Flame retardant composition and use thereof, polyamide composite

Abstract

The application provides a flame retardant composition and application thereof and a polyamide composite material, the flame retardant composition comprises 5-15 parts of a dialkyl phosphinic acid metal salt and 0.5-4 parts of an imidazolium dialkyl phosphinate salt in terms of weight parts. The flame retardant composition, by compounding the imidazolium dialkyl phosphinate salt with the dialkyl phosphinic acid metal salt, can effectively improve the flame retardant efficiency, mechanical properties and precipitation resistance of the material, and meanwhile can reduce the content of the dialkyl phosphinic acid metal salt in the resin system.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, specifically relating to a flame retardant composition and its application, and polyamide composite materials. Background Technology

[0002] Aluminum diethylphosphonate (ADP), with its high phosphorus content (23-24%) and biphase flame-retardant mechanism (gas-phase free radical capture and condensed-phase charring to isolate oxygen), can achieve UL94 V-0 rating (0.4 mm thin wall) in materials such as PA and PBT at an addition level of 15-20%. It also exhibits excellent thermal stability (decomposition temperature > 350℃) and high retention of mechanical properties (impact strength reduction < 15% in glass fiber reinforced nylon). This breakthrough overcomes the bottlenecks of traditional phosphorus-based flame retardants in terms of efficiency, environmental friendliness, and material compatibility. Its superior thermal stability and environmental safety perfectly align with the trends of thinner and lighter electronic and electrical products, lighter automotive components, and green manufacturing, making it a core solution for the halogen-free upgrading of engineering plastics.

[0003] However, with the rapid development of the plastics industry and the increasing pursuit of performance, aluminum diethylphosphinate still has the following core defects in its application: Flame retardant efficiency depends on high addition levels, but high addition levels can lead to deterioration of mechanical properties. ADP requires a relatively high addition level (usually 15-20%) to achieve the ideal flame retardant rating (such as UL94 V-0). For example, in PET, the ADP addition level needs to be >8% to achieve V-0, but the mechanical properties decrease significantly when the addition level reaches 12%; in NR / BR rubber, adding 20 parts of ADP can increase the LOI to 27.6%, but the tensile strength decreases by 7.7%; in bamboo fiber / polypropylene composites, adding ADP alone results in an LOI of 27.8%, but the tensile strength decreases by 71.0%. Sometimes, it can even lead to mechanical property collapse mechanisms: for example, poor interfacial compatibility. ADP is an inorganic particle, which has poor compatibility with organic polymer matrices (such as PA and rubber). High addition levels lead to stress concentration, causing brittle fracture. Moreover, high addition levels can lead to deterioration of processing fluidity. High filler content increases melt viscosity, causing defects such as melt fracture and flow marks, reducing product yield, and increasing material quality, which goes against the lightweight trend of "replacing steel with plastic" in the automotive and electronics industries.

[0004] To improve the flame retardant efficiency of aluminum diethylphosphinate, the current method mainly involves compounding flame retardant synergists (such as melamine polyphosphate MPP, halloysite nanotubes HNTs, etc.). However, although this type of synergist can reduce the amount of ADP used (the LOI increases to 24.5% when ADP:MPP=6:1), it introduces new defects: such as MPP being prone to precipitation and deposition in the mold, increasing equipment maintenance costs; uneven dispersion of HNTs leading to increased melt viscosity (torque increases by 20%), and the release of highly toxic phosphine (PH3) and smoke at high temperatures (total smoke production TSP increases by 10.7%).

