METHOD FOR PREPARING FLAME RETARDANTS CONTAINING PHOSPHORUS AND THEIR USE IN POLYMERIC COMPOSITIONS.

Abstract

A phosphorus-containing flame retardant is produced by preparing a reaction mixture, including phosphonic acid, a solvent for the phosphonic acid, and a suitable metal or metal compound, and reacting the phosphonic acid and the metal or metal compound under the conditions described herein. The chemical composition of the resulting flame retardant product leads to excellent flame retardancy and exhibits high thermal stability. The flame retardants disclosed herein are useful, for example, in polymer compositions, particularly thermoplastics processed at high temperatures, in a wide range of applications.

Description

METHOD FOR PREPARING PHOSPHORUS-CONTAINING FLAME RETARDANTS AND THEIR USE IN POLYMERIC COMPOSITIONS zi frfrnn / zznzB / viAi This application claims the priority benefit of the Provisional Application of the United States No. 62 / 923.444, filed on October 18, 2019, which is incorporated herein by reference in its entirety. A highly effective, thermally stable, phosphorus-containing flame retardant is produced by a process comprising preparing a reaction mixture, the reaction mixture comprising a phosphonic or pyrophosphonic acid, a solvent for the phosphonic or pyrophosphonic acid, and a suitable metal or metal compound, and reacting the phosphonic or pyrophosphonic acid and the suitable metal or metal compound under the conditions described herein. The chemical composition of the resulting flame retardant product, in many embodiments produced as a compound or predominantly as a compound, leads to excellent flame retardancy and exhibits high thermal stability. The flame retardants disclosed herein are useful, for example, in polymer compositions, particularly thermoplastics processed at high temperatures, in a wide range of applications. BACKGROUND Phosphonic acid salts, i.e., compounds with the formula directly below, are known flame retardants in many polymer compositions: either IUo R-----R / ζ IV|(+)y OH LJ p where R is an optionally substituted alkyl, aryl, alkyladyl or arylalkyl group, p is normally a number from 1 to 4, M is a metal, and ey is normally a number from 1 to 4, such that M<+)y is a metallic cation where (+)y represents the charge formally assigned to the cation. As revealed in document US 2007 / 0029532, the decomposition of phosphonic acid salts is known to occur at temperatures encountered during the processing of polyesters and polyamides, damaging the polymers in the process, for example, temperatures above 260 or 270 °C. U.S. Patent 5,053,148 reveals that heat-resistant and brittle foams can be obtained by heating phosphonic acid salts to high temperatures. In Comparative Examples 1 and 2 of U.S. Patent 9,745,449, glass-filled polyamide compositions comprising 10 to 25 wt% of the aluminum salt of methylphosphonic acid were processed at elevated temperatures. A decrease in torque was observed during compounding, consistent with polymer degradation, resulting in a final product material that was friable upon cooling, powdery after grinding, and unmoldable. Analysis of the composite material by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) provided further evidence of degradation. The observed loss of desired polymer properties is consistent with the polymer degradation described in U.S. Patent 2007 / 0029532 and with the brittle foam formed in U.S. Patent 5,053,148. Therefore, simple phosphonic acid salts are unsuitable for use in many polymers that are processed, or subsequently exposed, to high temperatures, such as 250 °C, 260 °C, 270 °C or higher, because at such temperatures they undergo a chemical transformation through processes that damage the polymer. This can occur during compounding, for example, in an extruder, or while the salt is present in a polymer in a high-temperature application. On the other hand, U.S. Patent 9,745,449 discloses that heating a phosphonic acid salt to sufficiently high temperatures, generally in the absence of other materials, thermally transforms the salt into a different, more thermally stable material that exhibits excellent flame-retardant activity when incorporated into polymer substrates. The thermally transformed materials do not degrade at high temperatures, nor do they cause polymer degradation, when processed into polymer compositions at elevated temperatures, for example, 240 °C, 250 °C, 260 °C, 270 °C or higher. This is a significant advantage over previously known phosphonate salts, which exhibit flame-retardant activity but frequently degrade the polymer during processing. The thermally transformed materials are described as comprising one or more compounds represented by the empirical formula (IV): zi frfrnn / zznzB / YiAi where R is alkyl or aryl, M is a metal, q is a number from 1 to 7, for example, 1, 2 or 3, r is a number from 0 to 5, for example, 0, 1 or 2, y is a number from 1 to 7, for example, from 1 to 4, and n is 1 or 2, on condition that 2(q)+r = n(y). However, challenges are encountered with the process and materials of U.S. Patent 9,745,449, such as the production of a product generally in the form of a solid mass that requires crushing, grinding, or other such physical processing before use; the formation of product mixtures containing water-soluble or thermally unstable compounds; and the difficulty in controlling the phosphorus-to-metal ratio of the resulting product. Furthermore, the Examples in U.S. Patent 9,745,449 describe the multi-stage production of a phosphorus-containing flame retardant in which an intermediate metal salt of phosphonic acid is produced, and the dried salt is then heated to temperatures above 200 °C. This disclosure addresses the challenges identified above, while producing a phosphorus-containing flame retardant without requiring the production or use of the intermediate salt as described in U.S. Patent 9,745,449. SUMMARY According to this disclosure, a phosphorus-containing flame retardant is prepared by a process comprising (i) preparing a reaction mixture, the reaction mixture comprising (a) an unsubstituted or alkyl or aryl-substituted phosphonic acid, (b) a solvent for the phosphonic acid, and (c) a metal capable of forming a polycation (i.e., a metal represented in its corresponding cationic form by the formula M Wy where M is a metal, (+)y represents the charge of the metal cation, and ey is 2 or more), or a suitable metal compound represented by the formula Mp(+)yxq where M is a metal, (+)y represents the charge of the metal cation, and y is 2 or more, X is an anion, and the values ​​of pyq provide a balanced-charge metal compound; and (ii) heating or reacting the reaction mixture at a reaction temperature of 105°C or more for a time sufficient to produce the phosphorus-containing flame retardant. A process for producing a phosphorus-containing flame retardant is also disclosed, comprising (i) preparing a reaction mixture, the reaction mixture comprising (a) an unsubstituted or alkyl or aryl-substituted pyrophosphonic acid, (b) a solvent for the pyrophosphonic acid, and (c) a metal capable of forming a polycation (i.e., a metal represented in its corresponding cationic form by the formula M<+>y as above), or a suitable metal compound represented by the formula MpW^Xq as above, and (ii) heating or reacting the reaction mixture at a reaction temperature of 20 °C or more for a time sufficient to produce the phosphorus-containing flame retardant. Frequently, the reaction product forms as a suspension as the flame retardant resulting from the present invention precipitates in the reaction mixture. The phosphonic acid, pyrophosphonic acid, and / or solvent remaining after the reaction can be removed along with any possible byproducts by filtration and / or washing, for example, with water. In many embodiments, a substantially pure flame retardant material is produced, for example, a flame retardant comprising essentially a single compound with flame-retardant activity or essentially a mixture of active compounds. The conversion based on the metal or metal compound is typically high, and the product can be easily isolated and, optionally, further purified if desired. The present process overcomes the difficulties observed in processes such as those found in U.S. Patent 9,745,449 because, for example, the production of water-soluble or thermally unstable compounds is reduced or avoided, and the flame retardant product, which normally crystallizes as a powder or small particles, can be produced directly in an easily processable form, i.e., without the need for crushing, granulation, or other such physical processing. Additionally, in many embodiments, the resulting flame retardant material produced according to this disclosure has a higher phosphorus-to-metal ratio than that observed with simple metal phosphonates, as further explained herein.High phosphorus-to-metal ratios in the produced flame retardant lead to greater efficiency and, therefore, may allow for lower loading levels when the flame retardant material forms thermoplastic compounds. Other embodiments of this disclosure include, but are not limited to, a phosphorus-containing flame retardant produced according to a process described herein; a flame-retardant polymer composition comprising (i) a polymer and (ii) a phosphorus-containing flame retardant of this disclosure; a process for enhancing the flame retardancy of a polymer by incorporating a flame retardant of this disclosure into the polymer; and a process for incorporating a flame-retardant composition comprising a flame retardant of this disclosure into a polymer. The foregoing summary is not intended to restrict in any way the scope of the claimed invention. Furthermore, it should be understood that both the preceding general description and the following detailed description are for illustrative and explanatory purposes only and are not restrictive of the invention as claimed. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 shows the result of the thermogravimetric analysis (TGA) of an example flame retardant material produced in accordance with Example 1 of this disclosure. DETAILED DESCRIPTION Unless otherwise specified, the word "a" or "an" in this application means one or more than one. The term alkyl in this application includes arylalkyl, unless the context dictates otherwise. The term "arilo" in this application includes "alquilarilo", unless the context dictates otherwise. The term phosphonic acid, as used herein, refers to phosphonic acid that is either unsubstituted or substituted with alkyl or aryl, unless the context dictates otherwise. The term pyrophosphonic acid, as used herein, refers to unsubstituted or alkyl or aryl substituted pyrophosphonic acid, unless the context dictates otherwise. zLhbnn / zznz / e / Yiñi According to one aspect of this disclosure, a suitable metal or metal compound and an unsubstituted or alkyl- or aryl-substituted phosphonic acid are reacted to form a phosphorus-containing flame retardant. The process includes (i) preparing a reaction mixture, the reaction mixture comprising (a) an unsubstituted or alkyl- or aryl-substituted phosphonic acid, (b) a solvent for the phosphonic acid, and (c) a suitable metal or metal compound; and (ii) heating or reacting the reaction mixture at a reaction temperature of 105°C or higher for a time sufficient to produce a phosphorus-containing flame retardant. In the reaction, the metal is oxidized and can be represented in its corresponding cationic form by the formula M(+)y, where M is a metal, (+)y represents the charge of the metal cation, and y is 2 or higher.The appropriate metallic compound can be represented by the formula Mp(+)y Xq, where M is a metal, (+)y represents the charge of the metallic cation, and is 2 or more, X is an anion, and the values ​​of pyq provide a balanced-charged metallic compound. In another aspect, a suitable metal or metal compound and an unsubstituted or alkyl- or aryl-substituted pyrophosphonic acid are reacted to form a phosphorus-containing flame retardant. The process includes (i) preparing a reaction mixture, the reaction mixture comprising (a) an unsubstituted or alkyl- or aryl-substituted pyrophosphonic acid, (b) a solvent for the pyrophosphonic acid, and (c) a suitable metal or metal compound as above; and (ii) heating or reacting the reaction mixture at a reaction temperature of 20°C or higher for a time sufficient to produce a phosphorus-containing flame retardant. In many embodiments, the molar ratio of phosphonic or pyrophosphonic acid to the suitable metal or metal compound in the reaction mixture is greater than 2:1, such as approximately 3:1 or more, approximately 4:1 or more, approximately 5:1 or more, approximately 6:1 or more, approximately 7:1 or more, or approximately 8:1 or more. Larger molar excesses of phosphonic or pyrophosphonic acid to the suitable metal or metal compound in the reaction mixture are frequently used, such as approximately 10:1 or more, approximately 15:1 or more, approximately 20:1 or more, approximately 25:1 or more, approximately 30:1 or more, or any intermediate range. A large molar excess of phosphonic or pyrophosphonic acid to the suitable metal or metal compound may be used.For example, the molar ratio can be up to approximately 50:1, up to approximately 100:1, up to approximately 300:1, up to approximately 500:1, or any intermediate range. However, as might be expected, the efficiency of the process can be affected at certain large molar excesses; for example, precipitation of the product in the reaction mixture may be hindered. In many embodiments, the molar ratio varies from approximately 4:1, approximately 5:1, approximately 6:1, approximately 8:1, or approximately 10:1 to approximately 100:1 or to approximately 50:1, such as from approximately 8:1, approximately 12:1, approximately 16:1, or approximately 20:1 to approximately 50:1 or to approximately 40:1. According to the process currently disclosed, the reaction mixture is heated to a reaction temperature as described herein for a time sufficient to produce the flame retardant product. As used herein, the step of heating the reaction mixture to a reaction temperature for a time sufficient to produce the phosphorus-containing flame retardant and the like includes, but is not limited to, embodiments