WO2021025562A1 - Procédé de modification du bois et produits associés - Google Patents

Procédé de modification du bois et produits associés Download PDF

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Publication number
WO2021025562A1
WO2021025562A1 PCT/NZ2020/050082 NZ2020050082W WO2021025562A1 WO 2021025562 A1 WO2021025562 A1 WO 2021025562A1 NZ 2020050082 W NZ2020050082 W NZ 2020050082W WO 2021025562 A1 WO2021025562 A1 WO 2021025562A1
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WO
WIPO (PCT)
Prior art keywords
wood
bar
period
heating
temperature
Prior art date
Application number
PCT/NZ2020/050082
Other languages
English (en)
Inventor
Paul Geoffrey DUNCAN
Original Assignee
Rakauco Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rakauco Limited filed Critical Rakauco Limited
Priority to AU2020326292A priority Critical patent/AU2020326292A1/en
Publication of WO2021025562A1 publication Critical patent/WO2021025562A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/0207—Pretreatment of wood before impregnation
    • B27K3/0214—Drying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
    • B27K5/0085—Thermal treatments, i.e. involving chemical modification of wood at temperatures well over 100°C
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/0207—Pretreatment of wood before impregnation
    • B27K3/0221—Pore opening
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/0278—Processes; Apparatus involving an additional treatment during or after impregnation
    • B27K3/0292—Processes; Apparatus involving an additional treatment during or after impregnation for improving fixation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/08—Impregnating by pressure, e.g. vacuum impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/15—Impregnating involving polymerisation including use of polymer-containing impregnating agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/34—Organic impregnating agents
    • B27K3/38—Aromatic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
    • B27K5/02—Staining or dyeing wood; Bleaching wood
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
    • B27K5/04—Combined bleaching or impregnating and drying of wood
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
    • B27K5/06—Softening or hardening of wood
    • B27K5/065—Hardening
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L97/00—Compositions of lignin-containing materials
    • C08L97/02—Lignocellulosic material, e.g. wood, straw or bagasse
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K2240/00—Purpose of the treatment
    • B27K2240/30—Fireproofing

Definitions

  • the invention relates to methods for preparing modified wood and wood products, for example to fortify wood by increasing the strength and/or density of wood to yield a fortified wood product, for example to improve the performance, alter the appearance, and/or improve durability.
  • the method comprises a combination of resin and thermal treatments to yield a fortified wood product.
  • thermally modifying the wood is by thermally modifying the wood at high temperatures. During heat modification, organic compounds present in the wood are removed, and this is believed to render the wood less able to support fungal growth and/or less palatable or desirable to insects. Heat modification can also alter wood moisture, for example by imparting lower equilibrium moisture content, less moisture deformation, or improved weather resistance.
  • thermally modified wood is the reduction in strength observed in the final product, both in tensile strength or rigidity, and in surface hardness and resistance to surface deformation. This reduction in strength can limit the applications to which the heat-treated wood can be put, and likewise can reduce the useful service life of the heat-treated material.
  • the invention in a first aspect relates to a wood treatment process comprising: a) selecting and grading wood suitable for treating; b) subjecting the wood to a torrefaction process comprising subjecting the wood to temperatures of between about 200 °C to about 320 °C; c) mixing resins and optionally colour with water to make to make a resin- impregnating composition to achieve the desired performance and appearance attributes; d) subjecting the torrified wood to a reduced pressure in a pressure vessel; e) immersing the torrified wood in the resin-impregnating composition; f) subjecting the resin-impregnated torrefied wood to a drying process.
  • the invention in another aspect relates to a method of treating wood, the method comprising: a) providing wood suitable for treating; b) at least partially torrefying the wood by heating the wood at a temperature of from about 200 °C to about 320 °C; c) contacting the torrefied wood with an aqueous resin composition while the torrefied wood is maintained at a pressure below atmospheric pressure; d) drying the torrefied, resin-impregnated wood; to yield a treated wood or wood product.
  • Any of the embodiments described herein can relate to any of the aspects presented herein.
  • the invention relates to a method of treating wood, the method comprising: a) providing wood suitable for treating; b) heating the wood; c) providing an aqueous resin composition; d) maintaining the wood at reduced pressure; e) contacting the wood with the aqueous resin composition; f) drying the wood; to yield a treated wood or wood product.
  • the method of treating wood comprises: a) providing wood suitable for treating; b) heating the wood at a temperature effective to torrefy the wood; c) contacting the torrefied wood with an aqueous resin composition while the torrefied wood is maintained at a pressure below atmospheric pressure; d) heating the wood at a first heating temperature below the boiling point of water; to yield a treated wood or wood product.
