Process for the continuous polymerization of phosphate compounds to form a polyphosphate composition

Abstract

The polyphosphate composition is produced by a process comprising the steps of: continuously introducing a phosphate compound into a polymerization vessel, polymerizing the phosphate compound at a temperature of 250-450° C. for a time sufficient to form the polyphosphate composition, and continuously discharging the polyphosphate composition from the polymerization vessel. The phosphate compound may be fed to the polymerization vessel in the form of an aqueous slurry containing 5-50% by weight of the phosphate compound. The resulting polyphosphate composition typically contains at least 8% by weight of polyphosphate and less than 35% by weight of the phosphate compound.

Description

[0001] Citation to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 014,740, filed on April 24, 2020, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates generally to the preparation of polyphosphate compositions useful as flame retardants and, more particularly, to the continuous polymerization of certain phosphate compounds to form polyphosphate compositions. Background Art

[0004] A variety of polyphosphates are useful as flame retardant additives in polymer-based formulations. However, the production of these polyphosphates is limited to solid phosphate feed materials and is subject to limitations in polymerization processes and equipment that suffer from poor operating efficiencies. Accordingly, the present invention is generally directed to methods of making polyphosphate compositions that overcome these drawbacks. Summary of the invention

[0005] This summary is provided to introduce some concepts in a simplified form, which are further described in the detailed description below. This summary is not intended to identify required or essential features of the claimed subject matter. This summary is also not intended to limit the scope of the claimed subject matter.

[0006] Disclosed and described herein are processes for producing polyphosphate compositions. For example, a first process for producing a polyphosphate composition may include (a) continuously introducing a phosphate compound into a polymerization vessel, (b) polymerizing the phosphate compound at a temperature in the range of about 250 to about 450° C. for a time sufficient to form the polyphosphate composition, and (c) continuously discharging the polyphosphate composition from the polymerization vessel. The polyphosphate composition may include at least about 8% by weight polyphosphate and less than or equal to about 35% by weight phosphate compound.

[0007] A second process for producing a polyphosphate composition consistent with aspects of the present invention may include (a) continuously introducing an aqueous slurry containing about 5% to about 50% by weight of a phosphate compound into a polymerization vessel, (b1) evaporating water from the aqueous slurry in a first zone of the polymerization vessel, (b2) polymerizing the phosphate compound in a second zone of the polymerization vessel at a temperature in the range of about 250 to about 450° C. for a time sufficient to form the polyphosphate composition, and (c) continuously discharging the polyphosphate composition from the polymerization vessel. The polyphosphate composition may include at least about 8% by weight polyphosphate and less than or equal to about 35% by weight of the phosphate compound.

[0008] Illustrative and non-limiting examples of phosphate compounds that can be polymerized as described herein include ammonium phosphate, melamine phosphate, melamine magnesium phosphate, and melamine zinc phosphate; thus, the resulting polyphosphates can include ammonium polyphosphate (ammonium polyphosphate), melamine polyphosphate (melamine polyphosphate), melamine poly(magnesium phosphate) (melamine poly(magnesium phosphate)), and melamine poly(zinc phosphate) (melamine poly(zinc phosphate)).

[0009] Both the above summary and the following detailed description provide examples and are merely illustrative. Accordingly, the above summary and the following detailed description should not be considered restrictive. Further, in addition to those listed herein, other features or variations may also be provided. For example, certain aspects may relate to various feature combinations and sub-combinations described in the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following drawings form part of this specification and are included to further illustrate certain aspects of the invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description and examples.

[0011] Figure 1 The polyphosphate composition and melamine zinc phosphate monomer produced at a constant temperature in Example 1 are presented. 31 Graph of the P MAS NMR spectrum.

[0012] Figure 2 Thermogravimetric analysis (TGA) graphs of the polyphosphate composition and melamine zinc phosphate monomer produced at a constant temperature in Example 1 are presented.

[0013] Figure 3 The polyphosphate composition and melamine zinc phosphate monomer produced at constant residence time in Example 2 are presented. 31 Graph of the P MAS NMR spectrum.

[0014] Figure 4 A graph of the heat release rate (HRR) curve of the flame retardant polymer composition of Example 3 is presented.

[0015] definition

[0016] In order to more clearly define the terms used in this article, the following definitions are provided. Unless otherwise stated, the following definitions apply to the present disclosure. If a term is used in the present disclosure, but it is not specifically defined herein, the definition from the second edition (1997) of the IUPAC Compendium of Chemical Terminology may be applicable, as long as the definition does not conflict with any other disclosure or definition used herein, or any claim to which the definition is applied becomes unclear or cannot be realized. To the extent that any definition or use provided by any document incorporated herein by reference conflicts with the definition or use provided herein, the definition or use provided herein is dominant.

[0017] Herein, the features of the subject matter are described such that within a particular aspect, combinations of different features are contemplated. For each and any aspect disclosed herein and each and any feature, all combinations that do not negatively affect the design, composition, process, or method described herein may be considered and interchangeable, regardless of whether a specific combination is explicitly described. Accordingly, unless otherwise explicitly stated, any aspect or feature disclosed herein may be combined to describe a design, composition, process, or method of the invention consistent with the present disclosure.

[0018] Although compositions and methods are described herein as "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components or steps, unless otherwise specified.

[0019] The terms "a", "an" and "the" are intended to include plural alternatives, such as at least one, unless otherwise stated.

[0020] In general, groups of elements are referred to using the numbering scheme specified in the version of the periodic table published in Chemical and Engineering News, 63(5), 27, 1985. In some cases, the group of an element may be indicated using the common name assigned to the group; for example, Group 1 elements are alkali metals, Group 2 elements are alkaline earth metals, and so on.

[0021] Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, typical methods and materials are described herein.

[0022] All publications and patents mentioned herein are incorporated herein by reference for the purpose of describing and disclosing, for example, constructs and methodologies described in the publications, which might be used in connection with the presently described invention.

