WO2006072952A2

WO2006072952A2 - Nano-sized halogenated flame retardants

Info

Publication number: WO2006072952A2
Application number: PCT/IL2006/000022
Authority: WO
Inventors: Itzhak Shalev; Royi Mazor
Original assignee: Bromine Compounds Ltd.
Priority date: 2005-01-05
Filing date: 2006-01-05
Publication date: 2006-07-13
Also published as: WO2006072952A3

Abstract

Novel flame retardant compositions containing a plurality of nano-sized particles of halogenated, in particular brominated, flame retardants and processes for their preparation are disclosed. Further disclosed are formulations containing these compositions and articles-of-manufacture having these formulations applied thereon. These novel formulations are particularly effective as textile flame retardants, requiring a low amount of binder and characterized by high washing fastness.

Description

NANO-SIZED HALOGENATED FLAME RET ARD ANTS

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to the field of flame retardants and, more particularly, to novel aqueous dispersions of nano-sized flame retardants.

Textiles are an essential part of everyday life and are found, for example, in draperies, cloths, furniture and vehicle upholsteries, toys, packaging material and many more applications. Consequently, textile flammability is a serious industrial concern. The flammability of textile fabrics is typically determined by the type of fiber of which the fabric is made. Thus, for example, some synthetic fibers, such as melamine, polyaramides, carbonized acrylic, and glass, are inherently flame resistant, whereas others, such as cotton, polyester and linen, can readily ignite. Fabric flammability also depends on fabric characteristics such as thickness and/or looseness. The term "fiber" as used herein refers to a natural or synthetic filament capable of being spun into a yam or made into a fabric.

The terms "fabric", "textile" and "textile fabric" are used herein interchangeably hereinafter to describe a sheet structure made from fibers.

Several approaches have been proposed heretofore for minimizing the fire hazard of flammable textiles.

One approach involves fiber copolymerization. In this technique several fiber monomers are mixed and copolymerized, thus improving the properties of a certain fiber (e.g., a flammable fiber) through the enhanced properties of another fiber (e.g., a fire resistant fiber). This technique, however, is limited by the number of existing fire resistant fibers and their properties, and cannot be tailor-made for any substrate or requirements. Furthermore, fiber t)φes (e.g. flammable fiber versus fire resistant fiber) are not necessarily compatible, for example, with regard to the type of polymerization (step polymerization or condensation polymerization etc.), thus further limiting the applicability of this technique. An additional disadvantage of this approach is the high cost of the fire resistant fibers. Another approach includes introduction of flame retardants (FR) in or on the fabric. Thus, flame retardants can be incorporated in the fabric either topically or as a part of the fabric.

Methods in which a flame retardant is applied topically suffer the disadvantage of the common need to apply the protective coating (which includes the FR) in large amounts (termed "high add-on") in order to obtain the required fabric characteristics. Often, such high add-on adversely affects otherwise desirable aesthetical and textural properties of the fabric. Thus, for example, upon application of a FR, fabrics may become stiff and harsh and may have duller shades, and poor tear strength and abrasion properties.

Selecting the right flame retardant and the right application method largely depends on the substrate which has to be protected: the protection of a garment, or the protection of an electrical appliance will inherently pose different requirements and restrictions of the flame retardant used.

In particular, when used in textiles, an applied flame retardant has to be: (a) compatible with the fabric, (b) non-damaging to the aesthetical and textural properties of the fabric, (c) transparent, (d) light stable, (e) resistant to extensive washing and cleaning, (f) environmentally and physiologically safe, (g) of low toxic gas emittance, and (h) inexpensive. Above all, a flame retardant or smoldering suppressant agent should pass the standard flammability and smoldering tests in the field.

Some of these properties such as stability to UV light, heat, water, detergents and air-pollutants, as well as chemical stability, may be summed-up under the term

"durability". Currently, there are no clear-cut standards to define fabric durability, and it is typically defined as a fabric meeting its performance standard after 5, 10, 25 or 50 washing cycles.

Presently, there are four main families of flame-retardant agents:

^■ Inorganic flame retardants (such as aluminum oxide, magnesium hydroxide and ammonium polyphosphate); ^■ Halogenated flame retardants, primarily based on bromine and chlorine;

^■ Organophosphorous flame retardants, which are primarily phosphate esters; and

^■ Nitrogen-based organic flame retardants.

Bromine-containing compounds have been long established as flame retardants. For example, U. S. Patent Nos. 3,955,032 and 4,600,606; and Mischutin ["Nontoxic Flame Retardant for Textiles" in J. Coated Fabrics, Vol. 7, 1978, pp. 308- 318] teach flame retardation of textiles using formulations containing aromatic bromine compounds which are adhered to the substrates by means of binders.

The use of bromine-containing compounds as FRs for textiles, however, suffers major disadvantages including, for example, high bromine content demand, high binder content demand, which together result in a relatively high add-on.

In textiles, the thickness of the coating layer determines the textural properties of the fabric. Thinner coating layer results in more flexible and softer fabric. The thickness of the layer evidently depends on the amount of the add-on.

The phrase "dry add-on" relates to the total amount of dry additives (mainly flame retardants, binders and synergists) which is left on the fabric after being coated.

Using existing bromine-containing FR formulations, a dry add-on of 60 % or higher (compared to the dry fabric weight) is often required to obtain satisfactory flame retardation. This high add-on is due in part to the large amount of binder needed to affix the FR agents to the textile. The binder used in bromine-containing formulations typically constitutes about 50 % by weight of the total FR formulation [Toxicological Risks of Selected Flame-Retardant Chemicals, page 506-507, V. Mischutin, Nontoxic Flame Retardant for Textiles, J. Coated Fabrics, Vol. 7, 1978, p. 315].

The substantial presence of the binder is further disadvantageous since the binder often contributes in itself to flammability and dripping, thus requiring even higher loading of bromine and creating an inefficient cycle.

Using existing bromine-containing FR formulations is further disadvantageous since the addition of additives such as flame retardant synergists and thickeners (thickening agents) is often required. Thickening agents are often added to flame retardant formulations in order to increase their viscosity and facilitate the application of the FR formulations on substrates such as textiles. However, as in the case of binders, the thickening agents are often flammable compounds themselves, and therefore an additional amount of FR agent and/or synergist in necessary to overcome this adverse effect. Over the years, several antimony-based compounds have been used as flame- retardants, including Sb₂O₃, Sb₂O₅ and Na₃SbO₄ [Touval, L, (1993) "Antimony and other inorganic Flame Retardants" in Kirk Othmer's Encyclopedia of Chemical Technology, Vol. 10, p. 936-954, 4^th Edition, John Wiley and Sons, N. Y.]. Antimony based compounds are very expensive and are therefore not used on their own, but are used as synergists with other flame retardants. The addition of antimony oxide to halogenated flame retardants increases their efficiency and reduces the amount of additives and/or halogenated FR agent to be used. However, the addition of such synergist is costly and further contributes to the high add-on of the formulation.

In addition, application of bromine-containing compounds on fabrics often result in streak marks on dark fabrics, excessive dripping during combustion of thermoplastic fibers, relatively high level of smoldering and a general instability of the flame retardant dispersion which may prevent a uniform application thereof on the fabric. Most of these drawbacks are inherent to the aromatic bromine compounds currently in use [see, for example, "Toxicological Risks of Selected Flame-Retardant Chemicals -2000", Donald E. Gardner (Chair) Subcommittee on Flame-Retardant Chemicals, Committee on Toxicology, Board on Environmental Studies and Toxicology, National Research Council]. Furtherrnore, brominated FR formulations often suffer from storage instability.

Hence, while the presently known flame retardants exhibit limited performance, particularly when applied on textiles, there is a widely recognized need for, and it would be highly advantageous to have, novel flame retardants which could be efficiently utilized in textile applications, while being devoid of the above limitations.

Ongoing research has therefore been conducted in order to obtain flame- retardants with improved performance, which are less detrimental to textile properties. Research has been particularly focused on providing an efficient FR which requires low binder content, is characterized by good dispersion properties, is non-damaging to the aesthetical and textural properties of the fabric (such as transparency, color, softness, flexibility etc.), is durable in terms of UV and/or washing fastness, is environmentally and physiologically safe and is inexpensive.

Nano-sized powders are known to those skilled in the art to adhere better to surfaces than coarser powders, due to increased surface area and better spreading, and are also known to have improved transparency compared to dispersions of coarser powders. For example, the transparency of liquid dispersions is maintained when the particle size is smaller than about 400 nanometers (0.4 micron).

Furthermore, nano sized powders are known to those skilled in the art to form stable dispersions, with an increased viscosity compared to dispersions containing coarser powders. The increased viscosity of nano-sized powders is also attributed to the high surface area of the powder.

While conceiving the present invention, it was envisioned that using nano- sized dispersions of halogenated FRs would result in a FR formulation with the desired improved performance. More specifically, it was envisioned that such a formulation would lead to a decrease in the amount of binder and/or synergist to be used and to improved textural and aesthetical properties of a textile substrate. Furthermore, it was envisioned that using nano-sized dispersions of halogenated FRs would facilitate the application of the FR formulation on substrates such as textiles, while decreasing the amount of thickening agent to be used. U.S. Patent No. 5,948,323, to McLaughlin, teaches FR compositions that are ground to colloidal sizes, and further suggests that FR compositions having particles smaller than about 1 micron would have improved properties, such as color, transparency and strength. The compositions, as taught in U.S. Patent No. 5,948,323, have an average volumetric length in the range of 0.07 to 0.25 micron, and a size cut- off (a size which 99 % of the particles do not exceed) between 0.3 to 2.7 microns. U.S. Patent No. 5,948,323 mentions decabromodiphenylether (also referred to herein interchangeably as DECA, or FR- 1210), a bromine-containing FR, in passing, as one of the agents used in the preparation of such compositions. According to the teachings of U.S. Patent No. 5,948,323, the nano-sized decabromodiphenylether particles have an average volumetric length of 0.25 micron and a size cut-off of 2.7 microns. While U.S. Patent No. 5,948,323 suggests the advantageous use of the compositions taught therein as FR formulations, U.S. Patent No. 5,948,323 fails to teach the actual application of these compositions to substrates such as textiles and further fails to characterize the FR properties of these compositions. SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a flame retardant composition comprising a plurality of halogenated flame retardant particles having an average size ranging from about 100 nanometers to about 250 nanometers. According to another aspect of the present invention there is provided a flame retardant composition comprising a plurality of halogenated flame retardant particles, wherein at least 90 % of the particles in the composition have a particle size smaller than 500 nanometers.

According to still another aspect of the present invention there is provided a flame retardant composition comprising a plurality of halogenated flame retardant particles wherein at least 10 % of the particles in the composition have a particle size smaller than 90 nanometers.

According to further features in preferred embodiments of the invention described below, each of the compositions described herein further comprises a carrier. Preferably, the carrier is an aqueous carrier. Further preferably, the aqueous carrier is water.

According to still further features in the described preferred embodiments the halogenated flame retardant is a brominated flame retardant.

According to still further features in the described preferred embodiments the brominated flame retardant is Decabromodiphenylether (FR-1210).

According to still further features in the described preferred embodiments the brominated flame retardant is l,2-Bis(2,3,4,5,6-pentabromophenyl)ethane (Saytex 8010).

According to still further features in the described preferred embodiments the brominated flame retardant is pentabromobenzyl acrylate (PBB-MA).

According to still further features in the described preferred embodiments an amount of the halogenated flame retardant ranges from about 1 weight percentage to about 70 weight percentages of the total weight of the composition.

