Method for preparing thermally stable phosphorus-containing flame retardant materials that are easy to handle

Abstract

The present disclosure provides a method for producing non-halogenated, heat-stable, phosphorus-containing flame retardant materials directly in powder or pellet form. The method generally comprises heating one or more phosphonates in a high-boiling, water-soluble, acid-stable solvent to a dehydration reaction temperature of 200° C. or higher.

Description

[0001] This application claims priority to U.S. Provisional Application No. 62 / 782,907, filed on December 20, 2018, the entire contents of which are incorporated herein by reference. Technical Field

[0002] An improved method for preparing a phosphorus-containing flame retardant material having high thermal stability is disclosed, the method comprising heating one or more phosphonates in a high boiling point water-soluble acid-inert solvent at an elevated temperature, the method producing the flame retardant material directly in the form of a powder or small particles, i.e., without the need or necessity for grinding, granulation or other such physical processing. Background Art

[0003] Polymers such as polyolefins, polyesters, polycarbonates, polyamides, polyurethanes, epoxy resins and other thermoplastic or thermosetting polymer resins are often made more flame retardant by incorporating phosphorus-containing compounds, halogen-containing compounds or mixtures thereof into them. For example, U.S. Pat. No. 3,689,602 discloses halogenated phosphoric acid esters as flame retardant additives for plastics.

[0004] Some polymers are processed at high temperatures, such as 200°C, 225°C, 250°C, 275°C or higher. Many known flame retardants are not suitable for these conditions because they are too volatile, have insufficient thermal stability, have adverse effects on processing, etc. Certain organophosphorus flame retardant compounds, such as certain phosphate esters, exhibit a plasticizing effect that may adversely affect the mechanical properties of the polymers to which they are added. Compounds such as some phosphate esters may be relatively unstable to hydrolysis, resulting in the undesirable formation of various phosphate compounds.

[0005] Many salts of phosphoric acid are known flame retardant additives suitable for use in, for example, thermoplastic polymers. U.S. Pat. No. 3,894,986 discloses flame retardant thermoplastic polyesters containing alkali metal salts of phosphonic acids, i.e., salts prepared from compounds of formula (X), wherein R is an alkyl group, for example, the monosodium salt of ethanephosphonic acid or the sodium salt of the monomethyl ester of an alkanephosphonic acid. U.S. Pat. No. 4,972,011 discloses aluminum salts of alkylphosphonic acids or aluminum salts of monoalkyl esters of alkanephosphonic acids, i.e., salts of compounds of formula (Xa), wherein R is, for example, an alkyl group or an alkyl group substituted with one or more halogens or hydroxy groups; and R' is hydrogen, methyl, ethyl, propyl or isopropyl.

[0006]

[0007] US 2006 / 0138391 discloses salts formed from compounds of formula (X) as flame retardants, which salts may contain any of a variety of metals. The only salt actually exemplified in US 2006 / 0138391 is the aluminum salt of methyl methylphosphonate, i.e., the aluminum salt of a compound of formula (Xa) above where R and R' are methyl groups.

[0008] DE 3833977 discloses metal salts prepared from compounds of the formula (Xa) prepared by reacting dimethyl methylphosphonate with metal oxides or hydroxides in water under high pressure and at temperatures of 120-200° C.; examples of the reaction are described for aqueous solutions in autoclaves at temperatures up to 190° C. under elevated pressure. Also disclosed are adducts of these salts with amines such as ethylenediamine and melamine, and the use of the adducts as flame retardants in thermoplastics.

[0009] Salts of phosphinic acids (ie compounds of formula (II) wherein R1 and R2 are alkyl or carbyl aromatic groups) are also known flame retardant additives for thermoplastic polymers.

[0010]

[0011] Salts where M is selected from Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Li, Na, K or protonated nitrogen bases are known. For example, US Pat. Nos. 5,780,534 and 6,013,707 disclose that calcium and aluminum phosphinates of formula (II) are particularly effective in polyesters, for example, calcium and aluminum salts of dimethylphosphinic acid, ethylmethylphosphinic acid, diethylphosphinic acid, n-propylmethylphosphinic acid, n-propylethylphosphinic acid, di-n-propylphosphinic acid, diisopropylphosphinic acid or diphenylphosphinic acid.

[0012] As with many flame retardant systems, the performance of phosphoric acid-containing derivatives can be enhanced by the presence of other flame retardants, synergists and adjuvants. US Patent 6,472,448 discloses flame retardant rigid polyurethane foams in which a combination of oxyalkylated alkylphosphonic acid and ammonium polyphosphate is present as a flame retardant.

[0013] U.S. Patent No. 6,365,071 discloses a synergistic flame retardant combination for thermoplastic polymers such as engineering plastics, especially polyesters, comprising: A) a phosphinate of the above formula (II), for example, aluminum dimethylphosphinate, aluminum methylethylphosphinate and aluminum methylpropylphosphinate; and B) a nitrogen compound, such as allantoin, benzoguanamine, glycoluril, urea cyanurate, melamine cyanurate and melamine phosphate.

[0014] U.S. Patent 6,255,371 discloses a flame retardant combination comprising: A) a phosphinate of the above formula (II), for example, diethylphosphinate wherein M is calcium, magnesium, aluminum and / or zinc, and B) a condensation or reaction product of melamine, for example, melamine polyphosphate, melam polyphosphate and melem polyphosphate.

[0015] U.S. Patent No. 6,547,992 discloses a flame retardant combination for thermoplastic polymers, comprising a phosphinate / ester and a small amount of a nitrogen-free inorganic and / or mineral compound. WO 2012 / 045414 discloses a flame retardant composition comprising: A) a phosphinate of the above formula (II), wherein M is selected from Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Li, Na, K or a protonated nitrogen base; and B) a metal salt of phosphorous acid; and other optional components.

[0016] The phosphinates cited above, such as in U.S. Pat. Nos. 6,365,071 and 6,255,371, are said to be thermally stable and will not decompose the polymer during processing, nor will they affect the process of preparing the polymer composition. Under conventional conditions of preparation and processing of thermoplastic polymers, the phosphinates are non-volatile. However, these materials are not necessarily suitable for all polymer systems and may cause processing problems or lack the flame retardant effect required for certain polymers.

[0017] Phosphonates, particularly metal phosphonates, are reported to be thermally stable. However, as disclosed in US 2007 / 0029532, such phosphonates are known to decompose at temperatures encountered during polyester and polyamide processing, destroying the polymer in the process and providing only "unstable brittle compositions" useful as engineering thermoplastics.

[0018] U.S. Pat. No. 5,053,148 also contains teachings on the thermal conversion of salts of phosphonic acids (also known as phosphonates), i.e., heating a metal phosphonate or metal phosphonate precursor to a temperature above 200° C., typically well above 200° C., results in the material forming an insoluble foam that is difficult to handle. The foam can be used as an electrical and / or thermal insulation material. U.S. Pat. No. 5,053,148 also discloses that the foam is formed by heating a metal phosphonate or metal phosphonate precursor in the presence of a thermoplastic such as an aromatic polyester, polyether, etc., and a porous polymer composition will be produced due to the decomposition of the polymer caused by the thermal conversion of the phosphonate or phosphonate precursor. Neither US 2007 / 0029532 nor US 5,053,148 contains any discussion on what the chemical composition of the salt conversion product might be, nor is there any teaching on first thermally converting the salt and then incorporating such conversion product into a polymer composition.