[0023] The scope of several types is disclosed in the present invention.When disclosing or claiming any type of scope, it is intended to disclose or claim each possible value that such scope can reasonably cover, including the end point of the scope and any sub-range and the combination of the sub-range covered therein.As a representative example, the amount of the phosphate compound in the aqueous slurry can be in some scopes in various aspects of the present invention.By disclosing that the aqueous slurry can contain the phosphate compound of about 5 weight % to about 50 weight %, it is intended to illustrate that the amount of the phosphate compound can be any amount in the scope, for example, can be equal to about 5 weight %, about 10 weight %, about 15 weight %, about 20 weight %, about 25 weight %, about 30 weight %, about 35 weight %, about 40 weight %, about 45 weight % or about 50 weight %.In addition, the amount of the phosphate compound can be in any range of about 5 weight % to about 50 weight % (for example, about 10 weight % to about 30 weight %), and this also includes any combination of the scope between about 5 weight % and about 50 weight %. Further, in all cases where "about" + a particular value is disclosed, the value itself is disclosed. Thus, a disclosure of an amount of phosphate compound in the range of about 5 wt % to about 50 wt % also discloses a range of phosphate compound of 5 wt % to 50 wt % (e.g., 10 wt % to 30 wt %), and this also discloses any combination of ranges between 5 wt % and 50 wt %. Likewise, all other ranges disclosed herein should also be interpreted in a manner similar to this example.

[0024] The term "about" means that the amount, size, formula, parameter and other quantity and characteristics are not exact or do not need to be exact, but can be roughly as needed to reflect tolerances, conversion factors, rounding off, measurement errors, etc., as well as other factors known to those skilled in the art. In general, whether or not so expressly expressed, the amount, size, formula, parameter or other amount or characteristic is "about" or "approximately". The term "about" also encompasses different amounts due to different equilibrium conditions for the composition obtained from a specific initial mixture. Whether or not modified by the term "about", the claims include equivalents of the amount. The term "about" can mean within 10% of the reported value, preferably within 5% of the reported value. DETAILED DESCRIPTION

[0025] The continuous processes disclosed herein for producing polyphosphate compositions have multiple advantages over conventional static batch operations. In addition to higher operating efficiency and cost effectiveness, these continuous processes also produce polyphosphate compositions with improved product consistency, which is partly due to the continuous rotation and mixing / agitation in the polymerization vessel (one of which is a rotary kiln). It is also beneficial that these processes have improved quality control of the compositional breakdown (monomer, dimer, polymer) in the polyphosphate composition, so that the thermal stability of the composition in the flame retardant formulation based on the polymer can be designed with certainty.

[0026] Further, the disclosed continuous process is not limited to solid or powdered phosphate monomers.Beneficially, water-based slurries of phosphate compounds can be used directly in the polymerization process, eliminating the need for expensive and time-consuming drying steps.

[0027] Process for preparing polyphosphate composition

[0028] Disclosed herein are processes for producing polyphosphate compositions. A first process for producing a polyphosphate composition may include (or consist essentially of, or consist of): (a) continuously introducing a phosphate compound into a polymerization vessel, (b) polymerizing the phosphate compound at a temperature in the range of about 250 to about 450° C. for a time sufficient to form the polyphosphate composition, and (c) continuously discharging the polyphosphate composition from the polymerization vessel. A second process for producing a polyphosphate composition consistent with aspects of the present invention includes (or consists essentially of, or consists of): (a) continuously introducing an aqueous slurry containing about 5% to about 50% by weight of a phosphate compound into a polymerization vessel, (b1) evaporating water from the aqueous slurry in a first zone of the polymerization vessel, (b2) polymerizing the phosphate compound in a second zone of the polymerization vessel at a temperature in the range of about 250 to about 450° C. for a time sufficient to form the polyphosphate composition, and (c) continuously discharging the polyphosphate composition from the polymerization vessel. The polyphosphate compositions in the first process and the second process can include at least about 8 weight percent polyphosphate and less than or equal to about 35 weight percent phosphate compounds.

[0029] In general, the features of the first process and the second process (e.g., phosphate compounds, process conditions for implementing step (b) or steps (b1) and (b2), and components and / or features of the polyphosphate composition, etc.) are described independently herein, and these features can be combined in any combination to further describe the disclosed first process and second process. In addition, any polyphosphate composition produced according to the first process or the second process is included herein.

[0030] Referring now to step (a) of the first process for producing a polyphosphate composition, a phosphate compound may be continuously introduced into a polymerization vessel. Generally, in the first process, the phosphate compound may be in solid form, for example, a solid phosphate compound containing up to about 12 wt % water / moisture. In most cases, the amount of entrained moisture in the solid phosphate compound may be less than or equal to about 10 wt %, less than or equal to about 5 wt %, or less than or equal to about 2 wt %. In some aspects, the phosphate compound used in step (a) of the first process may be a free-flowing solid or powder.

[0031] In step (b) of the first process, the phosphate compound may be polymerized at a temperature in the range of about 250 to about 450° C. for a time sufficient to form the polyphosphate composition. In one aspect, the temperature may be in the range of about 280° C. to about 420° C., while in another aspect, the temperature may be in the range of about 300° C. to about 400° C., and in still another aspect, the temperature may be in the range of about 320° C. to about 420° C. In these and other aspects, these temperature ranges are also meant to encompass situations in which the polymerization for forming the polyphosphate composition is conducted at a range of different temperatures falling within the respective ranges, rather than at a single fixed temperature.

[0032] Step (b) may be carried out for any suitable time, generally for a time sufficient to form the polyphosphate composition. As will be readily appreciated, higher polymerization temperatures may require shorter times while lower temperatures may require longer times; thus, the time in step (b) may vary significantly. Regardless, the average residence time in the polymerization vessel is typically in the range of about 30 minutes to about 300 minutes; alternatively, about 45 minutes to about 180 minutes; or alternatively, about 60 minutes to about 120 minutes.

[0033] The prevailing pressure in step (b) is not particularly limited, but in some aspects, step (b) can be carried out at a pressure ranging from ambient pressure to about 100 psig (689 kPag), ambient pressure to about 60 psig (414 kPag), or about 5 psig to about 60 psig (34 kPag to 414 kPag).

[0034] In step (c), the polyphosphate composition may be continuously withdrawn from the polymerization vessel.The components of the polyphosphate composition and their relative amounts are discussed further below.

[0035] Optionally, the amount of polyphosphate in the polyphosphate composition (i.e., discharged from the polymerization vessel) can be monitored and the polymerization process conditions can be controlled accordingly. For example, the first process can further include the steps of: (i) determining (or measuring) the amount of polyphosphate in the polyphosphate composition, and (ii) adjusting the time and / or temperature in step (b) based on the amount of polyphosphate in the polyphosphate composition. In this regard, the target amount or desired amount of polyphosphate in the composition can be effectively maintained by controlling the polymerization temperature, average residence time, etc.