According to still further features in the described preferred embodiments the composition further comprises at least one additional ingredient selected from the group consisting of a surface active agent, a wetting agent, a dispersing agent, a suspending agent, a pH buffer and any mixture thereof. Preferably, the dispersing agent is selected from the group comprising of Dispergator WA, AMP-95, Clorocontin NGD and Triton X-IOO. Further preferably, the wetting agent is Clorocontin NGD. Yet further preferably, the surface active agent is an anionic surface active agent.

According to still further features in the described preferred embodiments the composition is in a form of a dispersion, preferably an aqueous dispersion.

According to still further features in the described preferred embodiments the composition is characterized by a viscosity that ranges from about 100 centipoises to about 2000 centipoises.

According to still another aspect of the present invention there is provided a process of preparing an aqueous dispersion of each of the flame retardant compositions described herein, the process comprising: milling a dispersion which comprises a halogenated flame retardant and an aqueous carrier until particles smaller than about 1 microns are obtained.

According to further features in preferred embodiments of the invention described below, the dispersion which comprises a halogenated flame retardant and an aqueous carrier further comprises at least one ingredient selected from the group consisting of a surface active agent, a wetting agent, a dispersing agent, a suspending agent, a pH buffer and any mixture thereof, as described herein.

According to still further features in the described preferred embodiments the milling is conducted for at least 2 hours.

According to still further features in the described preferred embodiments the process is conducted under basic conditions.

According to an additional aspect of the present invention there is provided a flame retardant fonnulation comprising any of the compositions described herein and a carrier. Preferably, the flame retardant formulation further comprises at least one additive selected from the group consisting of an antifoaming agent, a preservative, a stabilizing agent, a binding agent, a thickening agent and any mixture thereof.

Preferably, the binding agent is selected from the group consisting of an acrylate, a polyurethane, a vinyl acetate, or a polyvinyl chloride (PVC). More preferably, the binding agent is an acrylate. Further preferably, an amount of the binding agent is lower than 40 weight percentages of the total weight of the formulation, more preferably lower than 30 weight percentages, and most preferably lower than 25 weight percentages of the total weight of the formulation.

Thus, according to still an additional aspect of the present invention there is provided a flame retardant formulation comprising a carrier, a plurality of halogenated flame retardant particles having an average size smaller than about 1 micron dispersed in the carrier, and a binding agent, wherein an amount of the binding agent is lower than 40 weight percents of the total weight of the formulation.

According to further features in preferred embodiments of the invention described below, in each of the formulations described herein the carrier is an aqueous earner.

According to still further features in the described preferred embodiments any of the above-described flame retardant formulations further comprises a flame retardant synergist. Preferably, the synergist is antimony oxide (ATO). More preferably, a molar ratio between an elemental antimony of the ATO and an elemental halogen of the halogenated flame retardant ranges from about 1 :1 to about 1:6.

Further preferably, an amount of the flame retardant synergist is lower than 30 weight percentages of the total weight of the composition, more preferably ranging from about 10 weight percentages to about 30 weight percentages.

According to still further features in the described preferred embodiments an amount of the thickening agent is lower than 5 weight percentages of the total weight of the formulation.

According to still further features in the described preferred embodiments any of the above-described flame retardant formulations is stable for at least three months upon storage at room temperature. Preferably, any of the above-described flame retardant formulations is stable for at least six months.

According to still further features in the described preferred embodiments any of the above-described flame retardant formulations is stable for at least 12 weeks upon storage at elevated temperatures.

According to still further features in the described preferred embodiments any of the above-described flame retardant formulations have a viscosity that ranges from about 100 to about 2,000 centipoises. According to an additional aspect of the present invention there is provided an article-of-manufacture comprising a flammable substrate and any of the above- described flame retardant formulations being applied thereon. Preferably, the flammable substrate comprises a flammable textile fabric. More preferably, the flammable textile fabric is selected from the group consisting of a synthetic textile fabric, a natural textile fabric and blends thereof. Even more preferably, the flammable textile fabric is selected from the group consisting of wool, silk, cotton, linen, hemp, ramie, jute, acetate fabric, acrylic fabric, latex, nylon, polyester, rayon, viscose, spandex, metallic composite, carbon or carbonized composite, and any combination thereof. Most preferably, the textile fabric is selected from the group consisting of cotton, polyester, and any combination thereof.

Further preferably, the substrate is selected from the group consisting of a drapery, a garment, linen, a mattress, a carpet, a tent, a sleeping bag, a toy, a decorative fabric, an upholstery, a wall fabric, and any other technical textile.

According to further features in preferred embodiments of the invention described below, the above-described article-of-manufacture is characterized by an after flame time, as defined by ASTM D-6413 12 seconds ignition test, of less than 5 seconds. Preferably, the after flame time of less than 5 seconds remains substantially unchanged upon subjecting the article-of-manufacture to at least 1 washing cycle. Most preferably, the after flame time of less than 5 seconds remains substantially unchanged upon subjecting the article-of-manufacture to at least 5 washing cycles.

According to further features in preferred embodiments of the invention described below, the above-described article-of-manufacture is characterized by an after glow time, as defined by ASTM D-6413 12 seconds ignition test, of less than 200 seconds. Preferably, the after glow time of less than 200 seconds remains substantially unchanged upon subjecting the article-of-manufacture to at least 1 washing cycle. Most preferably, the after glow time of less than 200 seconds remains substantially unchanged upon subjecting the article-of-manufacture to at least 5 washing cycles.

According to further features in preferred embodiments of the invention described below, the above-described article-of-manufacture is characterized by a char length, as defined by ASTM D-6413 12 seconds ignition test, of less than 15 centimeters. Preferably, the char length of less than 15 centimeters remains substantially unchanged upon subjecting the article-of-manufacture to at least 1 washing cycle. Most preferably, the char length of less than 15 centimeters remains substantially unchanged upon subjecting the article-of-manufacture to at least 5 washing cycles.

According to further features in preferred embodiments of the invention described below, any of the above-described articles-of-manufacture is characterized by at least one aesthetical or textural property which is substantially the same as that of the flammable substrate per se. Preferably, the at least one aesthetical or textural property is selected from the group consisting of flexibility, smoothness, streakiness and color vivacity. Further preferably, the property remains substantially unchanged upon subjecting the article-of-manufacture to at least 1 washing cycle. More preferably, the property remains substantially unchanged upon subjecting the article- of-manufacture to at least 5 washing cycles. The present invention successfully addresses the shortcomings of the presently known configurations by providing nano-sized halogen-containing flame retardant compositions and formulations containing same which are far superior to the presently known halogen-containing (particularly bromine-containing) flame retardant formulations for application on a substrates such as textile substrates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings:

FIGs. IA-B present plots showing the particle size distributions of a micron- sized milling-base of FR-1210 (before grinding, as the surface area versus particle size, Figure IA) and of a nano-sized FR-1210 dispersion (as the volume versus particle size, Figure IB), obtained by a Malvern Mastersizer 2002;

FIG. 2 presents a Cryogenic Tunneling Electron Microscopy (Cryo-TEM) image of a nano-sized FR-1210 dispersion, according to the present embodiments;

FIGs. 3A-E present scanning electron microscopy (SEM) images of a cotton fabric treated with a nano-sized FR-1210 dispersion, according to the present embodiments (x 43 resolution, Figure 3 A; x 2,200 resolution, Figure 3B; at the edge of the sample, at x 60 resolution, Figure 3 C; at fibers at inner side of yam in the sample, at x 430 resolution, Figure 3D; at fibers at inner side of yarn in the sample, at x 7,000 resolution, Figure 3E);

FIGs. 4A-D present a SEM image of a cotton fabric treated with a nano-sized FR-1210 dispersion, according to the present embodiments (x 2300 resolution, Figure 4A), and Energy Dispersive X-ray Spectra (EDS) of points 1, 2 and 3 on the surface displayed in Figure 5A (Figures 4B, 4C and 4D, respectively); and

FIGs. 5A-F present comparative Optical Microscope Micrograph images of untreated polyester fabric (Figure 5A), a polyester fabric treated with a micron-sized FR-1210 formulation (Figure 5B), a polyester fabric treated with a nano-sized FR- 1210 formulation according to the present embodiments (Figure 5C), untreated cotton fabric (Figure 5D), a cotton fabric treated with a micron-sized FR-1210 formulation (Figure 5E) and a cotton fabric treated with a nano-sized FR-1210 dispersion according to the present embodiments (Figure 5F). DESCRIPTION QF THE PREFERRED EMBODIMENTS

The present invention is of novel nano-sized halogenated flame retardant compositions and of flame retardant formulations containing same, which can be efficiently applied on flammable substrates such as textile fabrics. The present invention is further of articles-of-manufacture having these nano-sized flame retardant formulations applied thereon.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

Halogen-containing compounds, and particularly bromine-containing compounds, are commonly-used flame retardants (FRs). However, application of flame retardant formulations that incorporate halogenated FRs on textiles is limited due to excessive dripping during combustion, a relatively high level of smoldering and a general instability of the flame retardant formulation. Furthermore, these formulations do not adhere well to the textile, and therefore have a low washing fastness, further demanding large amounts of these FRs, as well as of binders and other additives, such as flame retardant synergists, to achieve the desired flame retardant properties. Thickening agents are also often added due to a low viscosity of these FR formulations, in order to facilitate application on the fabric. Unfortunately, many of these additives are flammable compounds by themselves, and their addition therefore requires increased amounts of the FR agent and/or FR synergist in order to overcome this adverse effect. Thus, a high dry add-on (the combined added weight of the FR, synergist and binder, and/or any other solid components in the formulation), which can reach 60 % or higher (compared to the dry fabric weight) is adversely obtained.

A textile having a high binder content and/or a high add-on is adversely characterized by undesirable texrural and/or aesthetical properties, such as streak marks on dark fabrics and a non-uniform application thereof on the fabric. Hence, the use of the presently available halogen-containing FR formulations in textiles often results in a coated substrate characterized by rigidness, uneven surfaces, faded colors and other undesirable textural and/or aesthetical properties. Moreover, since the halogenated FRs do not adhere well to fabrics, the coated textiles are typically characterized by a low washing fastness, which renders the fabric flammable once the FR has been washed-off (usually after just a few washing cycles). The adverse tradeoff between achieving the desired flame retardancy and washing fastness on one hand, and maintaining the fabric's feel and look, on the other hand, has not been resolved hitherto. While conceiving the present invention, it was envisioned that FR formulations containing nano-sized particles of halogenated FRs could be efficiently used in textile applications, while circumventing the limitations associated with halogenated FRs in this respect. Thus, it was envisioned that using such formulations would not require large amounts of the FR, the binder, the synergist and/or any other additive, so as to achieve efficient performance, and thus textural and aesthetical properties of a textile substrate, as well as its washing fastness, would be not be adversely affected.

While colloidal (smaller than about 1 micron) FR compositions have been suggested in U.S. Patent No. 5,948,323, to McLaughlin, the exemplary compositions taught in this patent are characterized by an average volumetric length in the range of 0.07 to 0.25 micron and a size cut-off of between 0.3 to 2.7 microns. U.S. Patent No. 5,948,323 teaches a decabromodiphenylether (referred to herein as FR-1210) composition which has an average volumetric length of 0.25 micron and a size cut-off of 2.7 microns. Such a composition is therefore characterized by particles having a relatively high average size at a nano scale and a size cut-off in the micron-size and not the nano-size scale. U.S. Patent No. 5,948,323 further fails to teach the actual application of the compositions taught therein to substrates such as textiles and to characterize the FR properties of these compositions.

