Patent Description:
Flame retardants inhibit, suppress, or delay ignition of flammable materials and prevent the spread of fire. They interfere with radical processes, which are important for the development of fire, act as chemical coolants and/or form a barrier between the fire and the flammable material.

Flame retardants comprising polymers are widely investigated. Char yield and barrier properties of the formed char layer are assumed to be improved with polymers as starting material.

<CIT> discloses a fireproof coating comprising a silicone-acrylic polymer, ammonium polyphosphate, melamine and dipentaerythritol as charring substance.

<CIT> discloses a flame retardant coating comprising epoxy acrylate resin, amino resin, fillers, ammonium polyphosphate, a flame-retardant charring agent and a film forming agent.

<CIT> discloses an intumescent flame retardant coating comprising modified ammonium polyphosphate, hyperbranched polyester, and polyvinyl alcohol. The coating composition is dissolved in ethanol.

<CIT> discloses an intumescent coating composition having improved char yield, comprising particulate (<NUM>-<NUM>) poly(phenylene ether), a film-forming binder, an acid source and a blowing agent.

<CIT> discloses an aqueous expansion-type fireproof coating, which is prepared by sufficiently grinding a film-forming material formed by compounding thermosetting polyurethane-acrylate emulsion and thermoplastic vinyl acetate-acrylate emulsion, ammonium polyphosphate used as an acid source, white sugar used as a carbon source, dicyandiamide and diammonium hydrogen phosphate used as gas sources and porous perlite used as a flame-retardant aid.

<CIT> discloses a fire protecting coating for steel structures, comprising a laminar silicate nano composite emulsion prepared by using an in-situ emulsion polymerization method as a film-forming base material, with charcoal-forming agent and catalyst added.

<CIT> discloses a flame retardant miscible with thermoplastics and thermosets comprising a cyclic phosphazene crosslinked by piperazine. Mixtures of the flame retardant with thermoplastics and/or thermosets have high flame-retardant effect by forming a thick char film on the surface of a resin.

All of these documents disclose flame retardants mixed with film forming polymers. Said polymers do not show an intrinsic low flammability or fire retardancy. Flame retardancy is provided by suitable flame retardant additives, which are mixed with the polymer. Variations in flame retardant performance of manufactured polymer comprising coating materials may occur due to different grade of mixing and dispersion of flame retardant additives. Furthermore leaching and ageing of flame retardant additives may occur after application of the coating material.

<CIT> discloses fire resistant materials based on inorganic-organic hybrids (IOHs) and polyamides. Improved charring of the fire resistant materials and possibly improved barrier properties of the formed char layer are mentioned but no details are disclosed. Film forming of IOHs alone is not described and fire resistance is limited to mixtures of IOHs and polyamides.

<CIT> discloses poly(silyloxytetraalkylbiphenyleneoxide)s as flame retardant film-forming materials useful as high performance injection moldable thermoplastic and dielectrics. A high charring yield is shown. The miscibility with thermosets, thermoplastics is not disclosed. The application as fire retardant coating is not disclosed.

<CIT> discloses a low smoke generating, high char forming, substantially nondripping flame resistant thermoplastic multi-block copolyester, containing a bromine flame retardant antimony trioxide, alumina trihydrate and other fillers and coupling agents. Bromine flame retardants and antimony trioxide are frequently not regarded as environmentally sustainable.

Brominated epoxy resins are widely known, e.g. from <CIT> and <CIT>. Film forming flame retardant coatings and compositions can be obtained. The same is true when brominated and other halogenated additives are used as teached in <CIT>, <CIT> and <CIT>. However brominated monomers, polymers and additives for polymer compositions are questionable from an environmental point of view and difficult to use in combination with materials from renewable sources such as cardboard, wood or polymers made from renewable monomers.

<CIT> and <CIT> disclose phosphorus-containing flame retardants and their use in polymer compositions. These flame retardants are frequently acceptable from an environmental point of view. However they often show large volatility, poor heat resistance and limited compatibility with the polymer matrix. Once phosphates have entered the water system, they can create a large proliferation of algae, which may be harmful to water quality.

Blade coating and curtain coating units are frequently used in industrial coating processes with high productivity ((<CIT>). Film forming properties of binders in flame retardant coating applications are therefore of high interest. Too low film forming properties of flame retardant coating formulations lead to reduced speed on the coating line as well as increased thickness and drying time of the coating. These issues may impair the usefulness of a flame retardant coating formulation because too low film forming properties leave it behind as unusable in industrial coating processes.

