NEW FLAME RETARDANT

Description

Subject matter of the invention

[0001] The invention relates to a flame retardant and a plastic composition comprising this flame retardant. Background of the invention

[0002] Numerous substances are known for flame-retardant treatment of plastics, which can be used alone or in combination with other substances that provide similar or synergistic flame-retardant properties.

[0003] The use of polyphosphate salts of 1,3,5-triazine compounds for such applications is known from the prior art. These are incorporated, in particular, into polyamides and polyesters (with and without glass fibers), which are typically processed by injection molding, i.e., at elevated temperatures, using plastic extrusion. WO 00 / 02869 A1 discloses such polyphosphate salts of 1,3,5-triazine compounds, which have a number-average degree of condensation > 20 and a triazine compound to phosphorus molar ratio (M / P) of < 1.1.

[0004] EP 0 974 588 B1 describes 1,3,5-triazine derivatives of polyacids containing phosphorus, sulfur, and oxygen, as well as a process for their preparation. The ratio of 1,3,5-triazine compound to phosphorus in the disclosed triazine polyphosphate derivatives is > 1.1.

[0005] EP 1 095 030 B1 also describes a polyphosphate salt of a 1,3,5-triazine compound. This has a 1,3,5-triazine content of 1.1 to 2.0 mol of a triazine compound selected from the group consisting of melamine, melam, melem, melon, ammelin, ammelide, 2-ureidomelamine, acetoguanamine, benzoguanamine and diaminephenyltriazine, per mol of phosphorus atom.

[0006] These polyphosphate salts, known from the prior art, generally only provide moderate flame retardancy when incorporated into a composition requiring protection. Furthermore, these phosphate salts tend to migrate out of the material over time. This not only further reduces the flame-retardant effect, but the release of these salts also poses health risks, particularly in household applications. Additionally, processing the product with an extruder, especially at temperatures above 250°C, leads to the decomposition of the flame retardant and a rough surface on the extruded material. This effect is particularly pronounced when the flame retardant is incorporated into a glass fiber reinforced plastic.Processing becomes particularly difficult when, in addition to the primary flame retardant and fillers, other synergistic flame retardants are also present, for example products based on phosphinates such as aluminium diethyl phosphinate.

[0007] US 2005 / 173684 A discloses a flame retardant composition comprising phosphinates (component A) in combination with nitrogen-containing compounds (component B). These may be selected from: a) Polyphosphate of melamine or one of its condensation products, wherein the pH of a 10 wt% aqueous solution is ≥ 4 (B1), b) Melamine polymetaphosphate, the 10 wt% aqueous solution of which has a pH between 2.5 and 4.5 (B2), c) Composite salt (= double salt, cf.

[0021] ) of melamine, melam and / or melem with polyphosphoric acid, wherein the amounts of the respective nitrogen carriers can vary in the range of 0.05 to 1 mol (B3). TASK

[0008] Against this background, the object of the present invention was therefore to provide a preferably halogen-free, environmentally friendly, and in particular recyclable flame retardant based on a polyphosphate salt of the aforementioned type, which exhibits similar or even better flame-retardant properties than those known from the prior art and which, moreover, has a lower tendency to migrate, so that a durable and safe flame retardant can be achieved, especially for polymer materials. The present invention is also intended to ensure unrestricted processability of the polymer material containing the flame retardant, even in multi-step processing and at high temperatures. Description of the invention

[0009] This problem is solved by a flame retardant according to claim 1.

[0010] The flame retardant according to the invention comprises at least one polyphosphate salt having cations of at least one 1,3,5-triazine compound, one of which is melamine. It is therefore a polyphosphate salt of a 1,3,5-triazine compound. Preferably, the polyphosphate salt comprises cations of two or more 1,3,5-triazine compounds. The "cations of at least one 1,3,5-triazine compound" of the polyphosphate salt are preferably the corresponding cations of the 1,3,5-triazine compound(s) obtained by protonation. These are generally the corresponding ammonium ions of the 1,3,5-triazine compound(s), which typically contain amino groups, such as melamine, melam, or melem.

[0011] According to the invention, the flame retardant further comprises at least one, i.e., one or more condensation products of melamine.

[0012] The term "condensation product" of melamine refers to molecules formed by a condensation reaction of two or more melamine molecules, such as melam, melem, or melon. The term also includes the protonated forms of these compounds, i.e., the corresponding cations obtained through protonation.

[0013] In a preferred embodiment of the invention, the flame retardant according to the invention has such a cationic form of a condensation product of melamine, wherein this cation is preferably a cation of the polyphosphate salt, i.e., another of the at least one 1,3,5-triazine compound of the polyphosphate salt. The polyphosphate salt then thus has at least cations of melamine and a condensation product of melamine, such as melam. In this case, the flame retardant can consist exclusively of the polyphosphate salt. Such a polyphosphate salt can be obtained by adding the condensation product of melamine during production.