[0005] Therefore, improving the flame retardant efficiency of ADP flame retardant and overcoming the problems of poor flame retardant effect due to low flame retardant addition and material mechanical property degradation caused by high flame retardant addition have become urgent issues to be addressed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a flame retardant composition and its application, as well as a polyamide composite material. The flame retardant composition effectively improves the flame retardant efficiency and mechanical properties of the material, and exhibits good resistance to exudation.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a flame retardant composition comprising, by weight, 5-15 parts of a dialkylphosphonic acid metal salt and 0.5-4 parts of a dialkylphosphonic acid imidazolium salt. The dialkylphosphonic acid imidazolium salt has the structure shown in Formula I; Formula I; in Formula I, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C10 straight-chain or branched alkyl groups; the substituted substituents are selected from at least one of halogens, C1-C6 straight-chain or branched alkyl groups.

[0008] In this invention, the dialkylphosphino acid imidazolium salt combines the properties of an ionic liquid with the flame-retardant function of a phosphine group. The synergistic effect of the imidazolium cation and the phosphino acid anion in its molecule endows it with high thermal stability, low toxicity, and designability. By compounding dialkylphosphino acid imidazolium salt with dialkylphosphino acid metal salt in a specific ratio and applying it to a flame-retardant nylon system, the amount of dialkylphosphino acid metal salt used can be reduced, and the flame-retardant efficiency can be greatly improved (while maintaining the flame-retardant rating of V-0). Simultaneously, the mechanical properties of the material are also improved to varying degrees, the flame retardant is less likely to precipitate, and the resulting composite material exhibits a small mass change rate before and after boiling in water.

[0009] In this invention, 5 to 15 parts of dialkylphosphinic acid metal salt, for example, can be 5.5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 14.5 parts or any range between the above values.

[0010] In this invention, the mass percentage of dialkylphosphine metal salt in the flame retardant composition is ≤70%, for example, it can be 40~70%, more preferably 50~69%.

[0011] In this invention, 0.5 to 4 parts of dialkylphosphinic acid imidazolium salt can be, for example, 0.55 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, or any of the above values, and more preferably 0.8 to 3 parts.

[0012] In this invention, the mass percentage of dialkylphosphino acid imidazolium salt in the flame retardant composition is ≥5%, for example, it can be 6~30%, more preferably 6.5~26%.

[0013] In this invention, the dialkylphosphino acid imidazolium salt inevitably also includes a second dialkylphosphino acid metal salt, an alkylimidazolium halide, etc.; the mass percentage of the second dialkylphosphino acid metal salt in the dialkylphosphino acid imidazolium salt is ≤0.5%; the second dialkylphosphino acid metal salt can be, for example, sodium diethylphosphinoate; the mass percentage of the alkylimidazolium halide in the dialkylphosphino acid imidazolium salt is ≤1%; the alkylimidazolium halide can be, for example, 1-ethyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, etc.

[0014] In this invention, the C1-C10 straight-chain or branched alkyl groups can be, for example, straight-chain or branched alkyl groups of C2, C3, C4, C5, C6, C7, C8, and C9, and exemplary include, but are not limited to: ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, isopentyl, neopentyl, 2-methylpentyl, 2-ethylpentyl, n-hexyl, neohexyl, 2-methylhexyl, 2-ethylhexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, etc.; the same expressions in the following text have the same meaning.

[0015] In this invention, C1 to C6 straight-chain or branched alkyl groups, for example, can be straight-chain or branched alkyl groups of C2, C3, C4, C5, and C6, including but not limited to: ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, isopentyl, neopentyl, 2-methylpentyl, n-hexyl, neohexyl, etc.; the same expressions in the following text have the same meaning.

[0016] In this invention, the halogens include F, Cl, Br, and I.

[0017] In this invention, the "substituent" can replace one substituent or multiple substituents. When there are multiple substituents (at least two), they can be the same or different substituents; the same expression in the following text has the same meaning.

[0018] Preferably, in Formula I, R1 and R2 are each independently selected from ethyl groups.

[0019] Preferably, in Formula I, R3 is selected from ethyl and R4 is selected from methyl.

[0020] Preferably, the D50 particle size of the dialkylphosphino acid imidazolium salt is ≤30μm, for example, it can be 1μm, 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 26μm, 28μm, 29μm or any of the above values, more preferably 5~20μm.