in which all or substantially all of component (b) of the reaction mixture, i.e., the solvent for the phosphonic or pyrophosphonic acid, is removed by boiling from the reaction mixture during the course of heating the reaction mixture to or at the reaction temperature.Therefore, it is understood that the reaction mixture described herein is still said to be heated to the reaction temperature even when all or substantially all of the solvent component (b) is removed by boiling during the course of heating the reaction mixture to or at the reaction temperature. The reaction temperature for producing a phosphorus-containing flame retardant according to this disclosure shall be chosen to facilitate the formation of monoanionic and / or dianionic pyrophosphonic acid ligands in the reaction product. For phosphonic acid, a reaction temperature of 105 °C or higher is used. Not bound by any particular theory, the reaction temperature is chosen to produce pyrophosphonic acid ligands through dehydration reaction(s). In many embodiments, the suitable metal or metal compound and phosphonic acid react at temperatures above 105 °C, such as approximately 115 °C or higher, approximately 120 °C or higher, approximately 130 °C or higher, or approximately 140 °C or higher. approximately 150 °C or higher, approximately 160 °C or higher, approximately 170 °C or higher, approximately 180 °C or higher, approximately 200 °C or higher, approximately 220 °C or higher, approximately 240 °C or higher, approximately 260 °C or higher, approximately 280 °C or higher, or any intermediate range. The reaction temperature may be higher than those described above, such as up to approximately 350 °C, up to approximately 400 °C, or higher, but it does not normally reach or exceed the boiling point of phosphonic acid. In many embodiments, the reaction temperature ranges from approximately 110 °C to approximately 350 °C, from approximately 115 °C to approximately 300 °C, from approximately 125 °C to approximately 280 °C, or from approximately 140 °C to approximately 260 °C. Through the dehydration reaction(s), water is formed, which can potentially lead to the undesired reverse reaction (hydrolysis). Therefore, in some embodiments, the reaction system is designed to facilitate the removal, such as continuous removal, of water from the reaction mixture.For example, the reaction temperature may be chosen above the boiling point of water to the extent necessary to remove by boiling at least a portion or the desired amount (e.g., most, substantially all, or all) of the water from the reaction. Additional means, such as gas purging, vacuum, and / or other known methods, may be used to facilitate the removal of water from the reaction system. For pyrophosphonic acid, a reaction temperature of 20 °C or higher is used. Since dehydration is unnecessary for pyrophosphonic acid, the reaction temperature may be lower than that described above for phosphonic acid. In many embodiments, the suitable metal or metal compound and pyrophosphonic acid react at temperatures above 20 °C, such as approximately 40 °C or higher, approximately 60 °C or higher, approximately 80 °C or higher, approximately 100 °C or higher, approximately 140 °C or higher, approximately 180 °C or higher, approximately 200 °C or higher, or any intermediate range. The reaction temperature may be higher than those described above, such as up to approximately 300 °C, up to approximately 400 °C, or higher, but normally does not reach or exceed the boiling point of pyrophosphonic acid. In many embodiments, the reaction temperature varies from approximately 25 °C to approximately 350 °C, from approximately 25 °C to approximately 280 °C, from approximately 30 °C to approximately 260 °C, from approximately 40 °C to approximately 260 °C, or from approximately 60 °C to approximately 240 °C. Depending, for example, on the metal compound used to react with the pyrophosphonic acid, water may be generated from the reaction. As described above, in some embodiments, the reaction system is designed to facilitate the removal, such as continuous removal, of water from the reaction.For example, the reaction temperature may be chosen above the boiling point of water to the extent necessary to remove by boiling at least a portion or the desired amount (e.g., most, substantially all, or all) of the water from the reaction. Additional means, such as gas purging, vacuum, and / or other known methods, may be used to facilitate the removal of water from the reaction system. In some embodiments, the solvent is a protic solvent (e.g., water), and the reaction system is designed to facilitate the removal, such as continuous removal, of the protic solvent during heating of the reaction mixture. For example, the reaction temperature may be chosen to be higher than the boiling point of the protic solvent to the extent necessary to remove by boiling at least a portion or the desired amount (e.g., most, substantially all, or all) of the protic solvent during heating of the reaction mixture. In certain embodiments, the solvent is water, and the reaction temperature is approximately 110 °C or higher. 115 °C or more, approximately 120 °C or more, approximately 130 °C or higher, approximately 140 °C or higher, approximately 150 °C or higher, or approximately 160 °C or higher, as the illustrative ranges described above. The reaction temperature may also be chosen to be equal to or higher than the melting point of phosphonic or pyrophosphonic acid, as described later in this document. As described above, the reaction mixture is heated or reacted at the reaction temperature for a sufficient amount of time to produce the phosphorus-containing flame retardant. Often, the flame retardant product will precipitate from the reaction mixture, so the reaction must be carried out long enough to achieve this precipitation. In general, the amount of time required to achieve at least substantial conversion to the flame retardant product, based on the appropriate metal or metal compound in the reaction mixture, will depend on the reaction temperature; higher temperatures generally result in shorter reaction times.Often, the heating or reaction takes place at the reaction temperature for approximately 0.1 to approximately 48 hours, such as from approximately 0.2 to approximately 36 hours, from approximately 0.5 to approximately 30 hours, from approximately 1 hour to approximately 24 hours, for example, from approximately 1 hour to approximately 12 hours, from approximately 1 hour to approximately 8 hours, or from approximately 1 hour to approximately 5 hours, although other durations may be used. The reaction mixture can be prepared in any manner suitable for combining or mixing (a) unsubstituted or alkyl- or aryl-substituted phosphonic or pyrophosphonic acid, (b) the solvent for the phosphonic or pyrophosphonic acid, and (c) the suitable metal or metal compound. For example, the components can be combined simultaneously or at different times. In some embodiments, the suitable metal or metal compound (c) is added to a mixture, such as a solution, of the phosphonic or pyrophosphonic acid (a) and solvent (b). The suitable metal or metal compound (c) can be added to the reaction mixture all at once or in portions. Similarly, the phosphonic or pyrophosphonic acid (a), solvent (b), or a mixture, such as a solution, of the phosphonic or pyrophosphonic acid (a) and solvent (b), can be added to the reaction mixture all at once or in portions. When preparing the reaction mixture, the phosphonic or pyrophosphonic acid (a), the solvent (b), and the suitable metal or metal compound (c) can be combined at a preparation temperature below the reaction temperature. The reaction mixture is then heated to the reaction temperature. A preparation temperature can be chosen, for example, to facilitate the dissolution of the phosphonic or pyrophosphonic acid (a) in the solvent (b) or to otherwise form a homogeneous liquid or solution of the phosphonic or pyrophosphonic acid (a) and the solvent (b). At the preparation temperature, and depending on the metal compound (c), the reaction mixture may form a solution, a suspension, or an aqueous suspension, such as a homogeneous or substantially homogeneous aqueous suspension. In some embodiments, such as at higher preparation temperatures, the reaction mixture may form a solution.Frequently, near or at the reaction temperature, the reaction mixture will be a solution. In many embodiments, the preparation temperature is approximately 0 °C or higher, but often below 150 °C, such as below 125 °C, below 115 °C, below 100 °C, below 85 °C, or below 65 °C. For example, the preparation temperature may range from approximately 0 °C to approximately 65 °C or from approximately 15 °C to approximately 40 °C. In some embodiments, the reaction mixture is prepared at room temperature (e.g., from approximately 15 °C to approximately 25 °C). In some embodiments, the solvent (b) is preheated to the preparation temperature and combined with the phosphonic or pyrophosphonic acid (a) and the suitable metal or metal compound (c).In some embodiments, a mixture of the solvent (b) and phosphonic or pyrophosphonic acid (a) is preheated to the preparation temperature and combined with the appropriate metal or metal compound (c). The reaction mixture can alternatively be prepared at the reaction temperature. That is, the reaction mixture is prepared by combining (a) phosphonic or pyrophosphonic acid, (b) the solvent for the phosphonic or pyrophosphonic acid, and (c) the suitable metal or metallic compound at the reaction temperature. For example, in some embodiments, preparing the reaction mixture comprises preheating a mixture of the solvent (b) and the phosphonic or pyrophosphonic acid (a) to the reaction temperature and combining it with the suitable metal or metallic compound (c). In some embodiments where the reaction temperature is higher than the melting point of phosphonic or pyrophosphonic acid and residual phosphonic or pyrophosphonic acid is present in the product reaction mixture after the desired conversion—for example, total or substantially total conversion to the flame retardant product—the product reaction mixture is cooled to a temperature above or no lower than the melting point of the residual phosphonic or pyrophosphonic acid to ensure that the phosphonic or pyrophosphonic acid remains in liquid form. This can be particularly useful in embodiments where an appreciable amount of the solvent for the phosphonic or pyrophosphonic acid (i.e., component (b)) is removed by boiling as a result of heating, so that the remaining excess phosphonic or pyrophosphonic acid may have a greater tendency to come out of solution.Excess phosphonic or pyrophosphonic acid and the solvent, if present in the product reaction mixture, can be removed by filtration / washing and optionally recovered. The recovered excess phosphonic or pyrophosphonic acid and / or the solvent can be recycled, for example, back to the reactor in which a suitable metal or metal compound (c) reacts with the phosphonic or pyrophosphonic acid (a). After conversion to the reaction product, a solvent for the phosphonic or pyrophosphonic acid, which may, but does not necessarily, be the same as the solvent component (b), can optionally be added to dissolve or otherwise assist in the removal of excess phosphonic or pyrophosphonic acid. The flame retardant product is frequently isolated by filtration, optionally followed by further treatment (e.g., washing, drying, screening, etc.).The resulting flame retardant product, which is generally in the form of a powder or small particles, is readily processable, meaning that crushing, grinding, or other such physical processing is not required or necessary before use. It should be understood that producing the flame retardant material directly in the form of a powder or small particles according to the process disclosed herein allows for the treatment of the reaction product, such as isolating the flame retardant product (e.g., separating the flame retardant product from the remaining solvent), which may include, for example, processing the reaction product by filtration, sieving, washing, drying, and the like. The process described herein produces a flame retardant comprising one or more metals and one or more mono- and / or bidentate pyrophosphonic acid ligands. In some embodiments, compounds may be produced that further comprise phosphonate ligands, but in all embodiments, compounds comprising a monoanionic pyrophosphonic acid ligand and / or a dianionic pyrophosphonic acid ligand are obtained. The process can produce mixtures of flame-retardant compounds, but in many embodiments, the process yields a flame-retardant material as a single, or predominantly single, compound with a high conversion based on the metal or metal compound, such as at least 70%, 80%, 85%, 90%, 95%, or higher conversion, or any intermediate range, unlike the mixtures of compounds obtained by prior art processes involving the heat treatment of metal phosphonate salts. In a general embodiment, in which phosphonate ligands may be present in the flame-retardant product, the reaction generally proceeds as shown: HO MpXq solvent Δ zLhbnn / zznz / e / Yiñi where M is a metal cation and (+)y represents the charge of the cation, e.g., M is a di-, tri-, tetra-, or pentacationic metal; X is an anionic ligand or ligands bonded to the metal, and the stoichiometry of M and X (i.e., pyq) gives a balanced-charge metal compound; R is H, an alkyl, aryl, alkyladyl, or arylalkyl group; a, b, and c and d represent the ratio of the corresponding components to each other in the reaction product; e and c, a, b, and c and d are values ​​that give a balanced-charge product, provided that y is 2 or more and only one of a and c can be 0 (often, c is not zero). In some embodiments, the phosphonic acid ligand above with coefficient d, when present, may be present as a dianion. In many embodiments, d is 0. In a further aspect, a flame retardant product produced in accordance with this disclosure, normally in the form of a powder or small particles, comprises a compound or a mixture of different compounds of empirical formula (II) where R is H, an alkyl, aryl, alkylaryl or arylalkyl group, a, b, c and d represent the ratio of the corresponding components to one another