Flame retardant cellulose-based products

Abstract

A flame retardant cellulose-based product formed from ingredients comprising : (i) a cellulose-based material selected from paper-based material, wood-based material and bamboo-based material; (ii) a brominated phosphate ester of Formula (la), wherein the brominated phosphate ester of Formula (la) is present in an amount of about 5% to about 20 % by weight of the cellulose- based product; and (iii) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole, wherein the melamine resin is present in an amount of about 10% to about 20% by weight of the cellulose-based product.

Description

[0001] FLAME RETARDANT CELLULOSE -BASED PRODUCTS

[0002] The present invention relates to the field of flame-retardant cellulose-based materials, especially paper-based, wood-based and bamboo-based materials and engineered products.

[0003] The present invention discloses successful application in paperbased, wood-based and bamboo-based materials and engineered products of an aqueous flame retardant composition (dispersion) that comprises: a) a brominated phosphate ester of Formula I: Formula I wherein each of R1, R2and R3is independently selected from a brominated alkyl group; and b) a melamine resin having a molecular weight above 150 gr / mole.

[0004] Hereinafter, the aqueous flame retardant composition (dispersion) as described above is abbreviated as "BPFR co-f ormulation" .

[0005] The invention provides in first aspect a flame retardant cellulose-based product that comprises a) a material selected from a paper-based material, a wood-based material and a bamboo-based material; b) a brominated phosphate ester flame retardant of Formula I (BPFR) ; and c) a melamine resin.

[0006] The flame retardant paper-based product, bamboo-based product and wood-based product of the invention are, for example paper-based laminates (e.g. paper-based high-pressure laminates) , cardboard products, wood-based products (e.g. engineered timber, for example Cross Laminated Timber (CLT) and Laminated Veneer Lumber (LVL) ; medium-density fibre (MDF) ; low-density fiberboard (LDF / Particle board) ; plywood and other engineered wood-based, and bamboobased products (e.g. engineered bamboo lumber, laminated bamboo lumber (LBL) , cross laminated bamboo (CLB) and laminated veneer lumber (LVL) ) .

[0007] Accordingly, one embodiment of the invention is a flame retardant cellulose-based product comprising: a) a material selected from paper-based material, a wood-based material and a bamboo-based material; b) a brominated phosphate ester of Formula I: Formula I wherein each of R1, R2and R3is independently selected from a brominated alkyl group; and c) a melamine resin having a molecular weight above 150 gr / mole.

[0008] The flame retardant cellulose-based products of the invention, selected from paper-based products, wood-based products and bamboo-based products, are obtained by application of the BPFR co- formulation to a natural cellulose-based material at a temperature and pressure sufficient to bond the BPFR coformulation and said natural cellulose-based material. Without being bound to any specific theory, it is thought that application of the BPFR co- formulation to a paper-based material, to a bamboobased material or to a wood-based material, results in chemical and / or physical adherence of the brominated phosphate ester and of the melamine resin to the cellulose polymer in the paper-based

[0009] / bamboo-based / wood-based material.

[0010] Accordingly, the present invention allows incorporating sufficient amounts of the brominated phosphate ester and the melamine resin into a cellulose-based product, thereby providing a flame-retardant cellulose-based product.

[0011] Natural cellulose-based material for use in the compositions and methods of the invention includes "virgin" or recycled paper, cardboard, wood, bamboo, and combinations thereof.

[0012] The amount of the brominated phosphate ester of Formula I bound on and / or incorporated into the flame retardant paper-based product, the bamboo-based product or the wood-based product is preferably about 5 to 20 % by weight of the cellulose-based product, preferably about 8 to 20 % by weight of the cellulose- based product, preferably about 10 to 20 % by weight of the cellulose-based product.

[0013] The amount of the melamine resin bound on and / or incorporated into the flame retardant paper-based product, the bamboo-based product or the wood-based product is preferably about 10 to 20 % by weight of the cellulose-based product, preferably about 12 to 20 % by weight of the cellulose-based product, preferably about 15 to 20 % by weight of the cellulose-based product.

[0014] Fixation of the brominated phosphate ester to a paper-based, bamboo-based and wood-based materials, such as paper laminate, cardboard, recycled chipboard, pine wood and bamboo, was confirmed by subjecting treated products to flammability testing. As taught in the examples detailed hereinbelow, treatment of a paper-based material with the BPFR co-f cumulation imparted flame retardancy to laminated paper and cardboard product, and dramatically improved the flame retardancy performance of wood-based and bamboo-based products.

[0015] As pointed out above, the BPFR co- formulation comprises a brominated phosphate ester of Formula I . We have found that one type of brominated phosphate esters that are well suited for use in the products and applications of the invention is represented by Formula I : Formula I wherein each of R1, R2and R3is independently selected from a brominated alkyl group; and wherein the bromine content of the brominated phosphate ester is not less than 55% by weight of the molecule.

[0016] The brominated alkyl group in the compounds of Formula I is preferably an alkyl group, such as methyl, ethyl, n-propyl, isopropyl, butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neo-pentyl, tert-pentyl, n-hexyl, iso-hexyl, and the like.

[0017] The brominated phosphate ester of Formula I may be synthesized as known in the art. For example, by reacting three moles of a brominated alkyl alcohol with one mole of a phosphorus oxyhalide under conditions well known in the art (see, for example, U.S. Pat. No. 5,710,309 and the references cited therein) . Especially preferred brominated phosphate esters of Formula I that are well suited to the applications of the invention have a bromine content of not less than 65% by weight of the molecule, preferably not less than 70% by weight of the molecule, especially brominated phosphate esters of Formula I that have a bromine content of about 70% by weight of the molecule.

[0018] Preferably, at least two of R1, R2and R3in the brominated phosphate esters of Formula I are substituted with bromine, i.e. brominated. More preferably, all of R1, R2and R3in the brominated phosphate esters of Formula I are substituted with bromine. Preferably, each of R1, R2and R3in the brominated phosphate esters of Formula I is substituted with a bromine atom. Most preferably, each of R1, R2and R3in the brominated phosphate esters of Formula I is substituted with multiple, i.e. two or more, bromine atoms, i.e. polybrominated.

[0019] Suitable commercially available brominated phosphate esters (BPFRs) of Formula I include tri s ( tribromoneopentyl ) phosphate (a brominated phosphate ester of Formula la) . Preferably, the BPFR of Formula I is tris ( tribromoneopentyl ) phosphate available as TexFRon® 3000 (FR-370) from ICL, Israel.

[0020] As pointed out above, the BPFR co- formulation comprises a melamine resin having a molecular weight above 150 gr / mole. Different types of melamine resins can be used in the BPFR co- formulation . Without being bound to any specific theory, it is thought that the melamine resin interacts with the brominated phosphate ester of Formula I to create a continuous, branched complex resin network that firmly binds to the cellulose f ibers / polymer in the cellulose-based product . Representative examples of suitable melamine resins, include melamine resins having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole. Some suitable resins have a molecular weight of about 500 gr / mole. Preferred melamine resins suitable for the BPFR co- formulation are methylol-based melamine resins and melamine-f ormaldehyde resins. These are especially desirable because they are rich in nitrogen which contributes to overall flame retardancy. Especially preferred melamine resins suitable for the BPFR co- formulation are methylated melamine formaldehyde resins, partially methylated melamine formaldehyde resins and methylated high imino melamine resins; having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole. Suitable commercially available melamine resins include Madurit® MW830, Saduren®, Maprenal®, Resimene®, Leaf, Cymel® 385. Preferred commercially available melamine resins include, e.g. , Astro Mel™ NW3A available from Hexion Specialty Chemicals Inc, Cymel® 385 available from Allnex GmbH, Madurit® MW 830 75% WA available from Prefere Resins Holding GmbH.

[0021] Accordingly, preferred flame retardant aqueous dispersions (BPFR co- formulation) for use in the applications and products of the invention comprise:

[0022] (a) a brominated phosphate ester of Formula I: Formula I wherein each of R1, R2and R3is independently selected from a brominated alkyl group; and b) a melamine resin having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about

[0023] 500 gr / mole or above 500 gr / mole.