[0019] U.S. Patents 9,534,108; 9,745,449; 9,752,009; 9,752,011; 9,758,640; and 9,765,204 disclose that heating a phosphonate at a sufficiently high temperature, typically in the absence of other materials, thermally converts the phosphonate into a different, more thermally stable material that exhibits excellent flame retardant activity when incorporated into a polymer matrix. When processed in a polymer composition at elevated temperatures, e.g., 240° C., 250° C., 260° C., 270° C. or higher, the thermally converted material does not degrade at the elevated temperatures nor does it cause polymer degradation, which is a significant advantage over previously known phosphonates, which exhibit flame retardant activity but often degrade the polymer during processing. The thermally converted material is described as comprising one or more compounds represented by empirical formula (IV) and complex dehydration products thereof:

[0020]

[0021] Wherein R is an alkyl or aryl group, M is a metal, q is a number from 1 to 7, for example, 1, 2 or 3, r is a number from 0 to 5, for example, 0, 1 or 2, usually 0 or 1, y is a number from 1 to 7, such as 1 to 4, and n is 1 or 2, provided that 2(q)+r=n(y). It is also disclosed that, like the inorganic coordination compound, formula (IV) is idealized, and the product may include coordination polymers, complex salts, salts sharing certain atomic valences, etc.

[0022] Although the materials of US 9,745,449 and the like are effective flame retardants that do not cause degradation of polymer properties during processing, they are typically formed into solid blocks according to the methods therein, requiring grinding or other such physical processing prior to incorporation into polymer compositions. Furthermore, the results of scale-up of the methods exemplified in the art tend to be inconsistent, and reproducibility between processing runs, such as conversion and physical properties, can be difficult to achieve.

[0023] Phosphorus acid salts of formula (VI) and their derivatives can be thermally converted to pyrophosphorus acid salts of formula (V) under appropriate conditions. U.S. Patent No. 4,859,466 discloses that pyrophosphonates of formula (V) have microbicide activity, and U.S. Published Patent Application No. 2016 / 0032076 discloses their use as flame retardants.

[0024]

[0025] Pyrophosphonates can be prepared by heating phosphites themselves or in the presence of diphenylmethane.

[0026] There remains a need for improvements in the preparation, handling, and batch reproducibility of at least the thermally convertible flame retardants of US Pat. Nos. 9,534,108 and 9,745,449. Summary of the invention

[0027] The present disclosure provides an improved method for preparing a thermally stable flame retardant material that exhibits less than 5%, e.g., less than 3% or less than 1% weight loss in thermogravimetric analysis (TGA) at temperatures above 350°C and up to, e.g., 400°C, 450°C or higher.

[0028] The method of the present disclosure improves several disadvantages of existing methods for thermally converting metal phosphonate salts into more thermally stable flame retardant materials. For example, the method of the present invention provides flame retardant materials with improved physical form and handling properties while also improving reproducibility, especially scale-up. Other advantages will be apparent to practitioners from this disclosure.

[0029] One embodiment of the present disclosure is a method of providing a flame retardant material in powder or granule form, the method comprising heating a mixture of: i) a high boiling water-soluble acid-stable solvent having a boiling point (bp) exceeding 200°C, 220°C, 240°C or 260°C, such as a sulfone solvent, and ii) one or more phosphonates of formula (I):

[0030]

[0031] wherein R is H, alkyl, aryl, alkaryl or aralkyl, p is a number from 2 to 7, such as 2 to 4, for example, 2, 3 or 4, M is a metal, y is a number from 2 to 7, such as 2 to 4, for example, 2, 3 or 4, typically 2 or 3, such that M (+)y is a metal cation, wherein (+)y represents the charge formally assigned to the cation, to produce a flame retardant material directly in the form of a powder or small particles, i.e., without or without the need for grinding, granulation, etc. It should be understood that the production of a flame retardant material "directly" in the form of a powder or small particles according to the method disclosed in the present invention allows for post-processing of the reaction product, for example, separating the flame retardant product (for example, separating the flame retardant product from the remaining solvent), which may include, for example, treating the reaction product by filtering, washing, drying, etc.

[0032] Good results are obtained when the high boiling point water-soluble acid-stable solvent is, for example, a sulfone having a bp in excess of 200° C., for example, about 220° C. or higher, about 240° C. or higher, about 260° C. or higher, or about 280° C. or higher. Non-limiting examples of such solvents include sulfolane having a bp of 285° C., and dimethyl sulfone.

[0033] Typically, the high boiling point water-soluble acid-stable solvent component i) is the major component in the heated solvent / phosphonate mixture, i.e., the high boiling point water-soluble acid-stable solvent accounts for 51 wt% or more of the solvent / phosphonate mixture, for example, the solvent concentration can be 60 wt% or more, 70 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more. For example, in a mixture of i) a high boiling point water-soluble acid-stable solvent and ii) a phosphonate, the high boiling point water-soluble acid-stable solvent can be present at about 60 wt%-99 wt%, 65 wt%-98 wt%, or 70 wt%-98 wt%, based on the total weight of i) and ii).

[0034] The reaction to produce the flame retardant of the present disclosure releases water as a byproduct and is generally referred to as a dehydration reaction. The solvent according to the present disclosure, in addition to transferring uniform heat to the reaction and suspending the starting materials and their formed products, is also miscible with water and it is believed that it can absorb water generated during the reaction and / or facilitate efficient mixing with the phosphonate in aqueous solution.

[0035] The present method directly (without grinding, etc.) produces a heat-stable flame retardant as a powder or small particles, which provides an important improvement over existing production methods, such as the methods described in 9,745,449, etc. Compared with the method of the present invention, the existing production methods produce heat-stable flame retardant materials as hard solid blocks by heating phosphonates, usually in the absence of other materials.

[0036] Another embodiment of the present disclosure provides a flame retardant material obtained by the above method, which is a powder or a collection of small particles. The powder or collection of small particles can have a median particle size (d50) of, for example, about 100 μm or less, such as about 80 μm or less, or about 60 μm or less, measured by laser diffraction according to ISO13320. For example, the powder or collection of small particles can have a median particle size (d50) of about 1 μm-about 100 μm, about 10 μm-about 90 μm, about 20 μm-about 80 μm, or about 20 μm-60 μm. As described herein, the powder or collection of small particles is obtained from the reaction product without the need for grinding or similar such physical treatments.

[0037] In another embodiment, the flame retardant polymer composition comprises:

[0038] a) a thermosetting or thermoplastic polymer, e.g. a thermoplastic polymer, and

[0039] b) 1% to 50% by weight of the above flame retardant material, based on the total weight of the flame retardant polymer composition, and

[0040] c) Optional other flame retardants or flame retardant synergists.

[0041] Another embodiment provides a method for preparing a flame retardant polymer composition, the method comprising heating one or more metal phosphonates of formula (I) in a high boiling point water-soluble acid-stable solvent under conditions that chemically convert the phosphonate to a more thermally stable flame retardant material as described above in the present disclosure, and then incorporating the thermally stable flame retardant prepared thereby into a polymer resin, for example, by melt processing. For example, the flame retardant can be introduced into the molten polymer by blending, extrusion, fiberization or film formation, etc.

[0042] In another embodiment, the flame retardant material in the form of a powder or granules comprises a compound of the empirical formula (IV) or a mixture of compounds of the empirical formula (IV)

[0043]

[0044] wherein R is H, alkyl, aryl, alkaryl or aralkyl, q is a number from 1 to 7, such as 1, 2 or 3, r is a number from 0 to 5, such as 0, 1 or 2, typically 0 or 1, M is a metal, y is a number from 2 to 7, such as 2 to 4, such as 2, 3 or 4, typically 2 or 3, such that M (+)y is a metal cation, wherein (+)y represents the charge formally assigned to the cation, and n is 1 or 2, provided that 2(q)+r=n(y). The flame retardant material may have a median particle size (d50) of, for example, about 100 μm or less, for example, about 80 μm or less, or about 60 μm or less, as determined by laser diffraction according to ISO 13320. The powder or small particle assembly may have a median particle size (d50) of about 1 μm to about 100 μm, about 10 μm to about 90 μm, about 20 μm to about 80 μm, or about 20 μm to about 60 μm. In some embodiments, the flame retardant material is essentially composed of a compound of empirical formula (IV) or a mixture of compounds of empirical formula (IV).

