A method of enhancing the fire resistance of wood

Abstract

Abstract Disclosed herein is a method of enhancing the fire resistance of wood. The method comprises heating wood to a temperature of about 180°C to about 260°C to produce thermally modified wood; vacuum impregnating the thermally modified wood with a thermosetting resin and a fire retardant to produce an impregnated thermally modified wood; and drying the impregnated thermally modified wood to produce a fire-resistant wood product.

Description

Field of Invention The invention relates to a method of manufacturing a fire-resistant wood product. In particular, the invention relates to a method of manufacturing a fire-resistant wood product, wherein the method comprises impregnating thermally modified wood with a thermoset resin and fire retardant. Background of the Invention Resistance to fire plays an important role in the use of wood products in the building and construction industry. While fire retardant treated wood is known, there is still a need for new and alternative fire retardant wood treatments. Most fire retardant chemicals suitable for wood impregnation are hygroscopic by nature and do not adhere to the wood cells very well or on a permanent basis. This can result in the fire retardant chemicals leaching out over time and the fire retardant treated wood losing its fire retardant capabilities. In exterior applications especially, fire retardant treated wood may lose effectiveness quickly when exposed to weather and subjected to direct rain and / or humidity. This means that fire retardant chemicals are often difficult and costly to apply to wood. In practice, this cost and loss in fire retardance is often underestimated, due to the difficulty in addressing this issue. It is also common to encounter problems with paint and stain applications onto fire retardant treated wood due to chemical compatibility issues, which can result in compromised fire resistance performance. Treating wood with a resin is also a complicated process, with the drying and curing process taking a long time at relatively high temperatures when compared with conventional wood drying methods. Such a process can be costly, due to time and energy cost. The high 2025203983   28 May 2025 temperature required to cure thermosetting resins can also compromise product quality, damaging the wood structure and physical characteristics of the wood (such of loss of strength, deformation, and wet core). It is an object of the invention to provide a method of enhancing the fire resistance of wood. Additionally, or alternatively, it is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or at least go some way to provide the public with a useful choice. Summary of the Invention The invention relates to methods of manufacturing a fire-resistant wood product, wherein the methods comprise impregnating thermally modified wood with a thermoset resin and fire retardant. According to a first aspect of the invention, there is provided a method of manufacturing a fireresistant wood product, wherein the method comprises: A. heating wood to a temperature of about 180°C to about 260°C to produce thermally modified wood; B. impregnating the thermally modified wood with a thermosetting resin and a fire retardant to produce an impregnated thermally modified wood, wherein the impregnating comprises: i.  applying a vacuum of about -90 to -95kPa to the thermally modified wood; ii.  flooding the thermally modified wood with the thermosetting resin and the fire retardant while maintaining the vacuum of about -90 to -95 kPa; and iii. following the flooding, applying a pressure of about 900 to about 1400kPa, and C. drying the impregnated thermally modified wood, to produce a fire-resistant wood product. In various embodiments, the method further comprises a step of applying a coating to the surface of the fire-resistant wood product. 2025203983   28 May 2025 In various embodiments, Step B comprises impregnating the thermally modified wood with a composition comprising the thermosetting resin, the fire retardant and a coating or pigment. In various embodiments, the coating is a water borne coating. In various embodiments, Step A comprises thermally modifying the wood at a temperature of at least about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C or about 260°C. In various embodiments, Step A comprises thermally modifying the wood at a temperature of about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C or about °C, preferably about 210°C to about 235°C. In various embodiments, Step A. comprises: i. drying the wood to produce a dried wood with a moisture content of less than about 1%, less than about 0.5%, less than about 0.2%, less than about 0.1%, or substantially about 0%; ii. heating the dried wood until it reaches a temperature of about 180°C to about 260°C, followed by; iii. maintaining the wood at the temperature in ii. for a period of about 1 to about 6 hours or for a period of time sufficient to cause at least 4% mass loss, followed by; iv. allowing the wood to cool, followed by; v. reconditioning the wood with water and / or steam until the moisture content of the wood is about 7%, to produce a thermally modified wood. In various embodiments, the moisture content in i. of Step A is substantially 0%. In various embodiments, the temperature in ii. of Step A is at least about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C or about 260°C, preferably about 210°C to about 230°C. In various embodiments, the temperature in ii. of Step A is about 200°C, about 2025203983   28 May 2025 210°C, about 220°C, about 230°C, about 240°C, about 250°C or about 260°C, preferably about 210°C to about 230°C. In various embodiments, the period in iii. of Step A is about 2 to 4 hours. In various embodiments, the period in iii. of Step A is about 1, 2, 3, 4, 5 or 6 hours, preferably wherein the period in step iii. is about 3 hours. In various embodiments, the period in iii. of Step A is sufficient to cause at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, at least about 10%, at least about 11%, at least about 12%, at least about 13%, at least about 14%, at least about 15%, at least about 16%, at least about 17%, at least about 18%, at least about 19%, at least about 20%, at least about 21%, at least about 22%, at least about 23%, at least about 24% or at least about 25% mass loss. In various embodiments, Step A iii. comprises maintaining the wood at about 230°C, for a period of time sufficient cause about 9% to 25% mass loss. In various embodiments, the fire retardant is a hygroscopic fire retardant. In various embodiments, the thermosetting resin is a phenolic resin or melamine resin. In various embodiments, the vacuum in ii. of Step B. is maintained for about 20 to about 40 minutes. In various embodiments, the vacuum in ii. of Step B. is maintained for about 30 minutes. In one embodiment, the pressure in iii. of Step B. is from about 900 to 1400kPa. In one embodiment, the pressure in iii. of Step B. is from about 1100 to 1400kPa. In one embodiment, the pressure in iii. of Step B. is at least about 1100kPa, about 1200kPa, about 1300kPa or about 1400kPa. In one embodiment, the pressure in iii. of Step B. is about 1100kPa, about 1200kPa, about 1300kPa or 1400kPa. In various embodiments, Step B. comprises: i. applying a vacuum of -90 to -95 kPa to the thermally modified wood for about 20 to 40 minutes, preferably about 30 minutes; followed by 2025203983   28 May 2025 ii. flooding the thermally modified wood with the thermosetting resin and the fire retardant while maintaining the vacuum of about -90 to -95 kPa; followed by iii. applying a pressure of about 1100 to about 1400 kPa for about 1 to 2 hours, preferably about 1 hour; followed by iv. removing excess thermosetting resin and a fire retardant; followed by v. applying a final vacuum of about 85kPa for about 10 to about 20 minutes, preferably about 15 minutes. In various embodiments, the excess thermosetting