Composite intumescent flame retardant and preparation method thereof

Abstract

The invention provides a composite intumescent flame retardant and a preparation method thereof. The composite intumescent flame retardant provided by the invention is prepared from the following components in parts by weight: 30-50 parts of a phytic acid derivative; 20 to 40 parts of MPP (modified polypropylene); 5 to 15 parts of modified nanosheets; and 10-20 parts of a hydrogen bond cross-linking agent. The design of a flame-retardant system is realized through'covalent grafting-hydrogen bond crosslinking-nano synergy '. The thermal stability of the composite material is improved by utilizing Si-O covalent bonds grafted with phytic acid; a hydrogen bond is formed by-NH2 in the melamine pyrophosphate and-COOH in the polyamide oligomer, and a cross-linked carbon layer is formed during combustion, so that the plasticizing defect of polyamide is overcome; and the montmorillonite is combined with a P = O bond hydrogen bond in the phytic acid derivative, so that the nanosheet is catalyzed to form carbon at high temperature and can be decomposed into a SiO2 / Al2O3 ceramic layer, and the thermal stability and interfacial compatibility of polyamide are improved. When the composite intumescent flame retardant is used for modifying a polyamide composite material, the limit oxygen index and the fireproof grade of the polyamide material can be remarkably improved under the condition of low addition amount.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a composite intumescent flame retardant and its preparation method. Background Technology

[0002] Polyamide (PA), as a core engineering plastic, is widely used in automotive engine parts, electrical connectors, industrial gears, and other fields due to its excellent wear resistance, high mechanical strength, and good self-lubricating properties. However, traditional intumescent flame retardants (such as melamine pyrophosphate) rely on physical addition, and their hydrogen bond network breaks at temperatures above 150°C, making them unsuitable for the processing temperature of PA (220-280°C), resulting in a decrease in flame retardant efficiency.

[0003] Traditional hydrogen-bonded complexes (such as melamine-gallic acid) improve the flame retardancy efficiency of PA and significantly increase the limiting oxygen index (LOI), but their mechanical properties, such as tensile strength, are significantly weakened (DOI:10.3390 / polym12071482). Using quaternary phosphine-modified montmorillonite (PMMT) in combination with melamine pyrophosphate (MPP) requires the addition of additional flame retardants to achieve a V-0 rating (UL 94), and the uneven dispersion of nanosheets results in poor carbon layer density (DOI:10.3969 / j.issn.1001-0041.2021.04.003). Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a composite intumescent flame retardant and its preparation method.

[0005] The composite intumescent flame retardant provided by this invention is made from the following components in parts by weight:

[0006] Phytic acid derivatives: 30-50 parts

[0007] Melamine pyrophosphate (MPP): 20-40 parts

[0008] Modified nanosheets: 5-15 parts

[0009] Hydrogen bond crosslinking agent: 10-20 parts

[0010] The phytic acid derivative is prepared by condensing phytic acid with a pre-hydrolyzed silane coupling agent.

[0011] The silane coupling agent may be selected from at least one of the following: γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), and γ-methacryloyloxypropyltrimethoxysilane (KH-570);

[0012] Specifically, the process can be as follows: Dissolve the silane coupling agent in anhydrous ethanol, add deionized water dropwise, and stir until the solution changes from turbid to clear and transparent to obtain a pre-hydrolyzed silane coupling agent. Add the obtained pre-hydrolyzed silane coupling agent dropwise to a phytic acid solution and heat it in an inert atmosphere to react, thus obtaining the final product.

[0013] The modified nanosheets are amine-modified montmorillonite.

[0014] The modified nanosheets were prepared by a method comprising the following steps:

[0015] 1) C through ion exchange 10 -C 20 Alkyl quaternary ammonium salts are intercalated into sodium-based montmorillonite (Na-MMT) sheets to obtain organomontmorillonite, i.e., C640. 10 -C 20 Alkyl quaternary ammonium salt - MMT;

[0016] 2) Place C 10 -C 20 Alkyl quaternary ammonium salt-MMT powder was dispersed in anhydrous ethanol, and then refluxed under a strong base and inert atmosphere with the addition of diamine or triamine. The precipitate was collected, washed, and dried to obtain amine-modified montmorillonite powder.