  • the method of treating wood comprises: a) providing wood suitable for treating; b) heating the wood at a temperature effective to torrefy at least about 20% of the lignocellulose present in the wood; c) contacting the torrefied wood with an aqueous resin composition while the wood is maintained at a pressure below atmospheric pressure; d) heating the wood at a first heating temperature below the boiling point of water; to yield a treated wood or wood product.
  • the invention in another aspect relates to a method of treating wood, the method comprising: a) providing wood suitable for treating; b) heating the wood at a temperature and for a period effective to torrefy at least about 20% of the lignocellulose present in the wood; c) maintaining the torrefied wood for a first period at a pressure of from about 0.7 to about 1.0 bar; d) contacting the torrefied wood with an aqueous resin composition while the torrefied wood is at a pressure of from less than 1 bar to about 0.7 bar; e) maintaining the torrefied wood for a second period at a pressure of from more than 1 bar to about 15 bar; f) maintaining the torrefied wood for a third period at a pressure of from about 0.7 to about 1.0 bar; g) heating the wood at a temperature to dry the wood; to yield a treated wood or wood product.
  • the suitability of the wood is determined by grading and/or selecting wood, for example, shortly before or during step a).
  • the suitability of the wood is determined by reference to information associated with the wood, for example, an identification tag, marker, information sheet, colour, bar code, RFID, or the like.
  • the wood is contacted with the resin by immersion or by spraying.
  • the wood is maintained at a pressure below atmospheric pressure in a pressure vessel. In various embodiments, the wood is maintained, for example for the first period, for the second period, or for the third period, or any combination thereof, in a pressure vessel.
  • the pressure at which the wood is maintained in each of the specified periods will be the same, for example, for ease of process management or plant requirements. In other embodiments, the pressure at which the wood is maintained in one or more of the specified periods will be different, for example, to accommodate the different processes that take place in each of the different periods.
  • factors such as the species and cut of wood being processed, the nature of the resin being used, the desired finish and/or other final characteristics of the wood product desired will usually influence process parameters, including the pressure maintained during one or more of the specified periods.
  • the method comprises maintaining the wood for one or more periods at a pressure below atmospheric pressure, generally being a pressure of less than 1 bar, for example, at a pressure of less than 1 bar to about 0.1 bar. In certain embodiments, the method comprises maintaining the wood for one or more periods at a pressure of less than 1 bar to about 0.2 bar, or at a pressure of less than 1 bar to about 0.3 bar, or at a pressure of less than 1 bar to about 0.4 bar, for example, at a pressure of less than 1 bar to about 0.5 bar, at a pressure of less than 1 bar to about 0.6 bar, or more commonly at a pressure of less than about 1 bar to about 0.7 bar.
  • the wood is maintained at a pressure of from less than 1 bar to about 0.8 bar, or from less than about 1 bar to about 0.9 bar.
  • the method comprises maintaining the wood for a third period at a pressure of from about 0.7 to about 0.9 bar, for example, at a pressure of about 0.8 bar.
  • the wood is maintained under vacuum in a pressure vessel.
  • pressures below atmospheric pressure are conveniently achieved using a vessel which can be at least partially evacuated, for example, by vacuum.
  • the method comprises maintaining the wood for a first period at a pressure of from about 0.7 to about 0.9 bar, for example, at a pressure of about 0.8 bar In various embodiments, the method comprises maintaining the wood for a third period at a pressure of from about 0.7 to about 0.9 bar, for example, at a pressure of about 0.8 bar.
  • the wood is contacted with the aqueous resin for a period sufficient to allow saturation of the wood with the aqueous resin.
  • the wood is contacted with the aqueous resin for a period sufficient to ensure no further uptake of aqueous resin into the wood occurs, that is, total saturation.
  • the wood is contacted with the aqueous resin for a period of at least about 1 hour, at least about 2 hours, at least about 6 hours, at least about 12 hours, or more than about 12 hours.
  • the aqueous resin is a resin selected from the group consisting of phenolic resins, phenol-formaldehyde urea resins, novolac resins, and resole resins.
  • the aqueous resin is a phenoplast resin.
  • the phenoplast resin has a solids content of from about 1% w/w to about 50% w/w of the aqueous resin composition, for example, from about 5% w/w to about 50% w/w of the aqueous resin composition.
  • the aqueous resin comprises a colourant, such as a dye or a pigment.
  • the wood is maintained at a pressure below atmospheric pressure for a period of at least about 1 hour, at least about 2 hours, at least about 6 hours, at least about 12 hours, or more than about 12 hours.
  • the first period, the second period, the third period, or any two or more thereof is at least about 1 hour, at least about 2 hours, at least about 6 hours, at least about 12 hours, or more than about 12 hours.