resin and fire retardant is removed by draining. In various embodiments, the drying in Step C comprises heating the wood to about 50°C to about 150°C. In various embodiments, the drying in Step C comprises heating the wood to about 50°C to about 150°C, for a period of time sufficient for the wood to reach an equilibrium moisture content (EMC) of about from 7% to about 8%. In various embodiments, the wood is selected from the groups consisting of Pinus species (pine), radiata pine (Pinus radiata), southern yellow pine, scots pine, ash, maple, beech, poplar, birch, aspen, rubber wood, cedar, redwood, Douglas fir, cypresses, spruce, larch, eucalyptus, western red cedar, yellow cedar, ayous, frake and teak. In various embodiments, the wood is Pinus species (pine), Douglas fir, poplar or rubber wood. In various embodiments, the wood is wood with Class 4 or lower durability (EN350) or equivalent. In various embodiments, the wood is, southern yellow pine, scots pine or Pinus radiata. In various embodiments, the wood is, southern yellow pine, scots pine or Pinus radiata. In various embodiments, the fire-resistant wood product has a minimum fire rating of ASTM E84 Class A. In various embodiments, the method is for preventing warping of the fire-resistant wood product, preventing cupping of the fire-resistant wood product, enhancing the penetration of the fire retardant and the resin, for reducing leaching of a fire retardant from the fire-resistant 2025203983   28 May 2025 wood product and / or for enhancing the performance of a waterborne coating when applied to the fire-resistant wood product. According to a second aspect of the invention, there is provided a fire-resistant wood product produced by the method of the first aspect. According to a third aspect of the invention, there is provided a fire-resistant timber product comprising the fire-resistant wood product of the second aspect. In various embodiments, the fire-resistant timber product is suitable for end use application as weatherboard cladding, wall / ceiling panelling, shiplap, tongue and groove, square dressed, rhombus, flooring, decking or screening. In various embodiments, the fire-resistant timber product is a board, panel, beam or post. In various embodiments, the wood is a board of about 70-290 x 17-32mm or a panel of about 15-25 mm thick x 600-1200 mm width x 2400-6000 mm length. In various embodiments, the fire-resistant timber product is a cladding or decking board of about 70-290 x 17-32mm or a panel of about 15-25 mm thick x 600-1200 mm width x 2400-6000 mm length. In various embodiments, the fire-resistant timber product comprises band sawn, brushed, textured or smooth dressed faces. According to a fourth aspect of the invention, there is provided a fire-resistant timber product comprising the wood produced by the method of the first aspect, as described with reference to any one of Figures 1 to 4. According to a fifth aspect of the invention, there is provided a fire-resistant timber product comprising the wood produced by the method of the first aspect, suitable for use on windows and doors. 2025203983   28 May 2025 As used herein the term “and / or” means “and” or “or”, or both. As used herein “(s)” following a noun means the plural and / or singular forms of the noun. The term “comprising” as used in this specification means “consisting at least in part of”. When interpreting statements in this specification which include that term, the features prefaced by that term in each statement all need to be present, but other features can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner. It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7). To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and application of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Further aspects of the invention, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the invention. Brief Description of the Drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1      shows a photo of wood samples A, B and C taken after they were processed according to the method outlined in Example 1. 2025203983   28 May 2025 Figure 2     shows a photo of wood samples A, B and C taken after they were processed according to the method outlined in Example 2 and left outside to weather for about 24 months. Figure 3     shows flame spread and smoke readings for Sample A. Figure 4     shows flame spread and smoke readings for Sample B. Detailed Description Definitions: A “board” is defined as a piece of wood sawn from a tree with a width greater than a depth, and a length greater than the width. The face of the board is defined as a plane with edges defined by the width and the length of the board. A cross sectional view of the board through the width and depth axis will typically be substantially rectangular, though it may also have edge detail to allow joining for example tongue and groove, and may also be sloped on one or more major surfaces or edge surfaces to form weather boards or similar. Boards may be cut from the tree in a variety of orientations as shown in Figure 1 and described in further detail below. “Plywood” is defined as a wooden board comprising two, three or more layers of wood veneer glued and pressed together with veneers positioned with grain at 90-degree angle to each other. “Dimensional stability” or simply “stability” means the degree of resistance to deformation, expansion or shrinkage that can result from changes in conditions such as temperature and humidity. “Weatherability” means the degree of cracking, checking, distortion, splintering or otherwise degrading in exposure to an exterior application. “Durable” means the degree of resistance to decay as a result of fungal or microorganism growth and degradation, and optionally the degree of resistance termite attack. 2025203983   28 May 2025 “EN350” refers to the European standards for durability of wood and wood-based products. The durability classes of wood-based materials to attack by fungi are split into 5 classes: Class 1 -Very durable; Class 2 - Durable; Class 3 - Moderately durable; Class 4 - Slightly durable; Class 5 - Not durable. “Clears grade” means a high quality grade of timber that contains no knots and only small defects on at least one face and two edges. “Dressing grade” means a mid-quality grade of timber which can contain some tight knots and small defects along with some timber without knots. “Merchantable grade” means a lower-quality grade of timber that can contain many knots and large defects “Standard grade” means a mid-quality grade of timber that contains tight knots. “Finger jointed” means pieces of timber with or without knots or defects that have been profiled with an interlocking shape at the ends and joined together with glue to form a longer length of timber. The inventors have developed a method of processing wood to increase the fire resistance of the wood. That is, increasing the fire resistance of the fire-resistant wood product compared to the fire resistance of the wood prior to processing. The method described herein may also enhance the performance of coatings applied to the fireresistant wood product. The method of the present invention may also increase the fire resistance of wood in a way that is less complex and less energy, chemical and time consuming to perform. The methods described herein are applicable to any wood, for example, but not limited to Pinus species (pine), radiata pine (Pinus radiata), southern yellow pine, bamboo, scots pine, ash, 2025203983   28 May 2025 maple, beech, poplar, birch, aspen, rubber wood, cedar, redwood, Douglas fir, cypresses, spruce, larch, eucalyptus, western red cedar, ayous, frake, hemlock, yellow cedar, oak, fir and teak. Accordingly, in one embodiment, the wood is selected from Pinus species (pine), radiata pine (Pinus radiata), southern yellow pine, scots pine, ash, maple, beech, poplar, birch, aspen, rubber wood, cedar, redwood, Douglas fir, cypresses, spruce, larch, eucalyptus, western