[0045] It has been found that the metal phosphonate of formula I can be stably converted into a more thermally stable flame retardant material with processing flexibility by heating the metal phosphonate in a high boiling point water-soluble acid-stable solvent. The present method provides greater consistency in the yield and quality of the flame retardant compared to previous methods. In addition, in contrast to solid blocks obtained using prior art methods, the product of the present method is obtained directly as a powder or finely particulate solid, which does not require grinding, granulation or other such physical treatment before use.

[0046] The foregoing summary is not intended to limit the scope of the claimed invention in any way. In addition, it should be understood that both the foregoing summary and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] 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.

[0048] Figure 2 The particle size distribution of the exemplary flame retardant of Example 1 is shown.

[0049] Figure 3 A scanning electron microscope (SEM) image of an exemplary flame retardant of Example 1 is shown.

[0050] Figure 4 Shown are the results of TGA of an exemplary flame retardant material produced according to Example 2 of the present disclosure.

[0051] Figure 5 The results of TGA of the flame retardant material produced according to Comparative Example 3 of the present disclosure are shown. DETAILED DESCRIPTION

[0052] In this application, the word "a" or "an" means "one or more" unless otherwise stated.

[0053] In this method, the following mixture

[0054] (i) a phosphonate of formula I,

[0055]

[0056] wherein R is H, alkyl, aryl, alkaryl or aralkyl, p is a number from 2 to 7, such as 2 to 4, for example 2, 3 or 4, M is a metal, y is a number from 2 to 7, such as 2 to 4, for example 2, 3 or 4, typically 2 or 3, such that M (+)y is a metal cation, wherein (+)y represents the charge formally assigned to the cation, and

[0057] (ii) a high boiling point water-soluble acid-stable solvent, wherein the solvent accounts for 51 wt% to 99 wt% of the mixture, for example, 60 wt% to 99 wt%, 65 wt% to 98 wt%, or 70 wt% to 98 wt%, based on the total weight of the phosphonate of formula I and the high boiling point water-soluble acid-stable solvent,

[0058] Heating to a dehydration temperature, typically in excess of 200°C, e.g., 220°C or higher (e.g., 250°C or higher), e.g., a temperature in the range of about 220°C to about 400°C, or about 240°C to about 360°C, to provide the flame retardant of the present disclosure as a powder or granules, typically a flowable powder or flowable granules.

[0059] In formula (I), y is 2 M (+)y Representatives such as Mg ++ , Ca ++ or Zn ++ Divalent cations (di-cation), y is 3 M (+)y Representatives such as Al +++ As with inorganic coordination compounds, this formula is idealized, and the starting materials and products may include coordination polymers or complex salts (e.g., salts that share certain atomic valences, such as one oxygen anion shared between two metal cations, etc.). Typically, the starting salt is a charge-balanced compound, i.e., a compound of formula (I) where p=y, e.g., when M (+)y For Al +++ When , p is 3, etc.

[0060] Phosphonates of formula (I) and their preparation methods are known in the art, and some are known to be flame retardants, for example, tris-[methylphosphonic acid] aluminum salt. The phosphonates used as starting materials herein can be found in the starting materials used for preparing flame retardants in U.S. Pat. Nos. 9,745,449 and 9,752,009, etc.

[0061] In contrast to the conventional method of heating the salt in the absence of other materials in the art, in the present disclosure, as described herein, the phosphonate is subjected to a dehydration temperature while being mixed with a high boiling point water-soluble acid-stable solvent as a dehydration medium. The dehydration reaction generates water, which will be compatible with the solvent of the present disclosure, which can help promote a smooth reaction. When the phosphonate is added as a solution in an aqueous solvent, the water solubility and acid stability of the solvent may also help promote mixing.

[0062] The solvent used in the dehydration stage of the present method should be stable under the dehydration reaction conditions. The dehydration reaction occurs at high temperatures, for example, the reaction temperature is generally in excess of 220°C, 230°C, 240°C or 250°C, for example, about 220°C to about 400°C, or about 240°C to about 360°C, for example, 240-290, or 300°C.

[0063] The water-soluble acid-stable solvents of the present disclosure have high boiling points, for example, bps exceeding 200°C, such as about 220°C or higher, about 240°C or higher, about 260°C or higher, about 270°C or higher, or about 280°C or higher, for example, from about 220°C to about 360°C, or from about 230°C to about 350°C. Exemplary solvents that meet all three criteria - high boiling point, acid stability, and water solubility - include sulfones. In some embodiments, the high boiling point acid-stable water-soluble solvent includes a sulfone of the formula R1R2SO2, wherein R1 and R2 are independently selected from C 1-6 Hydrocarbyl, for example, C 1-3 hydrocarbon group, or R1 and R2 together with S form a ring having 2, 3, 4 or 5 carbon atoms, which ring may be unsubstituted or C 1-3 In some embodiments, R1 and R2 together with S form a di-, tri-, tetra- or pentamethylene ring. In some embodiments, R1 and R2 are independently selected from C 1-6 In some embodiments, R1 or R2 is C 1-6 alkyl and the other is C 1-3 In some embodiments, R1 and R2 are independently selected from C 1-3 In some embodiments, R1 and R2 are both methyl, both ethyl, or both propyl. In other embodiments, R1 or R2 is methyl and the other is ethyl or propyl. In other embodiments, R1 or R2 is ethyl and the other is propyl. In some embodiments, the sulfone is sulfolane.

[0064] According to the present disclosure, the phosphonate of formula (I) is combined with a high boiling acid-stable water-soluble solvent and heated to a dehydration temperature as described herein to produce a flame retardant material of the present disclosure in the form of a powder or small particles. Typically, the phosphonate is mixed with a high boiling acid-stable water-soluble solvent under conditions sufficient to form a suspension or slurry such as a homogeneous suspension or slurry. For example, in some embodiments, at an elevated temperature, a phosphonate (i.e., a phosphonate of formula (I)) is mixed or combined with a high boiling acid-stable water-soluble solvent to form a suspension or slurry, and then the mixture is subjected to a dehydration temperature as described herein. Heating can but is not necessarily gradually increased to one or more elevated temperatures over time and / or is carried out under vacuum conditions such as under moderate vacuum. The elevated temperature may depend on the melting point of the high boiling acid-stable water-soluble solvent. For example, some useful high boiling acid-stable water-soluble solvents may be solid at room temperature, but may be converted into liquid solvents at elevated temperatures. Typically, the elevated temperature is above room temperature, for example, greater than 25, 30, 35, 40, 45, or 50°C, for example, about 30°C to about 160°C, about 60°C to about 160°C, about 40°C to about 130°C, about 80°C to about 120°C, about 40°C to about 100°C, or about 50°C to about 90°C. In some embodiments, the elevated temperature is below 100°C, such as any of the temperature ranges disclosed above, but below 100°C. The mixture can be heated and maintained at more than one elevated temperature. For example, the mixture can be heated to an elevated temperature for a period of time, then heated or cooled to one or more other elevated temperatures. For example, the mixture can be heated to an elevated temperature in the range of about 60°C to about 140°C, such as about 80°C to about 120°C for a period of time, and then heated to an elevated temperature in the range of about 140°C to about 160°C for another period of time.