While reducing the present invention to practice, it was surprisingly found that nano-sized halogenated FR compositions could be prepared and efficiently incorporated in stable formulations, which can be utilized as efficient flame retardant formulations for application onto fabrics. As is demonstrated in the Examples section that follows, it is shown herein that such formulations, when applied onto various fabrics, allow for smooth application thereof and are characterized by improved adherence to the fabric and yet good flame retardancy, even when relatively low amounts of a binder, a FR synergist and/or a thickener are used. In particular, is has been shown that fabrics treated by such formulations are non-flammable, exhibit an improved washing fastness and further maintain the textural and aesthetical properties thereof.

Thus, according to one aspect of the present invention there is provided a flame retardant composition which comprises a plurality of halogenated flame retardant particles.

As used herein, the phrase "flame retardant", which is also referred to herein, interchangeably, as "fire retardant", "flame resistant" and "fire resistant", describes a compound, a composition or a formulation which is capable of reducing or eliminating the tendency of a substance to ignite when exposed to a low-energy flame.

Some of the halogenated flame retardants that can be utilized within the context of the present invention are also known to act as smoldering suppressants, exhibiting smoldering suppression.

As used hereinafter the term "smoldering", also known in the art as "after flame burning" refers to a burning which continues after the open flame has been extinguished. The phrase "smoldering suppressant", which is also referred to herein interchangeably as "smoldering suppressing agent" or "SS", therefore describes a compound or a composition which reduces or eliminates the tendency of a substance to bum after no longer being exposed to a flame. Hence, the phrase "flame retardant", as used herein, also encompasses compounds, compositions and formulations that may further exhibit smoldering suppression.

The phrase "halogenated flame retardant", as used herein, describes a flame retardant compound that includes one or more halides (also referred to herein as halogens), namely, one or more of fluoride, chloride, bromide and iodide. While most of the presently known FRs are bromides, preferred halogenated flame retardants according to the present embodiments include brominated flame retardants.

Representative examples of brominated flame retardants that are suitable for use in the context of the present invention, include, without limitation, bromides of aliphatic or alicyclic hydrocarbons such as hexabromocyclododecane; bromides of aromatic compounds such as decabromodiphenyloxide, hexabromobenzene, 1,2- bis(2,3,4,5,6-pentabromophenyl)ethane, ethylene bis(pentabromodiphenyl), pentabromobenzyl acrylate, tetradecabromodiphenoxy benzene, octabromodiphenyl ether, 2,3-dibromopropyl pentabromophenyl ether and the like; brominated bisphenols and their derivatives such as tetrabromobisphenol A, tetrabromobisphenol A bis(2,3- dibromopropyl ether), tetrabromobisphenol A (2-bromoethyl ether), tetrabromobisphenol A diglycidyl ether, an adduct of tetrabromobisphenol A diglycidyl ether and tribromophenol; oligomers of brominated bisphenol derivatives such as tetrabromobisphenol A polycarbonate oligomer, and an epoxy oligomer of an adduct of tetrabromobisphenol A glycidyl ether and bromobisphenol; bromoaromatic compounds such as ethylene bistetrabromophthalimide, and bis(2,4,6- tribromophenoxy)ethane; brominated acrylic resins; ethylene bisdibromonorbornane dicarboxyimide, and the like.

Preferred brominated FR agents, according to an embodiment of the present invention, are decabromodiphenylether (FR-1210, also referred to herein and in the art as decabromodiphenyloxide, and also known as DECA), 1,2-Bis(2,3,4,5,6- pentabromophenyl)ethane (also referred to herein and in the art as decabromodiphenylethane, and also referred to herein as Saytex-8010) and pentabromobenzyl acrylate (FR-1025M, also known as PBB-MA). The term "composition", as used herein in the context of a "flame retardant composition", refers to any compound and/or a combination of compounds that have flame retardant properties. Flame retardant compositions may optionally include a carrier and additional, non-FR ingredients, which are typically used to stabilize the composition. The term "formulation" as used herein, refers to a composition, as defined hereinabove, which is formulated so as to facilitate and/or enable its application on a substrate. Thus, a flame retardant formulation, as used herein, typically includes a flame retardant composition as defined hereinabove, a carrier and optionally additives such a binder, a FR synergist, additional FRs, as well as non-FR additives. In one embodiment, the FR compositions described herein comprise halogenated FR particles having an average size that ranges from about 100 nanometers to about 250 nanometers.

As used herein the term "about" refers to + 10 %.

The term "average particle size", as used herein and is widely acceptable in the art, represents the average particle radius of the particles of a given FR, and is typically determined by conventional analytical techniques such as, for example, microscopic determination utilizing a scanning electron microscope or by means of a laser granulometer (such as a small angle scattering, for example, a Malvern). This term is interchangeably referred to herein and in the art as "d₅₀" and represents the particle size which 50 % of the particles do not exceed. The volumetric distribution of the sample relates to the weight distribution. While the average particle radius is derived from a volumetric average particle size or length and expresses the same values, this phrase is also referred to interchangeably herein and in the art as "volumetric average particle size", "volumetric average particle length" and "average particle length".

The terms "nano" , "nanoscale" or "nano-sized" all refer to a range of from about 1 nanometer to about 1000 nanometers (from about 1 x 10^"9 meters to about 1 x 10^'b meters). A "nanoscale" therefore describes a scale in the above cited range and "nano-sized" describe particles and/or a composition or a formulation containing the particles, whereby the particles size is within the above cited range.

The terms "micro", "microscale" or "micro-sized" (also referred to herein interchangeably as "micron", "micron-scale" or "micron-sized", respectively) all refer to a range of from about 1 micron to about 1000 microns (from about 1 x 10^"6 meters to about 1 x 10^"3 meters). A "microscale" therefore describes a scale in the above cited range and "micro-sized" describes particles and/or a composition or a formulation containing the particles, whereby the particles size is within the above cited range.

It is to be understood that particle sizes in the range of 600-1000 nanometers are in the higher nano-size range (higher nanoscale range), and may therefore exhibit characteristics close or similar to particles in the micro-size range (microscale). Thus, the teπn "nano-sized", as used herein, preferably relates to particles and/or a composition or a formulation containing the particles, whereby the average particles size is in the lower range of a nanoscale, namely, is 500 nanometers or less, and more preferably 250 nanometers or less.

The phrases "nano-sized compositions" and "micro-sized compositions" refer to compositions, as these are defined hereinabove, comprising "nano-sized particles" and "micro-sized particles", respectively.

The phrases "nano-sized formulations" and "micro-sized formulations" refer to formulations comprising "nano-sized compositions" and "micro-sized compositions", respectively.

The phrases "nano-sized dispersions" and "micro-sized dispersions" refer to "nano-sized compositions" or "nano-sized formulations" and to "micro-sized compositions" or "micro-sized formulations", as those have been defined hereinabove, which are in a form of a dispersion.

The halogenated flame retardant particles incorporated hi the composition presented herein have an average size ranging from about 1 nanometer to about 450 nanometers, and are preferably in the range of from about 50 nanometers to about 450 nanometers. More preferably, the halogenated flame retardant particles incorporated in the composition presented herein have an average size (d₅₀) that ranges from about 100 nanometers to about 250 nanometers.

Such an average size (100-250 ran) is highly advantageous in the context of the present invention, particularly as compared with compositions that contain particulate FRs having higher average particle size, since the lower the average particle size is, the better is the adhesion of the particles to the substrate, due to improved penetration of the particles to the substrate. Such a low average size is further advantageous since it beneficially results in increased viscosity of a composition containing same, due to large surface area thereof, as is discussed in detail herein.

In another embodiment, the flame retardant composition comprises a plurality of halogenated flame retardant particles characterized in that at least 90 % of these particles have a particle size smaller than 500 nanometers. In other words, the cut-off size of the particles is less than 500 nanometers. Thus, such compositions preferably do not Include more than 10 % of particles larger than 500 nanometers, more preferably do not include more than 5 % of particles larger than 500 nanometers, and even more preferably do not include any particles larger than 500 nanometers. As can be seen in Figure IB and in Table 2 in the Examples section that follows, an exemplary nano-sized composition according to the present embodiments, which contains FR- 1210 as the nano-sized flame retardant, was found to have a top cut-off of 360 nanometers.

Such a top cut-off is highly advantageous, particularly as compared with compositions that contain halogenated (e.g., brominated) FRs having a higher top cutoff, particularly in the microscale range, since a composition having a combination of small (e.g., 100-400 nm) particles and large (above 450 manometers) particles loses its uniformity and may lead to non-uniform application of such a composition on a substrate. In such a composition, the larger particles will not penetrate into the substrate at the same level as the smaller particles, will thus clog on the surface and may therefore result in an uneven coating on the substrate. Furthermore, as not all of the FR particles penetrate into the substrate, additional amounts of binder, FRs and FR synergists may be required so as to overcome the lower adhesion, and thus the textural and/or aesthetical properties of the substrate are further deteriorated, as explained in detail in the Background section above.

Thus, the FR compositions presented herein, by having 90 % of the particles that have a size lower than 1 micron and even lower than 500 nm (namely a size cutoff lower than 500 nanometers), are highly advantageous as compared, for example, with compositions having a size cut-off of about 2.7 microns, such as the compositions taught in U.S. Patent No. 5,948,323.

In still another embodiment, the flame retardant composition comprises a plurality of halogenated flame retardant particles characterized in that at least 10 % of these particles have a particle size smaller than 90 nanometers.

Having a portion of the particles as small as 90 nanometers and even less (e.g., 50 nanometers) is highly advantageous, and in fact, has never been disclosed in the art for halogen-containing and particularly bromine-containing FR compositions. Such an extremely small particle size further improves the adhesion of the FR particles to the substrate and further increases the viscosity of the composition.

Taken together, the FR particles incorporated in the composition described herein further have a narrow size distribution, as is shown, for example, in Figure 1 B and in Table 2 in the Examples section that follows. Such a narrow size distribution further provides for a uniform incorporation of the composition on a substrate.

As can be seen in Examples 12-15 in the Examples section that follows, textiles treated by formulations containing a nano-sized bromine-containing FR composition according to the present embodiments maintained their flexibility, smoothness, color vivacity and streak-free look, and have further passed flammability tests, even upon subjecting the treated fabrics to several washing cycles, thus demonstrating the advantageous features of the compositions presented herein. As can be further seen in the optical microscopy measurements conducted for polyester and cotton fabrics treated by formulations containing a nano-sized bromine- containing FR composition according to the present embodiments (see, for example, Figures 5A-F) and in corresponding SEM pictures (see, Figure 3), upon drying, the treated fabrics had a smooth and even coating and appear similar to untreated fabrics, thus further demonstrating the advantageous features of the compositions presented herein.

According to preferred embodiments of the present invention, each of the compositions described herein further comprises a carrier.

The term "carrier", as used herein, describes an inert material with which the composition is mixed or formulated to facilitate its application, or its storage, transport and/or handling. Since the flame retardant compositions described herein are particularly useful for the treatment of textiles, the carrier is preferably a textile acceptable carrier.

The term "textile acceptable carrier" as used herein refers to an inert, environmentally acceptable carrier, which is not harmful to the textile.

Preferably, the carrier is an aqueous carrier and more preferably the carrier is water, as is further discussed hereinbelow.

