AU2022241578A1

AU2022241578A1 - Improved fibreboard product

Info

Publication number: AU2022241578A1
Application number: AU2022241578A
Authority: AU
Inventors: Steven CHIUTA; Marcus Cameron Wong
Original assignee: Laminex Group Pty Ltd
Current assignee: Laminex Group Pty Ltd
Priority date: 2021-12-07
Filing date: 2022-09-30
Publication date: 2023-06-22

Abstract

A process for manufacturing a fibreboard product and a fibreboard product produced by the process, the process including chipping virgin bamboo culm to a size of less than 120mm, drying the bamboo chips; softening the chips and 5 refining to separate the softened chips into a fibrous consistency; spraying with a resin and optionally wax and crosslinking; drying and optionally mixing with wood and pressing to form a fibreboard product. 1/3 Figures Figure 1 Internal Bonding (IB) 1.4 12 10 -z smminex 0. -- -- - - - ---- - - -- 0.- AASNZS STJ 02 0.0 00 00 00 0 p' ,2$

Description

1/3

Figures

Figure 1

Internal Bonding (IB)

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Title of Invention

Improved Fibreboard Product

Technical Field

[0001] The present invention relates to a fibreboard product, preferably a medium density fibreboard (MDF), high density fibreboard (HDF) or low-density fibreboard (LDF). In particular, the present invention resides in a flat engineered wood panel produced from fibres of virgin bamboo culms, or a mix of wood and virgin bamboo culm fibres. These fibres are bound together with a thermoset or thermoplastic resin, optionally with other additives such as a wax. The fibreboard product of the invention may be used in building applications such as wall panels, as well as for interior applications such as furniture, mouldings, and cabinetry fit outs.

[0002] Often MDF, HDF and LDF may act as a substrate to which a decorative coating such as a low-pressure melamine (LPM), high pressure laminate (HPL), plastic film (for example PVC or polypropylene), metallic foil (for example copper or aluminium), EBC treated paper, a thermoformable PVC to a routed surface, acrylic, paint, veneer, or other coating may be applied. The MDF, HDF or LDF of the invention is durable, with high bending strength, as well as resistance to moisture, having high dimensional stability (low swelling), and minimal reduction in mechanical properties when exposed to water. The fibreboard of the invention is engineered to pass Australian and New Zealand (AS/NZS) standards, as well as global standards such as JIS, ANSI, EN and ISO. MDF in particular is relatively lightweight, often with lower density than most solid woods and may also be manufactured to customer thicknesses (3-35mm) and densities, allowing for easy fabrication, transportation, and incorporation in its desired end use.

[0003] Whereas this invention does relate fibreboards products and to each of MDF, HDF and LDF, it would be convenient herein to refer to its use for MDF as many advantages are most evident for MDF. MDF does have the advantage of being a lower cost option per cubic metre than other wood panels. This is because traditionally the wood chip used in production has been pine (softwood) sourced from sawmill offcuts, as well as lower value and undersized pulp log thinnings from plantations, leading to a lower cost of raw materials. However, the cost of wood chip has been rising due to increased volumes of export to overseas countries, minimal investment in new plantation land, and supply chain challenges within operating regions. Through the incorporation of bamboo into the production of a fibreboard, the Applicants have been able to find a new supply of raw material to ensure continuing supply at reasonable cost together with enhanced or modified properties.

[0004] Further, the Applicants have found that the use of bamboo culm may lead to increased capacity for carbon sequestration of atmospheric C02. The higher carbon sequestration capabilities of bamboo relative to pine, as well as reduced transportation distance due to establishment of more efficient supply chains, may lead to reduced C02 emissions. Additionally, bamboo is known to have improved yields of fibre per hectare of land relative to wood, due to its dense clumping nature of growth of its culms. This will lead to reduced land usage and further reduce the environmental impact.

Background of Invention

[0005] The manufacture of fibreboard products such as MDF, HDF and LDF together with particleboard and other engineered products is largely based on wood species, such as pine, beech, eucalyptus, and willow. In recent times, the forest and forest products industry in Australia has been facing the challenge of the rising cost of wood chip, due to a number of reasons including reduced availability and an increased volume of export to overseas jurisdictions, while there is minimal investment in new plantation land. The supply chain for engineered wood products cannot be guaranteed.

[0006] Some MDF manufacturers, predominantly in China where bamboo is naturally abundant, have explored using bamboo in MDF products. However, the vast majority utilize waste bamboo shavings, offcuts, planar waste or residues, which is derived from post-industrial engineering practices, such as creating laminated or strand-woven bamboo timber. The use of fresh/virgin bamboo that is grown and harvested for the express purpose of making MDF using reconstituted culms has not been utilised or explored to a significant degree. Moreover, due to the high presence of insects and fungi, along with high contaminants such as silica or dirt, these bamboo materials often undergo chemical or heat treatment prior to chipping. Therefore, the use of unprocessed, virgin bamboo culm is a different form of raw material for MDF production. Moreover, most works teach methods that may utilize 100% waste product bamboo or recovered bamboo as their form of cellulosic material and few mix bamboo with wood.

