Patent Description:
Apart from the resin and water, a coating formulation may contain pigments and additives, e.g., wetting and dispersing agents, coalescing agents, defoamers and rheology modifiers. Another additive to be considered in coating formulations is a flame retarding agent. One important category of flame retardants consists of brominated flame retardants. A number of studies were reported evaluating the performance of brominated flame retardants added to water-based acrylic resin for use in the wood coatings market.

<CIT> illustrates the use of a liquid halogenated phosphate ester as a major flame retardant in acrylic coatings for wood, alongside a brominated flame retardant as a secondary component. The formulations of <CIT> further contain a flame retardant which undergoes endothermic decomposition (alumina trihydrate (ATH) or magnesium hydroxide (MDH)). The brominated flame retardants tested in <CIT> include brominated bisphenol A (used in a small amount) and brominated polyol (a liquid flame retardant). The addition of the (mostly liquids) flame retardants to the coating formulation was achieved in a straightforward manner, through pre-mixing with the acrylic dispersion. As opposed to the approach shown in <CIT>, based mainly on liquid flame retardants, formulating large amounts of solid brominated flame retardants as coatings can be challenging. The approach was demonstrated in <CIT> and recently in <CIT>, illustrating incorporation of water-insoluble solid brominated flame retardant into water based acrylic/polyurethane coating formulations. In <CIT>, tribromophenol end-capped brominated epoxy polymer of the formula:
<CHM>
[classified as low molecular weight brominated epoxy polymer, e.g., m~ <NUM>-<NUM>; <NUM> < Molecular Weight (MW) < <NUM>; e.g., in a pulverised form, for example, d<NUM><<NUM>, d<NUM>< <NUM> and d<NUM>< <NUM>, determined by laser diffraction particle size analysis] was formulated as an aqueous dispersion, which was subsequently mixed with a commercial acrylic or polyurethane resin to form a varnish formulation. The varnish was applied on wood to give transparent/translucent coatings. The coated wood samples achieved good results in flammability tests.

The action of brominated flame retardants incorporated into combustible substances is almost always augmented by metallic oxides, especially antimony oxides, which act synergistically with brominated flame retardants. Indeed, the formulations illustrated in the publications mentioned above included metallic oxide synergists. Specifically, antimony oxides were the additives of choice in both <CIT> (antimony trioxide) and <CIT> (antimony pentoxide).

<CIT> describes a flame-retardant waterproof aqueous polyurethane coating and a preparation method thereof. The coating is prepared from the following raw materials in parts by weight: <NUM>-<NUM> parts of polyether polyol, <NUM>-<NUM> parts of <NUM>, <NUM>-diphenyl-methane-diisocyanate, <NUM>-<NUM> parts of toluene diisocynate, <NUM>-<NUM> parts of polydimethylsiloxane, <NUM>-<NUM> parts of nano cerium oxide, <NUM>-<NUM> parts of acetic ether, <NUM>-<NUM> parts of alkyl phosphate salt, <NUM>-<NUM> parts of chlorinated paraffin, <NUM>-<NUM> parts of talcum powder, <NUM>-<NUM> parts of pentaerythritol, <NUM>-<NUM> parts of trimethylolpropane, <NUM>-<NUM> parts of stannous octoate, <NUM>-<NUM> parts of dibutyltin dilaurate, <NUM>-<NUM> parts of an antioxidant TNP, <NUM>-<NUM> parts of nanotitanium dioxide, <NUM>-<NUM> parts of dicumyl peroxide, <NUM>-<NUM> parts of deionized water and <NUM>-<NUM> parts of auxiliaries.

<CIT> describes a textile comprising fiber and a brominated flame retardant that is a copolymer having copolymerized therein a butadiene moiety and a vinyl aromatic monomer moiety, the copolymer having, prior to bromination, a vinyl aromatic monomer content of from <NUM> to <NUM> percent by weight based upon copolymer weight, a <NUM>,<NUM>-butadiene isomer content of greater than zero percent by weight based upon butadiene moiety weight, and a weight average molecular weight of at least <NUM>, the brominated copolymer having an unbrominated, non-aromatic double bond content of less than or equal to <NUM> percent based upon non-aromatic double bond content of the copolymer prior to bromination as determined by proton nuclear magnetic resonance spectroscopy, a five percent weight loss temperature, as determined by thermogravimetric analysis of at least <NUM> degrees Celsius.

<CIT> describes a fire retardant, vapor impermeable coating composition, which is useful for protecting gypsum, wood, polyurethane, polystyrene, and other construction materials and surfaces, such as components for buildings. The composition does not require halogenated compounds and is considered environmentally friendly. The composition is provided in the form of a liquid-applicable aqueous latex comprising at least one latex polymer and an expandable graphite, optionally a hydrophobic thickener, and optionally other fire retardants such as metal hydroxides, wherein the polymer is selected such that the composition, when coated onto a substrate and allowed to dry, has a vapor permeability not exceeding one perm (<NUM>×<NUM>-<NUM> g/Pa. m<NUM> when tested according to ASTM E96B-<NUM> at an average dry film thickness of <NUM> mils). The invention provides fire retardant air barrier layers for construction materials, such as polyurethane or polystyrene insulation beads or panels, as well as vapor impermeable laminates for construction applications.

We have now studied the combustion performance of wood products coated with formulations based on the varnish described in <CIT>. Coatings were evaluated according to the Single Burning Item (SBI) test set out in EN <NUM>, which measures the rates of heat and smoke release produced by a test specimen which consists of two vertically positioned rectangular wood boards (<NUM> × <NUM> and <NUM> × <NUM>), joined perpendicularly along their equal side to create a <NUM>° corner. The test evaluates the performance of a product placed in a small room, under exposure to a flame produced by a single ignition source located adjacent to the test product (for example, to simulate a waste-paper basket in a corner of the room). Parameters measured by the SBI test include the fire growth rate index; the total heat release over the first ten minutes after the ignition of the burner; the smoke growth rate index; and the total smoke production over the first ten minutes after burner ignition.