  • the wood is pre-coloured prior to being subjected to a pressure other than atmospheric pressure, for example prior to being subjected to a pressure below atmospheric pressure, or prior to being introduced into a pressure vessel.
  • the wood is subjected to direct heating in contact with a surface heated at from about 70 °C to about 320 °C.
  • the wood is subjected to direct heating at a temperature sufficient to have the temperature at the centre of the wood to be from about 70 °C to about 320 °C.
  • the wood is heated, torrefied, and/or dried by heating in direct contact with a heated surface, for example, a platen drier or press, or a lineal drier, including a multistage lineal drier.
  • a heated surface for example, a platen drier or press, or a lineal drier, including a multistage lineal drier.
  • At least partially torrefying the wood comprises subjecting the wood to a temperature of from about 200 °C to about 320 °C.
  • at least partially torrefying the wood comprises heating the wood at a temperature of from about 200 °C to about 320 °C.
  • at least partially torrefying the wood comprises heating the wood to a temperature of from about 200 °C to about 320 °C.
  • heating the wood at a temperature effective to torrefy at least about 20% of the lignocellulose present in the wood comprises heating the wood at a temperature of from about 200 °C to about 320 °C.
  • heating the wood at a temperature effective to torrefy at least about 20% of the lignocellulose present in the wood comprises heating the wood to a temperature of from about 200 °C to about 320 °C.
  • the wood is dried at least until it has a moisture content of about 95% or less that of the moisture content of the wood prior to modification.
  • the wood is dried by heating at a temperature of from about 70 °C to about 320 °C.
  • heating the wood comprises a) maintaining the wood for a first heating period at a temperature below about 100 °C, for example, at a temperature of from about 70 °C to about 100 °C; b) maintaining the wood for a second heating period at a temperature above about 200 °C, for example from about 200 °C to about 320 °C.
  • heating the wood comprises a) maintaining the wood for a first heating period at a temperature of from about 70 °C to about 320 °C; b) maintaining the wood for a second heating period at a temperature of from about 200 °C to about 320 °C.
  • heating the wood comprises a) maintaining the wood for a first heating period at a temperature of from about 70 °C to about 100 °C; b) maintaining the wood for a second heating period at a temperature of from about 70 °C to about 320 °C; c) maintaining the wood for a third heating period at a temperature of from about 200 °C to about 320 °C.
  • heating the wood comprises a) maintaining the wood for a first heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 70 °C to about 100 °C; and b) maintaining the wood for a second heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 200 °C to about 320 °C.
  • the method of treating wood comprises: a) providing wood suitable for treating; b) heating the wood by c) maintaining the wood for a first heating period at a temperature of from about 70 °C to about 320 °C; d) maintaining the wood for a second heating period at a temperature of from about 200 °C to about 320 °C; e) maintaining the wood for a first period at a pressure of from less than 1 bar to about 0.7 bar; f) contacting the wood with an aqueous resin composition while the wood is at a pressure of from less than 1 bar to about 0.7 bar; g) maintaining the wood for a second period at a pressure of from more than 1 bar to about 15 bar; h) maintaining the wood for a third period at a pressure of from less than 1 bar to about 0.7 bar; and i) drying the wood.
  • heating the wood comprises a) maintaining the wood for a first heating period at a temperature of from about 70 °C to about 100 °C; b) maintaining the wood for a second heating period at a temperature of from about 100 °C to about 200 °C; c) maintaining the wood for a third heating period at a temperature of from about 200 °C to about 320 °C.
  • heating the wood comprises a) maintaining the wood for a first heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 70 °C to about 100 °C; b) maintaining the wood for a second heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 100 °C to about 200 °C; c) maintaining the wood for a third heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 200 °C to about 320 °C.
  • the wood is maintained at from about 200 °C to about 320 °C, or is maintained at a temperature sufficient to have the temperature at the centre of the wood to be from about 200 °C to about 320 °C, for a period sufficient to a) de-hydrolyse or degrade at least about 25% w/w of the lignocellulose present in the wood prior to contact with the aqueous resin composition; or b) degrade at least about 25% w/w of the cellulose present in the wood prior to contact with the aqueous resin composition; or c) degrade at least about 25% w/w of the hemicellulose present in the wood prior to contact with the aqueous resin composition; or d) degrade at least about 25% w/w of the lignin present in the wood prior to contact with the aqueous resin composition; or e) remove at least about 10% of the volatiles present in the wood prior to contact with the aqueous resin composition; or f) any combination of two or
  • heating the wood comprises subjecting the wood to a platen heating process, wherein the platen heating process comprises contacting at least one face of the wood with a heated surface, for example, the process comprises contacting two opposing faces of the wood with heated surfaces.
  • the platen heating process comprises applying pressure to the wood, for example, sufficient pressure to prevent the deformation of the wood during heating.