[0014] In another version, the flame retardant, which contains the condensation product of melamine in the form of a cation bound to the polyphosphate salt, may include further components.

[0015] However, the condensation product can also be present in the flame retardant as an additional component to the polyphosphate salt, so that the flame retardant is a composition that includes both the polyphosphate salt and the condensation product of melamine, and possibly other components. In such a composition, the condensation product can be present in non-ionic form and / or as a cation of a salt that is not the polyphosphate salt.

[0016] Of course, the flame retardant can also represent a combination of the above descriptions, i.e., one of the cations of the polyphosphate salt is the protonated form of a condensation product of melamine, and the flame retardant has as an additional component at least one condensation product of melamine in non-ionic form and / or as a cation of an additional salt.

[0017] The polyphosphate salt of the flame retardant according to the invention can be simplified and represented by the following general formula: where "T x" represents at least one 1,3,5-triazine compound and "n" indicates the average degree of condensation. The chain ends of the polyphosphate salt (formed by -H and -OH, respectively, in the structural formula above) can also be formed by a 1,3,5-triazine compound.

[0018] The inventors were able to determine that the combination according to the invention, comprising a polyphosphate salt containing melamine cations and at least one melamine condensation product, exhibits particularly pronounced flame-retardant properties. Furthermore, the migration behavior of the polyphosphate salt is advantageously influenced by such a combination; that is, the polyphosphate salt is washed out of the material to be protected, particularly a polymer material, to a significantly lesser extent.

[0019] Without being bound to this theory, the inventors assume that the condensation product of melamine bridges the individual macromolecules of the polyphosphate salt to one another via hydrogen bonds, i.e., that larger supramolecular agglomerates are formed through intermolecular interactions, which are significantly more difficult to migrate out of the material. The condensation product therefore acts as a kind of "supramolecular crosslinker" and thus strengthens the anchoring of the flame-retardant polyphosphate salt in or on the matrix material to be protected, into which the flame retardant is incorporated or onto which it is applied.

[0020] The at least one condensation product of melamine also stabilizes the polyphosphate salt. In synergistic combinations with acidic flame retardants such as the aluminum phosphinates mentioned earlier, for example, no acid-base exchange reactions occur, so these combinations can be used even at high temperatures, such as those common in extrusion, without decomposition of the polyphosphate salt.

[0021] In pure melamine polyphosphate, the melamine cation can be replaced in the first step by the more acidic aluminum cation. The melamine can then potentially sublimate and release phosphinic acid.

[0022] Furthermore, condensed melamine derivatives have a significantly higher decomposition temperature (> 600°C) and are therefore more stable than melamine (decomposition temperature > 350°C) during plastics processing.

[0023] The flame retardant according to the invention consequently ensures unrestricted processability of the plastic, even when processed over several process steps and at high temperatures.

[0024] While the flame-resistant plastic is repeatedly reshaped and processed within the value chain (extrusion, injection molding, etc.), the physical properties of the plastic are not changed or only minimally changed.

[0025] In addition, plastics containing flame retardants according to the invention are also ideally suited for recycling in a planned circular economy for plastics, since toxic and / or difficult-to-biodegrade flame retardants can be avoided.

[0026] Particularly preferred is the inclusion of at least one condensation product of melamine as one of the cations of the polyphosphate salt in the flame retardant, i.e., the condensation product of melamine is one of the at least one 1,3,5-triazine compound whose cations include the polyphosphate salt.

[0027] Such a polyphosphate salt can be represented by the following structural formula: where "T x1" is melamine and "T x2" is the condensation product of melamine, such as melam. The chain ends of the polyphosphate salt (formed by -H and -OH, respectively, in the structural formula above) can also be formed by a 1,3,5-triazine compound. One of the possible resonance structures of the protonated form of melam, i.e., a possible T x2 H +< , is shown below:

[0028] One of the possible resonance structures of the protonated form of Melem, i.e., a possible T x2 H +< , is shown below:

[0029] In embodiments where the condensation product of melamine is one of the cations of the polyphosphate salt, the effects according to the invention are particularly pronounced. Without being bound to this theory, the inventors assume that the existing bond to at least one macromolecule of the polyphosphate salt in this case facilitates the formation of supramolecular agglomerates with further macromolecules of the polyphosphate salt, which increase stability during processing.

[0030] In a particularly preferred embodiment of the invention, the flame retardant has a minimum amount of substance of the condensation product in relation to the amount of substance of the melamine cation of the polyphosphate salt.