red cedar, ayous, frake, hemlock, yellow cedar, oak fir and teak. In one embodiment, the wood is radiata pine (Pinus radiata). The wood may be timber that is clears grade, dressing grade, merchantable grade, or standard grade. In one embodiment, the wood is substantially vertical grain timber. In one embodiment the wood is timber that is quarter sawn. In one embodiment, the wood is timber that is solid, finger-jointed, laminated, plywood, cross laminated or laminated veneer lumber (LVL). In one embodiment, the wood is laminated timber with a vertical grain orientation. The timber with vertical grain orientation can be timber with the appearance of a vertical grain on the face of the timber, but be made from substantially flat grain timber. For example, the timber may be produced by the methods disclosed in United States Patent No. 10,059,027. In particular, at least two flat-grain thermally modified boards are laminated together by gluing to form a laminated block wherein each original board comprises a laminated layer. The block is then cut substantially perpendicular to the grain to produce individual laminated boards. Each laminated board comprises a front and a back face showing at least one glue line between the laminated layers and said faces have the appearance of a substantially vertical grain orientation. This technique produces boards with glue lines at the join of each original board which extend along the length of the laminated board. Timber processed in this way is more resistant to warping, splitting and surface checking and therefore more stable when used. 2025203983   28 May 2025 The method comprises a Step A of heating wood to a temperature of about 180°C to about 260°C to produce thermally modified wood. Thermal modification of the wood is carried out at a temperature of between about 160°C -about 260°C (also referred to below as ‘the temperature of thermal modification’). In some embodiments, the wood in Step A is heated to at least about 160°C - about 260°C. In some embodiments, the wood in Step A is heated to at least about 160°C, about 170°C, about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C or 250°C. In some embodiments, the wood in Step A is heated to at least about 160°C, about 170°C, about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C or about 250°C. Preferably the temperature is in a range of 200-260°C, in the range of about 200-240°C, in the range of about 200-230°C, in the range of about 210-230°C, in the range of about 220235°C, in the range of about 210-235°C, or about 250°C, about 245°C, about 240°C, about 235°C, about 230°C, about 225°C, about 220°C, about 215°C, about 210°C, about 205°C, or about 200°C. Thermal modification of the wood at 200-240°C imparts durability and stability to the wood in addition to a medium dark brown colour. Thermal modification at 160°C - 200°C does provide increased stability but only gives a lighter brown colour. The thermal modification treatment comprises maintaining the wood at the temperature of thermal modification for a period of 1 to 6 hours. In one embodiment, Step A comprises maintaining the wood at the temperature of thermal modification for a period of 1 to 6 hours, 2 to 6 hours, 3 to 6 hours, 4 to 6 hours, 2 to 5 hours, 2 to 4 hours, 3 to 6 hours, 3 to 5 hours, 3 to 4 hours, 4 to 6 hours, 4 to 5 hours or 5 to 6 hours. In one embodiment, the period is approximately 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours. In one particular embodiment, Step A comprises maintaining the wood at a temperature of 210-230°C for a period of 2 to 4 hours, or approximately 3 hours. Thermal modification of wood changes its chemical composition by degrading cell wall compounds and extractives (Esteves, B. M et al (2009). "Wood modification by heat treatment: A review," BioRes. 4(1), 370-404). The change in chemical composition caused by thermal 2025203983   28 May 2025 modification results in mass loss (ML). ML is commonly referred to as feature of thermal modification and as an indication of quality. The literature describes degradation of, for example, hemicellulose, cellulose and / or lignin as contributing to ML (see, for example, B. M et al (2009) or Xu, J et al “New Perspective on Wood Thermal Modification: Relevance between the Evolution of Chemical Structure and Physical-Mechanical Properties, and Online Analysis of Release of VOC’s. Polymers 2019, 11, 1145. https: / / doi.org / 10.3390 / polym11071145).ML is based on the mass of wood before and after thermal modification. ML can be calculated by the following equation, where m0 is the initial mass of the untreated wood and m1 is the mass of the wood after thermal modification: ML (%) = 100 x (mo - mi) / mo In one embedment, Step A comprises heating wood to a temperature of about 180°C to about 260°C to produce thermally modified wood having at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, at least about 10%, at least about 11%, at least about 12%, at least about 13%, at least about 14%, at least about 15%, at least about 16%, at least about 17%, at least about 18%, at least about 19%, at least about 20%, at least about 21%, at least about 22%, at least about 23%, at least about 24% or at least about 25% mass loss. In one embedment, Step A comprises heating wood to a temperature of about 180°C to about 260°C to produce thermally modified wood having 4% to 25% ML. In one embedment, Step A comprises heating wood to a temperature of about 180°C to about 260°C to produce thermally modified wood having ML of about 4% to about 25%, about 5% to about 25%, about 6% to about 25%, about 7% to about 25%, about 8% to about 25%, about 9% to about 25%, about 10% to about 25%, about 11% to about 25%, about 12% to about 25%, about 13% to about 25%, about 13% to about 25%, about 14% to about 25%, about 15% to about 25%, about 16% to about 25%, about 17% to about 25%, about 18% to about 25%, about 19% to about 25%, or about 20% to about 25%. In one embodiment, the ML is about 4% to about 20%, about 5% to about 20%, about 6% to about 20%, about 7% to about 20%, about 8% to about 20%, about 9% to about 20%, about 10% to about 20%, about 11% to about 20%, about 12% to about 20%, about 13% to about 20%, about 13% to about 20%, about 14% to about 20%, about 15% to about 20%, about 16% to about 20%, about 17% to about 20%, about 18% to about 20% or about 19% to about 20%. In one embodiment, the ML is about 4%, about 5%, 2025203983   28 May 2025 about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24% or about 25%. In one embedment, Step A comprises heating wood to a temperature of about 230°C to produce thermally modified wood having about 10% to about 25% ML. In one embodiment, Step A comprises maintaining the wood at a temperature of 210-230°C for a period of time sufficient to cause at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, at least about 10%, at least about 11%, at least about 12%, at least about 13%, at least about 14%, at least about 15%, at least about 16%, at least about 17%, at least about 18%, at least about 19%, at least about 20%, at least about 21%, at least about 22%, at least about 23%, at least about 24% or at least about 25% mass loss. In one embodiment, the Step A comprises maintaining the wood at a temperature of 210-230°C for a period of time sufficient to cause 4% to 25% ML. In one embodiment, the ML is about 4% to about 25%, about 5% to about 25%, about 6% to about 25%, about 7% to about 25%, about 8% to about 25%, about 9% to about 25%, about 10% to about 25%, about 11% to about 25%, about 12% to about 25%, about 13% to about 25%, about 13% to about 25%, about 14% to about 25%, about 15% to about 25%, about 16% to about 25%, about 17% to about 25%, about 18% to about 25%, about 19% to about 25%, or about 20% to about 25%. In one embodiment, the ML is about 4% to about 20%, about 5% to about 20%, about 6% to about 20%, about 7% to about 20%, about 8% to about 20%, about 9% to about 20%, about 