In each of the compositions described herein, the amount of the flame retardant can range from about 1 weight percentage to about 70 weight percentages of the total weight of the composition. Preferably, the amount of the halogenated flame retardant ranges from about 10 weight percentages to about 70 weight percentages, more preferably from about 20 weight percentages to about 70 weight percentages, more preferably from about 30 weight percentages to about 70 weight percentages, more preferably from about 40 weight percentages to about 60 weight percentages of the total weight of the composition, whereby in the presently most preferred composition that amount of the halogenated FR is about 50 weight percentages of the total weight of the composition.

The halogenated flame retardant compositions described herein can further comprise additional ingredients that may stabilize the composition, prolong its shelf- life and/or provide it with other desired properties such as certain viscosity, homogeneity, and adherence to the substrate. Thus, according to a preferred embodiment of the present invention, the FR composition may further comprise one or more of such additional ingredients. These include, for example, one or more of a surface active agent, a wetting agent, a dispersing agent, a suspending agent and a pH buffer and any mixture thereof.

The surface active agent and/or wetting agent can be nonionic or anionic agents.

Examples of nonionic agents that are suitable for use in the context of the present invention include, but are not limited to, polyoxyethylene (POE) alkyl ethers, preferably NP-6 (Nonylphenol ethoxylate, 6 ethyieneoxide units) such as DisperByk 101®. Examples of anionic agents that are suitable for use in the context of the present invention include, but are not limited to, free acids or organic phosphate esters or the dioctyl ester of sodium sulfosuccinic acid.

Examples of dispersing agents and/or suspending agents that are suitable for use in the context of the present invention include, but are not limited to, acrylic acids, acrylic acids ester copolymer neutralized sodium polycarboxyl such as naphthalene sulfonic acid-formaldehyde condensate sodium salt, alginates, cellulose derivatives and xanthan.

As demonstrated in the Examples section which follows, FR-1210 nano-sized dispersions were found to be more viscous by an order of magnitude than micron- sized FR-1210 dispersions having the same FR concentration (amount) (see, Examples 1 and 2), facilitating further processing of these compositions.

Hence, preferred compositions according to the present embodiments are characterized by a viscosity that ranges from about 100 centipoises to about 2,000 centipoises. As is demonstrated in the Examples section that follows, exemplary compositions were shown to have a viscosity in the range of from about 100 centipoises to about 800 centipoises. Compositions characterized by such a viscosity are highly advantageous since the relatively high viscosity circumvents the need to use large amounts of thickening agents when applying a formulation that contains the

FR composition to substrates. As discussed hereinabove, large amounts of thickening agents, which are often required so as to efficiently apply low-viscosity FR formulations onto textiles, are highly disadvantageous.

As discussed hereinabove, many of the presently known brominated FR compositions are unsatisfactory due to the instability of the compositions, which often results is the loss of FR effectiveness after long-term shelving, due to thermal or other degradation processes.

The present inventors have now uncovered that aqueous dispersions of a nano- sized halogenated (e.g., brominated) flame retardant form stable compositions. It has further been surprisingly uncovered that such compositions are stable even during long-term shelving. It was therefore demonstrated that the instability of compositions containing brominated FRs can be circumvented by using a nano-sized aqueous dispersion of the flame retardant.

Thus, according to preferred embodiments of the present invention, in each of the compositions described herein, the halogenated (e.g., brominated) flame retardant is utilized in a form of a dispersion, which comprises a plurality of halogenated flame retardant particles dispersed in the carrier.

A preferred carrier according to the present embodiments is an aqueous carrier and more preferably it is water. Thus, preferred compositions according to the present embodiments include an aqueous dispersion of halogenated flame retardant nanoparticles.

Thus, while further reducing the invention to practice, a process for preparing aqueous dispersions of the nano-sized halogenated FRs has been designed and successfully practiced. According to another aspect of the present invention there is provided a process of preparing flame retardant compositions comprising a plurality of halogenated flame retardant particles, as described herein, dispersed within an aqueous carrier.

The process, according to this aspect of the present invention, is effected by milling a dispersion which comprises a halogenated flame retardant and an aqueous carrier until particles smaller than about 1 microns are obtained.

In cases where the composition further comprises additional ingredients, as described hereinabove, such agents are added to the initial dispersion, prior to the milling.

While any of the commonly used dispersing agents can be added to the initial dispersion, exemplary dispersing agents which were found suitable for use in this context of the present invention (in the preparation of aqueous dispersions of nano- sized halogenated flame retardant) include dispergator WA, AMP-95, Clorocontin NGD and Triton X-IOO (see, for example, Examples 1 and 2 in the Examples section that follows).

While any of the commonly used Averting agents can be added to the initial dispersion, an exemplary wetting agent which was found suitable for use in this context of the present invention (in the preparation of aqueous dispersions of nano- sized halogenated flame retardant) is Clorocontin NGD.

The milling procedure can be conducted according to any of the known wet milling practices. Preferably, the milling is conducted during a time period of at least 2 hours. More preferably, the milling is conducted for a time period that ranges from three to four hours, so as to achieve the desired FR average particle size and particle size distribution. As is demonstrated in the Examples section that follows (see, for example, Example 2 in the Examples section that follows), when milling was conducted during such a time period, compositions of a brominated FR having the desired particles average size of 100-250 nanometers, a size cut-off lower than 1 micron and/or at least 10 % of the particles having an average particles size lower than 90 microns, as well as a desired, relatively narrow, particles size distribution, were obtained. For example, comparing the particles size distribution before and after the milling of FR-1210 particles (see, for example, Figure IA and Table 1, versus Figure IB and Table 2, respectively), shows that after milling, the size distribution is narrower and has a higher ratio of nano-sized particles: while before milling 90 % of the particles are 8.42 microns (8420 nanometers) or larger, after milling- 90 % of the particles are 205 nanometers (about 2.5 % of the original size) or smaller, and about 10 % of the particles are 71 nanometers (about 0.8 % of the original size) or larger.

The size distribution of the nano-sized dispersions is very different that the size distribution obtained for the colloidal FR-1210 compositions taught in U.S.

Patent No. 5,948,323. As discussed above, the compositions taught in U.S. Patent

No. 5,948,323 have an average size of about 0.25 micron (250 nanometers) and a size cut-off of about 2.7 microns (2700 nanometers). According to the present embodiments, 50 % of the nano-sized particles obtained by the process described herein are in the size range of 100-250 nanometers, and the top cut-off was found to be as small as 350-450 nanometers, about 17 % of the top cut-off displayed according to the teachings of U.S. Patent No. 5,948,323. Furthermore, while the compositions obtained by the process described herein include at least 10 % of the particles wliich have a particle size smaller than 90 nanometers, such compositions are not obtained using the process described in U.S. Patent No. 5,948,323.

According to another embodiment of this aspect of the present invention, the process is conducted under basic pH conditions. It has been shown that under these conditions, stable dispersions of the nano-sized brominated FRs are obtained.

The flame retardant compositions described herein are preferably incorporated in flame retardant formulations.

Hence, according to another aspect of the present invention there is provided a flame retardant formulation, as defined herein, which comprises any of the compositions described herein and a carrier.

These FR formulations preferably further comprise additional ingredients that may stabilize the formulation, prolong its shelf-life and/or provide it with other desired properties such as certain viscosity, homogeneity, stability and adherence to the substrate.

Exemplary additives include, but are not limited to, one or more of an antifoaming agent, a defoaming agent, a preservative, a stabilizing agent, a binding agent, a thickening agent and any mixture thereof.

Examples of defoaming and/or antifoaming agents that are suitable for use in the context of the present invention, include, but are not limited to, mineral oil emulsions, natural oil emulsions, and preferably are silicon oil emulsions, such as AF- 52.

Examples of preserving or stabilizing agents that are suitable for use in the context of the present invention, include, but are not limited to, formaldehyde and alkyl hydroxy benzoates; preferably the preserving or stabilizing agents is a mixture of methyl and propyl hydroxy benzoates.

The binding agent (also termed herein interchangeably as a "binder") is necessary to adhere the molecules of a flame retardant, herein a brominated flame retardant, to a substrate.

As discussed in detail hereinabove, brominated FRs are known as typically requiring a large amount of a binder, which may reach about 50 % by weight of the total FR formulation, to affix them to a textile substrate [Mischutin (1978) supra]. Such a large amount of a binder results is high add-on, which, as is further discussed in detail hereinabove, is undesirable since it causes a deterioration of the textile properties by, for example, stiffening the fabrics or fading of fabric shades, and may further lower the tear strength and abrasion properties of the fabric. Unfortunately, the high binder content also contributes in itself to flammability and dripping. Therefore when the binder is added in large amounts, yet higher amounts of the FR are needed, and as a result, more binder is needed to attach the extra FR to the substrate, thereby creating an endless cycle.

It has now been unexpectedly uncovered by the present inventors that the formulation described herein can be effectively applied on various substrates in the presence of relatively low concentrations of a binder. While the exact amount of binder used depends on the flame retardant type and concentration, as well as on the fabric type onto which the formulation is applied, it has been shown herein that an efficient application of the formulations described herein on, can be effected in cases where the concentration of the binding agent in the formulations described herein is lower than 40 weight percentages of the total weight of the formulation, lower than 30 weight percentages of the total weight of the formulation and even equal to or lower than 25 weight percentages.

As is demonstrated in the Examples section that follows, it was found that nano-sized brominated flame retardant formulations containing 20 weight percentages of a binder were well adhered to the substrates, and remained such even upon subjecting the substrate to several washing cycles, while maintaining the flame resistance properties. Thus, for example, it has been demonstrated that a 100 % Rib knitted cotton fabric having a nano-sized brominated flame retardant formulation that contains 20 % by weight of a binder applied thereon, passed a 12 seconds ignition test (ASTM D-6413) with an after flame time of 2 seconds, an after glow time of 151.5 seconds, and a char length of 15.3 centimeters, even after 5 cycles of washing (see, Example 12).

Thus, it has been shown that nano-sized halogenated (e.g., brominated) FR formulations have an improved adhesion to the fabric (evident from the lower amount of binder required to achieve wash-fastness). The binder concentrations are considerably lower as compared to traditional (e.g., micron-sized) brominated FR formulations (50 weight percent). Considering the lower binder amounts now needed, nano-sized halogenated (e.g., brominated) FR formulations can contain higher amounts of the halogen (e.g., bromine) at the same total add-on, as compared to conventional nano-sized brominated FR presently known.

Thus, according to yet another aspect of the present invention, there is provided a flame retardant formulation comprising a carrier, a plurality of halogenated flame retardant particles having an average size smaller than about 1 micron dispersed in the carrier, and a binding agent, wherein the amount of the binding agent is less than 40 weight percents of the total weight of the formulation.

The binder used in the formulations described herein is selected depending on the specific application. For example, different binders may be suitable to attach the FR formulation described herein to wood, plastic or textile. The binder can thus be selected from a large variety of suitable materials, such as, but not limited to, synthetic polymers, such as styrene-butadiene (SBR) copolymers, carboxylated-SBR copolymers, melamine resins, phenol-aldehyde resins, polyesters, polyamides, polyureas, polyvinylidene chloride, polyvinyl chloride (PVC), acrylic acid- methylmethacrylate copolymers, acetal copolymers, polyurethanes, and mixtures and cross-linked versions thereof.

Preferably, when the formulations described herein are applied on textiles, the binder is selected suitable for use on textiles, and is therefore selected to be both non- damaging to the aesthetical and textural properties of the fabric, and durable (to washing, drying, UV light etc.), and should further be compatible with the flame retardants and the additional additives in the formulation.

