Process for the preparation of phosphorus-containing flame retardants and their use in polymer compositions

Abstract

The present application provides a process for the preparation of phosphorus-containing flame retardants and their use in polymer compositions. The phosphorus-containing flame retardants are prepared by reacting at the reaction temperature a mixture comprising a metal or suitable metal compound and an unsubsti- tuted or alkyl- or aryl-substituted phosphonic acid or phosphonic acid in a stoichiometric excess relative to the metal or suitable metal compound, wherein the phosphonic acid or phosphonic acid is in a molten state at the reaction temperature. The chemical composition of the resulting flame retardant products leads to excellent flame retardancy and exhibits high thermal stability. The flame retardants of the present disclosure are suitable for use in, for example, polymer compositions, in particular thermoplastic plastics processed at high temperatures in a wide range of applications.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201980081081.3, filed December 18, 2019, entitled “Process for the Preparation of Phosphorus-Containing Flame Retardants and Their Use in Polymer Compositions.”

[0002] This application claims the priority benefit of U.S. Provisional Application No. 62 / 782,948, filed December 20, 2018, and U.S. Provisional Application No. 62 / 923,446, filed October 18, 2019, the entire contents of both of which are incorporated herein by reference. TECHNICAL FIELD

[0003] Highly efficient, thermally stable phosphorus-containing flame retardants are produced by a process that includes reacting a metal or suitable metal compound with a stoichiometric excess of a phosphonic or pyrophosphonic acid. In many embodiments, the chemical composition of the resulting flame retardant produced as one or the primary compound results in excellent flame retardancy and exhibits high thermal stability. The flame retardants of the present disclosure are suitable for use, for example, in polymer compositions, particularly in thermoplastic plastics processed at high temperatures over a wide range of applications. BACKGROUND

[0004] Phosphonates, i.e., compounds of the formula exactly:

[0005]

[0006] where R is an optionally substituted alkyl, aryl, alkylaryl, or arylalkyl group, p is typically a number from 1 to 4, M is a metal, and y is typically a number from 1 to 4, such that M (+)y is a metal cation, where (+)y represents the charge formally assigned to the cation.

[0007] As disclosed in US 2007 / 0029532, decomposition of phosphonates is known at temperatures encountered during processing of polyesters and polyamides, e.g., in processes at temperatures above 260 or 270 °C, which destroys the polymer.

[0008] U.S. Patent 5,053,148 discloses that brittle heat-resistant foams can be obtained by heating phosphonates at elevated temperatures.

[0009] In Comparative Examples 1 and 2 of U.S. Patent 9,745,449, glass-filled polyamide compositions containing 10-25 wt% of an aluminum salt of methylphosphonic acid were processed at elevated temperatures. A decrease in torque was observed during compounding, consistent with polymer degradation, and once cooled, a brittle final product material was produced, which was dusty after grinding and could not be formed. Analysis of the compounded material by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) provided additional evidence of degradation. The observed loss of desirable polymer properties is consistent with polymer degradation as indicated in US 2007 / 0029532 and the formation of brittle foam as in U.S. Patent 5,053,148.

[0010] Thus, simple phosphonate salts are not suitable for use in many polymers that are processed at high temperatures or subsequently exposed to high temperatures, such as 250°C, 260°C, 270°C or higher, because they undergo chemical transformation at this temperature by a process that damages the polymer. This can occur during compounding, such as in an extruder, or simultaneously with the presence of the salt in the polymer in high temperature applications.

[0011] On the other hand, U.S. Patent 9,745,449 discloses that heating a phosphonate salt at a temperature high enough, typically 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 a polymer substrate. The thermally transformed material does not degrade at high temperatures when processed in a polymer composition at elevated temperatures, such as 240°C, 250°C, 260°C, 270°C or higher, nor do they cause polymer degradation, which is an important advantage over previously known phosphonate salts that exhibit flame retardant activity but often degrade the polymer during processing. The thermally transformed material is described as containing one or more compounds represented by empirical formula (IV):

[0012]

[0013] where R is an alkyl or aryl group, M is a metal, q is a number from 1 to 7, e.g., 1, 2 or 3, r is a number from 0 to 5, e.g., 0, 1 or 2, y is a number from 1 to 7, e.g., 1 to 4, and n is 1 or 2, with the proviso that 2(q) + r = n(y).

[0014] However, the methods and materials of U.S. Patent 9,745,449 have encountered challenges, such as the product often being generated as a solid mass that requires grinding, milling, or other such physical treatment prior to use; formation of product mixtures containing water-soluble or thermally unstable compounds; and difficulty in controlling the phosphorus / metal ratio of the resulting product. In addition, the examples of U.S. Patent 9,745,449 describe the production of phosphorus-containing flame retardants in several steps, in which an intermediate metal salt of a phosphonic acid is produced, followed by heating the dried salt at temperatures in excess of 200 °C.

[0015] The present disclosure addresses the above-identified challenges while also producing phosphorus-containing flame retardants without the need to produce or use intermediate salts as described in U.S. Patent 9,745,449. SUMMARY

[0016] According to the present disclosure, a phosphorus-containing flame retardant is produced by a method comprising reacting at a reaction temperature a mixture comprising a metal or suitable metal compound and an unsubstituted or alkyl or aryl substituted phosphonic acid in a stoichiometric excess relative to the metal or suitable metal compound, wherein:

[0017] The metal is capable of forming a polycation (i.e., in its corresponding cationic form, a metal represented by the formula M (+)y where M is a metal, (+)y represents the charge of the metal cation, and y is 2 or higher), or a suitable metal compound is represented by the formula M p (+)y X q where M is a metal, (+)y represents the charge of the metal cation, y is 2 or higher, X is an anion, and the values of p and q provide a charge-balanced metal compound;

[0018] The molar ratio of unsubstituted or alkyl or aryl substituted phosphonic acid to metal or suitable metal compound in the mixture is higher than 4:1;

[0019] The reaction temperature is 105 °C or higher; and

[0020] The unsubstituted or alkyl or aryl substituted phosphonic acid is in a molten state at the reaction temperature.

[0021] Also disclosed is a method of producing a phosphorus-containing flame retardant comprising reacting at a reaction temperature a mixture comprising a metal or suitable metal compound and a stoichiometric excess of an unsubstituted or alkyl or aryl substituted phosphinic acid, wherein:

[0022] The metal is capable of forming a polycation (i.e., in its corresponding cationic form, a metal represented by the formula M (+)y where M is a metal, (+)y represents the charge of the metal cation, and y is 2 or higher), or a suitable metal compound is represented by the formula M p(+)y X p wherein M is a metal, (+)y represents the charge of the metal cation, y is 2 or higher, X is an anion, and the values of p and q provide a charge balanced metal compound.

[0023] The mole ratio of unsubstituted or alkyl or aryl substituted pyrophosphonic acid to metal or suitable metal compound in the mixture is higher than 2:1; and

[0024] The unsubstituted or alkyl or aryl substituted pyrophosphonic acid is in a molten state at the reaction temperature.

[0025] In the methods of the disclosure, the unsubstituted or alkyl or aryl substituted phosphonic or pyrophosphonic acid used in stoichiometric excess as described herein serves the function of both a reactant and a solvent. Typically, as the resulting flame retardant product of the invention precipitates out of the reaction mixture, the reactants form a slurry. The excess phosphonic or pyrophosphonic acid remaining after the reaction can be removed, along with any possible by-products, by filtration and / or washing, such as with water. In many embodiments, a substantially pure flame retardant material is produced, for example, a flame retardant that substantially comprises a single compound having flame retardant activity or is substantially a mixture of active compounds. The conversion based on the metal or metal compound is typically very high, and the product can be easily isolated and optionally further purified if desired.

[0026] The present methods overcome the difficulties observed in the methods given in U.S. Patent 9,745,449, for example, by reducing or avoiding the production of water-soluble or thermally unstable compounds, and the flame retardant product that crystallizes typically in a powder or small particle form can be produced directly in an easily processable form, i.e., without or without the need for milling, granulation or other such physical processing. In addition, in many embodiments, the resulting flame retardant material produced according to the disclosure has a higher phosphorus to metal ratio than seen with simple metal phosphonates, as explained further herein. The high phosphorus to metal ratio in the produced flame retardant results in higher efficiency, thus allowing lower loading levels when the flame retardant material is compounded into thermoplastic plastics.