  • the platen heating process comprises a) maintaining the wood for a first heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 200 °C to about 320 °C.
  • the platen heating process comprises a) maintaining the wood for a first heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 70 °C to about 100 °C; b) maintaining the wood for a second heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 200 °C to about 320 °C.
  • the platen heating process comprises a) maintaining the wood for a first heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 70 °C to about 100 °C; b) maintaining the wood for a second heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 100 °C to about 150 °C; c) maintaining the wood for a third heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 200 °C to about 320 °C.
  • the platen heating process applies hot plates to opposing faces of the wood and pressure is applied, wherein the pressure required will vary depending upon the species being dried.
  • the wood is moved through opposing hot plates on a conveyor with the temperature of the plates increasing from the first, to second, then third value as the wood progresses along the conveyor.
  • the wood is continuously heated in contact with a contiguous platen surface.
  • the wood is moved along a continuous conveyor from one heating station to another heating station, wherein the wood is maintained at each station for the requisite period.
  • the one or more of the heating stations are not contiguous.
  • one or more of the heating stations may be held at its operational temperature, for example to improve efficiency, but is positioned so as not to contact the wood, thus to allow for different heating periods without moving the wood from the station. It will be appreciated that such an arrangement allows for the simultaneous processing of multiple batches of wood in a continuous process, for example on a continuous conveyor, at different temperatures and for different heating periods, when required.
  • the method of treating wood comprises: a) providing wood suitable for treating; b) heating the wood by contacting the wood for a first heating period with a set of opposing plates at a temperature of from about 200 °C to about 320 °C; c) maintaining the wood for a first period at a pressure of from less than 1 bar to about 0.7 bar; d) contacting the wood with an aqueous resin composition while the wood is at a pressure of from less than 1 bar to about 0.7 bar; e) maintaining the wood for a second period at a pressure of from more than 1 bar to about 15 bar; f) maintaining the wood for a third period at a pressure of from less than 1 bar to about 0.7 bar; and g) drying the wood.
  • the method of treating wood comprises: a) providing wood suitable for treating; b) heating the wood by c) contacting the wood for a first heating period with a set of opposing plates at a temperature of from about 70 °C to about 100 °C; d) contacting the wood for a third heating period with a set of opposing plates at a temperature of from about 200 °C to about 320 °C; e) maintaining the wood for a first period at a pressure of from less than 1 bar to about 0.7 bar; f) contacting the wood with an aqueous resin composition while the wood is at a pressure of from less than 1 bar to about 0.7 bar; g) maintaining the wood for a second period at a pressure of from more than 1 bar to about 15 bar; h) maintaining the wood for a third period at a pressure of from less than 1 bar to about 0.7 bar; and i) drying the wood.
  • the method of treating wood comprises: a) providing wood suitable for treating; b) heating the wood by c) contacting the wood for a first heating period with a set of opposing plates at a temperature of from about 70 °C to about 100 °C; d) contacting the wood for a second heating period with a set of opposing plates at a temperature of from about 100 °C to about 200 °C; e) contacting the wood for a third heating period with a set of opposing plates at a temperature of from about 200 °C to about 320 °C.
  • the wood is contacted with a first set of opposing plates, for example, the wood is contacted with a first set of opposing plates configured to apply pressure to opposing faces of the wood.
  • the wood is contacted with a second set of opposing plates, for example, the wood is contacted with a second set of opposing plates configured to apply pressure to opposing faces of the wood.
  • the wood is contacted with a third set of opposing plates, for example, the wood is contacted with a third set of opposing plates configured to apply pressure to opposing faces of the wood.
  • Another aspect of the present invention relates to a modified wood product produced by a method as described herein.
  • the present invention relates to a modified wood or wood product comprising a resin, wherein the modified wood or wood product a) comprises at least about 5% w/w of one or more by-products of pyrolysis or torrefaction, or b) comprises at least about 10% w/w lignocellulose, wherein at least about 25% w/w of the lignocellulose is de-hydrolysed; or c) comprises at least about 10% w/w lignocellulose, wherein at least about 25% of the cellulose present in the wood prior to modification is degraded; or d) comprises at least about 10% w/w lignocellulose, wherein at least about 25% of the hemicellulose present in the wood prior to modification is degraded; or e) comprises at least about 10% w/w lignocellulose, wherein at least about 25% of the lignin present in the wood prior to modification is degraded; or f) has a volatiles content of at least about 10% w/w of one or more
  • the modified wood or wood product comprises lignocellulose, wherein at least about 30% of the hemicellulose present in the wood prior to modification is degraded. For example, at least about 35% of the hemicellulose present in the wood prior to modification is degraded, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99% of the hemicellulose present in the wood prior to modification is degraded. In one embodiment, substantially all of the hemicellulose present in the wood prior to modification is degraded.