in the compound, ya is generally a number from 0 to 8, for example, 0 to 6, 0 to 4, or 0 to 2, c is generally a number from 0 to 10, for example, 0 to 8, 0 to 6, 0 to 4 or 0 to 2, d is generally a number from 0 to 6, for example, 0 to 4 or 0 to 2, M is a metal, and y is a number from 2 to 5, such as 2, 3 or 4, frequently 2 or 3, and M<+>y is a metallic cation where (+)y represents the charge formally assigned to the cation. The values ​​of a, b, c, d, and y can vary, but they will satisfy the charge equilibrium equation 2(a)+c+d=b(y), and only one of a and c can be 0. In many embodiments, c is not zero. In cases where a dianionic phosphonic acid ligand may be present in the compound, the charge equilibrium equation becomes 2(a)+c+2(d)=b(y).The value for b is only limited in that it must satisfy the above equations, but in many embodiments b is a number from 1 to 4, e.g., 1 or 2. In some embodiments, a is 0, 1 or 2 (e.g., 0 or 1), c is 1 or 2, and d is 0, 1 or 2 (e.g., 0 or 1), and the product has balanced load. In many implementations, d is 0, as in: zLhbnn / zznz / e / Yiñi where R, M, y, a, byc are as described above and the product load balance equation becomes 2(a)+c=b(y). Often, c in formulas (II) and (III) above is not zero (for example, c is from 1 to 10, from 1 to 8, from 1 to 6, from 1 to 4, or 1 or 2). According to the process disclosed herein, it was surprisingly discovered in many embodiments, such as when employing dicationic or tricationic metals, that a flame retardant compound is produced in which c in the above formulas is not zero and the product has a more favorable ratio of phosphorus atoms to metal atoms (i.e., P to M) for providing flame retardancy compared to phosphorus-containing flame retardants described in the art. For example, tricationic metals (e.g., aluminum) and dicationic metals (e.g., zinc) are known to form trisubstituted and disubstituted balanced charge compounds, respectively.As noted in the art, aluminum triphosphonate salts, which have a phosphorus-to-aluminum ratio of 3:1, and zinc diphosphonate salts, which have a phosphorus-to-zinc ratio of 2:1, are known as flame retardants. However, according to the pyrophosphonic acid ligand formation process of the present disclosure, and particularly when c in the above formulas is not zero, the phosphorus-to-metal ratio in the flame retardant product is higher. For example, as demonstrated in the Examples disclosed herein, when the process of the present disclosure was employed, the phosphorus-to-aluminum ratio, or the phosphorus-to-iron ratio, in the resulting flame retardant product was 4:1.A higher phosphorus-to-metal ratio leads to high efficiency and can allow reduced loadings when forming thermoplastic polymer compounds. In certain specific embodiments, and in formula (III) is 2 (i.e., M^y is a dicationic metal, as described herein), a is 0, b is 1, and c is 2. In certain embodiments, the dicationic metal M is Mg, Ca, or Zn. In other embodiments, and in formula (III) is 3 (i.e., M(+)y is a tricationic metal, as described herein), a is 1, b is 1, and c is 1. In certain embodiments, the tricationic metal M is chosen from Al, Ga, Sb, Fe, Co, B, and B. In certain embodiments, the tricationic metal M is Al, Fe, Ga, Sb, or B. As is usual with inorganic coordination compounds, the reaction product in the reaction described above and the compounds of empirical formulas (II) and (III) are idealized so that the reaction product or compounds can be coordination polymers, complex salts, salts where certain atomic valencies are shared, etc. For example, in many embodiments, empirical formula (II) or (III), as described herein, represents a monomeric unit (i.e., a coordination entity) of a coordination polymer, thereby forming the extended coordination polymer structure of the flame retardant compound of this disclosure. In one example, where M is Al and ey is 3, a compound of empirical formula (III) is produced according to the following empirical formula (III): zi bt?nn / zznzB / YiAi !_ ΓL- (Illa). As shown herein, the absence of the subscripts a, b, and c in the empirical formulas indicates that the subscripts are each 1, signifying a 1:1:1 ratio of the components (in the case of empirical formula (Illa), a 1:1:1 ratio of dianionic pyrophosphonic acid ligand, metal atom, and monoanionic pyrophosphonic acid ligand). In this example, empirical formula (Illa) represents a repeating monomeric unit (i.e., a coordination entity) of a coordination polymer, thereby forming the extended coordination polymer structure of the flame retardant compound of this disclosure. Frequently, a compound of empirical formula (II) or (III) (for example, (Illa)), which in many embodiments is an extended coordination polymer as described herein, constitutes all, substantially all, or at least most of the flame retardant product, such as at least 75%, 85%, 90%, 95%, 98%, or more, or any intermediate range, by weight of the flame retardant product. A compound of empirical formula (II) or (III) (e.g., (Illa)) can be produced with a high conversion based on the metal or metal compound, such as at least 70%, 80%, 85%, 90%, 95%, 98%, or higher conversion, e.g., at least 70 to 95% or higher conversion. In certain embodiments, M is aluminum (i.e., the reaction product is produced using aluminum or one or more aluminum compounds, such as those described herein) or iron (i.e., the reaction product is produced using iron or one or more iron compounds, such as those described herein). The phosphonic acid used in the present process can be represented by the formula (I) zi bt?nn / zznzB / YiAi where R is H, alkyl, aryl, alkylaryl, or arylalkyl. In many embodiments, R is H, C1-12 alkyl, C6-10 aryl, C7-18 alkylaryl, or C7-18 arylalkyl, wherein said alkyl, aryl, alkylaryl, or arylalkyl is unsubstituted or substituted with halogen, hydroxyl, amino, C1-4 alkylamino, C1-4 dialkylamino, C1-4 alkoxy, carboxy, or C2-5 alkoxycarbonyl. In some embodiments, said alkyl, aryl, alkylaryl, or arylalkyl is unsubstituted C1-12 alkyl, Ce aryl, C7-10 alkylaryl, or C7-10 arylalkyl, for example, C1-6 alkyl, phenyl, or C7-9 alkylaryl. In some embodiments, R is a substituted or unsubstituted C1-6 alkyl, Ce aryl, C7-10 alkylaryl, or C7-12 arylalkyl, for example, C1-4 alkyl, Ce aryl, C7-9 alkylaryl, or C7-10 arylalkyl. In many embodiments, R is an unsubstituted C1-12 alkyl, for example, C1-6 alkyl.In many embodiments, lower alkyl phosphonic acids are used, for example, methyl-, ethyl-, propyl-, isopropyl-, butyl-, t-butyl- and the like. R as alkyl can be a linear or branched alkyl group having the specified number of carbons and includes, for example, unbranched alkyls such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and branched alkyls such as isopropyl, isobutyl, sec-butyl, t-butyl, ethyl, hexyl, t-octyl, and the like. For example, R as alkyl can be selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and t-butyl. In many embodiments, R is methyl, ethyl, propyl, or isopropyl, e.g., methyl or ethyl. Often, when R is aryl, it is phenyl. Examples of R as alkylaryl include phenyl substituted with one or more alkyl groups, for example, groups selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, and the like. Examples of R as arylalkyl include, for example, benzyl, phenethyl, styryl, cumyl, phenpropyl, and the like. In many embodiments, R is chosen from methyl, ethyl, propyl, isopropyl, butyl, phenyl, and benzyl. The pyrophosphonic acid used in the present process can be represented by the formula (a) ζΐΜτηη / ζζηζ / Β / γίΛΐ or —ohRII0(la). where R is as described above for formula (I). The general reaction scheme with a pyrophosphonic acid and a suitable metal compound can be represented as MpXq solvent Δ , where R, Μ, X, p, q, y, a, b and c zi frfrnn / zznzB / γΐΛΐ are as described herein. The process described herein may employ more than one phosphonic acid, more than one pyrophosphonic acid, or a combination of phosphonic and pyrophosphonic acids. In some embodiments, the phosphonic acid or pyrophosphonic acid is generated in situ. For example, the preparation of the reaction mixture may include the preparation of phosphonic or pyrophosphonic acid, such as by hydrolysis of starting materials of higher oligomeric phosphonic acid and / or cyclic phosphonic acid anhydride. The solvent (i.e., component (b)) can be any solvent capable of dissolving the phosphonic or pyrophosphonic acid component (a). It must be inert or substantially inert to the reaction between the phosphonic or pyrophosphonic acid (a) and the suitable metal or metal compound (c), and may be selected with regard to other reaction parameters, such as the preparation and / or reaction temperature or the type of metal or metal compound, in order to prepare a homogeneous or substantially homogeneous reaction mixture. In some embodiments, the solvent (b) may be a combination of solvents for the phosphonic or pyrophosphonic acid. Often, the phosphonic or pyrophosphonic acid (a) dissolves substantially or completely in the solvent (b). For example, the phosphonic or pyrophosphonic acid (a) and the solvent (b) may form a solution.In some embodiments, the phosphonic or pyrophosphonic acid (a) may be partially dissolved and partially suspended or dispersed in the solvent (b). The type of solvent, the amount of solvent relative to the phosphonic or pyrophosphonic acid, and the mixing conditions may be selected to achieve the desired level of dissolution of the phosphonic acid, such as to obtain a high concentration of phosphonic or pyrophosphonic acid in the mixture while maintaining the phosphonic or pyrophosphonic acid in solution. The ratio of phosphonic acid (a) to solvent (b) frequently varies between approximately 10:1 and 1:10, approximately 5:1 to 1:5, or approximately 3:1 to 1:3, by weight.In some embodiments where the phosphonic acid (a) is partially dissolved and partially suspended or dispersed in the solvent (b), the preparation temperature or reaction temperature may be selected to be equal to or higher than the melting temperature of the phosphonic acid in order to liquefy the phosphonic acid that is suspended or dispersed in the solvent. As described above, depending on the reaction temperature and the boiling point of the solvent for phosphonic or pyrophosphonic acid (i.e., component b in the reaction mixture), at least some of the solvent may be removed by boiling from the reaction mixture while heating to or at the reaction temperature. In some embodiments, all, substantially all, or at least most of the solvent (b) is removed by boiling from the reaction mixture during heating. The solvent (b) may be high-boiling (e.g., sulfolane or dimethyl sulfoxide (DIVISO)) or low-boiling (e.g., chloroform or tetrahydrofuran (THF)).For example, in some embodiments, the solvent boils at a temperature equal to or lower than the reaction temperature so that at least some of the solvent is removed by boiling during heating of the reaction mixture; for example, where all, substantially all, or most of the solvent is removed by boiling. The reaction temperature can be selected to be equal to or higher than the melting point of the phosphonic or pyrophosphonic acid to ensure that it remains in liquid form when the solvent is removed by boiling. Thus, using a larger excess of phosphonic or pyrophosphonic acid in the reaction mixture can allow the phosphonic or pyrophosphonic acid to serve as both a reactant and a solvent for the reaction. In other embodiments, the solvent has a boiling point higher than the reaction temperature, ensuring that it remains in the reaction mixture, from which the flame retardant product can be isolated, as described herein. In some embodiments, the reaction temperature is selected below the melting point of phosphonic or pyrophosphonic acid. Suitable solvents may be organic or inorganic. Examples of suitable solvents for phosphonic or pyrophosphonic acid include, but are not limited to, water, sulfones, sulfoxides, halogenated (e.g., chlorinated) hydrocarbons, aromatic hydrocarbons, and ethers. For example, in some embodiments, the solvent may be selected from water, sulfolane, dimethyl sulfone, tetrahydrofuran (THF), dimethoxyethane (DME), 1,4-dioxane, dimethyl sulfoxide (DMSO), 1,2-dichlorobenzene, chloroform, carbon tetrachloride, xylene, and mesitylene. In some embodiments, the solvent comprises water. In some embodiments, the solvent comprises an aqueous solution. In some embodiments, the reaction mixture is an aqueous reaction mixture. The solvent can be protic or aprotic. In many embodiments, the solvent for pyrophosphonic acid is an aprotic solvent. In some embodiments, the solvent (b) comprises a sulfone of formula R1R2SO2, wherein R1 and R2 are chosen independently of C1-6 hydrocarbon groups, for example, C1-3 hydrocarbon groups, or R1 and R2 taken together with S form a ring having 2, 3, 4, or 5 carbon atoms, which ring may be unsubstituted or substituted with a C1-3 alkyl group. In some embodiments, R1 and R2 taken together with S form a di-, tri-, tetra-, or pentamethylene ring. In some embodiments, R1 and R2 are chosen independently of a C1-6 alkyl group. In some embodiments, one R1 or R2 is a C1-6 alkyl group and the other is a C1-3 alkyl group. In some embodiments, R1 and R2 are chosen independently of a C1-3 alkyl group. The alkyl groups may be branched or linear. In some embodiments, R1 and R2 are both methyl, both ethyl, or both propyl. In other embodiments, R1 or R2 is methyl and the other is ethyl or propyl. In still other embodiments, R1 or R2 is ethyl and the other is propyl.In some embodiments, the sulfone is sulfolane. As used herein, suitable metallic compound and the like refer to a compound of formula MpW^Xq, where M is a metal capable of forming a polycation, e.g., a metal that forms a 2+, 3+, 4+, or 5+ cation, typically 2+, 3+, or 4+, and X is any anion that provides a balanced-charge compound with metal M. Suitable examples of X include, but are not limited to, anions that, together with metal M, form oxides, halides, alkoxides, hydroxides, carbonates, carboxylates, and phosphonates. Values ​​of p and q provide a balanced-charge metallic compound, e.g., alumina, Al₂O₃. In some embodiments, an unsubstituted metal, M, is used as described herein. Some examples of suitable metals (M) include, but are not limited