[0027] Other embodiments of the present disclosure include, but are not limited to, a method for preparing a phosphorus-containing flame retardant, comprising reacting a metal or a suitable metal compound with a molar excess of an unsubstituted or alkyl or aryl substituted phosphonic acid at a reaction temperature, wherein the reaction temperature is about 150°C or higher, the unsubstituted or alkyl or aryl substituted phosphonic acid is in a molten state at the reaction temperature, and the molar ratio of the unsubstituted or alkyl or aryl substituted phosphonic acid to the metal or suitable metal compound is greater than 4:1. In one embodiment, the reaction temperature ranges from about 150°C to about 300°C, such as about 150°C to about 280°C, about 160°C to about 260°C, or about 160°C to about 220°C. In one embodiment, the molar ratio of the unsubstituted or alkyl or aryl substituted phosphonic acid to the metal or suitable metal compound ranges from about 5:1 to about 30:1. In one embodiment, the suitable metal compound is a metal oxide, halide, alkoxide, hydroxide, carboxylate, or phosphonate. In one embodiment, the suitable metal compound is aluminum oxide, aluminum chloride, aluminum hydroxide, or aluminum isopropoxide.

[0028] Other embodiments include, but are not limited to, phosphorus-containing flame retardants produced according to the methods disclosed herein, flame retardant polymer compositions, methods for improving the flame retardancy of polymers by incorporating the flame retardants of the present disclosure therein, and methods for incorporating flame retardant compositions comprising the flame retardants of the present disclosure into polymers, the flame retardant polymer compositions comprising (i) a polymer and (ii) a phosphorus-containing flame retardant of the present disclosure.

[0029] The foregoing summary of the invention is not intended to limit the scope of the invention as claimed in any way. In addition, it should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to limit the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Shown are the results of thermogravimetric analysis (TGA) of an exemplary flame retardant material produced according to Example 1 of the present disclosure. DETAILED DESCRIPTION

[0031] Unless otherwise stated, in this application, the word "a" or "an" means "one or more".

[0032] Unless the context indicates otherwise, the term "alkyl" as used herein includes "aralkyl".

[0033] Unless the context indicates otherwise, the term "aryl" as used herein includes "alkaryl".

[0034] As used herein, unless the context indicates otherwise, the term "phosphonic acid" refers to unsubstituted or alkyl- or aryl-substituted phosphonic acids.

[0035] As used herein, the term "pyrophosphonic acid" means an unsubstituted or alkyl or aryl substituted pyrophosphonic acid, unless the context indicates otherwise.

[0036] As used herein, an "excess stoichiometry" of an unsubstituted or alkyl or aryl substituted phosphonic or pyrophosphonic acid relative to a metal or suitable metal compound means an amount of the phosphonic or pyrophosphonic acid in excess of the stoichiometric amount required for the reaction between the metal or suitable metal compound and the phosphonic or pyrophosphonic acid. As described herein, the excess stoichiometry is typically represented by the molar ratio of the phosphonic or pyrophosphonic acid to the metal or suitable metal compound in the reaction mixture.

[0037] According to one aspect of the disclosure, a metal or suitable metal compound is reacted with an excess stoichiometry of an unsubstituted or alkyl or aryl substituted phosphonic acid to form a phosphorus-containing flame retardant. The reaction temperature is 105 °C or higher, the phosphonic acid is in a molten state at the reaction temperature, and the molar ratio of the phosphonic acid to the metal or suitable metal compound in the reaction mixture is higher than 4: 1. In this reaction, the metal is oxidized and can be in its corresponding cationic form represented by the formula M (+)y where M is the metal, (+)y represents the charge of the metal cation, and y is 2 or higher. Suitable metal compounds can be represented by the formula M p (+)y X q where M is the metal, (+)y represents the charge of the metal cation, y is 2 or higher, X is an anion, and the values of p and q provide a charge balanced metal compound.

[0038] In another aspect, a metal or suitable metal compound as above is reacted with an excess stoichiometry of an unsubstituted or alkyl or aryl substituted pyrophosphonic acid to form a phosphorus-containing flame retardant. The pyrophosphonic acid is in a molten state at the reaction temperature, and the molar ratio of the pyrophosphonic acid to the metal or suitable metal compound in the reaction mixture is higher than 2: 1.

[0039] In many embodiments, the molar ratio of phosphonic acid to metal or suitable metal compound in the reaction mixture is 5: 1 or greater, for example, about 6: 1 or greater, about 8: 1 or greater, or about 10: 1 or greater. A large molar excess of phosphonic acid can be used in the reaction mixture relative to the metal or suitable metal compound, such as about 12: 1 or greater, about 15: 1 or greater, about 20: 1 or greater, about 25: 1 or greater, about 30: 1 or greater, or any range therebetween. A large molar excess of phosphonic acid can be used relative to the metal or suitable metal compound. For example, the molar ratio can be up to about 50: 1, up to about 100: 1, up to about 300: 1, up to about 500: 1, or any range therebetween. However, as should be appreciated, at certain large molar excesses, process efficiency can be compromised, for example, product precipitation from the reaction mixture can be hindered. In many embodiments, the molar ratio is in a range from about 8: 1, from about 10: 1, from about 12: 1, or from about 16: 1 to about 100: 1 or to about 50: 1, such as from about 10: 1, from about 15: 1, or from about 20: 1 to about 50: 1 or to about 40: 1.

[0040] In many embodiments, the molar ratio of pyrophosphonic acid to metal or suitable metal compound in the reaction mixture is 3: 1 or greater, such as about 4: 1 or greater, about 6: 1 or greater, or about 8: 1 or greater. A large molar excess value of pyrophosphonic acid is typically used in the reaction mixture relative to the metal or suitable metal compound, such as about 10: 1 or greater, about 12: 1 or greater, about 15: 1 or greater, about 18: 1 or greater, about 20: 1 or greater, or any range therebetween. A large molar excess of pyrophosphonic acid can be used relative to the metal or suitable metal compound. For example, the molar ratio can be up to about 30: 1, up to about 50: 1, up to about 100: 1, up to about 250: 1, or any range therebetween. However, as should be appreciated, at certain large molar excess values, process efficiency can be compromised, for example, product precipitation from the reaction mixture can be hindered. In many embodiments, the molar ratio is in a range from about 4: 1, from about 5: 1, from about 6: 1, or from about 8: 1 to about 50: 1 or to about 25: 1, such as from about 5: 1, from about 8: 1, or from about 10: 1 to about 25: 1 or to about 20: 1.

[0041] The reaction temperature for producing the phosphorus-containing flame retardant according to the present disclosure should be selected such that the phosphonic or pyrophosphonic acid is in a molten state at the reaction temperature. For example, phosphonic and pyrophosphonic acids (e.g., alkyl-substituted phosphonic or pyrophosphonic acids) are typically solids at room temperature (e.g., methyl phosphonic acid melts at about 105°C, while ethyl phosphonic acid melts at about 62°C), so heating the phosphonic or pyrophosphonic acid to produce a liquefied physical state (i.e., a molten state) is generally suitable for forming a uniform reaction mixture. As will be appreciated by one of skill in the art, the reaction temperature required for the phosphonic or pyrophosphonic acid to be in a molten state can vary depending on the reagents selected and the thermodynamic conditions.

[0042] The reaction temperature should also be selected to promote the formation of mono- and / or dianionic pyrophosphonic acid ligands in the reaction product. For phosphonic acids, a reaction temperature of 105°C or greater is used. Without being bound by a particular theory, the reaction temperature is selected to produce pyrophosphonic acid ligands through a dehydration reaction. In many embodiments, the metal or suitable metal compound is reacted with the phosphonic acid at a temperature greater than 105°C, such as about 115°C or greater, about 120°C or greater, about 130°C or greater, about 140°C or greater, about 150°C or greater, about 160°C or greater, about 170°C or greater, about 180°C or greater, about 200°C or greater, about 220°C or greater, about 240°C or greater, about 260°C or greater, about 280°C or greater, or any range therebetween. The reaction temperature can be greater than the above temperatures, such as up to about 350°C, up to about 400°C, or greater, but it is generally not meeting or exceeding the boiling point of the phosphonic acid. For example, the reaction temperature can be in the range of about 150°C to about 300°C, such as about 150°C to about 280°C, about 160°C to about 260°C, or about 160°C to about 240°C. In many embodiments, the reaction temperature is in the range of about 110°C to about 350°C, about 115°C to about 300°C, about 125°C to about 280°C, or about 140°C to about 260°C. The dehydration reaction generates water, which can potentially lead to undesirable reverse (hydrolysis) reactions. Thus, in some embodiments, the reaction system is designed to facilitate the removal of water from the reaction, such as continuous removal of water. For example, the reaction temperature can be selected to be greater than the boiling point of water to the extent necessary to evaporate at least a portion or a desired amount (e.g., a majority, substantially all, or all) of the water from the reaction. Other means such as gas purging, vacuum, and / or other known means can be used to facilitate the removal of water from the reaction system.

