Fire-retardant resin composition and composite products

Abstract

Provided herein is a thermosetting fire-retardant resin composition for use in a wood- resin composite product. The resin composition, and uses of the resin composition to produce wood-resin composite products that are fire-retardant. Also provided are methods of producing thermosetting fire-retardant resin compositions and wood-resin composite products.

Description

[0001] FIRE-RETARDANT RESIN COMPOSITION AND COMPOSITE PRODUCTS Related Applications

[0002] The present application claims priority from Australian Provisional Patent Application No.

[0003] 2024903629 filed on 6 November 2024, the entire contents of which is incorporated herein by this cross-reference.

[0004] Field

[0005] The present disclosure relates to resin compositions that are useful in the manufacture of composite wood products. The resin compositions are useful for binding wood-based materials, in the preparation of composite wood products, and provide fire-retardant properties to the resulting composite wood product.

[0006] Background

[0007] Wood and wood-based products are ubiquitous in the built environment due to their appearance, low cost to manufacture, and light weight compared to other building materials.

[0008] However, untreated wood is a flammable material and, in situations where a fire ignites, the presence of untreated wood-based products in building materials can propagate fire. In countries such as Australia, catastrophic bushfire events, exacerbated by the warming of our climate, and the potential for fires within homes and other buildings, have also accelerated the demand for fire-retardant wood products.

[0009] Fire retardancy in composite wood products is mainly achieved in two ways. The first method involves applying a protective coating or layer to the finished product, typically using noncombustible material or intumescent substances. A disadvantage of this method, for instance, is that a coating requires the panel to be finished first, and then the fire protection is applied to the product.

[0010] A second method involves the addition of fire-retardant additives, commonly in the form of solid borates or liquid phosphates. For this method, common fire-retardant additives are typically coated or soaked onto the fiber in a separate step, to prevent premature curing of the resin or to achieve homogeneous distribution, or they are mixed with the resin just prior to being applied to the chip material. Each of these methods requires engineering solutions, chemical procurement, and chemical storage. Fire retardant resins on the market often require a two-step production process whereby the resin and fire-retardant are prepared independently of each other and must subsequently be combined. This two-part system is relatively complex to use.

[0011] Currently, there are limited affordable, successful, simple and non-toxic fire-retardant resins available. Due to the limited options, many industries rely on halogenated fire retardants. Although these fire retardants work effectively, by degrading and reacting with free radicals in the flame, a large drawback is their production of chronic toxins which literature suggests can affect the human genome, reproductive and immune systems. Additionally, halogenated fire retardants have an immense resistance to degradation, resulting in them being classified as ‘persistent organic pollutants’, and thus threatening our environment.

[0012] Other commonly used fire retardants are phosphorus- or boron-based, both of which are nontoxic and environmentally friendly. However, a limitation to phosphorus-based fire retardants involves its tendency to increase the moisture content of the wood-based material, which may cause swelling, and concerns over their corrosive effects have grown. Furthermore, common liquid phosphate additives impact the mechanical performance of the finished product, requiring higher resin loading with higher melamine content to compensate for these effects.

[0013] The use of boron-based fire retardants is also restricted by their ability to reduce flame spread.

[0014] It would be desirable to provide a one-part resin composition which contains both resin and fire retardant material which is stable upon storage, is able to effectively bind wood-based fibers, which imparts good fire-retardant properties, and has low water uptake.

[0015] Summary

[0016] The present inventors have discovered that resin compositions containing a guanidine-based fire-retardant material show excellent stability, excellent binding properties to wood fibers, and provide excellent fire-retardant properties, acceptable formaldehyde emissions, and acceptably low swelling. Unlike traditional resins, the resin composition of the present disclosure contains a binding component and a fire-retardant component in the one composition, which simplifies the manufacturing process resulting in reduced time and costs.

[0017] Accordingly, in a first aspect, there is provided a thermosetting fire-retardant resin composition for use in a wood-resin composite product, including: a formaldehyde-based resin which incorporates a guanidine monomer as a fire- retardant component of the resin; and

[0018] wherein the composition has a pH of greater than 6.0.

[0019] In some embodiments, the composition is substantially stable to curing on storage at 35°C for a period of at least 8 days.

[0020] In some embodiments, the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

[0021] In some embodiments, the composition is produced from formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%.

[0022] In some embodiments, the composition is produced from melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%.

[0023] In some embodiments, the composition is produced from urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%.

[0024] In some embodiments, the guanidine fire-retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

[0025] In some embodiments, the guanidine monomer is a guanidine salt.

[0026] In some embodiments, the guanidine salt is guanidine sulfamate.

[0027] In some embodiments, the composition is produced from guanidine sulfamate in an amount of from 5 wt% to 70 wt%, optionally from 40 wt% to 70 wt% guanidine sulfamate.

[0028] In some embodiments, the composition is produced from:

[0029] formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%;

[0030] melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%; urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%; and guanidine sulfamate in an amount of from 5 wt% to 70 wt%, optionally from 40 wt% to 70wt%.

[0031] In some embodiments, the composition includes one or more pH-adjusting agents and / or pH buffers.

[0032] In some embodiments, the one or more pH-adjusting agents are selected from sodium hydroxide and formic acid.

[0033] In some embodiments, the pH buffer is triethanolamine.

[0034] In some embodiments, the composition has a pH of greater than 7.0. In some embodiments, the composition has a pH between 7.0 and 9.0.

[0035] In some embodiments, the composition has a pH of about 7.35.

[0036] In some embodiments, the composition has a water content of less than 35 wt%, optionally less than 20 wt%

[0037] In some embodiments, the composition has a solids content of at least 65 wt%, optionally at least 80 wt%.

[0038] There is also provided a thermosetting fire-retardant resin composition for use in a woodresin composite product, including:

[0039] precursor components for producing a formaldehyde-based resin; and

[0040] a guanidine fire-retardant material; and

[0041] wherein the composition has a pH of greater than 6.0.

[0042] In some embodiments, the composition is substantially stable to curing on storage at 35°C for a period of at least 8 days.

[0043] In some embodiments, the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

[0044] In some embodiments, the composition contains formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%.

[0045] In some embodiments, the composition contains melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%.

[0046] In some embodiments, the composition contains urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%.

[0047] In some embodiments, the guanidine fire-retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

[0048] In some embodiments, the guanidine fire-retardant material is a guanidine salt.

[0049] In some embodiments, the guanidine salt is guanidine sulfamate.

[0050] In some embodiments, the composition contains from 5 wt% to 70 wt% guanidine sulfamate, optionally from 40 wt% to 70 wt% guanidine sulfamate.

[0051] In some embodiments, the composition contains:

[0052] formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%; melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%; urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%; and guanidine sulfamate in an amount of from 5 wt% to 70 wt%, optionally from 40 wt% to 70wt%.

[0053] In some embodiments, the composition includes one or more pH-adjusting agents and / or pH buffers.

[0054] In some embodiments, the one or more pH-adjusting agents are selected from sodium hydroxide and formic acid.

[0055] In some embodiments, the pH buffer is triethanolamine.

[0056] In some embodiments, the composition has a pH of greater than 7.0.

[0057] In some embodiments, the composition has a pH between 7.0 and 9.0.

[0058] In some embodiments, the composition has a pH of about 7.35.

[0059] In some embodiments, the composition has a water content of less than 35 wt%, optionally less than 20 wt%

[0060] In some embodiments, the composition has a solids content of at least 65 wt%, optionally at least 80 wt%.

[0061] There is also provided a wood-resin composite product produced or producible by thermosetting of a mixture comprising wood fibers and a composition as defined herein.

[0062] In some embodiments, the composite product is in the form of medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), plywood, fiberboard, laminated timber, particleboard or panel board.

[0063] In some embodiments, the wood-resin composite product is in the form of medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), fiberboard, or particleboard.

[0064] In some embodiments, the composite product further comprises one or more of a hardener and a wax.

[0065] In some embodiments, the composite product comprises from 1 wt% to 30 wt% resin solids, optionally from 10 wt% to 30 wt%, or optionally from 20 wt% to 30 wt%.

[0066] In some embodiments, the composite product has a resin solids content in the range of from 30 wt% to 80 wt%.

[0067] In some embodiments, the guanidine fire-retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

[0068] There is also provided a method of producing a composition as defined herein, including: heating a mixture of precursor components for producing a formaldehyde-based resin; adding a guanidine monomer to the heated mixture; and

[0069] heating the guanidine monomer-containing mixture.

[0070] In some embodiments, the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

[0071] In some embodiments, the precursor components for producing a formaldehyde-based resin are heated at a temperature in the range of from 70°C to 90°C; and / or wherein the mixture containing the guanidine monomer is heated at a temperature in the range of from 70°C to 90°C.

[0072] In some embodiments, a mixture including formaldehyde, urea and melamine is heated at a temperature in the range of from 70°C to 90°C at a pH of from 5.5 to 6.5, until the mixture has a viscosity in the range of from 300 cP to 500 cP, and the mixture is then brought to ambient temperature and guanidine monomer, and optionally a pH-adjusting agent and / or a pH buffer, is added, such that the composition has a pH of greater than 7.0.

[0073] In some embodiments, the guanidine monomer is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

[0074] There is also provided a method of producing a composition as defined herein, including: admixing precursor components for producing a formaldehyde-based resin; and

[0075] a guanidine fire-retardant material.

[0076] In some embodiments, the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

[0077] In some embodiments, guanidine fire-retardant material is added to a mixture comprising precursor components for producing a formaldehyde-based resin.

[0078] In some embodiments, a mixture including formaldehyde, urea and melamine is heated at a temperature in the range of from 70°C to 90°C at a pH of from 5.5 to 6.5, until the mixture has a viscosity in the range of from 300 cP to 500 cP, and the mixture is then brought to ambient temperature and guanidine fire-retardant material, and optionally a pH-adjusting agent and / or a pH buffer, is added, such that the composition has a pH of greater than 7.0.