[0031] The amount of melamine cation present in the flame retardant is X, and the amount of melamine condensation product present in the flame retardant (e.g., as the polyphosphate salt cation) is Y. The sum of these two components is therefore X + Y. The proportion of the condensation product in this sum is ≥1%, i.e., Y X + Y ≥ 0 , 01

[0032] Preferably the mole fraction of Y is at least 2%, particularly preferably at least 3%, even more preferably at least 5%, and most preferably at least 10%.

[0033] Preferably, the mole fraction of Y is at most 50%, more preferably at most 20%, particularly preferably at most 15%, even more preferably at most 12%, and most preferably at most 10%.

[0034] The mole fraction of Y is preferably in the range of 0.1 to 20%, more preferably in the range of 1 to 15%, even more preferably in the range of 2 to 12% and most preferably in the range of at most 5 to 10%.

[0035] The average degree of condensation n of the polyphosphate salt is preferably at least 10, more preferably at least 20, even more preferably at least 50, and most preferably at least 100. A higher degree of condensation enhances the effect according to the invention, since this results in larger agglomerates of polyphosphate salt and condensation product, thus further reducing the migration tendency of the polyphosphate salt.

[0036] The mean degree of condensation n of the polyphosphate salt can be determined by known methods, such as NMR spectroscopy, J. Am. Chem. Soc. 78, 5715 (1956).

[0037] The mean degree of condensation is also referred to as the mean chain length of the polyphosphate salt.

[0038] The condensation product of melamine is preferably selected from the group consisting of melam, melem, or melon. Due to its linear structure, melam is particularly suitable for linking the macromolecules of the polyphosphate salt and is therefore especially preferred.

[0039] A 10 wt% aqueous suspension of the flame retardant comprising the polyphosphate preferably has a pH value of ≥ 5 at 25°C. The pH value of a 10 wt% aqueous suspension of the flame retardant according to the invention is determined by stirring 25 g of the flame retardant and 225 g of pure water at 25°C in a vessel and determining the pH value of the resulting aqueous suspension using conventional means such as a pH meter or indicator paper. A pH value in the range of 5 to 10 is particularly preferred, 5 to 8 is more preferably preferred, and 5 to 7 is most preferably preferred.

[0040] Preferably, a 10 wt% aqueous suspension of the polyphosphate of the flame retardant according to the invention has a pH value of ≥ 5 at 25°C. A pH value in the range of 5 to 10 is particularly preferred, 5 to 8 is more preferably preferred, and 5 to 7 is most preferably preferred.

[0041] By maintaining the pH value of the flame retardant and / or the polyphosphate salt within the ranges defined above, interactions with the matrix material to be protected, including any synergistic flame retardants it contains, are minimized. Consequently, the flame retardant can be used in a wide variety of matrix materials, particularly pH-sensitive ones.

[0042] The flame-retardant activity, and in particular the stability of the flame retardant during processing, can be improved by controlling the molar ratio of the sum of the amounts of the at least one 1,3,5-triazine compound and the amount of the condensation product to the amount of phosphorus in the polyphosphate salt. This ratio is also referred to as the M / P ratio in the relevant literature. The sum of the amounts of the at least one 1,3,5-triazine compound and the amount of the condensation product of melamine also includes the protonated forms, such as the protonated form of melamine bound to the polyphosphate salt.

[0043] The inventors were able to determine that with an M / P ratio ≤ 1.3, preferably ≤ 1.2, more preferably ≤ 1.1, particularly good flame-retardant properties and outstanding processability of the protected polymer material are obtained.

[0044] The polyphosphate salt according to the invention need not exclusively comprise cations of the at least one 1,3,5-triazine compound, but can also include other cations, such as ammonium ions. However, to maximize the flame-retardant effect, the majority of the cations are preferably formed from cations of the at least one 1,3,5-triazine compound.

[0045] In a particularly preferred embodiment, the mole fraction of the cations of the at least one 1,3,5-triazine compound relative to the mole fraction of the cations of the polyphosphate salt is preferably ≥ 50%, more preferably ≥ 70%, even more preferably ≥ 80%, most preferably ≥ 90%, and most preferably ≥ 95%. In one embodiment, the polyphosphate salt comprises exclusively cations of the at least one 1,3,5-triazine compound.

[0046] The mole fraction of the melamine cations in the cations of the at least one 1,3,5-triazine compound is ≥ 50%, preferably ≥ 70%, more preferably ≥ 80%, and most preferably ≥ 90%.

[0047] If the polyphosphate salt comprises cations of a condensation product of melamine, the mole fraction of these cations to the mole fraction of the cations of the polyphosphate salt is preferably ≥ 5%, more preferably ≥ 10%, even more preferably ≥ 15%, and most preferably ≥ 20%.