The coating formulation of <CIT> that was subjected to the SBI test is designated herein BER/APO (BER stands for the low molecular weight brominated epoxy resin flame retardant with the chemical structure depicted above, APO stands for the antimony pentoxide synergist). In addition, we also tested a ternary formulation, which included a combination of the low-molecular weight brominated epoxy polymer, antimony pentoxide and magnesium hydroxide (designated BER/APO/Mg(OH)<NUM>). The ternary system showed some improvement over the basic coating formulation BER/APO of <CIT>. However, much to our surprise, antimony oxide-free water-based acrylic coating comprising the low-molecular weight brominated epoxy polymer and magnesium hydroxide (designated herein BER/Mg(OH)<NUM>) performed consistently better than all the other coatings evaluated in the study.

Apart from the SBI test mentioned above, in which the flammability of coated (flame retarded) medium density fiberboard (MDF) samples was studied, we used a cone calorimeter test (a small-scale test) to examine the burning properties of coated pine wood samples. The trend observed in the SBI and cone calorimeter tests for the two types of wood was the same: the antimony oxide-free coating, based on BER/Mg(OH)<NUM>, was more efficient than the coating which was flame retarded by the ternary, antimony oxide containing combination BER/APO/Mg(OH)<NUM>.

The cone calorimeter test served us to evaluate different brominated flame retardants (in particular brominated polymeric flame retardants), formulated with either Mg(OH)<NUM>(MDH) or Al(OH)<NUM>(ATH) in acrylate and polyurethane based coatings. In the cone calorimeter test, radiant heat is projected onto a sample before ignition and during the burning of the sample, and several parameters, especially parameters related to the heat release profile of the tested sample, are measured. An effective flame retardant system should exhibit low values of peak and average heat release rate (HRR) and the lowest maximum average rate of heat emission (MARHE). The experimental work conducted in support of this invention shows that in the coating systems described herein, MDH and ATH can offset the exclusion of antimony oxide, e.g., antimony pentoxide. That is, the efficiency of combinations consisting of brominated polymeric flame retardant/MDH (or ATH) and brominated polymeric flame retardant/APO were found to be at least comparable, across the range of brominated polymeric flame retardant tested by us. Because the common practice of using antimony oxide synergist alongside brominated flame retardants may be objected to due to environmental considerations, the substitution of APO by MDH or ATH is highly desired.

Accordingly, the present invention provides a flame retardant coating formulation in the form of an aqueous dispersion comprising a binder according to claim <NUM>, a process for preparing a flame retardant coating formulation for wood according to claim <NUM> and a method of reducing the flammability of wood and wood products according to claim <NUM>.

A brominated polymeric flame retardant may be represented by formula (I):
<CHM>.

Preferred are tribromophenol end-capped brominated epoxy polymers of the formula IA:
<CHM>
specifically a low-molecular weight type resin, e.g., with <NUM> < MW < <NUM>, e.g., <NUM> ≤ MW < <NUM> (m~<NUM>-<NUM>).

A brominated polyacrylate, e.g., poly (pentabromobenzyl acrylate), may be represented by formula II:
<CHM>
(n=degree of polymerization).

The polymer (abbreviated PBBPA) is produced by polymerizing the corresponding monomer pentabromobenzyl acrylate, either in bulk (in an extruder at a temperature in the range from <NUM> to <NUM> as described in <CIT>), or in solution, see <CIT>, <CIT> and <CIT>. The polymer is also available on the market, being sold by ICL-IP (<CIT>).

A brominated polystyrene, may be represented by formula III:
<CHM>
(n=degree of polymerization; m= <NUM>, <NUM>, <NUM>, <NUM> or <NUM>).

The polymer is prepared by methods known in the art (see <CIT> and <CIT>). Suitable grades have weight average molecular weight in the range of about <NUM>,<NUM>-<NUM>,<NUM>, with bromine content preferably exceeding <NUM> or even <NUM> % by weight (that is, average of <NUM>-<NUM> bromine atoms per aromatic ring in the polymer backbone chain). Such polymers, in the form of a free-flowing powder, are available on the market, e.g., from ICL-IP (FR 803P).

Brominated poly[styrene-co-butadiene], e.g., brominated polystyrene-block-polybutadiene-block-polystyrene, is shown below (Formula IV):
<CHM>
where x, y and z indicate the numbers of the three types of repeat units, respectively. Such brominated products, in particular, polystyrene-block-brominated polybutadiene-block-polystyrene, are commercially available (e.g., FR-122P from ICL-IP).

Combinations of brominated nonpolymeric flame retardants with MDH were found to be less efficient than the corresponding combinations with APO. That is, MDH is not as effective as APO in coating formulations that are flame retarded by "small" brominated compounds, such as decabromodiphenyl ethane (abbreviated DPDPE; available commercially as <CIT> from ICL-IP). These "small" brominated compounds lean heavily on the presence of APO in coating formulations, as shown by the results reported below.

Hereinafter, a brominated polymeric flame retardant is abbreviated BFR. The preferred flame retardant, namely, the end-capped brominated epoxy polymer of Formula Ia, is abbreviated BER. Preferred coating formulations of the invention comprise:.

The formulation further contains customary coating additives. Major types of additives may include:.

Weight concentrations are based upon total formulation, unless indicated otherwise.

The composition of the invention is substantially free of Sb<NUM>O<NUM> or Sb<NUM>O<NUM>. By "substantially free" is meant that the concentration of the synergist (e.g., antimony trioxide or antimony pentoxide) in the composition is well below the acceptable amount used in conjunction with brominated additives in coating formulations for wood products, e.g., not more than <NUM> % by weight, more preferably, less than <NUM> % by weight, e.g., up to <NUM> % and even more preferably from <NUM> to <NUM> % by weight (based on the total weight of the composition). Most preferably, the compositions of the invention are totally devoid of metal oxide synergists.

The coating formulation may be prepared in two steps. In the first step, the solid flame retardants [BFR and Mg(OH)<NUM> or Al(OH)<NUM>] are dispersed in water to form a homogeneous FR dispersion (FR is an abbreviation of flame retardant). In the second step, the FR aqueous dispersion, containing BFR and Mg(OH)<NUM> or Al(OH)<NUM> is combined with a water-based (e.g., acrylate or polyurethane) resin.