Highly branched organic inorganic hybrid polymers exhibit excellent film forming properties. <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose methods for preparing such organic inorganic hybrid polymers. In all methods significantly large amounts of solvents compared to the amount of obtained hybrid polymer are used. The hybrid polymers are either isolated as solvent based solution or contain significant amounts of solvent. <CIT> claims a hybrid polymer which is suitable as UV absorber. The disclosed data for the preparation of the UV-absorber shows that the product is a mixture of solvent, hybrid polymer with claimed amide structure and hybrid polymer with claimed amidiner structure. None of the hybrid polymers is disclosed as flame retardant hybrid polymer.

<CIT> discloses a flame-retardant and bacteriostatic 3D printing material and a preparation method thereof. The 3D printing material comprises the following components in parts by weight: <NUM> to <NUM> parts of ABS resin (acrylonitrile butadiene styrene resin), <NUM> to <NUM> parts of <NUM>-aminopropyltriethoxysilane, <NUM> to <NUM> parts of magnesium acetate, <NUM> to <NUM> parts of dodecyl gallate, <NUM> to <NUM> parts of monochlorotriazine-beta-cyclodextrin, and <NUM> to <NUM> parts of <NUM>,<NUM>-naphthalene dicarboxylic acid. The thermal insulation 3D printing material not only has the advantages of good bacteriostatic effect and high fireproof and flame-retardant performance, but is safer to use, too. The thermal insulation 3D printing material is also relatively small in thermal conductivity, good in thermal insulation effect, good in mechanical performance, long in service life, and high in marketing value.

<CIT> relates to a method for manufacturing a surface-treated particulate inorganic material, and more particularly to methods for manufacturing lightweight particulate inorganic materials, such as expanded perlite or expanded clay, coated with one or more silsesquioxanes. The surface-treated particulate inorganic material according to the present invention is suited for introduction into construction materials, such as mortar, plaster, cement and lightweight concrete, to lower the loose bulk density and improve the mechanical strength of the mixture. There is a need for film forming flame retardants with intrinsic flame retardance and unquestioned environmental acceptance.

It is therefore an object of the present invention to provide a film forming polymer with intrinsic flame retardant properties. It is a further object to provide methods for the manufacture of film forming polymer with intrinsic flame retardant properties. It is still a further object to improve the fire resistance of flammable materials by processes such as, but not limited to, mixing or coating with film forming polymer with intrinsic flame retardant properties.

The above mentioned objects are achieved by a method as defined in claim <NUM>.

According to another aspect the present invention concerns a flame retardant or component in flame retardant mixtures as defined by claims <NUM> and <NUM>.

Preferred embodiments of the different aspects of the invention are disclosed by the dependent claims.

The method according to the invention comprises two steps:.

Conversion of primary and/or secondary amines with chemical substances, obtainable from carboxylic acids or carbonic acid can provide products, wherein said products exhibit at least three covalent bonds between the functional C-atom provided by the chemical substance, obtainable from carboxylic acids or carbonic acid and the N-atoms provided by the primary and/or secondary amines and wherein two covalent bonds between the functional C-atom and the N-atoms represent a C=N double bond (<NPL>.

Primary and/or secondary amines which are bound to at least partially hydrolysable silane moieties can be converted with chemical substances, obtainable from carboxylic acids or carbonic acid as mentioned above. An example is the conversion of <NUM>-Aminopropyl-triethoxysilan [<NPL>] having a primary amine moiety only, with Methyl parahydroxybenzoate [<NPL>]:
<CHM>.

The product contains two moieties of at least partially hydrolysable silane.

A similar conversion takes place with N-(<NUM>-Aminoethyl)-<NUM>-aminopropyl-triethoxysilane [<NPL>] having a primary and a secondary amine moiety and Methyl parahydroxybenzoate:
<CHM>.

The product contains one moiety of at least partially hydrolysable silane.

Table <NUM> shows examples for suitable amines covalently bound to silane moieties according to the invention.