[0048] As already described, the polyphosphate salt according to the invention is characterized by particularly advantageous migration behavior and high stability during processing. Even solvents such as water cannot remove the flame retardant according to the invention from the matrix material into which it is incorporated, or only to an extremely small extent. This effect is particularly pronounced when the flame retardant according to the invention has extremely low water solubility. This is of utmost importance for plastic products, especially for outdoor use or in applications with high humidity.

[0049] The water solubility of the flame retardant according to the invention is preferably less than 0.1 g / 100 ml, more preferably ≤ 0.05 g / 100 ml. The water solubility is determined in this context by preparing a 10 wt.% aqueous suspension of the flame retardant in water at 25 °C and measuring, after 24 h, how much of the flame retardant according to the invention has dissolved in the water.

[0050] The water solubility of the polyphosphate salt of the flame retardant according to the invention is preferably less than 0.1 g / 100 ml, more preferably ≤ 0.05 g / 100 ml.

[0051] The flame retardant according to the invention is characterized by an exceptionally high decomposition temperature. The decomposition temperature can be determined by thermogravimetric analysis (TGA).

[0052] In a preferred embodiment of the invention, the decomposition temperature, i.e. the temperature at which a mass loss of the dry flame retardant of 2 wt% occurs during a DSC measurement at a heating rate of 10 K / min, is above 300°C, particularly preferably above 320°C, and even more preferably above 350°C.

[0053] Preferably, the decomposition temperature of the polyphosphate salt of the flame retardant according to the invention, i.e., the temperature at which a mass loss of the dry flame retardant of 2 wt% occurs during a DSC measurement at a heating rate of 10 K / min, is above 300°C, particularly preferably above 320°C, and even more preferably above 350°C.

[0054] In a preferred embodiment, the flame retardant comprises at least one further flame-retardant component, preferably selected from nitrogen bases, melamine derivatives, phosphates, pyrophosphates, polyphosphates, organic and inorganic phosphinates, organic and inorganic phosphonates and derivatives of the aforementioned compounds, preferably selected from ammonium polyphosphate, ammonium polyphosphate particles coated and / or cross-linked with melamine, melamine resin, melamine derivatives, silanes, siloxanes, silicones or polystyrenes, as well as 1,3,5-triazine compounds, including melamine, melam, melem, melon, ammelin, ammelide, 2-ureidomelamine, acetoguanamine, benzoguanamine, diaminephenyltriazine, melamine salts and adducts, melamine cyanurate, melamine borate, melamine orthophosphate, melamine pyrophosphate, dimelamine pyrophosphate, aluminum diethylphosphinate. Melamine polyphosphate, oligomers and polymers 1,3,5-Triazine compounds and polyphosphates of 1,3,5-triazine compounds, guanine, piperazine phosphate, piperazine polyphosphate, ethylenediamine phosphate, pentaerythritol, dipentaerythritol, boron phosphate, zinc borate, zinc phosphate, zinc pyrophosphate, 1,3,5-trihydroxyethyl isocyanurate, 1,3,5-triglycidyl isocyanurate, triallyl isocyanurate, and derivatives of the aforementioned compounds. In a preferred embodiment, the flame retardant contains waxes, silicones, siloxanes, fats, or mineral oils to improve the dispersibility of the further flame retardant component.

[0055] The flame retardant according to the invention can also contain further polyphosphate salts, wherein the polyphosphate salt preferably comprises cations of at least one 1,3,5-triazine compound.

[0056] Furthermore, inorganic pigments and fillers (TiO₂, Al₂O₃, Ba₂SO₄, or similar) can be included in the flame retardant according to the invention. Inorganic pigments used for laser welding, laser marking, or laser structuring are particularly preferred. Examples include copper salts such as copper hydroxide phosphate, copper pyrophosphate, or similar compounds.

[0057] Particularly preferably, the flame retardant according to the invention comprises at least one compound selected from the group consisting of phosphinates, diphosphinates such as aluminium diethyl phosphinate, zinc borates and zinc phosphates.

[0058] In a preferred embodiment, the ratio of polyphosphate salt to the at least one further flame retardant component in the flame retardant is 1:18 to 1:4, more preferably 1:9 to 1:2, even more preferably 1:6 to 1:1.5 and particularly preferably 1:4 to 1:1.25.

[0059] The flame retardant according to the invention is particularly preferably halogen-free. In this context, halogen-free means that the weight fraction of halogen in the weight of the flame retardant is ≤ 1 wt.%, preferably ≤ 0.5 wt.%, particularly preferably ≤ 0.2 wt.% and most preferably ≤ 0.1 wt.%.