to, Mg, Ca, Ba, Zn, Zr, Ge, B, Al, Si, Ti, Cu, Fe, Co, Ga, zi frfrnn / zznzB / YiAi In some embodiments, M is chosen from Mg, Ca, Ba, Zn, Zr, Ga, B, Al, Si, Ti, Cu, Fe, Sn, or Sb. In some embodiments, M is chosen from Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Fe, Sn, or Sb; for example, M can be Mg, Zn, Ca, Fe, or Al. Suitable metal compounds include, but are not limited to, compounds having a metal-oxygen bond, metal-nitrogen bond, metal-halogen bond, metal-hydrogen bond, metal-phosphorus bond, metal-sulfur bond, metal-boron bond, etc., for example, oxides, halides, alkoxides, hydroxides, carboxylates, carbonates, phosphonates, phosphines, phosphonites, phosphates, phosphites, nitrates, nitrites, borates, hydrides, sulfonates, sulfates, sulfides, etc., of Mg, Ca, Ba, Zn, Zr, Ge, B, Al, Si, Ti, Cu, Fe, Co, Ga, Bi, Mn, Sn or Sb, for example, oxides, hydroxides, halides or alkoxides of Mg, Ca, Ba, Zn, Zr, Ga, B, Al, Si, Ti, Cu, Fe, Sn or Sb; such as oxides, hydroxides, halides or alkoxides of Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Fe, Sn or Sb, for example, oxides, hydroxides, halides or alkoxides of Mg, Zn, Ca, Fe or Al. In some embodiments, the metal, M, of the suitable metal or metallic compound is aluminum or iron. In some embodiments, the suitable metallic compound is selected from aluminum halides, oxides, hydroxides, alkoxides, carbonates, carboxylates, and phosphonates. In some embodiments, the suitable metallic compound is selected from aluminum halides, oxides, hydroxides, and alkoxides. In some embodiments, the suitable metallic compound is selected from alumina, aluminum trichloride, aluminum trihydroxide, aluminum isopropoxide, aluminum carbonate, and aluminum acetate. In other embodiments, the suitable metallic compound is selected from iron halides, oxides, alkoxides, carbonates, and acetates. In some embodiments, the suitable metallic compound is selected from iron(III) oxide, iron(III) chloride, iron(III) isopropoxide, and iron(III) acetate. In some embodiments, the suitable metal compound is a metal phosphonate salt. The metal of the metal phosphonate salt may be a metal, M, as described herein. In some embodiments, the metal phosphonate salt is prepared from the reaction of an initial metal compound and phosphonic acid with a solvent (e.g., water) for the phosphonic acid. The initial metal compound may be a compound according to the suitable metal compound described herein. In some embodiments, the initial metal compound and phosphonic acid are reacted at a temperature equal to or approximately ambient temperature or at a temperature ranging from approximately 0 to approximately 20 °C. The resulting metal phosphonate salt may then be used as the suitable metal compound according to the inventive process described herein.For example, a phosphonic acid, for instance, one or more alkylphosphonic acids as described above, and a solvent (for example, water) can be stirred to form a homogeneous solution. The solution can be cooled, for example, from approximately 0 to approximately 20 °C, and a starting metal compound, such as a metal oxide, halide, alkoxide, or hydroxide, is added to react with the phosphonic acid. A metal phosphonate salt is formed, which is then used as the appropriate metal compound according to the process disclosed herein. In certain embodiments, R as shown herein is methyl, ethyl, propyl, isopropyl, or butyl, and M is Al, Fe, Zn, or Ca. In further embodiments, X is oxygen, hydroxy, alkoxy, or halogen. The reaction as described in this document may, but does not necessarily, operate under reduced pressure or vacuum. The product reaction mixture formed from the reaction described herein, which is frequently in the form of a suspension, can be combined with an additional solvent, which may be the same as or a different solvent than the solvent used in the reaction mixture. The additional solvent can, for example, be selected from those described herein for the solvent component (b). The additional solvent / suspension mixture can be stirred as desired to break up any lumps that may have formed. The solid product can be isolated by filtration and, optionally, washed and dried to produce the product in the form of a powder or small particles. In some cases, the product can be sieved to refine the particle size. The reaction described herein may be optionally facilitated by a seeding material. For example, the use of a seeding material can reduce the time required to achieve conversion to the flame retardant product and can lead to greater uniformity in the product's physical characteristics. Therefore, in some embodiments, the reaction mixture further comprises a seeding material (d). The seeding material is frequently added to the reaction mixture upon heating it to the temperature. ZLhhnn / zznz / B / YW of reaction or after doing so. In many embodiments, the seeding material is added before the conversion and / or precipitation of the flame retardant product occurs. In some embodiments, the seeding material comprises a flame retardant material produced according to the process of the present disclosure, such as a flame retardant compound of empirical formula (II), (III), or (IIIa) as described herein. The seeding material may be selected or refined to have a desired particle size. zLhbnn / zznz / e / Yiñi In some embodiments, the suitable metallic compound is alumina, and the flame retardant material is produced as follows: oR\j] + Λ1,Ο3 / ^OH HO solvent △ In one example, a reaction mixture comprising a phosphonic acid, such as a C1-C12 alkylphosphonic acid (e.g., methyl, ethyl, propyl, isopropyl, butyl, or t-butylphosphonic acid), a solvent for the phosphonic acid, such as water, and an aluminum oxide, hydroxide, halide, alkoxide, carbonate, or carboxylate, such as alumina, aluminum chloride, aluminum trihydroxide, aluminum isopropoxide, aluminum carbonate, or aluminum acetate, is heated to a reaction temperature as described herein, such as approximately 115 °C or higher, approximately 125 °C or higher, approximately 150 °C or higher, or approximately 165 °C or higher. Typically, a suspension forms as the reaction progresses, and the solid flame retardant product can be isolated by filtration to produce the product in the form of a powder or small particles.Further treatment of the product reaction mixture may be performed before isolating the solid product, such as cooling the product reaction mixture above or below the melting point of the excess phosphonic acid and combining it with an additional solvent as described herein, e.g., water. The additional solvent / suspension mixture may optionally be stirred as described above. The solid flame retardant product may be isolated by filtration, optionally washed with additional solvent and dried, to produce the product in the form of a powder or small particles. The flame retardant product contains phosphorus and aluminum in a 4:1 phosphorus-to-aluminum ratio according to the following empirical formula: zi b+nn / zznzB / YiAi p—cr p—OH . In a further example, the example described directly above is carried out with iron or a suitable iron compound, such as iron halides, oxides, alkoxides, carbonates, or acetates, for example, iron(III) oxide, iron(III) chloride, iron(III) isopropoxide, or iron(III) acetate. The flame retardant product contains phosphorus and iron in a 4:1 ratio according to the following empirical formula: Frequently, the compound of the above empirical formulas (which in many embodiments is an extended coordination polymer as described herein) constitutes all, substantially all, or at least most of the flame retardant product, such as at least 75%, 85%, 90%, 95%, 98%, or more, or any intermediate interval, by weight of the flame retardant product. In a further embodiment, the suitable metal compound (c) may be a metal phosphonate salt of the following formula: M<+)y where R and M are as described above, p is a number from 2 to 5, for example, 2, 3, or 4, and e is a number from 2 to 5, for example, 2, 3, or 4, such that M(+)y is a metal cation where (+)y represents the charge formally assigned to the cation. Typically, the metal phosphonate salt has a balanced charge (i.e., p=y). The metal phosphonate salt can be prepared according to methods known in the art. In one example, a phosphonic acid, such as an alkyl phosphonic acid (e.g., methyl, ethyl, propyl, isopropyl, butyl, or t-butyl phosphonic acid), is combined with water (e.g., approximately 1:1 by weight) and stirred and cooled below room temperature (e.g., cooled to 10°C or lower, such as approximately 0°C). An initial metal compound is added to the phosphonic acid and water mixture to form a metal phosphonate salt. The metal phosphonate salt is then used as the suitable metal compound in the process of this disclosure to produce the flame retardant product in the form of a powder or small particles. In embodiments involving an aluminum phosphonate salt as the suitable metal compound, the flame retardant product contains phosphorus and aluminum in a 4:1 phosphorus-to-aluminum ratio according to the following empirical formula: zi b+nn / zznz / E / YiAi P—OH Frequently, the compound of the empirical formula (which in many embodiments is an extended coordination polymer as described herein) constitutes all, substantially all, or at least most of the flame retardant product, such as at least 75%, 85%, 90%, 95%, 98%, or more, or any intermediate range, by weight of the flame retardant product. The flame retardant of the invention can be used with a variety of other flame retardants and / or synergistic agents or flame retardant adjuvants as known in the art. For example, the flame retardant of the invention can be formulated with one or more materials selected from: carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes; polyphenylene ether (PPE), phosphine oxides and polyphosphine oxides, for example, benzyl phosphine oxides, polybenzyl phosphine oxides and the like; melamine, melamine derivatives and melamine condensation products, melamine salts such as, but not limited to, melamine cyanurate, melamine borate, melamine phosphates, melamine metallic phosphates, melam, melem, melon and the like; inorganic compounds, including clays, metallic salts such as hydroxides, oxides, oxide hydrates, borates, carbonates, sulfates, phosphates, phosphites, hypophosphites, silicates, mixed metallic salts, etc., for example, talc and other magnesium silicates, calcium silicate, aluminosilicate, aluminosilicate in the form of hollow tubes (DRAGONITE), calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, HALLOYSITE or boron phosphate, calcium molybdate, exfoliated vermiculite, zinc stannate, zinc hydroxystannate, zinc sulfide and zinc borate, zinc molybdate (or complexes thereof, for example, Kemgard 911B), zinc molybdate / magnesium hydroxide complex (for example, Kemgard MZM), zinc molybdate complex zinc / magnesium silicate (Kemgard 911C), calcium / zinc molybdate complex (e.g., Kemgard 911 A), zinc phosphate (or complexes thereof, e.g., Kemgard 981), magnesium oxide or hydroxide, aluminum oxide,Aluminum oxide hydroxide (Boehmite), aluminum trihydrate, silica, tin oxide, antimony (III and V) oxide hydrate, titanium oxide and zinc oxide or oxide hydrate, zirconium oxide and / or zirconium hydroxide and the like. Unless otherwise specified, in the context of this application, the term phosphate when used as a component in a phosphate salt, such as in metallic phosphate, melamine phosphate, melamine metallic phosphate, etc., refers to a phosphate, hydrogen phosphate, dihydrogen phosphate, pyrophosphate, polyphosphate or an anion or polyanion of phosphoric acid condensation products. Similarly, unless otherwise specified, in the context of this application, the term phosphite when used as a component in a phosphite salt, such as in metallic phosphite, etc., refers to a phosphite or hydrogen phosphite. The flame retardant of the invention can also be formulated with other flame retardants, such as halogenated flame retardants, alkyl or aryl phosphine oxide flame retardants, alkyl or aryl phosphate flame retardants, alkyl or aryl phosphonates, alkyl or aryl phosphinates, and alkyl or aryl phosphinic acid salts. In some embodiments, the flame retardant comprises a mixture of the flame retardant according to the present disclosure and a phosphine salt of the following formula (for example, an aluminum tris(dialkylphosphinate)), or ζΐΜτηη / ζζηζ / Β / γίΛΐ Ri and R2 can each independently be a group according to R as described herein, M is a metal as described herein (e.g., Al or Ca), and n is a number from 2 to 7, e.g., 2 to 4, frequently 2 or 3. In many embodiments, a flame retardant polymer composition according to this disclosure comprises (i) a polymer, (ii) a flame retardant material of this disclosure, and (iii) one or more additional flame retardants and / or one or more flame retardant synergists or adjuvants. For example, in some embodiments, the flame-retardant polymer composition comprises one or more additional flame retardants, for example, halogenated flame retardants, phosphine oxide flame retardants, alkyl or aryl phosphonates or salts of alkyl or aryl phosphinates, for example, an aluminum tris(dialkylphosphinate) such as aluminum tris(diethylphosphinate). In some embodiments, the flame retardant polymer composition comprises one or more flame retardant synergists or adjuvants, for example, melamine, melamine derivatives and melamine condensation products (for example, melam, melem, melon), melamine salts, phosphine oxides and polyphosphine oxides, metal salts such as hydroxides, oxides, oxide hydrates, borates, phosphates, phosphonates, phosphites, silicates and the like, for example, aluminum hydrogen phosphite, melem or a melamine metal phosphate, for example, a melamine metal phosphate wherein the metal comprises aluminum, magnesium or zinc.In particular embodiments, the one or more flame retardants, synergistic agents, or additional flame retardant adjuvants comprise aluminum tris(dialkylphosphinate), aluminum hydrogen phosphite, methylene diphenylphosphine oxide substituted polyaryl ether, xylenebis(diphenylphosphine oxide), 4,4'-bis(diphenylphosphinylmethyl)-1,1'-biphenyl, ethylene bis-1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane, melem, melam, melon, or dimelamine zinc pyrophosphate. Certain