10% to about 20%, about 11% to about 20%, about 12% to about 20%, about 13% to about 20%, about 13% to about 20%, about 14% to about 20%, about 15% to about 20%, about 16% to about 20%, about 17% to about 20%, about 18% to about 20% or about 19% to about 20%. In one embodiment, the ML is about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, about 20%, about 21%, about 22%, about 23%, about 24% or about 25%. In a one embodiment, Step A comprises maintaining the wood at a temperature of 230°C for a period of time sufficient to cause about 10% to about 25% ML. 2025203983   28 May 2025 Prior to thermal modification, the wood is preferably dried to reduce moisture content to substantially 0%. In one embodiment, drying is achieved by the application of heat and optionally steam to heat the wood to about 130°C. The duration of the drying step depends on the original moisture content of the wood. In one embodiment, Step A comprises a step of drying the wood to produce a dried wood. In one embodiment, the drying in Step A comprises heating the wood to a temperature of about 120°C to 140°C for a period of time sufficient to reduce the moisture content of the wood to less than 1%, less than 0.5%, less than 0.2%, less than 0.1%, or until the moisture content of the dried wood is substantially 0%. In one embodiment, Step A is carried out in a high-pressure cylinder and involves a high-pressure steam treatment of kiln dried wood. Preferably the kiln dried wood has a moisture content of about 16% or less. A high-pressure cylinder or kiln system that has been specifically designed for the elevated temperatures associated with thermal modification could be used for the thermal modification step. Such thermal modification kilns, as offered, by way of example, by Jartek™ or Stellac™, would be well known to the skilled person in the art. Closed cell thermal modification processes are also suitable for use as a thermal modification process. Such closed cell systems, as offered, by way of example, by Wood Treatment Technology™, would be known to those of skill in the art. In one embodiment, closed cell thermal modification is carried out at between 150°C and 190°C, more preferably 160-180°C. At 180 to 240°C the look of Western Red Cedar and Tropical Hardwoods is achieved. Elevated temperatures can result in a decrease in structural integrity of the wood. Thus, while higher temperatures may result in a more desirable darker colour, the resultant loss of structural integrity dictates the final applications for which the wood can be used. Thermal modification is preferably carried out over a period of between about 1 day and about 4 days, more preferably over 3 days to give a completely coloured and dried product (approximately 6-8% moisture content). 2025203983   28 May 2025 In one embodiment, the thermal modification of the wood in Step A provides preservative properties to the thermally modified wood. In particular, the thermally modified wood produced in Step A has increased resistance to degradation by fungi, insects, bacteria and / or algae. The use of thermal modification instead of a chemical preservative compound treatment provides advantages to the user including: • reduced cost of treatment and preservative compounds; • reduced toxicity to animal / human health; and • reduced toxicity to other species and therefore lower environmental impact. In one embodiment, the Step A. comprises: i. drying the wood to produce a dried wood with a moisture content of less than about 1%, less than about 0.5%, less than about 0.2%, less than about 0.1%, or substantially 0%; followed by ii. heating the dried wood until it reaches about 160°C to 260°C; followed by iii. maintaining the wood at the temperature in step ii. for a period of about 1 to 6 hours or for a period of time sufficient to cause at least 4% mass loss; followed by iv. allowing the wood to cool; followed by v. reconditioning the wood with steam and / or water until the moisture content of the wood is about 7%, to produce a thermally modified wood. In one embodiment, Step A. comprises: i. drying the wood to produce a dried wood with a moisture content of less than 1%, less than 0.5%, less than 0.2%, less than 0.1%, or substantially 0%; followed by ii. heating the dried wood until it reaches about 180°C to 260°C; followed by iii. maintaining the wood at the temperature in step ii. for a period of about 1 to 6 hours or for a period of time sufficient to cause at least 4% mass loss; followed by 2025203983   28 May 2025 iv. allowing the wood to cool; followed by v. reconditioning the wood with steam and / or water until the moisture content of the wood is about 7%, to produce a thermally modified wood. In one embodiment, Step A. comprises: i. drying the wood to produce a dried wood with a moisture content of substantially 0%; followed by ii. heating the dried wood until it reaches about 200°C to about 260°C; followed by iii. maintaining the wood at the temperature in step ii. for a period of about 1 to 6 hours, or a period of time sufficient to cause at least 4% mass loss; followed by iv. allowing the wood to cool to a temperature below about 140°C, about 135°C, about 130°C, about 125°C, about 120°C, about 115°C, about 110°C, about 105°C, about 100°C, about 95°C, about 90°C, about 85°C, about 80°C, about 75°C, about 70°C, about 65°C, about 60°C, about 55°C, about 50°C, about 40°C, about 45°C 30°C, about 35°C or about 20°C, or until the wood reaches an ambient temperature; followed by v. reconditioning the wood with steam and / or water until the moisture content of the wood is about 7%, to produce a thermally modified wood. In one embodiment, Step A. comprises: i. drying the wood to produce a dried wood with a moisture content of substantially 0%; followed by ii. heating the dried wood until it reaches about 200°C to about 260°C; followed by iii. maintaining the wood at the temperature in step ii. for a period of about 1 to 6 hours, or a period of time sufficient to cause at least about 4% mass loss; followed by iv. allowing the wood to cool to a temperature below about 140°C, about 135°C, about 130°C, about 125°C, about 120°C, about 115°C, about 110°C, about 105°C, about 100°C, about 95°C, about 90°C, about 85°C, about 80°C, about 75°C, about 70°C, about 65°C, about 60°C, about 55°C, about 50°C, about 40°C, about 45°C 30°C, about 35°C or 2025203983   28 May 2025 about 20°C, or until the wood reaches an ambient temperature; followed by v. reconditioning the wood with steam and / or water until the moisture content of the wood is about 7%, to produce a thermally modified wood. In one embodiment, Step A. comprises: i. drying the wood to produce a dried wood with a moisture content of substantially 0%; followed by ii. heating the dried wood until it reaches about 200°C to 240°C; followed by iii. maintaining the wood at the temperature in step ii. for a period of about 2 to about 4 hours, or a period of time sufficient to cause at least about 4% mass loss; followed by iv. allowing the wood to cool to a temperature of below about 140°C, about 135°C, about 130°C, about 125°C, about 120°C, about 115°C, about 110°C, about 105°C, about 100°C, about 95°C, about 90°C, about 85°C, about 80°C, about 75°C, about 70°C, about 65°C, about 60°C, about 55°C, about 50°C, about 40°C, about 45°C 30°C, about 35°C or about 20°C, or until the wood reaches an ambient temperature; followed by v. reconditioning the wood with steam until the moisture content of the wood is about 7%, to produce a thermally modified wood. In one embodiment, Step A. comprises: i. drying the wood to produce a dried wood with a moisture content of substantially 0%; followed by ii. heating the dried wood until it reaches about 230°C; followed by iii. maintaining the wood at the temperature in step ii. for a period of about 2 to about 4 hours, preferably about 3 hours, or a period of time sufficient to cause at least 4% mass loss; followed by 2025203983   28 May 2025 iv. allowing the wood