To incorporate the pair of solid flame retardants into water, it is more convenient to start with the magnesium hydroxide powder and then continue with the BFR powder, because their processing may require different conditions. Suitable grades of magnesium hydroxide consist of micron or submicron particles (for example, with the particle size distribution of d<NUM> ≤ <NUM> (e.g., d<NUM> ≤ <NUM>, more preferably d<NUM> ≤ <NUM>) and d<NUM> ≤ <NUM> (e.g., d<NUM> ≤ <NUM>, more preferably or d<NUM> ≤ <NUM>), measured by laser diffraction, e.g., by Malvern Mastersizer <NUM> using isopropanol. Commercial products suitable for use include FR-<NUM>-<NUM> from ICL-IP, such as the grade named FR-<NUM>-<NUM>-S10. Suitable aluminum trihydrate exhibits average median particle diameter from <NUM> to <NUM> and BET surface area from <NUM> to <NUM><NUM>/g, such as SB-<NUM> from HUBER with the average median particle diameter of <NUM> and BET surface area of <NUM><NUM>/g. The description that follows relates to formulating Mg(OH)<NUM> with BFR in water-based acrylic coatings. The description, however, applies equally to Al(OH)<NUM> instead of Mg(OH)<NUM> unless otherwise specifically indicated.

The Mg(OH)<NUM> powder may be added to a vessel that was previously charged with water, coalescing agent (e.g., to water/propylene glycol mixture, proportioned <NUM>:<NUM> to <NUM>:<NUM> by weight), and a dispersing agent. The wettability of magnesium hydroxide in water is fairly good, and therefore the presence of a wetting agent may not be necessary at this stage. A coalescing agent and a defoamer may also be incorporated into the water prior to the addition of the FR powders. To disperse these auxiliary additives in water (the dispersing, wetting, coalescing and defoaming agents), usually relatively low shear force is required, generated by a dissolver stirrer operating at <<NUM> rpm. Incorporation of the magnesium hydroxide powder into the water can be achieved with the aid of a high-shear or ultra-high shear disperser, for example, revolutions per minute (rpm) of the mixing shaft is not less than <NUM>,<NUM>, e.g., operating in a range of rotor tip speeds between <NUM>,<NUM> and <NUM>,<NUM> ft/min. The Mg(OH)<NUM> powder is added gradually, under a first agitation rate, say, from <NUM>,<NUM> to <NUM>,<NUM> rpm. After the addition of the total amount of magnesium hydroxide is completed, the mixture is homogenized for some time, with the high-shear disperser operating at a higher speed range, e.g., from <NUM>,<NUM> to <NUM>,<NUM> rpm.

Next, BFR is incorporated into the FR suspension. For example, a powder with particle size distribution of d<NUM><<NUM> (e.g., d<NUM><<NUM>) and preferably also d<NUM><<NUM> (e.g., d<NUM><<NUM>, d<NUM><<NUM>, d<NUM><<NUM>) and even more preferably also d<NUM>< <NUM> (e. , d<NUM>< <NUM>, d<NUM><<NUM>, d<NUM><<NUM>). Suitable pulverized forms may be produced by subjecting a BFR to particle size reduction with the aid of a jet mill (dry milling) to achieve particle size distribution as set out above (measured by Malvern Mastersizer <NUM> in water (<NUM> minutes ultrasonic treatment, <NUM> psi, <NUM> rpm)). A suitable commercially available product is TexFRon® <NUM> from ICL-IP (it is the BER of Formula Ia).

When the BFR has a low softening point (which is the case for the BER of Formula Ia), then its addition is not carried out under operation of a very high speed, high shear disperser as set out above for Mg(OH)<NUM>. Rather, a lower speed instrument (e.g., low to medium, such as < <NUM>,<NUM> rpm, e.g., < <NUM>,<NUM> rpm) may be used to enable the formation of homogeneous FR dispersion. To improve its storage stability, a thickener may be added to the BFR/Mg(OH)<NUM> dispersion, to minimize the settling of FR's with the passage of time. However, if little time is allowed to elapse before the BFR/Mg(OH)<NUM> dispersion is mixed with the binder (e.g., acrylic or polyurethane) resin, then the presence of a thickener in the FR dispersion is not mandatory; the thickener can just be added to the finished coating formulation.

The weight ratios between the components of the FR suspension, namely, water, Mg(OH)<NUM> or Al(OH)<NUM>, BFR, coalescing agent, dispersing agent (sometimes a single component serves a dual function of dispersant/wetting agent) and a defoamer are preferably in the ranges of <NUM>: <NUM>-<NUM>: <NUM>-<NUM>: <NUM>-<NUM>: <NUM>-<NUM>: <NUM>-<NUM>, respectively.

In the next step, the FR suspension is combined with a water-based binder resin (e.g., water-based acrylic or polyurethane resin).

Acrylic resin for use in the present invention usually falls into two categories (the term "acrylic", as used herein, is meant to include "methacrylic"):.

In both categories, the acrylic monomers structural units of the resin can be selected from alkyl acrylate and alkyl methacrylate (alkyl esters of acrylic acids or methacrylic acid), where the alkyl group is preferably C1-C5 alkyl, e.g., methyl, ethyl, propyl (e.g., n-propyl) and butyl (e.g., n-butyl). The parent acid - acrylic acid or methacrylic acid - may also be used in small amounts to provide the resin. The acrylic monomers may be optionally functionalized.

The water-based acrylic resin for use in the present invention may be provided in different forms. Two major forms are:.

The experimental results reported below indicate that self-crosslinking acrylic copolymer formulated in water (from <NUM> to <NUM> % solid content, e.g., from <NUM> to <NUM> %) in the form of slightly alkaline dispersion available, for example, from Alberdingk Boley, is compatible with the FR dispersion and the two mixtures can be combined to form an efficient flame retardant coating formulation.

Before it is mixed with the BFR/Mg(OH)<NUM> dispersion to form the finished coating formulation, it is beneficial to add to the commercially available water-based acrylic resin one or more dispersing agents, a substrate wetting agent and a defoamer, e.g., in the following weight ratios <NUM>: <NUM>-<NUM>: <NUM>-<NUM>: <NUM>-<NUM> (<NUM> parts by weight of a water-based acrylic resin include the water component of the commercial resin). These additives are readily incorporated into commercial water based acrylic resins, for example with the aid of a dissolver stirrer. A dispersing agent of choice for this part of the preparation (that is, to be incorporated into the water-based acrylic resin before the addition of the FR dispersion) is an anionic dispersant, especially a salt of polyacrylic acid, e.g., sodium polyacrylate.