[0007] Chinese patent CN103586958B assigned to Dare Wood Based Panel Ltd. discloses a method of producing wood/bamboo composite. This patent utilizes a narrow optimal range of a ratio of wood to bamboo in the order of 3.5:1 to 4:1, which is around 20-28% of bamboo, which compares a typical range of bamboo in the present application of from 50-70%, and optionally up to 100% bamboo.

[0008] This Chinese patent also teaches a method of defibrating bamboo chip as well as claiming a very narrow composition of resin, that is a 12-12.5% resin loading of a formaldehyde-based resin, as well as an ammonium chloride hardener added at 20% based on solids content of the resin. Wax is also included at a loading proportional to the operation rate of the process. The Examples in this Chinese patent teach of a starting chip size of 5-75mm. The Examples also show the MDF product can achieve high bending properties, with internal bond, surface soundness, and bending strength. The process described in the Chinese patent utilizes virgin bamboo culm, and not offcuts or shavings from post industrial waste. The MDF method taught by this Chinese patent yields very high-density MDF boards 770 - 860 kg/m3 .

[0009] However, the process conditions described in the Chinese patent use a narrow digester pressure range of 7.3 to 7.7 bar, for 1-2min, whereas the present application utilises a higher steam pressure of 8-8.5 bar for 30 seconds to 2 minutes. The higher steam pressure applied allows for a finer and more regular consistency of fibre to be produced, leading to a higher quality fibre. Low quality fibre contains uneven sizes, large strands, and fibre bundles (shives) which forms a surface that expands unevenly when exposed to moisture, leading to surface defects and damaged boards. Notably, the Chinese patent makes no reference to surface finishes or coatings.

[0010] The MDF boards produced by the process of the Chinese Patent are not moisture resistant, as evidenced by the very high 24h thickness swelling values of 18 22%. These would fail Australian and New Zealand standards for MDF for all thicknesses greater than 8mm, which require less than 15% swelling. This is a critical feature particularly in humid environments.

[0011] In Australia and New Zealand however, there has been very little if any use of bamboo in the manufacture of MDF products and pine is generally relied upon. The use of pine for the manufacture of MDF suffers from an environmental perspective as it has become evident that the carbon sequestration capabilities of pine is relatively low. Further, the yield period of pulp logs in a traditional pine plantation tends to be around 12 to 15 years for trees to mature or longer, which can lead to a reduced yield based on tonnes per hectare per year compared to that of faster growing plantation species.

[0012] Bamboo is a material that does have far higher carbon sequestration capabilities due to its fast growth rate. Whereas it has been used in the manufacture of MDF and other wood-based products, it has presented manufacturing difficulties as species that have generally been used for solid timber (engineered bamboo) products such as Bambusa balcooa or Dendrocalamus asper have high levels of silica of between 2-3%. This creates manufacturing and/or fabrication problems due to increased tool wear when cutting and sanding.

[0013] Furthermore, bamboo may be particularly stringy and often forms into long strands when cut. The use of such material can lead to entanglement, bridging and blocking during manufacturing processes as the particles are unable to flow freely.

[0014] Fibreboard products for example that have been manufactured with a bamboo content generally have a density in the order of greater than 750 kg/m 3 .

Thus, with a higher density, they require substantially longer than standard pressing cycles of greater than 6 minutes and up to 10 minutes. The focus in the manufacturing process for such prior art products has been on the final fibre size and the higher silica bamboo species, which subsequently tends to lead to a higher density final product.

[0015] It is a desired feature of the present invention to overcome or at least alleviate one or more of the difficulties associated with processes that rely on the use of softwoods such as pine for the manufacture of fibreboard products. This includes the difficulties with processes and products that rely solely on the use of bamboo or a mix of wood and bamboo particles in the manufacture of fibreboard products.

[0016] It is a further desired feature of the present invention to provide a standard, moisture-resistant, termite resistant or flame-retardant fibreboard product that is less reliant upon the use of softwoods such as pine in the manufacture.

[0017] It is a further desired feature of the present invention to provide a fibreboard product that incorporates virgin bamboo culm with or without wood particles so as to improve the carbon sequestration capabilities of the plantation source for the manufacturing of a fibreboard product of the invention.

[0018] It is a further desired feature of the present application to rely upon a lignocellulosic material that is able to be harvested within a relatively short period of time compared to woody species.

[0019] It is a further desired feature of the present invention to rely upon a lignocellulosic material that is high clumping so as to improve yields per hectare of land and increase carbon sequestration capabilities.