[0043] Because pyrophosphoric acid does not require dehydration, the reaction temperature for pyrophosphoric acid can be lower than the reaction temperatures described above for phosphonic acid. Generally, the limiting criteria for selecting a suitable reaction temperature when using a pyrophosphoric acid is the requirement that the pyrophosphoric acid be in a molten state at the reaction temperature. Typically, the metal or suitable metal compound is reacted with the pyrophosphoric acid at a temperature of 20 °C or greater. In many embodiments, the metal or suitable metal compound is reacted with the pyrophosphoric acid at a temperature greater than 20 °C, such as about 40 °C or greater, about 60 °C or greater, about 80 °C or greater, about 100 °C or greater, about 140 °C or greater, about 180 °C or greater, about 200 °C or greater, or any range therein. The reaction temperature can be greater than the temperatures described above, such as up to about 300 °C, up to about 400 °C, or greater, but it is typically not to meet or exceed the boiling point of the pyrophosphoric acid. In many embodiments, the reaction temperature is in the range of about 25 °C to about 350 °C, about 25 °C to about 280 °C, about 30 °C to about 260 °C, about 40 °C to about 260 °C, about 60 °C to about 260 °C, about 80 °C to about 240 °C, about 100 °C to about 240 °C, about 110 °C to about 240 °C, or about 120 °C to about 240 °C. For example, depending on the metal compound used to react with the pyrophosphoric acid, water can be generated from the reaction. As described above, in some embodiments, the reaction system is designed to facilitate removal of water from the reaction, such as continuous removal of water. For example, the reaction temperature can be selected to be above the boiling point of water to the extent necessary to evaporate at least a portion or a desired amount (e.g., a majority, substantially all, or all) of the water from the reaction. Other means such as gas purging, vacuum, and / or other known means can be used to facilitate removal of water from the reaction system.

[0044] Generally, as the reaction proceeds, the product will form as a slurry with the resulting flame retardant product precipitating out of the product reaction mixture. Thus, the reaction will generally be conducted for a time sufficient to achieve such precipitation. Generally, the amount of time required to achieve at least substantial conversion to the flame retardant product based on the metal or suitable metal compound will depend on the reaction temperature, with higher temperatures generally resulting in shorter reaction times. In many embodiments, the metal or suitable metal compound is heated with the phosphonic acid or pyrophosphoric acid at the reaction temperature for about 0.1 to about 48 hours, such as about 0.2 to about 36 hours, about 0.5 to about 30 hours, about 1 hour to about 24 hours, for example, about 1 hour to about 12 hours, about 1 hour to about 8 hours, or about 2 hours to about 5 hours, although other durations can be used.

[0045] The metal or suitable metal compound and the molar excess of phosphonic or pyrophosphonic acid can be combined in any manner suitable for forming a reaction mixture. For example, the phosphonic or pyrophosphonic acid and the metal or metal compound can be mixed together (e.g., stirred) to form a homogeneous reaction mixture. In some embodiments, the metal or suitable metal compound is added to the phosphonic or pyrophosphonic acid that has been preheated to the reaction temperature. In some embodiments, the phosphonic or pyrophosphonic acid is preheated and stirred while molten, such as under a nitrogen atmosphere or under reduced pressure / vacuum. In other further embodiments, the metal or metal compound is added as rapidly as possible without causing a large change in the reaction temperature due to the exothermic nature of the reaction. In some embodiments, the phosphonic or pyrophosphonic acid is combined with the metal or suitable metal compound without preheating the phosphonic acid, or without heating sufficiently to liquefy the phosphonic or pyrophosphonic acid, and the components are subsequently heated to the reaction temperature. The entire amount of the metal or suitable metal compound or the phosphonic or pyrophosphonic acid can be added to the reaction at once or in portions. No additional solvent is required because the phosphonic or pyrophosphonic acid used in molar excess acts as both the reagent and the solvent, although other solvents can be used if desired. In some embodiments, when the molar ratio of phosphonic or pyrophosphonic acid to metal or suitable metal compound is at or near the lower boundary of the molar ratios disclosed herein, additional solvent is used.

[0046] In some embodiments, after achieving the desired conversion, e.g., complete or substantially complete conversion to the flame retardant product, the product reaction mixture is cooled to a temperature that is above or not less than the melting temperature of the excess phosphonic or pyrophosphonic acid to maintain the excess phosphonic or pyrophosphonic acid in a liquefied state. The excess phosphonic or pyrophosphonic acid can be removed by filtration / washing and optionally recovered. The recovered excess phosphonic or pyrophosphonic acid can be recycled, e.g., back to the reactor where the metal or suitable metal compound is reacted with the phosphonic or pyrophosphonic acid. After conversion to the reaction product, a solvent such as water, an alcohol, and / or other suitable (e.g., polar) liquid can optionally be added to dissolve or aid in removal of the excess phosphonic or pyrophosphonic acid. The flame retardant product is typically isolated by filtration, optionally followed by further processing (e.g., washing, drying, sieving, etc.). The resulting flame retardant product is typically in the form of a powder or small particles, which is readily processable, i.e., does not require or need to be ground, milled, or otherwise physically processed prior to use. It will be appreciated that the process according to the present disclosure produces the flame retardant material "directly" in the form of a powder or small particles, which allows for post-processing of the reaction product, e.g., isolation of the flame retardant product (e.g., separation of the flame retardant product from the excess phosphonic or pyrophosphonic acid or remaining solvent), which can include processing the reaction product, e.g., by filtration, sieving, washing, drying, etc. After the reaction, the resulting product reaction mixture, which is typically a slurry, can be cooled to or just above the melting temperature of the excess phosphonic acid, and the slurry can be combined with water. The water / slurry mixture can be agitated as needed to break up any clumps that can form. The solid product can be isolated by filtration, optionally washed with water and dried to obtain the product in the form of a powder or small particles. In some cases, the product can be sieved to refine the particle size.

[0047] The process of the present disclosure produces a flame retardant comprising one or more metals and one or more monodentate and / or bidentate pyrophosphonic acid ligands. In some embodiments, a compound comprising a phosphonate ligand can be produced, but in all embodiments, a compound comprising a pyrophosphonic acid monoanionic ligand and / or a pyrophosphonic acid dianionic ligand is obtained.

[0048] The process can produce a mixture of flame retardant compounds, but in many embodiments, the process produces a flame retardant material as one or a primary compound having a high conversion of the metal or metal compound, e.g., at least 70%, 80%, 85%, 90%, 95%, 98%, or higher, or any range therebetween, relative to a mixture of compounds obtained using prior art processes involving thermal treatment of metal phosphonates. In general embodiments where a phosphonate ligand can be present in the flame retardant product, the reaction is typically carried out as shown below:

[0049]

[0050] where M is a metal cation and (+)y represents the charge of the cation, for example, M is a divalent, trivalent, tetravalent, pentavalent cationic metal; X is one anionic ligand or multiple anionic ligands attached to the metal, and the stoichiometry of M and X (i.e., p and q) provide a charge balanced compound; R is H, alkyl, aryl, alkylaryl, or arylalkyl; a, b, c, and d represent the ratio of the components in the reaction product that correspond to each other, and y, a, b, c, and d are values that provide a charge balanced product, with the proviso that y is 2 or greater, and only one of a or c can be 0 (typically, c is not zero). In some embodiments, when present, the aforementioned phosphonic acid ligand with the coefficient d can be present as a dianion. In many embodiments, d is 0.

[0051] In another aspect, the flame retardant product produced according to the present disclosure (typically in the form of a powder or small particles) comprises a compound of empirical formula (II) or a mixture of different compounds

[0052]

[0053] where R is H, alkyl, aryl, alkylaryl, or arylalkyl, a, b, c, and d represent the ratio of the components in the compound that correspond to each other, and a is typically a number from 0 to 8, for example, 0 to 6, 0 to 4, or 0 to 2, c is typically a number from 0 to 10, for example, 0 to 8, 0 to 6, 0 to 4, or 0 to 2, d is typically a number from 0 to 6, for example, 0 to 4 or 0 to 2, M is a metal, y is a number from 2 to 5, such as 2, 3, or 4, typically 2 or 3, and M (+)y is a metal cation, where (+)y represents the charge formally assigned to the cation. The values of a, b, c, d, and y can vary, but will satisfy the charge balance equation 2(a) + c + d = b(y), and only one of a or c can be 0. In many embodiments, c is not zero. In the case where a dianionic phosphonic acid ligand is present in the compound, the charge balance equation becomes 2(a) + c + d + 2(d) = b(y). Only the value of b is limited, as it must satisfy the preceding equation, but in many embodiments, b is a number from 1 to 4, for example, 1 to 2. In certain embodiments, a is 0, 1, or 2 (for example, 0 or 1), c is 1 or 2, and d is 0, 1, or 2 (for example, 0 or 1), while the product is charge balanced.