[0021] In this invention, the D50 of the dialkylphosphino acid imidazolium salt was obtained by laser particle size analyzer.

[0022] In this invention, the method for obtaining the dialkylphosphinoide imidazolium salt is not excessively limited. Any method that can obtain the dialkylphosphinoide imidazolium salt specific to this invention is acceptable, and it can be prepared using conventional methods in the prior art. Exemplarily, the preparation method of the dialkylphosphinoide imidazolium salt includes the following steps: The alkyl imidazole halide was reacted with a dialkyl phosphonate at 20–38 °C for 7.5–25 h, then extracted with an organic solvent, the organic phase was collected, and the crude product was obtained by vacuum distillation. The crude product was recrystallized and dried to obtain the flame retardant composition.

[0023] In this invention, the alkylimidazolium halide can be derived from commercially available sources or prepared using conventional methods; exemplary, the preparation method of the alkylimidazolium halide includes method one and / or method two.

[0024] Method 1 includes: refluxing N-alkylimidazolium with a haloalkane at 100-120°C for 40-56 h, cooling to room temperature, washing with an organic solvent to obtain a crude product; recrystallizing the crude product and drying it to obtain the alkylimidazolium halide.

[0025] In this invention, the molar ratio of N-alkylimidazole to haloalkanes in Method 1 is 1:(1.1~1.5); the reaction is carried out in the presence of a protective atmosphere (such as nitrogen); the haloalkanes are slowly added dropwise to the N-alkylimidazole to carry out the reaction, avoiding violent exothermic reactions that could lead to local overheating, and the addition time is ≤1h; the organic solvent includes, but is not limited to, anhydrous diethyl ether; the recrystallization is carried out using a mixed solvent of ethyl acetate and acetonitrile, and the volume ratio of ethyl acetate to acetonitrile is (1~3):1, such as 2:1.

[0026] In this invention, method two includes: mixing N-alkylimidazole with a haloalkane and a first solvent, and reacting at 70-76°C for 10-14 hours under a protective atmosphere and a pressure of 0.15-0.2 MPa, then further heating to 72-78°C for 8-12 hours, then cooling to 52-58°C, adding a second solvent and cooling to 10-20°C for 1-3 hours to crystallize, and then centrifuging and washing to obtain the alkylimidazole halide.

[0027] In this invention, the molar ratio of N-alkylimidazole to haloalkanes in Method 2 is 1:(1.1~1.5); the first solvent includes ethyl acetate, and the molar ratio of N-alkylimidazole to the first solvent is 1:(0.18~0.25); the second solvent includes ethyl acetate, and the molar ratio of N-alkylimidazole to the second solvent is 1:(0.6~0.8).

[0028] In this invention, the molar ratio of the alkyl imidazole halide to the dialkyl phosphonate is (1.02~1.1):1; the organic solvent used in the extraction step after the reaction of the alkyl imidazole halide and the dialkyl phosphonate includes, but is not limited to, anhydrous acetonitrile; the recrystallization of the crude product is specifically carried out using a mixed solvent of acetonitrile and n-hexane; the volume ratio of acetonitrile to n-hexane is 1:(2~4), such as 1:3.

[0029] Preferably, the dialkylphosphonic acid metal salt has the structure shown in Formula II.

[0030] Formula II.

[0031] In Equation II, R 11 R 12 Each of the substituents is independently selected from any one of substituted or unsubstituted C1-C10 straight-chain or branched alkyl groups, or substituted or unsubstituted C3-C6 cycloalkyl groups; the substituents are selected from at least one of halogens, or C1-C6 straight-chain or branched alkyl groups.

[0032] M m+ This represents a metal ion with a +m valence.

[0033] m is selected from integers ≥ 1.

[0034] Preferably, in formula II, R 11 R 12 Each is independently selected from C1-C6 straight-chain or branched alkyl groups, more preferably ethyl.