to cool to a temperature below about 140°C, about 135°C, about 130°C, about 125°C, about 120°C, about 115°C, about 110°C, about 105°C, about 100°C, about 95°C, about 90°C, about 85°C, about 80°C, about 75°C, about 70°C, about 65°C, about 60°C, about 55°C, about 50°C, about 40°C, about 45°C 30°C, about 35°C or about 20°C, or until the wood reaches an ambient temperature; followed by v. reconditioning the wood with steam until the moisture content of the wood is about 7%, to produce a thermally modified wood. Optionally wherein the reconditioning of the wood in v. of Step A occurs at about 155°C, about 150°C, about 140°C, about 135°C, about 130°C, about 125°C, about 120°C, about 115°C, about 110°C, about 105°C, about 100°C, about 95°C, about 90°C, about 85°C, about 80°C or 75°C. Without being bound by theory, the inventors believe that the thermal modification process described herein opens the fibres of the wood by burning off the hemicellulose and resins in the wood, making the structure of the wood more porous and permeable to impregnation with the resin and fire retardant. This facilitates the deep impregnation and curing process of the thermosetting resin and fire retardant, and accommodates the drying and curing steps of the methods. Thermally modifying the wood according to the methods described herein likely contributes to the enhanced penetration of the resin / fire retardant, when compared to penetration of resin / fire retardant in non-thermally modified wood. In one embodiment described herein, the methods enhance the penetration of the thermosetting resin and fire retardant into the wood. The method comprises a Step B of impregnating the thermally modified wood with a thermosetting resin and a fire retardant to produce an impregnated thermally modified wood, wherein the impregnating comprises: i. applying a vacuum of about -90 to -95kPa to the thermally modified wood; followed by 2025203983   28 May 2025 ii. flooding the thermally modified wood with the thermosetting resin and the fire retardant while maintaining the vacuum of about -90 to about -95 kPa; followed by iii. applying a pressure of about 900 to about 1400kPa. A person skilled in the art will readily be able to determine suitable fire retardants. A ‘fire retardant’ may refer to a substance that slows and / or stops a fire starting and / or spreading, and / or a substance that reduces the intensity of a fire. In one embodiment, the fire retardant is a hygroscopic fire retardant. In one embodiment, the fire retardant is a water soluble hygroscopic fire retardant. For example, but not limited to, the fire retardant may be selected from the fire retardants described in Sauerbier, P et al., (2020). Fire Retardant Treatment of Wood - State of the Art and Future Perspectives. In: Makovicka Osvaldova, L., Markert, F., Zelinka, S. (eds) Wood & Fire Safety. WFS 2020. Springer, Cham. https: / / doi.org / 10.1007 / 978-3-030-41235-7_14. A person skilled in the art will also readily be able to determine thermosetting resins suitable for impregnation into wood. In one embodiment, the resin is a thermosetting water borne polymer resin. In one embodiment, the resin is a thermosetting water soluble polymer resin. In one embodiment, the resin is a thermosetting phenolic, melamine, urea-formaldehyde or isocyanate resin. In one embodiment, the resin is a phenolic resin. Step B involves using pressure to force the resin and fire retardant into the wood. This increases the fire resistance, stability, durability and / or surface hardness characteristics of the wood. Colour may also be modified by using this technique. In one embodiment, the thermosetting resin and fire retardant are applied simultaneously. In one embodiment, the thermosetting resin is a composition comprising the fire retardant. Where thermosetting resins are used, drying and curing can take a long time and the high temperature required can compromise product quality, damaging the wood structure and physical aspects such of loss of strength, deformation and wet core. This can result in timber products with wood distortions and deformations, such as cupping. The inventors have 2025203983   28 May 2025 surprisingly found that thermally modifying the wood prior to Step B (i.e. in accordance with Step A. described herein) achieves a relatively short drying and curing cycle, and a high-quality fire-resistant wood product free from wood distortions or deformations. Another problem encountered by the inventors when using thermally modified wood, was resin seeping out of the wood during the drying / curing step. The inventors surprisingly found that applying a large vacuum of -90 to -95kPa prior to flooding the thermally modified wood with the thermosetting resin and fire retardant, followed by application of a high pressure of about 1100 to 1400kPa, addressed this problem. Accordingly, in a particular embodiment, the Step B comprises a step of applying a vacuum of -90 to -95 kPa to the thermally modified wood for about 20 to 40 minutes before flooding the thermally modified wood with the thermosetting resin and fire retardant. Without being bound by theory, the inventors believe that the large vacuum in Step B may contribute to the enhanced penetration of the resin / fire retardant into the wood. In one embodiment, the Step B comprises: i. applying a vacuum of -90 to -95 kPa to the thermally modified wood for about 20 to 40 minutes, preferably about 30 minutes; followed by ii. flooding the thermally modified wood with the thermosetting resin and fire retardant while maintaining the vacuum of about -90 to -95 kPa; followed by iii. applying a pressure of 1100 to 1400 kPa for 1 to 2 hours, preferably about 1 hour; iv. removing excess thermosetting resin and fire retardant; followed by v. applying a final vacuum of 85kPa for 10 to 20 minutes, preferably about 15 minutes to produce an impregnated thermally modified wood. In one particular embodiment, Step B comprises: i. applying a vacuum of -90 to -95 kPa to the thermally modified wood for about 30 minutes; followed by ii. flooding the thermally modified wood with the thermosetting resin and fire retardant while maintaining the vacuum of about -90 to -95 kPa; followed by iii. applying a pressure of 1100 to 1400 kPa for about 1 hour; followed by 2025203983   28 May 2025 iv. removing excess thermosetting resin and fire retardant; followed by v. applying a final vacuum of 85kPa for about 15 minutes to produce an impregnated thermally modified wood. Conventional vacuum / pressure vessels that has been specifically designed for the resin impregnation of timber could be used for Step B. Such conventional vacuum / pressure vessels, as offered, by way of example, by CT Engineering Services, Crusader Engineering Limites or IWT-Moldrup, would be well known to the skilled person. The high temperatures used during thermal modification or curing of thermoset resins can cause wood to warp or lose of strength. Wood warping can be caused by collapse of cells within the wood, for example, when stresses caused by high temperatures are so strong that cell wall structures are unable to stand up to the forces. Wood warping includes cupping, bowing, crooking, twisting and diamonding. Cupping is distortion of a board where there is deviation flatwise from a straight line across the width of a board. The greater the deviation the greater the cup. The inventors surprisingly found that the combination of thermal modification, impregnation with a resin and fire retardant, and drying / curing described herein, reduced cupping of the fireresistant wood product, added strength back into the wood fire-resistant product and increased the density of the fire-resistant wood product. In one embodiment, the methods described herein are for manufacturing a fire-resistant wood product with no cup or a reduced cup. The inventors also surprisingly found that the methods of the invention produce a fire-resistant wood product with reduced leaching of the fire retardant chemical. The fire-resistant wood product described herein retains the high performing hygroscopic retardant chemical within the wood, for example, locking in the fire retardant chemical for the duration of the lifetime of a building structure. In one embodiment, the methods described herein reduce the leaching of the fire retardant from the fire-resistant wood product during the lifetime of a building structure. 