Macromolecular bio-based phytate and modified flame-retardant polyformaldehyde composite material containing same

Abstract

The invention belongs to the technical field of flame retardance of high polymer materials, and relates to macromolecular bio-based phytate and a modified flame-retardant polyformaldehyde composite material containing the same. The macromolecular bio-based phytate is prepared from phytic acid, organic diamine, melamine and metal salt. The molecular structure of the phytate contains a plurality of flame-retardant elements for synergism, the flame-retardant efficiency is high, and the phytate can be independently used for flame retardance of a plurality of thermoplastic and thermosetting resins and can also be used for synergistic flame retardance with other flame-retardant systems. According to the synergistic flame-retardant polyformaldehyde composite material, 0.5-8.0 wt% of macromolecular bio-based phytate is added, so that the flame-retardant property of polyformaldehyde can be remarkably improved, the limit oxygen index of flame-retardant polyformaldehyde reaches 55% or above, UL-94 reaches the V-0 grade, and the mechanical property, especially the impact strength of the composite material, is also improved; and the cable can be widely applied to the application requirements of electronic and electrical, machinery and other special fields.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology of polymer materials, and particularly relates to a macromolecular bio-based phytate and a modified flame retardant polyoxymethylene composite material containing the phytate. Background Technology

[0002] Polyoxymethylene (POM) is a highly crystalline thermoplastic polymer with a flexible linear molecular structure. As one of the five major general-purpose engineering plastics, POM boasts excellent comprehensive properties, a smooth and glossy surface, good mechanical properties, excellent electrical insulation, solvent resistance, and processability. However, like most carbon-based polymers, POM is extremely flammable. Once ignited, it burns rapidly, releasing a large amount of heat and producing a large amount of toxic gases and smoke, posing a significant fire hazard and severely limiting the expansion of POM's application areas. Therefore, flame-retardant modification of POM is of significant research importance. Due to POM's poor thermal stability, narrow processing temperature range (approximately 10°C), and slightly low acid and alkali stability, POM exhibits high selectivity for flame retardants, thus increasing the difficulty of flame-retardant POM. Currently, very few flame-retardant POM products reported in the literature achieve the UL94 flame retardant rating. Chinese invention patent application CN109942894A discloses a halogen-free intumescent flame retardant system containing benzoxazine charring agent. By combining benzoxazine with an intumescent flame retardant, the flame retardant performance of polyoxymethylene (POM) composite materials is significantly improved. However, this requires the use of expensive benzoxazine containing a silane structure to achieve the UL94 V-0 rating. Furthermore, while the addition of the flame retardant system improves the flame retardant performance, it also deteriorates the mechanical properties to some extent, thus requiring further optimization.

[0003] On the other hand, the environmental issues of flame retardants have received widespread social attention, and phytate-based flame retardants have entered the public eye due to their advantages such as bio-based origin, environmental friendliness, and high flame retardancy. Phytate-based flame retardants mainly exert their flame retardant effect through catalytic char formation, release of inert gases, and formation of a dense char layer, while also possessing functions such as synergistic enhancement (e.g. with nitrogen compounds), UV shielding, and improved thermal stability. In 2025, Liu et al. (Liu L, Lai D, Wu H, et al. Self‐AssemblingMacromolecular Flame Retardant Polyvinyl Alcohol Films With Phytic Acid and Melamine[J]. Journal of Vinyl and Additive Technology, 2025.) synthesized a phytate-based bio-based flame retardant through supramolecular self-assembly of phytic acid and melamine, and introduced it into a polyvinyl alcohol (PVA) matrix to develop a high-performance composite film. Under the condition of only 10% addition, the LOI of the composite material increased to 31%, and the UL94 test achieved a V-0 rating. At the same time, the composite material also has high transparency. Tian H, Wang YC, Qu CL, et al. Synthesis of metal coordination polymers based aminotrimethylene phosphonic acid and zinc phytate to improve the flameretardancy of polylactic acid[J]. International Journal of Biological Macromolecules, 2025: 146922. synthesized a novel phytate-based flame retardant by controlling the ratio of zinc phytate and aminotrimethylene phosphonic acid. When added to polylactic acid (PLA), it successfully passed the UL94 V-0 test. Summary of the Invention