Thus, according to a preferred embodiment of the present invention, the binder is an aery late, a polyurethane, or PVC. More preferably, the binder is an acrylate.

Examples of acrylates that are suitable for use as binders in the context of the present invention include, but are not limited to, 2-phenoxyethylacrylate, propoxylated 2-neopentyl glycol diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, 2-(2-ethoxyethoxy) ethyl acrylate, and others. In addition to the nano-sized halogenated flame retardant, the carrier, the binder and optionally any of the other additives mentioned hereinabove, the formulations described herein may further comprise additional ingredients which may improve the flame retardancy performance of the formulation. An exemplary ingredient is a flame retardant synergist, which acts in synergy with the nano-sized halogenated flame retardant or with any other FR that is incorporated in the formulation described herein and thus enhances the flame resistance properties of the formulation.

Thus, according to preferred embodiments of the present invention, the formulation described herein further comprises at least one fire retardant synergist. An exemplary fire retardant synergist which is suitable for use in this context of the present invention is antimony oxide (ATO).

As is detailed in the Background section hereinabove, when a FR formulation is applied on textiles, large amounts of ATO are undesirable due to cost, toxicity, environmental concerns and increase in the total add-on. By using the FR formulations presented herein, the need to use large amounts of a FR synergist such as ATO is circumvented due to the relatively enhanced binding of the nano-sized FR to the substrate, and thus the resulting relatively high FR content on the substrate. Hence, lower amounts of a FR synergist, as compared to the presently known FR formulations, are required so as to maintain an efficient flame retardancy, washing fastness and desirable fabric properties. The FR synergist (e.g., ATO) incorporated in the FR formulations presented herein can be either nano-sized or non nano-sized (e.g., micron-sized or of higher particles size)

Thus, according to preferred embodiments of the present invention, the molar ratio between the fire retardant synergist and nano-sized halogenated flame retardant in the formulations described herein preferably ranges from about 1:1 to about 1:6 of the active atoms in each compound (antimony and the halogen, respectively).

According to further preferred embodiments of the present invention, the amount of the flame retardant synergist is lower than 30 weight percentages of the total weight of the composition, preferably ranging from about 10 weight percentages to about 30 weight percentages of the total weight of the composition.

According to still further embodiments of the present invention, the formulations described herein may further comprise additional flame retardants and/or smoldering suppressants. Any of the known FRs and/or smoldering suppressants can be utilized in this respect, whereby preferably no more than 10 different FR and/or SS agents are incorporated in the formulation.

The formulations described herein were found to be highly stable upon storage, being stable for more than three months, and even for more than six months at about room temperature. As is demonstrated in the Examples section that follows (see, for example, Examples 7-9), it was found that FR formulations containing nano-sized brominated FR, prepared as described hereinabove, were left on shelf at ambient temperature for approximately six months and remained stable during this time period.

It was further shown that these formulations are stable for at least 12 weeks when stored at elevated temperatures (e.g., above 30 °C, or by following the "Tropical

Storage Test", at 54 ⁰C). It is to be understood that at temperatures below room temperature, the stability of the formulation described herein is even higher.

Furthermore, it was found that the FR formulations described herein were smoother flowing, did not require stirring, and were easier to apply onto fabrics, as compared with corresponding micron-sized halogenated FR formulations (see Examples 6-9). Thus, these FR formulations were found to have a relatively high viscosity, which is highly suitable for easily applying the formulations onto fabrics. As a result, lower amounts of thickening agents are required, further decreasing the add-on of the treated fabric, and resulting in a coated textile with improved textural and aesthetical properties.

Thus, according to further preferred embodiments of the present invention, the above-described flame retardant formulations have a viscosity that ranges from about 100 to about 2,000 centipoises. It has thus been demonstrated that nano-sized halogenated FR formulations as described herein can be efficiently applied on textiles while circumventing the need to use high concentrations of binders, thickening agents and synergists, and further while maintaining the desirable aesthetical, textural properties and flame retardancy properties of the fabric, even after extensive washing. The flame retardant formulations described herein, can be applied to a substrate by simply contacting the substrate with the flame retardant formulation, whereby the contacting can be effected by any industrially acceptable manner. Optionally, subsequent to contacting the FR formulation, the substrate is heated. The industrially acceptable manner in which the contacting is effected includes, for example, spreading, padding, foaming and/or spraying the FR formulation onto the substrate. Padding is a process that is typically used for applying the formulation on a textile substrate and is defined as a process in which the fabric is first passed through a padder containing the FR formulation, and is then squeezed between heavy rollers to remove any excess formulation. The process described herein can be effected, for example, either during the dyeing or the finishing stages of the substrate manufacture. The resulting substrate thus may have the formulation., as is, applied thereon, or, if subjected to the appropriate procedures, may have a dry formulation applied thereon. The dry formulation typically includes the FRs, FR synergists, binders and any other solid substances present in the formulation. As is demonstrated in the Examples section that follows, the formulations and processes described herein were practiced so as to provide substrates having the FR formulation applied thereon.

Hence, according to a further aspect of the present invention there is provided an article-of-manufacture which comprises a flammable substrate and any of the flame retardant formulations described herein, being applied thereon.

It should be noted that the flame retardant formulations are being applied on the substrates as wet formulations comprising nano-sized particles. However, other particles of a larger non-nano-size may be present in the formulation (for example the FR synergist). Upon drying of the substrates, the obtained articles-of-manufacture comprise the substrates coated by the dry ingredients of the flame retardant compositions, e.g., a flame retardant and/or a FR synergist and/or a binder. At this stage, the particles of the FR composition may exist either as nano-sized particles, or may agglomerate to form larger particles, together with any of the other larger particles which may exist in the FR formulation. The favorable properties of the FR formulations of the present invention, and of the articles-of-manufacture obtained by applying these formulations upon the flammable substrates, are inherent to the existence of the nano-sized FR particles in the FR compositions comprised in these formulation, irrespective of the existence of other larger particles in the formulation, or on the dried FR coating on the substrate.

As used herein, the term "substrate" describes an article which has a surface that can be beneficially coated (either wholly or partially) with a flame retardant formulation. Exemplary articles include, without limitation, textiles, wood, furniture, toys, bricks, electrical appliances, electrical cables, plastics and more.

Preferred substrates onto which the flame retardant formulations described herein can be beneficially applied are textile fabrics. The textile fabrics can be synthetic, natural or a blend thereof. Non-limiting examples of textile fabrics that can be beneficially used in the context of the present invention include wool, silk, cotton, linen, hemp, ramie, jute, acetate fabric, acrylic fabric, latex, nylon, polyester, rayon, viscose, spandex, metallic composite, carbon or carbonized composite, and any combination thereof. Representative examples of textile fabrics which were shown to be suitable for use in the context of the present invention include, without limitation, cotton, polyester, and combinations thereof.

As is used herein, the term "flammable substrate" describes a substrate, as described hereinabove, that easily ignites when exposed to a low-energy flame. The flammability of different articles-of-manufacture can be tested according to international standards. For example, ASTM D-1230, a standard test method for flammability of apparel textiles; ASTM D-4151, a standard test method for flammability of blankets; ASTM D-4723, a standard index of and descriptions of textile heat and flammability test methods and performance specifications; ASTM D- 4804, a standard test method for determining the flammability characteristics of non- rigid solid plastics; ASTM D-6545, a standard test method for flammability of textiles used in children's sleepwear; ASTM D-777, standard test methods for flammability of treated paper and paperboard; ASTM D- 1317, a standard test method for flammability of marine surface finishes; ASTM D-1955, a standard test method for flammability of sleeping bags, and ASTM D-6413, a standard test method for flame resistance of textiles (vertical test).

The flame retardancy of the tested substrates was determined by methods acceptable in the industry, for example a 12 seconds ignition test, which is defined by ASTM D-6413, a test method used to measure the vertical flame resistance of textiles. According to this method a textile is classified on a pass/fail basis, according to predetermined criteria. More specifically, a textile is considered to have failed the 12 seconds ignition test, if its average "char length" exceeds 7 inches (17.8 cm) or an individual sample has a "char length" longer than 10 inches (25.4 cm). The flammability of a substrate may be further defined by its "after flame time" and by its "after glow time". A fabric is considered to have an excellent flame retardancy if either its "after flame time" is 10 seconds or less, or its "after glow time", is 200 seconds or less. A fabric is considered to have a superior flame retardancy if its "after flame time" is 5 seconds or less. "After-flame time" is defined herein and in the art as the time period during which the sample continues to burn after removal of the burner.

"After-glow time" is defined herein and in the art as the time period during which the sample glows after the flame is extinguished.

"Char length" is defined herein and in the art as the distance from the edge of the fabric that was exposed to the flame to the end of the area affected by the flame. A char is defined as a carbonaceous residue formed as the result of pyrolysis or incomplete combustion.

Using this method, it was demonstrated, for example, that a bone-dry (as defined hereinafter the term "bone-dry" describes a substrate having zero percent moisture content) dyed knitted cotton fabric, which was padded with a nano-sized FR- 1210 formulation (Example 12), according to preferred embodiments of the present invention, passed ASTM D-6413 12 seconds ignition test with no dripping, having an after flame time of 2 seconds, an after glow time of 151.3 seconds, and a char length of 15.3 centimeters. Similarly, a cotton fabric padded with a nano-sized Saytex-8010 formulation (Example 14), according to preferred embodiments of the present invention, was subjected to 3 laundry cycles and passed an ASTM D-6413 12-seconds ignition test with an after flame time of 1 second, an after glow time of 75 seconds and a char length of 15 centimeters. Yet further, a woven polyester fabric padded with a nano-sized FR-1210 formulation (Example 13) and with a nano-sized Saytex- 8010 formulation (Example 14) passed ASTM D-6413 12-seconds ignition test, with no dripping. These results demonstrate the excellent flame retardancy properties obtained by applying the nano-sized brominated FR formulations of the present embodiments on textile substrates.

The articles-of-manufacture described herein are therefore characterized by enhanced flame retardancy properties, which can be determined as described hereinabove. Thus, the articles-of-manufacture according to the present embodiments are characterized by an after flame time of 2 seconds and less; an after glow time of 150 seconds or less and a char length of 15 centimeters or less.

As is further demonstrated in the Examples section that follows, when an FR formulations of the present embodiments was applied onto various textile fabrics, the flame resistance of the fabric, as defined by the "after flame time", "after glow time" and "char length", was maintained even after the fabric was contacted with hot water and a detergent, while being subjected to one or more washing cycles, as defined by Standard Laboratory Practice for Home Laundering (AATCC technical manual/2001). In fact, the flame resistance properties of textile fabrics treated with the nano-sized halogenated FR formulations described herein were maintained even after the treated fabric was subjected to 1, 3 and even 5 washing cycles.

Hence, it has been shown that the treated textile fabrics are characterized by enhanced washing fastness.

The term "washing fastness", which is also referred to herein interchangeably as "washing durability" or "laundry stability", refers to the ability of a substrate treated with the nano-sized halogenated FR formulations of the present invention, to maintain its characteristic flame resistance and/or textural and/or aesthetical properties, after being subjected to at least one washing cycle, as defined by Standard Laboratory Practice for Home Laundering (AATCC technical manual/2001).