[0079] In some embodiments, the guanidine fire-retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

[0080] There is also provided a method of producing a wood-resin composite product, comprising coating wood fibers with a resin composition as defined herein, and then thermosetting the resulting mixture.

[0081] In some embodiments, the resin composition is sprayed onto the wood fibers. In some embodiments, the wood fibers are coated with a wax.

[0082] In some embodiments, the mixture is subjected to drying to reduce water content, prior to thermosetting.

[0083] In some embodiments, thermosetting is carried out by hot pressing of the mixture.

[0084] In some embodiments, the guanidine fire-retardant material or guanidine monomer is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

[0085] Brief Description of the Drawings

[0086] So that the present disclosure can be better understood, a more particular description of the aspects and embodiments, summarised above, may be had by reference to embodiments, some of which are illustrated in the appended Figures. It is to be noted, however, that the appended Figures illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope.

[0087] Figure 1 show's shelf life for a standard resin (standard melamine-urea-formaldehyde (MUF) resin, solid line ) versus a fire-retardant resin ( fire-retardant resin, dotted line) of the present disclosure, as a function of resin viscosity over time: a) resins stored at 35°C; and b) resins stored at 25°C.

[0088] Figure 2 shows internal bond strength results for panels prepared with a standard resin (standard melamine-urea-formaldehyde(MUF) resin) versus a fire-retardant resin (FR resin).

[0089] Figure 3 shows results for bench-scale fire testing using ISO 5660, showing rate of heat release over time: solid line (panel with standard resin, 12% solids); dotted line (panel with fire-retardant (FR) resin, 12% solids); dashed line (panel with fire-retardant (FR) resin, 24% solids).

[0090] Figure 4 show's results for fire-resistance testing: a) Panel prepared with a standard resin being heated with a blow-torch for 1 min 20 s; b) Panel from figure a) immediately after removal of blow-torch flame; c) Panel prepared with a fire retardant (FR) resin being heated with a blow'-torch for 1 min 20 s; and d) Panel from figure c) immediately after removal of blow-torch flame.

[0091] Detailed Description

[0092] Definitions

[0093] Unless specifically defined otherwise, all technical and scientific terms used herein shall be taken to have the same meaning as commonly understood by one of ordinary skill in the art. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, preferred methods and materials are described. For the purposes of the present disclosure, the following terms are defined below.

[0094] The present disclosure may refer to the contents of certain documents being incorporated herein by reference. In the event of any inconsistent teaching between the teaching of the present disclosure and the contents of those documents, the teaching of the present disclosure takes precedence.

[0095] 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.

[0096] As used herein, the term “and / or”, e.g., “X and / or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning.

[0097] For purposes of this present disclosure, and unless otherwise specified, all numerical values within the detailed description and the claims herein which are stated to be “about” or “approximately” the indicated value, are in consideration of experimental error and variations that would be expected by a person having ordinary skill in the art. For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited. In addition, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. For example, the recitation of the numerical range 1 to 5 includes the subranges 1 to 4, 1.5 to 4.5, 1 to 2, among other subranges. As another example, the recitation of the numerical ranges 1 to 5, such as 2 to 4, includes the subranges 1 to 4 and 2 to 5, among other subranges. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. For example, the recitation of the numerical range 1 to 5 includes the numbers 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, among other numbers. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.

[0098] Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e. one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. For example, reference to “a” includes a single as well as two or more; reference to “an” includes a single as well as two or more; reference to “the” includes a single as well as two or more and so forth.

[0099] Unless otherwise indicated, terms such as “first”, “second”, etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to a “second” item does not require or preclude the existence of lower-numbered item (e.g., a “first” item) and / or a higher-numbered item (e.g., a “third” item).

[0100] As used herein, the phrase “at least one of’, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of’ means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example and without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

[0101] As used herein, the word “comprise” and other forms of the word, such as “comprising” and “comprises,” are 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 disclosure.

[0102] The disclosure also includes all of the steps, features, compositions, layers and components thereof referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features.

[0103] Each embodiment of the present disclosure described herein is to be applied mutatis mutandis to each and every other embodiment unless specifically stated otherwise or required otherwise by context.

[0104] Abbreviations

[0105] The following abbreviations are used throughout this specification, as defined below: F Formaldehyde

[0106] FR Fire retardant

[0107] G Guanidine

[0108] GUS Guanidine sulfamate

[0109] IB Internal bond

[0110] M Melamine

[0111] MDF Medium density fiberboard

[0112] RI Refractive index

[0113] U Urea

[0114] wt% Weight percent

[0115] Thermosetting Fire-Retardant Resin Compositions

[0116] In one aspect, there is provided a thermosetting fire-retardant resin composition for use in a wood-resin composite product, including:

[0117] a formaldehyde-based resin which incorporates a guanidine monomer as a fire- retardant component of the resin; and

[0118] wherein the composition has a pH of greater than 6.0.

[0119] The resin composition contains the guanidine monomer, which is a guanidine fire-retardant material, incorporated into the formaldehyde-based resin. In other words, resin polymers, prepolymers and / or oligomers contain residues of guanidine fire-retardant material (i.e. derived from guanidine monomer) as part of the polymer, pre-polymer and / or oligomer chains.

[0120] There is also provided a thermosetting fire-retardant resin composition for use in a woodresin composite product, including:

[0121] precursor components for producing a formaldehyde-based resin; and a guanidine fire-retardant material; and

[0122] wherein the composition has a pH of greater than 6.0.

[0123] The fire-retardant resins are designed to provide wood-resin composite products with good fire retardancy properties.

[0124] The resin composition may in some embodiments be referred to as a one-part resin composition. As used herein, the term 'one-part’ means that a single composition is used, e.g. containing the formaldehyde-based resin which incorporates a guanidine monomer / guanidine fire- retardant material as a component of the resin, or containing a fire-retardant material together with at least the precursor components for producing a formaldehyde -based resin.

[0125] In some embodiments, the composition comprises a fire-retardant material together with at least the precursor components for producing a formaldehyde-based resin.

[0126] The resin composition has good storage stability properties. The examples also demonstrate that exemplary resin compositions according to the present disclosure form woodresin composite products which not only have good fire retardancy properties, but which also have good bonding strength and which have relatively low water uptake. Accordingly, the resin composition of the present disclosure is a simple and convenient to use substance which imparts wood-based materials with beneficial properties.

[0127] The use of such a one-part resin composition allows for simple preparation and use, and avoids the need in use for an additional step of adding in a fire-retardant material to a resin composition shortly before use. Compared with methods involving coating of or soaking into finished panels, the present resin composition again allows for simple use, being incorporated into the product during its manufacture, rather than requiring the panel to be manufactured and then a coating or soaking step carried out. In other words, the resin composition can be used with unbonded fibers, and used to bond those fibers together into materials such as MDF, HDF or fiberboard. In many cases, common fire-retardant additives either need to be coated or soaked onto the fibers separately to prevent premature curing of the resin or to achieve homogeneous distribution, or they are mixed with the resin just prior to being applied to the wood-based material. Each of these methods requires additional engineering solutions, chemical procurement, and chemical storage.

[0128] The resin composition is a thermosetting resin composition. As used herein, the term “thermosetting” refers to a resin composition which cures or sets on exposure to heat. “Set” means that the resin, after binding to other components such as wood fibers, hardens or polymerises, resulting in the other components being bound together.

[0129] Resin composition may in some cases cure or set on exposure to low pH, (e.g. a pH below 7). Some resins will cure or set over time, for example due to a drop in pH due to ageing. A drop in pH can occur due to factors such as oxidation of one or more components.

[0130] In some embodiments, the resin composition sets or cures at a temperature equal to or greater than 100°C, or equal to or greater than 175°C, or equal to or greater than 200°C. In some embodiments, the resin composition does not set or cure at a temperature below 100°C.

[0131] The resin composition is fire-retardant. As used herein, the term “fire-retardant” refers to the ability of a material to resist catching on fire, and / or to slow down or stop the spread of fire through the material.

[0132] In some embodiments, the term ‘fire-retardant’, when used in respect of the resin composition, refers to the resin composition when used in a wood-resin composite product, fulfilling the requirements of one or more of the following standards: ISO 9750, ISO 5660, AS / NZS 3837, and EN 13501-1:2007+Al:2009.

[0133] The resin composition is for use in a wood-resin composite product. As used herein, the term “wood-resin composite product” means a product prepared from a wood or wood-based material and the resin composition as defined herein. Typically, the product contains a cured mixture of the wood or wood-based material and the resin composition, and may optionally contain additional components. The product may for example contain multiple wood or wood-based layers, such as in the case of plywood, which is a composite material manufactured from thin layers or plies of wood that are glued together. As another example, the product may contain wood or wood-based particles, such as fibers or chips, that are mixed with resin, pressed into a desired shape and cured. Examples of wood-resin composite products include medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), plywood, fiberboard, laminated timber, particleboard and panel board. In some embodiments, the wood-resin composite product is in the form of medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), fiberboard or particleboard.

[0134] The resin composition comprises or is produced from precursor components for producing a formaldehyde-based resin. A formaldehyde-based resin is a resin which is produced from formaldehyde as one of the resin components.

[0135] Examples of such resins include phenol formaldehyde resins; melamine formaldehyde resins; urea formaldehyde resins; melamine, urea and formaldehyde resins; and novolacs.

[0136] Phenol formaldehyde resins include resins made with phenol and phenol-equivalents, such as cresols (ortho-, meta- or para-cresol) or / ert-butylphenols (2-z<?rt-butylphenol, 3-tert-butylphenol or 4-ter / -butylphenol ). NH2

[0137] N^N

[0138] A

[0139] Melamine has the stnictureH2N N NH2.

[0140] Any form of formaldehyde may be used, such as molecular formaldehyde, 1,3,5-trioxane (a molecular trimer of formaldehyde), paraformaldehyde, methanediol, and formaldehyde oligomers, or any mixture of two or more forms.