2025203983   28 May 2025 The fire-resistant wood product described herein has increased fire resistance compared to wood that has not been treated and / or impregnated with a fire retardant chemical. In one embodiment, the fire-resistant wood product described herein has a decreased heat release rate, flame spread, smoke or droplets compared to wood that has not been impregnated with a fire retardant. A wood product being “fire resistant” means a wood product with a minimum fire rating of ASTM E84 Class A, AS3959 BAL29 (Australian Standard 3959), and / or EN 13501-1 Euro Class B (European Standard 13501-1). In one embodiment, the fire-resistant wood product described herein has a minimum fire rating of ASTM E84 Class A, as measured in accordance with the ASTM E84-23d test methods. In one embodiment, the fire-resistant wood product has a minimum flame spread and / or a maximum smoke development rating of ASTM E84 Class A, when measured in accordance with the ASTM E84-23d test methods. In one embodiment, the fire-resistant wood product has a minimum flame spread of 0 to 25 and / or a maximum smoke development rating of 450, as measured in accordance with the ASTM E84-23d test methods. ASTM E84, Australian Standard 3959 and European Standard 13501-1 are standard test methods that would be well known to the skilled person in the art. For example, ASTM E84 (E84) is a standard test method used to assess the surface burning characteristics of a material used for interior wall and ceiling finishes. E84 results are measured by Flame Spread Index (SFI) and Smoke Developed Index (SDI). The methods comprise a Step C. comprising drying the impregnated thermally modified wood. Step C comprises heating the wood to about 50°C to 150°C, for a period of time. In one embodiment, Step C comprises heating the wood to about 50°C to about 150°C, for a period of time sufficient for the wood to reach an equilibrium moisture content (EMC) of about 6.5% to about 8%. In one embodiment, the period of time is sufficient for the wood to reach an EMC of about 6%, 7% or 8%. In one embodiment, the period of time is sufficient for the wood to reach an EMC of about 7.1%, about 7.2% , about 7.3% , about 7.4% , about 7.5% , about 7.6% , about 7.7% , about 7.8%, about 7.9% or about 8%. Unless stated otherwise, the EMC calculated 2025203983   28 May 2025 according to the European Standard EN 13183-1:2002 and is measured at 20°C ambient temperature and 65% relative humidity. In one embodiment, Step C comprises heating the wood to about 50°C to 150°C, for a period of 20 to 150 hours. In one embodiment, Step C comprises heating the wood to about 50°C to 100°C, for a period of about 20 hours, about 30 hours, about 40 hours, about 50 hours, about 60 hours, about 70 hours, about 80 hours, about 90 hours, about 100 hours, about 110 hours, about 120 hours, about 130 hours, about 140 hours or about 150 hours. Step C comprises heating the wood to about 50°C to about 150°C, for a period of time sufficient for the resin to cure. Step C is carried out in conventional high-temperature kilns. The kiln used for Step C could be the same or a different kiln as that used for the thermal modification Step (Step A). For example, a kiln system that has been specifically designed for the elevated temperatures associated with thermal modification could be used for the drying and curing Step C. Such kilns, as offered, by way of example, by Jartek™ or Stellac™, would be well known to the skilled person in the art. Other suitable dying kilns, as offered, by way of example, by Windsor™ or Mahild™, would be well known to the skilled person in the art. Closed cell thermal modification processes are also suitable. Such closed cell systems, as offered, by way of example, by Wood Treatment Technology™, would be known to those of skill in the art. The combination of the thermal modification, impregnation with a resin and fire retardant and the drying and curing Step results in a superior fire-resistant wood product. Following the drying and curing step, the wood achieves 100% resin curing and achieves the correct equilibrium of moisture content to lock in fire retardant chemicals (preventing leaching of the fire retardant over time). In one embodiment, the methods described herein enhance the performance of coatings. The inventors have found that the methods of the invention enhance the long term weatherability of coatings. In one embodiment, the methods described herein are for enhancing the performance of a coating applied to the fire-resistant wood product. 2025203983   28 May 2025 In one embodiment, the methods described herein comprise a step of applying a coating to the surface of the wood after the Step C. In one embodiment, the coating may be applied to the surface of the wood by brush, roller or spray after the Step C. In one embodiment, the methods described herein comprise applying a coating or pigment in Step B. Accordingly, in one embodiment Step B comprises contacting the thermally modified wood resulting from Step A with the thermosetting resin, the fire retardant and a pigment or coating. In one embodiment, the thermosetting resin, the fire retardant and the coating or pigment are applied simultaneously. In one embodiment, the thermosetting resin is a composition comprising the fire retardant and coating or pigment. In one embodiment, the coating is a water-borne coating, a penetrating oil, erosion stain, semitransparent acrylic, paint or stain. In one embodiment the coating is a water borne coating. In one embodiment the coating is a water borne coating that is synergistically compatible with the resin. In one embodiment, the coating is a waterborne coating comprising water, refined plant oil, medium oil alkyd, zinc & lead free driers, low volatile organic compound (VOC) co-solvent, mouldicide and an earth oxide pigment. In one embodiment, the methods further comprise modifying or preservative treating the wood prior to Step A. In one embodiment, the preservative treatment prior to Step A is Light Organic Solvent Preservative (LOSP), Copper Quaternary, Alkaline copper quaternary (ACQ), Chromated copper arsenate (CCA) minimum UC3A (American Wood Protection Association - AWPA), water based azoles, optionally with added insecticide and / or water repellent, Micronized Copper Azole (MCA), copper naphthenate or equivalent. In one embodiment, the modification prior to Step A is densification, thermo-mechanical densification, acetylation, furfylation, resin impregnation, Dimethyloldihydroxyethelenurea (DMDHEU) modification, alkaline copper quaternary (ACQ) modification, copper azole treatment and / or combinations thereof. 