As is well acceptable in the art, a textile is considered "durable" if it withstands five washing cycles without having remarkable change of a property thereof, whereby a textile is considered "semi durable" if it similarly withstands at least 1 washing cycle. The substrates treated with the formulations of the present embodiments were characterized by a washing fastness of three washing cycles, often exceeding 5 washing cycles. Hence, according to further embodiments of the present invention, the articles-of-manufacture described herein are characterized by washing fastness. This feature is particularly notable in view of the relatively low amount of the binder in the applied formulation.

Thus, according to a further embodiment of the present invention, the "after flame time", "after glow time" and "char length" properties, as defined hereinabove, of an article-of-manufacture having the FR formulation described herein applied thereon remain substantially unchanged upon subjecting the article-of-manufacture to one or more washing cycles, and even upon subjecting the article-of-manufacture to 5 or more washing cycles.

As used herein the term "substantially unchanged" refers to a change of less than 30 %, preferably less than 20 %, and more preferably less than 10 % in the tested property.

As discussed in detail in the Background section above, commonly used brominated FRs are characterized by a high add-on, which then results in inferior textural and aesthetical properties. By using nano-sized dispersions of these FRs, as presented herein, these textural and aesthetical properties are improved. For example, the transparency of liquid dispersions is maintained when the particle size is smaller than about 400 nanometers (0.4 micron).

Thus, as is further demonstrated in the Examples section that follows, it has been shown that upon applying the FR formulations described herein onto textile substrates, the substrates maintained textural and aesthetical properties. These textile substrates were characterized by feel and appearance similar to those of a non-treated flammable substrate. For example, properties such as the flexibility, smoothness, color vivacity and streak-free look of a non-treated textile were maintained upon application of the FR formulation (see, for example, Examples 12-15). As an example, when FR-1210 and/or Saytex-8010 nano-sized formulations were applied to dark shade fabrics, the final shade was relatively close to the original shade. Furthermore, these textural and aesthetical properties were maintained also upon subjecting the treated fabrics to several washing cycles. Additional proof lies in optical microscopy of polyester and cotton fabrics treated by the micron-sized and nano-sized formulations of the present invention. As shown, for example, in Figures 5A-F, fabrics treated by the nano-sized FR-1210 formulation had a smooth and even coating upon drying of the fabric (see, Figure 5C for nano-FR-1210 treated polyester, and Figure 5F for nano-FR-1210 treated cotton), and appear similar to untreated fabrics (see, Figure 5 A and Figure 5D), while fabrics treated by a micron-sized FR- 1210 formulation display a gritty texture with large uneven particles visibly adhering to the fibers (see, Figure 5B for micron-FR-1210 treated polyester, and Figure 5E for nano-FR-1210 treated cotton). This translates into a smoother and better feeling fabric when using nano-sized FR-1210. The smoothness of the fibers was also captured by SEM pictures of 100 % cotton fabric soaked with a nano-sized FR-1210 composition, upon drying (see, for example, Figure 3).

Hence, according to further embodiments of the present invention, the article- of-manufacture described herein is further characterized by at least one aesthetical or textural property which is substantially the same as that of the flammable substrate per se. The textural and/or aesthetical properties of the substrate or article-of-manufacture include, but are not limited to flexibility, smoothness, streakiness and color vivacity.

The term "per se" as used hereinafter, refers to the article-of-manufacture without the FR formulation.

According to still another embodiment of the present invention, each of these properties remains substantially unchanged upon subjecting the article-of-manufacture to one or more washing cycles, preferably to five or more washing cycles.

As is explained in the Background section, it is extremely undesirable to apply on a textile a flame retardant formulation in large amounts (also termed "high add-on") since high additive concentrations on the fabric result in inferior fabric properties, as well as increased cost of production. Thus, it should be appreciated that the substrates treated with the formulations of the present invention are characterized by a relatively low add-on, demonstrating the advantageous use of these formulations. It is suggested that for preferred formulations according to the present embodiments, which comprise an aqueous dispersion of nano-sized brominated FR, the low add-on is obtained since the nano-sized particles of the brominated FR adhere better to the substrate surface, thus strengthening the binding of the flame retardant to the fabric even at low binder concentration.

As a result, articles of manufacture, and particularly substrates, treated by the formulation described herein have superior properties as compared with the presently known FR-treated products. Exemplary articles-of-manufactures according to the present embodiments include any industrial product that comprises one or more flammable substrates and hence application of the FR formulation described herein thereon is beneficial. Such articles-of-manufacture include, for example, textiles, wood, furniture, toys, bricks, electrical appliances, electrical cables, plastics and more. Thus, for example, bricks or wooden articles, which are often used in building or as home furniture, can be easily coated with the FR formulation described herein, thus made flame resistant and applicable for home or industrial use. Electrical appliances and electrical cables, are in severed danger of catching fire, being easily ignitable by an electric spark from within. It is advantageous to apply a coating on these electrical appliances and electrical cables, in an easy manner, and coating by the FR formulation described herein is therefore advantageous. Toys, textiles and plastics, are used in every field of life, including by children. Therefore, fire proofing them is essential. Being cleaned and/or washed very frequently, it is imperative to use a FR agent that is washing durable, and will not wash off easily. Thus, the FR formulation described herein can be advantageously used for the fire-proofing of toys, textiles and plastics.

According to the presently most preferred embodiments of the present invention, the article-of-manufacture described herein comprises a flammable textile fabric. Examples of such articles-of-manufacture include, but are not limited to, textiles, wood, furniture, toys, bricks, electrical appliances, electrical cables, plastics and more.

The textile fabrics of this invention may be used as a single layer or as part of a multi-layer protective garment. A textile substrate may be incorporated in various products, where it is desired to reduce the substrate flammability. Such products include, for example, draperies, garments, linen, mattresses, carpets, tents, sleeping bags, toys, decorative fabrics, upholsteries, wall fabrics, and technical textiles. As discussed in the Background section hereinabove, textile flammability and textile smoldering are major concerns since textiles are used in all fields of life. Some textile-based articles of manufacture, such as garments, linen and some decorative or technical textiles, are subject to harsh usage (abrasion, exposure to various environmental conditions etc.) and therefore may need extensive, sometimes daily, cleaning and washing. Heretofore, fire proofing these articles of manufacture involved either using the few available non-flammable fabrics; coating flammable fabrics with large amounts of FR, thus often damaging the fabric properties; or applying low amounts of FR on the flammable fabric, but limiting its cleaning method to the expensive and burdensome dry cleaning method. Using the FR formulation presented herein, these garments or technical textiles may be fire proofed while maintaining the feel and look of the fabric, as a result of applying relatively small amounts of the formulation.

Other types of articles-of-manufacture, such as draperies, carpets, tents, sleeping bags, toys, wall fabrics, decorative fabrics, mattresses and upholsteries, are not washed as much as garments or linen. However, the major hazards that can be caused by the inherent flammability of these articles call for efficient fire proofing thereof, in addition to their durability during periodic cleaning. These articles of manufacture may easily be made fire proof, either by using a fabric treated by the formulation described herein during the manufacturing process, or by easily applying these formulations onto the final product.

Additional objects, advantages, and novel features of the present invention will become apparent to one ordinarily skilled in the art upon examination of the following examples, which are not intended to be limiting. Additionally, each of the various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below finds experimental support in the following examples. EXAMPLES

Reference is now made to the following examples, which together with the above descriptions, illustrate the invention in a non limiting fashion.

MA TERIALS AND ,4NAL YTICAL METHODS

Materials:

Alkyl alkanolamines dispersants (such as amino methylpropanol, AMP-95) were obtained from Dow.

Decabromodiphenylether (decabromodiphenyloxide, DECA, CAS No. 1 163- 19-5, labeled as FR-1210) and pentabromobenzyl acrylate (PBB-MA, CAS No. 59447.55.I₅ labeled as FR-1025M) was obtained from ICL-IP. l,2-Bis(2,3,4,5,6-pentabromophenyl)ethane (also known as

Decabromodiphenylethane, CAS No. 84852-53-9, labeled as Saytex-8010) was obtained from Advanced Technology & Industrial Co., Ltd. The wetting agent CLOROCONTIN NGD was obtained from CHT.

The anionic surfactant LABS 100 (CAS No. 25155-30-0) was obtained from Zohar Dalia.

Dispergator WA was obtained from Avco-Chem.

AC-200 W binder and GP acrylic thickening agent were obtained from B. G. Polymers.

Ammonium hydroxide 22 % (CAS No. 1336-21-6) was obtained from Merck.

Antimony trioxide (ATO, CAS No. 1309-64-4) was obtained from Campine.

Instrumental Data:

Mixing was conducted using an IKEA lab mixer. Milling was conducted on a Dyno Mill Multilab WAB (manufactured by

Wiley A. Bachofen (WAB) using 0.4-0.6 millimeter ceramic balls and running at medium speed (3 Kg/h).

Viscosity was measured using a Brookfϊeld viscometer (model DV-II).

Size distribution tests: Light scattering particle size measurement: This method was used to determine the particle size distribution of liquid particles, using a Malvem Mastersizer (Hydrogel 2000G), manufactured by Malvern Instruments. The instrument uses the principle of Mie scattering, has an accuracy of ± 1 %, and is set to measure particles in the size range 0.02-2000 microns. A spherical (general) model was used. The surface mean particle size (d₅₀) or 50 percentile, the 10 percentile (d₁₀) and the 90 percentile (dc_>0) are directly obtained from the data generated by the instrument. Ciyo-TEM:

Aqueous dispersion samples were characterized via direct imaging using cryo-TEM. In this method, a drop of the solution was deposited on a TEM grid (300 mesh Cu grid) coated with a holey carbon film (Lacey substrate-Ted Pella Ltd). The excess liquid was blotted and the specimen was vitrified by a rapid plunging into liquid ethane pre-cooled with liquid nitrogen, in a controlled environment vitrification system. The samples were examined at -178 ⁰C using a FEI Tecnai 12 G TWIN TEM equipped with a Gatan 626 cold stage, and the images were recorded (Gatan model 794 CCD camera) at 12OkV in a low-dose mode. Fabric Characterization Methods: Scanning electron microscope equipped with an energy dispersive x-ray spectrometer (SEM/EDS) was performed on a JEOL JSM-7400F ultrahigh resolution cold FEG-SEM. In this method a piece of fabric is coated with 10 nanometer of gold layer.

Flainmability tests: ASTM D-6413 12 seconds ignition test: In this method, samples are cut from the fabric to be tested, and are mounted in a frame that hangs vertically from inside the flame chamber. A controlled flame is exposed to the sample for a specified period of time (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 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). Washing Fastness Tests: Samples treated with the flame retardant formulations described herein were subjected to 5 successive washing cycles in accordance with the washing procedure set forth below, followed by one drying cycle in accordance with commonly used drying procedure, based on the Standard Laboratory Practice for Home Laundering (AATCC technical manual/2001), unless otherwise noted.

In all washing cycles, the temperature of the washing water is maintained between 58 °C and 62 ⁰C, for automatic washing machines, the washing cycle is set for normal washing cycle, and a synthetic detergent that conforms to Standard Laboratory Practice for Home Laundering (AATCC technical manual/2001) is used.

Optical Microscope Micrographs: Optical micrographs were obtained using a Nikon eclipse model ME600 with a Nikon optics X 100 lense.