[0036] Likewise, and optionally, the amount of phosphate compound in the polyphosphate composition (i.e., discharged from the polymerization vessel) can be monitored, and the polymerization process conditions can be controlled accordingly. For example, the first process can further include the steps of: (I) determining the amount of phosphate compound in the polyphosphate composition, and (II) adjusting the time and / or temperature in step (b) based on the amount of phosphate compound in the polyphosphate composition. In this aspect, the target or desired amount of phosphate in the composition can be effectively maintained (and the target or desired amount of phosphate conversion can be effectively maintained) by controlling the polymerization temperature, average residence time, etc.

[0037] Referring now to the second process for producing a polyphosphate composition, an aqueous slurry containing about 5% to about 50% by weight of a phosphate compound can be continuously introduced into a polymerization vessel in step (a). The amount of phosphate compound present in the aqueous slurry typically ranges from about 5% to about 50% by weight. More typically, the aqueous slurry contains an amount of phosphate compound in one or more of the following representative ranges: about 5% to about 40% by weight, about 8% to about 25% by weight, about 10% to about 40% by weight, or about 10% to about 30% by weight of a phosphate compound.

[0038] In step (b1) of the second process, water may be evaporated from the aqueous slurry in a first zone of the polymerization vessel, while in step (b2), the phosphate compound may be polymerized in a second zone of the polymerization vessel at a temperature in the range of about 250 to about 450° C. for a time sufficient to form the polyphosphate composition. Thus, it is contemplated that the polymerization vessel may have two or more zones, and that these zones may have independent temperature control.

[0039] The temperature in step (b2) of the second process may be the same as described above for step (b) of the first process. Therefore, in some aspects, the (polymerization) temperature range in step (b2) may be from about 280°C to about 420°C, from about 300°C to about 400°C, or from about 320°C to about 420°C. The evaporation conditions in step (b1) are not particularly limited, as long as the water in the aqueous slurry can be removed to allow sufficient polymerization in the second zone of the downstream polymerization vessel. The evaporation temperature in a typical first zone may include from about 300°C to about 800°C, from about 400°C to about 700°C, or from about 500°C to about 800°C. In these and other aspects, these evaporation temperature ranges are also intended to cover such a situation, in which the evaporation process is carried out at a series of different temperatures falling within each range (rather than at a single fixed temperature).

[0040] The prevailing pressure in step (b1) and step (b2) is not particularly limited, but in some aspects, steps (b1) and (b2) can be independently carried out at a pressure in the following range: ambient pressure to about 100 psig (689 kPag), ambient pressure to about 60 psig (414 kPag), or about 5 psig to about 60 psig (34 kPag to 414 kPag). In order to improve the evaporation rate in step (b1), it is also contemplated that step (b1) can be carried out under a suitable sub-atmospheric pressure.

[0041] As with the first process, the average residence time in the second process may vary significantly based on the process conditions used in step (b1) and step (b2). Nevertheless, the average residence time in the polymerization vessel typically ranges from about 1 hour to about 8 hours; alternatively, from about 2 hours to about 5 hours; or alternatively, from about 1.5 hours to about 3 hours. Similarly, the relative amount of time in the first zone and the second zone is also not particularly limited, but may vary significantly based on the process conditions used and the amount of water in the feed stream of the polymerization vessel. In one aspect, the ratio of the first average residence time in the first zone to the second average residence time in the second zone (first: second) may be from about 1:10 to about 5:1, while in another aspect, the ratio may be from about 1:5 to about 3:1, and in still another aspect, the ratio may be from about 1:3 to about 1:1.

[0042] In step (c) of the second process, the polyphosphate composition may be continuously withdrawn from the polymerization vessel.The components of the polyphosphate composition and their relative amounts are discussed further below.

[0043] Optionally, and similar to the first process, the amount of polyphosphate in the polyphosphate composition in the second process (i.e., discharged from the polymerization vessel) can be monitored, and the evaporation and polymerization process conditions can be controlled accordingly. For example, the second process can further include the steps of: (i) determining (or measuring) the amount of polyphosphate in the polyphosphate composition, (ii) adjusting the evaporation conditions in step (b1), the temperature in step (b2), and / or the time in step (b2) based on the amount of polyphosphate in the polyphosphate composition. In this regard, the target amount or expected amount of polyphosphate in the composition can be effectively maintained by controlling the evaporation conditions (e.g., evaporation temperature), polymerization temperature, average residence time, etc.

[0044] Likewise, and optionally, the amount of phosphate compounds in the polyphosphate composition in the second process (i.e., discharged from the polymerization vessel) can be monitored, and the evaporation and polymerization process conditions can be controlled accordingly. For example, the second process can further include the steps of: (I) determining the amount of phosphate compounds in the polyphosphate composition, and (II) adjusting the evaporation conditions in step (b1), the temperature in step (b2), and / or the time in step (b2) based on the amount of phosphate compounds in the polyphosphate composition. In this regard, the target amount or desired amount of phosphate in the composition can be effectively maintained (and the target amount or desired amount of phosphate conversion can be effectively maintained) by controlling the evaporation conditions, polymerization temperature, average residence time, etc.

[0045] For the first process and the second process, any polymerization vessel suitable for continuous polymerization and forming a polyphosphate composition can be used. For example, a rotary kiln can be used, a vertical kiln can be used, or a spiral kiln can be used. The vessel can have one or two or more zones, and in the latter case, each zone can have independent temperature control. The polymerization vessel can be configured for any suitable amount of mixing or agitation during evaporation and / or polymerization; thus, in some aspects, the polymerization vessel can rotate.

[0046] Generally, a rotary kiln contains a drum, tube or revolving drum that rotates about its axis. The drum is set at a slight angle to allow gravity to assist in moving the material through the rotating drum. There are two similar types of rotary kilns, differentiated based on how heat is introduced to process the material within the drum: direct-fired and indirect-fired. In a direct-fired kiln, hot gases are passed within and along the drum, sometimes in the same direction as the material being processed (co-flow), but usually in the opposite direction (counter-flow). The hot gases may be generated by a flame within the kiln. In an indirect-fired kiln, the material is heated by contact with the inner surface of the drum, which may be heated from the outside, either electrically or by hot gases.

[0047] After discharge from the polymerization vessel - after step (c) - the first process and the second process may further comprise a step of grinding the polyphosphate composition. This grinding step may be used to reduce the average particle size of the polyphosphate composition, or may be used to reduce agglomeration of the polyphosphate composition, or both.