[0004] This invention addresses the problem that existing flame-retardant polyoxymethylene (POM) systems lack sufficient flame-retardant efficiency and cannot effectively balance flame-retardant and mechanical properties. It provides a macromolecular bio-based phytate and a modified flame-retardant POM composite material containing this phytate. This macromolecular bio-based phytate exhibits synergistic flame-retardant properties from multiple flame-retardant elements and, compared to phytate metal salts and phytate melamine salts, demonstrates higher thermal stability, enabling it to withstand higher processing temperatures. This invention provides a modified flame-retardant POM composite material that significantly improves both the flame-retardant and mechanical properties of POM by introducing a macromolecular bio-based phytate as a synergist, while simultaneously significantly reducing the amount of flame retardant required.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a macromolecular bio-based phytate, which is a macromolecular bio-based phytate organic diamine melamine metal salt, and its structural formula is as follows: ; In the formula, R1 is an aliphatic or aromatic organic diamine linker, R2 is a melamine salt ion, R3 is a metal ion, and n = 1~100.

[0006] Secondly, the present invention provides a method for preparing the above-mentioned macromolecular bio-based phytate, comprising the following steps: Step 1: Mix an aliphatic or aromatic organic diamine ethanol solution with an aqueous phytic acid solution at room temperature and react. Specifically, slowly and uniformly add the organic diamine ethanol solution to the aqueous phytic acid solution and stir the reaction for 20-60 minutes.

[0007] The organic diamine is specifically one or two of the following: ethylenediamine, pentanediamine, hexanediamine, nonanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, polyetheramine, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane. Step 2: Add the aqueous solution containing metal ions to the reaction solution in Step 1 to carry out the reaction; specifically, slowly and uniformly add the aqueous solution containing metal ions to the reaction solution in Step 1, and continue to stir and react for 20-60 minutes while maintaining the temperature.

[0008] The metal ions are provided by a metal salt or a metal alkali, wherein the metal salt is at least one of nickel acetate, manganese acetate, zinc acetate, and copper acetate, and the metal alkali is at least one of magnesium hydroxide, calcium hydroxide, zinc hydroxide, copper hydroxide, aluminum hydroxide, and iron hydroxide.

[0009] Step 3: Heat the reaction solution from Step 2 to 50-95 °C, add melamine suspension, and react. The resulting white precipitate is the macromolecular bio-based phytate. Specifically, heat the reaction solution from Step 2 to 50-95 °C, then slowly and uniformly add melamine suspension. A large amount of precipitate will rapidly form. Maintain the temperature and continue stirring for 2-6 hours. After the reaction is complete, cool to room temperature, filter to obtain a white precipitate, wash repeatedly with deionized water until the final filtrate is neutral, and dry to obtain the final product.

[0010] The molar ratio of the organic diamine, phytic acid, metal ions, and melamine is (1–1.1):1:(1–3):(5–9). By adjusting the amount and ratio of the organic diamine, melamine, and metal salt, macromolecular bio-based phytates with different phosphorus, nitrogen, and metal ion contents can be obtained.

[0011] The macromolecular bio-based phytate can be used to prepare flame retardants for thermoplastic or thermosetting resins, and can also be used as a synergist for flame retardants.

[0012] A third aspect of the present invention provides a modified flame-retardant polyoxymethylene composite material, which is composed of raw materials in the following proportions: Polyoxymethylene (POM) 60-90 wt% Intumescent flame retardant (IFR) 10-30 wt%; Synergistic agent 0.5-8.0 wt%; Antioxidants and processing aids 0.1-1.0 wt%; The polyoxymethylene resin is at least one of copolymeric polyoxymethylene and homopolymeric polyoxymethylene resin.

[0013] The intumescent flame retardant IFR is a compound of ammonium polyphosphate, benzoxazine and melamine in a mass ratio of 10:2:3.

[0014] The synergist is a phytate, selected from at least one of phytate metal salt, phytate melamine salt, phytate melamine metal salt, or the macromolecular bio-based phytate (macromolecular bio-based phytate organic diamine melamine metal salt). More preferably, the synergist is a macromolecular bio-based phytate.