[0017] Wherein, the C 10 -C 20 Specifically, the alkyl quaternary ammonium salt can be a hexadecyl quaternary ammonium salt or an octadecyl quaternary ammonium salt, and more specifically, a hexadecyltrimethylammonium bromide (CTAB);

[0018] The diamine or triamine may be selected from at least one of: diethylenetriamine (DETA), decanediamine (DMDA), hexamethylenediamine (HMDA), and ethylenediamine (EDA);

[0019] The strong base may be selected from at least one of: potassium carbonate, CH3ONa, (CH3CH2O)3Al;

[0020] Step 1) involves dissolving sodium montmorillonite in water to obtain a suspension, and then adding C... 10 -C 20 Alkyl quaternary ammonium salt, stirred, centrifuged to collect the precipitate, washed, dried, and ground to obtain C. 10 -C 20 Alkyl quaternary ammonium salt - MMT.

[0021] The hydrogen-bonded crosslinking agent is a carboxyl-terminated nylon 6 / 66 copolymer with a relative molecular mass of 5000-7500 g / mol, a carboxyl-terminated content of ≥0.8 mmol / g, and a melt index of 10-20 g / 10 min.

[0022] The hydrogen-bonded crosslinking agent is prepared by a method comprising the following steps:

[0023] Caprolactam and PA66 were mixed, and water and adipic acid were added. The mixture was heated to 90℃-100℃ in an inert atmosphere to dehydrate the solution. The dehydrated solution was then transferred to a sealed high-pressure reactor, heated to 240-250℃, and pressured at 0.6-1 MPa. After reacting for 3-5 hours, the pressure was slowly released to atmospheric pressure, and then evacuated to -1 to 0 MPa. The mixture was reacted at 240-250℃ for 2-4 hours, and then purged with nitrogen to 0.2-0.4 MPa. The mixture was allowed to stand for 1-2 hours to defoam, extracted with boiling water for 10-14 hours, and then dried under vacuum to obtain a carboxyl-terminated nylon 6 / 66 copolymer, which is a hydrogen-bonded crosslinking agent.

[0024] The present invention also provides a method for preparing the above-mentioned composite intumescent flame retardant.

[0025] The composite intumescent flame retardant is prepared by a method comprising the following steps:

[0026] (1) Weigh the components;

[0027] (2) Dry the hydrogen-bonded crosslinking agent; other components do not need to be dried.

[0028] (3) Mix phytic acid derivatives, MPP and hydrogen bonding crosslinking agents in proportion to obtain hydrogen bond complex;

[0029] (4) Modified nanosheets are added to the well-mixed hydrogen-bonded complex, melt-blended in a twin-screw extruder, and extruded and granulated to obtain a composite intumescent flame retardant.

[0030] The drying described in step (2) of the above method is drying at 60-80℃ for 4-6 hours, specifically drying at 70℃ for 5 hours;

[0031] In step (4), the twin-screw extruder includes 9 temperature control zones: temperature zone 1 is 180-200℃, temperature zones 2-3 are 220-240℃, temperature zones 4-6 are 220-250℃, temperature zones 7-9 are 230-240℃, and the die temperature is 230-240℃; the main machine speed is 220-230 rpm; and the pelletizing speed is 300-420 rpm.

[0032] The application of the aforementioned composite intumescent flame retardant in the flame retardant modification of engineering plastics also falls within the scope of protection of this invention.

[0033] The engineering plastic is polyamide, more specifically PA6 or PA66.

[0034] Compared with the prior art, the advantages of this invention are:

[0035] This invention proposes a composite intumescent flame retardant and its preparation method, achieving a flame retardant system design through "covalent grafting-hydrogen bond crosslinking-nanosynergy". The Si-O covalent bonds of grafted phytic acid are utilized to enhance the thermal stability of the composite material; hydrogen bonds are formed between the -NH2 in melamine pyrophosphate and the -COOH in the polyamide oligomer, resulting in a crosslinked char layer during combustion, thus addressing the plasticizing defects of polyamide; and hydrogen bonds are formed between montmorillonite and the P=O bonds in the phytic acid derivative, catalyzing the char formation of nanosheets at high temperatures, which can decompose into a SiO2 / Al2O3 ceramic layer, thereby improving the thermal stability and interfacial compatibility of polyamide. The polyamide composite material modified with the composite intumescent flame retardant of this invention can significantly improve the limiting oxygen index and fire resistance rating with low addition amounts, without affecting the mechanical properties of the polyamide material. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0037] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0038] The γ-aminopropyltriethoxysilane used in the following examples, brand name JH-A110, was purchased from Jingzhou Jianghan Fine Chemical Co., Ltd.