[0035] Preferably, in formula II, M m+The ions selected are any one or a combination of at least two of the following ions with a +m valence: alkali metal ions, aluminum ions, calcium ions, copper ions, zinc ions, iron ions, and titanium ions, more preferably at least one of aluminum ions with a +m valence and zinc ions with a +m valence.

[0036] In this invention, the C3-C6 cycloalkyl group can be a C3, C4, C5, or C6 cycloalkyl group, such as cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl.

[0037] Preferably, the flame retardant composition further comprises, by weight, 0.5 to 4 parts (e.g., 0.55 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts or any range of the above values) of nitrogen-containing flame retardant, and / or, 0.5 to 4 parts (e.g., 0.55 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts or any range of the above values) of synergistic flame retardant.

[0038] Preferably, the nitrogen-containing flame retardant includes melamine phosphate (such as BUDIT3141 from Shanghai Kaiyin Chemical Co., Ltd.) and / or melamine cyanurate.

[0039] Preferably, the synergistic flame retardant includes at least one of zinc borate, zinc oxide, and antimony trioxide.

[0040] In a second aspect, the present invention provides the application of the flame retardant composition described in the first aspect in polymer materials.

[0041] Preferably, the polymer material includes any one or a combination of at least two of polyamide, polyester, polyurethane, styrene-based polymer, polyolefin, polyphenylene ether, and polyacrylate, more preferably polyamide and / or polyester.

[0042] Thirdly, the present invention provides a polyamide composite material comprising the flame retardant composition described in the first aspect.

[0043] Preferably, the polyamide composite material comprises, by weight, 45-70 parts polyamide, 5.5-27 parts flame retardant composition as described in the first aspect, and 15-40 parts glass fiber.

[0044] In this invention, 45 to 70 parts of polyamide can be, for example, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts or any range of the above values, and more preferably 49 to 61 parts.

[0045] In this invention, the polyamide composite material contains ≥50% by mass, more preferably ≥55% by mass.

[0046] In this invention, under dry conditions of 280°C and 2.16 kg, the melt index of the polyamide is 1~20 g / 10min, more preferably 10~16 g / 10min.

[0047] In this invention, the test standard for the melt index of the polyamide is ISO1133-2011.

[0048] In this invention, 5.5 to 27 parts of the flame retardant composition as described in the first aspect may be, for example, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, or any range of the above values.

[0049] In this invention, the mass percentage of the flame retardant composition in the polyamide is ≤25%, for example, it can be 8~24%.

[0050] In this invention, 15 to 40 parts of glass fiber can be, for example, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38 parts or any range of the above values.

[0051] In this invention, the diameter of the glass fiber is 1~20μm, for example, it can be 5~15μm, 8~12μm, etc.; the chopped length of the glass fiber is 2~6mm, for example, it can be 2.5~5mm, 3~4.5mm, etc.

[0052] In this invention, the polyamide includes polyamides formed by the condensation polymerization of a diacid and a diamine, and / or polyamides obtained by ring-opening polymerization of a lactam; the diacid includes aromatic diacids and / or aliphatic diacids, and exemplarily, the diacid includes terephthalic acid, furanyl dicarboxylic acid, adipic acid, sebacic acid, succinic acid, etc.; the diamine includes butanediamine, hexamethylenediamine, decanediamine, etc.; and the lactam includes caprolactam.

[0053] Preferably, by weight, the polyamide comprises 40 to 50 parts of polyhexamethylene adipamide (e.g., 41, 42, 43, 44, 45, 46, 47, 48, 49 parts or any range between the above values) and 5 to 20 parts of polycaprolactam (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 parts or any range between the above values).

[0054] Preferably, the polyamide composite material further includes 0.1 to 2 parts by weight of other additives, such as 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8 parts or any range of the above values.

[0055] Preferably, the other additives include at least one of antioxidants, lubricants, or nucleating agents.