[0048] Advantageously, the first and second processes of the present invention do not require or use a drying step, which can result in significant savings in both time and cost reduction.

[0049] Phosphate compounds and polyphosphate compositions

[0050] The polyphosphate compositions produced by the first and second processes described herein typically contain monomeric species (phosphate compounds), dimers (pyrophosphates), and polymers (polyphosphates). In general, the polyphosphate compositions may contain at least about 8% by weight polyphosphate and less than or equal to about 35% by weight phosphate compounds. These weight percentage values ​​are based only on the phosphorus-containing compounds in the polyphosphate composition, i.e., the presence of impurities, solvents / diluents, etc. is excluded from determining the weight percentages of the individual components of the polyphosphate composition.

[0051] In one aspect, at least about 8% by weight of the polyphosphate composition is polyphosphate, and in some cases, the polyphosphate composition contains at least about 15%, at least about 20%, or at least about 25% by weight of polyphosphate (any number of repeating units equal to or greater than 3). Illustrative and non-limiting ranges of the polyphosphate content of the polyphosphate composition may include about 15% to about 60%, about 15% to about 50%, or about 20% to about 40% by weight of polyphosphate.

[0052] In one aspect, up to about 35% by weight of the polyphosphate composition is phosphate compounds. In some aspects, the polyphosphate composition contains less than or equal to about 25% by weight or less than or equal to about 20% by weight of phosphate compounds. In other aspects, the polyphosphate composition contains less than or equal to about 15% by weight or less than or equal to about 10% by weight of phosphate compounds.

[0053] In one aspect, a significant portion of the polyphosphate composition may be a pyrophosphate compound. Although not limited thereto, the polyphosphate composition may contain from about 35% to about 80% by weight of a pyrophosphate compound; alternatively, from about 45% to about 75% by weight of a pyrophosphate compound; or alternatively, from about 55% to about 75% by weight of a pyrophosphate compound.

[0054] Suitable phosphate compounds that can be used in the first process and the second process to produce polyphosphate compositions may include (metal)(phosphate), (N-containing cation)(phosphate), (N-containing cation)(metal)(phosphate), etc., or combinations thereof; alternatively, (metal)(phosphate); alternatively, (N-containing cation)(phosphate); or alternatively, (N-containing cation)(metal)(phosphate).

[0055] For (metal)(phosphate), the metal may be zinc, molybdenum, calcium, magnesium, aluminum, copper, barium, tin, tungsten, iron, or nickel, although not limited thereto. Thus, the (metal)(phosphate)—the phosphate compound—may be zinc phosphate, molybdenum phosphate, calcium phosphate, magnesium phosphate, aluminum phosphate, copper phosphate, barium phosphate, tin phosphate, tungsten phosphate, iron phosphate, and / or nickel phosphate.

[0056] For (N-containing cation)(phosphate), the N-containing cation may be ammonium, arginine, lysine, histidine, melamine, or diethanolamine, although not limited thereto. Thus, (N-containing cation)(phosphate)—the phosphate compound—may be ammonium phosphate, arginine phosphate, lysine phosphate, histidine phosphate, melamine phosphate, and / or diethanolamine phosphate.

[0057] For (cations containing N) (metals) (phosphates), any combination of metals and cations containing N can be used to describe phosphate compounds. Illustrative and non-limiting examples include melamine zinc phosphate, melamine copper phosphate, ammonium tin phosphate, ammonium zinc phosphate, etc., and combinations thereof. Although not limited thereto, (cations containing N) (metals) (phosphates) can be prepared by processes involving: a mixture of water and cations containing N is combined (or reacted) with a mixture of water, phosphoric acid, and (metal) oxides to form phosphate compounds. In addition to (metal) oxides, (metal) hydroxides can also be used. Therefore, melamine zinc phosphate can be prepared by combining (or reacting) a mixture of water and melamine with a mixture of water, phosphoric acid, and zinc oxide (zinc oxide, zinc oxide) (or zinc hydroxide (zinc hydroxide, zinchydroxide)) to form melamine zinc phosphate.

[0058] Consistent with aspects of the first and second processes of the present invention, in one representative example, the phosphate compound may include ammonium phosphate, and the polyphosphate may include ammonium polyphosphate. In another representative example, the phosphate compound may include melamine phosphate, and the polyphosphate may include melamine polyphosphate. In still another representative example, the phosphate compound may include melamine zinc phosphate, and the polyphosphate may include melamine poly (zinc phosphate).

[0059] The polyphosphate composition may have unexpectedly high thermal stability, for example, characterized by a decomposition onset temperature on a TGA (thermogravimetric analysis) curve falling within the range of about 290°C to about 360°C; additionally or alternatively, characterized by a temperature at 2% weight loss falling within the range of about 290°C to about 360°C; or additionally or alternatively, characterized by a temperature at 5% weight loss falling within the range of about 290°C to about 360°C.

[0060] In one aspect, the polyphosphate composition may be characterized by a decomposition onset temperature on the TGA curve (or a temperature at which the weight loss is 2%, or a temperature at which the weight loss is 5%) in the range of about 300° C. to about 350° C. In another aspect, the polyphosphate composition may be characterized by a decomposition onset temperature on the TGA curve (or a temperature at which the weight loss is 2%, or a temperature at which the weight loss is 5%) in the range of about 310° C. to about 340° C.

[0061] Polymer-based flame retardant formulations

[0062] The present invention also relates to, and encompasses, any composition, formulation, composite, and article of manufacture containing any polyphosphate composition disclosed herein (and their respective properties or characteristics, such as TG temperature, amount of phosphate compound, amount of polyphosphate, etc.). In a particular aspect of the present invention, a polymer composition is disclosed, and in this aspect, the polymer composition may comprise any suitable polymer (one or more than one) and any polyphosphate composition disclosed herein.

[0063] In some aspects, the polymer may include polyethylene (e.g., ethylene homopolymer and / or ethylene / α-olefin copolymer), polypropylene, ethylene vinyl acetate copolymer (EVA), epoxy resin, polyamide (e.g., nylon 66, optionally with glass fiber reinforcement), polybutylene terephthalate (PBT), or polyurethane, etc., and combinations thereof.

[0064] In other aspects, the polymer may comprise one or more of: polyolefins, polylactic acid, polyurethane, polyester matrix, and / or polyamide. Polyolefins may include: polyethylene, i.e., low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE); and polypropylene (PP). Storage and transport containers may be made from high density polypropylene (HDPE) and impact modified polypropylene.

