WO2025117298A1 - Fire-retardant composition and wood product - Google Patents

Abstract

The invention relates to a composition comprising: (a) a water-soluble thermosetting resin; and (b) a water-soluble fire-retardant, wherein the composition has a resin: fire-retardant ratio range of 1:2 to 2:1. The invention also relates to a fire-retardant wood product comprising the composition, a method for producing a fire-retardant wood product comprising the composition, and a kit for preparing the composition, comprising: (a) a water-soluble thermosetting resin; and (b) a water-soluble fire-retardant.

Description

FIRE-RETARDANT COMPOSITION AND WOOD PRODUCT

RELATED APPLICATION DATA

[0001] This application claims benefit to U.S. Provisional Application No. 63/603861, tiled November 29, 2023, of which the entire contents of the application are incorporated by reference herein.

FIELD

[0002] The invention relates to a fire-retardant composition, a fire-retardant wood product comprising the composition, a method for producing a fire-retardant wood product comprising the composition, and a kit for preparing the composition.

BACKGROUND

[0003] Several engineered wood products have been developed over the years with improved properties and resistance to natural decay. However, despite these advances in wood technology, progress on providing a reliable fire-retardant wood product has been rather slow. The increase in wild fires in different parts of the world has emphasised the need to have a reliable fire-retardant composition that could be used to modify the properties of wood products. However, the solution to this problem must not come at a cost of lowering the aesthetic value of the wood product or by compromising the overall structural properties of the wood product.

[0004] Existing fire-retardant technology can be classified into two categories: (i) coatings that can be sprayed or applied on the surface of the wood product; and (ii) formulations that can be impregnated into the wood cell structures. However, there are certain limitations to the existing products. Coated products are not durable, as coatings are washed off due to weathering, thereby reducing functionality and aesthetic appeal of the product. On the other hand, existing impregnation formulations provide limited fire-retardancy and leaching of the fire-retardant is a common problem, thereby reducing the effectiveness, over time, and posing environmental concerns.

[0005] US 8642184 B2 discloses an oriented strand board (OSB) having a middle layer of wood flakes adjacent two outer layers of wood flakes. The middle layer comprises a guanidine salt fire-retardant at 5% to 25% w:w dry weight of the wood flakes. At least one outer layer may comprise the guanidine salt fire-retardant at 4% to 15% w:w dry weight of the wood flakes. US 8642184 B2 does not consider the problem of fire-retardant leaching.

[0006] WO 2016123655 Al (NZ 734108) discloses improved creosote formulations for wood preservation. Use of a fire-retardant is disclosed generally, but no fire-retardant is disclosed specifically.

[0007] US 2013/0298814 Al discloses production of thermally modified wood that may be impregnated with a melamine resin. US 2013/0298814 Al teaches against the use of fire protection adjuvants.

[0008] CN 102277789 relates to the field of papermaking. It discloses a fire-resistant carbon fibre electrothermal paper comprising fire-retardant at 15% to 30% of carbon fibre paper weight. The fire-retardant may be a guanidine salt. CN 102277789 does not consider the problem of fire-retardant leaching.

[0009] AU 2019222962 Al (NZ 710843, NZ 766816, AU 2020281173) discloses a flame-retardant modified wood produced using an alkali metal-based flame-retardant that is chemically fixed in the wood product using a heat process. AU 2019222962 Al does not consider the problem of fire-retardant leaching.

[0010] Accordingly, there is a need for an improved fire-retardant composition for wood products that addresses the problem of fire-retardant leaching from the wood product.

[0011] It is to be understood that if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art in any country.

SUMMARY

[0012] The invention relates to a fire-retardant composition for impregnating a wood product. The composition comprises a water-soluble thermosetting resin and a water-soluble fire-retardant in a specific ratio. While not wishing to be bound by theory, it is apparent that the thermosetting resin, when set, reduces leaching of the fire-retardant from the wood product, thereby resulting in a weatherproof treatment solution for wood products with improved fire- retardancy. Advantageously, a residual composition from one manufacturing process may be reused to manufacture further fire-retardant wood products in subsequent manufacturing processes. [0013] A first aspect provides a composition comprising:

(a) a water-soluble thermosetting resin; and

(b) a water-soluble fire-retardant, wherein the composition has a resimfire-retardant ratio range of 1 :2 weightweight to 2: 1 weight: weight.

[0014] A second aspect provides a fire-retardant wood product comprising the composition of the first aspect, wherein the wood product is selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood.

[0015] A third aspect provides a method for producing a fire-retardant wood product, comprising:

(i) impregnating a wood product selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood with (a) a solution of a water-soluble thermosetting resin and (b) a solution of a water-soluble fire-retardant in amounts to provide a resimfire-retardant ratio in the range of 1 :2 weightweight to 2: 1 weight:weight ; and

(ii) heating the impregnated wood product to a temperature sufficient to set the thermosetting resin.

[0016] A fourth aspect provides a kit comprising:

(a) a water-soluble thermosetting resin; and

(b) a water-soluble fire-retardant, wherein the thermosetting resin and fire-retardant are selected from the group consisting of:

(i) dry solids in amounts to provide a resimfire-retardant ratio in the range of 1:2 weight:weight to 2: 1 weight:weight;

(ii) one or more solution in amounts to provide a resimfire-retardant ratio in the range of 1:2 weightweight to 2: 1 weightweight;

(iii) a dry solid and a solution in amounts to provide a resimfire-retardant ratio in the range of 1:2 weightweight to 2: 1 weightweight.

[0017] Advantageously, the invention provides sufficient and uniform impregnation of the fire-retardant and resin into the wood product, while avoiding of separation of the two components. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 plots leach analysis data for cured and powdered (resin:fire-retardant) (R/FR) composition according to Example 6.

DETAILED DESCRIPTION

[0019] The present invention is related to a fire-retardant composition for wood products that is water based and is easy to prepare and handle. Once prepared, residual composition can be reused multiple times by adjusting the pH from the final pH to the starting pH. The composition comprises a water-soluble thermosetting resin and a water-soluble fire- retardant. This combination reduces leaching of the fire-retardant from the wood product once the thermosetting resin has set. Thus, a wood product comprising the composition is a durable and sustainable solution for exterior cladding applications, for example. In addition, a wood product comprising the composition is also amenable to interior uses.

[0020] A first aspect provides a composition comprising:

(a) a water-soluble thermosetting resin; and

(b) a water-soluble fire-retardant, wherein the composition has a resin: fire-retardant ratio of 1 :2 to 2: 1 weightweight.

[0021] As used herein, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features, but not to preclude the presence or addition of further features in various embodiments of the invention.