  • the modified wood such as the modified wood comprising a wood product has one or more of the following: a) increased density; b) decreased moisture by at least about 6%; c) increased tensile strength; d) increased hardness; e) increased weather resistance; f) managed colour; g) increased durability; h) improved fire resistance; i) any combination of two or more of any of a) to h) above.
  • the term “about” represents an amount close to and including the stated amount that still performs a desired function or achieves a desired result, e.g. "about 9%” can include 9% and amounts close to 9% that still perform a desired function or achieve a desired result.
  • the term “about” can refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, or within less than 0.01% of the stated amount. It is also intended that where the term “about” is used, for example with reference to a figure, concentration, amount, integer or value, the exact figure, concentration, amount, integer or value is also specifically contemplated.
  • Figure 1 depicts a representative example of a plant suitable for processing wood and wood products in accordance with the methods described herein.
  • the present invention relates to a method of treating wood by torrefaction and resin impregnation, where the treatment improves one or more characteristics of the wood.
  • the treated wood in certain embodiments has improved durability, increased density, better performance, more durable colour, and the like, as a result of the treatment method.
  • the method seeks to improve the wood, for example, to improve the durability of the wood structure, by fortifying wood that has been subjected to torrefaction.
  • the method involves subjecting an at least partially torrefied wood to resin-impregnation, followed by drying/curing.
  • the wood is subjected to a heating process that includes heating at temperatures above 200 °C, to remove water and torrefy the wood fibre, followed by resin impregnation and curing, to produce a modified wood product having desired functional and/or aesthetic performance.
  • the method described herein includes processing at temperatures between about 200 °C to about 320 °C to improve the durability of the wood fibre via torrefaction, and curing (for example, cross linking) an aqueous resin impregnated into the wood, which is selected to provide one or more advantageous or desired characteristic to the final product, such as, variously, added weight and/or density, increased strength, increased hardness, improved stability, improved resistance to fire, and/or improved colour management or durability.
  • the invention generally relates to a method of treating wood, the method comprising: a) providing wood suitable for treating; b) heating the wood to at least partially torrefy the wood; c) contacting the at least partially torrefied wood with an aqueous resin composition while the wood is maintained at a pressure below atmospheric pressure; d) drying the wood; to yield a treated wood or wood product.
  • the heating process will typically employ heating the wood for a given period at each of two or more temperatures.
  • the first heating period with a value below 100 °C seeks to begin the gentle movement of water from the wood without over stressing the wood fibres.
  • a further heating period is employed in certain embodiments to accelerate this process.
  • the heating process will typically comprise a further heating period in which the wood is heated for a period at a temperature above 200 °C, once excess water has been removed from the wood, so as to torrefy the wood.
  • torrefy refers to the process of subjecting a material, in the present instance wood, particularly at least partially dried wood, to heat, typically in the range of 200 °C to about 320 °C.
  • the related terms “torrefaction”, “torrefication”, and “torrefied” will be similarly understood.
  • torrefaction of wood and other lignocellulosics results in the removal of water and various volatile compounds, and the at least partial degradation of cellulose, hemicellulose, and/or lignin in the wood or lignocellulosic material.
  • torrefaction of wood carried out at temperatures at or above about 300 °C is effective to degrade the majority of hemicellulose present in the wood, and in certain embodiments is effective to degrade more than 90% of the hemicellulose initially present in the wood.
  • Methods to determine the degree of torrefaction include methods involving acid hydrolysis followed by analysis of glucan, mannan, and galactan by, for example, high performance liquid chromatography.
  • Related methods, for example to measure remaining lignin include the well-known Klason lignin/acid-soluble lignin test.
  • TMT thermally modified timber
  • kilns including high temperature kilns suitable for creating thermally modified timber (TMT), particularly those kilns relying on RAM air in a reduced air or reduced oxygen environment, or RAM air kilns with pressure, or by direct heat using a platen drier, such as a lineal multistage drier, to achieve the temperatures required to achieve torrefaction and resin cure.
  • TMT thermally modified timber
  • the heating is performed in a stationary pyrolysis plant, for example a stationary pyrolysis plant able to operate in a closed cycle, such as a plant that provides for substantially complete combustion of pyrolysis gases in the plant.
  • a stationary pyrolysis plant able to operate in a closed cycle, such as a plant that provides for substantially complete combustion of pyrolysis gases in the plant.
  • the drying, torreation and curing processes in the plant are aligned.
  • the vapour, steam and/or gases formed in the treatment method are completely collected in one or more volatiles collectors, and may, for example, be discharged into the heating chamber and burnt. As a consequence, the emission of exhaust volatiles is minimised.