[0015] The phytic acid metal salt is at least one selected from manganese phytate, magnesium phytate, zinc phytate, nickel phytate, copper phytate, calcium phytate, aluminum phytate, and iron phytate. Its preparation method includes: reacting metal ions and phytic acid in a solvent by mixing and stirring. The molar ratio of metal ions to phytic acid is (4.5-12.5):1. The metal ions are provided by a metal salt or a metal alkali, wherein the metal salt is at least one selected from nickel acetate, manganese acetate, zinc acetate, and copper acetate, and the metal alkali is at least one selected from magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and iron hydroxide. The solvent is one or two selected from deionized water, toluene, xylene, carbon tetrachloride, 1,4-dioxane, and ethanol.

[0016] The phytic acid melamine salt is prepared by reacting phytic acid and melamine in a solvent. The molar ratio of melamine to phytic acid is (4.5-12.5):1. The solvent is one or two of deionized water, toluene, xylene, carbon tetrachloride, 1,4-dioxane, and ethanol.

[0017] The phytic acid melamine metal salt is at least one of phytic acid melamine magnesium salt, phytic acid melamine calcium salt, phytic acid melamine zinc salt, phytic acid melamine iron salt, and phytic acid melamine aluminum salt. Its preparation method includes: mixing and stirring a metal alkali, melamine, and phytic acid in a solvent to form a reaction. The molar ratio of the metal alkali, melamine, and phytic acid is (2-6):(3-5):1. The metal alkali is at least one of magnesium hydroxide, calcium hydroxide, zinc hydroxide, copper hydroxide, aluminum hydroxide, and iron hydroxide. The solvent is one or two of deionized water, toluene, xylene, carbon tetrachloride, 1,4-dioxane, and ethanol.

[0018] The antioxidant is one of 2,4,6-tri-tert-butylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-methylenebis(2,6-di-tert-butylphenol), pentaerythritol tetrakis[methyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate.

[0019] The processing aid is one or two of the following: magnesium stearate, zinc stearate, calcium stearate, barium stearate, polyethylene wax, glyceryl monostearate, glyceryl distearate, glyceryl tristearate, ethylene bis-fatty acid amide, pentaerythritol stearate, polyethylene glycol, molybdenum disulfide, and silicone powder.

[0020] This invention also provides a method for preparing the above-mentioned modified flame-retardant polyoxymethylene composite material, which involves melt blending using a twin-screw extruder, as detailed below: First, weigh the raw materials according to the following weight ratio: polyoxymethylene (POM), intumescent flame retardant, synergist, antioxidant and processing aid, and premix them for 5-20 minutes; then place the mixed raw materials in a twin-screw extruder, melt extrude and granulate them at 160-190℃, and then injection mold them on an injection molding machine.

[0021] The beneficial effects of this invention are as follows: This invention constructs a macromolecular bio-based phytate with a unique multi-element synergistic flame-retardant structure containing phosphorus, nitrogen, and metal ions through the molecular assembly of phytic acid, organic diamine, melamine, and metal ions. This phytate molecule possesses both phosphorus and nitrogen flame-retardant elements and metal ions, exhibiting multi-element synergistic flame-retardant potential. Furthermore, the macromolecular bio-based phytate exhibits significantly lower thermal stability and hygroscopicity compared to phytic acid metal salts and phytic acid-melamine metal salts, while also improving its compatibility with polymer materials. During combustion, the metal ions in the macromolecular bio-based phytate molecule not only catalyze the esterification, dehydration, and char formation reactions between the acid source and char source, and migrate to the char layer surface to strengthen it, but also release certain amounts of amino compounds, NH3, H2O, and ·PO2 and ·PO free radicals upon heating, capturing active free radicals such as ·H and ·OH in the gas phase, thus enhancing the dilution and quenching effects. This macromolecular bio-based phytate can be used alone for flame retardancy of various thermoplastic or thermosetting resins, or it can be used in synergistic flame retardancy with other flame retardant systems.

[0022] Using the macromolecular bio-based phytate of this invention in synergistic flame-retardant polyoxymethylene (POM) composites reduces the amount of intumescent flame retardant required and improves the flame-retardant efficiency of the system, simultaneously achieving flame retardancy and toughening. Specifically, adding 0.5-8.0 wt% macromolecular bio-based phytate significantly enhances the flame-retardant properties of POM, achieving a limiting oxygen index of over 55% and a UL-94 V-0 rating. Mechanical properties are also improved, making it widely applicable to applications in electronics, electrical engineering, machinery, and other specialized fields. By simply adjusting the formulation of the flame-retardant POM composite material, a series of materials with different flame-retardant levels can be obtained, demonstrating excellent design flexibility. Attached Figure Description

[0023] Figure 1 Infrared spectrum of macromolecular bio-based phytate (Example 1).