embodiments provide a halogen-free polymer composition. In such embodiments, halogen-containing flame retardants or synergistic agents are excluded to the extent possible. The flame retardant material of this disclosure may be combined with an additional flame retardant, synergist, or adjuvant in a ratio of 100:1 to 1:100 by weight of the inventive flame retardant to the total weight of the additional flame retardant, synergist, and / or adjuvant. In some embodiments, the flame retardant material of this disclosure is present in a ratio of 10:1 to 1:10 by weight of the inventive flame retardant to the total weight of the additional flame retardant, synergist, and / or adjuvant, for example, weight ratios ranging from 7:1 to 1:7, 6:1 to 1:6, 4:1 to 1:4, 3:1 to 1:3, and 2:1 to 1:2.The inventive flame retardant is frequently the major component in such a combination, for example, a ratio of 10:1 to 1.2:1 or a ratio of 7:1 to 2:1 by weight of the inventive flame retardant material with respect to the total weight of the additional flame retardant, synergistic agent and / or adjuvant, but the inventive material may also be the minor component of the mixture, for example, a ratio of 1:10 to 1:1.2 or a ratio of 1:7 to 1:2. The thermally stable flame retardant of the invention can form thermoplastic polymer compounds at high temperatures, such as high-temperature polyamides and polyethylene terephthalate esters, without decomposing or adversely affecting the polymer's physical properties, and its flame retardant activity is excellent. The flame retardant of the invention can be used in other polymers, with other synergistic agents, and with conventional polymer additives. The polymer of the flame-retardant composition of the present invention may be any polymer known in the art, such as polyolefin homopolymers and copolymers, rubbers, polyesters, including polyalkylene terephthalates, epoxy resins, polyurethanes, polysulfones, polyimides, polyphenylene ethers, styrenic polymers and copolymers, polycarbonates, acrylic polymers, polyamides, polyacetals, and biodegradable polymers. Mixtures of different polymers, such as polyphenylene ether / styrenic resin mixtures, polyvinyl chloride / acrylonitrile butadiene styrene (ABS), or other impact-modified polymers, such as methacrylonitrile and α-methylstyrene containing zi frbnn / zznzB / γΐΛΐ ABS, and polyester / ABS or polycarbonate / ABS and polyester or polystyrene plus some other impact modifier can also be used. Such polymers are commercially available or manufactured by means well known in the art. The flame retardant of the invention is particularly useful in thermoplastic polymers that are processed and / or used at high temperatures, for example, styrenic polymers, including high impact polystyrene (HIPS), polyolefins, polyesters, polycarbonates, polyamides, polyurethanes, polyphenylene ethers, and the like. For example, the polymer may be a polyester resin, a styrenic resin, a polyamide resin, a polycarbonate resin, a polyphenylene oxide resin, a vinyl resin, an olefinic resin, an acrylic resin, an epoxy resin, or a polyurethane. The polymer may be a thermoplastic or a thermosetting resin and may be reinforced, for example, with glass. In some embodiments, the polymer is a thermoplastic polyurethane. In some embodiments, the polymer is a thermosetting epoxy resin. More than one polymer resin may be present.In particular embodiments, the polymer is an engineered polymer, for example, a thermoplastic or reinforced thermoplastic polymer, for example, a glass-reinforced thermoplastic polymer, such as a polyester optionally with glass filler, epoxy resin or polyamide, for example, a glass-filled polyester, such as a glass-filled polyalkylene terephthalate, or a glass-filled polyamide. Polyester series resins include homopolyesters and copolyesters obtained by, for example, polycondensation of a dicarboxylic acid component and a diol component, and polycondensation of a hydroxycarboxylic acid or a lactone component, for example, aromatic resin of the saturated polyester series, such as polybutylene terephthalate or polyethylene terephthalate. The polyamide (PA) series resins include polyamides derived from a diamine and a dicarboxylic acid; polyamides obtained from an aminocarboxylic acid, if necessary in combination with a diamine and / or a dicarboxylic acid; and polyamides derived from a lactam, if necessary in combination with a diamine and / or a dicarboxylic acid. Polyamide also ZLhhnn / zznz / B / YW includes a copolyamide derived from at least two different types of polyamide constituents. Examples of resins in the polyamide series include aliphatic polyamides such as PA 46, PA 6, PA 66, PA 610, PA 612, PA 11, and PA 12; polyamides obtained from an aromatic dicarboxylic acid, for example, terephthalic acid and / or isophthalic acid, and an aliphatic diamine, for example, hexamethylenediamine or nonamethylenediamine; and polyamides obtained from both aromatic and aliphatic dicarboxylic acids, for example, both terephthalic acid and adipic acid, and an aliphatic diamine, for example, hexamethylenediamine and others. These polyamides can be used individually or in combination. In some embodiments, the polymer comprises PA 6. In some embodiments, the polymer comprises PA 66. In some embodiments, the polymer comprises a polyphthalamide. Polyamides with melting points of at least 280°C are widely used to produce molding compounds that enable the manufacture of molded articles, for example, for the electrical and electronics industries, with excellent dimensional stability at high temperatures and very good flame-retardant properties. Such molding compounds are in demand, for example, in the electronics industry for producing components that are mounted on printed circuit boards using surface mount technology (SMT). In the present application, these components must withstand temperatures up to 270°C for short periods without dimensional changes. These high-temperature polyamides include certain polyamides produced from alkyl diamines and diacids, such as polyamide 4,6. However, many high-temperature polyamides are aromatic and semi-aromatic polyamides—that is, homopolymers, copolymers, terpolymers, or higher polymers derived from monomers containing aromatic groups. A single aromatic or semi-aromatic polyamide may be used, or mixtures of aromatic and / or semi-aromatic polyamides are employed. It is also possible for the aforementioned polyamides and polyamide mixtures to be blended with other polymers, including aliphatic polyamides. Los exemplos de estas poliamidas de temperatura alta aromáticas o semiamáticas incluyen poliamida 4T, poli(m-xilen adipamide) (poliamida MXD,6), poli(dodecametileno tereftalamida) (poliamida 12,T), poli(decametileno ζΐMτηη / ζζηζ / B / γίΛΐ tereftalamida) (poliamida 10,T), poli(nonametileno tereftalamida) (poliamida 9,T), copoliamida de hexametileno adipamida / hexametileno tereftalamida (poliamida 6,T / 6,6), copoliamida de hexametileno tereftalamida / 2-metilpentametileno tereftalamida (poliamida 6,T / D,T); hexamethylene adipamide / hexamethylene terephthalamide / hexamethylene isophthalamide copolyamide (polyamide 6,6 / 6,T / 6,I); poly(caprolactam-hexamethylene terephthalamide) (polyamide 6 / 6,T); hexamethylene terephthalamide / hexamethylene isophthalamide copolymer (6,T / 6,I); and similar products. Certain embodiments of the invention are, therefore, compositions comprising a polyamide that melts at high temperatures, for example, 280 °C or more, 300 °C or more, in some embodiments 320 °C or more, for example, from 280 to 340 °C, such as polyamide 4,6 and the aromatic and semi-aromatic polyamide described above, articles comprising high-temperature polyamides and the flame-retardant material of the invention, methods for preparing the compositions, and methods for shaping the articles. As described herein, in many embodiments of this disclosure, the flame-retardant polymer composition comprises (i) a polymer, (ii) the flame retardant of this disclosure, and (ii) one or more additional flame retardants and / or one or more synergistic agents or flame retardant adjuvants. Therefore, although the flame retardant (i) alone exhibits excellent activity in polymer systems, it may be used in combination with (ii) one or more compounds selected from other flame retardants, synergistic agents, and adjuvants.Example compounds (iii) include halogenated flame retardants, alkyl or aryl phosphine oxides, alkyl or aryl polyphosphine oxides, alkyl or aryl phosphates, alkyl or aryl phosphonates, alkyl or aryl phosphinates, salts of alkyl or aryl phosphinic acid, carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes, polyphenylene ether, melamine, melamine derivatives, melamine condensation products, melamine salts, metal hydroxides, metal oxides, metal oxide hydrates, metal borates, metal carbonates, metal sulfates, metal phosphates, metal phosphonates, metal phosphites, metal hypophosphites, metal silicates, and mixed metal salts.For example, one or more compounds (ii) may be selected from aluminum tris(dialkylphosphinate), aluminum hydrogen phosphite, benzyl phosphine oxides, polybenzyl phosphine oxides, melam, melem, melon, melamine phosphates, melamine metal phosphates, melamine cyanurate, melamine borate, talc, clays, calcium silicate, aluminosilicate, aluminosilicate in the form of hollow tubes, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, boron phosphate, calcium molybdate, exfoliated vermiculite, zinc stannate, zinc hydroxystannate, zinc sulfide, zinc borate, zinc molybdate, zinc phosphate, magnesium oxide, zinc hydroxide magnesium, aluminum oxide, aluminum oxide hydroxide, aluminum trihydrate, silica, tin oxide, antimony (III and V) oxide, antimony (III and V) oxide hydrate, titanium oxide, zinc oxide, zinc oxide hydrate, zirconium oxide and zirconium hydroxide.For example, one or more compounds (iii) may be selected from aluminum tris(dimethylphosphinate), aluminum tris(diethylphosphinate), aluminum tris(dipropylphosphate), aluminum tris(dibutylphosphinate), polyaryl ether substituted with methylene-diphenylphosphine oxide, xylenebis(diphenylphosphine oxide), 1,2-bis-(9,1O-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane, 4,4'-bis(diphenylphosphonimethyl)-1,1'-biphenyl, melam, melem, melon, and dimelamine zinc pyrophosphate. In some embodiments, the flame retardant synergist comprises a material selected from melamine, melem, melon, melamine cyanurate, melamine polyphosphate, and melamine poly(metal phosphate) (e.g., melamine poly(zinc phosphate) (Safire 400)). In some embodiments, the synergist comprises a triazine-based compound, such as a reaction product of trichlorotriazine, piperazine, and morpholine, e.g., poly-[2,4-(piperazin-1,4-1)-6-(morpholin-4-1)-1,3,5-triazine] / piperazine (MCA® PPM Triazine HF). In some embodiments, the synergist comprises a metal hypophosphite, such as aluminum hypophosphite (e.g., Italmatch Phoslite® IP-A). In some embodiments, the synergistic agent comprises an organic phosphinate, such as aluminum dialkylphosphinate, for example, aluminum diethylphosphinate (Exolit OP). In some embodiments, the flame retardant polymer composition comprises one or more compounds selected from hydrotalcite clays, metal borates, metal oxides and metal hydroxides, such as metal borates, metal oxides or metal hydroxides where the metal is zinc or calcium. The concentration of the inventive flame retardant in the polymer composition depends, of course, on the exact chemical composition of the flame retardant, the polymer, and other components present in the final polymer composition. For example, when used as the sole flame retardant component of a polymer formulation, the inventive flame retardant may be present at a concentration of 1 to 50%, or 1 to 30% by weight of the total weight of the final composition. Typically, when used as the sole flame retardant, there will be at least 2% of the inventive material present, for example, 3% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more. In many embodiments, the inventive flame retardant is present in amounts up to 45%, whereas in other embodiments, the amount of inventive flame retardant is 40% of the polymer composition or less, for example, 35% or less.When used in combination with other flame retardants or flame retardant synergists, a lesser amount of inventive material may be required. To prepare the flame-retardant polymer composition of this disclosure, any known compounding technique may be used; for example, the flame retardant may be introduced into molten polymer by mixing, extrusion, fiber or film forming, etc. In some cases, the flame retardant is introduced into the polymer at the time of polymer formation or curing; for example, the flame retardant of the invention may be added to a polyurethane prepolymer before crosslinking, or it may be added to a polyamine or alkyl-polycarboxyl compound before polyamide formation, or to an epoxy mixture before curing. The flame retardant polymer composition of the invention will frequently contain one or more of the common stabilizers or other additives frequently found in the art, such as phenolic antioxidants, hindered amine light stabilizers (HALS), ultraviolet light absorbers, phosphites, phosphonites, alkali metal salts of fatty acids, hydrotalcites, metal oxides, borates, epoxidized soybean oils, hydroxylamines, tertiary amine oxides, lactones, thermal reaction products of tertiary amine oxides, thiosynergistic agents, basic co-stabilizers, e.g., melamine, melem, etc., polyvinylpyrrolidone, dicyandiamide, trialyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamides, polyurethanes, hydrotalcites, alkali metal salts and alkaline earth metal salts of higher fatty acids, for example, Ca stearate, calcium stearoyl lactate, calcium lactate, Zn stearate, Zn octoate, Mg stearate, Na ricinoleate and K palmitate, antimony pyrocatecholate or zinc pyrocatecholate, nucleating agents, clarifying agents, etc. Other additives may also be present, for example, plasticizers, lubricants, emulsifiers, pigments, colorants, optical brighteners, other flame retardants, anti-aesthetic agents, blowing agents, anti-drip agents, for example, PTFE and the like. Optionally, the polymer may include fillers and reinforcing agents, such as calcium carbonate, silicates, glass