[0141] In some embodiments, the fire-retardant resin composition may be prepared using formalin (an aqueous solution of formaldehyde). While any concentration of formaldehyde known to be useful to those skilled in the art of preparing resins may be used, in some embodiments formalin having from 30 wt% to 60 wt% formaldehyde is used. Such formalins are widely available. In some embodiments, the formalin will have a concentration of about 35 wt% formaldehyde. In other embodiments, the formalin will have a concentration of about 50 wt% formaldehyde.

[0142] For avoidance of doubt, the term “wt%” means the weight of the component of interest divided by the total weight, multiplied by 100. For example, a formalin solution having 30 wt% formaldehyde means that there is 30 g of formaldehyde in a 100 g sample of formalin.

[0143] References to wt% of components in connection with the resin compositions of the disclosure refer either to the weight of the component of interest divided by the total weight, multiplied by 100, or to the weight of the component of interest used to produce the resin composition, divided by the total weight of components used to produce the resin composition, multiplied by 100.

[0144] In some embodiments, the resin composition contains formaldehyde in an amount of from about 10 wt% to about 60 wt%, such as from about 5 wt% to about 50 wt%, or from about 15 wt° / o to about 40 wt%, or from about 20 wt% to about 45 wt%.

[0145] In some embodiments, the composition contains or is produced from formaldehyde in an amount of from 10 wt% to 35 wt%.

[0146] In some embodiments, the composition contains formaldehyde in an amount of from 20 wt% to 30 wt%.

[0147] In some embodiments, the resin composition contains or is produced from formaldehyde in an amount of about 10 wt%, about 11 wt%, about 12 wt%, about 13 wt%, about 14 wt%, about 15 wt%, about 16 wt%, about 17 wt%, about 18 wt%, about 19 wt%, about 20 wt%, about 21 wt%, about 22 wt%, about 23 wt%, about 24 wt%. about 25 wt%, about 26 wt° / o, about 27 wt%, about 28 wt%, about 29 wt%, about 30 wt%, about 31 wt%, about 32 wt%, about 33 wt%, about 34 wt%, or about 35 wt%. In some embodiments, the amount of formaldehyde in a fire-retardant resin composition is about 23 wt%, or about 24 wt%.

[0148] Formaldehyde can be obtained from a range of commercial suppliers, such as Hexion (https: / www hexion.com).

[0149] In some embodiments, the resin composition comprises or is produced from precursor components for producing a phenol-formaldehyde resin. In such embodiments, the precursor components comprise formaldehyde (in any suitable form) and a phenol or a phenol-equivalents, such as cresols (ortho-, meta- or para-cresol) or tert-butylphenols (2-Zert-butylphenol, 3-tert-butylphenol or 4- / ert-butylphenol). Again, such materials can be obtained from a range of commercial suppliers.

[0150] However, in some other embodiments, the resin composition does not contain or is not produced from precursor components for producing a phenol formaldehyde resin (i.e. the resin produced is not a phenol formaldehyde resin). In some embodiments, the resin composition comprises or is produced from precursor components for producing a melamine-formaldehyde resin. In some embodiments, the resin composition comprises or is produced from precursor components for producing a melamine-urea-formaldehyde resin. In such embodiments, the precursor components are melamine, urea and formaldehyde (in any suitable form).

[0151] Where melamine is used, the melamine may be of any grade known to be useful to those of ordinary skill in the art of preparing resin compositions.

[0152] Where melamine is used, the amount of melamine in the fire-retardant resin composition or from which the fire-retar may for example be in the range of from about 1 wt% to about 30 wt%, such as from about 1 wt% to about 20 wt%, or from about 1.5 wt% to about 10 wt%, or from about 2 wt% to about 8 wt%.

[0153] In some embodiments, the composition contains or is produced from melamine in an amount of from 1 wt% to 4 wt%.

[0154] In some embodiments, the resin composition contains or is produced from an amount of melamine of about 1.5 wt%, about 1.6 wt%, about 1.7 wt%, about 1.8 wt%, about 1.9 wt%, about 2.0 wt%, about 2.1 wt%, about 2.2 wt%, about 2.3 wt%, about 2.4 wt%, about 2.5 wt%, about 2.6 wt%, about 2.7 wt%, about 2.8 wt%, about 2.9 wt%, about 3.0 wt%, about 3.1 wt%, about 3.2 wt%, about 3.3 wt%, about 3.4 wt%, about 3.5 wt%, about 3.6 wt%, about 3.7 wt%, about 3.8 wt%, about 3.9 wt%, or about 4.0 wt%. In some embodiments, the fire-retardant resin composition contains or is produced from an amount of melamine of about 2.6 wt%. In some embodiments, the resin composition comprises or is produced from urea, for example where the precursor components for a formaldehyde-based resin are precursor components for a urea-formaldehyde or melamine-urea-formaldehyde resin.

[0155] Any suitable form of urea may be used, in any grade suitable for producing the fire-retardant resin composition.

[0156] For example, in some embodiments the urea may be in the form of solid granules. In some embodiments, the urea has a purity of at least about 90% by weight, or at least about 95 % by weight, or at least about 97% by weight, or at least about 98% by weight, or at least about 99% by weight.

[0157] In some embodiments, the resin composition contains or is produced from urea in an amount of up to 65 wt%, for example from about 1 wt% to about 40 wt%, or from about 5 wt% to about 40 wt%, or from about 10 wt% to about 30 wt%.

[0158] In some embodiments, the composition contains or is produced from urea in an amount of from 5 wt% to 25 wt%.

[0159] In some embodiments, the resin composition contains or is produced from urea in an amount of about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, about 10 wt%, about 11 wt%, about 12 wt%, about 13 wt%, about 14 wt%, about 15 wt%, about 16 wt%, about 17 wt%, about 18 wt%, about 19 wt%, about 20 wt%, about 21 wt%, about 22 wt%, about 23 wt%, about 24 wt%, about 25 wt%, about 26 wt%, about 27 wt%, about 28 wt%, about 29 wt%, or about 30 wt%. In some embodiments, the amount of urea in the fire-retardant resin composition is about 14 wt%.

[0160] The resin compositions comprise or are produced from a guanidine fire-retardant material, e.g. a guanidine monomer. As used herein, the term “guanidine fire-retardant material” means a material which is guanidine, or a material which incorporates a guanidine structural motif, or a salt thereof. As used herein, the term “guanidine monomer” includes guanidine, or a salt thereof.

[0161] Guanidine itself has the structure:

[0162]

[0163] A guanidine structural motif is:

[0164]

[0165] Guanidine fire retardant materials and guanidine monomers may include for example compounds where one or more nitrogens, instead of being hydrogen, may each independently be selected from the group consisting of Ci-6 alkyl, Ci-6 alkenyl, Ci-6 alkynyl, or cyano.

[0166] In some embodiments, the guanidine fire-retardant material or guanidine monomer is

[0167] guanidine,

[0168]

[0169] thereof.

[0170] In some embodiments, the guanidine fire-retardant material or guanidine monomer is not cyanoguanidine.

[0171] In some embodiments, the guanidine fire-retardant material or guanidine monomer is not a guanidine phosphate.

[0172] In some embodiments, a salt of guanidine, or a salt of a material which incorporates a guanidine structural motif, is used. Salts include hydrofluoride, hydrochloride, hydrobromide, hydroiodide, nitrate, sulfate, carbonate, thiocyanate, isothiocyanate, acetate, p-toluenesulfonate, phosphate and sulfamate. In some embodiments, a sulfamate salt of guanidine, or a material which incorporates a guanidine structural motif, is used. In some embodiments, the guanidine fire-retardant material or guanidine monomer is guanidine sulfamate. In some embodiments, the guanidine fire-retardant material or guanidine monomer is guanidine phosphate.

[0173] In some embodiments, a single guanidine fire-retardant material or guanidine monomer is used. In other embodiments, a mixture of guanidine fire retardant materials or guanidine monomers is used, for example two or more.

[0174] In some embodiments, the composition contains or is produced from an amount in the range of 5 wt% to 70 wt% guanidine fire retardant material or guanidine monomer, or from 5 wt% to 60 wt% guanidine fire retardant material or guanidine monomer. In some embodiments, the composition contains or is produced from an amount in the range of about 10 wt% to about 60 wt% guanidine fire-retardant material or guanidine monomer, or from about 30 wt% to about 60 wt% guanidine fire retardant material or guanidine monomer, or from 40 wt% to 70 wt% guanidine fire retardant material or guanidine monomer, or from about 10 wt% to about 30 wt% guanidine fire-retardant material or guanidine monomer. In some embodiments, the composition contains or is produced from an amount of guanidine fire-retardant material or guanidine monomer selected from the group consisting of about 45 wt%, about 46 wt%, about 47 wt%, about 48 wt%, about 49 wt%, about 50 wt%, about 51 wt%, about 52 wt%, about 53 wt%, about 54 wt%, about 55 wt%, about 56 wt%, about 57 wt%, about 58 wt%, about 59 wt%, or about 60 wt%. In some embodiments, the composition contains or is produced from an amount of guanidine fire-retardant material or guanidine monomer of about 58 wt%.

[0175] In some embodiments, the guanidine fire-retardant materialor guanidine monomer is guanidine sulfamate, and the composition contains or is produced from guanidine sulfamate in an amount of from 5 wt% to 70 wt%.

[0176] In some embodiments, the guanidine fire-retardant material or guanidine monomer is guanidine sulfamate, and the composition contains or is produced from guanidine sulfamate in an amount of from 40 wt% to 70 wt%.

[0177] In some embodiments, the guanidine fire-retardant material is guanidine sulfamate, and the composition contains or is produced from guanidine sulfamate in an amount of from 45 wt% to 65 wt%.

[0178] In some embodiments, the guanidine fire-retardant material or guanidine monomer is guanidine sulfamate, and the composition contains or is produced from guanidine sulfamate in an amount of from 55 wt% to 60 wt%.

[0179] In some embodiments, the guanidine fire-retardant material or guanidine monomer is guanidine sulfamate, and the composition contains or is produced from guanidine sulfamate in an amount of about 58 wt%.