[0024] Figure 2 The figures show a comparative thermal analysis of phytate metal salt (manganese phytate, Comparative Example 2), calcium phytate melamine salt (Comparative Example 3), and macromolecular bio-based phytate (Example 1). The macromolecular phytate in the figures represents the macromolecular bio-based phytate prepared in Example 1. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0026] The polyoxymethylene used in the examples and comparative examples was M90 type copolyoxymethylene produced by Kaifeng Longyu Chemical Co., Ltd.; the intumescent flame retardant IFR was compounded from ammonium polyphosphate, bisphenol A benzoxazine and melamine in a mass ratio of 10:2:3; all raw materials used in the experiment were commercially available analytical grade and were not purified before use.

[0027] Preparation of raw material solutions in the examples and comparative examples: (1) A metal ion solution with a concentration of 0.2 mol / L was prepared by dissolving a metal salt or metal alkali in deionized water at room temperature; (2) A phytic acid aqueous solution with a concentration of 0.2 mol / L was prepared by dissolving phytic acid in deionized water; (3) A melamine suspension with a concentration of 0.2 mol / L was prepared by adding melamine to deionized water; (4) An organic diamine ethanol solution with a concentration of 0.5 mol / L was prepared by dissolving an organic diamine in ethanol. Solutions prepared from the relevant raw materials of this concentration were used in the following examples.

[0028] Example 1 0.15 mol (0.3 L) of the prepared 4,4'-diaminodiphenyl sulfone ethanol solution and 0.05 mol (0.1 L) of triethylenetetramine ethanol solution were slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. The reaction was maintained at the specified temperature and stirred for 30 min. Then, 0.6 mol (3 L) of manganese acetate ion solution was slowly and uniformly added dropwise to the above reaction solution. The reaction was continued at the specified temperature and stirred for another 30 min. The temperature was then raised to 85 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution. A large amount of precipitate was rapidly generated. The temperature was maintained and stirred continuously for 4 h. After the reaction was complete, the temperature was lowered to room temperature, and the precipitate was obtained by filtration. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. Drying yielded a powdery solid, which was the macromolecular bio-based manganese phytate melamine metal salt. The infrared spectrum of the obtained macromolecular bio-based phytate is shown below. Figure 1 As shown.

[0029] The modified flame-retardant polyoxymethylene composite material was obtained by mixing 3% (by weight) of macromolecular bio-based manganese phytate melamine metal salt, 26% of intumescent flame retardant IFR, 0.5% of antioxidant 264 and 70.5% POM in a high-speed mixer for ten minutes; then melt-extruded and granulated by a twin-screw extruder (170-180℃), and injection molded by an injection molding machine.

[0030] Example 2 0.1 mol (0.2 L) of the prepared 4,4'-diaminodiphenylmethane ethanol solution and 0.1 mol (0.2 L) of the 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane ethanol solution were slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. The mixture was stirred and reacted for 30 min while maintaining the temperature. Then, 0.6 mol (3 L) of zinc acetate ion solution was slowly and uniformly added dropwise to the above reaction solution. The mixture was stirred and reacted for another 45 min while maintaining the temperature. The temperature was then raised to 75 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution. A large amount of precipitate was rapidly generated. The mixture was stirred and maintained for 3 h. After the reaction was complete, the temperature was lowered to room temperature, and the precipitate was obtained by filtration. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. After drying, a white powder was obtained, which is the macromolecular bio-based zinc phytate melamine metal salt.

[0031] The modified flame-retardant polyoxymethylene composite material was obtained by mixing 3% (by weight) of macromolecular bio-based zinc phytate melamine metal salt, 25% of intumescent flame retardant IFR, 0.5% of antioxidant 264 and 71.5% POM in a high-speed mixer for ten minutes; then melt-extruded and granulated by a twin-screw extruder (170-180℃), and injection molded by an injection molding machine.