2025203983   28 May 2025 In one embodiment, the methods further comprise modifying or preservative treating the wood after Step C. In one embodiment, the preservative treatment after Step C is Light Organic Solvent Preservative (LOSP), Copper Quaternary, Alkaline copper quaternary (ACQ), Chromated copper arsenate (CCA) minimum UC3A (American Wood Protection Association - AWPA), water based azoles, optionally with added insecticide and / or water repellent, Micronized Copper Azole (MCA), copper naphthenate or equivalent. In one embodiment, the modification after Step C is densification, thermo-mechanical densification, acetylation, furfylation, resin impregnation, Dimethyloldihydroxyethelenurea (DMDHEU) modification, alkaline copper quaternary (ACQ) modification, copper azole treatment and / or combinations thereof. In one embodiment, the fire-resistant wood product is a fire-resistant timber product. In one embodiment, the fire-resistant timber product has an increased fire resistance or minimum fire resistance, as described above with respect to the fire resistance wood product. The fire-resistant timber product of the invention may be suitable for use in interior applications or for use in long term external applications. Interior applications include placement of the timber in wall panelling, flooring or ceiling panelling. Long term external applications include placement of the fire-resistant timber product where some part or all of the timber product is exposed to the outdoors / weather for about 2, about 3, about 6, about 12, about 18, about 24 or more months. In one embodiment, the fire-resistant timber product of the invention is suitable for use in an external application for greater than 12 months, greater than 18 months or greater than 24 months. In one embodiment, the fire-resistant timber product is suitable for the end use application including weatherboard cladding, shiplap, tongue and groove, square dressed, rhombus, decking or screening. In one embodiment, the timber product may be a board, panel or post. In one embodiment, the wood and / or the fire-resistant timber product is a cladding or decking board of about 140x18mm, about 140x27mm or about 90x20mm dimension or about 180x20mm (width x height). In one embodiment, wood and / or the fire-resistant timber product 2025203983   28 May 2025 is a cladding or decking board of about 70-290 x 17-32 mm or a panel of about 15-25 mm thick x 600-1200 mm width x 2400-6000 mm length. In one embodiment, the fire-resistant timber product comprises band sawn, brushed, textured or smooth dressed faces. The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference. Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world. 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. Wherein the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth. It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the scope of the invention. Examples Example 1 Three Pinus radiata wood samples were prepared (samples A, B and C) as outlined below. 2025203983   28 May 2025 For samples A, B and C, kiln dried (to about 12% moisture content) Pinus radiata wood samples were obtained. For sample A the Pinus radiata wood sample was thermally modified according to the following schedule: • dried until the wood reached a moisture content of substantially 0%; • heated until the wood reached about 230°C; • maintained the wood at about 230°C for a period of about 3 hours; • allowed the wood to cool to ambient temperature; and • reconditioned with steam until the moisture content of the wood is about 7%. The samples B, C and thermally modified sample A, were then treated with the same thermosetting resin (melamine) and hygroscopic fire retardant, according to the following schedule: • applying a vacuum of -90 to -95 kPa for 30 minutes; • flooding with the thermosetting resin and hygroscopic fire retardant; • applying a pressure of 1100 to 1400 kPa for 1 hour; • draining excess thermosetting resin and hygroscopic fire retardant; and • applying a final vacuum of 85kPa for 15 minutes. Samples A, B and C were then dried in a conventional high temperature kiln at a temperature of about 50°C to about 150°C, for a period of 20 to 50 hours. Figure 1 shows a photo of samples A, B and C taken after they were processed according to the method outlined above. Samples B and C had significant cell collapse, as evidenced by the warping and cupping of the board cross-sections. In contrast, sample A shows no evidence of cupping or cell collapse, with the cross-section of the board remaining straight. Example 2 Three Pinus radiata wood samples were prepared (samples A, B and C) as outlined below. 2025203983   28 May 2025 For samples A and C, a Pinus radiata wood sample was obtained and thermally modified according to the following schedule: • dried until the wood reached a moisture content of substantially 0%; • heated until the wood reached about 230°C; • maintained the wood at about 230°C for a period of about 3 hours; • allowed the wood to cool to ambient temperature; and • reconditioned with steam until the moisture content of the wood is about 7%. For sample B, a Pinus radiata wood sample was obtained and thermally modified according to the following schedule: •  dried until it reached a moisture content of substantially 0%; •  heated until it reached about 220°C; • maintained at about 220°C for a period of about 3 hours; • allowed to cool; and • reconditioned with steam until the moisture content of the wood is about 7%. Sample A was then treated with a thermosetting resin (melamine) and hygroscopic fire retardant, according to the following schedule: • applying a vacuum of -90 to -95 kPa for 30 minutes; • flooding with the thermosetting resin and hygroscopic fire retardant; • applying a pressure of 1100 to 1400 kPa for 1 hour; • draining excess thermosetting resin and hygroscopic fire retardant; and • applying a final vacuum of 85kPa for 15 minutes. Sample A was then dried in a conventional high temperature kiln at a temperature of about 50°C to about 150°C, for a period of 20 to 50 hours. A water borne penetrating timber finish was applied to each sample A, B and C. The specific water born penetrating timber finish used was ‘Abodo Protector” in the colour “Manuka” (comprises water, refined plant oil, medium oil alkyd, zinc & lead free driers, low VOC cosolvent, mouldicide, and earth oxide pigment). 2025203983   28 May 2025 Figure 2 shows a photo of samples A, B and C taken after they were processed according to the method outlined above and left outside to weather for about 24 months. Samples B and C had significant weathering and peeling of the coating. In contrast, the coating on sample A shows no peeling or degradation of the coating surface. Example 3 Two Pinus radiata wood samples were prepared (samples A and B) as outlined below. For samples A and B, Pinus radiata wood samples were obtained and thermally modified according to the following schedule: • dried until the wood reached a moisture content of substantially 0%; • heated until the wood reached about 230°C; • maintained the wood at about 230°C for a period of about 3 hours; • allowed the wood to cool to ambient temperature; and • reconditioned the wood with steam until the moisture content of the wood is about 7%. Samples A and B were then treated with a thermosetting phenolic resin and hygroscopic fire retardant, according to the following schedule: • applying a vacuum of -90 to -95 kPa for 30 minutes; • flooding with the thermosetting phenolic resin and hygroscopic fire retardant; • applying a pressure of 1100 to 1400 kPa for 1 hour; • draining excess thermosetting phenolic resin and fire retardant; and • applying a final vacuum of 85kPa for 15 minutes. Samples A and B were then dried in a conventional high temperature kiln at a temperature of about 50°C to about 150°C, for a period of 20 to 50 hours. 2025203983   28 May 2025 Sample B was then factory coated with Abodo ProtectorTM (ingredients: water, refined plant oil, medium oil alkyd, zinc & lead free driers, low VOC co-solvent, mouldicide, earth oxide pigment) in the colour Nero. Both samples A and B were then tested in accordance with the 2021 International Building Code (IBC) Section 2303.2 following ASTM E84 and ASTM E2768-11(2018) extended an additional 20 minutes. Flame spread and smoke reading results are shown in Figure 3 for sample A and in Figure 4 for sample B. Both samples resulted in a Class A during the first 10 minutes of testing. When compared to sample A, sample B had a lower flame spread result. Example 4 Another Pinus radiata sample was prepared in accordance with the method set out for sample A in Example 3 above. Following processing, the Pinus radiata sample had a density of 696.3 kg / m3 (+ / - 21.4 kg / m3) and an EMC% of 7.5% (+ / - 0.3%), when measured at 20°C ambient temperature and 65% relative humidity.