  • thermocouples or other temperature sensors to provide temperature measurement and temperature control
  • moisture probes and sensors to monitor moisture content, for example within the wood prior to or undergoing treatment, or the moisture of waste gases or volatiles, which can for example transmit data to a central processor, a display, a control panel, or the like.
  • thermocouples and/or moisture sensors are located at the inlet and outlet of the heating chamber, or for example in the flue to measure the exhaust or input gases from/to the heating and/or drying chambers.
  • wood is first stacked with spacing sticks between each board to allow airflow in the kiln.
  • the stacks of wood are then loaded into the pyrolysis kiln which is set to measure EMC using wood wafers and probes fixed into the wet timber to monitor moisture content. Probes and sensors are connected back to the kiln control unit that operates to a predetermined schedule to condition the timber to the required final moisture content.
  • kiln processes involve the evolution of volatiles, such that in certain embodiments the vapor-gas mixture formed during heating is collected in a volatiles collector and passed back into the kiln from the volatiles collector through a volatiles discharge conduit, where it can be burnt, reducing energy expenditure and emissions.
  • the wood is dried in a press drier.
  • a platen drier is used to heat the wood and/or cure the resin, or both.
  • FIG. 1 One representative embodiment of a plant comprising a platen drier and suitable for use in a method as described herein in shown in Figure 1.
  • the modified wood processing plant 1 enables incoming wood feedstock 10 to be stored in a feedstock storage 20 if necessary prior to entry into the modification process.
  • the feedstock storage 20 is suitable for wood grading and/or selection/rejection, for example, under the control of a process control station 25, if needed.
  • Wood to be treated is introduced into a kiln or platen heater 30 to be at least partially torrefied.
  • the at least partially torrefied wood is then introduced into a pressure vessel 40.
  • Resin is also introduced into the pressure vessel 40, either directly from one or more holding tanks 50, or from a mixing tank 60 in which a concentrated resin is diluted to the desired solids content or concentration using water from a water tank 70.
  • the pressure vessel is held at the required pressures as described herein, whereupon the resin-impregnated wood is introduced via a covenyor 80 to a platen drying stage 90 for conditioning, drying, and curing.
  • the cured modified wood is then transferred via a conveyor 100 to a machining stage 110 for finishing. Finished modified wood 120 is then ready for storage and/or distribution.
  • Platen heaters and driers suitable for use in the methods described herein are known in the art, and in certain embodiments include a platen drier used to make panel products and sheet material, such as equipment made by Siempelkamp GmbH 8i Co or Dieffenbacher GmbH & Co. It will be appreciated that a platen drier capable of achieveing one or more of the temperatures employed in the methods described herein is contemplated. However, in certain embodiments, a platen drier is employed for one or more lower temperature steps, for example, the first and/or second heating periods, and one or more of the higher temperature steps, such as the third heating period, employs different equipment, such as a kiln.
  • the platen heating process comprises a) maintaining the wood for a first heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 70 °C to about 100 °C; b) maintaining the wood for a second heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 100 °C to about 150 °C; c) maintaining the wood for a third heating period at a temperature sufficient to have the temperature at the centre of the wood to be from about 200 °C to about 320 °C.
  • the methods described herein have minimal environmental impact, in that they provide for substantially complete combustion of the mixture of volatiles evolved from the resin-impregnated wood during heating, torrefaction, and curing, or in that they provide for ready containment of the drying/torrefaction/curing process within, for example, a continuous or multistage platen drier, thereby enabling the ready control of emissions.
  • woods for treating will generally not have any corewood, as this often will not accept aqueous compounds.
  • woods for treating will generally not have any corewood, as this often will not accept aqueous compounds.
  • the wood is without knots or other imperfections.
  • Species that are suitable include, but are not limited to: Albizzia Balsa Iroko (chlorophora excelsa), Jelutong (dyera costulata), Merbau (intsia palembacia), Tawa (beilschmiedia tawa), Radiata Pine (pinus radiata), European Beech (gagus syivatica), Cotton Wood (populus deltoids), Aspen (populus tremuloides), Rubber Wood (hevea brasiliensis), Birch (betula alleghaniensis), Baltic Pine (pinus sylvestris), Ponderosa Pine (pinus ponderosa), Hoop Pine (araucaria cunninghamii), Caribbean Pine (pinus caribaea), Loblolly Pine (pinus taeda), Southern Yellow Pine (pinus rigida), Hemlock (tsuga canadensis), Western Juniper (juniperus occidentalis), Popl
  • one or more resins is selected so as to provide one or more advantageous characteristic in the final product, such as one or more of increased density, increased strength, increased durability, increased fire resistance, desired colour, or improved processibility.