[0056] In this invention, the antioxidant, lubricant, and nucleating agent in the polyamide composite material are each in an independent mass fraction of 0.1 to 1 part.

[0057] In this invention, the antioxidant includes at least one of hindered phenolic antioxidants, hindered amine antioxidants, thioester antioxidants, or phosphite antioxidants, and is more preferably a compound system of hindered phenolic antioxidants and phosphite antioxidants. For example, the antioxidant includes a compound system of antioxidant 1098 and antioxidant 168.

[0058] In this invention, the lubricant includes at least one of amide lubricants, fatty acid ester lubricants, silicone, polyethylene wax, or pentaerythritol ester; the amide lubricants include, but are not limited to, ethylene bis-stearamide (EBS), oleamide, erucamide, etc.; the fatty acid ester lubricants include, but are not limited to, glyceryl monostearate and / or TR044W lubricant.

[0059] In this invention, the nucleating agent includes, but is not limited to, at least one of calcium carbonate, silicon dioxide, kaolin, talc, barium sulfate, myristic acid, palmitic acid, stearic acid, behenic acid, monomethyl terephthalate, isophthalic acid, polyethylene glycol, polypropylene glycol, and long-chain carboxylic acid sodium salt nucleating agents (such as commercially available brand LICOMONT NAV101 PWD).

[0060] In this invention, the other additives are not limited to those mentioned above. Additives with corresponding functions can be added according to actual needs, such as colorants, fillers, toughening agents, compatibilizers, etc., which will not be described in detail here.

[0061] In this invention, the preparation method of the polyamide composite material includes the following steps: mixing the components evenly and granulating by twin-screw extrusion; wherein the extrusion process is: rotation speed 100~500rpm, feeding speed 200~600kg / h; extrusion temperature 180~480℃.

[0062] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, the flame retardant composition is made by compounding dialkylphosphonic acid imidazolium salt and dialkylphosphonic acid metal salt in a specific amount and applying it to polymer materials. This can help reduce the amount of dialkylphosphonic acid metal salt used and can also greatly improve the flame retardant efficiency. At the same time, the mechanical properties of the material are also improved to varying degrees, and the material has good resistance to precipitation. Detailed Implementation

[0064] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0065] All materials used in this invention can be purchased commercially or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are shown in Table 1. Other materials used are also commercially available unless otherwise specified.

[0066] Table 1 Preparation Example 1 This preparation example provides a dialkylphosphonic acid imidazolium salt, and the specific preparation method of the dialkylphosphonic acid imidazolium salt includes the following steps: (1) Using N-methylimidazole (1 mol) and bromoethane (1.1 mol) as raw materials, N-methylimidazole was added to a 250 mL three-necked flask, and bromoethane was slowly added dropwise over 1 hour under nitrogen protection. The reaction was carried out at 110 °C under oil bath temperature control and refluxed for 48 hours. After the reaction was completed, the mixture was cooled to room temperature (25 °C) and washed three times with an appropriate amount of anhydrous diethyl ether to remove unreacted bromoethane and water-soluble impurities, yielding a pale yellow solid crude product. The crude product was dissolved in a mixed solvent of ethyl acetate / acetonitrile (volume ratio 2:1, 10 mL solvent) by heating, and crystallized by slow cooling. After filtration, the crystals were dried under vacuum at 65 °C for 24 hours to obtain 1-ethyl-3-methylimidazole bromide (yield ≥93%, purity ≥99%).

[0067] (2) In a 250 mL three-necked flask, add an aqueous solution of sodium diethylphosphonate (30 wt%, 0.1 mol) and the 1-ethyl-3-methylimidazolium bromide (0.105 mol). After stirring at 25 °C for 12 hours, add anhydrous acetonitrile (50 mL) for extraction. Allow the mixture to stand in a separatory funnel to separate the layers and collect the acetonitrile phase. Remove the solvent under reduced pressure to obtain the crude product, then recrystallize it from acetonitrile / n-hexane (acetonitrile to n-hexane volume ratio of 1:3), and dry under vacuum to obtain 1-ethyl-3-methylimidazolium diethylphosphonate, which is the dialkylphosphonic imidazolium salt. The purity of the dialkylphosphonic imidazolium salt is ≥99%, and the D50 of the dialkylphosphonic imidazolium salt is 12 μm.