[0060] In a preferred embodiment of the invention, the polyphosphate salt of the flame retardant is halogen-free, i.e., it has a halogen content of ≤ 1 wt.%, preferably ≤ 0.5 wt.%, more preferably ≤ 0.2 wt.%, and most preferably ≤ 0.1 wt.%.

[0061] The present invention also relates to a plastic composition comprising a plastic matrix and the flame retardant according to the invention. The term "matrix" within the meaning of this invention includes any material, in particular any plastic or mixture of plastics, into which the flame retardant according to the invention can be incorporated or onto which the flame retardant according to the invention can be applied as a coating. Plastics are understood to be materials that consist of ≥ 50 wt.%, preferably ≥ 70 wt.%, of macromolecules.

[0062] "Macromolecules" are molecules composed of one or more identical or similar structural units, the constitutional repeating units (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"), A.D. McNaught, A. Wilkinson, Blackwell Scientific Publications, Oxford (1997), S.J. Chalk. ISBN 0-9678550-9-8). Such macromolecules have more than 10 repeating units, preferably more than 15. The molar mass is preferably at least 3,000 g / mol, more preferably at least 5,000 g / mol, even more preferably at least 7,000 g / mol, and most preferably at least 10,000 g / mol.

[0063] Plastics containing the flame retardant according to the invention, preferably halogen-free, are ideally suited for being returned to the cycle and recycled after use. This is especially true if they contain no or only a small proportion of halogens.

[0064] It has been shown that flame retardants according to the invention can be used advantageously, in particular, in the production of plastic compositions by extrusion. Without significantly affecting the processing properties of the various plastic matrices, the flame retardants according to the invention can be easily incorporated into these processes. When using the flame retardants according to the invention, the thermal and mechanical properties of the plastic matrix are also only minimally affected after processing.

[0065] The polymer matrices in which the flame retardant can be used are preferably selected from filled and unfilled vinyl polymers, olefin copolymers, thermoplastic elastomers based on olefins, cross-linked thermoplastic elastomers based on olefins, polyurethanes, filled and unfilled polyesters and copolyesters, styrene block copolymers, filled and unfilled polyamides and copolyamides, polycarbonates, and poly(meth)acrylates. Use in polymethacrylates and polyacrylates is particularly preferred, most preferably in polymethyl methacrylates. In this context, it is especially advantageous that the addition of the flame retardant according to the invention results in a transparent polymethacrylate or polyacrylate.

[0066] In principle, the flame retardants according to the invention can be used for any plastic matrices. They are suitable for polyamides (PA), polyesters such as polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyolefins such as polypropylene (PP), polyethylene (PE), polystyrene (PS), styrene block copolymers such as ABS, SBS, SEES, SEPS, SEEPS and MBS, polyurethanes (PU), especially rigid and flexible PU foams, poly(meth)acrylates, polycarbonates, polysulfones, polyetherketone, polyphenylene oxide, polyphenylene sulfide, epoxy resins, polyvinyl butyral (PVB), polyphenylene oxide, polyacetal, polyoxymethylene, polyvinyl acetal, polystyrene, acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), polycarbonate, polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polyethersulfone, polysulfonate, polytetrafluoroethylene (PTFE), polyurea, formaldehyde resins, Melamine resins, polyether ketone, polyvinyl chloride, polylactide, silicones, polysiloxane, phenolic resins, poly(imide), bismaleimide triazine,Thermoplastic elastomers (TPE), thermoplastic urethane-based elastomers (TPU-U), thermoplastic polyurethane, copolymers, rubbers and / or mixtures of the aforementioned polymers.

[0067] The flame retardant according to the invention is particularly suitable for use in plastic matrices processed at particularly high temperatures, such as polyamides or polyesters. Its use in PA 6.6 or PA 6, or also in high-temperature polyamides such as polyamide 4.6, semi-aromatic polyamides, and polyamide 12, is especially preferred. Due to the high thermal stability of the flame retardant according to the invention, it can also be used for such plastics. Its use in glass fiber-reinforced engineering plastics is particularly preferred, especially glass fiber-reinforced PA 6, PA 66, glass fiber-reinforced mixtures thereof, and glass fiber-reinforced PBT.

[0068] In a preferred embodiment, the polymer matrix is ​​selected from filled or unfilled and / or reinforced polyamides, polyesters, polyolefins, and polycarbonates. A filled polymer matrix is ​​understood to be a polymer matrix containing one or more fillers, in particular those selected from the group consisting of metal hydroxides, especially alkaline earth metal hydroxides, alkali metal hydroxides, and aluminum hydroxides; silicates, especially layered silicates and functionalized layered silicates such as nanocomposites; bentonite; alkaline earth metal silicates and alkali metal silicates; carbonates, especially calcium carbonate; as well as talc, clay, mica, silica, calcium sulfate, barium sulfate, aluminum hydroxide, magnesium hydroxide, glass fibers, glass particles and glass beads, wood flour, cellulose powder, carbon black, graphite, boehmite, and dyes.