[0022] In one embodiment, the water-soluble fire-retardant comprises a guanidine salt. Optionally, the guanidine salt may be guanidine sulfamate, guanidine sulfate, guanidine phosphate, guanidine carbonate, guanylurea phosphate, or a combination thereof.

[0023] As used herein, “fire-retardant” refers to a substance that inhibits, slows or stops a fire starting or spreading and/or reduces a fire’s intensity. Commonly, fire-retardants accomplish one or more of these effects through chemical reactions that reduce flammability of fuels or delay their combustion. Fire-retardants may also cool the fuel through physical action or endothermic chemical reactions.

[0024] In the context of the present invention, and without wishing to be bound by theory, it is thought that guanidine salts produce non-flammable gases, usually NH3 or N2, in the combustion process, which diffuse into the combustion zone, thus reducing the concentration of oxygen and gaseous fuel, thereby inhibiting gas phase combustion and thus producing fire-retardancy.

[0025] Fire-retardancy of the wood product of the disclosure may be assessed relative to a control wood product not comprising the composition of the disclosure. Fire-retardancy may be assessed according to ASTM E2768-11 standard, which is described in Example 4.

[0026] In one embodiment, the thermosetting resin is an amino-formaldehyde resin or a phenolic-formaldehyde resin.

[0027] Amino-formaldehyde resins (also known as aminoplasts) are a known class of resins, or polymers, based on the reaction product of formaldehyde with amino-functional molecules. Notable examples of amino-functional molecules used in the production of aminoformaldehyde resins are urea, melamine and combinations thereof. The amino-formaldehyde resin may, in some embodiments, be selected from the group consisting of urea formaldehyde (UF), melamine formaldehyde (MF), melamine urea formaldehyde (MUF), methylated melamine formaldehyde (MMF) or combinations of one or more thereof.

[0028] Phenolic-formaldehyde resins (also known as phenol-formaldehyde resins or phenolic resins) are a class of resins, or polymers, based on the reaction product of a phenol- based component and formaldehyde. By way of example, the phenol-based component may comprise one or more of phenol, resorcinol, alkyl-phenol (e.g. methylphenol), hydroxyalkyl phenols (e.g. hydroxymethyl phenol), or otherwise. In notable examples, the phenolic- formaldehyde resin is selected from the group consisting of phenol formaldehyde, phenol resorcinol formaldehyde, resorcinol formaldehyde, and combinations of one or more thereof.

[0029] In another embodiment, the thermosetting resin comprises phenol melamine urea formaldehyde (PMUF). This resin may be classified as both an amino-formaldehyde resin and a phenol-formaldehyde resin.

[0030] In the context of the present invention, and without wishing to be bound by theory, a thermosetting resin is a polymer obtained by hardening or curing a prepolymer or monomer. Hardening or curing is induced by heat, which may be from an external source and/or from an exothermic polymerisation reaction. Polymerisation, or thermosetting or simply setting, is irreversible. Herein, the term “set” may be used to refer to such hardening, curing, polymerisation and/or thermosetting. The water-soluble thermosetting resin according to the present disclosure is no longer water-soluble once set. It is this characteristic that is exploited in the present invention to reduce or prevent leaching of the fire-retardant from the wood product. Specifically, the thermosetting resin, when set, helps lock the fire-retardant into the cellular structure of the wood product. The drying cycle of the impregnated wood product carried out in an oven or kiln causes the resin to set or cure inside the wood product. This in turn also reduces or prevents the fire-retardant leaching from the wood product.

[0031] The invention addresses the issues of poor impregnation of high molecular weight resins and resins with poor water solubility. Low molecular weight resins, for example with MN <1000, may be advantageous in the invention, because they have improved impregnation into wood products.

[0032] The resin and fire-retardant must be compatible, and preferably maintain homogeneity in solution during impregnation. As such, the invention provides a system that impregnates the wood product well.

[0033] The invention also provides a system in which the resin cures well, which may be achieved by controlling temperature and/or pH. For instance, increasing the temperature cures the resin faster and this increased temperature may be achieved when the wood is dried. Alternatively/ additionally, reducing the pH will also hasten curing. Accordingly, it is advantageous if the fire-retardant solution has an alkaline pH. A further advantage of the invention is that residual or excess composition from the system is reusable provided the pH of the residual or excess composition is adjusted accordingly prior to reuse. Another advantage of the invention is that the system provides ready waste disposal by heating and/or reducing the pH of waste composition, thereby producing a solid for disposal.

[0034] The composition has a resin: fire-retardant ratio of 1 :2 weight:weight to 2:1 weight:weight. In some embodiments, the resimfire-retardant ratio is about 1: 1.9, about 1 : 1.8, about 1 :1.7, about 1:1.6, about 1 :1.5, about 1 :1.4, about 1 :1.3, about 1 :1.2, about 1 :1.1, about 1: 1, about 1.1:1, about 1.2: 1, about 1.3:1, about 1.4: 1, about 1.5:1, about 1.6:1, about 1.7:1, about 1.8:1, or about 1.9: 1. In some embodiments, the resin: fire-retardant ratio is 1 : 1.9, 1 :1.8, 1 :1.7, 1:1.6, 1 : 1.5, 1 : 1.4, 1 :1.3, 1:1.2, 1 : 1.1, 1:1, 1.1: 1, 1.2: 1, 1.3:1, 1.4:1, 1.5: 1, 1.6: 1, 1.7:1, 1.8:1, 1.9: 1, 2.1 : 1, 2.2:1, 2.3: 1, 2.4: 1 or 2.5: 1. A target range may fall between any lower and upper limit listed above, in any combination. Thus, the resimfire-retardant ratio may, for example, be between 1 :1.9 and 1.9:1, 1 :1.7 and 1.7:1, or 1 : 1.5 and 1.5: 1. [0035] As used herein, “about” refers to ±10% of the stated value. Alternatively, “about” refers to ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, or ±1% of the stated value. Where the stated value is expressed as a percentage, “about” refers to ±10%, ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, or ±1%. Where the stated value is a ratio, “about” refers independently to each part of the ratio.

[0036] For impregnating a wood product with the composition, the composition further comprises (c) water. As used herein, this composition comprising water may be referred to as a “treatment solution” or “impregnation solution”.

[0037] In one embodiment, the combined amount of thermosetting resin plus fire- retardant is 12% total solids content (TSC) in the treatment solution to 60% TSC in the treatment solution. In one embodiment, the combined amount of thermosetting resin plus fire- retardant is 20% TSC in the treatment solution to 40% TSC in the treatment solution.