[0180] In some embodiments, the composition contains or is produced from: formaldehyde in an amount of from 10 wt% to 35 wt%;

[0181] melamine in an amount of from 1 wt% to 30 wt%;

[0182] urea in an amount of up to 65 wt%; and

[0183] guanidine sulfamate in an amount of from 5 wt% to 70 wt%.

[0184] In some embodiments, the composition contains or is produced from:

[0185] formaldehyde in an amount of from 20 wt% to 30 wt%;

[0186] - melamine in an amount of from 1 wt% to 4 wt%;

[0187] urea in an amount of from 5 wt% to 25 wt%; and

[0188] guanidine sulfamate in an amount of from 40 wt% to 70 wt%. Without wishing to be bound by theory, the present inventors consider that, for formaldehyde resins containing urea (such as melamine-urea-formaldehyde resins), the guanidine material can be used to replace some or all of the urea present, maintaining good resin properties, providing strong fire retardancy, and a convenient resin formulation that can be readily used and which is stable on storage.

[0189] The guanidine fire-retardant material or guanidine monomer is non-toxic and not destructive to the environment, which is superior to other fire-retardant resins such as those which utilize halogens as fire retardants. In addition, the fire retardant being incorporated into the resin allows for convenience, efficiency and ease of use as there is no mixing required before application to wood products. Moreover, the resin has been proven to provide successful fire retardancy by its innate ability to self-extinguish.

[0190] These qualities are desirable in that with application they display the potential to play a fundamental role in tackling the growing concern of wildfires and domestic fires, and could lead to an increase in safety in the built environment.

[0191] The resin composition typically contains water, particularly prior to being cured. Water may be added together with one or more components of the composition (for example some components may be provided as solutions in water andrir the wood-based material may contain water) and / or water may be added separately to bring the water content to a desired level.

[0192] In some embodiments, the composition has a water content of less than 35 wt%, for example it may contain water in an amount of less than 20 wt%, or in an amount of from 5 wt% to 35 wt%, or from 5 wt% to 30 wt%, or from 5 wt% to 25 wt%, or from 5 wt% to 20 wt%, or from 5 wt% to 15 wt%, or from 5 wt% to 10 wt%.

[0193] In some embodiments, the total amount of water present in the fire-retardant resin composition may be about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, about 10 wt%, about 11 wt%, about 12 wt%, about 13 wt%, about 14 wt%, about 15 wt%, about 16 wt%, about 17 wt%, about 18 wt%, about 19 wt%, about 20 wt%, about 21 wt%, about 22 wt%, about 23 wt%, about 24 wt%, about 25 wt%, about 26 wt%, about 27 wt%, about 28 wt%, about 29 wt%, about 30 wt%, about 31 wt%, about 32 wt%, about 33 wt%, about 34 wt%, or about 35 wt%. In some embodiments, the total amount of water present in the fire-retardant resin composition is about 13 wt%.

[0194] In some embodiments, the fire-retardant resin composition may have high solids content. For example, in some embodiments, the composition has a solids content of at least 65 wt%, or at least 75 wt%, or at least 80 wt%, or at least 85 wt%, or at least 90 wt%. In some embodiments, the composition has a solids content in the range of from 65 wt% to 95 wt%, or from 65 wt% to 90 wt%, or from 80 wt% to 90 wt%.

[0195] The resin composition has a pH of greater than 6.0.

[0196] In some embodiments, the pH of the resin composition is in the range of from pH 6.0 to pH 9.0, or from about pH 6.0 to about pH 8.50, or from about pH 6.8 to about pH 7.5, or from about pH 7.2 to about pH 8.2. In some embodiments, the composition has a pH of great than about 7.0. hi some embodiments, the composition has a pH between about 7.0 and about 9.0.

[0197] In some embodiments, the pH of the resin composition is about pH 6.9, about pH 6.95, about pH 7.0, about pH 7.05, about pH 7.1, about pH 7.15, about pH 7.2, about pH 7.25, about pH 7.3, about pH 7.35, about pH 7.4, about pH 7.45, about pH 7.5, about pH 7.55, about pH 7.6, about pH 7.65, about pH 7.7, about pH 7.75, about pH 7.8, about pH 7.85, about pH 7.9, about pH 7.95, about pH 8.0, about pH 8.05, about pH 8.1, about pH 8.15, about pH 8.2, about pH 8.25, or about pH 8.3. In some embodiments, the pH of the resin composition is about pH 7.35.

[0198] The pH of the thermosetting fire-retardant resin composition can be adjusted by adding a suitable amount of one or more pH adjusting agents. To maintain pH within a suitable desired range, a pH buffer may also or instead be included in the composition.

[0199] Accordingly in some embodiments, the resin composition comprises one or more pH adjusting agents. In some embodiments, the resin composition comprises one or more pH buffers.

[0200] Examples of pH adjusting agents include acids and bases.

[0201] Acids are added to reduce pH. Acids include hydrohalic acids (hydrochloric acid, hydrobromic acid, hydroiodic acid), mineral acids (boric acid, nitric acid, phosphoric acid, sulfonic acid, sulfuric acid, sulfurous acid), and organic acids (formic acid, acetic acid, propionic acid, butyric acid, valeric acid, maleic acid, malic acid, tartaric acid, citric acid, para-toluenesulfonic acid, methanesulfonic acid). The amount of acid required to adjust the pH to a desirable level can be readily determined by the skilled person.

[0202] In some embodiments, the thermosetting fire-retardant resin composition comprises an acid in an amount of from 0 wt% to 1 wt%, such as from about 0.05 wt% to about 0.9 wt%, or from about 0.07 wt% to about 0.7 wt%, or from about 0.08 wt% to about 0.3 wt%, or from about 0.1 wt% to about 0.2 wt%. In some embodiments, the thermosetting fire-retardant resin composition comprises an acid in an amount of about 0.01 wt%, about 0.02 wt%, about 0.03 wt%, about 0.04 wt%, about 0.05 wt%, about 0.06 wt%, about 0.07 wt%, about 0.08 wt%, about 0.09 wt%, about 0.10 wt%, about 0.11 wt%, about 0.12 wt%, about 0.13

[0203]

[0204] about 0.14 wt%, about 0.15 wt%, about 0.16 wt%, about 0.17 wt%, about 0.18 wt%, about 0.19 wt%, or about 0.20 wt%. In some embodiments, the thermosetting fire-retardant resin composition comprises an acid in an amount of about 0.10 wt%.

[0205] In some embodiments, the resin composition comprises an acid which is formic acid. In some embodiments, the resin composition comprises no added base.

[0206] Bases are added to increase pH. Bases include metal hydroxides (lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide), metal oxides (silicon oxides, aluminium oxide, magnesium oxide, calcium oxide), and metal carbonates (lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate). The amount of base required to adjust the pH to a desirable level can be readily determined by the skilled person.

[0207] In some embodiments, the thermosetting fire-retardant resin composition comprises a base in an amount of from 0 wt% to 5 wt%, such as from about 0 wt% to about 3.5 wt%, or from about 0.01 wt% to about 2.50 wt%, or from about 0.02 wt% to about 1.80 wt%. hi some embodiments, the thermosetting fire-retardant resin composition comprises a base in an amount of about 0 wt%, about 0.01 wt%, about 0.02 wt%, about 0.03 wt%, about 0.04 wt%, about 0.05 wt%, about 0.06 wt%, about 0.07 wt%, about 0.08 wt%, about 0.09 wt%, or about 0.10 wt%. In some embodiments, the thermosetting fire-retardant resin composition comprises a base in an amount of about 0.10 wt%.

[0208] In some embodiments, the resin composition comprises a base which is sodium hydroxide. In some embodiments, the thermosetting fire-retardant resin composition comprises no added base.

[0209] A buffer can be used to maintain the pH at a relatively constant value. Exemplary buffers include monopotassium phosphate (KH2PO4), A-cyclohexyl-2-aminoethanesul fonic acid (CHES), borate, monoethanolamine, diethanolamine and triethanolamine.

[0210] The amount of buffer required to maintain the pH at a desirable level can be readily determined by the skilled person.

[0211] In some embodiments, the thermosetting fire-retardant resin composition comprises a buffer in an amount of from 0.01 wt% to 1 wt%, such as from about 0.03 wt% to about 0.80 wt%, or from about 0.05 wt% to about 0.60 wt%, or from about 0.08 wt% to about 0.25 wt%, or from about 0.10 wt% to about 0.15 wt%. In some embodiments, the thermosetting fire-retardant resin composition comprises a buffer in an amount of about 0.01 wt%, about 0.02 wt%, about 0.03 wt%, about 0.04 wt%, about 0.05 wt%, about 0.06 wt%, about 0.07 wt%, about 0.08 wt%, about 0.09 wt%, about 0.10 wt%, about 0.11 wt%, about 0.12 wt%, about 0.13 wt%, about 0.14 wt%, about 0.15 wt%, about 0.16 wt%, about 0.17 wt%, about 0.18 wt%, about 0.19 wt%, or about 0.20 wt%. In some embodiments, the thermosetting fire-retardant resin composition comprises a buffer in an amount of about 0.10 wt%.

[0212] In some embodiments, the resin composition comprises a buffer which is triethanolamine. In some embodiments, the resin composition comprises pH-adjusting agents and buffers which are sodium hydroxide, formic acid and triethanolamine.

[0213] Without wishing to be bound by theory, it is believed that the stability of the thermosetting fire-retardant resin compositions of this disclosure is due in part to control of pH of the composition, which may reduce or avoid unwanted instability before the article of manufacture is ready to be cured in the presence of wood fibres.

[0214] In some embodiments, the theimosetting fire-retardant resin composition comprises or is produced from formaldehyde:guanidine fire-retardant material (e.g. guanidine monomer) having a weight ratio of from about 1:2 to about 1:7, or about 1:3, or about 1:4, or about 1:5, or about 1:6, or about 1:7. In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from formaldehyde: guanidine fire-retardant material (e.g. guanidine monomer) having a weight ratio of about 1:5. Within the above embodiments, in some examples the guanidine fire-retardant material (e.g. guanidine monomer) is guanidine sulfamate. In some embodiments, the guanidine fire-retardant material (e.g. guanidine monomer) is guanidine phosphate.