[0020] It is a further desired feature to provide a fibreboard product that is of a smooth surface, with fine and regular fibre size, to enable easy coatings with laminates, foils, paints and other materials.

[0021] The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

[0022] Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.

Summary of the Invention

[0023] The present invention relates to a fibreboard product comprising bamboo as the sole lignocellulosic material or a combination of wood and bamboo chips together with a process for manufacturing such a fibreboard product. In a preferred embodiment, the fibreboard product is a medium density fibreboard (MDF), a high density fibreboard (HDF) or a low-density fibreboard (LDF) although it is convenient herein to refer generally to the MDF as the advantages of the invention are more evident in an MDF. In a further preferred embodiment, wood/bamboo fibres make up roughly 85-90% of the solids of the fibreboard, along with a thermoset or thermoplastic resin optionally together with a wax and crosslinker. In one form, it is a single, uniform layered product with the same material applied throughout the board, but the fibreboard could be produced as a multilayered composite board with different compositions in several layers including layers that may be 100% bamboo or 100% wood with the other layers being composites.

[0024] Accordingly, the present invention resides in a process for the manufacturing of a fibreboard product, said process including the steps of chipping virgin bamboo culm to a size less than 120mm, drying the bamboo chips to a moisture content of approximately 40-150 %, preferably 80-120 % of oven dried mass, softening the chips and subsequently refining to separate the softened chips into a fibrous consistency and optionally mixing with wood particles, spraying the fibres with resin and optionally wax and crosslinkers; oven drying the resinated fibres to a moisture content of from 6-16%, preferably 8-12%; forming the resinated fibres into a mattress and hot pressing to form an fibreboard product. Preferably the fibreboard has a density range of approximately 520-850 kg/m3 and thickness of 3 to 40 mm.

[0025] The fibreboard is most preferably a high-density fibreboard (HDF), a medium density fibreboard (MDF) or a low-density fibreboard (LDF).

[0026] In a further embodiment, the present invention resides in a fibreboard product comprising a lignocellulosic material selected from bamboo or a mix of bamboo and wood particles; wherein if the material is a mix of bamboo and wood particles, the bamboo to wood ratio is from 10:90 to 100:0, preferably 50:50 to 70:30. The bamboo being sourced from virgin bamboo culm and prepared by chipping to a size of less than 120mm, preferably 20-40mm wide and 10-15 mm thick, dried, and optionally mixed with the wood particles, softened and formed into a fibrous consistency, preferably with a thermoset or thermoplastic resin, with a loading based on the solids content of the bamboo/wood of 2-20%, depending on the resin type.

[0027] The wood chip component is sourced from a lignocellulosic species, preferably pine, more preferably hoop pine (Araucaria cunninghamii) or slash pine (Pinus elliottii), or a hardwood such as eucalypt. Bamboo chips are from the culm (above-ground jointed stem) of a fast growing, clumping (sympodial) species of bamboo, that preferably contains low silica/grit content. The preferred species of bamboo for use is Bambusa oldhamii but Phyllostachys pubescens or Phyllostachys edulis are also suitable based on clumping characteristics and low silica/grit content. The preferred silica/grit content is less than 1.5%. Other varieties that could be used include Bambusa balcooa, Bambusa textilis var, longinternode, Dendrocalamus asper, Dendrocalamus giganteus, Dendrocalamus latiforus, Dendrocalamus peculiaris although some have higher silica content making them less desirable. The basis of grit would not however exclude other varieties if appropriate cleaning systems were used.

[0028] The bamboo and optional wood are initially chipped separately but then are mixed, digested and refined (defibrated) to form a thoroughly mixed fibrous materials stream. Alternatively, the materials can be chipped together if suitable equipment is used to manage the different physical forms and properties of the fibrous materials.

[0029] The resin is preferably a melamine urea formaldehyde (MUF) resin. Alternatively, the resin may be a formaldehyde free resin including those that are based on natural materials or bio-based adhesive systems such as soy, soy-based proteins, animal protein-based adhesives, lignin, latex, acrylic, thermoplastic polymers or copolymers and bio-resins or other thermosetting/thermoforming plastics like polymeric diphenylmethane di-isocyanate (PMDI), resorcinol, phenolics, phenol formaldehyde (PF) or urea formaldehyde (UF).

[0030] A formaldehyde free resin may be used to produce a sustainable panel that does not produce formaldehyde emissions during and post-manufacturing. Alternatively, a standard resin system or reduced loadings of a MUF or PMDI resin may be used for "standard" or non-moisture resistant fibreboard

[0031] The resin systems may also include waterborne-acrylics, polyvinyl chloride, thermoplastic polymers and copolymers, polyvinyl alcohol, bio-resins such as polylactic acid (PLA), polyhydroxyl butyrate (PHB) and others, or epoxy resins.