[0054] In many embodiments, d is 0, as in:

[0055]

[0056] where R, M, y, a, b, and c are as described above, and the product charge balance equation becomes 2(a) + c = b(y).

[0057] Typically, c in the above formulae (II) and (III) is not zero (e.g., c is 1-10, 1-8, 1-6, 1-4, or 1 or 2).

[0058] According to the methods of the present disclosure, in many embodiments, as when using divalent or trivalent cationic metals, it is surprisingly found that c in the above formulae is not zero, and the product has a more favorable ratio of phosphorus atoms to metal atoms (i.e., P / M) for providing flame retardancy than phosphorus-containing flame retardants described in the prior art. For example, it is known that trivalent cationic metals (e.g., aluminum) and divalent cationic metals (e.g., zinc) form tri- and di-substituted charge balanced compounds, respectively. As seen in the art, aluminum triphosphonate salts having a phosphorus to aluminum ratio of 3:1 and zinc diphosphonate salts having a phosphorus to zinc ratio of 2:1 are known as flame retardants. However, according to the formation of the pyrophosphonic acid ligands of the present disclosure, particularly where c in the above formulae is not zero, the ratio of phosphorus to metal in the flame retardant product is higher. For example, as demonstrated in the examples disclosed herein, when employing the methods of the present disclosure, the ratio of phosphorus to aluminum or phosphorus to iron in the resulting flame retardant product is 4:1. Such a high ratio of phosphorus to metal results in high efficiency and is able to tolerate a reduced loading when compounded into a thermoplastic polymer.

[0059] In certain specific embodiments, y in formula (III) is 2 (i.e., M (+)y is a divalent cationic metal, as described herein), a is 0, b is 1, and c is 2. In certain embodiments, the divalent cationic metal M is Mg, Ca, or Zn. In other embodiments, y in formula (III) is 3 (i.e., M (+)y is a trivalent cationic metal, as described herein), a is 1, b is 1, and c is 1. In certain embodiments, the trivalent cationic metal M is selected from Al, Ga, Sb, Fe, Co, B, and Bi. In certain embodiments, the trivalent cationic metal M is Al, Fe, Ga, Sb, or B.

[0060] As with inorganic coordination compounds, the reaction products in the above reactions, as well as the compounds of empirical formulae (II) and (III), are idealized in that the reaction products or compounds can include coordination polymers, complex salts, salts sharing certain atomic valences, and the like.

[0061] For example, in many embodiments, empirical formulae (II) or (III) represent monomeric units of a coordination polymer (i.e., a ligand), and the expanded coordination polymer structure forms the flame retardant compounds of the present disclosure.

[0062] In one example, where M is Al and y is 3, the compounds of empirical formula (III) are produced according to the following empirical formula (IIIa):

[0063]

[0064] As shown herein, the absence of subscripts a, b, and c in the empirical formula indicates that each subscript is 1, indicating that the ratio of the components is 1:1:1 (in the case of empirical formula (IIIa), the ratio of the dianionic pyrophosphate ligand, the metal atom, and the monoanionic pyrophosphate ligand is 1:1:1). In this example, empirical formula (IIIa) represents the repeating monomer units (i.e., ligands) of the coordination polymer, and the expanded coordination polymer structure thereby forms the flame retardant compound of the present disclosure.

[0065] Typically, the compound of empirical formula (II) or (III) (which in many embodiments is an expanded coordination polymer as described herein) constitutes all, substantially all, or at least a majority of the flame retardant product, for example, at least 75%, 85%, 90%, 95%, 98%, or more, or any range therebetween, by weight of the flame retardant product.

[0066] Based on the metal or metal compound, the compound of empirical formula (II) or (III) (e.g., (IIIa)) can be produced with high conversion, such as at least 70%, 80%, 85%, 90%, 95%, 98% or higher, such as at least 70%-95%. In certain of these 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)).

[0067] The phosphonic acid used in the present method can be represented by formula (I)

[0068]

[0069] wherein R is H, alkyl, aryl, alkaryl, or aralkyl. In many embodiments, R is H, C 1-12 Alkyl, C 6-10 Aryl, C 7-18 Alkaryl or C 7-18 Aralkyl, wherein the alkyl, aryl, alkaryl or aralkyl is unsubstituted or substituted by halogen, hydroxy, amino, C 1-4 Alkylamino, di-C 1-4 Alkylamino, C 1-4 Alkoxy, carboxyl or C 2-5 In some embodiments, the alkyl, aryl, alkaryl or aralkyl group is an unsubstituted C 1-12 Alkyl, C6 aryl, C 7-10 Alkaryl or C 7-10 Arylalkyl, for example, C 1-6alkyl, phenyl, or C 7-9 alkyl, phenyl, or C 1-6 alkyl, C6aryl, C 7-10 alkyl, C6aryl, C 7-12 arylalkyl, e.g., C 1-4 alkyl, C6aryl, C 7-9 alkyl, C6aryl, C 7-10 arylalkyl. In many embodiments, R is unsubstituted C 1-12 alkyl, e.g., C 1-6 alkyl. In many embodiments, a lower alkyl phosphonic acid is used, e.g., methyl phosphonic acid, ethyl phosphonic acid, propyl phosphonic acid, isopropyl phosphonic acid, butyl phosphonic acid, t-butyl phosphonic acid, and the like.

[0070] R as alkyl can be straight chain or branched chain alkyl having the indicated number of carbons and includes, for example, straight chain alkyl such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and branched chain alkyl such as isopropyl, isobutyl, sec-butyl, t-butyl, ethylhexyl, t-octyl, and the like. For example, R as alkyl can be selected from the group consisting of 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.

[0071] Generally, when R is aryl, it is phenyl. Examples of R as alkaryl include phenyl substituted with one or more alkyl groups such as groups selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, and the like. Examples of R as aralkyl include groups such as benzyl, phenethyl, phenethenyl, cumyl, phenylpropyl, and the like.

[0072] In many embodiments, R is selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, phenyl, and benzyl.

[0073] The pyrophosphonic acid used in the present process can be represented by formula (la):

[0074]

[0075] wherein R is the same as disclosed above for formula (I).

[0076] The general reaction scheme for a pyrophosphonic acid and a suitable metal compound can be represented as:

[0077]

[0078] wherein R, M, X, p, q, y, a, b, and c are as described herein.

[0079] The methods of the present disclosure can use more than one phosphonic acid, more than one pyrophosphonic acid, or a combination of phosphonic acid and pyrophosphonic acid, so long as the mixture of phosphonic acid and / or pyrophosphonic acid is in a molten state at the reaction temperature. In some embodiments, the phosphonic acid or pyrophosphonic acid is generated in situ. For example, the phosphonic acid or pyrophosphonic acid can be prepared as by hydrolysis of a higher oligomeric phosphonic acid and / or cyclic phosphonic anhydride starting material.

[0080] As used herein, "suitable metal compound" and the like refer to compounds of the formula M p (+)y X q where M is a metal capable of forming a polyvalent cation, e.g., a metal that forms a 2+, 3+, 4+, or 5+ cation, typically a 2+, 3+, or 4+ cation, and X is any anion that provides charge balance to the compound with the metal M. Suitable examples of X include, but are not limited to, anions that form oxides, halides, alkoxides, hydroxides, carbonates, carboxylates, and phosphonates with the metal M. The values of p and q provide a charge balanced metal compound, e.g., aluminum oxide Al2O3. In some embodiments, as described herein, an unsubstituted metal M is used. 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, Bi, Mn, Sn, or Sb. In some embodiments, M is selected from Mg, Ca, Ba, Zn, Zr, Ga, B, Al, Si, Ti, Cu, Fe, Sn, or Sb. In some embodiments, M is selected from Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Fe, Sn, or Sb, e.g., M can be Mg, Zn, Ca, Fe, or Al.