[0069] All the listed fillers can be in the usual form and size known to those skilled in the art, as well as in nanoscale form, i.e. as particles with an average diameter in the range of approximately 1 to approximately 200 nm, and can be used in the plastic compositions.

[0070] Glass fibers are preferably added as a filler to reinforce the plastic composition and increase its mechanical stability.

[0071] In a preferred embodiment, the flame retardant is incorporated in an amount of 1 to 40 wt.%, more preferably between 1 and 30 wt.%, particularly preferably 1 to 25 wt.%, based on the total weight of the plastic composition with flame retardant.

[0072] These proportions ensure good flame retardancy while simultaneously preventing significant changes to the properties of the plastic matrix during both processing and use, particularly with regard to mechanical properties and heat resistance.

[0073] The flame retardant can be incorporated into the matrix material to be protected, in particular the plastic matrix material, by various methods. Firstly, the flame retardant can be incorporated during the molding process. If the plastic matrix material is processed, for example, by extrusion, the flame retardant can be added during the extrusion process, e.g., as an easily dosable powder mixture, as granules, or by means of a masterbatch. A masterbatch within the meaning of the present invention is a polymer material in the form of granules or powder, which contains the flame retardant and any other additives in concentrations higher than those in the final application. The masterbatch or various masterbatches are used to produce the plastic composition with the plastic matrix material without the flame retardant contained in the masterbatch in such quantities or concentrations as are required for the final application.Masterbatches are blended in proportions so that the final product has the desired concentration of the flame retardant. Compared to adding various substances in the form of pastes, powders, or liquids, masterbatches offer the advantage of high process reliability and are very easy to process and dose. Extrusion ensures that the flame retardant is evenly distributed throughout the plastic matrix.

[0074] The incorporation of the composition into the polymer material can be detected using suitable analytical techniques, in particular NMR spectroscopy or IR spectroscopy.

[0075] A polyphosphate salt is also described as defined in claims 1 to 10, preferably claims 2 to 10, in particular a polyphosphate salt comprising cations of at least two 1,3,5-triazine compounds, wherein one of the at least one 1,3,5-triazine compound is melamine and wherein another of the at least two 1,3,5-triazine compounds is a condensation product of melamine, preferably melam.

[0076] The invention also relates to the use of a condensation product of melamine to increase the flame-retardant effect and / or the stability and / or processability of a polyphosphate salt, which preferably comprises cations of melamine.

[0077] The invention also relates to the use of the flame retardant according to the invention for the flame-retardant treatment of materials, in particular plastic materials, preferably thermoplastic plastic materials.

[0078] The present invention also relates to the use of a flame retardant according to the invention as a coating material, preferably as a coating material for wood, metal, or a plastic matrix material. Its use for so-called natural fiber-reinforced plastics, preferably wood-plastic composites, i.e., composite materials made of wood fibers and plastics, is particularly preferred. Coating, according to DIN 8580, is understood to be a process in which a firmly adhering layer of formless material is applied to the surface of a workpiece. EXAMPLES Raw materials:

[0079] name Manufacturer Purity / M n CAS Phosphoric acid FOSFA 85% by weight in water 7664-38-2 melamine BASF 99.9 wt.% 108-78-1 Melam - 99.9 wt.% 3576-88-3 Aluminum diethyl phosphinate Exolit OP 1230 Clariant 99.9 wt.% 225789-38-8 Measurement methods: UL94 Test

[0080] For each measurement, five test specimens were clamped in a vertical position and held to the free end of a Bunsen burner flame. The burning time and the falling of burning parts were evaluated using a cotton ball placed under the test specimen. The tests and the application of a 2 cm high Bunsen burner flame were carried out according to the specifications of Underwriters Laboratories, standard UL94.