[0024] Preferably, the bromine content of the brominated phosphate ester of Formula I is not less than 55% by weight of the molecule, preferably exceeding 60% or even 65 % by weight of the molecule. Most preferred brominated phosphate esters of Formula I have a bromine content of not less than 70% by weight of the molecule, such as brominated phosphate esters of Formula I having a bromine content of about 70% by weight of the molecule.

[0025] Especially preferred flame retardant aqueous dispersions (BPFR co- formulation) for use in the applications and products of the invention comprise:

[0026] (a) a brominated phosphate ester of Formula I: Formula I wherein each of R1, R2and R3is independently selected from a brominated alkyl group; preferably the alkyl group is independently selected from brominated methyl, ethyl, n-propyl, iso-propyl, butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, neo-pentyl, tertpentyl, n-hexyl, and iso-hexyl; preferably, each of R1, R2and R3is independently substituted with two or more, bromine atoms; having a bromine content of not less than about 70% by weight of the molecule; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole.

[0027] In some preferred embodiments the flame retardant aqueous dispersions (BPFR co-formulation) for use in the applications and products of the invention comprise:

[0028] (a) a brominated phosphate ester of Formula la:

[0029] 'Formula la; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about 500 gr / mole. Preferably the melamine resin is a partially methylated melamine formaldehyde resin.

[0030] The aqueous BPFR co- formulations for use in the applications and products of the invention are typically prepared via a two-step process. In the first step, two individual preparations are prepared. The brominated phosphate ester of Formula I (BPFR) is dispersed in a water / aqueous medium (see for example Table 2, Preparation 1, hereinbelow) . The melamine resin is separately dispersed in a water / aqueous medium (see for example Table 3, Preparation 2, hereinbelow) . In the second step, the brominated phosphate ester (BPFR) dispersion and the melamine resin dispersion are combined to form a homogeneous, stable aqueous composition abbreviated herein as "BPFR co-f ormulation" (see for example Table 4, Co-formulation 1, hereinbelow) . The so prepared BPFR co- formulations are stable, showing no phase separation or settling of solids during storage, at least for 60 days.

[0031] To prepare the individual dispersion of the brominated phosphate ester of Formula I (BPFR) , e.g. the brominated phosphate ester of Formula la, the BPFR is added to a vessel that was previously charged with a mixed solution of deionized water, dispersing agent, wetting agent, and optionally a thickening agent. Incorporation of the BPFR into the aqueous mixture can be achieved with the aid of a dissolver stirrer / disperser operating at 100 to 300 rpm on a laboratory scale. The mixture is typically allowed to disperse for 10 to 60 minutes on a laboratory scale. A stable aqueous preparation of the brominated phosphate ester (BPFR) is formed. The content of the brominated phosphate ester of Formula I is typically not less than about 35%, preferably from about 40% to 55% by weight, preferably from about 40% to 50% by weight, preferably from about 45% to 55% by weight, based on the total weight of the individual BPFR preparation (dispersion) .

[0032] Suitable grades of brominated phosphate esters of Formula I consist of micron or sub-micron particles (for example, with a particle size distribution of dso 4 pm, more preferably dso 3 pm) and dgo d 15 pm (e.g. , dgo d 10 pm, more preferably dgo < 6 pm) , measured by laser diffraction. Such suitable grades may be obtained by methods known in the art, such as for example dry milling (JET MILL) of the BPFR. To prepare the individual dispersion of the melamine resin, the melamine resin is added to a vessel that was previously charged with a solution of a surfactant, optionally softener, and optionally deionized water. Since a sufficient amount of water is present in the surfactant commercial product, further addition of water is typically not required. Incorporation of the melamine resin into the aqueous mixed solution can be achieved with the aid of a dissolver stirrer / disperser operating at 100 to 300 rpm on a laboratory scale. The mixture is typically allowed to disperse for 10 to 60 minutes on a laboratory scale. A stable aqueous dispersion of the melamine resin is formed. The content of the melamine resin is typically not less than 49%, e.g. , from 49% to 63% by weight based on the total weight of the aqueous individual melamine resin preparation (dispersion) .

[0033] Next, the brominated phosphate ester (BPFR) dispersion and the melamine resin dispersion are combined to give the BPFR coformulation. The content of the brominated phosphate ester of Formula I in the BPFR co-formulation is generally in the range of about 10% to about 22% by weight, preferably from about 15 to about 22% by weight, preferably from about 16 to about 20% by weight, based on the total weight of the co-formulation. The content of the melamine resin in the BPFR co-formulation is generally in the range of about 35% to about 45% by weight, preferably from about 37% to 45% by weight, preferably from about 40% to 45% by weight, based on the total weight of the co- formulation. The weight percent values as specified herein refer to the dry weights of the BPFR and the melamine resin.

[0034] The order of addition of the individual dispersions to a vessel to create the BPFR co- formulation is not critical. One possible order of addition is to charge a vessel with the melamine resin dispersion, followed by addition of the brominated phosphate ester dispersion, under homogenization using a dissolver stirrer. The order of the addition of the BPFR dispersion and the melamine resin dispersion can be reversed.

[0035] Separate preparation of the BPFR dispersion and the melamine resin dispersion prior to combining the BPFR and the linker to give a co- formulation is required to achieve a stable co-dispersion .

[0036] The BPFR co- formulation for use in the applications and products of the invention comprises customary additives, such as for example one or more of dispersants, wetting agents, surfactants, softeners. Such customary additives are usually present in the formulation in an amount from 1 to 14% by weight each, e.g. from 1-7% by weight each.

[0037] The weight percent values as specified herein refer to the dry weight of the active agent present in the additive formulated product. The term "wet weight" as specified herein refers to the weight of the additive formulated product that includes the active agent, water / aqueous medium and optionally other components that form part of such formulations.

[0038] The aqueous flame retardant composition of the invention may further comprise one or more of additional types of additives such as, for example rheology modifiers, i.e. , thickeners and antisettling agents, usually from about 0.05 to 1% by weight of the total composition.

[0039] Preferably, one or several of surfactant, dispersing agent, wetting agent, and softener are present in each of the individual BPFR and melamine resin preparations. Typically, such additives are present at a concentration from 1 to 14% by weight each, based on the total weight of the individual preparation. Suitable surfactants, dispersing agents, wetting agents, and softeners are known in the field of cellulose-based materials flame retardation and can be easily determined by a person skilled in the art.

[0040] For example, the dispersant may be a nonionic dispersing agent, such as nonionic acrylate copolymer (e.g. , DYSPERBYK®-2010 , available in an emulsion form, possessing also wetting function) ; or an ionic dispersing agent, such as the alkali, alkaline earth, and ammonium salts of aromatic sulfonic acids, for example, alkylsubstituted aromatic sulfonic acids (for example, alkylsubstituted benzene and naphthalene sulfonic acids, e.g. , the sodium salt of di-isopropyl or di-butyl naphthalene sulfonic acid, available as SUPRAGIL® WP) . Suitable dispersants include acrylate copolymer surfactants such as 2-acrylamide-2-methyl-l- propanesul f onio acid and alkyl methacrylamide, alkyl methacrylate or alkyl acrylate, poly ( allylamine ) -supported phases, poly ( ethyleneimine ) . Commercially available dispersing agents include Disperbyk® 2010, EDPLAN 490 / 492, Agrilan® 788, Carbopol® Aqua SF-1. Preferably, the dispersing agent is Disperbyk® 2010.