fibers, talc, kaolin, mica, barium sulfate, metal oxides and hydroxides, carbon black, and graphite. These fillers and reinforcing agents are frequently present at relatively high concentrations, including formulations where the filler or reinforcement is present at concentrations exceeding 50% by weight based on the weight of the final composition. More typically, fillers and reinforcing agents are present at approximately 5% to approximately 50% by weight, for example, approximately 10% to approximately 40% by weight or approximately 15% to approximately 30% by weight based on the weight of the total polymer composition. In some embodiments, the flame-retardant polymer composition of this disclosure is formulated with one or more materials selected from carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes, talc, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, calcium silicate, magnesium silicate, aluminosilicate hollow tubes (Dragonite), halloysite, boron phosphate, calcium molybdate, exfoliated vermiculite, zinc stannate, zinc hydroxystannate, zinc sulfide, zinc borate, zinc molybdate (or complexes thereof, e.g., Kemgard 911B), zinc molybdate / magnesium hydroxide complex (e.g., Kemgard MZM), zinc molybdate / magnesium silicate complex (Kemgard 911C), calcium molybdate / zinc complex (for example, Kemgard 911 A), zinc phosphate (or complexes thereof, for example, Kemgard 981) and the like; hydroxides, oxides and oxide hydrates of (semi)metals of groups 2, 4, 12, 13, 14, 15, for example, magnesium oxide or hydroxide, aluminum oxide, aluminum oxide hydroxide (Boehmite), aluminum trihydrate, silica, silicates, tin oxide, antimony (III and V) oxide and oxide hydrate, titanium oxide and zinc oxide or oxide hydrate, zirconium oxide and / or zirconium hydroxide and the like; melamine and urea-based resins such as melamine cyanurate, melamine borate, melamine polyphosphate, melamine pyrophosphate, polyphenylene ether (PPE) and the like; and clays, including, for example, hydrotalcite, boehmite, kaolin, mica, montmorillonite, wollastonite, nanoclays or organically modified nanoclays and the like. In some embodiments, the flame retardant polymer composition of the present disclosure is formulated with one or more materials selected from zinc borate, zinc stannate, polysiloxanes, kaolin, silica, magnesium hydroxide, zinc molybdate complex (e.g., Kemgard 911B), zinc molybdate / magnesium hydroxide complex (e.g., Kemgard MZM), zinc molybdate / magnesium silicate complex (Kemgard 911C), calcium / zinc molybdate complex (e.g., Kemgard 911 A), zinc phosphate complex (e.g., Kemgard 981), and melamine poly(metal phosphate) (e.g., melamine poly(zinc phosphate) (Safire 400)). In some embodiments, in addition to a polymer (as described herein) and the flame retardant of this disclosure, the flame retardant polymer composition comprises melam and one or more materials selected from zinc borate, zinc stannate, zinc molybdate complex, zinc molybdate / magnesium hydroxide complex, zinc molybdate / magnesium silicate complex, calcium / zinc molybdate complex, zinc phosphate complex, and zinc oxide, optionally with additional additives, as described herein. In some embodiments, in addition to a polymer (as described herein) and the flame retardant of this disclosure, the flame retardant polymer composition comprises melon and one or more materials selected from zinc borate, zinc stannate, zinc molybdate complex, zinc molybdate / magnesium hydroxide complex, zinc molybdate / magnesium silicate complex, calcium / zinc molybdate complex, zinc phosphate complex, and zinc oxide, optionally with additional additives, as described herein. The Examples that follow provide additional non-limiting disclosure. EXAMPLES Example 1 Methylphosphonic acid (MPA) (3678.8 g, 38.3 mol, 30 equiv., 75% aqueous solution) and alumina (130.2 g, 1.28 mol, 1 equiv.) were mixed at room temperature, and a limited exothermic reaction (an increase of approximately 2 °C) was observed. The vessel temperature was set to 165 °C, with a stirrer at 200 RPM at atmospheric pressure and nitrogen purging (4 L / min). When no distilled water was observed in the condenser, 1.0 g of seed material, which was the flame retardant product produced from MPA and alumina according to this disclosure, was optionally added. The reaction mixture was heated to 165 °C for 3 hours. Next, the reaction mixture containing a white suspension product was cooled to approximately 130 °C and poured into 1.5 L of water in a beaker cooled in an ice water bath.The white suspension was then filtered, washed with water (500 ml x 3) and dried to produce fine crystals with a 92% yield. The product had a phosphorus to aluminum ratio of 4:1 (elemental analysis by ICP) according to the following empirical formula: either Me. II P—O' / either \ .P—O Me^ 11 EITHER O Me. II P—O / or \ ,P—OH Me^ 11 O zi frfrnn / zznzB / γΐΛΐ The empirical formula of the above product represents repeating monomeric units (i.e., coordination entities) of a coordination polymer that forms the pure crystalline product. The thermogravimetric analysis (TGA) of the product is shown in FIG. 1. Example 2 A 1 L flask was charged with 800 mL of xylenes and fitted with a Dean-Stark trap. The solution was heated to 115 °C and methylphosphonic acid (MPA) (33.89 g, 0.35 mol) was added. The acid was allowed to dissolve, and the temperature was increased so that the solution began to reflux. Alumina (4.01 g, 0.039 mol) was added in portions over 3 hours. Reflux was maintained at 142 °C overnight. The resulting solid product was isolated by filtration, washed with DMF (100 mL) and Et₂O (2 x 50 mL), and dried to produce a fine powder (18.86 g, 71% yield). The product had a phosphorus-to-aluminum ratio of 4:1 according to the following empirical formula: either Me^ 11 P—O' / O \ ,p—O Me^ 11 EITHER O Me^ I p—0' / o \ ,p—OH Mex11 O zi frfrnn / zznzB / γΐΛΐ The empirical formula of the above product represents repeating monomeric units (i.e., coordination entities) of a coordination polymer that forms the pure crystalline product. Example 3 Methylphosphonic acid (MPA) (2216 g, 23.1 mol, 15 equiv., aqueous solution) and aluminum trihydroxide (120 g, 1.5 mol, 1 equiv.) were mixed at room temperature. The vessel temperature was set to 165 °C, with a stirrer at 200 RPM at atmospheric pressure and nitrogen purging (4 L / min). When no distilled water was observed in the condenser, 1.0 g of seeding material, which was the flame retardant product produced from MPA and aluminum trihydroxide according to this disclosure, was optionally added. The reaction mixture was heated to 165 °C for 3 hours. Afterward, the reaction mixture, containing a white suspension product, was cooled to approximately 130 °C and poured into 1.5 L of water in a beaker cooled in an ice-water bath. The white suspension was filtered, washed with water (500 mi x 3) and dried to produce fine crystals with a yield of approximately 100%.The product had a phosphorus to aluminum ratio of 4:1 (elemental analysis by ICP) according to the following empirical formula:. / either _P—OMe II ai3+_p—OH Me II O The empirical formula of the above product represents repeating monomeric units (i.e., coordination entities) of a coordination polymer that forms the pure crystalline product. Example 4 EITHER Me^ II 30 SICKLE Fe2O3 H2O ~Δ~ Methylphosphonic acid (MPA) (1412.6 g, 14.7 mol, 30 equiv., 75% aqueous solution) and iron oxide (78.2 g, 0.49 mol, 1 equiv.) were mixed at room temperature. The temperature of the container was maintained at 130 °C for approximately 12 hours, with a stirrer at 250 RPM at atmospheric pressure and nitrogen purging (4 L / min). The reaction mixture was then heated to 165 °C for another 12 hours. The reaction mixture, containing a whitish suspension product, was then cooled to approximately 130 °C and poured into 1.5 L of water in a beaker cooled in an ice-water bath. The whitish suspension was filtered, washed with water (500 ml x 3), and dried to produce fine, whitish crystals with a 92% yield. The product had a phosphorus-to-iron ratio of 4:1 (elemental analysis by ICP) according to the following empirical formula: either Mex11 R—O' or \ ,P—O' Mex11 or Mex11 p—oo \ ,p—OH Mex11 O zLfrfrnn / zznz / B / YiAi The empirical formula of the above product represents repeating monomeric units (i.e., coordination entities) of a coordination polymer that forms the pure crystalline product. Example 5 Al(OiPr)3 H2O EITHER ai3+ Me Me Methylphosphonic acid (MPA) (1727 g, 18.4 mol, 15 equiv., 75% aqueous solution) was cooled to 5 °C in an ice-water bath under a nitrogen flow (1 L / min). Aluminum isopropoxide (250 g, 1.2 mol, 1 equiv.) was added in portions while the vessel temperature was maintained below 10 °C. The vessel temperature was then adjusted to 165 °C, with the stirrer running at 250 RPM. At 165 °C, 4.5 g of seed material, which was the flame retardant product produced from MPA and aluminum isopropoxide according to this disclosure, was optionally added, and the reaction mixture was maintained at 165 °C for 3 hours. Next, the reaction mixture containing a white suspension product was cooled to approximately 130 °C and poured into 1.5 L of water in a beaker cooled in an ice water bath.The white suspension was filtered, washed with water (500 ml x 3) and dried to produce fine crystals with a yield of 44%. The product had a phosphorus to aluminum ratio of 4:1 (elemental analysis by ICP) according to the following empirical formula: op—OK or .p—O' Me 11 Or Mex11 p—O o ,p—OH Mex11 O zi b+nn / zznzB / YiAi The empirical formula of the above product represents repeating monomeric units (i.e., coordination entities) of a coordination polymer that forms the pure crystalline product. Example 6 Ethylphosphonic acid (EPA) (55.0 g, 0.50 mol, 30 equiv.) and alumina (1.70 g, 17 mmol, 1 equiv.) were mixed at room temperature with 50 mL of water. The vessel temperature was set to 165 °C, with a stirrer at 250 RPM at atmospheric pressure and nitrogen purging (4 L / min). The reaction mixture was heated to 165 °C for 3 hours. The reaction mixture, containing a whitish suspension product, was then cooled to approximately 130 °C and poured into 100 mL of water in a beaker cooled in an ice-water bath. The white suspension was filtered, washed with water (50 mL x 3), and dried to produce fine crystals in 76% yield. The product had a phosphorus to aluminum ratio of 4:1 (elemental analysis by ICP) according to the following empirical formula: The empirical formula of the above product represents repeating monomeric units (i.e., coordination entities) of a coordination polymer that forms the pure crystalline product. Example 7 Polymer compositions were prepared and their flame retardant activity was evaluated in UL-94 tests. UL-94 V-0 ratings were measured at thicknesses of 0.8 mm and 1.6 mm for glass fiber-reinforced polyamide 6,6 polymer compositions containing the flame retardant produced according to Example 1 above: zi frbnn / zznzB / γΐΛΐ Table 1. Formulations with UL-94 V-0 classification at 0.8 and 1.6 mm Substrate Fiberglass RLL Inventive Melamine Zinc borate PA 6.6 30% by weight 13% by weight 10% by weight 1% by weight PA 6.6 30% by weight 13.7% by weight 10% by weight - UL-94 V-0 ratings were also measured at 0.8 mm for glass-filled polymer compositions of polyamide 6,6, polyamide 6, polybutylene terephthalate (PBT), and a high-temperature polyamide containing the flame retardant produced according to Examples 1, 2, 3, and 5 above: Table 2. Compositions with UL-94 V-0 classification at 0.8 mm Substrate Fiberglass RLL Inventive Melamine Melamine Cyanurate PA 6.6 30% 12.5% ​​10% - PA6 25% 15% - 10% PBT 25% 15% 15% - High Temperature Nylon 25% 18% - - Additional polymer compositions containing the flame retardant produced according to Examples 1, 2, 3, and 5 above, combined with various synergists in PA 66 glass filler, PBT, and polyphthalamide, were prepared and evaluated under the UL-94 test at 0.8 mm thickness. The results are provided in Table 3 (PA 66), Table 4 (PBT), and Table 5 (polyphthalamide). Formulations 17, 22, and 24, which did not contain the inventive flame retardant, did not pass the UL-94 test. Table 3. PA66 Formulation 7 8 9 1 0 1 1 1 1 2 13 14 15 16 17 % in 46, 46, 46, 4 4 5 40, 45, 45, 46, 70 weight of PA 66 3 5 5 6 5 3 3 30 by weight of glass 30 30 3 0 3 0 3 0 30 30 30 30 30 wt % of Inventive RLL 13, 7 10 10 1 3 1 4 1 2 13, 7 13, 7 13, 7 13, 7 wt % of melam - - - - - % by weight of melem - - - - - - 16 - - - - % by weight of melon - - - - - - - 10 10 - - % by weight of polyphosphate or melamine to 8% by weight of Exolit OP 1230 3.5% by weight of Exolit OP 1230 3.5% by weight of Exolit OP30, 15% by weight of PPM0 Triazine HF 10 wt % zinc borate 1 1 wt % zinc stannate or zinc 1 1 zLhbnn / zznz / e / New UL94a 0.8 mm (1 / 32) V0 V0 V0 V0 V0 V0 V- 1 V0 V0 V- 1 Suspension so ζι++ηη / ζζηζ / Β / γΐΛΐ Table 4. PBT Formulation 18 19 20 21 22 wt% PBT 50 50 50 45 75 wt% glass 25 25 25 25 25 wt% RLL Inventive 15 16 15 15 - wt% melamine 10 9 9 15 - wt% polysiloxane - - 1 - - UL 94 at 0.8 mm (1 / 32) V-0 V-0 V-0 V-0 Suspense zi frfrnn / zznz / Β / γΐΛΐ Table 5. Polyphthalamide (high temperature polyamide) Formulation 23 24 wt% polyphthalamide 57 70 wt% glass 25 30 wt% RLL Inventive 18 - UL 94 at 0.8 mm (1 / 32) V-0 Suspense Example 8 Polymeric compositions containing the flame retardant produced according to Example 4 above in PA 66 were prepared and evaluated for their flame retardant activity in UL-94 tests at a thickness of 0.8 mm. The results are provided in Table 6. Sample 27, which did not contain the inventive flame retardant, failed the UL-94 test. Table 6. PA 66 Formulation 25 26 27 wt% PA 66 45 45 70 wt% glass 30 30 30 wt% RLL Inventive 25 15 - wt% melamine - 10 - UL 94 at 0.8 mm (1 / 32) V-2 V-0 Suspense Although particular embodiments of the present invention have been illustrated and described, it will be evident to those skilled in the art, from consideration of the descriptive specification and the application of this disclosure, that various modifications and variations can be made without departing from the scope of the invention as claimed. Therefore, the specification and examples are intended to be considered illustrative only, and the true scope of the present invention is indicated by the following claims and their equivalents.