[0081] The results are classified into fire protection classes V-0 to V-2. V-0 means that the total burning time of the five tested specimens was less than 50 seconds and the cotton ball was not ignited by dripping, glowing, or burning components of the specimen. Classification V-1 means that the total burning time of the five tested specimens was more than 50 seconds but less than 250 seconds, and the cotton ball was also not ignited. V-2 means that while the total burning time of the five tested specimens was less than 250 seconds, the cotton ball was ignited by dripping components of the specimen in at least one of the five tests. The abbreviation NC stands for "not classifiable" and means that a total burning time of more than 250 seconds was measured. In many cases of non-classifiability, the specimen burned completely. Thermogravimetric analysis

[0082] Thermogravimetric analyses (TGA) were performed using a simultaneous thermogravimetric differential scanning calorimetry (STA / TG-DSC) instrument, model STA409 PC / 3 / H Luxx, manufactured by Netzsch Gerätebau GmbH, at temperatures ranging from 30 to 500°C under a nitrogen atmosphere with a heating rate of 10 K / min. Sample weights were 12–15 mg. The NETZSCH Proteus software was used to analyze the TGA curves. pH value determination, conductivity measurement

[0083] The pH value was determined according to EN ISO 787-9. For this purpose, a 10 wt% suspension of the flame retardant according to the invention was prepared in distilled water (temp. 25°C) by shaking. Two parallel samples were prepared, whereby the difference between the measured pH values ​​was not allowed to exceed 0.3 units.

[0084] A combined pH / conductivity sensor (Mettler Toledo, SevenMulti S470 Excellence) was used for the determination, so that the conductivity of the above suspension could be determined simultaneously with the pH value. Determination of the bound 1,3,5-triazine compounds

[0085] The concentrations of 1,3,5-triazine compounds bound ionically to the polyphosphate salt, i.e., melamine and its homologs, were determined using HPLC-UV. First, the free fraction of the corresponding compounds in a sample was determined, followed by the total fraction after hydrolysis with concentrated phosphoric acid. The concentration of bound 1,3,5-triazine compounds is calculated as the difference. For hydrolysis, between 20 and 30 mg (+ / - 0.1 mg) of a sample was placed on an analytical balance into a 100 ml beaker, made up to 50.00 g with 85% phosphoric acid, and kept at 100°C for 30 minutes.

[0086] The substances were identified in the UV range at a wavelength of 230 nm by determining the HPLC retention times on two different column phases, "reversed phase" and "strong cation exchanger" (see table below). SYNERGI 4u Hydro-RP Reversed phase PARTISIL 10-SCX Cation exchanger Wet nursery 2.4 + / - 0.11 min 3.6 + / - 1.0 min Ammelide 2.5 + / - 0.11 min 2.5 + / - 0.2 min melamine 2.8 + / - 0.11 min 4.6 + / - 1.0 min Melem 19.1 + / - 0.08 min 2.9 + / - 0.2 min Melam 41.6 + / - 0.3 min 11.8 + / - 4.0 min Assessment of processability, flame retardancy results

[0087] The processability was determined by incorporating PA6 with common processing agents during extrusion with a twin-screw extruder.

[0088] Using a Thermo Fisher Scientific Inc. Process 11 twin-screw extruder, a granulate with a particle size of approximately 3 x 1 x 1 mm was produced under typical PA6 extrusion conditions. The extrusion process was carried out at a throughput of approximately 5 kg / h, a screw speed of 300 rpm, and an extrusion zone temperature of approximately 280°C. Processability, particularly any irregularities and bubble formation, was assessed by microscopic examination.

[0089] Subsequent hot pressing yielded UL94-compliant test specimens exhibiting the flame-retardant properties listed in the table below. The weight fraction of the synergistic flame-retardant mixture of aluminum diethyl phosphinate Exolit OP 1230 and the flame retardant according to the invention (weight ratio 2:1) was 19% each. Determination of M / P ratios

[0090] The determination of the total phosphorus and nitrogen content for calculating the M / P ratio was carried out as described below.

[0091] The total phosphorus content was determined via a photometric P₂O₅ measurement. For this purpose, a sample was hydrolyzed using a closed acid digestion (65% nitric acid) in a microwave system at a maximum power of 1,000 watts for a total of 30 minutes. The photometric determination was performed at 430 nm against a reagent blank.

[0092] Nitrogen was determined titrimetrically. For this purpose, the nitrogen bound as ammonium in the sample was separated from the organic matrix by disrupting it. The oxidative acid digestion was carried out with concentrated sulfuric acid under boiling conditions in a closed digestion apparatus (heating bench with turbo suction). During this process, organic material was oxidatively destroyed, and the SO₂ produced by the reduction of the concentrated sulfuric acid was removed. The nitrogen was then converted into a volatile form by the addition of alkali, selectively distilled off, and measured volumetrically. The amount driven off was determined by titration with H₂SO₄. Production examples Inventive Example I

[0093] A 100-liter reactor equipped with a stirrer was filled with 50 liters of pure water. While stirring, 19.9 kg of orthophosphoric acid (85 wt% H₃PO₄) was added to the water at room temperature.