[0068] Preparation Example 2 This preparation example provides a dialkylphosphino acid imidazolium salt, and the specific preparation method includes the following steps: (1) Using N-methylimidazolium (1 mol) and chloroethane (1.12 mol) as raw materials, ethyl acetate (molar ratio of N-methylimidazolium to ethyl acetate 1:0.21) was added as solvent. After nitrogen replacement protection, the mixture was heated to 75°C in a 50°C water bath for 12 hours, and then heated to 77°C for 10 hours (total reaction time 22 hours). The reaction pressure was controlled at 0.18 MPa. After the reaction was completed, the mixture was cooled to 55°C, and ethyl acetate (molar ratio of the aforementioned N-methylimidazolium to the added ethyl acetate 1:0.76) was added. The mixture was then cooled to 15°C for 2 hours to crystallize. The product was centrifuged (500 r / min, 10 minutes) under nitrogen protection and washed with ethyl acetate. Finally, it was vacuum dried to obtain a white to pale yellow crystalline product, which is 1-ethyl-3-methylimidazolium chloride.

[0069] (2) In a 250 mL three-necked flask, add sodium diethylphosphonate aqueous solution (30 wt%, 0.1 mol) and 1-ethyl-3-methylimidazolium chloride (0.105 mol), and stir at 30 °C for 12 hours. After the reaction solution is cooled to room temperature, add anhydrous acetonitrile (50 mL) for extraction, allow to stand in a separatory funnel to separate the layers, and collect the acetonitrile phase. Remove the solvent under reduced pressure to obtain the crude product, recrystallize with acetonitrile / n-hexane (acetonitrile to n-hexane volume ratio of 1:3), and dry under vacuum to obtain a white solid, which is 1-ethyl-3-methylimidazolium diethylphosphonate, i.e., the dialkylphosphonate imidazolium salt. The purity of the dialkylphosphonate imidazolium salt is ≥99%, and the D50 of the dialkylphosphonate imidazolium salt is 15 μm.

[0070] Preparation Example 3 This preparation example provides a dialkylphosphino acid imidazolium salt, and the specific preparation method includes the following steps: (1) Using N-methylimidazolium (1 mol) and n-butane bromide (1.1 mol) as raw materials, N-methylimidazolium was added to a 250 mL three-necked flask, and n-butane bromide was slowly added dropwise over 1 hour under nitrogen protection. The reaction was maintained at 110 °C in an oil bath and refluxed for 48 hours. After the reaction was completed, the mixture was cooled to room temperature (25 °C) and washed three times with an appropriate amount of anhydrous diethyl ether to remove unreacted n-butane bromide and water-soluble impurities, yielding a light brown solid crude product. The crude product was dissolved in anhydrous toluene / acetonitrile mixed solvent (volume ratio 2:1, 10 mL solvent) by heating, and crystallized by slow cooling. After filtration, the crystals were dried under vacuum at 65 °C for 24 hours to obtain 1-butyl-3-methylimidazolium bromide (yield ≥90%, purity ≥98%).

[0071] (2) In a 250 mL three-necked flask, add sodium diethylphosphonate aqueous solution (30 wt%, 0.1 mol) and the 1-butyl-3-methylimidazolium bromide (0.105 mol). After stirring at 25 °C for 24 hours, add anhydrous acetonitrile (50 mL) for extraction. Allow the mixture to stand in a separatory funnel to separate the layers and collect the acetonitrile phase. Remove the solvent under reduced pressure to obtain the crude product, and then recrystallize it from acetonitrile / n-hexane (acetonitrile to n-hexane volume ratio of 1:3). Dry under vacuum to obtain 1-butyl-3-methylimidazolium diethylphosphonate, which is the dialkylphosphonic imidazolium salt. The purity of the dialkylphosphonic imidazolium salt is ≥99%, and the D50 of the dialkylphosphonic imidazolium salt is 12 μm.