[0065] Although not limited thereto, in the polymer composition, the weight ratio of the polymer: polyphosphate composition can generally range from about 100: 1 to about 100: 40. Illustrative and non-limiting weight ratios of the polymer: polyphosphate composition can include the following ranges: from about 100: 1 to about 100: 20, from about 100: 1 to about 100: 5, from about 100: 5 to about 100: 40, from about 100: 5 to about 100: 30, from about 100: 5 to about 100: 20, from about 100: 2 to about 100: 25, or from about 100: 2 to about 100: 15. Other suitable ranges of weight ratios of the polymer: polyphosphate composition are also readily apparent from this disclosure.

[0066] The manufactured article may be formed from any polymer composition described herein and / or may include any polymer composition described herein. In one aspect, the manufactured article may include a (polymeric) sheet or film. In another aspect, the manufactured article may include a tube or a molded article. In still another aspect, the manufactured article may include a wire or cable. For example, the polymer composition may be used as an insulating layer for wires and cables or in a sheath for wires and cables.

[0067] Other suitable articles of manufacture may be PCBs (printed circuit boards) containing epoxy resins. The polyphosphate composition may be used as a flame retardant for halogen-free epoxy resins, which may be used to make semi-cured preforms (prepregs) or films coated with resins, and to make metal clad laminates (clad laminates) and printed circuit boards. The epoxy resin may include, for example, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, stilbene epoxy resins, epoxy resins having a triazine skeleton, epoxy resins having a fluorene skeleton, triphenylmethane epoxy resins, biphenyl epoxy resins, xylene epoxy resins, biphenyl aralkyl epoxy resins, naphthalene epoxy resins, dicyclopentadiene epoxy resins, alicyclic epoxy resins, etc., and combinations thereof. Other suitable articles of manufacture and end uses are readily apparent from this disclosure.

[0068] Example

[0069] The following examples further illustrate the present invention, which should not be interpreted in any way as limiting the scope of the present invention. After reading the description herein, those skilled in the art may propose various other aspects, variations and equivalents thereof without departing from the spirit of the present invention or the scope of the appended claims.

[0070] The degree of polymerization of the phosphate polymer or composition is determined by solid state 31 P was confirmed by NMR analysis. 31 P NMR spectra were obtained on a Redstone (Tecmag) NMR spectrometer using direct polarization-Magic Angle Spinning at 147.085 MHz. 31 P frequency. Approximately 250 mg of powder sample was loaded into a 7 mm diameter cylindrical (zirconia) rotor equipped with a Kel-F cap and spun at 7 kHz in a Doty Scientific magic angle spinning probe. The presence of spinning sidebands is an artifact of MAS. High rpm rotation (7 kHz) eliminates interference with the peak resonance of the sidebands.

[0071] Further, a direct polarization sequence (optimized to obtain quantitative data) was used with a pulse length of 5 μs (30°) and a pulse delay of 60 seconds. In addition, in order to obtain quantitative data using the DP-MAS technique, the time delay between the two consecutive NMR pulses used should be much greater than the rotational lattice relaxation time. A total of 48-60 transients were collected for each sample, and the spectra were processed with 25-50 Hz line broadening. Data processing and calculation of the integrated peak areas were performed offline using the Acorn NMR NUTS software package. By 31 P NMR identification of functional groups is based on their chemical shift relative to an external phosphoric acid standard. Chemical shift values ​​are used to represent the differences in resonance frequencies of different P compound classes (e.g., orthophosphates, pyrophosphates, and polyphosphates). These values ​​are dimensionless and are expressed in parts per million (ppm) relative to a phosphoric acid standard set to 0 ppm.

[0072] TGA measurements were performed on a TA Instrument TGA Q-500. 5 mg to 20 mg of sample was placed in a platinum pan and loaded on a microbalance inside the TGA furnace. The sample was initially heated at 30 °C with N at a flow rate of 60 mL / min. 2Equilibrate, and heat the sample to 1000°C at a ramp rate of 20°C / min. Record the weight loss during the process. The decomposition onset temperature referred to herein is the "extrapolated" onset temperature, which is a repeatable temperature calculation described in ASTM E2550-11. The "extrapolated" onset temperature, as its name implies, is determined by calculating the intersection of two extrapolated straight lines: one is extrapolated from the initial baseline when there is no weight loss, and the other is the first tangent to the initial weight loss trend line. From the TGA data, the temperatures at 2% by weight and 5% by weight loss are also determined.

[0073] Example 1

[0074] Polymerization of melamine zinc phosphate as a function of residence time at constant temperature

[0075] The solid phosphate compound is fed to the upper end (upper end) of the drum of an indirect fired electric rotary kiln. As the kiln rotates, the compound gradually moves downward toward the lower end (lower end), accompanied by agitation and mixing provided by a three-pronged lift inside the drum or a lifting flight fixed to the surface of the rotating tube. The temperature and average residence time of the compound in the heated zone of the drum determine the degree of polymerization of the polyphosphate. The average residence time (t) in the heated drum can be determined from equation (1):

[0076]

[0077] Where L is the heated length of the drum in feet, θ is the angle of repose of the monomer powder in degrees, m is the slope of the drum along its axis of rotation in degrees, is the inner diameter of the drum in feet, and ω is the drum rotation speed in rpm. Above a certain necessary minimum rotary kiln temperature for polymerization, there is an inverse relationship between residence time and temperature; lower temperatures can be combined with longer residence times to achieve a degree of polymerization equivalent to higher temperatures and shorter residence times.

[0078] The operating temperature is controlled by a built-in temperature controller that sends a current signal to the SCR (Silicon Controlled Rectifier). The transformer steps down the voltage from the SCR to a value that keeps the heating element at the desired temperature.

[0079] For Example 1, the rotary kiln was set to a fixed temperature of 310° C. The average residence time was adjusted according to equation (1) by changing the slope (m) and / or the rotation speed (ω) of the drum to achieve values ​​of 30 to 120 minutes for 30 minute intervals and 120 to 240 minutes for 60 minute intervals. Samples were taken at each average residence time and solid 31P NMR analysis. NMR spectra are summarized in Figure 1 .