  • the one or more characteristics is increased or improved with respect to the comparable characteristic in the starting wood material prior to processing.
  • the resin is selected from the group comprising phenoplasts, polymeric diisocyanates, melamine resins, resorcinol resins, polyvinyl acetate resins, and hybrid thermoset compounds.
  • the aqueous resin is a phenoplast resin.
  • the aqueous resin is a phenoplast resin selected from the group consisting of phenolic resins, phenol-formaldehyde urea resins, novolac resins, and resole resins.
  • the resin is an aqueous phenoplast resin.
  • the aqueous phenoplast resin has a solids content of from about 1% w/w to about 50% w/w of the resin composition, for example, from about 5% w/w to about 50% w/w of the resin composition, from about 10% w/w to about 50% w/w, from about 15% w/w to about 50% w/w, from about 20% w/w to about 50% w/w, from about 25% w/w to about 50% w/w, from about 30% w/w to about 50% w/w, from about 35% w/w to about 50% w/w, from about 40% w/w to about 50% w/w, or from about 45% w/w to about 50% w/w of the resin composition.
  • resins suitable for use herein include phenoplast resins from Hexion (OH, USA), AICA, Huntsman, or ICA (Italy).
  • the aqueous resin composition comprises an additive selected from the group comprising one or more colourants, pigments, fire retardants, or other additives the presence of which provides one or more desired characteristics in the modified wood product.
  • additives suitable for use herein are those able to retain useful functionality under the processing conditions employed herein.
  • the one or more additives are able to retain useful functionality at the pH of the aqueous resin, and are able to retain useful functionality at the temperatures at which the wood product is maintained during the methods described herein.
  • Particularly contemplated are colourant and pigments capable of withstanding the alkalinity of the aqueous resin composition and the heat treatement process, without losing the colour contributing characteristics for which it has been selected, including the durability of colour in the final product, particularly when that product is exposed to exterior environmental conditions.
  • modified wood products suitable for a range of applications can be prepared using the methods described herein.
  • the final application to which the wood is to be put will typically influence the species and cut of wood, the aqueous resin chosen, the presence of any additives, and/or the specific parameters employed during the different steps of the method.
  • the wood processed by the methods described herein is particularly robust, and well- suited to outdoor/exposed use.
  • the modified wood is turned into a variety of outdoor products such as garden decking, but also products which have hitherto been formed from expensive wood, e.g. decking material for pleasure boats, decorative interior cladding and durable exterior cladding.
  • Example 1 Processing method using a kiln
  • This example describes the preparation of a modified wood product via a processing method as contemplated herein.
  • a batch of sapwood boards of dried sawn solid pine wood is graded and selected wood is transferred to a kiln and heated for a period of 1 hour at 90 °C, then the temperature of the kiln is raised to 120 °C and held for 1 hour, and finally the temperature of the kiln is raised to 320 °C and held for 2 hours to effect torrefaction.
  • the torrefied wood is then placed in a pressure vessel and the vessel evacuated to about 0.8 bar vacuum.
  • aqueous phenolic resole resin composition comprising pigment is then introduced into the evacuated vessel.
  • the vessel is then pressurised to about 15 bar for about 1 hour so as to impregnate all the boards through to the centre board.
  • the vessel is then evacuated briefly to about 0.8 bar, whereupon the wood is removed from the vessel.
  • the impregnated boards are then transferred to a platen drier for drying and resin cure.
  • the process reduces the final moisture content of the wood to between 6% - 16%, resulting in a modified wood product with improved hardness and strength.
  • the phenolic resole resin has fire retardancy properties
  • the fully cured modified wood will have improved resistance to fire compared with untreated wood.
  • Example 2 Processing method using multi-stage platen drier
  • This example describes the preparation of a modified wood product via a processing method as contemplated herein.
  • a batch of sapwood boards of dried sawn solid beech wood is transferred to a discontinuous platen system comprising three platen stations, each station comprising a pair of opposing heated plates.
  • the wood is conveyed to a first platen station heated at 85 °C and is held for 2 hours.
  • the wood is then conveyed to a second platen station having a temperature of 140 °C and is maintained 1 hour.
  • the wood is conveyed to a third platen station having a temperature of 300 °C and is held for 2 hours to effect torrefaction.
  • the torrefied wood is then placed in a pressure vessel and the vessel evacuated to about 0.9 bar vacuuum.
  • aqueous phenolic resole resin composition comprising dye is then introduced into the evacuated vessel.
  • the vessel is then pressurised to about 12 bar for 2 hours so as to impregnate all the boards through to the centre board.
  • the vessel is then evacuated briefly to about 0.8 bar, whereupon the wood is removed from the vessel.
  • the impregnated boards are then transferred to a platen dryer to dry the wood and cure the resin.