[0081] Suitable metal compounds include, but are not limited to, compounds having metal-oxygen bonds, metal-nitrogen bonds, metal-halogen bonds, metal-hydrogen bonds, metal-phosphorus bonds, metal sulfur bonds, metal boron bonds, and the like, e.g., oxides, halides, alkoxides, hydroxides, carboxylates, carbonates, phosphonates, phosphinates, phosphonites, phosphates, phosphites, nitrates, nitrites, borates, hydrides, sulfonates, sulfates, sulfides, and the like of Mg, Ca, Ba, Zn, Zr, Ge, B, Al, Si, Ti, Cu, Fe, Co, Ga, Bi, Mn, Sn, or Sb, e.g., oxides, hydroxides, halides, or alkoxides of Mg, Ca, Ba, Zn, Zr, Ga, B, Al, Si, Ti, Cu, Fe, Sn, or Sb; e.g., oxides, hydroxides, halides, or alkoxides of Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Fe, Sn, or Sb, e.g., oxides, hydroxides, halides, or alkoxides of Mg, Zn, Ca, Fe, or Al.

[0082] In some embodiments, the metal M of the metal or suitable metal compound is aluminum or iron. In some embodiments, the suitable metal compound is selected from the group consisting of halides, oxides, hydroxides, alkoxides, carbonates, carboxylates, and phosphonates of aluminum. In some embodiments, the suitable metal compound is selected from the group consisting of halides, oxides, hydroxides, and alkoxides of aluminum. In some embodiments, the suitable metal compound is selected from the group consisting of aluminum oxide, aluminum trichloride, aluminum hydroxide, aluminum isopropoxide, aluminum carbonate, and aluminum acetate. In other embodiments, the suitable metal compound is selected from the group consisting of halides, oxides, alkoxides, carbonates, and acetates of iron. In some embodiments, the suitable metal compound is selected from the group consisting of iron (III) oxide, iron (III) chloride, iron (III) isopropoxide, and iron (III) acetate.

[0083] In certain embodiments, R is methyl, ethyl, propyl, isopropyl, or butyl, and M is Al, Fe, Zn, or Ca. In further embodiments, X is oxygen, hydroxyl, alkoxy, or halogen.

[0084] The reactions described herein can, but need not, be conducted under reduced pressure or vacuum.

[0085] The product reaction mixture formed from the reactions described herein (typically presented as a slurry) can be combined with a liquid (e.g., water) and agitated as necessary to break up any clumps that can form. The solid product can be isolated by filtration, 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.

[0086] The reactions described herein can optionally be facilitated with a seeding material. For example, the use of a seeding material can reduce the time to achieve conversion to the flame retardant product and can result in improved consistency of product physical properties. Typically, the seeding material is added to the reaction mixture upon or after heating to the reaction temperature. In some embodiments, the seeding material comprises a flame retardant material produced according to the methods of the present disclosure, such as a flame retardant compound of empirical formula (II), (III), or (Ilia) as described herein. The seeding material can be selected or refined to have a desired particle size.

[0087] In some embodiments, the suitable metal compound is aluminum oxide, and the flame retardant material is produced as follows:

[0088]

[0089] In one embodiment, a phosphonic acid such as C1-C 12An alkylphosphonic acid (e.g., methyl, ethyl, propyl, isopropyl, butyl, or tert-butyl phosphonic acid) is heated to or above its melting point of 105 °C, such as to 115 °C, 125 °C, 140 °C, 150 °C, 160 °C, 180 °C, 200 °C, 220 °C, or 240 °C or higher, and once molten is stirred (e.g., under nitrogen). With stirring, an oxide, hydroxide, halide, alkoxide, carbonate, or carboxylate of Al, such as aluminum oxide, aluminum trichloride, aluminum hydroxide, aluminum isopropoxide, aluminum carbonate, or aluminum acetate, is added in a stoichiometric excess of the phosphonic acid, such as in a molar ratio of phosphonic acid to metal compound of 5: 1 or higher, 10: 1 or higher, or 15: 1 or higher, as described herein. Typically, a slurry forms as the reaction proceeds, and the solid flame retardant product can be isolated, e.g., by filtration, washing, etc., to obtain the product in the form of a powder or small particles. The product reaction mixture can be subjected to additional workup prior to isolating the solid product, such as cooling the product reaction mixture to above or not below the melting point of the excess phosphonic acid, and combining with a liquid such as water, and optionally stirring as above. The solid flame retardant product can be isolated by filtration, optionally washed with additional solvent, and dried to obtain the product in the form of a powder or small particles. The flame retardant product comprises phosphorus and aluminum in a 4: 1 ratio according to the following empirical formula:

[0090] In further examples, the examples directly described above are carried out with iron or a suitable iron compound, such as a halide, oxide, alkoxide, carbonate, or acetate of iron, e.g., iron (III) oxide, iron (III) chloride, iron (III) isopropoxide, or iron (III) acetate. The flame retardant product comprises phosphorus and iron in a 4: 1 ratio according to the following empirical formula:

[0091]

[0092] Typically, the compounds of the above empirical formula, which in many embodiments are the expanded coordination polymers described herein, make up all, substantially all, or at least a majority of the flame retardant product, such as at least 75%, 85%, 90%, 95%, 98%, or higher, or any range therebetween, by weight of the flame retardant product.

[0093] In some embodiments, the suitable metal compound is a metal phosphonate. As described herein, the metal in the metal phosphonate can be the metal M. A suitable metal compound can be a metal phosphonate of the following formula:

[0094]

[0095] where R and M are as described above, p is a number from 2 to 5, e.g., 2, 3, or 4, and y is a number from 2 to 5, e.g., 2, 3, or 4, such that M (+)yis a metal cation, where (+)y represents the formal charge assigned to the cation. Typically, the metal phosphonate is charge balanced (i.e., p = y). The metal phosphonate can be prepared according to methods known in the art.

[0096] In some embodiments, the metal phosphonate is prepared from an initial metal compound and a phosphonic acid using a solvent for the phosphonic acid (e.g., water). The initial metal compound can be a compound according to the suitable metal compounds described herein. In some embodiments, the initial metal compound and the phosphonic acid are reacted at room temperature or at a temperature of about room temperature or at a temperature in the range of about 0 to about 20 °C. The resulting metal phosphonate can then be used as a suitable metal compound according to the methods of the present application herein.

[0097] For example, a phosphonic acid such as an alkyl phosphonic acid (e.g., methyl, ethyl, propyl, isopropyl, butyl, or t-butyl phosphonic acid) and a solvent (e.g., water) can be stirred to form a homogeneous solution. Any suitable ratio of water to phosphonic acid can be used, for example, 10:1 to 1:10 by weight, more typically 5:1 to 1:5, and good results have been achieved using a mixture of 2:1 to 1:2. The solution can be cooled to a range of, for example, about 0 to about 20 °C, and an initial metal compound such as a metal oxide, halide, alkoxide, or hydroxide added to react with the phosphonic acid. The metal phosphonate is formed, which is then used as a suitable metal compound according to the methods of the present disclosure. For example, in a separate reactor, a molar excess of the phosphonic acid described herein (such as at a 5:1 molar ratio of phosphonic acid to metal phosphonate) is preheated to a molten state and reacted with the metal phosphonate to form a flame retardant product. In embodiments involving aluminum phosphonate salts as suitable metal compounds, the flame retardant product contains phosphorus and aluminum according to the empirical formula at a phosphorus to aluminum ratio of 4:1:

[0098] Typically, the compound of the empirical formula, which in many embodiments is an expanded coordination polymer described herein, constitutes all, substantially all, or at least a majority of the flame retardant product, for example, at least 75%, 85%, 90%, 95%, 98%, or higher, or any range therebetween, by weight of the flame retardant product.

[0099] The flame retardants of the present application can be used with a variety of other flame retardants and / or synergists or flame retardant aids known in the art. For example, the flame retardants of the present application can be formulated with one or more materials selected from the group consisting of: carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes; polyphenylene ethers (PPE), phosphine oxides and polyphosphine oxides, for example, benzylic phosphine oxides, polybenzylic phosphine oxides, and the like;

[0100] Melamine, melamine derivatives and melamine condensation products, melamine salts such as, but not limited to, melamine cyanurate, melamine borate, melamine phosphate, melamine metal phosphates, melam, melem, melon, and the like;

[0101] Inorganic compounds, including clays, metal salts such as hydroxides, oxides, hydrated oxides, borates, carbonates, sulfates, phosphates, phosphites, hypophosphites, silicates, mixed metal salts, and the like, for example, talc and other magnesium silicates, calcium silicate, aluminosilicates, aluminosilicates as 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 its composites, for example, Kemgard 911B), zinc molybdate / magnesium hydroxide composite (for example, Kemgard MZM), zinc molybdate / magnesium silicate composite (Kemgard 911C), calcium / zinc molybdate composite (for example, Kemgard 911A), zinc phosphate (or its composites, for example, Kemgard 981), magnesium oxide or hydroxide, aluminum oxide, aluminum hydroxide oxide (BOEHMITE), aluminum trihydrate (aluminum hydroxide), silicon dioxide, tin oxide, antimony oxide (III and V) and hydrated oxides, titanium oxide, and zinc oxide or hydroxide, zirconium oxide and / or hydroxide, and the like.