[0065] The mixing of the phosphonate with the high boiling acid-stable water-soluble solvent (such as at one or more elevated temperatures, optionally under vacuum) occurs within a certain time, for example, about 5 minutes or longer, about 10 minutes or longer, about 30 minutes or longer, about 1 hour or longer, about 3 hours or longer, about 4 hours or longer, about 6 hours or longer, about 8 hours or longer, about 12 hours or longer, about 24 hours or longer, about 36 hours or longer, or about 48 hours or longer, or any scope therebetween. For example, the amount of time can be about 30 minutes-about 72 hours, about 1 hour-about 48 hours, or about 2 hours-about 36 hours. During this period of time, unwanted volatiles can be removed, and a certain amount of water can be removed or evaporated from the mixture. Typically, the resulting mixture forms a suspension or slurry, such as a uniform suspension or slurry. It will be apparent to the practitioner that the conditions used to mix the phosphonate with the high boiling point acid stable water soluble solvent, such as temperature, pressure (e.g. vacuum conditions), stirring speed, time, etc., are interrelated and can be adjusted to achieve the formation of a suspension or slurry, such as to obtain a homogenous suspension or slurry.

[0066] In some embodiments, after forming a suspension or slurry (e.g., a slurry or suspension may occur after mixing a phosphonate and a high boiling acid-stable water-soluble solvent at an elevated temperature, for example, for about 10 minutes, about 30 minutes, about 1 hour, about 2 hours, about 4 hours, or about 6 hours), the suspension or slurry is stirred for a period of time at an elevated temperature, such as described herein. In some embodiments, the elevated temperature at which the suspension or slurry is stirred is reduced from the elevated temperature at which the mixture is heated to form the suspension or slurry. In some embodiments, the suspension or slurry is stirred at an elevated temperature of about 30°C to about 95°C or about 40°C to about 80°C. In some embodiments, the suspension or slurry is stirred for about 1 minute or more, about 10 minutes or more, about 30 minutes or more, about 1 hour or more, about 4 hours or more, about 12 hours or more, about 24 hours or more, about 36 hours or more, or about 48 hours or more, or any range therebetween.

[0067] When mixed with a high boiling point acid-stable water-soluble solvent, the phosphonate can be in a liquid medium or in solid form (e.g., a powder). For example, in some embodiments, the phosphonate is in an aqueous liquid (e.g., dissolved or partially dissolved in an aqueous liquid). For example, an aqueous solution of a salt of Formula I can be mixed with a high boiling point acid-stable water-soluble solvent.

[0068] In some embodiments, it may be desirable to add an aqueous solvent to the mixture of the phosphonate and the high boiling point acid-stable water-soluble solvent, for example, to avoid gelation during formation of the suspension or slurry, or to disrupt gelation if gel formation occurs. It is also believed that greater gelation may occur using certain metal-containing starting materials (i.e., certain metal compound precursors of the phosphonate) that provide metal cations for the salt of formula (I). The addition of the aqueous solvent may be repeated if necessary / desired during the mixing process.

[0069] In addition, in some embodiments, it may be necessary to add seed material (optionally in addition to aqueous solvent or in the absence of aqueous solvent) to a mixture of phosphonate and a high boiling point acid-stable water-soluble solvent to accelerate a suspension or slurry, for example, the formation of a homogeneous slurry. Reducing the time of slurry formation can also help to reduce gel formation as described above. If necessary / needed during the mixing process, seed material can be repeatedly added (optionally in addition to aqueous solvent or in the absence of aqueous solvent). In some embodiments, the seed material comprises an inert filler, which can be any material that is inert to the dehydration reaction and has a desired particle size. Silica, aluminum oxide, talc and titanium dioxide are all non-limiting examples of suitable inert fillers. In some implementations, the seed material comprises a flame retardant material (and optional inert filler) produced according to the method of the present disclosure, such as a flame retardant material of formula (IV) as described herein and / or a flame retardant material according to US9,745,449, etc. The seed material can have a median particle size (d50) of, for example, about 100 μm or less, e.g., about 80 μm or less, or about 60 μm or less, as determined by laser diffraction according to ISO 13320. For example, the seed material can have a median particle size (d50) of about 1 μm to about 100 μm, about 10 μm to about 90 μm, about 20 μm to about 80 μm, or about 20 μm to about 60 μm.

[0070] In one embodiment, an aqueous solution of tris[methylphosphonic acid]aluminum salt prepared from aluminum chloride hexahydrate starting material is mixed with sulfolane as a high boiling point water-soluble acid-stable solvent at an elevated temperature ranging from about 80°C to about 140°C, for example, from about 100°C to about 125°C, optionally under a slight vacuum, and a seed material is added to the mixture. In some embodiments, for example, if the mixture or a portion thereof forms a gel-like consistency, an aqueous solvent is also added to the mixture. In some embodiments, after heating for about 2-6 hours, for example, the mixture is heated to a further elevated temperature ranging from about 100°C to about 160°C, such as from about 120°C to about 160°C, or from about 140°C to about 160°C. In some embodiments, after forming a suspension or slurry, for example, after about 1-2 hours, the temperature is then reduced to a lower elevated temperature to stir the suspension or slurry described herein. As described herein, the resulting mixture is then heated to a dehydration temperature (eg, about 240°C to about 360°C) for a period of time (eg, about 2 hours to about 6 hours).

[0071] In another embodiment, an aqueous solution of tris[methylphosphonic acid]aluminum salt prepared from aluminum isopropoxide starting material and sulfolane as a high boiling point water-soluble acid-stable solvent are mixed at an elevated temperature ranging from about 60°C to about 100°C, such as from about 80°C to about 95°C, optionally under a slight vacuum. In some embodiments, the aqueous solution of the salt and sulfolane are mixed at an elevated temperature for an amount of time ranging from about 2 hours to about 6 hours. As described herein, after forming a suspension or slurry, the resulting mixture is heated to a dehydration temperature (e.g., about 240°C to about 360°C) for a period of time (e.g., about 2 hours to about 6 hours).

[0072] Phosphonates of formula (I) are known and various methods for their preparation are described in the prior art. For example, the phosphonates of formula (I) can be selected from salts disclosed in US 2006 / 0138391, US 2015 / 0031805, and elsewhere in the art. In some embodiments, the salt of formula (I) comprises wherein R is H, C 1-12 Alkyl, C 6-10 Aryl, C 7-18 Alkyl or C 7-18 Compounds wherein the group is further substituted as described in US 2006 / 0138391, but typically R is unsubstituted C 1-12 Alkyl, C 6-10 Aryl, C 7-18 Alkyl or C 7-18 For example, R may be substituted or unsubstituted, typically unsubstituted C 1-6 Alkyl, C6 aryl, C 7-10 Alkyl or C7-12 Arylalkyl, for example, C 1-4 alkyl.

[0073] The present disclosure is not limited to any particular metal cation M (+)y Examples of suitable metals include Mg, Ca, Ba, Zn, Zr, Ge, B, Al, Si, Ti, Cu, Fe, Sn, and Sb. In some embodiments, M is selected from Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Fe, Sn, and Sb. In some embodiments, M is selected from Mg, Ca, Ba, Zn, Zr, B, Al, Fe, Sn, and Sb. In some embodiments, M is selected from Al, Fe, Zn, and Ca.

[0074] R as an alkyl group is a straight or branched chain alkyl group having a designated carbon number, and includes, for example, straight chain alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and branched chain alkyl groups such as isopropyl, isobutyl, sec-butyl, tert-butyl, ethylhexyl, tert-octyl, etc. For example, R as an alkyl group may be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, and typically R is methyl, ethyl, propyl or isopropyl, for example, methyl.

[0075] Typically, when R is an aryl group, it is a phenyl or naphthyl group, for example, a phenyl group. Examples of R as an alkaryl group include phenyl substituted with one or more alkyl groups, for example, a group selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, etc. Examples of R as an aralkyl group include, for example, benzyl, phenethyl, styryl, cumyl, phenylpropyl, etc.