The FR dispersion is added to the water-based acrylic resin dispersion described immediately hereinabove, usually in <NUM>:<NUM> to <NUM>:<NUM> weight ratio, e.g., <NUM>: <NUM> to <NUM>:<NUM>, for example, roughly equal quantities of the FR dispersion and the water based acrylic resin are mixed to form a homogeneous formulation, followed by the addition of a rheology additive, e.g., which functions as a thickener and stabilizes the formulation. The density of the formulation of the invention varies from <NUM> to <NUM>/m<NUM>, e.g., from <NUM> to <NUM>/m<NUM>.

A specific process for preparing a flame retardant coating formulation for wood, according to the invention, comprises the steps of:.

The BFR/Mg(OH)<NUM> or BFR/Al(OH)<NUM> aqueous suspensions obtained in step 1b, comprising water, Mg(OH)<NUM> or Al(OH)<NUM>, BFR, a coalescing agent (e.g., propylene glycol), a dispersing agent (e.g., an agent serving a dual function of dispersant/wetting agent) and a defoamer, proportioned <NUM> : <NUM>-<NUM> (e.g., <NUM>-<NUM>) : <NUM>-<NUM> (e.g., <NUM>-<NUM>) : <NUM>-<NUM> (e.g., <NUM>-<NUM>) : <NUM>-<NUM> : <NUM>-<NUM>, by weight, respectively, forms another aspect of the invention.

Dispersant(s) are present in the coating formulation at a concentration from <NUM> to <NUM>% by weight each, based on total formulation. The use of two or more dispersants is beneficial: a first dispersing agent (e.g., nonionic) is incorporated into the water before addition of the FR powders, and is also added to the water-based binder (e.g., acrylic) resin component, together with a second dispersing agent (anionic), before the binder is combined with the FR dispersion. Polymeric dispersants are preferred, e.g., nonionic acrylate copolymer can serve as the first dispersing agent (such as DISPERBYK®-<NUM>, available in an emulsion form). A salt of polyacrylic acid (e.g., sodium polyacrylate, such as LOPON® <NUM> from ICL) or a salt of polyphosphoric acid (e.g., sodium polyphosphate, such as Calgon® N from ICL) can serve as the second dispersant (the anionic dispersant).

The good effect of a combination of nonionic and anionic surfactants as dispersing agent system on the storage stability of the formulations of the invention is shown in the experimental work reported below. Usually accelerated testing of paints/coating formulations is carried out at elevated temperature for a period of a few weeks and then the formulation is visually examined. The results indicate that in the absence of an anionic surfactant, the formulation transforms into a non-fluid mass (gel or solid). In the presence of an anionic surfactant, however, only little, temporary separation was observed at the end of the test period, as the formulation could be re-dispersed easily to restore its flowability and functionality. The ratio between the nonionic and anionic surfactants is usually in the range of <NUM>:<NUM> to <NUM>:<NUM> weight ratio, e.g., <NUM>: <NUM> to <NUM>:<NUM>.

Wetting agent(s) may be added to wet the particles of the flame retardants. Wetting agents are usually added at a concentration from <NUM> to <NUM> % by weight each based on total formulation, and include, for example nonionic surfactants such as alcohol alkoxylates and anionic surfactants such as alkyl aromatic sulfonates, e.g., sodium isopropyl naphthalene sulfonate. When used, the wetting agents are incorporated into water before addition of the FR powders. However, some dispersing agents possess the necessary wetting properties and hence a single additive can be used, such as DISPERBYK-<NUM>.

Coalescing agents (usually added at a concentration from <NUM> to <NUM> % by weight based on total formulation) may be, for example, hydrophilic coalescing agents, e.g., propylene glycol or water-soluble alkyl ethers of propylene glycols, such as di-propylene glycol monomethyl ether. Coalescing agents are usually incorporated into water before addition of the FR powders.

Defoaming agents (usually from <NUM> to <NUM> % by weight each) may be, for example, silicone-containing defoamers, or long chain decyne diols ethoxylated derivatives. Defoamers are incorporated into water before addition of the FR powders and can be separately added to the water-based binder before it is combined with the FR dispersion.

Substrate wetting agents, to improve the wettability of the wood substrate by the coating formulation (usually from <NUM> to <NUM> % by weight each) may be, for example, polyether-modified silicone surfactants, sometimes available in solution form in glycol and/or ether solvents. A substrate wetting agent is added to the water-based binder (e.g., acrylic resin), before it is mixed with the FR dispersion to form the coating formulation.

Rheology additive (usually from <NUM> to <NUM> % by weight each), e.g., thickening and anti-settling agent, for example, liquid rheology additives such as a solution of modified urea (in N-methyl pyrrolidone), or other types, polyurethanes, polymer modified clays and acrylic emulsions. Thickeners are usually the last added component, i.e., they are incorporated into the finished formulation.

Other types of additives include preservatives, stabilizers, pH buffers, curing agents, sequestering agents, suspending agents, detergents, and of course dyes and pigments.

As mentioned above, water-based polyurethane dispersions can also benefit from the addition of the BFR/Mg(OH)<NUM> dispersion to offer flame retardant polyurethane-based coatings. Examples of commercial polyurethane dispersions include ALBERDINGK® U9600 VP - Aliphatic polyester polyurethane dispersion and ALBERDINGK® PUR MATT <NUM> - (aliphatic) polyurethane dispersion. Another type of aqueous dispersions used in wood coating is based on vinyl acetate copolymer dispersions, such as ALBERDINGK® VA <NUM>.

The composition of the invention can be applied to coat/paint wood (oak, pine, beech, cherry) or wood products (e.g., engineered wood) by conventional techniques, e.g., with the aid of a sprayer, a brush, a roller-coater, to achieve loading levels of about <NUM>/m<NUM> to <NUM>/m<NUM>, e.g., from <NUM>/m<NUM> to <NUM>/m<NUM>, to create one or more coating layers onto the wooden surface. Wood products include glulam, plywood, parallel strand lumber (PSL), oriented strand board (OSB), oriented strand lumber (OSL), laminated veneer lumber (LVL), laminated strand lumber (LSL), particleboard, medium density fiberboard (MDF), cross-laminated timber, and hardboard, as described in <CIT> and <CIT>. The experimental results reported below indicate that the flammability of coated MDF and pine wood was effectively reduced with the aid of the flame retardants described herein.

Preferred antimony-free coating formulations of the invention, which are flame retarded by incorporating BFR/MDH or BFR/ATH aqueous suspension into commercial water-based acrylic or polyurethane resins, and preferred additives present in such formulations, are set out in Table A.