[0102] Unless otherwise indicated, in the context of the present application, the term "phosphate" when used as a component in "phosphate salts", such as metal phosphates, melamine phosphates, melamine metal phosphates, and the like, refers to phosphate, hydrogen phosphate, dihydrogen phosphate, pyrophosphate, polyphosphate, or phosphate condensation product anions or polyanions.

[0103] Likewise, unless otherwise indicated, in the context of the present application, the term "phosphite" when used as a component in "phosphite salts", such as metal phosphites, and the like, refers to phosphite or hydrogen phosphite.

[0104] The flame retardants of the present disclosure 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 phosphonate, alkyl or aryl phosphinate, and salts of alkyl or aryl phosphinates. In some embodiments, the flame retardant includes a flame retardant according to the present disclosure and a phosphinate salt of the formula

[0105]

[0106] R 1 and R 2 each independently can be a group according to R as described herein, M is a metal (e.g., Al or Ca) as described herein, and n is a number from 2 to 7, e.g., 2 to 4, typically 2 or 3.

[0107] In many embodiments, the flame-retardant polymer composition comprises (i) a polymer, (ii) a flame-retardant material of the present disclosure, and (iii) one or more other flame retardants and / or one or more synergists or flame-retardant adjuvants.

[0108] For example, in some embodiments, the flame-retardant polymer composition comprises one or more other flame retardants, e.g., a halogenated flame retardant, a phosphine oxide flame retardant, an alkyl or aryl phosphonate, or a salt of an alkyl or aryl phosphinate, e.g., aluminum tris(dialkylphosphinate), such as aluminum tris(diethylphosphinate).

[0109] In some embodiments, the flame-retardant polymer composition comprises one or more synergists or flame-retardant adjuvants, e.g., melamine, melamine derivatives and melamine condensation products (e.g., melam, melem, melo), melamine salts, phosphine oxides and polyphosphine oxides, metal salts such as hydroxides, oxides, hydrated oxides, borates, phosphates, phosphonates, phosphites, silicates, etc., e.g., aluminum hydrophosphite, melem or melamine metal phosphates, e.g., melamine metal phosphates where the metal comprises aluminum, magnesium or zinc. In particular embodiments, the one or more other flame retardants, synergists or flame-retardant adjuvants comprise aluminum tris(dialkylphosphinate), aluminum hydrophosphite, methylene diphenyl phosphine oxide substituted polyarylene ether, xylylene bis(diphenylphosphine oxide), 4,4'-bis(diphenylphosphinylmethyl)-1,1'-biphenyl, ethylene bis-1,2-bis-(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)ethane, melem, melam, melo or dimelamine zinc pyrophosphate.

[0110] Certain embodiments provide halogen-free polymer compositions. In such embodiments, halogen-containing flame retardants or synergists are excluded as much as possible.

[0111] The flame retardant materials of the present disclosure can be combined with other flame retardants, synergists, or adjuvants in a ratio of 100:1 to 1:100 weight of the flame retardant of the present disclosure to the total weight of the other flame retardants, synergists, and / or adjuvants. In some embodiments, the flame retardant materials of the present disclosure are present in a ratio of 10:1 to 1:10 weight of the flame retardant of the present disclosure to the total weight of the other flame retardants, synergists, and / or adjuvants, for example, in a weight ratio in the range of 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 flame retardant of the present invention is typically the major component of such a combination, such as a ratio of 10:1 to 1.2:1 of the weight of the flame retardant of the present invention to the total weight of the other flame retardants, synergists and / or adjuvants or a ratio of 7:1 to 2:1 of the weight of the flame retardant of the present invention to the total weight of the other flame retardants, synergists and / or adjuvants, but the material of the present invention can also be a 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.

[0112] The heat-stable flame retardant of the present invention can be compounded into thermoplastic polymers, such as high-temperature polyamides and polyterephthalates, at high temperatures without decomposing or adversely affecting the physical properties of the polymers, and exhibits excellent flame retardant activity. The flame retardant of the present invention can be used with other synergists and conventional polymer additives in other polymers.

[0113] The polymer of the flame retardant composition of the present invention can be any polymer known in the art, such as polyolefin homopolymers and copolymers, rubbers, polyesters including polyalkylene terephthalates, epoxy resins, polyurethanes, polysulfones, polyimides, polyphenylene oxides, styrenic polymers and copolymers, polycarbonates, acrylic polymers, polyamides, polyacetals, and biodegradable polymers. Mixtures of different polymers can also be used, such as polyphenylene oxide / styrenic resin blends, polyvinyl chloride / acrylonitrile butadiene styrene (ABS) or other impact-modified polymers such as methacrylonitrile and ABS containing α-methylstyrene, as well as polyester / ABS or polycarbonate / ABS and polyester or polystyrene plus some other impact modifier. Such polymers can be commercially available or prepared by methods well known in the art.

[0114] The flame retardants of the present invention are particularly suitable for use with 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.

[0115] For example, the polymer can be a polyester-based resin, a styrene-based resin, a polyamide-based resin, a polycarbonate-based resin, a polyphenylene ether-based resin, a vinyl-based resin, an olefin-based resin, an acrylic-based resin, an epoxy resin, or a polyurethane. The polymer can be a thermoplastic or a thermoset resin, and can be reinforced, e.g., glass reinforced. In some embodiments, the polymer is a thermoplastic polyurethane. In some embodiments, the polymer is a thermoset epoxy resin. More than one polymer resin can be present. In particular embodiments, the polymer is an engineering polymer, e.g., a thermoplastic or a reinforced thermoplastic polymer, e.g., a glass-reinforced thermoplastic polymer, such as a glass-filled polyester, epoxy, or polyamide, e.g., a glass-filled polyester such as a glass-filled polyalkylene terephthalate or a glass-filled polyamide.

[0116] Polyester-based resins include homopolymers and copolymers obtained by polycondensation of, for example, a dicarboxylic acid component and a diol component, and polycondensation of a hydroxycarboxylic acid or lactone component, e.g., aromatic saturated polyester-based resins such as polybutylene terephthalate or polyethylene terephthalate.

[0117] Polyamide (PA) based resins include polyamides derived from diamines and dicarboxylic acids; polyamides obtained from aminocarboxylic acids, if necessary in combination with diamines and / or dicarboxylic acids; and polyamides derived from lactams, if necessary in combination with diamines and / or dicarboxylic acids. Polyamides also include copolyamides derived from at least two different types of polyamide constituent components. Examples of polyamide-based resins include aliphatic polyamides such as PA 46, PA 6, PA 66, PA 610, PA 612, PA 11, and PA 12, polyamides obtained from aromatic dicarboxylic acids such as terephthalic acid and / or isophthalic acid and aliphatic diamines such as hexamethylene diamine or nonamethylene diamine, and polyamides obtained from both aromatic and aliphatic dicarboxylic acids such as terephthalic acid and adipic acid and aliphatic diamines such as hexamethylene diamine, etc. 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.

[0118] Polyamides having a melting point of at least 280°C are widely used for the production of molding compositions which make it possible to produce molded articles (for example for the electrical and electronic industry) which have excellent dimensional stability at high temperatures and very good flame- retardant properties. For example, in the electronics industry there is a need for molding compositions of this type for the production of components which are mounted on printed circuit boards according to the so-called surface mounting technology SMT. In this application, these components must withstand temperatures of up to 270°C without changing in size over short time periods.

[0119] Such 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, i.e. homopolymers, copolymers, terpolymers or higher polymers derived from monomers containing aromatic groups. Single aromatic or semi-aromatic polyamides can be used, or blends of aromatic and / or semi-aromatic polyamides can be used. Blending of the aforementioned polyamides and polyamide blends with other polymers including aliphatic polyamides is also possible.