Claims

1. A method of manufacturing a fire resistant wood product, wherein the method comprises:A. heating wood to a temperature of about 180°C to about 260°C to produce thermally modified wood;B. impregnating the thermally modified wood with a thermosetting resin and a fire retardant to produce an impregnated thermally modified wood, wherein the impregnating comprises:i. applying a vacuum of about -90 to -95kPa to the thermally modified wood; followed byii. flooding the thermally modified wood with the thermosetting resin and the fire retardant while maintaining the vacuum of about -90 to about -95 kPa; followed byiii. applying a pressure of about 900 to about 1400kPa, andC. drying the impregnated thermally modified wood, to produce a fire-resistant wood product.

2. The method of claim 1, wherein the method further comprises a step of applying a coating to the surface of the fire-resistant wood product.

3. The method of any one of the preceding claims, wherein Step B comprises impregnating the thermally modified wood with a composition comprising the thermosetting resin, the fire retardant and a coating or pigment.

4. The method of claim 2 or claim 3, wherein the coating is a water borne coating.

5. The method of any one of the preceding claims, wherein Step A comprises heating thewood to a temperature of at least about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C or about 260°C, to produce thermally modified wood.2025203983   28 May 20256. The method of any one of the preceding claims wherein Step A comprises heating the wood to a temperature of about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C or about 260°C, preferably about 210°C to about 235°C, to produce thermally modified wood;.

7. The method of any one of the preceding claims, wherein Step A. comprises:i. drying the wood to produce a dried wood with a moisture content of less than about 1%, less than about 0.5%, less than about 0.2%, less than about 0.1%, or substantially about 0%;ii. heating the dried wood until it reaches a temperature of about 180°C to about 260°C; followed byiii. maintaining the wood at the temperature in ii. of Step A for a period of about 1 to about 6 hours; followed byiv. allowing the wood to cool; followed byv. reconditioning the wood with water and / or steam until the moisture content of the wood is about 7%,to produce a thermally modified wood.

8. The method of claim 7 wherein the moisture content in i. of Step A is substantially 0%.

9. The method of claim 7 or claim 8, wherein the temperature in ii. of Step A is about 200°C,about 210°C, about 220°C, about 230°C, about 240°C, about 250°C or about 260°C, preferably about 210°C to 230°C.

10. The method of any one of claims 7 to 9 wherein the period in iii. of Step A is about 2 to about 4 hours.

11. The method of claim 10, wherein the period in iii. of Step A is about 1, 2, 3, 4, 5 or 6 hours, preferably wherein the period in step iii. is about 3 hours.2025203983   28 May 202512. The method of any one of the preceding claims, wherein the fire retardant is a hygroscopic fire retardant.

13. The method of any one of the preceding claims, wherein the thermosetting resin is a phenolic resin or melamine resin.

14. The method of any one of the preceding claims, wherein the vacuum in ii. of Step B. is maintained for about 20 to about 40 minutes.

15. The method of any one of the preceding claims wherein the vacuum in ii. of Step B. is maintained for about 30 minutes.

16. The method of any one of the preceding claims wherein the pressure in iii. of Step B. is from about 1100 to about 1400kPa.

17. The method of any one of the preceding claims, wherein Step B. comprises:i. applying a vacuum of -90 to -95 kPa to the thermally modified wood for about 20 to 40 minutes, preferably about 30 minutes; followed byii. flooding the thermally modified wood with the thermosetting resin and the fire retardant while maintaining the vacuum of about -90 to -95 kPa; followed byiii. applying a pressure of about 1100 to about 1400 kPa for about 1 to about 2 hours, preferably about 1 hour; followed byiv. removing excess thermosetting resin and a fire retardant; followed byv. applying a final vacuum of about 85kPa for about 10 to about 20 minutes, preferably about 15 minutes.

18. The method of any one of the preceding claims, wherein the drying in Step C comprises heating the wood to about 50°C to about 150°C19. The method of any one of the preceding claims, wherein the drying in Step C comprises heating the wood to a temperature of about 50°C to about 150°C, for a period of time2025203983   28 May 2025sufficient for the wood to reach an equilibrium moisture content (EMC) of from about 7% to about 8%.

20. The method of any one of the preceding claims wherein the wood is selected from the groups consisting of Pinus species (pine), ash, maple, beech, poplar, birch, aspen, rubber wood, cedar, redwood, Douglas fir, cypresses, spruce, larch, eucalyptus, western red cedar, yellow cedar, ayous, frake and teak.

21. The method of any one of the preceding claims wherein the wood has Class 4 or lower durability (EN350) or equivalent.

22. The method of any one of the preceding claims wherein the wood is Pinus species (pine), Douglas fir, poplar or rubber wood.

23. The method of any one of the preceding claims wherein the wood is southern yellow pine, scots pine or Pinus radiata.

24. The method of any one of the preceding claims wherein the fire-resistant wood product has a minimum fire rating of ASTM E84 Class A.

25. The method of any one of the preceding claims wherein the method is for preventing warping of the fire-resistant wood product, preventing cupping of the fire-resistant wood product, enhancing the penetration of the fire retardant and the resin into the thermally modified wood, for reducing leaching of a fire retardant from the fire-resistant wood product and / or for enhancing the performance of a waterborne coating applied to the fire-resistant wood product.

26. A fire-resistant wood product produced by the method of any one of the preceding claims.

27. A fire-resistant timber product comprising the fire-resistant wood product of claim 26.2025203983   28 May 202528. The fire-resistant timber product of claim 27, suitable for end use application as weatherboard cladding, wall / ceiling panelling, shiplap, tongue and groove, square dressed, rhombus, flooring, decking or screening.

29. The fire-resistant timber product of claim 27 wherein the product is a board, panel, beam or post.

30. The fire-resistant timber product of claim 27 wherein the timber product is a cladding or decking board of about 70-290 x 17-32 mm or a panel of about 15-25 mm thick x 6001200 mm width x 2400-6000 mm length.

31. The fire-resistant timber product of claim 27 wherein the timber product comprises band sawn, brushed, textured or smooth dressed faces.

32. A fire-resistant wood product produced by the method of any one of claims 1 to 25, as described with reference to any one of Figures 1 to 4.

33. A fire-resistant timber product comprising the wood produced by the method of any one of claims 1 to 25, suitable for use on windows and doors.

Images