[0094] While stirring continuously at 50°C, 20 kg of melamine and 7.18 kg of melam were slowly added. After addition, excess water was evaporated by increasing the temperature until a residual water content of ≤ 0.1 wt% was obtained in the mixture. The resulting phosphate salt was then heated to a temperature of 310°C, resulting in the conversion to polyphosphate. Inventive Example II

[0095] A 100-liter reactor equipped with a stirrer was filled with 50 liters of pure water. While stirring, 16.2 kg of orthophosphoric acid (85 wt% H₃PO₄) was added to the water at room temperature.

[0096] While stirring continuously at 50°C, 20 kg of melamine and 1.37 kg of melam were slowly added. After addition, excess water was evaporated by increasing the temperature until a residual water content of ≤ 0.1 wt% was obtained in the mixture. The resulting phosphate salt was then heated to a temperature of 310°C, resulting in the conversion to polyphosphate. Comparative example

[0097] A 100-liter reactor equipped with a stirrer was filled with 50 liters of pure water. While stirring, 17.4 kg of orthophosphoric acid (85 wt% H₃PO₄) was added to the water at room temperature.

[0098] While stirring continuously, 20 kg of melamine were slowly added at 50°C. After addition, excess water was evaporated by increasing the temperature until a residual water content of ≤ 0.1 wt% was obtained in the mixture. The resulting phosphate salt was then heated to a temperature of 310°C, resulting in the conversion to polyphosphate.

[0099] The resulting flame retardants exhibit the following physical properties: parameter Example I Example II Comparative example Bound melamine [wt%] 43,4 43,1 45,1 bound melam [wt%] 19,3 3,7 < 0,25 M / P ratio 1,27 1,21 1,05 pH value (10 wt%) 5,44 4,77 7,04 Conductivity [mS] 0,106 0,158 0,191 TGA 1% Weight Loss [°C] 380 - 369 TGA 2% weight loss [°C] 385 - 379 TGA 3% weight loss [°C] 389 - 384 TGA 5% weight loss [°C] 395 - 391 Processability PA 66 excellent good restricted UL-94 V0 1.6 mm V0 1.6 mm NC 1 < 1.6 mm V0 0.8 mm NC 1 < 0.8 mm 1 < Unclassified

Claims

1. A flame retardant comprising a polyphosphate salt, wherein the polyphosphate salt comprises cations of at least one 1,3,5-triazine compound, characterized in that one of the at least one 1,3,5-triazine compound is melamine, wherein the proportion of the molar amount of substance of the cations of melamine of the at least one 1,3,5-triazine compound is ≥50%, and the flame retardant comprises at least one condensation product of melamine, wherein "condensation product" of melamine refers to molecules formed by a condensation reaction of two or more melamine molecules, as well as the protonated forms of these compounds, wherein the molar amount of substance of the cations of melamine in the flame retardant is X and the molar amount of substance of the at least one condensation product of melamine is Y, and wherein the proportion of Y in the sum of the amounts of substance X+Y is ≥ 1%, preferably ≥ 2%.

2. The flame retardant according to claim 1, wherein the at least one condensation product of melamine is one of the at least one 1,3,5-triazine compound, the cations of which the polyphosphate salt comprises.

3. The flame retardant according to any one of the preceding claims, wherein the average degree of condensation n of the polyphosphate salt is 10 to 500, preferably 20 to 250.

4. The flame retardant according to any one of the preceding claims, wherein the at least one condensation product of melamine is preferably selected from the group consisting of melam, melem, or melon, preferably melam.

5. The flame retardant according to any one of the preceding claims, wherein the pH value of a 10 wt% slurry of the flame retardant and / or the polyphosphate salt in water at 25°C is ≥ 5.

6. The flame retardant according to any one of the preceding claims, wherein in said flame retardant, the molar amount-of-substance ratio of the sum of the molar amounts of substance of the at least one 1,3,5-triazine compound and the molar amount of substance of the at least one condensation product of melamine to phosphorus is ≤ 1.3, preferably ≤ 1.1.

7. The flame retardant according to any one of the preceding claims, wherein the cations of the at least one 1,3,5-triazine compound constitute ≥ 90% of the total proportion of the cations of the polyphosphate salt.

8. The flame retardant according to any one of the preceding claims, wherein the water solubility of the flame retardant and / or of the polyphosphate salt is ≤ 0.1 g / 100 ml, preferably ≤ 0.07 g / 100 ml.

9. The flame retardant according to any one of the preceding claims, wherein the decomposition temperature of the flame retardant and / or of the polyphosphate salt is > 320°C.

10. The flame retardant< / b> according to claim 9, wherein it comprises, as an additional component, at least one compound selected from the group consisting of phosphinates, diphosphinates, such as aluminium diethyl phosphinate, zinc borates, and zinc phosphates.

11. A polymer composition comprising a polymer matrix and a flame retardant as defined in any one of the preceding claims.