[0215] In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from melamine, and the melamine:guanidine fire-retardant material (e.g. guanidine monomer) weight ratio is in the range of from about 1:10 to about 1:40, or about 1:15, or about 1:16, or about 1:17, or about 1:18, or about 1:19, or about 1:20, or about 1:21, or about 1:22, or about 1:23, or about 1:24, or about 1:25. In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from melamine:guanidine fire-retardant material (e.g. guanidine monomer) having a weight ratio of about 1:22. Within the above embodiments, in some examples the guanidine fire-retardant material (e.g. guanidine monomer) is guanidine sulfamate. In some embodiments, the guanidine fire-retardant material (e.g. guanidine monomer) is guanidine phosphate. In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from urea, and the urea:guanidine fire-retardant material (e.g. guanidine monomer) weight ratio is in the range of from about 1:1 to about 1:10, or about 1:2, or about 1:3, or about 1:4, or about 1:5, or about 1:6, or about 1:7, or about 1:8. In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from urea:guanidine fire-retardant material (e.g. guanidine monomer) having a weight ratio of about 1:4.

[0216] In some embodiments, the thermosetting fire-retardant resin composition comprises no urea, for example such as when all of the urea is replaced with a guanidine fire-retardant material (e.g. guanidine monomer). Within the above embodiments, in some examples the guanidine fire-retardant material (e.g. guanidine monomer) is guanidine sulfamate. In some embodiments, the guanidine fire-retardant material (e.g. guanidine monomer) is guanidine phosphate.

[0217] In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from melamine, and the formaldehyde:melamine weight ratio is in the range of from about 2:1 to about 15:1, or about 3:1, or about 3.5:1, or about 4:1, or about 4.5:1, or about 5:1, or about 5.5:1, or about 6:1, or about 6.5:1, or about 7:1, or about 7.5:1, or about 8:1, or about 8.5:1. In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from formaldehyde:melamine having a weight ratio of about 4.5:1.

[0218] In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from urea, and the fonnaldehyde:urea weight ratio is in the range of from about 1:0.9 to about 1:2.1, or about 1:1, or about 1:1.1, or about 1:1.2, or about 1:1.3, or about 1:1.4, or about 1: 1.5, or about 1:1.6, or about 1:1.7, or about 1:1.8. In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from formaldehyde:urea having a weight ratio of about 1:1.2.

[0219] In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from melamine and urea, and the melamine:urea weight ratio is in the range of from about 1:1 to about 1:12, or about 1:3.0, or about 1:3.5, or about 1:4.0, or about 1:4.5, or about 1:5.0, or about 1:5.5, or about 1:6.0, or about 1:6.5, or about 1:7.0, or about 1:7.5, or about 1:8.0, or about 1:8.5, or about 1:9.0, or about 1:9.5, or about 1:10. In some embodiments, the thermosetting fire-retardant resin composition comprises or is produced from melamine:urea having a weight ratio of about 1:5.5.

[0220] Properties of thermosetting fire-retardant resin composition The resin composition has good storage stability properties. In some embodiments, the resin composition is substantially stable to curing at 35°C for a period of at least 8 days, or for at least 14 days, or for at least 1 month, or for at least 3 months, or for at least 6 months.

[0221] In some embodiments, the resin composition does not significantly degrade on storage at 25°C over a period of at least 3 days, over a period of at least 4 days, over a period of at least 5 days, over a period of at least 6 days, over a period of at least 7 days, over a period of at least 8 days, over a period of at least 9 days, over a period of at least 10 days, over a period of at least 11 days, over a period of at least 12 days, over a period of at least 13 days, over a period of at least 2 weeks, or over a period of at least 1 month, or over a period of at least 3 months.

[0222] The term “cure” for example means to interact with other compounds within a resin (e.g. polymerise) to produce a solid thermoset binding material. The present resin compositions are useful as they can be prepared and are usable for a significant period of time.

[0223] Generally speaking, for conventional MUF resins, the poor stability of low mole ratio resins results in significant viscosity gain that adversely affects resin distribution and results in decreased physical properties, unless resin dosage is dramatically increased. Increasing resin dosage is usually undesirable as this practice may increase costs to fabricators and the increased amounts of resins in products may offset or at least mitigate reductions in formaldehyde emissions. Another aspect of poor stability of conventional low mole ratio MUF resins is precipitation, sedimentation, and creation of two phases, which renders the resins unusable.

[0224] The stability can be measured by a change in viscosity of the composition, whereby a composition that does not increase in viscosity greatly over time is deemed to be stable, whereas a composition which does increase in viscosity significantly over time is no longer stable, wherein curing is taking place. Viscosity can be measured using various types of viscometers (such as a glass capillary viscometer) and rheometers. Viscosity may for example be measured for compositions at a temperature of 25°C, using for example a Brookfield cone and plate viscometer with a spindle 1 at 750 rpm.

[0225] In some embodiments, on storage at 25°C, the viscosity of the resin composition changes by no more than 50 cP when measured at 25°C, following storage over a 3-day period, or over a 7-day period.

[0226] In some embodiments, the composition is substantially stable if a viscosity of the composition increases by no more than 50 cP within a 24 hour period, when viscosity is measured at 25°C. In some embodiments, the composition is substantially stable if a viscosity of the composition increases by no more than 60 cP, or by no more than 70 cP, or by no more than 80 cP, or by no more than 90 cP, or by no more than 100 cP, within a 24 hour period, when viscosity is measured at 25°C.

[0227] The thermosetting fire-retardant resin compositions of this disclosure are particularly useful in preparing wood-resin composite products where the resin composition functions to bind or adhere wood fibres together, and the resulting wood-resin composite product is fire-retardant. The compositions are easy to use, avoiding the need for separate processing to introduce fire retardancy properties, and maintain good properties for the resulting wood-resin composite products. For example, the example compositions have properties such as good bonding strength between the resin and wood fibers, low water uptake / acceptable swelling, low formaldehyde emission levels, as well as having good fire retardancy properties. In contrast, some liquid phosphate fire-retardant additives impact the mechanical performance of the finished product.

[0228] Wood-Resin Composite Products

[0229] The present disclosure also relates to a wood-resin composite product produced or producible by thermosetting of a mixture comprising wood fibers and a composition as defined above.

[0230] Wood is a natural composite of cellulose fibers, derived from structural tissues in the stems and roots of trees and other woody plants. A wood-resin composite product includes products such as particleboard (PB), hardwood plywood (HWP), laminated veneer lumber (LVL), composite wood, marine plywood, multiply plywood, interior plywood, exterior plywood, medium-density overlay plywood, high-density overlay plywood, low-density fibreboard, strawboard, signboard, low-density fibreboard (LDF), medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), plywood, fiberboard, laminated timber, or panel board. The wood-resin composite product may be prepared using any method known to be useful to those of ordinaiy skill in the art. For example, particleboard may be prepared using the methods disclosed in U. S. Patent No. 4,482,699 to Williams, the entire contents of which is incorporated herein by reference.

[0231] In some embodiments, the the wood-resin composite product is in the form of medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), fiberboard, or particleboard. In some embodiments, wood or wood fibers may be in a form selected from the group consisting of particles, strands, veneers, chips, sawdust, and mixtures thereof.

[0232] In some embodiments, the composite product comprises from 1 wt% to 30 wt% resin solids. This is the amount of resin that remains after the product has been thermoset and all liquids removable by the thermosetting and any other drying steps have been removed. In some embodiments, the composite product comprises from 1 wt% to 18 wt% resin solids, or from 5 wt% to 16 wt% resin solids, or from 8 wt% to 18 wt% resin solids, or from 10 wt% to 14 wt% resin solids, or from 15 wt% to 24 wt% resin solids, or from 18 wt% to 28 wt% resin solids, or from 22 wt% to 30 wt% resin solids.

[0233] In some embodiments, the composite product comprises from 10 wt% to 30 wt% resin solids.

[0234] In some embodiments, the composite product comprises from 20 wt% to 30 wt% resin solids.

[0235] In some embodiments, the composite product comprises about 2 wt% resin solids, about 3 wt% resin solids, about 4 wt% resin solids, about 5 wt% resin solids, about 6 wt% resin solids, about 7 wt% resin solids, about 8 wt% resin solids, about 9 wt% resin solids, about 10 wt% resin solids, about 11 wt% resin solids, about 12 wt% resin solids, about 13 wt% resin solids, about 14 wt% resin solids, about 15 wt% resin solids, about 16 wt% resin solids, about 17 wt% resin solids, about 18 wt% resin solids, about 19 wt% resin solids, about 20 wt% resin solids, about 22 wt% resin solids, about 24 wt% resin solids, about 26 wt% resin solids, about 28 wt% resin solids, or about 30 wt% resin solids.

[0236] In some embodiments, the composite product has a resin solids content in the range of from 30 wt% to 80 wt%. As used herein, the term “resins solid content” means the mass of resin components after the composite product has been thermoset, divided by the mass of resin components before the composite product has been thermoset, multiplied by 100. The resins solid content is the reverse of water content, and is a measure of how much water or other volatile components have been lost or how much solids remain in the product, after thermosetting. It is also noted that polymerisation of one mole of formaldehyde results in production of one mole of water, which is then lost upon heating and processing of the composite product.

[0237] For example, in some embodiments the resin solids content is in the range of from about 40 wt% to about 80 wt%, or from about 55 wt% to about 75 wt%, or from about 65 wt% to about 74 wt%, or from about 70 wt% to about 73 wt%. In some embodiments, the composite product has a resin solids content of about 65 wt%, or about 66 wt%, or about 67 wt%, or about 68 wt%, or about 69 wt%, or about 70 wt%, or about 71 wt%, or about 72 wt%, or about 73 wt%, or about 74 wt%, or about 75 wt%, or about 76 wt%, or about 77 wt%, or about 78 wt%, or about 79 wt%, or about 80 wt%. In some embodiments, the composite product has a resin solids content of about 73 wt%.