[0041] Various surfactants such as anionic, cationic, non-ionic or amphoteric surfactants may be employed. For example, suitable commercially available surfactants include anionic surfactants, such as derivatives of isotridecyl alcohol, e.g. ethoxylated and sulphated isotridecyl alcohols. Commercially available surfactants include Sermul® EA 266, SULFOROKAnol®IT2030, ROKAnol® IT series. Preferably, the surfactant is Sermul® EA 266. Suitable wetting agents include, for example, alkyl-substituted benzene sulfonic acid and alkyl-substituted naphthalene sulfonic acid derivatives, e.g. sodium di-isopropyl naphthalene sulphonate and sodium di-butyl naphthalene sulphonate. Commercially available wetting agents include Supragil® WP, Morwet® IP, Powercon-100. Preferably, the wetting agent is Supragil® WP .

[0042] As pointed out above, the individual preparation of the brominated phosphate ester is preferably in a form of an aqueous dispersion. A stable aqueous dispersion of a brominated phosphate ester (BPFR) of Formula I, such as of Formula la, can be achieved with the aid of a dispersant and of a wetting agent. Dispersing agents of the polymeric nonionic kind are preferred. Water is preferably present in an amount of about 30 to 70% (or of about 40 to 60%) by weight of the BPFR preparation.

[0043] The brominated phosphate ester is present in an amount effective to provide a cellulose-based product treated therewith adequate resistance to fire, preferably in an amount of not less than about 30% by weight, preferably not less than about 35% by weight, preferably not less than about 40% by weight, preferably not less than about 45% by weight based on the total weight of the BPFR preparation. Preferably the brominated phosphate ester is present in an amount from about 30% to 60% by weight, preferably from about 45% to 50% by weight, based on the total weight of the BPFR preparation .

[0044] The dispersing agent and the wetting agent are present in an amount effective to stabilize the BPFR dispersion. Usually, the dispersing agent is present in an amount of about 1 to 5% by weight, in an amount of 2 to 4% by weight, preferably in an amount of 1.5 to 3% by weight of the BPFR dispersion. Usually, the wetting agent is present in an amount below 1% by weight of the BPFR dispersion, preferably in an amount of 0.15 to 0.5% by weight of the BPFR dispersion.

[0045] As pointed out above, the individual preparation of a melamine resin is preferably in a form of an aqueous dispersion and can be achieved with the aid of a surfactant. Various surfactants such as anionic, cationic, non-ionic or amphoteric surfactants may be employed. Preferred surfactants include isotridecylalcohol, ethoxylated, sulfated, sodium salt. Water is present in an amount of 15 to 30% by weight, preferably in an amount of 16 to 25% by weight, of the melamine resin preparation. Since a sufficient amount of water is present in the surfactant commercial product, further addition of water is typically not required. The melamine resin is present in an amount effective to bind sufficient amounts of the BPFR to the cellulose f iber / polymer , typically in an amount of not less than 49%, usually in an amount of 50 to 65% by weight, preferably in an amount of 60 to 65% by weight, of the melamine resin preparation. The surfactant is present in an amount effective to stabilize the melamine resin dispersion, usually in an amount of 10 to 20% by weight, preferably in an amount of 12 to 18% by weight (dry weight % that does not account for about 50% water that is typically present in the surfactant commercial product) , of the individual melamine resin dispersion.

[0046] As described before, the brominated phosphate ester (BPFR) preparation and the melamine resin preparation are combined in a co- formulation, i.e. , in a dispersion form, also referred to herein as an aqueous BPFR co- formulation . Preferred aqueous BPFR co- formulations for use in the applications and products of the invention comprise (percentage by weight based on the total weight of the co-formulation) : from about 10 to 30% by weight, preferably from 12 to 22% by weight, most preferably from 14% to 18% by weight, of brominated phosphate ester of Formula I, such as brominated phosphate ester of Formula la; and from 30 to 50% by weight, preferably from 39 to 45% by weight of melamine resin linking agent as defined hereinabove.

[0047] The BPFR co- formulations for use in the applications and products of the invention, further contain one or more customary dispersion additives. Major types of additives may include: one or more dispersing agent, usually from 0.5 to 5% by weight, e.g. , from 0.5 to 2.5% by weight (0.8 to 1.2%) ; one or more wetting agent, usually up to 1% by weight, e.g. from 0.05 to 0.25% by weight ( 0.05 to 0.15%) ; one or more surfactant, usually from 20-30 % by weight, e.g. , from 22-27 % ; and optionally one or more thickening agents, usually from 0.05 to 1% by weight of, e.g. , from 0.025 to 0.035%.

[0048] Especially preferred BPFR co- formulations for use in the applications and products of the invention comprise (percentage by weight based on the total weight of the aqueous composition) : from 50 to 70% by weight of water, e.g. , from 50 to 66%; from 10 to 30% by weight of compound of Formula la (tris- ( tribromoneopentyl ) -phosphate (FR-370) , e.g. , from 16 to 22%; from 39 to 45% by weight of alkyl modified melamine resin linking agent having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, e.g. , having a molecular weight of about or above 500 gr / mole; preferably selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin and methylated high imino melamine resin, e.g. , ASTRO™ MEL NW3A, Cymel® 385, Madurit® MW 830 75% WA, from 40 to 45%; from 1 to 2.5% by weight of nonionic polymeric dispersing agent, e.g. , Disperbyk® 2010, from 1 to 1.5 % ; from 0.05 to 0.25% by weight by weight of wetting agent, e.g. , Supragil® WP, from 0.05 to 0.15%; from 2 to 10% by weight of surfactant, corresponding to about from 10 to 20% by wet weight of surfactant, e.g. Sermul® EA 266, from 12 to 14% wet weight; and optionally from 0.05 to 1% by weight of thickening agent, e.g. hydroxyethyl cellulose, from 0.025 to 0.035% by weight.

[0049] The BPFR co- formulations were found to be suitable for applications on a variety of cellulose-based, especially paper-based, woodbased and bamboo-based, products (e.g. paper laminate, cardboard, wood particles, recycled wood particles, wood laminate, bamboo laminate, ) to obtain a cellulose-based product having adequate resistance to fire. Accordingly, another aspect of the invention is a method of imparting flame retardancy to a cellulose-based material, especially paper-based material, wood-based material and bamboo-based material, comprising applying to the cellulose-based material an aqueous flame retardant composition (BPFR coformulation) that comprises: a) a brominated phosphate ester of Formula I:

[0050] Formula I wherein each of R1, R2and R3is independently selected from brominated alkyl group; having a bromine content of not less than about 65% by weight of the molecule, preferably having a bromine content of at least about 70% by weight of the molecule; and b) a melamine resin having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole; at a temperature and pressure sufficient to bond the BPFR coformulation and the cellulose-based material.

[0051] One embodiment of the invention is a method of imparting flame retardancy to a cellulose-based material selected from paper-based material, wood-based material and bamboo-based material, comprising applying to the cellulose-based material an aqueous flame retardant BPFR co-formulation (dispersion) comprising: a) a brominated phosphate ester of Formula I: Formula I wherein each of R1, R2and R3is independently selected from a brominated alkyl group; having a bromine content of about 65% by weight of the molecule, preferably having a bromine content of not less than about 70% by weight of the molecule, most preferably having a bromine content of about 70% by weight of the molecule; and b) a melamine resin selected from methylated melamine formaldehyde resins, partially methylated melamine formaldehyde resins and methylated high imino melamine resins, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole. Preferably the melamine resin is a partially methylated melamine formaldehyde resin. The BPFR coformulation has a brominated phosphate ester of Formula I content of about 10% to about 22% by weight, preferably from about 15 to about 22% by weight, preferably from about 16 to about 20% by weight, by weight of the co-formulation; and a melamine resin content of about 35% to about 45% by weight, preferably from about 37% to 45% by weight, preferably from about 40% to 45% by weight of the co-formulation. The BPFR co-formulation is applied to the cellulose-based material at a temperature and pressure sufficient to bond the BPFR co-formulation and the cellulose-based material.