[0032] If the resin system is a PF, UF, MUF, or a combination of these materials, the resin has a solids content of 40-70%, preferably a solid content of 55-65%. If a wax is included, the resin is preferably applied with or after the wax. If a hardener is included, the resin will generally be mixed with the hardener before applying to the fibres to ensure maximum efficacy of the hardener.

[0033] In a further preferred embodiment, the hardener is an acidic catalyst having a pH of less than 6 depending on the acid buffering capacity of the fibrous mix. The hardener is used to speed up the polymerisation of the resin. Allowing the polymerisation to occur in a shorter period of time when hot pressing enables higher throughput and ultimately lower normalized production costs.

[0034] Separately, a crosslinker, such as urea, modified urea or cyclic urea, may be added, which further adds to the polymerization reaction to improve mechanical properties. This can be sprayed in as a liquid or incorporated as a solid which is preferable for easier distribution. Addition of crosslinker can be from loadings of 2 15%.

[0035] If the resin used is MUF, its mechanism of polymerisation takes place via condensation, whereby free protons H+ allows for an intermediate between melamine and formaldehyde or urea and formaldehyde to be formed, following which ejection of water occurs. Therefore, a mildly acidic catalyst, such as ammonium chloride or ammonium sulphate is preferred to provide a source of free protons, these catalysts may be added as optional hardeners. Moreover, this catalyst also contains a small amount of crosslinkers, such as urea, which can polymerize with the resin and further reinforce and strengthen the MDF. Urea and ammonium sulphate or urea and ammonium chloride solution may be sprayed onto the fibres to assist in the polymerisation reaction. The hardener preferably has a solids content of 25-40%.

[0036] The resin is sprayed and then mixed with the fibre mix in a loading based on solids content of wood of 2-20%. A typical commercial resin (UF, PF, or MUF) has a solids content of 40-70%, preferably 55-65%.

[0037] A paraffin wax may be added which acts as a water repellent agent to provide a coating to prevent excess absorption of water by the hydrophilic fibres. Preferably it has a solids content of 55-65% and is sprayed into the fibres as well. The wax may have a loading of 0.5-2%.

[0038] In the preferred process of the invention, the bamboo culm is chopped above the first node preferably using a mechanical process to increase efficiency. The felled culms are then brought to a central location for chipping.

[0039] The bamboo culm is preferably fed into a knife chipper to reduce to a size of less than 120mm long but preferably less than 120mm long, 20-40mm wide, and 10-15mm thick, suitable for transportation. The desired outcome of the chipping is to produce a bamboo chip of regular size by ensuring complete cut-through across the waxy epidermis skin of the virgin bamboo culm. This assists in realizing efficient manufacture of the fibreboard article. This also reduces the slithers (long and thin strands) which often results from inefficient chipping. These slithers cannot be used in manufacturing of the fibreboard as they may cause undesirable product and process challenges such as low fibre quality (shives), equipment malfunction and inefficiencies due to blockages.

[0040] The bamboo chips may then be air-dried naturally while sitting in pile storage on the log-yard to an approximate moisture content of 40-150 %, preferably about 80-120%. The drying allows for the chip to settle at an equilibrium moisture content depending on surrounding atmospheric conditions, allowing for ratios of chip types to be accurately weighed out in production.

[0041] If wood is to be added, the wood chips may be added to achieve a ratio of bamboo to wood from 10:90 to 100:0, but more preferably in the range of from 50:50 to 70:30 by mass. The ratio of bamboo to wood is controlled by the rate in which both chips are fed into the system, be it through separate metering into different bins, or rate of feeding through infeed hoppers, as examples. The bamboo and wood chip mix are then pre-digested by washing and screening to remove grit, dust, and residues.

[0042] The bamboo and wood chip mix, or potentially 100% bamboo, then undergoes digestion and then refining via a thermal mechanical process. First, the chip mix is heated in a pre-steamer at 80-90°C. Next the material is softened in a digester pressurised with steam preferably at 7-10 bar, but more preferably about 8 8.5 bar and steam temperature of from 150 to 180°C, but preferably about 155-170°C for about 0.5-6 minutes, but more preferably about 1-2 minutes. Then, it is preferably refined with a pressurized disc refiner at a predetermined plate gap setting of from 0.05 -0.50 mm, which separates the softened bamboo/wood chip into a thin fibrous consistency.

[0043] Blow line gluing then preferably takes place by spraying the bamboo/wood fibre mix with resin and optionally together with wax, crosslinkers and optionally other additives. Alternatively, the wax, crosslinkers, and other additives can be sprayed separately, either before or after the resin.

[0044] The resinated fibres are then passed through a heated oven to dry to a moisture content of 6-16%.

[0045] Air sifting is used to separate fibres and filter out larger clumps that have formed that would otherwise lead to an uneven consistency when pressed.

[0046] The fibres are then uniformly distributed into a one-layer mattress. Optionally the surfaces can be produced as separate skin layer compositions sandwiching a core layer to afford a multilayer board.