[0038] A suitable combined amount of thermosetting resin plus fire-retardant may, in some embodiments, be at least 12%, at least 15%, at least 20%, at least 22.5%, at least 25%, at least 27.5%, or at least 30% TSC in the treatment solution. The combined amount of thermosetting resin plus fire-retardant may be at most 60%, at most 55%, at most 50%, at most 45%, at most 42.5%, or at most 40% TSC in the treatment solution. A target range for the combined amount of thermosetting resin plus fire-retardant in the composition may fall between any lower and upper limit listed, in any combination. Thus, the combined amount of thermosetting resin plus fire-retardant may, for example, be between 15% and 55%, between 20% and 50%, or between 22.5% and 42.5% TSC in the treatment solution.

[0039] In one embodiment, the combined amount of thermosetting resin plus fire- retardant may be 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%, about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%, about 32%, about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about 39%, about 40%, about 41%, about 42%, about 43%, about 44%, about 45%, about 46%, about 47%, about 48%, about 49%, about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, about 56%, about 57%, about 58%, about 59%, or about 60% TSC in the treatment solution. In one embodiment, the combined amount of thermosetting resin plus fire-retardant may be 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25% , 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60% TSC in the treatment solution.

[0040] In one embodiment, the composition has pH 7.5 to pH 10. In another embodiment, the composition has pH 8 to pH 9.5.

[0041] A suitable pH may, in some embodiments, be at least 7.5, at least 7.7, or at least 7.9 or higher. The pH may be at most 9.9, or at most 9.7, or at most 9.5. A target pH range may fall between any lower and upper limit listed, in any combination. Thus, the pH may, for example, be between 7.7 and 9.9, or 7.9 and 9.7, as examples.

[0042] The composition may have pH of about 7.5, about 7.6, about 7.7, about 7.8, about 7.9, about 8, about 8.1, about 8.2, about 8.3, about 8.4, about 8.5, about 8.6, about 8.7, about 8.8, about 8.9, about 9, about 9.1, about 9.2, about 9.3, about 9.4, about 9.5, about 9.6, about 9.7, about 9.8, about 9.9, or about 10. The composition may have pH 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10. [0043] The components of the composition may have a suitable pH that provides an overall composition pH that is within the target range. However, if required for the desired pH, the composition may comprise a pH adjustor. The pH adjustor may comprise a base, such as a hydroxide. The hydroxide may be added in the form of a hydroxide solution. The hydroxide solution may, for example, comprise an alkali or alkaline earth metal hydroxide or ammonium hydroxide, or a combination of such hydroxides.

[0044] The thermosetting resin and fire-retardant preferably constitutes at least 80%, at least 90%, at least 95% or at least 98% by weight of the non-water components of the fire- retardant composition.

[0045] A second aspect provides a fire-retardant wood product comprising the composition of the first aspect described above, wherein the wood product is selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood.

[0046] Expressed in alternative terms, the present application provides a fire-retardant wood product comprising: a wood product selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood; and an impregnated and set fire-retardant composition of the first aspect described above. [0047] In one embodiment, the cured or set thermosetting resin prevents or reduces (relative to a control wood product comprising the wood component and fire-retardant but without the thermosetting resin) leaching of the fire-retardant from the fire-retardant wood product.

[0048] Leaching of the fire-retardant from the composition of the disclosure may be measured by a method described in Example 6.

[0049] As used herein, “wood product” refers to any product comprising wood. If the wood product comprises wood and one or more other component, the wood may be the major portion of the product or may be the minor portion of the product. The wood product may consist only of wood. By way of example only, “wood product” is a broad term and may include one or more of: wood in the rough (roundwood); wood simply worked or processed; wood chips and particles, residues and recoverable wood products; wood pellets and other agglomerates; sawnwood; veneer sheets; wood-based panels (including panels from other ligno-cellulosic materials); wood pulp; other pulp; recovered paper; paper and paperboard; cork; secondary wood products; and secondary paper products.

[0050] The wood product is selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood. [0051] In one embodiment, the wood product is kiln-dried timber. Kiln-dried timber is wood which has been dried in a kiln to reduce moisture content. Kiln drying does not substantially alter the cellular structure of the wood, but reduces the moisture content. Typical temperatures used in kiln-drying are up to 1 I5°C (e.g. for softwood), or up to 80°C (e.g. for hardwoods), with the temperature not exceeding 60°C for difficult to diy species. In one embodiment, the kiln-dried wood is a wood which has been dried at a temperature not exceeding 115 °C (i.e. the wood has not been exposed to a temperature above 115 °C), hi one embodiment, the kiln-dried wood is a wood which has been dried at a temperature not exceeding 80°C (i.e. the wood has not been exposed to a temperature above 80°C). In one embodiment, the kiln-dried wood is a wood which has been dried at a temperature not exceeding 60°C (i.e. the wood has not been exposed to a temperature above 60°C).

[0052] Moisture content of kiln-dried wood is typically less than 30%. In some embodiments, the kiln-dried wood has a moisture content of less than 20%. [0053] In one embodiment, the wood product is laminate wood, for example such as laminated veneer lumber (LVL), glulam or cross laminated timber (CLT).

[0054] In one embodiment, the wood product is oriented strandboard (OSB). In some embodiments, the wood product is a fiberboard (for example such as medium-density fiberboard (MDF)), chipboard or particleboard. In some embodiments, the wood product is plywood.

[0055] These wood products may be produced from Radiata pine, Southern yellow pine, or any other suitable wood species.

[0056] In one embodiment, the wood product is milled lumber, milled weatherboard (clapboard) whether or not in situ nailed and painted, or cladding. In one embodiment, a wood product may be a piece of furniture.

[0057] In one embodiment, the wood product comprises a hardwood, a softwood, or a hardwood and a softwood. The wood product may comprise sapwood, heartwood, or sapwood and heartwood.

[0058] The wood product may comprise genus Pinus. The wood product may comprise a pine species. Example pine species include: Eastern White pine (Pinus strobus); Limber pine (Pinus flexilis); Loblolly pine (Pinus taeda); Lodgepole pine (Pinus contorta); Longleaf pine (Pinus palustris); Pitch pine (Pinus rigida); Pond pine (Pinus serotina); Ponderosa pine (Pinus ponderosa); Red pine (Pinus resinosa/ Pinus sylvestris); Sand pine (Pinus clausa); Shortleaf pine (Pinus echinata); Slash pine (Pinus elliottii); Spruce pine (Pinus glabra}; Sugar pine (Pinus lambertiana); Table Mountain pine (Pinus pungens); Virginia pine (Pinus virginiana); Western White pine (Pinus monticola); and Radiata pine (Pinus radiata). The wood product may comprise Southern yellow pine, including Loblolly pine, Shortleaf pine, Longleaf Pine, and Slash pine. The wood product may comprise other species, for example Callitris gracilis, Araucaria cunninghamii, Halocarpus biformis, or Cryptomeriajaponica or sugi.