[0032] Example 3 0.2 mol (0.4 L) of the prepared 4,4'-diaminodiphenylmethane ethanol solution was slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. The mixture was stirred and reacted for 40 min while maintaining the temperature. Then, 0.6 mol (3 L) of calcium hydroxide ion solution was slowly and uniformly added dropwise to the above reaction solution. The mixture was stirred and reacted for another 20 min while maintaining the temperature. The temperature was then raised to 80 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution. A large amount of precipitate was rapidly generated. The mixture was stirred and reacted for 4.5 h while maintaining the temperature. After the reaction was complete, the temperature was lowered to room temperature, and the precipitate was obtained by filtration. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. After drying, a white powder was obtained, which is the macromolecular bio-based calcium phytate melamine metal salt.

[0033] The modified flame-retardant polyoxymethylene composite material was obtained by thoroughly mixing 3% (by weight) of macromolecular bio-based calcium phytate melamine metal salt, 26% of intumescent flame retardant IFR, 0.3% of antioxidant 264 and 70.7% POM in a high-speed mixer for ten minutes; then melt-extruded and granulated by a twin-screw extruder (170-180℃), and injection molded by an injection molding machine.

[0034] Example 4 0.2 mol (0.4 L) of the prepared 4,4'-diaminodiphenylmethane ethanol solution was slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. The mixture was stirred and reacted for 30 min while maintaining the temperature. Then, 0.6 mol (3 L) of magnesium hydroxide ion solution was slowly and uniformly added dropwise to the above reaction solution. The mixture was stirred and reacted for another 60 min while maintaining the temperature. The temperature was then raised to 70 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution. A large amount of precipitate was rapidly generated. The mixture was stirred and reacted for 6 h while maintaining the temperature. After the reaction was complete, the temperature was lowered to room temperature, and the precipitate was obtained by filtration. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. After drying, a powder was obtained, which is the macromolecular bio-based magnesium phytate melamine metal salt.

[0035] The modified flame-retardant polyoxymethylene composite material was obtained by mixing 3% (by weight) of macromolecular bio-based magnesium phytate melamine metal salt, 27% of intumescent flame retardant IFR, 0.5% of antioxidant 264 and 69.5% POM in a high-speed mixer for ten minutes; then melt-extruded and granulated by a twin-screw extruder (170-180℃), and injection molded by an injection molding machine.

[0036] Example 5 0.2 mol (0.4 L) of the prepared 4,4'-diaminodiphenylmethane ethanol solution was slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. The reaction was maintained at the temperature and stirred for 50 min. Then, 0.3 mol (1.5 L) of magnesium hydroxide and 0.3 mol (1.5 L) of calcium hydroxide ion solution were slowly and uniformly added dropwise to the above reaction solution. The reaction was continued at the temperature and stirred for another 45 min. The temperature was then raised to 85 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution. A large amount of precipitate was rapidly generated. The temperature was maintained and stirred continuously for 5.5 h. After the reaction was complete, the temperature was lowered to room temperature, and the precipitate was obtained by filtration. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. After drying, a powder was obtained, which is the macromolecular bio-based calcium magnesium phytate melamine metal salt.

[0037] 5% by weight of macromolecular bio-based calcium magnesium phytate melamine metal salt, 25% intumescent flame retardant IFR, 0.5% antioxidant 1010 and 69.5% POM were thoroughly mixed in a high-speed mixer for ten minutes; the mixture was then melt-extruded and granulated using a twin-screw extruder (170-180℃), and the extruded granules were dried at 100℃ and injection molded to obtain modified flame-retardant polyoxymethylene composite material.

[0038] Example 6 0.2 mol (0.4 L) of the prepared 4,4'-diaminodiphenyl ether ethanol solution was slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. After stirring and maintaining the temperature for 50 min, 0.4 mol (2 L) of aluminum hydroxide ion solution was slowly and uniformly added dropwise to the above reaction solution. The temperature was maintained and the reaction was stirred for another 30 min. Then, the temperature was raised to 80 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution. A large amount of precipitate was rapidly generated. The temperature was maintained and the mixture was stirred continuously for 5 h. After the reaction was completed, the temperature was lowered to room temperature, and the precipitate was obtained by filtration. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. After drying, a powder was obtained, which is the macromolecular bio-based aluminum phytate melamine metal salt.

[0039] The modified flame-retardant polyoxymethylene composite material was obtained by mixing 3% macromolecular bio-based aluminum phytate melamine metal salt, 26% intumescent flame retardant IFR, 0.5% antioxidant 264 and 70.5% POM in a high-speed mixer for ten minutes; then melt-extruded and granulated by a twin-screw extruder (170-180℃), and injection molded by an injection molding machine.