[0047] The formed mattress is then taken to a continuous press which presses the mattress along a decreasing temperature gradient start from a maximum temperature of 180-280°C, preferably 200-260°C, and a decreasing pressure gradient starting from a maximum pressure of 140-220 bar, preferably 150-200 bar, at a line speed of 50-2500 mm/s. An MDF product is formed of dimensions between 3-40mm thick, with a target density of 530-850 kg/m 3

.

[0048] Alternatively, the formed mattress can be processed via a discontinuous or "daylight" press, whereby the mattress is pressed for 3-5 minutes, preferably 3-4 minutes, preferably at 150-200°C. preferably 170-1800C and a maximum pressure of 150-300 bar. The preferred press factor is of about 5 to 15 s/mm for a daylight press.

[0049] The fibreboard product is sanded, then optionally cut to size and then is taken to be cooled to room temperature and stacked to be conditioned for several days before further transportation to customers.

Detailed Description

[0050] Wood and bamboo are comprised mainly of cellulose, hemicellulose, and lignin. These interact to form a lignocellulosic matrix which line the cell walls of plant based materials to provide bending and compressive strength. In the process and the product of this invention, the bamboo and optionally wood fibres are bonded together preferably with a thermoset or thermoplastic resin, such as MUF or a modified MUF.

[0051] The resin, if it is a liquid, can be applied by spraying onto the fibre mix. If the resin is a solid, or a liquid of higher viscosity, it can be applied via other methods such as pouring brushing or blending. When heated to temperatures of around 100 110°C, the resin forms into a polymeric matrix. This has the effect of hardening and binding the wood/bamboo fibres together into a solid engineered wood panel. This resin will coat and penetrate into the surface of these cellulosic fibres, reinforcing them as well as binding them together and allowing for stress redistribution throughout the material.

[0052] In the process of the present application, preferably no catalyst is used. The gel time for this MUF resin is longer than a resin system that includes a catalyst, but the lack of catalyst reduces the extent of precure in the final fibreboard product.

[0053] It is preferred that the resin composition contains a small amount of crosslinkers, preferably urea, which can polymerize with the resin and further reinforce and strengthen the board. The crosslinker may be added as a solid to reduce moisture content of the final board.

[0054] It is preferred that wax may also be included to provide hydrophobicity to the fibre mix. Wax is a hydrophobic material that is used to coat the surface of the cellulosic material and resin matrix. Since bamboo and wood fibres are hydrophilic, the mix may readily absorb water, which would lead to dimensional swelling in the final board, as well as reversal and hence weakening of the polymeric resin matrix. Thus, addition of a small amount of wax is preferred to provide the board with moisture resistant properties by reducing the penetration of water to these surfaces.

[0055] The melamine modification of the MUF resin also aids in providing greater moisture resistance than conventional urea formaldehyde (UF) resins, since melamine's heterocyclic structure lends to the formation of 3-dimensional crosslinking that is more stable than the more linear structures formed by urea.

[0056] Paraffin wax is a preferred wax. It acts as a water repellent agent to provide a coating to prevent excess absorption of water by the hydrophilic bamboo and wood particles. The wax preferably has a solids content of from 40-75%, more preferably 50-65% and is sprayed onto the bamboo/wood fibres at a loading of from 0.5-4%, preferably 0.5-2%. Other water repellent agents include but are not limited to silicones, silanes, fluorinated chemicals, fatty acid surfactants, and inorganic hydrophobising agents.

[0057] Other additives may be incorporated to achieve desirable properties. For example, additives such as boric acid, insecticides and/or pyrethroids may be used to afford termite resistance. Flame retarding agents including but not limited to ammonium polyphosphate, boric acid, cement, magnesium dihydroxide and/or aluminium trihydate or combinations of these additives can be used to improve the fire resistance of the fibreboard product. Dyes and pigments may be added to the mixture to colour the fibreboard for marketing and/or aesthetic reasons. Fillers such as talc or CaC03 may be used to decrease the cost of the MDF. Fillers such as pearlite or foamed polymers may be used to decrease the panel density.

[0058] The residence time or press factor of the board between the press platens or belt is about 5-15 seconds per millimetre thickness for a discontinuous press, or 2 8 seconds per millimetre thickness for a continuous press.

[0059] The formed mattress is then pressed between platens in a hot press. A discontinuous or "daylight" press may only be for 3-5 minutes, preferably 3-4 minutes, preferably at 150-200°C and a maximum pressure of 300 bar. The preferred press factor is about 5 to 15 s/mm for a daylight press. This allows the core to be heated to a temperature of preferably around 100-110C which consolidates the resin into a polymeric matrix. The fibreboard may then be taken to be cooled to room temperature and stacked on top of each other for several days as conditioning, to ensure the resin has fully set before further transportation.