[0238] The wood-resin composite product may contain additional components if desired.

[0239] In some embodiments, the wood-resin composite product comprises a hardener.

[0240] Hardeners are used to assist with crosslinking of the resin. Exemplary hardeners include hexamethylenetetramine and magnesium sulfate.

[0241] In some embodiments, the wood-resin composite product comprises a wax. Waxes are used to assist with waterproofing of the composite product to reduce swelling. An exemplary wax is paraffin wax.

[0242] Properties of wood-resin composite products

[0243] The wood-resin composite products of the present disclosure have good properties. For example, alongside having good fire retardancy properties, example wood-resin composite products may have one or more of the following properties: good bonding strength between the resin and wood fibers, low water uptake / acceptable swelling, and low formaldehyde emission levels.

[0244] In some embodiments, wood-resin composite products of the present disclosure have high internal bond strength, for example as measured by AS / NZS 4266.6:2004.

[0245] In some embodiments, the fire-retardant wood-resin composite product has an internal bond strength of from about 0.35 MPa to about 1.00 MPa, for example as measured by AS / NZS 4266.6:2004.

[0246] In some embodiments, the fire-retardant wood-resin composite product has an internal bond strength of from about 0.35 MPa to about 0.80 MPa, such as from about 0.40 MPa to about 0.70 MPa, or from about 0.45 MPa to about 0.60 MPa, for example as measured by AS / NZS 4266.6:2004. In some embodiments, the fire-retardant wood-resin composite product with 12 wt% resin solids has a mean internal bond strength of about 0.50 MPa, for example as measured by AS / NZS 4266.6:2004.

[0247] In some embodiments, the fire-retardant wood-resin composite product has an internal bond strength of from about from about 0.50 MPa to about 1.10 MPa, such as from about 0.60 MPa to about 1.00 MPa, or from about 0.70 MPa to about 0.90 MPa, for example as measured by AS / NZS 4266.6:2004. In some embodiments, the fire-retardant wood-resin composite product with 24 wt% resin solids has a mean internal bond strength of about 0.88 MPa, for example as measured by AS / NZS 4266.6:2004.

[0248] Wood-resin composite products of the present disclosure have good fire retardant properties, for example as measured by ISO 5660.

[0249] In some embodiments, the fire-retardant wood-resin composite product has a peak heat release rate of not more than 200 kW / m2, or not more than 175 kW / m2, or not more than 150 kW / m2, or not more than 125 kW / m2, for example as measured by ISO 5660. In some embodiments, the fire-retardant wood-resin composite product with 12 wt% resin solids has a peak heat release rate of not more than 160 kW / m2, for example as measured by ISO 5660. In some embodiments, the fire-retardant wood-resin composite product with 24 wt% resin solids has a peak heat release rate of not more than 110 kW / m2, for example as measured by ISO 5660.

[0250] In some embodiments, the fire-retardant wood-resin composite product has an average heat release rate from sustained flame to 700 seconds of not more than 100 kW / m2, or of not more than 90 kW / m2, or of not more than 80 kW / m2, or of not more than 70 kW / m2, for example as measured by ISO 5660. In some embodiments, the fire-retardant wood-resin composite product with 12 wt% resin solids has an average heat release rate from sustained flame to 700 seconds of not more than 86 kW / m2, for example as measured by ISO 5660. In some embodiments, the fire-retardant woodresin composite product with 24 wt% resin solids an average heat release rate from sustained flame to 700 seconds of not more than 70 kW / m2, for example as measured by ISO 5660.

[0251] Preparation of Fire-Retardant Resin Compositions

[0252] The present disclosure also relates to a method of producing a composition as defined herein, including: heating a mixture of precursor components for producing a formaldehyde-based resin;

[0253] adding a guanidine monomer to the heated mixture; and

[0254] heating the guanidine monomer-containing mixture.

[0255] The present disclosure also relates to a method of producing a fire-retardant resin composition as defined above, including: admixing precursor components for producing a formaldehyde-based resin; and a guanidine fire-retardant material.

[0256] The precursor components for producing a formaldehyde-based resin and guanidine fireretardant material (e.g. guanidine monomer), as described above, are commercially available from suppliers such as Hexion Merck

[0257]

[0258] (https: / / www.siauuialdricli.coin / Alj / en). and Fisher Scientific (h tips: / / w:: shersc i.

[0259]

[0260] The components of the resin composition may be combined in any suitable manner. In some embodiments, guanidine fire-retardant material (e.g. guanidine monomer) is added to a mixture comprising precursor components for producing a formaldehyde-based resin.

[0261] Preparation of a thermosetting fire-retardant resin composition may for example involve one or more cook stages, and a final addition stage. For example, precursor components may first be combined with heating, and then the mixture brought to ambient temperature and guanidine fire-retardant material (e.g. guanidine monomer) added.

[0262] In some embodiments of the above method, the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

[0263] In some embodiments, the precursor components for producing a formaldehyde-based resin are heated at a temperature in the range of from 70°C to 90°C; and / or wherein the mixture containing the guanidine fire-resistant material (e.g. guanidine monomer) is heated at a temperature in the range of from 70°C to 90°C.

[0264] In some embodiments of the above method, a mixture including formaldehyde, urea and melamine is heated at a temperature in the range of from 70°C to 90°C at a pH of from 5.5 to 6.5, until the mixture has a viscosity in the range of from 300 cP to 500 cP, and the mixture is then brought to ambient temperature and guanidine fire-retardant material (e.g. guanidine monomer), and optionally a pH-adjusting agent and / or a pH buffer, is added, such that the composition has a pH of greater than 7.0.

[0265] Preparation of Wood Resin Composite Products

[0266] The present disclosure also relates to a method of producing a wood-resin composite product, comprising coating wood fibers with a resin composition as defined above, and then thermosetting the resulting mixture.

[0267] Any suitable method for producing the wood-resin composite product may be used. For example, any suitable coating technique may be applied. In some embodiments of the above method, the resin composition is sprayed onto the wood fibers.

[0268] In other embodiments, for example in the case of plywood, a wood layer (containing wood fibers) may be coated with resin composition and then adhered to another layer of wood. Any suitable thermosetting technique may be utilised. In some embodiments, thermosetting is carried out by hot pressing of the mixture comprising the resin composition and the wood / wood fibers. In some embodiments, thermosetting may be carried out by hot pressing a mixture comprising the resin composition and the woodAvood fibers for a period of time of from 30 seconds to 500 seconds, or from 60 seconds to 400 seconds, or from 90 seconds to 300 seconds, or from 120 seconds to 200 seconds, or from 120 seconds to 160 seconds. In some embodiments, thermosetting may be carried out by hot pressing a mixture comprising the resin composition and the wood / wood fibers for a period of time of about 140 seconds.

[0269] Thermosetting may, for example, be earned out at a temperature above 100°C, or above 180°C, or above 200°C. In some embodiments, thermosetting may be carried out at a temperature of about 210°C.

[0270] Where hot pressing is used, thermosetting may for example be carried out at a pressure of at least 30 kg / cm2, or at least 35 kg / cm2, or at least 40 kg / cm2, or about 42 kg / enr.

[0271] In some embodiments, wood fibers are subjected to drying to reduce water content, prior to coating with a resin composition. For example, the wood fibers may be subjected to drying to reduce water content to a level of from about 1 wt% to about 20 wt%, or from about 5 wt% to about 15 wt%, or from about 8 wt% to about 12 wt%. In some embodiments, the water content of wood fibers after drying is about 5 wt%, or about 6 wt%, or about 7 wt%, or about 8 wt%, or about 9 wt%, or about 10 wt%, or about 11 wt%, or about 12 wt%, or about 13 wt%, or about 14 wt%, or about 15 wt%. In some embodiments, the water content of wood fibers after drying is about 10 vA° / o.

[0272] In some embodiments, a wax may be added. For example, wood fibers may be coated with wax before application of the resin composition, simultaneously with the resin composition, or after application of the resin composition. In some embodiments the amount of wax is from about 0 to about 5 wt% based on the weight of the wood fibers, such as from about 0.1 wt% to about 4 wt%, or from about 0.2 wt% to about 3 wt%, or from about 0.5 wt% to about 2 wt%. In some embodiments the amount of wax is about 0.96 wt% based on the weight of the wood fibers. In some embodiments the amount of wax added is about 0.84 wt% based on the weight of the wood fibers.

[0273] The wood-resin composite product may have any desired shape or size, depending on the intended use. In some embodiments, the thickness of the wood-resin composite product, after thermosetting, is in the range of from about 2 mm to about 500 mm, or from about 5 mm to about 250 mm, or from about 8 mm to about 100 mm, or from about 12 mm to about 50 mm. In some embodiments, the thickness of the wood-resin composite product, after thermosetting, is about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm, about 14 mm, about 15 mm, about 16 mm, about 17 mm, about 18 mm, about 19 mm, about 20 mm, about 21 mm, about 22 mm, about 23 mm, about 24 mm, about 25 mm, about 26 mm, about 27 mm, about 28 mm, about 29 mm, about 30 mm, about 31 mm, about 32 mm, about 33 nun, about 34 mm, about 35 mm, about 36 nun, about 37 mm, about 38 mm, about 39 mm, about 40 mm, about 41 mm, about 42 mm, about 45 mm, about 50 mm, about 60 mm, about 70 mm, about 80 mm, about 90 mm, about 100 mm, about 120 mm, about 130 mm, about 140 nun, about 150 mm, about 200 nun, about 250 mm, about 300 nun, about 350 mm, about 400 mm, about 450 mm, or about 500 mm.

[0274] Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications.

[0275] Examples

[0276] The present disclosure is further illustrated by the following non-limiting examples.