The invention is not limited to the above mentioned amines. Other suitable amines can easily be identified by simple trial and error. Prior to step i. the silanes may be partially hydrolysed and/or converted with metal oxide nanoparticles, wherein the nanoparticles are preferably dispersed in a suitable medium. A considerable number of such conversions of metal oxide nanoparticles with aminosilanes is presented in <CIT>.

Chemical substances obtainable from carboxylic acids or carbonic acid, which are suitable for the conversion of primary and/or secondary amines in step i. are carboxylic acids and carbonic acid, their esters, halogenides, amidoesters, amides, amidines, guanidines, isocyanates and isonitriles. Chemical substances obtainable from carboxylic acids or carbonic acid can be expressed by formula (I), (II) or (III)
<CHM>
<CHM>
<CHM>.

R<NUM>, R<NUM>, R<NUM>, R<NUM> are independently from one another selected from a group of chemical moieties of low polarity comprising at least hydrogen, saturated C<NUM>-C<NUM> alkyl, unsaturated C<NUM>-C<NUM> alkyl, N-alkyl, C<NUM>-C<NUM> alkylphenyl, aryl with <NUM> to <NUM> ring atoms, heterocyclyl with <NUM> to <NUM> ring atoms. All of these may optionally be substituted by moieties selected from a group of chemical moieties of high polarity comprising at least hydroxy, alkoxy, cyano and carbamoyl moieties. X<NUM>, X<NUM> and X<NUM> are independently from one another selected from a group comprising at least O, S and NH. One or more of R<NUM>-R<NUM> may be absent and a double or triple bond is present to the remaining R<NUM>-R<NUM> group(s);
The chemical substances used in the present invention are <NUM>-hydroxybenzoic acid, <NUM>-hydroxybenzoic acid, <NUM>-hydroxybenzoic acid, <NUM>-hydroxynaphtoic acid, <NUM>-hydroxynaphtoic acid, <NUM>-hydroxynaphtoic acid, <NUM>-hydroxynaphtoic acid and esters or amides thereof, <NUM>-hydroxybenzonitrile, <NUM>-hydroxybenzonitrile, <NUM>-hydroxybenzonitrile, <NUM>-hydroxynaphtonitrile, <NUM>- hydroxynaphtonitrile, <NUM>-hydroxynaphtonitrile, <NUM>-hydroxynaphtonitrile.

The reaction can be performed in state-of-the-art-reactors, typically at ambient pressure, moderate increased pressure (typically less then <NUM> bar) or reduced pressure (typically <NUM>-<NUM> bar). Typical temperatures for the conversion are <NUM> C°-<NUM> C°. High viscosities during conversion of polymeric amines with fatty acid which have to be dealt with by addition of solvent as described e.g. in <CIT> do not occur. The conversion of amine with carboxylic acids or substances derived thereof according to the present invention can be performed without addition of solvents. Lower viscosity means shorter reaction time and less danger for partly degrading the product.

In order to improve the inherent flame retardance of the flame retardant and to adjust its film forming properties the product from step i. is converted with at least one HO-functionalized substance of formula (IV) in step ii.

R<NUM> is selected from a group comprising at least H, saturated C<NUM>-C<NUM> alkyl, unsaturated C<NUM>-C<NUM> alkyl, and C<NUM>-C<NUM> alkylphenyl. Typical HO-functionalized substance of formula (IV) may be selected from the group consisting of water, alcohols, sugars, clays, metal hydroxides, polyalcohols and carbohydrates.

This conversion is typically performed after cooling the product from step i. to below <NUM> and proceeds rapidly. The HO-functionalized substance can react with Si-OR groups in the product from step i. Conversion with an alcohol of formula R<NUM>-OH, wherein x=y=z=<NUM> and M=H in formula (IV), can lead to at least partial exchange of R with R<NUM>. Different solubility and/or hydrophobicity of the product after step (ii) compared to the product after step (i) can thus be obtained. A special case is H<NUM>O, where x=<NUM>, y=z=<NUM> and R<NUM>=H in formula (IV). The formed Si-OH groups may perform condensation to Si-O-Si moieties. R-OH obtained from Si-OR groups can serve as diluent. Hydroxides of metals such as Al, Si, Fe may perform condensation reactions with Si-OH groups which are comparable to the condensation of two Si-OH groups. Typical hydrolysis and condensation reactions are shown below:.

