which the material is passed.
Process as in any of the preceding claims, 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, preferably together with hardeners and preferably with additives, such as for example paraffin or wax.
Process as in any of the preceding claims, wherein the adhesive-coated recycled chips and/or adhesive-coated recycled wood fibers are conveyed in a - preferably hot - turbulent air stream, wherein optionally the conveying in the turbulent air stream is followed by one or more separation units, for example for separating off water vapor and hot gases - for example by means of a cyclone - and/or for separating off heavy constituents - preferably by means of the force of gravity.
Process as in any of the preceding claims, wherein the mixing of the adhesive-coated recycled chips and/or the adhesive-coated recycled wood fibers with the new adhesive-coated chips and/or new adhesive-coated wood fibers takes place before, in or after a blowline which pneumatically conveys the new adhesive-coated base material to the dry production of the particle board, MDF board or HDF board, and wherein preferably the proportion of adhesive-coated recycled chips and/or the adhesive-coated recycled wood fibers to the combined adhesive-coated recycled chips and/or the adhesive-coated recycled wood fibers and new adhesive-coated chips and/or new adhesive-coated wood fibers is less than 50 percent by weight.
Process as in any of the preceding claims, wherein the particle board material, the MDF and/or HDF board material which is recycled comprises or involves production waste which originates from a process for the production of particle board, MDF board or HDF board as described in any of the preceding claims; and/or wherein the particle board material, the MDF and/or HDF board material comprises or involves post-consumer material.

Description

Technical field The invention relates to a process for the production of particle board or wood fiber board in which wood chips or wood fibers recovered from recycled particle board, from recycled MDF (Medium Density Fiber board) - or from recycled HDF (High Density Fiber board) panels are, at least to some degree, used as base material. Prior art WO2011/077155A1 describes a method for recycling "engineered wood panels", such as wood fiber boards, in which wood fibers are recovered which may be used instead of new wood fibers. The boards or panels are mechanically broken down and mixed with water to form a slurry. This slurry is then heated by passing an electrical current through the slurry. This heating causes a reduction in the strength of the bonds between the wood fibers. This heating may take place at a superatmospheric pressure. After heating, it is possible to release the slurry quickly, for example by spraying it via a valve, drying it and separating the fibers from each other. An apparatus is described for carrying out the method as a continuous process. It is a drawback of this method that the adhesive from the boards dissolves in the bath in which the slurry is heated. This may lead to saturation of the bath, as a result of which the bonds are no longer detached, or the electrical conductivity of the slurry - necessary for heating via the Joule effect - may change. Additives which are necessary to adjust the conductivity may also cause problems. US2003/0056873A1 describes a process for producing wood fiber boards - via recycling of waste from composite wood products - by means of a conventional dry production process for producing wood fiber boards. The process employs a modified treatment in a pre-heater, followed by mechanical refining in a refiner, resulting in recycled fibers. These recycled fibers then constitute at least 20 percent by weight of the fiber boards produced. In the pre-heater, the recycled wood products are chemically treated under pressure and in the presence of steam. It is a drawback of this process that chemicals have to be added in the pre-heater. This may result in corrosion problems. These chemicals also lead to polluted waste streams which have to be treated in a suitable manner. DE4224629 describes a process for recycling panel-shaped elements made of wood products glued together by means of urea-formaldehyde binder and with or without a plastic coating. The process relates in particular to the recycling of wood fiber boards or particle boards. The panel-shaped elements are broken into fragments in a pretreatment step. These fragments are treated in water vapor atmosphere for a certain amount of time - preferably in a saturated water vapor atmosphere - under high pressure and high temperature. As a result thereof, the fragments are transformed into fibrous, chip-like or platelet-like base material which is glued to form new panel-shaped elements. To this end, the recycled fibrous, chip-like or platelet-like base material may be coated with adhesive. Alternatively, chemically modified adhesive may be used, more specifically the urea-formaldehyde glue residues which are still attached to the recycled fibrous, chip-like or platelet-like base material. US5,804,035 describes a process for recovering chips and fibers from waste of wood products, old furniture, production waste, wood products glued together with urea-formaldehyde binders or with other binders which may be hydrolyzed or chemically broken down. These materials are treated at high temperature. In a first step of the process, these materials are impregnated with an impregnating liquid, as a result of which these materials absorb at least 50% of their weight in impregnating liquid. In a second step, heating to between 80 and 120 °C is performed. The materials disintegrated in this way are then sorted by means of sieving or other techniques. WO2003/026859 - by the same applicants and inventors as US5,804,035 - describes a process similar to that in US5,804,035, but which is more economical. It is a drawback of these processes that a mixture or wood fibers and wood chips is obtained which does not make it possible to manufacture high-quality products, since the production of high-quality products requires base material with uniform properties. WO2005/007968A1 describes a method for recovering wood constituents from a board material consisting of a matrix of lignocellulose material bonded by glue. The method comprises treating the material with a combination of electromagnetic radiation and soaking or immersing it in a liquid medium, and recovering constituents. It is a drawback that special equipment is required to generate the electromagnetic radiation to heat up the material, and that it is more difficult to incorporate such a process in a continuous process. WO00/01877 describes a process and an apparatus for treating and recovering wood fiber board waste and particle board waste. Wood fiber board waste and part