[0040] Example 7 0.2 mol (0.4 L) of the prepared 4,4'-diaminodiphenyl ether ethanol solution was slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. The reaction was maintained at the temperature and stirred for 30 min. Then, 0.3 mol (1.5 L) of magnesium hydroxide and 0.3 mol (1.5 L) of calcium hydroxide ion solution were slowly and uniformly added dropwise to the above reaction solution. The reaction was continued at the temperature and stirred for 45 min. The temperature was then raised to 70 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution. A large amount of precipitate was rapidly generated. The temperature was maintained and stirred continuously for 5 h. After the reaction was complete, the temperature was lowered to room temperature, and the precipitate was filtered. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. After drying for 12 h, a powder was obtained, which is the macromolecular bio-based calcium magnesium phytic acid melamine metal salt.

[0041] Mix 6% phytic acid magnesium melamine metal salt, 24% intumescent flame retardant IFR, 0.5% antioxidant 1010 and 69.5% POM in a high-speed mixer for ten minutes; melt extrude and granulate the mixture using a twin-screw extruder (170-180℃), then dry the extruded granules at 100℃ and injection mold them to obtain modified flame-retardant polyoxymethylene composite material.

[0042] Example 8 0.1 mol (0.2 L) of the prepared 4,4'-diaminodiphenyl sulfone ethanol solution and 0.1 mol (0.2 L) of the 4,4'-diaminodiphenyl ether ethanol solution were slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. After stirring and maintaining the temperature for 60 min, 0.3 mol (1.5 L) of magnesium hydroxide and 0.3 mol (1.5 L) of calcium hydroxide ion solution were slowly and uniformly added dropwise to the above reaction solution. The temperature was maintained and the reaction was stirred for another 45 min. Then, the temperature was raised to 90 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the above solution, which rapidly generated a large amount of precipitate. The temperature was maintained and the mixture was stirred continuously for 4.5 h. After the reaction was completed, the temperature was lowered to room temperature, and the precipitate was obtained by filtration. The precipitate was washed repeatedly with deionized water until the filtrate was neutral. After drying, a powder was obtained, which is the macromolecular bio-based calcium magnesium phytic acid melamine metal salt.

[0043] 4% by weight of macromolecular bio-based calcium magnesium phytate melamine metal salt, 26% intumescent flame retardant IFR, 0.2% antioxidant 264 and 69.8% POM were thoroughly mixed in a high-speed mixer for ten minutes; the mixture was melt-extruded and granulated using a twin-screw extruder (170-180℃), and the extruded granules were dried at 100℃ and injection molded to obtain modified flame-retardant polyoxymethylene composite material.

[0044] The following Comparative Examples 1-3 are examples of phytate metal salt, phytate melamine salt and phytate melamine metal salt, used to compare with the above-mentioned macromolecular phytates.

[0045] Comparative Example 1 Take 0.1 mol (0.5 L) of the prepared phytic acid aqueous solution, stir and heat to 75 °C. Slowly and uniformly add 1.2 mol (6 L) of melamine suspension to the phytic acid aqueous solution. A large amount of precipitate is rapidly generated. Maintain the temperature and continue stirring for 4 hours. After the reaction is complete, cool to room temperature and filter to obtain the precipitate. Wash it several times with deionized water until the filtrate is neutral. Dry to obtain a white powder solid, which is phytic acid melamine salt.

[0046] The modified flame-retardant polyoxymethylene composite material was obtained by mixing 3% phytic acid melamine salt, 27% intumescent flame retardant IFR, 0.3% antioxidant 264 and 69.7% POM in a high-speed mixer for ten minutes; then melt-extruded and granulated by a twin-screw extruder (170-180℃), and injection molded by an injection molding machine.

[0047] Comparative Example 2 Take 0.6 mol (3 L) of the prepared manganese acetate ion solution, heat it to 70 °C, and stir at a constant temperature for half an hour. Then, slowly and uniformly add 0.1 mol (0.5 L) of the prepared phytic acid aqueous solution. The reaction solution gradually becomes turbid. Maintain the temperature and stir for 3 hours until no more precipitate is formed. After the temperature drops to room temperature, filter to obtain manganese phytate precipitate. Wash it repeatedly with deionized water until the filtrate is neutral. Dry to obtain a powdery solid, which is the phytic acid metal salt - manganese phytate salt.