When M is selected from the group of H, Al, Si, Fe usually products with highly stable Si-O-M moieties can be obtained. When M additionally can be selected from the group of Ti, Cu, Zn usually products with fairly stable Si-O-M moieties can be obtained. The stability of the Si-O-M moieties can have influence on the flame retardant during preparation, processing and application.

The HO-functionalized substance can also react with the amidine moiety in the product from step (i).

However, since the amidine moiety significantly contributes to the flame retardant properties of the product from step i. the importance of such a conversion is often limited.

Typical film forming flame retardant according to the present invention are shown by the chemical structures in formula (V), (VI), (VII) and (VIII):
<CHM>
<CHM>
<CHM>
<CHM>.

The number n is an even integer from <NUM> to <NUM>. R<NUM> is typically H, alkyl or clay and optionally connected to each other by covalent bonds. The film forming flame retardants of formula (V) and (VI) can be obtained by the same procedure in step (i). R<NUM>=alkyl represents the product right after step (i). It can be isolated and stored as a stable product. R<NUM>=H is obtained when the HO-functionalized substance H<NUM>O is added and R<NUM>=alkyl is hydrolysed but not condensed. After condensation of the Si-OH groups (R<NUM>=H) the film forming flame retardant of formula (VI) is obtained. R<NUM>=clay is obtained when clay is added in step (i), after step (i), in step (ii) or after step (ii). The film forming flame retardants of formula (VII) and (VIII) can be obtained in a similar way.

Clay consists mainly of oxides and hydroxides of the metals Si, Al, Fe, Ca, Mg, K, Na. Additionally the oxides and hydroxides of the metals Ti, Mn (<NPL>), Cu, Co, Pb, Cd and Zn (<NPL>) can be present. Clay is therefore a preferred HO-functionalized substance according to the present invention comprising different metals M in formula (IV).

The film forming flame retardant according to the present invention may after preparation be brought into contact with at least one low flammable substance selected from the group consisting of inorganic oxides, hydroxides, carbonates, sulfates, phosphates, chlorides, bromides, carbohydrates, amides, melamines, ureas, guanidines, salts of guanidines, waxes, thermoplastic materials. The presence of the film forming flame retardant according to the present invention may further reduce the flammability of the low flammable substance or facilitate its use in flame retardant mixtures. The low flammable substances contain halogen.

An embodiment of the present invention is that M is at least partly chosen to be Fe and the low flammable substance is chosen to be a chlorinated sugar.

Another embodiment of the present invention is that the film forming flame retardant prior to step (i), after step (i) or after step (ii) is mixed with hydrophobic matter selected from a group consisting of binders, thermoplastics, thermosets, waxes, oils, fats, solvents. This procedure may yield stable mixtures with good distribution of the components.

Another embodiment of the present invention is that the Z<NUM> moles of one or more silane are partially hydrolysed, before or after step (i). This is the case if for instance an added material such as clay contains water which will be used up in a partial hydrolysation of the silane.

Another embodiment of the present invention is that the content of solvent in the film forming flame retardant is less than <NUM> per <NUM> flame retardant, more preferred less than <NUM> per <NUM> flame retardant and most preferred less than <NUM> per <NUM> flame retardant. Low content of solvent in the film forming flame retardant is preferred due to SHE (Safety Health and Environment) issues. Such low content of solvent can be easily obtained by the present invention, since no solvent is needed to reduce the viscosity during preparation or to improve the miscibility of the ingredients.

Yet another embodiment of the present invention are water based formulations of the film forming the flame retardant in the form of an aqueous or water-dilutable solution or dispersion. Such formulations can be obtained by application of known emulsifying techniques. Deprotonation of hydroxyl substituted aromatic moieties can significantly improve the water solubility of products after step (ii).

In another embodiment of the present invention the flame retardant is present on a surface selected among the group consisting of paper surface, cardboard surface, wooden surface or within wooden plates, boards, laminates, particle boards.

Yet another embodiment of the present invention are articles or products comprising at least one of binders, thermoplastics, thermosets, waxes, oils, fats, solvents, wooden plates, boards, laminates, particle boards together with at least one film forming flame retardant according to the present invention.

Preparation of film forming flame retardant step (i)
Z<NUM>=<NUM>
Z<NUM>=<NUM>
Z<NUM>/Z<NUM>=<NUM>.