[0120] Examples of these high temperature aromatic or semi-aromatic polyamides include polyamide 4T, poly(metaxylylene adipamide) (polyamide MXD,6), poly(p-xylylene dodecamide) (polyamide 12,T), poly(p-xylylene decanediamide) (polyamide 10,T), poly(p-xylylene nonanediamide) (polyamide 9,T), hexamethylene adipamide / p-xylylene hexanediamide copolyamide (polyamide 6,T / 6,6), p-xylylene hexanediamide / p-xylylene 2-methylpentanediamide copolyamide (polyamide 6,T / D,T), hexamethylene adipamide / p-xylylene hexanediamide / metaxylylene hexanediamide copolyamide (polyamide 6,6 / 6,T / 6,I), poly(caprolactam-p-xylylene hexanediamide) (polyamide 6 / 6,T), p-xylylene hexanediamide / metaxylylene hexanediamide (6,T / 6,I) copolymer, and the like.

[0121] Thus, certain embodiments of the present application are directed to compositions comprising polyamides that melt at high temperatures, such as 280°C or higher, 300°C or higher, in some embodiments, 320°C or higher, for example, 280-340°C, such as polyamide 4,6, and aromatic and semi-aromatic polyamides described above, articles comprising the high temperature polyamides and the flame retardant material of the present application, methods for making the compositions and methods for shaping the articles.

[0122] As described herein, in many embodiments of the present disclosure, the flame-retardant polymer composition comprises (i) a polymer, (ii) a flame retardant of the present disclosure, and (iii) one or more other flame retardants and / or one or more synergists or flame-retardant adjuvants. Thus, although the flame retardant (ii) exhibits excellent activity in the polymer system alone, it can be used in combination with (iii) one or more compounds selected from other flame retardants, synergists, and adjuvants. Exemplary 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 phosphinates, carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes, polyphenylene ethers, melamine, melamine derivatives, melamine condensation products, melamine salts, metal hydroxides, metal oxides, metal hydroxyl oxides, metal borates, metal carbonates, metal sulfates, metal phosphates, metal phosphonates, metal phosphites, metal phosphinates, metal silicates, and mixed metal salts. For example, the one or more compounds (iii) can be selected from aluminum tris(dialkylphosphinate), aluminum hydrophosphite, benzylphosphine oxide, polybenzylphosphine oxide, melam, melem, melemine, melamine phosphates, melamine metal phosphates, melamine cyanurate, melamine borate, talc, clay, calcium silicate, aluminosilicate, aluminosilicate as 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, magnesium hydroxide, aluminum oxide, aluminum hydroxide oxide, aluminum trihydrate, silicon dioxide, tin oxide, antimony oxide (III and V), antimony (III and V) hydroxyl oxide, titanium oxide, zinc oxide, zinc hydroxyl oxide, zirconium oxide, and zirconium hydroxide. For example, the one or more compounds (iii) can be selected from aluminum tris(dimethylphosphinate), aluminum tris(diethylphosphinate), aluminum tris(dipropylphosphinate), aluminum tris(dibutylphosphinate), polyarylether substituted with methylene diphenylphosphine oxide, xylylene bis(diphenylphosphine oxide), 1,2-bis-(9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide)ethane, 4,4'-bis(diphenylphosphinylmethyl)-1,1'-biphenyl, melam, melem, melemine, and zinc dimelamine pyrophosphate.

[0123] In some embodiments, the flame retardant synergist includes a material selected from the group consisting of melam, melem, melemine, melamine cyanurate, melamine polyphosphate, and melamine-poly(metal phosphinate) (e.g., melamine-poly(zinc phosphinate) (Safire 400)). In some embodiments, the synergist comprises a triazine-based compound, such as the reaction product of trichlorotriazine, piperazine, and morpholine, e.g., poly-[2,4-(piperazin-1,4-yl)-6-(morpholin-4-yl)-1,3,5-triazine] / piperazine PPM triazine HF). In some embodiments, the synergist comprises a metal hypophosphite salt, such as aluminum hypophosphite (e.g., Italmatch IP-A). In some embodiments, the synergist comprises an organic hypophosphite salt, such as a dialkyl aluminum hypophosphite, e.g., diethyl aluminum hypophosphite (Exolit OP).

[0124] 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 a metal borate, metal oxide, or metal hydroxide in which the metal is zinc or calcium.

[0125] The concentration of the flame retardant of the present application in the polymer composition, of course, depends on the precise chemical composition of the flame retardant, polymer, and other components found in the final polymer composition. For example, when used as the sole flame-retardant component of a polymer formulation, the flame retardant of the present application can be present at a concentration of 1% to 50%, e.g., 1% to 30%, based on the total weight of the final composition. Typically, when used as the sole flame retardant, at least 2%, e.g., 3% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more of the material of the present application will be present. In many embodiments, the flame retardant of the present application is present in an amount of up to 45%, while in other embodiments, the amount of the flame retardant of the present application is 40% or less, e.g., 35% or less, of the polymer composition. Less of the material of the present application can be required when used in combination with other flame retardants or flame-retardant synergists.

[0126] Any known compounding technique can be used to prepare the flame-retardant polymer compositions of the present disclosure, e.g., the flame retardant can be introduced into the molten polymer by blending, extrusion, fiber or film formation, etc. In some cases, the flame retardant is introduced into the polymer as it is being formed or cured, e.g., the flame retardant of the present application can be added to a polyurethane prepolymer prior to crosslinking, or it can be added to a polyamine or alkyl polycarboxylic compound prior to polyamide formation, or to an epoxy mixture prior to curing.

[0127] The flame-retardant polymer compositions of the present invention will typically include one or more of the common stabilizers or other additives often encountered 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 oil, hydroxylamines, tertiary amine oxides, lactones, thermal reaction products of tertiary amine oxides, thiosynergists, basic co-stabilizers such as melamine, benzoguanamine and the like, polyvinylpyrrolidone, dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamides, polyurethanes, hydrotalcites, alkali and alkaline earth metal salts of higher fatty acids such as calcium stearate, calcium steraryl-2-lactylate, calcium lactate, zinc stearate, zinc octoate, magnesium stearate, sodium ricinoleate and potassium palmitate, antimony or zinc pyrocatecholate, nucleating agents, clarifying agents and the like.

[0128] Other additives can also be present, such as plasticizers, lubricants, emulsifiers, pigments, dyes, optical brighteners, other flame retardants, antistatic agents, blowing agents, anti-dripping agents such as PTFE and the like.

[0129] Optionally, the polymers can 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. Such fillers and reinforcing agents can typically be present in relatively high concentrations, including formulations in which the filler or reinforcing agent is present in a concentration of more than 50 wt% based on the weight of the final composition. More typically, the fillers and reinforcing agents are present in a concentration of about 5 wt% to about 50 wt%, for example, about 10 wt% to about 40 wt%, or about 15 wt% to about 30 wt%, based on the weight of the total polymer composition.

[0130] In some embodiments, the flame-retardant polymer compositions of the present disclosure are formulated with any one or more of the materials selected from the group consisting of carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes, talc, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, calcium silicate, magnesium silicate, Dragonite, halloysite, boron phosphate, calcium molybdate, exfoliated vermiculite, zinc stannate, zinc hydroxystannate, zinc sulfide, zinc borate, zinc molybdate (or its composites, such as Kemgard 911B), zinc molybdate / magnesium hydroxide composite (such as Kemgard MZM), zinc molybdate / magnesium silicate composite (Kemgard 911C), calcium / zinc molybdate composite (such as Kemgard 911A), zinc phosphate (or its composites, such as Kemgard 981), and the like;

[0131] Hydroxides, oxides and hydrated oxides of Group 2, 4, 12, 13, 14 (semi)metals such as magnesium oxide or hydroxide, aluminum oxide, aluminum hydroxide oxide (boehmite), aluminum trihydrate, silicon dioxide, silicates, tin oxides, antimony oxides (III and V) and hydrated oxides, titanium oxides and zinc oxides or hydrated oxides, zirconium oxide and / or 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 hydrotalcite, boehmite, kaolin, mica, montmorillonite, wollastonite, nanoclays or organically modified nanoclays, and the like.

[0132] In some embodiments, the flame-retardant polymer composition of the present disclosure is formulated with any one or more materials selected from zinc borate, zinc stannate, polysiloxane, 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 911A), zinc phosphate complex (e.g., Kemgard 981), and melamine-poly(metal phosphate) (e.g., melamine-poly(zinc phosphate) (Safire 400)).

[0133] In some embodiments, the flame-retardant polymer composition comprises melam and any 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, in addition to the polymer (as described herein) and the flame retardant of the present disclosure, optionally, and additional additives as described herein.

[0134] In some embodiments, the flame-retardant polymer composition comprises melam and any 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, in addition to the polymer (as described herein) and the flame retardant of the present disclosure, optionally, and additional additives as described herein.

[0135] Further non-limiting disclosure is provided in the following examples.