[0060] For a continuous press, the press factor is approximately 4-8 s/mm. This compares to press cycles of greater than 20 s/mm found in the literature. The optimized and faster press cycle is achieved in part using a fast-curing MUF or modified MUF resin.

[0061] The final fibreboard may be decorated with resin impregnated printed or coloured decorative papers, which are fused to the board using a low pressure heated platen press. Alternatively, the inventive fibreboard may be decorated with metallic foils, PVC, acrylic foils or sheets, polypropylene films, and other foils or skins adhered using conventional adhesive systems. The decorative surface itself may be further modified with biocidal agents (for example silver, copper, titanium, and/or zinc ions, or ammonium compounds) to afford antibacterial, antifungal and antiviral surface properties.

[0062] The raw or decorated panels may be routed, machined and fabricated into articles including furniture, cabinetry, and wall or ceiling linings for internal or external applications. The raw panels may be routed and used for tongue and groove flooring applications. The raw panels may be painted, sealed or coated for decorative purposes, or sealed with waterproofing membranes for use in wet area applications. The acoustic properties of the panels can be modified with additives or the surface may be modified to achieve acoustic properties.

[0063] The invention utilises a low silica bamboo species, such as Bambusa oldhamii, which contains a level of silica/grit <1.5%. Traditional species of bamboo harvested for timber, such as Bambusa balcooa or Dendroclamous asper contain high levels of silica between 2-3%. However, this creates problems in manufacturing as well as customer complaints, due to increased cutting and sanding tool wear.

[0064] For a given board thickness, the mixed wood/bamboo MDF product is generally a lower density product (less than 750kg/m 3 ), whereas many previous MDF products that may be found in literature or available commercially are of high density greater than 800kg/m 3. The lower density of the MDF of the present application increases the scope of application, ensuring the material is lightweight enough to be used in furniture, improves ease of handling and transportation, and lowers the cost of production.

[0065] The present application optimizes the chip size (<120mm long, 20-40mm wide, 10-15mm thick) of the bamboo culm which is most optimal to feed into the MDF process. This chip size ensures that blockages are minimized throughout the production process, since bamboo culm is known to form chip that is longer and thinner than wood, leading to increased formation of bridging and blockages at areas where wood would not cause problems. Moreover, this is an optimum chip size to undergo the thermomechanical pulping process.

[0066] The present Applicants have identified the role that wood chips may play in preventing bamboo chip from entangling and blocking the flow of chip. Other literature works solely focus on finding the optimum bamboo to wood ratio to achieve the best mechanical properties. The present Applicants have found that a most preferred bamboo/wood ratio of 50:50 to 70:30 acts to force the bamboo along the process however up to 100% bamboo may be used.

[0067] The present Applicants have identified the synergistic effect that bamboo addition has on the mechanical performance of the inventive article improving the performance with increasing proportion of bamboo. We believe that this improvement is the result of the high aspect ratio of bamboo fibres for efficient interparticle bonding of the fibrous matrix.

[0068] In a preferred embodiment, the use of a MUF resin provides the advantage of achieving moisture resistance properties. Previous work has achieved AS/NZS or equivalent moisture resistant standards (EU, GB, ANSI etc), through use of a polymeric isocyanate resin, such as pMDI, acrylic, or polyurethane resin. In the preferred embodiment, the present application achieves moisture resistant standards by using an MUF resin which is more cost efficient than alternatives like pMDI and is easier to manufacture with conventional MDF processes.

[0069] Surprisingly, the Applicants have found that internal bond (IB) strength increased with increasing bamboo %, as seen in Figure 1 and Table 1. MDF product produced with greater than 70% bamboo showed IB that were statistically significantly increased (at p < .05) relative to wood based MDF. In prior art documents, increased % incorporation of bamboo fibres lowers mechanical properties. However, an increased internal bond may have been due to the superior fibre quality of bamboo relative to pine, along with increased fibre length. Bamboo cells are elongated relative to wood ones, allowing for longer fibres to be formed when defibrated. As fibre thickness and width remain relatively similar in fibreboard and in particular MDF fibres, longer fibres therefore have increased interparticle overlap, allowing for more efficient redistribution of stresses within the board.

Bamboo Density IB (MPa) MOR MOE (MPa) 24hTS (%) (%)/Wood (kg/mA3) (MPa) (%)

0/100 710 0.65 19.7 2635 8.2

30/70 697 0.79 21.4 2599 7.3

70/30 696 0.97 22.4 2774 6.9

80/20 678 1.00 21.8 2759 7.4

100/0 678 1.28 19.1 2502 8.2

Table 1

[0070] The Applicants have also found that there are Surprisingly, no significant reduction in other mechanical properties such as modulus of elasticity (MOE) modulus of rupture (MOR), or 24hour thickness swelling TS was seen with the increased use of bamboo content. In prior art technologies, increased bamboo fibre content tende to reduce MDF board performance.