EXAMPLE l

Preparation of a micron-sized FR-1210 dispersion (milling base)

Decabromodiphenylether (DECA, also known as decabromodiphenyl oxide, labeled bj' the inventors as FR-1210, 50 % by weight) was added to a mixture containing distilled water (46.2 % by weight), a dispersing agent (Dispergator WA, 2.5 % by weight), a wetting agent (CLOROCONTIN NGD, 0.4 % by weight) and an additional dispersant (AMP-95, 0.25 % by weight). The pH of the resulting mixture was adjusted to 7-8 using ammonium hydroxide and the mixture was thereafter stirred at 700 RPM for one hour, to afford a 1:1 (by weight) FR-1210:water milling base, containing approximately 41 % by weight bromine. The obtained FR-1210 milling base was characterized by Malvem particle sizer, determining a Di₀ of 1.298 micron, a D₅₀ of 3.050 micron and a D₉₀ of 8.42 microns, and had a viscosity of about 160 centipoises (cP). The size distribution of the obtained dispersion is presented in Table 1 below and in Figure IA.

Table 1

EXAMPLE 2 Preparation of a nano-sized FR-1210 dispersion

The micron-sized FR-1210 milling base, prepared as described in Example 1 above, was introduced into a milling unit. Samples were taken every hour and analyzed for particle size. Milling was conducted until the particles cut-off was below 1 micron, usually for about 3 hours. The obtained nano-sized FR-1210 dispersions were characterized by a Malveπi particle sizer, determining a D₅₀ in the range of 100- 250 nanometers, and a top cut-off in the range of 350-450 nanometers. In a representative example, a nano-sized FR-1210 dispersion prepared as described above was characterized by a D₁₀ of 71 nanometers, a D₅₀ of 120 nanometers and a D₉₀ of 205 nanometers. The size distribution of the obtained dispersion is presented in Table 2 below and in Figure IB.

As can be seen by comparing the FR-1210 particle size distribution before and after the milling (Figures IA and IB, respectively), most of the particles were in the micrometer range prior to the milling, and were later mostly in the nanometer range after the milling. Table 2

The dispersion was further characterized by Cryogenic Tunneling Electron Microscopy (Cryo-TEM), indicating that the particle size cut-off is well below 200 nanometers and that the particle size distribution is narrow. The obtained image is presented in Figure 2, and displays nano FR-1210 particles having a variety of shapes and different orientations. The particles size is in the range of 5 nanometers to 250 nanometers, with a size distribution typical to cryo-TEM, namely, the bigger structures are located close to the edges of the grid's original holes (where the vitrified ice is thicker) while the smaller ones are close to the middle of the holes. Some overlap of structures could be found as well, as indicated by the strong contrast (white arrows).

The viscosity of the nano-sized FR-1210 dispersion was measured and was determined to be about 1,270 cP, Thus, FR-1210 nano-sized dispersions were found to be more viscous by an order of magnitude than the same concentration of micron- sized FR-1210 dispersions (see, Examples 1).

EXAMPLE 3 Preparation of a micron-sized Saytex-8010 dispersion (Milling Base) l,2-Bis(2,3,4,5,6-pentabromophenyl)ethane (also known as decabromodiphenylethane, and labeled herein as Saytex-8010, 50 % by weight) was added to a mixture containing distilled water (42 % by weight), a dispersing agent (Dispergator WA, 3.7 % by weight) and a surfactant (Labs- 100, 0.6 % by weight). The pH of the resulting mixture was adjusted to 7-8 using ammonium hydroxide and the mixture was stirred at 700 RPM for one hour, to afford a Saytex-8010:water milling base, containing approximately 54 % of the Saytex-8010 FR, and a 50 % bromine content.

EXAMPLE 4 Preparation of a nano-sized Saytex-8010 dispersion (Milling Base)

The micron-sized Saytex-8010 milling base, prepared as described in Example 3 above, was milled according to the procedure described above for the FR- 1210 nano-sized dispersion (Example 2), to achieve a nano-sized Saytex-8010 dispersion (milling base). Particles size analysis showed that 99.95 % of the particles were under 1 micron and the largest particles (0.05 % of the particles) were 1.3 micron in size.

EXAMPLE 5

Preparation of a micron-sized dispersion (milling base) and of a nano sized dispersion of pentabromobenzyl acrylate

A milling base of pentabromobenzyl acrylate (also labeled herein as FR-

1025M) was prepared and was thereafter ball-milled, according to the procedures outlined in Examples 1 and 2 above for FR-1210 micron-sized and nano-sized dispersions, respectively. The dispersion was characterized by Malvern particle sizer and its D₉₀ was determined to be in the range of 0.2-0.5 microns.

EXAMPLE 6 Preparation of aflame retardant micron-sized FR-1210 formulation

Antimony trioxide (ATO, 14.5 grams) was added to micron-sized FR-1210 dispersion (56.8 grams) obtained in Example 1, and the resulting mixture was further diluted by water (33.0 grams). This mixture was then milled for about half an hour, so as to obtain a homogenous diluted mixture. A polyacrylate thickening agent (17.1 grams) was added while stirring at 400 RPM. The pH was adjusted to 7-8 using ammonium hydroxide and a binder (AC-200 W, 13.3 grams, 50 % by weight) was added to obtain a dispersion containing about 14 % by weight total solids.

A typical formulation of the micron-sized FR-1210 dispersion sample contained 15 % solids, of which FR-1210 comprises 9.6 % and ATO comprises 4.8 %, with the total calculated bromine content at about 8 %. The obtained micron-sized FR-1210 formulation was gritty, opaque, had a medium fluidity and required constant stirring to prevent partial settling.

EXAMPLE 7

Preparation of a flame retardant nano-sized FR-1210 formulation

Antimony trioxide (ATO, 175 grams) was added to the milled nano-sized FR-1210 dispersion (500 grams) obtained in Example 2, and the resulting mixture was further diluted by water (175 grams) so as to maintain a 50 % by weight of total solids. This mixture was then milled for an additional half an hour, so as to obtain a homogenous diluted mixture, containing approximately 30 % by weight FR-1210 (24.5 % bromine) and 20 % ATO. This mixture (350.7 grams) was yet further diluted with distilled water (176.3 grams), and a thickening agent (potyacrylate, 6.2 grams, 1.1 % by weight) was added while stirring at 400 RPM. The pH was adjusted to 7-8 using ammonium hydroxide and a binder (AC-200 W, 50 % by weight) was added to obtain a dispersion containing about 20 % by weight total solids.

A typical formulation of the nano-sized FR-1210 dispersion sample contained 17.5 % solids, of which FR-1210 comprises 11.3 % and ATO comprises 5.6 %, with the total calculated bromine content at about 9 %. The obtained nano-sized FR-1210 formulation was smooth, translucent and had good fluidity, remaining stable for 6 months.

EXAMPLE 8

Preparation of aflame retardant micron-sized and nano-sized Saytex- 8010 formulations

The micron-sized and nano-sized Saytex-8010 dispersions obtained in Examples 3 and 4 above were formulated according to the same procedure as described above for FR-1210 nano-sized formulations (see, Example 7). The formulation contained 17.2 % solids, whereas the calculated flame retardant content is 1 1.3 %, the calculated bromine content is 9.3 % and the calculated ATO content is 5.6 %. The viscosity of the formulation was measured and was determined to be in the range of 100-800 cP. The formulation derived from the nano-sized Saytex-8010 dispersion was smooth, translucent and had good fluidity. It remained stable for 6 months.

EXAMPLE 9 Preparation of a micron-sized and nano-sized pentabromobenzyl aery late formulations

The micron-sized and nano-sized pentabromobenzyl acrylate dispersions obtained in Example 5 above were formulated according to the same procedure as described above for FR-1210 nano-sized formulations (Example 7). The formulation derived from the nano-sized pentabromobenzyl acrylate dispersion was smooth, translucent and had good fluidity. It remained stable for 6 months.

EXAMPLE lO Application of micron-sized FR-1210 formulation to dyed knitted cotton fabric

A fabric comprising of 100% cotton fiber weighing 216 grams per square meter was padded with the micron-sized FR-1210 formulation, prepared as described in Example 6 above, using an SDL ATLAS lab padder at maximum pressure. The fabric was air-dried and the formulation was then cured at 160 °C for 4 minutes. The fabric was bone dried for 30 minutes at 105 °C and was thereafter washed with 1 gram per liter of a standard detergent at 60 °C for 30 minutes and dried. The process was repeated 5 times. The add-on was determined to be 38 %. The treated fabric passed Flammability Tests (ASTM D-6413).

EXAMPLE Il Application of micron-sized FR-1210 formulation to a woven polyester fabric

A polyester fabric weighing 164 grams per square meter was padded with the formulation of Example 7, using an SDL ATLAS lab padder at maximum pressure.

The fabric was air-dried and the formulation was then cured at 160 °C for 4 minutes. The fabric was bone dried for 30 minutes at 105 °C. The treated fabric passed flammability tests (ASTM D-6413).

A severe whitening effect and "flattening" of the color was observed when the FR-1210 micron-sized formulations were applied to dark shade fabrics. In addition, the fabrics were stiff and rough to the touch.

EXAMPLE 12

Application of a nano-sized FR-1210 formulation to dyed knitted cotton fabric A fabric composed of 100% cotton fiber weighing 216 grams per square meter was padded with the nano-sized FR-1210 formulation, prepared as described in Example 7 above and containing 20 % by weight of a binder, using same procedure as described in Example 10 above. The add-on was determined to be 22 %, with the fabric containing 14.1 % of the FR-1210 flame retardant (or 11.7 % bromine) and 7 % of the ATO.

The treated cotton fabric was found to pass an ASTM D-6413 12-seconds ignition flammability test after 5 washing cycles, having an after flame time of 2.0 seconds, an after glow time of 151.5 seconds, and a char length of 15.3 centimeters.

The application of the nano-sized FR-1210 dispersion on a cotton fabric was further characterized by SEM pictures, after soaking a 100 % cotton fabric with the nano-sized FR-1210 dispersion of Example 2. SEM pictures of the soaked fabric upon drying are presented in Figure 3 and show that the fibers are smooth (figure 3A). Furthermore, at higher resolution (figure 3B) it is evident that the nano-sized FR-1210 dispersion either covered the fiber or agglomerated between the fibers. Figures 3C-E, which present the edge of the sample, also demonstrate the penetration of the nano- sized FR-1210 composition to the middle of the yarn (Figure 3 C presents the edge of the yarn, Figure 3D presents a cluster of fibers comprising the yarn, and at the highest resolution (Figure 3E) presents a single fiber in the middle of the yarn). In order to confirm the nature of the fiber coating, X-Ray elemental analysis of different points on a SEM sample surface, was conducted on the SEM/EDS device, confirming the bromine content in the material that covered the fibers and was between the fibers (see Figure 4 B-D which present the X-Ray elemental analysis of points 1 , 2 and 3 on the surface of the sample presented in Figure 4A).

EXAMPLE 13 Application of a nano sized FR-1210 formulation to a woven polyester fabric

A polyester fabric weighing 164 grams per square meter was padded with the formulation of Example 7, using the same procedure as described in Example 1 1 above. The padded fabric passed ASTM D-6413 12-seconds ignition test, with no dripping.