[0059] As used herein, a “wood product” refers to a wood product that does not comprise or has not been impregnated w’ith the composition of the disclosure. The corollary is that, as used herein, a “fire-retardant wood product” refers to a wood product that does comprise or has been impregnated with the composition of the disclosure. In other words, the terms refer to treated and untreated wood products, respectively.

[0060] A third aspect provides a method for producing a fire-retardant wood product, comprising: (i) impregnating a wood product selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood with (a) a solution of a water-soluble thermosetting resin and (b) a solution of a water-soluble fire-retardant in amounts to provide a resin: fire-retardant ratio in the range of 1 :2 weight: weight to 2:1 weight: weight; and

(ii) heating the impregnated wood product to a temperature sufficient to set the thermosetting resin.

[0061] In one embodiment, the method comprises impregnating the wood product with the thermosetting resin and the fire-retardant separately, that is, from separate sources. The method may comprise impregnating the wood product with the thermosetting resin and the fire- retardant sequentially, that is, from separate sources and at different times. In this embodiment, care must be taken to ensure that the thermosetting resin does not set before impregnating the wood product w’ith the fire-retardant, if the wood product is impregnated with the thermosetting resin followed by the fire-retardant. This is particularly important if the wood product is to be dried prior to impregnating the wood product with the fire-retardant. Drying may be needed during sequential impregnation, because the wood product is likely to have a high water content derived from whichever of the thermosetting resin or fire-retardant is impregnated into the wood product first, thereby reducing efficiency of impregnation with the other of the thermosetting resin or fire-retardant impregnated into the wood product second. Accordingly, if sequential impregnation is desired, it may be advantageous to impregnate the fire-retardant followed by the thermosetting resin to reduce the risk of the thermosetting resin setting during drying.

[0062] Alternatively, although separate, the method may comprise impregnating the wood product with the thermosetting resin and the fire-retardant concurrently, that is, from separate sources but at the same time.

[0063] In a preferred embodiment, the method comprises impregnating the wood product with the thermosetting resin and the fire-retardant concurrently from the same source, that is, comprising impregnating the wood product with the composition of the first aspect.

[0064] Consequently, in some embodiments, the method for producing a fire-retardant wood product, comprises:

(i) impregnating a wood product selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB) fiberboard, chipboard, particleboard and plywood with a composition comprising (a) a water-soluble thermosetting resin and(b) a water-soluble fire-retardant in a ratio of resimfire-retardant in the range of 1:2 weightweight to 2:1 weightweight; and

(ii) heating the impregnated wood product to a temperature sufficient to set the thermosetting resin.

[0065] Advantageously, concurrent impregnation removes the need for drying the wood product between impregnating the wood product with the fire-retardant or the thermosetting resin, followed by the other of the fire-retardant or the thermosetting resin. Accordingly, concurrent impregnation is commercially beneficial with respect to time and cost. [0066] In one embodiment, the impregnation is performed under conditions sufficient to achieve an uptake density of the product into the wood product that is at least 300 kg/m³, where the uptake density (U) is calculated by the formula:

where: Wt refers to the weight of the wood product post-treatment and post-drying, in kilograms;

Wu refers to the weight of the weight of the wood product prior to treatment, in kilograms;

L refers to length in metres,

W refers to width in metres, and

T refers to thickness in metres.

[0067] The target uptake density will of course depend on the overall dimensions of the product - for a smaller-thickness product, a higher uptake density may be desired, given the higher surface area of the product. For a thicker product, a lower update density may be acceptable, given the smaller surface area.

[0068] Suitable uptake densities may, in some embodiments, be at least 350 kg/m³, 400 kg/m³, 450 kg/m³, 500 kg/m³ or higher. The uptake density may be as high as 1000 kg/m³, 900 kg/m³, or 800 kg/m³. A target range may fall between any lower and upper limit listed, in any combination. Thus, the uptake density may, for example, be between 300 - 1000 kg/m³, between 300 - 900 kg/m³, between 400 - 1000 kg/m³, 400 - 900 kg/m³, 450 - 1000 kg/m³, as examples. [0069] In one embodiment, impregnating comprises vacuum-pressure treatment, which is known in the art. Examples of vacuum-pressure treatment include full-cell and empty-cell methods. In the full-cell method, both cell wall and lumen are filled with the agent being impregnated, whereas in the empty-cell method only the cell wall is filled with the agent being impregnated.

[0070] In an example of a full-cell method, the wood product is loaded into an appropriate vessel, then a vacuum is applied to the wood product for a period of time, then the composition of the disclosure is added to the vessel, and then pressure of around 1000 kPa (around 140-150 psi) is applied to the wood product for several hours. An example full-cell method involves 30 min vacuum and 2 h pressure followed by 30 min vacuum. Residual composition may be collected from the vessel for reuse.

[0071] In an example of an empty-cell method, the wood product is loaded into an appropriate vessel, then pressure of around 260 kPa (around 35-40 psi) is applied to the wood product, then the composition of the disclosure is added to the vessel while maintaining pressure, then pressure is increased to around 1000 kPa (around 140-150 psi) and applied to the wood product for several hours. Residual composition may be collected from the vessel for reuse.

[0072] In one embodiment, the method further comprises (iii) drying the impregnated wood product. Drying may be performed in a kiln as is known in the art. As an example, softwood may be kiln-dried at around 115 °C or less, hardwood kiln-dried at 80°C or less, and difficult-to-dry species kiln-dried at 60°C or less. Drying time will depend on species, sapwood versus heartwood, total volume and thickness per unit, for example.

[0073] In a preferred embodiment, (ii) heating the impregnated wood product to a temperature sufficient to set the thermosetting resin and (iii) drying the impregnated wood product are performed concurrently.

[0074] In one embodiment, the method further comprises collecting residual composition not impregnated into the wood product. Collected residual composition may be reused for impregnating an additional wood product. Collection of the residual composition is optional. Accordingly, where the residual composition is re-used, the method for producing a fire-retardant wood product may comprise comprises:

(i) impregnating a wood product selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB) fiberboard, chipboard, particleboard and plywood with a fire-retardant composition comprising (a) a water-soluble thermosetting resin and(b) a water-soluble fire-retardant in a ratio of resimfire-retardant in the range of 1:2 weight: weight to 2: 1 weight:weight;

(ii) heating the impregnated wood product to a temperature sufficient to set the thermosetting resin;

(iii) drying the impregnated wood product; and

(iv) re-using residual fire-retardant composition to complete step (i) on another wood product, optionally following pH adjustment of the residual fire-retardant composition.