[0277] Example 1 - Preparation of standard resin ( comparator)

[0278] To a 5 L RBF equipped with a condenser 36.5 wt % of 50 % formaldehyde, 2.1 % of water, 0.1 % of 30 % Sodium hydroxide solution was heated to 50°C and adjusted to a pH 4.2. 22.4 wt % of urea and 3.8 % of melamine was then added and the solution was then heated to 80 degrees over 20 minutes through exotherm and external heating. The solution is then adjusted to a pH of 5.9 and condensed to a viscosity of 375 cP. The solution is then set to cool while 0.1 wt % of 85 % triethanolamine solution and 34.9 wt % of urea is added.

[0279] Example la - Preparation of exemplary fire-retardant resins

[0280] Resins were manufactured following the below procedure. To a 5 L round bottom flask equipped with a condenser was added 20 to 40 wt% of 50% formaldehyde, 1 to 2.5 wt% water, 0 to 1 wt% of 30% NaOH solution, 1 to 3.8 wt% melamine and 14 to 23 wt% of urea. The solution was heated to a temperature within the range of 70°C to 90°C and then adjusted to a pH range of approximately 6.0 and condensed until a viscosity of 300 cP to 500 cP was reached. The solution was then cooled to room temperature, before addition of 0 to 1% of triethanolamine followed by either 30% to 60% of urea or guanidine sulfamate (GUS) until folly incorporated. Depending on the end charge of urea or guanidine sulfamate, the resulting resin was a standard resin or a fire-retardant (FR) resin.

[0281] A typical preparation is as follows. To a 5 L RBF equipped with a condenser 23.5 wt % of 50 % formaldehyde, 1.4 % of water was heated to 50°C and adjusted to a pH 4.2. 14.4 wt % of urea and 2.6 % of melamine was then added and the solution is then heated to 80 degrees over 20 minutes through exotherm and external heating. The solution is then adjusted to a pH of 5.9 and condensed to a viscosity of 375 cP. The solution is then set to cool while 0.1 wt % of 85 % triethanolamine solution and 58.2 wt % of guanidine sulfamate is added. The resin was then heated for 30 minutes at 80 degrees and then set to cool.

[0282] The table below summarises resin components and their amounts for a standard resin and an FR resin according to the present disclosure.

[0283] Table 1: Resin components

[0284]

[0285]

[0286] Example lb - Preparation of exemplary fire-retardant resins

[0287] A fire-retardant resin composition was prepared in accordance with the amounts from Table 1: 1175g of 50% formaldehyde and water was charged into a round bottom flask. The flask was then heated to 50°C and the pH was adjusted to a pH of 3.5 to 4.5 with 10% formic acid. 130 g of melamine and 720g of urea were then added to the flask and continuous stirring was applied. The solution was then heated to a temperature of from 70°C to 80°C over 20 minutes. The pH was then adjusted to a pH from 5.0 to 6.0. The solution viscosity was monitored until it reached a viscosity of about 375 cP. 5g of triethanolamine was then added followed by 2910g of guanidine sulfamate, and the mixture was stirred until all material had dissolved. The solution was then cooled to 25°C, pH was adjusted to be within a range of from 7.0 to 9.0 with 46% NaOH solution and the resulting resin composition was decanted from the reactor before use.

[0288] Resins were characterized by standard methods including viscosity, measured on a Brookfield cone and plate viscometer with a spindle 1 at 750 rpm, refractive index measured on a RUDOLPH J57 automatic refractometer, pH measured on a JenWay pH probe, specific gravity measured by density cup and water tolerance measure by water titration.

[0289] The table below shows the properties of the standard resin and the FR resin.

[0290] Table 2: Resin properties

[0291]

[0292]

[0293] The results indicate that substitution of at least a portion of urea with a guanidine fire-retardant material (e.g. guanidine sulfamate) to prepare the fire-retardant resin, has a minor effect on standard characteristics overall, and is able to achieve a similar water tolerance, while only slightly differing in its solid content (affecting specific gravity and RI) and pH, which will change dependent on the amount of guanidine fire-retardant material used. Having a resin with similar properties to currently used resins is advantageous, as it will be a more easily transferable technology for current users.

[0294] The FR resins described herein are substantially stable against curing on storage at ambient temperatures. Initial data also suggests that the shelflife of the FR resin is either equivalent to or better than standard resins that do not contain a guanidine fire-retardant material, when stored at 35°C. The results of preliminary testing are summarised in Fig. la, which shows shelflife at 35°C for a standard resin (Std. MUF Resin) versus a fire-retardant (FR) resin of the present disclosure, as a function of resin viscosity over time. Fig. lb shows shelf life at 25°C for a standard resin (Std. MUF Resin) versus a fire-retardant (FR) resin of the present disclosure, as a function of resin viscosity over time. Resin viscosity was measured as discussed above, on a Brookfield cone and plate viscometer with a spindle 1 at 750 rpm.

[0295] Example 2 - Preparation of an exemplary wood-resin composite product

[0296] MDF manufacture

[0297] The resins from Example 1 were used to manufacture medium density fiberboard (MDF) panels. The MDF panels were approximately 12 mm thick and had a target density of approximately 750 kg / m\ Dry fiber (about 1094 g) with a 1% moisture content was loaded in a MDF fiber mixer and evenly spray-coated with resin mixture to disperse the resin mixture. The resin mixture comprised resin as described in Example 1, wax (60% solution; to give final solid content of 0.8 wt%), and water. A target resin solids loading of 12 or 24 wt%, compared to the weight of dry fiber, was prepared for each panel. The fiber was measured out to approximately the correct panel density and then compressed into a fiber mat of approximately 31 cm * 37 cm and 14 cm high, before being hot-pressed at about 210°C for 140 seconds at a pressure of about 42 kg / cm2. Typical ranges for components, and exemplary values for FR panels, are summarised below:

[0298] Table 3: MDF manufacturing ranges and examples

[0299]

[0300] The volume of water is dependent on the water content of the wood fiber, which ranges from 1 to 6%, and the water content of the added resin and wax. The total blend should have a target water content of 10% before hot pressing.

[0301] The above procedure describes how panels were made for the present work. In an industrial setting, the fiber is wet, and the resin is sprayed onto the wet fiber, which is then dried to a specific water content before being hot-pressed. The wax is sprayed separately and not mixed with the resin. MDF characterization

[0302] The MDF panels were characterized by 3 standard methods and one fire retardancy (FR) method:

[0303] • AS / NZS 4266.16:2004 - Formaldehyde emission-desiccator method;

[0304] • AS / NZS 4266.6:2004 - Tensile strength (Internal Bond Strength);

[0305] • AS / NZS 4266.8:2004 - Swell in thickness after immersion in water test; and

[0306] • ISO 5660 - Bench-scale fire testing.

[0307] The results of each test are discussed below.

[0308] AS / NZS 4266).16:2004 - Formaldehyde emission-desiccator method

[0309] Nine 150 mm x 50 mm samples (12 mm thickness) were stored in a room at 20°C and 65% humidity for seven days prior to being placed in a glass desiccator with 300 mL of water for 24 hours. A 5 mL sample of the water was then reacted with 5 mL acetylacetone solution for 10 minutes at 65°C. The solution was allowed to cool, and a UV / Vis measurement was taken and calibrated against a standard curve to determine formaldehyde emissions. Overall, the fire retardant (FR) MDF panel has higher formaldehyde emissions compared to the standard resin but it is still extremely low, being below the Super E0 emission standard of 0.3 mg / L. Further, that such a low formaldehyde emission level is obtained suggests that the guanidine-based fire-retardant material (guanidine sulfamate) may be reacting with the free formaldehyde. The results of the formaldehyde testing are summarised below:

[0310] Table 4: Formaldehyde emissions

[0311]

[0312] AS / NZS 4266.6:2004 Tensile strength (Internal Bond Strength) The internal bond (IB) strength was tested where 50 mm x 50 mm samples (at least 12) from each MDF panel were pulled apart at a rate of 2 ± 1 mm / min using a Lloyd LR1 OK Universal Materials Testing Machine. This recorded the maximum load sustained by the test piece in newtons (N) before a failure point was reached, which allows for the internal bond strength (tensile bond strength) in N / mm to be calculated for each panel. This has then been converted to MPa as is standard. The results are summarised in the below table and Fig. 2.

[0313] Table 5: Tensile strength

[0314]

[0315] The above results demonstrate that, surprisingly, substitution of urea with a guanidine fire-retardant material (guanidine sulfamate) had a positive impact on the panel tensile strength. This is normally not the ease when fire-retardant materials are added to MDF, which normally impact IB strength of the panel, and more resin is required. Without wishing to be bound by theory, the increase in IB could be attributed to the free formaldehyde observed from formaldehyde emission tests which may result in improved bond strength in finished panels. Standard general purpose low-density MDF panels IB strength for a 12 mm panel is expected to be 0.45-0.5 MPa.

[0316] AS / NZS 4266.8:2004 Swell in thickness after immersion in water test

[0317] Fifteen samples of dimensions 50 mm x 50 mm of each MDF panel were submerged in water at 20 ± 1°C for 24 hours. The results of swelling are summarised below.

[0318] Table 6: Swell test data for panels made with standard resin

[0319]

[0320] Table 7: Swell test data for panels made with FR resin (12% solids)

[0321]

[0322] Table 8: Swell test data for panels made with FR resin (24% solids)

[0323]

[0324]

[0325] Overall swell test indicates that MDF panels made using the standard resin have a slightly lower swell percentage of about 16%, compared to guanidine-based resins of about 24% and 18% for panels with 12% and 24% solids, respectively. However, overall, the increase in swell thickness is not significant, and the panels are within acceptable limits.

[0326] ISO 5660 Bench-scale fire testing

[0327] A 100 mm 100 mm sample from each panel was subjected to an ISO 5660-1:2015 test which measures the heat release rate of the samples when exposed to controlled levels of irradiance with an external igniter. The results are summarised below and in Fig. 3.