  • the process reduces the final moisture content of the wood to between 6% - 16%, resulting in a modified wood product with improved hardness and strength.
  • the phenolic resole resin has fire retardancy properties
  • the fully cured modified wood will have improved resistance to fire compared with untreated wood.
  • the boards are pressed by hot plates during torrefaction, and then drying and resin cure, the boards do not deform during processing, providing a dimensionally stable product amenable to downstream processing, or direct use.
  • Example 3 Processing method using TMT kiln and drier
  • This example describes the preparation of a modified wood product via a processing method as contemplated herein.
  • a batch of sapwood boards of dried sawn solid beech wood is transferred to a TMT kiln and heated for a period of 1 hour at 90 °C, then the temperature of the kiln is raised to 120 °C and held for 1 hour, and finally the temperature of the kiln is raised to 320 °C and held for 2 hours to effect torrefaction.
  • the torrefied wood is then placed in a pressure vessel and the vessel evacuated to about 0.9 bar vacuuum.
  • An aqueous thermoset resin composition comprising pigment is then introduced into the evacuated vessel.
  • the vessel is then pressurised to about 15 bar for 2 hours so as to impregnate all the boards through to the centre board.
  • the vessel is then evacuated briefly to about 0.8 bar, whereupon the wood is removed from the vessel.
  • the impregnated boards are then stacked using spacing sticks and transferred to a kiln dryer to dry the wood and cure the resin.
  • the process reduces the final moisture content of the wood to between 6% - 16%, resulting in a modified wood product with improved hardness and strength.
  • the thermoset resin has fire retardancy properties
  • the fully cured modified wood will have improved resistance to fire compared with untreated wood, while the pigment enables desired colour and colour stability over time to be achieved.
  • Example 4 Processing method using TMT kiln and platen drier
  • This example describes the preparation of a modified wood product via a processing method as contemplated herein.
  • a batch of sapwood boards of dried sawn solid beech wood is transferred to a TMT kiln and heated for a period of 1 hour at 90 °C, then the temperature of the kiln is raised to 120 °C and held for 1 hour, and finally the temperature of the kiln is raised to 320 °C and held for 2 hours to effect torrefaction.
  • the torrefied wood is then placed in a pressure vessel and the vessel evacuated to about 0.9 bar vacuuum.
  • thermoset resin composition comprising dye is then introduced into the evacuated vessel.
  • the vessel is then pressurised to about 15 bar for 2 hours so as to impregnate all the boards through to the centre board.
  • the vessel is then evacuated briefly to about 0.8 bar, whereupon the wood is removed from the vessel.
  • the impregnated boards are then transferred to a platen dryer to dry the wood and cure the resin.
  • the process reduces the final moisture content of the wood to between 6% - 16%, resulting in a modified wood product with improved hardness and strength.
  • the thermoset resin has fire retardancy properties
  • the fully cured modified wood will have improved resistance to fire compared with untreated wood.
  • the boards are pressed by hot plates during drying and resin cure, the boards do not deform during processing, providing a dimensionally stable product amenable to downstream processing, or direct use.
  • the invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

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Abstract

L'invention concerne des procédés de préparation de bois modifié et de produits de bois, y compris des procédés pour fortifier du bois par augmentation de la résistance et/ou de la densité de bois de façon à obtenir du bois fortifié ou un produit de bois. Les procédés peuvent être utilisés, par exemple, pour améliorer les performances, modifier l'aspect et/ou améliorer la durabilité du bois, et en particulier, du bois massif. Les procédés comprennent une combinaison de traitements thermiques et de résine pour produire du bois modifié et des produits de bois modifiés.
PCT/NZ2020/050082 2019-08-08 2020-08-04 Procédé de modification du bois et produits associés WO2021025562A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2641712A1 (fr) * 2012-03-20 2013-09-25 Timura Holzmanufaktur GmbH Procédé de traitement du bois et dispositif d'exécution du procédé
US20130298814A1 (en) * 2010-11-10 2013-11-14 Holger Militz Method for Treating Wood and Wood-Based Materials, and Wood and Wood-Based Materials Obtainable Therewith

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130298814A1 (en) * 2010-11-10 2013-11-14 Holger Militz Method for Treating Wood and Wood-Based Materials, and Wood and Wood-Based Materials Obtainable Therewith
EP2641712A1 (fr) * 2012-03-20 2013-09-25 Timura Holzmanufaktur GmbH Procédé de traitement du bois et dispositif d'exécution du procédé

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
BEHR ET AL.: "Improvement of mechanical properties of thermally modified hardwood through melamine treatment", WOOD MATERIAL SCIENCE AND ENGINEERING, vol. 13, 2018, pages 1 - 9 *

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