[0076] In some embodiments, R is H, methyl, ethyl, propyl, isopropyl, phenyl, or benzyl, e.g., methyl, ethyl, propyl, isopropyl, or phenyl, e.g., methyl, ethyl, propyl, or isopropyl, e.g., methyl.

[0077] In some embodiments, the phosphonate is a compound of formula (I), wherein R is H, methyl, ethyl, propyl, isopropyl, benzyl or phenyl, M is Al, Fe, Zn or Ca, and p is 2 or 3. In some embodiments, R is H, methyl, ethyl, propyl or isopropyl, p=3, and M is Al or Fe. In other embodiments, R is H, methyl, ethyl, propyl or isopropyl, p=2, and M is Zn or Ca, for example, Ca.

[0078] As described above, more than one phosphonate of formula (I) may be used with different R and / or M. In some embodiments, at least one R is selected from H, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, and phenyl, and at least one M is selected from Al, Fe, Zn, and Ca. In some embodiments, each R is selected from H, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, and phenyl, and each M is selected from Al, Fe, Zn, and Ca.

[0079] The amount of time it takes to convert the phosphonate of formula (I) to the flame retardant of the present invention will vary depending on a variety of factors including, for example, the chemical structure of the starting phosphonate, the temperature of the reaction, and the like.

[0080] By heating the mixture of the phosphonate of formula (I) and the high boiling point water-soluble acid-stable solvent at a temperature in the range of about 220°C to about 400°C, or about 240°C to about 360°C for 20 hours or less, for example, 12 hours or less, at a dehydration temperature as described herein, a good conversion rate of the salt into the flame retardant material disclosed herein is obtained. Typically, the mixture of the phosphonate of formula (I) and the high boiling point water-soluble acid-stable solvent is heated at a temperature of about 200°C (e.g., about 220°C) to about 400°C for about 1 minute to about 20 hours, for example, about 30 minutes to about 12 hours, about 1 hour to about 8 hours, or about 2 hours to about 6 hours. In one example, the mixture is heated at about 220°C to about 400°C for about 1 hour to about 12 hours or about 1 hour to about 8 hours. In another example, the mixture is heated at about 240° C. to about 360° C. for about 1 hour to about 6 hours or about 2 hours to about 6 hours. In some cases, such as at higher temperatures (e.g., temperatures of about 250° C. to about 400° C. or above) and / or when the reaction vessel or environment allows efficient heat transfer to the starting materials, heating may occur in minutes or seconds, e.g., less than 1 hour, less than 30 minutes, less than 15 minutes, less than 6 minutes, less than 1 minute or less than 30 seconds.

[0081] While not wishing to be bound by theory, it is believed that the flame retardant material obtained by the process of the present disclosure comprises a compound or a mixture of compounds represented by empirical formula (IV):

[0082]

[0083] wherein R is H, alkyl, aryl, alkaryl or aralkyl as above, M is a metal as above, 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, typically 0 or 1, y is a number from 2 to 7, e.g., 2 to 4, and n is 1 or 2, provided that 2(q)+r=n(y). Naturally, the characteristics of the groups R and M reflect well the groups used as R and M in the salts of formula (I) used as starting materials. As with the inorganic coordination compounds mentioned above, formula (IV) is empirical and includes coordination polymers and complex salts (e.g., salts in which certain valences are shared).

[0084] The flame retardant material comprising the compound or mixture of compounds represented by the empirical formula (IV) is produced in the form of powder or granules without the need for grinding, granulation or other such physical treatments. Such flame retardant materials generally have a median particle size (d50) of about 100 μm or less, for example, about 80 μm or less, or about 60 μm or less, measured by laser diffraction according to ISO13320. For example, the powder or granules can have a median particle size (d50) of about 1 μm to about 100 μm, about 10 μm to about 90 μm, about 20 μm to about 80 μm, or about 20 μm to about 60 μm.

[0085] As described above, even when starting from a single compound of formula (I) in which there is one R group and one metal, a mixture of compounds is generally formed according to the empirical formula (IV) described herein. In some embodiments, the flame retardant material is prepared from a mixture of phosphonates, wherein there are multiple values ​​of R and / or M, resulting in a mixture of compounds according to the empirical formula (IV) containing multiple R groups and / or metals. In some embodiments, the flame retardant material of the present disclosure is prepared by obtaining two or more flame retardant materials respectively according to the method described herein and mixing the two or more flame retardant materials together, so that the flame retardant obtained comprises a mixture of compounds with multiple R and / or M values ​​according to the empirical formula (IV). The technical disclosure of U.S. Patent No. 9,752,011 for preparing a mixture of phosphonates in which different R groups and / or metals are present is incorporated herein by reference.

[0086] The flame retardant disclosed herein can be used together with various other flame retardants, synergists or flame retardant adjuvants known in the art. For example, the flame retardant can be formulated with one or more materials selected from the following: carbon black, graphite, carbon nanotubes, siloxane, polysiloxane; polyphenylene ether (PPE), phosphine oxide and polyphosphine oxide, for example, benzyl phosphine oxide, polybenzyl phosphine oxide, etc.;

[0087] Melamine, melamine derivatives and melamine condensation products, melamine salts such as but not limited to melamine cyanurate, melamine borate, melamine phosphate, melamine metal phosphate, melam, melem, melon, etc.;

[0088] 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 silicates, aluminosilicates, aluminosilicates as hollow tubes (DRAGONITE), calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, halloysite (HALLOYSITE) or boron phosphate, calcium molybdate, expanded vermiculite, zinc stannate, zinc hydroxystannate, zinc sulfide and zinc borate, zinc molybdate (KEMGARD 911A / B), zinc phosphate (KEMGARD 981), magnesium oxide or magnesium hydroxide, aluminum oxide, aluminum hydroxide oxide (boehmite), aluminum trihydrate, silicon dioxide, tin oxide, antimony oxides (III and V) and hydrated oxides, titanium oxide, and zinc oxide or hydrated oxide, zirconium oxide and / or zirconium hydroxide, and the like.

[0089] Unless otherwise stated, in the context of this application, the term "phosphate" when used as a component in "phosphates" such as metal phosphates, melamine phosphates, melamine metal phosphates, etc., refers to phosphate, hydrogen phosphate, dihydrogen phosphate, pyrophosphate, polyphosphate or phosphoric acid condensation product anion or polyanion (polyanion, multivalent anion).

[0090] Likewise, in the context of the present application, the term "phosphite" when used as a component in a "phosphite" such as a metal phosphite, etc., refers to phosphite or hydrogen phosphite, unless otherwise specified.

[0091] The flame retardant of the present invention can also be formulated with other flame retardants such as halogenated flame retardants, alkyl or aryl phosphine oxide flame retardants, alkyl or aryl phosphate flame retardants, alkyl or aryl phosphonate, alkyl or aryl phosphinate and salts of alkyl or aryl phosphinic acid. In some embodiments, the flame retardant comprises a mixture of a flame retardant material according to the present invention and a phosphinate of formula (II) (e.g., tris(dialkylphosphinate)aluminum,

[0092]

[0093] R1 and R2 may each independently be a group according to R described herein, M is a metal as described herein (eg, Al or Ca), and n is a number from 2 to 7, such as 2 to 4, typically 2 or 3.

[0094] Thus, in many embodiments, the flame retardant polymer composition according to the present disclosure comprises (a) a polymer, (b) a flame retardant of the present disclosure, and (c) one or more other flame retardants, and / or one or more synergists or flame retardant aids.

[0095] For example, in some embodiments, the flame retardant polymer composition comprises one or more other flame retardants, for example, halogenated flame retardants, phosphine oxide flame retardants, alkyl or aryl phosphonates or alkyl or aryl phosphinates such as aluminum tris(dialkylphosphinate), such as aluminum tris(diethylphosphinate).