[0075] In one embodiment, the method further comprises adjusting the residual composition to pH 7.5 to pH 10. In one embodiment, the method further comprises adjusting the residual composition to pH 8 to pH 9.5.

[0076] The pH may, in some embodiments, be adjusted to at least 7.5, at least 7.7, or at least 7.9 or higher. The pH may be adjusted to at most 9.9, or at most 9.7, or at most 9.5. A target pH adjustment range may fall between any lower and upper limit listed, in any combination. Thus, the pH may, for example, be adjusted between 7.7 and 9.9, or 7.9 and 9.7, as examples.

[0077] Accordingly, the pH of the residual composition may be adjusted to about 7.5, about 7.6, about 7.7, about 7.8, about 7.9, about 8, about 8.1, about 8.2, about 8.3, about 8.4, about 8.5, about 8.6, about 8.7, about 8.8, about 8.9, about 9, about 9.1, about 9.2, about 9.3, about 9.4, about 9.5, about 9.6, about 9.7, about 9.8, about 9.9, or about 10. The pH of the residual composition may be adjusted to 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10.

[0078] The pH of the composition of the first aspect or the residual composition may be adjusted using any suitable pH adjusting agent. If required for the desired pH, the composition may comprise a pH adjusting agent. The pH adjusting agent may comprise a base, such as a hydroxide. The hydroxide may be added in the form of a hydroxide solution. The hydroxide solution may, for example, comprise an alkali or alkaline earth metal hydroxide or ammonium hydroxide, or a combination of such hydroxides. For example, sodium hydroxide may be added, preferably a solution of sodium hydroxide, for example 30% w:w, in an amount sufficient to adjust the pH to the target value or within a target range.

[0079] If the pH of the residual composition is too low, for example about pH 6, and is not adjusted as described above, the residual composition cannot be reused. [0080] A fourth aspect provides a kit comprising:

(a) a water-soluble thermosetting resin; and

(b) a water-soluble fire-retardant, wherein the thermosetting resin and fire-retardant are selected from the group consisting of:

(i) dry solids in amounts to provide a resin: fire-retardant ratio in the range of 1 :2 weightweight to 2: 1 weight:weight;

(ii) one or more solution in amounts to provide a resimfire-retardant ratio in the range of 1:2 weightweight to 2: 1 weightweight;

(iii) a dry solid and a solution in amounts to provide a resimfire-retardant ratio in the range of 1:2 weightweight to 2: 1 weightweight.

[0081] In one embodiment of the kit, the dry’ solids or the one or more solution are combined or separate. In one embodiment of the kit, the one or more solution is ready to use. In an alternative embodiment, the one or more solution is concentrated and requires dilution prior to use. In this maimer, the kit may comprise the composition as a single ready to use solution, a single solution requiring dilution before use, two solutions that may be combined and optionally diluted before use, two dry solids requiring dissolution and combination before use, or one dry solid requiring dissolution plus combination with one solution and optionally dilution before use. Similarly, the kit may comprise solutions that are ready to use or require dilution before use and/or one or more dry solid that require dissolution before use, but their combination is not required if the fire-retardant and the thermosetting resin are impregnated into the wood product separately.

[0082] In one embodiment the kit comprises:

(a) 50% w:w to 90% w:w thermosetting resin in water; and

(b) 30% w:w to 50% w:w fire-retardant in water.

[0083] In some embodiments, the kit comprises:

(a) about 55% w:w, about 60% w:w, about 65% w:w, about 70% w:w, about 75% w:w, about 80% w:w, or about 85% w:w thermosetting resin in water; and

(b) about 35% w:w, about 40% w:w, or about 45% w:w fire-retardant in water.

[0084] Accordingly, when read in conjunction with the definition of “about”, the composition may comprise:

(a) any one integer percent between 50% w:w and 90% w:w thermosetting resin in water; and (b) any one integer percent between 30% w:w and 50% w:w fire-retardant in water. [0085] In one embodiment, the kit is used according to the method of the third aspect. In one embodiment, the kit further comprises instructions to perform the method of the third aspect. [0086] In one embodiment, the kit comprises one or more containers containing the thermosetting resin, the fire-retardant, or the thermosetting resin and the fire-retardant.

EXAMPLES

Example 1. Preparation of composition 1

[0087] The composition comprises a water based fire-retardant and a water-based thermosetting resin. These may be purchased from various manufacturers or suppliers. In this example, the water-based thermosetting resin (R) was methylated melamine formaldehyde (MMF) resin. It was obtained from HEXION as the CASCOMEL® M3080 resin system. The water-soluble fire-retardant (FR) was guanidine sulfamate. It was obtained from HEXION as CASCOSET® MCAT9180.

[0088] The composition was prepared as follows. i) A stock FR solution 40% w:w was prepared by dissolving fire-retardant solids (40 parts by weight) in water (60 parts by weight). R was supplied as a stock solution at a concentration of 80% w:w. ii) To prepare a certain volume of the composition, FR stock solution and R solution were mixed at ambient temperature in suitable relative amounts to achieve the desired R/FR ratio, with addition of the required amount of water. The R/FR ratio in the composition is in the range 0.33 to 2.0 (i.e. 1 :2 to 2: 1 ) and the R plus FR total solids content of the composition is in the range 20% w:w - 40% w:w. iii) The mixture was stirred at ambient temperature for 10 minutes to ensure a homogenous and clear solution was formed. iv) The working pH range was 8 - 9.5.

Example 2. Impregnation

[0089] The composition of Example 1 was used to treat wood samples of Southern Yellow Pine (SYP), glue laminates and heartwood species of NZ Radiata pine using vacuumpressure treatment for impregnation. Specifically, impregnation comprised a 1st vacuum cycle of 30 min, a pressure cycle of 2 h at 560 kPa), and a 2nd vacuum cycle of 20 min. However, the parameters can vary based on the density of the wood species to be impregnated. [0090] The uptake density (U) of the wood samples was measured by the weight difference between the post-treated oven dried samples (Wt) and pre-treated wood sample (Wu) in grams and dividing it by the dimensions of the wooden board (L = length, W = width, T = thickness) in meters as shown in the following formula:

[0091] The uptake density U of the composition in the wood product for R/FR ratios ranging from 0.33 to 2.0 was in the range 650 kg/m³ to 750 kg/m³.

Example 3. Residual composition

[0092] The residual composition collected after wood treatment according to Example 2 was tested for its pH and was found to have dropped to pH 7 to pH 7.5. To the residual composition was added 30% aqueous sodium hydroxide (caustic) to increase the pH to pH 8 to pH 9.5. The residual composition was again used for wood treatment and the composition uptake was found to be like that observed when freshly prepared composition was used.