[0080] In solid state 31 In the P MAS NMR spectrum, on the chemical shift axis, a peak derived from a phosphate monomer is at 10 to 0 ppm, a peak derived from a pyrophosphate is located at 0 to -11 ppm, and a peak derived from a polyphosphate is at -21 to -24 ppm. Figure 1 It is shown that the degree of polymerization increases with increasing residence time at a fixed polymerization temperature (in this case, 310° C.) As the residence time increases, the amount of phosphate monomer decreases and the amount of polyphosphate increases (values ​​in wt %).

[0081] For these polyphosphate compositions, Figure 2 The TGA graph is shown and Table I summarizes the decomposition onset temperature, the temperature at 2% weight loss, and the temperature at 5% weight loss, as determined using TGA (thermogravimetric analysis). At a fixed polymerization temperature of 310° C., the thermal stability of the polyphosphate compositions (prepared from melamine zinc phosphate) generally increased with increasing residence time. Compositions with higher levels of polyphosphate produced superior thermal stability.

[0082] Table I. Comparison of thermal stability as a function of residence time at 310°C

[0083]

[0084] Example 2

[0085] Polymerization of melamine zinc phosphate as a function of temperature at a fixed mean residence time

[0086] Example 2 was conducted in the same manner as Example 1, except that the temperature was varied and the residence time was fixed. The parameters of the rotary kiln were set to produce a fixed residence time of 90 minutes. The test temperatures were 310°C and 320°C. Samples were taken at these temperatures and solid 31 P NMR analysis. NMR spectra are summarized in Figure 3 middle.

[0087] Figure 3 It is shown that at a fixed residence time (in this case 90 minutes), the degree of polymerization increases with increasing temperature. With increasing temperature, the amount of phosphate monomer decreases and the amount of polyphosphate increases (values ​​in wt %).

[0088] Table II summarizes the decomposition onset temperature, the temperature at 2% weight loss, and the temperature at 5% weight loss for these polyphosphate compositions, as determined using TGA (thermogravimetric analysis). At a fixed residence time of 90 minutes, the thermal stability of the polyphosphate compositions (prepared from melamine zinc phosphate) increases with increasing polymerization temperature. Higher levels of polyphosphate produce excellent thermal stability.

[0089] Table II. Comparison of thermal stability as a function of temperature at 90 minutes

[0090]

[0091] Example 3

[0092] Flame retardant properties of polyphosphate compositions prepared from melamine zinc phosphate

[0093] Ethylene vinyl acetate (EVA) formulations were produced as follows: no polyphosphate composition (Example 3A), 10 wt% polyphosphate composition produced in Example 2 at 320°C and 90 minutes (Example 3B), and 10 wt% polyphosphate composition similar to Example 3B except produced at 320°C and 30 minutes (Example 3C). Table III summarizes the formulations (DuPont Elvax 265 is manufactured by DuPont; Vertex 100 is magnesium hydroxide manufactured by JM Huber Corporation; Viton Z 200 is a processing aid manufactured by Chemours; and Irganox 1010 is a hindered phenolic antioxidant manufactured by BASF).

[0094] Figure 4 The heat release rate (HRR) curves of the three polymer compositions of Example 3 are shown. According to ASTM E 1354 at 35 kW / m 2 Cone calorimetry measurements were performed on 3 mm thick compression molded plaques at 100°C. Unexpectedly, the formulations of Examples 3B-3C (which contained the polyphosphate composition) had both longer ignition times and lower peak heat release rates (peaks of the curves).

[0095] Table III. Formulation of Example 3 (wt%)

[0096] Example 3A 3B 3C DuPont Elvax 265 29.1 29.1 29.1 Fusabond E BM 410D 6 6 6 Vertex 100 64 54 54 Polyphosphate composition 0 10 10 Viton Z-200 0.2 0.2 0.2 Calcium stearate 0.5 0.5 0.5 Irganox 1010 0.2 0.2 0.2 sum 100 100 100

[0097] The present invention has been described above with reference to various aspects and specific examples. Those skilled in the art will propose many variations of their own in view of the foregoing detailed description. All such obvious variations are within the full intended scope of the appended claims. Other aspects and / or features of the present invention may include, but are not limited to, the following (which are expressed as "comprising...", but alternatively, may be "essentially composed of..." or "consisting of..."):

[0098] Aspect 1. A process for producing a polyphosphate composition, the process comprising:

[0099] (a) continuously introducing a phosphate compound into a polymerization vessel;

[0100] (b) polymerizing the phosphate compound at a temperature in the range of about 250 to about 450° C. for a time sufficient to form a polyphosphate composition; and

[0101] (c) continuously discharging a polyphosphate composition from the polymerization vessel, wherein the polyphosphate composition comprises:

[0102] at least about 8% by weight polyphosphate; and

[0103] Less than or equal to about 35% by weight phosphate compounds.

[0104] Aspect 2. A process as defined in Aspect 1, wherein the (solid) phosphate compound contains an amount of water / moisture in any range disclosed herein, for example, up to about 12 wt. %, up to about 10 wt. %, up to about 5 wt. %, or up to about 2 wt. %.

[0105] Aspect 3. A process as defined in aspect 1 or 2, wherein the temperature in step (b) is any suitable range or any range disclosed herein, for example, about 280°C to about 420°C, about 300°C to about 400°C, or about 320°C to about 420°C.

[0106] Aspect 4. A process as defined in any of Aspects 1-3, wherein step (b) is carried out at a pressure in any suitable range or any range disclosed herein, for example, ambient pressure to about 100 psig (689 kPag), or about 5 to about 60 psig (34 to 414 kPag).

[0107] Aspect 5. A process as defined in any of Aspects 1-4, wherein the average residence time in the polymerization vessel is a time in any suitable range or in any range disclosed herein, for example, from about 30 minutes to about 300 minutes, from about 45 minutes to about 180 minutes, or from about 60 minutes to about 120 minutes.

[0108] Aspect 6. A process as defined in any one of aspects 1 to 5, further comprising:

[0109] (i) determining the amount of polyphosphate in the polyphosphate composition; and (ii) adjusting the time and / or temperature in step (b) based on the amount of polyphosphate in the polyphosphate composition.

[0110] Aspect 7. The process as defined in any one of aspects 1 to 6, further comprising:

[0111] (I) determining the amount of phosphate compound in the polyphosphate composition; and (II) adjusting the time and / or temperature in step (b) based on the amount of phosphate compound in the polyphosphate composition.