[0328] Table 9: Fire resistance results

[0329]

[0330] Overall, the FR resin significantly improved the fire resistance of the MDF panels. Specifically, the peak heat is reduced by 61 % or 73%, and the average heat released from ignition to 700 seconds is reduced by 33% and 45%, depending on solids loading. At a FR resin loading of 24% we see significant decrease in mass loss as well, retaining 78% of initial mass compared to 23% for the standard panel.

[0331] The FR resin overall shows improved internal bond strength and fire performance, but at the higher 24% resin loading the results are particularly surprising, demonstrating the strongest IB, swell performance comparable to standard resin, formaldehyde emission levels that still met EO standards, and significantly improved FR resistance with a 73% reduction in peak heat, 45% reduction in heat release of equivalent periods, 39% reduction in total heat release, and significant improvement in mass retention following exposure to flame.

[0332] Example 3 - Flammability of exemplary wood-resin composite product

[0333] This test method was used to evaluate the fire-resistance characteristics of standard resin and FR resin when exposed to a blow-torch heat source. Samples were directly subjected to a blowtorch flame (around 1250°C to 2000°C) for 1 minute and 20 seconds before removing the fire source. The results are shown in Fig. 4. As can be seen from Figs 4a and 4b, the panel made with standard resin is on fire after removal of the flame source (compare Figs 4a and 4b), whereas at Figs 4c and 4d the FR panel is seen to be smoking, with no fire, after removal of the flame (compare Figs 4c and 4d).

Claims

Claims1. A thermosetting fire-retardant resin composition for use in a wood-resin composite product, including:a formaldehyde-based resin which incorporates a guanidine monomer as a fire- retardant component of the resin; andwherein the composition has a pH of greater than 6.0.

2. A composition as claimed in claim 1, wherein the composition is substantially stable to curing on storage at 35°C for a period of at least 8 days.

3. A composition as claimed in claim 1 or 2, wherein the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

4. A composition as claimed in claim 3, wherein the composition is produced from formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%.

5. A composition as claimed in claim 3 or 4, wherein the composition is produced from melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%.

6. A composition as claimed in any of claims 3 to 5, wherein the composition is produced from urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%.

7. A composition as claimed in any of claims 1 to 6, wherein the guanidine fire-retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

8. A composition as claimed in claim 7, wherein the guanidine monomer is a guanidine salt.

9. A composition as claimed in claim 8, wherein the guanidine salt is guanidine sulfamate.

10. A composition as claimed in claim 9, wherein the composition is produced from guanidine sulfamate in an amount of from 5 wt% to 70 wt%, optionally from 40 wt% to 70 wt% guanidine sulfamate.

11. A composition as claimed in any of claims 1 to 10, wherein the composition is produced from:formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%;melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%; urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%; and guanidine sulfamate in an amount of from 5 wt% to 70 wt%, optionally from 40 wt% to 70wt%.

12. A composition as claimed in any of claims 1 to 11, wherein the composition includes one or more pH-adjusting agents and / or pH buffers.

13. A composition as claimed in claim 12, wherein the one or more pH-adjusting agents are selected from sodium hydroxide and formic acid.

14. A composition as claimed in claim 13, wherein the pH buffer is triethanolamine.

15. A composition as claimed in any of claims 1 to 14, wherein the composition has a pH of greater than 7.0.

16. A composition as claimed in claim 15, wherein the composition has a pH between 7.0 and 9.0.

17. A composition as claimed in claim 16, wherein the composition has a pH of about 7.35.

18. A composition as claimed in any of claims 1 to 17, wherein the composition has a water content of less than 35 wt%, optionally less than 20 wt%19. A composition as claimed in any of claims 1 to 18, wherein the composition has a solids content of at least 65 wt%, optionally at least 80 wt%.

20. A thermosetting fire-retardant resin composition for use in a wood-resin composite product, including:precursor components for producing a formaldehyde-based resin; anda guanidine fire-retardant material; andwherein the composition has a pH of greater than 6.0.

21. A composition as claimed in claim 20, wherein the composition is substantially stable to curing on storage at 35°C for a period of at least 8 days.

22. A composition as claimed in claim 20 or 21, wherein the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

23. A composition as claimed in claim 22, wherein the composition contains formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%.

24. A composition as claimed in claim 22 or 23, wherein the composition contains melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%.

25. A composition as claimed in any of claims 22 to 24, wherein the composition contains urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%.

26. A composition as claimed in any of claims 20 to 25, wherein the guanidine fire- retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

27. A composition as claimed in claim 26, wherein the guanidine fire-retardant material is a guanidine salt.

28. A composition as claimed in claim 27, wherein the guanidine salt is guanidinesulfamate.

29. A composition as claimed in claim 28, wherein the composition contains from 5 wt% to 70 wt% guanidine sulfamate, optionally from 40 wt% to 70 wt% guanidine sulfamate.

30. A composition as claimed in any of claims 20 to 29, wherein the composition contains:formaldehyde in an amount of from 10 wt% to 35 wt%, optionally from 20 wt% to 30 wt%;melamine in an amount of from 1 wt% to 30 wt%, optionally from 1 wt% to 4 wt%; urea in an amount of up to 65 wt%, optionally from 5 wt% to 25 wt%; and guanidine sulfamate in an amount of from 5 wt% to 70 wt%, optionally from 40 wt% to 70wt%.

31. A composition as claimed in any of claims 20 to 30, wherein the composition includes one or more pH-adjusting agents and / or pH buffers.

32. A composition as claimed in claim 31, wherein the one or more pH-adjusting agents are selected from sodium hydroxide and formic acid.

33. A composition as claimed in claim 32, wherein the pH buffer is triethanolamine.

34. A composition as claimed in any of claims 20 to 33, wherein the composition has a pH of greater than 7.0.

35. A composition as claimed in claim 34, wherein the composition has a pH between 7.0 and 9.0.

36. A composition as claimed in claim 35, wherein the composition has a pH of about 7.35.

37. A composition as claimed in any of claims 20 to 36, wherein the composition has a water content of less than 35 wt%, optionally less than 20 wt%38. A composition as claimed in any of claims 20 to 37, wherein the composition has a solids content of at least 65 wt%, optionally at least 80 wt%.

39. A wood-resin composite product produced or producible by thermosetting of a mixture comprising wood fibers and a composition as defined in any of claims 1 to 38.

40. A wood-resin composite product as claimed in claim 39, wherein the composite product is in the form of medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), plywood, fiberboard, laminated timber, particleboard or panel board.

41. A wood-resin composite product as claimed in claim 40, wherein the wood-resin composite product is in the form of medium density fiberboard (MDF), high density fiberboard (HDF), oriented strand board (OSB), fiberboard, or particleboard.

42. A wood-resin composite product as claimed in any of claims 39 to 41, wherein the composite product further comprises one or more of a hardener and a wax.

43. A wood-resin composite product as claimed in any of claims 39 to 42, wherein the composite product comprises from 1 wt% to 30 wt% resin solids, optionally from 10 wt% to 30 wt%, or optionally from 20 wt% to 30 wt%.

44. A wood-resin composite product as claimed in any of claims 39 to 42, wherein the composite product has a resin solids content in the range of from 30 wt% to 80 wt%.

45. A wood-resin composite product as claimed in any of claims 39 to 44, wherein the guanidine fire-retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

46. A method of producing a composition as defined in any of claims 1 to 19, including: heating a mixture of precursor components for producing a formaldehyde-based resin; adding a guanidine monomer to the heated mixture; andheating the guanidine monomer-containing mixture.

47. A method as claimed in claim 46, wherein the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

48. A method as claimed in claim 46 or 47, wherein the precursor components for producing a formaldehyde-based resin are heated at a temperature in the range of from 70°C to 90°C; and / or wherein the mixture containing the guanidine monomer is heated at a temperature in the range of from 70°C to 90°C.

49. A method as claimed in claim 46 or 47, wherein a mixture including formaldehyde, urea and melamine is heated at a temperature in the range of from 70°C to 90°C at a pH of from 5.5 to 6.5, until the mixture has a viscosity in the range of from 300 cP to 500 cP, and the mixture is then brought to ambient temperature and guanidine monomer, and optionally a pH-adjusting agent and / or a pH buffer, is added, such that the composition has a pH of greater than 7.0.

50. A method as claimed in any of claims 46 to 49, wherein the guanidine monomer is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

51. A method of producing a composition as defined in any of claims 20 to 38, including:admixing precursor components for producing a formaldehyde-based resin; and a guanidine fire-retardant material.

52. A method as claimed in claim 51, wherein the precursor components for producing a formaldehyde-based resin are formaldehyde, melamine and urea.

53. A method as claimed in claim 51 or 52, wherein guanidine fire-retardant material is added to a mixture comprising precursor components for producing a formaldehyde- based resin.

54. A method as claimed in any of claims 51 to 53, wherein a mixture including formaldehyde, urea and melamine is heated at a temperature in the range of from 70°C to 90°C at a pH of from 5.5 to 6.5, until the mixture has a viscosity in the range of from300 cP to 500 cP, and the mixture is then brought to ambient temperature and guanidine fire-retardant material, and optionally a pH-adjusting agent and / or a pH buffer, is added, such that the composition has a pH of greater than 7.0.

55. A method as claimed in any of claims 51 to 54, wherein the guanidine fire-retardant material is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

56. A method of producing a wood-resin composite product, comprising coating wood fibers with a resin composition as defined in any of claims 1 to 38, and then thermosetting the resulting mixture.

57. A method as claimed in claim 56, wherein the resin composition is sprayed onto the wood fibers.

58. A method as claimed in claim 56 or 57, wherein the wood fibers are coated with a wax.

59. A method as claimed in any of claims 56 to 58, wherein the mixture is subjected to drying to reduce water content, prior to thermosetting.

60. A method as claimed in any of claims 56 to 59, wherein thermosetting is carried out by hot pressing of the mixture.

61. A method as claimed in any of claims 56 to 60, wherein the guanidine fire-retardant material or guanidine monomer is guanidine, a material which incorporates a guanidine structural motif, or a salt thereof.

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