Brief Description of Drawings

[0071] Figure 1 is a graph showing Internal Bonding for MDF blends of 100% pine to 100% bamboo.

[0072] Figure 2 is a graph showing Modulus of Elasticity (MOE) for MDF blends of 100% pine to 100% bamboo.

[0073] Figure 3 is a graph showing the Modulus of Rupture (MOR) for MDF blends of 100% pine to 100% bamboo.

[0074] Figure 4 is a graph showing 24-hour Thickness Swelling (24h TS) for MDF blends of 100% pine to 100% bamboo.

Description of the Drawings

[0075] Figure 1 shows a graph of the internal bond (IB) strength in MPa in comparison to blends that range from 100% pine, 30%, 70%, 80% and 100% bamboo. What this graph illustrates is that there is increasing internal bond strength the more bamboo that is present. This is thought to be due to the improved fibre quality of bamboo relative to wood fibres as the fibre length is longer.

[0076] Figure 2 relates to a graph showing the Modulus of Elasticity (MOE) in MPa in comparison to blends that range from 100% pine, 30%, 70%, 80% and 100% bamboo. The graph does illustrate that there is an improved MOE as you include 70 and 80% bamboo into the mix.

[0077] Figure 3 relates to a graph showing the Modulus of Rupture (MOR) with blends ranging from 100% pine to 100% bamboo. This graph demonstrates the relative stability of blends incorporating 30%, 70%, 80% and 100% bamboo without significant effects to the MOR.

[0078] Figure 4 illustrate the 24-hour thickness swelling (TS) as a percentage in comparison to blends that range from 100% pine, 30%, 70%, 80% and 100% bamboo. Again, it can be seen that improved results are found with 30%, 70% and 80% bamboo content in comparison to 100% pine.

[0079] Overall, the Applicants have found that the bamboo/wood composite fibreboard panels will have comparable or superior performance to the 100% wood control. Without being bound by theory, the inventors hypothesize that the improvements in fibreboard properties relative to prior art bamboo-based boards is due to the increased aspect ratio of the fibres used in the fibreboard production.

[0080] Preliminary tests demonstrate that all MDF boards produced with 30-100% bamboo content passed the majority of all AS/NZS standards. Moreover, MDF with the preferred bamboo ratio of 50:50 to 70:30 bamboo to wood were shown to have no significant reduction in properties, or noticeable production difficulties, relative to the 100% wood. These findings point to the capability of bamboo as a direct substitute for softwood, in these preferred ratios, with no modification required to existing production settings

Claims

1. A process for the manufacturing of a fibreboard product , said process including the steps of chipping virgin bamboo culm to a size less than 120mm, drying the bamboo chips to a moisture content of approximately 40-150%, preferably 80-120% of oven dried mass, softening the chips and refining to separate the softened chips into a fibrous consistency and optionally mixing with wood particles, spraying the fibres with resin and optionally wax and crosslinkers; oven drying the resinated fibres to a moisture content of from 6 16%, preferably 8-12%; forming the resinated fibres into a mattress and hot pressing to form a fibreboard product.

2. A process according to claim 1 wherein the fibreboard is a high-density fibreboard (HDF), medium-density fibreboard (MDF) or a low-density fibreboard (LDF).

3. A process according to claim 1 or 2 wherein the formed mattress is pressed in a continuous belt press to press the mattress along a decreasing temperature gradient from a maximum temperature of 180-280°C, preferably 200-260C, and a decreasing pressure gradient starting from a maximum pressure of 140 220 bar, preferably 150-200 bar, at a line speed of 50-2000 mm/s.

4. A process according to anyone of claims 1 to 3 wherein the formed mattress is pressed in a discontinuous or "daylight" press to press the mattress at a constant temperature of 150-200°C, preferably 170-180 0C, at a maximum pressure of about 300 bar, at a line speed of 5-15 s/mm.

5. A process according to anyone of claims 1 to 4 wherein the bamboo chips are mixed with wood such that the ratio between the bamboo to wood is in the ratio of from 10:90 to 100:0, preferably 50:50 to 70:30.

6. A process according to anyone of claims 1 to 5 wherein the virgin bamboo culm is chipped to a size of less than 120mm long and formed into a fibrous consistency preferably with a thermoset or thermoplastic resin with a loading based on the solids content of the bamboo/wood of 2-20%.

7. A process according to anyone of the preceding claims wherein the fibreboard is an MDF and is formed as a single layer with dimensions of from 3-40mm thickness and a density of from 530-850 kg/m 3

. 8. A process according to anyone of the preceding claims wherein the wood particles are sourced from a softwood, preferably pine, more preferably hoop pine (Araucaria cunninghamii) or slash pine (Pinus elliottii) or a hardwood preferably eucalypt; the bamboo particles are from the culm of a fast growing, clumping (sympodial) species having low silica/grit of less than 1.5%, preferably Bambusa oldhamii, Phyllostachys pubescens or Phyllostachys edulis.