When the FR-1210 nano-sized formulations were applied to dark shade fabrics, the final shade was closer to the original shade. In addition, fabrics treated with the nano-sized formulations were noticeably softer to touch and did not require extensive post treatment after padding to soften up the treated fabric. Polyester and cotton fabrics treated by the micron-sized and nano-sized formulations of the present invention were further characterized by optical microscopy. Figures 5A-F present the comparative optical microscope micrograph images of untreated fabrics, and fabrics treated by the micro-sized FR-1210 formulation of Example 7, and by the nano-sized FR- 1210 formulation of Example 8. As seen in Figures 5A-F, the fabrics treated by the nano-sized FR-1210 formulation had a smooth and even coating (nano-FR-1210 treated polyester, Figure 5C and nano-FR-1210 treated cotton, Figure 5F), and appear quite similar to untreated fabrics (untreated polyester, Figure 5A and untreated cotton, Figure 5D), while fabrics treated by a micron-sized FR-1210 formulation display a gritty texture with large uneven particles visibly adhering to the fibers (micron-FR-1210 treated polyester, Figure 5B and nano-FR-1210 treated cotton, Figure5E).

EXAMPLE 14

Application of a nano-sized Say tex-8010 formulation on a dyed knitted cotton fabric

A fabric comprising of 100% cotton fiber weighing 216 grams per square meter was padded with the nano-sized Saytex-8010 formulation, prepared as described in Example 8 above, using the same procedure as described in Example 10 above. The add-on was determined to be 23.9 %, with the fabric containing 15.7 % of the Saytex-8010 flame retardant (or 12.9 % bromine) and 7.8 % of the ATO.

The treated fabric was subjected to 3 laundry cycles and passed an ASTM D- 6413 12-seconds ignition test with an after flame time of 1 second, an after glow time of 75 seconds and a char length of 15 centimeters.

EXAMPLE 15

Application of a nano-sized Saytex-8010 formulation to a woven polyester fabric

A polyester fabric weighing 164 grams per square meter was padded with the formulation of Example 8, using the same procedure as described in Example 11 above. The treated fabric passed an ASTM D-6413 12-seconds ignition test.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.

Claims

WHAT IS CLAIMED IS:

1. A flame retardant composition comprising a plurality of halogenated flame retardant particles having an average size ranging from about 100 nanometers to about 250 nanometers.

2. A flame retardant composition comprising a plurality of halogenated flame retardant particles, whereas at least 90 % of said particles have a particle size smaller than 500 nanometers.

3. A flame retardant composition comprising a plurality of halogenated flame retardant particles, whereas at least 10 % of said particles have a particle size smaller than 90 nanometers.

4. The composition of any of claims 1-3, further comprising a carrier.

5. The composition of claim 4, wherein said carrier is an aqueous carrier.

6. The composition of any of claims 1-5, wherein said halogenated flame retardant is a brominated flame retardant.

7. The composition of claim 6, wherein said brominated flame retardant is decabromodiphenylether (FR- 1210).

8. The composition of claim 6, wherein said brominated flame retardant is l,2-Bis(2,3,4,5,6-pentabromophenyl)ethane.

9. The composition of claim 6, wherein said brominated flame retardant is pentabromobenzyl acrylate.

10. The composition of any of claims 1-9, wherein an amount of said halogenated flame retardant ranges from about 1 weight percentage to about 70 weight percentages.

11. The composition of any of claims 4-10, further comprising at least one additional ingredient selected from the group consisting of a surface active agent, a wetting agent, a dispersing agent, a suspending agent, a pH buffer and any mixture thereof.

12. The composition of any of claims 4-1 1, being in a form of a dispersion.

13. The composition of any of claims 4-12, being characterized by a viscosity that ranges from about 100 centipoises to about 2,000 centipoises.

14. The composition of any of claims 4-13, being in a form of an aqueous dispersion.

15. A process of preparing the flame retardant composition of claim 14, the process comprising: milling a dispersion which comprises a halogenated flame retardant and an aqueous carrier until particles smaller than about 1 microns are obtained, thereby obtaining an aqueous dispersion of a plurality of halogenated flame retardant particles, wherein:

(i) said particles have an average size that ranges from about 100 nanometers to about 250 nanometers;

(ii) at least 90 % of said particles have a particle size smaller than 500 nanometers; and/or

(iii) at least 10 % of said particles have a particle size smaller than 90 nanometers.

16. The process of claim 15, wherein said dispersion which comprises a halogenated flame retardant and an aqueous carrier further comprises at least one ingredient selected from the group consisting of a surface active agent, a wetting agent, a dispersing agent, a suspending agent, a pH buffer and any mixture thereof.

17. The process of any of claims 15 and 16, wherein said milling is conducted for at least 2 hours.

18. The process of any of claims 15-17, being conducted under basic conditions.

19. A flame retardant formulation comprising the composition of any of claims 1-14.

20. The flame retardant formulation of claim 19, further comprising at least one additive selected from the group consisting of an antifoaming agent, a preservative, a stabilizing agent, a binding agent, a thickening agent and any mixture thereof.

21. The flame retardant formulation of claim 19, wherein said binding agent is selected from the group consisting of an acrylate, a polyurethane, a vinyl acetate, or a polyvinyl chloride (PVC).

22. The flame retardant formulation of claim 21, wherein said binding agent is an acrylate.

23. The flame retardant formulation of claim 19, wherein an amount of said binding agent is lower than 40 weight percentages of the total weight of the formulation.

24. The flame retardant formulation of claim 23, wherein said concentration is lower than 30 weight percentages of the total weight of the formulation.

25. The flame retardant formulation of any of claims 19-24, further comprising a flame retardant synergist.

26. The flame retardant formulation of claim 25, wherein said synergist is antimony oxide (ATO).

27. The flame retardant formulation of claim 26, wherein a molar ratio between an elemental antimony in said ATO and an elemental halogen in said halogenated flame retardant ranges from about 1:1 to about 1:6.

28. The flame retardant formulation of claim 26, wherein an amount of said flame retardant synergist is lower than 30 weight percentages of the total weight of the composition.

29. The flame retardant formulation of claim 19, wherein an amount of said thickening agent is lower than 5 weight percentages of the total weight of the formulation.

30. The flame retardant formulation of any of claims 19-29, being stable for at least three months upon storage at room temperature.

31. The flame retardant formulation of any of claims 19-29, being stable for at least 12 weeks upon storage at elevated temperatures.

32. The flame retardant formulation of any of claims 19-29, having a viscosity that ranges from about 100 to about 2,000 centipoises.

33. A flame retardant formulation comprising a carrier, a plurality of halogenated flame retardant particles having an average size smaller than about 1 micron dispersed in said carrier, and a binding agent_., wherein an amount of said binding agent is lower than 40 weight percents of the total weight of the formulation.

34. The flame retardant formulation of claim 33, wherein an average size of said plurality of halogenated flame retardant particles ranges from about 100 nanometers to about 250 nanometers.

35. The flame retardant formulation of claim 33, wherein at least 90 % of said plurality of halogenated flame retardant particles have a particle size smaller than 500 nanometers.

36. The flame retardant formulation of claim 33, wherein at least 10 % of said plurality of halogenated flame retardant particles have a particle size smaller than 90 nanometers.

37. The flame retardant formulation of any of claims 33-36, wherein said halogenated flame retardant is a brominated flame retardant.

38. The flame retardant formulation of claim 37, wherein said brominated flame retardant is decabromodiphenylether (FR-1210).

39. The flame retardant formulation of claim 37, wherein said brominated flame retardant is l,2-Bis(2,3,4,5,6-pentabromophenyl)ethane.

40. The flame retardant formulation of claim 37, wherein said brominated flame retardant is pentabromobenzyl acrylate.

41. The flame retardant formulation of any of claims 33-40, wherein an amount of said halogenated flame retardant ranges from about 1 weight percentage to about 70 weight percentages.

42. The flame retardant formulation of claim 33, further comprising at least one additive selected from the group consisting of a surface active agent, a wetting agent, a dispersing agent, a suspending agent, a pH buffer, an antifoaming agent, a preservative, a stabilizing agent, a thickening agent and any mixture thereof.

43. The flame retardant formulation of claim 33, wherein said binding agent is selected from the group consisting of an acrylate, a polyurethane, a vinyl acetate, or a polyvinyl chloride (PVC).

44. The flame retardant formulation of claim 43, wherein said binding agent is an acrylate.

45. The flame retardant formulation of claim 33, wherein said amount of said binding agent is lower than 30 weight percentages of the total weight of the formulation.

46. The flame retardant formulation of claim 45, wherein said amount is lower than 25 weight percentages of the total weight of the formulation.

47. The flame retardant formulation of any of claims 33-46, further comprising a flame retardant synergist.

48. The flame retardant formulation of claim 47, wherein said synergist is antimony oxide (ATO).

49. The flame retardant formulation of claim 48, wherein a molar ratio between an elemental antimony in said ATO and an elemental halogen in said halogenated flame retardant ranges from about 1 : 1 to about 1 :6.

50. The flame retardant formulation of claim 48, wherein an amount of said flame retardant synergist is lower than 30 weight percentages of the total weight of the composition.

51. The flame retardant formulation of claim 19, wherein an amount of said thickening agent is lower than 5 weight percentages of the total weight of the formulation.

52. The flame retardant formulation of any of claims 19-51, wherein said carrier is an aqueous carrier.

53. The flame retardant formulation of any of claims 33-51, being stable for at least three months upon storage at room temperature.

54. The flame retardant formulation of any of claims 33-51, being stable for at least 12 weeks upon storage at elevated temperatures.

55. The flame retardant formulation of any of claims 33-51, having a viscosity that ranges from about 100 to about 2,000 centipoises.

56. An article-of-manufacture comprising a flammable substrate and the flame retardant formulation of any of claims 19-55 being applied thereon.

57. The article-of-manufacture of claim 56, wherein said flammable substrate comprises a flammable textile fabric.

58. The article-of-manufacture of claim 57, wherein said flammable textile fabric is selected from the group consisting of a synthetic textile fabric, a natural textile fabric and blends thereof.

59. The article-of-manufacture of claim 58, wherein said flammable textile fabric is selected from the group consisting of wool, silk, cotton, linen, hemp, ramie, jute, acetate fabric, acrylic fabric, latex, nylon, polyester, rayon, viscose, spandex, metallic composite, carbon or carbonized composite, and any combination thereof.

60. The article-of-manufacture of claim 58, wherein said textile fabric is selected from the group consisting of cotton, polyester, and any combination thereof.

61. The article-of-manufacture of claim 57, wherein said substrate is selected from the group consisting of a drapery, a garment, linen, a mattress, a carpet, a tent, a sleeping bag, a toy, a decorative fabric, an upholstery, a wall fabric, and any other technical textile.

62. The article-of-manufacture of claim 57, characterized by an after flame time, as defined by ASTM D-6413 12 seconds ignition test, of less than 5 seconds.

63. The article-of-manufacture of claim 62, wherein said after flame time of less than 5 seconds remains substantially unchanged upon subjecting said article-of- manufacture to at least 1 washing cycle.

64. The article-of-manufacture of claim 57, characterized by an after glow time, as defined by ASTM D-6413 12 seconds ignition test, of less than 200 seconds.

65. The article-of-manufacture of claim 64, wherein said after glow time of less than 200 seconds remains substantially unchanged upon subjecting said article-of- manufacture to at least 1 washing cycle.

66. The article-of-manufacture of claim 57, characterized by a char length, as defined by ASTM D-6413 12 seconds ignition test, of less than 15 centimeters.

67. The article-of-manufacture of claim 66, wherein said char length of less than 15 centimeters remains substantially unchanged upon subjecting said article-of- manufacture to at least 1 washing cycle.

68. The article-of-manufacture of claim 57, being characterized by at least one aesthetical or textural property which is substantially the same as that of said flammable substrate per se.

69. The article-of-manufacture of claim 57, wherein said property remains substantially unchanged upon subjecting said article-of-manufacture to at least 1 washing cycle.