[0096] In some embodiments, the flame retardant polymer composition comprises one or more synergists or flame retardant aids, for example, melamine, melamine derivatives and melamine condensation products, melamine salts, phosphine oxides and polyphosphine oxides, metal salts such as hydroxides, oxides, hydrated oxides, borates, phosphates, phosphites, silicates, etc., for example, aluminum hydrogen phosphite, melem or melamine metal phosphates, for example, melamine metal phosphates wherein the metal comprises aluminum, magnesium or zinc. In a specific embodiment, one or more other flame retardants, synergists or flame retardant adjuvants include tri(dialkylphosphinate)aluminum, aluminum hydrogen phosphite, polyarylether substituted with methylenediphenylphosphine oxide, xylylenebis(diphenylphosphine oxide), 4,4'-bis(diphenylphosphinylmethyl)-1,1'-biphenyl, ethylenebis-1,2-bis-(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)ethane, melem, melam, melonamine or dimelamine zinc pyrophosphate.

[0097] Certain embodiments provide halogen-free polymer compositions. In such embodiments, halogen-containing flame retardants or synergists are excluded as much as possible.

[0098] The flame retardant material of the present disclosure can be combined with other flame retardants, synergists or adjuvants in a weight ratio of the flame retardant of the present disclosure to the total weight of other flame retardants, synergists and / or adjuvants in the range of 100:1-1:100. In some embodiments, the flame retardant material of the present disclosure is present in a weight ratio of the flame retardant of the present disclosure to the total weight of other flame retardants, synergists and / or adjuvants in the range of 10:1-1:10, for example, the weight ratio is in the range of 7:1-1:7, 6:1-1:6, 4:1-1:4, 3:1-1:3 and 2:1-1:2. The flame retardant of the present invention is generally the major component of such a combination, such as a ratio of 10:1-1.2:1 of the weight of the flame retardant of the present invention to the total weight of other flame retardants, synergists and / or adjuvants or a ratio of 7:1-2:1 of the weight of the flame retardant of the present invention to the total weight of 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 1:10-1:1.2 or a ratio of 1:7-1:2.

[0099] 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 has excellent flame retardant activity. The flame retardant of the present invention can be used in other polymers together with other synergists and conventional polymer additives.

[0100] The polymer of the flame retardant composition of the present disclosure 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 α-methylstyrene containing ABS, and polyester / ABS or polycarbonate / ABS and polyester or polystyrene plus some other impact modifiers. Such polymers can be commercially available or made by methods well known in the art.

[0101] The flame retardants of the present disclosure are particularly suitable for use with thermoplastic polymers that are processed and / or used at elevated temperatures, for example, styrenic polymers including high impact polystyrene (HIPS), polyolefins, polyesters, polycarbonates, polyamides, polyurethanes, polyphenylene ethers, and the like.

[0102] For example, the polymer can be a polyester resin, a styrene resin, a polyamide resin, a polycarbonate resin, a polyphenylene ether resin, a vinyl resin, an olefin resin, an acrylic resin, an epoxy resin or a polyurethane. The polymer can be a thermoplastic or thermosetting resin and can be reinforced, for example, glass reinforced. There can be more than one polymer resin. In a specific embodiment, the polymer is an engineering polymer, for example, a thermoplastic or reinforced thermoplastic polymer, for example, a glass reinforced thermoplastic polymer, such as optionally a glass-filled polyester, epoxy resin or polyamide, for example, a glass-filled polyester such as a glass-filled polyalkylene terephthalate or a glass-filled polyamide.

[0103] The polyester resin includes homopolyesters and copolyesters obtained by, for example, polycondensation of a dicarboxylic acid component and a diol component and polycondensation of a hydroxycarboxylic acid or a lactone component, for example, an aromatic saturated polyester resin such as polybutylene terephthalate or polyethylene terephthalate.

[0104] Polyamide (PA) resins include polyamides derived from diamines and dicarboxylic acids; polyamides obtained by 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 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 hexamethylenediamine or nonamethylenediamine, and polyamides obtained from aromatic and aliphatic dicarboxylic acids such as terephthalic acid and adipic acid and aliphatic diamines such as hexamethylenediamine, etc. These polyamides can be used alone or in combination. In some embodiments, the polymer comprises polyphthalamide.

[0105] Polyamides having a melting point of at least 280° C. are widely used for producing molding compositions which make it possible to produce molded articles (for example for the electrical and electronics industry) which have excellent dimensional stability at high temperatures and have very good flame retardant properties. For example, molding compositions of this type are required in the electronics industry for producing 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. for short periods of time without changing their dimensions.

[0106] 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. A single aromatic or semi-aromatic polyamide can be used, or a blend of aromatic and / or semi-aromatic polyamides can be used. It is also possible to blend the aforementioned polyamides and polyamide blends with other polymers, including aliphatic polyamides.

[0107] Examples of these high temperature aromatic or semi-aromatic polyamides include polyamide 4T, poly(meta-phenylenediamine adipamide) (polyamide MXD, 6), poly(dodecylene terephthalamide) (polyamide 12, T), poly(decane terephthalamide) (polyamide 10, T), poly(nonane terephthalamide) (polyamide 9, T), hexamethylene adipamide / hexamethylene terephthalamide copolyamide (polyamide 6, T / 6, 6), hexamethylene terephthalamide / 2-methylpentamethylene terephthalamide copolyamide (polyamide 6, T / D, T), hexamethylene adipamide / hexamethylene terephthalamide / hexamethylene isophthalamide copolyamide (polyamide 6, 6 / 6, T / 6, I), poly(caprolactam-hexamethylene terephthalamide) (polyamide 6 / 6, T), hexamethylene terephthalamide / hexamethylene isophthalamide (6, T / 6, I) copolymers, and the like.

[0108] Therefore, certain embodiments of the present disclosure are directed to compositions comprising polyamides such as polyamide 4,6 and the aromatic and semi-aromatic polyamides described above 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, articles comprising high temperature polyamides and the flame retardant materials of the present disclosure, methods for preparing the compositions, and methods for forming the articles.

[0109] As described herein, in many embodiments, the flame retardant polymer composition comprises (a) a polymer, (b) a flame retardant of the present disclosure, and (c) one or more other flame retardants, and / or one or more synergists or flame retardant adjuvants. Therefore, although the flame retardant (b) alone exhibits excellent activity in the polymer system, it can be used in combination with (c) one or more compounds selected from other flame retardants, synergists and adjuvants. Exemplary compounds (c) include halogenated flame retardants, alkyl or aryl phosphine oxides, alkyl or aryl polyphosphine oxides, alkyl or aryl phosphates, alkyl or aryl phosphonates, alkyl or aryl phosphinates, salts of alkyl or aryl phosphinic acids, carbon black, graphite, carbon nanotubes, siloxanes, polysiloxanes, polyphenylene ethers, melamine, melamine derivatives, melamine condensation products, melamine salts, metal hydroxides, metal oxides, metal hydrated oxides, metal borates, metal carbonates, metal sulfates, metal phosphates, metal phosphites, metal hypophosphites, metal silicates, and mixed metal salts. For example, the one or more compounds (iii) can be selected from aluminum tris(dialkylphosphinate), aluminum hydrogen phosphite, benzyl phosphine oxide, polybenzyl phosphine oxide, melam, melem, melonamine, melamine phosphate, melamine metal phosphate, 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, expanded 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) hydrated oxide, titanium oxide, zinc oxide, zinc hydrated oxide, zirconium oxide and zirconium hydroxide. For example, the one or more compounds (c) can be selected from tris(dimethylphosphinate)aluminum, tris(diethylphosphinate)aluminum, tris(dipropylphosphinate)aluminum, tris(dibutylphosphinate)aluminum, polyarylether substituted with methylenediphenylphosphine oxide, xylylenebis(diphenylphosphine oxide), 1,2-bis-(9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide)ethane, 4,4'-bis(diphenylphosphinylmethyl)-1,1'-biphenyl, melam, melem, melonamine and dimelamine zinc pyrophosphate.