[0052] Another embodiment of the invention is a method of imparting flame retardancy to a cellulose-based material selected from paperbased material, wood-based material and bamboo-based material, comprising applying to the cellulose-based material an aqueous flame-retardant aqueous dispersions (BPFR co-formulation) comprising :

[0053] (a) a brominated phosphate ester of Formula Ta: 'Formula Ta; b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about 500 gr / mole. The BPFR co- formulation is applied to the cellulose-based material at a temperature and pressure sufficient to bond or incorporate the brominated phosphate ester of Formula la and the melamine resin to the cellulose-based material. Preferably the melamine resin is a partially methylated melamine formaldehyde resin. The BPFR coformulation has a brominated phosphate ester of Formula la content of about 10% to about 22% by weight, preferably from about 15 to about 22% by weight, preferably from about 16 to about 20% by weight, by weight of the co-formulation . The melamine resin is present in an amount of about 35% to about 45% by weight, preferably from about 37% to 45% by weight, preferably from about 40% to 45% by weight, of the BPFR co-formulation. In some preferred embodiments of the method of the invention the BPFR co-formulation has a brominated phosphate ester of Formula la content of at least about 16% by weight of the co-formulation, and a melamine resin content of at least about 41% by weight of the co-formulation.

[0054] In some preferred embodiments of the method of the invention cellulose-based material is selected from "virgin" or recycled paper, cardboard, wood, bamboo, and combinations thereof.

[0055] Experimental work conducted in support of this invention demonstrates that treatment of a paper-based material with the BPFR co-formulation comprising a brominated phosphate ester of Formula la imparted flame retardancy to laminated paper (Examples 1 to 3 ) and cardboard (Example 4) , and dramatically improved the flame retardancy performance of wood-based and bamboo-based products (Examples 5 to 7) .

[0056] The BPFR co-formulation is added to the cellulose-based, i.e. paper-based / wood-based / bamboo-based material, in an amount effective to reduce flammability, also identified herein as "addon" level. The "add-on" level refers to the total amount of the BPFR co- formulation composition (including reactive compounds and non-active additives) loaded onto the treated cellulose-based product. The "add-on" level is calculated based on the difference between the initial and final weight of a dry cellulose-based material, i.e. paper, cardboard, wood, bamboo; before and after the treatment with the BPFR co- formulation . Adequate resistance to fire, fulfilling the criteria of acceptable flammability tests described in the experimental section below, is achieved with the aid of the BPFR co- formulation at "add-on" levels of 18% to 80% by weight, preferably of at "add-on" levels of least about 35% by weight of the cellulose-based material.

[0057] The amount of the brominated phosphate ester of Formula I bound on and / or incorporated into the cellulose-based material by the method of the invention is preferably about 5 to 20 % by weight, preferably about 8 to 20 % by weight, preferably about 10 to 20 % by weight of the cellulose-based material. The amount of the melamine resin bound on and / or incorporated into the cellulose-based material by the method of the invention is preferably about 10 to 20 % by weight, preferably about 12 to 20 % by weight, preferably about 15 to 20 % by weight of the cellulose-based material.

[0058] Accordingly, in another aspect the present invention is directed to a flame retardand composition comprising:

[0059] (i) a cellulose-based material selected from paper-based material, wood-based material and bamboo-based material; and

[0060] (ii) a flame retardant BPFR co- formulation that comprises: a) a brominated phosphate ester of Formula I: Formula I wherein each of R1, R2and R3is independently selected from a brominated alkyl group; having a bromine content of not less than about 65% by weight of the molecule, preferably having a bromine content of at least about 70% by weight of the molecule; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole. The brominated phosphate ester of Formula I is generally present in an amount of about 11% to about 22% by weight based on the total weight of the flame retardant coformulation. The melamine resin is generally present in an amount of about 40% to about 45% by weight based on the total weight of the flame retardant co-formulation . The flame retardant coformulation is present in an amount (at "add-on" levels) of about 18% to 80% by weight, preferably of at "add-on" levels of at least about 35% by weight of the flame retardant composition, calculated based on the difference between an initial weight of the dry cellulose-based material and a final weight the dry flame retardant composition .

[0061] One embodiment of the invention is a flame retardant composition comprising :

[0062] (i) a cellulose-based material selected from paper-based material, wood-based material and bamboo-based material; and

[0063] (ii) a flame-retardant co-formulation comprising: (a) a brominated phosphate ester of Formula la:

[0064] 'Formula la; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole. Preferably the melamine resin is a partially methylated melamine formaldehyde resin. The brominated phosphate ester of Formula la is present in an amount of at least about 16% by weight based on the total weight of the flameretardant BPFR co- formulation . The melamine resin is present in an amount of at least about 41% by weight based on the total weight of the in the BPFR co- formulation . The flame retardant composition is present in an amount (at "add-on" levels) of about 18% to 80% by weight, preferably of at least about 35% by weight of cellulose- based material, calculated based on the difference between an initial weight of the dry cellulose-based material and a final weight of the flame retardant composition.

[0065] A process of producing a flame retardant product, selected from a paper-based product, a wood-based product and a bamboo-based product, forms another aspect of the invention. Production of a flame retardant cellulose-based product, selected from a paperbased product, a wood-based product and a bamboo-based product, according to the present invention takes place in a process comprising the following steps:

[0066] (i) applying an effective amount of an aqueous BPFR co- formulation of the invention to a substrate material selected from paper-based product, a wood-based product and a bamboo-based product; followed by

[0067] (ii) curing at temperature between from about 90°C to 190°C at a pressure selected from about 8 MPa (80 Bar) to 18 MPa (180 Bar) , to form a flame retardant product.

[0068] The flame retardant cellulose-based product usually undergoes cooling at the end of the production process.

[0069] Another aspect of the invention is a process of producing a flame retardant cardboard product comprising the following steps:

[0070] (i) applying an effective amount of an aqueous BPFR co- formulation of the invention to a substrate cardboard material; followed by

[0071] (ii) curing at temperature between from about 90°C to 190°C at an atmospheric pressure, to form a flame retardant product.

[0072] In a preferred embodiments of the process of the invention the aqueous BPFR co- formulation comprises: a) a brominated phosphate ester of Formula la:

[0073] 'Formula la wherein the brominated phosphate ester of Formula la is present in an amount of about 10% to about 22% by weight based on the total weight of the flame retardant co-formulation; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole, wherein the melamine resin is present in an amount of about 35% to about 45% by weight based on the total weight of the BPFR co-formulation.

[0074] In some preferred embodiments of the process of the invention the BPFR co-formulation comprises a brominated phosphate ester of Formula la in an amount of about 16% to about 20% by weight based on the total weight of the flame retardant co-formulation. In some preferred embodiments of the process of the invention the BPFR co-formulation comprises a melamine resin in an amount of about 40% to 45% by weight, based on the total weight of the BPFR co- formulation. In some preferred embodiments of the process of the invention the melamine resin in the BPFR co-formulation is a partially methylated melamine formaldehyde resin.

[0075] In preferred embodiment of the process of the invention the BPFR co-formulation is applied in an effective amount of at least about 35% by weight of the cellulose-based material.

[0076] Preferably, the brominated phosphate ester is incorporated into the cellulose-based product in an amount of about 5 to 20 % by weight of the cellulose-based product. Preferably, the melamine resin is incorporated into the cellulose-based product in an amount of about 10 to 20 % by weight of the cellulose-based product . In various embodiments of the process of the invention, the cellulose-based product is selected from a paper-based product, wood-based product and a bamboo-based product. Non-limiting examples of cellulose based products of the process of the invention include paper laminate, cardboard, engineered timber, cross laminated timber (CLT) , laminated veneer lumber (LVL) , medium-density fibre (MDF) , low-density fiberboard (LDF) , particle board, plywood, laminated bamboo lumber (LBL) , cross laminated bamboo (CLB) and laminated veneer lumber (LVL) .

[0077] In one embodiment of the process of the invention for producing a flame retardant laminated paper product, the process comprising:

[0078] (i) contacting individual sheets of paper with a BPFR coformulation of the invention; followed by

[0079] (ii) placing the individual sheets of paper on top of each other and gluing the sheets together with the BPFR co-formulation to obtain a composite paper product; and followed by

[0080] (iii) curing the composite paper product while heating under pressure to obtain a laminated paper product.