[0039] The phytic acid derivatives, modified nanosheets, and hydrogen-bonded crosslinking agents in the following examples were prepared by the following methods:

[0040] (1) Preparation of phytic acid derivatives: 9.43 g of 70% phytic acid aqueous solution (10 mmol) was dissolved in 50 mL of anhydrous ethanol and sonicated for 10 min until fully dissolved. 3.98 g of APTES (18 mmol) was dissolved in 100 mL of anhydrous ethanol, and 1 mL of deionized water (water / APTES molar ratio = 1:3) was slowly added dropwise while stirring. The mixture was stirred thoroughly for 30 min at 50 °C until the solution changed from turbid to clear and transparent. Then, the pre-hydrolyzed APTES solution was added dropwise to the dissolved phytic acid solution at a rate of 1 mL / min. The reaction was carried out under N2 protection in an oil bath at 70 °C with stirring (500 rpm) for 2 h to obtain phytic acid derivatives.

[0041] (2) Preparation of hydrogen bond crosslinking agent: Dissolve 2g of PA66 in 1.8g of deionized water to prepare a 52.6wt% aqueous solution, and adjust the pH to 7.3 with 0.1M NaOH (to maintain amino stability). Mix 8g of caprolactam (CPL, ≥99.5%) and 3.8g of PA66 solution evenly, and then add 0.2g of water and 12.68g of adipic acid (-NH2:-COOH molar ratio = 1:1.05), [-NH2 is PA66, -COOH is adipic acid]. Heat to 90℃ under nitrogen protection and stir to dehydrate for 30min. The dehydrated solution was transferred to a sealed high-pressure reactor, heated to 245℃ and pressured at 0.8 MPa. After reacting for 4 hours, the pressure was slowly released to atmospheric pressure, then evacuated to -0.5 MPa and reacted at 245℃ for 3 hours. Nitrogen gas was then introduced to 0.3 MPa, and the mixture was allowed to stand for 1 hour to defoam. After boiling water extraction for 12 hours, the mixture was dried under vacuum at 120℃ to obtain the hydrogen-bonded crosslinking agent. The relative molecular mass was 6500 g / mol, the terminal carboxyl group content was 145 mmol / kg, and the melt index was 12 g / 10 min.

[0042] (3) Preparation of amino-modified montmorillonite nanosheets: 0.533 g of sodium-based montmorillonite (Na-MMT, interlayer spacing ≈ 1.25 nm) was dissolved in 26.65 g of deionized water (solid-liquid ratio 2%) and stirred thoroughly for 30 min to form a uniform suspension. 0.267 g of hexadecyltrimethylammonium bromide (CTAB, ≥99%) was added to the suspension and stirred thoroughly at 70 °C for 4 h. After removing the solution, the precipitate was washed 5 times by centrifugation with deionized water, dried under vacuum at 60 °C for 12 h, and ground to obtain CTAB-intercalated modified Na-MMT, which was labeled as CTAB-MMT powder.

[0043] 0.8 g of CTAB-MMT powder was weighed and dispersed in 26.67 g of anhydrous ethanol (solid-liquid ratio 3%). 0.158 g of EDA (EDA / CTAB molar ratio = 6:1) and 0.05 g of K₂CO₃ were added, and the mixture was stirred thoroughly. Under nitrogen protection, the mixture was refluxed at 80 °C for 8 h. The solution was then removed, washed three times by centrifugation with ethanol, and dried at 60 °C to obtain amino-modified montmorillonite powder, which was labeled as EDA-MMT powder.

[0044] Example 1: Preparation of Composite Intumescent Flame Retardant

[0045] The composite intumescent flame retardant is made from the following components in parts by weight:

[0046] Phytic acid derivative 9.5, melamine pyrophosphate (MPP) 7.2, modified nanosheets 3.2, hydrogen bond crosslinking agent 4.5;

[0047] It was prepared according to the following method:

[0048] (1) Weigh the components;

[0049] (2) Dry the hydrogen-bonded crosslinking agent at 70°C for 5 hours; other components do not need to be dried.

[0050] (3) Mix the phytic acid derivative, MPP and hydrogen bond crosslinking agent in a high-speed mixer for 12 minutes to obtain the hydrogen bond complex.

[0051] (4) Modified nanosheets are added to the well-mixed hydrogen-bonded complex, melt-blended in a twin-screw extruder, and extruded and granulated to obtain a composite intumescent flame retardant.