[0112] Aspect 8. A process for producing a polyphosphate composition, the process comprising:

[0113] (a) continuously introducing an aqueous slurry containing from about 5 weight percent to about 50 weight percent of a phosphate compound into a polymerization vessel;

[0114] (b1) evaporating water from the aqueous slurry in a first zone of the polymerization vessel;

[0115] (b2) polymerizing the phosphate compound in a second zone of the polymerization vessel at a temperature in the range of about 250 to about 450° C. for a time sufficient to form a polyphosphate composition; and

[0116] (c) continuously discharging a polyphosphate composition from the polymerization vessel, wherein the polyphosphate composition comprises:

[0117] at least about 8% by weight polyphosphate; and

[0118] Less than or equal to about 35% by weight phosphate compounds.

[0119] Aspect 9. A process as defined in Aspect 8, wherein the aqueous slurry contains an amount of phosphate compound in any range disclosed herein, for example, about 5 wt % to about 40 wt %, about 10 wt % to about 40 wt %, or about 10 wt % to about 30 wt % of the phosphate compound.

[0120] Aspect 10. A process as defined in aspect 8 or 9, wherein the temperature in step (b2) is in any suitable range or in any range disclosed herein, for example, about 280°C to about 420°C, about 300°C to about 400°C, or about 320°C to about 420°C.

[0121] Aspect 11. A process as defined in any of Aspects 8-10, wherein step (b1) is carried out at any suitable evaporation temperature or an evaporation temperature in any range disclosed herein, for example, about 300°C to about 800°C, about 400°C to about 700°C, or about 500°C to about 800°C.

[0122] Aspect 12. A process as defined in any of Aspects 8-11, wherein step (b1) and step (b2) are independently carried out at a pressure in any suitable range or any range disclosed herein, for example, ambient pressure to about 100 psig (689 kPag), or about 5 to about 60 psig (34 to 414 kPag).

[0123] Aspect 13. A process as defined in any of Aspects 8-12, wherein the average residence time in the polymerization vessel is a time in any suitable range or in any range disclosed herein, for example, from about 1 hour to about 8 hours, from about 2 hours to about 5 hours, or from about 1.5 hours to about 3 hours.

[0124] Aspect 14. A process as defined in any of Aspects 8-13, wherein the ratio of the first average residence time in the first zone to the second average residence time in the second zone (first:second) is in any suitable range or any range disclosed herein, for example, from about 1:10 to about 5:1, from about 1:5 to about 3:1, or from about 1:3 to about 1:1.

[0125] Aspect 15. A process as defined in any one of aspects 8 to 14, further comprising:

[0126] (i) determining the amount of polyphosphate in the polyphosphate composition; and (ii) adjusting the evaporation conditions in step (b1), the temperature in step (b2), and / or the time in step (b2) based on the amount of polyphosphate in the polyphosphate composition.

[0127] Aspect 16. A process as defined in any one of aspects 8 to 15, further comprising:

[0128] (I) determining the amount of phosphate compound in the polyphosphate composition; and (II) adjusting the evaporation conditions in step (b1), the temperature in step (b2), and / or the time in step (b2) based on the amount of phosphate compound in the polyphosphate composition.

[0129] Aspect 17. A process as defined in any one of aspects 8 to 16, wherein the polymerization vessel is any suitable vessel or any vessel disclosed herein, for example, a rotary kiln, a vertical kiln, or a spiral kiln.

[0130] Aspect 18. The process as defined in any one of aspects 1 to 17, further comprising, after step (c), a step of grinding the polyphosphate composition to reduce the average particle size of the polyphosphate composition and / or to reduce agglomeration of the polyphosphate composition.

[0131] Aspect 19. A process as defined in any of Aspects 1-18, wherein the polyphosphate composition comprises an amount of polyphosphate in any range disclosed herein, for example, at least about 20 weight %, about 15 weight % to about 60 weight %, about 15 weight % to about 50 weight %, or about 20 weight % to about 40 weight % polyphosphate.

[0132] Aspect 20. A process as defined in any of Aspects 1-19, wherein the polyphosphate composition comprises an amount of phosphate compound in any range disclosed herein, for example, up to about 25 weight %, up to about 20 weight %, up to about 15 weight %, or up to about 10 weight % of the phosphate compound.

[0133] Aspect 21. A process as defined in any of Aspects 1-20, wherein the polyphosphate composition further comprises an amount of a pyrophosphate compound in any range disclosed herein, for example, about 35 wt % to about 80 wt %, about 45 wt % to about 75 wt %, or about 55 wt % to about 75 wt % of the pyrophosphate compound.

[0134] Aspect 22. A process as defined in any one of aspects 1 to 21, wherein the phosphate compound comprises:

[0135] (metal)(phosphate),

[0136] (N-containing cation)(phosphate),

[0137] (N-containing cation)(metal)(phosphate), or

[0138] Its combination.

[0139] Aspect 23. A process as defined in aspect 22, wherein the N-containing cation is ammonium, arginine, lysine, histidine, melamine, or diethanolamine.

[0140] Aspect 24. A process as defined in aspect 22, wherein the metal is zinc, molybdenum, calcium, magnesium, aluminum, copper, barium, tin, tungsten, iron, or nickel.

[0141] Aspect 25. A process as defined in any one of aspects 22 to 24, wherein the phosphate compound comprises (metal)(phosphate).

[0142] Aspect 26. A process as defined in any one of aspects 22-24, wherein the phosphate compound comprises (N-containing cation)(phosphate).

[0143] Aspect 27. A process as defined in any one of aspects 22 to 24, wherein the phosphate compound comprises (N-containing cation)(metal)(phosphate).

[0144] Aspect 28. A process as defined in any one of aspects 1 to 23, wherein the phosphate compound comprises ammonium phosphate and the polyphosphate comprises ammonium polyphosphate.

[0145] Aspect 29. A process as defined in any one of aspects 1 to 23, wherein the phosphate compound comprises melamine phosphate and the polyphosphate comprises melamine polyphosphate.

[0146] Aspect 30. A process as defined in any one of aspects 1 to 24, wherein the phosphate compound comprises melamine zinc phosphate and the polyphosphate comprises melamine poly(zinc phosphate).

[0147] Aspect 31. The process as defined in any one of Aspects 1-24, further comprising the following step before step (a): reacting (or combining) a mixture of water and N-containing cations with a mixture of water, phosphoric acid and (metal) oxide (or (metal) hydroxide) to form a phosphate compound.

[0148] Aspect 32. The process as defined in any one of aspects 1 to 24, further comprising the step of reacting (or combining) a mixture of water and melamine with a mixture of water, phosphoric acid and zinc oxide to form melamine zinc phosphate before step (a).