[0136] Example

[0137] Example 1

[0138]

[0139] A three neck 250 mL flask was charged with 114.6 g of methyl phosphonic acid which was then heated. At 105 °C, the methyl phosphonic acid melted and was placed under a vigorous stirring under a blanket of N2. The methyl phosphonic acid was heated to 240 °C and 7.78 g of alumina was added as fast as possible without causing a large exotherm. The slurry was cooled until it was just above the melting point of excess methyl phosphonic acid - 110 °C, then added to 250 mL of H2O while ensuring the rate of addition did not cause excessive steam formation. The resulting mixture was stirred to break up any lumps that could have formed, the product was isolated by filtration, washed with an additional 750 mL of H2O and dried to yield 45.08 g of a colorless fine crystalline product in 87% yield. The empirical formula above represents the repeating monomer unit of the coordination polymer (i.e., the ligand) that forms the pure crystalline product. Figure 1 Thermogravimetric analysis (TGA) of the product is shown.

[0140] Example 2

[0141]

[0142] A three neck 250 mL flask was charged with 149.8 g of ethyl phosphonic acid which was heated to 62 °C to melt. The ethyl phosphonic acid was heated to 240 °C under a blanket of nitrogen and 6.9 g of alumina was added as fast as possible without causing a large exotherm. The slurry was cooled to ~ 80 °C, then added to 250 mL of H2O while ensuring the rate of addition did not cause excessive steam formation. The resulting mixture was stirred to break up any lumps that could have formed, the product was isolated by filtration, washed with an additional 750 mL of H2O and dried to yield 49.07 g of a colorless fine crystalline product in 84% yield. The empirical formula above represents the repeating monomer unit of the coordination polymer (i.e., the ligand) that forms the pure crystalline product.

[0143] Example 3

[0144]

[0145] A 1 L three necked flask was charged with 1305 g of methylphosphonic acid which was then heated. At 105 °C the methylphosphonic acid melted and was vigorously stirred under vacuum. The methylphosphonic acid was heated to 180 °C and 61 g of aluminum oxide was added as fast as possible without causing a large exotherm or excessive foaming. The slurry was cooled until it was just above the melting point of excess methylphosphonic acid ~ 110 °C and then added to 1 L of H2O while ensuring that the rate of addition did not cause excessive steam formation. The resulting mixture was stirred to break up any clumps that could form and the product was isolated by filtration, washed with an additional 1.5 L of H2O and dried to yield 408 g of a colorless fine crystalline product in 84% yield. The empirical formula above represents the repeating monomer unit of the coordination polymer (i.e., the ligand) that forms the pure crystalline product.

[0146] Example 4

[0147]

[0148] A 1 L three necked flask was charged with 1305 g of methylphosphonic acid which was then heated. At 105 °C the methylphosphonic acid melted and was vigorously stirred under vacuum. The methylphosphonic acid was heated to 180 °C and 61 g of aluminum oxide was added as fast as possible without causing a large exotherm or excessive foaming. The slurry was cooled until it was just above the melting point of excess methylphosphonic acid ~ 110 °C and then added to 1 L of H2O while ensuring that the rate of addition did not cause excessive steam formation. The resulting mixture was stirred to break up any clumps that could form and the product was isolated by filtration, washed with an additional 1.5 L of H2O and dried to yield 408 g of a colorless fine crystalline product in 84% yield. The empirical formula above represents the repeating monomer unit of the coordination polymer (i.e., the ligand) that forms the pure crystalline product.

[0149] The product of each of Examples 1-4 had a P / Al ratio (ICP elemental analysis) of 4:1.

[0150] Example 5

[0151]

[0152] A 1 L reaction vessel was charged with 1412.6 g of methylphosphonic acid and then heated to 165 °C under a nitrogen purge (4 L / min) with stirring at 250 RPM. 78.2 g of iron oxide (Fe203) was added in portions without causing a large exotherm. The reaction mixture was heated at 165 °C for about 24 hours. The product reaction mixture containing an off-white slurry of product was then cooled to about 130 °C and poured into 1.5 L of water in a flask cooled in an ice water bath. The product was isolated by filtration, washed with an additional 500 mL x 3 of water, and dried to yield off-white fine crystals in 83% yield. The product had a phosphorus to iron ratio (ICP elemental analysis) of 4: 1 according to the following empirical formula:

[0153]

[0154] The above product empirical formula represents the repeating monomer unit (i.e., ligand) of the coordination polymer that forms the pure crystalline product.

[0155] Example 6

[0156] Polymer compositions were prepared and evaluated for flame retardant activity under UL-94 testing. For glass-filled polymer compositions of polyamide 6,6; polyamide 6; polybutylene terephthalate (PBT) and high temperature polyamide containing the flame retardant produced according to Examples 1, 3 and 4 above (as shown below), UL-94 V-0 ratings at 0.8 mm thickness were measured:

[0157]

[0158] Table 1. Compositions utilizing UL-94 V-0 ratings at 0.8 mm

[0159] Substrate Glass fiber Inventive FR Melam Melamine cyanurate PA 6,6 30％ 12.5％ 10％ - PA 6 25％ 15％ - 10％ PBT 25％ 15％ 15％ - High temperature nylon 25％ 18％ - -

[0160] Additional polymer compositions containing the flame retardant produced according to Examples 1, 3 and 4 above in combination with various synergists in glass-filled PA 66, PBT and polyphthalamide were prepared and evaluated in UL-94 testing at 0.8 mm thickness. The results are provided in Table 2 (PA 66), Table 3 (PBT) and Table 4 (polyphthalamide). Samples 15, 20 and 22, which did not contain the inventive flame retardant, failed the UL-94 testing.

[0161] Table 2. PA 66

[0162]

[0163]

[0164] Table 3. PBT

[0165] Sample formulation 16 17 18 19 20 PBT wt% 50 50 50 45 75 Glass wt% 25 25 25 25 25 Inventive FR wt% 15 16 15 15 - Melam wt% 10 9 9 15 - Polysilicone wt% - - 1 - - UL 94 @ 1 / 32" V-0 V-0 V-0 V-0 Failed

[0166] Table 4. Polyphthalamides (high temperature polyamides)

[0167] Sample formulation 21 22 Polyphthalamide wt% 57 70 Glass wt% 25 30 Inventive FR wt% 18 - UL 94 @ 1 / 32" V-0 Failed

[0168] Example 7

[0169] Polymer compositions containing flame retardants according to Example 5 above in PA 66 were prepared and evaluated for flame retardant activity in UL-94 testing at a thickness of 0.8 mm. The results are provided in Table 5. Sample 24, which did not contain a flame retardant of the present application, failed the UL-94 test.

[0170] Table 5. PA 66

[0171]

[0172]

[0173] While particular embodiments of the present application have been illustrated and described, it would be obvious to those skilled in the art that various modifications and changes can be made without departing from the scope of the application as embodied in the application claimed and the disclosure thereof. Therefore, the aim of the specification and examples is to be considered only as exemplary and the true scope of the application is indicated by the appended claims and their equivalents.

Claims

1. A crystalline compound or a crystalline mixture of compounds of the empirical formula (III): Where R is unsubstituted C 1-6 alkyl groups; M is a metal selected from aluminum and iron and y is 3, such that M (+)y is a metal cation, wherein (+)y represents the charge formally assigned to the cation; a is a number from 1 to 8, b is a number from 1 to 4, and c is a number from 1 to 10. a, b, and c represent ratios of their components corresponding to each other in the compound, and satisfy the charge balance equation 2(a)+c=b(y).

2. The crystalline compound or crystalline mixture of compounds according to claim 1, wherein R is methyl, ethyl, propyl, isopropyl, butyl or tert-butyl.

3. The crystalline compound or crystalline mixture of compounds according to claim 2, wherein R is methyl or ethyl.

4. The crystalline compound or crystalline mixture of compounds according to claim 3, wherein a is 1, b is 1, and c is 1.

5. The crystalline compound or crystalline mixture of compounds according to claim 1, wherein the compound of empirical formula (III) is a compound of empirical formula (IIIa): Where R is unsubstituted C 1-6 alkyl.

6. The crystalline compound or crystalline mixture of compounds according to claim 5, wherein R is methyl or ethyl.

7. The crystalline compound or crystalline mixture of compounds according to any one of claims 1 to 6, wherein the compound of empirical formula (III) or the compound of empirical formula (IIIa) comprises at least 75 wt% of the flame retardant material.

8. The crystalline compound or crystalline mixture of compounds according to claim 5, wherein the compound of empirical formula (IIIa) comprises at least 90 wt% of the flame retardant material.

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