Example 4. Fire-retardancy - ASTM E2768-11

[0093] Fire-retardancy of the wood product of the disclosure may be assessed relative to a control wood product not comprising the composition of the disclosure. Fire-retardancy may be assessed according to ASTM E2768-11 Standard Test Method for Extended Duration Surface Burning Characteristics for Building

Materials (30 min Tunnel Test), which is described below.

1. Scope

[0094] 1.1 Tire purpose of this fire-test-response standard is to evaluate the ability of a product to limit the surface spread of flame when evaluated for 30 min. This fire-test-response standard uses the apparatus and procedure of Test Method E84 with the total test period extended to 30 min.

[0095] 1.2 Building applications affecting fire and life safety often require products with specific criteria for surface spread of flame and flame spread index. The resulting performance characteristics included in the conditions of classification for this fire-test- response standard are intended to be used for regulatory purposes to determine the suitability of materials or products for use in buildings under specified conditions where significantly reduced surface burning characteristics are required.

[0096] 1.3 Materials and products that are beyond the scope of Test Method E84 are beyond the scope of this standard.

[0097] 1.4 Materials or products which melt, drip or delaminate to the extent that the continuity of the flame front is destroyed are beyond the scope of this standard.

NOTE 1 — Testing of materials that melt, drip, or delaminate to such a degree that the continuity of the flame-front is destroyed, results in low flame spread indices that do not relate directly to indices obtained by testing materials that remain in place.

Materials or products that melt, drip, or delaminate, or that cannot support their own weight, have the potential for demonstrating reduced flame spread results as compared to the flame spread results where the materials or products remain in place during testing.

[0098] 1.5 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

[0099] 1.6 The text of this standard references notes and footnotes that provide explanatory information. These notes and footnotes, excluding tables and figures, shall not be considered as requirements of the standard.

[0100] 1.7 This standard is used to measure and describe the response of materials, products, or assemblies to heat and flame under controlled conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials, products, or assemblies under actual fire conditions.

[0101] 1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

[0102] 1.9 Fire testing is inherently hazardous. Adequate safeguards for personnel and property shall be employed in conducting these tests. 2. Referenced Documents (omitted)

3. Terminology

[0103] 3.1 Definitions — For definitions of terms used in this test method, refer to

Terminology El 76 and Test Method E84. The terms surface flame spread, flame spread index, and smoke developed index are of particular interest to this standard.

4. Summary of Test Method

[0104] 4.1 This test method is conducted using the same equipment, apparatus, calibration, and calculation of flame spread index and smoke developed index as Test Method E84.

[0105] 4.2 Test Method E84 exposes a nominal 24-ft long by 20-in wide (7.32 m by

508 mm) specimen to a controlled air flow and flaming fire exposure adjusted to spread the flame along the entire length of the select grade red oak specimen in 5.5 min (615 s). Test Method E84 measures the flame spread distance from a point beginning 4.5 ft (1.4 m) beyond the centerline of the burners.

[0106] 4.3 The flame spread index is determined during the initial 10 min of the test period and calculated as described in Test Method E84.

[0107] 4.4 In this test method, the Test Method E84 test is extended by 20 min to a 30 min test period. Determination is made of the distance traveled by the flame front (surface spread of flame) as measured from the centerline of the burners during the 30 min test period. [0108] 4.5 Hie test method has conditions for classification in Section 13.

5. Significance and Use

[0109] 5.1 This standard is useful to establish the relative surface burning characteristics of materials or products under laboratory conditions for a 30 min test period.

[0110] 5.2 The performance characteristics in the conditions of classification are intended to be used in specific applications as required by building codes or other regulatory requirements or specifications.

[0111] 5.3 This test method does not provide the measurement of heat transmission through the tested surface. [0112] 5.4 This test method does not provide the classification or definition of a material or product as non-combustible, by means of the results from this standard test or flame spread index by itself.

6. Apparatus/Test Equipment

[0113] 6.1 The apparatus, equipment, recording devices, and systems are to be the same as those detailed in Test Method E84.

7. Hazards

[0114] 7.1 This test is conducted using the equipment, apparatus, and procedure of Test

Method E84. The hazards described in Test Method E84 are applicable.

8. Sampling, Test Specimens and Test Units

[0115] 8.1 The test specimens shall be representative of the material or product being evaluated.

[0116] 8.2 Materials or products that are not homogeneous or are not symmetrical about their longitudinal axis shall have each surface evaluated separately.

[0117] 8.2.1 Surfaces of the material or product that, due to their small surface area, are impractical to test in accordance with Test Method E84 (for example, the edges of a piece of plywood) are excluded from this requirement.

[0118] 8.2.2 It shall be permissible to test and classify one or more surfaces of a material or product as meeting the conditions of classification of this standard and classify without testing the other surfaces as not meeting the conditions of classification of this standard.

[0119] 8.3 Test Specimens:

[0120] 8.3.1 The test specimen sizes shall comply with those described in Test Method

E84.

[0121] 8.3.2 Applicable practices listed in Test Method E84 and related provisions of

Test Method E84 shall be used for specimen preparation and mounting. 9. Calibration and Standardization

[0122] 9.1 The calibration and standardization of the apparatus and equipment for this standard shall be as described in Test Method E84.

10. Conditioning

[0123] 10.1 Conditioning of test specimens shall be conducted as described in Test

Method E84.

11. Procedure

[0124] 11.1 Conduct the test in accordance with Test Method E84 with the following additional requirements:

[0125] 11.1.1 The test shall be continued for a total period of 30 min.

[0126] 11.2 During the initial 10 min of the test, record the times and extent of flame front advancement in accordance with Test Method E84. Observe and record the maximum flame front travel from the centerline of the burners during the 30-min period of the test. This method uses the recording devices of Test Method E84 (see Note 2).

NOTE 2 — If for purpose of calculating the flame spread index the zero point of the recording equipment is at the base end of the ignition fire, the maximum flame front travel distance required in this standard shall be the recorded distance plus 4.5 ft. (1.4 m) In Test Method E84 and this standard, the calculation of the flame spread index is based on the flame spread distance measured from a point beginning 4.5 ft (1.4 m) beyond the centerline of the burners during the first 10 min.

[0127] 11.3 Follow all other procedures described in Test Method E84 including those for determination of flame spread index during the initial 10 min.

[0128] 11.4 The determination of the smoke developed index during the initial 10 min of this test is optional.

12. Interpretation of Results

[0129] 12.1 Determine the following:

[0130] 12.1.1 Flame spread index and smoke developed index (optional) during the initial 10 min in accordance with Test Method E84 (see Note 2). [0131] 12.1.2 The maximum distance of surface spread of flame as measured from the centerline of the burner during the 30 min test period.