[0052] In the above method, the temperatures of each heating zone of the twin-screw are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, and 235℃ respectively; the die head temperature is 235℃; the main machine speed is 225 rpm; the pelletizing speed is 400 rpm; and the feeding speed is 10 rpm.

[0053] Example 2: Preparation of Composite Intumescent Flame Retardant

[0054] The composite intumescent flame retardant is made from the following components in parts by weight:

[0055] Phytic acid derivatives 7.3, melamine pyrophosphate (MPP) 5, modified nanosheets 2.2, hydrogen bond crosslinking agent 2.8.

[0056] It was prepared according to the following method:

[0057] (1) Weigh the components;

[0058] (2) Dry the hydrogen-bonded crosslinking agent at 70°C for 5 hours; other components do not need to be dried.

[0059] (3) Mix the phytic acid derivative, MPP and hydrogen bond crosslinking agent in a high-speed mixer for 12 minutes to obtain the hydrogen bond complex.

[0060] (4) Modified nanosheets are added to the well-mixed hydrogen-bonded complex, melt-blended in a twin-screw extruder, and extruded and granulated to obtain a composite intumescent flame retardant.

[0061] In the above method, the temperatures of each heating zone of the twin-screw are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, and 235℃ respectively; the die head temperature is 235℃; the main machine speed is 225 rpm; the pelletizing speed is 400 rpm; and the feeding speed is 10 rpm.

[0062] Example 3: Preparation of Composite Intumescent Flame Retardant

[0063] The composite intumescent flame retardant is made from the following components in parts by weight:

[0064] The composition includes 5.2% phytic acid derivative, 3.7% melamine pyrophosphate (MPP), 1.7% modified nanosheets, and 2.5% hydrogen bonding crosslinking agent.

[0065] It was prepared according to the following method:

[0066] (1) Weigh the components;

[0067] (2) Dry the hydrogen-bonded crosslinking agent at 70°C for 5 hours; other components do not need to be dried.

[0068] (3) Mix the phytic acid derivative, MPP and hydrogen bond crosslinking agent in a high-speed mixer for 12 minutes to obtain the hydrogen bond complex.

[0069] (4) Modified nanosheets are added to the well-mixed hydrogen-bonded complex, melt-blended in a twin-screw extruder, and extruded and granulated to obtain a composite intumescent flame retardant.

[0070] The temperatures of each heating zone of the twin-screw extruder are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, 235℃, respectively; the die head temperature is 235℃; the main motor speed is 225 rpm; the pelletizing speed is 400 rpm; and the feeding speed is 10 rpm.

[0071] Example 4: Preparation of a composite intumescent flame retardant modified polyamide composite material

[0072] The polyamide composite material is made of the following substances in weight percentage: 75.2% PA66 resin, 24.4% composite intumescent flame retardant prepared in Example 1, 0.3% anti-dripping agent, and 0.1% other additives;

[0073] The PA66 resin is PA66 101L, purchased from DuPont.

[0074] The anti-dripping agent is polytetrafluoroethylene micro powder, brand name WRF403, purchased from DuPont.

[0075] The other additives are black masterbatches.

[0076] It was prepared according to the following method:

[0077] (1) Weigh the components;

[0078] (2) Dry the PA66 resin at 100℃ for 7 hours.

[0079] (3) The PA66 resin, the composite intumescent flame retardant prepared in Example 1, the anti-dripping agent and other additives are thoroughly mixed in a high-speed mixer at 120°C for 5 min;

[0080] (4) The well-mixed mixture is melt-blended in a twin-screw extruder, and the screw speed is controlled at 200-500 rpm to obtain composite intumescent flame retardant modified polyamide composite material particles.

[0081] In the above method, the temperatures of each heating zone of the twin-screw extruder are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, and 235℃ respectively, the die temperature is 235℃, the main extruder speed is 225r / min, and the feeding speed is 10r / min.

[0082] Example 5: Preparation of polyamide composite material modified with composite intumescent flame retardant

[0083] The polyamide composite material is made of the following substances in weight percentage: 82.3% PA66 resin, 17.3% composite intumescent flame retardant prepared in Example 2, 0.3% anti-dripping agent, and 0.1% other additives;

[0084] The PA66 resin is PA66 101L, purchased from DuPont.

[0085] The anti-dripping agent is polytetrafluoroethylene micro powder, brand name WRF403, purchased from DuPont.