<NUM> moles of <NUM>-aminopropyltriethoxysilane [<NUM>-<NUM>-<NUM>] are introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. <NUM> mole of <NUM>-hydroxymethylbenzoate [<NUM>-<NUM>-<NUM>] is added as powder within <NUM>-<NUM> minutes. Heating is increased and the reaction mixture becomes clear at <NUM>. The reaction mixture is slowly heated to <NUM> and about <NUM> of destillate is collected. A clear colourless and slightly viscous product is obtained.

Preparation of film forming flame retardant step (ii)
M=H.

The product of example <NUM> is introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. H<NUM>O (<NUM> moles) is added under vigorous stirring within <NUM>-<NUM> minutes. A clear product of low viscosity is obtained.

Preparation of film forming flame retardant step (ii)
M=H, Fe.

The product of example <NUM> is introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. A dispersion of freshly precipitated Fe(OH)<NUM> (<NUM> moles) in H<NUM>O (<NUM> moles), with pH adjusted to <NUM>-<NUM> with sodium hydroxide is added under vigorous stirring within <NUM>-<NUM> minutes. A slightly redish product is obtained.

The product of example <NUM> is introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. A dispersion of freshly precipitated Fe(OH)<NUM> (<NUM> moles) in H<NUM>O (<NUM> moles), which additionally contains <NUM> moles of sucralose (<NUM>,<NUM>-Dichloro-<NUM>,<NUM>-dideoxy-β-D-fructofuranosyl-<NUM>-chloro-<NUM>-deoxy-α-D-galactopyranosid, [<NUM>-<NUM>-<NUM>] and which pH is adjusted to <NUM>-<NUM> with sodium hydroxide is added under vigorous stirring within <NUM>-<NUM> minutes. A slightly redish product is obtained.

Preparation of film forming flame retardant step (i) and step (ii)
Z<NUM>=<NUM>
Z<NUM>=<NUM>
Z<NUM>=<NUM>.

Addition of sucralose (chlorinated sugar, <NUM>,<NUM>-Dichloro-<NUM>,<NUM>-dideoxy-β-D-fructofuranosyl-<NUM>-chloro-<NUM>-deoxy-α-D-galactopyranoside, <NPL>])
M=H, Fe.

<NUM> moles of <NUM>-aminopropyltriethoxysilane [<NUM>-<NUM>-<NUM>] are introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. A mixture of <NUM> mole of <NUM>-hydroxymethylbenzoate [<NUM>-<NUM>-<NUM>] and <NUM> mole of sucralose is added as powder within <NUM>-<NUM> minutes. Heating is increased and the reaction mixture becomes clear at <NUM>. The reaction mixture is slowly heated to <NUM> and about <NUM> of destillate is collected. A clear colourless and slightly viscous product is obtained.

The product is cooled to <NUM> under stirring. A dispersion of freshly precipitated Fe(OH)<NUM> (<NUM> moles) in H<NUM>O (<NUM> moles), with pH adjusted to <NUM>-<NUM> with sodium hydroxide is added under vigorous stirring within <NUM>-<NUM> minutes. A slightly redish product is obtained.

<NUM> mole of N-(<NUM>-Aminoethyl)-<NUM>-aminopropyl-trimethoxysilane [<NUM>-<NUM>-<NUM>] is introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. <NUM> mole of <NUM>-hydroxymethylbenzoate [<NUM>-<NUM>-<NUM>] is added as powder within <NUM>-<NUM> minutes. Heating is increased and the reaction mixture becomes clear at <NUM>. The reaction mixture is slowly heated to <NUM> and about <NUM> of destillate is collected. A clear colourless and slightly viscous product is obtained.

Packaging type cardboard (ca. <NUM>/m<NUM>) has been coated with products obtained in Example <NUM>, <NUM>, <NUM>, <NUM> and <NUM> and flame tested. The cardboard samples are about <NUM> in width and <NUM> in length. They are coated by brushing two times on the front side, which is exposed to the flame and one time on the backside. Drying has been performed for <NUM> in an air stream at <NUM>. Flame: butane lighter with about <NUM> flame, top of flame in contact with cardboard sample for <NUM> seconds.

A clear difference between the uncoated reference and the coated samples has been found. All coated samples were self extinguishing within <NUM> seconds after removal of the butane flame. Weight loss is thoroughly less than <NUM>% for the coated samples and more than <NUM>% for the uncoated reference.