9. A process according to anyone of the preceding claims wherein the resin comprises one or more of a melamine urea formaldehyde (MUF) or a modified MUF, phenol formaldehyde (PF), urea formaldehyde (UF), polymeric diphenylmethane diisocyanate (PMDI), non-formaldehyde resins such as latex, acrylic, epoxy, thermoplastic polymers or copolymers, bio-resins, bio-based adhesive systems such as soy-based proteins, lignin resins, and/or animal protein-based adhesives.

10. A process according to anyone of the preceding claims wherein the resin is a moisture resistant resin, preferably a modified melamine urea formaldehyde resin which has been sprayed upon the bamboo/wood fibres at a loading of 6 20% based on the solid resin relative to dry weight of the bamboo/wood.

11. A process according to anyone of the preceding claims wherein if the resin is UF, PF, MUF, or a combination thereof, the resin has a solids content of from 40-70 % preferably 55-65%.

12. A process according to anyone of the preceding claims wherein a hardener and/or wax are added together or in conjunction with the resin.

13. A process according to claim 11 wherein the hardener is an acidic catalyst of pH < 6 and optionally includes a crosslinker, preferably a urea.

14. A process according to anyone of the preceding claims wherein urea, ammonium sulphate and/or ammonium chloride solution is further sprayed or added onto the fibres, the ammonium sulphate and/or ammonium chloride solutions having a solids content of 25-40%.

15. A fibreboard product, preferably an HDF, MDF or an LDF comprising a lignocellulosic material selected from bamboo or a mix of bamboo and wood chips ; wherein if the material is a mix of bamboo and wood chips, the bamboo to wood ratio is from 10:90 to 100:0, preferably 50:50 to 70:30, the bamboo being sourced from virgin bamboo culm; the bamboo having been prepared by chipping to a size of less than 120mm, and mixed with the optional wood particles, softened and refined into a fibrous material, bound with 6-20% resin on a dry mass basis relative to the dry fibre.

16. A fibreboard product according to claim 15 wherein the wood particles are sourced from a softwood, preferably pine, more preferably hoop pine (Araucaria cunninghamii) or slash pine (Pinus elliottii) or a hardwood, preferably eucalypt; the bamboo particles are from the culm of a fast growing, clumping (sympodial) species having low silica/grit of less than 1.5%, preferably Bambusa oldhamii, Phyllostachys pubescens or Phyllostachys edulis.

17. A fibreboard product according to claims 15 and 16 wherein the bamboo has been chipped to a size of less than 120mm long and formed into a fibrous consistency preferably with a thermoset or thermoplastic resin with a loading based on the solids content of the bamboo/wood of 2-20%.

18. A fibreboard product according to anyone of claims 15-17 wherein the resin is preferably composed of one or more of the following: melamine urea formaldehyde (MUF), phenol formaldehyde (PF), urea formaldehyde (UF), PMDI, non-formaldehyde resins such as latex, acrylic, epoxy, thermoplastic polymers and copolymers, bio-resins, or biobased systems such as soy-based proteins, lignin resins, and/or animal protein-based adhesives.

19. A fibreboard product according to claim 18 wherein the resin is a moisture resistant resin, preferably a MUF.

20. A fibreboard product according to anyone of claims 15 to 19 wherein the resin has a solid content of from 40-70 % preferably from 55-65%.

21. A fibreboard product according to anyone of claims 15 to 20 wherein the particle mix further includes wax, a hardener and optionally water.

22. A fibreboard product according to claim 21 wherein the hardener is an acidic catalyst of pH < 6 and optionally includes a crosslinker, preferably a urea.

23. A fibreboard product according to anyone of claims 15 to 22 wherein urea and ammonium sulphate or ammonium chloride solution is sprayed into the wood/bamboo fibres, having a solids content of 25-40% with loadings of 1-5%.

24. A fibreboard product according to claim 21 wherein the wax is paraffin wax having a solids content of from 40-75%, more preferably 50-65% and is sprayed into the bamboo/wood fibres at a loading of from 0.5-4%, preferably 0.5-2%.

25. A fibreboard product according to anyone of claims 15-24 wherein additives are incorporated during manufacture to provide properties such as flame retardance, moisture resistance, termite resistance, light-weighting, acoustic properties, or improved insulation performance.

26. A fibreboard product according to anyone of claims 15-25 wherein the fibreboard is a moisture resistant MDF product.

27. Articles such as flooring, wall and ceiling linings, furniture and cabinetry made from the fibreboard according to anyone of claims 15-26.

Figure 1 1/3

Figures

Figure 3 Figure 2 2/3

Figure 4 3/3