A coating created by the formulation of the invention may be transparent (i.e., the texture and/or the wooden color can still be easily observed in the final coated wooden substrate) or translucent, (i.e., the wooden color can be seen through the coating of the invention to some extent, while giving rise to a coated substrate having a mat finishing). The transparency of the film of the invention can be measured using DATACOLOR <NUM>. The transparent film of the invention is characterized by having transparency values of between <NUM> % and <NUM> % as measured by DATACOLOR <NUM>, e.g., <NUM> %-<NUM>%, for example, <NUM>% -<NUM>% as measured by DATACOLOR <NUM>.

Also described are nonpolymeric brominated flame retardants which could benefit from the replacement of antimony oxide by magnesium hydroxide in coating formulations, such as Tris(<NUM>,<NUM>,<NUM>-tribromophenoxy)-s-triazine, represented by Formula V:
<CHM>.

The preparation of tris(<NUM>,<NUM>,<NUM>-tribromophenoxy)-s-triazine is generally based on the reaction of cyanuric chloride with <NUM>,<NUM>,<NUM>-tribromophenolate under various conditions well known in the art (see, for example, <CIT>, <CIT> and<CIT>). The flame retardant is also commercially available from ICL-IP under the name <CIT>. The results reported below indicate that unlike the brominated nonpolymeric compound DPDPE, which depends strongly on the presence of antimony oxide synergist, coatings which are flame retarded by FR-<NUM>/Mg(OH)<NUM> exhibit reduced flammability, akin to coatings which are flame retarded by FR-<NUM>/APO and FR-<NUM>/APO/Mg(OH)<NUM>.

Accordingly, also described is a flame retardant coating formulation, comprising:.

Also described is a suspension which comprises water, Mg (OH)<NUM> or Al(OH)<NUM>, tris(<NUM>,<NUM>,<NUM>-tribromophenoxy)-s-triazine, a coalescing agent (such as propylene glycol), a dispersing agent (sometimes a single component serves a dual function of dispersant/wetting agent) and a defoamer, proportioned <NUM>: <NUM>-<NUM>: <NUM>-<NUM>: <NUM>-<NUM>: <NUM>-<NUM>: <NUM>-<NUM>, by weight, respectively, forms aspect of the invention.

Materials used for preparing the coating formulations are tabulated in Table <NUM> (FR means flame retardant):.

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>) and DISPERBYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). BYK <NUM> (<NUM>) was slowly added. Next, TexFRon® <NUM> (<NUM>) was added slowly to the mixture, which was maintained under stirring to form homogeneous suspension. Lastly, BYK <NUM> (<NUM>) was added. Stirring was continued for an additional <NUM> minutes.

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>), DISPERBYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). Next, magnesium hydroxide (<NUM> of FR-<NUM>-<NUM>-S10 grade from ICL-IP) was introduced to the vessel under high shear rate at <NUM> rpm. After the total amount of the magnesium hydroxide was added, the rate was increased to <NUM> rpm for five minutes, to obtain a homogeneous suspension (high shear disperser was T <NUM> digital ULTRA-TURRAX instrument, equipped with S <NUM> KV - 25F dispersing tool, from IKA).

Lastly, TexFRon® <NUM> (<NUM>) was added slowly to the suspension, which was maintained under stirring (with the dissolver stirrer at <NUM> rpm for twenty minutes) to afford the final suspension.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). After ten minutes, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM> minutes.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA).

After ten minutes, the aqueous suspension of BER of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM> minutes.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) andBYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA).

After ten minutes, the aqueous suspension of BER of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Next, a water-based dispersion of antimony pentoxide (APO; <NUM> of <NUM> % by weight aqueous dispersion of nano-sized Sb<NUM>O<NUM>; NYACOL A1550) was introduced to the vessel and stirred for five minutes. Lastly, BYK <NUM> (<NUM>) was added. The mixture was stirred for an additional <NUM> minutes.

After ten minutes, the aqueous suspension of BER/Mg(OH)<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring (starting at <NUM> rpm, later switching to <NUM> rpm) to form a homogeneous formulation. Next, a water-based dispersion of antimony pentoxide (APO; <NUM> of <NUM> % by weight aqueous dispersion of nano-sized Sb<NUM>O<NUM>; NYACOL A1550) was introduced to the vessel and stirred for five minutes. Lastly, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM> minutes.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and Lopon <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). After ten minutes, the aqueous suspension of BER/Mg(OH)<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM>.

The coating formulations of Examples <NUM> to <NUM> were evaluated according to the EN <NUM> Single Burning Item (SBI) Test.

A coating formulation was applied to an assembly consisting of two vertically positioned rectangular fire-retarded MDF plates (<NUM> × <NUM> × <NUM>, and <NUM> × <NUM> × <NUM>, produced by QINGDAO EONCRED WOOD CO. , LTD), joined along their equal side to create a <NUM>° corner. The coating was applied by a brush. Three coats were formed; each coat was dried at room temperature for at least four hours before the application of the next coat. Then the wood assembly was dried for sixteen hours prior to testing.

Details of the SBI test can be found, for example, in http://virtual. fi/virtual/innofirewood/stateoftheart/database/euroclass/euro class. Briefly, the test was carried out in a small room (l=<NUM> × w=<NUM> × h=<NUM>), in which two vertical non-combustible boards served to hold the test specimen (the specimen holder consists of wings of sizes <NUM> × <NUM> and <NUM> × <NUM> positioned in a right-angled corner configuration, i.e., corresponding in shape and size to the test specimen). A propane gas burner was placed at the bottom of the <NUM> corner of the test specimen to produce heat output of <NUM> kW. Combustion gases generated during a test were collected by a hood and drawn to an exhaust duct equipped with sensors to measure the temperature, light attenuation, O<NUM> and CO<NUM> mole fractions and flow-induced pressure difference in the duct. The performance of the specimen was evaluated for an exposure period of <NUM> minutes. During the test, the heat release rate was measured by using oxygen consumption calorimetry. The smoke production rate was measured in the exhaust duct based on the attenuation of light. Falling of flaming droplets or particles was visually observed during the first <NUM> seconds of the heat exposure on the specimen.

The compositions of the five coating formulations that were tested are tabulated in Table <NUM> below, together with the results of the SBI test:.