[0086] The other additives are black masterbatches.

[0087] It was prepared according to the following method:

[0088] (1) Weigh the components;

[0089] (2) Dry the PA66 resin at 100℃ for 7 hours.

[0090] (3) The PA66 resin, the composite intumescent flame retardant prepared in Example 2, the anti-dripping agent and other additives were thoroughly mixed in a high-speed mixer at 120°C for 5 min;

[0091] (4) The well-mixed mixture is melt-blended in a twin-screw extruder, and the screw speed is controlled at 200-500 rpm to obtain composite intumescent flame retardant modified polyamide composite material particles.

[0092] In the above method, the temperatures of each heating zone of the twin-screw extruder are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, and 235℃ respectively, the die temperature is 235℃, the main extruder speed is 225 rpm, and the feeding speed is 10 rpm.

[0093] Example 6: Preparation of polyamide composite material modified with composite intumescent flame retardant

[0094] The polyamide composite material is made of the following substances in weight percentage: 86.5% PA66 resin, 13.1% composite intumescent flame retardant prepared in Example 3, 0.3% anti-dripping agent, and 0.1% other additives.

[0095] The PA66 resin is PA66 101L, purchased from DuPont.

[0096] The anti-dripping agent is polytetrafluoroethylene micro powder, brand name WRF403, purchased from DuPont.

[0097] The other additives are black masterbatches.

[0098] It was prepared according to the following method:

[0099] (1) Weigh the components;

[0100] (2) Dry the PA66 resin at 100℃ for 7 hours.

[0101] (3) The PA66 resin, the composite intumescent flame retardant prepared in Example 3, the anti-dripping agent and other additives were thoroughly mixed in a high-speed mixer at 120°C for 5 min;

[0102] (4) The well-mixed mixture is melt-blended in a twin-screw extruder, and the screw speed is controlled at 200-500 rpm to obtain composite intumescent flame retardant modified polyamide composite material particles.

[0103] In the above method, the temperatures of each heating zone of the twin-screw extruder are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, and 235℃ respectively, the die temperature is 235℃, the main extruder speed is 225 rpm, and the feeding speed is 10 rpm.

[0104] Comparative Example 1: Preparation of a phosphorus-nitrogen-based intumescent flame retardant modified polyamide composite material

[0105] The phosphorus-nitrogen intumescent flame retardant modified polyamide composite material is made of the following substances in weight percentage: 75.2% PA66 resin, 9.5% phosphorus-nitrogen intumescent flame retardant, 7.2% flame retardant synergist, 3.2% compatibilizer, 4.5% heat stabilizer, 0.3% anti-dripping agent, and 0.1% other additives.

[0106] The PA66 resin is PA66 101L, purchased from DuPont.

[0107] The phosphorus-nitrogen intumescent flame retardant was purchased from Hangzhou Nuowei New Materials Co., Ltd.

[0108] The flame retardant synergist is melamine urate, brand name MCA-25, purchased from Hangzhou Jiesheng Flame Retardant Chemical Co., Ltd.

[0109] The compatibilizer is maleic anhydride-grafted polyamide, brand name CMG5805-L, purchased from Jia Yi Rong Compatibilizer Jiangsu Co., Ltd.

[0110] The heat stabilizer is a hindered phenolic antioxidant, brand name Irganox 1098, purchased from BASF, Germany;

[0111] The anti-dripping agent is polytetrafluoroethylene micro powder, brand name WRF403, purchased from DuPont.

[0112] The other additives are black masterbatches.

[0113] It was prepared according to the following method:

[0114] (1) Weigh the components;

[0115] (2) Dry the PA66 resin at 100℃ for 7 hours; other components do not need to be dried.

[0116] (3) Mix the above substances thoroughly in a high-speed mixer at 120°C for 5 minutes according to the proportion;

[0117] (4) The well-mixed mixture is melt-blended in a twin-screw extruder to obtain phosphorus-nitrogen intumescent flame retardant modified polyamide composite particles.

[0118] In the above method, the temperatures of each heating zone of the twin-screw extruder are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, and 235℃ respectively, the die temperature is 235℃, the main extruder speed is 225 rpm, and the feeding speed is 10 rpm.