[0132] 12.2 Where separate tests are conducted on different surfaces of the test specimens (See 8.2) the information specified in 12.1.1 and 12.1.2 shall be determined for each tested surface.

13. Conditions of Classification

[0133] 13.1 The test method has the following conditions of classification for a material or product to be classified as meeting the requirements of this standard:

[0134] 13.1.1 The flame spread index shall be 25 or less as determined for the initial

10 min test period.

[0135] 13.1.2 The flame front shall not progress more than 10.5 ft (3.2 m) beyond the centerline of the burners at any time during the 30 min test period. This is considered evidence of no significant progressive combustion in this test method.

[0136] 13.2 For materials or products that are not homogeneous or symmetrical about their longitudinal axis, only surfaces that have been individually tested shall be eligible to be classified and reported as meeting the conditions of classification of this standard.

14. Report

[0137] 14.1 The report shall clearly state that it applies to all surfaces of the material or product tested in accordance with the standard or, where the material or product is not homogeneous or symmetrical about its longitudinal axis, the report shall state that it only applies to those surfaces that have been tested and so classified in accordance with this standard.

[0138] 14.2 The following shall be included in the test report:

[0139] 14.2.1 Report the material (or product) or separate surfaces of the material (or product) as meeting the conditions of classification if the test results for the test specimens meet the conditions of classification of 13.1. Test results shall be reported for each surface tested.

[0140] 14.2.2 Where a material or product is not homogeneous or symmetrical about its longitudinal axis and all surfaces have not been individually tested, those surfaces not tested shall be clearly identified and reported as unclassified in accordance with this standard. [0141] 14.2.3 Description of the material or product to include its thickness and the nominal width of the material or product used to construct the test specimens.

[0142] 14.2.4 Non-proprietary information on the process, treatment, or surface condition which forms the basis of identifying the material or product. For a manufactured or treated product, the date of manufacture or treatment.

[0143] 14.2.5 Date of test specimen construction and the construction details including the number of sections, methods of joining, and any deviations from construction details specified in any applicable Practice on the mounting of the test specimen.

[0144] 14.2.6 Conditioning of test specimens prior to evaluation.

[0145] 14.2.7 Description of the mounting method.

[0146] 14.2.7.1 If there is an applicable Practice (see Test Method E84) for the mounting of the test specimen, state the Practice designation and any deviations from the applicable Practice.

[0147] 14.2.8 The maximum measurement of surface spread of flame and time of occurrence for each test.

[0148] 14.2.9 The flame spread index for each test.

[0149] 14.2.10 If recorded, the smoke developed index for each test.

[0150] 14.2.11 Observation of the specimen during the total test period for factors which influence the interpretation of results including, but not limited to, delamination, sagging, shrinkage, fallout, disruption of the continuity of the flame front or smoldering.

[0151] 14.2.12 Graphical plots of the flame spread versus time for the test duration and if recorded, the smoke developed versus time for the initial 10 min of the test period. The distance axis of the flame spread graph shall be labeled to indicate the origin (either the burner centerline or +4.5 ft (1.4 m)).

15. Precision and Bias

[0152] 15.1 The precision and bias of this test method for measuring flame spread and smoke developed index are as specified in Test Method E84.

[0153] 15.2 No information is presented about either the precision or the bias for observing the occurrence of flame front progressing beyond 10.5 ft (3.2 m) since the test result is determinate. 16. Keywords

[0154] 16.1 flame spread index; surface burning characteristics; smoke develop index.

XI. COMMENTARY

[0155] X1.1 Introduction

[0156] X1.1.1 This commentary has been prepared to provide the user of this test method with background information on the standard.

[0157] X1.1.2 This standard is based on a modification of Test Method E84 that has been used for many years in provisions in the building codes and related specifications pertaining to fire-retardant-treated wood. Such codes include the International Building Code (IBC) and International Residential Code (IRC) as well as other documents. The test requirement is only one of the performance requirements for fire -retardant-treated wood in the building codes. There are other performance requirements and inherent characteristics of fire- retardant-treated wood that were considered relevant when provisions in the codes were approved to allow the use of fire-retardant-treated wood in specific applications.

[0158] X1.1.3 It was commonly referred to as the “30-minutes E84 tunnel test.” However, Test Method E84 has no provisions for extending the test to the 30 min duration.

[0159] X1.1.4 The “Extended Test Method E84 test” is increasingly being used in requirements that are not limited to fire-retardant-treated wood. For example, the International Wildland Urban Interface Code (IWUICIWUIC) and California Building Code (CBCCBC) use the test for assessing materials and products that can be designated as ignition-resistant materials.

[0160] X1.2 Development of this Standard

[0161] X1.2.1 At the time this standard was initially prepared, the existing requirements for fire-retardant-treated wood included a requirement that there be “no evidence of significant progressive combustion” when the Test Method E84 test was extended to 30 min. This requirement was also part of other applications of the test to other materials or products. The questions as to what constitutes “significant progressive combustion” and how one makes that determination had not been interpreted or otherwise clarified in the codes or in any other known document. In the development of this ASTM standard, it was concluded that no significant progressive combustion is evident if the flame front does not progress more than 10.5 ft (3.2 m) beyond the centerline of the burners at any time during the 30-min exposure. This evidence had been used by laboratories involved in testing fire-retardant-treated wood for many years. As a result, a statement to that effect was added to 13. 1.2 of the standard.

[0162] X1.3 Continued Progressive Combustion and Continued Propagation of Fire in

NFPA 101

[0163] X1.3.1 In some editions of the NFPA Life Safety Code (NFPA 101), requirements for “no continued progressive combustion” or for “no continued propagation of fire” are for the end of the 10-min test period of Test Method E84. They are not for the 30-min test period of this standard. Such provisions include: Xl.3.1.1 The 2003 and 2006 editions of the NFPA Life Safety Code (NFPA 101) required that there be no continued propagation of fire for materials or products tested in accordance with Test Method E84 in order to achieve a Class A interior finish classification.

[0164] X1.3.1.2 Recent editions of the NFPA Life Safety Code (NFPA 101) require a lack of evidence of continued progressive combustion for materials or products tested in accordance with Test Method E84. This requirement in the NFPA Life Safety Code (NFPA 101) is for the concept of limited combustible material.

Test Method E84

[0165] An E84 test is conducted by placing a 24” wide x 24' long sample into a Steiner Tunnel (see description of Steiner Tunnel below), wherein the test is administered through the use of two burners which provide 89kW of energy. During the test, the sample is mounted on the ceiling under a removable lid, and a forced draft is provided in order for the movement of air and products of combustion within the tunnel, and to the exhaust/scrubber system. The progress of the flame is then monitored through viewports on one side of the apparatus and recorded, with software computing the various data points to derive the Flame Spread Index (FSI) and Smoke Developed Index (SDI). Smoke developed is also measured through the optical density of a light obscuration meter.