To better illustrate trends observed in the study, the results of two test variables (Fire Growth Rate Index, FIGRA; and Smoke Growth Rate Index; SMOGRA) are presented graphically in the form of bar diagrams in <FIG>, respectively. In both <FIG>, the bars, from left to right, correspond to Examples <NUM> to <NUM>, respectively (FR-free coating, BER-added coating, BER/APO-added coating, BER/APO/Mg(OH)<NUM> added-coating and antimony free, BER/Mg(OH)<NUM>-added coating, respectively; all are comparative with the exception of Example <NUM>).

In <FIG> is seen that the FIGRA measured for the reference formulation (Example <NUM>) and the BER-added formulation (Example <NUM>) were comparable. As expected, addition of an antimony oxide synergist led to improvement (Example <NUM>), confirming the conventional wisdom that the action of brominated flame retardants leans heavily on the presence of antimony oxide synergist. Addition of another type of flame retardant to the coating - magnesium hydroxide - resulted in a further decrease of FIGRA (Example <NUM>). However, the antimony oxide-free coating of Example <NUM> - keeping the same levels of BER and magnesium hydroxide as in Example <NUM> - achieved the best result, i.e., lower FIGRA compared to the BER/APO/Mg(OH)<NUM> - added coating. It is of note that both BER/APO/Mg(OH)<NUM> - added coating and BER/Mg(OH)<NUM>-added coating met the requirements of the C classification of the EN <NUM> SBI test (FIGRA<NUM>. 4MJ ≤ <NUM> W/s), but the formulation of the invention demonstrated better performance.

In <FIG> it is seen that addition of flame retardants to a coating/paint applied to a wood, increases the production of smoke during fire. However, lower levels of smoke production were measured for the coating formulation of the invention (Example <NUM>), compared to other flame-retardant coating formulations that were tested.

To investigate the effect of magnesium hydroxide on the optical properties of the coatings, the formulations of Example <NUM> (reference; FR- free formulation), Example <NUM> (comparative; BER-added formulation), and Example <NUM> (of the invention; BER/Mg(OH)<NUM>-added formulation) were applied on a glass surface using an applicator (byko-drive - BYK Gardner GmbH). The tested coating formulation was poured into a rectangular shallow receptable (Film Applicator with <NUM> Gaps, frame-style by BYK), which moved along the surface; the bottom and top bases of the receptable were open, such that the formulation was spread on the surface when the receptable moved, creating a wet film). After <NUM> the dry film was removed from the glass. Haze and transparency were determined using DATACOLOR <NUM>. Results are tabulated below.

It is seen that addition of magnesium hydroxide (MDH) to the coating, to aid the brominated flame retardant, does not impair the optical properties of the coating.

The coating formulations of Examples <NUM>, <NUM> and <NUM> were applied on pine wood samples and evaluated in a cone calorimeter.

<NUM> thick, square shaped pine wood samples (<NUM> × <NUM>) were coated by the formulations of Examples <NUM>, <NUM> and <NUM>. The coatings were applied by a brush - three coats (of the same formulation) were formed; each coat was dried at room temperature for at least four hours before the application of the next coat. Then the samples were dried for at least a week prior to testing.

Data was collected by a cone calorimeter [FTT iCone Classic Calorimeter manufactured by Fire Testing Technology, West Sussex, UK] under a heat flux of <NUM> kW/m<NUM> over <NUM> seconds. The specimens were tested without an edged frame sample holder exposing a surface area of <NUM><NUM>. The FR treated samples were tested in the horizontal orientation <NUM> from the heat source. The samples were wrapped in aluminum foil to prevent edge burning effects.

The compositions of the coating formulations that were tested are tabulated in Table <NUM> below, together with the results of the cone calorimeter test. Parameters related to the heat release rate (HRR) were given the main consideration. An effective flame-retardant system should show low values of peak and average HRR and a low MARHE (Maximum Average Rate of Heat Emission). HRR curves versus time are shown in <FIG>.

The results obtained for coated pine wood samples by the cone calorimeter test confirm the trend observed in the SBI test for MDF samples (reported in Example <NUM>). That is, the antimony oxide-free coating of Example <NUM>, based on BER/Mg(OH)<NUM>, showed the best performance, i.e., better than the coating which was flame retarded by the ternary, antimony oxide containing combination BER/APO/Mg(OH)<NUM>.

The goal of the study was to evaluate the efficiency of different dispersing agents in maintaining the stability of the coating formulations at accelerated storage conditions. Three formulations were made by adding an aqueous suspension consisting of: <NUM> % water; <NUM> % propylene glycol; <NUM> % BYK <NUM>; <NUM> % BYK <NUM>; <NUM> % TexFRon® <NUM> and <NUM> % Mg(OH)<NUM> (prepared by the Procedure of Preparation <NUM>), to the acrylic resin in the manner described in Example <NUM>, using the same formulation aids, but testing three types of dispersing agents:.

Usually accelerated testing of paints/coating formulations is carried out at elevated temperature for a period of a few weeks and then the formulation is visually examined. The results tabulated in Table <NUM> indicate that long-term storage stability of the brominated flame retardant/Mg(OH)<NUM> formulation was achieved owing to a combination of a nonionic dispersing agent and an anionic dispersing agent, e.g., one that is based on polyphosphate or polyacrylate, in the form of their sodium salts. In the absence of the anionic surfactant, the formulation transformed into a non-fluid mass (gel or solid). In the presence of an anionic surfactant, little separation was observed at the end of the test (the four and eight weeks of test periods correspond to one and two years of storage under normal conditions, respectively), but the formulation was re-dispersed easily to restore its flowability and functionality.

As seen in Table <NUM>, a suspension exhibiting especially prolonged stability is achieved with the aid of anionic dispersant based on polyacrylate. This has been further confirmed by ~ one-year test under normal (room temperature) conditions.

An illustrative procedure for preparing <NUM> of the BER/Al(OH)<NUM> aqueous dispersion is as follows.

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>), DISPERBYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). Next, alumina trihydrate (<NUM> of SB-<NUM> from HUBER) was introduced to the vessel under high shear rate at <NUM> rpm. After the total amount of the alumina trihydrate was added, TexFRon® <NUM> (<NUM>) was added slowly to the suspension, which was maintained under stirring with the dissolver stirrer until homogeneous suspension was formed. Stirring continued for an additional <NUM> minutes to afford the final suspension.