[0119] Comparative Example 2: Preparation of a phosphorus-nitrogen-based intumescent flame retardant modified polyamide composite material

[0120] The phosphorus-nitrogen intumescent flame retardant modified polyamide composite material is made of the following substances in weight percentage: 65.7% PA66 resin, 14% phosphorus-nitrogen intumescent flame retardant, 10.2% flame retardant synergist, 4.2% compatibilizer, 5.5% heat stabilizer, 0.3% anti-dripping agent, and 0.1% other additives.

[0121] The PA66 resin is PA66 101L, purchased from DuPont.

[0122] The phosphorus-nitrogen intumescent flame retardant was purchased from Hangzhou Nuowei New Materials Co., Ltd.

[0123] The flame retardant synergist is melamine urate, brand name MCA-25, purchased from Hangzhou Jiesheng Flame Retardant Chemical Co., Ltd.

[0124] The compatibilizer is maleic anhydride-grafted polyamide, brand name CMG5805-L, purchased from Jia Yi Rong Compatibilizer Jiangsu Co., Ltd.

[0125] The heat stabilizer is a hindered phenolic antioxidant, brand name Irganox 1098, purchased from BASF, Germany;

[0126] The anti-dripping agent is polytetrafluoroethylene micro powder, brand name WRF403, purchased from DuPont.

[0127] The other additives are black masterbatches.

[0128] It was prepared according to the following method:

[0129] (1) Weigh the components;

[0130] (2) Dry the PA66 resin at 100℃ for 7 hours; other components do not need to be dried.

[0131] (3) Mix the above substances thoroughly in a high-speed mixer at 120°C for 5 minutes according to the proportion;

[0132] (4) The well-mixed mixture is melt-blended in a twin-screw extruder to obtain phosphorus-nitrogen intumescent flame retardant modified polyamide composite particles.

[0133] In the above method, the temperatures of each heating zone of the twin-screw extruder are 190℃, 225℃, 230℃, 240℃, 240℃, 230℃, 235℃, 235℃, and 235℃ respectively, the die temperature is 235℃, the main extruder speed is 225 rpm, and the feeding speed is 10 rpm.

[0134] Comparative Example 3, PA66 101L, purchased from DuPont.

[0135] Table 1. Composition of each component of the modified polyamide composite materials in Examples 4-6 and Comparative Examples 1-3

[0136]

[0137]

[0138] The performance results of the obtained products

[0139] Table 2. Performance comparison of the modified polyamide composites obtained in Examples 4-6 and the products obtained in Comparative Examples 1-3.

[0140]

[0141]

[0142] Compared with the prior art, the present invention has the following advantages:

[0143] Based on the above, both traditional phosphorus-nitrogen intumescent flame retardants and composite intumescent flame retardants show a significant improvement in flame retardant effect compared to the pure PA resin in Comparative Example 3. Examples 4-6 show that the higher the proportion of the composite intumescent flame retardant of the present invention, the better the flame retardant effect. When the proportion is 24.4%, the limiting oxygen index and fire rating are optimal. Traditional flame retardants need to be added to 33.9% to achieve a fire rating of V-0 (Comparative Example 2). To achieve the same fire rating, the composite intumescent flame retardant of the present invention only needs to be added at 17.3% (less than 25%), which is significantly lower than the amount of traditional flame retardants.

[0144] This invention utilizes the Si-O covalent bonds of grafted phytic acid to enhance the thermal stability of the composite material. Furthermore, hydrogen bonds are formed between the -NH2 group in melamine pyrophosphate and the -COOH group in the polyamide oligomer, resulting in a cross-linked char layer during combustion. This addresses the plasticizing defects of polyamide. Additionally, hydrogen bonds between montmorillonite and the phytic acid derivative allow for catalytic carbonization of the nanosheets at high temperatures, decomposing into a SiO2 / Al2O3 ceramic layer, thereby improving the thermal stability and interfacial compatibility of the polyamide. This results in a synergistic catalytic carbonization of the phytic acid derivative and nanosheets, achieving an LOI > 35%, avoiding halogen contamination, and exhibiting superior mechanical properties compared to traditional IFR systems.

[0145] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A composite intumescent flame retardant, comprising the following components in parts by weight: Phytic acid derivatives: 30-50 parts Melamine pyrophosphate (MPP): 20-40 parts Modified nanosheets: 5-15 parts Hydrogen bond crosslinking agent: 10-20 parts.