Corrugated cardboard has been coated with the product obtained in Example <NUM> and flame tested. The cardboard samples are about <NUM> in width and <NUM> in length. They are coated by brushing two times on the front side, which is exposed to the flame and one time on the backside. Drying has been performed for <NUM> in an air stream at <NUM>.

Flame: butane torch with <NUM>-<NUM> kW effective heat and <NUM>-<NUM> flame. Distance between corrugated cardboard surface and torch nozzle: <NUM>-<NUM>.

A clear difference between the uncoated reference and the coated sample has been found. The coated sample was self extinguishing within less than <NUM> seconds after removal of the butane flame. Weight loss is less than <NUM>% for the coated samples and more than <NUM>% for the uncoated reference.

Particle board samples have been prepared from <NUM> particle boards (Forestia <NUM>-vegg). Sample boards of <NUM> length and <NUM> width have been roll coated with the product from Example <NUM> and dried under infrared lamps (<NUM> kW). Coated boards with dry coating weight of <NUM>-<NUM>/m<NUM> are obtained. Two sample boards have been connected on their long sides by four metal screws to form a <NUM> degree corner. Similar a reference corner has been made from uncoated boards.

Each of the corners has been installed in a steel chamber which is suitable for medium scale burning tests. <NUM> above the upper corner a paper stripe has been attached in order to test if the flames can exceed the top of the corner and spread above the corner. <NUM> of gelatinized ethanol on about <NUM> rockwool has been placed at the lower corner of the sample and ignited. After <NUM> minutes, the residues of burning gelatinized ethanol on rockwool have been removed.

The reference sample started to burn vigorously after <NUM>:<NUM> minutes. After <NUM>:<NUM> minutes the flames reached and exceeded the upper corner. The paper stripe was ignited after <NUM>:<NUM> minutes. The coated sample started to burn moderately after <NUM>:<NUM> minutes. The flames reached a maximum height of <NUM> (<NUM>% of total sample height). The upper corner was not reached by the flames and the paper stripe was not ignited.

The coated particle board would withstand a fire of about <NUM> kW heat for <NUM>. The fire would not spread to burnable items above the board. The non-coated particle board would spread fire to burnable items above the board under similar conditions.

Preparation of film forming flame retardant step (i) with clay added before step (i)
Z<NUM>=<NUM>
Z<NUM>=<NUM>
Z<NUM>/Z<NUM>=<NUM>.

<NUM> moles of N-(<NUM>-Aminoethyl)-<NUM>-aminopropyl-trimethoxysilane [<NUM>-<NUM>-<NUM>] and <NUM> of clay (Montmorillonite K-<NUM>, Aldrich) are introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. <NUM> mole of <NUM>-hydroxymethylbenzoate [<NUM>-<NUM>-<NUM>] is added as powder within <NUM>-<NUM> minutes. Heating is increased and the reaction mixture becomes clear at <NUM>. The reaction mixture is slowly heated to <NUM> and about <NUM> of destillate is collected. A transparent greyish and slightly viscous product is obtained.

The product of example <NUM> is introduced in a <NUM> <NUM>-necked reaction flask and kept at <NUM> under stirring. H<NUM>O (<NUM> moles) is added under vigorous stirring within <NUM>-<NUM> minutes. The temperature raises to <NUM> due to the exothermal hydrolysis and condensation of the silane groups. This is a clear indication for the formation of amidine groups in the film forming flame retardant. Amide groups, which could be seen as an alternative product of the synthesis would not catalyse the hydrolysis and condensation in a similar way and thus the temperature would raise much slower and to a lower value.

<NUM> of a <NUM>% w/w solution of sodium hydroxide in water is thereafter added. A clear product of low viscosity is obtained.

<NUM>% w/w of the final product of example <NUM> is introduced in a <NUM> <NUM>-necked reaction flask and heated to <NUM> under stirring. A dispersion of freshly precipitated Fe(OH)<NUM> (<NUM> moles) in H<NUM>O (<NUM> moles), which additionally contains <NUM> moles of sucralose (<NUM>,<NUM>-Dichloro-<NUM>,<NUM>-dideoxy-β-D-fructofuranosyl-<NUM>-chloro-<NUM>-deoxy-α-D-galactopyranosid, [<NUM>-<NUM>-<NUM>] and which pH is adjusted to <NUM>-<NUM> with sodium hydroxide is added under vigorous stirring within <NUM>-<NUM> minutes. A slightly redish product is obtained.