An illustrative procedure for preparing <NUM> of the BER/Al(OH)<NUM> -containing acrylic coating formulation is as follows.

Alberdingk <NUM> (<NUM>) was added to a <NUM> plastic jar, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and Lopon <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). After ten minutes, the aqueous suspension of BER/A1(OH)<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring at <NUM> rpm for <NUM>.

The coating formulations of Examples <NUM>, <NUM> and <NUM> were applied on MDF samples and evaluated in a cone calorimeter.

<NUM> thick, square shaped MDF samples (<NUM> × <NUM>) were coated by the formulation of Examples <NUM>, <NUM> and <NUM>. The coatings were applied by a brush - three coats were formed; each coat was dried at room temperature for at least four hours before the application of the next coat. Then the samples were dried for at least a week prior to testing.

The compositions of the coating formulations that were tested are tabulated in Table <NUM> below, together with the results of the cone calorimeter test.

The results show that coatings based on BER/MDH and BER/ATH show nearly comparable average HRR and MARHE, with an advantage of the former type of coating in relation to the peak HRR.

For <NUM> formulation: Alberdingk PU 9600VP (<NUM>) was added to a mixing vessel, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). After ten minutes, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM> minutes.

For <NUM> formulation: Alberdingk PU 9600VP (<NUM>) was added to a mixing vessel, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA).

For <NUM> formulation: Alberdingk PU 9600VP (<NUM>) was added to a mixing vessel, followed by the addition of DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and Lopon <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). After ten minutes, the aqueous suspension of BER/Mg(OH)<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM>.

The coating formulations of Examples <NUM>, <NUM>, <NUM> and <NUM> were applied on MDF samples and evaluated in a cone calorimeter.

<NUM> thick, square shaped MDF samples (<NUM> × <NUM>) were coated by the formulation of Examples <NUM>, <NUM>, <NUM> and <NUM>. The coatings were applied by a brush - three coats (of the same formulation) were formed; each coat was dried at room temperature for at least four hours before the application of the next coat. Then the samples were dried for at least a week prior to testing.

The compositions of the coating formulations that were tested are tabulated in Table <NUM> below, together with the results of the cone calorimeter test. HRR curves versus time are shown in <FIG>.

The results indicate that polyurethane coatings could benefit from the combination of the invention, BER/Mg(OH)<NUM>, which performed very well in retarding the flammability of coated MDF samples, exhibiting lower HRR parameters compared to the conventional BER/antimony oxide combination.

An illustrative procedure for preparing <NUM> of the FR-122P aqueous dispersion is as follows.

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>), DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and Supragil WP (<NUM>) under stirring at a rate of <NUM>-<NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). Next, FR-122P (<NUM>) was added slowly to the mixture, which was maintained under stirring to form homogeneous suspension. Lastly, BYK <NUM> (<NUM>) was added slowly. Stirring was continued for additional <NUM> minutes at <NUM> ppm.

An illustrative procedure for preparing <NUM> of the FR-122P/Mg(OH)<NUM> aqueous dispersion is as follows.

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>), DISPERBYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) and Supragil WP (<NUM>) under stirring at a rate of <NUM>-<NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). Next, magnesium hydroxide (<NUM> of FR-<NUM>-<NUM>-S10 grade from ICL-IP) was introduced to the vessel under high shear rate at <NUM> rpm (high shear disperser was T <NUM> digital ULTRA-TURRAX instrument, equipped with S <NUM> KV - 25F dispersing tool, from IKA).

Lastly, FR-122P (<NUM>) was added slowly to the suspension, which was maintained under stirring (with the dissolver stirrer at <NUM> rpm) until homogeneous suspension was formed. Stirring continued for additional thirty minutes.

An illustrative procedure for preparing <NUM> of the FR-122P- containing acrylic coating formulation is as follows.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of BYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and DISPERBYK <NUM> (<NUM>), under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA).

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-122P of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM> minutes at <NUM> rpm.

An illustrative procedure for preparing <NUM> of the FR-122P/APO-containing acrylic coating formulation is as follows.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of BYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and DISPERBYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA).

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-122P of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Next, a water-based dispersion of antimony pentoxide (APO; <NUM> of <NUM> % by weight aqueous dispersion of nano-sized Sb<NUM>O<NUM>; NYACOL A1550) was introduced to the vessel under stirring. Lastly, BYK <NUM> (<NUM>) was added. The mixture was stirred for additional <NUM> minutes at <NUM> rpm.

An illustrative procedure for preparing <NUM> of the FR-122P/Mg(OH)<NUM> containing acrylic coating formulation is as follows.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of BYK <NUM> (<NUM>), BYK <NUM> (<NUM>), DISPERBYK <NUM> (<NUM>) and Lopon <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA).

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-122P/Mg(OH)<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was stirred for additional <NUM> minutes at <NUM> rpm.

<NUM> thick, square shaped MDF samples (<NUM> × <NUM>) were coated by the formulation of Examples <NUM>, <NUM> and <NUM>. The coatings were applied by a brush - three coats (of the same formulation) were formed; each coat was dried at room temperature for at least four hours before the application of the next coat. Then the samples were dried for at least a week prior to testing.

Data was collected by a cone calorimeter [FTT iCone Classic Calorimeter manufactured by Fire Testing Technology, West Sussex, UK] under a heat flux of <NUM> kW/m<NUM> over <NUM> seconds. The specimens were tested without an edged frame sample holder exposing a surface area of <NUM><NUM>. The FR treated plaques were tested in the horizontal orientation <NUM> from the heat source. The samples were wrapped in aluminum foil to prevent edge burning effects.

The results indicate that in coatings which are flame retarded by brominated poly[styrene-co-butadiene], Mg(OH)<NUM> could serve as a replacement for antimony oxide, generating antimony oxide-free coatings which show acceptable burning properties.

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>), DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and Supragil WP (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). Next, FR-803P (<NUM>) was added slowly to the mixture, which was maintained under stirring to form homogeneous suspension. Lastly, BYK <NUM> (<NUM>) was added slowly. Stirring was continued for additional <NUM> minutes at <NUM> ppm, to give <NUM> of an aqueous dispersion of brominated polystyrene.