[0081] Contacting the individual sheets of paper, with the BPFR co- formulation can be achieved by common techniques for applying a liquid formulation onto the paper, such as by impregnating, spraying and dipping. For example, paper is brushed with the BPFR co-formulation .

[0082] Subsequent to contacting with the BPFR co-formulation, the individual paper sheets are typically heated for drying. The drying temperature may be adjusted according to the type of paper. The typical drying temperature is about 70°C to 160°C, preferably about 160°C, for a drying period of several minutes, depending on the weight of the treated paper.

[0083] Next, the individual pieces are placed on top of each other and glued together with the BPFR co- formulation . Subsequent to gluing with the BPFR co- formulation, the composite paper product is heated under pressure for drying and curing. The typical curing temperature is about 110°C to 200°C, preferably about 160 °C, for a curing time of several minutes. Typical pressure is from about 8 MPa (80 Bar) to 18 MPa (180 Bar) , for a curing time period of several minutes. The curing temperature, time and pressure may be adjusted according to one or more considerations such as the type of paper, the melting temperature of the BPFR of Formula I, the curing equipment available and the curing temperature of the melamine resin.

[0084] A preferred process of the invention for producing a flame retardant laminated paper product comprises:

[0085] (i) contacting individual sheets of paper, with the BPFR coformulation of the invention; followed by

[0086] (ii) drying the paper sheets, preferably at a temperature from about 90°C to 170°C, more preferably about 160°C;

[0087] (iii) placing the individual sheets of paper on top of each other and gluing the sheets together with BPFR co- formulation to obtain a composite paper product; and followed by

[0088] (iv) curing the composite paper product at a temperature from about 90°C to 190°C, preferably at about 140°C to 160°C under pressure of about 14 MPa (140 Bar) to 18 MPa (180 Bar) to obtain a laminated paper product. In some embodiments, the curing stage (iv) of the composite paper product is performed while gradually increasing pressure, preferably at 140°C, under pressure of 140 bar for several minutes, followed by 160 bar for several minutes, followed by 180 bar for several minutes.

[0089] The flame retardant laminated paper product usually undergoes cooling at the end of the production process.

[0090] Another embodiment of the invention is a process for producing a flame retardant cardboard product, the process comprising:

[0091] (i) contacting sheets of cardboard, with the BPFR co-formulation of the invention; followed by

[0092] (ii) drying and curing the cardboard sheets.

[0093] Contacting cardboard with the BPFR co- formulation can be achieved by common techniques for applying a liquid formulation onto the cardboard, such as by coating, impregnation, spraying and dipping. For example, cardboard is brushed with the BPFR co-formulation .

[0094] Subsequent to contacting with the BPFR co-formulation, the cardboard sheets are heated for drying and curing.

[0095] The drying temperature may be adjusted according to the type of cardboard. The typical drying temperature is about 90°C to 160°C, preferably about 160°C, for a drying period of several minutes, depending on the weight of the treated cardboard.

[0096] The curing temperature and time may be adjusted according to one or more considerations such as the type of cardboard, the melting temperature of the BPFR of Formula I, the curing equipment available and the curing temperature of the melamine resin.

[0097] A preferred process of the invention for producing a flame retardant cardboard product comprises:

[0098] (i) contacting individual sheets of cardboard, with a BPFR coformulation of the invention; followed by

[0099] (ii) drying and curing the cardboard sheets preferably at a temperature from about 90°C to 160°C, preferably to about 160°C.

[0100] The flame retardant cardboard product usually undergoes cooling at the end of the production process.

[0101] Yet another embodiment of the invention is a process for producing a flame retardant molded wood particle product, the process comprising :

[0102] (i) contacting wood particles with a BPFR co- formulation of the invention; followed by

[0103] (ii) drying the wet wood particles; and followed by

[0104] (iii) placing the dry particles in a mold and heating the molded article under pressure to obtain a molded wood particle product .

[0105] Contacting of wood particles, such as for example crashed or grinded wood particles, with the BPFR co- formulation can be achieved by common techniques for applying a liquid formulation onto particles, such as by soaking, impregnating and saturating.

[0106] For example, wood particles are soaked in the BPFR co-formulation . Subsequent to contacting with the BPFR co-formulation, the wet wood particles are subjected to drying.

[0107] The drying temperature and time may be adjusted according to the size, weight and type of wood particles. Preferably, wet wood particles are first let dry at room temperature, followed by drying under heating, preferably at 80°C for several minutes followed by cooling to a room temperature.

[0108] Next, the wood particles are placed in a mold and heated under pressure for curing. The typical curing temperature is about 110°C to 200°C, preferably about 160 °C, for a curing time of several minutes. Typical pressure is from about 8 MPa (80 Bar) to 18 MPa (180 Bar) , for a curing period of several minutes. The curing temperature, time and pressure may be adjusted according to one or more considerations such as the type of wood, the melting temperature of the BPFR of Formula I, the curing equipment available and the curing temperature of the melamine resin.

[0109] A preferred process of the invention for producing a flame retardant molded wood particle product comprises:

[0110] (i) contacting wood particles with a BPFR co-formulation of the invention; followed by

[0111] (ii) drying the wet wood particles at a temperature of from a room temperature to about 80°C; preferably at a room temperature for an initial period, followed by heating to about 80°C, followed by cooling to a room temperature; and followed by

[0112] (iii) placing the dry wood particles in a mold and curing the molded article at a temperature from about 90°C to 190°C, preferably at about 140°C to 160°C under pressure of about 14 MPa (140 Bar) to 18 MPa (180 Bar) , to obtain a molded wood particle product .

[0113] In some preferred embodiments, the curing stage (iii) of the molded wood particle product is performed while gradually increasing pressure, preferably at 140°C, under pressure of 140 bar for several minutes, followed by 160 bar for several minutes, followed by 180 bar for several minutes.

[0114] The flame retardant wood-based product usually undergoes cooling at the end of the production process.

[0115] The present invention provides a process of producing a flame retardant laminated bamboo product, the process comprising:

[0116] (i) contacting individual bamboo pieces, with a BPFR co-formulation of the invention; followed by

[0117] (ii) placing the individual pieces of bamboo on top of each other and gluing the pieces together with a BPFR co-formulation to obtain a composite bamboo product; and followed by

[0118] (iii) heating the composite bamboo product under pressure to obtain a laminated bamboo product.

[0119] Contacting of the individual sheets of bamboo, with the BPFR co- formulation can be achieved by common techniques for applying a liquid formulation onto the paper, such as by impregnating, spraying and dipping. For example, bamboo pieces are brushed with the BPFR co-formulation.

[0120] Subsequent to contacting with the BPFR co-formulation, the individual bamboo pieces are heated for drying and curing. The drying temperature may be adjusted according to the size of bamboo pieces. Typical drying temperature is about 70°C to 80°C, preferably about 80°C, for a drying time of several minutes, depending on the weight of the treated bamboo piece.

[0121] Next, the individual bamboo pieces are placed on top of each other and glued together with the BPFR co- formulation . Subsequent to gluing with the BPFR co- formulation, the composite bamboo product is heated under pressure for drying and curing. The typical curing temperature is about 110°C to 200°C, preferably about 160 °C, for a curing time period of several minutes. Typical pressure is from about 8 MPa (80 Bar) to 18 MPa (180 Bar) , for a curing time period of several minutes. The curing temperature, time and pressure may be adjusted according to one or more considerations such as the weight of bamboo product, the melting temperature of the BPFR of Formula I, the curing equipment available and the curing temperature of the melamine resin.