[0110] In some embodiments, the flame retardant polymer composition comprises one or more compounds selected from hydrotalcite clay, metal borates, metal oxides, and metal hydroxides, such as metal borates, metal oxides, or metal hydroxides wherein the metal is zinc or calcium.

[0111] Of course, the concentration of the flame retardant of the present invention in the polymer composition depends on the exact chemical composition of the flame retardant, polymer and other components found in the final polymer composition. For example, when used as the only flame retardant component of a polymer formulation, the flame retardant of the present invention can be present in a concentration of 1%-50%, for example, 1%-30%, based on the total weight of the final composition. Typically, when used as the only flame retardant, there will be at least 2%, for example, 3% or more, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more of the present material. In many embodiments, the flame retardant of the present invention is present in an amount of up to 45%, while in other embodiments, the amount of the flame retardant of the present invention accounts for 40% or less of the polymer composition, for example, 35% or less. When used in combination with other flame retardants or flame retardant synergists, the present material may need to be less.

[0112] Any known compounding technique can be used to prepare the flame retardant polymer composition of the present disclosure, for example, the flame retardant can be introduced into the molten polymer by blending, extrusion, fiber or film forming, etc. In some cases, the flame retardant is introduced into the polymer during polymer formation or curing, for example, the flame retardant can be added to the polyurethane prepolymer before crosslinking, or it can be added to the polyamine or alkyl polycarboxyl compound before polyamide formation, or added to the epoxy mixture before curing.

[0113] The flame retardant polymer composition will typically contain one or more conventional stabilizers or other additives commonly encountered in the art, such as phenolic antioxidants, hindered amine light stabilizers (HALS), ultraviolet light absorbers, phosphites (phosphites, phosphites), phosphonites (phosphonites, phosphites), alkali metal salts of fatty acids, hydrotalcites, metal oxides, borates, epoxidized soybean oil, hydroxylamine, tertiary amine oxides, lactones, thermal reaction products of tertiary amine oxides, thioesters, synergist (thiosynergist), alkaline co-stabilizer, for example, melamine, melem, etc., polyvinyl pyrrolidone, dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamides, polyurethanes, hydrotalcite, alkali metal salts and alkaline earth metal salts of higher fatty acids, for example, calcium stearate, calcium stearoyl lactylate, calcium lactate, zinc stearate, zinc octoate, magnesium stearate, sodium ricinoleate and potassium palmitate, antimony catechol or zinc catechol, nucleating agents, clarifying agents, etc.

[0114] Other additives may also be present, for example, plasticizers, lubricants, emulsifiers, pigments, dyes, optical brighteners, other flame retardants, antistatic agents, blowing agents, anti-drip agents, for example, PTFE, and the like.

[0115] Alternatively, the polymer may include fillers and reinforcing agents, for example, calcium carbonate, silicates, glass fibers, talc, kaolin, mica, barium sulfate, metal oxides and hydroxides, carbon black and graphite. Such fillers and reinforcing agents may generally be present in relatively high concentrations, including formulations in which fillers or reinforcing agents are present in concentrations exceeding 50 wt % based on the weight of the final composition. More generally, fillers and reinforcing agents are present in 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.

[0116] In some embodiments, the flame retardant polymer composition of the present disclosure is formulated with one or more materials selected from the following: carbon black, graphite, carbon nanotubes, siloxane, polysiloxane, talc, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, calcium silicate, magnesium silicate, hollow aluminosilicate tubes (Dragonite), halloysite, boron phosphate, calcium molybdate, expanded vermiculite, zinc stannate, zinc hydroxystannate, zinc sulfide, zinc borate, zinc molybdate (Kemgard 911A / B), zinc phosphate (Kemgard 981), etc.;

[0117] Hydroxides, oxides and hydrated oxides of Group 2, 4, 12, 13, 14 and 15 (quasi) metals ((semi)metals) such as magnesium oxide or magnesium hydroxide, aluminum oxide, aluminum hydroxide oxide (boehmite), aluminum trihydrate, silica, silicates, tin oxides, antimony oxides (III and V) and hydrated oxides, titanium oxides and zinc oxides or hydrated oxides, zirconium oxide and / or zirconium hydroxide, etc.; melamine and urea-based resins such as melamine cyanurate, melamine borate, melamine polyphosphate, melamine pyrophosphate, polyphenylene ether (PPE), etc.; and clays including hydrotalcite, boehmite, kaolin, mica, montmorillonite, wollastonite, nanoclay or organically modified nanoclay, etc.

[0118] Further non-limiting disclosures are provided in the following examples.

[0119] Example

[0120] Example 1

[0121] An aqueous solution containing 400 g of tris[methylphosphonic acid]]aluminum salt prepared from aluminum chloride hexahydrate and methylphosphonic acid (MPA) was added to a reaction flask along with 2.5 kg of sulfolane. The reaction mixture was stirred under a slight vacuum and heating was applied to gradually increase the temperature. As the temperature rose, water was removed.

[0122] When about 400 mL of water was distilled out from the reaction mixture, the kettle temperature was 95°C and a gelatinous material was deposited on the wall of the reaction vessel. About 0.1 grams of seed material having a median particle size (d50) less than 100 μm and 200 mL of water were added, and the gelatinous material disappeared from the wall. Further addition of seed material and water prevented the formation of other gels. Heating was continued for about 4 hours, during which the temperature rose to about 120°C and the desired slurry began to form, at which time the vacuum was removed. Heating was continued, the kettle temperature rose to 160°C, and the temperature was subsequently maintained at 160°C for 2 hours to complete the formation of a uniform slurry. The kettle temperature was then reduced to 60°C, and the uniform slurry was stirred at 60°C for 36 hours.

[0123] The reaction mixture was then gradually heated to 250°C and maintained at this temperature for 3 hours, producing a suspension of white fine particles. The reaction mixture was cooled to 60°C, filtered, and the solid was washed with IPA (500 mL x 3) to obtain a white powder and a light yellow filtrate. 31 P NMR detected no phosphorus compounds in the filtrate. The solid was then dried at 160°C for 1 hour to give 370 g of the product as a white powder (99% yield). The powder sieved easily through a 325 mesh screen (87% of the material sieved within 1 day) and had a free-flowing and non-fluffy physical appearance. Thermogravimetric analysis (TGA) performed in N2 showed that the product was thermally stable at >400°C ( Figure 1 ). Elemental analysis (ICP-OES) was as follows: 31.0% P, 9.0% Al. The BET surface area of ​​the product was about 2.5-2.6 m 2 / g, and the bulk density is 0.53g / mL. The particle size distribution and SEM images of the product are Figure 2 and 3 Shown in.

[0124] Example 2

[0125] An aqueous solution of aluminum tris[methylphosphonate] salt prepared from MPA and aluminum isopropoxide was added along with sulfolane at a weight ratio of 100 grams of sulfolane per 15 grams of aluminum salt to a 4-neck 5 L round bottom flask equipped with an overhead stirrer, addition funnel, and Vigreux column with a Dean-Stark trap.

[0126] The reaction mixture was stirred at 90°C for 4 hours under nitrogen to obtain a uniform white suspension. The reaction mixture was then gradually heated to 250°C and maintained at 250°C for 3 hours. The off-white suspension was then cooled to 60°C, sulfolane was filtered out, and the solid was washed with isopropanol (500mL×3). The solid was then dried in an oven at 160°C for 1 hour to obtain a white powder product (142g) in a yield of 92%. TGA performed in N2 showed that the product was thermally stable at >400°C ( Figure 4 ). Elemental analysis (ICP-OES) was as follows: 26.7% P, 8.5% Al.