Particle board samples have been prepared from <NUM> particle boards (Forestia <NUM>-vegg). Sample boards of <NUM> length and <NUM> width have been roll coated with the product from Example <NUM> and <NUM> and dried under infrared lamps (<NUM> kW). Coated boards with dry coating weight of <NUM>-<NUM>/m<NUM> are obtained. Two sample boards have been connected on their long sides by four metal screws to form a <NUM> degree corner. Similar a reference corner has been made from uncoated boards.

Each of the corners has been installed in a steel chamber which is suitable for medium scale burning tests. <NUM> of gelatinized ethanol in an aluminium char has been placed at the lower corner of the sample and ignited. After <NUM> minutes, the residues of burning gelatinized ethanol in the aluminium char have been removed. The heat release measured by weight loss was <NUM>-<NUM> kW during the <NUM> minutes test and the area covered by heat from the burning ethanol was <NUM>-<NUM><NUM>. The results are shown in the table below:.

The weight loss and the maximum flame height of the particle board samples with film forming polymer according to the present invention is significantly lower than the respective weight loss and maximum flame height of the uncoated particle board sample.

<NUM> of the product of example <NUM> is mixed with <NUM> glycerol (HO-functionalized substance) and warmed to <NUM>. Strong foaming occurs due to the reaction of glycerol with the hydrolysable moieties followed by emission of methanol. The strong foaming is a clear indication for the melt strength and the film forming properties of the film forming flame retardant according to the present invention.

Claim 1:
Method for the preparation of a film forming flame retardant comprising nitrogen and silicon in its chemical composition, said method comprising the following steps:
i. conversion of Z<NUM> moles of amine moiety, selected from the group of primary and secondary amine and covalently bound to Z<NUM> moles of one or more at least partially hydrolysable silane moiety, with Z<NUM> moles of a chemical substance selected from a group of chemical substances obtainable from carboxylic acids or carbonic acid and represented by formula (I), (II) or (III)
<CHM>
<CHM>
<CHM>
wherein
Z<NUM> is a number ><NUM>
Z<NUM> is a number ><NUM>
<MAT>
Z<NUM> is an number ><NUM>
<MAT>
R<NUM>, R<NUM>, R<NUM>, R<NUM> are independently from one another selected from a group of chemical functional groups of low polarity consisting of hydrogen, saturated C<NUM>-C<NUM> alkyl, unsaturated C<NUM>-C<NUM> alkyl, N-alkyl, C<NUM>-C<NUM> alkylphenyl, aryl with <NUM> to <NUM> ring atoms, heterocyclyl with <NUM> to <NUM> ring atoms, all of these optionally substituted by moieties selected from a group of chemical moieties of high polarity consisting of hydroxy, alkoxy, cyano and carbamoyl moieties,
X<NUM>, X<NUM> and X<NUM> are independently from one another selected from a group consisting of O, S and NH;
ii. conversion with at least one HO-functionalized substance of formula (IV)

        Mx(OH)yR<NUM>z     (IV)
wherein M is selected from the group consisting of Al, Si, Ti, Fe, Cu, Zn,
x, z are integer numbers in the range from <NUM> to <NUM>,
y is an integer number in the range from <NUM> to <NUM>
<MAT>
and R<NUM> is selected from a group consisting of H, saturated C<NUM>-C<NUM> alkyl, unsaturated C<NUM>-C<NUM> alkyl, and C<NUM>-C<NUM> alkylphenyl, while
the chemical substance of formula (I), (II) or (III) is selected from a group consisting of <NUM>-hydroxybenzoic acid, <NUM>-hydroxybenzoic acid, <NUM>-hydroxybenzoic acid, <NUM>-hydroxynaphtoic acid, <NUM>-hydroxynaphtoic acid, <NUM>-hydroxynaphtoic acid, <NUM>-hydroxynaphtoic acid and esters or amides thereof, <NUM>-hydroxybenzonitrile, <NUM>-hydroxybenzonitrile, <NUM>-hydroxybenzonitrile, <NUM>-hydroxynaphtonitrile, <NUM>-hydroxynaphtonitrile, <NUM>- hydroxynaphtonitrile, hydroxynaphtonitrile.