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>), DISPERBYK <NUM> (<NUM>) and BYK <NUM> (<NUM>) and Supragil WP (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). Next, magnesium hydroxide (<NUM> of FR-<NUM>-<NUM>-S10 grade from ICL-IP) was introduced to the vessel under high shear rate at <NUM> rpm (high shear disperser was T <NUM> digital ULTRA-TURRAX instrument, equipped with S <NUM> KV - 25F dispersing tool, from IKA).

FR-803P (<NUM>) was added slowly to the suspension, which was maintained under stirring (with the dissolver stirrer at <NUM> rpm) until homogeneous suspension was formed. Lastly, BYK <NUM> (<NUM>) was added. Stirring continued for additional thirty minutes, to give <NUM> of the formulation.

An illustrative procedure for preparing <NUM> of the FR-803P containing acrylic coating formulation is as follows.

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-803P of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Then BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM> minutes at <NUM> rpm.

An illustrative procedure for preparing <NUM> of the FR-803P/APO-containing acrylic coating formulation is as follows.

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-803P/Mg(OH)<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Next, a water-based dispersion of antimony pentoxide (APO; <NUM> of <NUM> % by weight aqueous dispersion of nano-sized Sb<NUM>O<NUM>; NYACOL A1550) was introduced to the vessel under stirring. Lastly, BYK <NUM> (<NUM>) was added. The mixture was stirred for additional <NUM> minutes at <NUM> rpm.

An illustrative procedure for preparing <NUM> of the FR-803P/Mg(OH)<NUM> containing acrylic coating formulation is as follows.

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-803P/Mg (OH) <NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was stirred for additional <NUM> minutes at <NUM> rpm.

The coating formulations of Examples <NUM>, <NUM> and <NUM> were applied on MDF wood samples and evaluated in a cone calorimeter.

The results indicate that the antimony oxide-free coating of Example <NUM>, based on brominated polystyrene/Mg(OH)<NUM>, was comparable to the coating which was flame retarded by the ternary, antimony oxide containing combination consisting of brominated polystyrene/APO/Mg(OH)<NUM> (Example <NUM>).

Water (<NUM>) was added to a mixing vessel, followed by addition of propylene glycol (<NUM>), DISPERBYK <NUM> (<NUM>), BYK <NUM> (<NUM>) and Supragil WP (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA). Next, FR-<NUM> (<NUM>) was added slowly to the mixture, which was maintained under stirring to form homogeneous suspension. Lastly, BYK <NUM> (<NUM>) was added slowly. Stirring was continued for additional <NUM> minutes at <NUM> ppm, to give <NUM> of an aqueous dispersion of FR-<NUM>.

FR-<NUM> (<NUM>) was added slowly to the suspension, which was maintained under stirring (with the dissolver stirrer at <NUM> rpm) until homogeneous suspension was formed. Then BYK <NUM> (<NUM>) was added. Stirring continued for additional thirty minutes, to give <NUM> of an aqueous dispersion of FR-<NUM>/Mg (OH) <NUM>.

An illustrative procedure for preparing <NUM> of the FR-<NUM> containing acrylic coating formulation is as follows.

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was maintained under stirring for <NUM> minutes at <NUM> rpm.

An illustrative procedure for preparing <NUM> of the FR-<NUM>/APO-containing acrylic coating formulation is as follows.

Alberdingk <NUM> (<NUM>) was added to a mixing vessel, followed by the addition of BYK <NUM> (<NUM>), BYK <NUM> (<NUM>), DISPERBYK <NUM> (<NUM>) under stirring at a rate of <NUM> rpm (using R <NUM> dissolver stirrer IKA with EUROSTAR power control-vise motor, IKA).

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-<NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Next, a water-based dispersion of antimony pentoxide (APO; <NUM> of <NUM> % by weight aqueous dispersion of nano-sized Sb<NUM>O<NUM>; NYACOL A1550) was introduced to the vessel under stirring. Lastly, BYK <NUM> (<NUM>) was added. The mixture was stirred for additional <NUM> minutes at <NUM> rpm.

An illustrative procedure for preparing <NUM> of the FR- <NUM>/Mg(OH)<NUM> containing acrylic coating formulation is as follows.

The rotational speed was increased to <NUM> rpm and the aqueous suspension of FR-<NUM>/Mg (OH) <NUM> of Preparation <NUM> (<NUM>) was added. The mixture was maintained under stirring to form a homogeneous formulation. Lastly, BYK <NUM> (<NUM>) was added. The mixture was stirred for additional <NUM> minutes at <NUM> rpm.

<NUM> thick, square shaped MDF samples (<NUM> x <NUM>) were coated by the formulation of Examples <NUM>, <NUM> and <NUM>. The coatings were applied by a brush - three coats (of the same formulation) were formed; each coat was dried at room temperature for at least four hours before the application of the next coat. Then the samples were dried for at least a week prior to testing.

The results indicate that magnesium hydroxide can replace antimony oxide in FR-<NUM> based coatings, to provide coatings showing comparable, and perhaps even reduced, flammability.

The goal of the study was to examine the efficiency of Mg(OH)<NUM> as a replacement for APO in acrylic coatings which are flame retarded by a brominated compound, i.e., nonpolymeric flame retardant. The brominated compound chosen for the study was decabromodiphenyl ethane (DPDPE), a strong flame retardant with an exceptionally high (-<NUM>%) bromine content:
<CHM>.

Aqueous suspensions of DPDPE and DPDPE/Mg(OH)<NUM> were prepared using the procedures set out in Preparations <NUM> and <NUM>. The compositions (% by weight) are set out below.

Next, coating formulations were prepared and tested in cone calorimeter (see preparation procedures described in Examples <NUM>-<NUM>, and test protocol in Example <NUM>).

Claim 1:
Flame retardant coating formulation in the form of an aqueous dispersion comprising a binder, particles of a brominated polymeric flame retardant (BFR); and particles of at least one of magnesium hydroxide and aluminum trihydrate, wherein the aqueous dispersion is substantially free of antimony oxide so that the concentration of antimony oxide in the aqueous dispersion is not more than <NUM>% by weight, more preferably less than <NUM> % by weight, and even more preferably from <NUM> to <NUM> % by weight based on the total weight of the formulation; and wherein the brominated polymeric flame retardant is selected from tribromophenol end-capped brominated epoxy polymer of the formula Ia:
<CHM>
wherein m is the degree of polymerization; and brominated poly[styrene-co-butadiene].