[0072] In this invention, the structural formula of the 1-ethyl-3-methylimidazolium diethylphosphonate is as follows: The structural formula of the 1-ethyl-3-methylimidazolium bromide is: .

[0073] In this invention, the method for testing the purity of the dialkylphosphino acid imidazolium salt includes: determination by high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC), with the test standard referring to ASTM D5815-95.

[0074] In this invention, the particle size of the dialkylphosphino acid imidazolium salt was obtained by testing with a laser particle size analyzer (model NKT6100-D), and the testing standard followed the GB / T19077-2024 method standard.

[0075] Examples 1-8 and Comparative Examples 1-4 each provide a flame retardant composition. The formulations of the flame retardant compositions are shown in Tables 2 and 3 by weight. The preparation method of the flame retardant compositions includes mixing the components evenly.

[0076] Table 2 Table 3 The application of the flame retardant composition of the present invention will be described in detail below using application examples, but the application of the flame retardant composition is not limited to these application examples.

[0077] Application Examples 1-8, compared with Application Examples 1-4 A polyamide composite material, the formulation of which is shown in Tables 4-6 by weight.

[0078] The preparation method of the polyamide composite material includes: mixing polyamide 66, polyamide 6, glass fiber, flame retardant composition provided in the examples and comparative examples, antioxidant, lubricant, and nucleating agent according to the formula to obtain a premix; adding the premix to a twin-screw extruder, wherein the screw speed of the twin-screw extruder is 300 rpm, the feed speed is 400 kg / h, the extrusion temperature is 280℃, and after melt mixing and extrusion granulation, the polyamide composite material is obtained.

[0079] The polyamide composite material was subjected to the following performance tests: (1) Evaluation of toughness at room temperature: The notched impact strength at 23℃ was tested in accordance with the standard GB / T 1843-2006; (2) Flame retardant performance: tested according to UL94 standard, with a burning sample thickness of 0.8mm.

[0080] (3) Bending strength: Tested on a Zwick electronic universal testing machine in accordance with standard ASTM D790-2003.

[0081] (4) Resistance to exudation: The test shall be conducted in accordance with the standard T / CPCIF 0194-2022. Specifically, the initial weight of the polyamide composite material shall be weighed and recorded as m0. Then, the polyamide composite material shall be boiled in hot water at 70℃ for 72h and then dried in an oven at 80℃ for 24h. The weight shall be weighed again and recorded as m1. The mass change rate of the polyamide composite material before and after boiling is (m0-m1) / m0×100%. The mass change rate before and after boiling reflects the solubility of the flame retardant in the water medium, i.e., the exudation performance.

[0082] Table 4 Table 5 Table 6 As shown in Tables 4-6, the flame retardant composition provided by this invention uses a specific ratio of dialkylphosphine imidazolium salt and dialkylphosphine metal salt. When applied to polymer materials, it helps to reduce the amount of dialkylphosphine metal salt used and can also greatly improve the flame retardant efficiency. At the same time, the mechanical properties of the material are also improved to varying degrees, and it is resistant to precipitation and has a small mass change rate before and after boiling in water. In application examples 1-8, the polyamide composite material including the flame retardant composition has a 0.8mm burning time ≤14.5s, a flame retardant rating of V-1 or higher, a flexural strength ≥173MPa, and a cantilever beam notched impact strength ≥10 kJ / m. 2 The rate of change in quality before and after boiling is ≤0.5%.