[0122] Accordingly, a preferred process of the invention for producing a flame retardant laminated bamboo product comprises:

[0123] (i) contacting individual pieces of bamboo, with the BPFR coformulation of the invention; followed by

[0124] (ii) drying the bamboo pieces preferably at a temperature from about 70°C to 80°C, more preferably at about 80°C; followed by

[0125] (iii) placing the individual pieces of bamboo on top of each other and gluing the pieces together with BPFR co- formulation to obtain a composite bamboo product; and followed by

[0126] (iv) curing the composite paper product at a temperature from about 90°C to 190°C, preferably at about 140°C to 160°C under pressure of about 14 MPa (140 Bar) to 18 MPa (180 Bar) to obtain a laminated paper product. In some preferred embodiments, the curing stage (iv) of the composite bamboo product is performed while gradually increasing the pressure, preferably at 140°C, under pressure of 140 bar for several minutes, followed by 160 bar for several minutes, followed by 180 bar for several minutes.

[0127] The flame retardant bamboo-based product usually undergoes cooling at the end of the production process.

[0128] Brief description of the figures

[0129] Figure 1 shows a photograph of a technical cardboard paper specimen that was treated with a BPFR co- formulation (identified herein as "co- formulation 1" or "FR- 370_70" ) , following the flammability D6413-08 vertical test.

[0130] Figure 2 shows a photograph of a bamboo sample that was treated with a BPFR co- formulation (identified herein as " co- formulation 1" or "FR-370_70" ) , following flammability testing according to the ASTM 701 (Govmark 701S USA) method.

[0131] Examples

[0132] Materials

[0133] Materials used in the Examples are tabulated in Table 1. Table 1

[0134] Methods

[0135] Flammability tests were performed in accordance with ASTM 6413 and ASTM 701 flammability tests.

[0136] ASTM D 6413-08 12 seconds ignition test: In this method, samples are cut from the product to be tested, and are mounted in a frame that hangs vertically from inside the flame chamber. The sample is exposed to a controlled flame for a specified time period (in this case for 12 seconds, one of the strictest flammability tests) , and the "after-flame time" and the "after-glow time" are both recorded. Finally, the sample is torn by the use of weights and the char length is measured. To pass, the average char length of five samples cannot exceed 7 inches (17.8 cm) . In addition, none of the individual specimens can have a char length of 10 inches (25.4 cm) . The sample is further classified as passing the test if its "after flame time" is less than 5 seconds, and its "after glow time" is less than 150 seconds. In the tables shown below, "after-flame time", "after-glow time" and char length are abbreviated AFT, AGT, and CHL .

[0137] ASTM 701 test: is a standard fire test method for flame propagation in textiles and films. In this test, a substrate is hang and is exposed to flame for 45 seconds. The time between flame shut-down and the substrate flame extinguishing is the reported time. The test is standard for textiles. For wood, the comparison is relative and provides a good flammability assessment but does not meet the official standards.

[0138] Preparations 1 and 3-6 Aqueous Dispersions of Flame Retardant (FR) Compounds

[0139] Deionized water, dispersing agent and wetting agent were mixed using a dissolver stirrer for 5 minutes.

[0140] A flame retardant compound was added to the mixed solution of deionized water, dispersing agent and wetting agent. The mixture was allowed to disperse for fifteen (15) minutes at 300 rpm using a dissolver stirrer (by IKA) until a homogenous mixture was obtained, as observed by formation of an emulsion and absence of sedimentation .

[0141] The compositions of thus prepared aqueous dispersions of flame retardant (FR) compounds (Preparations 1 and 3-6) are provided in Table 2.

[0142] Table 2 provides the composition of thus prepared aqueous dispersion of brominated phosphate esters represented by Formula I of the invention (Preparation 1) . Table 2 further provides compositions of thus prepared aqueous dispersions of TexFRon® 4002, TexFRon® 5001, PNX and Fyrol® 6 (Preparations 3-6, respectively) that were prepared for comparative purposes. Preparation 2 Aqueous Dispersion of Linking Agent

[0143] Surfactant and melamine resin were mixed using a dissolver stirrer for 5 minutes .

[0144] The mixture was allowed to disperse for fifteen (15) minutes using a dissolver stirrer (by IKA) until a homogenous mixture was obtained, as observed by formation of an emulsion and absence of sedimentation .

[0145] The composition of thus prepared dispersion of melamine resin (Preparation 2) is provided in Table 3.

[0146] Table 3

[0147] Preparation 3

[0148] Preparation of Flame Retardant (FR) Co-formulation of Brominated Phosphate Esters Represented by Formula I (Co-formulation 1)

[0149] A flame retardant dispersion (Preparation 1) was added to a linker dispersion (Preparation 2) . The amounts of each of the individual dispersions are provided in Table 2.

[0150] The resultant mixture was allowed to mix for fifteen (15) minutes at room temperature at 100-600 rpm using a dissolver stirrer (by Ika) .

[0151] The composition of thus prepared flame retardant (FR) co- formulation is provided in Table 4 (co-formulation 1) .

[0152] Table 4

[0153] Preparations 4-7

[0154] Preparation of Comparative Flame Retardant (FR) Co-f emulations (Co-formulations 2-5)

[0155] A flame retardant dispersion (Preparations 3, 4, 5, or 6) was added to a linker dispersion (Preparation 2) . The amounts of each of the individual dispersions are provided in Tables 2 and 3.

[0156] The resultant mixture was allowed to mix for fifteen (15) minutes at room temperature at 100-600 rpm using a dissolver stirrer (by Ika) .

[0157] The compositions of thus prepared comparative flame retardant (FR) co-formulations are provided in Table 5 (co-formulations 2-5) .

[0158] Table 5 Example 1 Application of FR co-f ormulation to a paper laminate product (of the invention)

[0159] A paper sheet (0.012 g / cm2) was cut to pieces having the following dimensions: 30cm x 8cm. Then five pieces of paper (total weight of 14.9 g) were brushed with co-formulation 1 ( "FR-370_70" ) and inserted into a vacuum oven (Thermo Scientific VT 6060 M) at 160°C for 4 minutes, followed by cooling to room temperature.

[0160] Next, five individual pieces were placed on top of each other and glued together. The gluing was performed with co-formulation 1 ( "FR-370_70" ) . The glued multi-layered paper sample was placed in a vacuum oven and the curing stage was performed at 160°C for 4 minutes while preheated iron weights were placed on top of the sample, so as to apply pressure to the laminate.

[0161] The resulting sample weight was 32 gr. The sample was left for a few days at room temperature, and then tested using an ASTM 6413 standard test instrument ( Govmark D6413-08 vertical) . Test results are recorded in Table 6.

[0162] Table 6

[0163] The paper laminate sample passed the ASTM 6413 standard test criteria . Example 2 Application of FR co-f ormulation to a paper laminate product (of the invention)

[0164] A paper sheet (0.012 g / cm2) was cut to pieces having the following dimensions: 30cm x 8cm. Then 15 pieces of paper (total weight of 14.9 g) were brushed with co-formulation 1 ("FR-370_70") , and inserted into a vacuum oven (Thermo Scientific VT 6060 M) at 160°C for 4 minutes, followed by cooling to room temperature. A total of four sets of 15 pieces of paper were prepared this way. Each of the four sets was used to prepare Samples 1-4 described in Table 7, below. For each set a different amount of co-formulation 1 ("FR- 370_70") was applied to the individual paper pieces, as is evident from the added weight recorder for each of Samples 1-4 in Table 7.

[0165] Next, 15 individual pieces were placed on top of each other and glued together. The gluing was performed with co-formulation 1 ( "FR-370_70" ) . The curing stage of the glued sample was performed in a heated hydraulic press (LabTech LP-S-50 Thailand) at 140°C for 6 minutes while applying a pressure of 140 bar for 2 minutes, followed by 2 minutes at 160 bar, followed by 2 minutes at 180 bar. The sample was left for a few days at room temperature, and then tested using an ASTM 6413 standard test instrument (Govmark D6413-08 vertical) . Test results are recorded in Table 7. Table 7

[0166] Paper laminate samples 3 and 4 passed the ASTM 6413 standard test criteria. The performance of the samples depended on the amount of added flame retardant BPFR co-formulation. In order to pass the ASTM 6413 standard test, the co-formulation had to be applied to a paper laminate sample in an amount sufficient to provide at least about 40% of a weight gain as compared to initial sample weight.