[0048] The modified flame-retardant polyoxymethylene composite material was obtained by mixing 3% manganese phytate salt, 27% intumescent flame retardant IFR, 0.3% antioxidant 264 and 69.7% POM in a high-speed mixer for ten minutes; then melt-extruded and granulated by a twin-screw extruder (170-180℃), and injection molded by an injection molding machine.

[0049] Comparative Example 3 0.8 mol (4 L) of the prepared calcium acetate solution was slowly and uniformly added dropwise to 0.2 mol (1 L) of phytic acid aqueous solution. The mixture was stirred and kept at the same temperature for 25 min. Then, the temperature was raised to 75 °C, and 0.8 mol (4 L) of melamine suspension was slowly and uniformly added dropwise to the solution. A large amount of precipitate was rapidly formed. The mixture was stirred and kept at the same temperature for 4.5 h. After the reaction was complete, the temperature was lowered to room temperature, and the precipitate was filtered. The precipitate was then washed repeatedly with deionized water until the filtrate was neutral. After drying, a white powder solid was obtained, which was calcium phytate melamine salt.

[0050] 3% phytate calcium melamine salt, 27% intumescent flame retardant IFR, 0.3% antioxidant 264 and 69.7% POM by weight were thoroughly mixed in a high-speed mixer for ten minutes; the mixture was then melt-extruded and granulated using a twin-screw extruder (170-180℃), and injection molded to obtain a modified flame-retardant polyoxymethylene composite material.

[0051] The thermal analysis comparison spectra of the macromolecular bio-based phytate prepared in Example 1, the manganese phytate prepared in Comparative Example 2, and the calcium phytate melamine salt prepared in Comparative Example 3 are as follows: Figure 2 As shown.

[0052] Comparative Example 4 Mix 30% by weight of intumescent flame retardant IFR, 0.3% by weight of antioxidant 264 and 69.7% by weight of POM in a high-speed mixer for ten minutes; melt extrude and granulate the mixture using a twin-screw extruder (170-180℃), and then injection mold it to obtain a flame-retardant polyoxymethylene composite material.

[0053] The limiting oxygen index of the samples in Examples 1-8 and Comparative Examples 1-4 was tested according to GB / T 2406.2-2009, with methane as the combustible source. The vertical combustion performance of the samples was tested according to national standard GB / T2408-2008. The tensile strength of the samples was tested according to international standard ISO 527-1.2. The flexural strength of the samples was tested according to ISO-178, and the notched impact strength was tested according to national standard GB / T 1043-2008. The performance test results of Examples 1-8 and Comparative Examples 1-4 are shown in Table 1.

[0054] Table 1. Performance test results of the examples and comparative examples As shown in Table 1, the macromolecular bio-based phytate of this invention significantly improves the overall performance of flame-retardant polyoxymethylene (POM) composites. Regarding flame retardancy, the POM composites incorporating this macromolecular bio-based phytate all achieve a UL94 rating of V-0 and exhibit a high limiting oxygen index, demonstrating stable and excellent flame retardant performance. In contrast, the flame-retardant POM composites using only ordinary phytates or their metal salts cannot achieve a UL94 rating and have a lower limiting oxygen index. In terms of mechanical properties, the composites containing the macromolecular bio-based phytate of this invention show superior performance in notched impact resistance, flexural strength, and tensile strength, exhibiting balanced overall mechanical properties and making them more suitable for applications requiring high structural strength. The mechanical properties of the comparative examples 1-4 are relatively weaker. In summary, compared to ordinary phytate synergists, the macromolecular bio-based phytate synergist of this invention can simultaneously impart more reliable flame retardant properties and superior mechanical properties to POM composites, demonstrating significant comprehensive advantages.