[0127] Comparative Example 3

[0128] A pre-weighed 1 L resin kettle was charged with 282.3 g of ethylphosphonic acid (EPA) and 157 mL of DI H2O. The reactor was placed in an ice bath and an incremental amount of solid Al(O- i Pr)3 was added to the EPA solution, a total of 174.7 g Al(O- i Pr)3. After the addition, the kettle temperature was maintained at 20°C or lower for about 15 minutes using an ice bath, at which time the ice bath was removed and the kettle was warmed to room temperature. The mixture was stirred until no aluminum isopropoxide was seen (at least 5 hours). A milky white mixture was formed, which was then concentrated using a distillation head and a pump. The thickened mixture was poured into a 1L beaker, placed in a 100°C programmable oven, and heated to 160°C within 8 hours and maintained for 8 hours. The temperature was raised to 230°C within 2 hours and maintained for 6 hours. The resulting product was formed into a solid block and cooled to room temperature. The solid block was roughly broken up with a mortar and pestle, and heat treated again to 230°C within 1 hour and maintained for 4 hours. The product was reground and transferred to a dry container with a yield of 276.4g (96.2%). TGA performed in N2 showed that the product was thermally stable at >350°C ( Figure 5 ).

[0129] Example 4

[0130] The flame retardant activity of the materials produced according to the present disclosure is excellent and no difficulties were observed in compounding the materials into polymer compositions. UL-94 rating for the following measurements V-0@0.8 mm:

[0131] A) a polyamide 66 composition comprising 30 wt% glass fiber, 13.7 wt% FR 1 / 2 and 10% melem;

[0132] and

[0133] B) a polyphthalamide composition comprising 25 wt% glass fiber and 16.7 wt% FR 1 / 2,

[0134] Herein FR 1 / 2 represents the flame retardant material prepared according to Example 1 in one series of tests and represents the flame retardant material prepared according to Example 2 in another separate series of tests.

[0135] Specifically, as shown in Table 1 below, polymer compositions were prepared and evaluated for flame retardant activity according to the UL94 test. As shown in Table 1, some compositions also included melem (melamine condensation product) as a synergist. Formulations 1 and 2 containing 56.3 parts of nylon 66, 30 parts of glass, 13.7 parts of flame retardant FR 1 / 2 and 10 parts of melem were prepared by compounding at 265°C and molding into 1 / 16" and 1 / 32" strips at 280°C, respectively. Formulation 3 containing 58.3 parts of polyphthalamide, 25 parts of glass and 16.7 parts of flame retardant FR1 / 2 was prepared by compounding at 320-330°C and molding into 1 / 32" strips at 320-330°C. The formulations were evaluated according to UL 94, and the results are shown in Table 1.

[0136] The results show that the flame retardants produced according to Example 1 and Example 2 each achieved the best UL-94 vertical burning test rating of V-0 at different sample thicknesses (while the polymer composition without flame retardant (Formulation 4) failed the UL 94 test). The results of Formulation 3 also show that the flame retardants produced according to Example 1 and Example 2, each in a glass-filled semi-aromatic nylon, achieved the best UL-94 vertical burning test rating of V-0 at 1 / 32".

[0137] Table 1

[0138] Preparations 1 2 3 4 Nylon 66 56.3 56.3 - 70 Polyphthalamide - - 58.3 - Glass 30 30 25 30 FR 1 / 2 13.7 13.7 16.7 - Melem (synergist) 10 10 - - UL94@1 / 16″ V-0 - - Failed UL94@1 / 32″ - V-0 V-0 Failed

[0139] Although specific embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various modifications and variations can be made in light of the disclosure and practice without departing from the scope of the invention as claimed. Therefore, the present description and embodiments are intended to be considered exemplary only, with the true scope of the present invention being represented by the appended claims and their equivalents.

Claims

1. A method for preparing a thermally stable phosphorus-containing flame retardant material, comprising: The mixture is heated to a reaction temperature of 200° C. or higher to produce a flame retardant material directly in the form of powder or small particles, the mixture comprising i) a majority by weight, based on the weight of the mixture, of one or more high boiling point water soluble acid stable solvents, said solvent having a boiling point greater than 200°C, and ii) one or more phosphonates of formula (I): wherein R is H, an alkyl, aryl, alkaryl or aralkyl group, p is a number from 2 to 7, M is a metal, and y is a number from 2 to 7 such that M (+)y is a metal cation, wherein (+)y represents the charge formally assigned to the cation; wherein the one or more high boiling point water-soluble acid-stable solvents are selected from the group consisting of sulfones.

2. The method according to claim 1, further comprising, before the step of heating the mixture at a temperature of 200° C. or higher, a) providing one or more salts of formula (I) in solid or liquid form, and b) preparing the mixture by combining the one or more salts of formula (I) provided in a) with the one or more high boiling point water soluble acid stable solvents under conditions and for a time sufficient to form a suspension or slurry.

3. The method of claim 2, wherein the one or more salts of formula (I) are provided as a solution in an aqueous solvent.

4. A method according to claim 2 or 3, wherein the step of preparing the mixture is carried out at one or more elevated temperatures in the range of 30°C to 160°C.

5. The method according to claim 1, wherein the sulfone has the formula R1R2SO2, wherein R1 and R2 are independently selected from C 1-6 The hydrocarbon group or R1 and R2 together with S form a ring having 2, 3, 4 or 5 carbon atoms.

6. The method according to claim 5, wherein R1 and R2 are independently selected from C 1-3 alkyl.

7. The method according to claim 6, wherein R1 and R2 are both methyl or both ethyl.

8. The method according to claim 5, wherein R1 and R2 together with S form a tri-, tetra- or pentamethylene ring.

9. The method according to claim 8, wherein R1 and R2 together with S form a tetramethylene ring.

10. The method according to any one of claims 1 to 3, wherein p = y.

11. The process according to any one of claims 1 to 3, wherein the mixture is heated to a reaction temperature in the range of 220°C to 400°C.

12. The method according to any one of claims 1 to 3, wherein the powder or granules have a median particle size of 100 μm or less as measured by laser diffraction according to ISO 13320.

13. The method according to claim 12, wherein the median particle size is 20 μm to 80 μm.

14. The method according to any one of claims 1 to 3, wherein in formula (I), R is H, C 1-12 Alkyl, C 6-10 Aryl, C 7-18 Alkyl or C 7-18 Aralkyl, wherein the alkyl, aryl, alkaryl or aralkyl is unsubstituted or substituted by halogen, hydroxyl, amino, C 1-4 Alkylamino, di-C 1-4 Alkylamino, C 1-4 Alkoxy, carboxyl or C 2-5 and M is Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Cu, Fe, Sn or Sb.

15. The method according to claim 14, wherein in Formula I, R is C 1-12 alkyl, and M is Ca, Zn, B, Al, Fe or Sn.

16. The method of claim 15, wherein M is Fe, Ca or Al.

17. A method for improving the flame retardancy of a polymer, comprising: The mixture is heated to a reaction temperature of 200° C. or higher to form a flame retardant material, the mixture comprising i) a majority by weight, based on the weight of the mixture, of one or more high boiling point water soluble acid stable solvents, said solvent having a boiling point greater than 200°C, and ii) one or more phosphonates of formula (I): wherein R is H, an alkyl, aryl, alkaryl or aralkyl group, p is a number from 2 to 7, M is a metal, and y is a number from 2 to 7 such that M (+)y is a metal cation, wherein (+)y represents the charge formally assigned to the cation; separating the flame retardant material from the solvent to produce the flame retardant material in powder or granular form; and combining the flame retardant material with a polymer; wherein the one or more high boiling point water-soluble acid-stable solvents are selected from the group consisting of sulfones.

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