[0149] Aspect 33. A process as defined in any one of aspects 1 to 32, wherein the process does not comprise a drying step.

[0150] Aspect 34. A process as defined in any of Aspects 1-33, wherein the polyphosphate composition has (or is characterized by) a decomposition onset temperature on a TGA (thermogravimetric analysis) curve (or a temperature at a 2% weight loss on a TGA curve, or a temperature at a 5% weight loss on a TGA curve) in any range disclosed herein, for example, from about 290°C to about 360°C, from about 300°C to about 350°C, or from about 310°C to about 340°C.

Claims

1. A process for producing a polyphosphate composition, the process comprising: (a) continuously introducing an aqueous slurry containing 5 to 50 wt. % of a phosphate compound into a polymerization vessel, wherein the phosphate compound comprises melamine magnesium phosphate or melamine zinc phosphate; (b1) evaporating water from the aqueous slurry in a first zone of the polymerization vessel; (b2) polymerizing the phosphate compound in a second zone of the polymerization vessel at a temperature in the range of 250 to 450° C. for a time sufficient to form a polyphosphate composition; and (c) continuously discharging a polyphosphate composition from the polymerization vessel, wherein the polyphosphate composition comprises: at least 8 weight percent of a polyphosphate, wherein the polyphosphate comprises melamine poly(magnesium phosphate) or melamine poly(zinc phosphate); and Less than or equal to 35% by weight of phosphate compounds.

2. The process of claim 1, wherein the aqueous slurry contains 5 wt% to 40 wt%, 10 wt% to 40 wt%, or 10 wt% to 30 wt% of the phosphate compound.

3. The process of claim 1 or 2, wherein the temperature in step (b2) is in the range of 280°C to 420°C, 300°C to 400°C, or 320°C to 420°C.

4. The process of any one of claims 1 to 3, wherein step (b1) is performed at an evaporation temperature in the range of 300°C to 800°C, 400°C to 700°C, or 500°C to 800°C.

5. The process of any one of claims 1 to 4, wherein the average residence time in the polymerization vessel is in the range of 1 hour to 8 hours, 2 hours to 5 hours, or 1.5 hours to 3 hours.

6. The process of any one of claims 1 to 5, wherein the ratio of a first average residence time in the first zone to a second average residence time in the second zone (first:second) is in the range of 1:10 to 5:1, 1:5 to 3:1, or 1:3 to 1:

1.

7. The process of any one of claims 1 to 6, further comprising: (i) determining the amount of polyphosphate in the polyphosphate composition; and (ii) adjusting the evaporation conditions in step (b1), the temperature in step (b2), and / or the time in step (b2) based on the amount of polyphosphate in the polyphosphate composition.

8. The process of any one of claims 1 to 7, further comprising: (I) determining the amount of phosphate compound in the polyphosphate composition; and (II) Based on the amount of the phosphate compound in the polyphosphate composition, the evaporation conditions in step (b1), the temperature in step (b2), and / or the time in step (b2) are adjusted.

9. A process for producing a polyphosphate composition, the process comprising: (a) continuously introducing a phosphate compound into a polymerization vessel, wherein the phosphate compound comprises melamine magnesium phosphate or melamine zinc phosphate; (b) polymerizing the phosphate compound at a temperature in the range of 250 to 450° C. for a time sufficient to form a polyphosphate composition; and (c) continuously discharging a polyphosphate composition from the polymerization vessel, wherein the polyphosphate composition comprises: at least 8 weight percent of a polyphosphate, wherein the polyphosphate comprises melamine poly(magnesium phosphate) or melamine poly(zinc phosphate); and Less than or equal to 35% by weight of phosphate compounds.

10. The process of claim 9, wherein the phosphate compound contains less than or equal to 12 weight percent, less than or equal to 10 weight percent, less than or equal to 5 weight percent, or less than or equal to 2 weight percent water.

11. The process of claim 9 or 10, wherein the temperature in step (b) is in the range of 280°C to 420°C, 300°C to 400°C, or 320°C to 420°C.

12. The process of any one of claims 9-11, wherein the average residence time in the polymerization vessel is in the range of 30 minutes to 300 minutes, 45 minutes to 180 minutes, or 60 minutes to 120 minutes.

13. The process of any one of claims 9 to 12, further comprising: (i) determining the amount of polyphosphate in the polyphosphate composition; and (ii) adjusting the time and / or temperature in step (b) based on the amount of polyphosphate in the polyphosphate composition.

14. The process of any one of claims 9 to 13, further comprising: (I) determining the amount of phosphate compound in the polyphosphate composition; and (II) Based on the amount of phosphate compound in the polyphosphate composition, the time and / or temperature in step (b) are adjusted.

15. A process as claimed in any preceding claim wherein the polymerisation vessel is a rotary kiln, a vertical kiln or a spiral kiln.

16. A process as claimed in any one of the preceding claims, further comprising, after step (c), the step of grinding the polyphosphate composition to reduce the average particle size of the polyphosphate composition and / or to reduce agglomeration of the polyphosphate composition.

17. The process of any one of the preceding claims, wherein the polyphosphate composition comprises 15 wt% to 60 wt%, 15 wt% to 50 wt%, or 20 wt% to 40 wt% polyphosphate.

18. The process of any of the preceding claims, wherein the polyphosphate composition comprises less than or equal to 25 weight percent, less than or equal to 20 weight percent, less than or equal to 15 weight percent, or less than or equal to 10 weight percent phosphate compounds.

19. The process of any one of the preceding claims, wherein the polyphosphate composition further comprises 35 to 80 weight percent, 45 to 75 weight percent, or 55 to 75 weight percent of a pyrophosphate compound.

20. The process of any one of claims 1 to 19, further comprising, before step (a), the step of reacting the mixture of water and melamine with a mixture of water, phosphoric acid and zinc oxide to form melamine zinc phosphate.

21. The process of any one of the preceding claims, wherein the process does not comprise a drying step.

22. The process of any one of the preceding claims, wherein the polyphosphate composition has a decomposition onset temperature on a TGA (thermogravimetric analysis) curve of 290°C to 360°C, 300°C to 350°C, or 310°C to 340°C.

23. A process as claimed in any one of the preceding claims, wherein the polyphosphate composition has a temperature at 2% weight loss on the TGA curve and / or a temperature at 5% weight loss on the TGA curve of 290°C to 360°C, 300°C to 350°C, or 310°C to 340°C.

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