2. The composite intumescent flame retardant according to claim 1, characterized in that, The phytic acid derivative is prepared by condensing phytic acid with a pre-hydrolyzed silane coupling agent. The silane coupling agent is selected from at least one of the following: γ-aminopropyltriethoxysilane (KH-550), γ-glycidoxypropyltrimethoxysilane (KH-560), and γ-methacryloyloxypropyltrimethoxysilane (KH-570); The modified nanosheets are amine-modified montmorillonite.

3. The composite intumescent flame retardant according to claim 2, characterized in that, The phytic acid derivative is prepared by a method comprising the following steps: dissolving a silane coupling agent in anhydrous ethanol, adding deionized water dropwise, stirring until the solution changes from turbid to clear and transparent to obtain a pre-hydrolyzed silane coupling agent, adding the obtained pre-hydrolyzed silane coupling agent dropwise to a phytic acid solution, and heating the solution under an inert atmosphere to obtain the final product.

4. The composite intumescent flame retardant according to claim 1, characterized in that, The modified nanosheets were prepared by a method comprising the following steps: 1) C through ion exchange 10 -C 20 Alkyl quaternary ammonium salts are intercalated into sodium-based montmorillonite (Na-MMT) sheets to obtain organomontmorillonite, i.e., C640. 10 -C 20 Alkyl quaternary ammonium salt - MMT; 2) Place C 10 -C 20 Alkyl quaternary ammonium salt-MMT powder was dispersed in anhydrous ethanol, and then refluxed under a strong base inert atmosphere with the addition of diamine or triamine. The precipitate was collected, washed, and dried to obtain amino-modified montmorillonite powder. Wherein, the C 10 -C 20 The alkyl quaternary ammonium salt can be a hexadecyl quaternary ammonium salt or an octadecyl quaternary ammonium salt; The diamine or triamine may be selected from at least one of: diethylenetriamine (DETA), decanediamine (DMDA), hexamethylenediamine (HMDA), and ethylenediamine (EDA); The strong base may be selected from at least one of potassium carbonate, CH3ONa, and (CH3CH2O)3Al.

5. The composite intumescent flame retardant according to claim 1, characterized in that, The hydrogen-bonded crosslinking agent is a carboxyl-terminated nylon 6 / 66 copolymer with a relative molecular mass of 5000-7500 g / mol, a carboxyl-terminated content ≥0.1 mmol / g, and a melt index of 10-20 g / 10 min.

6. The composite intumescent flame retardant according to claim 5, characterized in that, The hydrogen-bonded crosslinking agent is prepared by a method comprising the following steps: Caprolactam and PA66 were mixed, and water and adipic acid were added. The mixture was heated to 90℃-100℃ in an inert atmosphere to dehydrate the solution. The dehydrated solution was then transferred to a sealed high-pressure reactor, heated to 240-250℃, and pressured at 0.6-1 MPa. After reacting for 3-5 hours, the pressure was slowly released to atmospheric pressure, and then evacuated to -1 to 0 MPa. The mixture was reacted at 240-250℃ for 2-4 hours, and then purged with nitrogen to 0.2-0.4 MPa. The mixture was allowed to stand for 1-2 hours to defoam, extracted with boiling water for 10-14 hours, and then dried under vacuum to obtain a carboxyl-terminated nylon 6 / 66 copolymer, which is a hydrogen-bonded crosslinking agent.

7. A method for preparing the composite intumescent flame retardant according to any one of claims 1-6, comprising the following steps: (1) Weigh the components; (2) Dry the hydrogen-bonded crosslinking agent; (3) Mix phytic acid derivatives, MPP and hydrogen bonding crosslinking agents in proportion to obtain hydrogen bond complex; (4) Modified nanosheets are added to the well-mixed hydrogen-bonded complex, melt-blended in a twin-screw extruder, and extruded and granulated to obtain a composite intumescent flame retardant.

8. The method according to claim 7, characterized in that, The drying process described in step (2) involves drying at 60-80℃ for 4-6 hours. In step (4), the twin-screw extruder includes 9 temperature control zones: temperature zone 1 is 180-200℃, temperature zones 2-3 are 220-240℃, temperature zones 4-6 are 220-250℃, temperature zones 7-9 are 230-240℃, and the die temperature is 230-240℃; the main machine speed is 220-230 rpm; and the pelletizing speed is 300-420 rpm.

9. The application of the composite intumescent flame retardant according to any one of claims 1-6 in the flame retardant modification of engineering plastics.

10. The application according to claim 9, characterized in that, The engineering plastic is polyamide, more specifically PA6 or PA66.

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