[0083] As can be seen from Application Example 1 and Comparative Application Examples 1 and 2, the flame retardant composition does not use a combination of dialkylphosphonic acid imidazolium salt and dialkylphosphonic acid metal salt. The resulting material has poorer flame retardant properties and / or mechanical properties, and poorer resistance to precipitation.

[0084] As can be seen from Application Example 1 and Comparative Application Examples 3 and 4, the dialkylphosphonic acid imidazolium salt and dialkylphosphonic acid metal salt in the flame retardant composition are not compounded in a specific amount, resulting in poor flame retardant properties and / or mechanical properties of the obtained material, as well as poor resistance to precipitation.

[0085] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flame retardant composition, characterized in that, The flame retardant composition comprises, by weight, 5-15 parts of a dialkylphosphonic acid metal salt and 0.5-4 parts of a dialkylphosphonic acid imidazolium salt; The dialkylphosphinoimidazolium salt has the structure shown in Formula I; Equation I; In Formula I, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C10 straight-chain or branched alkyl groups; The substituent is selected from at least one of halogens, C1-C6 straight-chain or branched alkyl groups.

2. The flame retardant composition according to claim 1, characterized in that, In Formula I, R1 and R2 are each independently selected from ethyl groups; Preferably, in Formula I, R3 is selected from ethyl and R4 is selected from methyl; Preferably, the D50 of the dialkylphosphino acid imidazolium salt is ≤30μm, more preferably 5~20μm.

3. The flame retardant composition according to claim 1 or 2, characterized in that, The dialkylphosphonic acid metal salt has the structure shown in Formula II; Formula II; In Equation II, R 11 R 12 Each of the substituents is independently selected from any one of substituted or unsubstituted C1-C10 straight-chain or branched alkyl groups, or substituted or unsubstituted C3-C6 cycloalkyl groups; the substituents are selected from at least one of halogens and C1-C6 straight-chain or branched alkyl groups. M m+ This represents a metal ion with a +m valence. m is selected from integers ≥ 1.

4. The flame retardant composition according to claim 3, characterized in that, In formula II, R 11 R 12 Each is independently selected from C1-C6 straight-chain or branched alkyl groups, more preferably ethyl; Preferably, in formula II, M m+ The ions selected are any one or a combination of at least two of the following ions with a +m valence: alkali metal ions, aluminum ions, calcium ions, copper ions, zinc ions, iron ions, and titanium ions, more preferably at least one of aluminum ions with a +m valence and zinc ions with a +m valence.

5. The flame retardant composition according to any one of claims 1 to 4, characterized in that, The flame retardant composition further includes, by weight, 0.5 to 4 parts of a nitrogen-containing flame retardant and / or 0.5 to 4 parts of a synergistic flame retardant.

6. The flame retardant composition according to claim 5, characterized in that, The nitrogen-containing flame retardant includes melamine phosphate and / or melamine cyanurate; Preferably, the synergistic flame retardant includes at least one of zinc borate, zinc oxide, and antimony trioxide.

7. The use of a flame retardant composition according to any one of claims 1 to 6 in a polymer material; Preferably, the polymer material includes any one or a combination of at least two of polyamide, polyester, polyurethane, styrene-based polymer, polyolefin, polyphenylene ether, and polyacrylate, more preferably polyamide and / or polyester.

8. A polyamide composite material, characterized in that, The polyamide composite material includes the flame retardant composition according to any one of claims 1 to 6.

9. The polyamide composite material according to claim 8, characterized in that, The polyamide composite material comprises, by weight, 45-70 parts polyamide, 5.5-27 parts flame retardant composition as described in any one of claims 1-6, and 15-40 parts glass fiber; Preferably, the polyamide comprises 40-50 parts by weight of polyhexamethylene adipamide and 5-20 parts by weight of polycaprolactam.

10. The polyamide composite material according to claim 8 or 9, characterized in that, The polyamide composite material further includes 0.1 to 2 parts by weight of other additives; Preferably, the other additives include at least one of antioxidants, lubricants, or nucleating agents.

Images