[0167] Example 3

[0168] Application of FR co-formulation to a paper laminate product (Samples 1 and 3-6, comparative; Sample 2, of the invention)

[0169] A paper sheet (0.012 g / cm2) was cut to pieces having the following dimensions: 30cm x 8cm. Then, 20 pieces of paper were brushed with a co-formulation as detailed below in Table 8, and inserted into a vacuum oven (Thermo Scientific VT 6060 M) at 160°C for 4 minutes, followed by cooling to room temperature. A total of six sets of 20 pieces of paper were prepared this way. Each of the sets was used to prepare Samples 1-6 described in Table 8, below. For each set a different FR co-formulation was applied to the individual paper pieces, as is evident from the FR column in Table

[0170] Next, for each sample, 20 individual pieces were placed on top of each other and glued together. The gluing was performed with the co- formulation of each sample as specified in Table 8. The curing stage of the glued sample was performed in a heated hydraulic press (LabTech LP-S-50 Thailand) at 140°C for 6 minutes while applying a pressure of 140 bar for 2 minutes, followed by 2 minutes at 160 bar, followed by 2 minutes at 180 bar. The sample was left for a few days at room temperature, and then tested using an ASTM 6413 standard test instrument ( Govmark D6413-08 vertical) . Test results are recorded in Table 8.

[0171] Table 8

[0172] The test results in Table 8 show that although the comparative sample 4 (treated with "PNX" co- formulation) showed a relatively good magnitude of flame retardant activity, only sample 2 (of the invention, with co- formulation 1 ( "FR-370_70" ) ) passed the ASTM

[0173] 6413 standard test criteria.

[0174] Example 4

[0175] Application of FR co-formulation to a cardboard product (of the invention)

[0176] Technical cardboard paper (0.056 g / cm2) was cut to pieces having the following dimensions: 30cm x 8cm. The cardboard pieces were then brushed with co-formulation 1 ( "FR-370_70" ) , placed in a laboratory fume hood and allowed to semi dry at room temperature for two hours .

[0177] Next, the samples were introduced into a vacuum oven (Thermo Scientific VT 6060 M) at 160°C for 8 minutes, followed by cooling to room temperature. The samples were left for a few days at room temperature, and subsequently tested using an ASTM 6413 standard test instrument ( Govmark D6413-08 vertical) .

[0178] Test results as well as the weight parameters are detailed in

[0179] Table 9.

[0180] Table 9

[0181] In Table 9, After Glow denotes that no after glow was observed.

[0182] A photograph of the specimens in Table 9, following the flammability test is presented in Figure 1.

[0183] The test results in Table 9 show that treatment with the BPFR coformulation ( co- formulation 1) dramatically improved the flame retardancy performance of the cardboard product (samples 1-3) . Contrasted with the untreated control (sample 5) that burned completely. The performance of the samples depended on the amount of added flame retardant BPFR co- formulation . In order to pass the ASTM 6413 standard test, the BPFR co- formulation had to be applied to a cardboard sample in an amount sufficient to provide at least about 37% of a weight gain as compared to initial cardboard sample weight. Treatment with the BPFR co- formulation in an insufficient amount resulted in decreased flame retardancy performance of the cardboard product (sample 4) . Example 5 Application of FR co-f ormulation to a recycled chipboard product (of the invention)

[0184] Commercially available chipboard (0.37gr / cm3) was mechanically crashed. Part of the sample was then followed by grinding the wood particle in a IKA TUBE MILL 100 at 4000 RPM. The mechanically crashed and the grinded particle samples were soaked with coformulation 1 ("FR-370_70") , then let dry in a laboratory fume hood at room temperature, and then inserted into a vacuum oven (Thermo Scientific VT 6060 M) at 80°C for 10 minutes, followed by cooling to room temperature. Sample weights were measured before and after the drying step. The weights are recorded in Table 10, below.

[0185] Next, the chipboard particle samples were placed in a 10cm X 20cm X 1cm template and a curing stage was performed in a heated hydraulic press (LabTech LP-S-50 Thailand) at 140°C for 6 minutes while applying a pressure of 140 bar for 2 minutes, followed by 2 minutes at 160 bar, and followed by 2 minutes at 180 bar. The sample was left for a few days at room temperature using a NFPA 701 standard test instrument (Govmark 701 vertical) (according to the ASTM 701 (Govmark 701S USA) ) testing method) . Test results are recorded in Table 10.

[0186] Table 10

[0187] The test results in Table 10 show that chipboard can be recycled for reuse as chipboard or MDF, and further that the fire resistance of chipboard can be significantly enhanced by treatment with a BPFR co-formulation (such as co-formulation 1) .

[0188] Example 6 Application of FR co-formulation to pine wood particles (of the invention)

[0189] Commercially available pine wood particles were soaked in co- formulation 1 ( "FR-370_70" ) and then let dry in a laboratory fume hood for two days. After the initial drying, the sample was inserted into a vacuum oven (Thermo Scientific VT 6060 M) at 80°C for 10 minutes, followed by cooling to room temperature. Sample weight was measured before the initial drying at room temperature and after the drying in a vacuum oven, as recorded in

[0190] Table 11, below.

[0191] Next, pine wood particles were placed in a mold and a curing stage was performed in a heated hydraulic press (LabTech LP-S-50 Thailand) at 140°C for 6 minutes while applying pressure of 140 bar for 2 minutes, followed by 2 minutes at 160 bar, and followed by 2 minutes at 180 bar. The sample was left for a few days at a room temperature and then tested using a NFPA 701 standard test instrument (Govmark 701) (according to the ASTM 701 (Govmark 701S USA) ) testing method) . Test results are recorded in Table 11.

[0192] Table 11

[0193] Comparison of the results in Table 11 with the control chipboard identified as Sample 3 in Table 10, shows that treatment with a BPFR co-formulation (such as co-formulation 1) can be used to manufacture a chipboard with fire retardant properties.

[0194] Example 7 Application of FR co-formulation to a bamboo product (of the invention)

[0195] A commercially available Bamboo (2mmx9mmx40cm) was shortened to a length of 27 cm. In total, 40 individual bamboo pieces were prepared. The bamboo pieces were then brushed with co-formulation 1 ( "FR-370_70" ) , placed in a laboratory fume hood and allowed to semi dry at room temperature for 24 hours.

[0196] Next, the bamboo pieces were introduced into a vacuum oven (Thermo Scientific VT 6060 M) at 80°C for 5 minutes, followed by cooling to room temperature. The samples were left for a few days at room temperature .

[0197] Next, the 40 individual pieces were placed on top of each other and glued together. The gluing was performed with co-formulation 1 ( "FR-370_70" ) . The curing stage of the glued specimen was performed in a vacuum oven (Thermo Scientific VT 6060 M) at 160°C for 10 minutes while applying pressure with wood clamps. The product was tested using a NFPA 701 standard test instrument (Govmark 701) (according to the ASTM 701 (Govmark 701S USA) ) testing method) . Test results, as well as the weight parameters of the specimen, are detailed in Table 12. "Initial sample weight refers", in Table 12, referred to the weight to before the gluing of the specimen. A photograph of the specimen following the flammability test is presented in Figure 2.

[0198] Table 12

[0199] An untreated bamboo is known to have a low fire rating because of its high heat release rate. The test results in Table 12 show that treatment with the BPFR co- formulation greatly improved the flame retardancy performance of bamboo .

Claims

Claims1. A flame retardant composition comprising:(i) a cellulose-based material selected from paper-based material , wood-based material and bamboo-based material; and(ii) a flame retardant co-formulation comprising: a) a brominated phosphate ester of Formula la:'Formula la, wherein the brominated phosphate ester of Formula la is present in an amount of about 10% to about 22% by weight of the flame retardant co-formulation; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole, wherein the melamine resin is present in an amount of about 35% to about 45% by weight of the flame retardant co-formulation.