Claims

1. A process for producing a phosphorus-containing flame retardant, comprising preparing a reaction mixture, the reaction mixture comprising (a) an unsubstituted or alkyl or aryl-substituted phosphonic acid, (b) a solvent for the phosphonic acid, and (c) a metal capable of forming a polycation, or a suitable metal compound represented by the formula Mp<+>yxq where M is a metal, (+)y represents the charge of the metal cation, and is 2 or more, X is an anion, and the values ​​of pyq provide a balanced-charge metal compound; and heating the reaction mixture to a reaction temperature of 105 °C or more for a time sufficient to produce the phosphorus-containing flame retardant.

2. A process for producing a phosphorus-containing flame retardant, comprising preparing a reaction mixture, the reaction mixture comprising (a) an unsubstituted or alkyl or aryl-substituted pyrophosphonic acid, (b) a solvent for the pyrophosphonic acid, and (c) a metal capable of forming a polycation, or a suitable metal compound represented by the formula Mph^Xq where M is a metal, (+)y represents the charge of the metal cation, and is 2 or more, X is an anion, and the values ​​of pyq provide a balanced-charge metal compound; and reacting the reaction mixture at a reaction temperature of 20 °G or more for a time sufficient to produce the phosphorus-containing flame retardant.

3. The process according to claim 1 or 2, wherein the reaction mixture is prepared at a preparation temperature below the reaction temperature. zLhbnn / zznz / e / Yiñi 4. The process according to claim 3, wherein the preparation temperature varies from approximately 15°C to approximately 40°C.

5. The process according to any one of the preceding claims, wherein the components (a) and (b) of the reaction mixture are in solution form, and preparing the reaction mixture comprises mixing component (c) with the solution.

6. The process according to claim 1, wherein the reaction temperature is approximately 150 °C or more.

7. The process according to claim 1, wherein the reaction temperature varies from approximately 140°C to approximately 260°C.

8. The process according to claim 2, wherein the reaction temperature is approximately 60 °C or more.

9. The process according to claim 2, wherein the reaction temperature varies from approximately 60 °C to approximately 240 °C.

10. The process according to any one of the preceding claims, wherein the molar ratio of component (a) to component (c) in the reaction mixture varies from approximately 4:1 to approximately 50:

1.

11. The process according to claim 1, wherein the solvent is selected from water, sulfones, sulfoxides, halogenated hydrocarbons, aromatic hydrocarbons, and ethers.