[0055] The innovation of this invention lies in the pioneering design and preparation of a class of macromolecular bio-based phytates. These macromolecular bio-based phytates, through the molecular assembly of phytic acid, organic diamines, melamine, and metal ions, construct a unique multi-element synergistic flame-retardant structure containing phosphorus, nitrogen, and metal ions. When used to modify flame-retardant polyoxymethylene composites, adding only 0.5-8.0 wt% significantly improves the flame-retardant level, achieving a limiting oxygen index of over 55% and reaching the UL-94 V-0 rating. Particularly noteworthy is that this invention successfully solves the industry challenge of simultaneously achieving flame retardancy and mechanical properties. While achieving highly efficient flame retardancy, the impact strength and other mechanical properties of the composite material are not only not deteriorated but are actually enhanced simultaneously. The composite material developed by this invention possesses significant advantages in terms of environmental friendliness, highly efficient flame retardancy, and mechanical toughening, providing a novel solution for high-end electronics, automotive, and other fields with stringent material performance requirements, with broad application prospects.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A macromolecular bio-based phytate, characterized in that, Its structural formula is as follows: ； Where R1 is an aliphatic or aromatic organic diamine linker, R2 is a melamine salt ion, R3 is a metal ion, and n=1~100.

2. The method for preparing macromolecular bio-based phytate according to claim 1, characterized in that, Includes the following steps: Step 1: Mix an ethanol solution of an aliphatic or aromatic organic diamine with an aqueous solution of phytic acid at room temperature and allow the reaction to proceed. Step 2: Add the aqueous solution containing metal ions to the reaction solution from Step 1 to carry out the reaction; Step 3: Heat the reaction solution from Step 2 to 50-95 ℃, add melamine suspension, and react. The resulting white precipitate is macromolecular bio-based phytate.

3. The preparation method according to claim 2, characterized in that, The organic diamine is one or two of the following: ethylenediamine, pentanediamine, hexanediamine, nonanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, polyetheramine, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane.

4. The preparation method according to claim 2, characterized in that, The metal ions are provided by a metal salt or a metal alkali, wherein the metal salt is at least one of nickel acetate, manganese acetate, zinc acetate, and copper acetate, and the metal alkali is at least one of magnesium hydroxide, calcium hydroxide, zinc hydroxide, copper hydroxide, aluminum hydroxide, and iron hydroxide.

5. The preparation method according to claim 2, characterized in that, The molar ratio of the organic diamine, phytic acid, metal ions, and melamine is (1-1.1):1:(1-3):(5-9).

6. The use of the macromolecular bio-based phytate as described in claim 1 in the preparation of flame retardants for thermoplastic resins, flame retardants for thermosetting resins, or synergists for flame retardants.

7. A modified flame-retardant polyoxymethylene composite material, characterized in that, It is composed of the following raw materials in the following proportions: Polyoxymethylene 60-90wt% Intumescent flame retardant 10-30 wt%; Synergistic agent 0.5-8.0 wt%; Antioxidants and processing aids 0.1-1.0 wt%; The synergist is a phytate, which is selected from at least one of phytate metal salt, phytate melamine salt, phytate melamine metal salt, or the macromolecular bio-based phytate.

8. The modified flame-retardant polyoxymethylene composite material according to claim 7, characterized in that, The phytate metal salt is at least one of manganese phytate, magnesium phytate, zinc phytate, nickel phytate, copper phytate, calcium phytate, aluminum phytate, and iron phytate. The phytic acid melamine metal salt is at least one of phytic acid melamine magnesium salt, phytic acid melamine calcium salt, phytic acid melamine zinc salt, phytic acid melamine iron salt, and phytic acid melamine aluminum salt.

9. The modified flame-retardant polyoxymethylene composite material according to claim 7, characterized in that, The antioxidant is one of 2,4,6-tri-tert-butylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-methylenebis(2,6-di-tert-butylphenol), pentaerythritol tetrakis[methyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and triethylene glycol bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate; The processing aid is one or two of the following: magnesium stearate, zinc stearate, calcium stearate, barium stearate, polyethylene wax, glyceryl monostearate, glyceryl distearate, glyceryl tristearate, ethylene bis-fatty acid amide, pentaerythritol stearate, polyethylene glycol, molybdenum disulfide, and silicone powder.

10. The method for preparing the modified flame-retardant polyoxymethylene composite material according to any one of claims 7-9, characterized in that, include: Weigh the raw materials according to the following weight ratio: polyoxymethylene, intumescent flame retardant, synergist, antioxidant and processing aid, and premix the raw materials for 5-20 minutes; The mixed raw materials are then placed in a twin-screw extruder and melt-extruded and granulated at 160-190℃, and then injection molded on an injection molding machine.

Images