2. The flame retardant composition according to claim 1, wherein the brominated phosphate ester of Formula la is present in anamount of about 16% to about 20% by weight of the flame retardant co- formulation .

3. The flame retardant composition according to claim 1 or 2, wherein the melamine resin is present in an amount of about 40% to about 45% by weight of the flame retardant co-formulation .

4. The flame retardant composition according to anyone of claims 1 to 3, wherein the melamine resin is partially methylated melamine formaldehyde resin.

5. The flame retardant composition according to anyone of claims 1 to 4, wherein the flame retardant co-formulation is present in an amount of at least about 35% by weight of the flame retardant composition .

6. The flame retardant composition according to anyone of claims1 to 5, wherein the cellulose-based material is paper-based material .

7. The flame retardant composition according to anyone of claims1 to 5, wherein the cellulose-based material is wood-based material .

8. The flame retardant composition according to anyone of claims1 to 5, wherein the cellulose-based material is bamboo-based material .

9. A flame retardant cellulose-based product formed from ingredients comprising:(i) a cellulose-based material selected from paper-based material , wood-based material and bamboo-based material;(ii) a brominated phosphate ester of Formula la:'Formula la, wherein the brominated phosphate ester of Formula la is present in an amount of about 5% to about 20 % by weight of the cellulose- based product; and(iii) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole, wherein the melamine resin is present in an amount of about 10% to about 20% by weight of the cellulose-based product.

10. The flame retardant cellulose-based product according to claim 9, wherein the brominated phosphate ester of Formula la is present in an amount of about 8% to about 20% by weight of the cellulose- based product.

11. The flame retardant cellulose-based product according to claim 9, wherein the brominated phosphate ester of Formula la is present in an amount of about 10% to about 20% by weight of the cellulose- based product.

12. The flame retardant cellulose-based product according to any one of claims 9 to 11, wherein the melamine resin is present in an amount of about 12% to about 20% by weight of the cellulose- based product.

13. The flame retardant cellulose-based product according to any one of claims 9 to 11, wherein the melamine resin is present in an amount of about 15% to about 20% by weight of the cellulose- based product.

14. The flame retardant cellulose-based product according to anyone of claims 9 to 13, wherein the melamine resin is partially methylated melamine formaldehyde resin.

15. The flame retardant cellulose-based product according to anyone of claims 9 to 14, wherein the product is a paper-based product .

16. The flame retardant cellulose-based product according to claim 15, wherein the paper-based product is selected from paper laminate and cardboard.

17. The flame retardant cellulose-based product according to anyone of claims 9 to 14, wherein the cellulose-based product is wood-based product.

18. The flame retardant cellulose-based product according to claim 17, wherein the wood-based product is selected from engineered timber, cross laminated timber (CLT) , laminated veneer lumber (LVL) , medium-density fibre (MDF) , low-density fiberboard (LDF) , particle board and plywood.

19. The flame retardant cellulose-based product according to anyone of claims 9 to 14, wherein the cellulose-based product is bamboo-based product.

20. The flame retardant cellulose-based product according to claim 19, wherein the bamboo-based product is selected from laminated bamboo lumber (LBL) , cross laminated bamboo (CLB) and laminated veneer lumber (LVL) .

21. A method of imparting flame retardancy to a cellulose-based material, comprising: applying to a cellulose-based material selected from paper-based material, wood-based material and bamboo-based material, an aqueous flame retardant co-formulation comprising: a) a brominated phosphate ester of Formula la:'Formula la, wherein the brominated phosphate ester of Formula la is present in an amount of about 10% to about 22% by weight of the flame retardant co-formulation; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weightof about or above 500 gr / mole, wherein the melamine resin is present in an amount of about 35% to about 45% by weight of the flame retardant co-formulation; at a temperature and pressure sufficient for incorporating an effective amount of the brominated phosphate ester and the melamine resin into the cellulose-based material.

22. The method according to claim 21, wherein the flame retardant co-formulation comprises a brominated phosphate ester of Formula la in an amount of about 16% to about 20% by of the flame retardant co- formulation .

23. The method according to claim 21 or 22, wherein the flame retardant co-formulation comprises a melamine resin in an amount of about 40% to 45% by weight of the flame retardant coformulation .

24. The method according to anyone of claims 21 to 23, wherein the flame retardant co-formulation comprises a melamine resin which is a partially methylated melamine formaldehyde resin.

25. The method according to anyone of claims 21 to 24, wherein the flame retardant co-formulation is applied in an amount of at least about 35% by weight of the cellulose-based material.

26. The method according to anyone of claims 21 to 25, wherein the amount of the brominated phosphate ester incorporated into the cellulose-based material is about 5 to 20 % by weight of the cellulose-based material.

27. The method according to anyone of claims 21 to 25, wherein the amount of the melamine resin incorporated into the cellulose-based material is about 10 to 20 % by weight of the cellulose- based material.

28. The method according to anyone of claims 21 to 25, wherein the cellulose-based material is paper-based material.

29. The method according to anyone of claims 21 to 25, wherein the cellulose-based material is wood-based material.

30. The method according to anyone of claims 21 to 25, wherein the cellulose-based material is bamboo-based material.

31. A process for producing a flame retardant cellulose-based product comprising:(i) applying an effective amount of an aqueous flame retardant co- formulation to a cellulose-based material selected from paperbased material, a wood-based material and a bamboo-based material; followed by(ii) curing at temperature between from about 90°C to 190°C at a pressure selected atmospheric pressure and pressure of from about 8 MPa (80 Bar) to 18 MPa (180 Bar) , to form the flame retardant product; wherein the flame retardant co-formulation comprises: a) a brominated phosphate ester of Formula Ta:'Formula Tawherein the brominated phosphate ester of Formula la is present in an amount of about 10% to about 22% by weight of the flame retardant co-formulation; and b) a melamine resin selected from partially methylated melamine formaldehyde resin, methylated melamine formaldehyde resin, and methylated high imino melamine resin, having a molecular weight above 150 gr / mole, above 180, above 300, above 400, above 500, above 600, above 700 gr / mole, preferably having a molecular weight of about or above 500 gr / mole, wherein the melamine resin is present in an amount of about 35% to about 45% by weight of the flame retardant co-formulation.

32. The process according to claim 31, wherein the flame retardant co-formulation comprises a brominated phosphate ester of Formula la in an amount of about 16% to about 20% by weight of the flame retardant co-formulation.

33. The process according to claim 31 or 32, wherein the flame retardant co-formulation comprises a melamine resin in an amount of about 40% to 45% by weight of the flame retardant co- formulation .

34. The process according to anyone of claims 31 to 33, wherein the flame retardant co-formulation comprises a melamine resin which is a partially methylated melamine formaldehyde resin.

35. The process according to anyone of claims 31 to 34, wherein the flame retardant co-formulation is applied in an effective amount of at least about 35% by weight of the cellulose-based material .

36. The process according to anyone of claims 31 to 35, wherein the brominated phosphate ester is incorporated into the cellulose- based product in an amount of about 5 to 20 % by weight of the cellulose-based product.

37. The process according to anyone of claims 31 to 36, wherein the melamine resin is incorporated into the cellulose-based product in an amount of about 10 to 20 % by weight of the cellulose-based product.

38. The process according to anyone of claims 31 to 37, wherein the cellulose-based product is a paper-based product.

39. The process according to claim 38, wherein the paper-based product is selected from paper laminate and cardboard.

40. The process according to anyone of claims 31 to 37, wherein the cellulose-based product is wood-based product.

41. The process according to claim 40, wherein the wood-based product is selected from engineered timber, cross laminated timber (CLT) , laminated veneer lumber (LVL) , medium-density fibre (MDF) , low-density fiberboard (LDF) , particle board and plywood.

42. The process according to anyone of claims 31 to 37, wherein the cellulose-based product is bamboo-based product.

43. The process according to claim 42, wherein the bamboo-based product is selected from laminated bamboo lumber (LBL) cross laminated bamboo (CLB) and laminated veneer lumber (LVL) .

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