12. The process according to claim 1, wherein the solvent comprises water.

13. The process according to claim 2, wherein the solvent is aprotic. ZLhhnn / zznz / B / YW 14. The process according to claim 1 or 2, wherein the reaction mixture component (c) comprises a metal capable of forming a 2+, 3+ or 4+ polycation.

15. The process according to claim 1 or 2, wherein the reaction mixture component (c) comprises a suitable metallic compound represented by the formula Mp^Xq where M is a metal, (+)y represents the charge of the metallic cation, and is 2, 3 or 4, X is an anion, and the values ​​of pyq provide a balanced-charged metallic compound.

16. The process according to claim 15, wherein y is 3.

17. The process according to claim 16, wherein M is selected from Al, Ga, Sb, Fe, Co, B and Bi.

18. The process according to claim 17, wherein M is Al or Fe.

19. The process according to claim 1 or 2, wherein the component (c) of the reaction mixture comprises the suitable metal compound, and the suitable metal compound is selected from a metal oxide, halide, alkoxide, hydroxide, carbonate, carboxylate, or phosphonate.

20. The process according to claim 19, wherein M in the formula MpWy xq is Al or Fe.

21. The process according to claim 20, wherein the suitable metal compound is selected from alumina, aluminum trichloride, aluminum trihydroxide, aluminum isopropoxide, aluminum carbonate, aluminum acetate, iron(III) oxide, iron(III) chloride, iron(III) isopropoxide, and iron(III) acetate.

22. The process according to claim 1, wherein the unsubstituted or alkyl or aryl substituted phosphonic acid is represented by formula (I) zi frfrnn / zznzB / YiAi zi frbnn / zznzB / γΐΛΐ where R is H, C1-12 alkyl, C6-10 aryl, C7-18 alkylaryl or C7-18 arylalkyl, wherein the alkyl, aryl, alkylaryl or arylalkyl is unsubstituted or is substituted with halogen, hydroxyl, amino, C1-4 alkylamino, C1-4 dialkylamino, C1-4 alkoxy, carboxy or C2-5 alkoxycarbonyl.

23. The process according to claim 2, wherein the unsubstituted or alkyl or aryl substituted pyrophosphonic acid is represented by the formula (a) or RJI P--OH O --OH R II 0 (a), wherein R is H, C1-12 alkyl, Ce-io aryl, C7-18 alkylaryl or C7-18 arylalkyl, wherein the alkyl, aryl, alkylaryl or arylalkyl are unsubstituted or are substituted with halogen, hydroxyl, amino, C1-4 alkylamino, C1-4 dialkylamino, C1-4 alkoxy, carboxy or C2-5 alkoxycarbonyl.

24. The process according to claim 22 or 23, wherein R is an unsubstituted C1-12 alkyl, Ce aryl, C7-10 alkylaryl or C7-10 arylalkyl.

25. The process according to claim 24, wherein R is an unsubstituted C16 alkyl.

26. The process according to claim 26 or 27, wherein R is methyl, ethyl, propyl, isopropyl, butyl or t-butyl.

27. A phosphorus-containing flame retardant produced according to the process of any one of claims 1 to 26, wherein the phosphorus-containing flame retardant comprises a compound of empirical formula (III) zi frfrnn / zznzB / γALA where R is H, an alkyl, aryl, alkylaryl or arylalkyl group; M is a metal and ey is 2 or 3, such that M(+)y is a metal cation where (+)y represents the charge formally assigned to the cation; a, b and c represent the ratio of the corresponding components to each other in the compound and satisfy the charge balance equation 2(a)+c=b(y); and c is not zero.

28. The phosphorus-containing flame retardant according to claim 27, wherein y is 3, a is 1, b is 1, and c is 1.

29. A flame retardant polymer composition comprising (i) a polymer and (ii) the phosphorus-containing flame retardant according to claim 27 or 28.

30. The flame retardant polymer composition according to claim 29, wherein the polymer comprises one or more of a homopolymer or copolymer of polyolefin, rubber, polyester, epoxy resin, polyurethane, polysulfone, polyimide, polyphenylene ether, styrenic polymer or copolymer, polycarbonate, acrylic polymer, polyamide, or polyacetal.

31. The flame retardant polymer composition according to claim 30, wherein the polymer comprises one or more of a styrenic polymer or copolymer, polyolefin homopolymer or copolymer, polyester, polycarbonate, acrylic polymer, epoxy resin, polyamide or polyurethane.

32. The flame retardant polymer composition according to claim 31, wherein the polymer comprises a polyalkylene terephthalate, high impact polystyrene (HIPS), epoxy resin or polyamide.

33. The flame retardant polymer composition according to claim 32, wherein the polymer comprises a glass-filled polyalkylene terephthalate, glass-reinforced epoxy resin, or a glass-filled polyamide.

34. The flame retardant polymer composition according to claim 32, wherein the polymer comprises a polyphthalamide.

35. The flame retardant polymer composition according to claim 32, wherein the polymer comprises polyamide 46, polyamide 6, polyamide 66, polyamide 4T or polyamide 9T.

36. The flame retardant polymer composition according to claim 32, wherein the polymer comprises polyamide MXD,6, polyamide 12,T, polyamide 10,T, polyamide 6,T / 6,6, polyamide 6,T / D,T, polyamide 6,6 / 6,176,1, polyamide 6 / 6,T or polyamide 6,176,1.

37. The flame retardant polymer composition according to claim 29, wherein the polymer comprises a mixture of polyphenylene ether / styrene resin, acrylonitrile butadiene styrene (ABS), polyvinyl chloride / ABS mixture, methacrylonitrile / ABS mixture, α-methylstyrene containing ABS, polyester / ABS, polycarbonate / ABS, impact-modified polyester, or impact-modified polystyrene.

38. The flame retardant polymer composition according to any one of claims 29 to 37, further comprising (ii) one or more compounds selected from additional flame retardants, synergistic agents and flame retardant adjuvants.

39. The flame-retardant polymer composition according to claim 38, wherein one or more of the compounds are selected from halogenated flame retardants, alkyl or aryl phosphine oxides, alkyl or aryl polyphosphine oxides, alkyl or aryl phosphates, alkyl or aryl phosphonates, alkyl or aryl phosphinates, salts of alkyl or aryl phosphinic acid, carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes, polyphenylene ether, melamine, melamine derivatives, melamine condensation products, melamine salts, metal hydroxides, metal oxides, metal oxide hydrates, metal borates, metal carbonates, metal sulfates, metal phosphates, metal phosphonates, metal phosphites, metal hypophosphites, metal silicates, and metal salts mixed.

40. The flame-retardant polymer composition according to claim 39, wherein one or more of the compounds are selected from aluminum tris(dialkylphosphinate), aluminum hydrogen phosphite, benzyl phosphine oxides, polybenzyl phosphine oxides, melam, melem, melon, melamine phosphates, melamine metal phosphates, melamine cyanurate, melamine borate, talc, clays, calcium silicate, aluminosilicate, aluminosilicate in the form of hollow tubes, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, boron phosphate, calcium molybdate, exfoliated vermiculite, zinc stannate, zinc hydroxystannate, zinc sulfide, zinc borate, zinc molybdate, zinc phosphate, magnesium oxide, zinc hydroxide magnesium, aluminum oxide, aluminum oxide hydroxide, aluminum trihydrate, silica, tin oxide, antimony (III and V) oxide, antimony (III and V) oxide hydrate, titanium oxide, zinc oxide,zinc oxide hydrate, zirconium oxide and zirconium hydroxide.

41. The flame retardant polymer composition according to claim 40, wherein the one or more compounds are selected from aluminum tris(dimethylphosphinate), aluminum tris(diethylphosphinate), aluminum tris(dipropylphosphate), aluminum tris(dibutylphosphinate), methylene-diphenylphosphine oxide substituted polyaryl ether, xylenebis(diphenylphosphine oxide), 1,2-bis-(9,1O-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane, 4,4'-bis(diphenylphosphinemethyl)-1,1'-biphenyl, melam, melem, melon, and dimelamine zinc pyrophosphate.

42. The flame-retardant polymer composition according to claim 29, further comprising one or more compounds selected from hydrotalcite clays, metal borates, metal oxides, and metal hydroxides.

43. The flame retardant polymer composition according to claim 42, wherein the metal of the metal borates, metal oxides and metal hydroxides is zinc or calcium.

44. The flame retardant polymer composition according to claim 38, wherein one or more compounds are selected from melam, melem, melon, melamine cyanurate, melamine polyphosphate, melamine poly(metal phosphate), poly-[2,4-(piperazin-1,4-11)-6-(morpholin-4-11)-1,3,5-triazine] / piperazine, aluminum hypophosphite, and aluminum dialkylphosphinate.

45. The flame retardant polymer composition according to claim 38, wherein one or more compounds are selected from zinc borate, zinc stannate, polysiloxanes, kaolin, silica, magnesium hydroxide, zinc molybdate complex, zinc molybdate / magnesium hydroxide complex, zinc molybdate / magnesium silicate complex, calcium / zinc molybdate complex, zinc phosphate complex, and poly(zinc phosphate) melamine.

46. ​​The flame retardant polymer composition according to claim 38, wherein the one or more compounds comprise melam and one or more materials selected from zinc borate, zinc stannate, zinc molybdate complex, zinc molybdate / magnesium hydroxide complex, zinc molybdate / magnesium silicate complex, calcium / zinc molybdate complex, zinc phosphate complex, and zinc oxide.

47. The flame retardant polymer composition according to claim 38, wherein the one or more compounds comprise melon and one or more materials selected from zinc borate, zinc stannate, zinc molybdate complex, zinc molybdate / magnesium hydroxide complex, zinc molybdate / magnesium silicate complex, calcium / zinc molybdate complex, zinc phosphate complex, and zinc oxide.

48. A flame retardant material comprising a compound of empirical formula (III) zi b+nn / zznz / B / YiAi zi frfrnn / zznzB / viAi wherein R is H, an alkyl, aryl, alkylaryl or arylalkyl group; M is a metal and ey is 2 or 3, such that M(+)y is a metallic cation wherein (+)y represents the charge formally assigned to the cation; a, b and c represent the ratio of the components to which they correspond to each other in the compound, and satisfy the charge balance equation 2(a)+c=b(y); and c is not zero.

49. The flame retardant material according to claim 48, wherein y is 3, a is 1, b is 1 and c is 1.

50. The flame retardant material according to claim 49, wherein M is Al, Ga, Sb, Fe, Co, B or B1.

51. The flame retardant material according to claim 50, wherein M is Al or Fe.

52. The flame retardant material according to any one of claims 48 to 51, wherein R is H or alkyl.

53. The flame retardant material according to claim 52, wherein R is C1-6 alkyl.

54. The flame retardant material according to claim 53, wherein R is methyl or ethyl.

55. The flame retardant material according to any one of claims 48 to 54, wherein the compound of empirical formula (III) constitutes at least 75% by weight of the flame retardant material.

56. The flame retardant material according to claim 55, wherein the compound of empirical formula (III) constitutes at least 90% by weight of the flame retardant material. 5 57. A flame retardant polymer composition comprising (i) a polymer and (ii) the flame retardant material according to any one of claims 48 to 56.

58. A process for increasing the flame resistance of a polymer, comprising incorporating a flame-retardant material according to any one of claims 48 to 56 into a polymer resin, optionally with one or more additional flame retardants, synergistic adjuvant, or flame retardant.

59. A process for increasing the flame resistance of a polymer, comprising incorporating a phosphorus-containing flame retardant according to claim 27 or 28 into a polymer resin, optionally with one or more additional flame retardants, synergistic adjuvant, or flame retardant.