Steiner Tunnel

[0166] The Steiner Tunnel is a steel box lined on its sides and floor with fire brick and featuring a removable lid. The tunnel contains a 12 inch high fire chamber with two burners at one end providing 89kW of energy. The Steiner Tunnel was adopted as an ASTM Standard in 1950 and given the designation of E84. Equivalent standards are maintained by NFPA and UL as NFPA 255, UL 732, and with certain modifications as CAN/ ULC-S102. The FSI and SDI indices are used to establish a scale for the rate at. which flame spreads and smoke develops during an E84 test. For example, reinforced cement board calibration material has an FSI of 0 and an SDI of 0, whereas red oak calibration material has an FSI and SDI of 100.

Example 5. Fire-retardancy

[0167] Flame spread testing was conducted in accordance with ASTM E2768-11 standard described in Example 4 to assess the fire performance of the SYP boards treated according to Example 2. The SYP boards were impregnated with composition having R/FR ratio 2.0 and R plus FR total solids content 30% w:w.

Table 1. Flame spread and smoke developed (at 10 min) for 25 mm x 150 mm (1” x 6”) tongue and groove SYP

Flame spread Flame spread Smoke developed Smoke developed index index

0 0 11 11

[0168] In the extended 20 min burn, the flame did not exceed 3.2 m (10’ 6”) past the centerline of the burners.

Example 6. Leaching of fire-retardant

[0169] Leaching of the fire-retardant from the composition of the disclosure may be measured by the following method.

[0170] Two compositions, (a) a composition with R/FR ratio 1.0, and (b) a composition with a R/FR ratio of 2.0 were prepared, and then cured in an oven overnight at 105°C. The cured samples were then ground to a powder using a mortar and pestle and then mixed with distilled water. Samples were left at 25 °C to allow the material to dissolve and then the amount of fire retardant in the water was measured. [0171] Leaching of fire-retardant from the compositions when in direct contact with water was determined. It was found that leaching of fire-retardant from the sample impregnated with the composition with a R/FR ratio of 1 .0 was 20%, and this reduced significantly to 5% for the sample impregnated with the composition with a R/FR ratio of 2.0.

Table 2: Setup data for powdered resin/FR oven dried blends.

Table 3: Setup data for powdered resin/FR oven dried blends.

Table 4: Measurement of leached FR content from resin/FR oven dried blends.

[0172] The amount of leaching from the first study of resin and fire retardant is shown in Figure 1. The panels labelled as ‘standard’ in our initial series were 2: 1 and the panels labelled as ‘modified’ in our initial series were 1.4: 1, which would limit leaching at ~10% for a raw resin/FR blend.

[0173] The 2:1 ratio of resin to fire retardant significantly reduces leaching in a powdered residue sample which would represent a ‘worst’ case scenario for the potential for leaching. This value was down around 5% and so there was still some level of leaching. This would indicate encapsulation by the resin rather than chemical binding to the resin. This increased to around 20% at a 1 : 1 ratio. This would be expected to be reduced in a treated timber sample due to surface area and moisture migration effects.

Claims

1. A composition comprising:

(a) a water-soluble thermosetting resin; and

(b) a water-soluble fire-retardant, wherein the composition has a resin: fire-retardant ratio range of 1 :2 weight:weight to 2: 1 weight:weight.

2. Tire composition of claim 1, wherein the fire-retardant comprises a guanidine salt.

3. Hie composition of claim 1, wherein the thermosetting resin is an amino-formaldehyde resin or a phenolic-formaldehyde resin.

4. The composition of claim 3, wherein the amino-formaldehyde resin is selected from the group consisting of urea formaldehyde (UF), melamine formaldehyde (MF), melamine urea formaldehyde (MUF), methylated melamine formaldehyde (MMF), or a combination of one or more thereof.

5. The composition of claim 3, wherein the phenolic-formaldehyde resin is selected from the group consisting of phenol formaldehyde, phenol resorcinol formaldehyde, resorcinol formaldehyde, or a combination of one or more thereof.

6. The composition of claim 1, wherein the thermosetting resin comprises phenol melamine urea formaldehyde (PMUF).

7. The composition of claim 1, further comprising:

(c) water.

8. The composition of claim 7, comprising 12% total solids content (TSC) in water to 60% TSC in water, wherein the TSC is the total thermosetting resin plus fire-retardant.

9. Hie composition of claim 7 comprising 20% TSC in water to 40% TSC in water.

10. The composition of claim 2 wherein the guanidine salt is selected from the group consisting of guanidine sulfamate, guanidine sulfate, guanidine phosphate, guanidine carbonate, guanylurea phosphate, and combinations thereof.

11. The composition of claim 7, wherein the composition has pH 7.5 to pH 10.

12. A wood product comprising the composition of claim 1, wherein the wood product is selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood.

13. The wood product of claim 12 wherein the thermosetting resin is set and reduces, relative to a control wood product lacking the thermosetting resin, or prevents, leaching of the fire-retardant from the wood product.

14. The wood product of claim 12 comprising a hardwood, a softwood, or a hardwood and a softwood.

15. The wood product of claim 12 comprising sapwood, heartwood, or sapwood and heartwood.

16. The wood product of claim 12 comprising Radiata pine, Southern yellow pine or a glue laminate wood.

17. A method for producing a fire-retardant wood product, comprising:

(i) impregnating a wood product selected from the group consisting of kiln-dried timber, laminate wood, oriented strandboard (OSB), fiberboard, chipboard, particleboard and plywood with (a) a solution of a water-soluble thermosetting resin and (b) a solution of a water-soluble fire-retardant wherein the composition has a resin: fire-retardant ratio range of 1:2 weight:weight to 2: 1 weight: weight; and

(ii) heating the impregnated wood product to a temperature sufficient to set the thermosetting resin.

18. The method of claim 17, comprising impregnating the wood product with the thermosetting resin and the fire-retardant separately.

19. The method of claim 17, comprising impregnating the wood product with the thermosetting resin and the fire-retardant sequentially.

20. The method of claim 17, comprising impregnating the wood product with the thermosetting resin and the fire-retardant concurrently.

21. The method of claim 17 wherein impregnating comprises a vacuum-pressure treatment.

22. The method of claim 17, further comprising:

(iii) drying the impregnated wood product, optionally concurrently with (ii) heating the impregnated wood product.

23. The method of claim 17 further comprising collecting residual composition not impregnated into the wood product.

24. The method of claim 23, further comprising adjusting the residual composition to pH 8 to pH 9.5.